Biotech stocks are having one of their best stretches in years. The iShares Biotechnology ETF (NASDAQ: IBB ) jumped nearly 5% Wednesday and pushed to new all-time highs, according to data from Benzinga Pro .
Moderna‘s (NASDAQ: MRNA ) more-than-100% surge gave the group an extra jolt, but the rally runs far wider than one headline-grabbing stock.
MRNA stock soared on its cancer vaccine data. See the chart here.Bespoke Investment Group’s data shows the 20 largest names in the IBB are up an average of more than 43% in 2026, with only two sitting in the red. The two laggards tell a story worth pulling apart.
Alnylam’s Guidance Cut Turns Ugly
Alnylam Pharmaceuticals, Inc. (NASDAQ: ALNY ) has shed roughly a quarter of its market value since late July, and the trouble traces back to a single earnings report.
Management cut full-year 2026 revenue guidance for the company’s Amvuttra franchise, explaining that early demand had been inflated by a rush of pent-up patients when the drug first launched.
Read Next MarketsModerna's Cancer Vaccine Win Is Merck's Story Too
Moderna and Merck announce success of personalized cancer therapy trial. MRNA stock surges, but MRK may be more important for investors.
3 min read Read this articleOnce that initial wave normalized, growth came in well below what Wall Street had priced in. Adding to the pressure, a rival treatment from AstraZeneca and Ionis Pharmaceuticals failed its own Phase 3 trial in July, raising fresh doubts about the broader class of drugs Alnylam’s pipeline depends on.
Latest Private Market Opportunities Join 400,000+ InvestorsMultiple law firms have since opened investigations into the guidance cut, a signal that the stock’s pain may not be finished playing out in headlines even if the selling has slowed.
Insmed’s Quiet Underperformance
Insmed Inc. (NASDAQ: INSM ) rounds out the list as the only other red name among IBB’s top 20 holdings. Its underperformance stands out precisely because it is so rare this year — nearly every other major biotech name has participated in the upswing, from Moderna’s cancer-vaccine breakout to steadier gains across the sector’s large-cap names.
The contrast raises a fair question for investors sifting through the rally. Sector-wide strength can mask company-specific damage, and Alnylam’s selloff looks driven almost entirely by its own numbers rather than any pushback against biotech broadly.
Whether Alnylam and Insmed eventually rejoin the group’s advance may hinge on catalysts specific to each company — a pipeline update, a legal resolution — rather than any tailwind the rest of the sector is currently enjoying.
Read Next MarketsSpaceX's Second Unlock Hits: 319 Million Shares Go Loose Today
SpaceX faces second post-IPO lockup expiration with 319 million shares becoming eligible for trading on Thursday.
2 min read Read this articlePhoto: Shutterstock
This content was partially produced with the help of AI tools and was reviewed and published by Benzinga editors.
Market News and Data brought to you by Benzinga APIs© 2026 Benzinga.com. Benzinga does not provide investment advice. All rights reserved.
To add Benzinga News as your preferred source on Google, click here .
Posted In: Markets Trading Ideas Movers ETFs Sector ETFs News Biotech Large Cap Mid Cap Equities Bespoke Investment Group