The graph shows that the van der Waals energy of the drug-protein complex initially fluctuates around a value of -190 kcal/mol. This suggests that the drug-protein complex is initially in a stable configuration with a strong van der Waals interaction between the protein and the ligand. However, the van der Waals energy then starts to decrease over time. This suggests that the drug-protein complex is becoming less stable over time and that the van der Waals interaction between the protein and the ligand is weakening.