Botulinum Toxin A for the Treatment of Chemotherapy Induced Peripheral Neuropathy

Chemotherapy Induced Peripheral Neuropathy Chemotherapy induced peripheral neuropathy (CIPN) is a common adverse effect of cancer therapy, effecting over half of all patients who receive chemotherapy. CIPN typically manifests as a symmetrical, predominately sensory peripheral neuropathy, and is most common in taxanes, vinca-alkaloids, and/or platinum compounds. Taxanes are microtubule stabilizing agents and are effective in the treatment of many solid organ cancers, often used as first line therapy in the treatment of breast cancer. Taxanes cause peripheral neuropathy by injuring neurons, disrupting axonal transport, and causing wide spread macrophage activation both in the periphery as well as at the dorsal root ganglion (DRG) and microglial activation in the spinal cord. The incidence of CIPN is high following taxane administration, and often occurs before patients have completed the prescribed course. In severe cases it can lead to dose modifications and early treatment discontinuation, effecting overall survivorship. Additionally, it has been demonstrated to have a profound effect on quality of life, found to correlate with increased fatigue, malaise, increased psychological distress and a less sense of well being and satisfaction with life. Current treatment options are inadequate, with suboptimal treatment effect size and dose limiting adverse effects. Various neuroprotective regimens have been trialed, including co-administration of thiols, neurotrophic factors, antioxidants and vitamin E; however none of these approaches are consistently effective in reducing peripheral neuropathy.

Botulinum Toxin (BoNT) Botulinum toxin (BoNT) is routinely used to treat a wide variety of disorders, traditionally by decreasing muscle activity through inhibiting the release of acetylcholine from the presynaptic nerve terminal. There has been a recent increase and growing body of evidence for the use of botulinum toxin in the treatment of neuropathic pain including postherpetic neuralgia, diabetic neuropathy, complex regional pain syndrome, trigeminal neuralgia, phantom limb pain, spinal cord injury-induced neuropathic pain, and central post-stroke pain.

The mechanism by which BoNT effects neuropathic pain is independent than the effect of BoNT on muscle relaxation. There are several proposed mechanisms by which BoNT decreases neuropathic pain, all of which likely contributing to the antinociceptive effect. First, it has been shown that BoNT inhibits the release of sensory neurotransmitters such as substance P, calcitonin gene related peptide, and glutamate from nerve endings into the peripheral nerve terminal. This not only directly mediates pain, but has also been shown to result in decreased inflammation. In addition, recent work in the rat model suggests that the antinociceptive mechanism of BoNT may in part be due to a reduction of TRPV1 expression. TRPV1 is a well-known pain receptor which responds to mechanical, thermal and chemical stimuli, is heavily expressed on the DRG. BoNT has been shown to exhibit retrograde axonal transport from the periphery, so effects on the DRG and central nervous system cannot be overlooked and likely play a role in the mechanism.

Recently, intradermal BoNT injections were found efficacious in treating diabetic peripheral neuropathy. Multiple studies have demonstrated a reduction in Visual Analog Scale (VAS) scores following intradermal BoNT injections on the dorsal aspect of the foot in diabetic patients with peripheral neuropathy. Similar to CIPN, diabetic neuropathy presents in a stocking-glove distribution with a predominant sensory neuropathy. BoNT has additionally been proven to be safe and efficacious when used specifically in a cohort of head, neck, and breast cancer patients who developed post surgical and post radiation neuropathic pain. In this study, affected patients underwent intradermal BoNT injections which resulted in improvement in VAS and clinical global impressions of change (CGI-C) scales. Together, this evidence suggests that intradermal BoNT injections are efficacious in the treatment of neuropathic pain, and is safe for use in the cancer population. If our hypothesis proves correct, we will demonstrate the efficacy of BoNT for treatment of CIPN, allowing for improved treatment options. An antihyperalgesic effect following intradermal BoNT injections was additionally observed in rats with Paclitaxel induced peripheral neuropathy, again suggesting that BoNT will be an effective treatment specifically in the CIPN patient population.

In controlled studies, BoNT has consistently demonstrated a minimal adverse effect profile. Typically, adverse effects occur within one week of BoNT injection and are transient. As with any injection, localized pain, infection, bleeding may be associated. A metaanalysis of two studies using BoNT for the treatment of diabetic neuropathic pain concluded that there were no statistically significant adverse effects associated with BoNT treatment. Intradermal injections for the treatment of hyperhidrosis have FDA approval, and the most common adverse events associated (3-10% of adult patients) were injection site pain and hemorrhage.

The specific aim of this study is to determine the efficacy of intradermal INA injections to reduce chemotherapy induced peripheral neuropathy in breast cancer patients who have undergone taxane-based chemotherapy. We hypothesize the treatment group who receives intradermal INA injections will have lower neuropathic pain scale (NPS) scores when compared to the control group who receives saline injections.

1.0 Objective

The purpose of this study is to examine the change in pain via the neuropathic pain scale (NPS) in patients with chemotherapy induced peripheral neuropathy (CIPN) following intradermal IncobotulinumtoxinA ((Xeomin®, Merz) (INA) injections.

2.0 Experimental Design

The study is a prospective, randomized, double-blinded placebo-controlled study. Forty study participants will be enrolled in this study and randomized into Control vs. Experimental groups

1. Study participants will be screened in the breast cancer clinics of Drs. Chitambar and Kamaraju and other breast oncology providers at the Medical College of Wisconsin/Froedtert Hospital for symptoms of Grade II neuropathic pain (per Common Terminology Criteria for Adverse Events [CTCAE] v5.0) thought secondary to chemotherapy.
2. Study participants interested in pursuing the study will be contacted by phone by a study team member and the protocols and consent form will be discussed. Interested participants will be scheduled for an appointment in the translational research unit (TRU) at the Medical College of Wisconsin.
3. The adult TRU is located within Froedtert Hospital and is dedicated strictly to conducting human research. Facilities include basic medical equipment, fully staffed nursing support, 5 exam rooms and 3 procedure rooms.
4. The study participant will have the opportunity to ask the investigator about any questions they may have. Following this, the consent form will be signed and a copy will be given to the patient.
5. Study participants will then be issued the DN4 questionnaire, a clinician administered questionnaire that has a high level of sensitivity and specificity in discriminating neuropathic pain. A score ≥4 represents likely neuropathic pain.
6. Study participants will then undergo nerve conduction velocity (NCV) exams to confirm diagnosis of sensory neuropathy. Exam will be administered by PM\&R physician or resident.
7. Study participants will complete baseline neuropathic pain scale (NPS) assessments
8. Study participants will complete baseline Neuropathic Pain Impact on Quality of Life (NePIQoL) assessment
9. Study participants will disclose and document current pain medication regimen. This will include scheduled and prn medications taken for treatment of chemotherapy induced peripheral neuropathy as well as scheduled and prn medications used for treatment of other nociceptive pain.
10. Recruited participants will then be randomized to Experimental vs Control groups
11. Study participants who meet inclusion criteria will then undergo intradermal injection of INA or placebo into the bilateral hands or feet, depending on the location of the neuropathic pain. The injecting physician, Dr. Erin McGonigle (PI)/Dr. Erin Beddows (Co-I) and the subject will be blinded to the contents of the injection.
12. INA will be reconstituted with preservative-free normal saline to a dilution of 5mL:100 units
13. Anatomical site of injections (hands vs feet) will be determined based on patient report of severity of pain and impact of pain on quality of life.
14. 2% lidocaine jelly will be applied as a topical anesthetic for 3 minutes to site of injections
15. Site of injections will then be thoroughly cleaned with antiseptic solution of 75% alcohol and allowed to dry

• Study participants undergoing intradermal injections of bilateral hands/feet will receive 50u INA (total volume 2.5mL) or equivalent volume normal saline injected into each limb, max 2 limbs per subject.
• INA or saline equivalent will be injected across the palmar surface of the digits in a grid like pattern covering a total of 25 sites per limb (0.1mL/site).
• INA will be injected across the dorsal surface of the feet also in a grid like pattern covering a total of 25 sites per limb (0.1mL/site).
• Injections will be performed intradermally using a 5/16-inch, 32-g needle

2.1 Study Duration

• The duration of this study will be 6 months following intervention. 2.2 Study Participants Responsibilities
• Study participants will need to attend one research-related clinic visit for NCS testing
• Study participants will need to attend one research-related clinic visit for injection
• This may be the same visit as the NCS
• Study participants will be requested to answer a telephone and/or RedCap survey pending the participant's preference.

2.3 Study participants

• Forty study participants will be enrolled in this double blinded, randomized, controlled trial and they will be grouped by treatment method: Experimental vs. Control, as determined by a randomization table
• Study participants will be over 18 years of age, both genders, all ethnicities, and currently diagnosed with chemotherapy induced peripheral neuropathy