The rapid emergence of synthetic cannabinoid receptor agonists (SCRAs) poses challenges for drug testing, particularly when analyzing urine samples due to the rapid metabolization of the parent compounds. In early 2023, two novel SCRAs were reported to the European Union Drugs Agency (EUDA): ADMB-3TMS-PrINACA and Cumyl-3TMS-PrINACA, which are both indazole SCRAs featuring a trimethylsilyl propyl moiety connected to the tertiary indazole nitrogen. Peaks corresponding to metabolites of ADMB-BINACA (also known as ADB-BUTINACA) and Cumyl-4CN-BINACA observed with retention time shifts in a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for detecting SCRAs were later identified as metabolites of ADMB- and Cumyl-3TMS-PrINACA. Pooled human liver microsome (pHLMs, 25 µmol/L) and pooled human hepatocyte (PHH, 20 µmol/L) assays were performed to generate metabolites. Additionally, human urine samples were analyzed by reversed phase liquid chromatography-quadrupole-time-of-flight-mass spectrometry (LC-QToF-MS), assisted by GLORYx and BioTransformer 3.0 for in silico metabolite prediction. Gas chromatography-mass spectrometry (GC-MS) was used to identify substances in seized materials. In total, 34 metabolites for ADMB-3TMS-PrINACA and 38 for Cumyl-3TMS-PrINACA were tentatively identified. Major biotransformations included side chain monohydroxylation (specific markers) and TMS-group cleavage, likely initiated by oxidative Si-demethylation followed by further hydroxylation resulting in an N-3-OH-propyl metabolite and further oxidation to the respective N-propionic acid. Most of these biomarkers were detected in the blood, urine, and stomach content of a deceased poly-drug user exposed to ADMB-3TMS-PrINACA. Overall, Cumyl-3TMS-PrINACA was more prevalent than ADMB-3TMS-PrINACA in Germany according to routine urine testing. This work provides the first investigation of the metabolic fate and suggests biomarkers for these new SCRAs.