MADRID – Tanezumab, an investigational monoclonal antibody directed against nerve growth factor that is under development to treat osteoarthritis pain, met most of the coprimary efficacy endpoints set for the drug in a randomized, double-blind, parallel-group, placebo-controlled phase 3 study.
At the end of a 24-week, double-blind treatment period, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and WOMAC physical function subscale scores were significantly improved, compared with placebo in the two tanezumab (2.5 mg and 5 mg) dose groups.
The least squares (ls) mean change from baseline in WOMAC pain scores were –2.24 for placebo, –2.70 for tanezumab 2.5 mg, and –2.85 for tanezumab 5 mg (P less than or equal to .01 and P less than or equal to .001 vs. placebo).
The ls mean change from baseline in WOMAC physical function scores were a respective –2.11, –2.70, and –2.82 (P less than or equal to .001 for both vs. placebo).
The coprimary endpoint of patients’ global assessment of OA (PGA-OA) was also significantly improved with tanezumab 5 mg (–0.90; P less than or equal to .05) but not 2.5 mg (–0.82) versus placebo (–0.72).
As the 2.5-mg dose of tanezumab didn’t meet one of the three coprimary endpoints, further hypothesis testing was not possible, but exploratory findings suggested that tanezumab at 2.5 mg or 5 mg yielded higher proportions of patients with reductions from baseline in WOMAC pain scores when compared against placebo. This was the case for reductions of at least 30% (65.6%, 68.7%, 56.6%, respectively), 50% (45.4%, 47.9%, 33.8%), or 70% (21.3%, 23.2%, 17.8%).
“I think that we have now a lot of studies with tanezumab showing a significant effect on hip and knee OA pain and function, so we have the studies in order to have the drug on the market,” study first author, of Saint-Antoine Hospital, Sorbonne Université in Paris, said in an interview at the European Congress of Rheumatology.
“Of course, because of the safety issue with rapid progressive osteoarthritis (RPOA), what we are discussing now is: ‘For which patients will there be an optimal benefit-to-risk?’ So, it’s now more a discussion around the population of patients who can benefit the most with the drug,” Dr. Berenbaum added.
A possible link between the use of tanezumab and a risk for developing RPOA was first suggested by preclinical and early clinical trial data, prompting the U.S. Food and Drug Administration to place partial holds on its clinical development in 2010, and again in 2012.
However, Dr. Berenbaum noted that a “mitigation plan” had been put in place for the phase 3 program to try to lower the likelihood of RPOA. This included: lowering the dose of the drug used and delivering it subcutaneously rather than intravenously; not prescribing it with NSAIDs and testing its possible effects and safety in a difficult-to-treat population of patients with no known risk factors for the potentially very serious adverse event.
“Based on this mitigation plan, the risk of rapid progressive osteoarthritis has considerably decreased,” Dr. Berenbaum observed. Indeed, in thehe presented at the meeting, he said that around 2% of patients developed RPOA, which is “exactly in line with what has already been shown.” RPOA was reported in none of the placebo-treated patients, in 1.4% of those treated with tanezumab 2.5 mg, and in 2.8% in those treated with tanezumab 5 mg.
However, a “striking” finding of the current study was that despite the small increase in RPOA seen, there was no difference between the tanezumab and placebo groups in the number of patients needing total joint replacement (TJR). The percentages of patients undergoing at least one TJR was 6.7% in the placebo group, 7.8% in the tanezumab 2.5-mg group, and 7.0% in the tanezumab 5-mg group.
The joint safety events seen in the study, including TJRs, were adjudicated as being part of the normal progression of OA in the majority (73.4%) of cases. Other joint events of note were one case of subchondral insufficiency fracture occurring in a patient treated with tanezumab 2.5 mg and one case of primary osteonecrosis in a patient treated with tanezumab 5 mg.
During his presentation of the findings in a late-breaking oral abstract session, Dr. Berenbaum noted that this was a difficult-to-treat population of patients. All 849 patients who had been recruited had moderate to severe OA pain of the knee or hip and had a history of insufficient pain relief or intolerance to treatment with acetaminophen, oral NSAIDs, and tramadol and were also not responding to, or unwilling to take, opioid painkillers. Patients had to have no radiographic evidence of specified bone conditions, including RPOA.
Patients had been treated with subcutaneous tanezumab 2.5 mg (n = 283) or 5 mg (n = 284) or placebo (n = 282) at baseline, week 8, and week 16, with the three coprimary efficacy endpoints assessed at week 24.
Discussing the risk-to-benefit ratio of the drug after his presentation, Dr. Berenbaum said: “You have to keep in mind that, first, it was in very difficult-to-treat patients, compared to the other trials in the field of OA symptoms.”
He added: “Second, is that compared to the other trials, this one was able to include patients with Kellgren-Lawrence grade 4, meaning that this is a more serious population,” and third, “when you look at the responders – WOMAC 30%, 50%, 70% – there is a strong difference in terms of responders.”
Dr. Berenbaum and his coauthors noted on the poster that accompanied the late-breaking oral presentation that “an active-controlledwill provide data to further characterize the risk-benefit of tanezumab in patients with OA.”
The study was sponsored by Pfizer and Eli Lilly. Dr. Berenbaum disclosed receiving research funding through his institution from Pfizer and acting as a consultant to, and speaker for, the company as well as multiple other pharmaceutical companies. Coauthors of the study also disclosed research funding or consultancy agreements with Pfizer or Eli Lilly or were employees of the companies.
SOURCE: Berenbaum F et al. Ann Rheum Dis. Jun 2019;78(Suppl 2):262-4.