Clarity Pharmaceuticals SECuRE Trial Posts 100% PSA Response in Phase II Cohort
Clarity Pharmaceuticals (ASX: CU6) has announced positive interim results from its SECuRE trial, with the Safety Review Committee confirming the Phase II Cohort Expansion will continue with no protocol modifications. The radiopharmaceutical company reported that six evaluable participants with at least two post-treatment PSA measurements demonstrated a 100% PSA response rate, with 66.7% (four participants) achieving PSA reductions of 50% or more (PSA50). The heavily pre-treated patient population (55.6% had received more than 5 prior anti-cancer regimens) and high incidence of bone metastases (66.7%) underscore the clinical significance of these results. Median baseline PSA measured 18.9 ng/mL (range 1.5-30.2 ng/mL), reflecting advanced disease at enrolment.
The Safety Review Committee’s decision to proceed without modifications validates the current 8 GBq dosing strategy established during the Phase I Dose Escalation phase. Seven participants received 67Cu-SAR-bisPSMA monotherapy, while two were treated with a combination regimen including enzalutamide. Data assessed at the 25 November 2025 cut-off date confirmed the favourable safety profile observed in earlier cohorts, with most adverse events classified as Grade 1 or 2.
What Do the SECuRE Trial Interim Results Mean for Clarity Pharmaceuticals Investors?
The Clarity Pharmaceuticals SECuRE trial results provide proof-of-concept data supporting the company’s Phase III registrational trial design. The therapeutic efficacy demonstrated in this heavily pre-treated population positions 67Cu-SAR-bisPSMA as a potential challenger to existing PSMA-targeted therapies in the metastatic castration-resistant prostate cancer (mCRPC) market.
Clarity Pharmaceuticals (ASX: CU6) holds three Fast Track Designations from the US Food and Drug Administration covering distinct clinical indications:
- Imaging in pre-definitive therapy (early diagnosis)
- Biochemical recurrence detection (disease monitoring)
- Therapy in mCRPC (late-stage treatment)
These designations accelerate regulatory review timelines and support commercialisation across multiple high-value market segments. The combined PSMA-targeted product market is estimated at US$10-15 billion by 2030, representing substantial revenue potential across the prostate cancer treatment continuum.
Phase II recruitment is expected to complete in 2026, with 24 participants enrolled in the Cohort Expansion phase. The company confirmed Phase III protocol development is actively underway, informed by robust Phase I/II datasets establishing the 8 GBq dose (up to 6 cycles per patient) for registrational studies. Fast Track status enables rolling submissions and priority review, potentially compressing approval timelines compared to standard pathways.
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Exceptional Efficacy: 100% PSA Response Rate in Evaluable Patients
PSA Reduction Data
All six evaluable participants with at least two post-treatment PSA measurements demonstrated PSA declines following 67Cu-SAR-bisPSMA therapy. Four participants (66.7%) achieved PSA50 response (reduction of ≥50%), while two participants (33.3%) achieved PSA80 response (reduction of ≥80%).
These results align with previous Cohort 2 findings from the Dose Escalation phase, where all three participants treated at 8 GBq achieved PSA80 responses. The consistency across cohorts, despite the heavily pre-treated patient population and high bone metastasis burden, strengthens the case for predictable therapeutic responses in Phase III trials.
| Response Level | Number of Patients | Percentage |
|---|---|---|
| Any PSA Decline | 6/6 | 100% |
| PSA50 (≥50% reduction) | 4/6 | 66.7% |
| PSA80 (≥80% reduction) | 2/6 | 33.3% |
The depth and consistency of PSA responses in this advanced disease setting demonstrate 67Cu-SAR-bisPSMA’s potential to address unmet clinical needs in patients who have exhausted multiple treatment lines.
Case Study: Complete Radiological Response
One participant in the Cohort Expansion achieved particularly exceptional outcomes. A 64-year-old man presenting with bone metastases and baseline PSA of 5.4 ng/mL demonstrated a dramatic 95.2% PSA reduction following his first 67Cu-SAR-bisPSMA cycle.
After receiving 3 cycles at 8 GBq each, the participant achieved undetectable PSA levels. Follow-up imaging, including bone scan and computed tomography, revealed no visible metastatic disease. The participant experienced only Grade 1 gastrointestinal adverse events, with no haematological or renal toxicity observed. He reported excellent quality of life following treatment.
“Although the number of participants with evaluable data to date is small, it is incredible to see yet another extraordinary case where a patient who had bone metastasis prior to entering the study achieved undetectable PSA following 67Cu-SAR-bisPSMA treatment, with no disease observed by anatomical and molecular imaging at the last assessments. This participant only experienced mild, transient AEs, most being gastrointestinal, and has reported having excellent quality of life following the treatment,” commented Executive Chairperson Dr Alan Taylor.
This case demonstrates 67Cu-SAR-bisPSMA’s potential to deliver durable complete responses in advanced disease, supporting premium pricing strategies and differentiated market positioning. Complete radiological responses in heavily pre-treated mCRPC populations are rare with existing therapies, highlighting the compound’s competitive advantage.
How Effective is 67Cu-SAR-bisPSMA Treatment for Prostate Cancer Patients?
67Cu-SAR-bisPSMA represents a novel approach to PSMA-targeted radioligand therapy. The compound delivers targeted radiation directly to cancer cells expressing the prostate-specific membrane antigen (PSMA) protein, which is highly expressed in prostate cancer cells. This selective targeting minimises damage to healthy tissue while concentrating therapeutic radiation at disease sites.
The technology comprises three integrated components:
- SAR chelator: Clarity’s proprietary sarcophagine technology creates a cage-like structure that securely holds copper isotopes, preventing leakage into the body. This addresses a key limitation of conventional chelators used with other radioisotopes.
- Bis dimer structure: Unlike single-targeting agents, 67Cu-SAR-bisPSMA connects two PSMA-binding motifs, enhancing cancer cell binding and retention. This dual-targeting approach is reflected in the “bis” designation.
- Copper isotopes: The platform utilises 64Cu for diagnostic imaging (patient selection via PET scan) and 67Cu for therapy. This theranostic approach enables precise patient stratification before treatment initiation.
67Cu-SAR-bisPSMA is typically administered in the mCRPC setting after patients have progressed through androgen receptor pathway inhibitors (ARPIs) and often chemotherapy. The SECuRE trial population reflects this advanced treatment line, with more than half of participants having received >5 prior systemic regimens. The demonstrated efficacy in this refractory population positions the therapy as a potential late-line treatment option with activity in chemotherapy-exposed patients, expanding its addressable market beyond first-line PSMA-targeted competitors.
Favourable Safety Profile Maintained Across Expansion Cohort
The majority of adverse events in the Cohort Expansion were classified as Grade 1 or 2, consistent with the safety profile observed in Phase I. The most common adverse events were nausea and lymphopenia, each occurring in 3 out of 9 participants (33.3%).
Grade 3 or higher adverse events were limited to lymphopenia in three participants. Clinical context is important, as these participants presented with bone metastasis at baseline and/or had received multiple prior treatment lines, including taxane chemotherapy and investigational agents, before SECuRE trial enrolment. Bone marrow involvement and prior myelotoxic therapy contribute to lymphopenia risk independent of 67Cu-SAR-bisPSMA exposure.
Notably, no renal toxicity or electrocardiogram changes were observed across the nine evaluable participants. Renal safety is particularly significant for PSMA-targeted agents, as PSMA is expressed in healthy kidney tissue. The absence of renal adverse events suggests Clarity’s SAR chelator technology successfully prevents copper leakage, which could otherwise accumulate in kidneys and cause toxicity.
In the combination therapy arm (67Cu-SAR-bisPSMA plus enzalutamide), no new adverse events or worsening of existing adverse events related to 67Cu-SAR-bisPSMA were reported. This supports the feasibility of combination regimens, which may enhance efficacy compared to monotherapy based on recent ENZA-p trial findings demonstrating improved outcomes with PSMA-targeted therapy plus ARPI combinations.
| Adverse Event Type | Frequency | Grade | Context |
|---|---|---|---|
| Nausea | 3/9 (33.3%) | Grade 1-2 | Manageable GI events |
| Lymphopenia | 3/9 (33.3%) | Grade 3 | Bone metastases, prior taxane |
| Renal Toxicity | 0/9 (0%) | N/A | No events observed |
| ECG Changes | 0/9 (0%) | N/A | No events observed |
The clean safety profile supports broad patient eligibility criteria and reduces the risk of dose-limiting toxicities in Phase III trials. It also enhances the commercial viability of combination therapy strategies, which are increasingly favoured in mCRPC treatment paradigms based on synergistic efficacy benefits observed in recent clinical trials.
When Will Clarity Pharmaceuticals Begin Phase III Trials for SECuRE?
Phase II enrolment continues through 2026, with the Cohort Expansion targeting 24 participants. Clarity Pharmaceuticals (ASX: CU6) confirmed that Phase III registrational trial planning is actively underway, informed by data generated across Phase I and Phase II cohorts.
The Phase III dose has been established at 8 GBq (up to 6 cycles per patient), based on the favourable benefit-risk profile observed at this dose level. Dose optimisation completed during Phase I/II reduces execution risk by eliminating the need for dose-finding studies within the pivotal programme.
A subset of Phase II participants are receiving combination therapy with enzalutamide plus 67Cu-SAR-bisPSMA. This combination arm was designed based on positive ENZA-p trial results and guidance from Clarity’s Clinical Advisory Board, which includes Prof Louise Emmett and Prof Oliver Sartor, leading global experts in prostate cancer management and PSMA-targeted therapeutics.
Anticipated timeline:
- 2025-2026: Complete Phase II Cohort Expansion (24 patients)
- 2026: Finalise Phase III protocol based on completed Phase II dataset
- Post-2026: Initiate registrational Phase III study under Fast Track designation
Fast Track status from the FDA enables rolling submissions of Phase III data as it becomes available, accelerating regulatory review compared to standard procedures. This expedited pathway, combined with robust Phase II proof-of-concept data, positions Clarity Pharmaceuticals to advance towards commercialisation with reduced timeline risk.
The company’s Clinical Advisory Board involvement ensures Phase III trial design aligns with regulatory expectations and clinical practice standards. Advisory Board guidance has informed patient selection criteria, combination therapy strategies, and endpoint selection to maximise the probability of successful registration.
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Executive Commentary: Dr Alan Taylor on Market Positioning
“SAR-bisPSMA continues generating world-class data in both theranostic and diagnostic trials. The combination of the optimised dimer ‘bis’ structure with the benefits of copper isotopes, enabled by the proprietary sarcophagine technology, is proving to have created a product that is here to challenge the current treatment and diagnostic paradigms in radiopharmaceuticals. With three Fast Track Designations for the SAR-bisPSMA product and positive interactions with the US Food and Drug Administration to date, we are working towards bringing this agent to clinicians and their patients around the world through the entirety of the prostate cancer journey, from first diagnosis to late-stage disease. All of these indications, being imaging in pre-definitive therapy and biochemical recurrence, as well as therapy in mCRPC, are blockbuster markets individually for prostate-specific membrane antigen targeted products, with an estimated combined market value of approximately US$10-15 billion by 2030,” stated Dr Alan Taylor, Executive Chairperson of Clarity Pharmaceuticals.
Dr Taylor’s commentary highlights Clarity’s positioning strategy to address multiple high-value indications across the prostate cancer treatment continuum. The US$10-15 billion combined market opportunity encompasses diagnostic imaging applications and therapeutic interventions, creating multiple revenue streams from a single technology platform. This vertical integration across the cancer care pathway differentiates Clarity’s approach from competitors focused solely on therapeutic applications, potentially commanding premium pricing based on comprehensive diagnostic-therapeutic solutions.
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