ongoing effort and will continue to be for the foreseeable future. Recently, an FEP protocol that gives excellent performance in predicting relative binding affinity over a broad range of protein-ligand complexes was reported. This approach used replica exchange with solute tempering (REST2) in combination with the OPLS2.1 force field which was carefully parameterized using an extensive training set of relevant torsional and covalent interactions. The AMBER/GAFF class of force fields are widely used, but have not been extensively validated against such a large data set (8 systems and 330 mutations). To fill this gap we employed the recently implemented GPU-accelerated TI module of Amber18 to repeat the calculations for these systems in order to assess the capabilities of another force field model on this same data set. Overall, our computed results are comparable to the FEP+ result, albeit with slightly larger average errors, indicating that the GPU-TI module of AMBER using the AMBER/GAFF force field is an emerging alternative choice for high-throughput relative binding free energy calculations.