In its many embodiments, the present invention provides a novel class of compounds of structural formula IA or IB where R.sup.1-R.sup.8 are as disclosed herein ##STR00001## as inhibitors of the CCR5 receptors, methods of preparing such compounds, pharmaceutical compositions containing one or more such compounds, methods of preparing pharmaceutical formulations comprising one or more such compounds, and methods of treatment, prevention, inhibition, or amelioration of one or more diseases associated with CCR5 using such compounds or pharmaceutical compositions. The invention also relates to the use of a combination of a compound of this invention and one or more antiviral or other agents useful in the treatment of Human Immunodeficiency Virus (HIV). The invention further relates to the use of a compound of this invention, alone or in combination with another agent, in the treatment of solid organ transplant rejection, graft v. host disease, arthritis, rheumatoid arthritis, inflammatory bowel disease, atopic dermatitis, psoriasis, asthma, allergies or multiple sclerosis.