MBX's three largest insider shareholders as of September 26, 2026 are Patrick J Heron (Director, 5.22Mn shares), Life Sciences X, L.P. Frazier (TenPercentOwner, 4.55Mn shares), Advisors Llc Orbimed (Director, 3.81Mn shares).
| # | Insider | Position | Direct | Indirect | Total | Share of Insiders | Last Filed |
|---|---|---|---|---|---|---|---|
| 1 | Patrick J Heron | Director, TenPercentOwner | 0 | 5,219,440 | 5,219,440 | 10.0% | 30 Sep, 2025 |
| 2 | Life Sciences X, L.P. Frazier | TenPercentOwner | 4,552,774 | 0 | 4,552,774 | 8.7% | 17 Sep, 2024 |
| 3 | Scott D Sandell | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 4 | Forest Baskett | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 5 | Edward T Mathers | Director, TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 6 | Rick Yang | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 7 | Mohamad Makhzoumi | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 8 | Carmen Chang | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 9 | Anthony A. Jr. Florence | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 10 | Ali Behbahani | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 11 | Paul Edward Walker | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 12 | Enterprise Associates 17, L.P. New | TenPercentOwner | 3,614,486 | 0 | 3,614,486 | 6.9% | 17 Sep, 2024 |
| 13 | Tiba Aynechi | Director | 0 | 2,136,335 | 2,136,335 | 4.1% | 17 Sep, 2024 |
| 14 | Biomedical Innovation Master Investors (Cayman) Ii L.P. Wellington | TenPercentOwner | 1,790,122 | 0 | 1,790,122 | 3.4% | 17 Sep, 2024 |
| 15 | Advisors Llc Orbimed | Director, TenPercentOwner | 0 | 747,887 | 747,887 | 1.4% | 19 Feb, 2025 |
| 16 | Carl L Gordon | Director, TenPercentOwner | 0 | 747,887 | 747,887 | 1.4% | 19 Feb, 2025 |
| 17 | P. Kent Hawryluk | President Ceo | 727,667 | 0 | 727,667 | 1.4% | 08 May, 2026 |
| 18 | James M Cornelius | Director | 102,082 | 0 | 102,082 | 0.2% | 17 Sep, 2024 |
| 19 | Steven L. Hoerter | President And Ceo | 82,938 | 0 | 82,938 | 0.2% | 04 Aug, 2026 |
| 20 | John W Smither | Chief Financial Officer | 28,000 | 0 | 28,000 | 0.1% | 04 Aug, 2026 |
| 21 | Ora H. Pescovitz | Director | 24,329 | 0 | 24,329 | 0.0% | 10 Apr, 2025 |
| 22 | Richard Bartram | Chief Financial Officer | 15,000 | 0 | 15,000 | 0.0% | 03 Feb, 2026 |
| 23 | Salomon Azoulay | Chief Medical Officer | 14,399 | 0 | 14,399 | 0.0% | 05 Aug, 2026 |
Each row is that insider’s most recently reported position, from Form 4 filings over the last 60 months — which is why this total does not tie to the quarterly series above, where a quarter counts only the insiders who filed in it. Shares held through a fund or institutional portfolio are counted on the institutional ownership page instead.
| Date | Insider | Position | Transaction | Shares | Price | Value | Shares Held After | Ownership |
|---|---|---|---|---|---|---|---|---|
| 04 Aug, 2026 | Salomon Azoulay | Chief Medical Officer | Disposed S | 370 | $65.77 | $24.33K | 14,399 | Direct |
| 03 Aug, 2026 | Steven L. Hoerter | President And Ceo | Acquired A | 71,000 | $0.00 | $0 | 82,938 | Direct |
| 03 Aug, 2026 | John W Smither | Chief Financial Officer | Acquired A | 28,000 | $0.00 | $0 | 28,000 | Direct |
| 03 Aug, 2026 | John W Smither | Chief Financial Officer | Acquired A | 130,000 | $0.00 | $0 | 130,000 | Direct |
| 03 Aug, 2026 | Steven L. Hoerter | President And Ceo | Acquired A | 331,000 | $0.00 | $0 | 331,000 | Direct |
| 04 Jun, 2026 | Patrick J Heron | Director, TenPercentOwner | Acquired A | 12,500 | $0.00 | $0 | 12,500 | Direct |
| 04 Jun, 2026 | Edward T Mathers | Director | Acquired A | 12,500 | $0.00 | $0 | 12,500 | Direct |
| 04 Jun, 2026 | Tiba Aynechi | Director | Acquired A | 12,500 | $0.00 | $0 | 12,500 | Direct |
| 04 Jun, 2026 | Laurie Stelzer | Director | Acquired A | 12,500 | $0.00 | $0 | 12,500 | Direct |
| 04 Jun, 2026 | Steven Ryder | Director | Acquired A | 12,500 | $0.00 | $0 | 12,500 | Direct |
| 04 Jun, 2026 | Ora H. Pescovitz | Director | Acquired A | 12,500 | $0.00 | $0 | 12,500 | Direct |
| 04 Jun, 2026 | Steven L. Hoerter | Director | Acquired A | 12,500 | $0.00 | $0 | 12,500 | Direct |
| 08 May, 2026 | Salomon Azoulay | Chief Medical Officer | Acquired M | 55,000 | $10.46 | $575.30K | 69,769 | Direct |
| 08 May, 2026 | Salomon Azoulay | Chief Medical Officer | Disposed S | 55,000 | $38.38 | $2.11Mn | 14,769 | Direct |
| 08 May, 2026 | Salomon Azoulay | Chief Medical Officer | Acquired M | 15,003 | $16.00 | $240.05K | 29,772 | Direct |
| 08 May, 2026 | Salomon Azoulay | Chief Medical Officer | Disposed S | 15,003 | $38.30 | $574.61K | 14,769 | Direct |
| 08 May, 2026 | Salomon Azoulay | Chief Medical Officer | Acquired M | 55,000 | $0.00 | $0 | 194,540 | Direct |
| 08 May, 2026 | Salomon Azoulay | Chief Medical Officer | Acquired M | 15,003 | $0.00 | $0 | 30,008 | Direct |
| 06 May, 2026 | Salomon Azoulay | Chief Medical Officer | Disposed S | 231 | $29.54 | $6.82K | 14,769 | Direct |
| 06 May, 2026 | P. Kent Hawryluk | President Ceo | Disposed S | 607 | $29.54 | $17.93K | 727,667 | Direct |