One day after flying sky high, Biogen (BIIB -0.92%) stock quickly obeyed gravity by falling marginally on Tuesday.

Interestingly, this came on a day when several analysts raised their price targets and/or recommendations on the stock. This was entirely expected, after the Food and Drug Administration (FDA) approved the company's aducanumab on Monday.

Patient, wearing a mask, conferring with a doctor, similarly masked.

Image source: Getty Images.

The drug, which was developed with partner Eisai and will be marketed under the brand name Aduhelm, is a controversial treatment for Alzheimer's disease. It is the first Alzheimer's drug to receive an FDA nod since 2003.

Among the Biogen raisers was Stifel's Paul Matteis, who dramatically lifted his price target on the stock by $100 to $446 per share while maintaining his buy rating. In his view, with Aduhelm on the market "our peak revenue opportunity in the U.S. is now doubled at [approximately] $9 billion in 2030."

Other prognosticators becoming notably more bullish on Biogen Tuesday included William Blair's Matt Phipps; he cranked his recommendation one notch higher, to outperform (read: buy) from the previous market perform (neutral). Michael Yee of Jefferies tagged the stock with the Street High designation, and a new price target of $500 (up from the former $450).

But the controversy over Aduhelm isn't likely to melt away anytime soon. There are questions about its efficacy and concerns about its high price tag. On Tuesday, Sen. Ron Wyden, Democrat of Oregon, wrote in a tweet that it was "unconscionable to ask seniors and taxpayers to pay $56,000 a year for a drug that has yet to be proven effective."