X4 Pharmaceuticals officer proposes $33.7K share sale

The notice describes the transaction as an issuer-mandated tax-withholding sale, not a discretionary trade by the officer.

Rhea-AI Filing Summary

X4 Pharmaceuticals, Inc. officer David Kirske reported a proposed sale of 11,767 common shares, with an aggregate market value of $33,658.47. The notice lists October 1, 2026, as the approximate sale date and Morgan Stanley Smith Barney LLC as the broker. The sale is described as required to cover tax withholding on vested restricted stock units under the issuer’s equity incentive plans, not as a discretionary trade. A separate line lists 32,209 shares acquired through restricted stock unit vesting on September 30, 2026.

Key Figures

Shares proposed for sale: 11,767 shares Aggregate market value: $33,658.47 Shares outstanding: 99,146,743 shares +1 more

4 metrics

Shares proposed for sale 11,767 shares X4 Pharmaceuticals common stock

Aggregate market value $33,658.47 For the proposed sale

Shares outstanding 99,146,743 shares Issuer figure listed with the proposed sale

Shares acquired through restricted stock unit vesting 32,209 shares September 30, 2026

Key Terms

sell to cover, restricted stock unit vesting, tax withholding obligation, equity incentive plans

4 terms

sell to cover financial

"completing a "sell to cover" transaction"

Sell to cover is when a person who receives company stock through options or awards sells just enough shares immediately to pay required taxes, exercise costs, or fees, keeping the rest. Think of it like cashing part of a bonus to cover the tax bill so you can keep the remainder. For investors, it can create predictable small selling pressure and slightly change the number of shares actually held by insiders without increasing long‑term dilution.

restricted stock unit vesting financial

"Restricted Stock Unit Vesting"

tax withholding obligation financial

"to cover the tax withholding obligation"

equity incentive plans financial

"under its equity incentive plans"

Equity incentive plans are company programs that pay employees, executives, or directors with company stock, stock options, or share units instead of or in addition to cash, aiming to align their interests with shareholders—like giving team members a stake in the house they help build. For investors this matters because such plans can motivate better company performance but also dilute existing ownership and increase reported compensation costs, so they affect future earnings, voting power, and share value.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many shares did XFOR officer David Kirske report for sale?

David Kirske’s notice lists 11,767 X4 Pharmaceuticals common shares for sale, with an aggregate market value of $33,658.47.

How many XFOR shares did David Kirske acquire through restricted stock unit vesting?

The notice lists 32,209 common shares acquired through restricted stock unit vesting on September 30, 2026.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 10/01/2026 - 08:06 PM Accepted by SEC EDGAR 10/01/2026 - 08:05 PM Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0001276750
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	X4 Pharmaceuticals, Inc
SEC File Number	001-38295
Address of Issuer	61 NORTH BEACON STREET 4TH FLOOR BOSTON MASSACHUSETTS 02134
Phone	508-633-4447
Name of Person for Whose Account the Securities are To Be Sold	David Kirske
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Officer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common Stock	Morgan Stanley Smith Barney LLC New York Plaza, 38th Floor New York NY 10004	11767	33658.47	99146743	10/01/2026	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common Stock	09/30/2026	Restricted Stock Unit Vesting	Issuer			32209	09/30/2026	Compensation

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Nothing to Report

144: Remarks and Signature

Remarks	Represents the number of shares required to be sold by the Reporting Person to cover the tax withholding obligation in connection with the settlement of vested restricted stock units. This sale is mandated by the Issuer's election under its equity incentive plans to require the Reporting Person to fund this tax withholding obligation by completing a "sell to cover" transaction with a brokerage firm designated by the Issuer. This sale does not represent a discretionary trade by the Reporting Person.
Date of Notice	10/01/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ Mitch Buckley as attorney-in-fact for David Kirske
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)