Many HIV meds need a lift—another drug that increases their level in the blood, making them more effective. The processing of drugs in the body is called pharmacokinetics (PK, for short), so a booster is called a PK booster.

Does this sound similar to the “PI booster” Norvir (ritonavir)? For good reason. Until now, the protease inhibitor Norvir has had this job (and market) to itself. At low doses, it raises blood levels of other PIs in HIV combos—and brings along a high price and some gastrointestinal side effects as well. Now both Gilead Sciences and Sequoia Pharmaceuticals have PK boosters in early stages of development—GS 9350 and SPI-452, respectively—to play the same role. For more on boosters, check out the PK enhancers entries on