NGF – the TrkA to successful pain treatment

Vinayak Kumar,¹ Brandon A Mahal<sup>2

1</sup>Department of Chemistry, College of Arts and Sciences, University of Pennsylvania Philadelphia, PA, USA; ²Beth Israel Deaconess Medical Center, Harvard Medical School, Harvard University, Cambridge, MA, USA

Abstract: Chronic pain arising from various pathological conditions such as osteoarthritis, low back or spinal injuries, cancer, and urological chronic pelvic pain syndromes presents significant challenges in diagnosis and treatment. Specifically, since the underlying cause of these pain syndromes is unknown or heterogeneous, physicians diagnose and treat patients based on the symptoms presented. Nerve growth factor (NGF) has been recognized as an important mediator of chronic pain in many pathological conditions, and has been shown to be upregulated in a subset of individuals suffering from such pain syndromes. These findings have led to the development of anti-NGF monoclonal antibodies such as tanezumab as potentially effective therapeutics for chronic pain. Although tanezumab has reached Phase II and III clinical trials, the trials of anti-NGF antibodies were halted due to safety concerns. Some of these trials of anti-NGF treatment have had statistically significant decreases in pain, while others have yielded inconclusive results. These findings are suggestive of, though do not prove, target (NGF) neutralization in chronic pain syndromes. A biomarker-driven anti-NGF clinical study layout is proposed that incorporates NGF measurements in the relevant samples before and after treatment, in addition to collecting the pain scores. This approach might not only confirm the mechanism of tanezumab's action in these chronic pain patients, but should establish NGF levels as a predictive biomarker for patients who can benefit from anti-NGF treatment, thereby creating a personalized approach to pain treatment.

Keywords: nerve growth factor, chronic pain, anti-NGF antibodies, neurotrophic factor, nociceptor neurons