Announcement • Aug 05
Clarity Pharmaceuticals Provides Update On SECuRE Trial For 8 GBq 67Cu-SAR-bisPSMA Dose Level
Clarity Pharmaceuticals had nineteen participants from the SECuRE trial (NCT04868604) included in this assessment of the safety and efficacy of the 8 GBq 67Cu-SAR-bisPSMA dose level. This includes 3 participants from cohort 2 of the Dose Escalation phase and 16 participants from the ongoing Cohort Expansion phase (data cut-off: July 20, 2026). The SECuRE trial continues to recruit new and treat existing participants in the Cohort Expansion phase. Prostate-specific antigen (PSA) declines were substantial with 74% of evaluable participants at data cut-off achieving PSA25 (i.e. reductions of =25% in PSA), 63% PSA50, 53% PSA75 and 26% PSA90. Responses continue to mature in participants remaining on treatment. A total of 81% (n=13) of the evaluable participants for radiographic assessment at data cut-off (n=16) achieved disease control (50% [n=8] stable disease and 31% [n=5] complete response/undetectable disease). Across all 19 participants, the median number of treatment cycles of 8 GBq 67Cu-SAR-bisPSMA was two (range: 1-4), with average cycles per participant being 2.1±1.0 (standard deviation, SD) as of data cut-off date. Most participants had bone metastases (63%) and were exposed to multiple lines of therapy, with 79% having received 5 or more previous anti-cancer regimens, prior to being enrolled in the SECuRE trial. The most common related adverse events (AEs) were gastrointestinal and haematological disorders, with the majority being mild or moderate (Grade 1/2) and transient. The prevalence and severity of related AEs observed in this group of participants were generally lower compared to the overall trial population. Two new participants that were evaluable at data cut-off in the Cohort Expansion phase of the SECuRE trial achieved a complete response as assessed by Response Evaluation Criteria in Solid Tumors 1.1 (RECIST, included in the above complete response count). This brings the total number of participants who have achieved a complete response (assessed by RECIST) or undetectable disease (assessed by bone scan and/or PSA) across the 67Cu-SAR-bisPSMA program to seven, five of whom were from the 8GBq dose cohorts, based on the most recent clinical assessments. The SECuRE trial is currently recruiting in the Cohort Expansion phase at the 8 GBq 67Cu-SAR-bisPSMA dose level (up to 6 doses). This preliminary efficacy and safety assessment includes all trial participants who received 8 GBq treatment cycles, comprising 16 participants from the ongoing Cohort Expansion phase and 3 participants from cohort 2 of the Dose Escalation phase (19 participants in total), by the data cut-off of 20 July 2026. Most participants had bone metastases (63%) and had received multiple lines of therapy prior to being enrolled in the trial (79% received 5 or more previous anti-cancer regimens). Previous standard treatments included androgen deprivation therapy (ADT), radiation, first- and/or second-generation androgen receptor pathway inhibitor (ARPI), with some participants having received taxane-based therapy for metastatic hormone-sensitive disease. Some participants were exposed to an experimental prostate-specific membrane antigen (PSMA) T-Cell Engager prior to their enrolment into the SECuRE study. The median number of treatment cycles of 67Cu-SAR-bisPSMA across participants was two (range: 1-4, mean 2.1±1.0 [SD]). Three of these participants from the Cohort Expansion phase were treated with concomitant enzalutamide. A substantial reduction in PSA was observed, with 74% (n=14) of participants achieving a PSA25 response (i.e. reductions of =25% in PSA), 63% (n=12) PSA50, 53% (n=10) PSA75, and 26% (n=5) PSA90. A total of 81% (n=13) of the participants who were evaluable for radiographic assessment (n=16) achieved disease control. This includes 50% (n=8) with stable disease and 31% (n=5) with complete response/undetectable disease (as assessed by RECIST and/or bone scan). Participants who received 8 GBq cycles, including those in the Cohort Expansion Phase, generally developed a lower prevalence and severity of related AEs compared to the overall trial population. The most frequently reported related AEs were dry mouth and nausea, each occurring in 9 (47%) and 8 (42%) participants, respectively. Anaemia and decreased neutrophil count were each reported in 4 (21%) participants, while fatigue was reported in 5 (26%) participants. Most events were low grade (mild/moderate) and transient, with two Grade 3 events (lymphocyte and white blood cell count decreases) in 1 (5%) participant. No Grade =4 related events were reported. Two new participants in the Cohort Expansion phase of the SECuRE trial who were evaluable at data cut-off achieved complete response as assessed by RECIST. Combined with the five previously announced cases, this brings the total number of participants who achieved complete response or undetectable disease (assessed by RECIST, bone scan and/or PSA) across the 67Cu-SAR-bisPSMA program to seven. Five out of these seven participants received treatment at the 8 GBq 67Cu-SAR-bisPSMA dose level. This represents almost a third (31%) of all participants evaluable for radiographic assessment treated at the 8 GBq 67Cu-SAR-bisPSMA dose level. The median baseline PSA among these seven participants was 90.3 ng/mL (range 3.3 – 490.3). They had received a median of 5 prior anti-cancer regimens (range 4-7). Bone metastases were present in four of seven participants (57%). Among the participants who had received 8 GBq doses, the median number of cycles was 3 (range 1-4, mean 2.8±0.8 [SD]). All seven participants had received prior second-generation ARPI. These observations demonstrate considerable anti-tumour activity of 67Cu-SAR-bisPSMA following a small number of 8 GBq treatment cycles in metastatic castration-resistant prostate cancer (mCRPC) patients who have failed multiple lines of therapy. The SECuRE trial (NCT04868604) is a Phase I/IIa theranostic trial for identification and treatment of participants with PSMA-expressing mCRPC using 64Cu/67Cu-SAR-bisPSMA. 64Cu-SAR-bisPSMA is used to visualise PSMA-expressing lesions and select candidates for subsequent 67Cu-SAR-bisPSMA therapy. The trial is a multi-centre, single arm study, planning to enroll approximately 54 participants in the US. The overall aim of the trial is to determine the safety and efficacy of 67Cu-SAR-bisPSMA for the treatment of prostate cancer. The SECuRE trial consists of the Dose Escalation (Phase I) and Cohort Expansion (Phase II) Phases.