Thursday after the bell, Optimer Pharmaceuticals Inc. (OPTR) announced positive results from the second of two late-stage trial of its investigational antibiotic, Fidaxomicin in patients with CDI (Clostridium difficile infection). Investors pleased with the news, which confirmed a high cure rate and simultaneously, a low recurrence rate for Fidaxomicin, compared to Vancocin, the only FDA-approved therapy for CDI, bid up the stock price over 17% in after-hours trading.
Clostridium difficile infection is one of the most common and devastating hospital-acquired infections. The bacterial infection occurs when patients are treated with antibiotics for other diseases. A prolonged treatment with antibiotics has a negative impact on beneficial bacteria that live in gastrointestinal tract, making the patients prone to bacterial infection. Clostridium difficile can cause diarrhea, ranging from a mild disturbance to a very severe illness with ulceration and bleeding from the colon. In severe conditions, the bacterium can cause perforation of the intestine leading to peritonitis, which can be fatal.
The Clostridium difficile infection is one of the most serious problems facing the U.S. healthcare system. The most commonly used drug to treat Clostridium difficile infection is the generic antibiotic Metronidazole. However, if the infection is severe, ViroPharma Inc.'s (VPHM) Vancocin is the only approved treatment.
The second phase III trial of Fidaxomicin, whose results were released Thursday, was conducted in about 100 clinical sites throughout North America and Europe while the first phase III study, whose results were reported in November 2008, was conducted at sites throughout North America.
Optimer Pharma plans to submit a New Drug Application for Fidaxomicin to the FDA in the second half of this year.
The second phase III trial enrolled 535 adult subjects with confirmed Clostridium difficile infection and they were administered either Fidaxomicin (200 mg q12h) or Vancocin (125 mg q6h). The study was designed to evaluate safety and compare the response to treatment in subjects during and after a 10-day course of therapy.
Optimer Pharma noted that the study met the primary endpoint of non-inferiority in clinical cure with 91.7% of patients treated with Fidaxomicin requiring no further CDI therapy two days after completion of study medication, compared to 90.6% for Vancocin.
According to the company, only 12.8% of patients treated with Fidaxomicin in the trial, experienced a recurrence during the subsequent four-week period, compared to 25.3% of patients treated with Vancocin.
The results of the first phase I study of Fidaxomicin have also demonstrated the non-inferiority of clinical cure and reduction in CDI recurrence of Fidaxomicin compared to Vancocin.
As mentioned earlier, ViroPharma's Vancocin is the only approved treatment for CDI. ViroPharma derives a major chunk of its revenue from Vancocin sales. For the nine months ended September 30, 2009, Vancocin sales totaled $161.3 million, accounting for 72% of the company's revenue.
Even though the patent covering Vancocin expired long back in 1996, it doesn't have an approved generic yet. Because of the complexities in the way Vancocin works, in order for a generic copy of Vancocin to be approved by the FDA, it has to prove itself to be truly bioequivalent to Vancocin in comparative clinical trials.
Usually generic drugs do not have to go through clinical trials and they are approved based on the bioequivalence data from the laboratory. No generic drug company has come forward to conduct clinical trials for generic Vancocin to establish the bioequivalence because of the huge expenses involved in conducting clinical trials.
However, in March 2006, the FDA's Office of Generic Drugs, or OGD revised the standard for the approval of generic copies of Vancocin saying that a clinical trial for generic Vancocin is not necessary.
With the U.S. Advisory panel endorsing the FDA guidelines for generic version of ViroPharma's Vancocin last August, the generic threat remains an overhang on the future of Vancocin and commercial success of Optimer Pharma's Fidaxomicin.
Commenting on the trial results, Michael Chang, CEO of Optimer Pharma said, "A higher global cure demonstrates the potential for Fidaxomicin to improve patient outcomes, reduce repeat visits to the hospital and reduce person-to-person transmission, which may result in a lower cost burden to the healthcare system."
OPTR, which has been trading in the range of $9.54-$15.17 in the last twelve months, closed Thursday's regular trading at $11.86, down 6.17% on a volume of 298 thousand shares. In after-hours trading the stock was up 17.96% to $13.99.
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