Background: Novel treatments for clinically advanced GUca including castrate resistant prostate ca (PC), bladder urothelial ca (BUC) and clear cell renal ca (ccRCC) are widely needed. Recently, the targeting of cancer cells with arginine accumulation caused by MTAP loss has emerged as a new synthetic lethality-based anti-cancer program. Methods: 8,436 mCRPC, 2,683 BUC and 841 ccRCC underwent hybrid-capture based comprehensive genomic profiling (CGP) to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on up to 114 loci. PD-L1 tumor cell expression was determined by IHC (Dako 22C3). Results: 1.3% of PC, 24.2% of BUC and 5.5% of ccRCC featured MTAP loss. There were no significant age or gender differences associated with MTAP loss. CDKN2A/B loss ranged from 94% in ccRCC to > 99% in PC and BUC. The GA/tumor frequencies were similar when CDKN2A/B GA are excluded. In PC, GA in TP53, PTEN and BRCA1 were more frequent, while GA in AR, CDK12, RB1 and BRCA2 were less frequent in cases with MTAP loss. In BUC, GA in TSC1 and FGFR3 were more frequent and GA in RB1and TP53 were less frequent in cases with MTAP loss. In ccRCC, GA in NF2 were more frequent in cases with MTAP loss, while GA in VHL and PBRM1 were less frequent in cases with MTAP loss. “Targetable” kinase GA were rare in all groups, except for FGFR3 GA in MTAP loss BUC. Immunotherapy (IO) putative biomarkers varied among tumors, with MSI-high status less frequent and TMB ≥ 10 mut/Mb more frequent in BUC MTAP-intact than BUC with MTAP loss. PD-L1 expression was similar except for high PD-L1 expression more frequent in MTAP-intact BUC. Conclusions: When compared with PC and ccRCC, the clinical development of novel drugs, such as PRMT5 and MTA2 inhibitors in GUca will likely be focused on BUC given the 24% frequency of MTAP loss in that tumor type. CGP of PC, BUC and ccRCC reveal significant differences in GA in MTAP-intact and tumors with MTAP loss, which may impact future combinatorial clinical trial designs.