Who owns Rallybio (RLYB)
Which tracked institutional funds hold RLYB, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See RLYB company fundamentals →
Ownership as of the 2026-Q2 13F filings (latest filed 2026-09-22). 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.
How the tape is positioned
13 tracked funds added or opened RLYB while 6 trimmed or exited it between 2026-Q1 and 2026-Q2 — the tape is split. When large holders disagree on a name, the funds moving first are sometimes ahead of the story.
A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.
Conviction spread
RLYB’s largest tracked holder by dollar value, ADAR1 Capital Management, LLC, sizes it at 0.7% of its own reported 13F book, while the median holder sizes it at 0.0% of theirs — a 0.7pp conviction gap — its largest holder concentrates the name more heavily than the typical one.
Book-share is each fund’s reported value in RLYB divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.
Institutional & insider positioning
Between 2026-Q1 and 2026-Q2, across 36 tracked filers holding RLYB, 16 increased or opened the position and 18 reduced or closed it; over the same quarter, open-market insider Form 4s were net purchases.
This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.
New buyers & exits
Funds opening or closing a position in RLYB between the 2026-Q1 and 2026-Q2 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.
New buyers 1
- JANE STREET GROUP, LLC$759K
Full exits 6
- Cormorant Asset Management, LP$4M
- BALYASNY ASSET MANAGEMENT L.P.$3M
- Laurion Capital Management LP$3M
- 5AM Venture Management, LLC$3M
- JOHNSON & JOHNSON$1M
- AJU IB Investment Co., Ltd.$846K
Largest adds
- ADAR1 Capital Management, LLC$15M
- CITADEL ADVISORS LLC$13M
- FMR LLC$6M
- VIKING GLOBAL INVESTORS LP$4M
- TPG GP A, LLC$3M
- Pivotal bioVenture Partners Investment Advisor LLC$2M
Institutional holders
One row per tracked fund, largest reported value first. “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding. Rows marked stale are from an earlier filing than the security’s latest quarter — that fund is absent from the newest snapshot (position exited, or reported under a different name).
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| ADAR1 Capital Management, LLC added | 926,352 | $15M | 15.6% | 2026-Q2 |
| CITADEL ADVISORS LLC added | 7,705,787 | $13M | 13.4% | 2026-Q2 |
| FMR LLC added | 794,720 | $13M | 13.4% | 2026-Q2 |
| VIKING GLOBAL INVESTORS LP | 524,347 | $8M | 8.8% | 2026-Q2 |
| TPG GP A, LLC | 378,551 | $6M | 6.4% | 2026-Q2 |
| Pivotal bioVenture Partners Investment Advisor LLC | 300,579 | $5M | 5.1% | 2026-Q2 |
| RENAISSANCE TECHNOLOGIES LLC added | 199,907 | $3M | 3.4% | 2026-Q2 |
| Nantahala Capital Management, LLC trimmed | 188,422 | $3M | 3.2% | 2026-Q2 |
| VANGUARD CAPITAL MANAGEMENT LLC added | 172,497 | $3M | 2.9% | 2026-Q2 |
| Almitas Capital LLC trimmed | 120,682 | $2M | 2.0% | 2026-Q2 |
| Rangeley Capital, LLC added | 104,850 | $2M | 1.8% | 2026-Q2 |
| Mariner, LLC | 50,566 | $809K | 0.9% | 2026-Q2 |
| JANE STREET GROUP, LLC added | 47,423 | $759K | 0.8% | 2026-Q2 |
| GEODE CAPITAL MANAGEMENT, LLC trimmed | 32,047 | $513K | 0.5% | 2026-Q2 |
| BlackRock, Inc. added | 30,332 | $485K | 0.5% | 2026-Q2 |
| XTX Topco Ltd added | 21,497 | $344K | 0.4% | 2026-Q2 |
| VANGUARD FIDUCIARY TRUST CO added | 16,820 | $269K | 0.3% | 2026-Q2 |
| TWO SIGMA INVESTMENTS, LP trimmed | 16,619 | $266K | 0.3% | 2026-Q2 |
| STATE STREET CORP trimmed | 12,996 | $208K | 0.2% | 2026-Q2 |
| Quadrature Capital Ltd new | 12,995 | $208K | 0.2% | 2026-Q2 |
| DIMENSIONAL FUND ADVISORS LP | 11,280 | $180K | 0.2% | 2026-Q2 |
| Vanguard Global Advisers, LLC | 1,442 | $23K | 0.0% | 2026-Q2 |
| Hartford Financial Management Inc. | 812 | $13K | 0.0% | 2026-Q2 |
| SBI Securities Co., Ltd. trimmed | 506 | $8K | 0.0% | 2026-Q2 |
| Caitong International Asset Management Co., Ltd new | 434 | $7K | 0.0% | 2026-Q2 |
| UBS Group AG trimmed | 146 | $2K | 0.0% | 2026-Q2 |
| Truvestments Capital LLC new | 129 | $2K | 0.0% | 2026-Q2 |
| MORGAN STANLEY trimmed | 125 | $2K | 0.0% | 2026-Q2 |
| BNP PARIBAS FINANCIAL MARKETS | 120 | $2K | 0.0% | 2026-Q2 |
| Fortitude Family Office, LLC | 53 | $848 | 0.0% | 2026-Q2 |
| WELLS FARGO & COMPANY/MN | 37 | $592 | 0.0% | 2026-Q2 |
| EverSource Wealth Advisors, LLC new | 31 | $496 | 0.0% | 2026-Q2 |
| JPMORGAN CHASE & CO trimmed | 9 | $145 | 0.0% | 2026-Q2 |
| Allworth Financial LP | 6 | $96 | 0.0% | 2026-Q2 |
| BARCLAYS PLC trimmed | 3 | $48 | 0.0% | 2026-Q2 |
| DANSKE BANK A/S | 1 | $16 | 0.0% | 2026-Q2 |
| Cormorant Asset Management, LP new | 400,000 | $4M | 3.8% | 2026-Q1 stale (1 quarter behind) |
| BALYASNY ASSET MANAGEMENT L.P. new | 376,573 | $3M | 3.6% | 2026-Q1 stale (1 quarter behind) |
| Laurion Capital Management LP trimmed | 302,756 | $3M | 2.9% | 2026-Q1 stale (1 quarter behind) |
| 5AM Venture Management, LLC trimmed | 291,788 | $3M | 2.8% | 2026-Q1 stale (1 quarter behind) |
| JOHNSON & JOHNSON trimmed | 152,901 | $1M | 1.4% | 2026-Q1 stale (1 quarter behind) |
| AJU IB Investment Co., Ltd. trimmed | 94,334 | $846K | 0.9% | 2026-Q1 stale (1 quarter behind) |
| DELTEC ASSET MANAGEMENT LLC new | 33,750 | $303K | 0.3% | 2026-Q1 stale (1 quarter behind) |
| GTS SECURITIES LLC new | 22,016 | $197K | 0.2% | 2026-Q1 stale (1 quarter behind) |
| ACADIAN ASSET MANAGEMENT LLC trimmed | 10,433 | $92K | 0.1% | 2026-Q1 stale (1 quarter behind) |
| Tower Research Capital LLC (TRC) trimmed | 907 | $8K | 0.0% | 2026-Q1 stale (1 quarter behind) |
| VANGUARD GROUP INC added | 1,016,249 | $697K | 0.7% | 2025-Q4 stale (2 quarters behind) |
| Canaan Partners XI LLC | 450,000 | $309K | 0.3% | 2025-Q4 stale (2 quarters behind) |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP trimmed | 100,724 | $69K | 0.1% | 2025-Q4 stale (2 quarters behind) |
| NORTHERN TRUST CORP | 38,124 | $26K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| PRUDENTIAL FINANCIAL INC trimmed | 29,100 | $20K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| Virtu Financial LLC trimmed | 27,132 | $19K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| HRT FINANCIAL LP trimmed | 21,387 | $14K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| OneDigital Investment Advisors LLC | 20,000 | $14K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| TWO SIGMA ADVISERS, LP trimmed | 19,300 | $13K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| GSA CAPITAL PARTNERS LLP new | 19,303 | $13K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| Ground Swell Capital, LLC new | 15,399 | $11K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| GREAT VALLEY ADVISOR GROUP, INC. | 15,000 | $10K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| Utah Retirement Systems | 13,240 | $9K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| ACT Advisors, LLC. new | 13,153 | $9K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| CAPTRUST FINANCIAL ADVISORS | 10,000 | $7K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| MERCER GLOBAL ADVISORS INC /ADV | 10,000 | $7K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| CITIGROUP INC trimmed | 3,932 | $3K | 0.0% | 2025-Q4 stale (2 quarters behind) |
| BANK OF AMERICA CORP /DE/ added | 251 | $172 | 0.0% | 2025-Q4 stale (2 quarters behind) |
| New Leaf Venture Partners, L.L.C. | 3,301,603 | $2M | 1.7% | 2025-Q3 stale (3 quarters behind) |
| Rockefeller Capital Management L.P. new | 550 | $274 | 0.0% | 2025-Q3 stale (3 quarters behind) |
| JONES FINANCIAL COMPANIES LLLP new | 90 | $50 | 0.0% | 2025-Q3 stale (3 quarters behind) |
| Aberdeen Group plc trimmed | 1,595,262 | $539K | 0.6% | 2025-Q2 stale (4 quarters behind) |
| MILLENNIUM MANAGEMENT LLC trimmed | 179,839 | $61K | 0.1% | 2025-Q2 stale (4 quarters behind) |
| TWO SIGMA SECURITIES, LLC new | 15,153 | $5K | 0.0% | 2025-Q2 stale (4 quarters behind) |
| HSBC HOLDINGS PLC trimmed | 10,520 | $4K | 0.0% | 2025-Q2 stale (4 quarters behind) |
| FEDERATED HERMES, INC. | 2,209 | $747 | 0.0% | 2025-Q2 stale (4 quarters behind) |
| RAYMOND JAMES FINANCIAL INC new | 850 | $288 | 0.0% | 2025-Q2 stale (4 quarters behind) |
| CONCOURSE FINANCIAL GROUP SECURITIES, INC. | 0 | — | 0.0% | 2025-Q2 stale (4 quarters behind) |
Ownership over time
Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.
Reading this table
Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.
About 13F filings
A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.