Bisphosphonate compounds and related methods of making and using are disclosed, including pyridinium-1-yl, quinolinium-1-yl, and related compounds. The activity of compounds is disclosed in the context of functional assays such as Leishmania major farnesyl diphosphate synthase (FPPS) inhibition, Dictyostelium discoideum growth inhibition, human gamma delta T cell activation, and bone resorption. The applicability of bisphosphonate compounds in the context of parasitic infections, for example against trypanosomes, is disclosed. Further potential applications of the invention are disclosed regarding the treatment of one or more conditions such as bone resorption disorders, cancer, bone pain, infectious diseases, and in immunotherapy.