The Effect of Fremanezumab on Pain in Patients with Complex Regional Pain Syndrome: Study Protocol of a Randomized, Double-Blind, Proof-of-Concept, Placebo-Controlled Trial.

Background/

Objectives: Complex regional pain syndrome (CRPS) is a primary pain condition that can develop in a limb after a trauma. Although the condition is rare, it may cause lifelong pain and disability. Evidence-based treatments are limited. Neurogenic inflammation induced by the release of neuropeptides, such as calcitonin gene-related peptide (CGRP), is thought to play an important role in the pathophysiology of CRPS. Recently, drugs targeting CGRP have proven to be effective and well tolerated in the treatment of migraine, but their efficacy in other pain conditions, including CRPS, is unclear. The aim of this study is to assess the efficacy of the anti-CGRP antibody fremanezumab on pain in CRPS.

Methods: In this randomized, double-blind, placebo-controlled, proof-of-concept study, 60 adult patients with CRPS with a disease duration of 3-36 months are randomized to treatment for eight weeks with fremanezumab 225 mg or placebo administered subcutaneously at a 1:1 rate. The primary objective is to compare the change in pain intensity from baseline to the last week of treatment between fremanezumab and the placebo. Other objectives are to assess pain relief and differences in clinical signs between the groups and to examine if the effect can be predicted by CGRP biomarkers. Adverse events and blinding will also be assessed.

Conclusions: If found effective, fremanezumab and other anti-CGRP antibodies may emerge as a mechanism-based treatment option for patients with CRPS, which could hopefully improve the overall care of patients with this devastating disease.