Updated

Gradually increasing the dose of Biogen Inc's experimental Alzheimer's disease drug appeared to cause less risk of brain swelling than fixed doses, according to interim 12-month results from a small study released on Thursday.

The closely watched drug, aducanumab, led to significant reductions in amyloid plaques in the brain compared with a placebo among the 31 patients who received titrated, or gradually increased dosing, data from the Phase I study showed.

The amyloid reduction and slowing of mental decline seen in patients in the titration portion of the study after 12 months of treatment was similar to what was reported earlier this year for patients who received fixed doses of aducanumab.

Details of the study were being presented at an Alzheimer's meeting in San Diego.

Patients in the study had either mild or prodromal, meaning early pre-symptomatic, Alzheimer's disease, researchers said.

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They said the new and previously reported data support further study of aducanumab in much larger trials of patients with early Alzheimer's disease, researchers concluded.

Biogen shares rose 1.49 percent to $289.54.