TheraP: 177Lu-PSMA-617 (LuPSMA) versus cabazitaxel in metastatic castration-resistant prostate cancer (mCRPC) progressing after docetaxel—Overall survival after median follow-up of 3 years (ANZUP 1603)

5000

Background: We previously reported that in men with mCRPC progressing after docetaxel randomly assigned LuPSMA vs. cabazitaxel (Lancet 2021), those assigned LuPSMA has significant improvements in PSA response rate (66% vs. 37%), RECIST response rate (49% vs. 24%), progression-free survival (HR 0.63), less G3-4 toxicities (33% vs. 53%) and better patient-reported outcomes. We now report the secondary endpoint of overall survival (OS) with mature follow-up, for trial participants, and also those initially excluded because of low PSMA-expression or discordant disease on imaging with PSMA-PET and FDG-PET. Methods: Eligibility for the TheraP trial required mCRPC progressing after docetaxel, PET imaging with 68Ga-PSMA-11 that showed high PSMA-expression (at least one site with SUVmax≥20), and 18F-FDG demonstrating no sites of disease of FDG-positive and PSMA-negative (discordant disease). Participants were randomly assigned treatment with LuPSMA (8.5-6GBq every 6 weeks, maximum 6 cycles) vs cabazitaxel (20mg/m2 every 3 weeks, maximum 10 cycles). OS was analyzed by intention-to-treat and summarized by restricted mean survival time (RMST) to account for non-proportional hazards. Results: 291 patients were screened from 6 Feb 2018 to 3 Sep 2019: 200 were eligible and randomly assigned LuPSMA (99) or cabazitaxel (101); 80 of 291 (27%) registered after initial eligibility were excluded after PSMA/FDG-PET(51 SUVmax < 20, 29 discordant), with follow-up available in 61 of the 80 (76%). After a median follow-up time of 36 months (data cut-off 31 Dec 2021), death was reported in 70/101 assigned cabazitaxel, 77/99 assigned LuPSMA, and 55/61 excluded after PSMA/FDG-PET. Subsequent treatments among those assigned cabazitaxel included cabazitaxel in 21, and LuPSMA in 20; and among those assigned LuPSMA included additional LuPSMA in 5, and cabazitaxel in 32. Overall survival was similar in those randomly assigned LuPSMA versus cabazitaxel (RMST to 36 months was 19.1 vs. 19.6 months, difference -0.5, 95% CI -3.7 to + 2.7). No additional safety signals were identified with longer follow-up. Among 61 men excluded by imaging with PSMA/FDG-PET before randomisation, RMST to 36 months was 11.0 months (95% CI 9.0 to 13.1), following treatment that included cabazitaxel in 29 (48%) and LuPSMA in 3 (5%). Conclusions: LuPSMA is a suitable option for men with mCRPC progressing after docetaxel, with lower adverse events, higher response rates, improved patient-reported outcomes, and similar OS compared with cabazitaxel. Median survival was considerably shorter for patients excluded on PSMA/FDG-PET due to either low PSMA expression or FDG-discordant disease who would otherwise be eligible for LuPSMA. Clinical trial information: NCT03392428.

PSMA PET and FDG PET as predictors of response and prognosis in a randomized phase 2 trial of 177Lu-PSMA-617 (LuPSMA) versus cabazitaxel in metastatic, castration-resistant prostate cancer (mCRPC) progressing after docetaxel (TheraP ANZUP 1603)

10

Background: The TheraP trial showed that LuPSMA improved PSA≥50% response rate (PSA50-RR), PSA-PFS, and radiographic PFS (rPFS) compared with cabazitaxel in mCRPC progressing after docetaxel. Study inclusion required high PSMA uptake (SUVmax≥20) and no lesions that were FDG+ and PSMA-. Here we report on PSMA PET and FDG PET as potential predictive and prognostic biomarkers. Methods: We prospectively analysed semi-automated quantitative PET parameters in centrally- collected 68Ga-PSMA-11 PET and 18F-FDG PET in 200 eligible men. SUVmean ≥10 on PSMA PET was evaluated as a predictive biomarker for response to Lu-PSMA vs cabazitaxel. Metabolic tumor volume (MTV) ≥200mL on FDG PET was tested as a prognostic biomarker accounting for the randomly assigned treatment. Quantitative PET cut-offs were pre-specified from prior research (PMID:32140802). Responses were defined according to PSA50-RR (primary endpoint), PSA-PFS and rPFS. Binary and PFS endpoints were analyzed using logistic and Cox regression, respectively. Results: Very high PSMA uptake on PSMA PET (SUVmean≥10) was seen in 35/99 (35%) assigned LuPSMA and 30/101 (30%) assigned cabazitaxel. The odds of a response to LuPSMA vs. cabazitaxel were significantly higher for men with SUVmean≥10 (OR 12.2, 95%CI 3.4-59 vs. 2.2, 95%CI 1.1-4.5; p = 0.03). In men with SUVmean≥10, the PSA50-RR for LuPSMA vs. cabazitaxel were 32/35 (91%) vs. 14/30 (47%). In men with PSMA SUVmean < 10, the PSA50-RR were 33/64 (52%) vs. 23/71 (32%). High-volume metabolic disease on FDG PET (MTV ≥200mL) was seen in 30/99 (30%) assigned LuPSMA and 30/101 (30%) assigned cabazitaxel. The PSA50-RR in these men was 17/30 (57%) for LuPSMA vs. 6/30 (20%) for cabazitaxel. In comparison, the PSA50-RR for men with MTV < 200mL on FDG PET was 48/69 (70%) for LuPSMA vs. 31/71 (44%) for cabazitaxel. After accounting for treatment, the odds of a PSA50-response was lower among men with high MTV (OR 0.44; p = 0.01). The HR for PSA-PFS for LuPSMA vs cabazitaxel was 0.45 (95%CI 0.25-0.80) for SUVmean≥10 vs. 0.77 (95%CI 0.53-1.12) for SUVmean < 10 (p = 0.2). Findings were similar for rPFS. The HRs for high MTV on FDG PET adjusted for treatment were 1.44 (95%CI 1.03-2.02) for PSA-PFS (p = 0.03); and 1.79 (95%CI 1.28-2.52) for rPFS (p < 0.001). Conclusions: In men with mCRPC, PSMA SUVmean≥10 was predictive of a higher likelihood of favourable response to LuPSMA than cabazitaxel, whilst a high volume of disease on FDG PET was associated with a worse prognosis regardless of randomly assigned treatment. Clinical trial information: NCT03392428.

ENZA-p: A randomized phase II trial using PSMA as a therapeutic agent and prognostic indicator in men with metastatic castration-resistant prostate cancer treated with enzalutamide (ANZUP 1901)

TPS205

Background: 177Lu‐PSMA‐617 (LuPSMA) is a novel radionuclide with promising activity and tolerability in metastatic castration-resistant prostate cancer (mCRPC). Pre-clinical studies have shown that androgen receptor blockade with enzalutamide upregulates PSMA-receptor expression, and that PSMA-receptor blockade increases treatment response to enzalutamide. We hypothesize that concurrent administration of LuPSMA and enzalutamide will be synergistic in mCRPC. The aims of ENZA-p are to determine the activity and safety of LuPSMA combined with enzalutamide in men with mCRPC at high-risk of early progression on enzalutamide alone; and to identify prognostic and predictive biomarkers from imaging, blood, and tissue. Methods: This open-label, randomized, multicentre, phase 2 trial will recruit 160 men with mCRPC. Key eligibility criteria include progression on androgen deprivation therapy, 2 or more risk factors for early cancer progression on enzalutamide (LDH ≥ULN; ALP ≥ULN; albumin < 35 g/L; M1 disease at diagnosis; < 3 years since initial diagnosis; > 5 bone metastases; visceral metastases; PSA doubling time < 3 months; pain requiring opiates > 14 days; for castration-sensitive disease), no prior treatment with an androgen receptor pathway inhibitor (except abiraterone), no prior chemotherapy for mCRPC, and PSMA-avid disease on positron emission tomography (PET) with 68Ga-PSMA. Participants are randomly assigned (1:1) to enzalutamide 160 mg daily or enzalutamide 160 mg daily plus LuPSMA 7.5 GBq on days 15 and 57. Two subsequent doses of Lu-PSMA will be administered if the 68Ga-PSMA PET on day 92 shows persistent PSMA expression in the tumour. Imaging assessments include CT and technetium bone scan at baseline, day 99, then every 12 weeks; 68Ga-PSMA-11 PET at baseline, days 15, 92, and first progression; and 18F FDG PET at baseline and first progression. Translational samples including circulating tumor cells (CTCs), circulating tumor DNA (ctDNA) and biopsies (optional) will be collected at baseline, day 92, and first progression. The primary endpoint is PSA progression-free survival (PSA-PFS). Secondary endpoints include radiological-PFS, PSA-response rate, pain response and PFS, clinical-PFS, overall survival, health related quality of life, adverse events, and cost-effectiveness. Correlative studies include identification of prognostic and predictive biomarkers from 68Ga-PSMA, 18F FDG PET/CT, CTCs, and ctDNA. A sample size of 160 provides 80% power with a 2-sided type 1- error rate of 5% to detect a HR of 0.625 assuming a median PSA-PFS of 5 months with enzalutamide alone. Accrual was 90 on 12 October 2021. Clinical trial information: NCT04419402.

ENZA-p: A randomized phase II trial using PSMA as a therapeutic agent and prognostic indicator in men with metastatic castration-resistant prostate cancer treated with enzalutamide (ANZUP 1901)

TPS177

Background: 177Lu‐PSMA‐617 (LuPSMA) is a novel radionuclide with promising activity and tolerability in metastatic, castration-resistant prostate cancer (mCRPC). Pre-clinical studies have shown that androgen receptor blockade with enzalutamide upregulates PSMA-receptor expression, and that PSMA-receptor blockade increases treatment response to enzalutamide. We hypothesise that concurrent administration of LuPSMA and enzalutamide will be synergistic in mCRPC. The aims of ENZA-p are to determine the activity and safety of LuPSMA and enzalutamide in men with mCRPC at high-risk of early progression on enzalutamide alone; and to identify potential prognostic and predictive biomarkers from imaging, blood, and tissue. Methods: This open-label, randomised, multicentre, phase 2 trial will recruit 160 men with mCRPC. Key eligibility criteria include progression on androgen deprivation therapy, 2 or more high-risk features for early (LDH ≥ULN; ALP ≥ULN; albumin <35 g/L; M1 disease at diagnosis; <3 years from initial diagnosis to randomisation; >5 bone metastases; visceral metastases; PSA doubling time <84 days; pain requiring opiates >14 days; prior abiraterone), no prior treatment with a novel androgen signalling inhibitor (except abiraterone), no prior chemotherapy for mCRPC, and PSMA-avid disease on positron emission tomography (PET) with 68Ga-PSMA. Participants are randomly assigned (1:1) enzalutamide 160 mg daily or enzalutamide 160 mg daily plus LuPSMA 7.5 GBq on days 15 and 57. Two subsequent doses of Lu-PSMA will be administered if the 68Ga-PSMA PET on day 92 shows persistent PSMA expression in the tumour. Imaging assessments include CT and technetium bone scan at baseline, day 99, then every 12 weeks; 68Ga-PSMA-11 PET at baseline, days 15, 92, and first progression; and 18F FDG PET at baseline and first progression. Translational samples including circulating tumour cells (CTCs), circulating tumour DNA (ctDNA) and biopsies (optional) will be collected at baseline, day 92, and first progression. The primary endpoint is PSA progression-free survival (PSA-PFS). Secondary endpoints include radiological-PFS, PSA-response rate, pain response and PFS, clinical-PFS, overall survival, health related quality of life, adverse events, and cost-effectiveness. Correlative studies include identification of prognostic and predictive biomarkers from 68Ga-PSMA, 18F FDG PET/CT, CTCs, and ctDNA. A sample size of 160 provides 80% power with a 2-sided type 1-error rate of 5% to detect a HR of 0.625 assuming a median PSA-PFS of 5 months with enzalutamide alone. Accrual was 5 on 13 October 2020. ENZA-p is an investigator-initiated, academic trial led by ANZUP in collaboration with the NHMRC Clinical Trials Centre, University of Sydney. Clinical trial information: NCT04419402.

177Lu-PSMA-617 (LuPSMA) versus cabazitaxel in metastatic castration-resistant prostate cancer (mCRPC) progressing after docetaxel: Updated results including progression-free survival (PFS) and patient-reported outcomes (PROs) (TheraP ANZUP 1603)

6

Background: TheraP is a randomized phase 2 trial that showed LuPSMA significantly improved the primary endpoint of PSA≥50% reduction (66% vs. 37%) compared to cabazitaxel in men with docetaxel-treated mCRPC. We now report results on other clinical endpoints and PROs reached the pre-specified target of 170 PFS events. Methods: 200 men with mCRPC (median age 72 y, prior enza/abi 91%) and high PSMA-expression by 68Ga-PSMA-11 and no sites of FDG-positive/PSMA-negative disease, were randomly assigned (1:1) to LuPSMA (6-8.5GBq q6wk up to 6 cycles; N = 99) or cabazitaxel (20mg/m2 q3wk up to 10 cycles; N = 101). Secondary endpoints include PSA/radiologic PFS (PCWG3), pain response (≥2 point reduction on McGill-Melzack Present Pain Intensity scale, objective response rate (ORR) (RECIST 1.1), adverse events (CTCAE), PROs (EORTC QLQ-C30) and overall survival (OS). Cut-off date for analysis of 20JUL20. Results: At a median follow-up of 18.4 months, PFS was significantly longer in those assigned Lu-PSMA rather than cabazitaxel (rates at 1y 19% [95%CI 12-27%] vs 3% [1-9%], hazard ratio (HR) 0.63, 95%CI 0.46-0.86; p = 0.003; 173 events). Similar benefit was seen for rPFS (HR 0.64, 95%CI 0.46-0.88; p = 0.007; 160 events) and PSA-PFS (HR 0.60 95%CI 0.44-0.83; p = 0.002; 172 events). ORR in 78 men with measurable disease was significantly greater in the LuPSMA arm (49% vs 24%, RR 2.1, 95%CI 1.1-4.1; p = 0.019). In 90 men with pain at baseline, pain responses occurred in 60% in the Lu-PSMA arm vs 43% for cabazitaxel (RR 1.42, 95%CI 0.84-4.48; p = 0.10). Patient-reported global health status was similar (LuPSMA 64 [95%CI 61-67] vs cabazitaxel 60 [57-64]) with significantly better outcomes reported for fatigue (34 [95%CI 31-37] vs 40 [36-43]), social functioning (79 [76-82] vs 73 [69-77]), insomnia (24 [20-27] vs 29 [25-33]) and diarrhoea (8.3 [5.6-11.0] vs 15.6 [12.6-18.6]) domains. No PRO domains were superior for cabazitaxel. G3-4 AEs were similar to previously reported (33% vs 53%). OS data remains immature (90 deaths). Conclusions: In men with docetaxel-treated mCRPC, LuPSMA is a promising alternative to cabazitaxel with significantly higher activity (PSA≥50%, PFS, ORR), fewer G3-4 AEs, similar effects on global health status, and improvements in some PRO domains. Clinical trial information: NCT03392428.

TheraP: A randomised phase II trial of 177Lu-PSMA-617 (LuPSMA) theranostic versus cabazitaxel in metastatic castration resistant prostate cancer (mCRPC) progressing after docetaxel: Initial results (ANZUP protocol 1603)

5500

Background: LuPSMA is a radiolabeled small molecule that delivers therapeutic β-radiation to PSMA-expressing tumors. Encouraging efficacy and safety has been shown in non-randomized studies of mCRPC. TheraP is a randomized phase II trial comparing LuPSMA vs cabazitaxel in men with mCRPC progressing after docetaxel. Methods: Men with mCRPC, and imaging with 68Ga-PSMA-11 and 18F-FDG PET/CT that confirmed high PSMA-expression and no sites of FDG-positive/PSMA-negative disease, were randomly assigned (1:1) to LuPSMA (6-8GBq q6weeks up to 6 cycles) vs cabazitaxel (20mg/m2 q3weeks up to 10 cycles); stratified by disease burden (>20 vs ≤20 sites), prior novel antiandrogens (NAA; abiraterone or enzalutamide), and study site. The primary endpoint was PSA response rate (PSA50-RR) defined by ≥50% reduction. Secondary efficacy endpoints included PSA-progression-free survival (PSA-PFS) and overall survival (OS). Data cut-off was 31DEC19 at this first pre-specified analysis. Results: 200 (median age 72 y, prior NAA 91%, >20 lesions 78%) of 291 PET screened men were randomised to LuPSMA (N=99) or cabazitaxel (N=101). 17 patients withdrew or died before receiving study treatment (1 LuPSMA vs 16 cabazitaxel). The PSA50-RR was higher in those assigned LuPSMA than cabazitaxel (65/99 [66%; 95%CI 56-75] vs 37/101 [37%; 95%CI 27-46]; P<0.001). At a median follow-up of 11.3 months, LuPSMA significantly improved PSA-PFS (HR 0.63, 95%CI 0.45-0.88, P=0.007; 143 events with next pre-specified analysis planned after 170 events). Efficacy results were similar when analyses were restricted to per-protocol treated men. OS data remains immature (57 deaths). Grade III-IV adverse events (AEs) occurred in 31/98 (32%) LuPSMA-treated men vs 42/85 (49%) in cabazitaxel-treated men. Discontinuations for toxicity occurred in 1/98 (1%) LuPSMA vs 3/85 (4%) cabazitaxel-treated. There were no treatment-related deaths. Conclusions: In men with docetaxel-treated mCRPC, LuPSMA was more active (PSA50-RR) than cabazitaxel with relatively fewer G3-4 AEs and PSA-PFS favoring LuPSMA. Clinical trial information: NCT03392428 .

Pembrolizumab with chemoradiotherapy as treatment for muscle invasive bladder cancer: A planned interim analysis of safety and efficacy of the PCR-MIB phase II clinical trial (ANZUP 1502)

485

Background: In patients (pts) with muscle invasive bladder (MIBC) suitable for curative definitive chemoradiotherapy (CRT), we hypothesise that the addition of pembrolizumab may be safe and improve efficacy. A pre-planned safety analysis was performed after the first 10 of planned 30 pts were enrolled and completed treatment. Methods: Patients with maximally resected non-metastatic MIBC and ECOG 0-1, who desire bladder preservation or are ineligible for cystectomy were treated with 64Gy in 32 daily radiation fractions to the whole bladder alone over 6.5 weeks in combination with 6 concurrent doses of weekly cisplatin at 35mg/m2 IV. Pembrolizumab was commenced concurrently with radiation and given flat-dose 200mg IV q21 days for 7 doses. Surveillance cystoscopy, urine cytology and CT chest-abdomen-pelvis were performed 12 & 24 weeks post CRT. The primary endpoint is feasibility, defined by a satisfactory low rate of unacceptable toxicity of a) G3-4 non-urinary adverse events (AE) or b) failure of completion of planned CRT according to defined parameters. Secondary endpoints include complete cystoscopic response without metastatic disease at 12 & 24 weeks, loco-regional PFS, metastatic DFS, and overall survival. A 2-stage design was planned, with accrual to be halted if >5 of the first 10 pts experienced unacceptable toxicity up to 12 weeks post treatment. Results: All 10 pts completed the course of CRT and pembrolizumab without alteration in radiation dose or schedule. 1 patient had a dose of cisplatin withheld. 4/10 pts experienced G3-4 non-urinary adverse events within 12 weeks of completing treatment. One immune related AE interrupted pembrolizumab delivery (G2 nephritis). By week 24, 9/10 pts achieved a complete cystoscopic response to treatment post CRT and were free of distant metastatic disease. Conclusions: Interim results indicate that pembrolizumab and CRT shows satisfactory safety, and promising efficacy. There were no unexpected safety signals. Follow up of these and additional pts will better define the efficacy and safety of the combination. Enrolment is ongoing with 20 pts recruited out of a planned total of 30. Clinical trial information: NCT02662062.

TheraP: A randomized phase II trial of [177Lu]-PSMA-617 theranostic versus cabazitaxel in progressive metastatic castration-resistant prostate cancer

TPS332

Background: Lutetium-177 [177Lu]-PSMA-617 is a novel radiolabelled small molecule that binds with high affinity to prostate-specific membrane antigen (PSMA), which is commonly overexpressed in prostate cancer. This treatment has demonstrated promising activity and tolerability in men progressing after multiple lines of chemotherapy and endocrine therapy. This trial will determine the activity and safety of 177Lu-PSMA-617 compared to cabazitaxel chemotherapy in men with progressive metastatic castrate resistant prostate cancer. Methods: TheraP is an open-label, randomised, two-arm, multi-centre, phase 2 trial comparing the activity and safety of experimental treatment with [177Lu]-PSMA-617 versus standard 2nd line chemotherapy with cabazitaxel. Key eligibility criteria include prior chemotherapy with docetaxel; rising serum PSA; sufficient PSMA avidity according to central reviewed of imaging with PSMA PET/CT and FDG PET/CT; no discordance between FDG PET and PSMA PET. The trial will include 200 participants randomised in a 1:1 ratio to either [177Lu]-PSMA-617 intravenously every 6 weeks, 8.5 GBq for cycle 1, decreasing by 0.5 GBq with each subsequent cycle, up to maximum 6 cycles (experimental group); or, chemotherapy with cabazitaxel (20 mg/m2) intravenously every 3 weeks, for 10 cycles (standard group). In the event of an exceptional response to [177Lu]-PSMA-617, according to centrally-reviewed, post-therapy SPECT imaging, treatment is suspended but can recommence subsequently on progression. The primary endpoint is a 50% or greater reduction from baseline in serum PSA. Secondary endpoints include overall survival, progression-free survival (PFS), PSA-PFS, pain-PFS, radiographic-PFS, health-related quality of life, pain response, and adverse events. The outcomes of patients excluded because of discordant disease on FDG PET and PSMA PET will be reported as a tertiary objective. The study has accrued 79 of 200 planned participants from 29 January 2018 to 23 October 2018. Clinical trial information: NCT03392428.