Biogen’s key Alzheimer’s disease drug is facing potential signs of trouble
Biogen Inc.’s crucial Alzheimer’s disease drug aducanumab is still a year or two from releasing key clinical trial results, but the company’s latest news may leave some investors feeling more circumspect.
Because the company saw “more variability on the primary endpoint than assumed,” Biogen BIIB, +0.91% decided to increase the sample size of two ongoing trials by about 255 patients each, Chief Medical Officer Alfred Sandrock said at a Leerink Partners conference on Wednesday.
The change, done to maintain 90% statistical power for the study, won’t affect the study’s blinded nature, which refers to how neither patients nor doctors know which is the drug and which is the placebo, Sandrock said. He also suggested that the decision shouldn’t raise questions about the therapy’s effectiveness.
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“We don’t know the treatment effect and we don’t believe this changes our assumptions about efficacy,” he said, adding that such changes in sample size “are pretty standard practice these days,” noting that it did so with its multiple sclerosis drug Tecfidera, according to a FactSet transcript of his comments. Biogen still plans to finish enrollment by the summer.
Several Wall Street analysts agreed, saying that the change should not translate to concerns about the drug working, though they acknowledged it could leave some feeling rattled.
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Aducanumab aims to remove beta-amyloid protein fragments in the brain that some believe are responsible for the brain function decline that is characteristic of Alzheimer’s disease. However, it’s still an open question as to whether that plaque removal will help treat the disease, experts say.
Biogen’s latest update could be a good thing, said SunTrust Robinson Humphrey analyst Yatin Suneja, adding that “we welcome the opportunity for a larger sample size (without a significant delay in enrollment timelines) to maintain 90% powering on the primary endpoint.”
But Suneja is still cautious about the coming clinical trial readouts, which he now expects early data for in the first half of 2020.
The change also implies that Biogen needs to enroll more patients to increase the chance that the clinical trial will be successful, said Mizuho analyst Salim Syed.
The latest news “adds uncertainty to the trial,” especially amid dismal results in the Alzheimer’s disease space, said Stifel analyst Alex Schwartz.
But “this may simply be a case of a smart trial design getting penalized,” Syed said.
At the time that Biogen was designing its trial, Eli Lilly & Co.’s LLY, +0.86% Alzheimer’s disease drug was in a late-stage trial, so the company may have tried for enrollment that was as efficient as possible as a strategic response, he said.
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“The fact that patients are being added to the Biogen study based on such an analysis does not imply a greater or lower chance of success as nothing has been learned about the effect size so far,” Syed said.
Moreover, the “variability” that Biogen was referring to simply indicated standard deviation, or the way that scores were distributed, without any indication of which represented the drug and which represented the placebo, Syed said.
And there’s always the hope of low expectations, Schwartz said.
“Lastly, we remind investors that the FDA bent over backward to help [Eli Lilly’s] solanezumab show a signal (combined trials and delayed start endpoints are examples) so the bar is pretty low,” he said.
Biogen shares dropped 6.6% in Wednesday trade. Shares rose 0.05% in Thursday trade, and have declined 4.6% over the last three months, compared with a 5.2% rise in the S&P 500 SPX, +0.32%