Mycophenolate Treatment for Longstanding Complex Regional Pain Syndrome (MYPS I)

INTERVENTION: Trade Name: Mycophenolate mofetil Product Name: Mycophenolate mofetil Product Code: LS017‐15 Pharmaceutical Form: Tablet INN or Proposed INN: Mycophenolate mofetil CAS Number: 128794‐94‐5 Current Sponsor code: L017‐15 Concentration unit: mg milligram(s) Concentration type: equal Concentration number: 500‐ CONDITION: Complex Regional Pain Syndrome (CRPS) Therapeutic area: Analytical, Diagnostic and Therapeutic Techniques and Equipment [E] ‐ Anesthesia and Analgesia [E03] PRIMARY OUTCOME: Main Objective: To provide first prospective proof of concept data on the activity (pain relief, and change in objective markers: quantitative sensory testing (QST), limb volume) of mycophenolate, an immune suppressant drug, in patients with longstanding, moderate to severe complex regional pain syndrome (CRPS). ; ; Also to provide first feasibility data on the tolerability of mycophenolate in a UK CRPS patient setting, including the typical time required for up‐titration to maximal dose; also to provide feasibility data on the standard deviation of the pain outcome measure. ; Primary end point(s): Primary outcome: the average pain relief at the primary endpoint (average 24h pain intensity on an 11‐point NRS scale over a 14 day period starting 5 months after randomization (from day 150) versus baseline (baseline=14‐day period following screening), compared between active and control groups. Secondary Objective: To gain first data on the safety of mycophenolate treatment in patients with moderate to severe CRPS; explore time to pain‐return‐to‐baseline; and explore treatment effect on function, quality of life, and healthcare costs. Timepoint(s) of evaluation of this end point: Participants will fill in daily pain diaries for 14 days before randomisation (baseline data). This will be from day ‐21 onwards and the average pain score calculated. ; ; Participants in both active and control groups will fill in daily pain diaries from day 150 for 14 days. The average pain score will be calculated for comparison to baseline data. The change in pain intensity between the active and control groups will be compared. SECONDARY OUTCOME: Secondary end point(s): 1: the average pain relief over the final 14 days of active treatment, compared with baseline in the active group (combined data from active group on active treatment, and control group on active treatment).; ; 2: the average change in QST parameters at the end of active treatment, compared with baseline. Timepoint(s) of evaluation of this end point: 1. Pain intensity data collected at baseline (‐21 for 14 days) and between 150‐164 days for active group and pain intensity data collected between 150‐164 days and between 314‐328 days.; ; 2. For the active group this is comparing the QST at randomisation (day 0) and day 164. For the control group this is comparing the QST at day 164 and day 328. INCLUSION CRITERIA: 1. Diagnosis of Complex Regional Pain Syndrome I or II according to Budapest research criteria (appendix 2) 2. Disease duration of >2 years, and a mean pain intensity on an 11‐point (0‐10) Numeric Rating Scale (NRS) over the first fourteen daily entries after screening of 5 or higher (and no single daily pain intensity value below 5, a minimum of 13 valid scores need to be available). 3. Failure to respond (poor efficacy or unacceptable side effects) to drugs recommended for the treatment of neuropathic pain, including pregabalin or gabapentin, a tricyclic antidepressant, and mild and strong opioids (where not contraindicated or refused by the patient). 4. Previous pain‐physiotherapy (where not contraindicated or refused) 5. Willingness to confirm the use of adequate birth control while on the trial will be required in pre‐menopausal women without evidence for an inability to become pregnant. 6. Willingness to not start any other treatment for CR