Immunostimulation of neutrophil phagocytic function by RU41740 (Biostim) in elderly subjects

On this randomized, double-blind trial we investigated the effect of RU41740, a glycoprotein extracted from Klebsiella pneumoniae, on human neutrophil function after oral administration to elderly subjects with a previously demonstrated phagocytic defect. Six subjects were given RU41740 orally at a daily dose of 2 mg for one week the first month and of 1 mg for one week the second month, while six subjects received placebo. Already after the first week of treatment with RU41740 (T1) and more evidently 3 weeks after the last administration of the first course of therapy (T2), a significant improvement of the neutrophil phagocytic capacity was observed; at the time T2, as well as at the end of the second course of therapy (T3), the phagocytic capacity was completely restored with no differences between control and aged subjects. Similar results were obtained in the chemiluminescence assays. As expected, placebo had no significant effect on neutrophil functions. No significant differences were observed between the two group of elderly subjects for total or differential leukocyte number. These results suggest that RU41740 exerts, almost in part, its clinical effect, i.e. the prevention of recurrent infections, by stimulating blood neutrophil phagocytic function.