News|Articles|May 18, 2026

Regeneron Enters $2.3 Billion Collaboration with Parabilis Medicines to Discover & Develop Multiple Therapeutic Candidates

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Key Takeaways

A $125 million near-term package comprises $50 million upfront and a $75 million equity commitment, with total potential value up to $2.325 billion including milestones and tiered low–double-digit royalties.
Helicons are stabilized, cell-penetrant alpha-helical peptides engineered to bind intracellular targets, including flat protein–protein interaction surfaces that are typically refractory to small molecules.
AHCs adapt the ADC paradigm by swapping cytotoxic payloads for Helicons, enabling targeted intracellular modulation or degradation rather than nonspecific cell killing.
Initial scope covers five targets, with additional targets accessible via option payments; Regeneron assumes downstream development, manufacturing, and worldwide commercialization responsibilities.
The platform rationale centers on expanding druggability to intracellular, disease-driving proteins—particularly in oncology—where decades of conventional modality limitations have left key nodes therapeutically inaccessible.

Regeneron and Parabilis Medicines partner to discover and develop antibody-Helicon conjugates, aiming to create a new class of therapies capable of targeting historically “undruggable” intracellular proteins.

Regeneron entered a strategic research collaboration with Parabilis Medicines to advance and discover therapeutic candidates based on Parabilis's novel cell-penetrant peptide platform.

The collaboration is expected to focus on AHC’s, a class of novel therapeutics designed to target challenging and historically “undruggable” targets.¹

Mathai Mammen, MD, PhD, chairman, CEO, and president of Parabilis Medicines, said, "We are thrilled to enter into a collaboration with Regeneron that builds on this foundation, combining the intracellular access and binding capabilities of our Helicons against challenging targets with antibodies from Regeneron."

What are the details of deal?

Under the terms of the agreement, Parabilis is set to receive $50 million upfront and a commitment from Regeneron to invest $75 million in Parabilis's next equity financing, for total near-term consideration of $125 million.¹Parabilis is also eligible for upwards of $2.2 billion in development, regulatory, and commercial milestone payments across five initial targets, plus tiered royalties up to the low double digits on future net sales.¹The total value of the deal is worth up to $2.325 billion.

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Additional targets may be pursued through further option payments from Regeneron and will make Regeneron responsible for advancing any resulting therapies through development, manufacturing, and worldwide commercialization.¹

What is the Helicon platform and why is it significant?

Helicons are stabilized, cell-penetrant alpha-helical peptides designed to engage intracellular protein targets, including flat protein surfaces that are poorly suited to traditional small molecule binding.¹ Most approved drugs work by targeting proteins on the surface of cells or in the bloodstream. The vast majority of disease-driving proteins, however, operate inside cells, and many of those intracellular targets, including key oncology proteins, have resisted drug development efforts for decades because their structures do not accommodate conventional therapeutic approaches.

Helicons address this by physically entering cells and binding to intracellular targets in ways that small molecules cannot. Parabilis has already demonstrated the potential of the platform through its own pipeline to directly inhibit or degrade proteins in oncology that have long been considered out of reach.

What are Antibody-Helicon Conjugates?

The most novel element of the collaboration is the development of AHC’s, a new therapeutic class that pairs Regeneron's VelocImmune-derived antibodies with Helicon payloads.

The concept draws on the same delivery logic as antibody-drug conjugates, using an antibody to guide a payload selectively into target cells, but replaces the cytotoxic drug payload with a Helicon designed to modulate specific intracellular proteins rather than simply kill the cell.²The approach, in theory, could be applied across multiple therapeutic areas wherever specific intracellular targets drive disease.

"In addition to the potential of Helicons to address previously undruggable targets, the collaboration's intent to couple Helicons to our VelocImmune-derived antibodies so as to precisely deliver them to cells of interest represents an exciting new approach with the potential to create an entirely new therapeutic class that can span multiple therapeutic areas," said George D. Yancopoulos, M.D., Ph.D., board co-chair, president, and chief scientific officer of Regeneron.

Sources

Regeneron Announces Strategic Collaboration with Parabilis Medicines to Advance Novel Antibody-Helicon Conjugates Across Multiple Therapeutic Areas Regeneron May 18, 2026 https://investor.regeneron.com/news-releases/news-release-details/regeneron-announces-strategic-collaboration-parabilis-medicines
Parabilis Medicines Announces Strategic Collaboration with Regeneron Pharmaceuticals to Advance Novel Antibody-Helicon™ Conjugates Across Multiple Therapeutic Areas Parabilis Medicines May 18, 2026 https://parabilismed.com/press-release/parabilis-medicines-announces-strategic-collaboration-with-regeneron-pharmaceuticals-to-advance-novel-antibody-helicon-conjugates-across-multiple-therapeutic-areas/

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