Eikon Therapeutics reports EIK1003 and EIK1004 data at ESMO 2026

Eikon Therapeutics, Inc. (Nasdaq: EIKN) presented updated data for its selective PARP1 inhibitors EIK1003 and EIK1004, along with initial results for WRN helicase inhibitor EIK1005, at the 2026 European Society for Medical Oncology Congress in Madrid, Spain.

The presentation, announced on October 23, 2026, included updated safety and efficacy metrics for EIK1003 monotherapy and combination cohorts, as well as initial findings for the central nervous system-penetrant EIK1004. Roy Baynes, M.D., Ph.D., Chief Medical Officer of Eikon, stated that the data support continued development of the pipeline across monotherapy and combination strategies.

In the updated Cohort 1A data for EIK1003 monotherapy, 65 participants with breast, ovarian, prostate, or pancreatic cancer were treated as of the July 13, 2026, safety data cutoff. Among the 49 efficacy-evaluable participants, the objective response rate was 14.3%, comprising five confirmed partial responses and two unconfirmed partial responses. The response rate was 31.3% in participants who had not previously received a PARP inhibitor and 6.1% in those who had. Grade 3 or higher treatment-emergent adverse events occurred in 28 participants, with anemia and neutropenia being the most common. No treatment-related adverse events led to death.

Initial data from Cohort 1B evaluated EIK1003 in combination with abiraterone in 40 participants with metastatic prostate cancer. Among the 24 efficacy-evaluable participants, the objective response rate was 20.8%. The disease control rate was 83.3%, and a PSA response of at least 50% reduction from baseline was observed in 30.8% of PSA-evaluable participants. Grade 3 or higher adverse events were reported in 45% of participants, with anemia being the most frequent.

Cohort 1C data involved 61 participants with platinum-resistant ovarian cancer or HER2-negative breast cancer treated with EIK1003 in combination with weekly paclitaxel. Signals of antitumor activity were observed, with a safety profile consistent with known paclitaxel toxicities. Dose-limiting toxicities of febrile neutropenia and tachycardia were reported in one participant.

For EIK1004, initial results demonstrated a generally well-tolerated safety profile across multiple dose levels in an ongoing Phase 1/2 study. Minimal Grade 3 or higher hematologic toxicities were observed as of the safety data cutoff. Preliminary data for EIK1005 supported its continued development as a monotherapy and in combination with pembrolizumab, with a pharmacokinetic profile supporting weekly administration.

Eikon stated that additional data from its PARP1-selective and WRN helicase programs are expected in 2027.