Regeneron and Parabilis Medicines Announce $2.325B Antibody-Helicon Conjugate Collaboration (May 18) — $50M Upfront + $75M Equity + $2.2B Milestones Across Five Initial Targets
Regeneron Pharmaceuticals and Parabilis Medicines announced May 18 a strategic research collaboration to discover and develop antibody-Helicon conjugates (AHCs) — a novel modality combining Regeneron's antibody platform with Parabilis's Helicon stabilized helical peptide technology. Deal structure: $50M upfront, $75M equity commitment, and up to $2.2B in development and regulatory milestones across an initial five targets, plus tiered royalties. The Helicon platform locks peptides into their bioactive helical conformation, enabling targeting of historically undruggable protein-protein interaction surfaces that small molecules cannot access. The conjugate format pairs antibody-mediated tissue homing with peptide payload delivery — an extension of the broader peptide-drug-conjugate field that included Bicycle Therapeutics' bicyclic peptide-MMAE conjugates and Avacta's FAP-activated PDCs. The deal is the largest single peptide-platform partnership announced in 2026.