Periganglionic Resiniferatoxin for the Treatment of Intractable Pain Due to Cancer-induced Bone Pain

Background: Cancer-induced bone pain (CIBP) is common in people with cancer. Bone cancer can also lead to anxiety, depression, and reduced mobility and quality of life. Researchers believe a research drug called resiniferatoxin (RTX) may be able to help. Objective: To learn whether RTX is safe and can reduce cancer induced bone pain. Eligibility: People ages 18 and older with CIBP that is not relieved by standard treatments Design: Participants will have up to 6 outpatient visits over about 7 months. These will include: Medical history Physical exam Blood and urine tests. Thermal testing: a disk placed on the skin to test ability to sense temperature in and around the area of pain Chest x-ray EKG: stickers are placed on the chest to measure heart signals ECG: measures electrical activity of the heart Participants will have 1 inpatient visit lasting 2-4 days. This will include: Catheter inserted into a vein in the arm. They are given anesthesia, sedation, and x-ray contrast. A needle is passed through the skin of the back to inject the RTX. Participants will keep a log of the pain medications they take after surgery. Participants will be called 1 week and 2, 3, and 4 months after the injection. Participants will be mailed surveys and questionnaires to complete 2, 3, and 4 months after the injection. ...

Cancer-induced bone pain (CIBP) is a common clinical problem. While primary osteosarcoma is relatively uncommon, bone metastases frequently cause cancer-related pain with metastatic spread to bone in 60-84% of cases. Resiniferatoxin (RTX) is an ultrapotent agonist analog of capsaicin that targets a receptor expressed on specific dorsal root sensory ganglia (DRG) neurons and is expected to reduce pain within the targeted zone. The overall program goal is to develop a new treatment for intractable chronic pain below the mid-thoracic level resulting from CIBP that has not been controlled with conservative treatments. Objectives: The primary objective it to determine the maximum tolerated dose (MTD) of RTX when injected near one or more DRGs, to characterize its safety/toxicity profile, and to identify any dose-limiting toxicity (DLT). The secondary objectives are to determine the relative change in pain reduction, the change in opioid analgesic consumption and quality of life prior to RTX injection and at the various post RTX timepoints. Study Population Up to 30 adult subjects are estimated to be necessary for enrollment to have up to 16 subjects who will receive RTX and provide study-related assessment results through the 30-day time point. Design The study is a single center, open-label Phase 1b dose escalation safety and efficacy trial for adult subjects with intractable pain due to CIBP below the mid-thoracic level. Those subjects who meet all inclusion and exclusion criteria will undergo various study procedures and then be scheduled for the unilateral periganglionic (PG) DRG injection(s) (a maximum of 3 contiguous levels) under fluoroscopic guidance to treat the targeted DRGs demonstrated to be responsible for the chronic CIBP. The RTX will be injected at 1 of 4 dose levels, 0.8mcg/DRG, 1.6 mcg/DRG, 3.2 mcg/DRG or 6.4 mcg/DRG. The adaptivedesign algorithm for this study utilizes outcome dependent randomization, a process that selects the dose to be administered to the next subject based on all previous outcomes. In this schema, DLT is the measure that will be used to determine if it is safe to escalate to the next highest dose level. Subjects who are screen failures and those who prematurely terminate participation will be replaced until 16 subjects have received the injection(s) and completed study-related assessments through the day 30 (D30) timepoint. There is no placebo group because of the invasive nature of the injection and the dose escalation performed in the study. Outcome Measures The primary outcome is to achieve a dose-response relationship for safety. All subjects will receive RTX. The secondary outcome measures are: 1) change in NRS and VAS scores at the post-RTX assessments compared to pre RTX assessment, 2) change of opioid usage (in MME) at post RTX assessments compared to pre RTX assessment; 3) comparison SF-36 and BDI at pre RTX injection and Days 14, 37, and 187. The efficacy outcome variable will be evaluated by establishing dose-response curves, with dose plotted on the x-axis and changes in efficacy endpoints (before RTX treatment and at the post RTX assessment visits) plotted on the y-axis. If, at the end of the study, all dose levels of RTX have equal pain-relieving efficacy, the Data Safety Monitoring Committee (DSMC) may determine if it is appropriate to include a dose lower than 0.8 mcg and/or a control group. On the other hand, if the dose-response curves show that higher doses could result in greater pain-relieving efficacy, the protocol may be amended to include higher doses of RTX.