Parabilis filed for an IPO a day after signing an up-to-$2.3 billion strategic research collaboration with Regeneron. The company’s IPO filing (Form S-1) followed a concurrent private placement in which Regeneron agreed to buy about $75 million of Parabilis shares at 90% of the IPO price per share. The partnership centers on antibody-Helicon conjugates and contemplates an initial five candidates. Parabilis said it aims to continue clinical development of its lead Helicon peptide candidate zolucatetide (formerly FOG-001) in desmoid tumors, including dose expansion and a planned Phase III registrational trial, alongside expansions across other indications. For biotech financing, the sequence highlights how large platform collaborations are being used to support equity market participation, potentially improving perceived pipeline de-risking as Parabilis enters the public markets.