Phase 1 Nature Medicine trial: WRN inhibitor shows disease control in MSI solid tumors

On 29 September 2026 Nature Medicine published peer-reviewed results from part 1 of an open-label, multicenter, first-in-human phase 1 trial (NCT06004245) of RO7589831 (also known as VVD-133214), a first-in-class covalent inhibitor of Werner syndrome helicase (WRN), in patients with microsatellite instability (MSI) and/or mismatch-repair–deficient advanced solid tumors. A same-day News & Views piece by Jia Liu discussed the synthetic-lethal rationale.

Key reported results

Among 88 enrolled patients, treatment-emergent adverse events were mostly grade 1–2; common events included nausea, diarrhea, fatigue, anemia and vomiting. No grade 5 treatment-emergent adverse events occurred. Among MSI efficacy-evaluable patients (n = 66), the disease control rate was 74.2% (49/66); seven patients had confirmed RECIST v1.1 partial responses (ORR 10.6%); median duration of response was 10.2+ months; median progression-free survival was 6.7 months (95% CI 4.1–8.5); median overall survival was 17.6 months. About 95% had prior immune checkpoint inhibitor therapy. The authors selected 150 mg and 600 mg twice daily as recommended phase 2 doses for optimization. Direct WRN target engagement in tumor tissue could not be demonstrated (mucin-rich biopsies), though exploratory ctDNA and FDG-PET signals supported biological activity.

Study type and limitations — read carefully

This is an early-phase, open-label, single-arm dose-escalation study without a randomized control arm. Objective responses were uncommon relative to disease stabilization; the population was heavily pretreated and heterogeneous. Findings support further testing, not a new standard of care. This article is not personal medical advice — patients should discuss options with their oncology team.