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MBX Biosciences, Inc.

MBX
Exchange
Nasdaq
Industry
Pharmaceutical Preparations
SEC CIK
0001776111

In the last 90 days, MBX Biosciences, Inc. insiders filed 0 open-market purchases and 1 sale; 172 institutions reported holding it in 13F filings for Q2 2026, worth $3.06B in total; no superinvestor holds it.

Holders of 5% or more of MBX

Holders whose latest Schedule 13D or 13G filing reports 5% or more of MBX Biosciences, Inc., largest stake first. The change is against the holder's previous filing.

Holders of 5% or more of MBX
HolderLatest formStakeChangeFirst filedLatest filingFiling
FMR LLC13G/A15.00%7.22M shares+3.80 ppfrom 11.20%May 6, 20263 filingsNov 5, 2026SEC
Frazier Life Sciences Public Fund, L.P.13D/A11.70%5.24M shares0.00 ppfrom 11.70%Sep 23, 20244 filingsAug 10, 2026SEC
Wellington Management Group LLP13G/A10.50%4.98M shares+3.00 ppfrom 7.50%Nov 8, 20246 filingsJul 8, 2026SEC
New Enterprise Associates 17, L.P.13D/A8.10%3.62M shares–Sep 23, 20242 filingsNov 10, 2025SEC
OrbiMed Advisors LLC13D/A6.40%3.07M shares−1.30 ppfrom 7.70%Sep 23, 20244 filingsAug 10, 2026SEC
BlackRock, Inc.13G5.50%2.63M shares+0.70 ppfrom 4.80%Jan 21, 20263 filingsJul 29, 2026SEC
Paradigm Biocapital Advisors LP13G5.20%2.49M sharesNewJun 24, 20261 filingJun 24, 2026SEC

Stakes are as of each holder's latest filing. Holders whose last filing was in the old format (before December 18, 2024) have no stake on record and are not listed, and after an acquisition or delisting holders usually stop filing.

13D and 13G filings

32 Schedule 13D and 13G filings on MBX Biosciences, Inc., newest first, including old-format filings without a stake.

Schedule 13D and 13G filings on MBX
Filed (ET)FilerFormStakeChangeEvent dateFiling
Nov 5, 20261:22 PM ETFMR LLCand 1 other13G/A15.00%7.22M shares+3.80 ppfrom 11.20%Sep 30, 2026SEC
Aug 14, 20268:27 AM ETDeep Track Capital, LPand 2 others13G/A3.64%1.73M shares−2.91 ppfrom 6.55%Below 5%Jun 30, 2026SEC
Aug 10, 20265:35 PM ETFrazier Life Sciences Public Fund, L.P.and 10 others13D/A11.70%5.24M shares0.00 ppfrom 11.70%Aug 6, 2026SEC
Aug 10, 20264:44 PM ETOrbiMed Advisors LLCand 2 others13D/A6.40%3.07M shares−1.30 ppfrom 7.70%Aug 6, 2026SEC
Jul 29, 20263:19 PM ETBlackRock, Inc.13G5.50%2.63M shares+0.70 ppfrom 4.80%Jun 30, 2026SEC
Jul 8, 202612:59 PM ETWellington Management Group LLPand 3 others13G/A10.50%4.98M shares+3.00 ppfrom 7.50%Jun 30, 2026SEC
Jul 8, 202610:11 AM ETFMR LLCand 1 other13G/A11.20%5.32M shares+5.00 ppfrom 6.20%Jun 30, 2026SEC
Jun 24, 20264:05 PM ETParadigm Biocapital Advisors LPand 3 others13G5.20%2.49M sharesNewJun 16, 2026SEC
May 6, 202611:30 AM ETFMR LLCand 1 other13G6.20%2.94M sharesNewMar 31, 2026SEC
Apr 27, 20264:12 PM ETBlackRock, Inc.13G/A4.80%2.29M shares−0.30 ppfrom 5.10%Below 5%Mar 31, 2026SEC
Feb 11, 20266:42 PM ETOrbiMed Advisors LLCand 2 others13D/A7.70%3.64M shares−1.30 ppfrom 9.00%Feb 5, 2026SEC
Feb 10, 202611:21 AM ETWellington Management Group LLPand 3 others13G/A7.50%3.35M shares−3.30 ppfrom 10.80%Dec 31, 2025SEC
Jan 21, 202612:30 PM ETBlackRock, Inc.13G5.10%2.27M sharesNewDec 31, 2025SEC
Nov 14, 20254:05 PM ETHawryluk P. Kent13G/A4.30%2.00M shares–Below 5%Sep 30, 2025SEC
Nov 12, 20256:44 PM ETWellington Biomedical Innovation Master Investors (Cayman) II L.P.13G/A4.50%2.02M shares–Below 5%Sep 30, 2025SEC
Nov 10, 20255:08 PM ETNew Enterprise Associates 17, L.P.and 11 others13D/A8.10%3.62M shares–Nov 6, 2025SEC
Oct 6, 202512:22 PM ETWellington Management Group LLPand 3 others13G/A10.80%4.82M shares+4.00 ppfrom 6.80%Sep 30, 2025SEC
Sep 30, 20257:06 PM ETOrbiMed Advisors LLCand 2 others13D/A9.00%4.00M shares–Sep 26, 2025SEC
Sep 30, 20256:15 PM ETNorwest Venture Partners XVI, LPand 5 others13D/A4.80%2.14M shares–Below 5%Sep 26, 2025SEC
Sep 30, 20255:01 PM ETFrazier Life Sciences Public Fund, L.P.and 13 others13D/A11.70%5.22M shares−1.90 ppfrom 13.60%Sep 26, 2025SEC
Aug 20, 20255:23 PM ETFrazier Life Sciences Public Fund, L.P.and 16 others13D/A13.60%4.56M shares–Aug 18, 2025SEC
Aug 14, 20258:48 AM ETDeep Track Capital, LPand 2 others13G/A6.55%2.19M shares–Jun 30, 2025SEC
Aug 12, 202510:34 AM ETWellington Management Group LLPand 3 others13G/A6.80%2.27M shares−1.10 ppfrom 7.90%Jun 30, 2025SEC
May 12, 202510:44 AM ETWellington Management Group LLPand 3 others13G/A7.90%2.64M shares–Mar 31, 2025SEC
Nov 8, 2024Wellington Management Group LLP13GOld format–New–SEC
Nov 1, 2024Hawryluk P. Kent13GOld format–New–SEC
Sep 23, 2024Frazier Life Sciences Public Fund, L.P.13DOld format–New–SEC
Sep 23, 2024Deep Track Capital, LP13GOld format–New–SEC
Sep 23, 2024Norwest Venture Partners XVI, LP13DOld format–New–SEC
Sep 23, 2024New Enterprise Associates 17, L.P.13DOld format–New–SEC
Sep 23, 2024OrbiMed Advisors LLC13DOld format–New–SEC
Sep 20, 2024Wellington Biomedical Innovation Master Investors (Cayman) II L.P.13GOld format–New–SEC

Form 144: proposed insider sales

19 notices from officers, directors and other affiliates planning to sell MBX Biosciences, Inc. shares, newest first.

Form 144 notices for MBX
Filed (ET)SellerShares to sellMarket valuePlanned saleBrokerFiling
Nov 10, 20267:25 PM ETHoerter Steven L.Director4.89K$268.2KNov 10, 2026Fidelity Brokerage Services LLCSEC
Nov 4, 20263:12 PM ETAzoulay SalomonOfficer373$20.1KNov 4, 2026Fidelity Brokerage Services LLCSEC
Aug 17, 20263:41 PM ETHawryluk P. KentFormer officer3.75K$255.7KAug 17, 2026Fidelity Brokerage Services LLCSEC
Aug 4, 20264:44 PM ETHawryluk P. KentOfficer · Director936$61.6KAug 4, 2026Fidelity Brokerage Services LLCSEC
Aug 4, 20264:42 PM ETAzoulay SalomonOfficer370$24.3KAug 4, 2026Fidelity Brokerage Services LLCSEC
Jun 10, 202612:41 PM ETBartram RichardFormer officer9.17K$280.0KJun 10, 2026Fidelity Brokerage Services LLCSEC
Jun 9, 20264:38 PM ETBartram RichardFormer officer10.8K$321.3KJun 9, 2026Fidelity Brokerage Services LLCSEC
May 13, 20264:17 PM ETBartram RichardFormer officer15.0K$554.3KMay 13, 2026Fidelity Brokerage Services LLCSEC
May 11, 20263:54 PM ETBartram RichardFormer officer22.5K$991.9KMay 11, 2026Fidelity Brokerage Services LLCSEC
May 8, 20264:10 PM ETAzoulay SalomonOfficer70.0K$2.69MMay 8, 202610b5-1Fidelity Brokerage Services LLCSEC
May 8, 202612:21 PM ETBartram RichardFormer officer10.0K$379.6KMay 8, 2026Fidelity Brokerage Services LLCSEC
May 7, 202612:47 PM ETBartram RichardFormer officer10.0K$322.1KMay 7, 2026Fidelity Brokerage Services LLCSEC
May 6, 20263:29 PM ETHawryluk P. KentOfficer · Director607$17.9KMay 6, 2026Fidelity Brokerage Services LLCSEC
May 6, 20263:12 PM ETAzoulay SalomonOfficer231$6.82KMay 6, 2026Fidelity Brokerage Services LLCSEC
May 1, 20262:59 PM ETBartram RichardFormer officer5.00K$159.0KMay 1, 2026Fidelity Brokerage Services LLCSEC
Apr 22, 202611:59 AM ETBartram RichardFormer officer10.4K$341.4KApr 22, 2026Fidelity Brokerage Services LLCSEC
Mar 25, 20263:20 PM ETBartram RichardFormer officer1.06K$30.2KMar 25, 2026Fidelity Brokerage Services LLCSEC
Mar 16, 20262:47 PM ETBartram RichardFormer officer10.0K$300.5KMar 16, 2026Fidelity Brokerage Services LLCSEC
Jan 12, 20263:41 PM ETCornelius James MFormer director30.9K$1.10MJan 12, 2026Fidelity Brokerage Services LLCSEC