For a randomized, double-blind (DB), parallel-group research, investigators sought to compare the effectiveness and safety of paliperidone palmitate 6-month (PP6M) formulation to paliperidone palmitate 3-month (PP3M) formulation in patients with schizophrenia. Following the screening, participants started an open-label (OL) maintenance phase and received 1 injectable cycle of paliperidone palmitate (PP1M; 100 or 150 mg eq.) or PP3M per month (350 or 525 mg eq.). In a 12-month DB phase, clinically stable patients were randomized (2:1) to receive PP6M (700 or 1000 mg eq., gluteal injections) or PP3M (350 or 525 mg eq.); 2 PP6M dosages (equivalent to PP1M and PP3M doses) were chosen.

Overall, 1,036 patients were assessed, 838 were admitted to the OL phase, and 702 (mean age: 40.8) were randomized (PP6M: 478; PP3M: 224); 618 (88.0%) patients completed the DB phase (PP6M: 416 [87.0% ]; PP3M: 202 [90.2%]). The PP6M relapse rate was 7.5%(n=36), while the PP3M relapse rate was 4.9% (n=11). The Kaplan-Meier estimate of the difference (95% CI) in the percentages of patients who remained relapse-free between treatment groups (PP6M – PP3M) was -2.9% (-6.8%, 1.1%), meeting noninferiority criteria (the lower bound of the 95% CI was greater than the prespecified noninferiority margin of 10%). The primary analysis was confirmed by secondary efficacy outcomes. The rates of treatment-emergent adverse events were comparable in PP6M (62.1%) and PP3M (58.5%). There were no new safety issues.

In patients with schizophrenia who had been satisfactorily treated with PP1M or PP3M, a twice-yearly dosage schedule of PP6M was non-inferior to that of PP3M in avoiding recurrence.