Chemotherapy agents were fixed at the 90% lethal dose for each agent. Each EC₅₀ measurement comprised six concentrations with four wells per concentration, and each dose response was performed twice for each protectant. EC₅₀ concentrations, in micrograms per milliliter are reported as the average ± pooled standard deviation for two independent experiments. For the combination ofd-methionine with melphalan, protection was not detected. For each chemoprotectant, t test comparisons were done for melphalan versus cisplatin, cisplatin versus carboplatin, and carboplatin versus melphaln, and significant differences are indicated.

• ↵1-160  P < 0.01;

• ↵1-165  P < 0.001.