MBX Biosciences, Inc. (MBX)
Every FINRA and SEC series the site collects for MBX Biosciences, Inc.: short interest with days to cover, daily short sale volume, fails to deliver and Form 4 insider trades. Listed on Nasdaq.
5.0M
Short interest
settlement 2026-08-14
11.2
Days to cover
-4.6% vs prior
55.6%
Short share of volume
2026-09-11
30
Fails to deliver
settlement 2026-08-04
-$24K
Insider flow, 90 days
0 buys, 1 sells
As of 2026-09-11.
Short interest
FINRA, twice a month; the last 12 months shown, all 46 settlements in the JSONAs of 14 August 2026, short interest in MBX is 4,950,102 shares, down 826,607 shares over the last month. Over the last 46 readings it ranged from 311,843 shares (15 October 2024) to 5,895,340 shares (30 June 2026). At the reported average volume of 443K shares a day that is 11.2 days to cover, a crowded short.
Embed this chartfree, with the attribution line it carries
<iframe src="https://xoomar.com/embed/stocks/mbx" width="100%" height="440" style="border:0;max-width:100%" loading="lazy" title="XOOMAR chart"></iframe>
| Settlement | Shares short | Change | Avg daily volume | Days to cover |
|---|---|---|---|---|
| 2026-08-14 | 4,950,102 | -4.6% | 442,769 | 11.18 |
| 2026-07-31 | 5,188,562 | -10.2% | 609,309 | 8.52 |
| 2026-07-15 | 5,776,709 | -2.0% | 930,195 | 6.21 |
| 2026-06-30 | 5,895,340 | +3.2% | 1,116,750 | 5.28 |
| 2026-06-15 | 5,710,506 | +18.7% | 960,306 | 5.95 |
| 2026-05-29 | 4,811,025 | +12.3% | 568,896 | 8.46 |
| 2026-05-15 | 4,284,613 | +6.2% | 857,788 | 4.99 |
| 2026-04-30 | 4,033,554 | +6.5% | 420,990 | 9.58 |
| 2026-04-15 | 3,786,542 | +5.4% | 490,818 | 7.71 |
| 2026-03-31 | 3,593,407 | +20.4% | 450,952 | 7.97 |
| 2026-03-13 | 2,983,725 | +24.6% | 596,352 | 5.00 |
| 2026-02-27 | 2,395,339 | +8.7% | 532,466 | 4.50 |
| 2026-02-13 | 2,202,822 | +12.1% | 714,619 | 3.08 |
| 2026-01-30 | 1,965,975 | -14.8% | 641,060 | 3.07 |
| 2026-01-15 | 2,307,824 | -40.0% | 800,131 | 2.88 |
| 2025-12-31 | 3,843,943 | +6.4% | 871,163 | 4.41 |
| 2025-12-15 | 3,611,905 | -11.9% | 832,256 | 4.34 |
| 2025-11-28 | 4,101,744 | -11.4% | 604,673 | 6.78 |
| 2025-11-14 | 4,629,382 | +1.0% | 750,881 | 6.17 |
| 2025-10-31 | 4,581,641 | +17.2% | 963,157 | 4.76 |
| 2025-10-15 | 3,909,541 | +0.2% | 998,549 | 3.92 |
| 2025-09-30 | 3,900,619 | -7.7% | 4,108,084 | 1.00 |
| 2025-09-15 | 4,226,517 | +10.0% | 411,736 | 10.27 |
| 2025-08-29 | 3,843,321 | -5.5% | 239,312 | 16.06 |
Daily short volume
FINRA Reg SHO, last 60 sessions. JSONAs of 11 September 2026, the short share of MBX volume is 55.6%, up 0.2 points over the last five sessions. Over the last 52 readings it ranged from 36.4% (14 August 2026) to 81.2% (7 July 2026). The latest reading is in line with the 30-session average of 56.1%, on 116K shares reported.
| Date | Short volume | Total volume | Short share | Exempt |
|---|---|---|---|---|
| 2026-09-11 | 65K | 116K | 55.6% | 0 |
| 2026-09-10 | 91K | 155K | 58.5% | 50 |
| 2026-09-09 | 77K | 105K | 73.6% | 0 |
| 2026-09-08 | 70K | 117K | 60.0% | 0 |
| 2026-09-04 | 51K | 105K | 48.4% | 0 |
| 2026-09-03 | 69K | 125K | 55.3% | 0 |
| 2026-09-02 | 77K | 135K | 56.9% | 0 |
| 2026-09-01 | 115K | 154K | 75.0% | 0 |
| 2026-08-31 | 119K | 194K | 61.0% | 203 |
| 2026-08-28 | 84K | 142K | 59.1% | 4,612 |
| 2026-08-27 | 73K | 102K | 71.2% | 0 |
| 2026-08-26 | 51K | 65K | 78.7% | 0 |
| 2026-08-25 | 64K | 115K | 55.3% | 0 |
| 2026-08-24 | 112K | 247K | 45.3% | 0 |
| 2026-08-21 | 108K | 169K | 64.0% | 0 |
| 2026-08-20 | 92K | 190K | 48.5% | 0 |
| 2026-08-19 | 145K | 240K | 60.6% | 0 |
| 2026-08-18 | 126K | 264K | 47.6% | 173 |
| 2026-08-17 | 105K | 202K | 52.3% | 201 |
| 2026-08-14 | 105K | 288K | 36.4% | 0 |
| 2026-08-13 | 66K | 163K | 40.6% | 0 |
| 2026-08-12 | 63K | 149K | 42.1% | 0 |
| 2026-08-11 | 92K | 151K | 60.7% | 0 |
| 2026-08-10 | 76K | 122K | 62.6% | 0 |
| 2026-08-07 | 105K | 209K | 50.3% | 0 |
| 2026-08-06 | 84K | 202K | 41.6% | 100 |
| 2026-08-05 | 107K | 205K | 52.3% | 300 |
| 2026-08-04 | 153K | 322K | 47.6% | 0 |
| 2026-08-03 | 100K | 185K | 54.2% | 200 |
| 2026-07-31 | 165K | 246K | 67.1% | 41 |
Fails to deliver
SEC, by settlement date. JSONAs of 4 August 2026, the fails-to-deliver balance in MBX is 30 shares, down 2,268 shares over the last settlement date. Over the last 52 readings it ranged from 1 share (4 February 2026) to 42,395 shares (21 November 2025). The latest reading sits at the bottom of that range.
| Settlement | Shares failed | Price | Value |
|---|---|---|---|
| 2026-08-04 | 30 | $64.41 | $2K |
| 2026-07-27 | 2,298 | $62.00 | $142K |
| 2026-07-24 | 3,296 | $63.57 | $210K |
| 2026-07-23 | 300 | $58.30 | $17K |
| 2026-07-22 | 680 | $60.28 | $41K |
| 2026-07-20 | 380 | $62.92 | $24K |
| 2026-07-17 | 798 | $58.32 | $47K |
| 2026-07-16 | 1,724 | $60.68 | $105K |
| 2026-07-15 | 170 | $56.59 | $10K |
| 2026-07-09 | 976 | $61.74 | $60K |
| 2026-07-08 | 2 | $62.00 | $124 |
| 2026-06-30 | 145 | $53.85 | $8K |
| 2026-06-29 | 7,308 | $52.31 | $382K |
| 2026-06-18 | 75 | $41.59 | $3K |
| 2026-06-17 | 3,952 | $40.09 | $158K |
| 2026-06-15 | 720 | $35.51 | $26K |
| 2026-06-11 | 1,853 | $30.99 | $57K |
| 2026-04-20 | 2,200 | $33.77 | $74K |
| 2026-03-16 | 487 | $28.00 | $14K |
| 2026-03-13 | 10,711 | $27.95 | $299K |
| 2026-03-12 | 435 | $28.94 | $13K |
| 2026-03-10 | 166 | $27.94 | $5K |
| 2026-03-06 | 191 | $31.44 | $6K |
| 2026-03-02 | 7,145 | $32.55 | $233K |
| 2026-02-26 | 2,127 | $35.64 | $76K |
| 2026-02-19 | 130 | $40.31 | $5K |
| 2026-02-13 | 117 | $38.00 | $4K |
| 2026-02-11 | 534 | $37.68 | $20K |
| 2026-02-09 | 311 | $37.67 | $12K |
| 2026-02-06 | 70 | $36.05 | $3K |
Insider trades
SEC Form 4, newest first. JSONInsiders at MBX reported 1 open-market sell worth $24K in the last 90 days and no open-market buys. Sells alone are a weak signal; insiders sell for tax, diversification and estate reasons all the time. Latest filing: Azoulay Salomon (Chief Medical Officer) on 2026-08-04.
| Date | Insider | Title | Type | Shares | Price | Value | Owned after |
|---|---|---|---|---|---|---|---|
| 2026-08-04 | Azoulay Salomon | Chief Medical Officer | Sell | 370 | $65.77 | $24K | 14K |
| 2026-08-03 | Smither John W | Chief Financial Officer | Grant | 28K | $0.00 | $0 | 28K |
| 2026-08-03 | Hoerter Steven L. | President and CEO | Grant | 71K | $0.00 | $0 | 83K |
| 2026-05-08 | Azoulay Salomon | Chief Medical Officer | Sell | 15K | $38.30 | $575K | 15K |
| 2026-05-08 | Azoulay Salomon | Chief Medical Officer | Option exercise | 15K | $16.00 | $240K | 30K |
| 2026-05-08 | Azoulay Salomon | Chief Medical Officer | Sell | 55K | $38.38 | $2.1M | 15K |
| 2026-05-08 | Azoulay Salomon | Chief Medical Officer | Option exercise | 55K | $10.46 | $575K | 70K |
| 2026-05-06 | Hawryluk P. Kent | President & CEO | Sell | 607 | $29.54 | $18K | 728K |
| 2026-05-06 | Azoulay Salomon | Chief Medical Officer | Sell | 231 | $29.54 | $7K | 15K |
| 2026-05-01 | Hoerter Steven L. | n/a | Grant | 12K | $0.00 | $0 | 12K |
| 2026-03-13 | Hawryluk P. Kent | President & CEO | Buy | 19K | $28.41 | $526K | 487K |
| 2026-02-26 | Hawryluk P. Kent | President & CEO | Option exercise | 29K | $16.00 | $460K | 728K |
| 2026-02-02 | Hawryluk P. Kent | President & CEO | Grant | 35K | $0.00 | $0 | 700K |
| 2026-02-02 | Bartram Richard | Chief Financial Officer | Grant | 15K | $0.00 | $0 | 15K |
| 2026-02-02 | Azoulay Salomon | Chief Medical Officer | Grant | 15K | $0.00 | $0 | 15K |
| 2025-10-24 | Hawryluk P. Kent | President & CEO | Option exercise | 183K | $3.25 | $594K | 664K |
| 2025-10-20 | Hawryluk P. Kent | President & CEO | Buy | 20K | $13.64 | $273K | 468K |
| 2025-10-17 | Hoerter Steven L. | n/a | Buy | 20K | $13.25 | $265K | 20K |
| 2025-09-26 | Heron Patrick J | n/a | Buy | 667K | $18.00 | $12.0M | 5.2M |
Form 4 filings are due within two business days of the trade. Insiders sell for many reasons that say nothing about the company; open-market buys are the rarer, stronger signal.
Planned sales (Form 144)
Newest first. JSON3 Form 144 notices on file for MBX worth $342K at the prices reported; 3 in the last 90 days worth $342K. Latest: Hawryluk P. Kent filed on 2026-08-17 to sell 3,745 shares ($256K) from 2026-08-17.
| Filed | Seller | Shares | Market value | Of outstanding | Sale from | Broker |
|---|---|---|---|---|---|---|
| 2026-08-17 | Hawryluk P. KentFormer Officer | 4K | $256K | 0.008% | 2026-08-17 | Fidelity Brokerage Services LLC |
| 2026-08-04 | Hawryluk P. KentOfficer, Director | 936 | $62K | 0.002% | 2026-08-04 | Fidelity Brokerage Services LLC |
| 2026-08-04 | Azoulay SalomonOfficer | 370 | $24K | 0.001% | 2026-08-04 | Fidelity Brokerage Services LLC |
Large holders (13D and 13G)
One row per reporting person, newest filing first. JSON14 holders above 5% have filed on MBX, 14 on Schedule 13D (active intent). The largest reported stake is Patrick J. Heron at 11.7% of the class (5,243,421 shares), filed 2026-08-10 for an event on 2026-08-06.
| Filed | Form | Holder | Shares | Of class | Event |
|---|---|---|---|---|---|
| 2026-08-10 | 13D/Ano. 3 | Patrick J. Heronindividual | 5.2M | 11.7% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | James N. Topperindividual | 5.2M | 11.7% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | FHMLS X, L.P.partnership | 5.2M | 10.8% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | FHMLS X, L.L.C.other entity | 5.2M | 10.8% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | Frazier Life Sciences X, L.P.partnership | 5.2M | 10.8% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | ORBIMED ADVISORS LLCinvestment adviser | 3.1M | 6.4% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | ORBIMED CAPITAL GP VII LLCother entity | 2.5M | 5.2% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | FHMLSP, L.P.partnership | 1.4M | 3.0% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | Frazier Life Sciences Public Fund, L.P.partnership | 1.4M | 3.0% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | FHMLSP, L.L.C.other entity | 1.4M | 3.0% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | ORBIMED GENESIS GP LLCother entity | 570K | 1.2% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | FHMLS XI, L.L.C.other entity | 3K | 0.0% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | FHMLS XI, L.P.partnership | 3K | 0.0% | 2026-08-06 |
| 2026-08-10 | 13D/Ano. 3 | Frazier Life Sciences XI, L.P.partnership | 3K | 0.0% | 2026-08-06 |
13F holders
Tracked managers holding MBX at their latest 13F. JSON5 of the 30 tracked managers held MBX at their latest 13F, $31.5M in total at quarter-end prices. Millennium Management is the largest at $12.5M (0.0% of its portfolio) as of 2026-06-30. Over the prior quarter 0 added shares and 5 cut.
| Fund | Quarter | Shares | Value | Of portfolio | Change in shares |
|---|---|---|---|---|---|
| Millennium Management | 2026-06-30 | 226K | $12.5M | 0.00% | -592K |
| D. E. Shaw & Co. | 2026-06-30 | 183K | $10.1M | 0.00% | -106K |
| Two Sigma Investments | 2026-06-30 | 113K | $6.3M | 0.00% | -2K |
| Citadel Advisors | 2026-06-30 | 26K | $1.4M | 0.00% | -942K |
| AQR Capital Management | 2026-06-30 | 23K | $1.2M | 0.00% | -5K |
Only the 30 tracked managers on the funds hub; a 13F reports long positions in US listed stock at quarter end, 45 days late, and says nothing about shorts or positions sold since.
What this page is
MBX Biosciences, Inc. in the regulatory record
Regulators publish company data in separate files that never sit next to each other: FINRA's twice-monthly short interest, its daily short sale volume, the SEC's fails-to-deliver counts, and each insider's Form 4. A company page pulls every series the site collects for one ticker onto one URL, keyed by the SEC's own ticker list, so the short position, the daily flow, the settlement fails and what insiders are doing can be read together.
Each section has its own history table, a summary sentence built from the rows (last value, change, range with dates) and its own JSON and CSV links. Nothing on the page is written by a model; the sentences change only when the data does. A page exists only for companies with data in at least two series, and every section says when its source last updated.
This page follows MBX Biosciences, Inc. (MBX), SEC CIK 1776111, listed on Nasdaq. The cross-market tables live on the short interest and insider transactions hubs.
Source and method
- Short interest
- FINRA consolidated short interestTwice a month, about eight business days after settlement. Latest 2026-08-14.JSON and CSV
- Daily short volume
- FINRA Reg SHO daily filesEvery trading day, loaded the following morning. Latest 2026-09-11.JSON and CSV
- Fails to deliver
- SEC fails-to-deliver dataTwice a month, a few weeks after the half month ends. Latest 2026-08-04.JSON and CSV
- Planned sales
- SEC EDGAR Form 144EDGAR read every 30 minutes; a notice is filed on or before the sell order. Latest 2026-08-17.JSON and CSV
- Large holders
- SEC EDGAR Schedule 13D and 13GEDGAR read every 30 minutes; 13D within five business days of crossing 5%, 13G on the passive schedule. Latest 2026-08-10.JSON and CSV
- 13F holders
- SEC EDGAR Form 13F-HRQuarterly, filed within 45 days of quarter end; 30 tracked managers. Latest 2026-06-30.JSON and CSV
- Insider trades
- SEC EDGAR Form 4EDGAR read every 30 minutes; filings are due two business days after the trade. Latest 2026-08-04.JSON and CSV
- Company record
- EDGAR filing index for CIK 1776111Ticker, name and exchange from the SEC's company list, refreshed weekly.
- Rate limits
- 30 requests a minute without a key, 120 a minute with a key from a free account.
Data checks. Every dataset is checked against its source once a day. This dataset passed the last run, 12 Sep 05:40 UTC.
How to read it
- Read the position against the flow: rising short interest with a high daily short share is new shorting; rising short interest with a normal short share is old shorts holding on.
- Insider buys next to a crowded short are the combination that has historically preceded squeezes; insider sells next to a crowded short are common and mean little.
- Fails to deliver matter relative to the float, not in absolute shares; a million failed shares in a mega cap is noise.
Analysis of what the data shows, not advice. XOOMAR does not recommend buying, selling or holding anything.
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Datasets
Frequently Asked Questions
How much of MBX is sold short?
What is MBX's daily short volume?
Does MBX have fails to deliver?
Are MBX insiders buying or selling?
Have MBX insiders filed to sell?
Who owns more than 5% of MBX?
Which funds hold MBX?
Data on this page is provided for informational purposes only and is not financial advice. See our editorial policy.