Subacute toxicity of muroctasin in mice and dogs

The subacute toxicity of N2-[(N-acetylmuramoyl)-L-alanyl-D-isoglutaminyl]-N6-stearoyl-L-lysine (MDP-Lys (L18), muroctasin), a synthetic muramyl dipeptide, was investigated in mice and dogs. Both species exhibited leukocytosis, immunologically activated appearances of the axillary lymphnode and splenic white pulp, and irritatic lesions at the injection site, when treated with MDP-Lys(L18) for 4 weeks. Anemia, and synovitis were also found in dogs. These findings reflected main pharmacological action of MDP-Lys(L18), though there was some species difference.