OM-89 MODULATION OF CHRONIC INFLAMMATION: RELEVANCE TO CLINICAL USE

The modulatory effects of a glycoprotein-rich endotoxin-free extract of Escherichia coli (OM-89) have been studied using the cotton pellet model of chronic inflammation in the male Wistar rat. OM-89 had a suppressive effect on the size of granuloma surrounding implanted cotton pellets at both 4 and 40 mg/kg given three times weekly. The lower dosage of 4 mg was effective throughout and there was little to be gained by increasing the dose as further reduction of granuloma size was not obtained. Whether given prior to, at the same time as, or after an inflammatory stimulus, OM-89 had suppressive effects. However, if given before, animals at first went through a phase of 'sensitization' before suppressive effects were seen on further exposure to OM-89 antigens, a phenomenon which might have bearing on clinical findings in rheumatoid arthritis. In animals presensitized to a cotton pellet, OM-89 was statistically as effective as indomethacin in suppressing a second granuloma. OM-89 combined with indomethacin showed additive effects and was highly effective. The results indicate that OM-89 could be efficacious in the treatment of chronic inflammatory conditions and there is the possibility that in appropriate circumstances OM-89 might replace some drugs currently used and in others reduce their dosage.