Why is Twist Bioscience stock sliding today?

Shares of Twist Bioscience Corp fell 11.6% in mid-day trading after short-seller The Bear Cave, a publication owned by Hunterbrook Media, released a report today arguing that the synthetic biology company’s stock price has risen far beyond what its core business fundamentals can support. The report contends that despite a compelling growth narrative, Twist operates primarily as a life sciences tools vendor in a crowded market, and that no comparable peer trades at a higher valuation multiple — even as customers retain meaningful alternatives.

A key pillar of the bear thesis targets the AI-driven enthusiasm that has fueled Twist’s recent rally. The report pushes back on investor assumptions that the company holds a strategic partnership with artificial intelligence developer Anthropic, characterizing the relationship instead as a contract services arrangement. This reframing strikes at the heart of the speculative premium that helped propel the stock back toward its 2021 highs following a short squeeze earlier this year. Adding to the pressure, insiders have sold over $93 million worth of shares in the past three months, a pattern that may reinforce market concerns about insider confidence ahead of the company’s fiscal Q4 2026 earnings release scheduled for November 12.

Today’s decline unfolds against a deeply negative broader market backdrop. The Nasdaq Composite has dropped roughly 4.5% as investors aggressively sold AI infrastructure and semiconductor stocks, reversing the prior session’s post-midterm election rally. The S&P 500 is off 3.3% and the Dow Jones Industrial Average has shed 2.5%, with the selloff reflecting investor anxiety that Democratic control of Congress could bring increased regulatory scrutiny of AI-related spending.

The combination of a targeted short-seller attack on Twist’s valuation and an unusually hostile macro environment for high-multiple growth names has compounded the selling pressure. With the stock now trading at $126.03 — well off its 52-week high of $219.71 — and a major earnings report just days away, investors appear to be reassessing whether the AI-fueled premium that drove the recent rally was ever fully warranted.