A Randomized Phase II Study of AGS-16C3F Versus Axitinib in Previously Treated Patients with Metastatic Renal Cell Carcinoma.

LESSONS LEARNED: The primary endpoint of this phase II study that evaluated the efficacy and safety of the investigational compound, AGS-16C3F, versus axitinib in previously treated patients with metastatic renal cell carcinoma (mRCC) was not met. Median progression-free survival, the primary endpoint, was 2.9 months with AGS-16C3F and 5.7 months with axitinib (HR, 1.676; 95% CI, 1.107-2.537; p = .015), per investigator assessment The safety profile for each study drug was as expected, with the most commonly reported adverse events being fatigue (53%) and nausea (47%) in the AGS-16C3F arm and fatigue (57%) and diarrhea (48%) in the axitinib arm. These results provide a benchmark for axitinib use in heavily pretreated patients with mRCC. BACKGROUND: AGS-16C3F is a novel antibody-drug conjugate that targets cell-surface ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3) and is conjugated to a microtubule disruptive agent. Here we present findings from a phase II study of AGS-16C3F versus axitinib in metastatic renal cell carcinoma (mRCC). METHODS: Patients with mRCC of any histology and disease progression during or after their last treatment regimen were randomized 1:1 to intravenous AGS-16C3F 1.8 mg/kg every 3 weeks or oral axitinib 5 mg twice daily (starting dose). The primary objective was investigator-assessed progression-free survival (PFS) of AGS-16C3F versus axitinib (RECIST version 1.1). RESULTS: In the total population (N = 133), 63% (n = 84) of patients had completed the study at data cutoff (August 21, 2019). Median PFS was 2.9 months with AGS-16C3F and 5.7 months with axitinib (hazard ratio [HR], 1.676; 95% confidence interval [CI], 1.107-2.537; p = .015). There were no significant differences between arms in secondary efficacy endpoints, including overall survival (13.1 months, AGS-16C3F and 15.4 months, axitinib; HR, 1.079; 95% CI, 0.681-1.707; p = .747). In the safety population (n = 131), the most commonly reported adverse events were fatigue (53%) and nausea (47%) in the AGS-16C3F arm and fatigue (57%) and diarrhea (48%) in the axitinib arm. The incidence of diarrhea was lower in the AGS-16C3F arm than in the axitinib arm (17% vs. 48%), and ocular toxicities were more frequent in the AGS-16C3F arm than in the axitinib arm (44% vs. 26%). CONCLUSION: The investigational compound, AGS-16C3F, did not meet the primary endpoint of this trial. These study results provide a benchmark for axitinib use in heavily pretreated patients with mRCC.

Phase I Dose-Escalation Study of the Safety and Pharmacokinetics of AGS15E Monotherapy in Patients with Metastatic Urothelial Carcinoma.

PURPOSE: Effective treatment of locally advanced or metastatic urothelial carcinoma (mUC) remains an unmet need. Antibody-drug conjugates (ADC) providing targeted drug delivery have shown antitumor activity in this setting. AGS15E is an investigational ADC that delivers the cytotoxic drug monomethyl auristatin E to cells expressing SLITRK6, a UC-associated antigen. PATIENTS AND METHODS: This was a multicenter, single-arm, phase I dose-escalation and expansion trial of AGS15E in patients with mUC (NCT01963052). During dose escalation, AGS15E was administered intravenously at six levels (0.10, 0.25, 0.50, 0.75, 1.00, 1.25 mg/kg), employing a continual reassessment method to determine dose-limiting toxicities (DLT) and the recommended phase II dose (RP2D) for the dose-expansion cohort. The primary objective was to evaluate the safety and pharmacokinetics of AGS15E in patients with and without prior chemotherapy and with prior checkpoint inhibitor (CPI) therapy. Best overall response was also examined. RESULTS: Ninety-three patients were recruited, including 33 patients previously treated with CPI. The most common treatment-emergent adverse events were fatigue (54.8%), nausea (37.6%), and decreased appetite (35.5%). Peripheral neuropathy and ocular toxicities occurred at doses of ≥0.75 mg/kg. AGS15E increased in a dose-proportional manner after single- and multiple-dose administration; accumulation was low. Five DLT occurred from 0.50 to 1.25 mg/kg. The RP2D was assessed at 1.00 mg/kg; the objective response rate (ORR) was 35.7% at this dose level. The ORR in the total population and CPI-exposed subgroup were 18.3% and 27.3%, respectively. CONCLUSIONS: DLT with AGS15E were observed at 0.75, 1.00, and 1.25 mg/kg, with an RP2D of 1.00 mg/kg being determined.