Earlier this month, Biogen (BIIB) stock popped on news of the FDA (U.S. Food and Drug Administration) approving its Alzheimer’s treatment aducanumab (to be marketed as Aduhelm).

On the day of the announcement, the biotech giant soared from $286.14 per share, to as much as $468.55 per share, before settling at $395.85 per share. Since its 38.3% one-day pop on June 7, shares have traded sideways, sliding slightly in recent days. (See Biogen Stock Chart on TipRanks)

The question now is whether shares have more room to run. The verdict? Right now, it’s hard to tell. On the one hand, given the high demand to help slow down the effects of this disease, sales could be massive. Analyst consensus already projects it to be a multi-billion dollar drug, with some analysts even more bullish about its long-term potential.

On the other hand, until the controversy surrounding the FDA’s approval is in the rearview mirror, investors will likely be less willing to push the stock higher. With this in mind, it may be reasonable to expect shares to continue to trade sideways.

What’s Next for BIIB Stock After The Aduhelm Approval?

Even with its double-digit run-up in early June, Biogen shares may still have ample runway. That's because it’s an understatement to say Aduhelm is a blockbuster drug in the making.

Analyst consensus projects the Alzheimer’s therapy will generate annual revenue of $3.7 billion in 2024, and $5.4 billion in 2025. Piper Sandler analyst Christopher Raymond projects an even higher level of sales ($5.7 billion in 2024, and $7.5 billion in 2025).

Raymond is so bullish due to the high likelihood that the U.S. Medicare system will foot the bill for the $56,000 per year treatment. Health care advocates have balked at the high sticker price for Aduhelm. However, given Biogen's argument that the retail cost of Aduhelm is a drop in the bucket compared to the annual economic impact of the disease, Biogen may face few objections from Medicare about its price.

Yet, this isn’t the only concern on the table for this product’s possible windfall-level success. Controversy surrounding its FDA approval has impacted, and will likely continue to impact, the stock’s post-pop performance.

Controversy May Limit Gains from Here

There are two takeaways from the Aduhelm news with BIIB stock. First, as discussed above, is how massive a hit this therapy will be for the company, once it becomes commercialized. Second, though, is the controversy surrounding its approval from the FDA.

The controversy regards concerns about whether the treatment actually works. All but one of the advisory panel who assessed it advised against approval. Yet, the FDA did so anyway. As a result, three members of that panel have resigned.