By Pat Anson, Editor

Two pharmaceutical companies have announced positive results from a Phase 3 study of an experimental non-opioid pain reliever that has a history of safety concerns.

Teva and Regeneron are jointly developing fasinumab as a treatment for chronic pain from osteoarthritis of the knee and hip. The companies say patients treated for 16 weeks with fasinumab injections had significantly less pain and improved function compared to a placebo.

"We are encouraged by these data and look forward to advancing our pivotal Phase 3 fasinumab program in patients with osteoarthritis of the knee or hip, who currently have very limited therapeutic choices to treat their chronic pain, other than with non-steriodal anti-inflammatory drugs or opioids," said George Yancopoulos, MD, President and Chief Scientific Officer of Regeneron.

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

Teva and Regeneron say fasinumab was “generally well tolerated” in the Phase 3 study, with similar adverse events (AEs) as in previous trials. Treatment was discontinued due to AEs in 6 percent of the fasinumab patients, about the same as the placebo group. The companies plan to present further details at an upcoming medical conference.

Regeneron recently halted high-dose trials of fasinumab because the risk of harm outweighed the benefits of the drug. There is some concern that NGF antibodies work too well and encourage osteoarthritis patients to become more active, which accelerates joint deterioration. No cases of joint damage were observed in the current study.

Regeneron and Teva are currently enrolling osteoarthritis patients in three additional Phase 3 clinical trials, including one assessing the long-term safety of fasinumab and two trials comparing fasinumab to standard pain therapies.

There is intense competition about drug companies to develop non-opioid pain relievers that don’t have the risk of addiction and overdose. Pfizer and Eli Lilly are jointly developing a similar NGF inhibitor called tanezumab, which was given fast track designation by the FDA in 2017 to speed its development.

Like fasinumab, there are safety concerns about tanezumab. The FDA ordered a partial halt to clinical studies of tanezumab in 2010 after Pfizer said a small number of osteoarthritis patients taking the drug needed joint replacements. Another safety issue arose in 2012 because the drug caused “adverse changes in the sympathetic nervous system of mature animals.”  Most clinical studies of tanezumab did not resume until 2015.