(New throughout, adds background on hearings, details on drug and share price reaction of Palatin, which is developing another drug)
By Toni Clarke
WASHINGTON, June 4 (Reuters) - A drug to treat low female sexual desire should be approved with strict measures in place to ensure patients are fully aware of its risks, an advisory panel to the U.S. Food and Drug Administration concluded on Thursday.
If approved, the drug would be the first to treat low sexual desire in women. The FDA has twice rejected the drug, flibanserin, made by privately held Sprout Pharmaceuticals.
Eighteen panelists favored approval, but only with a risk management program. Six voted against approval. None voted to approve the product without such a program.
The drug's benefits are marginal, panelists said, but meaningful for some patients. Serious side effects include the risk of fainting at unpredictable times, accidental injury and low blood pressure.
Palatin Technologies Inc is also developing a drug, bremelanotide, for female sexual dysfunction, and its shares jumped 20 percent to $1.08 in extended trade. Palatin estimates the combined global market for the two drugs at between $1.5 billion and $2 billion.
The panel's recommendation follows months of lobbying by Sprout, aided by a number of women's advocacy groups which accused the FDA of gender bias since the agency long ago approved Viagra and other drugs to treat erectile dysfunction in men. The FDA rejected that charge.
Others characterized Sprout's lobbying campaign as an attempt to bully the FDA into approving a drug with modest benefits and real risks. Some panelists expressed concern that patients could faint while driving a car or in other circumstances that could lead to serious injury or death.
Both Sprout's and Palatin's drugs work differently from Viagra, which has been available since 1998. Flibanserin and bremelanotide work on the brain while Viagra affects blood flow to the genitals.
Dozens of women spoke to the panel about distress caused by their low sexual desire and urged the FDA to approve the drug, whose proposed trade name is Addyi. The FDA is not obliged to follow the advice of its advisory panels but typically does so.
Flibanserin is a daily pill that takes several weeks to begin working. Palatin's drug, bremelanotide, is taken by injection only when needed. It is in late stage clinical trials and could be approved in the first half of 2017.
Alcohol use exacerbates fainting associated with flibanserin, and some panelists suggested the label should contain a black box warning about the risks of using the drug with alcohol.
Flibanserin was developed as an antidepressant by Boehringer Ingelheim, which sold the drug to Sprout following a negative advisory panel meeting in 2010. The FDA again rejected the drug in 2013, saying the risks outweighed the modest benefit.
From an average baseline of two to three satisfying sexual events (SSEs) a month, and after adjusting for a placebo effect, women had an increase of 0.5 to 1.0 SSEs a month.
The panel suggested several risk management measures such as requiring physicians to be certified before they can prescribe the drug and requiring pharmacies to confirm physician certification.
Recommendations also included establishment of a patient registry and additional safety studies after the drug is on the market. (Reporting by Toni Clarke; Editing by Sandra Maler and David Gregorio)
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