The purpose of the study is to determine if an investigational drug, NGX-4010 (high-concentration capsaicin patch), is effective in treating painful HIV-associated neuropathy.

The C107 study is a randomized, double-blind, controlled dose finding study of NGX-4010 for the treatment of painful symptoms of HIV-associated neuropathy. Participants will be randomly assigned to receive initial treatment according to one of three doses (application durations), and to receive double-blind NGX-4010 patch (high-concentration capsaicin) or matching control (low-concentration capsaicin).

Participants who complete study evaluations through Week 12 will have the option of receiving up to 3 additional open-label treatments.

Inclusion Criteria:

• At least 18 years of age
• Documented evidence of HIV-1 infection
• Documented diagnosis of painful HIV-associated distal symmetrical polyneuropathy established by a neurologist resulting from HIV disease and/or antiretroviral drug exposure, with primary symptoms of pain, burning or dysesthetic discomfort in both feet for at least 2 months prior to Screening Visit, and absent or diminished ankle reflexes, and at least one of the following: distal diminution of vibration sensation or pain or temperature sensation in the legs
• Either no neurotoxic antiretroviral (didanosine, zalcitabine or stavudine) exposure for at least 8 weeks prior to Screening Visit, or currently on stable dose(s) of any neurotoxic antiretroviral(s) for at least 8 weeks prior to Screening Visit
• Screening Pain Sum Score of 12 to 36
• Karnofsky Performance Score of greater than or equal to 60
• Intact, unbroken skin over the painful area(s) to be treated
• If taking chronic pain medications, be on a stable (not PRN) regimen for at least 21 days prior to Treatment Visit and willing to maintain these medications at the same stable dose(s) and schedule throughout the study
• Female subjects with child-bearing potential: negative serum pregnancy test performed at Screening Visit
• Willing to use effective methods of birth control and/or refrain from participating in a conception process during study and for 30 days following experimental drug exposure
• Willing and able to comply with protocol requirements for duration of study

Exclusion Criteria:

• Concomitant opioid medication, unless orally or transdermally administered and not exceeding a total daily dose of morphine 60 mg/day, or equivalent. Parenteral opioid use is excluded, regardless of dose
• Unavailability of an effective rescue medication strategy for the subject, such as unwillingness to use opioid analgesics during treatment, or high tolerance to opioids precluding the ability to relieve treatment-associated discomfort with Roxicodone® or Vicodin®, as judged by the Investigator
• Active substance abuse or history of chronic substance abuse within the past year, or prior chronic substance abuse judged likely to recur during the study period by the investigator
• Recent use (within 21 days preceding the Treatment Visit of any topically applied pain medication, such as non-steroidal anti-inflammatory drugs, menthol, methyl salicylate, local anesthetics (including Lidoderm®), steroids or capsaicin products on the painful areas
• Current use of any investigational agent or Class 1 anti-arrhythmic drugs
• Significant pain of an etiology other than painful HIV-associated neuropathy; significant ongoing pain from other cause(s) that may interfere with judging HIV-associated neuropathy pain
• Evidence of another contributing cause for peripheral neuropathy, e.g., diabetes mellitus requiring medication control (i.e., oral hypoglycemics, insulin); hereditary neuropathy; vitamin B12 deficiency (B12 level ≤ 200 pg/mL) or less than 3 months of B12 supplementation prior to Screening Visit; or treatment within 90 days prior to Screening Visit with any drug that may have contributed to the sensory neuropathy
• Any implanted medical device (spinal cord stimulator, intrathecal pump or peripheral nerve stimulator) for the treatment of neuropathic pain
• Treatment for acute opportunistic infections within 14 days before Treatment Visit
• Presence of acute, active opportunistic infection, except oral thrush; oral, genital, or rectal herpes; and Mycobacterium avium bacteremia within 2 weeks prior to Screening Visit
• Currently have active malignant disease
• Significant ongoing or untreated abnormalities in cardiac, renal, hepatic, or pulmonary function that may interfere either with the ability to complete the study or the evaluation of adverse events
• Hypersensitivity to capsaicin (i.e., chili peppers or OTC capsaicin products), local anesthetics, Roxicodone®, Vicodin®, or adhesives