Pfizer Suspends More Tanezunab Trials

Pfizer on Monday announced that it would cease two trials for its painkiller tanezunab after reports that the drug was actually causing worse pains. This is the second set of trials involving investigational treatment that has been canned in the past few weeks.

According to Pfizer, the drug firm suspended trials, at the behest of FDA, for patients being treated for chronic lower back pain and painful diabetic peripheral neuropathy. On June 23, Pfizer ended trials for patients taking tanezunab for osteoarthritis after reports that patients taking the treatment had to undergo hip replacement. Pfizer still hasn’t pinpointed the correlation between the hip replacement and the tanezunab.

“There’s no causal relationship that’s been established between tanezunab and these adverse events,” said Pfizer spokesperson MacKay Jimeson in an interview with Pharm Exec. “We’re still trying to understand what’s taking place in these particular trials and it’s something that the FDA is clearly taking an interest in. We are going to continue to work with FDA to learn more about tanezunab and make decisions in regards to the trials that are in the best interest of patients.”

Pfizer acquired tanezunab when it purchased Rinat Neuroscience in 2006. Then called RN624, tanezunab is a monoclonal antibody that turns off the nerve growth factor-the central point of pain in certain inflammatory conditions. The compound showed positive safety and tolerability levels in early-stage clinical trials.

Tanezunab trials focused on more severe patients that weren’t able to take standard opioids. Many of the patients were candidates for certain surgical procedures, such as joint replacement.

“The adverse events have only been experienced to date in the osteoarthritis trials,” Jimeson said. “The event was a worsening of the osteoarthritis symptoms that led to joint replacement.”

Troubled Treatments
In the meantime, analysts have begun grumbling at the number of Pfizer trials that have been cancelled in the past year as well as compounds that have been shelved.

“The latest setback to tanezunab is a worrying development for Pfizer given that the company has faced an accumulation of negative news flow regarding its pipeline over the last 18 months,” Datamonitor analyst Simon King stated in an e-mail. “This follows the recent confirmation that the acute myeloid leukemia therapy Mylotarg is to be withdrawn from the US market. Latest Datamonitor forecasts suggest that just 10 percent of Pfizer’s 2015 sales will be derived from new launches, suggesting that the company will continue to face competitive threats associated with a mature product offering.”

Jimeson said that biopharmaceutical research is a risky business, and affirmed that Pfizer is invested in the area and will continue to try to bring new treatments to patients.

Trials for tanezunab will continue in cancer pain, chronic pancreatitis, and interstitial cystitis.