Clinical Trial and Regulatory Failure Risk: Drug development is inherently risky, with high rates of failure in clinical trials or challenges in securing regulatory approvals for new therapies, leading to substantial R&D expenditure without commercial returns.

Intense Competition Risk: Biogen faces significant competition from other pharmaceutical companies developing treatments for similar conditions, potentially leading to erosion of market share, pricing pressures, and reduced profitability for its key products.

Patent Expiry and Generic Competition Risk: The company's established drugs are subject to patent expirations, which opens the door for generic and biosimilar competition, resulting in significant revenue declines as seen with Tecfidera.