Anti-HIV-1 activity of the neurokinin-1 receptor antagonist aprepitant and synergistic interactions with other antiretrovirals

Abstract

Objectives: Neurokinin-1 receptor (NK1R) antagonists interfere with binding of neuropeptide substance P to NK1R and exhibit novel anti-HIV-1 activities. Since NK1R antagonists effectively penetrate the blood-brain barrier to reduce the inflammatory response within the brain, we wished to evaluate their potential as anti-HIV-1 candidates for targeting HIV-1 infections of the central nervous system.

Design: A series of small molecule agents were evaluated for anti-NK1R and anti-HIV-1 activity using peripheral blood mononuclear cells (PBMCs). The most promising of these, aprepitant (Emend, Merck and Co. Inc.), was investigated for potential synergies with other antiretroviral drugs.

Methods: Anti-NK1R activity was tested by measuring intracellular calcium increase triggered by substance P. Anti-HIV-1 activity was evaluated by measuring p24 antigen in culture supernatants of PBMC following exposure to HIV. The concentration of drug which produced 50% reduction in intracellular calcium levels or viral production in 7-day PBMC cultures was determined. The combined effect of aprepitant with each of the major classes of anti-HIV-1 drugs was evaluated in synergy studies.

Results: Aprepitant had the highest anti-HIV-1 activity of the NK1R antagonists examined and was equally active against all major HIV-1 subtypes. Aprepitant acted synergistically with protease inhibitors (ritonavir and saquinavir), but not with nucleoside reverse transcriptase, non-nucleoside reverse transcriptase, or viral entry inhibitors.

Conclusion: The ability of aprepitant to penetrate the blood-brain barrier, its safety record as an FDA-approved drug for reducing nausea and vomiting in chemotherapy, and synergistic activity with other anti-HIV-1 drugs make it a promising candidate for treatment of HIV infection.

Figures

Figure 1

A. Viral replication in isolated PBMC was measured by assaying p24 in cell culture media collected from cells infected with either HIV-1 BaL or HIV-1 NL4-3, at varying concentrations of aprepitant to determine the concentration at which virus replication is inhibited by 50% (IC50). B. The 50% cytotoxic concentrations (CC50) were determined in uninfected cells. All results represent the average of triplicate measurements.

Figure 2. Effect of NK1R Antagonists on SP-Induced Intracellular Calcium

Effect of NK1R antagonists on SP-induced intracellular calcium increase in U373MG astrocytoma cells. U373 MG cells were incubated in the presence of different concentrations of antagonist then substance P (100 nM) was added to medium while intracellular calcium concentrations were recorded as described under Materials and Methods. Curves were fitted to data by non-linear regression and they were used to calculate the EC50 values listed in Table 1.

Figure 3. Synergy Studies of Aprepitant with HAART Drugs

Synergy studies of aprepitant with known HAART drugs. Serial dilutions of aprepitant (0×, 0.1×, 0.5× and 2.0× IC50) with the respective drugs were tested on PBMC infected with HIV-1 BaL virus. The 1 × IC50 values for each drug (in μM) are shown under each figure. Viral inhibition as measured by p24 after 5 days of infection is shown..