An experimental osteoarthritis drug developed by Pfizer Inc and Eli Lilly and Co achieved its main goal of lowering pain in a late stage trial, the companies said on Wednesday, potentially offering a safer alternative to opioids.

The experimental drug tanezumab is undergoing clinical trials for the treatment of various pain entities, including chronic low back pain, bone cancer pain, and interstitial cystitis. Tanezumab is part of an investigational class of pain medications known as nerve growth factor (NGF) inhibitors.

Tanezumab works by selectively targeting, binding to and inhibiting NGF. NGF levels increase in the body as a result of injury, inflammation or in chronic pain states.

By inhibiting NGF, tanezumab may help to keep pain signals produced by muscles, skin and organs from reaching the spinal cord and brain.

Tanezumab has a novel mechanism that acts in a different manner than opioids and other analgesics, including nonsteroidal anti-inflammatory drugs (NSAIDs), and in studies to date tanezumab has not demonstrated a risk of addiction, misuse or dependence.

The study demonstrated that patients who received two doses of tanezumab separated by eight weeks experienced a statistically significant improvement in pain, physical function and the patients’ overall assessment of their OA, compared to those receiving placebo.

“There is a substantial need for innovative new treatment options for osteoarthritis, as many patients are unable to find relief with currently available medicines and continue to suffer,” said Ken Verburg, tanezumab development team leader, Pfizer Global Product Development.

“We are encouraged by these results, which speak to the potential of tanezumab as a non-opioid treatment option for pain reduction and improvement in physical function in people living with osteoarthritis pain.”

Preliminary safety data showed that tanezumab was generally well tolerated, with approximately 1% of patients discontinuing treatment due to adverse events. Rapidly progressive osteoarthritis was observed in tanezumab-treated patients at a frequency of less than 1.5%, and was not observed in the placebo arm. There were no events of osteonecrosis observed in the trial. No new safety signals were identified.

In June 2017, Pfizer and Lilly announced that the U.S. Food and Drug Administration (FDA) granted Fast Track designation for tanezumab for the treatment of OA pain and CLBP.

Tanezumab is the first NGF inhibitor to receive Fast Track designation, a process designed to facilitate the development and expedite the review of new therapies that treat serious conditions and fill unmet medical needs.