0001741830-24-000034 | 10-Q | XBRL Viewer

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Condensed Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
Stockholders’ equity:
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	60,089,000	58,946,000
Common stock, shares outstanding (in shares)	60,089,000	58,946,000

Collaboration and License Agreement	3 Months Ended
Collaboration and License Agreement	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
COLLABORATION AND LICENSE AGREEMENT	COLLABORATION AND LICENSE AGREEMENT On January 6, 2023, the Company entered into a Collaboration and License Agreement with Genentech, Inc., a member of the Roche Group (Genentech). Pursuant to the agreement, the parties agreed to initially collaborate on two discovery research programs in oncology, each focused on a designated transcription factor, to discover small-molecule GLP-Tox-ready candidates that modulate transcription factor targets selected by Genentech. Each discovery research program primarily consists of (i) a mapping phase with the goal of identifying the transcription regulatory network for such designated transcription factor, and (ii) a screening phase having the goal of identifying and characterizing multiple screening hits suitable for nomination as a preclinical development program. The Company leads discovery and research activities under the discovery research programs and uses its proprietary drug discovery platform, including the small molecule microarray (SMM), for hit finding. Following the completion of initial discovery and research activities, Genentech will have the exclusive right to pursue further preclinical and clinical development and commercialization of compounds identified in the discovery research programs and designated by Genentech (each, a “Hit Program”). Pursuant to the agreement, the Company received an upfront payment of $20.0 million from Genentech. In addition, the Company is eligible for additional milestone payments upon achievement of certain preclinical, clinical and regulatory (including first-sale) milestones, totaling up to $177 million for the first development candidate per Hit Program, and is eligible to receive net sales milestones of up to $100 million for the first licensed product per Hit Program. The Company is also eligible to receive tiered royalties in the low- to high-single digits on any products that are commercialized by Genentech as a result of the collaboration. The term of the discovery research programs under the agreement is up to 24 months, which may be extended by six months at the Company’s option subject to satisfying certain conditions. Unless earlier terminated, the agreement will remain in effect for each product licensed under the agreement until expiration of the royalty term for such licensed product. Genentech has the right to terminate this agreement in its entirety, or with respect to a particular discovery research program or Hit Program, in its sole discretion, at any time by providing 60 days’ advance written notice to the Company. Each party may also terminate the agreement upon the other party’s material breach that remains uncured for 90 days (or 45 days in the event of nonpayment), or in the event of certain insolvency events involving the other party. The Company evaluated the agreement and determined it was within the scope of ASC 606. The Company determined there were performance obligations to perform research and development services. Each consists of various exclusive and non-exclusive licenses to use the Company’s intellectual property and know-how, initial discovery activities, and substitution of the designated transcription factor. The Company also identified customer options contained within the contract to perform further research and development services and the renewal of the licenses that were deemed a material right as these involved a discount to Genentech that they would not have otherwise received. As a result, the material rights for various options were recognized as separate performance obligations and the transaction price was allocated to the material rights based on the relative standalone selling price, the identified discount and the probability that the customer will exercise the option or the option is cancelled. Amounts allocated to a material right are not recognized as revenue until the option is exercised. The transaction price was determined to consist of the upfront payment of $20.0 million. Potential development and regulatory milestones have been fully constrained. The Company is expected to perform research and development services for each selected target up until a defined point at which time Genentech will decide whether or not to exercise an option to nominate a development candidate and take over future development and commercialization. The Company concluded this is not a material right. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as these amounts have been determined to relate predominantly to the license granted to Genentech. The Company determined that the obligations to perform research and development services are satisfied over time, and therefore, the related revenue will be recognized as services are provided. The Company recognized $2.5 million and $1.2 million in revenue during the three months ended March 31, 2024 and 2023, respectively, using the cost-based input model related to the research and development activities associated with the identified performance obligations. The remaining $11.2 million of the upfront payment is included in short and long-term deferred revenue as of March 31, 2024 and will be recognized as the performance obligations are satisfied.

Related Parties	3 Months Ended
Related Parties	Mar. 31, 2024
Related Party Transactions [Abstract]
RELATED PARTIES	RELATED PARTIES On December 1, 2017, the Company entered into a services agreement with Two River Consulting, LLC (Two River) to provide various clinical development, operational, managerial, accounting and financial, and administrative services to the Company. Arie Belldegrun, M.D., FACS, the Chairman of the Board of Directors, is the Chairman of Two River. Mr. Joshua Kazam and Mr. David Tanen, each a director of the Company, are each partners of Two River. During the three months ended March 31, 2024 and 2023, the Company incurred expenses of $126,250 and $24,000, respectively, for these services. In 2019, the Company entered into a consulting agreement with Bellco Capital, LLC (Bellco) to provide various executive services to the Company. Arie Belldegrun, M.D., FACS, the Chairman of the Board of Directors, is the Chairman of Bellco. The Company incurred expense of $6,300 for each of the three months ended March 31, 2024 and 2023 for these services.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
-Section 50
-Paragraph 6
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-URI https://asc.fasb.org//1943274/2147480990/946-20-50-6

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Section 50
-Paragraph 6
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-URI https://asc.fasb.org//1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

+ Details

Nature of Operations and Basis of Presentation (Details)
$ in Thousands

3 Months Ended

Mar. 31, 2024

USD ($)

segment

Dec. 31, 2023

USD ($)

^[1]

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Number of operating segments | segment

Accumulated deficit | $

$ 538,819

$ 508,861

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Balance Sheet Components - Schedule of Property, Plant and Equipment (Details) - USD ($)
$ in Thousands

3 Months Ended

Mar. 31, 2024

Mar. 31, 2023

Dec. 31, 2023

Property and equipment

Property, plant and equipment, gross

$ 15,880

$ 17,542

Less: Accumulated depreciation

(7,765)

(7,290)

Total property and equipment, net

8,115

10,252

^[1]

Depreciation

475

$ 569

Lab equipment

Property and equipment

Property, plant and equipment, gross

8,055

Leasehold improvements

Property and equipment

Property, plant and equipment, gross

7,038

8,703

Furniture, fixtures and computer equipment

Property and equipment

Property, plant and equipment, gross

$ 787

$ 784

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Investments - Contractual Maturity (Details) $ in Thousands	Mar. 31, 2024 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in 1 year or less	$ 112,528
Due in 1 to 2 years	0
Total	$ 112,528

Collaboration and License Agreement (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 06, 2023	Mar. 31, 2024	Mar. 31, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue		$ 2,520	$ 1,221
Genentech, Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration and license agreement, termination notice period, prior written notice	60 days
Collaboration and license agreement, termination notice period, uncured material breach	90 days
Collaboration and license agreement, termination notice period, uncured material breach, nonpayment	45 days
Genentech, Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expected timing of satisfaction, extension period	6 months
Genentech, Inc. \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-07
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Expected timing of satisfaction, period	24 months
Genentech, Inc. \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment	$ 20,000	$ 11,200
Maximum aggregate milestone payments	177,000
Maximum aggregate milestone payments from net sales	$ 100,000

Net Loss Per Share

3 Months Ended

Mar. 31, 2024

Earnings Per Share [Abstract]

NET LOSS PER SHARE

The following table summarizes the computation of basic and diluted net loss per share of the Company for the three months ended March 31, 2024 and 2023 (in thousands, except per share amounts):


	Three months ended March 31,
	2024		2023
Net loss	$	(29,958)	$	(26,238)
Weighted-average common stock outstanding, basic and diluted	59,521		57,147
Net loss per share, basic and diluted	$	(0.50)	$	(0.46)

The Company’s potentially dilutive securities, which include options to purchase shares of the Company's common stock and restricted stock subject to future vesting, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share.

The Company excluded the following potential shares of common stock, presented based on amounts outstanding at each stated period end, from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands):


	March 31, 2024	March 31, 2023
Stock options to purchase common stock	8,972	9,031
Early exercised stock options subject to future vesting	—	222
Restricted stock awards subject to future vesting	—	46
Restricted stock units subject to future vesting	1,451	2,844

Expected shares to be purchased under Employee Stock Purchase Plan	858	1,076
Total	11,282	13,219

In addition to the potentially dilutive securities noted above, the Company also has the option under its agreement with Tempus to issue common shares upon the achievement of specified milestones. Please refer to Note 9, “Commitment and Contingencies” for further details. Because the necessary conditions for issuance of the shares had not been met as of March 31, 2024, the Company excluded these shares from the table above.

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Revenue	$ 2,520	$ 1,221
Operating expenses:
Research and development	14,222	19,658
General and administrative	7,506	10,056
Impairment of long-lived assets and restructuring	12,786	0
Total operating expenses	34,514	29,714
Loss from operations	(31,994)	(28,493)
Other income (expense), net:
Interest income and other expense, net	2,036	2,255
Total other income (expense), net	2,036	2,255
Net loss	(29,958)	(26,238)
Other comprehensive loss:
Net unrealized gain (loss) on available-for-sale securities	(68)	432
Net comprehensive loss	$ (30,026)	$ (25,806)
Net loss per share, basic (in dollars per share)	$ (0.50)	$ (0.46)
Net loss per share, diluted (in dollars per share)	$ (0.50)	$ (0.46)
Weighted-average shares of common stock, basic (in shares)	59,521	57,147
Weighted-average shares of common stock, diluted (in shares)	59,521	57,147

Commitment and Contingencies - Narrative (Details)

1 Months Ended

3 Months Ended

30 Months Ended

Apr. 30, 2023

USD ($)

service

Feb. 28, 2021

USD ($)

ft²

Mar. 31, 2020

USD ($)

ft²

Mar. 31, 2024

USD ($)

Mar. 31, 2023

USD ($)

Mar. 31, 2024

USD ($)

Dec. 31, 2023

USD ($)

Schedule Of Asset Acquisition [Line Items]

Operating lease right-of-use assets

$ 13,902,000

$ 19,657,000

^[1]

Present value of operating lease liabilities

27,474,000

28,272,000

Lease payments

1,400,000

$ 900,000

Prepaid expenses and other current assets

6,375,000

5,781,000

^[1]

Sales milestone payable

Tempus Labs, Inc.

Schedule Of Asset Acquisition [Line Items]

Payments to purchase obligation

800,000

$ 1,400,000

5,500,000

Purchase obligation, quarterly payment terms

30 days

Prepaid expenses and other current assets

400,000

700,000

Tempus Labs, Inc. | Research And Development Services

Schedule Of Asset Acquisition [Line Items]

Services contract term

4 years

Number of primary services | service

Annual minimum commitment payment in year one

$ 1,500,000

Annual minimum commitment payment in year two

2,500,000

Annual minimum commitment payment in year three

3,000,000

Annual minimum commitment payment in year four

2,500,000

Purchase obligation due, remainder of fiscal year

1,500,000

Sales milestone payment

$ 22,400,000

Sales milestone payment in shares of common stock, percent threshold

50.00%

Cambridge, Massachusetts

Schedule Of Asset Acquisition [Line Items]

Lease term

11 years

Facility size | ft²

40,514

Initial annual base rent

$ 4,100,000

Escalating rent payments, percent

3.00%

Letter of credit

$ 2,000,000

Tenant improvement allowances

$ 3,700,000

Operating lease right-of-use assets

12,400,000

17,900,000

Present value of operating lease liabilities

$ 25,000,000

25,600,000

Remaining lease term

6 years 11 months

Incremental borrowing rate

8.50%

San Mateo, California. February 2021 Lease Agreement

Schedule Of Asset Acquisition [Line Items]

Facility size | ft²

17,340

Initial annual base rent

$ 1,200,000

Escalating rent payments, percent

3.00%

Operating lease right-of-use assets

$ 1,500,000

1,700,000

Present value of operating lease liabilities

$ 2,500,000

$ 2,700,000

Remaining lease term

2 years 3 months

Incremental borrowing rate

11.18%

Security deposit

$ 59,000

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Related Parties (Details) - USD ($)	3 Months Ended
Related Parties (Details) - USD ($)	Mar. 31, 2024	Mar. 31, 2023
Service Agreement, Charges
Related Party Transaction [Line Items]
Expenses from transaction with related party	$ 126,250	$ 24,000
Consulting Agreement
Related Party Transaction [Line Items]
Expenses from transaction with related party	$ 6,300	$ 6,300

Commitment and Contingencies

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Leases

In March 2020, the Company entered into an 11-year lease agreement to move its research and development operations to a 40,514 square-feet facility in Cambridge, Massachusetts (Cambridge facility). The lease commenced on February 28, 2020 with an initial annual base rent of $4.1 million with rent payments escalating 3.0% annually. The Company executed a letter of credit for $2.0 million in connection with the lease. The lease includes $3.7 million in certain tenant improvement allowances, which the Company included in its calculation of the right-of-use asset in the lease at commencement and all costs incurred by the Company were reimbursed by the lessor and were included within the total lease liability. In connection with the lease, the Company recognized an operating lease right-of-use asset of $12.4 million and $17.9 million as of March 31, 2024 and December 31, 2023, respectively. The Company recognized an aggregate lease liability of $25.0 million and $25.6 million as of March 31, 2024 and December 31, 2023, respectively. The remaining lease term is 6 years and 11 months, and the estimated incremental borrowing rate is 8.50%.

In February 2021, the Company entered into a lease agreement for its office space in San Mateo, California totaling 17,340 square-feet. The initial annual base rent for the space was $1.2 million, and such amount increases by 3% annually on each anniversary of the premises commencement date. In connection with the lease, the Company made a one-time cash security deposit in the amount of $59,000. The lease commenced in April 2021 and terminates August 31, 2026. In connection with the lease, the Company recognized an operating lease right-of-use asset of $1.5 million and $1.7 million as of March 31, 2024 and December 31, 2023, respectively. The Company recognized an aggregate lease liability of $2.5 million and $2.7 million as of March 31, 2024 and December 31, 2023, respectively. The remaining lease term is 2 years and 3 months, and the estimated incremental borrowing rate is 11.18%.

The following table summarizes the presentation of the Company’s operating leases in its balance sheets as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31, 2024		December 31, 2023
Assets:
Operating lease assets	$	13,902	$	19,657
Liabilities:
Current portion of operating lease liabilities	$	3,017	$	2,893
Noncurrent operating lease liabilities	24,457		25,379
Total operating lease liabilities	$	27,474	$	28,272

The following table summarizes the effect of operating lease costs in the Company’s statements of operations and comprehensive loss for the three months ended March 31, 2024 and 2023 (in thousands):


	Three months ended March 31,
	2024		2023
Research and development	$	880	$	767
General and administrative	549		511
Total operating lease cost	$	1,429	$	1,278

Under the lease agreements, the Company made cash payments of $1.4 million and $0.9 million during the three months ended March 31, 2024 and 2023, respectively.

The undiscounted future non-cancellable lease payments under the Company's operating leases as of March 31, 2024 for the next five years and thereafter is expected to be as follows (in thousands):


	Amount
Remaining nine months of 2024	$	3,852
2025	5,921
2026	5,405
2027	4,874
2028	5,020
Thereafter	11,404
Total undiscounted lease payments	36,476
Less: Present value adjustment	(9,002)
Present value of operating lease liabilities	$	27,474

Amended Tempus Research and Development Agreement

In October 2021, as subsequently amended in April 2023, the Company entered into an agreement for research and development services (the Amended Tempus Agreement) with Tempus AI, Inc. (formerly known as Tempus Labs, Inc., and referred to herein as Tempus), pursuant to which Tempus agreed to provide the Company with research and development services for a period of four years. The three primary services are analytical services, data licensing, and organoid services. The Company intends to utilize the services contemplated under the Amended Tempus Agreement to advance the development of KB-0742.

In consideration for the access to the services throughout the term of the Amended Tempus Agreement, the Company has agreed to pay an annual minimum commitment of $1.5 million in year one, $2.5 million in year two, $3.0 million in year three and $2.5 million in year four. The Company may decline to have the term extended into contract year four. Payments are made in quarterly installments. As of March 31, 2024, the Company has paid cumulatively $5.5 million under the Amended Tempus Agreement, including $0.8 million and $1.4 million paid for the three months ended March 31, 2024 and 2023, respectively. The annual minimum commitment is nonrefundable and is invoiced quarterly in advance due within 30 days. As of March 31, 2024, the Company had a non-cancellable purchase commitment of $1.5 million in the remaining nine months of 2024.

Tempus provides detailed reporting monthly which serves as the unit of account for calculating expense for actual services utilized for the analytical services, data licensing, and organoid services. As of March 31, 2024 and December 31, 2023 the prepaid expenses relating to Tempus were $0.4 million and $0.7 million, respectively. The prepaid expenses are assessed on a periodic basis to determine whether it is probable that services will be provided under the agreement. If the Company does not expect that services will be rendered, the prepaid expense is immediately recognized.

The Company is required to make milestone payments upon successful achievement of certain regulatory milestones for KB-0742, lanraplenib, and other discovery pipeline compounds up to a combined maximum of

$22.4 million. For each milestone payment that becomes due, the Company has the right to pay up to 50% of such milestone payment amount in shares of its common stock as long as certain regulatory requirements are met. As of March 31, 2024 and December 31, 2023, the Company determined that achievement of the milestones is not probable and therefore no corresponding liability has been recorded.

Gilead Asset Purchase Agreement

In July 2020, the Company entered into an asset purchase agreement (Gilead Asset Purchase Agreement) with Gilead Sciences, Inc. (Gilead), pursuant to which the Company acquired certain assets from Gilead related to entospletinib and lanraplenib, and patents and other intellectual property covering or related to the development, manufacture and commercialization of entospletinib and lanraplenib. Under the agreement, the Company is required to make milestone payments upon successful achievement of certain regulatory and sales milestones for lanraplenib, entospletinib and other SYK inhibitor compounds covered by the patent rights acquired pursuant to the Gilead Asset Purchase Agreement and developed by us as a back-up to entospletinib or lanraplenib. The Company is also committed to pay royalties ranging from high-single digits to the mid-teens on annual worldwide net sales of any SYK inhibitor compounds. The Company is currently unable to estimate the timing or likelihood of achieving remaining milestones or generating future product sales.

Purchase Commitments

In the normal course of business, the Company enters into contracts with contract research organizations (CROs) for preclinical and clinical studies and other vendors for services and products. These agreements generally provide for termination or cancellation, other than for costs already incurred and certain wind down costs that may be associated with the termination of a contract or clinical trial program.

Contingencies

In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown, because it involves claims that may be made against the Company in the future, but have not yet been made. The Company accrues liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated.

Indemnification

In accordance with the Company’s amended and restated certificate of incorporation and amended and restated bylaws, the Company has indemnification obligations to its officers and directors for certain events or occurrences, subject to certain limits, while they are serving in such capacity. There have been no claims to date, and the Company has a directors and officers liability insurance policy that may enable it to recover a portion of any amounts paid for future claims.

Restructurings - Narrative (Details) $ in Thousands	3 Months Ended
Restructurings - Narrative (Details) $ in Thousands	Mar. 31, 2024 USD ($)	Mar. 05, 2024	Jan. 24, 2024 officer
February 2024 Restructuring
Restructuring Cost and Reserve [Line Items]
Number of executive officers, terminated \| officer			3
Restructuring costs	$ 5,536
March 2024 Restructuring
Restructuring Cost and Reserve [Line Items]
Reduction of workforce (as a percent)		21.00%
Stock-based Compensation \| February 2024 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs	4,379
Severance and Benefits Costs \| February 2024 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs	1,157
Severance and Benefits Costs \| March 2024 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 627

- 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

Nature of Operations and Basis of Presentation	3 Months Ended
Nature of Operations and Basis of Presentation	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
NATURE OF OPERATIONS AND BASIS OF PRESENTATION	NATURE OF OPERATIONS AND BASIS OF PRESENTATION Kronos Bio, Inc. (Kronos or the Company), a Delaware corporation, was incorporated on June 2, 2017. The Company is an integrated discovery through clinical development biopharmaceutical company, with a focus on developing therapeutics that target the deregulated transcription that causes cancer and other serious diseases. The Company operates in one business segment which is the development of biopharmaceutical products. Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (SEC). Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. Unaudited Interim Financial Information The accompanying condensed balance sheet as of March 31, 2024, the condensed statements of operations and comprehensive loss for the three months ended March 31, 2024 and 2023, the condensed statements of stockholders’ equity as of March 31, 2024 and March 31, 2023, the condensed statements of cash flows for the three months ended March 31, 2024 and 2023 (collectively referred to as the “condensed financial statements”), and the financial data and other financial information disclosed in the notes to the condensed financial statements are unaudited. The unaudited interim condensed financial statements have been prepared on a basis consistent with the Company’s audited annual financial statements and, in the opinion of management, reflect all adjustments, consisting solely of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of March 31, 2024 and the results of its operations for the three months ended March 31, 2024 and 2023. The results for the three months ended March 31, 2024 are not necessarily indicative of results to be expected for the full year ending December 31, 2024, any other interim periods, or any future year or period. These condensed financial statements should be read in conjunction with the Company's audited financial statements included in its Annual Report on Form 10-K for the year ended December 31, 2023, filed with the SEC on March 21, 2024 (Annual Report). Need for Additional Capital The Company has incurred net losses since its inception of $538.8 million as of March 31, 2024. The Company expects that its cash, cash equivalents and investments as of March 31, 2024 will be sufficient to fund its operations for a period of at least one year from the date of issuance of these condensed financial statements. Management expects to incur additional losses in the future to fund its operations and conduct product research and development and recognizes the need to raise additional capital. The Company intends to raise additional capital through the issuance of equity securities, debt financings or other sources in order to continue its operations. However, if such financing is not available when needed and at adequate levels, the Company will need to reevaluate its operating plan and may be required to delay the development of its product candidates. The future viability of the Company is dependent on its ability to generate cash from operating activities or to raise additional capital to finance its operations. The Company’s failure to raise capital as and when needed could have a material adverse effect on its financial condition and ability to pursue business strategies. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaboration arrangements or obtain government grants. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce, or eliminate its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. In the event that the Company requires additional funding, there can be no assurance that it will be successful in obtaining sufficient funding on terms acceptable to the Company to fund its continuing operations, if at all.

Stock-Based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Number of Options
Beginning Balance (in shares)	8,253,000
Granted (in shares)	1,928,000
Forfeited (in shares)	(1,153,000)
Exercised (in shares)	(56,000)
Ending Balance (in shares)	8,972,000	8,253,000
Weighted-Average Exercise Price
Beginning Balance (dollars per share)	$ 8.92
Granted (dollars per share)	1.08
Forfeited (dollars per share)	9.53
Exercised (dollars per share)	3.74
Ending Balance (dollars per share)	$ 7.19	$ 8.92
Stock Option Activity, Additional Disclosures
Weighted-Average Remaining Contractual Term	7 years 10 months 9 days	6 years 8 months 26 days
Aggregate Intrinsic Value	$ 426	$ 19

Investments (Tables)

3 Months Ended

Mar. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments Classified by Contractual Maturity Date

The fair value and amortized cost of available-for-sale securities by major security type as of March 31, 2024 and December 31, 2023 were as follows (in thousands):


	March 31, 2024
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Money market funds	$	30,590	$	—	$	—	$	30,590
Certificates of deposit	490		—		(1)		489
Corporate bonds	19,605		—		(22)		19,583
U.S. treasury securities	92,482		4		(30)		92,456
Total cash equivalents and investments	$	143,167	$	4	$	(53)	$	143,118


	December 31, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Money market funds	$	36,009	$	—	$	—	$	36,009
Certificates of deposit	735		—		(2)		733
Corporate bonds	3,662		—		—		3,662
U.S. treasury securities	126,345		74		(53)		126,366
Total cash equivalents and investments	$	166,751	$	74	$	(55)	$	166,770

These available-for-sale securities were classified on the Company’s condensed balance sheets as of March 31, 2024 and December 31, 2023 as (in thousands):


	Fair Value
	March 31, 2024		December 31, 2023
Cash equivalents	$	37,331	$	56,110
Short-term investments	105,787		108,671
Long-term investments	—		1,989
Total cash equivalents and investments	$	143,118	$	166,770

The fair values of available-for-sale securities, excluding money market funds, by contractual maturity as of March 31, 2024 were as follows (in thousands):


	March 31, 2024
Due in 1 year or less	$	112,528
Due in 1 to 2 years	—

Total	$	112,528

Investments - Fair Value and Amortized Cost (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule of Held-to-maturity Securities [Line Items]
Money market funds, amortized cost	$ 37,331	$ 56,110
Unrealized Gains	4	74
Unrealized Losses	(53)	(55)
Fair Value	112,528
Total cash equivalents and investments, amortized cost	143,167	166,751
Total cash equivalents and investments, fair value	143,118	166,770
Money market funds
Schedule of Held-to-maturity Securities [Line Items]
Money market funds, amortized cost	30,590	36,009
Certificates of deposit
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	490	735
Unrealized Gains	0	0
Unrealized Losses	(1)	(2)
Fair Value	489	733
Corporate bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	19,605	3,662
Unrealized Gains	0	0
Unrealized Losses	(22)	0
Fair Value	19,583	3,662
U.S. treasury securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	92,482	126,345
Unrealized Gains	4	74
Unrealized Losses	(30)	(53)
Fair Value	$ 92,456	$ 126,366

Significant Accounting Policies, Estimates and Judgments (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (SEC). Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements.
Use of Estimates	Use of Estimates The preparation of condensed financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of assets and liabilities at the date of the condensed financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed financial statements include, but are not limited to, revenue, the accrual of research and development expenses, the fair value of investments, the fair value of the long-lived assets, income tax uncertainties, the valuation of equity instruments and the incremental borrowing rate for determining the operating lease assets and liabilities. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In December 2023, the Financial Accounting Standards Board (FASB) issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the disclosures required for income taxes in the Company’s annual financial statements. ASU 2023-09 is effective for the Company in its annual reporting for fiscal 2025 on a prospective basis. Early adoption and retrospective reporting are permitted. The Company does not plan to adopt this standard early. The adoption of this standard is not expected to have a material impact on the Company’s financial statements. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280). The amendments in this update expand segment disclosure requirements, including new segment disclosure requirements for entities with a single reportable segment among other disclosure requirements. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The adoption of this standard is not expected to have a material impact on the Company’s financial statements. There have been no other recent accounting pronouncements during the three months ended March 31, 2024 that are of significance to the Company.

Fair Value Measurements

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

The Company follows authoritative accounting guidance, which among other things, defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability.

The Company measures and reports its cash equivalents and investments at fair value.

Money market funds, Certificates of deposit and U.S. treasury securities are measured at fair value on a recurring basis using quoted prices and are classified as Level 1. Investments measured at fair value based on inputs other than quoted prices that are derived from observable market data are classified as Level 2.

Financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements by major security type as of March 31, 2024 and December 31, 2023 were as follows (in thousands):


	March 31, 2024
	Level 1		Level 2		Level 3		Fair Value
Financial Assets:
Money market funds	$	30,590	$	—	$	—	$	30,590
Certificates of deposit	489		—		—		489
Corporate bonds	—		19,583		—		19,583
U.S. treasury securities	92,456		—		—		92,456
Total financial assets	$	123,535	$	19,583	$	—	$	143,118


	December 31, 2023
	Level 1		Level 2		Level 3		Fair Value
Financial Assets:
Money market funds	$	36,009	$	—	$	—	$	36,009
Certificates of deposit	733		—		—		733
Corporate bonds	—		3,662		—		3,662
U.S. treasury securities	126,366		—		—		126,366
Total financial assets	$	163,108	$	3,662	$	—	$	166,770

The carrying amounts of accounts payable and accrued expenses approximate their fair values due to their short-term maturities. The Company’s Level 2 securities are valued using third-party pricing sources. The pricing services utilize industry standard valuation models, including both income- and market-based approaches, for which all significant inputs are observable, either directly or indirectly.

- 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

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2024
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company did not record any income tax expense for the three months ended March 31, 2024 and 2023. The Company has incurred net operating losses for all the periods presented and has not reflected any benefit of such net operating loss carryforwards in the accompanying condensed financial statements. The Company has recorded a full valuation allowance against all of its deferred tax assets as it is not more likely than not that such assets will be realized in the near future. It is the Company’s policy to record penalties and interest related to income taxes as a component of income tax expense. The Company has not recorded any interest or penalties related to income taxes during the three months ended March 31, 2024 and 2023. The Company has not identified any new uncertain tax positions as of March 31, 2024. Unrecognized tax benefits are not expected to change during the next 12 months. The reversal of the unrecognized tax benefits would not affect the effective tax rate. The Company is subject to examination by U.S. federal and state tax authorities for all years since its inception.

- 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
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

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(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Property, Plant and Equipment

Property and equipment, net consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31, 2024		December 31, 2023
Lab equipment	$	8,055	$	8,055
Leasehold improvements	7,038		8,703
Furniture, fixtures and computer equipment	787		784

Total property and equipment	15,880		17,542
Less: Accumulated depreciation	(7,765)		(7,290)
Total property and equipment, net	$	8,115	$	10,252

Schedule of Accrued Expenses

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


	March 31, 2024		December 31, 2023
Accrued compensation	$	1,001	$	3,904
External research and development	2,546		5,821
Accrued outside services	1,278		807
Accrued taxes	—		133
Other accrued expenses	162		266
Total accrued expenses	$	4,987	$	10,931

Restructurings

3 Months Ended

Mar. 31, 2024

Restructuring and Related Activities [Abstract]

RESTRUCTURINGS

In early 2024, the Company announced corporate restructuring plans designed to optimize its resource allocation and contain costs. In connection with the restructuring plans, the Company recorded the following costs in restructuring charges 1) one-time employee termination benefits such as severance and related benefit costs and 2) stock-based compensation expense resulting from the acceleration in full of outstanding unvested stock options and stock awards for certain employees at the separation date.

February 2024 Restructuring

On January 24, 2024, the Company and three executive officers: the Chief Medical Officer and Executive Vice President, Clinical Development; the Chief Operating Officer and General Counsel; and the Chief Scientific Officer (the “Officers") mutually agreed to the termination of employment effective February 16, 2024 (the “Separation Date”). The separation agreements signed with the Officers outlined the terms of severance and contemplate the engagement of each as a consultant to the Company through December 31, 2024. Total costs of $5.5 million were recorded for the three months ended March 31, 2024, including non-cash stock-based compensation of $4.4

million resulting from the acceleration in full of outstanding unvested stock options and stock awards at the Separation Date for the Officers.

The following table is a summary of accrued restructuring costs included within “Accrued Expenses” on the Company’s balance sheet as of March 31, 2024 (in thousands):


	Severance and Benefits Costs		Stock-based Compensation		Total
Balance at December 31, 2023	$	—	$	—	$	—
Restructuring costs	1,157		4,379		5,536
Cash payments	(1,093)		—		(1,093)
Non-cash charges	—		(4,379)		(4,379)
Balance at March 31, 2024	$	64	$	—	$	64

March 2024 Restructuring

On March 5, 2024, the Company approved an approximate 21% reduction in its workforce as part of a strategic resource allocation and cost containment plan. The workforce reduction was completed on March 7, 2024. Costs of $0.6 million were recorded for the three months ended March 31, 2024 related to this restructuring.

The following table is a summary of accrued restructuring costs included within “Accrued Expenses” on the Company’s balance sheet as of March 31, 2024 (in thousands):


	Severance and Benefits Costs
Balance at December 31, 2023	$	—
Restructuring costs	627
Cash payments	(527)
Balance at March 31, 2024	$	100

Commitments and Contingencies - Schedule of Maturities on Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Remaining nine months of 2024	$ 3,852
2025	5,921
2026	5,405
2027	4,874
2028	5,020
Thereafter	11,404
Total undiscounted lease payments	36,476
Less: Present value adjustment	(9,002)
Present value of operating lease liabilities	$ 27,474	$ 28,272

Restructurings - Schedule of Accrued Restructuring Costs (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
February 2024 Restructuring
Restructuring Reserve [Roll Forward]
Beginning balance	$ 0
Restructuring costs	5,536
Cash payments	(1,093)
Non-cash charges	(4,379)
Ending balance	64
Severance and Benefits Costs \| February 2024 Restructuring
Restructuring Reserve [Roll Forward]
Beginning balance	0
Restructuring costs	1,157
Cash payments	(1,093)
Non-cash charges	0
Ending balance	64
Severance and Benefits Costs \| March 2024 Restructuring
Restructuring Reserve [Roll Forward]
Beginning balance	0
Restructuring costs	627
Cash payments	(527)
Ending balance	100
Stock-based Compensation \| February 2024 Restructuring
Restructuring Reserve [Roll Forward]
Beginning balance	0
Restructuring costs	4,379
Cash payments	0
Non-cash charges	(4,379)
Ending balance	$ 0

Stock-Based Compensation - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	Oct. 31, 2020	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Future tax benefit		$ 0		$ 0
Weighted-average grant-date fair value, options granted (in dollars per share)		$ 0.77
Stock options, unrecognized cost		$ 9,300,000
2020 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Shares that may be issued, percent increase as total of common stock outstanding	5.00%
Number of shares that may have been issued (in shares)		23,364,521
Options, exercise price, percent of fair market value	100.00%
Vesting period	4 years
Number of shares reserved for future issuance (in shares)		6,528,388
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options recognized, weighted average period		2 years 25 days
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock based compensation		$ 2,300,000
Expected shares to be purchased under Employee Stock Purchase Plan \| The ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares that may have been issued (in shares)	688,000
Number of shares reserved for future issuance (in shares)		2,190,659
Number of shares that may be issued, increase percentage	1.00%
Number of shares that may be issued, increase (in shares)	1,376,000
Employee stock purchase plan (in shares)		0	0

Fair Value Measurements (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	$ 143,118	$ 166,770
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	30,590	36,009
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	489	733
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	19,583	3,662
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	92,456	126,366
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	123,535	163,108
Level 1 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	30,590	36,009
Level 1 \| Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	489	733
Level 1 \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Level 1 \| U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	92,456	126,366
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	19,583	3,662
Level 2 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Level 2 \| Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Level 2 \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	19,583	3,662
Level 2 \| U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	0	0
Level 3 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Level 3 \| Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Level 3 \| Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Level 3 \| U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 0	$ 0

Restructurings (Tables)

3 Months Ended

Mar. 31, 2024

Restructuring and Related Activities [Abstract]

Schedule of Accrued Restructuring Costs

The following table is a summary of accrued restructuring costs included within “Accrued Expenses” on the Company’s balance sheet as of March 31, 2024 (in thousands):


	Severance and Benefits Costs		Stock-based Compensation		Total
Balance at December 31, 2023	$	—	$	—	$	—
Restructuring costs	1,157		4,379		5,536
Cash payments	(1,093)		—		(1,093)
Non-cash charges	—		(4,379)		(4,379)
Balance at March 31, 2024	$	64	$	—	$	64

The following table is a summary of accrued restructuring costs included within “Accrued Expenses” on the Company’s balance sheet as of March 31, 2024 (in thousands):


	Severance and Benefits Costs
Balance at December 31, 2023	$	—
Restructuring costs	627
Cash payments	(527)
Balance at March 31, 2024	$	100

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis


	March 31, 2024
	Level 1		Level 2		Level 3		Fair Value
Financial Assets:
Money market funds	$	30,590	$	—	$	—	$	30,590
Certificates of deposit	489		—		—		489
Corporate bonds	—		19,583		—		19,583
U.S. treasury securities	92,456		—		—		92,456
Total financial assets	$	123,535	$	19,583	$	—	$	143,118


	December 31, 2023
	Level 1		Level 2		Level 3		Fair Value
Financial Assets:
Money market funds	$	36,009	$	—	$	—	$	36,009
Certificates of deposit	733		—		—		733
Corporate bonds	—		3,662		—		3,662
U.S. treasury securities	126,366		—		—		126,366
Total financial assets	$	163,108	$	3,662	$	—	$	166,770

Impairment of Long-Lived Assets	3 Months Ended
Impairment of Long-Lived Assets	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
IMPAIRMENT OF LONG-LIVED ASSETS	IMPAIRMENT OF LONG-LIVED ASSETS The Company at each reporting period reviews for impairment indicators for its long-lived assets. The sustained decline in the Company’s market capitalization as compared to the Company’s net asset value remained as the indicator of impairment, in addition to the Company’s shift in strategy to consider subleasing its Massachusetts facility. The Company determined all of its long-lived assets represent a single asset group for the purpose of the long-lived asset impairment assessment. The Company concluded that the carrying value of the single asset group was not recoverable as it exceeded the future net undiscounted cash flows that are expected to be generated from the use and eventual disposition of the assets within the asset group. To allocate and recognize the impairment loss, the Company, with the assistance of a third-party valuation firm, determined the fair value of the Company using the adjusted net asset method under the cost approach. The implied allocated impairment loss to any individual asset within the long-lived asset group shall not reduce the carrying amount of that asset below its fair value. To determine the fair value of the individual assets within the asset group, the Company utilized the discounted cash flow method of the income approach. During the three months ended March 31, 2024, the Company recognized a non-cash impairment charge of $6.6 million, including $5.0 million to its right-of-use assets and $1.6 million to leasehold improvements (refer to Note 5, Balance Sheet Components, the “Property and Equipment, Net” section for further details). No impairment charge was recorded for the three months ended March 31, 2023. These represent a level 3 nonrecurring fair value measurement. Calculating the fair value of the assets involves significant estimates and assumptions. These estimates and assumptions include, among others, projected future cash flows, risk-adjusted discount rates and market rental rates. Changes in the factors and assumptions used could materially affect the amount of impairment loss recognized in the period the long-lived assets were considered impaired.

Commitments and Contingencies - Schedule of Assets and Liabilities, Operating Leases, Lessee (Details) - USD ($)
$ in Thousands

Mar. 31, 2024

Dec. 31, 2023

Assets:

Operating lease assets

$ 13,902

$ 19,657

^[1]

Liabilities:

Current portion of operating lease liabilities

3,017

2,893

^[1]

Noncurrent operating lease liabilities

24,457

25,379

^[1]

Total operating lease liabilities

$ 27,474

$ 28,272

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Investments - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
Investments - Narrative (Details) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Realized losses on available-for-sale securities	$ 0	$ 0
Fair value of securities with continuous net unrealized loss position for more than 12 months	500,000	0
Accumulated loss on securities with continuous net unrealized loss position for more than 12 months	$ 1,193	$ 0

Significant Accounting Policies, Estimates and Judgments	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
SIGNIFICANT ACCOUNTING POLICIES, ESTIMATES AND JUDGMENTS	SIGNIFICANT ACCOUNTING POLICIES, ESTIMATES AND JUDGMENTS Use of Estimates The preparation of condensed financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of assets and liabilities at the date of the condensed financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed financial statements include, but are not limited to, revenue, the accrual of research and development expenses, the fair value of investments, the fair value of the long-lived assets, income tax uncertainties, the valuation of equity instruments and the incremental borrowing rate for determining the operating lease assets and liabilities. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates. Significant Accounting Policies There have been no significant changes to the accounting policies during the three months ended March 31, 2024, as compared to the significant accounting policies described in Item 8 Financial Statements and Supplementary Data, Note 2 of the “Notes to Financial Statements” of the Company’s audited financial statements included in its Annual Report. Recent Accounting Pronouncements In December 2023, the Financial Accounting Standards Board (FASB) issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the disclosures required for income taxes in the Company’s annual financial statements. ASU 2023-09 is effective for the Company in its annual reporting for fiscal 2025 on a prospective basis. Early adoption and retrospective reporting are permitted. The Company does not plan to adopt this standard early. The adoption of this standard is not expected to have a material impact on the Company’s financial statements. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280). The amendments in this update expand segment disclosure requirements, including new segment disclosure requirements for entities with a single reportable segment among other disclosure requirements. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The adoption of this standard is not expected to have a material impact on the Company’s financial statements. There have been no other recent accounting pronouncements during the three months ended March 31, 2024 that are of significance to the Company.

Balance Sheet Components

3 Months Ended

Mar. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

BALANCE SHEET COMPONENTS

Property and Equipment, net

Property and equipment, net consisted of the following as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31, 2024		December 31, 2023
Lab equipment	$	8,055	$	8,055
Leasehold improvements	7,038		8,703
Furniture, fixtures and computer equipment	787		784

Total property and equipment	15,880		17,542
Less: Accumulated depreciation	(7,765)		(7,290)
Total property and equipment, net	$	8,115	$	10,252

Depreciation expense was $0.5 million and $0.6 million for the three months ended March 31, 2024 and 2023, respectively.

During the three months ended March 31, 2024, the Company recognized a non-cash impairment charge of $1.6 million to the leasehold improvements. There was no charge in the three months ended March 31, 2023. Please refer to Note 7 “Impairment of Long-lived Assets” for further details.

Accrued Expenses

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


	March 31, 2024		December 31, 2023
Accrued compensation	$	1,001	$	3,904
External research and development	2,546		5,821
Accrued outside services	1,278		807
Accrued taxes	—		133
Other accrued expenses	162		266
Total accrued expenses	$	4,987	$	10,931

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net loss	$ (29,958)	$ (26,238)
Adjustments to reconcile net loss to cash used in operating activities:
Stock-based compensation expense	3,327	6,607
Depreciation	475	569
Net amortization (accretion) on available-for-sale securities	(1,106)	(1,253)
Change in accrued interest on available-for-sale securities	(7)	212
Non-cash lease expense	797	585
Impairment of long-lived assets and restructuring	11,166	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(450)	274
Other noncurrent assets	0	(2)
Accounts payable	1,347	1,005
Accrued expenses	(6,109)	(6,365)
Right-of-use operating assets and lease liabilities, net	(797)	(115)
Deferred revenue	(2,519)	18,779
Current portion of other liabilities and other noncurrent liabilities	(65)	(5)
Net cash used in operating activities	(23,899)	(5,947)
Cash flows from investing activities:
Purchase of property and equipment	(7)	(126)
Purchase of available-for-sale marketable securities	(48,754)	(102,595)
Maturities of marketable securities	54,531	96,366
Net cash provided by (used in) investing activities	5,770	(6,355)
Cash flows from financing activities:
Net cash provided by (used in) financing activities	0	0
Net decrease in cash and cash equivalents	(18,129)	(12,302)
Cash, cash equivalents and restricted cash at beginning of period	66,352	77,999
Cash, cash equivalents and restricted cash at end of period	48,223	65,697
Supplemental disclosures of non-cash activities:
Property and equipment additions included in accounts payable and accrued expenses	0	7
Cash and cash equivalents at end of period	46,197	61,646
Restricted cash at end of period	2,026	4,051
Cash, cash equivalents and restricted cash at end of period	$ 48,223	$ 65,697

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

Stock option activity under the 2020 Plan as of March 31, 2024 is summarized as follows:


	Number of Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term	Aggregate Intrinsic Value
	(in thousands)			(in years)	(in thousands)
Balance, December 31, 2023	8,253	$	8.92	6.74	$	19
Granted	1,928	1.08
Forfeited	(1,153)	9.53
Exercised	(56)	3.74
Balance, March 31, 2024	8,972	$	7.19	7.86	$	426

Schedule of Nonvested Share Activity

Restricted stock awards and restricted stock units as of March 31, 2024 are summarized as follows:


	Number of Restricted Stock	Weighted-Average Grant Date Fair Value		Weighted-Average Remaining Vesting Life
	(in thousands)			(in years)
Unvested, December 31, 2023	1,657	$	3.76	1.92
Granted	1,089	1.08
Vested and converted to shares	(1,087)	4.03
Forfeited	(208)	2.05
Unvested, March 31, 2024	1,451	$	1.79	2.38

Schedule of Total Stock-based Compensation

Total stock-based compensation expense related to stock options, restricted stock units, restricted stock awards and the employee stock purchase plan for the three months ended March 31, 2024 and 2023 is as follows (in thousands):


	Three months ended March 31,
	2024		2023
Research and development expense	$	1,163	$	3,112
General and administrative expense	2,164		3,495
Restructuring costs	4,379		$	—
Total stock-based compensation expense	$	7,706	$	6,607

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2024

Earnings Per Share [Abstract]

Schedule of Net Loss Per Share, Basic and Diluted

The following table summarizes the computation of basic and diluted net loss per share of the Company for the three months ended March 31, 2024 and 2023 (in thousands, except per share amounts):


	Three months ended March 31,
	2024		2023
Net loss	$	(29,958)	$	(26,238)
Weighted-average common stock outstanding, basic and diluted	59,521		57,147
Net loss per share, basic and diluted	$	(0.50)	$	(0.46)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share


	March 31, 2024	March 31, 2023
Stock options to purchase common stock	8,972	9,031
Early exercised stock options subject to future vesting	—	222
Restricted stock awards subject to future vesting	—	46
Restricted stock units subject to future vesting	1,451	2,844

Expected shares to be purchased under Employee Stock Purchase Plan	858	1,076
Total	11,282	13,219

Balance Sheet Components - Schedule of Accrued Expenses (Details) - USD ($)
$ in Thousands

Mar. 31, 2024

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Accrued compensation

$ 1,001

$ 3,904

External research and development

2,546

5,821

Accrued outside services

1,278

807

Accrued taxes

133

Other accrued expenses

162

266

Total accrued expenses

$ 4,987

$ 10,931

^[1]

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Impairment of Long-Lived Assets (Details) - USD ($)	3 Months Ended
Impairment of Long-Lived Assets (Details) - USD ($)	Mar. 31, 2024	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Impairment of long-lived assets and restructuring	$ 6,600,000
Impairment of long-lived assets, right-of-use asset	5,000,000
Impairment of long-lived assets, related leasehold improvements	$ 1,600,000	$ 0
Impairment charge		$ 0

Condensed Statements of Stockholders’ Equity (Unaudited) - USD ($)
shares in Thousands, $ in Thousands

Total

Common Stock

Additional Paid-in Capital

Accumulated Other Comprehensive Income (Loss)

Accumulated Deficit

Common stock, beginning balance (in shares) at Dec. 31, 2022

56,967

Beginning balance at Dec. 31, 2022

$ 244,499

$ 57

$ 641,422

$ (792)

$ (396,188)

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Issuance of common stock upon vesting of options and restricted stock (in shares)

386

Issuance of common stock upon vesting of options and restricted stock

305

Stock-based compensation expense

6,607

Net unrealized gain (loss) on available-for-sale securities

432

Net loss

(26,238)

Common stock, ending balance (in shares) at Mar. 31, 2023

57,354

Beginning balance at Mar. 31, 2023

$ 225,605

$ 57

648,334

(360)

(422,426)

Common stock, beginning balance (in shares) at Dec. 31, 2023

58,946

Beginning balance at Dec. 31, 2023

$ 159,078

^[1]

$ 59

667,861

(508,861)

Increase (Decrease) in Stockholders' Equity [Roll Forward]

Issuance of common stock upon vesting of options and restricted stock (in shares)

1,143

Issuance of common stock upon vesting of options and restricted stock

210

$ 1

209

Stock-based compensation expense

7,706

Net unrealized gain (loss) on available-for-sale securities

(68)

Net loss

$ (29,958)

(29,958)

Common stock, ending balance (in shares) at Mar. 31, 2024

60,089

Beginning balance at Mar. 31, 2024

$ 136,968

$ 60

$ 675,776

$ (49)

$ (538,819)

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

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+ Details

Investments - Balance Sheet (Details) - USD ($)
$ in Thousands

Mar. 31, 2024

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Cash equivalents

$ 37,331

$ 56,110

Short-term investments

105,787

108,671

^[1]

Long-term investments

1,989

^[1]

Total cash equivalents and investments

$ 143,118

$ 166,770

[1]	The balance sheet as of December 31, 2023 is derived from the audited financial statements as of that date.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION

2020 Equity Incentive Plan

In October 2020, the Company adopted its 2020 Equity Incentive Plan (the 2020 Plan) which replaced the 2017 Equity Incentive Plan (Prior Plan) upon completion of the IPO. The 2020 Plan provides for the grant of incentive stock options or nonqualified stock options, stock appreciation rights, restricted stock awards (“RSA”), restricted stock units (“RSU”), performance awards and other forms of awards to employees, directors, and consultants of the Company. The number of shares of common stock reserved for issuance under the 2020 Plan will automatically increase each year for a period of ten years, beginning in 2021 and continuing through 2030, in an amount equal to (1) 5.0% of the total number of shares of the Company’s common stock outstanding on December 31 of the immediately preceding year, or (2) a lesser number of shares determined by the Board of Directors no later than December 31 of the immediately preceding year. As of March 31, 2024, the maximum number of shares of common stock that may be issued was 23,364,521 shares.

The Company recognizes the impact of forfeitures on stock-based compensation expense as forfeitures occur. The Company applies the straight-line method of expense recognition to all awards with only service-based vesting conditions. Options shall not have an exercise price less than 100% of the fair market value of the Company’s common stock on the grant date. Vesting periods are determined at the discretion of the Board of Directors. Stock options typically vest over four years. The maximum contractual term is 10 years.

As of March 31, 2024, there were 6,528,388 shares reserved by the Company under the 2020 Plan for the future issuance of equity awards.

Stock Options

Stock option activity under the 2020 Plan as of March 31, 2024 is summarized as follows:


	Number of Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term	Aggregate Intrinsic Value
	(in thousands)			(in years)	(in thousands)
Balance, December 31, 2023	8,253	$	8.92	6.74	$	19
Granted	1,928	1.08
Forfeited	(1,153)	9.53
Exercised	(56)	3.74
Balance, March 31, 2024	8,972	$	7.19	7.86	$	426

The aggregate intrinsic values of options outstanding was calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock on the Nasdaq Global Select Market on March 31, 2024. There was no future tax benefit related to options exercised, as the Company had accumulated net operating losses as of March 31, 2024 and December 31, 2023.

The weighted-average grant-date fair value per share of stock options granted, using the Black–Scholes option pricing model, was $0.77 during the three months ended March 31, 2024.

As of March 31, 2024, there was $9.3 million of unrecognized stock-based compensation related to stock options, respectively, which is expected to be recognized over a weighted-average period of 2.07 years.

Restricted Stock

Restricted stock awards and restricted stock units as of March 31, 2024 are summarized as follows:


	Number of Restricted Stock	Weighted-Average Grant Date Fair Value		Weighted-Average Remaining Vesting Life
	(in thousands)			(in years)
Unvested, December 31, 2023	1,657	$	3.76	1.92
Granted	1,089	1.08
Vested and converted to shares	(1,087)	4.03
Forfeited	(208)	2.05
Unvested, March 31, 2024	1,451	$	1.79	2.38

As of March 31, 2024, there was $2.3 million of unrecognized stock-based compensation related to RSUs, which is expected to be recognized over a weighted average remaining vesting life.

As of March 31, 2024, all RSA were fully vested.

2020 Employee Stock Purchase Plan

In October 2020, the Company adopted its 2020 Employee Stock Purchase Plan (ESPP), which initially reserved 688,000 shares of the Company’s common stock for employee purchase under terms and provisions established by the Board of Directors. The number of shares of our common stock reserved for issuance under the ESPP automatically increased in 2021 and continues to increase through 2030, by the lesser of (i) 1.0% of the total number of shares of common stock outstanding on December 31 of the immediately preceding year, and (ii) 1,376,000 shares, except before the date of any increase, the Board of Directors may determine that such increase will be less than the amount set forth in clauses (i) and (ii). The Company did not issue any shares of common stock during both the three months ended March 31, 2024 and 2023. The Company has 2,190,659 shares reserved for future issuance as of March 31, 2024.

Stock-Based Compensation Summary


	Three months ended March 31,
	2024		2023
Research and development expense	$	1,163	$	3,112
General and administrative expense	2,164		3,495
Restructuring costs	4,379		$	—
Total stock-based compensation expense	$	7,706	$	6,607

Commitments and Contingencies - Schedule of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 1,429	$ 1,278
Research and development
Lessee, Lease, Description [Line Items]
Operating lease cost	880	767
General and administrative
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 549	$ 511

Investments

3 Months Ended

Mar. 31, 2024

Investments, Debt and Equity Securities [Abstract]

INVESTMENTS

The fair value and amortized cost of available-for-sale securities by major security type as of March 31, 2024 and December 31, 2023 were as follows (in thousands):


	March 31, 2024
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Money market funds	$	30,590	$	—	$	—	$	30,590
Certificates of deposit	490		—		(1)		489
Corporate bonds	19,605		—		(22)		19,583
U.S. treasury securities	92,482		4		(30)		92,456
Total cash equivalents and investments	$	143,167	$	4	$	(53)	$	143,118


	December 31, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Money market funds	$	36,009	$	—	$	—	$	36,009
Certificates of deposit	735		—		(2)		733
Corporate bonds	3,662		—		—		3,662
U.S. treasury securities	126,345		74		(53)		126,366
Total cash equivalents and investments	$	166,751	$	74	$	(55)	$	166,770

These available-for-sale securities were classified on the Company’s condensed balance sheets as of March 31, 2024 and December 31, 2023 as (in thousands):


	Fair Value
	March 31, 2024		December 31, 2023
Cash equivalents	$	37,331	$	56,110
Short-term investments	105,787		108,671
Long-term investments	—		1,989
Total cash equivalents and investments	$	143,118	$	166,770

The fair values of available-for-sale securities, excluding money market funds, by contractual maturity as of March 31, 2024 were as follows (in thousands):


	March 31, 2024
Due in 1 year or less	$	112,528
Due in 1 to 2 years	—

Total	$	112,528

As of March 31, 2024 and December 31, 2023, there have been no realized losses on available-for-sale securities for any of the periods presented in the accompanying condensed financial statements. As of March 31, 2024 and December 31, 2023, securities with a fair value of $0.5 million and zero, respectively, were in a continuous net unrealized loss position of $1,193 and zero, respectively, for more than 12 months. Unrealized losses on available-for-sale securities are not attributed to credit risk for any of the periods presented. The Company believes that it is more likely than not that investments in an unrealized loss position will be held until maturity and all interest and principal will be received. The Company believes that an allowance for credit losses is unnecessary because the unrealized losses on certain of the Company’s available-for-sale securities are due to market factors. To date, the Company has not recorded any impairment charges on available-for-sale securities.

Commitment and Contingencies (Tables)

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Schedule of Assets and Liabilities, Operating Leases, Lessee

The following table summarizes the presentation of the Company’s operating leases in its balance sheets as of March 31, 2024 and December 31, 2023 (in thousands):


	March 31, 2024		December 31, 2023
Assets:
Operating lease assets	$	13,902	$	19,657
Liabilities:
Current portion of operating lease liabilities	$	3,017	$	2,893
Noncurrent operating lease liabilities	24,457		25,379
Total operating lease liabilities	$	27,474	$	28,272

Schedule of Lease Costs


	Three months ended March 31,
	2024		2023
Research and development	$	880	$	767
General and administrative	549		511
Total operating lease cost	$	1,429	$	1,278

Schedule of Maturities on Lease Liabilities

The undiscounted future non-cancellable lease payments under the Company's operating leases as of March 31, 2024 for the next five years and thereafter is expected to be as follows (in thousands):


	Amount
Remaining nine months of 2024	$	3,852
2025	5,921
2026	5,405
2027	4,874
2028	5,020
Thereafter	11,404
Total undiscounted lease payments	36,476
Less: Present value adjustment	(9,002)
Present value of operating lease liabilities	$	27,474

Cover Page - shares	3 Months Ended
Cover Page - shares	Mar. 31, 2024	May 03, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
Document Transition Report	false
Entity File Number	001-39592
Entity Registrant Name	Kronos Bio, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-1895605
Entity Address, Address Line One	1300 So. El Camino Real
Entity Address, Address Line Two	Suite 400
Entity Address, City or Town	San Mateo
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94402
City Area Code	650
Local Phone Number	781-5200
Title of 12(b) Security	Common stock, $0.001 par value per share
Trading Symbol	KRON
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		60,094,409
Entity Central Index Key	0001741830
Current Fiscal Year End Date	--12-31
Document Fiscal Year End	2024
Document Fiscal Period Focus	Q1
Amendment Flag	false

Stock-Based Compensation - Schedule of Total Stock-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7,706	$ 6,607
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,163	3,112
General and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2,164	3,495
Restructuring costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4,379	$ 0

- 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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-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

+ Details

Net Loss Per Share - Schedule of Net Loss Per Share, Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Earnings Per Share [Abstract]
Net loss	$ (29,958)	$ (26,238)
Weighted-average common stock outstanding, basic (in shares)	59,521	57,147
Weighted-average common stock outstanding, diluted (in shares)	59,521	57,147
Net loss per share, basic (in dollars per share)	$ (0.50)	$ (0.46)
Net loss per share, diluted (in dollars per share)	$ (0.50)	$ (0.46)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

- Definition

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

+ References

+ Details

Stock-Based Compensation - Schedule of Nonvested Share Activity (Details) - Restricted Stock And Restricted Stock Units - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Number of Restricted Stock
Unvested Beginning Balance (in shares)	1,657,000
Granted (in shares)	1,089,000
Vested and converted to shares (in shares)	(1,087,000)
Forfeited (in shares)	(208,000)
Unvested Ending Balance (in shares)	1,451,000	1,657,000
Weighted-Average Grant Date Fair Value
Unvested Beginning Balance (in dollars per share)	$ 3.76
Granted (in dollars per share)	1.08
Vested and converted to shares (in dollars per share)	4.03
Forfeited (in dollars per share)	2.05
Unvested Ending Balance (in dollars per share)	$ 1.79	$ 3.76
Restricted Stock Awards, Additional Disclosures
Weighted-Average Remaining Vesting Life	2 years 4 months 17 days	1 year 11 months 1 day

Income Taxes (Details) - USD ($)	3 Months Ended
Income Taxes (Details) - USD ($)	Mar. 31, 2024	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Income tax expense	$ 0	$ 0
Interest on income taxes expense	0	0
Income tax penalties expense	$ 0	$ 0

- Definition

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

+ References + Details

Balance Sheet Components - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Impairment of long-lived assets, related leasehold improvements	$ 1,600,000	$ 0

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - 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 (in shares)	11,282	13,219
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	8,972	9,031
Early exercised stock options subject to future vesting
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	0	222
Restricted stock awards subject to future vesting
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	0	46
Restricted stock units subject to future vesting
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	1,451	2,844
Expected shares to be purchased under Employee Stock Purchase Plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	858	1,076