Stop NorvirAs I mentioned last month, Gilead has an experimental pharmacokinetic (PK) enhancer in development that does the same thing as Norvir, Abbott's overpriced "booster" which most of us take to increase the blood levels of our protease inhibitors. We first heard they were studying the new booster, called GS-9350, as part of a possible 4-drugs-in-1 combo pill that would potentially supplant Atripla as the antiviral regimen du jour.

AIDS activists have been begging Gilead to study a stand-alone version of this booster with currently marketed protease inhibitors as well, offering the first potential competition to Norvir. Yesterday, at the CROI conference in Montreal, Gilead announced just that (see their full press release), saying they are "examining GS 9350?s potential to boost HIV protease inhibitors, which are used in many HIV treatment regimens. Gilead has initiated a pharmacokinetic study of GS 9350 that will assess its ability to boost atazanavir, one of the most widely prescribed HIV protease inhibitors."

Besides its exorbitant price, Norvir has some other issues which Gilead hopes to exploit. As AIDSmeds reported yesterday, Norvir is "associated with side effects such as gastrointestinal problems and lipid increases, and may contribute to the emergence of drug-resistant virus due to the fact that it does have anti-HIV activity even at low doses. In turn, pharmaceutical companies have been eager to develop a safe and effective PK booster, without activity against HIV, that can be used in place of Norvir."

GS-9350 has no anti-HIV activity, so it won't cause resistance. And thus far, it's showing none of Norvir's side effects.

Even better news -- while these two pharma Goliaths prepare for a PK face-off, a little David called Sequoia Pharmaceuticals might muscle its way in with their own experimental booster, SPI-452 (see the AIDSmeds story). In fact, they've already tested it successfully with Reyataz, Prezista and Invirase.

Expect to see one or both of these boosters on the market in about two years. I'm looking forward to throwing out my last bottle of Norvir.