Rallybio (RLYB) 10-Q 10 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 08, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Entity Central Index Key	0001739410
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Document Period End Date	Sep. 30, 2021
Current Fiscal Year End Date	--12-31
Entity File Number	001-40693
Entity Registrant Name	RALLYBIO CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	85-1083789
Entity Address, Address Line One	234 Church Street
Entity Address, Address Line Two	Suite 1020
Entity Address, City or Town	New Haven
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06510
City Area Code	203
Local Phone Number	859-3820
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	RLYB
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Document Transition Report	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Bankruptcy Proceedings, Reporting Current	true
Entity Common Stock, Shares Outstanding		32,129,970

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 186,978	$ 140,233
Prepaid expenses and other assets	5,414	1,028
Total current assets	192,392	141,261
Property and equipment, net	445	287
Investment in joint venture	1,028	310
Total assets	193,865	141,858
Current liabilities:
Accounts payable	2,599	1,579
Accrued expenses	4,745	4,264
Total current liabilities	7,344	5,843
Accrued expenses long-term	35	12
Total liabilities	7,379	5,855
Commitments and contingencies (Note 7)
Stockholders' equity
Common stock, value	3	2
Preferred stock, value		0
Additional paid-in capital	268,095	183,015
Accumulated deficit	(81,612)	(47,014)
Total stockholders' equity	186,486	136,003
Total liabilities and stockholders' equity	$ 193,865	$ 141,858

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheet (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Common stock, par value	$ 0.0001	$ 0.0001
Common Stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	32,129,970	23,410,348
Common stock, shares outstanding	32,129,970	23,410,348
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred Stock, Shares Issued	0	0
Preferred stock, shares outstanding	0	0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating expenses:
Research and development	$ 4,960	$ 5,130	$ 20,815	$ 10,135
General and administrative	5,021	1,580	12,520	5,081
Total operating expenses	9,981	6,710	33,335	15,216
Loss from operations	(9,981)	(6,710)	(33,335)	(15,216)
Other income (expenses):
Interest income	12	42	42	144
Interest expense	0	13	10	37
Other income (expense)	105	52	(13)	173
Total other income, net	117	81	19	280
Loss before income taxes	(9,864)	(6,629)	(33,316)	(14,936)
Income tax benefit	0	0	0	(16)
Loss on investment in joint venture	332	526	1,282	1,009
Net loss and comprehensive loss	$ (10,196)	$ (7,155)	$ (34,598)	$ (15,929)
Net loss per common share, basic and diluted	$ (0.37)	$ (0.32)	$ (1.44)	$ (1.01)
Weighted average common shares outstanding, basic and diluted	27,527,770	22,142,148	24,011,862	15,772,918

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	IPO	Common Shares	Common SharesIPO	Additional Paid-In Capital	Additional Paid-In CapitalIPO	Accumulated Deficit	Accumulated DeficitIPO
Beginning Balance at Dec. 31, 2019	$ 16,859		$ 1		$ 37,425		$ (20,567)
Beginning Balance (in shares) at Dec. 31, 2019			6,363,455
Issuance of common stock, net of offering costs (in shares)			16,402,235
Issuance of common stock, net of offering costs	144,886		$ 1		144,885
Issuance of restricted common stock			620,161
Share-based compensation expense	475				475
Net loss and comprehensive loss	(15,929)						(15,929)
Ending Balance (in shares) at Sep. 30, 2020			23,385,851
Ending Balance at Sep. 30, 2020	146,291		$ 2		182,785		(36,496)
Beginning Balance at Jun. 30, 2020	153,171		$ 2		182,510		(29,341)
Beginning Balance (in shares) at Jun. 30, 2020			22,793,410
Issuance of restricted common stock			592,441
Share-based compensation expense	275				275
Net loss and comprehensive loss	(7,155)						(7,155)
Ending Balance (in shares) at Sep. 30, 2020			23,385,851
Ending Balance at Sep. 30, 2020	146,291		$ 2		182,785		(36,496)
Beginning Balance at Dec. 31, 2020	136,001		$ 2		183,013		(47,014)
Beginning Balance (in shares) at Dec. 31, 2020			23,410,348
Issuance of common stock, net of offering costs (in shares)				7,130,000
Issuance of common stock, net of offering costs		$ 82,967		$ 1		$ 82,966
Issuance of restricted common stock			1,589,622
Share-based compensation expense	2,116				2,116
Net loss and comprehensive loss	(34,598)		$ (34,598)				(34,598)
Ending Balance (in shares) at Sep. 30, 2021			32,129,970
Ending Balance at Sep. 30, 2021	186,486		$ 3		268,095		(81,612)
Beginning Balance at Jun. 30, 2021	112,660		$ 2		184,074		(71,416)
Beginning Balance (in shares) at Jun. 30, 2021			24,999,970
Issuance of common stock, net of offering costs (in shares)				7,130,000
Issuance of common stock, net of offering costs		$ 82,967		$ 1		$ 82,966		$ 0
Share-based compensation expense	1,055				1,055
Net loss and comprehensive loss	(10,196)						(10,196)
Ending Balance (in shares) at Sep. 30, 2021			32,129,970
Ending Balance at Sep. 30, 2021	$ 186,486		$ 3		$ 268,095		$ (81,612)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Offering costs			$ 319
IPO
Offering costs	$ 9,721	$ 9,721

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash Flows from Operating Activities:
Net loss	$ (34,598)	$ (15,929)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	74	42
Stock-based compensation	2,116	475
Loss on investment in joint venture	1,282	1,009
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(4,386)	(75)
Accounts payable	(607)	(109)
Accrued expenses	472	(191)
Net cash used in operating activities	(35,647)	(14,778)
Cash Flows used in Investing Activities:
Purchase of property and equipment	(196)	(31)
Investment in joint venture	(2,000)	(1,585)
Net cash used in investing activities	(2,196)	(1,616)
Cash Flows from Financing Activities:
Proceeds from the issuance of common stock upon completion of the initial public offering, net of underwriting commissions and discounts of $6,488	86,200	0
Proceeds from issuance of common stock	0	145,205
Payments of offering costs	(1,612)	(309)
Net cash provided by financing activities	84,588	144,896
Net increase in cash and cash equivalents	46,745	128,502
Cash and cash equivalents - beginning of period	140,233	19,458
Cash and cash equivalents - end of period	186,978	147,960
Supplemental Disclosures of Noncash Investing and Financing Activities:
Offering costs in accounts payable and accrued expenses	1,621	10
Property and equipment in accounts payable and accrued expenses	$ 36	$ 6

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Statement of Cash Flows [Abstract]
Underwriting commissions and discounts	$ 6,488

Business and Liquidity

Business and Liquidity	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Liquidity	1. BUSINESS AND LIQUIDITY Rallybio Corporation and subsidiaries (the "Company", "we", "our", or "us") is a clinical-stage biotechnology company built around a team of seasoned industry experts with a shared purpose and a track record of success in discovering, developing, manufacturing, and delivering therapies to meaningfully improve the lives of patients suffering from severe and rare diseases. In August 2021, the Company completed its initial public offering (“IPO”), pursuant to which it issued and sold 7,130,000 shares of the Company’s common stock, inclusive of 930,000 shares sold pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $ 13.00 per share. The gross proceeds from the IPO, including the exercise of the underwriter's option to purchase additional shares were $ 92.7 million and the net proceeds were approximately $ 83.0 million, after deducting underwriting discounts and commissions and other offering costs. Prior to the IPO, the Company was a 100% owned subsidiary of Rallybio Holdings, LLC ("Rallybio Holdings"), a Delaware limited liability company which was incorporated in Delaware on March 22, 2018 and Rallybio Holdings held 100% of the outstanding membership units in five wholly-owned subsidiaries; Rallybio, LLC, Rallybio IPA, LLC, Rallybio IPB, LLC, Rallybio IPD, LLC, and IPC Research, LLC prior to the IPO and it's liquidation . On June 30, 2021, Rallybio Holdings completed a series of transactions pursuant to which (i) Rallybio IPD, LLC, a direct subsidiary of Rallybio Holdings that was formed in Delaware in May 2020, was converted from a Delaware limited liability company to a Delaware corporation and changed its name to Rallybio Corporation, and (ii) four direct subsidiaries of Rallybio Corporation, each a Delaware limited liability company (collectively the "Merger Subs"), each consummated a separate merger with one of Rallybio Holdings direct subsidiaries, other than Rallybio IPD, LLC (collectively the "Asset Subsidiaries"), with the Asset Subsidiaries surviving the mergers and Rallybio Holdings receiving common stock of the Company in exchange for its interest in each Asset Subsidiary, which resulted in the Asset Subsidiaries becoming subsidiaries of the Company and the Company becoming the only direct subsidiary of Rallybio Holdings. On July 28, 2021, immediately prior to the completion of the IPO, Rallybio Holdings liquidated and distributed 100% of the capital stock of the Company, consisting solely of common stock, to the unitholders of Rallybio Holdings. The liquidation of Rallybio Holdings and distribution of the capital stock of Rallybio Corporation to the unitholders of Rallybio Holdings is referred to as the “Liquidation” and these other transactions are collectively referred to as the “Reorganization.” As a result of the Reorganization and subsequent Liquidation, the unitholders of Rallybio Holdings became the holders of common stock of Rallybio Corporation, and the Company's condensed consolidated financial statements are subsequently reported from Rallybio Corporation. See Note 2 for the basis of presentation of these financial statements after the Reorganization and Liquidation discussed herein. The Company had cash and cash equivalents of $ 187.0 million at September 30, 2021. The Company currently expects that its cash and cash equivalents will be sufficient to fund its operating expenses and capital requirements for more than 12 months from the date the condensed consolidated financial statements are issued. However, w e do not anticipate that the current cash and cash equivalents as of September 30, 2021 will be sufficient for us to fund any of our product candidates through regulatory approval, and we will need to raise substantial additional capital to complete the development and commercialization of our product candidates, if approved. We may satisfy our future cash needs through the sale of equity securities, debt financings, working capital lines of credit, corporate collaborations or license agreements, grant funding, interest income earned on invested cash balances or a combination of one or more of these sources. In March 2020, the World Health Organization characterized the novel coronavirus as a global pandemic. Although there is significant uncertainty as to the likely effects this disease may have in the future, to date there has not yet been a significant impact to the Company’s operations or financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION IPO and Reorganization — As discussed in Note 1 , in connection with the Reorganization, all of Rallybio Holdings' direct subsidiaries, other than Rallybio Corporation, became direct subsidiaries of the Company prior to the Liquidation of Rallybio Holdings. Prior to the completion of the Company's IPO, Rallybio Holdings liquidated and unitholders of Rallybio Holdings became the holders of common stock of Rallybio Corporation. Subsequent to the Reorganization and the Liquidation of Rallybio Holdings the condensed consolidated financial statements are reported from Rallybio Corporation. The capital structure of Rallybio Holdings prior to the Liquidation consisted of four classes of membership units: common units; Series A-1 preferred units; Series A-2 preferred units; Series B preferred units; and incentive common units ("incentive units"). The number of shares of common stock that the holders of each class of units received in the Liquidation was based on the value of Rallybio Holdings prior to the Liquidation, determined by reference to the initial public offering price per share of $ 13.00 . The common stock of the Company was allocated to the holders of existing units in Rallybio Holdings as follows:  holders of 33,478,255 Series A-1 preferred units and Series A-2 preferred units of Rallybio Holdings received an aggregate of 5,257,590 shares of common stock of the Company;  holders of 104,442,965 Series B preferred units of Rallybio Holdings received an aggregate of 16,402,235 shares of common stock of the Company;  holders of 4,500,000 common units and 1,200,000 of performance based incentive common units of Rallybio Holdings received an aggregate of 706,701 and 188,454 , respectively, in shares of common stock of the Company. Shares of common stock issued in respect of unvested common units and performance based incentive common units as of the Liquidation are shares of restricted common stock and subject to vesting in accordance with the vesting schedule applicable to such units; and  holders of 20,869,704 incentive units in Rallybio Holdings received an aggregate of 2,444,990 shares of common stock of the Company. Shares of common stock issued in respect of unvested incentive units as of the Liquidation are shares of restricted common stock and continue to be subject to vesting in accordance with the vesting schedule applicable to such incentive units. As a result of the Liquidation, the holders of units in Rallybio Holdings collectively were issued an aggregate of 24,999,970 shares of common stock of the Company prior to the completion of the IPO. The Reorganization and subsequent Liquidation resulted in a change in reporting entity as described in ASC 250. In accordance with the guidance applicable to these circumstances, the equity structure has been adjusted in all comparative periods up to the Liquidation to reflect the number of shares of the Company’s common stock, issued to Rallybio Holdings unitholders' in connection with the Liquidation. As such, historical Rallybio Holdings convertible redeemable preferred units, common units, and incentive units have been retroactively adjusted in these financial statements to shares and earnings per share in accordance with the ratio of common shares received by each membership unit class. Rallybio Holdings' convertible redeemable preferred units previously classified as mezzanine equity have been retroactively adjusted in these financial statements, converted into common stock, and reclassified to permanent as a result of the retrospective application of the Liquidation and change in reporting entity. Unaudited Financial Information — The unaudited condensed consolidated financial statements of the Company have been prepared in conformity with accounting principles generally accepted in the United States of America ("GAAP"), and pursuant to the rules and regulations of the Securities and Exchange Commission (the "SEC"). In the opinion of the Company, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the financial position and results of operations for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. The Company reviews new accounting standards as issued. As of September 30, 2021 the Company has not identified any new standards that it believes will have a significant impact on the financial statements of the Company. However, the Company is still evaluating the impact of adopting ASU 20 16- 02, Leases on its condensed consolidated financial statements. There were no changes to significant accounting policies of the Company during the nine months ended September 30, 2021 other than noted below. These accompanying unaudited condensed consolidated financial statements and notes should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2020 and notes thereto contained in the Company’s final prospectus for its IPO filed with the SEC on July 30, 2021 pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the “IPO Prospectus”) . Deferred Offering Costs — The Company capitalizes incremental legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such equity financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders' equity as a reduction of additional paid-in-capital generated as a result of the offering. Should the planned equity financing no longer be considered probable of being consummated, the offering costs are expensed immediately as a charge to operating expense. Upon completion of the Company's IPO in the third quarter of 2021, $ 3.2 million of deferred offering costs were charged against additional paid-in-capital. As a result, as of September 30, 2021 , the Company did no t have any deferred offering costs.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2021
Accrued Liabilities, Current [Abstract]
Accrued Expenses	3. ACCRUED EXPENSES Accrued expenses consisted of the following as of September 30, 2021 and December 31, 2020: (in thousands) SEPTEMBER 30, DECEMBER 31, Research and development $ 1,981 $ 1,065 Employee expenses 2,097 1,912 Professional fees 364 185 Other 303 112 Asset purchase obligation — 990 $ 4,745 $ 4,264

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2021
Stockholders' Equity Note [Abstract]
Stockholders' Equity	4. STOCKHOLDERS' EQUITY Following the closing of the Company's IPO, the Company's authorized capital stock consists of 200,000,000 shares of common stock, with a par value of $ 0.0001 per share, and 50,000,000 shares of preferred stock, with a par value of $ 0.0001 per share, all of which preferred stock are undesignated. See Note 2 for a summary of the Reorganization and Liquidation of Rallybio Holdings that was completed prior to the Company's IPO, which resulted in a change in reporting entity. In accordance with the applicable accounting guidance related to changes in reporting entities, the financial statements for all periods presented have been retrospectively adjusted giving effect to the Reorganization and Liquidation as applicable to all periods presented. All preferred unit financing activity prior to the completion of the Company's IPO has been retrospectively adjusted in these financial statements to reflect the shares in Rallybio Corporation that were obtained in the Liquidation. For additional information on preferred unit financing prior to the Company's IPO and the Liquidation of Rallybio Holdings see the Company's audited consolidated financial statements for the year ended December 31, 2020 and notes thereto contained in the Company’s IPO Prospectus. During the nine months ended September 30, 2020, the Company entered into a Series B Preferred Stock Agreement with a total aggregate purchase price of $ 145.2 million which has been retrospectively adjusted to reflect the shares of common stock obtained during the Reorganization and Liquidation of Rallybio Holdings, see Note 2 .

Share-based Compensation

Share-based Compensation	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Share-based Compensation	5. SHARE-BASED COMPENSATION As discussed in Note 2 of these condensed consolidated financial statements, prior to the Company’s IPO, Rallybio Holdings was Liquidated and as a result of the Liquidation, the unitholders of Rallybio Holdings received 100% of the common stock of the Company outstanding prior to the completion of the IPO. The number of shares of common stock that the holders of each class of units received in the Liquidation was based on the value of Rallybio Holdings prior to the Liquidation, determined by the initial public offering price per share of $ 13.00 . Additionally, any shares of common stock issued in respect of unvested common or incentive units were issued as shares of restricted common stock and continue to be subject to vesting in accordance with the vesting schedule applicable to the initial awards. The Company evaluated the liquidation of Rallybio Holdings units and subsequent issuance of common stock awards of the Company as a modification under ASC 718, Share Based Payments. Under ASC 718, a modification is a change in the terms or conditions of a stock-based compensation award. In assessing the modification, the Company considered the fair value, vesting conditions and classification as an equity or liability award before liquidation and replacement, compared to the Company’s common stock received as of the Liquidation to determine whether modification accounting must be applied. As the number of shares of common stock of the Company that the unitholders of Rallybio Holdings received in the Liquidation was based on the fair value of those units in Rallybio Holdings immediately prior to the Liquidation, unvested units were replaced with restricted common shares with the same vesting terms as the initial awards, and the classification of the awards as equity awards did not change from this action, no incremental stock-based compensation expense resulted from the modification. 2021 Equity Incentive Plan — In connection with the Company's IPO, the board of directors adopted the Rallybio Corporation 2021 Equity Incentive Plan (the "2021 Plan"). The 2021 Plan reserves 5,440,344 shares of common stock for future issuances of shares to employees, directors and consultants in the form of stock options, SARs, restricted and unrestricted stock and stock units, performance awards and other awards that are convertible into or otherwise based on the Company's common stock. Dividend equivalents may also be provided in connection with awards under the 2021 Plan. The share pool will automatically incr ease on January 1st of each year from 2022 to 2031 by the lesser of (i) five percent of the number of shares of the Company's common stock outstanding as of such date and (ii) the number of shares of the Company's common stock determined by the board of directors on or prior to such date. Additionally, in connection with the Company's IPO, the board of directors adopted the 2021 Employee Stock Purchase Plan, ("ESPP"), which reserves 291,324 shares of common stock for future issuances under this plan. Restricted Common Shares — In 2018, founders were issued 706,701 common shares, including 530,027 common shares that were to vest over a four year period. In 2018, founders were also issued 188,454 restricted common shares, pursuant to restricted share agreements, which were to begin vesting upon achievement of certain performance conditions. Restricted common shares issued to the founders were to vest 25% upon the one-year anniversary of the initiation of a clinical program through one of its controlled subsidiaries, and monthly thereafter over the next 36 months. In 2019, it was determined that the performance condition of these restricted common shares became probable, vesting started, and the shares started expensing over the vesting period. The weighted average fair value of both the 530,027 and 188,454 restricted common shares granted during 2018 was $ 0.96 per share. During the nine months ended September 30, 2021, the Company granted 1,589,622 restricted common shares to employees. The weighted average fair value of restricted common shares granted to employees for the nine months ended September 30, 2021 was $ 3.65 per share. No grants of restricted common shares were made during the three months ended September 30, 2021. The restricted common shares that were granted during the nine months ended September 30, 2021 resulted from the Liquidation of profit interest incentive units of Rallybio Holdings that were granted during the nine months ended September 30, 2021, see Note 2 . The assumptions that went into the option pricing models for determining the fair value of Rallybio Holdings incentive units granted during the nine months ended September 30, 2021 and 2020, prior to the Liquidation of Rallybio Holdings are as follows and do not include the retrospective adjustments described in Note 2 : NINE MONTHS ENDED 2021 2020 Expected volatility 71.7 % - 99.5 % 95.0 % Expected term (years) 0.58 - 1.00 1.50 Risk free interest rate 0.04 % - 0.10 % 0.16 % Expected dividend yield — — A summary of the status of our nonvested restricted common stock at September 30, 2021 and changes during the nine months ended September 30, 2021 is as follows: Restricted Shares Nonvested restricted stock at December 31, 2020 1,184,252 Shares granted 1,589,622 Shares vested ( 365,520 ) Outstanding nonvested restricted stock at September 30, 2021 2,408,354 — During the three months ended September 30, 2021, the Company granted 1,232,759 non-qualified stock options to employees and directors. Non-employee directors were granted 80,640 stock options on the date of the IPO that vest on the earlier of the one-year anniversary of the date of grant or the next annual meeting of the Company's stockholders that follows the date of grant, subject to the director’s continued service on our board of directors through the vesting date at a grant date fair value of $ 9.15 per share. Executive officers and the Company's Chief Medical Officer were granted 640,000 stock options on the date of the IPO that vest 25 % on the one-year anniversary of the date of grant, and monthly thereafter over the next 36 months , generally subject to the employee’s continued service through the applicable vesting date at a grant date fair value of $ 9.47 per share. The remaining option grants for the three months ended September 30, 2021 vest over four years and relate to new hires and service award grants and were granted at a grant date fair value of $ 9.34 per share. All options granted during the three months ended September 30, 2021 remain unvested and all are expected to vest. The fair value of the stock options granted during the three months ended September 30, 2021 was determined using the Black-Scholes option pricing model with the following assumptions: THREE MONTHS ENDED 2021 Expected volatility 87.76 % - 87.87 % Expected term (years) 5.50 - 6.08 Risk free interest rate 0.79 % - 0.97 % Expected dividend yield — Exercise price 12.80 - 13.00 Given the Company’s common stock has not been trading for a sufficient period of time, the Company utilizes a collection of volatilities of peer companies to estimate the expected volatility of its common stock. The expected term is calculated utilizing the simplified method. Share-based compensation is classified in the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2021 and 2020 as follows: THREE MONTHS ENDED NINE MONTHS ENDED (in thousands) 2021 2020 2021 2020 Research and development $ 266 $ 47 $ 620 $ 107 General and administrative 789 228 1,496 368 $ 1,055 $ 275 $ 2,116 $ 475

Investment In Joint Venture

Investment In Joint Venture	9 Months Ended
	Sep. 30, 2021
Equity Method Investments and Joint Ventures [Abstract]
INVESTMENT IN JOINT VENTURE	6. INVESTMENT IN JOINT VENTURE The Company, through one of its wholly-owned subsidiaries, has a 50 % interest of the joint venture entity, RE Ventures I, LLC, a limited liability company (“REV-I”). For the nine months ended September 30, 2021 , the Company funded $ 2.0 million, associated with development costs to REV-I. For the nine months ended September 30, 2020 , the Company funded $ 1.6 million, associated with development costs, including $ 0.6 million related to the initial investment in REV-I, that was included in accrued expenses on the consolidated balance sheets as of December 31, 2019. The Company did not provide any additional financial support outside of capital contributions to REV-I during the three and nine months ended September 30, 2021 and 2020. The Company held a 50% interest in the joint venture as of September 30, 2021. As of September 30, 2021, based on management’s analysis, the Company is not the primary beneficiary of REV-1 and accordingly, the entity is not consolidated in the Company's financial statements. During the three months ended September 30, 2021 and 2020 , the Company recorded its allocable share of REV-I’s losses, which totaled $ 0.3 million and $ 0.5 million, respectively and $ 1.3 million and $ 1.0 million during the nine months ended September 30, 2021 and 2020, respectively, as a loss on investment in joint venture within the condensed consolidated statements of operations and comprehensive loss. After recognition of its share of losses for the period, the carrying value and maximum exposure to risk of the REV-I investment as of September 30, 2021 and December 31, 2020 , was $ 1.0 million and $ 0.3 million, respectively, which was recorded in investment in joint venture in the accompanying condensed consolidated balance sheets.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. COMMITMENTS AND CONTINGENCIES Purchase Commitments —The Company enters contracts in the normal course of business with contract research organizations and other third-party vendors for clinical trials and testing and manufacturing services. These contracts generally do not contain minimum purchase commitments and are cancellable by us upon written notice. Payments that may be due upon cancellation consist of payments for services provided or expenses incurred prior to cancellation. As of September 30, 2021 and December 31, 2020 there were no amounts accrued related to termination charges. There have been no significant changes to the disclosure of payments we have committed to make under our contractual obligations as summarized in our audited consolidated financial statements and related notes included in the IPO Prospectus.

Net Loss Per Common Share

Net Loss Per Common Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Common Share	8. NET LOSS PER COMMON SHARE Basic and diluted loss per common share were calculated as follows: THREE MONTHS ENDED NINE MONTHS ENDED 2021 2020 2021 2020 Net loss $ ( 10,196 ) $ ( 7,155 ) $ ( 34,598 ) $ ( 15,929 ) Weighted average number of common shares 27,527,770 22,142,148 24,011,862 15,772,918 Net loss per common share, basic and diluted $ ( 0.37 ) $ ( 0.32 ) $ ( 1.44 ) $ ( 1.01 ) The weighted average number of common shares outstanding diluted for the three and nine months ended September 30, 2021 excludes approximately 3.6 million stock options and unvested restricted common shares, which were not dilutive and not included in the computation of net loss per common share. The weighted average number of common shares outstanding diluted for the three and nine months ended September 30, 2020 excludes approximately 1.0 million unvested restricted common shares, which were not dilutive and not included in the computation of net loss per common share.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
IPO and Reorganization	IPO and Reorganization — As discussed in Note 1 , in connection with the Reorganization, all of Rallybio Holdings' direct subsidiaries, other than Rallybio Corporation, became direct subsidiaries of the Company prior to the Liquidation of Rallybio Holdings. Prior to the completion of the Company's IPO, Rallybio Holdings liquidated and unitholders of Rallybio Holdings became the holders of common stock of Rallybio Corporation. Subsequent to the Reorganization and the Liquidation of Rallybio Holdings the condensed consolidated financial statements are reported from Rallybio Corporation. The capital structure of Rallybio Holdings prior to the Liquidation consisted of four classes of membership units: common units; Series A-1 preferred units; Series A-2 preferred units; Series B preferred units; and incentive common units ("incentive units"). The number of shares of common stock that the holders of each class of units received in the Liquidation was based on the value of Rallybio Holdings prior to the Liquidation, determined by reference to the initial public offering price per share of $ 13.00 . The common stock of the Company was allocated to the holders of existing units in Rallybio Holdings as follows:  holders of 33,478,255 Series A-1 preferred units and Series A-2 preferred units of Rallybio Holdings received an aggregate of 5,257,590 shares of common stock of the Company;  holders of 104,442,965 Series B preferred units of Rallybio Holdings received an aggregate of 16,402,235 shares of common stock of the Company;  holders of 4,500,000 common units and 1,200,000 of performance based incentive common units of Rallybio Holdings received an aggregate of 706,701 and 188,454 , respectively, in shares of common stock of the Company. Shares of common stock issued in respect of unvested common units and performance based incentive common units as of the Liquidation are shares of restricted common stock and subject to vesting in accordance with the vesting schedule applicable to such units; and  holders of 20,869,704 incentive units in Rallybio Holdings received an aggregate of 2,444,990 shares of common stock of the Company. Shares of common stock issued in respect of unvested incentive units as of the Liquidation are shares of restricted common stock and continue to be subject to vesting in accordance with the vesting schedule applicable to such incentive units. As a result of the Liquidation, the holders of units in Rallybio Holdings collectively were issued an aggregate of 24,999,970 shares of common stock of the Company prior to the completion of the IPO. The Reorganization and subsequent Liquidation resulted in a change in reporting entity as described in ASC 250. In accordance with the guidance applicable to these circumstances, the equity structure has been adjusted in all comparative periods up to the Liquidation to reflect the number of shares of the Company’s common stock, issued to Rallybio Holdings unitholders' in connection with the Liquidation. As such, historical Rallybio Holdings convertible redeemable preferred units, common units, and incentive units have been retroactively adjusted in these financial statements to shares and earnings per share in accordance with the ratio of common shares received by each membership unit class. Rallybio Holdings' convertible redeemable preferred units previously classified as mezzanine equity have been retroactively adjusted in these financial statements, converted into common stock, and reclassified to permanent as a result of the retrospective application of the Liquidation and change in reporting entity.
Unaudited Financial Information	Unaudited Financial Information — The unaudited condensed consolidated financial statements of the Company have been prepared in conformity with accounting principles generally accepted in the United States of America ("GAAP"), and pursuant to the rules and regulations of the Securities and Exchange Commission (the "SEC"). In the opinion of the Company, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the financial position and results of operations for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. The Company reviews new accounting standards as issued. As of September 30, 2021 the Company has not identified any new standards that it believes will have a significant impact on the financial statements of the Company. However, the Company is still evaluating the impact of adopting ASU 20 16- 02, Leases on its condensed consolidated financial statements. There were no changes to significant accounting policies of the Company during the nine months ended September 30, 2021 other than noted below. These accompanying unaudited condensed consolidated financial statements and notes should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2020 and notes thereto contained in the Company’s final prospectus for its IPO filed with the SEC on July 30, 2021 pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended (the “IPO Prospectus”)
Deferred Offering Costs	Deferred Offering Costs — The Company capitalizes incremental legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such equity financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders' equity as a reduction of additional paid-in-capital generated as a result of the offering. Should the planned equity financing no longer be considered probable of being consummated, the offering costs are expensed immediately as a charge to operating expense. Upon completion of the Company's IPO in the third quarter of 2021, $ 3.2 million of deferred offering costs were charged against additional paid-in-capital. As a result, as of September 30, 2021 , the Company did no t have any deferred offering costs.

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2021
Accrued Liabilities, Current [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following as of September 30, 2021 and December 31, 2020: (in thousands) SEPTEMBER 30, DECEMBER 31, Research and development $ 1,981 $ 1,065 Employee expenses 2,097 1,912 Professional fees 364 185 Other 303 112 Asset purchase obligation — 990 $ 4,745 $ 4,264

Share-based Compensation (Table

Share-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Summary of Assumptions of Fair Value of Option Pricing Granted	The fair value of the stock options granted during the three months ended September 30, 2021 was determined using the Black-Scholes option pricing model with the following assumptions: THREE MONTHS ENDED 2021 Expected volatility 87.76 % - 87.87 % Expected term (years) 5.50 - 6.08 Risk free interest rate 0.79 % - 0.97 % Expected dividend yield — Exercise price 12.80 - 13.00
Summary of Nonvested Restricted Common Stock	A summary of the status of our nonvested restricted common stock at September 30, 2021 and changes during the nine months ended September 30, 2021 is as follows: Restricted Shares Nonvested restricted stock at December 31, 2020 1,184,252 Shares granted 1,589,622 Shares vested ( 365,520 ) Outstanding nonvested restricted stock at September 30, 2021 2,408,354
Summary of Equity-based Compensation	Share-based compensation is classified in the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2021 and 2020 as follows: THREE MONTHS ENDED NINE MONTHS ENDED (in thousands) 2021 2020 2021 2020 Research and development $ 266 $ 47 $ 620 $ 107 General and administrative 789 228 1,496 368 $ 1,055 $ 275 $ 2,116 $ 475
Restricted Shares
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Summary of Assumptions of Fair Value of Restricted Common Shares Pricing Granted	The assumptions that went into the option pricing models for determining the fair value of Rallybio Holdings incentive units granted during the nine months ended September 30, 2021 and 2020, prior to the Liquidation of Rallybio Holdings are as follows and do not include the retrospective adjustments described in Note 2 : NINE MONTHS ENDED 2021 2020 Expected volatility 71.7 % - 99.5 % 95.0 % Expected term (years) 0.58 - 1.00 1.50 Risk free interest rate 0.04 % - 0.10 % 0.16 % Expected dividend yield — —

Net Loss Per Common Share (Tabl

Net Loss Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Summary of Basic and Diluted Loss Per Common Share	Basic and diluted loss per common share were calculated as follows: THREE MONTHS ENDED NINE MONTHS ENDED 2021 2020 2021 2020 Net loss $ ( 10,196 ) $ ( 7,155 ) $ ( 34,598 ) $ ( 15,929 ) Weighted average number of common shares 27,527,770 22,142,148 24,011,862 15,772,918 Net loss per common share, basic and diluted $ ( 0.37 ) $ ( 0.32 ) $ ( 1.44 ) $ ( 1.01 )

Business and Liquidity - Additi

Business and Liquidity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended
	Aug. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash and cash equivalents		$ 186,978		$ 140,233
Proceeds from issuance of common stock		$ 0	$ 145,205
IPO
Stock issued during period, shares, new issues	7,130,000
Shares issued price per share	$ 13
Proceeds from issuance of common stock	$ 92,700
Net proceeds	$ 83,000
Over-Allotment Option [Member]
Stock issued during period, shares, new issues	930,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation (Additional Information) (Details) - USD ($)	1 Months Ended	9 Months Ended
	Aug. 31, 2021	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2018
Subsidiary, Sale of Stock [Line Items]
Common stock shares outstanding		32,129,970	23,410,348
Common stock, shares issued		32,129,970	23,410,348	706,701
Common stock, shares issued on liquidation		24,999,970
Deferred offering costs		$ 0
Common Stock Allocated to Series A-1 And Series A-2 Preferred Unit Holders [Member]
Subsidiary, Sale of Stock [Line Items]
Stock issued during period, shares, new issues		5,257,590
Common Stock Allocated To SeriesB Preferred Units Holders [Member]
Subsidiary, Sale of Stock [Line Items]
Stock issued during period, shares, new issues		16,402,235
Common Stock Allocated to Common Unit Holders [Member]
Subsidiary, Sale of Stock [Line Items]
Stock issued during period, shares, new issues		706,701
Common Stock Allocated To Performance Based Incentive Common Unit Holders Member
Subsidiary, Sale of Stock [Line Items]
Stock issued during period, shares, new issues		188,454
Common Stock Allocated To Incentive Units Holders [Member]
Subsidiary, Sale of Stock [Line Items]
Stock issued during period, shares, new issues		2,444,990
Additional Paid-In Capital [Member]
Subsidiary, Sale of Stock [Line Items]
Deferred offering costs		$ 3,200,000
IPO [Member]
Subsidiary, Sale of Stock [Line Items]
Shares issued price per share	$ 13
Stock issued during period, shares, new issues	7,130,000
Prior to IPO [Member] | Series A-1 and A-2 Redeemable Convertible Preferred Unit [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock shares outstanding		33,478,255
Prior to IPO [Member] | Series B Redeemable Convertible Preferred Unit [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock shares outstanding		104,442,965
Prior to IPO [Member] | Common Units [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock shares outstanding		4,500,000
Prior to IPO [Member] | Performance Based Incentive Common Units [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock shares outstanding		1,200,000
Prior to IPO [Member] | Incentive units [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock shares outstanding		20,869,704

Accrued Expenses - Schedule Of

Accrued Expenses - Schedule Of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accrued Liabilities, Current [Abstract]
Research and development	$ 1,981	$ 1,065
Employee expenses	2,097	1,912
Professional fees	364	185
Other	303	112
Asset purchase obligation	0	990
Accrued expenses	$ 4,745	$ 4,264

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common Stock, shares authorized		200,000,000	200,000,000
Common Stock, Par or Stated Value Per Share		$ 0.0001	$ 0.0001
Preferred Stock, Shares Authorized		50,000,000	50,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.0001	$ 0.0001
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Aggregate purchase price of common stock	$ 145.2
IPO [Member]
Class of Stock [Line Items]
Common Stock, shares authorized		200,000,000
Common Stock, Par or Stated Value Per Share		$ 0.0001
Preferred Stock, Shares Authorized		50,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.0001

Share-based Compensation - Addi

Share-based Compensation - Additional Information (Details) - $ / shares	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2018	Aug. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Shares, Issued	32,129,970	32,129,970	706,701		23,410,348
Vested Upon Initiation of Clinical Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Shares, Issued			530,027
Vesting period			4 years
Fair value of underlying shares			$ 0.96
2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for issuance	5,440,344	5,440,344
2021 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for issuance	291,324	291,324
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights			Restricted common shares issued to the founders were to vest 25% upon the one-year anniversary of the initiation of a clinical program through one of its controlled subsidiaries, and monthly thereafter over the next 36 months.
Restricted common shares granted	0
Restricted Shares | Vested Upon Initiation of Clinical Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted common shares granted			530,027
Restricted Shares | Remaining Vesting Term
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Shares, Issued			188,454
Restricted common shares granted			188,454
Weighted average fair value of restricted common shares			$ 0.96
Restricted Shares | Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted common shares granted		1,589,622
Weighted average fair value of restricted common shares		$ 3.65
Employee Stock Options | 2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Fair value of underlying shares	$ 9.34
Employee Stock Options | Employees And Directors [Member] | 2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares granted	1,232,759
Employee Stock Options | Non Employee Director [Member] | 2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares granted	80,640
Fair value of underlying shares	$ 9.15
Employee Stock Options | Executive Officer And Chief Medical Officer [Member] | 2021 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares granted	640,000
Fair value of underlying shares	$ 9.47
Vesting percentage	25.00%
IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Issued, Price Per Share				$ 13

Share-based Compensation - Summ

Share-based Compensation - Summary of Assumptions of Fair Value of Option Pricing Granted (Details) - 2021 Equity Incentive Plan - $ / shares	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum		71.70%
Expected volatility			95.00%
Expected volatility, maximum		99.50%
Expected term (years)			1 year 6 months
Risk-free interest rate, minimum		0.04%
Risk-free interest rate			0.16%
Risk-free interest rate, maximum		0.10%
Restricted Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)		1 year
Restricted Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)		6 months 29 days
Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	87.76%
Expected volatility, maximum	87.87%
Risk-free interest rate, minimum	0.79%
Risk-free interest rate, maximum	0.97%
Fair value of underlying shares	$ 9.34
Employee Stock Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 years 29 days
Exercise Price	$ 13	$ 13
Employee Stock Options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	5 years 6 months
Exercise Price	$ 12.80	$ 12.80

Share-based Compensation - Su_2

Share-based Compensation - Summary of Nonvested Restricted Common Stock Activity (Details) - Nonvested Restricted Common Stock [Member]	9 Months Ended
	Sep. 30, 2021shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning balance	1,184,252
Shares granted	1,589,622
Shares vested	(365,520)
Outstanding, ending balance	2,408,354

Share-based Compensation - Su_3

Share-based Compensation - Summary of Equity-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 1,055	$ 275	$ 2,116	$ 475
Research and Development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	266	47	620	107
General and Administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 789	$ 228	$ 1,496	$ 368

Investment In Joint Venture - A

Investment In Joint Venture - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Joint venture investment payments			$ 2,000	$ 1,600
Allocable share of losses recorded	$ (332)	$ (526)	(1,282)	(1,009)
Investment in joint venture	1,028		$ 1,028		$ 310
RE Ventures I, LLC
Schedule of Equity Method Investments [Line Items]
Percentage of interest of joint venture entity			50.00%
Allocable share of losses recorded	300	$ 500	$ 1,300	$ 1,000
Investment in joint venture	$ 1,000		$ 1,000		$ 300
RE Ventures I, LLC | Accrued Expenses
Schedule of Equity Method Investments [Line Items]
Initial Investment in Joint Venture						$ 600

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Other Commitments [Line Items]
Termination charges	$ 0	$ 0

Net Loss Per Common Share - Sum

Net Loss Per Common Share - Summary of Basic and diluted loss per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net loss	$ (10,196)	$ (7,155)	$ (34,598)	$ (15,929)
Weighted average common shares outstanding, basic and diluted	27,527,770	22,142,148	24,011,862	15,772,918
Net loss per common share	$ (0.37)	$ (0.32)	$ (1.44)	$ (1.01)

Net Loss Per Common Share - Add

Net Loss Per Common Share - Additional Information (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Unvested Restricted Common Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount		1		1
Stock Options And Unvested Restricted Common Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	3.6		3.6