How full is the glass at Biogen?

The perennial question facing Biogen — when are you going to tell us whether your Alzheimer’s drug works? — again went unanswered yesterday, when the company presented its annual results. But Biogen made a related disclosure that, like so much in Alzheimer’s disease, invites wildly divergent conclusions.

The company said it plans to enroll a late-stage trial testing aducanumab (the drug upon which its future hinges) in patients who don’t yet show symptoms of Alzheimer’s but who have some telltale signs in brain scans. You could be forgiven for thinking:

This is a good sign. We probably won’t know until 2020 whether aducanumab can help patients with mild forms of the disease, but Biogen’s decision to start a new study without seeing those data is a sign of management’s confidence in the drug.

This is a bad sign. If you’ve been following the metronomic disappointments in Alzheimer’s these past few years, you know that nearly every company has explained its failure by saying it should have tested the drug earlier in the disease process. By pre-empting that conversation and going earlier without seeing the data, Biogen is telegraphing that 2020 is likely to bring disappointment.

This doesn't matter. Biogen has no idea whether aducanumab will work, and it's running another clinical trial because that's what drug companies do.