Sumitomo Pharma and Otsuka announce topline results from phase III DIAMOND 1 and DIAMOND 2 clinical studies evaluating ulotaront in schizophrenia.

The multicenter, randomized, double-blind, parallel-group, fixed-dosed DIAMOND 1 study, evaluated the efficacy, safety, and tolerability of ulotaront (50 mg/day and 75 mg/day) versus placebo over six weeks in 435 acutely psychotic adults with schizophrenia.

In the DIAMOND 1 study all three groups showed a reduction in the Positive and Negative Syndrome Scale (PANSS) total score over time, however neither ulotaront treatment group was superior to placebo on the primary endpoint of change from baseline in PANSS total score at Week 6 (least squares [LS] mean: -16.9 and -19.6 in ulotaront 50 mg/day and 75 mg/day-treated patients, respectively, compared to -19.3 in placebo-treated patients). The multicenter, randomized, double-blind, parallel-group, fixed-dosed DIAMOND 2 study, evaluated the efficacy, safety, and tolerability of ulotaront (75 mg/day and 100 mg/day) versus placebo over six weeks in 464 acutely psychotic adults with schizophrenia. In the DIAMOND 2 study, ulotaront 75 mg/day and 100 mg/day treatment groups did not demonstrate statistically significant improvement compared to placebo on the primary endpoint. At Week 6 both ulotaront treatment groups showed numerically larger mean reductions in PANSS total score from baseline compared to placebo (LS mean: -16.4 and -18.1 in ulotaront 75 mg/day and 100 mg/day-treated patients, respectively, compared to -14.3 in placebo-treated patients).In both the DIAMOND 1 study and the DIAMOND 2 study, a large placebo effect was observed which may have masked the molecule's therapeutic effect. Ulotaront was generally safe and well-tolerated in both studies.

Hiroshi Nomura, representative director, president and CEO of Sumitomo Pharma commented, "Sumitomo Pharma and our collaborator Otsuka Pharmaceutical have done preliminary analyses of the data and we believe that a high placebo response may have masked the therapeutic effect of this innovative molecule. High placebo responses, like those seen in DIAMOND 1 and DIAMOND 2, are well documented in psychiatric clinical studies. The placebo response in DIAMOND 1 was particularly high. These studies were conducted throughout the COVID-19 pandemic and initial analyses of these data suggest an impact of COVID-19 on the placebo responses that were seen. We continue to work closely with Otsuka and analyze the data to determine our next steps and plan to discuss with the U.S. FDA how to proceed based on these results."