Alkermes PLC's stock soared in after-market trading Thursday after the biotech company released positive clinical data from its trial of an experimental depression drug.
The drug candidate, ALKS 5461, which chief executive Richard Pops called potentially the biggest advance in depression treatment in two decades, met its clinical goals in a late-stage study of 407 patients across the United States with major depressive disorder.
All were patients who had seen inadequate improvement with an existing class of antidepressants. But they continued to take those drugs during the trial, in which some participants also got ALKS 5461 and others got a placebo, so their responses could be compared.
Alkermes, based in Dublin, has more than 500 employees in Waltham. Its shares shot up 43 percent to $62.25 in after-hours trading but remained well below their recent peak of $80.71 at the start of the year.
Investors dumped Alkermes stock in late January when ALKS 5461, a once-a-day oral treatment, failed to meet its goals in two previous clinical trials. In both of those trials, along with the latest one, patients in the placebo arm also improved during the study.
Pops said data from the earlier studies understated the benefits of the drug because of the way it was analyzed. While the prior studies recorded the benefit to patients in the fifth week after taking the drugs, the new study averaged the improvement recorded in each week of taking the drug, resulting in what he called a more accurate reading.
"Depression is a notoriously difficult disease to test new drugs in," Pops said, partly because there is often improvement among patients taking placebos as well as those taking experimental drugs. "We're thrilled by this outcome because it's so clear."
Unlike many other biotech companies developing therapies for relatively small patient populations, Alkermes is hoping to target about 7 million people with major depressive disorder in the United States who haven't got adequate relief from another antidepressant, as well as 5 million who haven't got adequate relief from two or more other drugs.
Standard antidepressants often cause side effects such as nausea, insomnia, and sexual dysfunction. In the latest Alkermes trial, some patients reported side effects, including nausea, dizziness, and fatigue.
ALKS 5461 would probably be prescribed as an adjunct therapy for patients already taking another drug rather than as a so-called first-line medicine. Pops said Alkermes hopes to consult with the Food and Drug Administration and could file a new drug application as early as next year.
Alkermes markets about 20 products, many acquired when it purchased a division of the Irish drug maker Elan PLC in 2011. After that acquisition, Alkermes, which had been based in Massachusetts, moved its global headquarters to Dublin, where corporate tax rates are lower.
The company's best-known products in the United States are Vivitrol, which treats alcohol and opiod dependence, and Aristada, a long-acting antipsychotic therapy.