Biogen Inc. will discontinue the development of gosuranemab in certain neurodegenerative disorders after the medicine failed to improve symptoms of an uncommon brain disease in a mid-stage study.

The Cambridge, Mass.-based biotechnology company was evaluating gosuranemab, or BIIB092, in a phase 2 trial called Passport to treat progressive supranuclear palsy. The disorder causes deterioration of cells in the brain that control body movement and thinking, leading to problems with walking, balance and eye movements.

Following 52 weeks of treatment, the study did not meet its main goal as gosuranemab did not show statistical significance in improving the severity of the disease. Biogen said in a Dec. 13 press release that the trial did not demonstrate efficacy on other key secondary goals of the study. Safety results were generally consistent with previous studies of the drug.

Biogen has decided to discontinue development of gosuranemab for progressive supranuclear palsy and other primary tauopathies, a group of neurodegenerative disorders characterized by the presence of tau protein in the brain. Common disorders in this category include Alzheimer's disease.

An ongoing phase 2 trial of gosuranemab called Tango will continue, however, testing the therapy in patients with mild cognitive impairment due to Alzheimer's disease or with mild Alzheimer's disease due to differences in disease pathology.

Stifel called the Passport failure another blow to the theory that tau protein can be tackled with an antibody in a Dec. 13 note. However, the firm said that gosuranemab's failure will not damage Biogen's stock, as investors had given little credit for drugs in the company's pipeline. Investors are instead focused on the Alzheimer's drug aducanumab, which was revived in October after initially failing in clinical trials. Biogen's stock was trading at $296, up 0.73%, as of 8:19 a.m. ET on the Nasdaq on Dec. 13.

The analysts said one concern about gosuranemab was its ability to get enough of the active antibody into the brain to be effective. As for the Tango trial, Stifel believed the progressive supranuclear palsy indication was stronger for gosuranemab.

Biogen will report detailed results of the Passport trial at a future scientific forum.