Schwannomatosis is a rare neurogenetic condition characterized by multiple schwannomas and severe chronic pain. Elevated nerve growth factor (NGF) levels identified in painful schwannomas prompted our study on tanezumab, an anti-NGF antibody, as a treatment for SWN-related pain.

We enrolled subjects (≥18 years) with moderate-to-severe SWN-related pain intensity [Numerical Rating Scale (NRS-11) score ≥5, range: 0-10 (no pain-worst pain)] despite use of neuropathic pain medications, NSAIDS, and opioids; able to discontinue NSAIDS; and without osteoarthritis.  The study included a double-blind period with patients randomized to tanezumab 10 mg SQ or placebo (days 1-56), followed by unblinded tanezumab 10 mg SQ treatment (days 57-112) for all patients, and safety follow-up (days 113-281) without treatment. We measured weekly changes in pain intensity from Baseline-Day 57, Day 57-Day 113, and Day 113-Day 169 and performed a one-tailed t-test (p<0.05) to evaluate tanezumab's efficacy.

9 subjects (median age: 44, range: 33-65, 7 females) were enrolled. The mean baseline NRS-11 score was 7.6 (SD 2.1).  During the double-blind period, 4 patients received tanezumab and 5 received placebo.  The mean change in NRS-11 score was -2.5 (SD 4.5) in the tanezumab/tanezumab group and -0.4 (SD 2.1) in the placebo/tanezumab group.  During unblinded treatment, the mean change in NRS-11 scores were 0 (SD 0) for the tanezumab/tanezumab group and -1.4 (SD 1.9) for the placebo/tanezumab group. During safety follow-up, the mean change in NRS-11 score was 0.8 (SD 1.6).