By Pat Anson, PNN Editor

A decade long effort to bring a new non-opioid pain reliever on the market is a step closer to reality – although lingering questions remain over the safety of the drug.

Pfizer and Eli Lilly have announced that the U.S. Food and Drug Administration has accepted for review a Biologics License Application for tanezumab as a treatment of chronic pain due to moderate-to-severe osteoarthritis (OA). The FDA set December 2020 as a goal for making a decision on the application.

Tanezumab is a humanized monoclonal antibody that targets nerve growth factor (NGF), a protein that increases in the body because of injury, inflammation or chronic pain. Tanezumab binds to NGF and inhibits pain signals from muscles, skin and organs from reaching the brain.

"The FDA acceptance of the tanezumab application represents a significant milestone, and the breadth of our regulatory submission reflects the extensive clinical data we have gathered for tanezumab over the course of its development," Ken Verburg, Pfizer’s tanezumab development team leader, said in a statement.

"There is an urgent need for innovation in the treatment of osteoarthritis, as there have been no new classes of medicines available for this debilitating condition in more than a decade. If approved, tanezumab would be a first-in-class treatment for patients suffering from chronic pain due to moderate-to-severe osteoarthritis who have experienced inadequate pain relief with other analgesics."

Pfizer and Eli Lilly are jointly developing tanezumab, which was given “fast track” designation by the FDA in 2017 to help speed its development. The companies submitted data to the FDA from 39 clinical studies evaluating the safety and efficacy of tanezumab on more than 18,000 patients.

A Phase 3 clinical study in 2018 found that osteoarthritis patients who were given two injections of tanezumab had significant improvement in their pain and physical function compared to a placebo.

Not all of the studies have been positive, however. Another Phase 3 study last year found that over 6% of osteoarthritis patients taking a 5 mg dose of tanezumab experienced rapidly progressive OA 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 in the same study 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. The license application accepted by the FDA is for that smaller 2.5 mg dose.

In 2010, Pfizer reported some osteoarthritis patients taking tanezumab experienced worsening of their disease and needed joint replacements. Another safety issue arose in 2012 because the drug caused “adverse changes in the sympathetic nervous system of mature animals.”

There is some concern that NGF antibodies work too well and encourage osteoarthritis patients to become more active, which accelerates joint deterioration. More than 27 million Americans live with osteoarthritis, 11 million of whom have moderate-to-severe OA.

Tanezumab is also being evaluated as a treatment for cancer pain due to bone metastases in a Phase 3 study. At one time, it was studied as a possible treatment for low back pain, but Pfizer and Eli Lilly are now mainly focused on tanezumab as a treatment for osteoarthritis.