The phase II trial evaluated four intravenous doses of secretin versus a placebo in refractory schizophrenia. Initial results showed that secretin did not significantly improve symptoms as measured by the clinical global impression (CGI) or the positive and negative syndrome scale (PANSS).
The mean change in CGI in the secretin group was not significantly different compared to placebo. There were two responders (13%) in the placebo group, three (20%) in the low dose secretin group and four (29%) in the high dose group; however, this trend was not significant given the low power of this study.
However, some more promising trends were observed, including improvement on the PANSS dysphoric mood scale and transient changes in the social interaction of patients at the time of the infusion.
In addition, several patients participated in a cognitive testing paradigm within two hours of the first dose to assess the impact of secretin on one of the cognitive deficits characteristic of patients with schizophrenia. The results suggest that further investigation of this symptom is warranted and Repligen is currently discussing the design of a follow-up study to determine if this observation is reproducible and related to drug treatment.
The phase II study was designed to confirm the results of a phase I trial of secretin in schizophrenia which was carried out independently by investigators at the University of North Carolina. In that study, several patients in the secretin group had marked, but transient improvements in symptoms compared to none in the placebo group.