Parabilis Medicines starts dose-ranging FAP cohort for zolucatetide
Parabilis Medicines has initiated a dose-ranging clinical cohort evaluating zolucatetide in patients with familial adenomatous polyposis (FAP), expanding its ongoing Phase 1/2 study to target the rare hereditary condition directly. The Nasdaq-listed company said the move is supported by early signals seen in FAP patients who were already enrolled in the trial for a separate but related indication.
Zolucatetide is an investigational peptide designed to directly inhibit the interaction between β-catenin and the TCF family of transcription factors, a downstream node in the Wnt signalling pathway. The company says it is the first and only agent to target this specific protein-protein interaction. FAP is caused by germline loss-of-function mutations in the APC gene, which results in constitutive Wnt/β-catenin activation and the development of hundreds to thousands of precancerous gastrointestinal polyps. Without surgical intervention, colorectal cancer is an near-certainty; even after colectomy, patients remain at risk of duodenal and other gastrointestinal malignancies.
Early clinical signals
The rationale for the dedicated FAP cohort rests on results observed in two patients with FAP and concomitant desmoid tumours who underwent routine endoscopy while receiving zolucatetide. In one patient, polyp burden reduced from Spigelman Stage IV to a near-normal duodenum; in the second, staging improved from Spigelman Stage II to Stage I. Parabilis acknowledged that zolucatetide has shown a favourable tolerability profile to date, though no formal safety data were released alongside the announcement.
The new cohort will enrol adults with documented APC mutations who have already undergone colectomy and carry measurable duodenal polyp burden. Parabilis expects to disclose additional data from FAP patients with concurrent desmoid tumours in the first quarter of 2027, which will likely serve as the near-term clinical proof-of-concept read the market is watching.
Mathai Mammen, chairman, chief executive and president of Parabilis, said the company was "highly encouraged by the significant reductions in precancerous duodenal polyp burden we have observed with zolucatetide in our first patients with FAP," and described the dose-ranging initiation as an important step toward defining a registrational dose and schedule.
Market context and competitive landscape
FAP represents a significant unmet need with no currently approved systemic therapy. Management of the condition relies on lifelong endoscopic surveillance, repeated polypectomy and major surgery. Sulindac and celecoxib have been used off-label in some patients to reduce polyp burden, but neither carries a formal indication for FAP and neither addresses the underlying Wnt pathway driver.
The broader Wnt/β-catenin space has attracted growing interest from drug developers, though the pathway has historically proved difficult to drug selectively. Several companies have pursued upstream targets such as porcupine inhibitors, and others have explored β-catenin degradation strategies. Parabilis is itself advancing a follow-on β-catenin degrader programme. The competitive dynamic here is not purely within FAP: zolucatetide is also being evaluated in desmoid tumours, hepatocellular carcinoma and the rare brain tumour adamantinomatous craniopharyngioma, meaning the Phase 1/2 platform is generating readouts across several rare oncology niches simultaneously.
A Phase 3 registrational trial in desmoid tumours is already planned, suggesting the company views that indication as the more advanced path to approval. The FAP programme, if it generates compelling dose-ranging data in 2027, could follow a similar registrational trajectory, potentially supported by an accelerated approval pathway given the absence of any approved systemic option and the well-characterised surrogate endpoint of polyp burden reduction.