New painkiller that seemed destined for greatness may only get limited FDA nod

With the country reeling from the opioid epidemic, pharma companies have been scrambling to develop alternative pain relievers. One of the buzziest new drugs in trials for the last few years has been Pfizer and Ely Lilly’s tanezumab, which works by selectively targeting, binding to and blocking nerve growth factor. 

The companies have been looking to target the markets for lower back pain and osteoarthritis — two of the biggest prizes in the chronic pain market — and received fast track designation from the FDA.

But safety data from a phase 3 trial cast a cloud over the potential of tanezumab. In April, the companies reported that at a 5 mg dose, the drug met several study goals but also caused an increased risk of rapidly progressing osteoarthritis, compared to NSAIDs. 

In the same study, patients who took 2.5 mg did not experience a significant improvement in pain or physical function compared to NSAIDs.

Despite the discouraging results, Pfizer said in its Q2 earnings report this week that it is pushing ahead with FDA approval for 2.5 mg in patients with moderate-to-severe osteoarthritis. It said that it does not plan to pursue approval for 5 mg or for a back pain indication, but that it is in an open dialogue with regulatory bodies about a future pathway for the drug.

Even if the drug wins approval, analysts are skeptical that it will rake in big sales at a lower dose that has not shown to be as effective.

Regeneron, meanwhile, has been developing its own nerve growth factor med, fasinumab, to treat arthritis pain. In April, the company reported that it may have found a minimally effective dose that mitigates skeletal side effects.