This subproject constitutes the central pharmacological platform for investigating the action of inhibitors on human CatSper and Slo3 channels. This involves screening compound libraries, determining the efficacy and selectivity of novel compounds, and supporting design-make-test-analyse cycles. In addition, functional in vitro assays are used to phenotype sperm from men with CatSper- or Slo3-related infertility and to examine whether selective inhibitors of CatSper and/or Slo3 mimic the functional loss of these channels.