EXHIBIT A
Agreement of Joint Filing
The undersigned hereby agree that a single Schedule 13G (or any amendment thereto) relating to the Common Stock of Magenta Therapeutics, Inc. shall be filed on behalf of each of the undersigned and that this Agreement shall be filed as an exhibit to such Schedule 13G.
Date: February 11, 2019
GV 2016, L.P.
By: GV 2016 GP, L.P., its General Partner
By: GV 2016 GP, L.L.C., its General Partner
By: Alphabet Holdings LLC, its Sole Member
| By: | /s/ Kathryn W. Hall | |
| Name: | Kathryn W. Hall | |
| Title: | Secretary |
GV 2016 GP, L.P.
By: GV 2016 GP, L.L.C., its General Partner
By: Alphabet Holdings LLC, its Sole Member
| By: | /s/ Kathryn W. Hall | |
| Name: | Kathryn W. Hall | |
| Title: | Secretary |
GV 2016 GP, L.L.C.
By: Alphabet Holdings LLC, its Sole Member
| By: | /s/ Kathryn W. Hall | |
| Name: | Kathryn W. Hall | |
| Title: | Secretary |
Alphabet Holdings LLC
| By: | /s/ Kathryn W. Hall | |
| Name: | Kathryn W. Hall | |
| Title: | Secretary |
XXVI Holdings Inc.
| By: | /s/ Kathryn W. Hall | |
| Name: | Kathryn W. Hall | |
| Title: | Assistant Secretary |
Alphabet Inc.
| By: | /s/ Kathryn W. Hall | |
| Name: | Kathryn W. Hall | |
| Title: | Assistant Secretary |
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