A Blinded, Randomized, Placebo-Controlled Study to Investigate the Efficacy and Safety of Ferric Carboxymaltose in Iron-Deficient Patients with Fibromyalgia

Introduction This study sought to compare efficacy and safety of ferric carboxymaltose vs. placebo in iron-deficient patients with fibromyalgia. Methods This blinded, placebo-controlled, phase 2 study randomized adults with fibromyalgia and Revised Fibromyalgia Impact Questionnaire (FIQR) scores ≥ 60, ferritin levels < 0.05 µg/ml, and transferrin saturation < 20% (1:1) to receive ferric carboxymaltose [15 mg/kg (up to 750 mg)], or placebo (15 cc normal saline) intravenously on study days 0 and 5. Patients visited the clinic on days 14, 28, and 42 for efficacy and safety assessments. The primary efficacy endpoint was proportion of patients with a ≥ 13-point improvement from baseline to day 42 in FIQR scale score. Secondary endpoints included changes from baseline in FIQR scale, Brief Pain Inventory (BPI) total score, Medical Outcomes Study (MOS) Sleep scale, Fatigue Visual Numeric Scale (VNS), iron indices (transferrin saturation and ferritin), and safety. Results The efficacy analysis group comprised 80 patients, and the safety analysis group comprised 81. More ferric carboxymaltose patients (77%) vs. placebo patients (67%) achieved the primary endpoint, but the difference was not significant. Greater improvements from baseline to day 42 were observed for ferric carboxymaltose vs. placebo in FIQR total score, BPI total score, Fatigue VNS score, and iron indices. Mean changes in MOS Sleep scale scores were similar between groups. Ferric carboxymaltose was safe and well tolerated. Conclusions Compared with placebo, ferric carboxymaltose improved measures of fibromyalgia severity and was well tolerated. The current results suggest that ferric carboxymaltose shows benefit in iron-deficient patients with concurrent fibromyalgia. Funding Luitpold Pharmaceuticals, Inc. Trial Registration ClinicalTrials.gov identifier, NCT02409459.