A Study In Patients With Neuropathic Pain From Post-Herpetic Neuralgia (PHN)

The purpose of this study is to determine whether gabapentin enacarbil (XP13512/GSK1838262), hereafter referred to as GEn is effective in the treatment of neuropathic pain associated with post-herpetic neuralgia (PHN).

The primary purpose of study PXN110748 was to evaluate efficacy and safety of 3 fixed doses of GEn in the treatment of PHN.

Eligibility Criteria:
Inclusion Criteria:

* 18 years or older
* Female subjects are eligible if of non-childbearing potential or not lactating, has a negative pregnancy, and agrees to use one a specified highly effective method for avoiding pregnancy
* Documented medical diagnosis of PHN of with pain present for at least three months from the healing of a herpes zoster rash
* Baseline 24-hour average pain intensity score ≥ 4.0 based on an 11-point PI-NRS
* Provides written informed consent in accordance with all applicable regulatory requirements

Exclusion Criteria:

* Other chronic pain conditions not associated with PHN. However, the subject will not be excluded if:
* The pain is located at a different region of the body; and
* The pain intensity is not greater than the pain intensity of the PHN; and
* The subject can assess PHN pain independently of other pain
* Is unable to discontinue prohibited medications or non-drug therapies or procedures throughout the duration of the study
* Hepatic impairment defined as ALT or AST \> 2x upper limit of normal (ULN), or alkaline phosphatase or bilirubin \> 1.5x ULN
* Chronic hepatitis B or C
* Impaired renal function defined as creatinine clearance \<60 mL/min or requiring hemodialysis
* Corrected QT (QTc) interval ≥ 450 msec or QTc interval ≥480 msec for patients with Bundle Branch Block
* Uncontrolled hypertension at screen (sitting systolic \>160 mmHg and/or sitting diastolic \>90 mmHg)
* Current diagnosis of active epilepsy or any active seizure disorder requiring chronic therapy with antiepileptic drugs
* Medical condition or disorder that would interfere with the action, absorption, distribution, metabolism, or excretion of GEn, or, in the investigator's judgment
* Is considered to be clinically significant and may pose a safety concern, or,
* Could interfere with the accurate assessment of safety or efficacy, or,
* Could potentially affect a subject's safety or study outcome
* Meets criteria defined by the DSM-IV-TR for a major depressive episode or for active significant psychiatric disorders within last year
* Depression in remission, with or without antidepressant treatment, may participate, unless stable antidepressant regimen is a prohibited medication
* Antidepressant medication may not be changed or discontinued to meet entry criteria and must be stable for at least three months prior to enrollment
* History of clinically significant drug or alcohol abuse (DSM-IV-TR) or is unable to refrain from substance abuse throughout the study. Benzodiazepines or atypical benzodiazepines as hypnotic sleep agents permitted.
* Currently participating in another clinical study in which the subject is, or will be exposed to an investigational or non-investigational drug or device
* Has participated in a clinical study and was exposed to investigational or non-investigational drug or device:
* Within preceding month for studies unrelated to PHN, or
* Within preceding six months for studies related to PHN
* Treated previously with GEn
* History of allergic or medically significant adverse reaction to investigational products (including gabapentin) or their excipients, acetaminophen or related compounds