RLYB Stock: Insider Activity, Filings & Research

Rallybio Corporation (RLYB) — Drillr’s hub for RLYB insider activity, SEC filings, earnings signals and AI research. Over the trailing 3 months, RLYB insiders filed 14 open-market buys and 0 sales (SEC Form 4).

Sentiment

100/100

Buys (3m)

Sells (3m)

Net (3m)

$4.2M

Insiders buying

Insider trades by month Buys Sells

May

Jun

Nov

Mar

Feb

May

Context3-month price +52.9%Institutions accumulating (13F)

Date	Insider	Type	Shares	Price
May 20, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	200	$13.80
May 20, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	6,009	$13.98
May 20, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	10,000	$13.98
May 15, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	100	$13.80
May 15, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	200	$13.95
May 15, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	4,081	$13.80
May 15, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	75,178	$14.00
May 13, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	25,000	$14.00
May 13, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	800	$13.83
May 13, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	5,100	$14.00
May 13, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	19,900	$14.00
May 6, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	3,900	$13.90
May 6, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	35,101	$14.00
May 6, 2026	ADAR1 Capital Management, LLC10 percent owner	Buy	116,904	$13.97
Feb 23, 2026	Lieber Jonathan Iofficer: Chief Financial Officer	Sell	789	$5.06

Source: RLYB SEC Form 4 filings, latest May 20, 2026. For informational purposes only — not investment advice.

Overview

Rallybio Corporation (NASDAQ:RLYB) is a clinical-stage biotechnology company founded in 2018 and headquartered in New Haven, Connecticut. The company went public in July 2021 and focuses on discovering, developing, manufacturing, and delivering therapies for patients suffering from severe and rare diseases. Since its founding, Rallybio has concentrated its efforts on developing innovative treatments for conditions with significant unmet medical needs, particularly in areas where current therapeutic options are limited or nonexistent.

Business

Rallybio operates in the biotechnology sector, specifically focusing on rare disease therapeutics. The company's primary area of expertise lies in developing treatments for severe and rare medical conditions that affect small patient populations but have devastating impacts on those afflicted. The company's lead product candidate is RLYB212, a monoclonal anti-HPA-1a antibody currently in Phase I clinical trials. This drug is being developed to prevent fetal and neonatal alloimmune thrombocytopenia (FNAIT), a serious condition where a mother's immune system attacks her baby's platelets during pregnancy, potentially causing severe bleeding complications in the newborn. FNAIT occurs when there is an incompatibility between maternal and fetal platelet antigens, similar to how Rh incompatibility affects red blood cells. Rallybio is also developing RLYB211, a polyclonal anti-HPA-1a antibody in Phase 1/2 clinical trials for the same indication. Additionally, the company has two complement-targeted therapies in development: RLYB114, a pegylated complement factor 5 (C5)-targeted Affibody molecule in preclinical development for complement-mediated eye diseases, and RLYB116, a subcutaneous C5 inhibitor for treating paroxysmal nocturnal hemoglobinuria (a rare blood disorder) and generalized myasthenia gravis (a neuromuscular disease). The complement system is part of the immune system that helps clear pathogens and damaged cells, but when overactive, it can cause tissue damage and disease. By targeting complement factor C5, Rallybio's therapies aim to modulate this immune response to treat various complement-mediated conditions.

Revenue model

As a clinical-stage biotechnology company, Rallybio does not yet generate meaningful revenue from product sales. The company's minimal revenue of approximately $636,000 in 2024 likely comes from research collaborations, licensing agreements, or grant funding rather than commercial drug sales. The company has a collaboration with Exscientia, a drug discovery company, for developing small molecule therapeutics for rare diseases. Rallybio's future business model will depend on successfully advancing its drug candidates through clinical trials and obtaining regulatory approval. Once approved, the company would generate revenue through direct sales of its therapies to hospitals, specialty pharmacies, and healthcare providers treating patients with the targeted rare diseases. Given the rare disease focus, the company would likely employ a specialized sales force and work closely with key opinion leaders and treatment centers. Several factors could significantly impact Rallybio's future profitability. The rare disease market typically allows for premium pricing due to limited treatment options and small patient populations, which could support higher margins. However, the company faces substantial risks including clinical trial failures, regulatory setbacks, and competition from larger pharmaceutical companies with greater resources. The lengthy and expensive drug development process, particularly for rare diseases where patient recruitment can be challenging, creates significant cash burn pressures. Additionally, the company's success depends heavily on the regulatory environment for rare disease drugs and potential changes in healthcare reimbursement policies.

Competitive moat

Rallybio's competitive moat is relatively narrow, typical of early-stage biotechnology companies. The company's primary competitive advantage lies in its specialized focus on FNAIT prevention, an area with significant unmet medical need and limited current treatment options. The company's expertise in developing anti-HPA-1a antibodies and its clinical progress with both monoclonal and polyclonal approaches provide some differentiation. However, this moat is not particularly strong or durable. The biotechnology industry is highly competitive, with numerous companies and academic institutions working on rare disease treatments. Larger pharmaceutical companies with substantially greater financial resources could potentially develop competing therapies or acquire promising competitors. Additionally, the company's intellectual property portfolio, while important, may not provide insurmountable barriers to entry for well-funded competitors. The company's complement-targeted therapies face even more intense competition, as several established companies are developing C5 inhibitors and other complement-targeted treatments. The regulatory pathway for rare disease drugs, while potentially offering advantages like orphan drug designation and expedited review processes, does not guarantee commercial success or protection from competition. Rallybio's long-term competitive position will ultimately depend on its ability to successfully complete clinical trials, obtain regulatory approvals, and establish strong relationships with key stakeholders in the rare disease treatment ecosystem before competitors can match its progress.

Risks & safety

Rallybio presents a mixed margin of safety profile typical of clinical-stage biotechnology companies, with strong liquidity but significant execution risks. • Cash Position: The company maintains a solid cash position with $14.8 million in cash and short-term investments as of Q1 2025, down from $25.3 million in Q3 2024, indicating ongoing cash burn. • Debt Level: Minimal debt with a debt-to-equity ratio of just 0.002, indicating very low financial leverage and no immediate solvency concerns from debt obligations. • Liquidity: Excellent short-term liquidity with a current ratio of 14.7 and quick ratio of 14.7, indicating the company can easily meet its short-term obligations. • Cash Burn: Significant cash burn of approximately $10.2 million in Q1 2025 and $49.3 million for full year 2024, suggesting the current cash position may last only 3-4 quarters at current burn rates. • Valuation: Trading at a price-to-book ratio of 0.54, suggesting the stock trades below book value, though this may reflect the speculative nature of the business rather than a bargain. • Other Considerations: The company's small market capitalization of approximately $16.4 million makes it highly volatile and susceptible to significant price swings based on clinical trial results or other developments.

Recent development

Based on the available financial data, Rallybio has been steadily advancing its clinical programs while managing cash resources. The company has maintained focus on its core FNAIT prevention program with both RLYB212 and RLYB211 progressing through clinical trials. The advancement from preclinical to Phase I and Phase 1/2 trials represents significant progress in the drug development process. The company's cash position has declined from over $56 million in 2022 to under $15 million in early 2025, reflecting the substantial investment required for clinical trial operations. This cash burn pattern is typical for biotechnology companies advancing multiple programs through clinical development, but it also indicates the company will likely need additional funding to complete its clinical programs. Revenue generation has remained minimal, with only small amounts likely from collaboration agreements or research grants. The collaboration with Exscientia for small molecule therapeutics represents a strategic partnership that could provide additional development opportunities beyond the company's primary antibody-based programs. The company's complement-targeted programs (RLYB114 and RLYB116) represent diversification beyond the FNAIT indication, potentially expanding the addressable market and providing multiple shots at commercial success.

RLYB company profile · for informational purposes only — not investment advice.

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