BioWorld International Correspondent

MUNICH, Germany - Boehringer Ingelheim pressed the fight against the increased resistance in HIV by starting a global Phase III trial of tipranavir, a non-peptidic protease inhibitor. The compound would be the company's second antiretroviral drug, following Viramune, which is a non-nucleoside reverse transcriptase inhibitor.

The trial is a set of studies to evaluate tipranavir's effectiveness and safety in combination therapies for HIV-1. It will evaluate triple class-experienced patients at more than 280 clinical sites worldwide.

Boehringer Ingelheim pointed to unmet need caused by the rising resistance in patients being treated for HIV-1 as a driving force of the research. "Resistance is reaching levels of approximately 25 percent among patients in France, for example," Judith von Gordon, a spokeswoman for the company, told BioWorld International. "We think that tipranavir will be effective against a high number of resistance mutations."

The Phase III trial will involve more than 1,500 patients, which the company said made it the largest trial program ever conducted in this patient population. It will study tipranavir, boosted by low-dose ritonavir, vs. a low-dose ritonavir-boosted protease inhibitor chosen by the patient's physician on the basis of treatment history and baseline resistance testing. One study will draw more than 500 patients from the U.S., Canada and Australia, while another will enroll more than 800 in Europe and South America. Companion studies will examine the effects in even more advanced patients.

Tipranavir's non-peptide chemical structure allows it to bind more flexibly to the active site of the HIV protease, which the company thinks explains why its resistance profile is different from available peptidic protease inhibitors. Phase II studies showed that HIV resistance to tipranavir was associated with at least 16 protease inhibitor mutations at baseline.

"In addition to Viramune and tipranavir, we are working on a third, very promising compound for HIV, which is in a very early stage of clinical development," von Gordon said.