So far, Alzheimer’s disease is one puzzle the medical community has been unable to solve, and there are currently no available treatments to halt the progress of the memory obliterating disease.

That could all change today, when Biogen’s (BIIB) controversial Alzheimer’s drug aducanumab’s fate is decided by the regulators. The FDA’s decision will act as a major catalyst to send the stock higher or lower. The consensus on Wall Street is that the drug’s chances of approval are slim. Jefferies analyst Michael Yee, however, has a more optimistic take.

“We think approval is 50-60% and higher than consensus 25-30%,” the analyst said. “We get the sense HC specialists agree it's reasonably possible FDA could approve it while the broader market doesn’t think it will get approved and cannot get over a unanimous negative Adcom panel. In fact, the stock hasn't recovered much since the negative vote in Q4 as a reflection it was a pretty ominous sign.”

Recall, last year an FDA advisory panel voted against approving the drug, and while the FDA does not have to follow the panel’s lead, the decision was a blow to investors’ confidence.

So, what kind of impact will a positive or negative decision have on the stock’s performance? Yee reckons that a positive outcome will send shares up to $400 – a 40% jump from current levels. Should the FDA reject aducanumab, Yee expects the stock to drop to between $175 and $200, a 34% decline at the mid-point.

That said, Yee believes that if the shares do end up taking a beating, there could be an opportunity for investors to get in at a discounted price, as Yee sees “strategic value for the business and pipeline.”

For now, Yee’s $450 price target exceeds his bullish approval target and implies upside of 57% from current levels. Needless to say, Yee’s rating is a Buy. (To watch Yee’s track record, click here)

The Jefferies analyst sits squarely in the BIIB bull camp, while the Street, as a whole, has a more measured view. Based on 9 Buys and Holds, each, plus 2 Sells, the stock has a Moderate Buy consensus rating. The average price target stands at $309.87, suggesting shares could appreciate by 8% in the year ahead. (See Biogen stock analysis on TipRanks)

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Disclaimer: The opinions expressed in this article are solely those of the featured analyst. The content is intended to be used for informational purposes only. It is very important to do your own analysis before making any investment.