(Recasts lead with Nektar's statement, adds details)
By Saumya Joseph and Vishwadha Chander
Jan 14 (Reuters) - Nektar Therapeutics said on Tuesday it was withdrawing the application for its opioid painkiller for adults with chronic low back pain, after a U.S. Food and Drug Administration (FDA) panel unanimously voted against the drug's approval.
Independent advisers to the U.S. FDA voted 27-0 against the approval of the oral pill, NKTR-181, on concerns over the chances of its misuse or abuse as well as the lack of data to determine the possible abuse when snorted or injected and its potential for liver toxicity.
Shares of the company fell 14.5% in extended trading after the FDA panel's vote.
The company also said it would stop investing in the program, leading to cost savings of between $75 million and $125 million in 2020.
By reducing the rate at which the drug enters the brain, Nektar had aimed to relieve pain without triggering the euphoric effect of opioids that could lead to abuse and addiction.
The company had also said that the rate of the drug's entry into the brain when snorted or injected would be similar to that when taken orally.
"Just too much (data) was missing... I couldn't say the benefits outweighed the risks," said panel member Lee Hoffer from Case Western Reserve University in Cleveland, Ohio.
As the United States grapples with the problem of opioid addiction that has claimed the lives of over 47,000 people, the FDA has been increasingly reluctant to greenlight new opioid-based drugs.
Compared to commercially available opioids, the more gradual effects of NKTR-181 could make it less attractive as a drug of abuse for people seeking a rapid onset of a "high", according to the company.
Low back pain is generally treated with anti-inflammatory drugs, acetaminophen and opioids based on the severity of pain.
"I voted no even though I liked the idea of what they are trying to do. The data, I don't think at the end of the day was sufficient from the standpoint of efficacy and safety," said panel member Dr. Sherif Zaafran, vice chairman of the clinical governance board at U.S. Anesthesia Partners. (Reporting by Vishwadha Chander, Saumya Sibi Joseph and Shubham Kalia in Bengaluru; Editing by Amy Caren Daniel and Anil D'Silva)