STOCK TITAN

MBX Biosciences (MBX) CEO logs small 607-share tax sell-to-cover trade

Filing Impact
(Neutral)
Filing Sentiment
(Negative)
Form Type
4

Rhea-AI Filing Summary

MBX Biosciences President & CEO P. Kent Hawryluk reported a small share sale primarily to cover taxes. On May 6, he sold 607 shares of common stock at a weighted average price of $29.54 per share to satisfy tax obligations tied to vesting restricted stock units under a mandatory sell-to-cover arrangement.

After this transaction, he directly holds 727,667 common shares and also has 486,777 shares held indirectly through the P. Kent Hawryluk Revocable Trust dated January 25, 2011. The filing notes that he disclaims beneficial ownership of the trust shares except to the extent of any pecuniary interest.

Positive

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Negative

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Insider Hawryluk P. Kent
Role President & CEO
Sold 607 shs ($18K)
Type Security Shares Price Value
Sale Common Stock 607 $29.54 $18K
holding Common Stock -- -- --
Holdings After Transaction: Common Stock — 727,667 shares (Direct, null); Common Stock — 486,777 shares (Indirect, By Trust)
Footnotes (1)
  1. The sales reported on this Form 4 represent shares of common stock sold by the Reporting Person to cover tax obligations in connection with the vesting of restricted stock units, pursuant to a mandatory sell-to-cover agreement between the Reporting Person and the Company. The price reported in Column 4 is a weighted average price. These shares were sold on an aggregrate basis for all Company participants, at prices ranging from $29.23 to $29.88, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the aggregrate number of shares sold at each separate price within the range set forth in this footnote. Shares held by the P. Kent Hawryluk Revocable Trust dated January 25, 2011, of which the Reporting Person serves as trustee. The Reporting Person disclaims beneficial ownership except to the extent of any pecuniary interest therein, and this report shall not be deemed an admission that such shares are beneficially owned by him for Section 16 or any other purpose.
Shares sold 607 shares Common stock sold May 6, 2026 to cover tax obligations
Weighted average sale price $29.54 per share Price for 607 shares sold in tax-related transaction
Post-transaction direct holdings 727,667 shares Common stock directly held by CEO after sale
Indirect trust holdings 486,777 shares Shares held by P. Kent Hawryluk Revocable Trust
Sale price range $29.23–$29.88 per share Range of market prices for aggregated participant sales
sell-to-cover financial
"pursuant to a mandatory sell-to-cover agreement between the Reporting Person and the Company"
Sell-to-cover is when part of newly issued or exercised company stock is immediately sold to pay required taxes and fees, so the recipient keeps the remaining shares. For investors this matters because it reduces the number of shares insiders or employees actually hold after a grant, can create small, routine share sales that aren’t signal of cashing out, and slightly increases share supply on the market—like selling a portion of a paycheck to cover the tax bill.
restricted stock units financial
"to cover tax obligations in connection with the vesting of restricted stock units"
Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.
weighted average price financial
"The price reported in Column 4 is a weighted average price."
Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.
Revocable Trust financial
"Shares held by the P. Kent Hawryluk Revocable Trust dated January 25, 2011"
A revocable trust is a legal arrangement where the person who creates it keeps control and can change or cancel the trust at any time, while naming who will manage and receive the assets later. Think of it like a flexible folder for your investments and property that can be relabeled or reworked as circumstances change; it matters to investors because it determines how ownership is recorded, how easily assets transfer on incapacity or death, and whether holdings bypass public probate proceedings.
beneficial ownership financial
"The Reporting Person disclaims beneficial ownership except to the extent of any pecuniary interest therein"
Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.
Section 16 regulatory
"not be deemed an admission that such shares are beneficially owned by him for Section 16 or any other purpose."
Section 16 is a U.S. securities law rule that governs the trading and disclosure obligations of company insiders — typically officers, directors and large shareholders — to promote transparency and deter unfair profit-taking. It requires insiders to publicly report their stock trades and allows companies or the issuer to reclaim quick, short-term profits from certain insider trades, like a scoreboard and a refund policy that help investors see and limit possible insider advantage.
SEC Form 4
FORM 4UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
OMB APPROVAL
OMB Number:3235-0287
Estimated average burden
hours per response:0.5
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.
1. Name and Address of Reporting Person*
Hawryluk P. Kent

(Last)(First)(Middle)
C/O MBX BIOSCIENCES, INC.
11711 N. MERIDIAN STREET, SUITE 300

(Street)
CARMEL INDIANA 46032

(City)(State)(Zip)

UNITED STATES

(Country)
2. Issuer Name and Ticker or Trading Symbol
MBX Biosciences, Inc. [ MBX ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
XDirector10% Owner
XOfficer (give title below)Other (specify below)
President & CEO
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
05/06/2026
6. Individual or Joint/Group Filing (Check Applicable Line)
XForm filed by One Reporting Person
Form filed by More than One Reporting Person
4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year)2A. Deemed Execution Date, if any (Month/Day/Year)3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeVAmount(A) or (D)Price
Common Stock05/06/2026S(1)607D$29.54(2)727,667D
Common Stock486,777IBy Trust(3)
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year)3A. Deemed Execution Date, if any (Month/Day/Year)4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 6. Date Exercisable and Expiration Date (Month/Day/Year)7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Explanation of Responses:
1. The sales reported on this Form 4 represent shares of common stock sold by the Reporting Person to cover tax obligations in connection with the vesting of restricted stock units, pursuant to a mandatory sell-to-cover agreement between the Reporting Person and the Company.
2. The price reported in Column 4 is a weighted average price. These shares were sold on an aggregrate basis for all Company participants, at prices ranging from $29.23 to $29.88, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the aggregrate number of shares sold at each separate price within the range set forth in this footnote.
3. Shares held by the P. Kent Hawryluk Revocable Trust dated January 25, 2011, of which the Reporting Person serves as trustee. The Reporting Person disclaims beneficial ownership except to the extent of any pecuniary interest therein, and this report shall not be deemed an admission that such shares are beneficially owned by him for Section 16 or any other purpose.
/s/ P. Kent Hawryluk05/08/2026
** Signature of Reporting PersonDate
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did MBX (MBX) report for CEO P. Kent Hawryluk?

MBX reported that CEO P. Kent Hawryluk sold 607 shares of common stock at a weighted average price of $29.54 per share. The sale was made to cover tax obligations related to vesting restricted stock units under a mandatory sell-to-cover arrangement.

Why did MBX (MBX) CEO P. Kent Hawryluk sell 607 shares?

The 607-share sale by MBX CEO P. Kent Hawryluk was to cover tax obligations arising from the vesting of restricted stock units. The filing states this occurred under a mandatory sell-to-cover agreement between the executive and the company, rather than a discretionary stock sale.

How many MBX (MBX) shares does CEO P. Kent Hawryluk hold after the reported sale?

Following the reported transaction, CEO P. Kent Hawryluk holds 727,667 MBX common shares directly. In addition, 486,777 shares are held indirectly through the P. Kent Hawryluk Revocable Trust, for which he serves as trustee, with beneficial ownership disclaimed except for pecuniary interest.

How are MBX (MBX) shares held through the P. Kent Hawryluk Revocable Trust treated in the Form 4?

The Form 4 shows 486,777 MBX shares held by the P. Kent Hawryluk Revocable Trust dated January 25, 2011. Hawryluk, as trustee, disclaims beneficial ownership of these shares except to the extent of any pecuniary interest, a standard Section 16 reporting disclaimer for trust-held securities.

Was the MBX (MBX) CEO’s share sale part of a discretionary trading plan?

The disclosure indicates the CEO’s 607-share sale was made to cover tax obligations from restricted stock unit vesting under a mandatory sell-to-cover agreement. This framing emphasizes a tax-related, mechanical transaction rather than a discretionary decision to reduce his MBX share exposure.