X4 Pharma CFO sells 16,961 shares for taxes

X4 Pharmaceuticals Chief Financial Officer David Kirske reported an open-market sale of common stock.

Rhea-AI Filing Summary

X4 Pharmaceuticals Chief Financial Officer David Kirske reported an open-market sale of common stock. On May 12, 2026, he sold 16,961 shares of X4 Pharmaceuticals stock at a weighted average price of $4.2934 per share. According to the footnotes, this sale was made to cover a personal income tax obligation arising from the settlement of a restricted stock unit award, making it a largely tax-driven transaction rather than a discretionary portfolio move. After the sale, Kirske directly owned 176,293 shares, of which 128,836 shares are in the form of restricted stock units, so he continues to hold a substantial equity stake in the company.

Insider Trade Summary

Net Seller: 16,961 shares

Net Sell 1 txn

Insider KIRSKE DAVID

Role Chief Financial Officer

Sold 16,961 shs ($73K)

Type	Security	Shares	Price	Value
Sale	Common Stock	16,961	$4.2934	$73K

Holdings After Transaction: Common Stock — 176,293 shares (Direct)

Footnotes (3)

1. F1. Sale of shares to cover personal income tax obligation upon settlement of restricted stock unit award.
2. F2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $4.20 to $4.45, inclusive. The Reporting Person undertakes to provide the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
3. F3. Of the shares of common stock reported, 128,836 shares represent restricted stock units.

Key Figures

Shares sold: 16,961 shares Weighted average sale price: $4.2934 per share Shares owned after transaction: 176,293 shares +1 more

4 metrics

Shares sold 16,961 shares Open-market sale on May 12, 2026

Weighted average sale price $4.2934 per share Common stock sale range $4.20–$4.45

Shares owned after transaction 176,293 shares Direct holdings following May 12, 2026 sale

Restricted stock units within holdings 128,836 shares Portion of total post-transaction holdings

Key Terms

restricted stock unit award, weighted average price, open-market sale, restricted stock units

4 terms

restricted stock unit award financial

"Sale of shares to cover personal income tax obligation upon settlement of restricted stock unit award."

A restricted stock unit award is a promise by a company to give an employee a specified number of company shares at a future date if certain conditions are met, such as staying with the company or hitting performance goals. For investors, these awards matter because they can increase the total number of shares outstanding when converted, diluting existing holders, and they align employees’ incentives with shareholders’ interests much like giving a rising bonus that becomes real only after conditions are satisfied.

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.

open-market sale financial

"transaction_action": "open-market sale""

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

restricted stock units financial

"Of the shares of common stock reported, 128,836 shares represent 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.

FAQ

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

What insider transaction did XFOR report for CFO David Kirske?

X4 Pharmaceuticals reported that CFO David Kirske sold 16,961 shares of common stock. The sale was disclosed as an open-market transaction and was undertaken primarily to cover a personal income tax obligation tied to the settlement of a restricted stock unit award.

How many X4 Pharmaceuticals (XFOR) shares did the CFO sell and at what price?

CFO David Kirske sold 16,961 X4 Pharmaceuticals shares at a weighted average price of $4.2934 per share. The footnotes note that individual trades occurred in a price range between $4.20 and $4.45 during the transaction.

Why did X4 Pharmaceuticals CFO David Kirske sell XFOR shares?

The filing explains that David Kirske sold shares to cover a personal income tax obligation resulting from the settlement of a restricted stock unit award. This indicates the sale was primarily tax-related rather than purely discretionary portfolio rebalancing or a change in outlook.

How many XFOR shares does the CFO hold after this Form 4 transaction?

After the reported sale, CFO David Kirske directly owns 176,293 X4 Pharmaceuticals shares. The filing notes that 128,836 of these shares are in the form of restricted stock units, which typically vest over time subject to continued service or performance conditions.

What portion of the CFO’s remaining X4 Pharmaceuticals holdings are restricted stock units?

Of CFO David Kirske’s 176,293 shares reported after the sale, 128,836 are restricted stock units. Restricted stock units generally represent share-based compensation that vests over time, aligning executive incentives with longer-term company performance and shareholder value.

How was the weighted average sale price for the XFOR shares described?

The filing states the $4.2934 figure is a weighted average sale price. It explains that the 16,961 shares were sold in multiple transactions with individual prices ranging from $4.20 to $4.45, and detailed trade breakdowns are available upon request from the company or regulators.

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

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Accepted by SEC EDGAR 05/13/2026 - 04:02 PM Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED 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^*

KIRSKE DAVID

(Last) (First) (Middle)

C/O X4 PHARMACEUTICALS INC.

61 N BEACON STREET, 4TH FLOOR

(Street)

BOSTON MASSACHUSETTS 02134

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
X4 Pharmaceuticals, Inc [ XFOR ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Financial Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/12/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form 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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	05/12/2026		S(1)		16,961	D	$4.2934(2)	176,293(3)	D

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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Sale of shares to cover personal income tax obligation upon settlement of restricted stock unit award.

2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $4.20 to $4.45, inclusive. The Reporting Person undertakes to provide the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

3. Of the shares of common stock reported, 128,836 shares represent restricted stock units.

Remarks:

	/s/ Mitch Buckley, attorney-in-fact	05/13/2026
	** Signature of Reporting Person	Date
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)