A molecular mechanism involved both in HIV-entry and -fusion steps has been disclosed in detail: The interaction of an HIV envelope protein, gp120, with chemokine receptors, CXCR4 and CCR5, which were identified as major co-receptors in association with CD4, triggers conformational changes in the gp120-gp41 (another envelope protein) complex, and subsequently forms the trimer-of-hairpins structure of gp41 followed by virus-cell membrane fusion. The elucidation of the above dynamic supramolecular mechanism in HIV-entry and -fusion has provided insights into new type of drugs that can block HIV infection. Based on this, we have developed not only coreceptor antagonists (1) but also fusion inhibitors (2). (1) Potent CXCR4 antagonists, T22 and T140, have been developed through the structure-activity relationship studies on tachyplesins and polyphemusins that are horseshoe crabs antimicrobial peptides. T22, which was initially found to bind gp120 and CD4, and T140 selectively suppress T-cell line-tropic HIV-1 (X4-HIV-1) entry based on their specific binding to CXCR4. Furthermore, molecular-size reduction of T140 using cyclic pentapeptide templates brought us to find low molecular weight CXCR4 antagonists, such as FC131. (2) Artificial remodeling of a gp41 fragment, C34, has led to development of strong inhibitors of HIV-fusion into cells. These fusion inhibitors effectively block the formation of the trimer-of-hairpins structure of gp41. HIV-entry/fusion inhibitors such as CXCR4 antagonists and C34 analogs would improve the clinical chemotherapy of AIDS and HIV-infected patients. This review article focuses on our recent research on the development of the above two types of inhibitors, including comparative studies with several CXCR4 antagonists besides T22/T140-related compounds and other fusion inhibitors such as Fuzeon (T-20).
Keywords: aids, chemokine, low molecular weight cxcr antagonist, x-hiv entry, cancer metastasis, rheumatoid arthritis, fusion inhibitor, artificial remodeling