(Bloomberg) — Biogen Inc.’s experimental drug for Alzheimer’s disease failed to show a statistically significant cognitive benefit for patients on a closely watched dose, complicating the company’s quest to develop a treatment.
The findings, in data released Wednesday, leave unresolved questions about the appropriate dosage for the drug, even as Biogen (Nasdaq:BIIB) moves into the next phase of trials. Investors have pinned their hopes on the treatment, driving shares up 33 percent since initial data was announced in December.
Earlier data had already demonstrated that the drug showed a better response at higher doses, though it also showed harsher side effects. The new results didn’t provide clear direction on whether a dose somewhere in the middle would be the answer.
Biogen shares dropped 3.9 percent to $393.35 at 9:37 a.m. in New York. The stock had gained 35 percent in the last year, as of Tuesday’s close.
At a dose of 6 milligrams per kilogram, patients on Biogen’s drug BIIB037 had a cognitive decline of 1.96 points on the 30-point Mini Mental State Examination scale, compared with 2.81 for people on a placebo — suggesting cognitive decline was slower on the drug, though not enough to be statistically significant. And patients on a lower dose of 3 milligrams actually declined even less, with a change of 0.7 point.
On a different measure of cognitive function, called the Clinical Dementia Rating sum of boxes, patients deteriorated less on the 6 milligram dose than on the 3 milligram dose and those on a placebo. But those results also weren’t statistically significant.
Like other doses, the 6 milligram amount showed signs of reducing beta amyloid — protein fragments linked to the memory-erasing disease.
The results were from an early-stage trial of 166 patients. The most recent data examined 30 of those patients.