Immunopharmocological studies of PTT.119, a new synthetic bis-(2-chloroethyl)amino-l-phenylalanine derivative

The new synthetic tripeptide p-F-Phe-m-bis-(2-chloro-ethyl) amino-Phe-Met-etoxy HCI, PTT.119, was studied for its effects on the host immune system. Doses of PTT.119 ranging from 3 to 18 mg/kg were administered i.p. to recipient mice which, at different times after drug treatment, were tested for allograft response, competence in producing lymphocytes active in lethal graft- versus-host disease, delayed-type hypersensitivity, mitogen responsiveness, humoral antibody production and natural resistance against microbial infections. At therapeutically active dosages, PTT.119 appeared to selectively inhibit functions mediated by B lymphocytes, leaving the majority of those involving T-cell subsets largely unaffected, even at the highest doses employed. Moreover, drug treatment had also a limited impact on the in vivo resistance of mice to microbial infection, which was only affected by a drug injection of 18 mg/kg, a dose well within the confidence limits of the mean lethal dose of the drug.