Magenta Therapeutics announced progress and encouraging early data in its MGTA-117 Phase 1/2 targeted conditioning clinical trial and a prioritization of its operating plan to more narrowly focus its capital allocation on the MGTA-117 targeted conditioning program, the CD45-ADC (antibody-drug conjugate) IND-enabling activities and the MGTA-145 stem cell mobilization efforts in sickle cell disease. The Company's most significant near-term clinical milestone is its anticipated data from the MGTA-117 Phase 1/2 clinical trial in patients with relapsed/refractory acute myeloid leukemia and myelodysplasia-excess blasts. Multiple patients have been dosed in Cohort 1 of the ongoing clinical trial.

Based on a preliminary review of the data from the trial to date, Magenta believes that the data suggest early signals of positive pharmacodynamic activity and that MGTA-117 has been well-tolerated, with no reports of unexpected or significant drug-related adverse events. Magenta looks forward to translating data from this clinical trial for use in transplant-eligible patients in the future. In its First Quarter 2022 earnings release scheduled for early May 2022, Magenta plans to disclose a summary of clinical observations from these initial patients with respect to CD117 target binding, drug clearance, cell depletion and tolerability.

Due to both its early positive experience with the MGTA-117 clinical trial and in response to the uncertain capital market environment for biotechnology companies, Magenta recognizes the need for an increased focus on MGTA-117 while also de-prioritizing other portfolio investments. The revised operating plan includes reductions in spending related to general and administrative expenses and research platform-related investments in new disease targets, as well as pausing certain MGTA-145 investments, including the program's planned MGTA-145 dosing and administration optimization clinical trial in healthy subjects. Magenta's revised operating plan also reduces the Company's workforce by 14% and allows Magenta to extend its cash runway into second quarter of 2024.