0000950170-22-009013 | 10-Q | XBRL Viewer

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Net Loss Per Common Share - Additional Information (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
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		2.7
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	4.3

Accrued Expenses (Tables)

3 Months Ended

Mar. 31, 2022

Accrued Liabilities, Current [Abstract]

Schedule of Accrued Expenses

Accrued expenses consisted of the following as of March 31, 2022 and December 31, 2021:


(in thousands)	MARCH 31, 2022		DECEMBER 31, 2021
Research and development	$	2,435	$	1,937
Employee expenses		1,043		2,955
Professional fees		457		539
Other		660		517
	$	4,595	$	5,948

Stockholder's Equity - Summary of stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Beginning Balance	1,357,784
Granted - Shares	1,091,655	0
Options Exercised - Shares	0
Options Forfeited - Shares	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	2,449,439		1,357,784
Options exercisable, end of period (in shares)	78,053
Options outstanding, beginning of period - weighted average exercise price per share	$ 12.72
Weighted-Average Exercise Price Granted	14.80
Options exercised - weighted average exercise price per share	0
Options forfeited - weighted average exercise price per share	0
Options outstanding, end of period - weighted average exercise price per share	13.65		$ 12.72
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 13.14
Options outstanding, beginning of period - weighted average remaining contractual term (years)	9 years 7 months 6 days		9 years 8 months 12 days
Options outstanding, end of period - weighted average remaining contractual term (years)	9 years 7 months 6 days		9 years 8 months 12 days
Options exercisable, end of period - weighted average remaining contractual term (years)	9 years 7 months 6 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

Leases - Schedule of Future Minimum Annual Lease Payments (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Leases [Abstract]
2022	$ 128	$ 170
2023	200	195
2024	230	230
2025	156	176
Thereafter		0
Total lease payments	714	$ 771
Less: imputed discount rate	(49)
Carrying value of operating lease liabilities	$ 665

Investment In Joint Venture - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Joint venture investment payments	$ 0	$ 500
Allocable share of losses recorded	(390)	(482)
Investment in joint venture	$ 415		$ 805
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	$ 400	$ 500
Investment in joint venture	$ 400		$ 800

Commitments and Contingencies

3 Months Ended

Mar. 31, 2022

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

9. 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, 2022 and December 31, 2021 there were no amounts accrued related to termination charges.

Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation (Policies)	3 Months Ended
	Mar. 31, 2022
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, 2021 (our "Annual Report") which includes a description of reorganization and liquidation of Rallybio Holdings, LLC ("Rallybio Holdings") prior to our IPO that resulted in a change in reporting entity as described in Accounting Standards Codification ("ASC") 250. In accordance with the guidance applicable to these circumstances, the equity structure has been adjusted in all comparative periods 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 condensed consolidated financial statements to shares and earnings per share in accordance with the ratio of common shares received by each membership unit class during the liquidation. Our significant accounting policies are described in Note 2 of the Notes to the Consolidated Financial Statements included in our Annual Report. Updates to our accounting policies, including impacts from the adoption of new accounting standards are discussed below.
Marketable Securities	Marketable Securities — We invest our excess cash balances in highly rated U.S. government-backed debt securities and treasuries. We classify our marketable securities as available-for-sale and accordingly, record such securities at fair value. Debt securities with original maturities of greater than 90 days are classified as available-for-sale marketable securities and debt securities with original maturities of less than 90 days from the date of purchase are classified as cash equivalents. Unrealized gains and losses on our marketable debt securities that are deemed temporary are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. If any adjustment to fair value reflects a significant decline in the value of the security, we evaluate the extent to which the decline is determined to be other-than-temporary and would mark the security to market through a charge to our condensed consolidated statements of operations and comprehensive loss. Credit losses are identified when we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security. In the event of a credit loss, only the amount associated with the credit loss is recognized in operating results, with the amount of loss relating to other factors recorded in accumulated other comprehensive income (loss).
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements In February 2016, the Financial Accounting Standards Board ( the "FASB") issued Accounting Standards Update ("ASU") 2016-02 "Leases" that requires lessees to recognize leases on-balance sheet and to make certain disclosures associated with their leasing arrangements. The new standard establishes a right-of-use ("ROU") model that requires a lessee to recognize an ROU asset and lease liability on the condensed consolidated balance sheets for all leases with a term longer than twelve months. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the statements of operations and comprehensive loss. The Company adopted ASU 2016-02 Leases on January 1, 2022 using the modified retrospective approach and elected to apply the transition method that allows companies to continue applying guidance under the lease standard in effect at that time in the comparative periods condensed consolidated financial statements and recognize a cumulative-effect adjustment to the condensed consolidated balance sheets on the date of adoption. The Company elected the package of practical expedients to not reassess its prior conclusions about lease identification, lease classification and initial direct costs. At adoption we recognized approximately $0.7 million of ROU assets and corresponding lease liabilities. See Note 5. In June 2016, the FASB issued ASC 2016-13 "Financial Instruments - Credit Losses", a new standard intended to improve reporting requirements specific to loans, receivables and other financial instruments. The new standard requires that credit losses on financial assets measured at amortized cost be determined using an expected loss model, instead of the current incurred loss model, and requires that credit losses related to available-for-sale debt securities be recorded through an allowance for credit losses and limited to the amount by which carrying value exceeds fair value. We adopted the new standard on January 1, 2022 and have completed our assessment of the standard based on the composition of our portfolio of financial instruments. Our significant financial assets that are within the scope of the new standard consist available for sale debt securities. There was no impact to our condensed consolidated statements of operations and comprehensive loss or condensed consolidated balance sheets upon adoption. See Note 3 for discussion of unrealized losses on our available for sale marketable securities.

Subsequent Events

3 Months Ended

Mar. 31, 2022

Subsequent Events [Abstract]

Subsequent Events

11. SUBSEQUENT EVENTS

In May 2022, we obtained worldwide exclusive rights to Sanofi’s KY1066, now referred to as RLYB331, a preclinical potentially first-in-class antibody. RLYB331 has the potential to address a significant unmet need for patients with severe anemias with ineffective erythropoiesis and iron overload, including beta thalassemia and a subset of myelodysplastic syndromes. Currently these patients are underserved by the existing standard of care. RLYB331 is a monoclonal antibody that inhibits Matriptase-2 ("MTP-2"). The inhibition of MTP-2 significantly increases levels of hepcidin, decreases iron load and treats ineffective erythropoiesis. We plan to initiate IND-enabling activities for RLYB331 to support transition of the asset into clinical development. Under the terms of the agreement, we will make an upfront payment of $3.0 million for the exclusive license to KY1066. We could also be required to pay up to up to an aggregate of $43.0 million in development and regulatory milestones and up to an aggregate of $150.0 million in commercial milestones for a product in its first indication, plus tiered low-to-mid double digit percentages of such milestone amounts for up to three additional indications, and mid to high single digit royalties on net sales.

Leases - Summary of company's operating lease on the condensed consolidated balance sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating lease right-of-use assets	$ 657	$ 0
Operating lease liabilities	148	0
Operating lease liabilities, noncurrent	517	$ 0
Total operating lease liabilities	$ 665

Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($)
Lease, Cost [Abstract]
ROU assets	$ 700
Lease liability	$ 665

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash And Cash Equivalents	$ 81,425	$ 175,334
Transfers of securities between fair value levels	$ 0
Money Market Funds Member \| Fair Value Inputs Level1 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash And Cash Equivalents		$ 4,000

Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
Common stock, par value	$ 0.0001	$ 0.0001
Common Stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	32,130,970	32,129,970
Common stock, shares outstanding	32,130,970	32,129,970
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 Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash Flows from Operating Activities:
Net loss	$ (14,498)	$ (13,275)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	42	23
Net accretion of discounts/premiums on debt securities	36	0
Stock-based compensation	2,054	522
Loss on investment in joint venture	390	482
Changes in operating assets and liabilities:
Prepaid expenses, right-of-use assets and other assets	(794)	61
Accounts payable	447	1,430
Accrued expenses and operating lease liability	(1,408)	(1,172)
Net cash used in operating activities	(13,731)	(11,929)
Cash Flows used in Investing Activities:
Purchases of marketable securities	80,142	0
Purchase of property and equipment	(36)	(62)
Investment in joint venture	0	(500)
Net cash used in investing activities	(80,178)	(562)
Cash Flows from Financing Activities:
Net cash provided by financing activities	0	0
Net decrease in cash and cash equivalents	(93,909)	(12,491)
Cash and cash equivalents - beginning of period	175,334	140,233
Cash and cash equivalents - end of period	81,425	127,742
Supplemental Disclosures of Noncash Investing and Financing Activities:
Property and equipment in accounts payable	$ 8	$ 0

Business and Liquidity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Aug. 31, 2021	Mar. 31, 2022
Cash, cash equivalents and marketable securities		$ 161.4
IPO
Stock issued during period, shares, new issues	7,130,000
Shares issued price per share	$ 13.00
Proceeds from issuance of common stock	$ 92.7
Net proceeds	$ 83.0
Over-Allotment Option [Member]
Stock issued during period, shares, new issues	930,000

Marketable Securities - Summary of Available-for-Sale Marketable Securities (Details) $ in Thousands	Mar. 31, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 100,785
Gross Unrealized Gains	1
Gross Unrealized Losses	(123)
Fair Value	100,663
U S Treasury Securities Member
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	89,610
Gross Unrealized Gains	1
Gross Unrealized Losses	(123)
Fair Value	89,488
Money Market Funds Member
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,175
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	$ 11,175

Stockholders' Equity

3 Months Ended

Mar. 31, 2022

Equity [Abstract]

Stockholders' Equity

7. STOCKHOLDERS' EQUITY

In August 2021, the Company completed its 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.

A reorganization and liquidation of Rallybio Holdings, LLC was completed prior to the Company's IPO, which resulted in a change in reporting entity to Rallybio Corporation. 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.

Preferred Stock—The Company had 50,000,000 shares of preferred stock authorized as of March 31, 2022 and December 31, 2021, respectively, of which no shares were outstanding as of March 31, 2022 and December 31, 2021.

Common Stock—The Company had 200,000,000 shares of common stock authorized as of March 31, 2022 and December 31, 2021, respectively, of which 32,130,970 and 32,129,970 shares were issued and outstanding as of March 31, 2022 and December 31, 2021.

Share-based Compensation—

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 increase 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, 2022, the 2021 Plan share pool was automatically increased by 1,606,549 shares. As of March 31, 2022, the total number of shares of common stock that were issuable under the 2021 Plan was 4,659,970 shares, of which 2,131,231 shares remained available for future issuance.

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. During the three months ended March 31, 2022, there was no activity under the 2021 ESPP.

Share-based compensation for stock options, restricted stock awards and restricted stock units is classified in the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2022 and 2021 was as follows:


	FOR THE THREE MONTHS ENDED MARCH 31,
(in thousands)	2022		2021
Research and development	$	725	$	161
General and administrative		1,329		361
	$	2,054	$	522

The following table summarizes stock option activity for the three months ended March 31, 2022:


Stock Options	Number of Option Shares		Weighted-Average Exercise Price		Weighted-Average Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2021		1,357,784	$	12.72	9.7		$	—
Granted		1,091,655	$	14.80
Exercised		—	$	—
Forfeited		—	$	—
Outstanding at March 31, 2022		2,449,439	$	13.65		9.6	$	—
Options exercisable at March 31, 2022		78,053	$	13.14		9.6	$	—

The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock options and the estimated fair value of the Company's common stock. Options outstanding and exercisable with an exercise price above the closing price as of March 31, 2022 are considered to have no intrinsic value. Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the three months ended March 31, 2022 was $10.96 per share. There were no stock options granted during the three months ended March 31, 2021. Options vested during the three months ended March 31, 2022 with an exercise price above the closing price as of March 31, 2022 are considered to have no intrinsic value. As of March 31, 2022, there was unrecognized share-based compensation expense related to unvested stock options of $21.7 million, which the Company expects to recognize over a weighted-average period of approximately 3.5 years.

The fair value of the stock options granted during the three months ended March 31, 2022 was determined using the Black-Scholes option pricing model with the following assumptions:


	FOR THE THREE MONTHS ENDED MARCH 31,
	2022
Expected volatility	89.3% - 89.6%
Expected term (years)	5.50 - 6.08
Risk free interest rate	1.42% - 1.79%
Expected dividend yield		—
Exercise price	$9.91 - $15.04

A summary of the status of the Company's nonvested restricted common stock awards at March 31, 2022 and changes during the three months ended March 31, 2022 was as follows:


Restricted Stock Awards	Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested restricted stock awards at December 31, 2021		2,272,707		$	3.22
Shares granted		—		$	—
Shares vested		(525,222	)	$	2.68
Outstanding nonvested restricted stock awards at March 31, 2022		1,747,485		$	3.38

As of March 31, 2022, there was unrecognized share-based compensation expense related to unvested restricted stock awards of $5.5 million, which the Company expects to recognize over a weighted-average period of approximately 2.8 years.

A summary of the status of the Company's nonvested restricted common stock units at March 31, 2022 and changes during the three months ended March 31, 2022 was as follows:


Restricted Stock Units	Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested restricted stock units at December 31, 2021		2,000		$	10.76
Shares granted		78,300		$	15.04
Shares vested		(1,000	)	$	10.76
Outstanding nonvested restricted stock units at March 31, 2022		79,300		$	14.99

As of March 31, 2022, there was unrecognized share-based compensation expense related to unvested restricted stock units of $1.1 million, which the Company expects to recognize over a weighted-average period of approximately 2.8 years.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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+ Details

Commitments and Contingencies - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Other Commitments [Line Items]
Termination charges	$ 0	$ 0

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 81,425	$ 175,334
Marketable securities	79,984	0
Prepaid expenses and other assets	6,373	5,535
Total current assets	167,782	180,869
Property and equipment, net	499	511
Operating lease right-of-use assets	657	0
Investment in joint venture	415	805
Total assets	169,353	182,185
Current liabilities:
Accounts payable	1,057	603
Accrued expenses	4,595	5,948
Operating lease liabilities	148	0
Total current liabilities	5,800	6,551
Accrued expenses, noncurrent	0	32
Operating lease liabilities, noncurrent	517	0
Total liabilities	6,317	6,583
Commitments and contingencies (Note 9)
Stockholders' equity
Common stock, value	3	3
Preferred stock, value	0	0
Additional paid-in capital	271,680	269,626
Accumulated other comprehensive loss	(122)	0
Accumulated deficit	(108,525)	(94,027)
Total stockholders' equity	163,036	175,602
Total liabilities and stockholders' equity	$ 169,353	$ 182,185

Fair Value Measurements - Summary of Fair Value Measurements on a Recurring Basis and Level of Inputs (Details) - Fair Value Measurements Recurring Member $ in Thousands	Mar. 31, 2022 USD ($)
Fair Value Inputs Level1 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total financial assets	$ 100,663
Fair Value Inputs Level2 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total financial assets	0
Fair Value Inputs Level3 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total financial assets	0
U S Treasury Securities Member \| Fair Value Inputs Level1 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total financial assets	89,488
U S Treasury Securities Member \| Fair Value Inputs Level2 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total financial assets	0
U S Treasury Securities Member \| Fair Value Inputs Level3 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total financial assets	0
Money Market Funds Member \| Fair Value Inputs Level1 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total financial assets	11,175
Money Market Funds Member \| Fair Value Inputs Level2 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total financial assets	0
Money Market Funds Member \| Fair Value Inputs Level3 Member
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total financial assets	$ 0

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2022

Fair Value Disclosures [Abstract]

Summary of Fair Value Measurements on a Recurring Basis and Level of Inputs

Financial assets subject to fair value measurements on a recurring basis and the level of inputs used in such measurements by major security type as of March 31, 2022 was as follows:


	March 31, 2022
(in thousands)	Level 1		Level 2		Level 3
Financial assets:
Money market fund	$	11,175	$	—	$	—
U.S. treasury securities		89,488		—		—
Total financial assets	$	100,663	$	—	$	—

Fair Value Measurements

3 Months Ended

Mar. 31, 2022

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. FAIR VALUE MEASUREMENTS

ASC Topic 820, Fair Value Measurement (“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). ASC 820 identifies fair value as the price that would be received to sell an asset or paid to transfer a liability, in an orderly transaction between market participants at the measurement date. The Company’s principal financial instruments comprise cash, marketable securities. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tiered value hierarchy that distinguishes between the following:

Level 1—Quoted market prices in active markets for identical assets or liabilities.

Level 2—Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves.

Level 3—Unobservable inputs for the asset or liability (i.e. supported by little or no market activity). Level 3 inputs include management’s own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk).

In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible, as well as considers counterparty credit risk in its assessment of fair value.

Financial assets subject to fair value measurements on a recurring basis and the level of inputs used in such measurements by major security type as of March 31, 2022 was as follows:


	March 31, 2022
(in thousands)	Level 1		Level 2		Level 3
Financial assets:
Money market fund	$	11,175	$	—	$	—
U.S. treasury securities		89,488		—		—
Total financial assets	$	100,663	$	—	$	—

There were no securities transferred between Level 1, 2 and 3 during the three months ended March 31, 2022.

For the year ended December 31, 2021 the Company held money market funds that are classified as cash and cash equivalents on the Company's condensed consolidated balance sheets of $4.0 million. These money market funds are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices in active markets.

- Definition

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

+ References + Details

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, 2022 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	89.30%
Expected volatility, maximum	89.60%
Risk-free interest rate, minimum	1.42%
Risk-free interest rate, maximum	1.79%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 years 29 days
Exercise Price	$ 15.04
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	5 years 6 months
Exercise Price	$ 9.91

Accrued Expenses

3 Months Ended

Mar. 31, 2022

Accrued Liabilities, Current [Abstract]

Accrued Expenses

6. ACCRUED EXPENSES

Accrued expenses consisted of the following as of March 31, 2022 and December 31, 2021:


(in thousands)	MARCH 31, 2022		DECEMBER 31, 2021
Research and development	$	2,435	$	1,937
Employee expenses		1,043		2,955
Professional fees		457		539
Other		660		517
	$	4,595	$	5,948

Subsequent Events - Additional Information (Details) - SubsequentEventMember $ in Millions	1 Months Ended
	May 31, 2022 USD ($)
Subsequent Event [Line Items]
Upfront payment	$ 3.0
Aggregate development and regulatory milestone	43.0
Obligation To Payment Upon Maximum Achievement Of Certain Clinical And Commercial Milestones	$ 150.0

Stockholder's Equity (Tables)

3 Months Ended

Mar. 31, 2022

Equity [Abstract]

Share-based compensation for stock options, restricted stock awards and restricted stock units


	FOR THE THREE MONTHS ENDED MARCH 31,
(in thousands)	2022		2021
Research and development	$	725	$	161
General and administrative		1,329		361
	$	2,054	$	522

Summary of stock option activity

The following table summarizes stock option activity for the three months ended March 31, 2022:


Stock Options	Number of Option Shares		Weighted-Average Exercise Price		Weighted-Average Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2021		1,357,784	$	12.72	9.7		$	—
Granted		1,091,655	$	14.80
Exercised		—	$	—
Forfeited		—	$	—
Outstanding at March 31, 2022		2,449,439	$	13.65		9.6	$	—
Options exercisable at March 31, 2022		78,053	$	13.14		9.6	$	—

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, 2022 was determined using the Black-Scholes option pricing model with the following assumptions:


	FOR THE THREE MONTHS ENDED MARCH 31,
	2022
Expected volatility	89.3% - 89.6%
Expected term (years)	5.50 - 6.08
Risk free interest rate	1.42% - 1.79%
Expected dividend yield		—
Exercise price	$9.91 - $15.04

Summary of Nonvested Restricted Common Stock Awards

A summary of the status of the Company's nonvested restricted common stock awards at March 31, 2022 and changes during the three months ended March 31, 2022 was as follows:


Restricted Stock Awards	Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested restricted stock awards at December 31, 2021		2,272,707		$	3.22
Shares granted		—		$	—
Shares vested		(525,222	)	$	2.68
Outstanding nonvested restricted stock awards at March 31, 2022		1,747,485		$	3.38

Summary of Nonvested Restricted Common Stock Units

A summary of the status of the Company's nonvested restricted common stock units at March 31, 2022 and changes during the three months ended March 31, 2022 was as follows:


Restricted Stock Units	Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested restricted stock units at December 31, 2021		2,000		$	10.76
Shares granted		78,300		$	15.04
Shares vested		(1,000	)	$	10.76
Outstanding nonvested restricted stock units at March 31, 2022		79,300		$	14.99

Business and Liquidity

3 Months Ended

Mar. 31, 2022

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.

The Company had cash, cash equivalents and marketable securities of $161.4 million at March 31, 2022. 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, we do not anticipate that the current cash, cash equivalents and marketable securities as of March 31, 2022 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.

Investment In Joint Venture

3 Months Ended

Mar. 31, 2022

Equity Method Investments and Joint Ventures [Abstract]

INVESTMENT IN JOINT VENTURE

8. 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 three months ended March 31, 2022, the Company did not provide funding to REV-I. For the three months ended March 31, 2021, the Company funded $0.5 million to REV-I associated with the Company's commitment and its share of REV-1 development costs. The Company did not provide any additional financial support outside of capital contributions to REV-I during the three months ended March 31, 2022 and 2021. While the Company held a 50% interest in the joint venture as of March 31, 2022, 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.

For the three months ended March 31, 2022 and 2021, the Company recorded its allocable share of REV-I’s losses, which totaled $0.4 million and $0.5 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, 2022 and December 31, 2021 was $0.4 million and $0.8 million, respectively, which was recorded in investment in joint venture in the accompanying condensed consolidated balance sheets.

Net Loss Per Common Share

3 Months Ended

Mar. 31, 2022

Earnings Per Share [Abstract]

Net Loss Per Common Share

10. NET LOSS PER COMMON SHARE

Basic and diluted loss per common share was calculated as follows:


	FOR THE THREE MONTHS ENDED MARCH 31,
(in thousands except share and per share amounts)	2022			2021
Net loss	$	(14,498	)	$	(13,275	)
Weighted average number of common shares outstanding, basic and diluted		30,318,405			22,244,883
Net loss per common share, basic and diluted	$	(0.48	)	$	(0.60	)

The weighted average number of common shares outstanding diluted for the 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. The weighted average number of common shares outstanding

diluted for the three months ended March 31, 2021 excludes approximately 2.7 million unvested restricted common shares, which were not dilutive and not included in the computation of net loss per common share.

Leases

3 Months Ended

Mar. 31, 2022

Leases [Abstract]

Leases

5. LEASES

At the inception of an arrangement, we determine if an arrangement is, or contains, a lease based on the facts and circumstances present in that arrangement. Lease classification, recognition, and measurement are then determined at the lease commencement date. For arrangements that contain a lease we i) identify lease and non-lease components, ii) determine the consideration in the contract, iii) determine whether the lease is an operating or financing lease; and iv) recognize lease ROU assets and liabilities. Lease liabilities and their corresponding ROU assets are recorded based on the present value of fixed, or in substance fixed, lease payments over the expected lease term. When the interest rate

implicit in lease contracts is not readily determinable we use our incremental borrowing rate based on the information available at the lease commencement date, which represents an internally developed rate that would be incurred to borrow, on a collateralized basis, over a similar term, an amount equal to the lease payments in a similar economic environment. The weighted average discount rate utilized on our operating lease liabilities as of March 31, 2022 was 4.00%.

We have operating leases for approximately 9,000 square feet of corporate office space. We have elected to combine lease components with non-lease components on our office real estate asset class. Fixed, or in substance fixed, lease payments on operating leases are recognized over the expected term of the lease on a straight-line basis. Variable lease expenses that are not considered fixed, or in substance fixed, are recognized as incurred. Fixed and variable lease expense on operating leases is recognized within operating expenses within our condensed consolidated statements of operations and comprehensive loss. Some leases include options to extend or terminate the lease and the Company includes these options in the recognition of the Company’s ROU assets and lease liabilities when it is reasonably certain that the Company will exercise such options. We have elected the short-term lease exemption and, therefore, do not recognize a ROU asset or corresponding liability for lease arrangements with an original term of 12 months or less. The weighted average remaining lease term is 3.3 years.

Operating leases are included in ROU operating assets, other current liabilities, and noncurrent operating lease liabilities in our condensed consolidated balance sheets as of March 31, 2022.

The following table summarizes the presentation of the Company's operating lease as presented on the condensed consolidated balance sheets:


(in thousands)	March 31, 2022
Assets:
Operating lease right-of-use assets	$	657
Liabilities:
Operating lease liabilities	$	148
Operating lease liabilities, noncurrent		517
Total operating lease liabilities	$	665

Future minimum lease payments from March 31, 2022 until the expiration of the operating lease are as follows:


(in thousands)
2022	$	128
2023		200
2024		230
2025		156
Total lease payments		714
Less: imputed discount rate		(49	)
Carrying value of operating lease liabilities	$	665

The Company incurred $51 thousand and $26 thousand in operating lease rent expense for the three months ended March 31, 2022 and 2021, respectively. Lease payments made were $43 thousand and $19 thousand for the three months ended March 31, 2022 and 2021, respectively, with such amounts reflected in the condensed consolidated statements of cash flows in operating activities.

As the result of adopting ASU 2016-02 Leases using the modified retrospective transition method, we did not restate periods prior to the adoption date of January 1, 2022. These periods continue to be presented in accordance with ASC 840. As of December 31, 2021 the future undiscounted minimum lease payments on our operating leases was as follows:


YEAR ENDING DECEMBER 31,
(in thousands)
2022	$	170
2023		195
2024		230
2025		176
Thereafter		—
	$	771

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, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Net loss	$ (14,498)	$ (13,275)
Weighted average common shares outstanding, basic and diluted	30,318,405	22,244,883
Net loss per common share	$ (0.48)	$ (0.60)

- Definition

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

+ References

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-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

+ Details

Net Loss Per Common Share (Tables)

3 Months Ended

Mar. 31, 2022

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 MARCH 31,
(in thousands except share and per share amounts)	2022			2021
Net loss	$	(14,498	)	$	(13,275	)
Weighted average number of common shares outstanding, basic and diluted		30,318,405			22,244,883
Net loss per common share, basic and diluted	$	(0.48	)	$	(0.60	)

Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2022

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, 2022 was as follows:


	March 31, 2022
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. treasury securities	$	89,610	$	1	$	(123	)	$	89,488
Money market funds		11,175		—		—			11,175
	$	100,785	$	1	$	(123	)	$	100,663

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:


(in thousands)	March 31, 2022
Cash and cash equivalents	$	20,679
Marketable securities		79,984
	$	100,663

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, 2022 , by contractual maturity, are summarized as follows:


	March 31, 2022
Due in one year or less	$	100,663
Due after one year through two years		—
	$	100,663

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

- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

+ References + Details

Stockholder's Equity - Summary of Nonvested Restricted Common Stock Awards (Details) - Restricted Stock Awards	3 Months Ended
	Mar. 31, 2022 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, Beginning Balance \| $ / shares	$ 3.22
Weighted average grant date fair value, shares granted \| $ / shares	0
Weighted average grant date fair value, shares vested \| $ / shares	2.68
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, Ending Balance \| $ / shares	$ 3.38
Outstanding, beginning balance \| shares	2,272,707
Shares granted \| shares	0
Shares vested \| shares	(525,222)
Outstanding, ending balance \| shares	1,747,485

Marketable Securities

3 Months Ended

Mar. 31, 2022

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, 2022 was as follows:


	March 31, 2022
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. treasury securities	$	89,610	$	1	$	(123	)	$	89,488
Money market funds		11,175		—		—			11,175
	$	100,785	$	1	$	(123	)	$	100,663

The fair values of marketable securities by classification in the condensed consolidated balance sheets was as follows:


(in thousands)	March 31, 2022
Cash and cash equivalents	$	20,679
Marketable securities		79,984
	$	100,663

The fair values of available-for-sale debt securities as of March 31, 2022 , by contractual maturity, are summarized as follows:


	March 31, 2022
Due in one year or less	$	100,663
Due after one year through two years		—
	$	100,663

The aggregate fair value of available-for-sale debt securities in an unrealized loss position as of March 31, 2022 was $70.0 million. We did not have any investments in a continuous unrealized loss position for more than twelve months as of March 31, 2022. As of March 31, 2022, 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, 2022.

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating expenses:
Research and development	$ 7,648	$ 9,037
General and administrative	6,670	3,787
Total operating expenses	14,318	12,824
Loss from operations	(14,318)	(12,824)
Other income (expenses):
Interest income	97	17
Interest expense	0	(10)
Other income	113	24
Total other income, net	210	31
Loss from continuing operations	(14,108)	(12,793)
Loss on investment in joint venture	390	482
Net loss	$ (14,498)	$ (13,275)
Net loss per common share, basic and diluted	$ (0.48)	$ (0.60)
Weighted average common shares outstanding, basic and diluted	30,318,405	22,244,883
Net unrealized loss on marketable securities	$ 122	$ 0
Other comprehensive loss	(122)	0
Comprehensive loss	$ (14,620)	$ (13,275)

Leases (Tables)

3 Months Ended

Mar. 31, 2022

Leases [Abstract]

Summary of company's operating lease on the condensed consolidated balance sheets

The following table summarizes the presentation of the Company's operating lease as presented on the condensed consolidated balance sheets:


(in thousands)	March 31, 2022
Assets:
Operating lease right-of-use assets	$	657
Liabilities:
Operating lease liabilities	$	148
Operating lease liabilities, noncurrent		517
Total operating lease liabilities	$	665

Schedule of Future Minimum Annual Lease Payments

Future minimum lease payments from March 31, 2022 until the expiration of the operating lease are as follows:


(in thousands)
2022	$	128
2023		200
2024		230
2025		156
Total lease payments		714
Less: imputed discount rate		(49	)
Carrying value of operating lease liabilities	$	665

As of December 31, 2021 the future undiscounted minimum lease payments on our operating leases was as follows:


YEAR ENDING DECEMBER 31,
(in thousands)
2022	$	170
2023		195
2024		230
2025		176
Thereafter		—
	$	771

Leases - Additional Information (Details) - Office [Member] $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($) ft²	Mar. 31, 2021 USD ($)
Operating Leased Assets [Line Items]
Operating Lease, Weighted Average Remaining Lease Term (Year)	3 years 3 months 18 days
Operating Lease, Weighted Average Discount Rate, Percent	4.00%
Operating lease rent expense	$ 51	$ 26
Lease payments	$ 43	$ 19
Lessor operating lease description	We have operating leases for approximately 9,000 square feet of corporate office space. We have elected to combine lease components with non-lease components on our office real estate asset class. Fixed, or in substance fixed, lease payments on operating leases are recognized over the expected term of the lease on a straight-line basis. Variable lease expenses that are not considered fixed, or in substance fixed, are recognized as incurred. Fixed and variable lease expense on operating leases is recognized within operating expenses within our condensed consolidated statements of operations and comprehensive loss. Some leases include options to extend or terminate the lease and the Company includes these options in the recognition of the Company’s ROU assets and lease liabilities when it is reasonably certain that the Company will exercise such options. We have elected the short-term lease exemption and, therefore, do not recognize a ROU asset or corresponding liability for lease arrangements with an original term of 12 months or less. The weighted average remaining lease term is 3.3 years.
Area of real estate property \| ft²	9,000

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Jan. 01, 2022	Aug. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Class of Stock [Line Items]
Common stock, shares issued			32,130,970		32,129,970
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			32,130,970		32,129,970
Fair value of underlying shares			$ 10.96
Granted - Shares			1,091,655	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value			$ 0
Unrecognized share-based compensation expense			$ 21,700
Options exercisable, end of period - weighted average remaining contractual term (years)			9 years 7 months 6 days
Total unrecognized compensation cost, period for recognition			3 years 6 months
Restricted Stock Awards [Member]
Class of Stock [Line Items]
Unrecognized share-based compensation expense			$ 5,500
Options exercisable, end of period - weighted average remaining contractual term (years)			2 years 9 months 18 days
Restricted Stock Units (RSUs) [Member]
Class of Stock [Line Items]
Unrecognized share-based compensation expense, Restricted stock units			$ 1,100
Total unrecognized compensation cost, period for recognition			2 years 9 months 18 days
2021 Equity Incentive Plan
Class of Stock [Line Items]
Common stock, share increased	1,606,549
Common stock issuable			4,659,970
Common shares reserved for issuance			5,440,344
Common shares remained for issuance			2,131,231
2021 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common shares reserved for issuance			291,324
IPO [Member]
Class of Stock [Line Items]
Common stock, shares issued		7,130,000
Stock issued during period, shares, new issues		7,130,000
Shares issued price per share		$ 13.00
Proceeds from issuance of common stock, gross including exercise of the underwriter's option to purchase additional shares		$ 92,700
Net proceeds		$ 83,000
Over-Allotment Option [Member]
Class of Stock [Line Items]
Stock issued during period, shares, new issues		930,000

Stockholder's Equity - Summary of Nonvested Restricted Common Stock Units (Details) - Restricted Stock Units	3 Months Ended
	Mar. 31, 2022 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, beginning balance \| shares	2,000
Shares granted \| shares	78,300
Shares vested \| shares	(1,000)
Outstanding, ending balance \| shares	79,300
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, Beginning Balance \| $ / shares	$ 10.76
Weighted average grant date fair value, shares granted \| $ / shares	15.04
Weighted average grant date fair value, shares vested \| $ / shares	10.76
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, Ending Balance \| $ / shares	$ 14.99

Stockholders' Equity - Summary of Equity-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 2,054	$ 522
Research and Development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	725	161
General and Administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 1,329	$ 361

Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation

3 Months Ended

Mar. 31, 2022

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, 2021 (our "Annual Report") which includes a description of reorganization and liquidation of Rallybio Holdings, LLC ("Rallybio Holdings") prior to our IPO that resulted in a change in reporting entity as described in Accounting Standards Codification ("ASC") 250. In accordance with the guidance applicable to these circumstances, the equity structure has been adjusted in all comparative periods 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 condensed consolidated financial statements to shares and earnings per share in accordance with the ratio of common shares received by each membership unit class during the liquidation.

Our significant accounting policies are described in Note 2 of the Notes to the Consolidated Financial Statements included in our Annual Report. Updates to our accounting policies, including impacts from the adoption of new accounting standards are discussed below.

Marketable Securities — We invest our excess cash balances in highly rated U.S. government-backed debt securities and treasuries. We classify our marketable securities as available-for-sale and accordingly, record such securities at fair value. Debt securities with original maturities of greater than 90 days are classified as available-for-sale marketable securities and debt securities with original maturities of less than 90 days from the date of purchase are classified as cash equivalents.

Unrealized gains and losses on our marketable debt securities that are deemed temporary are included in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity. If any adjustment to fair value reflects a significant decline in the value of the security, we evaluate the extent to which the decline is determined to be other-than-temporary and would mark the security to market through a charge to our condensed consolidated statements of operations and comprehensive loss. Credit losses are identified when we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security. In the event of a credit loss, only the amount associated with the credit loss is recognized in operating results, with the amount of loss relating to other factors recorded in accumulated other comprehensive income (loss).

Recently Adopted Accounting Pronouncements

In February 2016, the Financial Accounting Standards Board ( the "FASB") issued Accounting Standards Update ("ASU") 2016-02 "Leases" that requires lessees to recognize leases on-balance sheet and to make certain disclosures associated with their leasing arrangements. The new standard establishes a right-of-use ("ROU") model that requires a lessee to recognize an ROU asset and lease liability on the condensed consolidated balance sheets for all leases with a term longer than twelve months. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the statements of operations and comprehensive loss. The Company adopted ASU 2016-02 Leases on January 1, 2022 using the modified retrospective approach and elected to apply the transition method that allows companies to continue applying guidance under the lease standard in effect at that time in the comparative periods condensed consolidated financial statements and recognize a cumulative-effect adjustment to the condensed consolidated balance sheets on the date of adoption. The Company elected the package of practical expedients to not reassess its prior conclusions about lease identification, lease classification and initial direct costs. At adoption we recognized approximately $0.7 million of ROU assets and corresponding lease liabilities. See Note 5.

In June 2016, the FASB issued ASC 2016-13 "Financial Instruments - Credit Losses", a new standard intended to improve reporting requirements specific to loans, receivables and other financial instruments. The new standard requires that credit losses on financial assets measured at amortized cost be determined using an expected loss model, instead of the current incurred loss model, and requires that credit losses related to available-for-sale debt securities be recorded through an allowance for credit losses and limited to the amount by which carrying value exceeds fair value. We adopted the new standard on January 1, 2022 and have completed our assessment of the standard based on the composition of our portfolio of financial instruments. Our significant financial assets that are within the scope of the new standard consist available for sale debt securities. There was no impact to our condensed consolidated statements of operations and comprehensive loss or condensed consolidated balance sheets upon adoption. See Note 3 for discussion of unrealized losses on our available for sale marketable securities.

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, 2020	$ 136,003	$ 2	$ 183,015	$ (47,014)
Beginning Balance (in shares) at Dec. 31, 2020		23,410,348
Issuance of restricted common stock (in shares)		1,579,915
Share-based compensation expense	522		522
Net loss	(13,275)			(13,275)
Other comprehensive loss	0
Ending Balance (in shares) at Mar. 31, 2021		24,990,263
Ending Balance at Mar. 31, 2021	123,250	$ 2	183,537	(60,289)
Beginning Balance at Dec. 31, 2021	175,602	$ 3	269,626	(94,027)
Beginning Balance (in shares) at Dec. 31, 2021		32,129,970
Share-based compensation expense	2,054		2,054
Issuance of common stock under the stock award plan (in shares)		1,000
Net loss	(14,498)			(14,498)
Other comprehensive loss	(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)

- Definition

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

+ References

+ Details

- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

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

- Definition

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

+ References

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+ Details

Accrued Expenses - Schedule Of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accrued Liabilities, Current [Abstract]
Research and development	$ 2,435	$ 1,937
Employee expenses	1,043	2,955
Professional fees	457	539
Other	660	517
Accrued expenses	$ 4,595	$ 5,948

Marketable Securities - Schedule of Fair Values of Available-For-Sale Debt Securities By Contractual Maturity (Details) $ in Thousands	Mar. 31, 2022 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less	$ 100,663
Due after one year through two years	0
Total available-for-sale debt securities by contractual maturity	$ 100,663

Marketable Securities - Schedule of Available-for-Sale Securities by Balance Sheet Location Classification (Details) $ in Thousands	Mar. 31, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt securities available-for-sale	$ 100,663
Cash and Cash Equivalents Member
Debt Securities, Available-for-sale [Line Items]
Debt securities available-for-sale	20,679
Marketable Securities Member
Debt Securities, Available-for-sale [Line Items]
Debt securities available-for-sale	$ 79,984