Pharmacokinetics and Safety of a Novel Extended‐Release Microsphere Formulation of Risperidone in Patients with Schizophrenia or Schizoaffective Disorder

Risperidone extended-release injectable suspension (R-ERIS; marketed as RYKINDO) is a novel immediate-release version of risperidone formulated as extended-release microspheres for biweekly intramuscular injection to treat schizophrenia in adults. The pharmacokinetics (PK) and safety of R-ERIS were evaluated in a multicenter, randomized, open-label, multiple-dose study in patients with stable schizophrenia or schizoaffective disorder. Eligible patients (N = 108) 18 to 65 years old were randomized (1:1) to receive IM injections of R-ERIS 25 mg or the comparator, a biweekly risperidone long-acting injectable (BW-RLAI; marketed as RISPERDAL CONSTA) 25 mg for a total of 5 injections. The primary objective was to evaluate the relative bioavailability of active moiety (risperidone plus 9-hydroxyrisperidone) at steady state. Blood samples were analyzed for risperidone and 9-hydroxyrisperidone using a validated, specific, and sensitive liquid chromatography with tandem mass spectrometry method. Plasma concentration-time data were analyzed using non-compartmental methods. Pharmacokinetic parameters were calculated based on individual patient PK profiles. Safety was assessed using standard measures. At steady state, mean plasma concentrations of the active moiety were similar for R-ERIS and BW-RLAI. R-ERIS rapidly released risperidone after the injection without apparent lag time. Plasma active moiety levels reached steady state after the second injection of R-ERIS. The elimination of the drug was completed approximately 2 weeks earlier for R-ERIS as compared to that for BW-RLAI. R-ERIS was safe and well tolerated. Overall, R-ERIS exhibited a faster onset and offset than BW-RLAI and statistical analysis of exposure parameters demonstrated bioequivalence at steady state.