SCHEDULE 13D/A

MBX Biosciences Inc

Common Stock, par value $0.0001 per share · CUSIP: 55287L101

Event date: 2025-11-06

Reporting persons may disclose overlapping interests. Their amounts are shown individually and are not added into a filing total.

Filing-level shares

Unavailable

Percent of class

Unavailable

• New Enterprise Associates 17, L.P.Reported CIK 0001768564

  Shares: 3,614,486.00 · Class: 8.1%

• NEA Partners 17, L.P.Reported CIK 0001796820

  Shares: 3,614,486.00 · Class: 8.1%

• NEA 17 GP, LLCReported CIK 0001796821

  Shares: 3,614,486.00 · Class: 8.1%

• Forest BaskettReported CIK 0001277631

  Shares: 3,614,486.00 · Class: 8.1%

• Ali BehbahaniReported CIK 0001613867

  Shares: 3,614,486.00 · Class: 8.1%

• Carmen ChangReported CIK 0001746342

  Shares: 3,614,486.00 · Class: 8.1%

• Anthony A. Florence, Jr.Reported CIK 0001559827

  Shares: 3,614,486.00 · Class: 8.1%

• Mohamad H. MakhzoumiReported CIK 0001630226

  Shares: 3,614,486.00 · Class: 8.1%

• Edward T. MathersReported CIK 0001328625

  Shares: 3,619,474.00 · Class: 8.1%

• Scott D. SandellReported CIK 0001237289

  Shares: 3,614,486.00 · Class: 8.1%

• Paul WalkerReported CIK 0001553150

  Shares: 3,614,486.00 · Class: 8.1%

• Rick YangReported CIK 0001851328

  Shares: 3,614,486.00 · Class: 8.1%

Amounts are as disclosed in this filing. Schedule type alone does not establish investment intent.