Biogen's experimental treatment for Alzheimer's disease is back in the spotlight, this time because a different drug that has also been met with skepticism just received an unexpected approval.
On Thursday afternoon, the Food and Drug Administration announced it had cleared Sarepta Therapeutics' Vyondys 53 for Duchenne muscular dystrophy. The decision was surprising, given the agency rejected Sarepta's drug only four months earlier due to safety concerns, and because the company didn't tell investors it had resubmitted its approval application.
Vyondys 53 is meant for a very small number of young boys whose bodies don't produce a protein needed for muscle growth and function. How well the drug works, and whether safety risks outweigh its potential benefit, has been a point of contention. In clinical testing, patients treated with Vyondys 53 developed on average 1% the normal amount of protein.
But what does Biogen's drug have to do with any of this?
Vyondys 53 was initially reviewed and then rejected by the FDA's neurology division, which operates under the direction of a man named Billy Dunn. Sarepta's appeal of that rejection went to the much larger Office of New Drugs, headed by Peter Stein, a well-known researcher who held high-up positions at Janssen and Merck & Co. before joining the FDA in 2016.
Sarepta said Stein resolved the problems identified when the agency turned down Vyondys 53, and granted the company's appeal. The FDA then quickly approved the drug. That reversal has some on Wall Street asking whether the regulator could show similar flexibility for Biogen's Alzheimer's drug aducanumab, which the company plans on submitting to the FDA's neurology regulators soon.
Biogen's approval application hinges on a Phase 3 study that, while declared positive, raises more questions than answers. Many researchers remain unsure about the reliability of that study, given the statistical methods used to analyze its data and the fact that another, identically designed trial found Biogen's drug performed worse than placebo.
In a note to Biogen investors, Jefferies analysts Michael Yee and Andrew Tsai wrote that, while the FDA's neurology division has a perception of being "tough and harsh under Dr Billy Dunn historically," the agency clearly became willing to approve Sarepta's drug once the decision moved over to the Office of New Drugs.
"We raise the question of whether this could apply to [Biogen] and Alzheimer's due to similar dynamics," the analysts wrote.
But at least a few fellow analysts don't seem to think that logic will apply. Brian Skorney of investment bank Baird wrote on Twitter how Vyondys 53 benefited from the 2016 approval of another Sarepta drug known as Exondys 51 or eteplirsen. Exondys 51 was itself controversial, as its effects on muscle protein development were also small.
"Eteplirsen had already set a precedent for the amount of Becker-like dystrophin that would be regarded as reasonably likely to predict a clinical benefit," Skorney noted. "Aducanumab review has no such precedent to rely on and will therefore be precedent setting."
Brian Abrahams of RBC Capital Markets highlighted the precedent of Exondys 51 in his own note, and also pointed out that Vyondys 53 is for a much smaller patient pool, compared to the millions of U.S. Alzheimer's patients who could foreseeably seek out Biogen's drug if approved.
While Biogen shares may be up on the approval prospects of aducanumab following the Vyondys 53 news, the RBC team "continue[s] to believe approval of adu based on the current mixed data would substantially lower the bar for approval of drugs in a broad indication..."
Biogen shares were up almost 2% in late-morning trading, before falling back to close up 1%.