Study to Evaluate the Safety and Analgesic Activity of ATx08-001 in Subjects With Postherpetic Neuralgia

Inclusion Criteria: * Is able to provide written informed consent prior to study entry * Is male or female, 18 - 85 years of age * Has a diagnosis of postherpetic neuralgia that has been present for at least 3 months since the resolution of the skin rash (shingles), and has been associated with at least moderate pain * Has a body mass index (BMI) between 17 and 36, inclusive * Has on average postherpetic neuralgia pain severity of at least "4" on the 11-point NPRS-12 scale over three days prior to the Treatment Visit. * At the Treatment Visit, entry into the study for dosing will require a baseline score of 4 or greater on the following 'Numerical Pain Rating Scale' (NPRS-NOW): "How would you rate your pain RIGHT NOW using a zero to ten scale, where zero equals no pain and ten is the worst pain you can imagine." If the subject fails to qualify for the Treatment Visit because of a baseline pain score below 4, he or she may return on any day within a fourteen day period to attempt to qualify again. A subject will be allowed a maximum of two reassessments to qualify on the basis of the NPRS-NOW scale. * Female subjects must be of non childbearing potential (defined as postmenopausal for at least 1 year or surgically sterile \[bilateral tubal ligation, bilateral oophorectomy or hysterectomy\]) or must be using adequate contraception (practicing one of the following methods of birth control): * Total abstinence from sexual intercourse (minimum of one complete menstrual cycle before study entry), * A partner who is physically unable to impregnate the subject (e.g., vasectomized) * Contraceptives (oral, parenteral, or transdermal) for 3 consecutive months prior to study drug administration, * Intrauterine device (IUD), or * Double barrier method (condoms, sponge, diaphragm, or vaginal ring with spermicidal jellies or cream) * If female of childbearing potential, subject must have a negative serum pregnancy test at screening * Able to communicate meaningfully with the study observer and staff * No known allergies to study medication Exclusion Criteria: * Has another source of moderate-to-severe pain apart from the postherpetic neuralgia that might be confused with the PHN pain * Is actively abusing alcohol or drugs * Is unable to refrain from alcohol for a period beginning 24 hours prior to the treatment visit until the end of the study * Is scheduled to undergo any surgical procedures during the period of study duration * Has a history of any active serious medical conditions including cancer (with the exception of benign uterine dysplasia or removed skin carcinomas), cardiovascular, respiratory, renal, hepatic, gastrointestinal, endocrine, immunologic, hematologic, neurologic or psychiatric disease that would contraindicate study participation * Has moderate to severe (New York Heart Association \[NYHA\] Class 3 or 4) heart failure defined as heart failure which significantly limits physical activity by provoking fatigue, palpitations or dyspnea. * Has a history of either type 1 or type 2 diabetes mellitus * Has taken a fixed scheduled opioid regimen within 3 days prior to the Treatment Visit. A fixed scheduled regimen of another type of analgesic, e.g., nonsteroidal antiinflammatory drug (NSAID) or an adjuvant analgesic will be allowed as long as the dose and schedule of administration were not changed for at least 2 weeks prior to dosing. * Has used a short-acting "as needed" opioid less than 12 hours prior to dosing or an "as needed" NSAID dose less than 24 hours prior to dosing * Has used extended duration oral analgesics up to 48 hours prior to the Treatment Visit * Has applied lidocaine patches or dermal analgesics within 7 days prior to the Treatment Visit * Has received an anesthetic block within two weeks of the Screening Visit * Has received any prior neurolytic nerve block in the area of the PHN pain * Is taking tricyclic, selective serotonin reuptake inhibitor (SSRI) or serotonin and noradrenaline reuptake inhibitor (SNRI) antidepressants for PHN (or for indications other than pain) and the dosage has been changed within 14 days of the Treatment Visit. Only subjects on stable doses from at least 14 days prior to the Treatment Visit through the duration of the study will be eligible to participate * Is taking gabapentin (Neurontin), pregabalin (Lyrica), or duloxetine (Cymbalta) and the dosage has been changed within 14 days of the Treatment Visit. Only subjects receiving stable doses for at least 14 days prior to the Treatment Visit and are willing to continue taking the same doses for the duration of the study will be eligible to participate * Has taken any medication that is a substrate of the cytochrome P450 enzyme CYP2C9 within 4 days of dosing with study drug or is unwilling to refrain from such medications through the course of study drug treatment * Has taken any prescription or over-the-counter medication within three days prior to the Treatment Visit, or herbal agents or other nutraceutical products within 14 days prior to the Treatment Visit, that in the opinion of the Investigator would be expected to confound the analgesic response * Has documented liver failure or a serum ALT, AST, alkaline phosphatase, or GGT greater than 2.5 times the upper limit of normal, or total bilirubin greater than 1.5 times the upper limit of normal without a known, not clinically significant explanation * Has a Brain Natriuretic Peptide (BNP) level \> 150 pg/mL * Has a history of poorly controlled hyperthyroidism or hypothyroidism or Thyroid Stimulating Hormone (TSH) levels that are \< 0.3 or \> 5.5 µlU/mL * Has moderate or severe renal failure defined as a calculated creatinine clearance of \< 60mL/min from the Cockcroft \& Gault formula * Has a clinically significant abnormality on 12-lead electrocardiogram * Has a known history of a positive Human Immunodeficiency Virus (HIV) antibody test or known HIV infection * Has a history of a positive Hepatitis B core antibody, or anti-HCV antibody test * Has previously been admitted to this study * Has received an investigational medication within 30 days prior to the Treatment Visit