For the relative binding free energy prediction portion of the challenge, BACE_10 was specified as the reference ligand by GC4 organizers. We subtracted the MM-GBSA score of BACE_10 from our MM-GBSA scores and submitted the results as relative binding free energy predictions in Stage 1a and Stage 2. The predictions aren't necessarily relative binding free energies, but we wanted to see whether there might be any correlation with relative binding free energies with this approximation. Although we had initially planned to do alchemical free energy calculations for the binding free energy predictions, the short time frame of this challenge and the complexity of handling macrocycles in alchemical calculations made us favor MM-GBSA calculations.