Parabilis Medicines, a clinical-stage biopharmaceutical company based in Cambridge, Massachusetts, announced on January 8, 2026, that it had closed an oversubscribed $305 million Series F financing round. The company, formerly known as FogPharma, is developing engineered peptide therapeutics designed to target intracellular protein-protein interactions that have historically been considered undruggable by conventional small molecules and antibodies.
Financing Details
The Series F round was co-led by RA Capital Management, Fidelity Management and Research Company, and Janus Henderson Investors. New investors included Frazier Life Sciences and Soleus Capital. Existing investors who participated in the round included venBio Partners, Cormorant Asset Management, ARCH Venture Partners, GV (formerly Google Ventures), T. Rowe Price, General Catalyst, Foresite Capital, Rock Springs Capital, HBM Healthcare Investments, and Samsara BioCapital. The round was completed at a higher valuation than the company's prior $145 million raise in early 2024. Total funding raised by the company now exceeds $735 million across multiple rounds ($107 million in 2021, $178 million in 2022, $145 million in 2024).
Lead Candidate: Zolucatetide
The financing will primarily support advancement of zolucatetide (formerly FOG-001), a first-in-class direct inhibitor of the beta-catenin:TCF (T-cell factor) protein-protein interaction. The Wnt/beta-catenin signaling pathway is implicated in millions of cancer cases annually but has eluded drug development efforts since beta-catenin's discovery in the early 1990s. Major pharmaceutical companies including Merck and Johnson and Johnson previously attempted and failed to develop beta-catenin inhibitors. Zolucatetide is the first and only direct inhibitor of this interaction to reach clinical trials.
In the ongoing Phase 1/2 clinical trial (NCT05919264), more than 150 patients have been dosed to date across dose-escalation and expansion phases. Early clinical data presented in late 2025 demonstrated single-agent activity across five tumor types: desmoid tumors, adamantinomatous craniopharyngioma, hepatocellular carcinoma, familial adenomatous polyposis, and ameloblastoma. One patient with familial adenomatous polyposis and a desmoid tumor showed a 52.2% reduction in tumor diameter after 60 weeks of treatment. The FDA granted Fast Track Designation for zolucatetide in desmoid tumors in late 2025, and the company is now preparing for a registrational (Phase 3) trial in this indication.
The Helicon Peptide Platform
Parabilis's proprietary Helicon platform produces stabilized, cell-penetrant alpha-helical peptides. Unlike conventional peptide drugs that primarily target extracellular receptors, Helicon peptides are engineered to enter cells and modulate intracellular protein-protein interactions. The company estimates that approximately 80% of intracellular proteins are considered undruggable by traditional modalities. The platform uses AI- and physics-based algorithms for peptide design, enabling rapid identification of candidates against novel targets.
Beyond zolucatetide, the company's pipeline includes programs in prostate cancer, including an ERG degrader expected to enter clinical trials in 2026 and an allosteric ARON degrader in preclinical development.
Significance for Peptide Therapeutics
The $305 million raise represents one of the largest private financing rounds in the peptide therapeutics sector and reflects growing investor confidence in peptide-based approaches to oncology. The global peptide therapeutics market has expanded substantially in recent years, driven in part by the success of GLP-1 receptor agonists in metabolic disease. Parabilis's approach differs fundamentally from metabolic peptides in that it targets intracellular cancer pathways rather than extracellular hormone receptors, but the company's ability to attract this level of funding signals broader recognition that engineered peptides may address therapeutic challenges that other modalities cannot.
The company is led by Dr. Mathai Mammen, M.D., Ph.D., who serves as Chairman, CEO, and President. Dr. Mammen previously headed research and development at Johnson and Johnson. The original press release is available via Parabilis Medicines and BusinessWire. The clinical trial is registered at ClinicalTrials.gov (NCT05919264).