As of August 29, 2026, MBX Biosciences's top three insider holders are Patrick J Heron (Director, 5.22Mn shares), Life Sciences X, L.P. Frazier (TenPercentOwner, 4.55Mn shares), Life Sciences X, L.P. Frazier (TenPercentOwner, 4.55Mn shares).
| # | Insider | Position | Direct | Indirect | Total | Share of Insiders | Last Filed |
|---|---|---|---|---|---|---|---|
| 1 | Patrick J Heron | Director, TenPercentOwner | 0 | 5,219,440 | 5,219,440 | 11.0% | 30 Sep, 2025 |
| 2 | Life Sciences X, L.P. Frazier | TenPercentOwner | 4,552,774 | 0 | 4,552,774 | 9.6% | 17 Sep, 2024 |
| 3 | Forest Baskett | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 7.6% | 17 Sep, 2024 |
| 4 | Carmen Chang | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 7.6% | 17 Sep, 2024 |
| 5 | Scott D Sandell | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 7.6% | 17 Sep, 2024 |
| 6 | Anthony A. Jr. Florence | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 7.6% | 17 Sep, 2024 |
| 7 | Ali Behbahani | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 7.6% | 17 Sep, 2024 |
| 8 | Mohamad Makhzoumi | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 7.6% | 17 Sep, 2024 |
| 9 | Enterprise Associates 17, L.P. New | TenPercentOwner | 3,614,486 | 0 | 3,614,486 | 7.6% | 17 Sep, 2024 |
| 10 | Rick Yang | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 7.6% | 17 Sep, 2024 |
| 11 | Paul Edward Walker | TenPercentOwner | 0 | 3,614,486 | 3,614,486 | 7.6% | 17 Sep, 2024 |
| 12 | Tiba Aynechi | Director | 0 | 2,136,335 | 2,136,335 | 4.5% | 17 Sep, 2024 |
| 13 | Biomedical Innovation Master Investors (Cayman) Ii L.P. Wellington | TenPercentOwner | 1,790,122 | 0 | 1,790,122 | 3.8% | 17 Sep, 2024 |
| 14 | Carl L Gordon | Director, TenPercentOwner | 0 | 747,887 | 747,887 | 1.6% | 19 Feb, 2025 |
| 15 | P. Kent Hawryluk | President Ceo | 0 | 486,777 | 486,777 | 1.0% | 16 Mar, 2026 |
| 16 | James M Cornelius | Director | 102,082 | 0 | 102,082 | 0.2% | 17 Sep, 2024 |
| 17 | Ora H. Pescovitz | Director | 24,329 | 0 | 24,329 | 0.1% | 10 Apr, 2025 |
| 18 | Richard Bartram | Chief Financial Officer | 15,000 | 0 | 15,000 | 0.0% | 03 Feb, 2026 |
| 19 | Salomon Azoulay | Chief Medical Officer | 14,399 | 0 | 14,399 | 0.0% | 05 Aug, 2026 |
| 20 | Steven L. Hoerter | Director | 11,938 | 0 | 11,938 | 0.0% | 04 May, 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 |
| 04 Jun, 2026 | Edward T Mathers | 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 | Patrick J Heron | Director, TenPercentOwner | 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 | Ora H. Pescovitz | 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 |
| 01 May, 2026 | Steven L. Hoerter | Director | Acquired A | 11,938 | $0.00 | $0 | 11,938 | Direct |
| 01 May, 2026 | Steven L. Hoerter | Director | Acquired A | 74,249 | $0.00 | $0 | 74,249 | Direct |
| 13 Mar, 2026 | P. Kent Hawryluk | President Ceo | Acquired P | 18,500 | $28.41 | $525.66K | 486,777 | Indirect |
| 26 Feb, 2026 | P. Kent Hawryluk | President Ceo | Acquired M | 28,768 | $16.00 | $460.29K | 728,274 | Direct |
| 26 Feb, 2026 | P. Kent Hawryluk | President Ceo | Disposed M | 28,768 | $0.00 | $0 | 91,668 | Direct |
| 02 Feb, 2026 | P. Kent Hawryluk | President Ceo | Acquired A | 35,250 | $0.00 | $0 | 699,506 | Direct |
| 02 Feb, 2026 | Richard Bartram | Chief Financial Officer | Acquired A | 15,000 | $0.00 | $0 | 15,000 | Direct |