SMART: A phase II study of sacituzumab govitecan (SG) with or without atezolizumab immunotherapy in rare genitourinary (GU) tumors such as small cell, adenocarcinoma, and squamous cell bladder/urinary tract cancer, renal medullary carcinoma (RMC) and penile cancer.
Andre R. Kydd, Elias Chandran, Nicholas I. Simon, Saad Atiq, Tzu-fang Wang, Lisa M. Cordes, Elizabeth Smith, Matthew Lindsley, Lisa Ley, Salah Boudjadi, Scot A. Niglio, Sally Weng, Ian Stukes, Md Shahid Sarwar, Rouf Banday, Dilara Akbulut, Sandeep Gurram, Bernadette Redd, Seth M. Steinberg, Andrea B. Apolo
Abstract
TPS4627 Background: Rare tumors of the GU tract often exhibit aggressive clinical behavior, yet lack effective standard of care treatment options. SG is an antibody-drug conjugate (ADC) targeting trophoblastic cell surface antigen 2 (Trop2) with a payload of SN-38, a topoisomerase inhibitor. SG monotherapy gained accelerated approval in pts with metastatic urothelial carcinoma (mUC) post platinum and immune-checkpoint inhibitor (ICI) therapy based on the TROPHY-U-01 trial (Tagawa S et al., JCO 2021). Atezolizumab is an anti-PD-L1 ICI approved for use in multiple solid tumors. SMART will evaluate the efficacy and safety of SG monotherapy or SG plus atezolizumab in select rare GU tumors. Methods: SMART is an open-label, non-randomized, Phase 2 trial. Pts must have locally advanced (unresectable) or metastatic GU tumors of the following histologies: small cell carcinoma, squamous cell carcinoma, or primary adenocarcinoma of the bladder or urinary tract, RMC, or squamous cell carcinoma of the penis. Pts may be treatment-naïve or have received any number of prior therapies; pts with small cell carcinoma must have received a platinum-based regimen. Pts treated with a PD-1/PD-L1 ICI will be assigned to Cohort A/Treatment Arm 1 and will receive SG monotherapy (10mg/kg IV, D1 and D8 of 21 day cycles). Pts without prior ICI treatment will be assigned to Cohort B/Treatment Arm 2 and will receive SG (10mg/kg IV, D1 and D8 of 21 day cycles) with concomitant atezolizumab (1200mg IV, D1 of 21 day cycles). Treatment will continue until disease progression (max duration of treatment 5 years) or intolerable side effects. The primary endpoint is objective response rate (ORR) (RECIST v1.1) for each Cohort, with restaging every 3 cycles. Secondary endpoints include safety, clinical benefit rate (CR+PR+SD), median PFS/OS for each Cohort, and ORR for each histology. Exploratory analyses include determination of baseline tumor mutation and transcriptional profile, Trop2 expression, ctDNA/CTCs, peripheral blood immune subsets and cytokine profile correlation with response, and correlation of UGT1A1 allele genotype with response and safety. This study utilizes a Simon minimax two-stage design, with enrollment of up to 43 evaluable pts (accrual ceiling of 60 pts). Cohort A will enroll 11 pts in Stage 1; if 1 or more of the first 11 pts has a response (unacceptably low rate of 5%, p0=0.05; alpha 0.10, beta=0.20), accrual will continue into Stage 2 up to 18 evaluable pts. Cohort B will enroll 16 evaluable pts in Stage 1; if 2 or more pts have a response (unacceptably low rate of 10%, p0=0.10; alpha 0.10, beta=0.10), accrual will continue in Stage 2 up to a total of 25 evaluable pts. This study is open at the NIH Clinical Center (CC); enrollment may open at 1-2 additional centers. Clinical trial information: NCT06161532 .