Racura Oncology Doses First Patient in Phase 1 HARNESS-1 Trial of RC220 in EGFR-Mutant Non-Small Cell Lung Cancer

Racura Oncology has dosed the first patient in the HARNESS-1 Phase 1a/b trial of RC220 in combination with osimertinib for EGFR-mutant non-small cell lung cancer. The study will assess safety, pharmacokinetics, ctDNA

dynamics and early clinical activity of RC220 as a strategy to address therapeutic TKI resistance.

SYDNEY, June 25, 2026 /PRNewswire/ -- Racura Oncology Limited (ASX: RAC), a clinical-stage biopharmaceutical company developing new small molecule based approaches to cancer treatment, today announced that the first patient has been dosed with RC220 in HARNESS-1, a Phase 1a/b clinical trial evaluating RC220 in combination with osimertinib in patients with epidermal growth factor receptor-mutant (EGFR-mutant) non-small cell lung cancer (NSCLC). The first patient received RC220 at 50 mg/m² by intravenous infusion. No adverse events were observed.

HARNESS-1 is designed to test whether RC220, Racura's proprietary formulation of (E,E)-bisantrene, can be safely combined with osimertinib (Tagrisso^®; AstraZeneca), a third-generation EGFR tyrosine kinase inhibitor (TKI) and standard-of-care therapy for EGFR-mutant NSCLC to delay or prevent TKI treatment resistance. Although EGFR TKIs have transformed outcomes for many patients with EGFR-driven lung cancer, acquired treatment resistance remains a central therapeutic challenge.

Daniel Tillett, Ph.D., Chief Executive Officer of Racura Oncology, said: "Dosing the first patient in HARNESS-1 is an important milestone for Racura and for the clinical development of RC220. The scientific rationale for this trial is grounded in the urgent need to address TKI therapeutic resistance in EGFR-mutant NSCLC. RC220 gives us the opportunity to explore whether targeting G4-DNA and RNA structures, including MYC-associated growth pathways, can delay EGFR TKI resistance arising and support a new therapeutic combination for patients treated with osimertinib. We are grateful to Associate Professor Surein Arulananda and the Monash Health team for enrolling and treating the first participant, and to the patients and families who make this research possible."

Scientific Rationale

EGFR-mutant NSCLC is a molecularly stratified lung adenocarcinoma subtype driven by constitutive EGFR kinase signaling and initial sensitivity to EGFR inhibition. However, responses to EGFR tyrosine kinase inhibitors, including osimertinib, are typically limited by acquired resistance, arising through heterogeneous mechanisms such as secondary EGFR alterations, bypass receptor tyrosine kinase activation, MAPK/PI3K pathway reactivation, oncogenic fusions, lineage plasticity, epithelial-to-mesenchymal transition and histologic transformation.

RC220 is being developed to target the non-canonical G-quadruplex DNA and RNA structures enriched in oncogenic regulatory regions, including promoters, untranslated regions and highly transcribed loci. Stabilization of these structures can disrupt transcriptional and post-transcriptional control networks that sustain malignant proliferation, including silencing the c-MYC-regulated growth and survival pathways.

HARNESS-1 is designed to evaluate the safety and tolerability of RC220 with continued osimertinib-mediated EGFR suppression, while generating pharmacokinetic, pharmacodynamic, molecular response and translational biomarker data.

HARNESS-1 Trial Design

HARNESS-1 is a multi-center Phase 1a/b clinical study in patients with EGFR-mutant NSCLC receiving osimertinib. The study includes an observational screening stage using ctDNA to help identify eligible patients and characterize tumor molecular status before treatment.

The Phase 1a dose-escalation stage will evaluate RC220 administered by intravenous infusion on Day 1 of each 21-day cycle in combination with standard-of-care maintenance osimertinib. The first three dose levels will use single-patient cohorts at 50 mg/m², 100 mg/m² and 150 mg/m², before progressing to larger cohorts to identify the maximum tolerated dose and an appropriate dose for further study. Between 12 and 40 patients are expected to participate in the dose-escalation stage.

Following review of available safety and pharmacokinetic data, the study is expected to advance into a double-blind, randomized Phase 1b expansion stage. In this dose expansion stage, 40 patients will receive one of two RC220 dose levels in combination with osimertinib. Patients will be monitored for safety, pharmacokinetics and early signals of clinical activity, including progression-free survival, overall survival, ctDNA dynamics and changes in cancer-specific mutations.

The first patient was treated by Principal Investigator Associate Professor Surein Arulananda and his team at Monash Health in Clayton, Victoria. Additional clinical trial sites are expected to open in the coming months to support patient recruitment and study progress.

Clinical Trial Information

Further details about HARNESS-1, including open and recruiting sites, are available through the Australian and New Zealand Clinical Trial Registry at www.anzctr.org.au under trial code ACTRN12626000325303. Clinical trial inquiries may be directed to Racura Oncology at trials@racuraoncology.com.

About RC220 & (E,E)-bisantrene

RC220 is a proprietary formulation of (E,E)-bisantrene designed to overcome drug solubility issues that prevent safe peripheral intravenous infusion. (E,E)-bisantrene, is a clinical validated small molecule anticancer agent that primarily functions via G4-DNA and RNA binding, leading to potent transcriptional silencing of the important cancer growth regulator c-MYC.

About Racura Oncology

Racura Oncology (ASX: RAC) is a Phase 3 clinical-stage biopharmaceutical company with a mission to silence cancer. Our lead asset, (E,E)-bisantrene, is a small molecule anticancer agent that primarily functions via G4-DNA and RNA binding, leading to potent silencing of the important cancer growth regulator MYC.

Racura is advancing RC220 to address the high unmet needs of patients across multiple oncology indications, including a Phase 3 clinical program in acute myeloid leukemia (AML), a Phase 1 program in mutant epidermal growth factor receptor non-small cell lung cancer (EGFRm NSCLC), and a Phase 1 program in combination with the anthracycline doxorubicin, where we aim to deliver both cardioprotection and enhanced anticancer activity for solid tumor patients.

Learn more at www.racuraoncology.com.

Forward-Looking Statements

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