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Antioxidant molecules can be used both to replenish the depletion of reduced glutathione (GSH) occurring during HIV infection, and to inhibit HIV replication. The purpose of this work was to assess the efficacy of two pro-GSH molecules able to cross the cell membrane more easily than GSH. We used an experimental animal model consisting of C57BL/6 mice infected with the LP-BM5 viral complex; the treatments were based on the intramuscular administration of I-152, a pro-drug of N-acetylcysteine and S-acetyl-beta-mercaptoethylamine, and S-acetylglutathione, an acetylated GSH derivative. The results show that I-152, at a concentration of 10.7 times lower than GSH, caused a reduction in lymph node and spleen weights of about 55% when compared to infected animals and an inhibition of about 66% in spleen and lymph node virus content. S-acetylglutathione, at half the concentration of GSH, caused a reduction in lymph node weight of about 17% and in spleen and lymph node virus content of about 70% and 30%, respectively. These results show that the administration of pro-GSH molecules may favorably substitute for the use of GSH as such.

Oxidative stress and glutathione deficiency seem to play a major role in the pathogenesis of HIV infection, as suggested by the increased survival of HIV-infected patients treated with N-acetylcysteine, a prodrug of glutathione. However, beneficial effects of GSH-replenishing drugs are restricted in vivo by the high concentrations needed to obtain biological effects and their low bioavailability. In this study, we evaluated the antiretroviral and antioxidant activities of new more lipophilic GSH-replenishing molecules, in macrophages infected in vitro with HIV-1. In these experimental conditions, a prodrug of N-acetylcystéine and beta-mercaptoethylamine, I-152 demonstrated a potent anti-HIV activity, increased intracellular GSH level, and decreased TNF-alpha production. Altogether, these results suggest that I-152 could be beneficial as adjuvant therapy of antiretrovirals in HIV-infected patients, especially in those with damages to the central nervous system or with mitochondrial damages associated with highly active antiretroviral therapy.

I-152 is a prodrug of NAC and MEA with potent pro-GSH effects in human macrophages, astrocytes and lymphocytes. This molecule could be of interest in HIV infection in respect to its antioxidant and anti-HIV activities, but also in other diseases to counteract oxidative stress, that is, inflammation, cardiovascular diseases, and neurodegenerative diseases.

A new cysteamine-based compound, I109 (N-glycylglycyl-S acetylcysteamine trifluoroacetate) was tested on both normal tissues and tumors to evaluate its radioprotective potential. I109, which is three times less toxic than WR-2721, was injected at a dose approximately equal to half the LD50(30 days). The Protection Factor (PF = gamma ray dose ratio) after whole body irradiation was 1.3-1.4 for intestinal death and 1.4-1.5 for hemopoietic death when intervals of 40 or 20 min elapsed between injection and the end of irradiation. A crypt cell assay was done for both I109 and WR-2721; PFs were 1.1 and 1.4, respectively. I109 was then tested on five solid tumors. For each cell line (4 human, 1 murine) one dose of radiation was delivered. Surviving fraction ratios with and without drug ranged between 2.4 and 14.1 when an interval of 20 min elapsed between injection and the end of irradiation. The degree of radioprotection proved time dependent for EMT6 and HRT18; radioprotection afforded by WR-2721 on these tumors is either similar or greater than radioprotection afforded by I109 depending on the time interval between injection and irradiation.

1. The disposition of S-acetyl-N-glycyl cysteamine (I) labelled with 14C on the cysteamine group (label 1), the glycyl group (label 2) and the acetyl group (label 3) has been studied in mice bearing EMT6 tumours. 2. Label 1 was mainly excreted in urine (63.1% dose in 24 h). Label 2 elimination was both in urine (36.0% dose in 24 h) and in expired air as 14CO2 (12.1% dose in 24 h). Label 3 was essentially eliminated in expired air as 14CO2 (55.4% dose in 24 h). 3. Tissue distribution studies of label 1 and label 2 showed that concentrations in tissues were higher than blood concentration as early as 10 min after administration. Whichever label was used, only little radio-activity was found in EMT6 tumour and brain. 4. Analysis of the urinary elimination products showed the presence of unchanged I and of cystamine, N-acetylcystamine, N-acetyl-S-methyl cysteamine sulphoxide and taurine. I is a prodrug of cysteamine which is released after deacetylation and hydrolysis of the amide bond. A metabolic pathway is proposed for this new radioprotective agent.

A variety of N-(aminoalkanoyl)-S-acylcysteamine and N,N'-bis(aminoalkanoyl)cystamine salt derivatives were synthesized. Toxicity and radioprotective activity (as the dose reduction factor DRF) were determined in vivo on mice and compared to WR 2721 and S-acetylcysteamine hydrochloride. One of the most interesting compounds of this series was N-glycyl-S-acetylcysteamine trifluoroacetate (16, I 102). Structure-activity relationships are discussed.

Some N-(dipeptidyl)-S-acetylcysteamine and N,N'-(dipeptidyl)cystamine salt derivatives were synthesized and evaluated as candidate radioprotector agents. Toxicity and radioprotective activity as the dose reduction factor (DRF) were determined in vivo on mice and compared to N-glycyl-S-acetylcysteamine trifluoroacetate. One of the most interesting compounds of this series was N-glycylglycyl-S-acetylcysteamine trifluoroacetate (8).

Although WR-2721 preferentially protects normal tissues against irradiation, it seemed desirable to find other drugs presenting a lower toxicity and the same radioprotective properties. A new compound, I 102, was selected; it was characterized on one hand by a coupling between cysteamine and an amino-acid, and on the other hand by an acetyl-group, which protects the thiol function. The effects of WR-2721 and of I 102 were studied on EMT6 tumors grafted on BALB/c mice. Whatever the size of the tumor, the cell survival increased as a function of the time elapsed between the injection of I 102 and the end of the irradiation (TI). In contrast, the radioprotection afforded by WR-2721 was found to be independent of TI. The survival curves suggest that, like WR-2721, I 102 protects essentially oxygenated cells.