Parabilis Medicines priced what it is described as the largest-ever U.S. IPO by a drug developer, raising $770.5 million in gross proceeds after an upsized offering that began with 33.5 million shares at $20 each. Shares jumped 58% on the first full trading day and then moved lower over the remainder of the week. The IPO’s total proceeds—including underwriter option exercise—were reported at $711.7 million net, reflecting strong investor demand despite broader market conditions. Parabilis said the capital will support a tumor-focused pipeline built around stabilized helical peptide (Helicon) platforms and ADCs aimed at historically undruggable targets. Analyst commentary highlighted the contrast with earlier blockbuster listings, pointing to a longer path to public markets for Parabilis compared with peers. The debut adds to a fast-moving wave of biotech listings after a prior period of low issuance.