Results from recently completed studies suggested that the NH2-naphthyl-diarylpyrimidine JX-7 displayed remarkable inhibitory activity against wild-type HIV-1 (EC50 = 5 nM) and numerous clinically observed variants in MT-4 cells; however, its high cytotoxicity (CC50 = 19 μM) precluded its further development as a clinical candidate. One approach we took to improve the safety involved replacing the naphthyl of JX-7 with biphenyl to provide a series of novel NH2-biphenyl-DAPYs. Investigation of the structure-activity relationships (SARs) led to the identification of 4ab, a potent NNRTI with significantly reduced cytotoxicity (CC50 = 120 μM), approximately 6-fold lower than JX-7, which maintained remarkable anti-HIV-1 activity against wild-type HIV-1 (EC50 = 1.9 nM) and multiple mutant strains simultaneously. Also, 4ab displayed weak CYP sensitivity, little inhibition of hERG, and no apparent in vivo acute toxicity. These promising results demonstrate that 4ab can be used as a drug candidate for HIV-1 therapy.