SC 13D/A

NUMBER OF

SHARES

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

0

SHARED VOTING POWER

2,950,487(1)

SOLE DISPOSITIVE POWER

0

SHARED DISPOSITIVE POWER

2,950,487(1)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 2)

DIANTHUS THERAPEUTICS, INC.

(Name of Issuer)

Common Stock, $0.001 par value

(Title of Class of Securities)

252828 108

(CUSIP Number)

Ms. Erin O’Connor

Fairmount Funds Management LLC

200 Barr Harbor Drive, Suite 400

West Conshohocken, PA 19428

(267) 262-5300

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

-with copy to-

Ryan A. Murr

Gibson, Dunn & Crutcher LLP

One Embarcadero Center Suite 2600

San Francisco, CA 94111

April 1, 2024

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition which is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(b)(3) or (4), check the following box ☐.


1		NAME OF REPORTING PERSON Fairmount Funds Management LLC
2		CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒ (b) ☐
3		SEC USE ONLY
4		SOURCE OF FUNDS AF
5		CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e) ☐
6		CITIZENSHIP OR PLACE OF ORGANIZATION Delaware

(1)

The securities include (i) 2,762,837 shares of common stock, $0.001 par value (“Common Stock”), and (ii) pre-funded warrants to purchase up to 187,650 shares of Common Stock (the “Pre-Funded Warrants”), the exercise of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Common Stock. The securities exclude shares of Common Stock issuable upon exercise of the Pre-Funded Warrants in excess of the beneficial ownership limitation.

(2)	Based on 29,346,760 shares of Common Stock outstanding as of March 14, 2024.


1		NAME OF REPORTING PERSON Fairmount Healthcare Fund LP
2		CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒ (b) ☐
3		SEC USE ONLY
4		SOURCE OF FUNDS AF
5		CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e) ☐
6		CITIZENSHIP OR PLACE OF ORGANIZATION Delaware


1		NAME OF REPORTING PERSON Fairmount Healthcare Fund II LP
2		CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒ (b) ☐
3		SEC USE ONLY
4		SOURCE OF FUNDS AF
5		CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e) ☐
6		CITIZENSHIP OR PLACE OF ORGANIZATION Delaware

(1)

The securities include (i) 2,700,691 shares of Common Stock, and (ii) Pre-Funded Warrants to purchase up to 256,694 shares of Common Stock, the exercise of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Common Stock. The securities exclude shares of Common Stock issuable upon exercise of the Pre-Funded Warrants in excess of the beneficial ownership limitation.

(2)	Based on 29,346,760 shares of Common Stock outstanding as of March 14, 2024.


1		NAME OF REPORTING PERSON Fairmount SPV III, LLC
2		CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒ (b) ☐
3		SEC USE ONLY
4		SOURCE OF FUNDS AF
5		CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e) ☐
6		CITIZENSHIP OR PLACE OF ORGANIZATION Delaware

(1)	Based on 29,346,760 shares of Common Stock outstanding as of March 14, 2024.


1		NAME OF REPORTING PERSON Peter Harwin
2		CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒ (b) ☐
3		SEC USE ONLY
4		SOURCE OF FUNDS AF
5		CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e) ☐
6		CITIZENSHIP OR PLACE OF ORGANIZATION United States

(1)

The securities include (i) 2,762,837 shares of Common Stock, and (ii) Pre-Funded Warrants to purchase up to 187,650 shares of Common Stock, the exercise of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Common Stock. The securities exclude shares of Common Stock issuable upon exercise of the Pre-Funded Warrants in excess of the beneficial ownership limitation.

(2)	Based on 29,346,760 shares of Common Stock outstanding as of March 14, 2024.


1		NAME OF REPORTING PERSON Tomas Kiselak
2		CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) ☒ (b) ☐
3		SEC USE ONLY
4		SOURCE OF FUNDS AF
5		CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e) ☐
6		CITIZENSHIP OR PLACE OF ORGANIZATION Slovak Republic

(1)

(2)	Based on 29,346,760 shares of Common Stock outstanding as of March 14, 2024.

Item 1.

Security and Issuer

This Amendment No. 2 amends and supplements the statement on Schedule 13D originally filed with the Securities and Exchange Commission on September 21, 2023 and Amendment No. 1 filed on January 24, 2024 (as amended, the “Statement” or the “Schedule 13D”) by the Reporting Persons with respect to the common stock, $0.001 par value (“Common Stock”), of Dianthus Therapeutics, Inc. (the “Company”). Unless otherwise defined herein, capitalized terms used in this Amendment No. 2 shall have the meanings ascribed to them in the Statement. Unless amended or supplemented below, the information in the Statement remains unchanged. The address of the principal executive offices of the Company is 7 Times Square, 43rd Floor, New York, NY 10036.

Item 2.

Identity and Background

(a)

This Schedule 13D is being filed jointly by (1) Fairmount Funds Management LLC, a Delaware limited liability company and Securities and Exchange Commission registered investment adviser under the Investment Advisers Act of 1940 (“Fairmount Funds Management”); (2) Fairmount Healthcare Fund LP, a Delaware limited partnership (“Fund I”); (3) Fairmount Healthcare Fund II LP, a Delaware limited partnership (“Fund II”); (4) Fairmount SPV III, LLC, a Delaware limited liability company (“SPV”); (5) Peter Harwin; and (6) Tomas Kiselak (Mr. Harwin and Mr. Kiselak, Fairmount Funds Management, Fund I, Fund II and SPV are collectively referred to herein as the “Reporting Persons”). The joint filing agreement of the Reporting Persons is attached as Exhibit 99.1 to this Schedule 13D.

Fairmount Funds Management serves as investment manager for Fund I and Fund II and the Class A member for SPV and may be deemed a beneficial owner for purposes of Section 13(d) of the Securities Exchange Act of 1934 (the “Act”) of any securities of the Company held by Fund I, Fund II and SPV. Fund I and Fund II have delegated to Fairmount Funds Management the sole power to vote and the sole power to dispose of all securities held in Fund I’s and Fund II’s portfolio, including the shares of Common Stock reported herein. Because Fund I and Fund II have divested themselves of voting and investment power over the reported securities they hold and may not revoke that delegation on less than 61 days’ notice, Fund I and Fund II disclaim beneficial ownership of the securities they hold for purposes of Section 13(d) of the Act and therefore disclaim any obligation to report ownership of the reported securities under Section 13(d) of the Act. As the Class A member for SPV, Fairmount Funds Management has the sole power to vote and the sole power to dispose of all of the securities held in SPV’s portfolio, including the shares of Common Stock reported herein. Because SPV has no voting or investment power over the reported securities it holds, SPV disclaims beneficial ownership of the securities it holds for purposes of Section 13(d) of the Act and therefore disclaims any obligation to report ownership of the reported securities under Section 13(d) of the Act. The general partner of Fairmount Funds Management is Fairmount Funds Management GP LLC (“Fairmount GP”). As managing members of Fairmount GP, Mr. Harwin, and Mr. Kiselak may be deemed beneficial owners, for purposes of Section 13(d) of the Act, of any securities of the Company beneficially owned by Fairmount Funds Management. Fairmount Funds Management, Fairmount GP, Mr. Harwin and Mr. Kiselak disclaim beneficial ownership of the securities reported in this Schedule 13D other than for the purpose of determining their obligations under Section 13(d) of the Act, and the filing of this Schedule 13D shall not be deemed an admission that any of Fairmount Funds Management, Fairmount GP, Mr. Harwin or Mr. Kiselak is the beneficial owner of such securities for any other purpose.

(b)	The principal business address of each of the Reporting Persons is 200 Barr Harbor Drive, Suite 400, West Conshohocken, PA 19428.

(c)	The principal business of Fairmount Funds Management is to provide discretionary investment management services to qualified investors through Fund I, Fund II and SPV, which are each private pooled investment vehicles. The principal occupation of Mr. Harwin and Mr. Kiselak is investment management.

(d)(e)

During the last five years, none of the Reporting Persons (i) has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or (ii) has been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceedings was or is subject to a judgment, decree, or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violations with respect at such laws.

Item 3.

Source and Amount of Funds or Other Consideration

Item 3 of the Statement is hereby amended and supplemented as follows:

In aggregate, the Reporting Persons have voting and dispositive power over 2,950,487 shares of Common Stock of the Company, which is comprised of (a) 2,762,837 shares of Common Stock, and (b) Pre-Funded Warrants to purchase up to 187,650 shares of Common Stock, the exercise of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Common Stock. The securities exclude shares of Common Stock issuable upon exercise of the Pre-Funded Warrants in excess of the beneficial ownership limitation.

On April 1, 2024, in connection with the wind down of Fund I, all shares of Common Stock held by Fund I were transferred to Fund II. The number of shares of Common Stock and Pre-Funded Warrants beneficially owned by the Reporting Persons has not changed since Amendment No. 1 to the Statement, filed on January 24, 2024.

Item 5.

Interest in Securities of the Company

The percentages used in this Schedule 13D are calculated based upon 29,346,760 shares of Common Stock outstanding as of March 14, 2024. The Reporting Persons’ securities consist of 2,762,837 shares of Common Stock, and (b) Pre-Funded Warrants to purchase up to 187,650 shares of Common Stock, the exercise of which is subject to a beneficial ownership limitation of 9.99% of the outstanding Common Stock. The securities exclude shares of Common Stock issuable upon exercise of the Pre-Funded Warrants in excess of the beneficial ownership limitation.

Fairmount Funds Management is the investment manager to Fund I and Fund II and the Class A member for SPV, and has voting and dispositive power over shares of Common Stock held on behalf of Fund I, Fund II and SPV.

Other than the transfer of shares of Common Stock from Fund I to Fund II described herein, the Reporting Persons have not engaged in any transactions in the Company’s securities in the past 60 days.

Item 7.

Material to be Filed as Exhibits


Exhibit No.		Description

99.1		Joint Filing Agreement (incorporated by reference to Exhibit 99.1 of the Reporting Persons’ Schedule 13D filed with the SEC on September 21, 2023).

SIGNATURES

After reasonable inquiry and to the best of our knowledge and belief, we certify that the information set forth in this statement as of April 1, 2024.


FAIRMOUNT FUNDS MANAGEMENT LLC

By:	/s/ Peter Harwin	/s/ Tomas Kiselak
	Peter Harwin	Tomas Kiselak
	Managing Member	Managing Member

FAIRMOUNT HEALTHCARE FUND LP

By:	/s/ Peter Harwin	/s/ Tomas Kiselak
	Peter Harwin	Tomas Kiselak
	Managing Member	Managing Member

FAIRMOUNT HEALTHCARE FUND II LP

By:	/s/ Peter Harwin	/s/ Tomas Kiselak
	Peter Harwin	Tomas Kiselak
	Managing Member	Managing Member

FAIRMOUNT SPV III, LLC

By: Fairmount Funds Management LLC, its Class A Member

/s/ Peter Harwin		/s/ Tomas Kiselak
Peter Harwin		Tomas Kiselak
Managing Member		Managing Member

/s/ Peter Harwin
Peter Harwin

/s/ Tomas Kiselak
Tomas Kiselak