Magenta Therapeutics has stopped dosing a group of patients after a serious adverse event was reported in a phase 1/2 trial for the biotech’s leukemia med.
MGTA-117 is being tested in the split-phase dose-escalation trial in relapsed/refractory acute myeloid leukemia and myelodysplastic syndrome. Magenta is assessing several doses including 0.13 mg/kg in cohort 4. After dosing three patients in this group, two experienced dose-limiting toxicities.
The reports of the first adverse event arrived Dec. 13 after Magenta hosted an investor presentation touting the therapy. The second event was reported two days later on Dec. 15.
The first patient to receive MGTA-117 had no issues related to dose-limiting toxicities. But the second patient experienced a grade 4 serious adverse event that was respiratory in nature and considered possibly related to the study drug, Magenta said in a Tuesday press release. This was later determined to be a “suspected unexpected” serious adverse reaction due to lung involvement, per the release. The patient also had Grade 4 liver enzyme elevations.
On Dec. 15, Magenta received a report that the third patient dosed experienced a respiratory serious adverse event. This triggered prespecified rules to stop dosing.
As of today, the first patient to experience the adverse event has shown improvement in respiratory status and liver enzyme levels, while the second patient has improved respiratory status. Data on the first patient have been reported to the FDA as of today, and the agency has been advised of the second event while a report is being prepared, Magenta said.
Magenta will continue on with cohort 3 of the trial, which is testing a lower dose of 0.08 mg/kg. The company presented data on the first 15 patients from the cohort at the annual American Society of Hematology meeting this month, finding no dose-limiting toxicities. At this dose, Magenta believes that the risk-benefit profile is balanced enough to continue enrolling.
Back in April, Magenta laid off 14% of staff and trimmed down its pipeline. At that time, MGTA-117 became the lead asset from the company’s targeted conditioning program. The therapy was previously subject to a clinical hold before getting started, as the FDA wanted an additional test to inform dose escalation and safety monitoring in the proposed phase 1/2 clinical trial. The hold delayed initiation of the trial by a few months.