MBX Biosciences, Inc. (MBX) Ownership
MBX ownership summary
as of October 18, 2026- Institutions
- 115.9% of shares outstanding
- Insiders
- 2.82% of shares outstanding
- Shares outstanding
- 48.2M
- Float
- 31.0M shares available to trade
- Short interest
- 12.95% 4.5M shares short
- Days to cover
- 8.58 short interest up 8.1% vs prior month
- Institutions 115.94%
- Insiders 2.82%
MBX top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Frazier Life Sciences Management, L.P. | 13.81% | 6.7M | $330.0M | — | June 30, 2026 |
| 2 | FMR Inc | 11.05% | 5.3M | $264.1M | +2.4M (+81.3%) | June 30, 2026 |
| 3 | Wellington Management Company LLP | 10.34% | 5.0M | $246.9M | +1.8M (+55.9%) | June 30, 2026 |
| 4 | NEA Management Company, LLC | 7.51% | 3.6M | $179.3M | — | June 30, 2026 |
| 5 | Orbimed Advisors LLC | 7.12% | 3.4M | $170.1M | −209,151 (−5.7%) | June 30, 2026 |
| 6 | BlackRock Inc | 6.90% | 3.3M | $164.9M | +382,266 (+13.0%) | June 30, 2026 |
| 7 | Paradigm Biocapital Advisors LP | 5.21% | 2.5M | $124.4M | +2.5M (0.0%) | June 30, 2026 |
| 8 | NVP Associates LLC | 4.44% | 2.1M | $106.0M | — | June 30, 2026 |
| 9 | Deep Track Capital, LP | 3.60% | 1.7M | $86.0M | −1.0M (−37.2%) | June 30, 2026 |
| 10 | Polar Capital Holdings PLC | 3.34% | 1.6M | $79.8M | −13,672 (−0.8%) | June 30, 2026 |
| 11 | Vanguard Capital Management, LLC | 3.07% | 1.5M | $73.3M | −204 (−0.0%) | June 30, 2026 |
| 12 | Aaron Wealth Advisors LLC | 2.42% | 1.2M | $57.9M | −377 (−0.0%) | June 30, 2026 |
| 13 | Driehaus Capital Management LLC | 2.19% | 1.1M | $52.4M | +38,367 (+3.8%) | June 30, 2026 |
| 14 | Kynam Capital Management, LP | 1.94% | 935K | $46.4M | — | June 30, 2026 |
| 15 | Woodline Partners LP | 1.87% | 900K | $44.7M | +29 (+0.0%) | June 30, 2026 |
| 16 | Eventide Asset Management, LLC | 1.81% | 873K | $43.3M | −16,508 (−1.9%) | June 30, 2026 |
| 17 | State Street Corp | 1.79% | 864K | $42.9M | +77,258 (+9.8%) | June 30, 2026 |
| 18 | T. Rowe Price Associates, Inc. | 1.69% | 815K | $40.4M | −214,200 (−20.8%) | June 30, 2026 |
| 19 | Parkman Healthcare Partners LLC | 1.66% | 800K | $39.7M | +136 (+0.0%) | June 30, 2026 |
| 20 | Geode Capital Management, LLC | 1.61% | 773K | $38.4M | +102,687 (+15.3%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 9 holders added 7.3M shares and 7 cut 1.5M.
MBX top mutual fund and ETF holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Polar Capital Biotech S Inc | 3.16% | 1.5M | $75.6M | — | August 31, 2026 |
| 2 | Vanguard MStar Total Stk Mkt Idx Invest | 2.36% | 1.1M | $56.5M | −1,497 (−0.1%) | August 31, 2026 |
| 3 | Eventide Healthcare & Life Sciences I | 1.81% | 873K | $43.3M | −16,508 (−1.9%) | June 30, 2026 |
| 4 | Fidelity Advisor Biotechnology I | 1.70% | 818K | $40.6M | — | August 31, 2026 |
| 5 | iShares Russell 2000 ETF | 1.67% | 806K | $40.0M | −9,280 (−1.1%) | September 30, 2026 |
| 6 | Fidelity Select Health Care | 1.41% | 680K | $33.7M | — | August 31, 2026 |
| 7 | Fidelity Stock Selector Small Cap | 1.32% | 636K | $31.6M | — | July 31, 2026 |
| 8 | T. Rowe Price Health Sciences | 0.92% | 444K | $22.0M | −141,900 (−24.2%) | August 31, 2026 |
| 9 | Fidelity Small Cap Growth | 0.86% | 416K | $20.7M | +114,780 (+38.1%) | July 31, 2026 |
| 10 | Fidelity Series Small Cap Opps | 0.76% | 365K | $18.1M | −23,900 (−6.1%) | July 31, 2026 |
| 11 | Fidelity Small Cap Index | 0.70% | 339K | $16.8M | +2,882 (+0.9%) | July 31, 2026 |
| 12 | BlackRock Health Sciences Opps Inv A | 0.69% | 333K | $16.5M | — | August 31, 2026 |
| 13 | Fidelity Advisor Health Care I | 0.68% | 328K | $16.3M | — | August 31, 2026 |
| 14 | Fidelity | 0.67% | 321K | $15.9M | — | July 31, 2026 |
| 15 | Heptagon Driehaus US Micro Cap Eq C$ Acc | 0.62% | 297K | $14.7M | — | August 31, 2026 |
| 16 | Candriam Eqs L Biotech C USD Cap | 0.61% | 294K | $14.6M | — | March 31, 2026 |
| 17 | iShares Russell 2000 Growth ETF | 0.60% | 291K | $14.4M | −368 (−0.1%) | September 30, 2026 |
| 18 | Fidelity Select Biotechnology | 0.50% | 241K | $12.0M | — | August 31, 2026 |
| 19 | iShares Biotechnology ETF | 0.49% | 238K | $11.8M | −1,800 (−0.8%) | September 30, 2026 |
| 20 | Strategic Advisers Fidelity US TtlStk | 0.48% | 232K | $11.5M | +6,243 (+2.8%) | August 31, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
MBX insider transactions
latest 4| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2026-03-13 | P. Kent Hawryluk | Buy | $28.41 | 18,500 | $525,585 |
| 2025-10-20 | P. Kent Hawryluk | Buy | $13.64 | 20,000 | $272,800 |
| 2025-10-17 | Steven L Hoerter | Buy | $13.25 | 20,000 | $265,000 |
| 2025-09-26 | Patrick J Heron | Buy | $18.00 | 666,666 | $12.0M |
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.
MBX shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns MBX
Institutional investors own 115.9% of MBX Biosciences's shares and insiders 2.82%. The largest holder is Frazier Life Sciences Management, L.P. with 13.81% of the shares (6.7M), as of June 30, 2026. Among the top 20 institutions, 9 added shares and 7 reduced their stake in the latest filings. Short interest is 12.95% of the float, or 8.58 days of average trading volume. The share count rose 3,550.6% since 2022.
Related: MBX analyst forecast, MBX key metrics. See the MBX stock overview for the latest quote and news.
MBX ownership FAQ
Who owns the most MBX Biosciences stock?
The largest shareholders of MBX Biosciences are Frazier Life Sciences Management, L.P. (13.81%), FMR Inc (11.05%), Wellington Management Company LLP (10.34%), NEA Management Company, LLC (7.51%), Orbimed Advisors LLC (7.12%).
What percentage of MBX Biosciences is owned by institutions?
Institutions hold 115.9% of MBX Biosciences's shares outstanding; insiders hold 2.82%.
Which funds own MBX Biosciences?
The largest fund holders of MBX Biosciences are Polar Capital Biotech S Inc (3.16%), Vanguard MStar Total Stk Mkt Idx Invest (2.36%), Eventide Healthcare & Life Sciences I (1.81%), Fidelity Advisor Biotechnology I (1.70%), iShares Russell 2000 ETF (1.67%).
What is MBX Biosciences's short interest?
4.5M shares of MBX Biosciences were sold short, 12.95% of the float; at the average daily volume it would take 8.58 days to cover.
Are insiders buying or selling MBX Biosciences?
Of the latest 4 reported insider transactions in MBX Biosciences (since September 26, 2025), 4 were purchases and 0 were sales.
How many shares of MBX Biosciences are outstanding?
MBX Biosciences has 48.2M shares outstanding, of which 31.0M are in the public float.