Optimer Wins FDA Panel’s Backing for Antibiotic Fidaxomicin

Optimer Pharmaceuticals Inc. won a U.S. panel’s unanimous backing for an antibiotic that fights a deadly bacterium linked to intestinal infections often caught in hospitals.

The drug, fidaxomicin, is safe and effective for curing such illnesses, outside advisers to the Food and Drug Administration said today in a 13-0 vote in Silver Spring, Maryland. The panel later split on whether the drug works better than standard treatments in preventing relapses. The FDA usually follows its advisory panels’ recommendations.

Fidaxomicin would be San Diego-based Optimer’s initial product and the first drug cleared in more than 25 years for Clostridium difficile, which can cause severe diarrhea and attack the lining of the colon. The germ sickens about 500,000 people a year in the U.S. and kills about 30,000, according to the Centers for Disease Control and Prevention.

The results of clinical trials “were very positive,” panel member Christina Surawicz, a professor at the University of Washington School of Medicine in Seattle, said before the vote. “I have no reservations.”

Sales of fidaxomicin may reach $250 million by 2016, George Farmer, an analyst at Canaccord Adams Inc. in New York, said April 1 in a note to investors. The FDA appears “highly predisposed” to approve the drug, said Farmer, who recommends buying Optimer shares.

Optimer lost 32 cents, or 2.3 percent, to $13.48 at 5:28 p.m. New York time in extended trading on the Nasdaq Stock Market. Trading was halted during today’s FDA panel meeting.

Recurrence Data

Optimer rose 11 percent -- the most in 22 months -- on April 1 after FDA staff reviewers said fidaxomicin is as effective as ViroPharma Inc.’s vancomycin in curing illnesses and prevented more recurrences in clinical trials.

The advisory panel tied, 6-6, with one abstention, on whether it was clinically significant that patients on fidaxomicin were less likely to have suffered relapses 31 days after starting treatment. Surawicz, the abstaining member, later asked to be recorded as a “no” vote.

A finding that the recurrence data lacked clinical significance wouldn’t prevent the drug from being approved, Edward Cox, director of the FDA’s Office of Antimicrobial Products, told reporters after the meeting. If the agency does clear the drug, it will consider the panel’s vote in deciding what the drug’s label should say about the potential to cut relapse risks, he said.

Labeling Discussion

“I think we’ll be in a good position to have a fruitful discussion with the agency” about the label, Sherwood Gorbach, Optimer’s chief scientific officer, told reporters after the meeting. “We’ve got to find the right language.”

The FDA is evaluating fidaxomicin under a six-month priority review and aims to make a decision by May 30. While the FDA typically takes at least 10 months to rule on drug applications, it grants priority status to therapies that may provide major advances in treatment.

C. difficile is the most common cause of hospital-acquired diarrhea, Gorbach said in a March 31 interview.

People over the age of 65 are among those at risk for C. difficile illnesses, according to the Mayo Clinic in Rochester, Minnesota. Infections often strike after a patient is treated with antibiotics that destroy the so-called good bacteria normally found in the intestine. About 25 percent of patients suffer relapses.

Enzyme Inhibitor

Fidaxomicin is the first in a new class of antibiotics that kill harmful bacteria by inhibiting an enzyme known as RNA polymerase without weakening the normal intestinal flora, according to a fact sheet from Optimer.

An Optimer-funded study of 548 patients found that infections subsided in 88 percent of those treated with fidaxomicin and 86 percent of those taking vancomycin, the only drug approved by the FDA for C. difficile infections.

Fidaxomicin also cut the recurrence rate by almost half, according to a Feb. 2 report in the New England Journal of Medicine. About 13 percent of patients who took Optimer’s drug suffered relapses, compared with 24 percent of those treated with vancomycin.

FDA staff said in last week’s report that they agreed with the company’s conclusions about the drug’s efficacy, and found that the overall incidence of side effects with fidaxomicin was similar to that of vancomycin.

Vancomycin, approved by the FDA for C. difficile in 1986 under the brand name Vancocin, is one of two standard C. difficile treatments. The other is an unapproved use of metronidazole, sold by Pfizer Inc. as Flagyl and available in generic form. ViroPharma bought Vancocin from Eli Lilly & Co. in 2004.

Broad-Spectrum Antibiotics

Metronidazole and vancomycin are broad-spectrum antibiotics that disrupt the intestine’s normal protective bacteria, leaving patients vulnerable to relapse, Gorbach said in the interview.

Optimer hasn’t determined yet how much it will charge for fidaxomicin, he said. While it will probably cost patients more than metronidazole and vancomycin, it may reduce long-term health costs by cutting the number of relapses, Gorbach said.

Before it's here, it's on the Bloomberg Terminal. LEARN MORE