Randomized phase II study of docetaxel (D) + abiraterone acetate (AA) versus D after disease progression to first-line AA in metastatic castration-resistant prostate cancer (mCRPC): ABIDO-SOGUG Trial

95

Background: Abiraterone acetate (AA) improves OS and rPFS in first line mCRPC patients (pts). After AA progression D is commonly used as standard second line therapy. However, the value of maintaining AA in combination with D despite progression has not been tested beyond small exploratory studies (Tagawa ST, Eur Urol 2016) ABIDO is a randomized-phase II trial that evaluates efficacy and safety of D + AA vs D after first-line AA progression in mCRPC. Methods: Asymptomatic or minimally symptomatic mCRPC pts with no visceral metastases, ECOG PS 0-1, and adequate organ functions were included. The study has two stages: In stage I pts receive AA (1000 mg/d + prednisone (P) 10 mg qd) until radiological or unequivocal clinical progression. In stage II pts were randomized to D 75 mg/m2 q3wk in combination with AA 1000 mg/d (arm A) or without AA (arm B) The primary endpoint was rPFS and the secondary endpoints radiological response (RR), OS, PSA-response, PSA-PFS and safety. Results: 88 pts were randomized, (46 arm A, 42 Arm B). Median age was 69 y/o, 43% had ECOG 0 and 91%/11%/5% had bone, liver and lung metastases. Median rPFS was 11.4 months (m) in arm A vs 10.5 m in ARM B; 12-m rPFS was 43% vs 45%; Median PSA PFS was 6.2 vs 5.5 m and median OS was 17.3 vs 16.9 m. Twenty four pts (52%) in arm A and 19 (46%) in arm B achieve ≥50% PSA response. RR was achieved in 15% vs 7% of pts and disease control rate in 74% in both arms. No statistically significant differences were found in efficacy parameters. Half of pts received 10 cycles of D (median 7 and 8). D median dose intensity was 86% and 90% for each arm and 91% for AA. Eleven pts discontinued treatment due to non-hematological toxicity, 5 in arm A and 6 in arm B. Most frequent G3-4 toxicities per arm (A/B) were: neutropenia (57%/29%; P=0.027), febrile neutropenia (17%/10%), diarrhea (9%/7%), and asthenia (11%/10%). Conclusions: ABIDO trial was unable to demonstrate the significant clinical benefit of maintenance AA approach + D after AA first-line therapy. No differences were observed in RR, PSA PFS, rPFS and OS. In AA + D cohort, more frequent and severe hematological toxicity (neutropenia and febrile neutropenia) were reported. Clinical trial information: NCT02036060.

Atezolizumab (atezo) therapy for upper tract (UT) urothelial carcinoma (UC): Subgroup analysis of the single-arm international SAUL study in pretreated locally advanced/metastatic urinary tract carcinoma

488

Background: UTUC is rarer than bladder UC and typically responds poorly to standard chemotherapy. Analysis of 220 biomarker-evaluable atezo-treated patients (pts) in phase II/III trials suggested worse outcomes in UT vs lower tract UC [Galsky, ESMO 2018]. We explored clinical outcomes in pts with UTUC (renal pelvis or ureter) treated with atezo in the SAUL study. Methods: The single-arm SAUL study (NCT02928406) [Sternberg, Eur Urol 2019] enrolled a broader pt population, including pts with poor clinical characteristics and/or immune-mediated conditions, more representative of real-world practice than typically enrolled in randomized phase III immunotherapy trials. Pts with urinary tract carcinoma received atezo 1200 mg q3w until disease progression/unacceptable toxicity. Baseline characteristics, safety and efficacy were analyzed in subgroups of pts with UTUC (subdivided into renal pelvis or ureter UC) vs bladder UC. Results: Baseline characteristics in the 4 subgroups were generally similar, except for a numerically lower proportion of pts with 0 prior lines of therapy for metastatic disease in the UTUC vs bladder UC subgroup (30% vs 41%). Treatment exposure, safety and efficacy are shown below. Conclusions: These exploratory analyses of SAUL showed very similar efficacy and safety in UT vs bladder UC. This provides reassurance that atezo is active and has an acceptable safety profile in pts with UTUC, who are generally expected to have worse outcomes than bladder UC pts. Clinical trial information: NCT02928406 . [Table: see text]

Overall survival results for durvalumab and savolitinib in metastatic papillary renal cancer

619

Background: There is a strong rationale for investigating MET and PD-L1 inhibition in metastatic papillary renal cancer (PRC). We previously reported response rates (RR) and progression free survival (PFS) for savolitinib (MET inhibitor) and durvalumab (PD-L1 inhibitor) together. Here we report overall survival (OS) data available 12 months after the last patient was enrolled. Methods: This single arm phase I/II trial explores durvalumab (1500mg Q4W) and savolitinib (600mg OD) together in PRC, with a 4wk savolitinib run in. Treatment naïve or previously treated patients with metastatic PRC were included. Confirmed RR (RECIST v1.1), PFS, tolerability (CTCAE v4.03) and overall survival (OS) were analysed. MET and PD-L1 biomarkers were explored (NCT02819596). Results: 42 patients were enrolled with 41 receiving at least one dose of study treatment. Safety and efficacy analyses were performed on these 41 patients. The median follow up was 14.3 months. IMDC good, intermediate and poor risk disease occurred in 29%, 63%, and 7% of patients respectively. Overall confirmed RR was 27% while median PFS was 4.9 months (95% CI: 2.5 – 12.0 months). Median OS was 12.3 months (95% CI: 5.8 – 21.3 months). Confirmed RR and median OS in the previously untreated cohort (N=27) were 33% and 12.3 months (95% CI: 4.7 – not reached (NR) months) respectively. Treatment related Grade 3/4 toxicity occurred in 34% of patients. No new safety signals were seen. PD-L1 and MET expression were not associated with higher RR (25% and 40% respectively) or longer OS. Conclusions: The combination of savolitinib and durvalumab has clinical activity in PRC and outcomes were not enhanced in biomarker positive cancers. Clinical trial information: NCT02819596.