資料來源：https://www.reuters.com/article/regeneron-pharms-study-idUSL4N1CN3U4

Regeneron Pharmaceuticals Inc and partner Teva Pharmaceutical Industries Ltd said the U.S. health regulator placed a clinical hold on a study testing their pain treatment, dealing another blow to companies looking to develop a safer alternative to opioid painkillers.

The Food and Drug Administration (FDA) imposed the hold in the mid-stage trial in patients with chronic lower back pain, after a form of joint damage was observed in an advanced osteoarthritis patient who was given a high dose of the injectable drug, fasinumab.

Monday's announcement suggests fasinumab will be plagued by the same limitations as other drugs in its class, including heightened scrutiny, repeated delays, and labeling restrictions, Leerink Partners' Geoffrey Porges said.

The brokerage reduced its probability of success for the drug to zero, and cut Regeneron's price target to $513 from $530.

The treatment is designed to block nerve growth factor (NGF), a protein involved in transmission of pain signals.

Fasinumab has the potential to be an alternative to prescription opioids, that are effective for pain relief but are associated with high rates of addiction, overdose and death.

Following the FDA decision, Regeneron has completed an unplanned interim review of data and has stopped dosing patients, the companies said.

The analysis showed clear evidence of an improvement in pain scores in patients dosed with fasinumab, compared with placebo.

Regeneron was "lucky" to sell half the drug to Teva in a timely fashion," noted Sanford C. Bernstein's Ronny Gal.

The news of the hold comes less than a month after Regeneron announced the up to $1.3 billion deal with Teva to co-develop fasinumab.

The two drugmakers now plan to discuss with the FDA a late-stage study for chronic lower back pain, excluding patients with advanced osteoarthritis.

Fasinumab is also being tested for use in osteoarthritis-related pain.

Rival drugmakers Eli Lilly and Co and Pfizer Inc plan by 2018 to seek approval for their similar treatment, tanezumab, which is being tested as part of a $1.8 billion collaboration.

Regeneron has been attempting for years to develop an anti-NGF drug for pain, but has been stymied by safety concerns.

The FDA had placed fasinumab and other experimental agents targeting NGF on partial clinical hold in late 2012, after reports that animals on the drugs had suffered nerve damage.

The hold has since been lifted.

(Reporting by Natalie Grover in Bengaluru; Editing by Anil D'Silva)