My research focuses on the biotechnological production of hydroxylated metabolites of Salmeterol and ACP-105 to generate high-quality referencematerials for anti-doping analysis. Using recombinant Schizosaccharomyces pombe strains expressing human CYP enzymes, I optimize whole-cellbiotransformation processes through a design-of-experiments approach toachieve efficient metabolite formation. After establishing optimal conditions on the analytical scale, the process is scaled up in a bioreactor to produce the required amounts. The generated compounds arepurified by chromatography and comprehensively characterized usinghigh-resolution mass spectrometry, NMR, and qNMR. This work enables the provision of stable, well-defined reference materials for WADA-accredited laboratories.