Initial and updated cohort data from ongoing Phase 1/2 study of highly selective non-brain-penetrant PARP1 inhibitor EIK1003 continue to support potentially differentiated profile of EIK1003 in combination strategies within the PARP inhibitor landscape Initial results from ongoing Phase 1/2 study of highly selective CNS-penetrant PARP1 inhibitor EIK1004 demonstrate a generally well-tolerated safety profile across multiple dose levels, with minimal Grade 3 or higher hematologic toxicities as of the safety data cutoff Preliminary data for Werner (WRN) helicase inhibitor EIK1005 support continued development as monotherapy and in combination with pembrolizumab, with pharmacokinetic (PK) profile supporting weekly administration Additional data from PARP1-selective and WRN helicase programs expected in 2027 MILLBRAE, Calif. , Oct. 23, 2026 (GLOBE NEWSWIRE) -- Eikon Therapeutics, Inc. (Nasdaq: EIKN) (“Eikon”), a late-stage clinical biopharmaceutical company dedicated to developing innovative medicines to address serious unmet medical needs, today announced the presentation of initial and updated data for EIK1003 and initial data for EIK1004 and EIK1005 at the 2026 European Society for Medical Oncology (ESMO) Congress in Madrid, Spain . “These data strengthen the foundation of our clinical-stage pipeline, with encouraging evidence of activity and tolerability across our selective PARP1 programs,” said Roy Baynes , M.D., Ph.D., Chief Medical Officer of Eikon. “The EIK1003 results support continued development both as monotherapy and in combination with established cancer treatments, while the initial EIK1004 findings support further evaluation of our CNS-penetrant PARP1 inhibitor. The first clinical results for EIK1005, our internally derived WRN helicase inhibitor, mark an important step in translating Eikon’s discovery science into potential new medicines for patients.” EIK1003 Clinical Update: Updated data from EIK1003-001 demonstrate that highly selective non-brain-penetrant PARP1 inhibitor EIK1003 as monotherapy (Cohort 1A) was generally well-tolerated across multiple dose levels. In Cohort 1B, EIK1003 in combination with the novel hormonal agent abiraterone is observed to have a favorable tolerability profile with preliminary signs of clinical activity. In Cohort 1C, signals of antitumor activity were observed with EIK1003 in combination with weekly paclitaxel, with a combination safety profile consistent with paclitaxel’s known toxicities. These data support a potentially unique profile for EIK1003 in combination strategies within the evolving PARP inhibitor landscape. Cohort 1A: Updated EIK1003 monotherapy data As of the July 13, 2026 , safety data cutoff, 65 participants with breast, ovarian, prostate, or pancreatic cancer with tumors harboring deleterious or suspected deleterious germline or somatic mutations in homologous recombination repair (HRR) genes have been treated in Cohort 1A with EIK1003 monotherapy at doses ranging from 10 mg to 160 mg once daily (QD), using a Bayesian optimal interval dose-escalation design to assess safety, tolerability, pharmacokinetics and antitumor activity. This represents an expansion of the dataset previously presented at the 2026 Annual Meeting of the American Society of Clinical Oncology (ASCO), with longer follow-up. The updated safety profile in Cohort 1A has remained generally consistent with data previously presented at ASCO 2026. Treatment-emergent adverse events (TEAEs) were reported in 63 of 65 participants (96.9%). Grade 3 or higher TEAEs occurred in 28 participants (43.1%); the most common were anemia (9.2%, 6/65), neutropenia (7.7%, 5/65), ascites (6.2%, 4/65), and thrombocytopenia (3.1%, 2/65). 4 of the 6 participants who developed Grade 3 or higher anemia had Grade 1-2 anemia at baseline. TEAEs led to dose interruptions in 22 participants (33.8%), reductions in 7 participants (10.8%) and treatment discontinuation in 4 participants (6.2%). No treatment-related adverse events (TRAEs) leading to death were reported. Among efficacy-evaluable participants in Cohort 1A (n=49), objective response rate (ORR) was 14.3% (7/49) overall, consisting of 5 confirmed partial responses (PR) and 2 unconfirmed PRs. ORR was 31.3% (5/16) in PARP-naïve participants, and 6.1% (2/33) in participants previously treated with a PARP inhibitor. Objective responses by tumor type were 14.8% (4/27) in ovarian cancer, 12.5% (2/16) in breast cancer, and one participant (1/1) with prostate cancer. The disease control rate (DCR) for the cohort was 38.8% (19/49), clinical benefit rate (CBR) was 22.4% (11/49) for ≥18 weeks, and the median duration of response (DOR) among confirmed responders (n=5) was 6.3 months at the efficacy data cutoff of October 1, 2026 . Cohort 1B: Initial data on EIK1003 in combination with the novel hormonal agent abiraterone in metastatic prostate cancer As of the July 13, 2026 , safety data cutoff, 40 participants with metastatic prostate cancer, including mCRPC or