UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): February 0424, 2026

MBX Biosciences, Inc.

(Exact name of Registrant as Specified in Its Charter)


Delaware	001-42272	84-1882872
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(IRS Employer Identification No.)

11711 N. Meridian Street Suite 300
Carmel, Indiana		46032
(Address of Principal Executive Offices)		(Zip Code)

     Registrant’s Telephone Number, Including Area Code: (317) 659-0200

    

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:


Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, $0.0001 par value per share	MBX	Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 81.01 OtherEntry Eventsinto a Material Definitive Agreement.

SalesOn PursuantFebruary 24, 2026, MBX Biosciences, Inc. (the “Company”) entered into a lease agreement (the “Lease Agreement") with 5 Burlington Woods, LLC ("5 Burlington Woods") to At-lease approximately 13,642 square feet of new office and laboratory space in Burlington, MA ("the-Market Premises"). The Lease Agreement provides an estimated lease commencement date for the Premises of May 1, 2026 ("ATMLease Commencement Date"), Offeringwith Programthe rent commencing five months from the Lease Commencement Date ("Rent Commencement Date").

On February 4Additionally, 2026,the MBXLease Biosciences,Agreement Inc.provides (that the “Company”),lease closedterm onwill thebe salefour andyears, issuancebeginning ofon anthe aggregateRent ofCommencement 2,250,986Date sharesand ofexpiring itson common stock (the "Shares")last atday aof volumethe weightedmonth averagein pricewhich perthe sharefourth anniversary of $38.76the forRent grossCommencement proceedsDate ofoccurs approximately(the $87.1"Lease millionTerm'). The SharesCompany werehas solda pursuantone-time option to extend the Company'sLease OpenTerm Marketfor Salea AgreementSMperiod withof Jefferies,three LLCyears ("JefferiesExtension Option"). datedIn Novemberexchange 6,for 2025leasing andthe aPremises, shelfthe registrationCompany statementwill onpay Form5 S-3Burlington (FileWoods No.base 333-291308)rent previouslyof filedapproximately by$68,200 for the Companyfirst andtwelve declaredmonths, effectiveor bya thetotal Securitiesof and$818,000 Exchange Commission (the"base rent"SEC") on December 8, 2025,with whichannual includedincreases aof prospectusapproximately supplement relating to the Company's at the market offering program3.0%. The Companyaggregate currentlybase intendsrent toover use the netfour-year proceedslease fromterm thisis saleapproximately for$3.4 costsmillion. associatedThe withLease theAgreement developmentprovides ofthat itsthe clinical-stageCompany programs,will itspay discovery research and development activities and additional clinicalexpenses development,to and5 forBurlington generalWoods corporaterelated purposes,to workingthe capital and capital expenditures. The Company's mayshare also use a portion of theoperating remainingexpenses, nettaxes proceeds and itsutilities existingrelated cash,to cashthe equivalentsPremises andusing marketablea securitiesratable topercentage in-license,set acquire,forth or invest in complementarythe businesses,Lease technologies,Agreement products("Additional or assetsRent"). FollowingNeither theseparty sales, the Company may offerterminate andthe selllease additionalfor sharesthe ofPremises itsother commonthan stockin havingaccordance anwith aggregatecertain offeringprovisions price of upthe toLease $62.9related million from time to timebreach throughor Jefferies pursuant to the Open Market Sale AgreementSMbankruptcy.

This Currentdescription Report on Form 8-K contains forward-looking statements within the meaning of the PrivateLease SecuritiesAgreement Litigationis Reforma Actsummary ofand 1995,does asnot amended.purport Forward-lookingto statements can be identifiedcomplete by words such as “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “future,” “goal,” “intend,” “look forward to,” “may,” “plan,” “potential,” “predict,” “project,” “seek,” “strategy,” “should,” “target,” “will,” “would” and similaris expressionsqualified regardingin futureits periods.entirety Theseby forward-lookingreference statements include, but are not limited to, statements regarding the Company’sfull intendedtext use of the saleLease proceeds. Any forward-looking statements in this 8-K are based on management’s current expectations and beliefs and are subject to a number of risksAgreement, uncertainties and important factors that may cause actual events or results to differ materially from those expressed or implied by any forward-looking statements contained in this 8-K, including, without limitation, those risks and uncertainties set forth more fully under the caption “Risk Factors” in the Company’s prospectus supplement included in the Company's registration statement on Form S-3 filed with theconfidential SECportions on November 6redacted, 2025, the Company's most recent Annual Report on Form 10-K filed withunder theItem SEC and subsequent filings with the SEC9.01 The Company cautions you not to place undue reliance on any forward-looking statements, which speak only as ofexhibit the date they are made10.1 The Company disclaims any obligation to publiclythis updatecurrent orreport revise any such statements to reflect any change in expectations or in events, conditions or circumstances on whichForm any such statements may be based, or that may affect the likelihood that actual results will differ from those set forth in the forward-looking statements. Any forward-looking statements contained in this 8-K represent the Company’s views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date.

SIGNATURESItem 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

~~Pursuant~~Departure ~~to the requirements~~ of ~~the~~Chief ~~Securities~~Financial ~~Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.~~Officer

			MBX BIOSCIENCES, INC.
Date:	February 5, 2026	By:	/s/ P. Kent Hawryluk
			President and Chief Executive Officer (Principal Executive Officer)

On February 25, 2026, the Company and Richard Bartram entered into a separation agreement pursuant to which Mr. Bartram will resign as Chief Financial Officer of the Company. He will continue his employment with the Company as its Chief Financial Officer through March 15, 2026. Mr. Bartram has agreed to serve as a consultant to the Company following his resignation to assist with the transition, under the terms of a consulting agreement entered into with the Company that will become effective upon Mr. Bartram’s resignation. Mr. Bartram’s departure is not due to a dispute or disagreement with the Company or the Company’s auditors. The Company has commenced a search for a new Chief Financial Officer.

During the transition period, Mr. Bartram will be entitled to: (a) continued payments of his then-effective base salary in accordance with the Company’s standard payroll practices; and (b) the right to participate in the Company’s standard benefits where permitted by such plans and programs. In addition, subject to the terms and conditions of the agreement, Mr. Bartram will be entitled to the severance set out in his employment agreement, as well as (i) the extension of the time period for him to exercise any vested equity awards that are stock options for a period of nine (9) months immediately following the termination of the consulting period; and (ii) a lump sum payment of $13,400, which is equal to the employer’s portion of the premium to continue healthcare under COBRA for an additional six (6) months. During the consulting period, Mr. Bartram will provide mutually agreeable consulting services on an as needed basis in exchange for a mutually agreed fee. During both the transition period and the consulting period, Mr. Bartram’s outstanding equity awards will continue to vest in accordance with their terms; provided, however, that if the Company terminates Mr. Bartram’s consultancy during the consulting period without cause, all outstanding equity awards will immediately vest as to that portion of such equity awards that would have vested had Mr. Bartram continued to remain a consultant of the Company for one full month following the end of the transition period.

The foregoing description of the separation agreement and the consulting agreement does not purport to be complete and is subject to, and qualified in its entirety by, the agreements which are filed herewith as Exhibits 10.2 and 10.3 and incorporated by reference.

Appointment of Interim Chief Financial Officer

John Smither has been appointed as the Company’s Interim Chief Financial Officer, effective March 16, 2026.

Mr. Smither, age 73, has over 40 years of experience in finance and accounting in the biotechnology industry. Mr. Smither previously served as the Chief Financial Officer of Arcutis Biotherapeutics, Inc. (Nasdaq: ARQT) from May 2019 until March 2021, and again as Interim Chief Financial Officer from September 2023 to April 2024, and the Chief Financial Officer of Sienna Biopharmaceuticals, Inc. (Nasdaq: SNNA) from April 2018 until March 2019. Mr. Smither also served as the interim Chief Financial Officer at Kite Pharma (a Gilead Sciences, Inc. company) from October 2017 until April 2018 during its integration with Gilead. Mr. Smither presently serves on the board of directors of NewAmsterdam Pharma Company N.V. (Nasdaq: NAMS) as chair of its audit committee

and Genelux Corporation (Nasdaq: GNLX) serving as chair of its compensation committee and as a member of its audit committee. Mr. Smither also served on the board of directors and audit committee chair of eFFECTOR Therapeutics, Inc. (Nasdaq: EFTR) from March 2018 to September 2023 and Applied Molecular Transport, Inc. (Nasdaq: AMTI) from January 2022 to December 2023. Mr. Smither also served as a member of the nomination and corporate governance committee of eFFECTOR Therapeutics and the compensation committee of Applied Molecular Transport. Mr. Smither previously served on the board of directors of Achaogen, Inc. and Principia Biopharma Inc and as the chair of their audit committees. Mr. Smither also has 15 years’ experience as a practicing CPA (inactive), including time spent as an audit partner with Ernst & Young LLP.

The Company has entered into an employment agreement and its standard form of indemnification agreement with Mr. Smither. The employment agreement with Mr. Smither provides for Mr. Smither’s services as a part-time employee, and among other things, (i) a base annual salary of $325,000, (ii) a target annual bonus equal to 40% of his earned income, pro rated for the first year and payable upon the conclusion of the assignment; and (iii) a sign-on bonus of $25,000.

There are no other arrangements or understandings between Mr. Smither and any other persons pursuant to which Mr. Smither was appointed as interim CFO of the Company. There is no family relationship between Mr. Smither and any director or executive officer of the Company. There are no transactions between Mr. Smither and the Company that would be required to be reported under Item 404(a) of Regulation S-K.

The foregoing description of the employment agreement does not purport to be complete and is subject to, and qualified in its entirety by, the final employment agreement which is filed herewith as Exhibit 10.4 and incorporated by reference.

Item 9.01 Financial Statements and Exhibits.


Exhibit No.		Description
10.1+		Lease Agreement between MBX Biosciences, Inc. and 5 Burlington Woods, LLC dated February 24, 2026
10.2		Separation Agreement between MBX Biosciences, Inc. and Richard Bartram dated February 25, 2026
10.3		Consulting Agreement between MBX Biosciences, Inc. and Richard Bartram dated February 25, 2026
10.4		Employment Agreement between MBX Biosciences, Inc. and John Smither dated February 25, 2026
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

+ Certain exhibits and schedules to these agreements have been omitted pursuant to Item 601(a)(5) and (6) of Regulation S-K. The registrant will furnish copies of any of the exhibits and schedules to the SEC upon request.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.


			MBX Biosciences, Inc.

Date:	February 27, 2026	By:	/s/ P. Kent Hawryluk
			President and Chief Executive Officer (Principal Executive Officer)

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