immediately observed in any of the tumor cell models at these concentrations the cancericidal activity of the tripeptide compound was also greater against uncultured human tumor cells than any of the tumor cell lines after 24 hrs of treatment table 3______________________________________efficacy of thetripeptide salt against human cellshuman leukemic cells obtained by leukophoresis from untreatedpatients were treated with 1 to 50 ug of the tripeptide salt for24 hr tumor cell viability was determined on duplicate samplesfollowing 1 4 and 24 hr exposure concentration tumor cell survival tripeptide exposure hr ug ml 1 4 24______________________________________hairy cell leukemia 5 100 80 34 10 100 71 81 25 92 71 12 50 37 21 7amml 1 95 85 66 5 50 52 66 10 60 41 21 25 20 15 14 50 4 3 4all n cell 1 98 76 25leukemia 5 46 29 7 10 32 15 0 25 15 15 0 50 0 0 0______________________________________ several of the tumor cell models and the primary human leukemias displayed tripeptide compound induced cytotoxicity within 1 to 4 hours of exposure to the tripeptide compound indicating that continuous 24 hr treatment may not be required for the reduction of the tumor cell populations to delineate the minimum concentrations and duration of the tripeptide compound exposure to induce cytolysis mjy alpha and b 16 melanoma cell layers and l 1210 leukemia cell suspensions were exposed to 0 5 to 50 ug of.