[ 177 Lu]Lu-PSMA-617 plus enzalutamide in patients with metastatic castration-resistant prostate cancer (ENZA-p): an open-label, multicentre, randomised, phase 2 trial.

Background: Enzalutamide and lutetium-177 [ ¹⁷⁷ Lu]Lu-prostate-specific membrane antigen (PSMA)-617 both improve overall survival in patients with metastatic castration-resistant prostate cancer. Androgen and PSMA receptors have a close intracellular relationship, with data suggesting complementary benefit if targeted concurrently. In this study, we assessed the activity and safety of enzalutamide plus adaptive-dosed [ ¹⁷⁷ Lu]Lu-PSMA-617 versus enzalutamide alone as first-line treatment for metastatic castration-resistant prostate cancer.
Methods: ENZA-p was an open-label, randomised, controlled phase 2 trial done at 15 hospitals in Australia. Participants were men aged 18 years or older with metastatic castration-resistant prostate cancer not previously treated with docetaxel or androgen receptor pathway inhibitors for metastatic castration-resistant prostate cancer, gallium-68 [ ⁶⁸ Ga]Ga-PSMA-PET-CT (PSMA-PET-CT) positive disease, Eastern Cooperative Oncology Group performance status of 0-2, and at least two risk factors for early progression on enzalutamide. Participants were randomly assigned (1:1) by a centralised, web-based system using minimisation with a random component to stratify for study site, disease burden, use of early docetaxel, and previous treatment with abiraterone acetate. Patients were either given oral enzalutamide 160 mg daily alone or with adaptive-dosed (two or four doses) intravenous 7·5 GBq [ ¹⁷⁷ Lu]Lu-PSMA-617 every 6-8 weeks dependent on an interim PSMA-PET-CT (week 12). The primary endpoint was prostate-specific antigen (PSA) progression-free survival, defined as the interval from the date of randomisation to the date of first evidence of PSA progression, commencement of non-protocol anticancer therapy, or death. The analysis was done in the intention-to-treat population, using stratified Cox proportional hazards regression. This trial is registered with ClinicalTrials.gov, NCT04419402, and participant follow-up is ongoing.
Findings: 162 participants were randomly assigned between Aug 17, 2020, and July 26, 2022. 83 men were assigned to the enzalutamide plus [ ¹⁷⁷ Lu]Lu-PSMA-617 group, and 79 were assigned to the enzalutamide group. Median follow-up in this interim analysis was 20 months (IQR 18-21), with 32 (39%) of 83 patients in the enzalutamide plus [ ¹⁷⁷ Lu]Lu-PSMA-617 group and 16 (20%) of 79 patients in the enzalutamide group remaining on treatment at the data cutoff date. Median age was 71 years (IQR 64-76). Median PSA progression-free survival was 13·0 months (95% CI 11·0-17·0) in the enzalutamide plus [ ¹⁷⁷ Lu]Lu-PSMA-617 group and 7·8 months (95% CI 4·3-11·0) in the enzalutamide group (hazard ratio 0·43, 95% CI 0·29-0·63, p<0·0001). The most common adverse events (all grades) were fatigue (61 [75%] of 81 patients), nausea (38 [47%]), and dry mouth (32 [40%]) in the enzalutamide plus [ ¹⁷⁷ Lu]Lu-PSMA-617 group and fatigue (55 [70%] of 79), nausea (21 [27%]), and constipation (18 [23%]) in the enzalutamide group. Grade 3-5 adverse events occurred in 32 (40%) of 81 patients in the enzalutamide plus [ ¹⁷⁷ Lu]Lu-PSMA-617 group and 32 (41%) of 79 patients in the enzalutamide group. Grade 3 events that occurred only in the enzalutamide plus [ ¹⁷⁷ Lu]Lu-PSMA-617 group included anaemia (three [4%] of 81 participants) and decreased platelet count (one [1%] participant). No grade 4 or 5 events were attributed to treatment on central review in either group.
Interpretation: The addition of [ ¹⁷⁷ Lu]Lu-PSMA-617 to enzalutamide improved PSA progression-free survival providing evidence of enhanced anticancer activity in patients with metastatic castration-resistant prostate cancer with risk factors for early progression on enzalutamide and warrants further evaluation of the combination more broadly in metastatic prostate cancer.
Funding: Prostate Cancer Research Alliance (Movember and Australian Federal Government), St Vincent's Clinic Foundation, GenesisCare, Roy Morgan Research, and Endocyte (a Novartis company).
Competing Interests: Declaration of interests LE reports research grant support (to their institution) from Novartis and Clarity Pharma; consulting fees for lectures or advisory boards from Astellas, Janssen, AstraZeneca, Clarity, Novartis, and Telix in the past 5 years; and philanthropic grant support from the Prostate Cancer Foundation, St Vincent's Clinic Research Foundation, and Curran Foundation. SSa reports grants from Novartis/AAA, AstraZeneca, Merck Sharp & Dohme, Genentech, Pfizer, Amgen, and Senhwa to their institution; and personal fees from AstraZeneca, Merck Sharp & Dohme, Bristol Myers Squibb, and AstraZeneca to their institution, outside the submitted work. CG donated personal fees from Astellas, Janssen, AstraZeneca, Bristol Myers Squibb, Pfizer/EMD Serono, Ipsen, Astellas, and MSD, direct and complete, to a third party not-for-profit. CG declares consulting fees (unrelated to this work) from Novotech, Cadex Geonomics, and BCAL Diagnostics; and participation on an advisory board for Alloplex. MSH reports grants and receipt of equipment, materials, drugs, medical writing, gifts, or other services from the Prostate Cancer Foundation, National Health and Medical Research Council (NHRMC), Movember, US Department of Defense, Medical Research Future Fund, Bayer, Peter MacCallum Foundation, Isotopia, and the Australian Nuclear Science and Technology Organisation; consulting fees from Merck Sharp & Dohme and Novartis; honoraria from Janssen, Novartis, AstraZeneca, and Astellas; support for meetings from Merck Sharp & Dohme, Novartis, Janssen, AstraZeneca, and Astellas; leadership or fiduciary role in other board from Australian Friends of Sheba; and other financial or non-financial interests from Peter MacCallum Cancer Centre and the University of Melbourne. DAP reports personal fees from Ipsen and Eisai, all outside the submitted work. RJF reports institution funding and consulting fees from AIQ Solutions, outside the submitted work; and committee involvement in the Australasian Radiopharmaceutical Trials Network (unpaid). MRS reports grants to his institution from the Australian NHMRC, Cancer Australia, Astellas, Amgen, AstraZeneca, Bayer, Bionomics, Bristol Myers Squibb, Celgene, Medivation, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, and Tilray, all outside the submitted work. IDD reports grants from the NHMRC, during the conduct of the study; and institutional payments to support prostate cancer trials from Pfizer, ANZUP Cancer Trials Group, Bayer, Astellas, Janssen, Movember Foundation, and Merck Sharp & Dohme, outside the submitted work. IDD is unremunerated Chair of the ANZUP Cancer Trials Group and is supported in part by an Australian NHMRC Investigator Grant (grant number 2016274). AMJ reports consulting or advisory roles (to their institution) from Janssen Oncology, Pfizer, and Astellas Pharma; and research funding (to their institution) from Bristol Myers Squibb, Janssen Oncology, Merck Sharp & Dohme, Mayne Pharma, Roche/Genentech, Bayer, Lilly, Pfizer, and AstraZeneca. AW declares consulting fees from MSD, Eisai, Bristol Myers Squibb, and Astellas; honoraria from Eisai and MSD; and participation on an advisory board from Loxo-Lilly, MSD, and Astellas. DP declares support for travel from Astellas and participation on an advisory board from Astellas. MC reports advisory board fees from Astellas. MV reports personal fees from AstraZeneca and MSD. AYZ reports grants or contracts from Astellas, Amgen, AstraZeneca, Bionomics, Bristol Myers Squibb, Celgene, Medivation, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, and Tilray; consulting fees from Merck Sharpe & Dohme; honoraria from Merck Sharpe & Dohme, Astellas, Bayer, Pfizer, Merck, Mundipharma, Janssen, and AstraZeneca; and participation on a data safety monitoring board or advisory board from Merck, Merck Sharpe & Dohme, Astellas, and Bayer. JCG reports consulting fees from Bristol Myers Squibb, GlaxoSmithKline, and MSD; honoraria from Bayer, Ipsen, Eisai, Janssen, GlaxoSmithKline, and MSD; support to attend meetings from Bayer and BeiGene; and participation on a data safety monitoring board or advisory board from AstraZeneca. LH reports support for the present manuscript from Astellas; research funding from Astellas, Bayer, and Imagion; participation on advisory boards from Astellas, Bayer, Janssen, and MSD; payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing, or educational events from Astellas, Bayer, Janssen, and MSD; support for attending meetings from Bayer; a provisional patent (Australian number 2022902527, Prognostic Markers [plasma lipid prognostic signature in metastatic prostate cancer]; patent owned by the Chris O'Brien Lifehouse [their institution]); participation on a data safety monitoring board or advisory board from Astellas, Bayer, and Imagion; advisory board leadership role for ANZUP; and stock or stock options from Connected Medical Solutions. SY reports grants or contracts from NHMRC, Cancer Australia, Astellas, Amgen, AstraZeneca, Bionomics, Bristol Myers Squibb, Celgene, Medivation, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, and Tilray; and support for attending meetings from Bayer. All other authors declare no competing interests.
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