The drug efavirenz inhibits:

Ans. b. HIV reverse transcriptase (Ref: Katzung 12/e p870; Goodman Gilman 12/e p1626)The drug efavirenz inhibits HIV reverse transcriptase."NNRTIs (Efavirenz) bind to HIV-1 reverse transcriptase at a different site than NRTIs and induces a conformational change in the enzyme and disrupts catalytic activity."Non-Nucleoside Reverse Transcriptase Inhibitor (NNRTI)NNRTIs bind to HIV-1 reverse transcriptase at a different site than NRTIs and induces a conformational change in the enzyme and disrupts catalytic activityWell absorbed from GIT; bioavailability increased with a high fat mealPlasma-protein binding: 99%; Poor penetration into blood brain barrierMetabolized by oxidation by CYP2D6 and CYP3A4All NNRTIs are specific for HIV-1 with no action against HIV-2Saquinavir is a protease inhibitor."Saquinavir, the first approved HIV protease inhibitor, is a peptidomimetic hydroxyethylamine--Goodman Gillman 12/e p1648Anti-Retroviral TherapyThere are five classes of drugs, which are usually used in combination, to treat HIV infection.Use of these drugs in combination can be termed anti-retroviral therapy (ART), combination anti-retroviral therapy (cART) or highly active anti-retroviral therapy (HAART)Anti-retroviral (ARV) drugs are broadly classified by the phase of the retrovirus life cycle that the drug inhibits.Typical combinations include 2 NRTIs as a "backbone" along with 1 NNRTI, PI or INSTI as a "base".Name of GroupExamplesMechanismEntry inhibitor (Fusion inhibitors)MaravirocQEnfuvirtideQ* Interfere with binding, fusion & entry of HIV- 1 to host cell by blocking a target.* Maraviroc works by targeting CCR5, a co-receptor located on human helper T-cellsNucleoside Reverse Transcriptase Inhibitors (NRTI) & Nucleotide Reverse Transcriptase Inhibitors (NtRTI)Zidovudine, Abacavir, La- mivudine, Emtricitabine & Tenofovir (NtRTI)* Nucleoside & nucleotide analogues which inhibit reverse transcription* Both act as competitive substrate inhibitorsNon-Nucleoside reverse transcriptase inhibitors (NNRTI)1st generation: Nevirapine & EfavirenzQ2nd generation: Etravirine & RilpivirineQ* Inhibit reverse transcriptase by binding to an allosteric site of the enzyme* NNRTIs act as non-competitive inhibitors of reverse transcriptase.* HIV-2 is naturally resistant to NNRTIs.Integrase inhibitors (Integrase Nuclear Strand Transfer Inhibitors or INSTIs)RaltegravirQElvitegravirQDolutegravirQ* Inhibit the viral enzyme integrase. which is responsible for integration of viral DNA into the DNA of the infection cell.Protease inhibitorsLopinavir, Indinavir, Nelfinavir, Ritonavir, Amprenavir; Daruna- vir & Atazanavir (1st line)* Block the viral protease enzyme necessary to produce mature virions upon budding from the host membrane.