A Randomized, Double-Blind, Placebo-Controlled, Parallel Group Study Evaluating the Efficacy and Tolerability of Oral SLC022 300 mg TID, a Glial Cell Modulating Agent,

INTERVENTION: Product Name: propentofylline Product Code: SLC022 Pharmaceutical Form: Capsule* INN or Proposed INN: propentofylline CAS Number: 55242‐55‐2 Current Sponsor code: SLC022 Other descriptive name: HWA‐285 Concentration unit: mg milligram(s) Concentration type: equal Concentration number: 150‐ Pharmaceutical form of the placebo: Capsule* Route of administration of the placebo: Oral use CONDITION: Post herpetic neuralgia ; MedDRA version: 9.1 Level: LLT Classification code 10036376 Term: Post herpetic neuralgia PRIMARY OUTCOME: Main Objective: To compare the efficacy of SLC022 300 mg three times daily (TID) versus placebo TID over 28 days of treatment in subjects with PHN (postherpetic neuralgia). Primary end point(s): The primary efficacy endpoint of this study is the reduction of PHN‐related pain as reported on an 11‐point numerical pain rating scale via the electronic subject diary. Actual values and change from baseline will be summarized by visit. The mean pain score at the end of the Treatment Phase (last 5 pain scores reported during treatment) will be compared to the mean pain score from baseline (last 5 pain scores reported prior to randomization). An Analysis of Covariance (ANCOVA) with baseline pain as a covariate will be performed on the difference in mean pain from baseline to end of treatment. Primary efficacy analysis will utilize the last observation carried forward (LOCF) imputation methodology outlined below. An observed case analysis using mixed model repeated measures (MMRM) will also be presented as a secondary sensitivity analysis. Secondary Objective: ‐‐ To determine the safety and tolerability of SLC022 300 mg three times daily (TID) compared to placebo TID over 28 days of treatment in subjects with PHN (postherpetic neuralgia).; ; ‐‐ To establish a population‐based pharmacokinetic (PK) model for comparing inter‐subject variances in exposure. INCLUSION CRITERIA: 1. Male or female age 18 years or older. 2. A history of cutaneous herpes zoster infection and sustained pain associated with the site of the herpes zoster skin rash for >6 months, after onset of the herpes zoster skin rash. 3. Pain intensity score of =4 on an 11‐point numerical rating scale for at least 5 of 7 days immediately prior to randomization. 4. Mean pain intensity of =4 on an 11‐point numerical rating scale during the Baseline Phase. 5. Completion of at least 5 out of 7 daily pain reports during the Baseline Phase. 6. Completed a washout period of 7 days for any of the following medications: a2‐d antagonists (e.g., gabapentin), opiate analgesics, topical lidocaine, anticonvulsants, TCAs, serotonin‐norepinephrine reuptake inhibitors (SNRIs) (e.g., duloxetine), skeletal muscle relaxants, orally administered steroids, capsaicin, mexiletene, and centrally acting analgesics (dextromethorphan, tramadol). 7. Eviden