The hepatitis C wars between the two drugmakers have been percolating for a few years, but Roche took a harsh swipe after its rival released the results of a study indicating fewer patients receiving its Peg-Intron combo therapy relapsed after the end of treatment. The trial compared two different dosing regimens with Roche’s Pegasys.

“With these results, we now have, for the first time, a large body of well-controlled clinical data demonstrating how the similarities and differences of the two leading combination therapies for hepatitis C affect outcomes for patients,” Robert Spiegel, chief medical officer and senior vice president at Schering-Plough Research Institute, crowed in a statement.

Roche quickly issued its own statement and accused Schering-Plough of “clear biases” in designing its trial. Of course, drugmakers are sometimes accused of favoring their own products, but Schering-Plough is particularly vulnerable to such charges today. The drugmaker also released results of its failed Vytorin study, which caused a ruckus because Merck and Schering-Plough delayed results and, briefly, changed the endpoint without consulting their lead researcher.

For instance, Roche accused Schering-Plough of using different starting doses in the different study arms; of skewing the dosing to favor its own med and for failing to blind the arm of the trial involving the Roche product. Roche went on to add that, after the FDA required Schering-Plough to conduct a post-approval trial in 2001, Schering-Plough added Pegasys, creating a “mismatch” due to dosing of ribavirin, the second component in each company’s combo therapy.

UPDATE: The lead investigator for the Schering-Plough trial, John McHutchinson of Duke University, acknowledged the design may bias the results in favor of the Schering-Plough med. “Unfortunately life is not perfect and this study is not perfect as well,” he told Reuters nearly three years ago when the trial was launched. “The dose reductions for ribavirin are not equivalent in the two arms of the study and could therefore introduce a potential bias.” The FDA, however, wouldn’t allow any dose reductions, according to HIVandHepatitisC.com.