Phase I Study of the Investigational Anti-Guanylyl Cyclase Antibody–Drug Conjugate TAK-264 (MLN0264) in Adult Patients with Advanced Gastrointestinal Malignancies

Abstract Purpose: To assess the safety, tolerability, and preliminary antitumor activity of the investigational anti–guanylyl cyclase C (GCC) antibody–drug conjugate TAK-264 (formerly MLN0264) in adult patients with advanced gastrointestinal malignancies. Experimental Design: Adult patients with GCC-expressing gastrointestinal malignancies (H-score ≥ 10) were eligible for inclusion. TAK-264 was administered as a 30-minute intravenous infusion once every 3 weeks for up to 17 cycles. Dose escalation proceeded using a Bayesian continual reassessment method. At the maximum tolerated dose (MTD), 25 patients with metastatic colorectal cancer were enrolled in a prespecified dose expansion cohort. Results: Forty-one patients were enrolled, including 35 (85%) with metastatic colorectal cancer. During dose escalation (0.3–2.4 mg/kg), four of 19 patients experienced dose-limiting toxicities of grade 4 neutropenia; the MTD was determined as 1.8 mg/kg. Patients received a median of two cycles of TAK-264 (range, 1–12); nine received ≥four cycles. Common drug-related adverse events (AEs) included nausea and decreased appetite (each 41%), fatigue (32%), diarrhea, anemia, alopecia, and neutropenia (each 27%); grade ≥3 AEs included neutropenia (22%), hypokalemia, and febrile neutropenia (each 7%). Peripheral neuropathy was reported in four (10%) patients. Pharmacokinetic data showed approximately dose proportional systemic exposure and a mean plasma half-life of around 4 days, supporting the dosing schedule. Overall, 39 patients were response-evaluable; three experienced durable stable disease; and one with gastric adenocarcinoma had a partial response. GCC expression did not appear to correlate with treatment duration. Conclusions: These findings suggest that TAK-264 has a manageable safety profile, with preliminary evidence of potential antitumor activity in specific gastrointestinal malignancies. Further investigation is underway. Clin Cancer Res; 22(20); 5049–57. ©2016 AACR.