Amendment #1 to Project Rider #3, effective as of August 26, 2019, pursuant to the Collaboration Agreement by and between the Registrant and National Marrow Donor Program d/b/a Be The Match BioTherapies, dated as of November 10, 2017

Exhibit 10.1

[***] Certain information in this document has been omitted from this exhibit because it is both (i) not material and (ii) would be competitively harmful if publicly disclosed.

AMENDMENT #1

TO

PROJECT RIDER #3

COLLABORATION AGREEMENT

This Amendment #1 (“Amendment #1”) is entered into effective as of the date of the final signature executing this Amendment #1 (“Amendment #1 Effective Date”), by and between Magenta Therapeutics, Inc. (“Magenta”) and National Marrow Donor Program d/b/a Be The Match Biotherapies (“BTMB”), (each a “Party” and collectively the “Parties”) as those Parties are defined in Attachment A, Project Rider #3, effective September 6, 2018 (collectively, the “Project Rider #3”).

WHEREAS, the Parties executed a Collaboration Agreement, effective November 10, 2017, and Project Rider #3, effective September 6, 2018; and

WHEREAS, the Parties agree to extend the term of the Project Rider #3.

NOW, THEREFORE, for the valuable consideration contained herein, and intending to be legally bound, Magenta and BTMB agree to the following amendment to be effective as of the Amendment #1 Effective Date as follows:

Amendment to Project Rider #3

“The term of this Rider shall commence on the Rider effective date set forth above and continue in effect through [***].”

This Amendment #1 is executed by individuals who are duly authorized to legally bind their respective parties as of the Amendment #1 Effective Date: