Clinical Trial Failures: The significant investment in research and development (R&D) for new drug candidates carries inherent risks, as many investigational products may not demonstrate sufficient efficacy or safety in clinical trials, leading to abandonment and substantial financial losses.

Regulatory Approval Delays or Denials: Even successfully developed drug candidates face rigorous review processes by regulatory authorities globally, and there is no guarantee of timely approval or approval at all, which can significantly impact market entry and revenue projections.

Patent Expirations and Generic Competition: Eli Lilly's revenue stream is highly dependent on proprietary products, and the expiration of patents or challenges to intellectual property rights can lead to the entry of generic or biosimilar competitors, resulting in a rapid decline in sales for those products.