Animal experiment:

Mice[2]D,L-Buthionine-(S,R)-sulfoximine is dissolved in sterile 0.9% saline, filtered through a 0.2-p.m polysulfone membrane filter, and administered by 48-h continuous iv. infusion at a dose of 300 mg/kg/day and 600 mg/kg/day starting at 24 h before doxorubicin administration. In vivo GSH levels after treatment with D,L-Buthionine-(S,R)-sulfoximine at a dose of 300 mg/kg and 600 mg/kg for 24 h as an iv. continuous infusion in munine plasma and in tumor tissue of HT1080 and HT1080/DR4 xenografts is measured[2].

D,L-Buthionine-(S,R)-sulfoximine is a potent inhibitor of glutamylcysteine synthetase biosynthesis.

Buthionine sulfoximine is an analogs of methionine sulfoximine and inhibits gamma-glutamylcysteine synthetase about 20 times more effectively than prothionine sulfoximine and at least 100 times more effectively than methionine sulfoximine[1].

Treatment of mice bearing HT1080 and HT1080/DR4 xenografts with a continuous i.v infusion of nontoxic doses of D,L-Buthionine-(S,R)-sulfoximine (300 and 600 mg/kg/day) produce a 60% reduction of GSH plasma levels and greater than 95 % reduction in GSH tumor levels in both parental and multidrug-resistant tumors[2].

[1]. Griffith OW, et al. Potent and specific inhibition of glutathione synthesis by buthionine sulfoximine (S-n-butyl homocysteine sulfoximine). J Biol Chem. 1979 Aug 25;254(16):7558-60. [2]. Vanhoefer U, et al. d,l-buthionine-(S,R)-sulfoximine potentiates in vivo the therapeutic efficacy of doxorubicin against multidrug resistance protein-expressing tumors. Clin Cancer Res. 1996 Dec;2(12):1961-8.