Rallybio Corporation (RLYB) Ownership
RLYB ownership summary
as of October 18, 2026- Institutions
- 84.3% of shares outstanding
- Insiders
- 24.88% of shares outstanding
- Shares outstanding
- 5.3M
- Float
- 1.7M shares available to trade
- Short interest
- 1.11% 49K shares short
- Days to cover
- 4.52 short interest down 11.4% vs prior month
- Institutions 84.33%
- Insiders 24.88%
RLYB top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | ADAR1 Capital Management LLC | 17.44% | 926K | $15.1M | +905,817 (+4,411.1%) | June 30, 2026 |
| 2 | FMR Inc | 14.96% | 795K | $12.9M | +1,269 (+0.2%) | June 30, 2026 |
| 3 | Viking Global Investors LP | 9.87% | 524K | $8.5M | — | June 30, 2026 |
| 4 | TPG GP A, LLC | 7.13% | 379K | $6.2M | — | June 30, 2026 |
| 5 | Nantahala Capital Management, LLC | 7.09% | 377K | $6.1M | +76,209 (+25.3%) | June 30, 2026 |
| 6 | Pivotal bioVenture Partners Investment Advisor LLC | 5.66% | 301K | $4.9M | — | June 30, 2026 |
| 7 | Renaissance Technologies Corp | 3.76% | 200K | $3.3M | +43,380 (+27.7%) | June 30, 2026 |
| 8 | Vanguard Capital Management, LLC | 3.25% | 172K | $2.8M | +60,457 (+54.0%) | June 30, 2026 |
| 9 | Almitas Capital LLC | 2.27% | 121K | $2.0M | −70,524 (−36.9%) | June 30, 2026 |
| 10 | AJU IB Investment Co Ltd | 1.78% | 94K | $1.5M | −1 (−0.0%) | March 31, 2026 |
| 11 | Citadel Advisors Llc | 1.36% | 72K | $1.2M | +52,314 (+263.1%) | June 30, 2026 |
| 12 | Mariner Wealth Advisors LLC | 0.95% | 51K | $823,214 | — | June 30, 2026 |
| 13 | Jane Street Group LLC | 0.89% | 47K | $772,046 | +47,423 (0.0%) | June 30, 2026 |
| 14 | Geode Capital Management, LLC | 0.60% | 32K | $521,725 | −3,378 (−9.5%) | June 30, 2026 |
| 15 | BlackRock Inc | 0.57% | 30K | $493,805 | +12,846 (+73.5%) | June 30, 2026 |
| 16 | HRT FINANCIAL LLC | 0.48% | 26K | $417,696 | +25,657 (0.0%) | June 30, 2026 |
| 17 | XTX Topco Ltd | 0.40% | 21K | $349,971 | +10,271 (+91.5%) | June 30, 2026 |
| 18 | Vanguard Fiduciary Trust Co | 0.32% | 17K | $273,830 | +3,273 (+24.2%) | June 30, 2026 |
| 19 | Two Sigma Investments LLC | 0.31% | 17K | $270,557 | +16,619 (0.0%) | June 30, 2026 |
| 20 | State Street Corp | 0.24% | 13K | $211,575 | +12,996 (0.0%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 13 holders added 1.3M shares and 3 cut 74K.
RLYB top mutual fund and ETF holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Fidelity Growth Company Fund | 3.90% | 207K | $3.4M | — | August 31, 2026 |
| 2 | Vanguard MStar Total Stk Mkt Idx Invest | 2.53% | 135K | $2.2M | — | August 31, 2026 |
| 3 | Fidelity Growth Company K6 | 1.07% | 57K | $924,346 | — | August 31, 2026 |
| 4 | Fidelity Series Growth Company | 1.01% | 54K | $872,608 | — | August 31, 2026 |
| 5 | Fidelity Extended Market Index | 0.24% | 13K | $209,084 | −994 (−7.2%) | August 31, 2026 |
| 6 | BSF Systematic US Eq Abs Ret A2 USD | 0.20% | 10K | $169,426 | — | December 31, 2025 |
| 7 | Dimensional US Small Cap ETF | 0.13% | 6,675 | $108,669 | — | September 30, 2026 |
| 8 | DFA US Micro Cap I | 0.11% | 5,891 | $95,905 | +1,286 (+27.9%) | August 31, 2026 |
| 9 | Fidelity Series Total Market Index | 0.08% | 4,508 | $73,390 | — | August 31, 2026 |
| 10 | Fidelity Total Market Index | 0.08% | 4,406 | $71,730 | +327 (+8.0%) | August 31, 2026 |
| 11 | Vanguard MStar Inst Ttl StkMktIdxInstlPl | 0.06% | 3,141 | $51,135 | — | August 31, 2026 |
| 12 | Fidelity Nasdaq Composite Index | 0.05% | 2,788 | $45,389 | — | August 31, 2026 |
| 13 | Vanguard Balanced Index Inv | 0.04% | 2,289 | $37,265 | — | August 31, 2026 |
| 14 | Avantis US Small Cap Equity ETF | 0.03% | 1,562 | $25,429 | — | September 30, 2026 |
| 15 | Vanguard U.S. Eq Idx £ Acc | 0.03% | 1,442 | $23,476 | — | August 31, 2026 |
| 16 | 1290 VT Micro Cap K | 0.01% | 795 | $12,943 | — | August 31, 2026 |
| 17 | Dimensional International Core Eq Acc | 0.01% | 724 | $11,787 | +724 (0.0%) | August 31, 2026 |
| 18 | DFA US Vector Equity I | 0.01% | 719 | $11,705 | +719 (0.0%) | August 31, 2026 |
| 19 | Dimensional US Core Equity 1 ETF | 0.01% | 684 | $11,136 | — | September 24, 2026 |
| 20 | DFA US Vector Equity Class F | 0.01% | 651 | $10,598 | +651 (0.0%) | July 31, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
RLYB insider transactions
latest 1| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2026-02-23 | Jonathan I Lieber | Sell | $5.06 | 789 | $3,992 |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
RLYB shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns RLYB
Institutional investors own 84.3% of Rallybio's shares and insiders 24.88%. The largest holder is ADAR1 Capital Management LLC with 17.44% of the shares (926K), as of June 30, 2026. Among the top 20 institutions, 13 added shares and 3 reduced their stake in the latest filings. Short interest is 1.11% of the float, or 4.52 days of average trading volume. The share count rose 90.0% since 2020.
Related: RLYB analyst forecast, RLYB key metrics. See the RLYB stock overview for the latest quote and news.
RLYB ownership FAQ
Who owns the most Rallybio stock?
The largest shareholders of Rallybio are ADAR1 Capital Management LLC (17.44%), FMR Inc (14.96%), Viking Global Investors LP (9.87%), TPG GP A, LLC (7.13%), Nantahala Capital Management, LLC (7.09%).
What percentage of Rallybio is owned by institutions?
Institutions hold 84.3% of Rallybio's shares outstanding; insiders hold 24.88%.
Which funds own Rallybio?
The largest fund holders of Rallybio are Fidelity Growth Company Fund (3.90%), Vanguard MStar Total Stk Mkt Idx Invest (2.53%), Fidelity Growth Company K6 (1.07%), Fidelity Series Growth Company (1.01%), Fidelity Extended Market Index (0.24%).
What is Rallybio's short interest?
49K shares of Rallybio were sold short, 1.11% of the float; at the average daily volume it would take 4.52 days to cover.
Are insiders buying or selling Rallybio?
Of the latest 1 reported insider transactions in Rallybio (since February 23, 2026), 0 were purchases and 1 were sales.
How many shares of Rallybio are outstanding?
Rallybio has 5.3M shares outstanding, of which 1.7M are in the public float.