Rallybio (RLYB) 10-Q 9 May 23 2023 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2023	May 04, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Amendment Flag	false
Entity Central Index Key	0001739410
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Document Period End Date	Mar. 31, 2023
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
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		37,747,433

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 39,519	$ 56,958
Marketable securities	110,870	112,036
Prepaid expenses and other assets	10,887	10,502
Total current assets	161,276	179,496
Property and equipment, net	346	385
Operating lease right-of-use assets	479	524
Investment in joint venture	217	30
Total assets	162,318	180,435
Current liabilities:
Accounts payable	782	1,114
Accrued expenses	5,821	9,449
Operating lease liabilities	197	181
Total current liabilities	6,800	10,744
Operating lease liabilities, noncurrent	321	374
Total liabilities	7,121	11,118
Commitments and contingencies (Note 7)
Stockholders' equity
Common stock, value	4	4
Preferred stock, value	0	0
Additional paid-in capital	333,253	330,208
Accumulated other comprehensive loss	(61)	(214)
Accumulated deficit	(177,999)	(160,681)
Total stockholders' equity	155,197	169,317
Total liabilities and stockholders' equity	$ 162,318	$ 180,435

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Mar. 31, 2023	Dec. 31, 2022
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	37,746,214	37,837,369
Common stock, shares outstanding	37,746,214	37,837,369
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
	Mar. 31, 2023	Mar. 31, 2022
Operating expenses:
Research and development	$ 11,202	$ 7,648
General and administrative	7,172	6,670
Total operating expenses	18,374	14,318
Loss from operations	(18,374)	(14,318)
Other income (expenses):
Interest income	1,546	97
Other income	73	113
Total other income, net	1,619	210
Loss from continuing operations	(16,755)	(14,108)
Loss on investment in joint venture	563	390
Net loss	$ (17,318)	$ (14,498)
Net loss per common share, basic	$ (0.43)	$ (0.48)
Net loss per common share, diluted	$ (0.43)	$ (0.48)
Weighted average number of common shares outstanding, basic	40,248,893	30,318,405
Weighted average number of common shares outstanding, diluted	40,248,893	30,318,405
Other comprehensive income (loss):
Net unrealized income (loss) on marketable securities	$ 153	$ (122)
Other comprehensive income (loss)	153	(122)
Comprehensive loss	$ (17,165)	$ (14,620)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Shares	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning Balance at Dec. 31, 2021	$ 175,602	$ 3	$ 269,626	$ (94,027)
Beginning Balance (in shares) at Dec. 31, 2021		32,129,970
Issuance of common stock under the stock award plan, vested (in shares)		1,000
Share-based compensation expense	2,054		2,054
Net loss	(14,498)			(14,498)
Other comprehensive (loss) income	(122)				$ (122)
Ending Balance (in shares) at Mar. 31, 2022		32,130,970
Ending Balance at Mar. 31, 2022	163,036	$ 3	271,680	(108,525)	(122)
Beginning Balance at Dec. 31, 2022	169,317	$ 4	330,208	(160,681)	(214)
Beginning Balance (in shares) at Dec. 31, 2022		37,837,369
Share-based compensation expense	3,045		3,045
Forfeiture of restricted common stock, shares		(91,155)
Net loss	(17,318)			(17,318)
Other comprehensive (loss) income	153				153
Ending Balance (in shares) at Mar. 31, 2023		37,746,214
Ending Balance at Mar. 31, 2023	$ 155,197	$ 4	$ 333,253	$ (177,999)	$ (61)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash Flows used in Operating Activities:
Net loss	$ (17,318)	$ (14,498)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	39	42
Net accretion of discounts/premiums on debt securities	(895)	36
Stock-based compensation	3,045	2,054
Loss on investment in joint venture	563	390
Changes in operating assets and liabilities:
Prepaid expenses, right-of-use assets and other assets	(340)	(794)
Accounts payable	(295)	447
Accrued expenses and operating lease liabilities	(3,564)	(1,408)
Net cash used in operating activities	(18,765)	(13,731)
Cash Flows Provided By (Used In) Investing Activities:
Purchases of marketable securities	(29,285)	(80,142)
Proceeds from maturities of marketable securities	31,500	0
Purchase of property and equipment	0	(36)
Investment in joint venture	(750)	0
Net cash provided by (used in) investing activities	1,465	(80,178)
Cash Flows Used In Financing Activities:
Payments of offering costs	(139)	0
Net cash used in financing activities	(139)	0
Net decrease in cash and cash equivalents	(17,439)	(93,909)
Cash and cash equivalents-beginning of period	56,958	175,334
Cash and cash equivalents-end of period	39,519	81,425
Supplemental Disclosures of Noncash Investing and Financing Activities:
Property and equipment in accounts payable and accrued expenses	$ 0	$ 8

Business and Liquidity

Business and Liquidity	3 Months Ended
	Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Liquidity	1. BUSINESS AND LIQUIDITY Rallybio Corporation and subsidiaries ("Rallybio", the "Company", "we", "our", or "us") is a clinical-stage biotechnology company with a mission to develop and commercialize life-transforming therapies for patients with severe and rare diseases. Rallybio has built a broad pipeline of promising product candidates aimed at addressing diseases with unmet medical need in areas of maternal fetal health, complement dysregulation, hematology, and metabolic disorders. The Company has two clinical stage programs: RLYB212, an anti-HPA-1a antibody for the prevention of fetal and neonatal alloimmune thrombocytopenia ("FNAIT") and RLYB116, a complement factor 5 ("C5") complement inhibitor with the potential to treat several diseases of complement dysregulation, as well as additional programs in preclinical development. The Company had cash, cash equivalents and marketable securities of $ 150.4 million as of March 31, 2023. The Company currently expects that its cash, cash equivalents and marketable securities 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, cash equivalents and marketable securities as of March 31, 2023 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, corporate collaborations or license agreements, working capital lines of credit, grant funding, interest income earned on invested cash balances or a combination of one or more of these sources.

Summary of Significant Accounti

Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation	3 Months Ended
	Mar. 31, 2023
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 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 accompanying unaudited condensed consolidated financial statements include the accounts of Rallybio Corporation and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. These accompanying unaudited condensed consolidated financial statements and notes should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2022 (our "Annual Report"). Our significant accounting policies are described in Note 2 of the Notes to the Consolidated Financial Statements included in our Annual Report. There have been no new accounting policies, including the adoption of new accounting standards during the three months ended March 31, 2023 , which could be expected to materially impact the Company's unaudited condensed consolidated financial statements.

Marketable Securities

Marketable Securities	3 Months Ended
	Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	3. MARKETABLE SECURITIES The amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of our marketable securities by type of security as of March 31, 2023 and December 31, 2022 was as follows: MARCH 31, 2023 (in thousands) Fair Value Hierarchy Level Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Money market funds Level 1 $ 19,187 $ — $ — $ 19,187 U.S. treasury securities Level 1 14,195 1 ( 26 ) 14,170 U.S. government agency securities Level 2 96,736 27 ( 63 ) 96,700 $ 130,118 $ 28 $ ( 89 ) $ 130,057 DECEMBER 31, 2022 (in thousands) Fair Value Hierarchy Level Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Money market funds Level 1 $ 12,647 $ — $ — $ 12,647 U.S. treasury securities Level 1 39,372 — ( 169 ) 39,203 U.S. government agency securities Level 2 76,860 37 ( 82 ) 76,815 $ 128,879 $ 37 $ ( 251 ) $ 128,665 The fair values of marketable securities by classification in the condensed consolidated balance sheets was as follows as of March 31, 2023 and December 31, 2022: (in thousands) MARCH 31, 2023 DECEMBER 31, 2022 Cash and cash equivalents $ 19,187 $ 16,629 Marketable securities 110,870 112,036 $ 130,057 $ 128,665 The fair values of available-for-sale debt securities as of March 31, 2023 and December 31, 2022, by contractual maturity, are summarized as follows: (in thousands) MARCH 31, 2023 DECEMBER 31, 2022 Due in one year or less $ 125,526 $ 127,667 Due after one year through two years 4,531 998 $ 130,057 $ 128,665 The aggregate fair value of available-for-sale debt securities in an unrealized loss position as of March 31, 2023 and December 31, 2022 was $ 50.9 million and $ 70.0 million, respectively. As of March 31, 2023 , we believe that the cost basis of our available-for-sale debt securities is recoverable. No allowance for credit losses was recorded as of March 31, 2023 .

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	4. BALANCE SHEET COMPONENTS Prepaid expenses and other assets— Prepaid expenses and other assets consisted of the following as of March 31, 2023 and December 31, 2022: (in thousands) MARCH 31, DECEMBER 31, Research and development $ 8,653 $ 7,904 Insurance 539 933 Other prepaids 633 615 Other assets 1,062 1,050 $ 10,887 $ 10,502 Accrued Expenses— Accrued expenses consisted of the following as of March 31, 2023 and December 31, 2022: (in thousands) MARCH 31, DECEMBER 31, Research and development $ 3,255 $ 3,582 Compensation and related expenses 1,411 4,703 Professional fees 506 510 Other 649 654 $ 5,821 $ 9,449

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Stockholders' Equity	5. STOCKHOLDERS' EQUITY Common Stock 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 underwriters' 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. In November 2022, the Company completed a follow-on offering in which we raised gross proceeds of $ 54.8 million from the sale of 5,803,655 shares of common stock, inclusive of 803,654 shares of common stock sold pursuant to the partial exercise of the underwriters' option to purchase additional shares at the price of $ 6.00 per share and to certain investors in lieu of common stock, pre-funded warrants to purchase up to an aggregate of 3,333,388 shares of common stock at a price of $ 5.9999 , which represents the per share public offering price for the shares less the $ 0.0001 per share exercise price for each pre-funded warrant. The net proceeds from the November 2022 follow-on offering were approximately $ 50.8 million, after deducting underwriting discounts and commissions and other offering costs. The Company had 200,000,000 shares of common stock authorized as of March 31, 2023 and December 31, 2022 , respectively, of which 37,746,214 and 37,837,369 shares were issued and outstanding as of March 31, 2023 and December 31, 2022. Preferred Stock The Company had 50,000,000 shares of preferred stock authorized as of March 31, 2023 and December 31, 2022, respectively, of which no shares were outstanding as of March 31, 2023 and December 31, 2022. Pre-Funded Warrants In connection with the follow-on offering entered into in November 2022, the Company entered into an agreement with certain investors for pre-funded warrants in lieu of common stock to purchase up to an aggregate of 3,333,388 shares of common stock at a price of $ 5.9999 , which represents the per share public offering price at the November 2022 follow-on offering for common stock less a $ 0.0001 per share exercise price for each pre-funded warrant. The Company may not effect the exercise of any pre-funded warrant, and a holder will not be entitled to exercise any portion of any pre-funded warrant if, upon giving effect to such exercise, the aggregate number of shares of common stock beneficially owned by the holder (together with its affiliates) would exceed 9.99 % of the number of shares of common stock outstanding immediately after giving effect to the exercise, which percentage may be increased or decreased at the holder’s election upon 61 days’ notice to the Company subject to the terms of such pre-funded warrants, provided that such percentage may in no event exceed 19.99 %. The Company has assessed the pre-funded warrant for appropriate equity or liability classification. During this assessment, the Company determined the pre-funded warrant is a freestanding instrument that does not meet the definition of a liability pursuant to ASC 480 and does not meet the definition of a derivative pursuant to ASC 815. The pre-funded warrant is indexed to the Company’s common stock and meets all other conditions for equity classification under ASC 480 and ASC 815. Accordingly, the pre-funded warrant classified as equity and accounted for as a component of additional paid-in capital at the time of issuance. All of the pre-funded warrants related to our November 2022 follow-on offering remain outstanding and unexercised as of March 31, 2023. Share-based Compensation Share-based compensation comprised of stock options, restricted stock awards, restricted stock units and the employee stock purchase plan is classified in the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2023 and 2022 as follows: FOR THE THREE MONTHS ENDED (in thousands) 2023 2022 Research and development $ 1,063 $ 725 General and administrative 1,982 1,329 $ 3,045 $ 2,054 2021 Equity Incentive Plan In 2021, the board of directors adopted the Rallybio Corporation 2021 Equity Incentive Plan (the "2021 Plan"). The 2021 Plan reserves 5,440,344 for shares of the Company's common stock that have been issued in respect of outstanding equity awards granted prior to the registrant’s IPO and 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. On January 1, 2023 and January 1, 2022, the 2021 Plan share pool was automatically increased by 1,891,868 shares and 1,606,549 shares, respectively. As of March 31, 2023 , the total number of shares of common stock that were issuable under the 2021 Plan was 6,779,094 shares, of which 2,346,595 shares remained available for future issuance. The following table summarizes stock option activity for the three months ended March 31, 2023: Stock Options Number of Option Shares Weighted-Average Exercise Price Weighted-Average Contractual Term Aggregate Intrinsic Value Outstanding at December 31, 2022 2,609,314 $ 13.01 8.8 $ — Granted 1,864,150 $ 6.58 Forfeited ( 146,500 ) $ 13.65 Expired ( 32,490 ) $ 14.07 Exercised — $ — Outstanding at March 31, 2023 4,294,474 $ 10.19 9.0 $ — Options exercisable at March 31, 2023 843,035 $ 13.01 7.9 $ — was $ 4.99 per share and $ 10.96 per share, respectively. Options vested during the three months ended March 31, 2023 and 2022 with an exercise price above the closing price as of March 31, 2023 were considered to have no intrinsic value. As of March 31, 2023 , there was unrecognized share-based compensation expense related to unvested stock options of $ 23.0 million, which the Company expects to recognize over a weighted-average period of approximately 3.06 years. The fair value of the stock options granted during the three months ended March 31, 2023 was determined using the Black-Scholes option pricing model with the following assumptions: FOR THE THREE MONTHS ENDED MARCH 31, 2023 Expected volatility 89.37 % - 92.27 % Expected term (years) 5.50 - 6.08 Risk free interest rate 3.68 % - 4.52 % Expected dividend yield — Exercise price $ 6.19 - $ 7.83 A summ ary of the status of the Company's nonvested restricted common stock awards at March 31, 2023 and changes during the three months ended March 31, 2023 was as follows: Restricted Stock Awards Shares Weighted-Average Grant Date Fair Value Per Share Nonvested restricted stock awards at December 31, 2022 1,006,368 $ 3.48 Granted — $ — Vested ( 211,332 ) $ 2.87 Forfeited ( 91,155 ) $ 2.77 Outstanding nonvested restricted stock awards at March 31, 2023 703,881 $ 3.75 As of March 31, 2023 , there was unrecognized share-based compensation expense related to unvested restricted stock awards of $ 2.5 million, which the Company expects to recognize over a weighted-average period of approximately 1.91 years. A summary of the status of the Company's nonvested restricted common stock units at March 31, 2023 and changes during the three months ended March 31, 2023 was as follows: Restricted Stock Units Shares Weighted-Average Grant Date Fair Value Per Share Nonvested restricted stock units at December 31, 2022 128,600 $ 11.12 Granted 9,425 $ 6.50 Forfeited — $ — Vested — $ — Outstanding nonvested restricted stock units at March 31, 2023 138,025 $ 10.81 , there was unrecognized share-based compensation expense related to unvested restricted stock units of $ 1.0 million, which the Company expects to recognize over a weighted-average period of approximately 2.04 years. 2021 Employee Stock Purchase Plan In connection with the Company's IPO, the board of directors adopted the Rallybio Corporation 2021 Employee Stock Purchase Plan (the "2021 ESPP"), which reserves 291,324 shares of the Company's common stock for future issuances under this plan. The share pool will automatically increase on January 1st of each year from 2022 to 2031 by the lesser of (i) one percent of the number of shares of the Company's common stock outstanding as of such date, (ii) 582,648 shares of the Company’s common stock and (iii) the number of shares of the Company's common stock determined by the board of directors on or prior to such date . On January 1, 2023 and January 1, 2022, the 2021 ESPP share pool was automatically increased by 378,373 shares and 321,309 shares, respectively. As of March 31, 2023 , the total number of shares of the Company's common stock that were available for future issuance under the 2021 ESPP was 952,161 shares. During the three months ended March 31, 2023 , the Company did no t issue any shares under the 2021 ESPP. For the three months ended March 31, 2023 , the total share-based compensation for ESPP was $ 60 thousand.

Investment In Joint Venture

Investment In Joint Venture	3 Months Ended
	Mar. 31, 2023
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, LL C, a limited liability company (“REV-I”). For the three months ended March 31, 2023 the Company funded $ 0.8 million associated with the Company's commitment and its share of REV-I development. For the three months ended March 31, 2022 , the Company did no t provide funding to REV-I. The Company did not provide any additional financial support outside of capital contributions to REV-I during the three months ended March 31, 2023 and 2022. While the Company held a 50% interest in the joint venture as of March 31, 2023, based on management’s analysis, the Company is not the primary beneficiary of REV-I and accordingly, the entity is not consolidated in the Company's condensed consolidated financial statements. For the three months ended March 31, 2023 and 2022, the Company recorded its allocable share of REV-I’s losses, which totaled $ 0.6 million and $ 0.4 million, 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 March 31, 2023 and December 31, 2022 was $ 0.2 million and $ 30 thousand, respectively, which was recorded in investment in joint venture in the accompanying condensed consolidated balance sheets.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2023
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 March 31, 2023 and December 31, 2022 there were no amounts accrued related to termination charges.

Net Loss Per Common Share

Net Loss Per Common Share	3 Months Ended
	Mar. 31, 2023
Earnings Per Share [Abstract]
Net Loss Per Common Share	8. NET LOSS PER COMMON SHARE Basic and diluted loss per common share was calculated as follows: FOR THE THREE MONTHS ENDED 2023 2022 Net loss $ ( 17,318 ) $ ( 14,498 ) Weighted-average number of common shares 40,248,893 30,318,405 Net loss per common share, basic and diluted $ ( 0.43 ) $ ( 0.48 ) Basic net loss per share of common stock is based on the weighted-average number of shares of common stock outstanding during the period. Pre-funded warrants to purchase 3,333,388 shares of common stock that were issued in connection with the November 2022 follow-on offering were included in the weighted-average number of common shares outstanding for the three months ended March 31, 2023. The weighted average number of common shares outstanding diluted for the three months ended March 31, 2023 excludes approximately 5.1 million stock options and unvested restricted share awards/units, 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 three months ended March 31, 2022 excludes approximately 4.3 million stock options and 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)	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
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 accompanying unaudited condensed consolidated financial statements include the accounts of Rallybio Corporation and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. These accompanying unaudited condensed consolidated financial statements and notes should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2022 (our "Annual Report"). Our significant accounting policies are described in Note 2 of the Notes to the Consolidated Financial Statements included in our Annual Report. There have been no new accounting policies, including the adoption of new accounting standards during the three months ended March 31, 2023 , which could be expected to materially impact the Company's unaudited condensed consolidated financial statements.

Marketable Securities (Tables)

Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Summary of Fair Value of Marketable Securities by Type of Marketable Securities	The amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of our marketable securities by type of security as of March 31, 2023 and December 31, 2022 was as follows: MARCH 31, 2023 (in thousands) Fair Value Hierarchy Level Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Money market funds Level 1 $ 19,187 $ — $ — $ 19,187 U.S. treasury securities Level 1 14,195 1 ( 26 ) 14,170 U.S. government agency securities Level 2 96,736 27 ( 63 ) 96,700 $ 130,118 $ 28 $ ( 89 ) $ 130,057 DECEMBER 31, 2022 (in thousands) Fair Value Hierarchy Level Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Money market funds Level 1 $ 12,647 $ — $ — $ 12,647 U.S. treasury securities Level 1 39,372 — ( 169 ) 39,203 U.S. government agency securities Level 2 76,860 37 ( 82 ) 76,815 $ 128,879 $ 37 $ ( 251 ) $ 128,665
Schedule of Marketable Securities by Balance Sheet Location Classification	The fair values of marketable securities by classification in the condensed consolidated balance sheets was as follows as of March 31, 2023 and December 31, 2022: (in thousands) MARCH 31, 2023 DECEMBER 31, 2022 Cash and cash equivalents $ 19,187 $ 16,629 Marketable securities 110,870 112,036 $ 130,057 $ 128,665
Schedule of Fair Values of Available-for-Sale Debt Securities by Contractual Maturity	The fair values of available-for-sale debt securities as of March 31, 2023 and December 31, 2022, by contractual maturity, are summarized as follows: (in thousands) MARCH 31, 2023 DECEMBER 31, 2022 Due in one year or less $ 125,526 $ 127,667 Due after one year through two years 4,531 998 $ 130,057 $ 128,665

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Schedule of Prepaid Expenses and Other Assets	Prepaid expenses and other assets consisted of the following as of March 31, 2023 and December 31, 2022: (in thousands) MARCH 31, DECEMBER 31, Research and development $ 8,653 $ 7,904 Insurance 539 933 Other prepaids 633 615 Other assets 1,062 1,050 $ 10,887 $ 10,502
Schedule of Accrued Expenses	Accrued expenses consisted of the following as of March 31, 2023 and December 31, 2022: (in thousands) MARCH 31, DECEMBER 31, Research and development $ 3,255 $ 3,582 Compensation and related expenses 1,411 4,703 Professional fees 506 510 Other 649 654 $ 5,821 $ 9,449

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Share-Based Compensation for Stock Options, Restricted Stock Awards and Restricted Stock Units and the Employee Stock Purchase Plan	Share-based compensation comprised of stock options, restricted stock awards, restricted stock units and the employee stock purchase plan is classified in the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2023 and 2022 as follows: FOR THE THREE MONTHS ENDED (in thousands) 2023 2022 Research and development $ 1,063 $ 725 General and administrative 1,982 1,329 $ 3,045 $ 2,054
Summary of Stock Option Activity	The following table summarizes stock option activity for the three months ended March 31, 2023: Stock Options Number of Option Shares Weighted-Average Exercise Price Weighted-Average Contractual Term Aggregate Intrinsic Value Outstanding at December 31, 2022 2,609,314 $ 13.01 8.8 $ — Granted 1,864,150 $ 6.58 Forfeited ( 146,500 ) $ 13.65 Expired ( 32,490 ) $ 14.07 Exercised — $ — Outstanding at March 31, 2023 4,294,474 $ 10.19 9.0 $ — Options exercisable at March 31, 2023 843,035 $ 13.01 7.9 $ —
Summary of Assumptions of Fair Value of Option Pricing Granted	The fair value of the stock options granted during the three months ended March 31, 2023 was determined using the Black-Scholes option pricing model with the following assumptions: FOR THE THREE MONTHS ENDED MARCH 31, 2023 Expected volatility 89.37 % - 92.27 % Expected term (years) 5.50 - 6.08 Risk free interest rate 3.68 % - 4.52 % Expected dividend yield — Exercise price $ 6.19 - $ 7.83
Summary of Nonvested Restricted Common Stock Awards	A summ ary of the status of the Company's nonvested restricted common stock awards at March 31, 2023 and changes during the three months ended March 31, 2023 was as follows: Restricted Stock Awards Shares Weighted-Average Grant Date Fair Value Per Share Nonvested restricted stock awards at December 31, 2022 1,006,368 $ 3.48 Granted — $ — Vested ( 211,332 ) $ 2.87 Forfeited ( 91,155 ) $ 2.77 Outstanding nonvested restricted stock awards at March 31, 2023 703,881 $ 3.75
Summary of Nonvested Restricted Common Stock Units	A summary of the status of the Company's nonvested restricted common stock units at March 31, 2023 and changes during the three months ended March 31, 2023 was as follows: Restricted Stock Units Shares Weighted-Average Grant Date Fair Value Per Share Nonvested restricted stock units at December 31, 2022 128,600 $ 11.12 Granted 9,425 $ 6.50 Forfeited — $ — Vested — $ — Outstanding nonvested restricted stock units at March 31, 2023 138,025 $ 10.81

Net Loss Per Common Share (Tabl

Net Loss Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2023
Earnings Per Share [Abstract]
Summary of Basic and Diluted Loss Per Common Share	Basic and diluted loss per common share was calculated as follows: FOR THE THREE MONTHS ENDED 2023 2022 Net loss $ ( 17,318 ) $ ( 14,498 ) Weighted-average number of common shares 40,248,893 30,318,405 Net loss per common share, basic and diluted $ ( 0.43 ) $ ( 0.48 )

Business and Liquidity - Additi

Business and Liquidity - Additional Information (Details) $ in Millions	Mar. 31, 2023 USD ($)
Cash, cash equivalents and marketable securities	$ 150.4

Marketable Securities - Summary

Marketable Securities - Summary of available-for-sale marketable securities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 130,118	$ 128,879
Gross Unrealized Holding Gains	28	37
Gross Unrealized Holding Losses	(89)	(251)
Fair Value	130,057	128,665
Level 1 | Money Market Funds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	19,187	12,647
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	19,187	12,647
Level 1 | U S Treasury Securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	14,195	39,372
Gross Unrealized Holding Gains	1	0
Gross Unrealized Holding Losses	(26)	(169)
Fair Value	14,170	39,203
Level 2 | U.S. government agency securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	96,736	76,860
Gross Unrealized Holding Gains	27	37
Gross Unrealized Holding Losses	(63)	(82)
Fair Value	$ 96,700	$ 76,815

Marketable Securities - Schedul

Marketable Securities - Schedule of Available-for-Sale Securities by Balance Sheet Location Classification (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale [Line Items]
Debt securities available-for-sale	$ 130,057	$ 128,665
Cash and cash equivalents
Debt Securities, Available-for-Sale [Line Items]
Debt securities available-for-sale	19,187	16,629
Marketable securities
Debt Securities, Available-for-Sale [Line Items]
Debt securities available-for-sale	$ 110,870	$ 112,036

Marketable Securities - Sched_2

Marketable Securities - Schedule of Fair Values of Available-For-Sale Debt Securities By Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Due in one year or less	$ 125,526	$ 127,667
Due after one year through two years	4,531	998
Total available-for-sale debt securities by contractual maturity	$ 130,057	$ 128,665

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Aggregate fair value of available-for-sale debt securities in an unrealized loss position	$ 50,900,000	$ 70,000,000
Allowance for credit losses	$ 0

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Prepaid Expenses and Other Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Research and development	$ 8,653	$ 7,904
Insurance	539	933
Other prepaids	633	615
Other assets	1,062	1,050
Prepaid expenses and other assets	$ 10,887	$ 10,502

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule Of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Accrued Liabilities, Current [Abstract]
Research and development	$ 3,255	$ 3,582
Compensation and related expenses	1,411	4,703
Professional fees	506	510
Other	649	654
Accrued expenses	$ 5,821	$ 9,449

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		3 Months Ended
	Jan. 01, 2023	Jan. 01, 2022	Nov. 30, 2022	Aug. 31, 2021	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Class of Stock [Line Items]
Common stock, shares issued					37,746,214		37,837,369
Preferred stock, shares authorized					50,000,000		50,000,000
Preferred stock, shares outstanding					0		0
Common stock, shares authorized					200,000,000		200,000,000
Common stock, shares outstanding					37,746,214		37,837,369
Weighted average grant date fair value					$ 4.99	$ 10.96
Intrinsic value of stock options vested					$ 0
Unrecognized share-based compensation expense					$ 23,000
Total unrecognized compensation costs, weighted average period for recognition					3 years 21 days
Pre-Funded Warrants
Class of Stock [Line Items]
Common stock price per share			$ 5.9999
Pre-funded warrants exercise price			$ 0.0001
Number of securities called by warrants or rights			3,333,388
Restricted Stock Awards
Class of Stock [Line Items]
Total unrecognized compensation costs, weighted average period for recognition					1 year 10 months 28 days
Unrecognized share-based compensation expense, restricted stock awards					$ 2,500
Restricted Stock Units (RSUs)
Class of Stock [Line Items]
Unrecognized share-based compensation expense, restricted stock units					$ 1,000
Total unrecognized compensation costs, weighted average period for recognition					2 years 14 days
2021 Equity Incentive Plan
Class of Stock [Line Items]
Common stock issuable					6,779,094
Share-based compensation arrangement by share-based payment award, number of shares authorized					5,440,344
Share-based compensation arrangement by share-based payment award, number of shares available for grant					2,346,595
No of shares increased	1,891,868	1,606,549
2021 Employee Stock Purchase Plan
Class of Stock [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized					291,324
Share-based compensation arrangement by share-based payment award, number of shares available for grant					952,161
Common stock shares outstanding					582,648
No of shares increased	378,373	321,309
Shares issued					0
Total share based compensation					$ 60
IPO
Class of Stock [Line Items]
Stock issued during period, shares, new issues				7,130,000
Common stock price per share				$ 13
Proceeds from issuance of common stock				$ 92,700
Net proceeds				$ 83,000
Over Allotment On Follow On Offering
Class of Stock [Line Items]
Stock issued during period, shares, new issues			803,654
Over Allotment On Initial Public Offering
Class of Stock [Line Items]
Stock issued during period, shares, new issues				930,000
Follow On Offering
Class of Stock [Line Items]
Stock issued during period, shares, new issues			5,803,655
Common stock price per share			$ 6
Proceeds from issuance of common stock			$ 54,800
Net proceeds			$ 50,800
Number of securities called by warrants or rights					3,333,388
Follow On Offering | Pre-Funded Warrants
Class of Stock [Line Items]
Pre-funded warrants exercise price			$ 0.0001
Exceed Limit Percentage With Exercise To Aggregate Shares Of Common Stock Beneficially Owned					9.99%
Percentage of common stock beneficially owned not exceed					19.99%
Number of securities called by warrants or rights			3,333,388
Days of notice					61 days

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Equity-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 3,045	$ 2,054
Research and Development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	1,063	725
General and Administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 1,982	$ 1,329

Stockholder's Equity - Summary

Stockholder's Equity - Summary of stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Share-based compensation arrangement by share-based payment award, options, outstanding, number, beginning balance	2,609,314
Options granted - shares	1,864,150
Options forfeited - shares	(146,500)
Options expired - shares	(32,490)
Options exercised - shares	0
Share-based compensation arrangement by share-based payment award, options, outstanding, number, ending balance	4,294,474	2,609,314
Options exercisable, end of period (in shares)	843,035
Options outstanding, beginning of period - weighted average exercise price per share	$ 13.01
Options granted - weighted average exercise price per share	6.58
Options forfeited - weighted average exercise price per share	13.65
Options expired - weighted average exercise price per share	14.07
Options exercised - weighted average exercise price per share	0
Options outstanding, end of period - weighted average exercise price per share	10.19	$ 13.01
Options exercisable, end of period - weighted average exercise price per share	$ 13.01
Options outstanding, beginning of period - weighted average remaining contractual term (years)	9 years	8 years 9 months 18 days
Options outstanding, end of period - weighted average remaining contractual term (years)	9 years	8 years 9 months 18 days
Options exercisable, end of period - weighted average remaining contractual term (years)	7 years 10 months 24 days
Options outstanding, beginning of period - aggregate intrinsic value	$ 0
Options outstanding, end of period - aggregate intrinsic value	0	$ 0
Options exercisable, end of period - aggregate intrinsic value	$ 0

Stockholder's Equity - Summar_2

Stockholder's Equity - Summary of Assumptions of Fair Value of Option Pricing Granted (Details) - Employee Stock Options - Two Thousand and Twenty One Equity Incentive Plan [Member]	3 Months Ended
	Mar. 31, 2023 $ / shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility, minimum	89.37%
Expected volatility, maximum	92.27%
Risk-free interest rate, minimum	3.68%
Risk-free interest rate, maximum	4.52%
Expected dividend yield	0%
Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (years)	6 years 29 days
Exercise price	$ 7.83
Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (years)	5 years 6 months
Exercise price	$ 6.19

Stockholder's Equity - Summar_3

Stockholder's Equity - Summary of Nonvested Restricted Common Stock Awards (Details) - Restricted Stock Awards	3 Months Ended
	Mar. 31, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted average grant date fair value, beginning balance | $ / shares	$ 3.48
Weighted average grant date fair value, shares granted | $ / shares	0
Weighted average grant date fair value, shares vested | $ / shares	2.87
Weighted average grant date fair value, shares forfeited | $ / shares	2.77
Weighted average grant date fair value, ending balance | $ / shares	$ 3.75
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning balance | shares	1,006,368
Shares granted | shares	0
Shares vested | shares	(211,332)
Shares forfeited | shares	(91,155)
Outstanding, ending balance | shares	703,881

Stockholder's Equity - Summar_4

Stockholder's Equity - Summary of Nonvested Restricted Common Stock Units (Details) - Restricted Stock Units	3 Months Ended
	Mar. 31, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding, beginning balance | shares	128,600
Shares granted | shares	9,425
Shares forfeited | shares	0
Shares vested | shares	0
Outstanding, ending balance | shares	138,025
Weighted average grant date fair value, beginning balance | $ / shares	$ 11.12
Weighted average grant date fair value, shares granted | $ / shares	6.50
Weighted average grant date fair value, shares forfeited | $ / shares	0
Weighted average grant date fair value, shares vested | $ / shares	0
Weighted average grant date fair value, ending balance | $ / shares	$ 10.81

Investment In Joint Venture - A

Investment In Joint Venture - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Allocable share of losses recorded	$ (563)	$ (390)
Investment in joint venture	217		$ 30
Funding for joint venture	$ 750	0
RE Ventures I, LLC
Schedule of Equity Method Investments [Line Items]
Percentage of interest of joint venture entity	50%
Allocable share of losses recorded	$ 600	400
Investment in joint venture	200		$ 30
Funding for joint venture	$ 800	$ 0

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
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
	Mar. 31, 2023	Mar. 31, 2022
Earnings Per Share [Abstract]
Net loss	$ (17,318)	$ (14,498)
Weighted average number of common shares outstanding, basic	40,248,893	30,318,405
Weighted average number of common shares outstanding, diluted	40,248,893	30,318,405
Net loss per common share, basic	$ (0.43)	$ (0.48)
Net loss per common share, diluted	$ (0.43)	$ (0.48)

Net Loss Per Common Share - Add

Net Loss Per Common Share - Additional Information (Details) - shares	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Follow-On Offering [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of securities called by warrants or rights	3,333,388
Stock Options And Unvested Restricted Share
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	5,100,000	4,300,000