Concert Pharmaceuticals has announced that its Phase II clinical trial of CTP-692 as an adjunctive treatment in patients with schizophrenia failed to meet the primary endpoint or other secondary endpoints.

CTP-692 is a deuterated form of D-serine, an endogenous amino acid that is a co-agonist of the NMDA receptor.

The double-blind, randomised, placebo-controlled study analysed the safety and efficacy of CTP-692 as an adjunctive treatment in adult patients with schizophrenia.

The trial had 325 patients, who were on a stable course of an antipsychotic medication. They were randomly given either 1g, 2g, or 4g doses of CTP-692 or placebo once daily.

The change in the Positive and Negative Syndrome Scale (PANSS) total score at 12 weeks compared to baseline formed the trial’s primary endpoint.

Data from the trial showed that CTP-692 did not demonstrate a statistically significant improvement versus placebo at any of tested dose levels.

Furthermore, no significant improvements were noted in either the positive or negative symptoms subscales of the PANSS scale at any of the treatment doses.

CTP-692 treatment was generally well-tolerated in the Phase II trial while adverse events noted were mostly mild in severity and equally distributed across the dose groups, including placebo.

Concert Pharmaceuticals president and CEO Roger Tung said: “The body of evidence in the field supporting D-serine as an adjunctive treatment for schizophrenia was compelling and led us to advance CTP-692 into a Phase II proof of concept study.

“Unfortunately, we didn’t see the results we hoped for to support continuation of this programme.

“Going forward, we will focus our internal resources on the advancement of CTP-543, which is currently in Phase III evaluation for the treatment of alopecia areata, and evaluation of additional pipeline candidates.”

In June 2019, Concert Pharmaceuticals revealed plans to initiate a Phase II clinical trial of CTP-692 as an adjunctive treatment for schizophrenia, based on positive data from the Phase I programme.