Waltham, Mass.-based Repligen said its phase IIb study of RG2417, an oral formulation of uridine, failed to reflect a statistically significant distance between the bipolar depression drug and a placebo.

However, investigators said patients who had been recruited at academic centers did better on the drug than patients enrolled at commercial sites. "While we are disappointed with the top-line results of the study, we plan to conduct further evaluation of the data including the observation of differences between the patients treated in academic and commercial sites to determine if there is a path forward with RG2417," said Repligen CEO Walter Herlihy.