- Parabilis Medicines raised $305 million in a Series F round led by RA Capital, Fidelity, and Janus Henderson at a higher valuation than its 2024 financing.
- The cash will advance FOG-001 (zolucatetide), positioned as the first direct inhibitor of the β-catenin:TCF interaction in the Wnt/β-catenin pathway, with early Phase 1/2 signals in desmoid and other low-complexity tumors.
- Its Helicon platform uses stabilized, cell-penetrant α-helical peptides to drug intracellular protein-protein interactions and is expanding into prostate cancer programs including ERG and allosteric ARON degraders.
- Near-term upside centers on rare-tumor regulatory paths like FDA Fast Track in desmoid, while key risks include proving durable safety/efficacy and scaling peptide manufacturing for broader cancers.
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Parabilis’s latest financing round marks a significant inflection point both for the company and for the broader landscape of biotech innovation targeting intracellular ‘undruggable’ proteins. The $305 million Series F financing, signed on January 8, 2026, co-led by major institutional players including RA Capital, Fidelity Management, and Janus Henderson, reinforces strong investor confidence and implies a valuation that has increased relative to its previous $145 million round in early 2024.
The lead asset, FOG-001 (also known as zolucatetide), is the first clinical candidate shown to directly inhibit the β-catenin:TCF interaction, a central node of the Wnt/β-catenin signaling pathway long considered untouchable by conventional drug modalities. In Phase 1/2 trials (data as of mid-August 2025), the therapy demonstrated 100% disease control across 12 desmoid tumor patients (all dose levels), and an objective response rate (ORR) of 80% in patients with more than one post-baseline scan. Early single-agent activity was also observed in additional low-complexity tumor types such as adamantinomatous craniopharyngioma.
The Helicon platform underpins Parabilis’s approach: peptides stabilized into α-helices with non-canonical amino acids to improve membrane penetration, binding to flat protein surfaces, and reduction in immunogenicity. This platform is now generating preclinical “Helicon degrader” programs targeting historically difficult prostate cancer targets ERG and allosteric ARON, signaling that the company expects to build multiple value streams.
Strategic implications are multi-fold. First, expedited regulatory opportunities in rare tumors—such as desmoid tumors, which FOG-001 has already received FDA Fast Track Designation for—present a near-term path to market. Second, there is potential for broader oncology applications, especially in genetically simple, Wnt-driven low-complexity tumors, with combination therapy strategies being evaluated for more complex cancers.
However, several risks and open questions should be weighed. The durability and safety profile in more heterogeneous, biologically complex cancers remains unproven. Ensuring manufacturability, consistency, in vivo stability, and favorable ADME/toxicology for the peptide modality are major technical and regulatory challenges. Also, competition is likely as other groups attempt to target Wnt/β-catenin signaling or downstream transcription factors. Finally, commercial scalability in rare tumor markets must be balanced with investments needed for broader indications.
Key open questions include: What are the long-term response durations and potential relapses? What biomarkers or patient selection strategies will optimize response? How will combination therapies with immune checkpoint inhibitors or standard of care enhance efficacy? And how will Parabilis navigate the costs and logistics of scaling peptide therapeutics and potential protein degraders? The investment positions them to address many of these questions but also increases the stakes.
Supporting Notes
- Parabilis closed a $305 million Series F financing on January 8, 2026, co-led by RA Capital Management, Fidelity, and Janus Henderson, with participation from both new and existing investors.
- Series F valuation is higher than the previous round ($145 million) raised in early 2024.
- FOG-001 (zolucatetide) is Parabilis’s lead Helicon peptide candidate; first and only direct inhibitor of β-catenin:TCF interaction.
- Early Phase 1/2 trial data in desmoid tumors: in 12 patients across dose levels, all showed tumor reductions; among 5 patients with more than one scan, ORR was 80%, with 100% disease control rate.
- Single-agent activity observed in low-complexity tumors including adamantinomatous craniopharyngioma, desmoid tumors, etc.; rationale for combination therapy in more complex cancers.
- Regulatory progress: desmoid tumors indication has Fast Track Designation from the FDA.
- Helicon platform capabilities include stabilized α-helical, cell-penetrant peptides using non-canonical amino acids, with tunable ADME, low immunogenicity, and ability to bind flat protein surfaces.
- Preclinical Helicon degrader programs targeting ERG and allosteric ARON in prostate cancer are underway.
- Risk: safety and durability of responses in complex tumors are not yet established; long-term data are lacking.
- Potential strategic paths include registrational trials, basket studies, combination approaches, and partnership opportunities.