ImmunoGen, Inc. announced that the first patient has been treated with IMGN632 in a Phase 1 clinical trial of patients with CD123-positive hematological malignancies, including acute myeloid leukemia (AML) and blastic plasmacytoid dendritic cell neoplasm (BPDCN). IMGN632 uses ImmunoGen's novel indolino-benzodiazepine payload, DGN549, which alkylates DNA without crosslinking, as well as novel linker technology with a CD123-targeting antibody. In preclinical studies with IMGN632, ImmunoGen has reported potent and selective activity against AML cells with lower cytotoxicity to normal myeloid progenitor cells than an ADC designed to crosslink DNA.1 Supporting preclinical data for IMGN632 have also shown compelling activity in AML and acute lymphoblastic leukemia (ALL) models with single and multi-dose regimens.2,3 These data suggest that IMGN632 has the potential to be a highly effective, yet tolerable ADC. The Phase 1 trial in AML and BCPDN will follow a once every three week dosing schedule while in its dose-finding stage. The selected dose will then be used in expansion cohorts assessing IMGN632 in patients with BPDCN, AML, ALL, and other CD123-positive hematologic malignancies. This is the second clinical trial using IGNs, a new class of cancer-killing agents developed by ImmunoGen for use in ADCs. ImmunoGen recently reported findings from the Company’s ongoing Phase 1 study of IMGN779 in patients with relapsed or refractory adult AML whose tumors express CD33.5 The data demonstrate that IMGN779 is well-tolerated with no dose-limiting toxicities, pharmacokinetic exposures and pharmacodynamic CD33 saturation increasing with dose, and anti-leukemia activity observed in patients with poor prognostic features.