Background:This phase I, open-label, first-in-human study determined dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of PD 0332991, an oral cyclin-dependent kinase 4/6 inhibitor with potent anti-proliferative activity in vitro/vivo.Methods:A total of 33 patients with retinoblastoma protein-positive advanced solid tumours or non-Hodgkin's lymphoma refractory to standard therapy or for which no therapy was available received PD 0332991 once daily (QD) for 14 days followed by 7 days off treatment (21-day cycles; Schedule 2/1).Results:Six patients had DLTs (18% four receiving 200 mg QD; two receiving 225 mg QD); the MTD was 200 mg QD. Treatment-related, non-haematological adverse events occurred in 29 patients (88%) during cycle 1 and 27 patients (82%) thereafter. Adverse events were generally mild–moderate. Of 31 evaluable patients, one with testicular cancer achieved a partial response; nine had stable disease (⩾10 cycles in three cases). PD 0332991 was slowly absorbed (mean Tmax 4.2 h) and eliminated (mean half-life 26.7 h). Volume of distribution was large (mean 3241 l) with dose-proportional exposure. Using a maximum effective concentration model, neutropenia was proportional to exposure.Conclusion:PD 0332991 was generally well tolerated, with DLTs related mainly to myelosuppression. The MTD, 200 mg QD, is recommended for phase II study.

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No increase in systemic DM1 concentration was observed in patients with mild or moderate hepatic impairment versus those with normal hepatic function. The faster T-DM1 clearance observed at cycle 1 in patients with hepatic impairment appeared to be transient. After repeated dosing (three cycles), T-DM1 exposure in patients with mild and moderate hepatic impairment was within the range seen in those with normal hepatic function.