Anthropic says Claude ran a 64-hour protein-design campaign, from one initial prompt and four follow-ups, aimed at five scorpion neurotoxins from Mexico, Brazil, North Africa and the Middle East. Working mostly autonomously in Claude Science, the model used 12 design tools to generate 318,484 designs and screen 553,052 design-toxin pairs, on roughly 10,000 GPU hours.

Outside labs at Adaptyv Bio and Twist Bioscience then tested 211 selected designs. Seventeen met Anthropic's strict binding criteria, all against single toxins — the two strongest, Cn2-B1 and Cn2-B2, bound in the single-digit nanomolar range — while every multi-toxin binder attempt failed.

Anthropic is explicit about the limit: it has not confirmed whether the binders neutralize venom in cells or animals, tested them only against recombinant toxins, and does not claim to have produced an antivenom. The company is releasing all 211 designs and the binding data for other researchers to use.