Abstract P6-10-01: A Randomized Phase 2 Study of the Antibody-Drug Conjugate CDX-011 in Advanced GPNMB-overexpressing Breast Cancer: the EMERGE Study

Abstract Background: GPNMB is an internalizable transmembrane glycoprotein overexpressed in multiple tumor types, including breast cancer (BC). GPNMB promotes BC metastases in a murine model and is a poor prognostic marker in patients (pts) (Rose 2010). CDX-011 (glembatumumab vedotin) is a fully human GPNMB-specific monoclonal antibody conjugated to the potent cellular toxin MMAE via a protease-sensitive peptide linker, designed to cleave upon cellular internalization. In Phase I/II studies of CDX-011 in BC (n = 42), an objective response rate (ORR) (including confirmed and unconfirmed response) of 12% overall and 20% for “triple-negative” (ER/PR/HER2−; TN) pts was observed (Saleh, ASCO 2010). Methods: The Phase II EMERGE study examined the efficacy of CDX-011 by level of GPNMB expression. Refractory BC (2–7 prior cytotoxic regimens in metastatic setting), GPNMB expression in ≥ 5% of tumor or stroma cells (as centrally determined on archival tumor), and no persistent treatment-related toxicity (including neuropathy) of ≥ Grade 2 severity were required for enrollment. Pts were stratified by GPNMB expression pattern (any tumor, low stromal or high stromal) and randomized 2:1 to CDX-011 (1.88 mg/kg IV q 21 days) or “investigator's choice” (IC) single-agent chemotherapy, and treated until progression (PD) or intolerance with IC pt crossover permitted to CDX-011 at PD. Endpoints: ORR (primary), progression-free survival (PFS), safety, pharmacokinetics, pharmacodynamics. Results: 99% of screened tumor samples expressed GPNMB. 122 treated pts (81 CDX-011 vs. 41 IC) had median age = 56 vs. 56 years; median # prior anticancer regimens = 6 vs. 5; visceral disease (liver/lung) = 83% vs. 80%; TN = 33% vs 27%, respectively. To date, 15 IC pts have crossed over to CDX-011, and 14 pts (8 CDX-011, 6 IC) continue on treatment. CDX-011 was well tolerated with less hematologic toxicity than IC; CDX-011-related toxicity included rash (overall = 38%; Grade 1 = 20%; Grade 2 = 15%; Grade 3 = 3%) and neuropathy (overall = 18%; Grade 1 = 8%; Grade 2 = 7%; Grade 3 = 2%). Conclusions: CDX-011 was a well-tolerated and active agent in this heavily pre-treated BC pt population. Preliminary analysis of the EMERGE study demonstrates enhanced activity of CDX-011 in TN as well as high GPNMB expressing BC tumors, confirming that CDX-011 is a targeted agent. This noted promising activity in advanced TN and hGPNMB enriched pt populations warrants further evaluation. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-10-01.