# EDGAR Filing Document

**Accession Number:** 0001776111
**File Stem:** 0001193125-25-282917
**Filing Date:** 2025-11
**Character Count:** 8493
**Document Hash:** e59ff3c4242795c75c752b0c49e2fae8
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-25-282917.hdr.sgml**: 20251114

**ACCESSION NUMBER**: 0001193125-25-282917

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13G/A

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20251114

**DATE AS OF CHANGE**: 20251114

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** MBX Biosciences, Inc.
- **CENTRAL INDEX KEY:** 0001776111
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-94623
- **FILM NUMBER:** 251485860

**BUSINESS ADDRESS:**
- **STREET 1:** 11711 N. MERIDIAN STREET
- **STREET 2:** SUITE 300
- **CITY:** CARMEL
- **STATE:** IN
- **ZIP:** 46032
- **BUSINESS PHONE:** 3179893100

**MAIL ADDRESS:**
- **STREET 1:** 11711 N. MERIDIAN STREET
- **STREET 2:** SUITE 300
- **CITY:** CARMEL
- **STATE:** IN
- **ZIP:** 46032
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Hawryluk P. Kent
- **CENTRAL INDEX KEY:** 0001673991

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G/A

**MAIL ADDRESS:**
- **STREET 1:** 17199 N. LAUREL PARK DRIVE
- **STREET 2:** SUITE 401
- **CITY:** LIVONIA
- **STATE:** MI
- **ZIP:** 48152

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13G

### Under the Securities Exchange Act of 1934

**(Amendment No. 1)**

**Issuer:** MBX Biosciences, Inc.

**Title of Class of Securities:** Common Stock, par value $0.0001 per share

**CUSIP Number:** 55287L101

**Date of Event Which Requires Filing of this Statement:** 09/30/2025

**Check the appropriate box to designate the rule pursuant to which this Schedule is filed:**

- [ ] Rule 13d-1(b)

- [ ] Rule 13d-1(c)

- [x] Rule 13d-1(d)

---

| 1. | Names of Reporting Persons<br>P. Kent Hawryluk | Names of Reporting Persons<br>P. Kent Hawryluk |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>X1 | Citizenship or Place of Organization<br>X1 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>1995759 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>1995759 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>0 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>1995759 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>1995759 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>4.3% | Percent of Class Represented by Amount in Row (9)<br>4.3% |
| 12. | Type of Reporting Person (See Instructions)<br>IN | Type of Reporting Person (See Instructions)<br>IN |

**Comment for Type of Reporting Person:** The percentage of class was calculated based on (i) 44,902,302 shares of Common Stock outstanding as of November 3, 2025, as disclosed in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on November 6, 2025, plus (ii) an aggregate of 1,066,085 shares of Common Stock issuable upon exercise of stock options exercisable within 60 days of September 30, 2025, which are deemed outstanding pursuant to SEC Rule 13-3(d)(1)(i) only for purposes of computing the percentage ownership of the Reporting Person.

---

**Item 1(a). Name of Issuer:**
MBX Biosciences, Inc.

**Item 1(b). Address of Issuer's Principal Executive Offices:**
11711 N. Meridian Street, Suite 300, Carmel, Indiana 46032

**Item 2(a). Name of Person Filing:**
P. Kent Hawryluk (the "Reporting Person").

**Item 2(b). Address of Principal Business Office:**
The business address of the Reporting Person is c/o MBX Biosciences, Inc., 11711 N. Meridian Street, Suite 300, Carmel, Indiana 46032.

**Item 2(c). Citizenship:**
The Reporting Person is a citizen of the United States of America.

**Item 2(d). Title of Class of Securities:**
Common Stock, par value $0.0001 per share

**Item 2(e). CUSIP Number:**
55287L101

**Item 3. If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:**

(a) [ ] Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b) [ ] Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c) [ ] Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d) [ ] Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).

(e) [ ] An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);

(f) [ ] An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);

(g) [ ] A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h) [ ] A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i) [ ] A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j) [ ] A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), if filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:

(k) [ ] Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).

**Item 4. Ownership:**

**(a) Amount beneficially owned:**

The Reporting Person may be deemed to be the beneficial owner of 1,995,759 shares of Common Stock, which includes: (i) 481,397 shares of Common Stock, $0.0001 par value per share (the "Common Stock") held directly by the Reporting Person, (ii) 1,066,085 shares of Common Stock issuable upon exercise of stock options exercisable within 60 days of September 30, 2025 held directly by the Reporting Person, and (iii) 448,277 shares of Common Stock held by the P. Kent Hawryluk Revocable Trust dated January 25, 2011, of which the Reporting Person serves as trustee.
The percentage of class was calculated based on (i) 44,902,302 shares of Common Stock outstanding as of November 3, 2025, as disclosed in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on November 6, 2025, plus (ii) an aggregate of 1,066,085 shares of Common Stock issuable upon exercise of stock options exercisable within 60 days of September 30, 2025, which are deemed outstanding pursuant to SEC Rule 13-3(d)(1)(i) only for purposes of computing the percentage ownership of the Reporting Person.

**(b) Percent of class:**

4.3%

**(c) Number of shares as to which the person has:**

**(i) Sole power to vote or to direct the vote:**

1,995,759

**(ii) Shared power to vote or to direct the vote:**

0

**(iii) Sole power to dispose or to direct the disposition of:**

1,995,759

**(iv) Shared power to dispose or to direct the disposition of:**

0

**Item 5. Ownership of Five Percent or Less of a Class.**

[ ] If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following.

**Item 6. Ownership of More than 5 Percent on Behalf of Another Person.**

Not Applicable

**Item 7. Identification and Classification of the Subsidiary**

Not Applicable

**Item 8. Identification and Classification of Members of the Group**

Not Applicable

**Item 9. Notice of Dissolution of Group**

Not Applicable

**Item 10. Certification:**

—

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**P. Kent Hawryluk**

**Date:** 11/14/2025

**By:** /s/ P. Kent Hawryluk

**Name & Title:** P. Kent Hawryluk