Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
Q: Increased nerve growth factor levels are associated with chronic pain conditions, including chronic low back pain (LBP). This study examined safety and analgesic efficacy of tanezumab, a humanized anti-nerve growth factor antibody, in adults with chronic LBP. Patients received intravenous tanezumab 200 g/kg plus oral placebo (n=88), intravenous placebo plus oral naproxen 500 mg twice a day (n=88), or intravenous placebo plus oral placebo (n=41). Primary outcome was average LBP intensity (aLBPI) at Week 6. Secondary outcomes were proportion of patients with 30% or 50% reduction in aLBPI, Roland-Morris Disability Questionnaire and Brief Pain Inventory-short form scores, Patients' Global Assessment of LBP, Patients' Global Evaluation of study medication, and rescue medication use. Mean aLBPI change from baseline to Week 6 was greater with tanezumab vs naproxen (P=0.004) and placebo (P<0.001). Greater proportions of patients reported 30% and 50% reduction in aLBPI with tanezumab vs naproxen (P0.013) and placebo (P<0.001), and greater improvements in Roland-Morris Disability Questionnaire (P<0.001) and other secondary outcomes except rescue medication use. Tanezumab was associated with adverse events (AEs) of abnormal peripheral sensation that were generally mild and resolved before study completion; however, there were no serious AEs. Nine patients (4 of whom were tanezumab-treated) discontinued due to AEs. In conclusion, tanezumab resulted in analgesic efficacy that was clinically and statistically superior to placebo and naproxen in patients with chronic LBP. Tanezumab clinical development is on regulatory hold due to AEs in osteoarthritis patients.
A:
What is the target of tanezumab?