Dianthus Therapeutics (DNTH) 10-Q 2019 Q2 Quarterly report

Exhibit 32.1

CERTIFICATIONS OF PRINCIPAL EXECUTIVE OFFICER AND PRINCIPAL

FINANCIAL OFFICER PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THESARBANES-OXLEY ACT OF 2002

In connection with this Quarterly Report on Form10-Q of Magenta Therapeutics, Inc. (the “Company”) for the quarter ended June 30, 2019 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), each of the undersigned officers hereby certifies, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of theSarbanes-Oxley Act of 2002, that to the best of his or her knowledge:

1. the Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: August 8, 2019

/s/ Jason Gardner

Jason Gardner, D.Phil.

Director, President and Chief Executive Officer

(Principal Executive Officer)

/s/ Jason Ryan

Jason Ryan

Chief Operating and Financial Officer

(Principal Financial and Accounting Officer)