Attenuation of Responses to Endotoxin by the Triggering Receptor Expressed on Myeloid Cells-1 Inhibitor LR12 in Nonhuman Primate

Background: The triggering receptor expressed on myeloid cells-1 is an immunoreceptor that amplifies the inflammatory response mediated by toll-like receptors engagement. Triggering receptor expressed on myeloid cells-1 inhibitory peptides such LR12 have been shown to prevent hyperresponsiveness and death in several experimental models of septic shock. Methods: Twelve adult male Cynomolgus (Macaca fascicularis) monkeys exposed to an intravenous bolus of endotoxin (10 g/kg) were randomized to receive LR12 or placebo (n = 6 per group) as an initial intravenous bolus followed by an 8-h continuous intravenous infusion. An additional group of four only received vehicle infusion. Vital signs were monitored for 8 h. Blood was sampled at H0, 1, 2, 4, and 8 for analysis of clinical chemistries, leukocyte count, coagulation parameters, and cytokine plasma concentration. Results: LR12 showed no effect on heart rate and body temperature. By contrast to the placebo group, which experienced a 25 to 40% blood pressure decrease after endotoxin administration, LR12-treated monkeys remained normotensive. Endotoxin induced leukopenia at 2 h (mean leukocyte count, 7.62 g/l vs. 21.1 at H0), which was attenuated by LR12. LR12 also attenuated cytokine production. Conclusions: The triggering receptor expressed on myeloid cells-1 inhibitor LR12 is able to mitigate endotoxin-associated clinical and biological alterations, with no obvious side effects. This study paves the way for future phases Ia and Ib trials in humans.