Radiopharmaceutical company Clarity Pharmaceuticals’ (ASX: CU6) first patient ever to be dosed with two cycles of its cancer therapy achieved a complete response to treatment based on RECIST criteria.
The patient received the first cycle of 67Cu-SAR-bisPSMA as part of cohort 2 of Clarity’s theranostic trial, SECuRE (NCT04868604)1, evaluating 64Cu/67Cu-SAR-bisPSMA in patients with mCRPC, and a second cycle under the US FDA EAP, as requested by the patient’s clinician. Prior to 67Cu-SAR-bisPSMA, the patient had failed multiple lines of treatment, including hormone therapy, an investigational agent and chemotherapy.
Following the administration of the first cycle of 67Cu-SAR-bisPSMA, the patient showed a reduction of PSA level of >99%. The patient then received a second cycle of 67Cu-SAR-bisPSMA, which resulted in further reduction of his PSA to undetectable levels (confirmed by two consecutive tests).
PSA is a well characterised marker of tumour burden and clinical response to treatment as well as an indicator of the recurrence of disease for prostate cancer2-4. Moreover, PSA decline is an independent prognostic indicator of improved overall survival following radioligand therapy.
A complete response (absence of detectable cancer after treatment) was observed in all but one lesion assessed by computed tomography (CT) in November 2023 (one lesion showed a reduction in size from 27 mm to 12 mm, missing the complete response cut-off by only 2 mm based on RECIST assessment). No PSMA uptake was observed in any of the lesions using 64Cu-SAR-bisPSMA following the second cycle of 67Cu-SAR-bisPSMA.
A complete response (no detectable cancer) has now been confirmed by CT at the last follow-up (April 2024, based on RECIST assessment). The patient’s PSA remains undetectable for almost 6 months since the administration of the second cycle of 67Cu-SAR-bisPSMA.
No adverse events were reported as related to 64Cu-SAR-bisPSMA. Adverse events related to 67Cu-SAR-bisPSMA included dry mouth, altered taste, thrombocytopenia (all Grade 1, improved), fatigue (Grade 2, resolved) and anaemia (Grade 3, improved to Grade 2). At the last follow-up, haematological parameters were considered non-clinically significant. No DLTs have been reported in the SECuRE trial in any of the patients dosed with 67Cu-SAR-bisPSMA to date. Recruitment is ongoing into cohort 4, the first multi-dose cohort in the trial, at the dose level of 12GBq.
“This was a very special moment, delivering the news to this patient that his cancer is now
undetectable following the treatment with 2 doses of 8GBq of 67Cu-SAR-bisPSMA,” Dr Luke Nordquist, CEO, Urologic Medical Oncologist and Principal Investigator at the Urology Cancer Centre, said.
“After going through a number of therapies over the years with all of them having limited effect on the progression of his cancer, we have now been unable to detect any signs of his cancer, using PSA assessment, CT and PET imaging. The safety profile of 67Cu-SAR- bisPSMA appears to be favourable with few side effects observed following treatment, which is remarkable for a patient who was heavily pre-treated with ADT, ARPIs, chemotherapy and a PARP inhibitor.
“We are very excited to continue working with Clarity on the SECuRE trial as it has now entered a multi-dose cohort at a dose level of 12GBq, exploring the potential therapeutic benefit we might see from multiple doses of the product. The EAP has given us an early insight into what these benefits might look like, and we believe that 67Cu-SAR-bisPSMA might become a best-in-class therapeutic agent once approved, providing patients with an effective treatment option with a manageable safety profile.”