Pre-steady state kinetic analysis was utilized for biochemical evaluation of a series of cyclobutyl adenosine nucleotide analogs with HIV-1 RTWT. The phosphonyl-diphosphate form of the cyclobutyl nucleotide, 5, was the most efficiently incorporated of the series. Nucleotide 5 was fourfold more efficiently incorporated than the FDA approved TFV-DP by RTWT. The kinetics of incorporation for 5 using the drug resistant mutant enzyme K65R ...