Rhodanine derivatives as potent anti-HIV and anti-HSV microbicides

Abstract

Although highly active antiretroviral therapies (HAART) remarkably increased life expectancy of HIV positive people, the rate of novel HIV-1 infections worldwide still represent a major concern. In this context, pre-exposure prophylaxis (PrEP) approaches such as vaginal microbicide gels topically releasing antiretroviral drugs, showed to have a striking impact in limiting HIV-1 spread. Nevertheless, the co-presence of other genital infections, particularly those due to HSV-1 or 2, constitute a serious drawback that strongly limits the efficacy of PrEP approaches. For this reason, combinations of different compounds with mixed antiviral and antiretroviral activity are thoroughly investigated Here we report the synthesis and the biological evaluation of a novel series of rhodanine derivatives, which showed to inhibit both HIV-1 and HSV-1/2 replication at nanomolar concentration, and were found to be active also on acyclovir resistant HSV-2 strains. The compounds showed a considerable reduction of activity in presence of serum due to a high binding to serum albumin, as determined through in vitro ADME evaluations. However, the most promising compound of the series maintained a considerable activity in gel formulation, with an EC50 comparable to that obtained for the reference drug tenofovir. Moreover, the series of compounds showed pharmacokinetic properties suitable for topical formulation, thus suggesting that the novel rhodanine derivatives could represent effective agents to be used as dual anti HIV/HSV microbicides in PrEP approaches.

Fig 1. 2D structures of HIV-1 inhibitors previously published.

Fig 2. Synthesis of aldehyde 6 and derivatives 9a-f.

Synthesis scheme of aldehyde 6: i) Pd(PPh₃)₂Cl₂, Na₂CO₃, DMF/EtOH, RT, 1h; ii) 1N NaOH (aq), MeOH/THF, reflux 2h. Synthesis scheme of derivatives 9a-f: iii) DME, Et₃N, MW (300 W), 90°C, 10 min. iv) aldehyde 6, MW (300 W), 110°C, 5 min.

Fig 3. Antiviral activity of the novel series of rhodanine derivatives on TZM-bl cell line infected with two laboratory strains (NL4.3 and AD8).

Maraviroc (MAR) and raltegavir (RAL) were used as reference compounds. Values represent mean±S.D of three independent experiments. Differences between pre-incubation in complete medium containing FBS are shown, together with the corresponding fold change (ratio). EC₅₀ = Half maximal effective concentration. CC₅₀ = Half maximal cytotoxic concentration. ^apre-incubation in complete medium containing fetal bovine serum (FBS).

Fig 4. Effect of different concentrations of fetal bovine serum (0%, 2%, 5% and 10%) on the antiviral activity of compound 2.

Compound 2 was tested in TZM-bl cells infected with AD8 HIV-1 laboratory strain.

Fig 5. Effect of different concentrations of purified bovine serum albumin on the antiviral activity of compound 2 and maraviroc.

Compounds were tested on TZM-bl cells infected with AD8 HIV-1 strain. No BSA = absence of BSA; 1X = 35 mg/mL BSA; 5X = 175 mg/mL BSA; 10X = 350 mg/mL BSA.

Fig 6. Anti-HIV-1 activity of compound 2 (black line) and tenofovir (T, grey line) in gel, formulation, in human TZM-bl cell line.

Each concentration of both compounds was evaluated in triplicate.