0000950170-24-053921 | 10-Q | XBRL Viewer | Apellis Pharmaceuticals INC

Leases (Tables)

3 Months Ended

Mar. 31, 2024

Schedule of Additional Information Related to Operating Lease Assets and Liabilities

Additional information related to the operating lease assets and liabilities is as follows (in thousands):


	March 31,			December 31,
	2024			2023
Right-of-use assets	$	14,994		$	16,745
Operating Lease Liabilities	$	16,027		$	17,895
Weighted Average Remaining Term in years		2.64		2.83
Weighted Average discount rate used to measure outstanding lease liabilities		7.25	%		7.20	%

Supplemental Cash Flow Information Related to Operating Leases

Supplemental cash flow information related to operating leases for the three months ended March 31, 2024 and 2023 is as follows (in thousands):


	2024		2023
Operating cash flows from operating leases	$	2,311	$	2,022

Maturities of Operating Lease Liabilities

The maturities of the Company’s operating lease liabilities as of March 31, 2024 are as follows (in thousands):


2024		5,352
2025		6,188
2026		5,278
2027		858
Total future minimum lease payments		17,676
Less Imputed interest		(1,649	)
Total operating lease liabilities	$	16,027

Development Liability

3 Months Ended

Mar. 31, 2024

Research and Development [Abstract]

Development Liability

6. Development Liability

On February 28, 2019, the Company entered into a development funding agreement with SFJ (the “SFJ agreement”), under which SFJ agreed to provide funding to the Company to support the development of pegcetacoplan for the treatment of patients with PNH. Pursuant to the SFJ agreement, SFJ paid the Company $60.0 million following the signing of the agreement and agreed to pay the Company up to an additional $60.0 million in the aggregate in three equal installments upon the achievement of specified development milestones with respect to the Company’s Phase 3 program for pegcetacoplan in PNH and subject to the Company having cash resources at the time sufficient to fund at least 10 months of the Company’s operations.

In June 2019 the Company amended the SFJ agreement to include an additional $20.0 million funding payment. SFJ paid the Company $80.0 million under the amended SFJ agreement between June 2019 and January 2020.

Under the SFJ agreement, following regulatory approval by the FDA in May 2021 for the use of systemic pegcetacoplan as a treatment for PNH, the Company became obligated to pay SFJ an initial payment of $4.0 million and then an additional $226.0 million in the aggregate in six additional annual payments with the majority of the payments being made from the third anniversary to the sixth anniversary of regulatory approval. The Company paid SFJ the initial payment of $4.0 million in June 2021, its first annual payment of $11.5 million in May 2022 and its second annual payment of $24.5 million in May 2023. The subsequent annual payments remaining are due and payable in May of each year from 2024 through 2027.

Following regulatory approval of systemic pegcetacoplan for the treatment of PNH by the European Medicines Agency (“EMA”) in December 2021, the Company became obligated to pay SFJ an initial payment of $5.0 million and then an additional $225.0 million in the aggregate in six additional annual payments with the majority of the payments being made from the third anniversary to the sixth anniversary of regulatory approval. The Company paid SFJ the initial payment of $5.0 million in January 2022 its first annual payment of $18.0 million in December 2022 and its second annual payment of $31.0 million in December 2023. The subsequent annual payments are due and payable in December of each year from 2024 through 2027.

The Company has paid SFJ a total of $94.0 million as of March 31, 2024. The Company is obligated to pay SFJ $37.5 million in May 2024 and $61.3 million in December 2024.

Additionally, the Company granted a security interest to SFJ in all of its assets, excluding intellectual property and license agreements to which it is a party. In connection with the grant of the security interest, the Company agreed to certain affirmative and negative covenants, including restrictions on its ability to pay dividends, incur additional debt or enter into licensing transactions with respect to its intellectual property, other than specified types of licenses.

From December 15, 2021 to the final annual payment due in December 2027, the development liability will be accreted from its initial carrying amount to the total payment amount using the effective interest rate method over the remaining life of the SFJ agreement. The difference between the carrying amount and the total payment amount is presented as a discount to the development liability. The accretion is recorded as interest expense in the unaudited condensed consolidated statement of operations.

The following table summarizes the development liability (in thousands):


	March 31, 2024			December 31, 2023			Effective Interest Rate
Development liability	$	366,000		$	366,000			7.91	%
Less: Unamortized discount to development liability		(44,287	)		(50,353	)
Less: Current portion of development liability, net of discount		(77,287	)		(75,830	)
Total long-term development liability	$	244,426		$	239,817

For the three months ended March 31, 2024 and 2023 interest expense of $6.1 million and $6.6 million were recorded for the accretion of the development liability.

Future minimum SFJ payments as of March 31, 2024 is as follows (in thousands):


2024	$	98,750
2025		103,000
2026		109,000
2027		55,250
Total future minimum payments		366,000

Product Revenues, Accounts Receivable, and Reserves for Product Sales - Schedule of Customer Accounted for 10% of More of Gross Product Revenues and Accounts Receivable (Detail) - Customer Concentration Risk [Member]	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Gross Product Revenues [Member] \| Customer A [Member]
Revenue, Major Customer [Line Items]
Concentration risk	15.00%	52.00%
Gross Product Revenues [Member] \| Customer C [Member]
Revenue, Major Customer [Line Items]
Concentration risk	19.00%	9.00%
Gross Product Revenues [Member] \| Customer D [Member]
Revenue, Major Customer [Line Items]
Concentration risk	59.00%	33.00%
Product Sales Receivable [Member] \| Customer A [Member]
Revenue, Major Customer [Line Items]
Concentration risk	3.00%	25.00%
Product Sales Receivable [Member] \| Customer C [Member]
Revenue, Major Customer [Line Items]
Concentration risk	21.00%	15.00%
Product Sales Receivable [Member] \| Customer D [Member]
Revenue, Major Customer [Line Items]
Concentration risk	67.00%	52.00%

License and Collaboration Agreements	3 Months Ended
Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License and Collaboration Agreements	12. License and Collaboration Agreements Sobi License and Collaboration Agreement In October 2020, the Company and its subsidiaries, Apellis International GmbH (f/k/a Apellis Switzerland GmbH) and APL DEL Holdings, LLC, entered into a Collaboration and License Agreement (the “Sobi collaboration agreement”) with Sobi, concerning the development and commercialization of pegcetacoplan and specified other structurally and functionally similar compstatin analogues or derivatives for use systemically or for local non-ophthalmological administration (collectively referred to as the “Licensed Products”). Under the Sobi collaboration agreement, the Company granted Sobi an exclusive (subject to certain retained rights of the Company), sublicensable license of certain patent rights and know-how to develop and commercialize Licensed Products in all countries outside of the United States. The Company retains the right to commercialize Licensed Products in the United States, and, subject to specified limitations, to develop Licensed Products worldwide for commercialization in the United States. Under the Sobi collaboration agreement, the Company and Sobi have agreed to collaborate to develop Licensed Products for the treatment of PNH, CAD, HSCT-TMA, C3G, IC-MPGN and ALS (collectively the “Initial Indications”), and any other indications subsequently agreed upon by the parties, for commercialization by or on behalf of the Company in the United States and by or on behalf of Sobi outside of the United States. If the parties do not agree to jointly pursue any development activities for the Licensed Products (whether for an Initial Indication or otherwise), the party proposing to pursue such activities may conduct such activities at its sole expense (with the non-proposing party having the right to obtain rights to the data generated by such development activities by paying a specified percentage of that expense), subject to agreed-upon exceptions that limit each party’s unilateral development rights. The initial development plan sets forth the initial development activities to be conducted by each of the Company and Sobi, with the Company bearing all costs incurred in conducting the activities set forth in such initial development plan, as well as certain specified additional costs that are not included in the initial development plan that may be incurred by the parties in developing Licensed Products for PNH in the European Union and the United Kingdom. The Company and Sobi have formed several governance committees to oversee the development and manufacture, and to review and discuss the commercialization, of Licensed Products. The Company and SOBI discontinued the development programs in ALS and CAD. The Company shall supply Licensed Products to Sobi for development and for commercialization outside of the United States in accordance with a supply agreement between the parties. The Sobi collaboration agreement grants Sobi the right to perform or have performed drug product manufacturing of Licensed Products for development and for commercialization outside the United States and to manufacture or have manufactured drug substance under certain circumstances. Sobi paid the Company an upfront payment of $250.0 million in November 2020 and has agreed to pay up to an aggregate of $915.0 million upon the achievement of specified one-time regulatory and commercial milestone events, of which the Company received $50.0 million in April 2022 for the achievement of a regulatory development milestone in Europe. Sobi also agreed to reimburse the Company for up to $80.0 million in development costs, of which the Company received $65.0 million and waived payment of $15.0 million. The Company will also be entitled to receive tiered, double-digit royalties (ranging from high teens to high twenties) on sales of Licensed Products outside of the United States, subject to customary deductions and third-party payment obligations, until the latest to occur of: (i) expiration of the last-to-expire of specified licensed patent rights; (ii) expiration of regulatory exclusivity; and (iii) ten (10) years after the first commercial sale of the applicable Licensed Product, in each case on a Licensed Product-by-Licensed Product and country-by-country basis. Under the Sobi collaboration agreement, the Company remains responsible for its license fee obligations (including royalty obligations) to the Trustees of the University of Pennsylvania (“Penn”), as a licensor of the Company and for its payment obligations to SFJ. Under the Sobi collaboration agreement, for the three months ended March 31, 2024 and 2023, the Company recognized $4.5 million and $1.6 million of royalty revenue, respectively. The Company did not recognize any contra-research and development expense for the three months ended March 31, 2024 and 2023. Since contract inception, the Company has recognized $65.0 million in contra-research and development expenses. As of December 31, 2023, the Company recorded $15.0 million in current assets, which represented the receivable for contra-research and development expenses incurred but not yet reimbursed from Sobi. In January 2024, the Company waived the remaining reimbursement payment of $15.0 million in connection with the decision to discontinue the CAD program. University of Pennsylvania License Agreement The Company is a party to a license agreement with Penn for an exclusive, worldwide license to specified patent rights. The Company is required to make milestone payments aggregating up to $3.2 million based upon the achievement of specified development and regulatory milestones and up to $5.0 million based upon the achievement of specified annual sales milestones with respect to each licensed product, and to pay low single-digit royalties based on net sales of each licensed product and with minimum quarterly royalty thresholds. In addition, the Company is obligated to pay a specified portion of income it receives from sublicensees. In April 2023, the Company paid $2.3 million for the achievement of a regulatory milestone as a result of the FDA approval of SYFOVRE in February 2023. In 2023, the Company incurred $5.0 million as a result of the achievement of sales milestones for SYFOVRE of which the Company paid $2.0 million in October 2023 and the remaining $3.0 million in January 2024. As of March 31, 2024, the Company has incurred an aggregate royalty expense of $13.4 million on sales of SYFOVRE. In addition, the Company is also party to a license agreement with Penn for an exclusive, worldwide license to specified patent rights for the development and commercialization of products in fields of use, as defined therein. The Company is required to make milestone payments aggregating up to $1.7 million, based upon the achievement of development and regulatory approval milestones, and up to $2.5 million, based upon the achievement of annual sales milestones with respect to each of the first two licensed products. The license agreement also requires the Company to pay low single digit royalties based on net sales of each licensed product, subject to minimum quarterly royalty thresholds. In addition, the Company is obligated to pay a specified portion of income it receives from sublicensees. In January 2021, the Company paid $25.0 million for a sublicense fee owed to Penn related to the Sobi collaboration agreement and another licensing transaction. In August 2021, the Company paid $1.0 million to Penn upon the achievement of a development milestone, net of a credit for the annual license maintenance payment. In June 2022, the Company paid an additional $5.0 million to Penn upon the achievement of a development milestone. In January 2023, the Company paid $1.0 million to Penn upon the achievement of a sales milestone for EMPAVELI in 2022. In January 2024, the Company paid $0.5 million for a sublicense fee owed to Penn related to Sobi obtaining regulatory approval in Japan. Additionally, in January 2024, the Company paid $1.5 million as a result of the achievement of a sales milestone for EMPAVELI and Aspaveli. As of March 31, 2024, the Company has incurred an aggregate royalty expense of $9.5 million on sales of EMPAVELI and Aspaveli. Beam Research Collaboration In June 2021, the Company entered into an exclusive five-year research collaboration (the “Beam collaboration agreement”) with Beam Therapeutics, Inc. (“Beam”) focused on the use of Beam’s proprietary base editing technology to discover new treatments for complement-driven diseases. The Company and Beam agreed to collaborate on up to six research programs focused on C3 and other complement targets in the eye, liver and brain. Under the terms of the Beam collaboration agreement, the Company is responsible for selecting specific genes within the complement system in various organs including the eye, liver and brain (the “Target List”) and providing analytical support while Beam will apply its base editing technology and conduct preclinical research on up to six base editing programs for the Target List. During the first five years of the Beam collaboration agreement, Beam is prohibited from developing on its own or with a third party any base editing therapies associated with the items on the Target List but does not prevent Beam from licensing its intellectual property to a third-party for another purpose outside of the Target List. The Company will have exclusive rights to license each of the six programs and will assume responsibility for subsequent development and commercialization. Beam may elect to enter a 50-50 co-development and U.S. co-commercialization agreement with the Company with respect to any one program licensed under the Beam collaboration agreement and upon such election any license agreement in place at that time, would be terminated. As part of the Beam collaboration agreement, the Company agreed to pay a $50.0 million up-front, non-refundable payment to Beam, which the Company paid in July 2021. The Company paid an additional $25.0 million on the first anniversary of the Beam collaboration agreement in June 2022. The Company and Beam are each responsible for their own costs during the research collaboration. If and after the opt-in license rights are exercised for each of the up to six programs, Beam will be eligible to receive development, regulatory and sales milestones from the Company, as well as royalty payments on sales. The Beam collaboration agreement has an initial term of five years and may be extended up to two years on a per year program-by-program basis. The Company analyzed the Beam collaboration agreement pursuant to ASC 808 to assess whether the agreement involved joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities. Since each party is actively participating in this activity and exposed to significant risks and rewards related to the activity through each party’s costs will be accounted for under ASC 808. Since ASC 808 does not provide recognition guidance, the Company referred to the guidance under FASB ASC Topic 730, Research and Development (“ASC 730”), to arrangements involving payments by the Company. ASC 730 requires the Company to recognize research and developments costs as expense as incurred since the payment was made for the use of Beam’s intellectual property and research and development services and there is no alternative use.

License and Collaboration Agreements

3 Months Ended

Mar. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

License and Collaboration Agreements

12. License and Collaboration Agreements

Sobi License and Collaboration Agreement

In October 2020, the Company and its subsidiaries, Apellis International GmbH (f/k/a Apellis Switzerland GmbH) and APL DEL Holdings, LLC, entered into a Collaboration and License Agreement (the “Sobi collaboration agreement”) with Sobi, concerning the development and commercialization of pegcetacoplan and specified other structurally and functionally similar compstatin analogues or derivatives for use systemically or for local non-ophthalmological administration (collectively referred to as the “Licensed Products”).

Under the Sobi collaboration agreement, the Company granted Sobi an exclusive (subject to certain retained rights of the Company), sublicensable license of certain patent rights and know-how to develop and commercialize Licensed Products in all countries outside of the United States.

The Company retains the right to commercialize Licensed Products in the United States, and, subject to specified limitations, to develop Licensed Products worldwide for commercialization in the United States.

Under the Sobi collaboration agreement, the Company and Sobi have agreed to collaborate to develop Licensed Products for the treatment of PNH, CAD, HSCT-TMA, C3G, IC-MPGN and ALS (collectively the “Initial Indications”), and any other indications subsequently agreed upon by the parties, for commercialization by or on behalf of the Company in the United States and by or on behalf of Sobi outside of the United States. If the parties do not agree to jointly pursue any development activities for the Licensed Products (whether for an Initial Indication or otherwise), the party proposing to pursue such activities may conduct such activities at its sole expense (with the non-proposing party having the right to obtain rights to the data generated by such development activities by paying a specified percentage of that expense), subject to agreed-upon exceptions that limit each party’s unilateral development rights.

The initial development plan sets forth the initial development activities to be conducted by each of the Company and Sobi, with the Company bearing all costs incurred in conducting the activities set forth in such initial development plan, as well as certain specified additional costs that are not included in the initial development plan that may be incurred by the parties in developing Licensed Products for PNH in the European Union and the United Kingdom. The Company and Sobi have formed several governance committees to oversee the development and manufacture, and to review and discuss the commercialization, of Licensed Products. The Company and SOBI discontinued the development programs in ALS and CAD.

The Company shall supply Licensed Products to Sobi for development and for commercialization outside of the United States in accordance with a supply agreement between the parties. The Sobi collaboration agreement grants Sobi the right to perform or have

performed drug product manufacturing of Licensed Products for development and for commercialization outside the United States and to manufacture or have manufactured drug substance under certain circumstances.

Sobi paid the Company an upfront payment of $250.0 million in November 2020 and has agreed to pay up to an aggregate of $915.0 million upon the achievement of specified one-time regulatory and commercial milestone events, of which the Company received $50.0 million in April 2022 for the achievement of a regulatory development milestone in Europe. Sobi also agreed to reimburse the Company for up to $80.0 million in development costs, of which the Company received $65.0 million and waived payment of $15.0 million. The Company will also be entitled to receive tiered, double-digit royalties (ranging from high teens to high twenties) on sales of Licensed Products outside of the United States, subject to customary deductions and third-party payment obligations, until the latest to occur of: (i) expiration of the last-to-expire of specified licensed patent rights; (ii) expiration of regulatory exclusivity; and (iii) ten (10) years after the first commercial sale of the applicable Licensed Product, in each case on a Licensed Product-by-Licensed Product and country-by-country basis. Under the Sobi collaboration agreement, the Company remains responsible for its license fee obligations (including royalty obligations) to the Trustees of the University of Pennsylvania (“Penn”), as a licensor of the Company and for its payment obligations to SFJ.

Under the Sobi collaboration agreement, for the three months ended March 31, 2024 and 2023, the Company recognized $4.5 million and $1.6 million of royalty revenue, respectively. The Company did not recognize any contra-research and development expense for the three months ended March 31, 2024 and 2023. Since contract inception, the Company has recognized $65.0 million in contra-research and development expenses.

As of December 31, 2023, the Company recorded $15.0 million in current assets, which represented the receivable for contra-research and development expenses incurred but not yet reimbursed from Sobi. In January 2024, the Company waived the remaining reimbursement payment of $15.0 million in connection with the decision to discontinue the CAD program.

University of Pennsylvania License Agreement

The Company is a party to a license agreement with Penn for an exclusive, worldwide license to specified patent rights. The Company is required to make milestone payments aggregating up to $3.2 million based upon the achievement of specified development and regulatory milestones and up to $5.0 million based upon the achievement of specified annual sales milestones with respect to each licensed product, and to pay low single-digit royalties based on net sales of each licensed product and with minimum quarterly royalty thresholds. In addition, the Company is obligated to pay a specified portion of income it receives from sublicensees.

In April 2023, the Company paid $2.3 million for the achievement of a regulatory milestone as a result of the FDA approval of SYFOVRE in February 2023. In 2023, the Company incurred $5.0 million as a result of the achievement of sales milestones for SYFOVRE of which the Company paid $2.0 million in October 2023 and the remaining $3.0 million in January 2024.

As of March 31, 2024, the Company has incurred an aggregate royalty expense of $13.4 million on sales of SYFOVRE.

In addition, the Company is also party to a license agreement with Penn for an exclusive, worldwide license to specified patent rights for the development and commercialization of products in fields of use, as defined therein. The Company is required to make milestone payments aggregating up to $1.7 million, based upon the achievement of development and regulatory approval milestones, and up to $2.5 million, based upon the achievement of annual sales milestones with respect to each of the first two licensed products. The license agreement also requires the Company to pay low single digit royalties based on net sales of each licensed product, subject to minimum quarterly royalty thresholds. In addition, the Company is obligated to pay a specified portion of income it receives from sublicensees.

In January 2021, the Company paid $25.0 million for a sublicense fee owed to Penn related to the Sobi collaboration agreement and another licensing transaction. In August 2021, the Company paid $1.0 million to Penn upon the achievement of a development milestone, net of a credit for the annual license maintenance payment. In June 2022, the Company paid an additional $5.0 million to Penn upon the achievement of a development milestone. In January 2023, the Company paid $1.0 million to Penn upon the achievement of a sales milestone for EMPAVELI in 2022. In January 2024, the Company paid $0.5 million for a sublicense fee owed to Penn related to Sobi obtaining regulatory approval in Japan. Additionally, in January 2024, the Company paid $1.5 million as a result of the achievement of a sales milestone for EMPAVELI and Aspaveli.

As of March 31, 2024, the Company has incurred an aggregate royalty expense of $9.5 million on sales of EMPAVELI and Aspaveli.

Beam Research Collaboration

In June 2021, the Company entered into an exclusive five-year research collaboration (the “Beam collaboration agreement”) with Beam Therapeutics, Inc. (“Beam”) focused on the use of Beam’s proprietary base editing technology to discover new treatments for complement-driven diseases. The Company and Beam agreed to collaborate on up to six research programs focused on C3 and other complement targets in the eye, liver and brain. Under the terms of the Beam collaboration agreement, the Company is responsible for selecting specific genes within the complement system in various organs including the eye, liver and brain (the “Target List”) and providing analytical support while Beam will apply its base editing technology and conduct preclinical research on up to six base editing programs for the Target List. During the first five years of the Beam collaboration agreement, Beam is prohibited from developing on its own or with a third party any base editing therapies associated with the items on the Target List but does not prevent Beam from licensing its intellectual property to a third-party for another purpose outside of the Target List. The Company will have exclusive rights to license each of the six programs and will assume responsibility for subsequent development and commercialization. Beam may elect to enter a 50-50 co-development and U.S. co-commercialization agreement with the Company with respect to any one program licensed under the Beam collaboration agreement and upon such election any license agreement in place at that time, would be terminated.

As part of the Beam collaboration agreement, the Company agreed to pay a $50.0 million up-front, non-refundable payment to Beam, which the Company paid in July 2021. The Company paid an additional $25.0 million on the first anniversary of the Beam collaboration agreement in June 2022. The Company and Beam are each responsible for their own costs during the research collaboration. If and after the opt-in license rights are exercised for each of the up to six programs, Beam will be eligible to receive development, regulatory and sales milestones from the Company, as well as royalty payments on sales. The Beam collaboration agreement has an initial term of five years and may be extended up to two years on a per year program-by-program basis.

The Company analyzed the Beam collaboration agreement pursuant to ASC 808 to assess whether the agreement involved joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities. Since each party is actively participating in this activity and exposed to significant risks and rewards related to the activity through each party’s costs will be accounted for under ASC 808.

Since ASC 808 does not provide recognition guidance, the Company referred to the guidance under FASB ASC Topic 730, Research and Development (“ASC 730”), to arrangements involving payments by the Company. ASC 730 requires the Company to recognize research and developments costs as expense as incurred since the payment was made for the use of Beam’s intellectual property and research and development services and there is no alternative use.

Long-term Debt (Tables)

3 Months Ended

Mar. 31, 2024

Debt Disclosure [Abstract]

Schedule of Outstanding Balance of Convertible Notes

The outstanding balance of the Convertible Notes as of March 31, 2024 and December 31, 2023 consisted of the following (in thousands):


	March 31,			December 31,
	2024			2023
Liability
Principal		93,897			93,897
Less: debt discount and issuance costs, net		(788	)		(864	)
Net carrying amount	$	93,109		$	93,033

Schedule of Interest Expense Recognized Related to Convertible Notes

The following table sets forth total interest expense recognized related to the Convertible Notes during the three months ended March 31, 2024 and 2023 (in thousands):



	Three Months Ended March 31,
		2024		2023
Amortization of debt issuance costs			76		73
Contractual interest expense			822		822
Total interest expense		$	898	$	895

Schedule of Future Minimum Payments on Convertible Notes Payable

Future minimum payments on Convertible Notes payable as of March 31, 2024 are as follows (in thousands):


2024	$	2,465
2025		3,286
2026		96,225
Total future minimum payments		101,976
Less: interest		(8,079	)
Less: debt discount and issuance costs, net		(788	)
Less: current portion		—
Convertible senior notes		93,109

Prepaid and Other Current Assets - Summary of Prepaid and Other Current Assets (Parenthetical) (Details) $ in Millions	1 Months Ended
	Jan. 31, 2024 USD ($)
Prepaid Expense and Other Assets, Current [Abstract]
Development cost reimbursement received	$ 15.0

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, issued	121,267,000	119,556,000
Common stock, outstanding	121,267,000	119,556,000

Inventory (Tables)

3 Months Ended

Mar. 31, 2024

Inventory Disclosure [Abstract]

Schedule of Inventory Current

The Company’s inventory consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31,		December 31,
	2024		2023
Raw materials	$	42,089	$	32,724
Semi-finished goods		106,161		82,924
Finished goods		13,033		30,714
Total Inventory	$	161,283	$	146,362

Inventory

3 Months Ended

Mar. 31, 2024

Inventory Disclosure [Abstract]

Inventory

4. Inventory

The Company’s inventory consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31,		December 31,
	2024		2023
Raw materials	$	42,089	$	32,724
Semi-finished goods		106,161		82,924
Finished goods		13,033		30,714
Total Inventory	$	161,283	$	146,362

Inventory amounts written down as a result of excess, obsolete, unmarketability or other reasons are charged to cost of sales. The Company's reserve for excess and obsolete inventory was $7.9 million and $9.3 million as of March 31, 2024 and December 31, 2023, respectively.

Net Loss per Share

3 Months Ended

Mar. 31, 2024

Earnings Per Share [Abstract]

Net Loss per Share

14. Net Loss per Share

Basic and diluted net loss per share is calculated based upon the weighted average number of shares of common stock outstanding during the period. Shares of the Company’s common stock underlying pre-funded warrants are included in the calculation of basic and diluted earnings per share. Since the Company was in a loss position for all periods presented, basic net loss per common share is the same as diluted net loss per common share for all periods presented as the inclusion of all potential common shares outstanding would have been anti-dilutive. Convertible notes and shares outstanding presented below were excluded from the calculation of diluted net loss per share, prior to the use of the treasury stock method, as their effect is anti-dilutive (in thousands):


	As of March 31,
	2024		2023
Convertible notes		2,379		2,379
Common stock options		8,576		12,002
Restricted stock units		4,587		4,764
Total		15,542		19,145

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2024

Fair Value, Nonrecurring [Member]

Schedule of Financial Instruments and the Related Fair Value Hierarchy of the Valuation Techniques Utilized

The following table presents the fair value of financial instruments recorded originally at amortized cost or fair value and not remeasured on a recurring basis (in thousands):


		March 31, 2024
Balance Sheet Classification	Type of Instrument	Level 1		Level 2		Level 3		Total
Financial Assets:
Cash and cash equivalents:	Money market funds	$	231,740	$	—	$	—	$	231,740
Total Financial Assets		$	231,740	$	—	$	—	$	231,740

		December 31, 2023
Balance Sheet Classification	Type of Instrument	Level 1		Level 2		Level 3		Total
Financial Assets:
Cash and cash equivalents	Money market funds	$	276,391	$	—	$	—	$	276,391
Total Financial Assets		$	276,391	$	—	$	—	$	276,391

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Income tax expense	$ 170,000	$ 282,000
U.S. federal statutory rate	21.00%
Minimum percentage of tax position likelihood of being realized upon examination by taxing authorities	50.00%
Unrecognized tax benefits	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Basis of Presentation and Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Basis of Presentation and Summary of Significant Accounting Policies

2. Basis of Presentation and Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and following the requirements of the Securities and Exchange Commission (the “SEC”), for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted and, accordingly, the condensed consolidated balance sheet as of December 31, 2023 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair presentation of the Company’s financial information. The results of operations for the three months ended March 31, 2024 are not

necessarily indicative of the results to be expected for the year ending December 31, 2024 or for any other interim period or for any other future year.

The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2023 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 27, 2024, as amended by Amendment No. 1 thereto filed with the SEC on February 29, 2024 (the “2023 Form 10-K”).

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Estimates are used in the following areas, among others: development liability, accrued expenses, prepaid expenses, convertible debt, reserves for variable consideration, reserves for excess or obsolete inventories, and income taxes.

Summary of Significant Accounting Policies

Reference is made to Note 2 Summary of Significant Accounting Policies in our 2023 Form 10-K for a detailed description of significant accounting policies. There have been no significant changes to our accounting policies as disclosed in our 2023 Form 10-K.

Recently Issued Accounting Standards

In December 2023, the Financial Accounting Standards Board (“FASB”) issued an amendment to the accounting guidance on income taxes which requires entities to provide additional information in the rate reconciliation and additional disaggregated disclosures about income taxes paid. This guidance requires public entities to disclose in their rate reconciliation table additional categories of information about federal, state, and foreign income taxes and to provide more details about the reconciling items in some categories if the items meet a quantitative threshold. The guidance is effective for annual periods beginning after December 15, 2024. The Company is currently evaluating this guidance to determine the impact it may have on its consolidated financial statements and disclosures.

In November 2023, the FASB issued an amendment to the accounting guidance on segment reporting. The amendments require disclosure of significant segment expenses and other segment items and requires entities to provide in interim periods all disclosures about a reportable segment's profit or loss and assets that are currently required annually. The amendment also requires disclosure of the title and position of the chief operating decision maker (“CODM”) and an explanation of how the CODM uses the reported measure(s) of segment profit or loss in assessing segment performance and deciding how to allocate resources. The guidance is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15,

2024. Retrospective application is required, and early adoption is permitted. The Company is currently evaluating the impact the guidance will have on its consolidated financial statements.

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (66,423)	$ (177,778)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

Nature of Organization and Operations - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 325,923	$ 351,185	$ 765,083
Accumulated deficit	$ (2,903,911)	$ (2,837,488)

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 325,923	$ 351,185
Accounts receivable, net	267,837	206,442
Inventory	161,283	146,362
Prepaid assets	43,163	38,820
Restricted cash	1,103	1,114
Other current assets	12,119	22,408
Total current assets	811,428	766,331
Non-current assets:
Right-of-use assets	14,994	16,745
Property and equipment, net	4,195	4,345
Other assets	1,313	1,309
Total assets	831,930	788,730
Current liabilities:
Accounts payable	26,788	37,516
Accrued expenses	101,399	127,806
Current portion of development liability	77,287	75,830
Current portion of lease liabilities	6,257	6,441
Deferred Revenue	3,560
Total current liabilities	215,291	247,593
Long-term liabilities:
Long-term development liability	244,426	239,817
Convertible senior notes	93,109	93,033
Lease liabilities	9,770	11,454
Other liabilities	2,658	2,312
Total liabilities	565,254	594,209
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized, and zero shares issued and outstanding at March 31, 2024 and December 31, 2023	0	0
Common stock, $0.0001 par value; 200,000 shares authorized at March 31, 2024 and December 31, 2023; 121,267 shares issued and outstanding at March 31, 2024, and 119,556 shares issued and outstanding at December 31, 2023	12	12
Additional paid-in capital	3,174,100	3,035,539
Accumulated other comprehensive loss	(3,525)	(3,542)
Accumulated deficit	(2,903,911)	(2,837,488)
Total stockholders' equity	266,676	194,521
Total liabilities and stockholders' equity	$ 831,930	$ 788,730

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenue:
Total revenue	$ 172,325	$ 44,846
Operating expenses:
Cost of sales	20,209	7,809
Research and development	84,701	110,027
Selling, general and administrative	129,505	102,093
Total operating expenses:	234,415	219,929
Net operating loss	(62,090)	(175,083)
Interest income	3,303	5,393
Interest expense	(6,967)	(7,529)
Other (expense)/ income, net	(499)	(277)
Net loss before taxes	(66,253)	(177,496)
Income tax expense	170	282
Net loss	(66,423)	(177,778)
Other comprehensive gain/(loss):
Foreign currency translation	17	100
Total other comprehensive income	17	100
Comprehensive loss, net of tax	$ (66,406)	$ (177,678)
Net loss per common share, basic	$ (0.54)	$ (1.56)
Net loss per common share, diluted	$ (0.54)	$ (1.56)
Weighted-average number of common shares used in net loss per common share, basic	122,957	113,872
Weighted-average number of common shares used in net loss per common share, diluted	122,957	113,872
Product revenue, net [Member]
Revenue:
Total revenue	$ 163,075	$ 38,800
Licensing and other revenue [Member]
Revenue:
Total revenue	$ 9,250	$ 6,046

Leases - Supplemental Cash Flow Information Related to Operating Leases (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Leases [Abstract]
Operating cash flows from operating leases	$ 2,311	$ 2,022

Income Taxes

3 Months Ended

Mar. 31, 2024

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes

For the three months ended March 31, 2024 and 2023, the Company recorded $0.2 million and $0.3 million of income tax expense, respectively, primarily pertaining to state and foreign income taxes.

The income tax provision during interim periods is computed by applying an estimated annual effective tax rate to year-to-date pre-tax income, plus adjustments for significant unusual or infrequently occurring items, in accordance with FASB ASC Topic 740-270, Income Taxes – Interim Reporting. The income tax provision differs from the U.S. federal statutory rate of 21% primarily due to the effect of valuation allowance against the Company’s net deferred tax assets, which reduces the Company’s net tax benefit.

Deferred tax assets and deferred tax liabilities are determined based on temporary differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some portion or all of the deferred tax assets will not be realized. The Company has recorded a full valuation allowance against its net deferred tax assets for the period ended March 31, 2024.

The Company does not recognize a tax benefit for uncertain tax positions unless it is more likely than not that the position will be sustained upon examination by tax authorities, including resolution of any related appeals or litigation processes, based on the technical merits of the position. The tax benefit that is recorded for these positions is measured at the largest amount of cumulative benefit that has greater than a 50 percent likelihood of being realized upon ultimate settlement. Deferred tax assets that do not meet these recognition criteria are not recorded and the Company recognizes a liability for uncertain tax positions that may result in tax payments. The Company has not recorded any amounts for unrecognized tax positions for the period ended March 31, 2024. If such unrecognized tax benefits were realized, the entire amount would impact the tax provision. Our policy is to review and update unrecognized tax positions as facts and circumstances change.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

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+ Details

Leases - Maturities of Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Leases [Abstract]
2024	$ 5,352
2025	6,188
2026	5,278
2027	858
Total future minimum lease payments	17,676
Less Imputed interest	(1,649)
Total operating lease liabilities	$ 16,027	$ 17,895

Nature of Organization and Operations

3 Months Ended

Mar. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Organization and Operations

1. Nature of Organization and Operations

Apellis Pharmaceuticals, Inc. (the “Company”) is a commercial-stage biopharmaceutical company focused on the discovery, development and commercialization of novel therapeutic compounds to treat diseases with high unmet needs through the inhibition of the complement system, which is an integral component of the immune system, at the level of C3, the central protein in the complement cascade.

The Company was incorporated in September 2009 under the laws of the State of Delaware. The Company’s principal executive offices are located in Waltham, Massachusetts.

The Company’s operations since inception have been limited to organizing and staffing the Company, acquiring rights to product candidates, business planning, raising capital, developing its product candidates, commercializing EMPAVELI (pegcetacoplan) for the treatment of paroxysmal nocturnal hemoglobinuria (“PNH”) and the commercialization of SYFOVRE (pegcetacoplan injection) for the treatment of geographic atrophy secondary to age-related macular degeneration (“GA”).

The Company is subject to risks common in the biotechnology industry including, but not limited to, raising additional capital, development by its competitors of new technological innovations, its ability to successfully complete preclinical and clinical development of product candidates and receive timely regulatory approval of products, market acceptance of the Company’s products, protection of proprietary technology, healthcare cost containment initiatives, and compliance with governmental regulations, including those of the U.S. Food and Drug Administration (“FDA”).

Liquidity and Going Concern

The accompanying unaudited condensed consolidated financial statements have been prepared on the basis of the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. From inception to March 31, 2024, the Company has incurred cash outflows from operations, losses from operations and had an accumulated deficit of $2.9 billion primarily as a result of expenses incurred through a combination of research and development activities related to the Company’s various product candidates and expenses supporting those activities. The Company has primarily financed its operations through public offerings of its common stock, convertible debt, private placements of preferred stock prior to its initial public offering, the development funding agreement with SFJ Pharmaceuticals Group (“SFJ”), and the collaboration agreement with Sobi. The Company has financed a portion of its operations through product sales but has not yet achieved profitability.

As of May 7, 2024, the date of issuance of these unaudited condensed consolidated financial statements, the Company believes that its cash and cash equivalents of $325.9 million as of March 31, 2024 together with cash anticipated to be generated from sales of EMPAVELI and from SYFOVRE will be sufficient to fund its operations and capital expenditure requirements for at least the next twelve months.

Accrued Expenses (Tables)

3 Months Ended

Mar. 31, 2024

Payables and Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31,		December 31,
	2024		2023
Accrued research and development	$	22,912	$	28,318
Accrued royalties		6,224		10,197
Accrued payroll liabilities		20,789		51,781
Accrued goods received not invoiced		15,829		5,902
Product revenue reserves		19,222		16,625
Other		16,423		14,983
Total	$	101,399	$	127,806

Fair Value Measurements

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

10. Fair Value Measurements

The Company is required to disclose information on the fair value of financial instruments and inputs that enable an assessment of the fair value. The three levels of the fair value hierarchy prioritize valuation inputs based upon the observable nature of those inputs as follows:

Level 1 – Quoted prices in active markets for identical assets or liabilities;

Level 2 – Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly;

Level 3 – Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability.

The following table presents the fair value of financial instruments recorded originally at amortized cost or fair value and not remeasured on a recurring basis (in thousands):


		March 31, 2024
Balance Sheet Classification	Type of Instrument	Level 1		Level 2		Level 3		Total
Financial Assets:
Cash and cash equivalents:	Money market funds	$	231,740	$	—	$	—	$	231,740
Total Financial Assets		$	231,740	$	—	$	—	$	231,740

		December 31, 2023
Balance Sheet Classification	Type of Instrument	Level 1		Level 2		Level 3		Total
Financial Assets:
Cash and cash equivalents	Money market funds	$	276,391	$	—	$	—	$	276,391
Total Financial Assets		$	276,391	$	—	$	—	$	276,391

The Company’s Convertible Notes and development liability are financial instruments that are reported in the consolidated financial statements at historical cost. The Convertible Notes are Level 1 within the fair value level hierarchy as of March 31, 2024 and December 31, 2023. The fair value of the Convertible Notes was $151.7 million as of March 31, 2024 and $140.8 million as of December 31, 2023. The Convertible Notes accrue a semi-annual coupon at an annual rate of 3.5%, which was included in accrued expenses in the condensed consolidated balance sheets as of March 31, 2024 and December 31, 2023.

The fair value of the development liability was $316.9 million and $306.9 million as of March 31, 2024 and December 31, 2023, respectively. The development liability is Level 2 within the fair value hierarchy based on the discounting of fixed cash flows using an observed bond yield for borrowers with similar credit rating.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Inventory - Schedule of Inventory Current (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Inventory Disclosure [Abstract]
Raw materials	$ 42,089	$ 32,724
Semi-finished goods	106,161	82,924
Finished goods	13,033	30,714
Total Inventory	$ 161,283	$ 146,362

Long-term Debt - Schedule of Interest Expense Recognized Related to Convertible Notes (Detail) - Convertible Senior Notes Due 2026 [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Debt Instrument [Line Items]
Amortization of debt discounts	$ 76	$ 73
Contractual interest expense	822	822
Total interest expense	$ 898	$ 895

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

Inventory - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Inventory Disclosure [Abstract]
Reserve for excess and obsolete inventory	$ 7.9	$ 9.3

Net Loss per Share (Tables)

3 Months Ended

Mar. 31, 2024

Earnings Per Share [Abstract]

Summary of Shares Outstanding that were Excluded from Calculation of Diluted Net Loss Per Share

Convertible notes and shares outstanding presented below were excluded from the calculation of diluted net loss per share, prior to the use of the treasury stock method, as their effect is anti-dilutive (in thousands):


	As of March 31,
	2024		2023
Convertible notes		2,379		2,379
Common stock options		8,576		12,002
Restricted stock units		4,587		4,764
Total		15,542		19,145

Prepaid and Other Current Assets (Tables)

3 Months Ended

Mar. 31, 2024

Prepaid Expense and Other Assets, Current [Abstract]

Summary of Prepaid and Other Current Assets

Prepaid and other current assets consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31,		December 31,
	2024		2023
Down payments for inventory		13,828		16,296
Prepaid research and development		12,626		13,931
Other prepaid expenses		16,709		8,593
Total prepaid expenses	$	43,163	$	38,820


	March 31,		December 31,
	2024		2023
Royalties receivable	$	4,499	$	3,054
Receivable from collaboration agreement(1)		—		15,000
Deposits and other current assets		7,620		4,354
Total other current assets	$	12,119	$	22,408

(1) In January 2024 the Company waived the remaining reimbursement payment of $15.0 million from Sobi in connection with the decision to discontinue the cold agglutinin disease (CAD) program.

Long-term Debt - Schedule of Outstanding Balance of Convertible Notes (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Principal	$ 101,976
Less: debit discount and issuance costs, net	(788)
Net carrying amount	93,109
Convertible Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Principal	93,897	$ 93,897
Less: debit discount and issuance costs, net	(788)	(864)
Net carrying amount	$ 93,109	$ 93,033

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Prepaid and Other Current Assets - Summary of Prepaid and Other Current Assets (Detail) - USD ($)
$ in Thousands

Mar. 31, 2024

Dec. 31, 2023

Prepaid Expense and Other Assets, Current [Abstract]

Down payments for inventory

$ 13,828

$ 16,296

Prepaid research and development

12,626

13,931

Other prepaid expenses

16,709

8,593

Total prepaid expenses

43,163

38,820

Royalties receivable

4,499

3,054

Receivable from collaboration agreement

^[1]

15,000

Deposits and other current assets

7,620

4,354

Total other current assets

$ 12,119

$ 22,408

[1]	In January 2024 the Company waived the remaining reimbursement payment of $15.0 million from Sobi in connection with the decision to discontinue the cold agglutinin disease (CAD) program.

Accrued Expenses

3 Months Ended

Mar. 31, 2024

Payables and Accruals [Abstract]

Accrued Expenses

7. Accrued Expenses

Accrued expenses consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31,		December 31,
	2024		2023
Accrued research and development	$	22,912	$	28,318
Accrued royalties		6,224		10,197
Accrued payroll liabilities		20,789		51,781
Accrued goods received not invoiced		15,829		5,902
Product revenue reserves		19,222		16,625
Other		16,423		14,983
Total	$	101,399	$	127,806

Product Revenues, Accounts Receivable, and Reserves for Product Sales - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Product Revenues Accounts Receivable And Reserves For Product Sales [Line Items]
Revenue	$ 172,325	$ 44,846
Accounts receivable, net	267,837		$ 206,442
Accrued Expenses [Member]
Product Revenues Accounts Receivable And Reserves For Product Sales [Line Items]
Product sales reserves	19,200		$ 16,600
Product revenue, net [Member]
Product Revenues Accounts Receivable And Reserves For Product Sales [Line Items]
Revenue	$ 163,075	$ 38,800

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
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+ Details

Net Loss per Share - Summary of Shares Outstanding that were Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	15,542	19,145
Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	2,379	2,379
Common Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	8,576	12,002
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	4,587	4,764

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and following the requirements of the Securities and Exchange Commission (the “SEC”), for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted and, accordingly, the condensed consolidated balance sheet as of December 31, 2023 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair presentation of the Company’s financial information. The results of operations for the three months ended March 31, 2024 are not necessarily indicative of the results to be expected for the year ending December 31, 2024 or for any other interim period or for any other future year. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2023 included in the Company’s Annual Report on Form 10-K filed with the SEC on February 27, 2024, as amended by Amendment No. 1 thereto filed with the SEC on February 29, 2024 (the “2023 Form 10-K”).
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Estimates are used in the following areas, among others: development liability, accrued expenses, prepaid expenses, convertible debt, reserves for variable consideration, reserves for excess or obsolete inventories, and income taxes.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In December 2023, the Financial Accounting Standards Board (“FASB”) issued an amendment to the accounting guidance on income taxes which requires entities to provide additional information in the rate reconciliation and additional disaggregated disclosures about income taxes paid. This guidance requires public entities to disclose in their rate reconciliation table additional categories of information about federal, state, and foreign income taxes and to provide more details about the reconciling items in some categories if the items meet a quantitative threshold. The guidance is effective for annual periods beginning after December 15, 2024. The Company is currently evaluating this guidance to determine the impact it may have on its consolidated financial statements and disclosures. In November 2023, the FASB issued an amendment to the accounting guidance on segment reporting. The amendments require disclosure of significant segment expenses and other segment items and requires entities to provide in interim periods all disclosures about a reportable segment's profit or loss and assets that are currently required annually. The amendment also requires disclosure of the title and position of the chief operating decision maker (“CODM”) and an explanation of how the CODM uses the reported measure(s) of segment profit or loss in assessing segment performance and deciding how to allocate resources. The guidance is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Retrospective application is required, and early adoption is permitted. The Company is currently evaluating the impact the guidance will have on its consolidated financial statements.

Development Liability - Additional Information (Detail) $ in Thousands		1 Months Ended									3 Months Ended		8 Months Ended
	Feb. 28, 2019 USD ($) Installment	Dec. 31, 2024 USD ($)	May 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	May 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	May 31, 2022 USD ($)	Jan. 31, 2022 USD ($)	Dec. 31, 2021 USD ($) Installment	Jun. 30, 2021 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Jan. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Interest expense											$ 6,967	$ 7,529
SFJ Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from SFJ agreement	$ 60,000
Additional funding amount upon achievement of development milestones	$ 60,000
Number of milestone payments \| Installment	3
Development funding for minimum period of operating expense	10 months
Increase in additional funding for development costs														$ 20,000
Obligated to pay initial payment									$ 5,000		366,000
Aggregate amount of additional annual payments									$ 225,000
Number of additional annual payments \| Installment									6
Payment made under agreement								$ 5,000		$ 4,000	94,000		$ 80,000
First annual payment under agreement						$ 18,000	$ 11,500
Second annual payment under agreement				$ 31,000	$ 24,500
Interest expense											$ 6,100	$ 6,600
SFJ Agreement [Member] \| Forecast [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment made under agreement		$ 61,300	$ 37,500
SFJ Agreement [Member] \| Regulatory Approval Granted US Food and Drug Administration [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Obligated to pay initial payment	$ 4,000
Aggregate amount of additional annual payments	$ 226,000
Number of additional annual payments \| Installment	6

Product Revenues, Accounts Receivable, and Reserves for Product Sales - Summary of Product Revenue Allowance and Reserve Categories (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Chargebacks, Discounts, and Fees [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 5,674	$ 164
Provision related to sales in the current year	9,575	1,466
Adjustments related to prior period sales	146
Credits and payments made	(9,724)	(184)
Ending balance	5,671	1,446
Government and Other Rebates [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	8,898	1,936
Provision related to sales in the current year	13,125	2,566
Adjustments related to prior period sales	(19)	(2)
Credits and payments made	(9,906)	(1,639)
Ending balance	12,098	2,861
Returns [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	2,053	251
Provision related to sales in the current year	1,355	651
Adjustments related to prior period sales	(96)	(249)
Credits and payments made	(1,859)
Ending balance	1,453	653
Product Revenue Allowance and Reserves [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	16,625	2,351
Provision related to sales in the current year	24,055	4,683
Adjustments related to prior period sales	31	(251)
Credits and payments made	(21,489)	(1,823)
Ending balance	$ 19,222	$ 4,960

Insider Trading Arrangements

3 Months Ended

Mar. 31, 2024

Trading Arrangements, by Individual

Material Terms of Trading Arrangement

The following table describes, for the quarterly period covered by this report, each trading arrangement for the sale or purchase of our securities adopted or terminated by our directors and officers that is either (1) a contract, instruction or written plan intended to satisfy the affirmative defense conditions of Rule 10b5-1(c), or a Rule 10b5-1 trading arrangement, or (2) a “non-Rule 10b5-1 trading arrangement” (as defined in Item 408(c) of Regulation S-K):


Name (Title)	Action Taken (Date of Action)	Type of Trading Arrangement	Nature of Trading Arrangement	Duration of Trading Arrangement	Aggregate Number of Securities
Alec Machiels Director	Adoption 2/29/2024	Rule 10b5-1 trading arrangement	Sale	Until 11/28/2025, or such earlier date upon which all transactions are completed or expire without execution	Up to 18,000 shares
David Watson General Counsel	Adoption 2/29/2024	Rule 10b5-1 trading arrangement	Sale	Until 2/28/2025, or such earlier date upon which all transactions are completed or expire without execution	Up to 23,872 shares
Mark DeLong Chief Business & Strategy Officer	Adoption 3/1/2024	Rule 10b5-1 trading arrangement	Sale	Until 2/28/2025, or such earlier date upon which all transactions are completed or expire without execution	Up to 24,799 shares
A. Sinclair Dunlop (1) Independent Director	Adoption 3/2/2024	non-Rule 10b5-1 trading arrangement	Sale	Until 12/31/2024, or such earlier date upon which all transactions are completed or expire without execution	Up to 174,000 shares
Cedric Francois President and Chief Executive Officer	Adoption 3/8/2024	Rule 10b5-1 trading arrangement	Sale	Until 5/30/2025 or such earlier date upon which all transactions are completed or expire without execution	Up to 592,034 shares
Caroline Baumal Chief Medical Officer	Adoption 3/13/2024	Rule 10b5-1 trading arrangement	Sale	Until 12/31/2024 or such earlier date upon which all transactions are completed or expire without execution	Up to 6,136 shares
Jeffrey R Eisele Chief Development Officer	Adoption 3/15/2024	Rule 10b5-1 trading arrangement	Sale	Until 2/28/2025 or such earlier date upon which all transactions are completed or expire without execution	Up to 207,256 shares
James Chopas Vice President, Corporate Controller and Chief Accounting Officer	Adoption 3/18/2024	Rule 10b5-1 trading arrangement	Sale	Until 8/30/2024 or such earlier date upon which all transactions are completed or expire without execution	Up to 4,000 shares
Karen L Lewis Chief People Officer	Adoption 3/19/2024	Rule 10b5-1 trading arrangement	Sale	Until 3/31/2025, or such earlier date upon which all transactions are completed or expire without execution	Up to 101,422 shares
Nur Nicholson Chief Technical Operations Officer	Adoption 3/30/2024	Rule 10b5-1 trading arrangement	Sale	Until 11/15/2024, or such earlier date upon which all transactions are completed or expire without execution	Up to 28,747 shares

(1) The non-Rule 10b5-1 trading plan relates to Epidarex Capital I LP, an affiliated entity of the named director.

Alec Machiels [Member]

Trading Arrangements, by Individual

Name

Alec Machiels

Title

Director

Rule 10b5-1 Arrangement Adopted

true

2/29/2024

11/28/2025

639 days

18,000

David Watson [Member]

Trading Arrangements, by Individual

Name

David Watson

Title

General Counsel

Rule 10b5-1 Arrangement Adopted

true

2/29/2024

2/28/2025

366 days

23,872

Trading Arrangements, by Individual

Name

Mark DeLong

Title

Chief Business & Strategy Officer

Rule 10b5-1 Arrangement Adopted

true

3/1/2024

2/28/2025

365 days

24,799

A Sinclair Dunlop [Member]

Trading Arrangements, by Individual

Name

A. Sinclair Dunlop

Title

Independent Director

Rule 10b5-1 Arrangement Adopted

true

3/2/2024

12/31/2024

305 days

174,000

Cedric Francois [Member]

Trading Arrangements, by Individual

Name

Cedric Francois

Title

President and Chief ExecutiveOfficer

Rule 10b5-1 Arrangement Adopted

true

3/8/2024

5/30/2025

449 days

592,034

Caroline Baumal [Member]

Trading Arrangements, by Individual

Name

Caroline Baumal

Title

Chief Medical Officer

Rule 10b5-1 Arrangement Adopted

true

3/13/2024

12/31/2024

294 days

6,136

Jeffrey R Eisele [Member]

Trading Arrangements, by Individual

Name

Jeffrey R Eisele

Title

Chief Development Officer

Rule 10b5-1 Arrangement Adopted

true

3/15/2024

2/28/2025

351 days

207,256

James Chopas [Member]

Trading Arrangements, by Individual

Name

James Chopas

Title

Vice President, Corporate Controller and Chief Accounting Officer

Rule 10b5-1 Arrangement Adopted

true

3/18/2024

8/30/2024

166 days

4,000

Karen L Lewis [Member]

Trading Arrangements, by Individual

Name

Karen L Lewis

Title

Chief People Officer

Rule 10b5-1 Arrangement Adopted

true

3/19/2024

3/31/2025

378 days

101,422

Nur Nicholson [Member]

Trading Arrangements, by Individual

Name

Nur Nicholson

Title

Chief Technical Operations Officer

Rule 10b5-1 Arrangement Adopted

true

3/30/2024

11/15/2024

231 days

28,747

Leases - Schedule of Additional Information Related to Operating Lease Assets and Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Leases [Abstract]
Right-of-use assets	$ 14,994	$ 16,745
Operating Lease Liabilities	$ 16,027	$ 17,895
Weighted Average Remaining Term in years	2 years 7 months 20 days	2 years 9 months 29 days
Weighted Average discount rate used to measure outstanding lease liabilities	7.25%	7.20%

License and Collaboration Agreements - Additional Information (Detail)		1 Months Ended								3 Months Ended		12 Months Ended	41 Months Ended
	Nov. 30, 2020 USD ($)	Jan. 31, 2024 USD ($)	Oct. 31, 2023 USD ($)	Apr. 30, 2023 USD ($)	Jan. 31, 2023 USD ($)	Jun. 30, 2022 USD ($)	Apr. 30, 2022 USD ($)	Aug. 31, 2021 USD ($)	Jun. 30, 2021 Program	Mar. 31, 2024 USD ($) License	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2024 USD ($) License	Jul. 31, 2021 USD ($)	Jan. 31, 2021 USD ($)	Oct. 31, 2020 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development cost reimbursement received		$ 15,000,000
Revenue										$ 172,325,000	$ 44,846,000
Accrued expenses										101,399,000		$ 127,806,000	$ 101,399,000
EMPAVELI [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue										25,610,000	20,440,000
SYFOVRE [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue										137,465,000	18,360,000
Regulatory milestone payments		3,000,000	$ 2,000,000	$ 2,300,000
Regulatory milestone incurred												5,000,000
Royalty expense incurred										13,400,000			13,400,000
Empaveli And Aspaveli [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments based on annual sales milestones		1,500,000
Royalty expense incurred										9,500,000			9,500,000
Swedish Orphan Biovitrum AB (Publ) [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty revenue										4,500,000	1,600,000
Collaboration and License Agreement [Member] \| Swedish Orphan Biovitrum AB (Publ) [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	$ 250,000,000
Milestone payment received for achievement of regulatory development milestone							$ 50,000,000
Development cost reimbursement										80,000,000
Development cost reimbursement received										65,000,000
Waived Payment										$ 15,000,000
Royalties entitled to receive after first commercial sale of applicable licensed product period										10 years
Contract research and development expense										$ 0	$ 0		65,000,000
Contract research and development current												$ 15,000,000
Remaining reimbursement payment		15,000,000
Collaboration and License Agreement [Member] \| Swedish Orphan Biovitrum AB (Publ) [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate milestone payments upon achievement of specified one time regulatory development and commercial milestone events																$ 915,000,000
University of Pennsylvania [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone achievement						$ 5,000,000		$ 1,000,000
University of Pennsylvania [Member] \| Empaveli And Aspaveli [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments based on annual sales milestones					$ 1,000,000
University of Pennsylvania [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate milestones payments										3,200,000			$ 3,200,000
Milestone payments based on annual sales milestones										$ 5,000,000
2010 License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of licensed products \| License										2			2
2010 License Agreement [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate milestones payments										$ 1,700,000			$ 1,700,000
Milestone payments based on annual sales milestones										$ 2,500,000
Sobi Agreement and Another Licensing Transaction [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sublicense fee owed		$ 500,000													$ 25,000,000
Research Collaboration Agreement [Member] \| Beam [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement term									5 years
Number of research programs \| Program									6
Up-front non-refundable payment														$ 50,000,000
Up-front payment on first anniversary of agreement on June 30, 2022						$ 25,000,000
Collaboration agreement maximum extendable term						2 years

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating Activities
Net loss	$ (66,423)	$ (177,778)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	30,349	28,823
Loss on disposal of fixed assets		19
Depreciation expense	444	421
Amortization of discounts for convertible notes	76	73
Accretion of discount to development liability	6,066	6,633
Changes in operating assets and liabilities:
Accounts receivable	(61,415)	(23,778)
Inventory	(14,921)	144
Prepaid assets	(4,338)	(107)
Other current assets	10,697	2,308
Other assets	98	14,969
Accounts payable	(10,730)	(5,854)
Accrued expenses	(26,330)	(23,471)
Deferred revenue	3,560
Net cash used in operating activities	(132,983)	(177,620)
Investing Activities
Purchase of property and equipment	(293)	(259)
Net cash used in investing activities	(293)	(259)
Financing Activities
Proceeds from settlement of capped call	98,763
Proceeds from issuance of common stock and pre-funded warrant offering, net of issuance costs		384,387
Proceeds from exercise of stock options	9,477	17,718
Payments of employee tax withholding related to equity-based compensation	(28)	(10,999)
Net cash provided by financing activities	108,212	391,106
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(209)	56
Net (decrease) increase in cash, cash equivalents and restricted cash	(25,273)	213,283
Cash, cash equivalents and restricted cash at beginning of period	352,299	553,075
Cash, cash equivalents and restricted cash at end of period	327,026	766,358
Reconciliation of cash, cash equivalents and restricted cash to the consolidated balance sheets:
Cash and cash equivalents	325,923	765,083
Restricted cash	1,103	1,275
Total cash, cash equivalents, and restricted cash	327,026	766,358
Supplemental Disclosure of Financing Activities
Cash paid for interest	1,643	1,643
Cash paid for income taxes		$ 250
Proceeds from income tax refunds net of income taxes paid	$ 257

Long-term Debt - Schedule of Future Minimum Payments on Convertible Notes Payable (Detail) $ in Thousands	Mar. 31, 2024 USD ($)
Debt Disclosure [Abstract]
2024	$ 2,465
2025	3,286
2026	96,225
Total future minimum payments	101,976
Less: interest	(8,079)
Less: debit discount and issuance costs, net	(788)
Net carrying amount	$ 93,109

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Product Revenues, Accounts Receivable, and Reserves for Product Sales (Tables)

3 Months Ended

Mar. 31, 2024

Product Revenues Accounts Receivable And Reserves For Product Sales [Abstract]

Schedule of Disaggregation of Product Revenue by Major Source

The table reflects product revenue by major source for the following periods (in thousands):


	Three Months Ended March31,
	2024		2023
Products:
EMPAVELI	$	25,610	$	20,440
SYFOVRE		137,465		18,360
Total Product revenue, net	$	163,075	$	38,800

Summary of Product Revenue Allowance and Reserve Categories

The following table summarizes activity in each of the product revenue allowance and reserve categories for the three months ended March 31, 2024 and 2023 (in thousands):


	Chargebacks, Discounts, and Fees			Government and other rebates			Returns			Total
Ending balance at December 31, 2023	$	5,674		$	8,898		$	2,053			16,625
Provision related to sales in the current year		9,575			13,125			1,355			24,055
Adjustments related to prior period sales		146			(19	)		(96	)		31
Credits and payments made		(9,724	)		(9,906	)		(1,859	)		(21,489	)
Ending balance at March 31, 2024	$	5,671		$	12,098		$	1,453		$	19,222


	Chargebacks, Discounts, and Fees			Government and other rebates			Returns			Total
Ending balance at December 31, 2022	$	164		$	1,936		$	251			2,351
Provision related to sales in the current year		1,466			2,566		651				4,683
Adjustments related to prior period sales		—			(2	)		(249	)		(251	)
Credits and payments made		(184	)		(1,639	)		—			(1,823	)
Ending balance at March 31, 2023	$	1,446		$	2,861		$	653		$	4,960

Schedule of Customer Accounted for 10% of More of Gross Product Revenues and Accounts Receivable

Significant customers - Gross product revenues and product sales receivable from the Company's customers who individually accounted for 10% of more of total gross product revenues and/or 10% or more of total product sales receivable consisted of the following:


	Percent of Total Gross Product Revenues
	Three Months Ended March31,
	2024	2023
Customer A	15%	52%
Customer C	19%	9%
Customer D	59%	33%


	Percent of Product Sales Receivable
	As of March 31,
	2024	2023
Customer A	3%	25%
Customer C	21%	15%
Customer D	67%	52%

Commitments and Contingencies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2024 USD ($)
Commitments And Contingencies [Line Items]
Incurred any cost to defend lawsuits or settle claims	$ 0
Vehicles [Member]
Commitments And Contingencies [Line Items]
Operating lease, term of contract	36 months
Bachem Americas, Inc [Member]
Commitments And Contingencies [Line Items]
Non-cancellable purchase commitments	$ 70,700,000
Other non-cancellable purchase commitments	$ 19,700,000

Condensed Consolidated Statements of Changes in Stockholder's Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2022	$ 169,872	$ 11	$ 2,479,596	$ (875)	$ (2,308,860)
Beginning balance, Shares at Dec. 31, 2022		110,772,000
Issuance of common stock and pre-funded warrants in common stock offering	384,387	$ 1	384,386
Issuance of common stock and pre-funded warrants in common stock offering, shares		4,008,000
Issuance of common stock upon exercise of stock options	17,718		17,718
Issuance of common stock upon exercise of stock options, shares		951,000
Vesting of restricted stock units, net of shares withheld for taxes	(10,999)		(10,999)
Vesting of restricted stock units, net of shares withheld for taxes. shares		448,000
Share-based compensation expense	28,823		28,823
Net Income (Loss)	(177,778)				(177,778)
Foreign currency translation	100			100
Ending balance at Mar. 31, 2023	412,123	$ 12	2,899,524	(775)	(2,486,638)
Ending balance, Shares at Mar. 31, 2023		116,179,000
Beginning balance at Dec. 31, 2023	194,521	$ 12	3,035,539	(3,542)	(2,837,488)
Beginning balance, Shares at Dec. 31, 2023		119,556,000
Proceeds from settlement of capped call	98,763		98,763
Issuance of common stock upon exercise of stock options	9,477		9,477
Issuance of common stock upon exercise of stock options, shares		714,000
Vesting of restricted stock units, net of shares withheld for taxes	(28)		(28)
Vesting of restricted stock units, net of shares withheld for taxes. shares		997,000
Share-based compensation expense	30,349		30,349
Net Income (Loss)	(66,423)				(66,423)
Foreign currency translation	17			17
Ending balance at Mar. 31, 2024	$ 266,676	$ 12	$ 3,174,100	$ (3,525)	$ (2,903,911)
Ending balance, Shares at Mar. 31, 2024		121,267,000

Development Liability - Summary of Development Liability (Detail) - SFJ Agreement [Member] - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development liability	$ 366,000	$ 366,000
Less: Unamortized discount to development liability	(44,287)	(50,353)
Less: Current portion of development liability, net of discount	(77,287)	(75,830)
Total long term development liability	$ 244,426	$ 239,817
Effective Interest Rate	7.91%	7.91%

Product Revenues, Accounts Receivable, and Reserves for Product Sales

3 Months Ended

Mar. 31, 2024

Product Revenues Accounts Receivable And Reserves For Product Sales [Abstract]

Product Revenues, Accounts Receivable, and Reserves for Product Sales

3. Product Revenues, Accounts Receivable, and Reserves for Product Sales

The Company received FDA approval for the sale of EMPAVELI in the United States in May 2021 and approval for the sale of SYFOVRE in the United States in February 2023. The Company’s product revenues, net of sales discounts, allowances and reserves, for the three months ended March 31, 2024 and 2023 were $163.1 million and $38.8 million, respectively. The Company’s product revenues consist of sales of EMPAVELI and SYFOVRE to specialty pharmacies and specialty distributors.

The table reflects product revenue by major source for the following periods (in thousands):


	Three Months Ended March31,
	2024		2023
Products:
EMPAVELI	$	25,610	$	20,440
SYFOVRE		137,465		18,360
Total Product revenue, net	$	163,075	$	38,800

The Company’s accounts receivable balance of $267.8 million as of March 31, 2024 and $206.4 million as of December 31, 2023, consisted of EMPAVELI and SYFOVRE product sales receivable and licensing and other revenue receivables from our collaboration with Swedish Orphan Biovitrum AB (Publ) (“Sobi”). The Company does not have a reserve related to expected credit losses against its accounts receivable balance and expects to collect its accounts receivable in the ordinary course of business.

The Company’s product sales reserves totaled $19.2 million and $16.6 million as of March 31, 2024 and December 31, 2023, respectively. These amounts are included in accrued expenses on the Company’s unaudited condensed consolidated balance sheets.

The following table summarizes activity in each of the product revenue allowance and reserve categories for the three months ended March 31, 2024 and 2023 (in thousands):


	Chargebacks, Discounts, and Fees			Government and other rebates			Returns			Total
Ending balance at December 31, 2023	$	5,674		$	8,898		$	2,053			16,625
Provision related to sales in the current year		9,575			13,125			1,355			24,055
Adjustments related to prior period sales		146			(19	)		(96	)		31
Credits and payments made		(9,724	)		(9,906	)		(1,859	)		(21,489	)
Ending balance at March 31, 2024	$	5,671		$	12,098		$	1,453		$	19,222


	Chargebacks, Discounts, and Fees			Government and other rebates			Returns			Total
Ending balance at December 31, 2022	$	164		$	1,936		$	251			2,351
Provision related to sales in the current year		1,466			2,566		651				4,683
Adjustments related to prior period sales		—			(2	)		(249	)		(251	)
Credits and payments made		(184	)		(1,639	)		—			(1,823	)
Ending balance at March 31, 2023	$	1,446		$	2,861		$	653		$	4,960


	Percent of Total Gross Product Revenues
	Three Months Ended March31,
	2024	2023
Customer A	15%	52%
Customer C	19%	9%
Customer D	59%	33%


	Percent of Product Sales Receivable
	As of March 31,
	2024	2023
Customer A	3%	25%
Customer C	21%	15%
Customer D	67%	52%

Long-term Debt

3 Months Ended

Mar. 31, 2024

Debt Disclosure [Abstract]

Long-term Debt

8. Long-term Debt

Convertible Senior Notes

On September 16, 2019, the Company completed a private offering of convertible notes (the “2019 Convertible Notes”) with an aggregate principal amount of $220.0 million issued pursuant to an indenture (the “Indenture”) with U.S. Bank National Association, as trustee.

The net proceeds from the sale of the 2019 Convertible Notes were approximately $212.9 million after deducting the initial purchasers’ discounts and commissions of $6.6 million and offering expenses of $0.5 million paid by the Company. The Company used $28.4 million of the net proceeds from the sale of the 2019 Convertible Notes to pay the cost of the capped call transactions in September 2019 described below.

On May 12, 2020, the Company issued convertible notes (the “2020 Convertible Notes”) with an aggregate principal amount of $300.0 million. The net proceeds from the sale of the 2020 Convertible Notes were approximately $322.9 million after deducting the purchasers’ discounts and commission of $5.7 million and offering expenses of $0.3 million. The Company used $43.1 million of the net proceeds from the sale of the 2020 Convertible Notes to pay the cost of the additional capped call transactions in May 2020 described below.

The 2019 Convertible Notes and the 2020 Convertible Notes are referred to together as the Convertible Notes. The Convertible Notes are senior unsecured obligations of the Company and bear interest at a rate of 3.5% per year payable semiannually in arrears on March 15 and September 15 of each year, beginning on March 15, 2020. The Convertible Notes will mature on September 15, 2026, unless converted earlier, redeemed or repurchased in accordance with their terms.

The Convertible Notes are convertible into shares of the Company’s common stock at an initial conversion rate of 25.3405 shares per $1,000 principal amount of Convertible Notes (equivalent to an initial conversion price of approximately $39.4625 per share of common stock). The conversion rate is subject to customary anti-dilution adjustments. In addition, following certain events that occur prior to the maturity date or if the Company delivers a notice of redemption, the Company will increase the conversion rate for a holder who elects to convert its Convertible Notes in connection with such corporate event or a notice of redemption, as the case may be, in certain circumstances as provided in the Indenture.

Prior to March 15, 2026, the Convertible Notes are convertible only under the following circumstances:

•

during any calendar quarter, if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day;

•

during the five business day period after any five consecutive trading day period in which the trading price per $1,000 principal amount of the Convertible Notes for each such trading day was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day;

•

if the Company calls any or all of the Convertible Notes for redemption, at any time prior to the close of business on the second scheduled trading day immediately preceding the redemption date; or

•

upon the occurrence of corporate events specified in the Indenture.

On or after March 15, 2026 until the close of business on the second scheduled trading day immediately preceding the maturity date of the Convertible Notes, holders may convert the Convertible Notes at any time. Upon conversion of the Convertible Notes, the Company will pay or deliver, as the case may be, cash, shares of the Company’s common stock or a combination of cash and shares of common stock, at the Company’s election.

Prior to September 20, 2023, the Company could not redeem the Convertible Notes. From and after September 20, 2023, the Company may redeem for cash all or a portion of the Convertible Notes, at its option, if the last reported sale price of the Company’s common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including the trading day immediately preceding the date on which the Company provides a notice of redemption, during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which the Company provides notice of redemption. The redemption price will be equal to 100% of the principal amount of the Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. If the Company calls any Convertible Notes for redemption, it will constitute a “make-whole fundamental change” with respect to such Convertible Notes, in which case the conversion rate applicable to

the conversion of such Notes, if converted in connection with the redemption, will be increased in certain circumstances. The Company has not called for redemption or redeemed any of the Convertible Notes as of March 31, 2024.

If the Company undergoes a “fundamental change,” as defined in the Indenture, prior to maturity, subject to certain conditions, holders may require the Company to repurchase for cash all or any portion of their Convertible Notes at a fundamental change repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus any accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

In January 2021, July 2021 and July 2022, the Company entered into separate, privately negotiated exchange agreements to modify the conversion terms with certain holders of its 2019 Convertible Notes and 2020 Convertible Notes. Under the terms of these exchange agreements, in January 2021, July 2021 and July 2022, the holders exchanged approximately $126.1 million of 2019 Convertible Notes, $201.1 million of 2019 Convertible Notes and 2020 Convertible Notes, and $98.1 million of 2020 Convertible Notes, respectively, in aggregate principal amount held by them for an aggregate of 3,906,869 shares, 5,992,217 shares and 3,027,018 shares, respectively, of common stock issued by the Company. In accordance with ASC Topic 470-20, “Debt – Debt with Conversion and Other Options,” (“ASC 470-20”) the Company accounted for the exchange as an induced conversion based on the short period of time the conversion offer was open and the substantive conversion feature offer. The Company accounted for the conversion of the debt as an inducement by expensing the fair value of the shares that were issued in excess of the original terms of the Convertible Notes.

The conditional conversion feature of the Convertible Notes was triggered as of December 31, 2023, and as a result the Convertible Notes were convertible at the option of the holders until March 31, 2024. No Convertible Notes were converted during this period.

The conditional conversion feature of the Convertible Notes was triggered as of March 31, 2024, and as a result the Convertible Notes are convertible at the option of the holders until June 30, 2024.

As of March 31, 2024, the Company held in treasury Convertible Notes in principal amount of $425.4 million which have not been cancelled.

The outstanding balance of the Convertible Notes as of March 31, 2024 and December 31, 2023 consisted of the following (in thousands):


	March 31,			December 31,
	2024			2023
Liability
Principal		93,897			93,897
Less: debt discount and issuance costs, net		(788	)		(864	)
Net carrying amount	$	93,109		$	93,033

The following table sets forth total interest expense recognized related to the Convertible Notes during the three months ended March 31, 2024 and 2023 (in thousands):



	Three Months Ended March 31,
		2024		2023
Amortization of debt issuance costs			76		73
Contractual interest expense			822		822
Total interest expense		$	898	$	895

Future minimum payments on Convertible Notes payable as of March 31, 2024 are as follows (in thousands):


2024	$	2,465
2025		3,286
2026		96,225
Total future minimum payments		101,976
Less: interest		(8,079	)
Less: debt discount and issuance costs, net		(788	)
Less: current portion		—
Convertible senior notes		93,109

Capped Call Transactions

On September 11, 2019 and May 6, 2020, concurrently with the pricing of the 2019 Convertible Notes and the 2020 Convertible Notes, respectively, the Company entered into capped call transactions with two counterparties. The capped call transactions are expected generally to reduce the potential dilution to the Company’s common stock upon any conversion of Convertible Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of converted Convertible Notes, as the case may be, in the event that the market price per share of the Company’s common stock, as measured under the terms of the capped call transactions, is greater than the strike price of the capped call transactions, which is initially $39.4625 (the conversion price of the Convertible Notes) and is subject to anti-dilution adjustments substantially similar to those applicable to the conversion rate of such Convertible Notes. If, however, the market price per share of the Company’s common stock, as measured under the terms of the capped call transactions, exceeds the cap price of the capped call transactions, which is initially $63.14 per share, there would nevertheless be dilution and/or there would not be an offset of such potential cash payments, in each case, to the extent that such market price exceeds the cap price of the capped call transactions.

On February 27, 2024, the Company entered into agreements with the capped call counterparties to unwind a portion of the capped call transactions. The unwind transactions were settled based on the volume-weighted average price of the Company’s common stock over a 7-day averaging period beginning on and including February 27, 2024. The settlement of the unwind transactions was completed on March 8, 2024 at volume-weighted average price per share of $64.11, which resulted in cash proceeds to the Company of $98.8 million. As of March 31, 2024, the capped call transactions remaining is a notional amount corresponding to $93.9 million principal amount of Convertible Notes.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued research and development	$ 22,912	$ 28,318
Accrued royalties	6,224	10,197
Accrued payroll liabilities	20,789	51,781
Accrued goods received not invoiced	15,829	5,902
Product revenue reserves	19,222	16,625
Other	16,423	14,983
Total accrued expenses	$ 101,399	$ 127,806

Long-term Debt - Additional Information (Detail)				1 Months Ended			3 Months Ended
Long-term Debt - Additional Information (Detail)	Mar. 08, 2024 USD ($) $ / shares	May 12, 2020 USD ($)	Sep. 16, 2019 USD ($)	Jul. 31, 2022 shares	Jul. 31, 2021 USD ($) shares	Jan. 31, 2021 USD ($) shares	Mar. 31, 2024 USD ($) Days d $ / shares	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Sep. 11, 2019 CounterParty $ / shares
Debt Instrument [Line Items]
Long-term debt							$ 93,109,000
Capped Call Transactions [Member]
Debt Instrument [Line Items]
Number of counterparties \| CounterParty										2
Initial conversion price \| $ / shares										$ 39.4625
Initial cap price \| $ / shares										$ 63.14
Volume-weighted average price per share \| $ / shares	$ 64.11
Proceeds from issuance of common stock	$ 98,800,000
Convertible Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Debt instrument, stated percentage			3.50%
Debt instrument, due and payment description							The Convertible Notes are senior unsecured obligations of the Company and bear interest at a rate of 3.5% per year payable semiannually in arrears on March 15 and September 15 of each year, beginning on March 15, 2020.
Debt instrument, frequency of periodic payment							semiannually
Maturity date			Sep. 15, 2026
Threshold trading days \| Days							20
Threshold consecutive trading days \| Days							30
Threshold percentage of stock price trigger							130.00%
Redemption period, start date							Sep. 20, 2023
Redemption price, percentage							100.00%
Debt interest expense							$ 898,000	$ 895,000
Long-term debt							$ 93,109,000		$ 93,033,000
Convertible Senior Notes Due 2026 [Member] \| Prior to March 15, 2026 Convertible [Member]
Debt Instrument [Line Items]
Threshold trading days \| d							20
Threshold consecutive trading days \| d							30
Threshold percentage of stock price trigger							130.00%
Trading price per principal amount							$ 1,000
Convertible Senior Notes Due 2026 [Member] \| Prior to March 15, 2026 Convertible [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Threshold percentage of stock price trigger							98.00%
Convertible Senior Notes Due 2026 [Member] \| Common Stock [Member]
Debt Instrument [Line Items]
Terms of conversion							The Convertible Notes are convertible into shares of the Company’s common stock at an initial conversion rate of 25.3405 shares per $1,000 principal amount of Convertible Notes (equivalent to an initial conversion price of approximately $39.4625 per share of common stock). The conversion rate is subject to customary anti-dilution adjustments. In addition, following certain events that occur prior to the maturity date or if the Company delivers a notice of redemption, the Company will increase the conversion rate for a holder who elects to convert its Convertible Notes in connection with such corporate event or a notice of redemption, as the case may be, in certain circumstances as provided in the Indenture.
Conversion ratio							0.0253405
Conversion price \| $ / shares							$ 39.4625
Convertible Senior Notes Due 2026 [Member] \| 2019 Convertible Notes [Member]
Debt Instrument [Line Items]
Net proceeds from the sale of the notes			$ 212,900,000
Payment of convertible debt discounts and commissions			6,600,000
Payment of convertible debt offering expenses			500,000
Payments of transactions cost			28,400,000
Convertible Senior Notes Due 2026 [Member] \| 2019 Convertible Notes [Member] \| Exchange Agreements [Member]
Debt Instrument [Line Items]
Aggregate principal amount converted						$ 126,100,000
Convertible Senior Notes Due 2026 [Member] \| 2019 Convertible Notes [Member] \| Common Stock [Member] \| Exchange Agreements [Member]
Debt Instrument [Line Items]
Aggregate principal amount converted into shares \| shares						3,906,869
Convertible Senior Notes Due 2026 [Member] \| 2020 Convertible Notes [Member]
Debt Instrument [Line Items]
Net proceeds from the sale of the notes		$ 322,900,000
Payment of convertible debt discounts and commissions		5,700,000
Payment of convertible debt offering expenses		300,000
Payments of transactions cost		43,100,000
Convertible Senior Notes Due 2026 [Member] \| 2020 Convertible Notes [Member] \| Exchange Agreements [Member]
Debt Instrument [Line Items]
Aggregate principal amount converted					$ 98,100,000
Convertible notes held in treasury							$ 425,400,000
Convertible Senior Notes Due 2026 [Member] \| 2020 Convertible Notes [Member] \| Common Stock [Member] \| Exchange Agreements [Member]
Debt Instrument [Line Items]
Aggregate principal amount converted into shares \| shares				3,027,018	5,992,217
Convertible Senior Notes Due 2026 [Member] \| 2019 and 2020 Convertible Notes [Member] \| Exchange Agreements [Member]
Debt Instrument [Line Items]
Aggregate principal amount converted					$ 201,100,000
Convertible Senior Notes Due 2026 [Member] \| Capped Call Transactions [Member]
Debt Instrument [Line Items]
Call transactions remaining is a notional amount							$ 93,900,000
Convertible Senior Notes Due 2026 [Member] \| Private Offering [Member] \| 2019 Convertible Notes [Member]
Debt Instrument [Line Items]
Principal amount			$ 220,000,000
Convertible Senior Notes Due 2026 [Member] \| Private Offering [Member] \| 2020 Convertible Notes [Member]
Debt Instrument [Line Items]
Principal amount		$ 300,000,000

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Level 1 [Member] \| Convertible Senior Notes [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Convertible notes	$ 151.7	$ 140.8
Convertible notes, interest rate	3.50%	3.50%
Level 2 [Member] \| Development Liability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value	$ 316.9	$ 306.9

Development Liability (Tables)

3 Months Ended

Mar. 31, 2024

Research and Development [Abstract]

Summary of Development Liability

The following table summarizes the development liability (in thousands):


	March 31, 2024			December 31, 2023			Effective Interest Rate
Development liability	$	366,000		$	366,000			7.91	%
Less: Unamortized discount to development liability		(44,287	)		(50,353	)
Less: Current portion of development liability, net of discount		(77,287	)		(75,830	)
Total long-term development liability	$	244,426		$	239,817

Schedule of Future Minimum SFJ Payments

Future minimum SFJ payments as of March 31, 2024 is as follows (in thousands):


2024	$	98,750
2025		103,000
2026		109,000
2027		55,250
Total future minimum payments		366,000

Leases - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Lessee Lease Description [Line Items]
Operating lease expense	$ 1.5	$ 1.7

Commitments and Contingencies

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

13. Commitments and Contingencies

The Company has certain non-cancelable purchase obligations related to the manufacturing of drug substance and drug product, with Bachem Americas, Inc., under which the Company has agreed to purchase a significant portion of its requirements for the pegcetacoplan drug substance over the initial term of the agreement, which continues until December 31, 2025, and a commercial supply agreement with NOF Corporation, under which the Company has agreed to purchase activated polyethylene glycol derivative, or PEG, which is a component of pegcetacoplan. Under these agreements, as of March 31, 2024, the Company is obligated to pay up to $70.7 million to these vendors. In addition, the Company has other non-cancelable purchase agreements as of March 31, 2024, under which it is obligated to pay up to $19.7 million to vendors.

The Company is a party to a master lease agreement under which the Company leases vehicles with initial terms of 36 months from the date of delivery. If the Company were unable to take delivery of a previously ordered vehicle, the Company may incur nominal fees.

Indemnifications—In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend indemnified parties for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third-party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has not incurred any cost to defend lawsuits or settle claims related to these indemnification provisions.

Legal—During the normal course of business, the Company may be a party to legal claims that may not be covered by insurance.

On August 2, 2023, Judith M. Soderberg filed a putative class action in the United States District Court for the District of Delaware against the Company and certain current and former executive officers of the Company (the “Complaint”). The Complaint alleges, among other things, that the defendants violated Sections 10(b) and/or 20(a) of the Exchange Act and Rule 10b-5 promulgated thereunder by misrepresenting and/or omitting certain material facts related to the design of SYFOVRE’s clinical trials and the risks

associated with SYFOVRE’s commercial adoption. The Complaint seeks, among other relief, compensatory damages and equitable relief in favor of the alleged class against all defendants, including interest, and reasonable costs and expenses incurred by plaintiffs, including attorneys’ and expert fees.

On October 23, 2023, the Court appointed Ray Peleckas and Michigan Laborers’ Pension Fund together as Co-Lead Plaintiffs and assigned the action the caption In Apellis Pharmaceuticals, Inc. Securities Litigation, Case 1:23-cv-00834-MN. The Co-Lead Plaintiffs filed an amended complaint on February 8, 2024 (the “Amended Complaint”). The Amended Complaint is brought on behalf of a class of all persons and entities who purchased or otherwise acquired Apellis common stock between January 28, 2021 and July 28, 2023, inclusive, names the Company and Cedric Francois, our chief executive officer, as defendants, and makes similar allegations, asserts the same claims and seeks the same relief as the Complaint.

On October 2, 2023, the defendants moved to transfer the action to the United States District Court for the District of Massachusetts. The Court has not yet ruled on this motion.

The outcome of the matter described above cannot be predicted with certainty and therefore any loss is neither probable nor reasonably estimable. However, the Company intends to vigorously defend against the litigation.

Development Liability - Schedule of Future Minimum SFJ Payments (Detail) - SFJ Agreement [Member] - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
2024	$ 98,750
2025	103,000
2026	109,000
2027	55,250
Total future minimum payments	$ 366,000	$ 5,000

Leases

3 Months Ended

Mar. 31, 2024

Leases [Abstract]

Leases

9. Leases

The underlying assets of the Company’s leases primarily relate to office space leases, but also include some equipment leases. The Company determines if an arrangement qualifies as a lease at its inception.

As of March 31, 2024 and December 31, 2023, all leases were classified as operating leases. Additional information related to the operating lease assets and liabilities is as follows (in thousands):


	March 31,			December 31,
	2024			2023
Right-of-use assets	$	14,994		$	16,745
Operating Lease Liabilities	$	16,027		$	17,895
Weighted Average Remaining Term in years		2.64		2.83
Weighted Average discount rate used to measure outstanding lease liabilities		7.25	%		7.20	%

For the three months ended March 31, 2024 and 2023, the lease cost for operating lease expense was $1.5 million and $1.7 million, respectively.

Supplemental cash flow information related to operating leases for the three months ended March 31, 2024 and 2023 is as follows (in thousands):


	2024		2023
Operating cash flows from operating leases	$	2,311	$	2,022

The maturities of the Company’s operating lease liabilities as of March 31, 2024 are as follows (in thousands):


2024		5,352
2025		6,188
2026		5,278
2027		858
Total future minimum lease payments		17,676
Less Imputed interest		(1,649	)
Total operating lease liabilities	$	16,027

Product Revenues, Accounts Receivable, and Reserves for Product Sales - Schedule of Disaggregation of Product Revenue by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Product Revenues Accounts Receivable And Reserves For Product Sales [Line Items]
Total Product revenue, net	$ 172,325	$ 44,846
EMPAVELI [Member]
Product Revenues Accounts Receivable And Reserves For Product Sales [Line Items]
Total Product revenue, net	25,610	20,440
SYFOVRE [Member]
Product Revenues Accounts Receivable And Reserves For Product Sales [Line Items]
Total Product revenue, net	137,465	18,360
Product Revenue, Net [Member]
Product Revenues Accounts Receivable And Reserves For Product Sales [Line Items]
Total Product revenue, net	$ 163,075	$ 38,800

- Definition

+ References

+ Details

Prepaid and Other Current Assets

3 Months Ended

Mar. 31, 2024

Prepaid Expense and Other Assets, Current [Abstract]

Prepaid and Other Current Assets

5. Prepaid and Other Current Assets

Prepaid and other current assets consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31,		December 31,
	2024		2023
Down payments for inventory		13,828		16,296
Prepaid research and development		12,626		13,931
Other prepaid expenses		16,709		8,593
Total prepaid expenses	$	43,163	$	38,820


	March 31,		December 31,
	2024		2023
Royalties receivable	$	4,499	$	3,054
Receivable from collaboration agreement(1)		—		15,000
Deposits and other current assets		7,620		4,354
Total other current assets	$	12,119	$	22,408

(1) In January 2024 the Company waived the remaining reimbursement payment of $15.0 million from Sobi in connection with the decision to discontinue the cold agglutinin disease (CAD) program.

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2024	May 01, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Entity Registrant Name	APELLIS PHARMACEUTICALS, INC.
Entity Central Index Key	0001492422
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity File Number	001-38276
Entity Tax Identification Number	27-1537290
Entity Address, Address Line One	100 Fifth Avenue
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451
City Area Code	617
Local Phone Number	977-5700
Entity Common Stock, Shares Outstanding		121,365,555
Entity Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes
Document Quarterly Report	true
Document Transition Report	false
Security 12b Title	Common Stock, $0.0001 par value per share
Trading Symbol	APLS
Security Exchange Name	NASDAQ

Fair Value Measurements - Schedule of Financial Instruments and the Related Fair Value Hierarchy of the Valuation Techniques Utilized (Detail) - Fair Value, Nonrecurring [Member] - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total Financial Assets	$ 231,740	$ 276,391
Money Market Funds [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total Financial Assets	231,740	276,391
Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total Financial Assets	231,740	276,391
Level 1 [Member] \| Money Market Funds [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total Financial Assets	$ 231,740	$ 276,391