Parabilis Medicines filed for an initial public offering a day after signing an up-to-$2.3 billion strategic research collaboration with Regeneron. Under the deal, the companies will discover and develop an initial set of five antibody-Helicon conjugate candidates targeting traditionally undruggable proteins, with Regeneron purchasing about $75 million of Parabilis stock in a concurrent private placement at 90% of the IPO price. Parabilis’ filing also highlighted plans to continue Phase III development in desmoid tumors for its lead Helicon peptide candidate zolucatetide (FOG-001, now zolucatetide) and expand into additional indications, including FAP and hepatocellular carcinoma.