By Jed Seltzer
NEW YORK (Reuters) - Pozen Inc. on Tuesday said U.S. regulators rejected its experimental migraine drug because it was not more effective than an existing treatment, sending the company's stock down 40 percent.
Pozen said the Food and Drug Administration issued a non-approval letter on its experimental drug MT100, a combination of naproxen and another treatment, because it did not prove substantially more effective than naproxen alone at sustaining pain relief.
Pozen also said that while one of its clinical trials showed the treatment was significantly more effective than a comparison product in reducing pain and three other symptoms of migraines, a second clinical trial did not meet those standards.
Aside from pain, the symptoms tested were photophobia, or an abnormal sensitivity to light, phonophobia, or sensitivity to sound, and nausea.
Pozen said it disagreed with the FDA about the statistical measure the agency used to conclude that its combination therapy did not demonstrate significantly superior sustained pain relief over naproxen.
The company, based in Chapel Hill, North Carolina, said it would continue to seek approval for the product but has not yet determined the best approach.
Analysts were skeptical.
"It will probably take a miracle to get MT100 back on track," said analyst Jason Zhang of Independent Research Group. "The FDA is often difficult to deal with because they change the rules sometimes, but as a company you should know better."
SIDE EFFECTS A WORRY TOO
The FDA was also concerned with the risk that patients could suffer from tardive dyskinesia, a neurological syndrome caused by the long-term use of certain medicines used for psychiatric disorders.
The drug that Pozen combined with naproxen in MT100, called metoclopramide, has been associated with uncontrollable motions characteristic of tardive dyskinesia patients.
Tardive dyskinesia is characterized by repetitive, involuntary, purposeless movements, such as grimacing, tongue protrusion, lip smacking, puckering and pursing, rapid eye blinking and rapid movements of the arms, legs, and trunk.
The FDA did not observe any raised risk of tardive dyskinesia in clinical trials of MT100, but was apparently still concerned by it.
"Given the number of patients exposed to MT 100 for at least one year in your database (about 300), the absence of any detected cases is consistent with a true rate of TD of about 1 percent, an unacceptably high risk in the absence of any demonstrated advantage of the product," the FDA said in its letter to the company.
Zhang speculated that the FDA was concerned that a total of 300 patients was not enough to determine whether tardive dyskinesia might arise.
In addition, the FDA noted that animal studies of MT100 showed a possible increased cancer risk.
Shares of Pozen slumped $3.98 to $5.94 on the Nasdaq, where it was the top percentage loser. Earlier, the shares fell to a one-year low of $5.61.