BOSTON (

TheStreet

) -- More than 80% of hepatitis C patients were cured after treatment with a new twice-daily dose of the experimental drug telaprevir made by

Vertex Pharmaceuticals

(VRTX) - Get Vertex Pharmaceuticals Incorporated Report

, according to data from a phase II study released Saturday.

Data from the new study demonstrates that a more convenient twice-daily dose of telaprevir is just as effective and safe as the thrice-daily dose, Vertex said.

The hepatitis C cure rates of greater than 80% across all four patient groups of the study are also the highest ever recorded in any telaprevir study to date and exceed the cure rates reported in separate studies of boceprevir, a competing hepatitis C drug under development by

Schering-Plough

(SGP)

.

Generally speaking, investors were looking for telaprevir cure rates of greater than 70%, with a difference between the twice-daily and three-times-daily dosing group of 10% or less. The data from the telaprevir study exceeded those expectations on both measures.

"These data greatly enhance the potential for twice-daily telaprevir dosing," said Vertex chief medical officer Bob Kauffman.

Vertex and partner

Johnson & Johnson

(JNJ) - Get Johnson & Johnson (JNJ) Report

will formally present data from this new telaprevir study -- dubbed "C208" -- Tuesday at the annual meeting of the American Association for the Study of Liver Disease, a large gathering of hepatitis C researchers.

TheStreet Recommends

Investors are keenly interested in the outcome of the C208 study because it has the potential to strengthen telaprevir against competing hepatitis C drugs that while still in earlier stages of testing are being dosed once or twice a day.

The ongoing phase III studies of telaprevir incorporate a three-times-daily dosing schedule, but Vertex plans to have discussions with regulators here and in Europe to allow future studies to switch to a twice-daily dose.

Twice-daily dosing will become more important later this year, when Vertex intends to start a new study testing the combination of telaprevir with its other hepatitis C drug VX-222, said Kauffman.

C208 is also unique because the study was the first to allow doctors to adjust treatment depending on the individual response of the patient. The goal with this "response-guided therapy" was to improve cure rates and reduce the percentage of patients who dropped out due to side effects, said Kauffman.

The C208 study enrolled 161 treatment-naïve hepatitis C patients and divided them into four treatment groups. Two of these groups were treated with twice-daily doses of telaprevir in combination with standard of care therapy (long-acting interferon plus ribavirin) made by

Roche

or Schering-Plough, respectively. The other two groups were treated with telaprevir three times daily plus the standard of care.

The SVR rates for hepatitis C patients treated with the twice-daily telaprevir regimens were 83% and 82%. This compared to SVR rates of 85% and 81% for patients treated with three-times-daily telaprevir.

To place these results in perspective, prior phase II studies of telaprevir in treatment-naïve patients yielded cure rates in the range of 61% to 69% after 24 weeks of treatment.

The current standard of care therapy for hepatitis C -- long-acting interferon and ribavirin dosed for 48 weeks -- results in cure rates of around 40-50%.

Schering-Plough's boceprevir, which is the closest competitor to telaprevir, has demonstrated a maximum cure rate of 75%, although that required 48 weeks of total treatment.

Most of the patients in the study were treated for a total of 24 weeks, including 12 weeks of telaprevir. But 18% of the patients had their treatment extended to 48 weeks (still only 12 weeks of telaprevir) as part of the response-guided therapy. These patients didn't exhibit strong anti-viral response to telaprevir and standard of care early in the treatment cycle.

Serious adverse events forcing patients to drop out of the study occurred in 5% of patients, and were mainly related to rash (3%) and anemia (2%).

Vertex shares closed Friday at $33.56.

-- Reported by Adam Feuerstein in Boston

Adam Feuerstein writes regularly for TheStreet.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

click here

to send him an email.