Topical RM191A gel for chronic peripheral neuropathic pain: randomized, double-blind, placebo-controlled, crossover...

Area of Science:

• Pain Management
• Pharmacology
• Clinical Trials

Background:

• Neuropathic pain (NPP) treatment options are limited.
• RM191A, a novel copper-amino acid complex, mimics superoxide dismutase and shows anecdotal evidence for analgesia.
• A pilot randomized clinical trial (RCT) was conducted to assess topical RM191A gel for NPP.

Purpose of the Study:

• To evaluate the safety and efficacy of a topical gel containing RM191A compared to placebo.
• To assess the impact of RM191A on Numerical Pain Rating Scale (NPRS) scores in patients with chronic peripheral NPP.
• To explore secondary outcomes including safety, tolerability, and neuropathic pain characteristics.

Main Methods:

• A single-site, randomized, placebo-controlled, crossover pilot study.
• Participants applied active or placebo gel four times daily for 3 days, followed by a 4-day washout and crossover.
• Co-primary outcomes included changes in NPRS average pain scores from baseline to Days 1 and 3.

Main Results:

• The Day 3 co-primary outcome showed a trend toward significance (p=0.073), with significant reduction in NPRS Average Pain for active gel (p=0.012) versus placebo (p=0.485).
• Post hoc analysis indicated superiority of RM191A in participants with DN4 scores ≥4 (p=0.047).
• The number needed to treat (NNT) for 50% pain reduction by Day 3 was 8. RM191A was effective against burning pain, paroxysmal pain, and paresthesia/dysesthesia. Mild skin irritation was reported by 16% of participants, with no serious adverse events.

Conclusions:

• This pilot RCT suggests that 3 days of topical RM191A gel can modestly reduce chronic peripheral neuropathic pain.
• The NNT of 8 is comparable to existing treatments like duloxetine and gabapentinoids.
• Larger, longer-term studies in well-defined neuropathic pain populations are warranted to confirm efficacy and safety.