To Evaluate the Efficacy and Safety of SR419 in Patients With Postherpetic Neuralgia (PHN)

Study Overview
=================
Brief Summary
-----------------
This is a Phase II, international multicenter, double-blind, placebo-controlled, crossover study to assess the efficacy of SR419 in PHN subjects.

Detailed Description
-----------------
The study will evaluate the efficacy and safety of SR419 in PHN patients. Each subject will participate in the study for up to approximately 14 weeks. This includes a screening period, drug treatment period, and post-treatment safety follow-up period. This is a crossover design study, in which subjects will be administered with SR419 and placebo according to their randomized sequence, that is, eligible subjects will be randomized in a 1:1 ratio to 1 of 2 double-blind treatment sequences: 30 mg of SR419 administered TID followed by placebo administered TID or placebo administered TID followed by 30 mg of SR419 administered TID.

Official Title
-----------------
A Phase II, Randomized, Double-Blind, Placebo-Controlled, Multicenter, Crossover Study to Assess the Efficacy, Safety, and Tolerability of SR419 in Patients With Postherpetic Neuralgia (PHN)

Conditions
-----------------
Postherpetic Neuralgia

Intervention / Treatment
-----------------
* Drug: SR419


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Adult male or female over 18 years old; Having neuropathic pain of postherpetic neuralgia (PHN) that persists for >3 months after the herpes zoster rash is healed, with the pain area of a continuous area of affected rash. DN4 score is ≥4 at Screening; Average PI-NRS score of PHN-associated neuropathic pain over the last 24 hours at Screening is ≥4 and ≤9; Female subjects must be non-pregnant and non-lactating; Exclusion Criteria: Other pains that cannot be clearly differentiated from PHN and may interfere with PHN assessment; Circumstances that may affect pain assessment as determined by the investigator, such as skin disorders in the affected skin area that may affect sensation; Active herpes zoster infection at screening; Serious acute or chronic medical condition that, as assessed by the investigator, could increase the risks in subjects for participating in the trial or taking the study drug, or interfere with the study results; Previous administration of other study drugs within 30 days or 5 half-lives before the study intervention used in this study (whichever is longer).

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: SR419-Placebo sequence<br>30 mg of SR419 administered TID for 4 weeks followed by placebo administered TID for 4 weeks | Drug: SR419<br>* SR419 capsule<br>|
| Experimental: Placebo-SR419 sequence<br>placebo administered TID for 4 weeks followed by 30 mg of SR419 administered TID for 4 weeks | Drug: SR419<br>* SR419 capsule<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Daily Average Pain Score (DAPS) | To assess the difference between the two treatment periods in the weekly average of Daily Average Pain Score (DAPS) at the last week. The pain intensity numerical rating scale (PI-NRS) consists of an 11-point numeric scale ranging from 0 (no pain) to 10 (worst imaginable pain). Participants described their pain during the past 24 hours by choosing the appropriate number between 0 and 10. | up to Day 64 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Patient Global Impression of Change (PGIC) | To assess the proportion of subjects who rate their pain as much improved or very much improved on the Patient Global Impression of Change (PGIC) at the end of each treatment period. | up to Day 64 | 
| Daily Sleep Interference Score | To assess the within-subject difference between the two treatment periods in the weekly average of daily sleep interference scores at the last week. Pain-related sleep interference score was assessed on Daily Sleep Interference Scale (DSIS) which is an 11-point numerical rating scale ranging from 0 (did not interfere with sleep) to 10 (completely interfered [unable to sleep due to pain]). Participants were to describe how their pain had interfered with their sleep during the past 24 hours by choosing the appropriate number between 0 and 10. | up to Day 64 | 
| Adverse events | To collect the adverse events during the study | up to Day 70 |