A comparative study of the antitumor effectiveness of E. coli and Erwinia asparaginases.

The relative antineoplastic effectiveness of E. coli and Erwinia asparaginases was tested against lymphoid leukemias EARAD-1 and L5178Y/CA55. E. coli and Erwinia asparaginases had similar clearance rates from plasma in mice, and at a dose of 250 IU/kg body weight both enzymes lowered plasma asparagine to undetectable levels. Nevertheless, the dosage of Erwinia asparaginase needed to cause similar prolongation of median survival time in leukemic mice was at least twice that of E. coli asparaginase. The factors which may be responsible for the more potent therapeutic effectiveness of the E. coli asparaginase are discussed.