# EDGAR Filing Document

**Accession Number:** 0001501697
**File Stem:** 0001501697-26-000021
**Filing Date:** 2026-3
**Character Count:** 20476
**Document Hash:** 414b7552af9904a7448e4dbd1e4ffe89
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001501697-26-000021.hdr.sgml**: 20260318

**ACCESSION NUMBER**: 0001501697-26-000021

**CONFORMED SUBMISSION TYPE**: S-8

**PUBLIC DOCUMENT COUNT**: 14

**FILED AS OF DATE**: 20260318

**DATE AS OF CHANGE**: 20260317

**EFFECTIVENESS DATE**: 20260318

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** X4 Pharmaceuticals, Inc
- **CENTRAL INDEX KEY:** 0001501697
- **STANDARD INDUSTRIAL CLASSIFICATION:** BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 273181608
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** S-8
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-294391
- **FILM NUMBER:** 26764387

**BUSINESS ADDRESS:**
- **STREET 1:** 61 NORTH BEACON STREET
- **STREET 2:** 4TH FLOOR
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02134
- **BUSINESS PHONE:** 857-529-8300

**MAIL ADDRESS:**
- **STREET 1:** 61 NORTH BEACON STREET
- **STREET 2:** 4TH FLOOR
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02134

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Arsanis, Inc.
- **DATE OF NAME CHANGE:** 20100920

**As filed with the Securities and Exchange Commission on March 17, 2026**

**Registration No. 333-**

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**WASHINGTON, DC 20549**

**FORM S-8**

**REGISTRATION STATEMENT**

***UNDER***

***THE SECURITIES ACT OF 1933***

***____________________________________________***

**X4 Pharmaceuticals, Inc.**

**(Exact name of registrant as specified in its charter)**

___________________________________________

---

| | |
|:---|:---|
| **Delaware** | **27-3181608** |
| (State or Other Jurisdiction of<br>Incorporation or Organization) | (I.R.S. Employer<br>Identification No.) |
| **61 North Beacon Street, 4th Floor**<br>**Boston, Massachusetts** | **02134** |
| (Address of Principal Executive Offices) | (Zip Code) |

---

**X4 Pharmaceuticals, Inc. Amended and Restated 2017 Equity Incentive Plan**

**(Full title of the plan)**

**Adam R. Craig, M.D., Ph.D.**

**Executive Chairman**

**X4 Pharmaceuticals, Inc.**

**61 North Beacon Street, 4th Floor**

**Boston, MA 02134**

**(857) 529-8300**

**(Name, address, including zip code, and telephone number, including area code, of agent for service)**

_________________________________

***Copies to:***

**Ryan A. Murr**

**Melanie Neary**

**Gibson, Dunn & Crutcher LLP**

**One Embarcadero Center, Suite 2600**

**San Francisco, CA 94111-3715**

**Telephone: (415) 393-8200**

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company" and "emerging growth company" in Rule 12b-2 of the Exchange Act.

---

| | | | |
|:---|:---|:---|:---|
| Large accelerated filer | ☐ | Accelerated filer | ☐ |
| Non-accelerated filer | ☒ | Smaller reporting company | ☒ |
| | | 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 7(a)(2)(B) of the Securities Act. ☐

------

**INCORPORATION OF DOCUMENTS BY REFERENCE**

This Registration Statement on Form S-8 is being filed by X4 Pharmaceuticals, Inc. (the "Company" or the "Registrant") relating to 5,136,276 shares of its common stock, par value $0.001 per share (the "Common Stock") available for issuance pursuant to future awards to eligible persons under the Registrant's Amended and Restated 2017 Equity Incentive Plan (the "2017 Plan").

Accordingly, pursuant to General Instruction E to Form S-8, this Registration Statement incorporates by reference the contents of (i) the Registration Statement on Form S-8 (File No. 333-221622) filed with the Securities and Exchange Commission ("***SEC***") on <u>[November 16, 2017](https://www.sec.gov/Archives/edgar/data/1501697/000119312517345721/d493744ds8.htm)</u> relating to the 2017 Plan and certain other employee benefit plans of the Registrant; (ii) the Registration Statement on Form S-8 (File No. 333-223539) filed with the SEC on <u>[March 9, 2018](https://www.sec.gov/Archives/edgar/data/1501697/000119312518076441/d535539ds8.htm)</u> relating to the 2017 Plan; (iii) the Registration Statement on Form S-8 (File No. 333-230181) filed with the SEC on <u>[March 11, 2019](https://www.sec.gov/Archives/edgar/data/1501697/000119312519070143/d715399ds8.htm)</u> relating to the 2017 Plan and certain other employee benefit plans of the Registrant; (iv) the Registration Statement on Form S-8 (File No. 333-237164) filed with the SEC on <u>[March 13, 2020](https://www.sec.gov/Archives/edgar/data/1501697/000119312520072921/d884915ds8.htm)</u> relating to the 2017 Plan and certain other employee benefit plans of the Registrant; (v) the Registration Statement on Form S-8 (File No 333-239082) filed with the SEC on <u>[June 10, 2020](https://www.sec.gov/Archives/edgar/data/1501697/000162828020009216/xfor-2020062020xsx8.htm)</u> relating to the 2017 Plan; (vi) the Registration Statement on Form S-8 (File No 333-254618) filed with the SEC on <u>[March 23, 2021](https://www.sec.gov/Archives/edgar/data/1501697/000162828021005363/a032021s-8.htm)</u> relating to the 2017 Plan and certain other employee benefit plans of the Registrant; (vii) the Registration Statement on Form S-8 (File No 333-263430) filed with the SEC on <u>[March 10, 2022](https://www.sec.gov/Archives/edgar/data/1501697/000162828022005734/a032022s-8.htm)</u> relating to the 2017 Plan and certain other employee benefit plans of the Registrant; (viii) the Registration Statement on Form S-8 (File No 333-269335) filed with the SEC on <u>[January 20, 2023](https://www.sec.gov/Archives/edgar/data/1501697/000162828023001353/a032023s-8.htm)</u> relating to the 2017 Plan and certain other employee benefit plans of the Registrant; (ix) the Registration Statement on Form S-8 (File No 333-273960) filed with the SEC on <u>[August 14, 2023](https://www.sec.gov/Archives/edgar/data/1501697/000162828023029154/a082023s-8.htm)</u> relating to the 2017 Plan and certain other employee benefit plans of the Registrant; (x) the Registration Statement on Form S-8 (File No 333-276691) filed with the SEC on <u>[January 25, 2024](https://www.sec.gov/Archives/edgar/data/1501697/000162828024002243/a012024s-8.htm)</u> relating to the 2017 Plan; and (xi) the Registration Statement on Form S-8 (File No 333-284320) filed with the SEC on <u>[January 16, 2025](https://www.sec.gov/Archives/edgar/data/1501697/000162828025001740/a012025s-8.htm)</u> relating to the 2017 Plan, in each case except for Item 8, Exhibits, with respect to which the Exhibit Index below is incorporated herein by reference.

------

**PART II**

**INFORMATION REQUIRED IN THE REGISTRATION STATEMENT**

**Item 8. Exhibits.**

The exhibits to this Registration Statement are listed in the Exhibit Index attached hereto and incorporated by reference herein.

---

| | | | | | |
|:---|:---|:---|:---|:---|:---|
| | | **Incorporated by Reference** | **Incorporated by Reference** | **Incorporated by Reference** | |
|<br>**Exhibit No.** |<br>**Exhibit Description** | **Form** | **Number** | **Filing Date** |<br>**Filed Herewith** |
| 4.1 | <u>[Restated Certificate of Incorporation, as amended, as of September 1, 2022](https://www.sec.gov/Archives/edgar/data/1501697/000162828022024161/x4-ex31to8xkxcharteramen.htm)</u> | 8-K | 3.1 | 09/1/2022 |  |
| 4.2 | <u>[Certificate of Amendment to Restated Certificate of Incorporation of X4 Pharmaceuticals, Inc.](https://www.sec.gov/Archives/edgar/data/1501697/000162828025019507/ex31amendmenttotherestatec.htm)</u> | 8-K | 3.1 | 04/24/2025 |  |
| 4.3 | <u>[Amended and Restated By-laws of the Company](https://www.sec.gov/Archives/edgar/data/1501697/000119312517348213/d495338dex32.htm)</u> | 8-K | 3.2 | 11/20/2017 |  |
| 4.3 | <u>[Form of Common Stock Certificate](https://www.sec.gov/Archives/edgar/data/1501697/000119312519073465/d702482dex41.htm)</u> | 8-K | 4.1 | 03/13/2019 |  |
| 4.4 | <u>[X4 Pharmaceuticals Inc. Amended and Restated 2017 Equity Incentive Plan](https://www.sec.gov/Archives/edgar/data/1501697/000162828020009216/xfor_06102020xamendedandre.htm)</u> | S-8 | 99.1 | 6/10/2020 |  |
| 5.1 | <u>[Opinion of Gibson, Dunn & Crutcher LLP](xforex51march2026s-8.htm)</u> |  |  |  | X |
| 23.1 | <u>[Consent of Independent Registered Public Accounting Firm](ex-231x4xsx8pwcconsentmar2.htm)</u> |  |  |  | X |
| 23.2 | <u>[Consent of Gibson, Dunn & Crutcher LLP (included in Exhibit 5.1)](xforex51march2026s-8.htm)</u> |  |  |  | X |
| 24.1 | <u>[Power of Attorney (included on the signature page to this Registration Statement)](#ib3551a68db9b42b89a43c5ead93608d1_10)</u> |  |  |  | X |
| 107.1 | <u>[Filing Fee Table](exfilingfees.htm)</u> |  |  |  | X |

---

------

**SIGNATURES**

Pursuant to the requirements of the Securities Act of 1933, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston, Commonwealth of Massachusetts, on March 17, 2026.

**X4 Pharmaceuticals, Inc.**

By: <u>/s/ Adam R. Craig</u> 

Adam R. Craig, M.D., Ph.D., M.B.A.

*Executive Chairman*

**POWER OF ATTORNEY**

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints each of Adam Raymond Craig, M.D., Ph.D. and David Kirske, and each of them acting individually, as his or her true and lawful attorneys-in-fact and agents, each with full power of substitution and resubstitution in each of them singly, for him or her and in his or her name, place and stead, and in any and all capacities, to sign any and all amendments (including post-effective amendments) to this Registration Statement, and to file the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting to the attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in or about the premises, as full to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that the attorneys-in-fact and agents or any of each of them or their substitutes may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1993, this Registration Statement has been signed by the following persons in the capacities indicated on the dates indicated.

---

| | | |
|:---|:---|:---|
| **Signature** | **Title** | **Date** |
| /s/ Adam R. Craig | Executive Chairman, Chairman of the Board of Directors (principal executive officer) | March 17, 2026 |
| Adam R. Craig, M.D., Ph.D., M.B.A. | Executive Chairman, Chairman of the Board of Directors (principal executive officer) | March 17, 2026 |
| /s/ David Kirske | Chief Financial Officer and Treasurer<br>(principal financial officer and principal accounting officer) | March 17, 2026 |
| David Kirske | Chief Financial Officer and Treasurer<br>(principal financial officer and principal accounting officer) | March 17, 2026 |
| /s/ Michael S. Wyzga | Lead Independent Director of the Board of Directors | March 17, 2026 |
| Michael S. Wyzga | Lead Independent Director of the Board of Directors | March 17, 2026 |
| /s/ Gary J. Bridger | Director | March 17, 2026 |
| Gary J. Bridger, Ph.D. | Director | March 17, 2026 |
| /s/ Francoise De Craecker | Director | March 17, 2026 |
| Francoise De Craecker | Director | March 17, 2026 |
| /s/ Murray W. Stewart | Director | March 17, 2026 |
| Murray W. Stewart, M.D. | Director | March 17, 2026 |

---

## Ex-Filing

?xml version='1.0' encoding='ASCII'? exfilingfees

**EXHIBIT 107**

**CALCULATION OF FILING FEE TABLE**

**Form S-8**

**X4 Pharmaceuticals, Inc.**

**Table 1: Newly Registered Securities**

---

| | | | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|:---|:---|
| **Security Type** | **Security Type** | **Security Class Title** | **Fee Calculation Rule** | **Amount to be**<br>**Registered (1)** | **Maximum Offering Price**<br>**Per Unit** | **Maximum Aggregate**<br>**Offering Price** | **Fee Rate** | **Amount of Registration Fee** |
| Equity | (2) | Common Stock, $0.001 par value per share ("Common Stock") to be issued under the X4 Pharmaceuticals, Inc. Amended and Restated 2017 Equity Incentive Plan (the "2017 Plan") | Rule 457(h) | 3636276 | $4.00 | $14545104 | 0.0001381 | $2008.68 |
| Equity | (3) | Common Stock, $0.001 par value per share, X4 Pharmaceuticals Inc. 2017 Equity Incentive Plan | Rule 457(h) | 1060000 | $4.07 | $4314200 | 0.0001381 | $595.79 |
| Equity | (4) | Common Stock, $0.001 par value per share, X4 Pharmaceuticals Inc. 2017 Equity Incentive Plan | Rule 457(h) | 440000 | $4.00 | $1760000 | 0.0001381 | $243.06 |
| **Total Offering Amounts** | **Total Offering Amounts** | **Total Offering Amounts** | **Total Offering Amounts** | **Total Offering Amounts** |  | $20619304 |  | $2847.53 |
| **Total Fee Offsets** | **Total Fee Offsets** | **Total Fee Offsets** | **Total Fee Offsets** | **Total Fee Offsets** |  |  |  | $0.00 |
| **Net Fees Due** | **Net Fees Due** | **Net Fees Due** | **Net Fees Due** | **Net Fees Due** |  |  |  | $2847.53 |

---

(1) Pursuant to Rule 416 of the Securities Act of 1933, as amended (the "***Securities Act***"), this Registration Statement shall also cover any additional shares of the Registrant's Common Stock, that become issuable under the 2017 Plan by reason of any stock dividend, stock split, recapitalization or other similar transaction effected without receipt of consideration that increases the number of the Registrant's outstanding shares of Common Stock.

(2) Consists of 3,636,276 shares of Common Stock that were automatically added to the shares authorized for issuance under the 2017 Plan on January 1, 2026, pursuant to an "evergreen" provision contained in the 2017 Plan. Pursuant to such "evergreen" provision contained in the 2017 Plan, on January 1 of each year from 2021 until (and including) 2027, the number of shares authorized for issuance under the 2017 Plan is automatically increased by a number equal to the amount equal to the least of (1) 4% of the total number of shares of Common Stock outstanding on December 31st of the preceding calendar year, or (2) a number of shares determined by the Registrant's Board of Directors. The proposed maximum offering price per unit is estimated

------

in accordance with Rule 457(a) and Rule 457(h) solely for the purpose of calculating the registration fee pursuant to Rule 457(h) under the Securities Act and is based upon the exercise price of the options, which is $4.00 per share of Common Stock.

(3) Consists of 1,060,000 shares of Common Stock that are to be approved for issuance under the 2017 Plan by the Registrant's shareholders at the Registrant's 2026 Annual Meeting of Stockholders. The proposed maximum offering price per unit is estimated in accordance with Rule 457(c) and Rule 457(h) solely for the purpose of calculating the registration fee. The offering price per share and the aggregate offering price are calculated based on the average of the high and low sale prices per share of the Common Stock as reported on The Nasdaq Capital Market on March 12, 2026.

(4) Consists of 440,000 shares of Common Stock subject to previously granted stock options, which shares are to be approved for issuance under the 2017 Plan by the Registrant's shareholders at the Registrant's 2026 Annual Meeting of Stockholders. The proposed maximum offering price per unit is estimated in accordance with Rule 457(a) and Rule 457(h) solely for the purpose of calculating the registration fee pursuant to Rule 457(h) under the Securities Act and is based upon the exercise price of the options, which is $4.00 per share.

## Exhibit 5.1

![picture1.jpg](picture1.jpg)&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;**EXHIBIT 5.1**

March 17, 2026

X4 Pharmaceuticals, Inc. &nbsp;&nbsp;&nbsp;&nbsp;

61 North Beacon Street, 4<sup>th</sup> Floor

Boston, MA 02134

Re:&nbsp;&nbsp;&nbsp;&nbsp;*Registration Statement on Form S-8*

Ladies and Gentlemen:

We have examined the Registration Statement on Form S-8 (the "***Registration Statement***") of X4 Pharmaceuticals, Inc., a Delaware corporation (the "***Company***"), to be filed with the Securities and Exchange Commission (the "***Commission***") pursuant to the Securities Act of 1933, as amended (the "***Securities Act***"), in connection with the offering by the Company of up to 5,136,276 shares of the Company's Common Stock, par value $0.001 per share (the "***Shares***"). The Shares are to be issued under the X4 Pharmaceuticals, Inc. Amended and Restated 2017 Equity Incentive Plan (the "***Plan***").

In arriving at the opinions expressed below, we have examined originals, or copies certified or otherwise identified to our satisfaction as being true and complete copies, of the originals, of such documents, corporate records, certificates of officers of the Company and of public officials and other instruments as we have deemed necessary or advisable to enable us to render the opinions set forth below. In our examination, we have assumed without independent investigation the genuineness of all signatures, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals and the conformity to original documents of all documents submitted to us as copies.

We have also assumed that there are no agreements or understandings between or among the Company and any participants in the Plan that would expand, modify or otherwise affect the terms of the Plan or the respective rights or obligations of the participants thereunder. Based upon the foregoing, and subject to the assumptions, exceptions, qualifications and limitations set forth herein, we are of the opinion that the Shares, when issued and sold against payment therefor in accordance with the terms set forth in the Plan as set forth in the Registration Statement, will be validly issued, fully paid and non-assessable.

We render no opinion herein as to matters involving the laws of any jurisdiction other than the Delaware General Corporation Law (the "DGCL"). We are not admitted to practice in the State of Delaware; however, we are generally familiar with the DGCL as currently in effect and have made such inquiries as we consider necessary to render the opinions above. This opinion is limited to the effect of the current state of the DGCL and the facts as they currently exist. We assume no obligation to revise or supplement this opinion in the event of future changes in such law or the interpretations thereof or such facts.

We consent to the filing of this opinion as an exhibit to the Registration Statement, and we further consent to the use of our name under the caption "Legal Matters" in the Registration Statement and the prospectus that forms a part thereof. In giving these consents, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the Rules and Regulations of the Commission.

Very truly yours,

/s/ Gibson, Dunn & Crutcher, LLP

Gibson, Dunn & Crutcher, LLP

## Exhibit 23.1

**Exhibit 23.1**

**CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM**

We hereby consent to the incorporation by reference in this Registration Statement on Form S-8 of X4 Pharmaceuticals, Inc. of our report dated March 17, 2026 relating to the financial statements, which appears in X4 Pharmaceuticals, Inc.'s Annual Report on Form 10-K for the year ended December 31, 2025.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

March 17, 2026

<br>