Biogen BIIB is in the midst of a major portfolio transition. The company is seeing declining sales of its key multiple sclerosis (“MS”) drugs like Tecfidera and Tysabri and spinal muscular atrophy (SMA) treatment, Spinraza, due to generic erosion, increasing competition from newer therapies and pricing headwinds.
To combat the pressure on key drugs, Biogen has been aggressively building a new growth engine around recently launched products, Eisai-partnered Leqembi for Alzheimer’s disease, Skyclarys for Friedreich’s ataxia, Qalsody for amyotrophic lateral sclerosis (ALS) and Supernus Pharmaceuticals SUPN-partnered Zurzuvae for depression.
The key question for investors is whether these products can eventually compensate for the erosion of blockbuster drugs like Tecfidera, Tysabri and Spinraza. Let us discuss.
Key Multiple Sclerosis Drugs, Spinraza Face Increased Competition
Biogen’s MS sales are declining due to generic competition for Tecfidera globally, biosimilar competition for Tysabri in Europe and rising competitive pressure in the MS market.
In 2026, Biogen expects revenues for MS products, excluding Vumerity, to decline by a mid-teen percentage versus 2025 due to increased competitive pressure on the ex-U.S. MS business, particularly accelerating generic competition for Tecfidera in Europe.
Spinraza’s sales are also declining due to lower demand amid increasing competitive pressure from newer SMA treatments, including gene therapies and oral medicines that offer greater convenience. Spinraza faces competition from Novartis’ NVS gene therapy, Zolgensma, and Roche and PTC Therapeutics’ PTCT Evrysdi (risdiplam), which comes as either a liquid solution or an oral tablet.
BIIB’s New Drug Contributing to Top-Line Growth
Amid declining demand for MS drugs and Spinraza, Biogen believes its new products, Leqembi, Skyclarys and Zurzuvae have the potential to return the company to revenue growth.
The largest opportunity in Biogen's new portfolio is arguably Leqembi. Leqembi/lecanemab gained approval for early Alzheimer’s disease in the United States in 2023. Though the Leqembi launch was slow, it picked up in 2024 and 2025. Leqembi has also been launched in Japan, China, the EU and some other countries. Leqembi commands over 60% of the anti-amyloid therapy market share in the United States.
A less frequent maintenance intravenous dosing version of Leqembi was approved by the FDA in January 2025. A subcutaneous autoinjector for maintenance dosing called Leqembi Iqlik was launched in October 2025, while a supplemental filing seeking approval of the Leqembi Iqlik subcutaneous autoinjector for initiation dosing has been granted priority review by the FDA, with a decision expected in August. Biogen and Eisai believe that the introduction of blood-based diagnostics (which can help earlier detection of Alzheimer’s) and the subcutaneous autoinjector for maintenance and initiation should drive Leqembi’s growth from 2027 onward.
Other new products, Qalsody, Biogen/Supernus’ Zurzuvae and Skyclarys (added from the 2023 acquisition of Reata Pharmaceuticals) are also seeing strong demand trends in the United States.
Skyclarys is seeing strong demand trends in the United States as well as the EU. Biogen expects Skyclarys’ future growth to come from ex U.S. markets as the launches advance. Zurzuvae’s launch also exceeded the company’s internal expectations, with sales more than doubling in 2025. Skyclarys and Zurzuvae’s sales are expected to continue to rise in 2026.
Biogen’s growth products (Skyclarys, Qalsody, Zurzuvae, Vumerity and Spinraza plus Alzheimer’s revenues from the Leqembi collaboration) generated sales of $851 million in the first quarter, rising 12% year over year.
In April, Biogen closed its acquisition of Apellis Pharmaceuticals, adding the commercialized medicines Empaveli and Syfovre for immune-mediated retinal disease and nephrology to its commercial portfolio. These drugs should also contribute to Biogen’s growth in future quarters.
Can BIIB’s New Drugs Offset Key Drugs’ Erosion?
After declining for several years, Biogen’s revenues have somewhat stabilized since 2024 due to contributions from newer products and pipeline progress. However, its newer drugs, Leqembi, Skyclarys, Qalsody and Zurzuvae, are currently insufficient to offset the near-term top-line decline of the MS franchise. Though all these new drugs are showing signs of growth, replacing lost revenues from Tecfidera, Tysabri and Spinraza will likely take time.
BIIB’s Price Performance, Valuation and Estimates
Biogen’s stock has risen 14.8% so far this year compared with an increase of 5.4% for the industry.
From a valuation standpoint, Biogen is reasonably priced. Going by the price/earnings ratio, the company’s shares currently trade at 13.44 forward earnings, which is lower than 17.72 for the industry. The stock is trading above its five-year mean of 13.17.
The Zacks Consensus Estimate for earnings has declined from $15.04 per share to $13.99 per share for 2026 over the past 60 days. For 2027, the consensus mark for earnings has declined from $16.61 to $16.22 per share over the same time frame.
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).