A Phase I, dose-finding and pharmacokinetic study of olaparib (AZD2281) in Japanese patients with advanced solid tumors.

Olaparib (AZD2281) is an orally active Poly(ADP-ribose) polymerase (PARP) inhibitor with favorable antitumor activity in advanced ovarian and breast cancers with BRCA1/2 mutations in Western (USA and European) studies. This Phase I dose-finding study evaluated the tolerability, pharmacokinetics, PARP inhibitory activity, and antitumor activity of olaparib in Japanese patients with solid tumors. Olaparib was administered as a single-dose on day 1, followed by twice-daily dosing for 28 days from 48 h after a single dose. Doses were escalated from 100 mg b.i.d. in successive cohorts, up to a maximum of 400 mg b.i.d. The present study enrolled 12 patients (n = 3, 3, and 6 in 100, 200 and 400-mg b.i.d. levels, respectively). The most common adverse events were nausea, increased blood creatinine, decreased hematocrit, leukopenia and lymphopenia; dose-limiting toxicities were not observed up to and including the 400-mg b.i.d. dose level. Following twice-daily dosing, olaparib showed no marked increase in exposure at steady state over that expected from the single-dose pharmacokinetics. PARP-1 inhibition was observed from the 100-mg b.i.d. dose level in peripheral blood mononuclear cells from 6 h post-dose on day 1 during the multiple-dosing period. A patient with metastatic breast cancer (100 mg b.i.d.) had a partial response for 13 months and four patients (two each in the 200 and 400-mg b.i.d. levels) had stable disease >8 weeks. Olaparib was well tolerated up to the 400-mg b.i.d. dose in Japanese patients with solid tumors. Preliminary evidence of antitumor activity was observed.