Methylthio-capping of selenocysteamine: preliminary studies on selective toxicity for cancer chemotherapy

Dimethyl disulfide markedly increased the cytotoxicity of selenocystamine by 2 orders of magnitude, from 40 microM to 0.5 microM for 50% inhibition of growth in 45 hr. When mice were injected ip with 22 microMole/Kg of selenocystamine on Day 0, all were dead on Day 4. If dimethyl disulfide (500 microMole/Kg) was either mixed with the selenocystamine or injected immediately prior to it, the mice survived treatment for at least 21 days afterwards, suggesting that methylthio-capping of selenocysteamine reduced host toxicity. Such combined treatment may be of value in chemotherapy.