Xencor pauses testing leukemia bispecific antibody molecule as FDA inspects two possibly related deaths

Xencor has put on hold one of its studies on myeloid leukemia CD123 x CD3 bispecific antibody molecule XmAb14045, until the FDA lifts the hold, the company said Wednesday in a press release.

XmAb14045 is being tested in patients with relapsed or refractory acute myeloid leukemia and other CD123-expressing hematologic malignancies. Xencor said that patients currently on treatment and benefiting from treatment may continue treatment on the study.

Xencor said that the partial clinical hold was initiated following recent safety reports submitted to the FDA on two patient deaths that were considered at least possibly related to XmAb14045.

According to the press release, one patient experienced cytokine release syndrome (CRS) after their first dose, the treatment of which was complicated by the patient’s decision to withdraw care. One patient developed acute pulmonary edema following several doses of XmAb14045. The FDA will now review additional details related to the case.

Bassil Dahiyat, president and chief executive officer at Xencor, said: “Patient safety is Xencor’s highest concern and the company will work with the investigators and the FDA and will provide an update when more information about resuming enrollment can be shared.”

Dahiyat noted that the company’s ongoing Phase 1 studies evaluating its other CD3 bispecific antibodies, XmAb13676 and XmAb18087, are not affected.