SA 96 (N-(2-mercapto-2-methylpropanoyl)-L-cysteine) in rheumatoid arthritis.

SA 96 (N-(2-mercapto-2-methylpropanoyl)-L-cysteine) is a new sulfhydryl compound having a relatively similar chemical structure to Tiopronin and D-penicillamine. An open trial of SA 96 treatment (300 mg/day after meals for 16 weeks) was carried out in 11 patients with definite or classical rheumatoid arthritis and with therapeutic failure of previous gold salts and/or D-penicillamine therapy. Two cases were withdrawn from the trial, because of a side effect (hepatitis) in one patient and an unrelated illness in another. The results in the 9 patients completing the trial demonstrated statistically significant improvement in the clinical and laboratory measurements. A marked abatement of disease activity was noted in 5 of 9 patients who did not benefit from, or suffered a relapse during previous chrysotherapy and in 1 of 5 patients without benefit, or with relapse following previous D-penicillamine treatment. Among 4 patients who had discontinued D-penicillamine because of its intolerable cutaneous side effects, 3 patients completed the trial, with favourable results. The results of this trial seem to indicate that SA 96 is possibly of value as a slow-acting antirheumatic drug in some patients with therapeutic failure of gold salts or D-penicillamine.