By Pat Anson, PNN Editor
Disappointing results from a Phase 3 clinical study are raising new safety concerns about an experimental class of pain-relieving drugs once considered a promising alternative to opioids.
Pfizer and Eli Lilly say 6.3% of osteoarthritis patients taking a 5 mg dose of tanezumab experienced rapidly progressive osteoarthritis in their joints. There was significant improvement in their pain and physical function, but the patients’ overall assessment of their condition was no better than those treated with non-steroidal anti-inflammatory drugs (NSAIDs).
Patients taking a lower 2.5 mg dose of tanezumab did not have any significant improvement in their pain, quality of life or overall condition. And 3.2% experienced rapidly progressive osteoarthritis.
“We are analyzing these findings in the context of the recent Phase 3 results as we assess potential next steps for tanezumab,” Ken Verburg, Pfizer Global Product Development, said in a statement. “We plan to review the totality of data from our clinical development program for tanezumab with regulatory authorities.”
Tanezumab is a humanized monoclonal antibody that targets nerve growth factor (NGF), a protein that increases as a result of injury, inflammation or chronic pain. Tanezumab binds to NGF and inhibits pain signals from reaching the brain.
Tanezumab was considered so promising a therapy that it was given fast track designation from the FDA in 2017, a process that speeds up the development of new therapies to treat serious conditions.
Ironically, it was the FDA that slowed the development of NGF inhibitors in 2010 because of concerns that tanezumab made osteoarthritis worse in some patients. Most clinical studies of tanezumab did not resume until 2015.
The reappearance of the same safety issue and the marginal pain relief provided by tanezumab could be the last straw for the drug, according to one analyst.
“It is hard for us to imagine how these results could have been much worse. Pfizer indicated that they ‘plan to review the totality of data’ with regulatory authorities, which suggests to us that the co-sponsors will try to find a way to resurrect the program for some subset or sub-population of patients, but recognizes that this result puts the drug’s entire future in doubt,” SVB Leerink research analyst Geoffrey Porges said in a note to clients.
A clinical study of fasinumab, another NGF inhibitor being developed by Teva and Regeneron Pharmaceuticals, was stopped by the FDA in 2016 after a patient showed signs of severe joint disease. Regeneron and Teva are continuing to study fasinumab in patients with chronic low back pain.
Pfizer and Eli Lilly are also studying tanezumab as a treatment for low back pain, and reported promising results from a Phase 3 trial in February. Rapidly progressive osteoarthritis was also reported in a small number of patients involved in that study.