A Study of IMGN632, a Novel CD123-Targeting Antibody-Drug Conjugate, for Patients with Frontline and Relapsed/Refractory Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)
Pemmaraju, N; Marconi, G; Todisco, E; Montesinos, P; Lane, AA; Sweet, K; Wang, ES; Deconinck, E; Rizzieri, DA; Walter, RB; Aribi, A; Lebon, D ...
Published in: Blood
Background: Overexpression of CD123 (IL-3Rα receptor) is a hallmark of blastic plasmacytoid dendritic cell neoplasm (BPDCN), thus making this antigen an attractive target for the development of new therapeutics. IMGN632 is a CD123-targeting antibody-drug conjugate (ADC) comprising a novel anti-CD123 antibody coupled, via a highly-stable peptide linker, to a unique DNA-alkylating cytotoxic payload of the recently developed IGN (indolinobenzodiazepine pseudodimer) class. Preclinically, IMGN632 has demonstrated potent activity against BPDCN cells with remarkable sensitivity of patient derived xenografts to IMGN632 (Blood 2018 132:3956). IMGN632 has demonstrated a wide therapeutic index in vitro and in vivo (PMIDs: 29661755, 30361418). Importantly IMGN632 has demonstrated favorable safety profile and has demonstrated evidence of promising efficacy in patients with BPDCN (ASH 2020: Blood 2020, vol 136, suppl 1, 11-13) and AML (ASH 2019: Blood 2019, vol 134, suppl 1, 734). Based on this data, IMGN632 was granted FDA Breakthrough Therapy Designation for BPDCN (Oct 2020). Initial experience with 3 frontline BPDCN patients showed clinical complete remissions (CRc) in all three patients. Subsequently an FDA-aligned pivotal cohort enrolling frontline BPDCN patients has been added to this study.Methods: This study is currently enrolling two expansion cohorts for adults with CD123 positive BPDCN. The pivotal cohort is enrolling patients with frontline/untreated (no prior systemic therapy) BPDCN who do not have CNS involvement and meet other basic eligibility. This cohort is designed to support an application for FDA approval for IMGN632 in patients with BPDCN. An additional cohort is enrolling patients with relapsed/refractory BPDCN, which may have had up to 3 prior lines of therapy, including CD123-targeted therapies and prior hematopoietic stem cell transplant (after 120 days) and may have CNS involvement (if cleared with intrathecals), but who must not have prior history of veno-occlusive disease of the liver, or history of grade 4 capillary leak syndrome or non-cardiac grade 4 edema, and other eligibility. Both cohorts are enrolling patients at the RP2D (0.045 mg/kg IV Q 3 weeks) in the US and EU (NCT03386513, https://BPDCNtrial.com).
