FMR LLC and Abigail P. Johnson filed Amendment No. 2 to a Schedule 13G with the SEC on November 4, 2026, disclosing beneficial ownership of common stock in MBX Biosciences Inc. (NASDAQ:MBX) as of September 30, 2026.

Key Highlights

  • Aggregate beneficial ownership: FMR LLC and Abigail P. Johnson each reported aggregate beneficial ownership of 7,224,009.10 shares of MBX Biosciences common stock.
  • Percent of class: The reported holdings represent 15.0% of the outstanding common stock, according to the filing.
  • Sole voting power (FMR LLC): FMR LLC reported sole voting power over 7,211,235.00 shares, with 0.00 shares subject to shared voting power.
  • Sole dispositive power: Both FMR LLC and Abigail P. Johnson reported sole dispositive power over 7,224,009.10 shares, with no shared dispositive power.
  • Triggering event date: The date of the event requiring this filing was September 30, 2026, as stated in the document.
  • Certifying party: The filing was signed by Stephanie J. Brown, acting under powers of attorney on behalf of both FMR LLC and Abigail P. Johnson.

FMR LLC Discloses Large Passive Stake in MBX Biosciences as of September 30, 2026

According to the filing, FMR LLC, a Delaware-organized holding company headquartered at 245 Summer Street, Boston, Massachusetts 02210, submitted Amendment No. 2 to its Schedule 13G regarding common stock of MBX Biosciences Inc., whose principal executive offices are located at 11711 N. Meridian Street, Suite 300, Carmel, Indiana 46032. The event triggering this amendment occurred on September 30, 2026, and the amendment was signed on November 4, 2026.

The filing discloses that FMR LLC beneficially owns 7,224,009.10 shares, representing 15.0% of MBX Biosciences' outstanding common stock (CUSIP 55287L101). Of that total, the filing states FMR LLC holds sole voting power over 7,211,235.00 shares and sole dispositive power over the full 7,224,009.10 shares. Abigail P. Johnson, identified as a United States individual, is also listed as a reporting person with the same aggregate beneficial ownership figure of 7,224,009.10 shares and sole dispositive power over the same amount, though she is reported as holding 0.00 shares with sole or shared voting power.

The filing states that one or more other persons are known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the common stock, but that no single other person's interest exceeds five percent of the total outstanding common stock. The filing certifies that the securities "were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer," consistent with a passive investment classification.

What Was Disclosed

FMR LLC and Abigail P. Johnson filed Amendment No. 2 to a Schedule 13G reporting combined beneficial ownership of 7,224,009.10 shares, or 15.0%, of MBX Biosciences common stock as of September 30, 2026, with the filing signed on November 4, 2026.