Parabilis Medicines IPO Supports Cancer Drug Pipeline Targeting “Undruggable” Proteins

Parabilis plans to start a global registrational Phase III trial of its lead candidate zolucatetide in desmoid tumors, in the first half of 2027.

Parabilis Medicines closed its upsized IPO on June 11, one day after its shares began trading on the Nasdaq Global Select Market under the ticker symbol PBLS.

The Cambridge, Massachusetts-based clinical-stage biopharmaceutical company sold 38.5 million shares at $20 each, raising $770.5 million in gross proceeds. Regeneron Pharmaceuticals also purchased $75 million of common stock in a concurrent private placement.

Parabilis said it has raised more than $1.2 billion in 2026 through public and private financings and strategic collaborations.

The company is developing drug candidates called Helicons. These stabilized helical peptides are designed to enter cells and bind disease-driving proteins that are difficult for many existing drug types to reach.

Many disease-driving proteins sit inside cells and have broad, flat surfaces that are hard for standard medicines to bind. Small molecules can often enter cells, but they may not attach well to these surfaces. Antibody-based drugs can bind targets with high precision, but they generally cannot reach proteins inside cells.

To find and refine Helicon candidates, Parabilis uses a discovery platform that combines AI, physics-based modeling, high-speed peptide synthesis and lab screening. The company is also building what it calls the Helicon Foundry, an internal system meant to make this process faster and more scalable as its pipeline grows.

Its lead drug candidate is zolucatetide, an investigational therapy being studied in several solid tumors linked to changes in the Wnt/beta-catenin signaling pathway. This pathway helps control how cells grow and develop, but when altered, it can help drive tumor growth.

Zolucatetide is designed to block the interaction between beta-catenin and T-cell factor (TCF), a key step in that pathway. Parabilis is first focusing on desmoid tumors, which are rare soft tissue tumors that usually do not spread to distant organs but can grow aggressively into nearby tissue. Depending on where they form, they can cause pain, mobility problems and other long-term complications.

In ongoing studies, Parabilis said all 25 response-evaluable desmoid tumor patients treated with zolucatetide had tumor reductions. Among 19 patients with at least two follow-up scans, 14 had an objective response, meaning their tumors met a standard measure of shrinkage. The company said the drug’s tolerability profile supports further development.

Parabilis plans to start a global registrational Phase III trial of zolucatetide in desmoid tumors in the first half of 2027.

The company is entering a field with limited but growing treatment options. Ogsiveo (nirogacestat), a gamma secretase inhibitor, is already approved for adults with progressing desmoid tumors who need systemic therapy. Immunome has also submitted an FDA application for varegacestat, another gamma secretase inhibitor, for adults with desmoid tumors.

Parabilis is also studying zolucatetide in familial adenomatous polyposis (FAP), a rare inherited condition that causes many precancerous polyps to form in the gastrointestinal tract. In early observations from two patients with FAP-associated desmoid tumors, the company reported improvement in duodenal polyp burden after treatment. A dedicated FAP cohort is planned for the second half of 2026.

Zolucatetide is also being evaluated in hepatocellular carcinoma, colorectal cancer and other rare tumors linked to Wnt/beta-catenin pathway changes. In colorectal cancer, Parabilis is testing the drug with chemotherapy and other cancer therapies.

Beyond zolucatetide, Parabilis is developing earlier-stage Helicon programs in prostate cancer. One targets ERG, a protein involved in many prostate cancers, while another targets the androgen receptor in its active state through a binding site that differs from those used by current androgen receptor-targeted drugs.

The company is also working with Regeneron on antibody-Helicon conjugates, which pair antibody targeting with Helicon payloads designed to reach proteins inside cells.

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