Can Biogen Stock Rebound as New Drugs Aim to Offset MS Sales Declines?

Sales of Biogen’s BIIB key multiple sclerosis (“MS”) drugs like Tecfidera and Tysabri and spinal muscular atrophy (SMA) treatment, Spinraza, are being hurt due to competitive pressure, which is hurting top-line growth.

Biogen believes that some of its new drugs, Eisai-partnered Leqembi for Alzheimer’s disease, Skyclarys for Friedreich’s ataxia and Zurzuvae for depression, have the potential to revive long-term growth as they are seeing strong demand trends. Can Biogen achieve this goal? Let us discuss this in detail.

Key Multiple Sclerosis Drugs, Spinraza Face Increased Competition

Sales of MS drugs and Spinraza are declining due to competitive pressure. Tecfidera revenues are declining as multiple generic versions have been launched in North America, Brazil and certain European countries. Tysabri sales are declining due to increased competition in the United States and biosimilar launches in Europe. Regulatory applications seeking approval for a biosimilar referencing Tysabri have been approved in both the United States and Europe. A Tysabri biosimilar is now available in some European countries, with a biosimilar entry in the United States expected in the fourth quarter of 2025.

Biogen’s U.S. MS sales were better than expected in the first half. However, the MS revenue decline is expected to be steeper in the second half due to increased competitive pressure on the ex-U.S. MS business, particularly accelerating generic competition for Tecfidera in Europe.

Spinraza revenues in the second half of the year are expected to be lower than in the first half due to the unfavorable timing of shipments. Spinraza faces competition from two other drugs used to treat SMA — Novartis’ NVS gene therapy, Zolgensma, and Roche and PTC Therapeutics’ PTCT Evrysdi (risdiplam).

BIIB’s New Drug Contributing to Top-Line Growth: Is it Enough?

Biogen and partner Eisai’s Leqembi was approved in the United States in 2023. Though the Leqembi launch was slow, sales improved sequentially in the past four quarters. Biogen records Alzheimer’s collaboration revenues from Leqembi, which is Biogen’s 50% share of net product revenues and cost of sales (including royalties) from Eisai.

Biogen believes Leqembi  has the potential to generate blockbuster sales as there remains a massive unmet need for Alzheimer's disease. Leqembi has been launched in Japan, China, and some other countries and was approved in the European Union in April. A less frequent maintenance intravenous dosing version of Leqembi was approved by the FDA in January 2025, while a subcutaneous autoinjector for maintenance dosing, called Leqembi Iqlik, was approved in August and launched in October.

Biogen and Eisai have also begun rolling submission of a supplemental filing seeking approval of a subcutaneous autoinjector for initiation dosing, which, if approved, is expected to be launched in 2026. Biogen and Eisai believe that the introduction of blood-based diagnostics (which can help earlier detection of Alzheimer’s) and a subcutaneous autoinjector for maintenance and initiation should drive Leqembi’s growth.

Skyclarys is seeing strong demand trends in the United States as well as the EU, with ex-U.S. sales becoming a more important driver of growth in 2025, as some Medicare discount dynamics are hurting sales in the United States, partially offsetting demand growth. Skyclarys is now available in 29 markets. Zurzuvae's launch also exceeded the company’s internal expectations.

Biogen had a collaboration with Sage Therapeutics for Zurzuvae. Supernus Pharmaceuticals SUPN acquired Sage Therapeutics in July 2025.

In the first half of 2025, Biogen’s total revenues rose 7% as lower sales of Tecfidera, Tysabri and Spinraza were offset by higher revenues from new drugs. Biogen’s four launch products (Leqembi, Skyclarys, Zurzuvae and Qalsody) delivered approximately $252 million of revenues in the second quarter, up 26% on a sequential basis and 91% year over year. Backed by a strong first-half revenue performance and an improved business outlook for the second half of the year, Biogen raised its total revenue and earnings guidance for 2025.

Total revenues in 2025 are expected to be approximately flat in constant currency terms versus the 2024 level, reflecting an improvement from the prior expectation of a decline by a mid-single-digit percentage.

Although the contribution from Biogen’s new drugs is rising, we believe they are not yet generating enough sales to offset the declining revenues of MS drugs and Spinraza, resulting in a lack of clarity on the growth trajectory of the commercial portfolio.

BIIB’s Price Performance, Valuation and Estimates

Biogen’s stock has declined 2.2% so far this year against an increase of 8.7% for the industry. 

From a valuation standpoint, Biogen appears attractive relative to the industry and is trading below its 5-year mean. Going by the price/earnings ratio, the company’s shares currently trade at 9.49 forward earnings, lower than 15.88 for the industry and the stock’s 5-year mean of 13.55.

The Zacks Consensus Estimate for 2025 earnings has risen from $14.87 per share to $15.68 per share, while that for 2026 has gone up from $15.54 to $15.81 per share over the past 90 days.

Biogen has a Zacks Rank #3 (Hold). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.

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This article originally published on Zacks Investment Research (zacks.com).

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