Phase I trial of ASG-5ME in metastatic castration-resistant prostate cancer (CRPC).

4568 Background: SLC44A4 is a 710 amino acid protein that is expressed on prostate, pancreas and other cancers. SLC44A4 is found in 95% of primary prostate tumors (75% express moderate to high levels). ASG-5ME is an antibody drug conjugate (ADC) comprised of a fully human antibody targeting SLC44A4, conjugated to the microtubule-disrupting agent monomethyl auristatin E. ASG-5ME has dose-dependent cytotoxic effects in vitro and significant anti-tumor activity in xenograft models. We report results of a phase I study to establish the maximum tolerated dose (MTD) of ASG-5ME for CRPC, conducted by the Prostate Cancer Clinical Trials Consortium. Methods: Patients (pts) had progressive metastatic CRPC. Prior chemotherapy was allowed. Treatment cohorts were 0.3, 0.6, 1.2, 1.8, 2.4, and 3.0 mg/kg. ASG-5ME was given IV q3 weeks. Safety, pharmacokinetic properties, anti-tumor effects, circulating tumor cell (CTC) enumeration, and CTC molecular profiles were assessed. Pts were treated until disease progression or un...