849 patients with chronic low back pain (equal or > 3 months) were randomized to receive three intravenous injections of 10 mg or 20 mg of tanezumab followed by up to 4 subcutaneous injections every 8 weeks. This extension study aimed to compare the long-term safety and effectiveness of two different tanezumab doses. Ten and 20 mg doses of tanezumab produced similar effectiveness outcomes at 24 weeks post-intervention, but tanezumab 20 mg had a higher overall incidence of adverse events. This trial was discontinued before it could reach its preplanned follow-up of 64 weeks due a temporary clinical hold being place on the drug by the FDA.