Clarity Pharmaceuticals Reports Strong PSA Responses and Disease Control in SECuRE Trial

Clarity Pharmaceuticals (ASX: CU6) announced preliminary results from the SECuRE trial showing substantial prostate-specific antigen (PSA) declines and disease control in participants treated with the 8 GBq dose of 67Cu-SAR-bisPSMA, and the company's shares jumped 14% to A$4.00 on Monday.

The SECuRE trial (NCT04868604) is a Phase I/IIa theranostic study evaluating 64Cu-SAR-bisPSMA for imaging and 67Cu-SAR-bisPSMA for therapy in patients with advanced prostate cancer. The preliminary assessment included 19 participants who received 8 GBq treatment cycles: 3 from cohort 2 of the Dose Escalation phase and 16 from the ongoing Cohort Expansion phase, with a data cut-off of July 20, 2026. Most participants had bone metastases (63%) and 79% had received 5 or more previous anti-cancer regimens.

PSA declines were substantial, with 74% (n=14) achieving PSA25 (reductions of ≥25% in PSA), 63% (n=12) PSA50, 53% (n=10) PSA75, and 26% (n=5) PSA90. Among the 16 participants evaluable for radiographic assessment, 81% (n=13) achieved disease control, including 50% (n=8) with stable disease and 31% (n=5) with complete response/undetectable disease. The median number of treatment cycles was two (range: 1-4).

Two new participants in the Cohort Expansion phase achieved a complete response as assessed by RECIST 1.1. This brings the total number of participants who have achieved a complete response or undetectable disease across the 67Cu-SAR-bisPSMA program to seven, five of whom were from the 8 GBq dose cohorts.

Investors also responded to news that another patient in the SECuRE trial achieved undetectable disease. A 76-year-old participant with metastatic castration-resistant prostate cancer (mCRPC) achieved undetectable PSA levels just seven weeks after the first treatment cycle, and after the second cycle a PSMA PET scan showed no detectable disease. All related adverse events were mild (Grade 1), with no haematological or renal side effects observed to date. This marks the fifth patient in the SAR-bisPSMA theranostic program to achieve undetectable disease by radiographic assessment.

The company also provided an update on a previously reported participant in the same Cohort Expansion phase, who continues to show undetectable disease after four treatment cycles, with no new safety signals observed. Across the 19 participants in the 8 GBq assessment, the most common related adverse events were gastrointestinal and haematological disorders, with the majority being mild or moderate (Grade 1/2) and transient. Dry mouth occurred in 9 (47%) participants and nausea in 8 (42%), while fatigue was reported in 5 (26%) and anaemia and decreased neutrophil count each in 4 (21%) participants. The prevalence and severity of related adverse events in this group were generally lower compared to the overall trial population.

Recruitment into the Cohort Expansion phase is ongoing, with completion expected in 2026. Planning for a registrational Phase III trial is also underway based on data generated so far. Clarity Pharmaceuticals is a clinical-stage radiopharmaceutical company.