Parabilis filed for an initial public offering one day after signing a strategic collaboration with Regeneron that could reach up to $2.3 billion. The deal centers on “antibody-Helicon conjugates,” a next-generation approach to antibody-drug conjugates designed to tackle historically undruggable targets. As part of the IPO process, Regeneron agreed to buy about $75 million of Parabilis common stock in a concurrent private placement at 90% of the eventual IPO price. Parabilis also outlined continued clinical development for zolucatetide, including a planned Phase III registrational trial and dose expansion across additional indications.