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A series of dipyridodiazepinones have been shown to be potent inhibitors of human immunodeficiency virus-1 (HIV-1) reverse transcriptase (RT). One compound, BI-RG-587, had a Ki of 200 nanomolar for inhibition of HIV-1 RT that was noncompetitive with respect to deoxyguanosine triphosphate. BI-RG-587 was specific for HIV-1 RT, having no effect on feline and simian RT or any mammalian DNA polymerases. BI-RG-587 inhibited HIV-1 replication in vitro as demonstrated by in situ hybridization, inhibition of protein p24 production, and the lack of syncytia formation in cultured human T cell lines and freshly isolated human peripheral blood lymphocytes. Cytotoxicity studies of BI-RG-587 on human cells showed a high therapeutic index (greater than 8000) in culture.

Rhinoviruses belong to the picornavirus family and cause about 50% of common colds. Most rhinoviruses and some coxsackie viruses share a common receptor on human cells. The glycoprotein intercellular adhesion molecule-1 (ICAM-1) has recently been identified as the cellular receptor for the subgroup of rhinoviruses known as the major groups. ICAM-1 is a member of the immunoglobulin supergene family and is a ligand for lymphocyte function-associated antigen-1 (LFA-1); these ICAM-1/LFA-1 interactions are critical to many cell adhesion processes involved in the immunological response. Because anti-ICAM-1 antibodies can block binding of major-group rhinoviruses to cells, we considered that antagonism of virus-receptor interaction might be a way of preventing rhinovirus infection. We have constructed and purified a soluble form of the ICAM-1 molecule, which is normally membrane-bound, and demonstrated that it is a potent and specific inhibitor of rhinovirus infection.

A series of dipyridodiazepinones have been shown to be potent inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase. The lead compound, BI-RG-587, had a 50% inhibitory concentration of 84 nM against HIV-1 reverse transcriptase activity. This compound reduced plaque formation of HIV-1 in HeLa cells expressing the CD4 receptor by 50% at 15 nM. BI-RG-587 at comparable concentrations inhibited the production of p24 antigen following the acute infection of CEM T-lymphoblastoid cells or primary human monocyte-derived macrophages with HIV-1. No inhibitory effects against HIV-2 or against three picornaviruses were detected. Zidovudine (3'-azido-3'-deoxythymidine [AZT])-susceptible and AZT-resistant isolates of HIV-1 were equally susceptible to BI-RG-587. AZT and BI-RG-587 exhibited synergistic inhibition of HIV-1BRU at all concentrations examined.

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