This invention relates to novel compounds that are piperazine derivatives, and pharmaceutically acceptable salts thereof. More specifically, the invention relates to novel piperazine compounds that are derivatives of the chemokine CCR5 receptor antagonist, vicriviroc. This invention also provides pyrogen-free compositions comprising one or more compounds of the invention and a carrier and the use of the disclosed compounds and compositions in methods of treating diseases and conditions that are treated by administering chemokine CCR5 receptor antagonists, such as vicriviroc. The invention also relates to the use of one or more of the disclosed compounds as reagents in analytical studies involving vicriviroc.