Who owns OmniAb, Inc. (OABI)
Which tracked institutional funds hold OABI, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See OABI company fundamentals →
Ownership as of the 2026-Q1 13F filings (latest filed 2026-05-18). 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
The tracked-fund tape on OABI is one-sided between 2025-Q4 and 2026-Q1: 6 added or opened and 19 trimmed or exited — on balance reducing.
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
OABI’s largest tracked holder by dollar value, Whitefort Capital Management, LP, sizes it at 7.0% of its own reported 13F book, while the median holder sizes it at 0.0% of theirs — a 7.0pp conviction gap — its largest holder concentrates the name more heavily than the typical one.
Book-share is each fund’s reported value in OABI 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 2025-Q4 and 2026-Q1, across 140 tracked filers holding OABI, 68 increased or opened the position and 64 reduced or closed it; over the same quarter, open-market insider Form 4 buying and selling roughly offset.
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 OABI between the 2025-Q4 and 2026-Q1 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 3
- VANGUARD CAPITAL MANAGEMENT LLC$6M
- VANGUARD PORTFOLIO MANAGEMENT LLC$1M
- VANGUARD FIDUCIARY TRUST CO$1M
Full exits 2
- VANGUARD GROUP INC$10M
- Woodline Partners LP$529K
Largest adds
- NOMURA HOLDINGS INC$820K
- EverSource Wealth Advisors, LLC$546K
- TLS Advisors LLC$256K
Largest trims
- Whitefort Capital Management, LP$4M
- BlackRock, Inc.$2M
- CADIAN CAPITAL MANAGEMENT, LP$2M
- DIMENSIONAL FUND ADVISORS LP$1M
- Stonepine Capital Management, LLC$1M
- PRIVATE MANAGEMENT GROUP INC$664K
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 |
|---|---|---|---|---|
| Whitefort Capital Management, LP | 14,223,658 | $22M | 14.2% | 2026-Q1 |
| BlackRock, Inc. added | 8,106,881 | $13M | 8.1% | 2026-Q1 |
| CADIAN CAPITAL MANAGEMENT, LP trimmed | 4,157,129 | $7M | 4.1% | 2026-Q1 |
| VANGUARD CAPITAL MANAGEMENT LLC new | 3,993,652 | $6M | 4.0% | 2026-Q1 |
| GEODE CAPITAL MANAGEMENT, LLC added | 2,925,579 | $5M | 2.9% | 2026-Q1 |
| RICE HALL JAMES & ASSOCIATES, LLC added | 2,547,255 | $4M | 2.5% | 2026-Q1 |
| PRIVATE MANAGEMENT GROUP INC added | 2,429,166 | $4M | 2.4% | 2026-Q1 |
| STATE STREET CORP added | 2,067,143 | $3M | 2.1% | 2026-Q1 |
| DIMENSIONAL FUND ADVISORS LP trimmed | 1,745,248 | $3M | 1.7% | 2026-Q1 |
| TOWERVIEW LLC | 1,000,000 | $2M | 1.0% | 2026-Q1 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC trimmed | 959,573 | $2M | 1.0% | 2026-Q1 |
| VANGUARD PORTFOLIO MANAGEMENT LLC new | 903,799 | $1M | 0.9% | 2026-Q1 |
| NORTHERN TRUST CORP added | 880,895 | $1M | 0.9% | 2026-Q1 |
| ISTHMUS PARTNERS, LLC added | 756,674 | $1M | 0.8% | 2026-Q1 |
| VANGUARD FIDUCIARY TRUST CO new | 725,608 | $1M | 0.7% | 2026-Q1 |
| ADAR1 Capital Management, LLC added | 705,190 | $1M | 0.7% | 2026-Q1 |
| NOMURA HOLDINGS INC added | 705,048 | $1M | 0.7% | 2026-Q1 |
| Nuveen, LLC trimmed | 623,876 | $979K | 0.6% | 2026-Q1 |
| TWO SIGMA INVESTMENTS, LP added | 512,741 | $805K | 0.5% | 2026-Q1 |
| GOLDMAN SACHS GROUP INC trimmed | 419,024 | $658K | 0.4% | 2026-Q1 |
| MORGAN STANLEY added | 407,933 | $640K | 0.4% | 2026-Q1 |
| MILLENNIUM MANAGEMENT LLC trimmed | 523,918 | $630K | 0.4% | 2026-Q1 |
| EverSource Wealth Advisors, LLC added | 10,510 | $550K | 0.3% | 2026-Q1 |
| D. E. Shaw & Co., Inc. trimmed | 292,368 | $459K | 0.3% | 2026-Q1 |
| Bank of New York Mellon Corp added | 274,451 | $431K | 0.3% | 2026-Q1 |
| RENAISSANCE TECHNOLOGIES LLC added | 269,600 | $423K | 0.3% | 2026-Q1 |
| TLS Advisors LLC added | 250,185 | $393K | 0.2% | 2026-Q1 |
| CITADEL ADVISORS LLC trimmed | 228,684 | $359K | 0.2% | 2026-Q1 |
| BRIDGEWAY CAPITAL MANAGEMENT, LLC | 198,900 | $312K | 0.2% | 2026-Q1 |
| Arbiter Partners Capital Management LLC | 192,585 | $302K | 0.2% | 2026-Q1 |
| FMR LLC trimmed | 189,536 | $298K | 0.2% | 2026-Q1 |
| ALLIANCEBERNSTEIN L.P. | 150,592 | $279K | 0.2% | 2026-Q1 |
| Stonepine Capital Management, LLC trimmed | 164,045 | $258K | 0.2% | 2026-Q1 |
| RHUMBLINE ADVISERS trimmed | 159,235 | $250K | 0.2% | 2026-Q1 |
| Cornerstone Capital, Inc. added | 142,286 | $223K | 0.1% | 2026-Q1 |
| Invesco Ltd. trimmed | 135,087 | $212K | 0.1% | 2026-Q1 |
| BANK OF AMERICA CORP /DE/ added | 121,656 | $191K | 0.1% | 2026-Q1 |
| JPMORGAN CHASE & CO trimmed | 120,102 | $187K | 0.1% | 2026-Q1 |
| AQR CAPITAL MANAGEMENT LLC added | 115,647 | $182K | 0.1% | 2026-Q1 |
| DEUTSCHE BANK AG\ added | 92,670 | $145K | 0.1% | 2026-Q1 |
| PRICE T ROWE ASSOCIATES INC /MD/ added | 77,040 | $122K | 0.1% | 2026-Q1 |
| SEI INVESTMENTS CO added | 60,578 | $95K | 0.1% | 2026-Q1 |
| Vanguard Global Advisers, LLC new | 51,396 | $81K | 0.1% | 2026-Q1 |
| WELLS FARGO & COMPANY/MN trimmed | 50,133 | $79K | 0.1% | 2026-Q1 |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. added | 50,113 | $79K | 0.1% | 2026-Q1 |
| Shay Capital LLC new | 49,662 | $78K | 0.0% | 2026-Q1 |
| MetLife Investment Management, LLC added | 48,132 | $76K | 0.0% | 2026-Q1 |
| LMR Partners LLP | 897,392 | $72K | 0.0% | 2026-Q1 |
| XTX Topco Ltd added | 44,659 | $70K | 0.0% | 2026-Q1 |
| BLAIR WILLIAM & CO/IL added | 43,216 | $68K | 0.0% | 2026-Q1 |
| JACOBS LEVY EQUITY MANAGEMENT, INC trimmed | 42,966 | $67K | 0.0% | 2026-Q1 |
| ARISTEIA CAPITAL, L.L.C. | 679,919 | $65K | 0.0% | 2026-Q1 |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP added | 41,629 | $65K | 0.0% | 2026-Q1 |
| LPL Financial LLC added | 36,164 | $57K | 0.0% | 2026-Q1 |
| Tower Research Capital LLC (TRC) added | 35,306 | $55K | 0.0% | 2026-Q1 |
| AMERICAN CENTURY COMPANIES INC trimmed | 34,816 | $55K | 0.0% | 2026-Q1 |
| WOODSTOCK CORP trimmed | 34,418 | $54K | 0.0% | 2026-Q1 |
| NINE MASTS CAPITAL Ltd new | 29,062 | $46K | 0.0% | 2026-Q1 |
| MANUFACTURERS LIFE INSURANCE COMPANY, THE | 28,943 | $45K | 0.0% | 2026-Q1 |
| INTECH INVESTMENT MANAGEMENT LLC trimmed | 28,937 | $45K | 0.0% | 2026-Q1 |
| BARCLAYS PLC trimmed | 28,760 | $45K | 0.0% | 2026-Q1 |
| Legato Capital Management LLC trimmed | 28,196 | $44K | 0.0% | 2026-Q1 |
| JANE STREET GROUP, LLC trimmed | 27,551 | $43K | 0.0% | 2026-Q1 |
| JANUS HENDERSON GROUP PLC added | 8,058,228 | $20M | 12.4% | 2025-Q1 stale |
| MACQUARIE GROUP LTD added | 4,422,738 | $11M | 6.7% | 2025-Q1 stale |
| VANGUARD GROUP INC added | 5,625,197 | $10M | 6.6% | 2025-Q4 stale |
| Rubric Capital Management LP | 2,850,588 | $7M | 4.3% | 2025-Q1 stale |
| Chicago Capital, LLC trimmed | 2,620,454 | $6M | 4.0% | 2025-Q1 stale |
| VILLERE ST DENIS J & CO LLC trimmed | 1,437,944 | $3M | 2.2% | 2025-Q1 stale |
| Knott David M Jr trimmed | 982,336 | $2M | 1.5% | 2025-Q1 stale |
| Impax Asset Management Group plc | 761,387 | $2M | 1.2% | 2025-Q1 stale |
| ROYCE & ASSOCIATES LP added | 867,080 | $2M | 1.0% | 2025-Q2 stale |
| FIRST SABREPOINT CAPITAL MANAGEMENT LP trimmed | 410,000 | $984K | 0.6% | 2025-Q1 stale |
| Murchinson Ltd. trimmed | 502,810 | $875K | 0.6% | 2025-Q2 stale |
| Kent Lake PR LLC trimmed | 500,000 | $800K | 0.5% | 2025-Q3 stale |
| MARSHALL WACE, LLP trimmed | 359,665 | $626K | 0.4% | 2025-Q2 stale |
| Woodline Partners LP trimmed | 285,714 | $529K | 0.3% | 2025-Q4 stale |
| TANG CAPITAL MANAGEMENT LLC | 300,000 | $480K | 0.3% | 2025-Q3 stale |
| GSA CAPITAL PARTNERS LLP added | 262,371 | $420K | 0.3% | 2025-Q3 stale |
| TWO SIGMA ADVISERS, LP added | 197,530 | $365K | 0.2% | 2025-Q4 stale |
| Graham Capital Management, L.P. added | 167,172 | $267K | 0.2% | 2025-Q3 stale |
| Universal- Beteiligungs- und Servicegesellschaft mbH new | 108,111 | $259K | 0.2% | 2025-Q1 stale |
| Northeast Financial Consultants Inc | 110,996 | $193K | 0.1% | 2025-Q2 stale |
| MIRABELLA FINANCIAL SERVICES LLP | 100,381 | $175K | 0.1% | 2025-Q2 stale |
| CONNORS INVESTOR SERVICES INC | 61,941 | $115K | 0.1% | 2025-Q4 stale |
| Corebridge Financial, Inc. added | 46,712 | $112K | 0.1% | 2025-Q1 stale |
| HRT FINANCIAL LP added | 70,215 | $112K | 0.1% | 2025-Q3 stale |
| Gallagher Fiduciary Advisors, LLC added | 43,696 | $105K | 0.1% | 2025-Q1 stale |
| Atria Investments, Inc added | 43,563 | $105K | 0.1% | 2025-Q1 stale |
| Henshaw Capital LLC | 37,507 | $90K | 0.1% | 2025-Q1 stale |
| BOOTHBAY FUND MANAGEMENT, LLC trimmed | 47,596 | $88K | 0.1% | 2025-Q4 stale |
| ACADIAN ASSET MANAGEMENT LLC new | 47,625 | $88K | 0.1% | 2025-Q4 stale |
| AMERIPRISE FINANCIAL INC trimmed | 32,749 | $61K | 0.0% | 2025-Q4 stale |
| Mesirow Financial Investment Management, Inc. | 30,764 | $59K | 0.0% | 2025-Q1 stale |
| SHERBROOKE PARK ADVISERS LLC added | 20,388 | $49K | 0.0% | 2025-Q1 stale |
| Cerity Partners LLC added | 29,562 | $47K | 0.0% | 2025-Q3 stale |
| STATE BOARD OF ADMINISTRATION OF FLORIDA RETIREMENT SYSTEM | 26,753 | $47K | 0.0% | 2025-Q2 stale |
| Brevan Howard Capital Management LP trimmed | 24,415 | $45K | 0.0% | 2025-Q4 stale |
| Corient Private Wealth LLC trimmed | 27,289 | $44K | 0.0% | 2025-Q3 stale |
| SG Americas Securities, LLC added | 23,141 | $43K | 0.0% | 2025-Q4 stale |
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.