Parabilis Medicines Partners With Regeneron Pharmaceuticals to Develop Antibody-Helicon™ Conjugates Across Multiple Diseases
Parabilis Medicines has entered into a major strategic research collaboration with Regeneron Pharmaceuticals aimed at advancing a new generation of targeted medicines designed to tackle some of the most difficult disease-driving proteins in medicine. The partnership centers on Parabilis’s proprietary Helicon™ peptide platform and introduces a novel therapeutic category known as Antibody-Helicon™ Conjugates (AHCs), which the companies believe could open new possibilities for treating diseases associated with historically “undruggable” targets.
The announcement marks an important milestone for Parabilis as it seeks to expand the reach of its intracellular peptide technologies through a partnership with one of the biotechnology industry’s most established drug development and commercialization companies. At the same time, the collaboration underscores Regeneron’s continuing strategy of investing in innovative therapeutic platforms capable of addressing complex biological mechanisms that have remained difficult to modulate with traditional drug approaches.
The collaboration will initially focus on discovering and developing multiple therapeutic candidates that combine Parabilis’s Helicon technology with Regeneron’s antibody capabilities. Together, the companies aim to create therapies capable of selectively entering diseased cells and interacting with intracellular proteins that have historically resisted conventional therapeutic strategies.
Helicons represent a distinct category of stabilized alpha-helical peptides engineered to penetrate cells and bind intracellular proteins with high specificity. Unlike traditional small molecules, which often struggle to interact effectively with broad or flat protein surfaces, Helicons are designed to engage these challenging molecular structures directly. Many disease-driving proteins involved in oncology and other serious illnesses rely on such surfaces, making them difficult to inhibit using conventional pharmaceutical methods.
The Helicon platform was specifically developed to overcome these longstanding scientific limitations. By stabilizing alpha-helical peptide structures and enabling them to penetrate cell membranes efficiently, Parabilis aims to access intracellular protein interactions previously considered inaccessible to modern therapeutics. These proteins often play central roles in disease progression, especially in cancers driven by complex signaling pathways and protein-protein interactions.
Through this collaboration, the companies will explore Helicons both as independent therapeutic agents and as payloads integrated into Antibody-Helicon Conjugates. The AHC approach builds conceptually on the success of antibody-drug conjugates, or ADCs, which have emerged as an important therapeutic modality in oncology over the last decade.
Traditional ADCs work by attaching highly potent cytotoxic compounds to antibodies that selectively recognize proteins expressed on the surface of cancer cells. Once the antibody binds to its cellular target, the toxic payload is delivered inside the cell, leading to cell death while ideally minimizing damage to healthy tissue.
The AHC platform expands on this delivery concept but replaces traditional toxic payloads with Helicon peptides designed to modulate specific intracellular proteins selectively. Rather than merely killing cells through generalized toxicity, AHCs could potentially influence disease biology more precisely by directly targeting intracellular disease mechanisms. This may allow researchers to address biological pathways that have remained beyond the reach of conventional therapies.
According to the companies, the AHC strategy may be particularly useful for proteins that have long been considered “undruggable.” In drug development, this term refers to proteins that cannot easily be targeted using existing small molecule drugs or conventional biologic therapies. Many such proteins are involved in cancer growth, resistance mechanisms, and cellular signaling networks that contribute to disease progression.
Parabilis leadership emphasized that the company has already demonstrated encouraging progress within its internal research pipeline. The company says its Helicon peptides have shown the ability to inhibit or degrade several oncology-related proteins that have historically been difficult to target therapeutically.
Dr. Mathai Mammen, Chairman, Chief Executive Officer, and President of Parabilis Medicines, described the collaboration as a natural extension of the company’s scientific foundation and platform capabilities.
According to Mammen, Parabilis has already established evidence that Helicon peptides can directly interfere with important disease-driving proteins that conventional therapeutic technologies have struggled to address. He noted that the collaboration with Regeneron combines Parabilis’s intracellular targeting expertise with Regeneron’s extensive experience in antibody engineering and drug development.
The partnership also provides substantial financial support for Parabilis as the company advances its research platform and therapeutic pipeline. Under the agreement, Regeneron will provide Parabilis with $125 million in total consideration consisting of a $50 million upfront payment and a commitment to invest an additional $75 million in Parabilis’s next equity financing round, subject to certain conditions.
Beyond the initial financial package, the agreement includes significant long-term milestone opportunities tied to development, regulatory approvals, and commercial performance. With five initial targets already incorporated into the collaboration, Parabilis could potentially receive up to approximately $2.2 billion in total milestone payments if all programs achieve specified goals.
The structure of the agreement also allows for future expansion. Additional therapeutic targets may be pursued under the collaboration through further option payments from Regeneron, potentially broadening the scope of the partnership over time.
In addition to milestone payments, Parabilis will be eligible to receive tiered royalties reaching the low double-digit percentage range on future net sales of any approved medicines resulting from the collaboration. This royalty structure gives Parabilis ongoing participation in the long-term commercial success of any therapies that ultimately reach the market.
The operational structure of the partnership assigns distinct responsibilities to each company based on their respective expertise. Parabilis and Regeneron will work together during the discovery phase to identify and optimize new Helicons and Antibody-Helicon Conjugates. Following discovery and early research activities, Regeneron will assume responsibility for advancing selected candidates through preclinical development, clinical testing, manufacturing, regulatory processes, and worldwide commercialization.
For Regeneron, the collaboration adds another innovative platform to its growing portfolio of advanced therapeutic technologies. The company has built a reputation for leveraging cutting-edge science across multiple therapeutic modalities, including monoclonal antibodies, bispecific antibodies, genetics-based discovery approaches, and next-generation biologics. The addition of Helicon-based therapeutics and AHCs reflects Regeneron’s broader interest in expanding beyond conventional extracellular targeting strategies and into intracellular biology.
The partnership also reflects a broader trend within the biotechnology sector, where pharmaceutical and biotech companies are increasingly investing in novel drug modalities designed to address difficult biological targets. Over the last several years, growing interest has emerged around technologies capable of modulating intracellular protein interactions, targeted protein degradation pathways, and peptide-based therapeutics.
Researchers across the industry have recognized that many diseases remain inadequately treated because current drug classes cannot effectively reach or manipulate critical intracellular proteins. As a result, companies developing technologies capable of overcoming these barriers have attracted increasing attention from major pharmaceutical organizations seeking access to differentiated scientific platforms.
Peptide therapeutics in particular have become an area of rising interest because of their ability to bridge the gap between traditional small molecules and larger biologic therapies. Stabilized peptides like Helicons can potentially combine the precision and selectivity associated with biologics while retaining the intracellular access often associated with smaller compounds.
The use of antibody-guided delivery systems further strengthens this therapeutic concept. By combining antibodies with intracellularly active Helicon payloads, the companies hope to create therapies capable of selectively reaching diseased tissues while minimizing unintended effects on healthy cells.
Although the collaboration is still in the research stage, the financial scale of the agreement highlights the confidence both companies place in the technology’s future potential. If successful, the collaboration could contribute to the development of entirely new treatment strategies for cancer and potentially other diseases driven by difficult intracellular targets.
For Parabilis, the agreement provides both financial resources and strategic validation of its Helicon platform from a globally recognized biotechnology partner. For Regeneron, the partnership offers access to a potentially transformative therapeutic modality that may expand the company’s future pipeline opportunities in oncology and beyond.
As the collaboration progresses, industry observers will likely watch closely to see whether Antibody-Helicon Conjugates can deliver on their promise of unlocking new approaches to previously inaccessible disease targets and reshape the future landscape of targeted therapeutics.
About Parabilis Medicines
Parabilis Medicines is a clinical-stage biopharmaceutical company dedicated to creating extraordinary medicines that unlock high-impact protein targets long-considered undruggable. The company has developed a new class of stabilized, cell-penetrant alpha-helical peptides – Helicons™ – capable of modulating intracellular proteins that are inaccessible to traditional drug modalities.
Headquartered in Cambridge, Mass., Parabilis is advancing a focused pipeline of multiple first-in-class therapies across both rare and common cancers. Its lead candidate, zolucatetide (previously FOG-001), is the first direct inhibitor of the interaction between β-catenin and the T-cell factor (TCF) family of transcription factors, implicated in colorectal cancer, desmoid tumors, and a range of other Wnt/β-catenin-driven tumors. Parabilis is also advancing investigational degraders of ERG and ARON for the treatment of prostate cancer, as well as other preclinical programs.
Learn more about how the company is advancing a new generation of precision cancer medicines with the potential to meaningfully alter the trajectory of disease for patients in need: www.parabilismed.com.
