Parabilis Medicines Prices Record $670M Biotech IPO; Regeneron Takes $75M Concurrent Stake

The Cambridge biotech, built on stabilized alpha-helical peptides targeting historically 'undruggable' proteins, eclipsed Moderna's 2018 listing to set a new high-water mark for venture-backed biotech IPOs.

Parabilis Medicines raised $670 million in its initial public offering on Tuesday, pricing 33.5 million shares at $20 apiece and listing on the Nasdaq under the ticker PBLS — the largest IPO ever recorded for a venture-backed biotechnology company, eclipsing Moderna’s 2018 debut.

Shares opened at $33.35 on June 10, up 66.75 percent from the offer price, on the first day of trading.

The Cambridge, Massachusetts company — founded as FogPharma by chemist Gregory Verdine in 2015 and rebranded as Parabilis in 2024 — is developing a class of medicines it calls Helicon peptides: stabilized, cell-penetrant alpha-helical molecules engineered to reach intracellular protein targets that have resisted both small molecules and biologics. The company had raised more than $800 million in private financing before going public.

Concurrent with the IPO, Regeneron Pharmaceuticals purchased 4.166 million shares at $18.00 per share — 90 percent of the offer price — generating approximately $75 million in additional proceeds as part of a broader research collaboration. The collaboration, announced in May, carries potential value of up to approximately $2.325 billion, comprising a $50 million upfront payment, the $75 million equity commitment, and up to $2.2 billion in milestone payments. The two companies will work jointly to create antibody-Helicon conjugates — a novel drug class designed to deliver Helicon payloads to difficult intracellular targets — across five initial oncology programs, with Regeneron retaining worldwide development and commercialization rights.

Parabilis’s lead program, zolucatetide (formerly FOG-001), is the first direct inhibitor of the beta-catenin/TCF protein-protein interaction, a node in the Wnt signaling pathway long considered undruggable. The drug is currently in dose-expansion stages of a Phase 1/2 trial in desmoid tumors, a rare soft-tissue cancer driven by Wnt pathway mutations, where it has demonstrated a disease control rate of 100 percent and a 74 percent objective response rate in early data. Zolucatetide holds FDA Fast Track and Orphan Drug designations for that indication; the company plans to initiate a Phase 3 trial in the first half of 2027. Parabilis has earmarked approximately $150 million of IPO proceeds for continued zolucatetide development in desmoid tumors.

Trials Today

Phase III SKYSCRAPER-15: Tiragolumab + atezolizumab vs. placebo + atezolizumab in resected PD-L1+ NSCLC (n=56) — Terminated — primary efficacy objective abandoned, converted to safety-only follow-up. Fourth consecutive TIGIT Phase 3 failure for Roche.

Phase III INTEGRATE IIb: Regorafenib + nivolumab vs. chemotherapy in refractory gastro-oesophageal adenocarcinoma (n=462) — Results first-posted to ClinicalTrials.gov this week. International trial; OS data now available.

Phase III DanNORMS: Rituximab vs. ocrelizumab in active MS (n=600) — Primary completion June 10, 2026 — data lock imminent. Non-inferiority result would challenge $65,000/year ocrelizumab pricing.

Phase III REIMAGINE 5: CagriSema vs. tirzepatide 5mg in type 2 diabetes (n=1,023) — Primary completion June 2, 2026. First head-to-head of two leading obesity/T2D platforms; topline results awaited.