Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Context: To assess the efficacy and safety of tanezumab, a humanized monoclonal antibody directed against the pain-mediating neurotrophin, nerve growth factor, to treat pain and other symptoms of chronic prostatitis/chronic pelvic pain syndrome in a Phase IIa, proof-of-concept clinical trial powered to provide 2-sided 90% confidence interval around the primary endpoint. Patients received a single intravenous dose of tanezumab (20 mg) or placebo. The primary efficacy endpoint was the change from baseline to week 6 in average daily numerical rating scale pain score. The secondary endpoints included the change from baseline to week 6 in the National Institutes of Health Chronic Prostatitis Symptom Index and urinary symptoms. Safety was also assessed. Overall, 62 patients were randomized (30 to tanezumab and 32 to placebo). At week 6, tanezumab marginally improved the average daily pain (least-squares mean difference from placebo -0.47, 90% confidence interval -1.150-0.209) and urgency episode frequency (least-squares mean difference from placebo -1.37, 90% confidence interval -3.146-0.401). No difference was seen in the National Institutes of Health chronic prostatitis symptom index total score or micturition frequency at week 6. The most common adverse events were paresthesia and arthralgia. The odds of having a 30% reduction in pain were 1.75-fold greater (90% confidence interval 0.65-4.69) for patients receiving tanezumab versus placebo. Tanezumab might improve symptoms for some patients with chronic prostatitis/chronic pelvic pain syndrome. Although proof of concept was not demonstrated in the present study, additional studies with larger populations and stricter inclusion criteria according to patient phenotype might identify populations in which antinerve growth factor treatment will provide clinical benefit.
Question: What is the target of tanezumab?
ngf