Specifically looking at each individual case, we start with a fragment elaboration for the PWWP1 domain of NSD3 by Böttcher et al. . Here 11 ligands were elaborated from an initial 160 µM fragment hit (ligand 8), eventually resulting in the 170 nM ligand BI-9321 ( SI Fig. , Table ). As shown in Fig. , the ABFE results correlate very well with experiment, with an RMSE of 1.14 ± 0.16 kcal/mol, the lowest of all four optimisation campaigns investigated. In the original elaboration study, seven specific elaboration decisions were outlined (SI Table ). Of these, only two would have been definitively supported by our ABFE results, that is to say -there is a greater-than-error difference between the calculated ligand binding energies in each decision. Whilst the ABFE results accurately predict the direction of the affinity change for six of the seven decisions, the majority of the changes in free energy remained within the range of the errors of the estimates. We note that the one decision where the wrong sign is predicted involves experimental ΔΔG values of -0.12 and -0.23 kcal/mol, which is well within the limit of both experimental and force field 99 accuracy.