Resiniferatoxin for the Management of Refractory Morton s Neuroma Pain

Morton s neuroma is an irritation of the nerves that affect the feet. People with this condition may have burning or shooting pain in the balls of their feet. They may also have numbness in adjacent areas. These symptoms may become more frequent and severe over time. The pain may become permanent. Current treatments tend to be short-lived, and they do not work in all people. Better treatments are needed. Objective: To test a study drug, resiniferatoxin (RTX), in people with Morton s neuroma. Eligibility: Healthy people aged 18 and older who have Morton s neuroma and have tried other standard treatments that did not ease their pain. Design: Participants will be involved in the study up to 4 months. They will be screened. They will have a physical exam with blood tests. They will have a test of their heart function. They will have X-rays of their affected feet. They will have tests to assess their pain and how their feet react to touch and changes in temperature. They will complete questionnaires about their pain. RTX is injected into the foot at the site of the nerve pain. Participants will receive a shot to numb the area before the RTX is administered. They will be monitored in the clinic for 4 hours after they receive the RTX. Participants will receive up to 5 follow-up phone calls per week. Each call will take 5 to 10 minutes. They will be asked about their foot pain and whether they have had any side effects from the RTX. Participants will return to the clinic 4 weeks after the treatment. Previous tests will be repeated.

Study Description: This is an interventional protocol to determine the safety and tolerability of resiniferatoxin (RTX) for treatment of pain from Morton's neuroma with a single ultrasound-guided perineural injection of (RTX). It is hypothesized that RTX will provide a long-lasting reduction of the intensity of spontaneous and evoked pain and improve daily function without interfering with other sensory modalities or motor function. The safety and efficacy of the interventional procedure will be assessed during the trial. The 3+3 design of RTX treatment will be used to assess safety and determine the Dose Limiting Toxicity (DLT). Pre- and post-procedure pain intensity assessments, including graded interference of pain with daily function and graded descriptors of neuropathic pain, will be performed to assess efficacy. This protocol is intended to test RTX as a new method for long-term relief of refractory Morton s neuroma pain. Potentially this new treatment will reduce the need for radical procedures to treat unrelenting Morton s neuroma pain. Objectives: Primary Objective: -To determine the safety and tolerability of resiniferatoxin (RTX) for treatment of pain from Morton's neuroma. Secondary Objective: -To determine the efficacy of RTX intervention on pain intensity, interference of pain with daily function and incidence and intensity of neuropathic qualities of pain. Endpoints: Primary Endpoint: -The number of related Adverse Events (Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials) experienced between day 0 (injection day) and day 28 post-injection. Secondary Endpoints: * Change in average worst pain (NRS) between day 21 and day 28 compared to baseline average worst pain. * Change in pain interference on day 28 compared to screening (preinjection) using PROMIS pain tools. Change in neuropathic pain score on day 28 compared to screening (preinjection)using painDETECT.