Since 2003, researchers have experimented with Kaletra monotherapy, which would cut an HIV combo to just one med and simplify dosing and side effects. Kaletra contains the protease inhibitor (PI) lopinavir and a low booster dose of the PI Norvir (ritonavir). The low-dose Norvir doesn’t suppress HIV, leaving lopinavir as monotherapy. Other boosted PIs have been tried solo too (no monotherapy regimen is FDA approved).

Conflicting results of two studies may help plot a way to use monotherapy. In the one study (MONARK), Kaletra solo didn’t suppress HIV as well as Kaletra plus two nukes. But in another (OK04), monotherapy was effective as a second step, after a regular combo had fully (and rapidly) suppressed HIV. More testing will show whether OK04’s approach belongs at the HIV-treatment table.