Pharmacokinetics of ixazomib, an oral proteasome inhibitor, in solid tumour patients with moderate or severe hepatic impairment

AimThe aim of the present study was to characterize the pharmacokinetics of the oral proteasome inhibitor, ixazomib, in patients with solid tumours and moderate or severe hepatic impairment, to provide posology recommendations. MethodsEligible adults with advanced malignancies for which no further effective therapy was available received a single dose of ixazomib on day 1 of the pharmacokinetic cycle; patients with normal hepatic function, moderate hepatic impairment or severe hepatic impairment received 4mg, 2.3mg or 1.5mg, respectively. Blood samples for single-dose pharmacokinetic characterization were collected over 336h postdose. After sampling, patients could continue to receive ixazomib on days 1, 8 and 15 in 28-day cycles. ResultsOf 48 enrolled patients (13, 15 and 20 in the normal, moderate and severe groups, respectively), 43 were pharmacokinetics-evaluable. Ixazomib was rapidly absorbed (median time to reach peak concentration was 0.95-1.5h) and highly bound to plasma proteins, with a similar mean fraction bound (similar to 99%) across the three groups. In patients with moderate/severe hepatic impairment (combined group), the geometric least squares mean ratios (90% confidence interval) for unbound and total dose-normalized area under the plasma concentration vs. time curve from time zero to the time of the last quantifiable concentration in reference to the normal hepatic function group were 1.27 (0.75, 2.16) and 1.20 (0.79, 1.82), respectively. Seven (15%) of the 48 patients experienced a grade 3 drug-related adverse event; there were no drug-related grade 4 adverse events. ConclusionsIn patients with moderate/severe hepatic impairment, unbound and total systemic exposures of ixazomib were 27% and 20% higher, respectively, vs. normal hepatic function. A reduced ixazomib starting dose of 3mg is recommended for patients with moderate or severe hepatic impairment.