Tipranavir, a new protease inhibitor under development by Boehringer-Ingelheim, is to be made available to any person with HIV in the UK who has a CD4 cell count of 50 cells/mm3 or below and viral load of 10,000 copies/ml or above who needs the drug to construct a viable treatment regimen.
The 50 CD4 cell threshold is designed to ration the drug to patients at immediate risk of disease progression despite treatment with highly active antiretroviral therapy. Patients may not use tipranavir alongside any other protease inhibitor apart from ritonavir (used at a low dose of 200mg to boost tipranavir levels). This is because drug interaction studies with saquinavir, amprenavir, atazanavir and lopinavir have not been completed.
A study of tipranavir/ritonavir in the UK called Resist 2 involving patients with experience of at least two protease inhibitors who have viral load above 1,000 copies/ml is now fully recruited. For the time being, the emergency use programme is the only way to obtain the drug. The company says that eligibility criteria for the emergency use programme will be reviewed on a regular basis as further data become available on issues such as drug interactions.
For the time being, the only new drug likely to be suitable for use alongside tipranavir will be T-20, which is not known to have an interaction with tipranavir. The nature of any interaction between tenofovir and tipranavir is unknown, and therapeutic drug monitoring is advisable given the recent isolated reports of unusual tenofovir levels associated with use alongside lopinavir or atazanavir.
Doctors should contact Boehringer-Ingelheim's medical information department for further information on how to obtain tipranavir for any patient likely to qualify.
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