Study of NGX-4010 for the Treatment of Painful HIV-Associated Neuropathy

Inclusion Criteria: * Documented evidence of HIV-1 infection * Documented diagnosis of painful HIV-associated distal symmetric polyneuropathy resulting from HIV disease and/or antiretroviral drug exposure To be confirmed based on 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 OR at least one of following: distal diminution of vibration sensation or pain or temperature sensation in legs * Average NPRS scores during screening period of 3 to 9, inclusive * Life expectancy of 12 months or longer per Investigator's judgment * Intact, unbroken skin over painful areas to be treated * If taking chronic pain medications, be on stable regimen for at least 21 days prior to Day 0 and willing to maintain medications at same stable dose(s) and schedule throughout 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 conception process during study and for 30 days following study drug exposure * Willing and able to comply with protocol for duration of study Exclusion Criteria: * Concomitant opioid medication, unless orally or transdermally administered and not exceeding total daily dose of morphine 80 mg/day or equivalent; parenteral opioids not allowed * Unavailability of effective rescue medication strategy for subject, such as unwillingness to use opioid analgesics during study treatment or high tolerance to opioids precluding ability to relieve treatment-associated discomfort as judged by investigator * Active substance abuse or history of chronic substance abuse within past year or prior chronic substance abuse (including alcoholism) judged likely to recur during study period by investigator * Recent use (within 21 days preceding Day 0) of any topically applied pain medication, such as non-steroidal anti-inflammatory drugs, menthol, methyl salicylate, local anesthetics including Lidoderm® (lidocaine patch 5%), steroids or capsaicin products on painful areas * Started or stopped treatment with one or more neurotoxic antiretroviral agents (ie, didanosine \[ddI\], zalcitabine \[ddC\], or stavudine \[d4T\] during 8 weeks prior to Day 0 * Participation in previous clinical trial in which subject received either blinded or open-label NGX-4010 * Current use of any investigational agent or Class 1 anti-arrhythmic drugs (such as tocainide and mexiletine) * Evidence of another contributing cause for peripheral neuropathy, e.g., current uncontrolled diabetes mellitus (HbA1c≥9%) or history of diabetes mellitus preceding onset of HIV-associated neuropathy (HIV-AN); hereditary neuropathy; vitamin B12 deficiency (B12 level ≤200pg/mL at screening); or treatment within 90 days prior to Screening Visit with any drug that may have contributed to sensory neuropathy * Hypertension, unless adequately controlled by medication * Significant ongoing pain from other cause(s) that may interfere with judging HIV-AN related pain * Any implanted medical device for treatment of neuropathic pain * Hypersensitivity to capsaicin (i.e., chili peppers or over-the-counter (OTC) capsaicin products), local anesthetics, opioid-based oral analgesics or adhesives * Significant medical conditions (including active malignancy defined as treatment required in last 5 years) that in opinion of investigator would interfere with ability to complete study or evaluation of AEs * Recent significant medical-surgical intervention that in judgment of Investigator would interfere with ability to complete study or evaluation of AEs; examples include to major surgery, or receipt of immunosuppressive therapy within 3 months prior to Day 0 * Evidence of cognitive impairment including dementia that may interfere with subject's ability to complete daily pain diaries requiring recall of average HIV-associated neuropathy pain level in past 24 hours