Nasdaq Biotechnology Index slides 3% as gene therapy stocks lead selloff

The Nasdaq Biotechnology Index fell more than 3% on Thursday, its steepest decline in months, as gene therapy and gene-editing stocks led a broad sector rout that erased billions in market value. The selloff was concentrated among small- and mid-cap developers with pre-commercial pipelines, while the broader S&P 500 healthcare sector held relatively steady.

The breadth of the decline — spanning gene therapy, gene editing and CAR-T platforms — points to a sector-wide trigger rather than company-specific news, according to exchange data. Kyverna Therapeutics, a clinical-stage developer of CAR T-cell therapies for autoimmune diseases, dropped 12.45%. Prime Medicine, which uses CRISPR-based gene editing to correct genetic mutations, fell 12.29%.

Regenxbio, whose gene therapy platform delivers therapeutic genes via adeno-associated virus vectors, slid 11.18%. Solid Biosciences, focused on gene therapies for Duchenne muscular dystrophy, declined 10.28%. On the upside, First Tracks Biotherapeutics surged 16.42%, Aardvark Therapeutics gained 4.20%, Mesoblast rose 3.81% and SIGA Tech added 2.29%.

What Drove the Selloff

The concentration of losses among gene therapy and gene-editing names suggests the selloff may have been triggered by a regulatory or policy concern specific to that technology class. The four biggest decliners all rely on viral vector delivery or CRISPR-based approaches — platforms that have faced heightened FDA scrutiny over safety and manufacturing consistency. No single company issued a negative disclosure, reinforcing the case for a macro or policy-driven trigger.

Investor Implications

The selloff raises concerns about investor appetite for pre-commercial biotech names heading into the second half of 2026. Many of the hardest-hit companies lack approved products and rely on equity financing to fund clinical trials. A sustained downturn could force developers to raise capital at depressed valuations, diluting existing shareholders. The index's next major catalyst is the upcoming FDA decision cycle in late July, which could either restore confidence or deepen the rout depending on the outcomes.

This article is for informational purposes only and does not constitute investment advice.