Phase I dose-escalation study of milciclib in combination with gemcitabine in patients with refractory solid tumors

BACKGROUND: This phase I trial evaluated the safety and tolerability of milciclib, an inhibitor of multiple cyclin-dependent kinases and tropomycin receptor kinase A, in combination with gemcitabine in patients with refractory solid tumors.

DESIGN: Sixteen patients were enrolled and treated with milciclib at three dose levels (45 mg/m2/day, n = 3; 60 mg/m2/day, n = 3; and 80 mg/m2/day, n = 10) with a fixed dose of gemcitabine (1000 mg/m2/day). Milciclib was administered orally once daily for 7 days on/7 days off in a 4-week cycle, and gemcitabine was administered intravenously on days 1, 8 and 15 in a 4-week cycle.

RESULTS: All 16 enrolled patients were evaluable for safety and toxicity. Dose-limiting toxicities, which occurred in only one out of nine patients treated at the maximum dose tested (milciclib 80 mg/m2/day and gemcitabine 1000 mg/m2/day), consisted of Grade 4 thrombocytopenia, Grade 3 ataxia and Grade 2 tremors in the same patient. Most frequent treatment-related AEs were neutropenia and thrombocytopenia. Among 14 evaluable patients, one NSCLC patient showed partial response and 4 patients (one each with thyroid, prostatic, pancreatic carcinoma and peritoneal mesothelioma) showed long-term disease stabilization (>6-14 months). Pharmacokinetics of the orally administered milciclib (~t1/2 33 h) was not altered by concomitant treatment with gemcitabine.

CONCLUSION: The combination treatment was well tolerated with manageable toxicities. The recommended phase II dose was 80 mg/m2/day for milciclib and 1000 mg/m2/day for gemcitabine. This combination treatment regimen showed encouraging clinical benefit in ~36% patients, including gemcitabine refractory patients. These results support further development of combination therapies with milciclib in advanced cancer patients.