Shares in Alkermes had jumped nearly 10% by late-afternoon trading on the Nasdaq Wednesday after its experimental schizophrenia drug met efficacy targets in a mid-stage trial pitting it against olanzapine, and also showed an advantage on the weight gain front.

ALKS 3831 is made of samidorphan, a novel, potent mu-opioid antagonist, and the veteran antipsychotic drug olanzapine. The Phase II study, involving 300 patients, showed that the therapy was equivalent to olanzapine in efficacy, but caused less weight gain than the latter alone.

According to the data, out of the full patient population those taking ALKS 3831 had a 37% lower mean weight gain than those on olanzapine at week 12, but this was 51% lower gain in a pre-specified subset of patients who had put on weight during the one-week olanzapine lead-in. 

On the safety side, the pill was generally well tolerated, the firm said, with common adverse events in the ALKS 3831 treatment groups relative to olanzapine being somnolence, sedation and dizziness. 

On the back of the data, Alkermes said it has requested a meeting with the US Food and Drug Administration with a view to advancing ALKS 3831 into a pivotal development program this year.