Biogen Inc.

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Somewhat Bullish +50

What Is Driving Biogen’s Recent Drop and What Comes Next - Trefis

🧬 Biogen (NASDAQ: BIIB), founded by Nobel laureates, has seen its stock drop from a February high of ~$202 to ~$172 by early April 2026.

⏳ The primary driver for the recent decline is not company failure but market impatience regarding legacy business risks.

💊 Investors are worried about shrinking sales of older multiple sclerosis drugs facing generic competition, with management warning of mid-single-digit revenue declines in 2026.

📉 Biogen recorded a $34 million research and development charge in Q1 2026, expected to reduce earnings per share by approximately $0.19.

🚀 Despite the slide, Q4 2025 results were strong, with revenue of $2.28 billion beating analyst expectations of roughly $2.25 billion (adjusted EPS $1.99 vs $1.61).

🧠 Leqembi, the Alzheimer's treatment, was the standout performer with Q4 sales reaching $134 million, signaling strong demand despite a slow rollout.

💡 Another new product, Skyclarys for a rare neurological disease, contributed $133 million in revenue during the last quarter of 2025.

⚖️ The core challenge remains replacing the former $3 billion multiple sclerosis business with growth from newer products before legacy sales fall too far.

🤝 Biogen announced a $5.6 billion acquisition of Apellis Pharmaceuticals on March 31, 2026, betting heavily on immunology and rare diseases to boost immediate revenue.

📅 The company is targeting earnings guidance of $15.25 to $16.25 per share for the remainder of 2026 while managing merger integration costs.

📈 Key investors will watch the May 7, 2026, earnings report to determine if Leqembi sales continue accelerating and the Apellis deal remains smooth.

Bullish Signals
  • Biogen reported fourth quarter results on February 6, 2026, with revenue of $2.28 billion which beat analyst expectations.
  • Adjusted earnings per share came in at $1.99, significantly exceeding the $1.61 estimate from experts.
  • Leqembi, Biogen's new Alzheimer's treatment, generated $134 million in quarterly sales, demonstrating strong demand.
  • Skyclarys, a drug for a rare neurological disease, contributed another $133 million in revenue last quarter.
  • Biogen announced a $5.6 billion acquisition of Apellis Pharmaceuticals on March 31, 2026, to expand into immunology and rare diseases.
  • Apellis has existing products like Syfovre already generating hundreds of millions in annual revenue.
  • Biogen has set earnings guidance of $15.25 to $16.25 per share for the rest of 2026.
  • The strategic acquisition aims to make the company look much better in terms of earnings by 2027.
  • New products launched since 2023 are finally starting to pull their weight to replace declining legacy business.
Risk Factors
  • Biogen stock has declined from highs of $202 in February 2026 to approximately $172 by early April, indicating significant investor uncertainty.
  • Management warned that total revenue for 2026 will likely decline by a mid-single-digit percentage due to the rapid loss of legacy multiple sclerosis drugs to generic competition.
  • The company recently flagged a $34 million research and development charge for the first quarter of 2026, which is expected to reduce earnings per share by about $0.19.
  • While new products are growing, they are still fighting to cover the holes left by the shrinking multiple sclerosis business, which used to be a $3 billion powerhouse.
  • The market is concerned that the old business is dying faster than the new ones can grow during this transition period.
  • Biogen's massive $5.6 billion acquisition of Apellis Pharmaceuticals announced on March 31, 2026, means the company must deal with high merger costs in the short term.
  • The $5.6 billion bet is described as a 'huge all in bet on immunology and rare diseases,' which concentrates risk in new market segments.
  • Investors are worried about whether Leqembi sales will continue to accelerate, especially given the slow rollout mentioned in recent quarters.
  • Biogen's guidance of $15.25 to $16.25 per share for the remainder of 2026 relies on the assumption that the Apellis deal integration won't be too messy.
Full Analysis
Biogen's stock, trading under the ticker BIIB on NASDAQ, experienced significant volatility following a strong performance at the beginning of February 2026 where it reached highs near $202. By early April 2026, however, the shares had declined to approximately $172. While the company boasts a prestigious history of scientific innovation involving Nobel laureates Walter Gilbert and Phillip Sharp during its founding, recent market movements have been driven by investor impatience rather than fundamental business failure. The primary cause for the slide is the market's reaction to the ongoing transition away from legacy multiple sclerosis drugs that are facing erosion from generic competition. Management warned that total revenue for 2026 is projected to decline by a mid-single-digit percentage as these older treatments lose ground, even as new drug portfolios grow. Financial nuances have further pressured sentiment in the short term, highlighted by a recently flagged $34 million research and development charge for the first quarter of 2026, which analysts expect will reduce earnings per share by about $0.19. This charge has prompted fair-weather investors to exit positions despite strong operational performance from newer products. In the fourth quarter of 2025, Biogen reported revenue of $2.28 billion and adjusted earnings of $1.99 per share, significantly beating analyst expectations of $1.61. The standout performers were Leqembi, an Alzheimer's treatment with quarterly sales reaching $134 million, and Skyclarys for a rare neurological condition, which generated $133 million. However, these new successes are currently struggling to offset the rapid decline of the former $3 billion multiple sclerosis business, creating a race against time that concerns investors worried about the speed of the old revenue stream dying versus the growth rate of new products. Looking ahead, Biogen is making a substantial strategic move through its acquisition of Apellis Pharmaceuticals for $5.6 billion, announced on March 31, 2026. This transaction represents a major all-in bet on immunology and rare diseases, aiming to improve earnings visibility by 2027 by leveraging Apellis's existing products like Syfovre, which already generates hundreds of millions in revenue. For the remainder of 2026, Biogen has provided earnings guidance ranging between $15.25 and $16.25 per share. Key milestones to watch include the May 7, 2026 reporting date for first-quarter results, where the market will scrutinize whether Leqembi sales continue to accelerate and whether the integration of Apellis remains manageable without excessive immediate cost impact. The stock's current trajectory reflects a challenging transition period where the company is attempting to rebuild its revenue engine while still operating under a significant legacy burden, making it a high-conviction opportunity that requires careful monitoring of both new drug growth and merger execution.