A Randomized Multiple Dose Pharmacokinetic Study of a Novel PDE10A Inhibitor TAK-063 in Subjects with Stable Schizophrenia and Japanese Subjects and Modeling of Exposure Relationships to Adverse Events

BACKGROUND Phosphodiesterase 10A (PDE10A) is selectively expressed in medium spiny neurons of the striatum. TAK-063 is a selective inhibitor of PDE10A in clinical development for the treatment of schizophrenia. OBJECTIVES Safety, tolerability, and pharmacokinetics (PK) of TAK-063 were evaluated following multiple rising oral doses, and PK/adverse event (AE) models were developed to characterize the relationship between TAK-063 exposure and incidence of specific AEs. METHODS Healthy Japanese subjects (HJS) aged 20-55 years and subjects with stable schizophrenia (SSS) aged 18-55 years were enrolled and randomized to either TAK-063 or placebo. Study medication was administered as a tablet once daily (at night) with food over a 7-day period. RESULTS TAK-063 and placebo groups consisted of 62 and 15 subjects, respectively. A majority of subjects (71 of 77) completed the study. AEs were mostly of mild or moderate severity, and no deaths were reported. The most common AE was somnolence. For equivalent doses, the rate of extrapyramidal syndromes (EPS) was higher in SSS than in HJS. PK parameters were comparable between HJS and SSS at equivalent doses. The incidence of somnolence and EPS symptoms increased with exposure, and this was described with the PK/AE model. A maximum tolerated dose was not determined. CONCLUSIONS Multiple doses of TAK-063 were safe and well tolerated. PK/AE models characterized the incidence of somnolence and EPS with increasing TAK-063 exposure, and simulations suggested that a once-daily dose range of up to 30 mg would be suitable for future studies. CLINICALTRIALS. GOV IDENTIFIER NCT01879722.