IMPACT Therapeutics, Inc. (IMPACT Therapeutics) released updated Phase 1/2 clinical results for its PARP1-selective inhibitor IMP1734 (EIK1003) during the 2026 American Society of Clinical Oncology Annual Meeting in Chicago, USA. The study evaluated IMP1734 as a standalone therapy and in combination with weekly paclitaxel in patients with advanced solid tumours.

Monotherapy (Cohort 1A) • Among 49 efficacy-evaluable patients, the objective response rate (ORR) reached 14.3%, with seven partial responses. • The disease control rate was 38.8%. Confirmed responders recorded a median duration of response of 7.8 months (range 6.0–15.9+ months). • In PARP-inhibitor-naïve patients, ORR improved to 26.7%. • Safety remained favourable and consistent with earlier findings.

Combination with weekly paclitaxel (Cohort 1C) • In 53 efficacy-evaluable patients, IMP1734 plus paclitaxel achieved an ORR of 24.5%, comprising one complete response and 12 partial responses. • Antitumour activity persisted despite prior taxane exposure in 92% of responders. • By tumour type, ORR was 29.6% in epithelial ovarian cancer and 19.2% in HER2-negative breast cancer. • Grade ≥3 treatment-emergent adverse events occurred in 75.0% of patients, mainly neutropenia (50.0%) and anaemia (13.3%). All participants with Grade ≥3 anaemia had baseline Grade 1–2 anaemia. No unexpected safety signals were detected.

Clinical implications The data indicate durable antitumour activity and a manageable safety profile for IMP1734 as both monotherapy and in combination with chemotherapy, providing the first clinical evidence that a PARP1-selective inhibitor can be safely paired with cytotoxic agents—an approach previously limited by haematologic toxicity from non-selective PARP inhibitors.

Programme background IMP1734 exhibits high selectivity for PARP1 with minimal PARP2 activity, supporting a wider therapeutic window than existing non-selective PARP1/2 inhibitors. Additional combinations, including with abiraterone, are under evaluation. Outside Greater China, global rights for development and commercialisation are licensed to Eikon Therapeutics, Inc.

Regulatory note IMP1734 remains under clinical investigation, and successful development and commercialisation are not guaranteed. Shareholders and potential investors are advised to exercise caution when dealing in IMPACT Therapeutics shares.