A phase I safety and efficacy clinical trial of plocabulin and gemcitabine in patients with advanced solid tumors

Abstract

Plocabulin (Plo) induces depolymerization of tubulin fibers with disorganization and fragmentation of the microtubule network leading to mitosis. Plo combined with gemcitabine (Gem) showed synergistic anti-tumor activity in preclinical studies. This phase I trial evaluated the safety, pharmacokinetics (PK) and efficacy of Plo 10-min infusion plus Gem on Day 1 and 8 every 3-week in patients with advanced solid tumors. Fifty-seven patients were enrolled into 8 dose levels (DLs); 74%: females; 74%: ECOG performance status 1; median age: 62 years; median number of prior lines of therapy:3. Dose-limiting toxicities (DLT) in Cycle 1 were grade (G) 3 intestinal obstruction at the maximum tolerated dose (MTD), G3 peripheral sensory neuropathy (PSN), G3 abdominal pain, and G4 thrombocytopenia (1 patient each). The highest DL (DL8: Plo 10.5 mg/m²/Gem 1000 mg/m²) was the MTD. Accrual into DL7 (Plo 10.0 mg/m²/Gem 1000 mg/m²) was stopped before it was formally defined as the recommended dose (RD). Most common treatment-related adverse events (AEs) were fatigue (56%), nausea (55%), diarrhea (31%); G3/4 hematologic toxicities comprised anemia (35%), neutropenia (27%) and thrombocytopenia (17%). No treatment-related deaths occurred. PK parameters for Gem or dFdU at all DLs were in line with reference values from the literature. Six of 46 evaluable pts were responders (overall response rate:13%). Of note, 2 partial responses (PR) and 2 stable disease (SD) ≥ 4 months occurred among 13 pts with ovarian cancer. The combination of Plo and Gem is well tolerated. The MTD was Plo 10.5 mg/m²/Gem 1000 mg/m². No PK drug-drug interaction was found. The most encouraging outcome occurred in ovarian cancer patients.

Keywords: Gemcitabine; Ovarian cancer; Phase I; Plocabulin.

Fig. 1

Waterfall plot of best response among the 41 patients who had measurable lesions at baseline. Each tumor type is color-coded. An upward pointing bar that exceeds 20% represents progressive cancer, a downward bar exceeding 30% indicates a partial response, and the rest of bars are stable diseases. One patient had a partial response of target lesions, but not of non-target lesions. One patient experienced a complete response (not shown). CUP, cancer of unknown primary site; GCT, germ cell tumor; GIST, gastrointestinal stromal tumor; HN, head and neck squamous cell carcinoma; MBC, metastatic breast cancer; NSCLC, non-small cell lung cancer; PR, partial response

Fig. 2

Swimmer’s plot of 46 patients with color codes for each tumor type. The time of first documented response is indicated by a diamond plot. CR, complete response; CUP, cancer of unknown primary site; GCT, germ cell tumor; GIST, gastrointestinal stromal tumor; HN, head and neck squamous cell carcinoma; MBC, metastatic breast cancer; NSCLC, non-small cell lung cancer; PR, partial response