TORONTO – , according to a secondary analysis of a phase 3 randomized trial.
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Dr. Thomas J. Schnitzer
“The onset is relatively quick. It’s a monoclonal antibody, so it doesn’t work overnight, but by 3-5 days you see a significant difference,” Thomas J. Schnitzer, MD, PhD, reported at the OARSI 2019 World Congress.
He had previously presented the primary outcomes of this 696-patient, phase 3, randomized trial at the 2018 annual meeting of the American College of Rheumatology. At OARSI 2019, the rheumatologist presented new data focusing on the speed and durability of the pain relief provided by tanezumab, a humanized monoclonal antibody designed to help keep pain signals produced in the periphery from reaching the CNS.
The double-blind trial included U.S. patients with an average 9.3-year disease duration who were randomized to either two 2.5-mg subcutaneous injections of the nerve growth factor inhibitor 8 weeks apart, a 2.5-mg dose followed 8 weeks later by a 5-mg dose, or two placebo injections. Eighty-five percent of subjects had knee OA, and the rest had hip OA. The patients had fairly severe pain, with average baseline Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain scores of 7.1-7.4. Notably, all study participants had to have a documented history of previous failure to respond to at least three pain relievers: acetaminophen, oral NSAIDs, and tramadol or opioids, according to Dr. Schnitzer, a rheumatologist who is professor of physical medicine and rehabilitation, anesthesiology, and medicine at Northwestern University in Chicago.
As previously reported, the co–primary endpoint of change from baseline to week 16 in WOMAC pain was –3.22 points with the 2.5-mg tanezumab regimen and –3.45 with the 2.5/5–mg strategy, both significantly better than the 2.56-point improvement with placebo. Improvement in WOMAC physical function followed suit, he said at the meeting sponsored by the Osteoarthritis Research Society International.
Assessments were made at office visits every 2 weeks during the study. By the first visit at week 2, tanezumab was significantly better than placebo on both WOMAC measures, an advantage maintained for the rest of the 16 weeks. Pain relief in the tanezumab-treated groups was maximum at weeks 4 and 12; that is, 4 weeks following the first and second injections.
“This suggests that there’s an immediate effect of the antibody, which then tends to wane as the antibody begins to get cleared,” Dr. Schnitzer observed.
Study participants kept a structured daily pain diary, which enabled investigators to zero in on the timing of pain relief. Statistically significant separation from placebo was documented by day 3 in one group on tanezumab and by day 5 in the other.
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An increased rate of rapidly progressive OA was a concern years ago in earlier studies of a now-abandoned intravenous formulation of tanezumab. However, in the phase 3 trial of the subcutaneous humanized monoclonal antibody, rapidly progressive OA occurred in only six patients, or 1.3%, during the 24-week safety follow-up period. Interestingly, the phenomenon was not dose related, as five of the six cases occurred in patients on the twin 2.5-mg regimen, and only one in the 2.5/5-mg group. No cases of osteonecrosis occurred in the trial.
One audience member rose to say she and her fellow rheumatologists are very excited about the prospect of possible access to a novel and more effective OA therapy. But she took issue with the trial’s reliance on WOMAC pain and physical function scores as primary endpoints, noting that OARSI experts have developed and validated several more comprehensive and globally informative assessment tools. Dr. Schnitzer readily agreed. The investigators utilized WOMAC pain and physical function because that’s what the U.S. and European regulatory agencies insist upon, he explained.
Clinicians should stay tuned because the results of much larger, longer-term phase 3 trials of tanezumab are due to be presented soon, he added.
Dr. Schnitzer reported serving as a consultant to Pfizer and Eli Lilly, which are jointly developing tanezumab and sponsored the trial, as well as to a handful of other pharmaceutical companies.
SOURCE: Bessette L et al. Osteoarthritis Cartilage. 2019 Apr;27[suppl 1]:S85-6, Abstract 88.