Biogen (NASDAQ: BIIB) posted first-quarter results that beat the Wall Street consensus forecast, with the company raising its 2021 earnings guidance.

However, Biogen’s outlook for the rest of the year largely hinges on FDA decisions regarding its pipeline drugs aducanumab and zuranolone.

The Cambridge, Mass.-based biotech earned $410 million, or $2.69 per share, off sales of $2.69 billion for the quarter ended March 31, 2021, with earnings down 71% and sales reduced by 24% compared with Q1 2020.

Adjusted to exclude one-time items, earnings per share were $5.34. Analysts at Canaccord Genuity were looking for EPS of $5.06 on sales of $2.68 billion. The consensus forecast was also for EPS of $5.06.

[Related: Biogen moves forward with aducanumab launch plans]

“Our first quarter 2021 results were consistent with our expectations across MS, SMA, and biosimilars despite increased competition,” said CEO Michel Vounatsos in a statement.

The company’s sales of Tecfidera, Spinraza and biosimilar drugs lagged as a result of growing competition.

Analysts are keeping an eye on how global regulators respond to submissions for the Alzheimer’s drug aducanumab, which analysts often refer to as “adu.” “Predicting an outcome on adu remains difficult and investors remain generally skeptical on approval in our view,” said Canaccord Genuity analyst Sumant Kulkarni.

The depression drug candidate zuranolone could provide a “quicker path to replace lost revenues” for Biogen compared with aducanumab, according to Kulkarni. Zuranolone is delivered orally while aducanumab is an intravenous drug.

Biogen needs to win the regulatory green light for either zuranolone or aducanumab “for the stock to work,” Kulkarni concluded.

Biogen said it expects to log adjusted EPS of $17.50 to $19.00 this year, up from prior guidance of $17.00 to $18.50. It expects to earn $10.45 to $10.75 billion in total revenue, which is unchanged from its prior guidance.

Investors reacted by sending BIIB shares up 0.8% to $261.08 apiece today in mid-day trading.