Targeted sialidases can also reduce tumor burden in in vivo cancer models, as was observed with T-sia 2 delaying HER2+ tumor growth in a mouse breast cancer model.5 Follow-up in vivo work used a further optimized antibody-enzyme conjugate from Palleon Pharmaceuticals (E-301), comprised of two Salmonella typhimurium sialidase domains fused to the anti-HER2 antibody, trastuzumab. This evidence concerns the gene ERBB2 and breast cancer.