Development of Trojan Horse Dimeric Inhibitors of P-Glycoprotein to Target HIV Reservoirs in the Brain

HIV/AIDS has emerged as an incredibly serious infectious disease. The complete eradication of HIV is hindered by virus reservoir formation in the host. Some of the locations of these reservoirs include the central nervous system (CNS), resting memory CD4+ T-cells and macrophages. One of the reasons reservoirs of HIV are maintained in the brain is attributed to the limited accessibility of many anti-HIV drugs across the blood-brain barrier (BBB). Therefore, improving the penetration of anti-HIV therapeutics across the BBB is a significant challenge in the eradication of HIV. P glycoprotein (P-gp), an ATP Binding Cassette (ABC) family transporter expressed at the apical side of BBB, has been shown to restrict the permeation of anti-HIV therapies across the BBB and hence, contribute to the limited penetration by anti-HIV drugs. The inhibition of P-gp efflux activity is a promising strategy for improving the penetration of ARTs across the BBB and thereby, leading to the prevention of HIV reservoir formation. Here, we present an innovative approach towards the development of Trojan Horse heterodimeric prodrugs based on the HIV-1 nucleoside reverse transcriptase inhibitor (NRTI) –abacavir and protease inhibitors (PIs)-atazanavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir. We have designed TH prodrugs to be functionally equivalent to HAART with better permeability at the sites protected by P gp. TH heterodimers are expected to be bifunctional: (1) inhibit P glycoprotein by occupying the substrate binding sites in the transmembrane domain and (2) act as antiviral prodrugs that gain entry into the cell and revert to two different therapeutics in the reducing environment of the cell. The Trojan Horse heterodimeric prodrugs are expected to deliver two different therapies inside the same cell with higher permeation due to P gp inhibition. All the TH heterodimeric were found to inhibit P-gp mediated efflux of fluorescent substrates in T-cells as well as model blood-brain barrier cell lines. Two TH heterodimeric were found to inhibit HIV-1 replication in 12D7 cells most effectively which proved that they were taken up by the cells and reverted into active drugs intracellularly to inhibit HIV 1 replication. Thus, our TH heterodimers fulfilled the two essential criteria for the eradication of HIV reservoirs in the body: penetration across the cell membrane and release of monomeric drug in the intracellular reducing environment