Phase II trial of iboctadekin (rhIL-18) on a daily X 5 schedule in metastatic melanoma (MM)
10043 Background: Interleukin-18 (IL-18) is an immunostimulatory cytokine with potent antitumor activity in preclinical models. Two phase I studies of recombinant human (rh) IL-18 explored a wide dose range (0.03–1.0 mg/kg) without reaching a maximum tolerated dose (MTD) on the daily × 5 schedule. Pharmacodynamic data including inflammatory cytokine production and activation of lymphocyte subsets revealed optimal biologic activity at the lower end of the dose range (0.01–0.2 mg/kg) as did 2 unconfirmed partial responses (PRs) in a MM and a renal cancer patient (pt) at 0.1 mg/kg. Methods: An open-label, randomized, phase II trial in 60 adult pts with previously untreated MM was conducted to evaluate the efficacy and safety of rhIL-18 administered as a 2-hour IV infusion daily × 5 every 28 days for 6 cycles. Pts with PS ≤ 1, without known CNS involvement, and with adequate end organ function were randomized in stage 1 to 3 dose levels of IL-18 stratified according to AJCC M stage 1a/b vs. 1c. Two confirmed responses for a given dose level in Stage 1 were required to enroll 20 additional pts/level in Stage 2. The 1° objective was determination of overall response rate (ORR) for each dose level. Progression-free survival (PFS), tolerability, and immunogenicity were 2° endpoints. Results: 64 pts were treated at 3 dose levels. Nine pts remain on study. One pt experienced a confirmed PR. Based on preliminary data, the difference in PFS 6 months (mos) was significant (p=0.03) for 0.01 vs 0.1 mg/kg. Most common toxicities were mild to moderate fever, rigors, chills, n/v, and headache. Anti-IL18 antibody (Ab) development correlated with dose level. No clinically significant adverse events were associated with Ab development. Conclusion: Iboctadekin has an acceptable tolerability profile and has activity in MM but insufficient confirmed responses have been observed at this time to initiate Stage 2. Preliminary PFS 6 months indicates an advantage for pts treated at the lowest dose. [Table: see text] [Table: see text]