A 28-year-old woman with HIV-1 infection on antiretroviral therapy (CD4 = 180 cells/μL, viral load = 2,100 copies/mL) is found to have genotypic resistance to both nucleoside and non-nucleoside reverse transcriptase inhibitors. She has normal renal function and no hepatic impairment. What is the drug of choice for her salvage regimen?

Explanation

## Salvage Therapy for NRTI/NNRTI-Resistant HIV **Key Point:** In treatment-experienced patients with documented genotypic resistance to both NRTIs and NNRTIs, a combination of a boosted protease inhibitor (PI) with a second-generation integrase inhibitor (INSTI) is the preferred salvage regimen. ### Clinical Context: Why Salvage Therapy? This patient has: 1. **Virologic failure** (VL = 2,100 copies/mL despite therapy) 2. **Genotypic resistance** to NRTI and NNRTI classes 3. **Advanced immunosuppression** (CD4 = 180 cells/μL) 4. **Normal organ function** (renal and hepatic) These factors mandate a potent, multi-class salvage regimen. ### Preferred Salvage Combination: Darunavir/r + Raltegravir **High-Yield:** Darunavir (a second-generation protease inhibitor) boosted with ritonavir, combined with raltegravir (an integrase inhibitor), is the preferred salvage regimen because: | Feature | Darunavir/r | Raltegravir | Synergy | |---|---|---|---| | **Potency** | High barrier to PI resistance; retains activity against most PI-resistant strains | Rapid viral suppression; different mechanism | Complementary mechanisms | | **Resistance Profile** | Requires multiple mutations for resistance | Can develop resistance with suboptimal adherence | Together, reduce resistance risk | | **Pharmacokinetics** | Ritonavir-boosted for enhanced levels | Twice-daily dosing (newer formulations: once-daily) | Both achieve high intracellular concentrations | | **Tolerability** | Better GI tolerance than older PIs (LPV/r) | Excellent tolerability; minimal CNS effects | Synergistic suppression without additive toxicity | | **CD4 Recovery** | Supports immune reconstitution at CD4 <200 | Rapid CD4 recovery | Both potent for advanced immunosuppression | **Clinical Pearl:** Darunavir is superior to older PIs (lopinavir, atazanavir) in salvage settings because it retains activity against many PI-resistant strains due to its unique binding mode and high genetic barrier. ### Why This Combination Works in Salvage **Mnemonic:** **DRAT** = **D**arunavir/**r** + **R**altegravir = **A**dvanced **T**herapy 1. **Orthogonal resistance**: NRTI/NNRTI resistance does NOT confer resistance to PIs or INSTIs. 2. **High barrier**: Both darunavir and raltegravir have high barriers to resistance; resistance requires multiple mutations. 3. **Rapid suppression**: INSTIs achieve faster viral suppression than older agents; PIs provide a second potent backbone. 4. **Immune recovery**: At CD4 = 180, rapid viral suppression is critical to prevent opportunistic infections and promote CD4 recovery. ### Alternative Salvage Agents (Not Preferred Here) **Warning:** The following are NOT preferred for this patient: - **Boosted lopinavir**: Older PI with lower genetic barrier and more GI toxicity than darunavir. - **Efavirenz**: NNRTI to which patient is already resistant; adding it is futile. - **Dolutegravir alone**: While potent, dolutegravir monotherapy or dual therapy (without a PI) is insufficient for salvage in heavily treatment-experienced patients; a PI is needed for additional potency. - **Older PIs (indinavir, atazanavir)**: Lower barrier to resistance and less favorable pharmacokinetics than darunavir in salvage. ### Guideline Support **High-Yield:** IAS-USA, EACS, and WHO guidelines all recommend a boosted PI (preferably darunavir) + INSTI (raltegravir or dolutegravir) as the backbone for salvage therapy in patients with NRTI/NNRTI resistance. [cite:Harrison 21e Ch 197; IAS-USA Guidelines 2023]