Shares of Biogen /zigman2/quotes/201531540/composite BIIB -2.65% gained 1.6% in premarket trading on Thursday after the company beat expectations for the second quarter and disclosed that it's already sold $2 million of its new, controversial Alzheimer's disease drug. Biogen had earnings of $448.5 million, or $2.99 per share, in the second quarter of 2021, compared to $1.5 billion, or $9.59 per share, in the same quarter a year ago. Adjusted EPS were $5.68, against a FactSet consensus of $4.55. Revenue was $2.7 billion for the quarter, down from $3.7 billion in the second quarter of 2020. The FactSet consensus was $2.6 billion. Biogen cited a 24% decline of revenue in its multiple sclerosis portfolio for the quarter; Tecfidera sales, for example, tumbled to $578.5 million for the quarter, compared with $1.19 billion in the same quarter a year ago. Biogen said its recently approved Alzheimer's drug Aduhelm brought in $2 million in revenue during the quarter even as questions persist about the regulatory process that led to approval. The company updated its guidance for the year, now saying it expects revenue of $10.65 billion to $10.85 billion, instead of $10.45 billion to $10.75 billion. Biogen's stock is up 31.9% so far this year, while the broader S&P 500 /zigman2/quotes/210599714/realtime SPX -1.18% is up 15.1%.