Single doses of p38 MAP kinase inhibitors or prednisolone affect CRP and IL-6 in patients with active Rheumatoid Arthritis (RA)

Abstract

Purpose: To investigate the effects of single doses of losmapimod, dilmapimod (inhibitors of p38 MAPK) and prednisolone on biomarkers of systemic inflammation (serum C-reactive protein (CRP) and interleukin (IL)-6) in subjects with active rheumatoid arthritis (RA). Methods: Two randomized, double blind, placebo controlled, parallel group, single dose studies investigated the CRP and IL-6 dose-response relationships for losmapimod (study A) and dilmapimod and prednisolone (study B) in patients with active RA on stable weekly doses of methotrexate. CRP, IL-6 and other exploratory biomarkers were measured in blood at baseline and up to 72 hours post-dosing. Results: In study A, 51 subjects were randomized to receive losmapimod (7.5, 20 and 60 mg) or placebo and in study B, 77 subjects were randomized to receive dilmapimod (7.5, 15 and 25 mg) or prednisolone (10, 20 and 50 mg) or placebo. Single doses of prednisolone caused a decrease in circulating IL-6 detectable at 3 and 24 hours post-dose as well as a CRP single-dose relationship at 48 hours post-dose in patients with active RA. All doses of losmapimod produced a statistically significant reduction in serum IL-6, 3 hours post-dose but had no effect on CRP. Dilmapimod had no effect on IL-6 or CRP at any dose or time. Conclusion: This single-dose response clinical study design could be useful in the early clinical development of anti-inflammatory agents for the treatment of rheumatoid arthritis. Inhibition of both circulating IL-6 and CRP would increase confidence that a new chemical entity may have the potential to deliver clinical benefit in RA. Trial registration: [clinicaltrials.gov: NCT00256919 and NCT00134693].