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 μg/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 
(P≤0.013) 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.