My group employs a wide range of techniques to study drug metabolism. These include chemical and enzymatic synthesis of drugs and their metabolites, methods of in vitro metabolism coupled with analysis by GC-MS-MS or LC-MS-MS and molecular biology to engineer improved enzymes with anti-doping applications.
Novel methods to detect designer steroids
Designer steroids are steroidal compounds that have been developed to evade methods of drug detection. Typically containing unusual structural features, these compounds have never been studied for use as therapeutic agents and little if anything is known about their safety or efficacy. Given the absence of toxicological data, ethical considerations usually preclude the in vivo study of these compounds in humans. Work in collaboration with Racing NSW - Australian Racing Forensic Laboratory (Drug Test. Anal. 2015, see here) has developed a pipeline involving the in vitro metabolism, chemical synthesis and characterisation to study designer steroid metabolism leading to the development of new detection methods for these compounds (ARC Linkage Project). The detailed study of designer steroid metabolism offers the potential to develop untargeted testing strategies that will lead to the early detection of new designer agents.
Pipeline to study designer steroid metabolism with local capabilities highlighted in red and designer steroid hemapolin inset.
New enzymes for the analysis of sulfate metabolites
Sulfate esters are a major class of drug metabolite. Recent research shows that some steroid sulfates can act as long term indicators of steroid administration or serve as markers to distinguish between steroids of exogenous and endogenous origin. Despite the emerging importance of steroid sulfates in drug detection there are no generally accepted methods for the hydrolysis of steroid sulfates, which is required prior to employing many methods of analysis. Recently (Drug Test. Anal. 2015, see here), we discovered that the arylsulfatase from Pseudomonas aeruginosa serves as a catalyst for the mild hydrolysis of a range of steroid sulfates (Commonwealth of Australia, Anti-Doping Research Program). This purified enzyme is available on large scale and provides an ample supply of sulfatase activity or anti-doping applications. The enzyme also serves as a useful starting point to engineer improved variants of the parent sulfatase with greater activity and broader substrate scope (WADA Scientific Research Grants).
Hydrolysis of testosterone 17-sulfate to testosterone by the P. aeruginosa arylsulfatase and a cartoon of the sulfatase (PDB 1HDH) looking into the enzyme active site.
Other projects within the group include the development of new chemical and enzymatic methods for the synthesis of drug metabolites and the discovery of innovative strategies for drug metabolite detection based on phase II conjugates.