Dose and schedule selection for the anti-CTLA4 monoclonal antibody ticilimumab in patients (pts) with metastatic melanoma

Abstract

8032 Background: Ticilimumab therapy has demonstrated anti-tumor activity in pts with metastatic melanoma. Its indirect, immune-mediated antitumor effects pose unique challenges for dose/regimen selection. Methods: It was our original intention to select the clinical dose/regimen of ticilimumab based on (1) clinical safety and tolerability and (2) attainment of target plasma concentrations derived from pre-clinical work using an ex vivo assay of ticilimumab-induced enhancement of cytotoxic T-cell function. Because numerous pts with metastatic melanoma experienced clinical benefit (i.e., durable objective responses [OR] and/or long-term survival) in early clinical trials of ticilimumab, we are using (1) safety and tolerability and (2) clinical benefit to guide dose/regimen selection. Data for evaluating these criteria come from a single-dose Phase 1 trial (0.01, 0.1, 1, 3, 6, 10 and 15 mg/kg) and an ongoing multiple-dose Phase 1/2 trial in pts with melanoma (Phase 1 portion: 3, 6 and 10 mg/kg Q1M; Phase 2 portion: 10 mg/kg Q1M and 15 mg/kg Q3M). Results: In the single-dose Phase 1 trial, 10 mg/kg was the Protocol-defined MTD but a high rate of clinical benefit was seen in the 15 mg/kg dose cohort (6/6 pts). Because the DLTs seen at 15 mg/kg (Gr 3 diarrhea, Gr 3 rash) were moderate and resolved completely within 3 months of dosing, 15 mg/kg Q3M was proposed as a safe and tolerable dose and is being studied in the Phase 2 portion of the multiple-dose Phase 1/2 trial. The Phase 1 portion of the multiple-dose Phase 1/2 trial revealed that 10 mg/kg is safe and tolerable with monthly dosing so 10 mg/kg Q1M is also being studied in the Phase 2 portion of the trial. At the end of the Simon Optimum-defined Stage 1 of the Phase 2 portion of the ongoing trial, the OR rate (3/18 pts) is the same for both dosing regimens. However, with 15 mg/kg Q3M, Gr 3/4 adverse events were less frequent (6% versus 34%). Conclusions: 15 mg/kg Q3M is proposed as the clinical dose/regimen for ticilimumab in metastatic melanoma. This dose/regimen appears to have anti-tumor activity approximately equal to 10 mg/kg Q1M but it appears to have a superior safety profile. [Table: see text]