A Parallel Synthesis Approach to the Identification of Novel Diheteroarylamide-Based Compounds Blocking HIV Replication: Potential Inhibitors of HIV-1 Pre-mRNA Alternative Splicing

Abstract

A 256-compound library was evaluated in an anti-HIV screen to identify structural "mimics" of the fused tetracyclic indole compound 1 (IDC16) that conserve its anti-HIV activity without associated cytotoxicity. Four diheteroarylamide-type compounds, containing a common 5-nitroisobenzothiazole motif, were identified as active. In subsequent screens, the most potent compound 9 (1C8) was active against wild-type HIV-1IIIB (subtype B, X4-tropic) and HIV-1 97USSN54 (subtype A, R5-tropic) with EC50's of 0.6 and 0.9 μM, respectively. Compound 9 also inhibited HIV strains resistant to drugs targeting HIV reverse transcriptase, protease, integrase, and coreceptor CCR5 with EC50's ranging from 0.9 to 1.5 μM. The CC50 value obtained in a cytotoxicity assay for compound 9 was >100 μM, corresponding to a therapeutic index (CC50/EC50) of approximately 100. Further comparison studies revealed that, whereas the anti-HIV activity for compound 9 and the parent molecule 1 are similar, the cytotoxic effect for compound 9 was, as planned, markedly suppressed.

Modulation of the splicing regulatory function of SRSF10 by a novel compound that impairs HIV-1 replication

“…Using the T cell-based CEM-GXR reporter cell line, 1C8 was the most active compound (Figure 1A). With half maximal effective concentration (EC 50 ) values ranging between 0.6 and 1.5 μM, 1C8 inhibited replication of wild-type HIV-1 (subtypes A and B), as well as representative strains resistant to drugs that target viral reverse transcriptase, protease, integrase and the cellular co-receptor CCR-5 (17). Moreover, 1C8 elicited very modest changes in cell viability (17).…”

“…With half maximal effective concentration (EC 50 ) values ranging between 0.6 and 1.5 μM, 1C8 inhibited replication of wild-type HIV-1 (subtypes A and B), as well as representative strains resistant to drugs that target viral reverse transcriptase, protease, integrase and the cellular co-receptor CCR-5 (17). Moreover, 1C8 elicited very modest changes in cell viability (17). Here, we now show that 1C8 also inhibits HIV-1 replication in human peripheral blood mononuclear cells (PBMCs) (Figure 1B), with no significant impact on cell viability (Figure 1C).…”

“…Compound 1C8 was identified as the most active compound, and subsequent viability studies revealed that it displayed very low cellular toxicity (17). Given that 1C8 was inspired by the structure of the SRSF1 inhibitor IDC16 (16), we tested the impact of 1C8 on HIV-1 expression, splicing, and the activity of selected SR proteins.…”

Can the HIV-1 splicing machinery be targeted for drug discovery?

“…It was also able to inhibit viral production in isolates from patients where the infection had developed resistance to HIV multi-therapies. This small fused tetracyclic indole molecule functions by inhibiting the splicing activity of ASF 47,48. Other advantages to IDC16 include low cellular toxicity, based on initial reports, and the fact that the virus would struggle to develop resistance to the drug.…”

“…In order to improve the activity and decrease the cytotoxicity of these compounds, a parallel synthesis of IDC16 mimics was performed and an active diheteroarylamide-type compound was identified. This compound was named compound 9 (1C8), and although it had the same antiviral activity as IDC1, it had a lower level of cytotoxicity 48. Another inhibitor of SR proteins is the isonicotinamide compound SRPIN340, which inhibits the SR protein kinases SRPK1 and SRPK2.…”