0000950170-23-017874 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2023	Apr. 28, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Trading Symbol	ALEC
Entity File Number	001-38792
Entity Tax Identification Number	82-2933343
Entity Address, Address Line One	131 Oyster Point Blvd
Entity Address, Address Line Two	Suite 600
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	415
Local Phone Number	231-5660
Document Transition Report	false
Document Quarterly Report	true
Entity Registrant Name	Alector, Inc.
Entity Central Index Key	0001653087
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		83,351,778
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Current assets:
Cash and cash equivalents	$ 195,555	$ 154,323	$ 454,620
Marketable securities	473,774	558,528
Receivable from Collaboration partner	4,699	2,587
Prepaid expenses and other current assets	11,974	10,997
Total current assets	686,002	726,435
Property and equipment, net	24,998	25,521
Operating lease right-of-use assets	27,066	27,811
Restricted cash	1,472	1,472	1,472
Other assets	8,804	6,409
Total assets	748,342	787,648
Current liabilities:
Accounts payable	3,126	4,189
Accrued clinical supply costs	7,691	5,559
Accrued liabilities	18,580	27,771
Deferred revenue, current portion	61,773	48,231
Operating lease liabilities, current portion	8,130	8,059
Total current liabilities	99,300	93,809
Deferred revenue, long-term portion	431,079	443,370
Operating lease liabilities, long-term portion	34,050	35,268
Other long-term liabilities	898	759
Total liabilities	565,327	573,206
Commitments and Contingencies
Stockholders' equity:
Common stock, $0.0001 par value; 200,000,000 shares authorized; 83,351,778 and 82,895,718 shares issued and outstanding as of March 31, 2023 and December 31, 2022	8	8
Additional paid-in capital	810,750	798,696
Accumulated other comprehensive loss	(2,199)	(4,575)
Accumulated deficit	(625,544)	(579,687)
Total stockholders' equity	183,015	214,442	$ 267,537
Total liabilities and stockholders’ equity	$ 748,342	$ 787,648

Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Mar. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	83,351,778	82,895,718
Common stock, shares outstanding	83,351,778	82,895,718

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Total revenue	$ 16,549	$ 24,474
Type of Revenue [Extensible List]	Collaboration Revenue [Member]	Collaboration Revenue [Member]
Operating expenses:
Research and development	$ 51,887	$ 53,043
General and administrative	14,777	15,554
Total operating expenses	66,664	68,597
Loss from operations	(50,115)	(44,123)
Other income, net	5,159	264
Loss before income taxes	(44,956)	(43,859)
Income tax expense	901	758
Net loss	(45,857)	(44,617)
Unrealized gain (loss) on marketable securities	2,376	(2,992)
Comprehensive loss	$ (43,481)	$ (47,609)
Net loss per share, basic	$ (0.55)	$ (0.54)
Net loss per share, diluted	$ (0.55)	$ (0.54)
Shares used in computing net loss per share, basic	83,102,296	82,102,191
Shares used in computing net loss per share, diluted	83,102,296	82,102,191

Condensed Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance at Dec. 31, 2021	$ 300,724	$ 8	$ 748,036	$ (943)	$ (446,377)
Beginning balance (in shares) at Dec. 31, 2021		81,986,192
Exercise of stock options	2,483		2,483
Exercise of stock options (in shares)		234,117
Vesting of restricted stock units		104,368
Stock-based compensation	11,939		11,939
Unrealized gain (loss) on marketable securities	(2,992)			(2,992)
Net loss	(44,617)				(44,617)
Ending balance at Mar. 31, 2022	267,537	$ 8	762,458	(3,935)	(490,994)
Ending balance (in shares) at Mar. 31, 2022		82,324,677
Beginning balance at Dec. 31, 2022	$ 214,442	$ 8	798,696	(4,575)	(579,687)
Beginning balance (in shares) at Dec. 31, 2022	82,895,718	82,895,718
Exercise of stock options	$ 1,079		1,079
Exercise of stock options (in shares)		132,191
Vesting of restricted stock units		323,869
Stock-based compensation	10,975		10,975
Unrealized gain (loss) on marketable securities	2,376			2,376
Net loss	(45,857)				(45,857)
Ending balance at Mar. 31, 2023	$ 183,015	$ 8	$ 810,750	$ (2,199)	$ (625,544)
Ending balance (in shares) at Mar. 31, 2023	83,351,778	83,351,778

- Definition

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

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- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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+ Details

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net loss	$ (45,857)	$ (44,617)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,360	1,589
Stock-based compensation	10,975	11,939
Amortization of premiums and accretion of discounts on marketable securities	(2,596)	570
Amortization of right-of-use assets	742	670
Changes in operating assets and liabilities:
Receivable from collaboration partner	(2,112)	(5,428)
Prepaid expenses and other current assets	(977)	(2,465)
Other assets	(2,395)	(358)
Accounts payable	(914)	2,043
Accrued liabilities and accrued clinical supply costs	(7,020)	(3,383)
Deferred revenue	1,251	175,526
Lease liabilities	(1,144)	(995)
Other long-term liabilities	139	0
Net cash provided by (used in) operating activities	(48,548)	135,091
Cash flows from investing activities:
Purchase of property and equipment	(1,025)	(692)
Purchase of marketable securities	(120,274)	(30,114)
Maturities of marketable securities	210,000	18,700
Net cash provided by (used in) investing activities	88,701	(12,106)
Cash flows from financing activities:
Proceeds from the exercise of options to purchase common stock	1,079	2,483
Net cash provided by financing activities	1,079	2,483
Net increase in cash, cash equivalents, and restricted cash	41,232	125,468
Cash, cash equivalents, and restricted cash at beginning of period	155,795	330,624
Cash, cash equivalents, and restricted cash at end of period	197,027	456,092
Non-cash investing and financing activities:
Property and equipment purchases included in accounts payable and accrued liabilities	$ 305	$ 499

The Company and Liquidity

3 Months Ended

Mar. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The Company and Liquidity

1. The Company and Liquidity

Alector, Inc. (Alector or the Company) is a Delaware corporation headquartered in South San Francisco, California. Alector is a clinical stage biopharmaceutical company pioneering immuno-neurology, a novel therapeutic approach for the treatment of neurodegeneration.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2023

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The condensed consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (GAAP) as defined by the Financial Accounting Standards Board (FASB). In the opinion of management, these unaudited condensed consolidated financial statements include all normal, recurring adjustments that are necessary to present fairly the results of the interim periods presented. The condensed consolidated financial statements include the accounts of Alector, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2022, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 28, 2023.

Use of Estimates

The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenue and expense during the reporting period. The Company evaluates its estimates, including those related to revenue recognition, manufacturing accruals, clinical accruals, fair value of assets and liabilities, income taxes uncertainties, stock-based compensation, and related assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, and short-term marketable securities. Cash and cash equivalents are deposited in checking and sweep accounts at financial institutions. Such deposits may, at times, exceed federally insured limits.

Cash, Cash Equivalents, and Restricted Cash

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash and cash equivalents. Cash equivalents, which consist of amounts invested in money market funds, are stated at fair value.

Restricted cash relates to a letter of credit established for a lease entered into in June 2018.

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows:


	Three Months Ended March 31,
	2023		2022
	(In thousands)
Cash and cash equivalents	$	195,555	$	454,620
Restricted cash		1,472		1,472
Total cash, cash equivalents, and restricted cash	$	197,027	$	456,092

Marketable Securities

All marketable securities have been classified as “available-for-sale” and are carried at fair value, based upon quoted market prices. The Company considers its available-for-sale portfolio as available for use in current operations. Accordingly, the Company may classify certain investments as short-term marketable securities, even though the stated maturity date may be one year or more beyond the current balance sheet date. For available-for-sale debt securities, unrealized gains, net of any related tax effects, are excluded from earnings and are included in other comprehensive income and reported as a separate component of stockholders’ equity until realized. The Company assesses available-for-sale debt securities on a quarterly basis to see if any unrealized loss is due to credit-related factors. Factors considered in determining whether an impairment is credit-related include the extent to which the investment’s fair value is less than its cost basis, declines in published credit ratings, changes in interest rates, and any other adverse factors related to the security. If it is determined that a credit-related impairment exists, the Company will measure the credit loss based on a discounted cash flows model. Credit-related impairments on available-for-sale debt securities are recognized as an allowance for credit losses with a corresponding adjustment to other income, net in the Company’s consolidated statement of operations. The unrealized loss position that is not credit-related is recorded, net of any related tax effects, in other comprehensive income until realized. There were no credit-related losses recognized for the periods presented.

The cost of securities sold is based on the specific-identification method. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. In accordance with our investment policy, management invests in money market funds, U.S. treasury securities, corporate bonds, agency bonds, certificates of deposit, and commercial paper. The Company has not experienced any losses on its deposits of cash, cash equivalents, and marketable securities.

Fair Value of Financial Instruments

The Company’s financial instruments include cash and cash equivalents, marketable securities, receivable from collaboration partner, current and noncurrent prepaid expenses, accounts payable, and accrued liabilities. The Company’s financial instruments approximate fair value due to their relatively short maturities.

The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines the fair value of its financial instruments based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels:

Level 1 – Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date;

Level 2 – Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

Level 3 – Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data.

Revenue Recognition

The Company recognizes revenue when control of promised goods or services is transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under arrangements, the Company performs the following steps: (i) identify the contract(s) with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract, and (v) recognize revenue when (or as) the entity satisfies the performance obligation. If it is determined that multiple performance obligations exist, the transaction price is allocated at the inception of the agreement to all identified performance obligations based on the relative standalone selling price (SSP). The relative SSP for each performance obligation is estimated using external sourced evidence if it is available. If external sourced evidence is not available, we use our best estimate of the SSP for the performance obligation.

The Company recognizes collaboration revenue at a point in time if control of the promised good or service has been transferred to the customer. The Company recognizes collaboration revenue over time by measuring the progress

toward complete satisfaction of the performance obligation using an input measure. In order to recognize revenue over the research and development period, the Company measures actual costs incurred to date compared to the overall total expected costs to satisfy the performance obligation. Revenues are recognized as the program costs are incurred. The Company re-evaluates the estimate of expected costs to satisfy the performance obligation each reporting period.

Stock-based Compensation

Stock-based compensation is measured on the grant date based on the fair value of the awards. The fair value of options to purchase common stock is measured using the Black-Scholes option-pricing model. Stock-based compensation associated with restricted stock units (RSUs) is based on the fair value of the Company's common stock on the grant date, which equals the closing price of the Company's common stock on the grant date. The Company recognizes expense over the vesting period of the awards. Expense for options and RSUs that vest based only on a service condition is recognized on a straight-line basis.

The fair value of RSUs with market conditions is estimated using a Monte Carlo simulation model. Assumptions and estimates utilized in the model include the stock price on grant date, risk-free interest rate, dividend yield, expected stock volatility, and estimated period to achieve the market condition. The expense is recognized based on continued employment of the participants, regardless of achievement of the market condition. Expense related to the RSUs with market conditions is recognized using the accelerated attribution method.

The Company accounts for forfeitures as they occur for all awards.

Comprehensive Loss

Comprehensive loss includes net loss and certain changes in stockholders’ equity that are the result of transactions and economic events other than those with stockholders. The Company’s only element of comprehensive loss was net unrealized loss on marketable securities.

Fair Value Measurements

3 Months Ended

Mar. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurements

3. Fair Value Measurements

The following tables summarize the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy:


	March 31, 2023
	Fair Value Hierarchy	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Market Value
	(In thousands)
Money market funds	Level 1	$	115,383	$	—	$	—		$	115,383
U.S. government treasury securities	Level 1		340,904		25		(2,079	)		338,850
Certificate of deposit	Level 2		6,847		—		(2	)		6,845
Commercial paper	Level 2		58,136		—		(6	)		58,130
Agency bond	Level 2		4,489		8		—			4,497
Corporate bonds	Level 2		65,746		29		(174	)		65,601
Total cash equivalents and marketable securities		$	591,505	$	62	$	(2,261	)	$	589,306

	December 31, 2022
	Fair Value Hierarchy	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Market Value
	(In thousands)
Money market funds	Level 1	$	74,848	$	—	$	—		$	74,848
U.S. government treasury securities	Level 1		506,372		7		(4,569	)		501,810
Commercial paper	Level 2		44,438		2		(8	)		44,432
Corporate bonds	Level 2		29,352		4		(10	)		29,346
Total cash equivalents and marketable securities		$	655,010	$	13	$	(4,587	)	$	650,436

The Company’s Level 2 securities are valued using third-party pricing sources. The pricing services utilize industry standard valuation models for which all significant inputs are observable. The Company classifies marketable securities available to fund current operations as current assets. As of March 31, 2023, the remaining contractual maturities of $565.1 million of investments were less than one year and $24.2 million of investments were after one year through

two years. As of March 31, 2023, fourteen U.S. government treasury securities with an aggregate fair value of $124.5 million and an aggregate unrealized loss of $1.6 million were in a loss position for more than twelve months. The Company does not intend to sell the investments that are currently in an unrealized loss position, and it is highly unlikely that the Company will be required to sell the investments before recovery of their amortized cost basis, which may be at maturity.

- 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

Collaboration Agreements

3 Months Ended

Mar. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Collaboration Agreements

4. Collaboration Agreements

GSK

On July 1, 2021, the Company entered into a Collaboration and License Agreement with Glaxo Wellcome UK Limited, a subsidiary of GlaxoSmithKline plc (GSK), pursuant to which the Company and GSK collaborate on the global development and commercialization of progranulin-elevating monoclonal antibodies, including latozinemab and AL101 (GSK Agreement). The GSK Agreement became effective on August 17, 2021.

Under the terms of the GSK Agreement, the Company received $700 million in upfront payments, of which $500 million was received in August 2021 and $200 million was received in January 2022. In addition, based on the development and commercialization plan for latozinemab and AL101, the Company may be eligible to receive up to an additional $1.5 billion in clinical development, regulatory, and commercial launch-related milestone payments. In the United States, the Company and GSK will equally share profits and losses from commercialization of latozinemab and AL101. Outside of the United States, the Company will be eligible for double-digit tiered royalties.

The Company and GSK will jointly develop latozinemab and AL101 with GSK conducting Phase 3 clinical trials for Alzheimer’s disease and Parkinson’s disease and other non-orphan indications. The Company and GSK will share development costs 60% by GSK and 40% by the Company, except that the Company will solely bear the development costs of the initial Phase 2 clinical trials under the development plan, and the parties will share manufacturing development costs equally.

Collaboration revenue under the GSK Agreement during the three months ended March 31, 2023 and 2022 was $11.4 million and $21.2 million, respectively. The deferred revenue related to the GSK Agreement was $433.6 million and $444.9 million as of March 31, 2023 and December 31, 2022, respectively. The deferred revenue is expected to be recognized over the research and development period of the programs through the completion of initial Phase 2 clinical trials.

Costs associated with co-development activities performed under the agreement are included in research and development expenses in the condensed consolidated statements of operations, with any reimbursement of costs by GSK reflected as a reduction of such expenses. For the three months ended March 31, 2023 and 2022, the Company recognized a reduction of research and development expense of $2.1 million and $5.4 million, respectively, under the GSK Agreement.

AbbVie

The Company entered into an agreement in October 2017 with AbbVie Biotechnology, Ltd. (AbbVie) to co-develop antibodies to two program targets in preclinical development (AbbVie Agreement). Under the terms of the AbbVie Agreement, AbbVie made $205.0 million in upfront payments, of which $5.0 million and $200.0 million were received by the Company in October 2017 and January 2018, respectively. The Company was to perform research and development services for the two programs through the end of Phase 2 clinical trials, which were each considered to be separate performance obligations. AbbVie decided to terminate one of the two collaboration programs, the CD33 collaboration program, after AbbVie and Alector collaboratively reviewed next steps for AL003, the asset being developed under that program, and concluded that further development of AL003 was not warranted. AbbVie provided written notice to terminate the CD33 collaboration program on June 30, 2022. The Company will no longer continue development of this program and will not be eligible for any future milestones related to that program from AbbVie. The Company continues to develop the AL002 program under the AbbVie Agreement. AbbVie has the exclusive right to exercise an option under the AbbVie Agreement with the Company for $250.0 million. If AbbVie exercises its option for the AL002 program, AbbVie would take over development of the product candidate, and the program costs will be split between the parties. The Company would also share in profits and losses upon commercialization of any products. However, following AbbVie’s exercise of its option for the AL002 program, the Company may opt out of sharing in development costs and profits or losses for that program and instead receive tiered royalties. Additionally, under the terms of the AbbVie Agreement, the Company will be eligible to earn up to an additional $225.0 million in milestone payments related to the regulatory approval for up to three indications. The Company assessed its collaboration agreement with AbbVie in the context of the delivery of the research and development services.

In February 2023, the Company and AbbVie amended the AbbVie Agreement (AbbVie Amendment), which resulted in the Company receiving a $17.8 million milestone payment in March 2023 for the dosing of the first patient in a long-term extension (LTE) trial. The performance obligation to conduct the LTE trial is not considered distinct from the AL002 program performance obligation. In addition, under the terms of the AbbVie Amendment, the Company will be eligible to earn up to an additional $12.5 million to support the enrollment of additional patients in the ongoing INVOKE-2 trial to replace discontinuations. The consideration related to this potential milestone was constrained as of March 31, 2023. The transaction price as of March 31, 2023 included fixed consideration consisting of the upfront payments of $205 million and the $17.8 million LTE milestone payment.

Collaboration revenue under the AbbVie Agreement during the three months ended March 31, 2023 and 2022 was $5.2 million and $3.3 million, respectively. The deferred revenue related to the AbbVie Agreement was $59.3 million and $46.7 million as of March 31, 2023 and December 31, 2022, respectively. The deferred revenue is expected to be recognized over the research and development period of the AL002 program through the completion of the ongoing Phase 2 and Phase 2 LTE clinical trials.

Stock-based Compensation

3 Months Ended

Mar. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

5. Stock-based Compensation

The Company recognized stock-based compensation as follows:


	Three Months Ended March 31,
	2023		2022
	(In thousands)
Research and development	$	5,655	$	6,626
General and administrative		5,320		5,313
Total stock-based compensation	$	10,975	$	11,939

2019 Equity Incentive Plan and 2022 Inducement Plan

On January 1, 2023, the Company added 4,144,785 shares to the shares reserved for issuance under the 2019 Equity Incentive Plan (2019 Plan). As of March 31, 2023, the Company had reserved 24,195,457 shares of common stock for issuance under the 2019 Plan, of which 10,247,399 shares were available for issuance of future awards. On January 1, 2022, the Company adopted the 2022 Inducement Plan (Inducement Plan) for the grant of equity-based awards to individuals who were not previously employees or non-employee directors of the Company. As of March 31, 2023, 1,402,807 shares were available for issuance of future awards under the Inducement Plan.

Option activity is shown below:


	Number of Options			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(In years)		(In thousands)
Outstanding as of December 31, 2022		13,713,272		$	14.62
Granted		66,918			9.15
Exercised		(132,192	)		8.16
Forfeited		(985,811	)		12.85
Outstanding as of March 31, 2023		12,662,187		$	14.80	$	7.7	$	—
Exercisable as of March 31, 2023		7,169,954		$	14.94	$	7.0	$	—
Vested and expected to vest as of March 31, 2023		12,662,187		$	14.80	$	7.7	$	—

The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock options and the fair value of the Company’s common stock for stock options that were in-the-money. As of March 31, 2023, total unrecognized stock-based compensation related to unvested stock options was $52.8 million, which the Company expects to recognize over a remaining weighted-average period of 2.5 years.

Restricted Stock Activity

Activity for the RSUs is shown below. In May 2021 and January 2022, the Company issued RSUs with market conditions to certain executives, which are also included in the table below. The RSUs with market conditions are earned based on stock price performance and continued service by the employee.


	Number of Shares			Weighted Average Grant Date Fair Value per Share
Unvested restricted stock units as of December 31, 2022		3,044,618		$	11.68
Granted		467,432			7.73
Vested		(323,868	)		12.36
Forfeited		(64,927	)		12.77
Unvested restricted stock units as of March 31, 2023		3,123,255		$	10.81

As of March 31, 2023, total unrecognized stock-based compensation related to unvested restricted stock units was $29.2 million, which the Company expects to recognize over a remaining weighted-average period of 2.4 years.

2019 Employee Stock Purchase Plan

The 2019 Employee Stock Purchase Plan (2019 ESPP) enables eligible employees of the Company to purchase shares of common stock at a discount. On January 1, 2023, 591,397 shares were added to the shares reserved for issuance under the 2019 ESPP pursuant to the annual automatic increase. As of March 31, 2023, the Company has reserved for issuance 3,373,816 shares of common stock pursuant to the 2019 ESPP. Each offering period is approximately six months long. 2019 ESPP participants will purchase shares of common stock at a price per share equal to 85% of the lesser of (1) the fair market value per share of the common stock on the first trading day of the offering period or (2) the fair market value of the common stock on the purchase date.

Income Taxes

3 Months Ended

Mar. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

6. Income Taxes

For the three months ended March 31, 2023 and 2022, the Company's effective tax rate was (2.2)% and (1.1)%, respectively. The difference between the effective tax rate as of March 31, 2023 and 2022, respectively, and the U.S. federal statutory rate of 21% was primarily due to the recognition of a certain amount of current year income tax as a result of the capitalization of research and development expenses under Section 174 of the Internal Revenue Code, effective beginning in 2022. Section 174 of the Internal Revenue Code requires capitalization of research and development expenses to then be amortized over five years for U.S. based research and 15 years for research conducted outside of the U.S., which limits the amount of research and development expenses that can be used to offset income in the current year.

- 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI https://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Related Party Transactions

3 Months Ended

Mar. 31, 2023

Related Party Transactions

7. Related Party Transactions

In 2014, the Company entered into a collaboration agreement with Adimab, LLC (Adimab) under which the Company is developing antibodies discovered by Adimab in its latozinemab and AL101 programs and is developing antibodies optimized by Adimab in its AL002 program (2014 Adimab Agreement). The 2014 Adimab Agreement also provided for the Company’s development of antibodies optimized by Adimab in its AL003 program. However, AbbVie decided to terminate the CD33 collaboration program, after AbbVie and Alector collaboratively reviewed next steps for AL003, the asset being developed under that program, and concluded that further development of AL003 was not warranted. In August 2019, the Company signed a collaboration agreement with Adimab for research and development of additional antibodies, the term of which was extended effective August 2022 (2019 Adimab Agreement). In December 2021, the Company signed another collaboration agreement with Adimab for antibody engineering research programs (2021 Adimab Agreement). The 2021 Adimab agreement expired at the end of the option period for the research program that was conducted under the agreement. Tillman Gerngross, Ph.D, the former Chief Executive Officer of Adimab through May 2022 is a co-founder and director of Alector. Dr. Gerngross will step down as Chairperson of the Company’s Board of Directors, effective June 13, 2023, and as a Director of our Board, effective June 15, 2023. For the three months ended March 31, 2023 and 2022, the Company incurred expenses of zero and $0.1 million, respectively. The Company had zero and $0.1 million accrued liabilities due to Adimab as of March 31, 2023 and 2022. Under the 2014 Adimab Agreement, the Company has made milestone payments and will owe low- to mid- single-digit royalty payments for commercial sales of the product candidate. Under the 2019 Adimab Agreement, the Company will owe certain milestone payments and low single-digit royalty payments for commercial sales of any covered product candidates.

Net Loss Per Share

3 Months Ended

Mar. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Share

8. Net Loss Per Share

The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share for the periods presented due to their anti-dilutive effect:


	Three Months Ended March 31,
	2023		2022
Restricted stock subject to future vesting		3,123,255		1,335,370
Options to purchase common stock		12,662,187		12,524,807
Shares committed under 2019 ESPP		167,133		70,406
Total		15,952,575		13,930,583

Restructuring

3 Months Ended

Mar. 31, 2023

Restructuring and Related Activities [Abstract]

Restructuring

9. Restructuring

On March 28, 2023, the Company committed to a plan to reduce its workforce by approximately 11% to better align the Company’s resources with its previously announced strategic prioritization of its late-stage immuno-neurology programs, including its TREM2 and progranulin product candidates. The Company initiated a reduction in force impacting approximately 30 employees across the organization effective March 29, 2023. One-time restructuring charges associated with the reduction in force are expected to be approximately $2.1 million, primarily consisting of personnel expenses such as salaries, one-time severance payments, and other benefits. For the three months ended March 31, 2023, the Company incurred restructuring costs of $1.7 million that were included in operating expenses and accrued liabilities as of March 31, 2023. The Company expects to incur additional restructuring costs of approximately $0.4 million prior to the end of 2023.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Concentration of Credit Risk

Cash, Cash Equivalents, and Restricted Cash

Restricted cash relates to a letter of credit established for a lease entered into in June 2018.


	Three Months Ended March 31,
	2023		2022
	(In thousands)
Cash and cash equivalents	$	195,555	$	454,620
Restricted cash		1,472		1,472
Total cash, cash equivalents, and restricted cash	$	197,027	$	456,092

Marketable Securities Policy

Marketable Securities

Fair Value of Financial Instruments

Level 1 – Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date;

Level 3 – Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data.

Revenue Recognition

Stock-based Compensation

The Company accounts for forfeitures as they occur for all awards.

Comprehensive Loss

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2023

Accounting Policies [Abstract]

Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash


	Three Months Ended March 31,
	2023		2022
	(In thousands)
Cash and cash equivalents	$	195,555	$	454,620
Restricted cash		1,472		1,472
Total cash, cash equivalents, and restricted cash	$	197,027	$	456,092

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2023

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on a Recurring Basis

The following tables summarize the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy:


	March 31, 2023
	Fair Value Hierarchy	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Market Value
	(In thousands)
Money market funds	Level 1	$	115,383	$	—	$	—		$	115,383
U.S. government treasury securities	Level 1		340,904		25		(2,079	)		338,850
Certificate of deposit	Level 2		6,847		—		(2	)		6,845
Commercial paper	Level 2		58,136		—		(6	)		58,130
Agency bond	Level 2		4,489		8		—			4,497
Corporate bonds	Level 2		65,746		29		(174	)		65,601
Total cash equivalents and marketable securities		$	591,505	$	62	$	(2,261	)	$	589,306

	December 31, 2022
	Fair Value Hierarchy	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Market Value
	(In thousands)
Money market funds	Level 1	$	74,848	$	—	$	—		$	74,848
U.S. government treasury securities	Level 1		506,372		7		(4,569	)		501,810
Commercial paper	Level 2		44,438		2		(8	)		44,432
Corporate bonds	Level 2		29,352		4		(10	)		29,346
Total cash equivalents and marketable securities		$	655,010	$	13	$	(4,587	)	$	650,436

Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Recognized Stock-Based Compensation

The Company recognized stock-based compensation as follows:


	Three Months Ended March 31,
	2023		2022
	(In thousands)
Research and development	$	5,655	$	6,626
General and administrative		5,320		5,313
Total stock-based compensation	$	10,975	$	11,939

Summary of Options to Purchase Common Stock

Option activity is shown below:


	Number of Options			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(In years)		(In thousands)
Outstanding as of December 31, 2022		13,713,272		$	14.62
Granted		66,918			9.15
Exercised		(132,192	)		8.16
Forfeited		(985,811	)		12.85
Outstanding as of March 31, 2023		12,662,187		$	14.80	$	7.7	$	—
Exercisable as of March 31, 2023		7,169,954		$	14.94	$	7.0	$	—
Vested and expected to vest as of March 31, 2023		12,662,187		$	14.80	$	7.7	$	—

Summary of Restricted Stock Units

Activity for the RSUs is shown below.


	Number of Shares			Weighted Average Grant Date Fair Value per Share
Unvested restricted stock units as of December 31, 2022		3,044,618		$	11.68
Granted		467,432			7.73
Vested		(323,868	)		12.36
Forfeited		(64,927	)		12.77
Unvested restricted stock units as of March 31, 2023		3,123,255		$	10.81

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2023

Earnings Per Share [Abstract]

Schedule of Dilutive Shares Excluded from Calculation of Diluted Net Loss Per Share

The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share for the periods presented due to their anti-dilutive effect:


	Three Months Ended March 31,
	2023		2022
Restricted stock subject to future vesting		3,123,255		1,335,370
Options to purchase common stock		12,662,187		12,524,807
Shares committed under 2019 ESPP		167,133		70,406
Total		15,952,575		13,930,583

Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)
Accounting Policies [Abstract]
Credit losses on marketable securities	$ 0

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 195,555	$ 154,323	$ 454,620
Restricted cash	1,472	1,472	1,472
Total cash, cash equivalents, and restricted cash	$ 197,027	$ 155,795	$ 456,092	$ 330,624

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Money Market Funds \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents and marketable securities, Amortized Cost	$ 115,383	$ 74,848
Cash equivalents and marketable securities, Unrealized Gains	0	0
Cash equivalents and marketable securities, Unrealized Losses	0	0
Cash equivalents and marketable securities, Fair Market Value	115,383	74,848
U.S Government Treasury Securities \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents and marketable securities, Amortized Cost	340,904	506,372
Cash equivalents and marketable securities, Unrealized Gains	25	7
Cash equivalents and marketable securities, Unrealized Losses	(2,079)	(4,569)
Cash equivalents and marketable securities, Fair Market Value	338,850	501,810
Certificate of Deposit [Member] \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents and marketable securities, Amortized Cost	6,847
Cash equivalents and marketable securities, Unrealized Gains	0
Cash equivalents and marketable securities, Unrealized Losses	(2)
Cash equivalents and marketable securities, Fair Market Value	6,845
Commercial Paper [Member] \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents and marketable securities, Amortized Cost	58,136	44,438
Cash equivalents and marketable securities, Unrealized Gains	0	2
Cash equivalents and marketable securities, Unrealized Losses	(6)	(8)
Cash equivalents and marketable securities, Fair Market Value	58,130	44,432
Agency Bond [Member] \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents and marketable securities, Amortized Cost	4,489
Cash equivalents and marketable securities, Unrealized Gains	8
Cash equivalents and marketable securities, Unrealized Losses	0
Cash equivalents and marketable securities, Fair Market Value	4,497
Corporate Bonds \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents and marketable securities, Amortized Cost	65,746	29,352
Cash equivalents and marketable securities, Unrealized Gains	29	4
Cash equivalents and marketable securities, Unrealized Losses	(174)	(10)
Cash equivalents and marketable securities, Fair Market Value	65,601	29,346
Cash Equivalents and Marketable Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents and marketable securities, Amortized Cost	591,505	655,010
Cash equivalents and marketable securities, Unrealized Gains	62	13
Cash equivalents and marketable securities, Unrealized Losses	(2,261)	(4,587)
Cash equivalents and marketable securities, Fair Market Value	$ 589,306	$ 650,436

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2023	Mar. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Remaining contractual maturities of investments were less than one year	$ 565.1
Remaining contractual maturities of investments were less than one year through two years		$ 24.2
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of instruments in loss position	124.5
Unrealized loss	$ 1.6

Collaboration Agreements - Additional Information (Details) $ in Thousands			1 Months Ended			3 Months Ended
	Aug. 17, 2021 USD ($)	Jul. 01, 2021 USD ($)	Jan. 31, 2022 USD ($)	Jan. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Feb. 28, 2023 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue						$ 433,600	$ 444,900
Research and development expense						51,887	$ 53,043
GlaxoSmithKline plc
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Effective date of agreement	Aug. 17, 2021
Upfront payments		$ 700,000
Upfront payment received	$ 500,000		$ 200,000
Percentage of development cost							0.60
Collaboration revenue						11,400	$ 21,200
Research and development expense						2,100	5,400
GlaxoSmithKline plc \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional milestone payments per program related to initiation of certain clinical studies and regulatory approval							$ 1,500,000
Alector
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of development cost							0.40
AbbVie Biotechnology Limited
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payments					$ 205,000	205,000
Upfront payment received				$ 200,000	5,000
Exclusive option rights exercised for each program					250,000
Milestone payment received						17,800		$ 17,800
Collaboration revenue						5,200	$ 3,300
Deferred revenue						$ 59,300	$ 46,700
AbbVie Biotechnology Limited \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional milestone payments per program related to initiation of certain clinical studies and regulatory approval					$ 225,000			$ 12,500

Stock-based Compensation - Summary of Recognized Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 10,975	$ 11,939
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	5,655	6,626
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 5,320	$ 5,313

Stock-based Compensation - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Jan. 01, 2023
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Un-recognized compensation expense	$ 29.2
Expected weighted average period	2 years 4 months 24 days
2019 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected weighted average period	2 years 6 months
Common stock reserved for issuance	24,195,457	4,144,785
Common stock, shares available for issuance	10,247,399
Unrecognized stock-based compensation	$ 52.8
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	3,373,816	591,397
Purchase price of common stock, percentage	85.00%
Subsequent offering period	6 months
2022 Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares available for issuance	1,402,807

Stock-based Compensation - Summary of Options to Purchase Common Stock (Details) - 2019 Equity Incentive Plan $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, Outstanding, beginning balance \| shares	13,713,272
Number of Options, Granted \| shares	66,918
Number of Options, Exercised \| shares	(132,192)
Number of Options, Forfeited \| shares	(985,811)
Number of Options, Outstanding, ending balance \| shares	12,662,187
Number of Options, Exercisable \| shares	7,169,954
Number of Options, Vested and expected to vest \| shares	12,662,187
Weighted average exercise price, Outstanding, beginning balance \| $ / shares	$ 14.62
Weighted average exercise price, Granted \| $ / shares	9.15
Weighted average exercise price, Exercised \| $ / shares	8.16
Weighted average exercise price, Forfeited \| $ / shares	12.85
Weighted average exercise price, Outstanding, ending balance \| $ / shares	14.80
Weighted average exercise price, Exercisable \| $ / shares	14.94
Weighted average exercise price, Vested and expected to vest \| $ / shares	$ 14.80
Weighted Average Remaining Contractual Term, Outstanding (in years)	7 years 8 months 12 days
Weighted Average Remaining Contractual Term, Exercisable (In years)	7 years
Weighted Average Remaining Contractual Term, Vested and expected to vest (In years)	7 years 8 months 12 days
Aggregate Intrinsic Value, Outstanding \| $	$ 0
Aggregate Intrinsic Value, Exercisable \| $	0
Aggregate Intrinsic Value, Vested or expected to vest \| $	$ 0

Stock-based Compensation - Summary of Restricted Stock Awards and Restricted Stock Units (Details) - Restricted Stock Units	3 Months Ended
	Mar. 31, 2023 $ / shares shares
Number of Shares
Number of Shares, Unvested, beginning balance \| shares	3,044,618
Number of Shares, Granted \| shares	467,432
Number of Shares, Vested \| shares	(323,868)
Number of Shares, Forfeited \| shares	(64,927)
Number of Shares, Unvested, ending balance \| shares	3,123,255
Weighted-average grant-date fair value
Weighted Average Grant Date Fair Value per Share, Unvested, beginning balance \| $ / shares	$ 11.68
Weighted Average Grant Date Fair Value per Share, Granted \| $ / shares	7.73
Weighted Average Grant Date Fair Value per Share, Vested \| $ / shares	12.36
Weighted Average Grant Date Fair Value per Share, Forfeited \| $ / shares	12.77
Weighted Average Grant Date Fair Value per Share, Unvested, ending balance \| $ / shares	$ 10.81

Income Taxes - Additional Information (Details)	3 Months Ended
Income Taxes - Additional Information (Details)	Mar. 31, 2023	Mar. 31, 2022
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%
Effective tax rate	2.20%	1.10%

Related Party Transactions - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Adimab
Related Party Transaction [Line Items]
Accrued liabilities due to related parties	$ 0.0	$ 0.1
Two Thousand Fourteen Adimab Agreement
Related Party Transaction [Line Items]
Related party transaction expenses	$ 0.0	$ 0.1

- Definition

Carrying amount as of the balance sheet date of obligations due all related parties. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(C))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(B))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(a))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

+ Details

Net Loss Per Share - Schedule of Dilutive Shares Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive shares	15,952,575	13,930,583
Restricted Stock subject to future vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive shares	3,123,255	1,335,370
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive shares	12,662,187	12,524,807
Shares Committed Under 2019 ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive shares	167,133	70,406

Restructuring - Additional Information (Details) $ in Millions		3 Months Ended
	Mar. 29, 2023 USD ($) Employees	Mar. 31, 2023 USD ($)	Mar. 28, 2023
Restructuring Cost and Reserve [Line Items]
Percentage of reduction in workforce			11.00%
Number of reduction in workforce \| Employees	30
Restructuring Charges	$ 2.1
Additional restructuring cost expected		$ 0.4
Operating Expenses
Restructuring Cost and Reserve [Line Items]
Restructuring costs incurred		$ 1.7