Aducanumab reduced deposits of the amyloid plaque associated with Alzheimer’s disease in the brains of early-stage patients who took part in a three-year extension trial, Biogen reports.
After the study ended, deposits of the protein were lower in many patients’ brains than the level that a scan would identify as constituting Alzheimer’s, researchers said. The treatment is now in Phase 3 clinical treats.
Imaging showed that a fourth of the 143 patients in the extension study experienced brain swelling from the treatment. But most did not experience symptoms from it, and it was temporary in the majority of cases.
Researchers in the Phase 1 trial (NCT01677572) randomly assigned patients with early-stage or mild Alzheimer’s to various doses of aducanumab or a placebo.
The 143 patients in the extension study were divided into four groups.
One consisted of 18 people whom researchers assigned to an increasing-dose schedule of aducanumab or a placebo for 12 months. Patients on the placebo were switched to aducanumab after the first year. Biogen followed these patients for two years.
The researchers followed 69 patients who received various-strength fixed doses for 36 months. Another group included patients who received a very low dose of adcanumab during the first year, and higher doses in the extension study. All patients who were on a placebo during the Phase 1 clinical trial received adcanumab during the extension.
Biogen reported in a press release that the treatment lowered amyloid-beta brain deposits in a dose- and time-dependent manner, meaning that the larger the dose and the longer a patient took it, the better the results. Researchers used positron emission tomography (PET) scans of deposits in patients’ brains to assess the treatment’s effectiveness.
The amyloid levels of patients treated for 36 months fell below the cut-off for a scan indicating Alzheimer’s, researchers said. In addition, symptom assessments suggested that patients continued to benefit in their second and third years of treatment.
Researchers said the most common adverse events patients experienced were headache, falls, and amyloid-related imaging abnormalities, or ARIAs. A fourth of patients who received aducanumab developed brain swelling, or ARIA edema, that showed up on scans.
Scientists have known about the side effect from earlier studies of aducanumab and similar drugs.
Biogen said further brain swelling did not show up in patients who remained on the same dose. Six patients had more than one brain swelling episode, but most had no symptoms, so they stayed in the study, researchers said.
Biogen plans to share the complete results of the extension study at a scientific meeting.
While the Phase 1 study was primarily concerned with safety, the Phase 3 trials will assess both safety and aducanumab’s ability to slow cognitive decline and disability progression in early Alzheimer’s patients.