Phase I study of ON-01910.Na, a novel cell cycle inhibitor in adult patients with solid tumors

13026 Background: ON-1910.Na is a new chemical entity, novel cell cycle inhibitor which arrests cells in G2/M, affects phosphorylation of several regulatory kinases and lacks cross resistance to other standard chemotherapy agents. This is a first-in-man Phase I dose escalation study to determine the dose limiting toxicities, recommended Phase II dose, and pharmacokinetic (PK) profile, and to document any antitumor activity of ON-01910.Na. Methods: Patients had histologically confirmed solid tumors refractory to standard therapy. ON-1910.Na, formulated as a solution in PEG400, was administered as a 2-hour infusion on days 1, 4, 8, 11, 15, and 18 followed by a 10 day observation period for a total of 28 days per cycle. The initial dose was 80 mg and was escalated using an accelerated titration schedule; one patient was treated per cohort until grade 2 toxicity was documented. A dose confirmation cohort of up to 12 patients will be treated at the maximun tolerated dose (MTD). A comprehensive PK study was performed on days 1 and 15 of the first cycle, plus trough samples were collected. Results: Thirteen patients (7F, 6M; ages 46–73) have received 20 cycles. Dose levels of 80, 160, 320, 480, 800, 1280, 2080, and 3120 mg were evaluated in 8 patients, and a further dose of 4370 mg has been evaluated in 5 patients. Toxicities have been anemia (2 G1, 1 G2), leucopenia (1 G1, 1 G2), hyperglycemia (2 G1), elevated AST/ALT (1 G1, 1 G2), nausea (3 G1), diarrhea (3 G1), skeletal pain (5 G1, 1 G2), abdominal pain (2 G1), tumor pain (1 G2), and fatigue (3 G1, 1 G2), and have clustered at the latter 3 dose levels. PK analysis shows increasing ON-1910.Na exposure with increasing doses. ON-1910.Na has a low clearance (13 L/h), long half-life (20 h), distribution in excess of blood volume (58 L) and PK parameters are similar on days 1 and 15. Approximately 3-fold and 5-fold inter-subject variation in ON-1910.Na clearance was observed on days 1 and 15, respectively. No antitumor activity has been documented by standard criteria. Conclusions: Dose escalation is continuing. [Table: see text]