Regeneron and Parabilis announced a collaboration worth up to roughly $2.3 billion to develop Antibody-Helicon Conjugates aimed at historically undruggable intracellular targets. The program combines Regeneron’s VelocImmune-derived antibodies with Parabilis’ Helicon peptides—engineered, stabilized alpha-helical molecules designed to engage flat intracellular surfaces. Under the deal, Regeneron will pay Parabilis $50 million in upfront payments and invest $75 million in its next equity financing, with additional milestone payments tied to development, regulatory, and commercial achievements. The agreement also includes tiered royalties on net sales of resulting therapies. The collaboration’s “five initial targets” structure could expand via option payments, signaling how large pharma is experimenting with peptide-based targeting modalities beyond conventional ADC and small-molecule approaches.