Modeling BoNT/A4 HCC with the SV2C β-peptide showed that D1141 of HCC/A4 inserts into the phenyl ring R-group of SV2C F563 (Figure 5), where the close proximity of the negatively charged aspartic acid and the aromatic phenylalanine may disrupt binding via anion–pi pair repulsion [45], leading to a steric distortion of the Hcc-LD4 binding interface. Here, SV2C is linked to hepatocellular carcinoma.