Efficacy and safety of the novel glycine transporter inhibitor BI 425809 once daily in patients with schizophrenia: a double-blind, randomised, placebo-controlled phase 2 study.

BACKGROUND

Cognitive impairment associated with schizophrenia predicts poor functional outcomes, but currently no approved pharmacotherapy is available. This study investigated whether the glycine transporter-1 inhibitor BI 425809 improves cognition in patients with schizophrenia.

METHODS

This phase 2, randomised, double-blind, placebo-controlled, parallel-group trial (81 centres, 11 countries), randomly assigned outpatients (aged 18-50 years) with schizophrenia on stable treatment to add-on once-daily oral BI 425809 2 mg, 5 mg, 10 mg, or 25 mg or placebo (1:1:1:1:2) for 12 weeks. Treatment was assigned in blocks using interactive response technology; patients, investigators, and all trial personnel were masked to group assignment. The primary endpoint was change from baseline in MATRICS Consensus Cognitive Battery (MCCB) overall composite T-score at week 12. Six predefined dose-response models were evaluated using a multiple comparison procedure and modelling approach with mixed model repeated measures to assess evidence for a non-flat dose-response relationship for cognitive improvements with BI 425809. Adverse events were monitored. Safety analyses included all randomly allocated patients who received one or more doses of trial medication; efficacy analyses included patients from this set who also had available baseline data and at least one post-baseline on-treatment measurement for the primary or secondary endpoint. This study is registered with ClinicalTrials.gov, number NCT02832037.

FINDINGS

509 patients were randomly assigned between April 25, 2018, and Oct 4, 2019 (BI 425809 2 mg, n=85; 5 mg, n=84; 10 mg, n=85; 25 mg, n=85; placebo, n=170 444 (87%) completed the 12-week treatment. Five of six dose-response models showed a statistically significant benefit of BI 425809 over placebo (linear [t=2·55, p=0·015], linear in log [t=2·56, p=0·015]; Emax [t=2·75, p=0·0089], sigmoid Emax [t=2·98, p=0·0038], logistic [t=2·77, p=0·0085]). Pairwise comparisons showed greater mean improvement from baseline in MCCB overall composite T-score at week 12 with BI 425809 10 mg and 25 mg versus placebo (adjusted mean difference 1·98 [95% CI 0·43-3·53] for 10 mg and 1·73 [0·18-3·28] for 25 mg; standardised effect size 0·34 for 10 mg and 0·30 for 25 mg). Adverse events were balanced across groups, reported in 50 (59%) of 85 patients on BI 425809 2 mg, 44 (52%) of 84 on 5 mg, 35 (41%) of 85 on 10 mg, 36 (42%) of 85 on 25 mg, and 74 (44%) of 170 on placebo.

INTERPRETATION

BI 425809 improved cognition after 12 weeks in patients with schizophrenia; doses of 10 mg and 25 mg showed the largest separation from placebo. If these encouraging results are confirmed in phase 3 trials, BI 425809 could provide an effective treatment for cognitive impairment associated with schizophrenia.

FUNDING

Boehringer Ingelheim.

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