A Crossover Study to Evaluate the Safety, Tolerability and Efficacy of XPF-002 in Subjects With Postherpetic Neuralgia (PHN)

The purpose of this trial is to determine if XPF-002 is safe and effective for the treatment of pain in subjects with Postherpetic Neuralgia


Eligibility Criteria:
Inclusion Criteria:

* Age 18 to 80 years (inclusive);
* Males or females of non-childbearing potential (ie, 12 months or more of spontaneous amenorrhea, bilateral oophorectomy at least 6 months prior to randomization, hysterectomy with bilateral oophorectomy at least 6 months prior to randomization, or for females over 50 years of age, hysterectomy without bilateral oophorectomy at least 6 months prior to randomization);
* Male subjects with sexual partners of childbearing potential must agree to use contraception (abstinence, birth control pills, rings or patches, diaphragm and spermicide, intrauterine device, condom and vaginal spermicide, surgical sterilization, vasectomy, progestin implant or injection);
* Persistent pain for more than 6 months from the appearance of herpes zoster rash that is not located on the face, above the scalp hairline, or in proximity to mucous membranes;
* Diagnosis of PHN;
* Persistent neuropathic pain that involves at least 1 dermatome and covering no more than 400 cm2;
* Mean daily pain intensity score in the target area of greater than or equal to 4 on an 11-point Likert NRS for a minimum of 4 days during the single-blind, placebo run-in period;
* Subject agrees to take only the protocol-defined rescue medication as prescribed;
* Intact skin over the painful area to be treated; and
* Able and willing to provide informed consent and comply with study procedures.

Exclusion Criteria:

* Subject with systemic disease that would put him/her at an additional risk or limit his/her ability to participate in the study in the opinion of the investigator;
* Creatinine clearance less than 30 mL/min;
* Subject with known history of human immunodeficiency virus, hepatitis C, or hepatitis B;
* Malignancy other than basal cell carcinoma and carcinoma in situ within the past 2 years;
* Subject with history of serious mental illness or psychiatric illness such as dementia, depression, or schizophrenia, that will limit his/her ability to comply with study procedures;
* Subject who is unable to apply, or have a care giver apply, study ointment to the area of most painful skin segments, BID, once within 2 hours of waking and once in the evening after dinner;
* Subject with known sensitivity to topical products;
* Subject with active herpes zoster lesions or dermatitis;
* Other severe or chronic pain that may impair the self-assessment of the pain due to PHN;
* Treatment with local anesthetic in the last 2 weeks or nerve blocks within the last 30 days;
* Subject who is taking any opioid medications to treat his/her PHN pain and is unable to washout of these medications for the duration of the study;
* Subject who is taking any prohibited medication and is unable to washout of these treatments for the duration of the study;
* Subject who is taking more than 2 permitted concomitant medications for the treatment of PHN and is unable to washout of all but 2 of these treatments for the duration of the study;
* Subject who is taking any local prescription or non-prescription therapy (lidocaine patch, transcutaneous electrical nerve stimulation, etc.) and is unable to washout of these treatments for the duration of the study;
* Subject who has used Qutenza® patches in the 90 days prior to screening or has used other capsaicin preparations on a daily basis in the 90 days prior to screening;
* Subject who has participated in more than 1 other topical study for pain and more than 3 other PHN clinical studies;
* Pregnant or lactating females;
* Subject who has an active history of alcohol or drug abuse;
* Subject who has participated in any other investigational study within 60 days prior to screening;
* Subject who is employed by the Sponsor, study staff, and their families; or
* Subject who has any condition that would make him/her, in the opinion of the investigator or Sponsor, unsuitable for the study.