Subsequent optimization studies on 65 generated molecules strongly able to inhibit HIV-1 infection in vitro [187,188,189,190], including indolylglyoxylamide 66 (Table 3), which possessed nanomolar EC50 values (4.0 and 4.9 nM against two different viral strains, C-C chemokine receptor type 5 (CCR5)-dependent JRFL and CXC-chemokine receptor 4 (CXCR4)-dependent LAI strains of HIV-1, respectively) and no cytotoxicity to the HeLa host cell line, with a 20-fold improvement in potency compared to 65 (EC50 = 86 ± 24 nM in CXCR4-dependent LAI strain of HIV-1) [188]. This evidence concerns the gene CXCR4 and HIV-1 infection.