Cobicistat, Elvitegravir, Emtricitabine, And Tenofovir Alafenamide

Introduction Overview

Generic Name

cobicistat, elvitegravir, emtricitabine, and tenofovir alafenamide

Brand Name

Genvoya

Dosage Form

oral tablet

Drug Class

Antiviral combinations

Pharmacokinetics

Absorption:
Genvoya is administered orally as a single fixed-dose combination tablet containing elvitegravir, cobicistat, emtricitabine, and tenofovir alafenamide (TAF). The absorption of elvitegravir and cobicistat is enhanced by administering the tablet with food, increasing bioavailability significantly compared to fasting. Elvitegravir achieves peak plasma concentration approximately 4 hours post-dose, with cobicistat serving as a pharmacokinetic enhancer by selectively inhibiting CYP3A enzymes, thereby boosting elvitegravir plasma levels and prolonging half-life. Emtricitabine exhibits high oral bioavailability (>90%) and rapid absorption, reaching peak levels within 1 to 2 hours. TAF, a novel prodrug of tenofovir, exhibits enhanced cellular uptake and hepatic first-pass metabolism minimizes systemic exposure to tenofovir, resulting in lower plasma tenofovir levels compared to older formulations.

Distribution:
Elvitegravir is extensively bound to plasma proteins (approximately 99%) primarily albumin, influencing its pharmacokinetic profile. Cobicistat is highly protein-bound (~97%-98%) and distributes widely to tissues while exhibiting minimal penetration into cerebrospinal fluid. Emtricitabine has low plasma protein binding (<4%) allowing widespread distribution to various tissues including genital secretions, vital for HIV treatment. Tenofovir derived from TAF exhibits moderate protein binding (~7%), with substantial bone and renal tissue distribution, integral for its antiviral effect but also necessitating monitoring for nephrotoxicity and bone mineral density changes.

Metabolism:
Elvitegravir undergoes extensive hepatic metabolism predominantly via cytochrome P450 3A enzymes (CYP3A). Cobicistat acts as a potent CYP3A inhibitor, resulting in decreased metabolism of elvitegravir and increased plasma concentrations enhancing antiviral efficacy. Cobicistat itself is metabolized primarily by CYP3A and eliminated via bile. Emtricitabine is minimally metabolized, with the majority excreted unchanged in urine. TAF is rapidly converted intracellularly by cathepsin A to tenofovir; unlike tenofovir disoproxil fumarate (TDF), systemic conversion is limited thereby lowering circulating tenofovir levels and associated toxicities.

Elimination:
Elvitegravir and cobicistat have elimination half-lives of approximately 12-15 hours and 3-4 hours respectively, primarily excreted in feces and bile with minor renal clearance. Emtricitabine is eliminated mainly via renal excretion (approximately 86% unchanged in urine) with a half-life of 10 hours. Tenofovir, the active metabolite from TAF, is predominantly cleared renally by a combination of glomerular filtration and active tubular secretion. The overall elimination half-life of tenofovir allows once-daily dosing. Renal function impacts clearance significantly, necessitating monitoring in patients with impaired kidney function.

Dosage Forms

Available Dosage Forms:
Genvoya is available exclusively as a fixed-dose combination oral tablet intended for once-daily dosing.

Dosages for Adults and Adolescents:
- Adults and adolescents aged 12 years and older, weighing at least 35 kg (approximately 77 lbs), should take one tablet once daily with food.
- The tablet contains specific quantities of active ingredients combined to provide effective antiviral activity.

Specific Patient Populations:
- Prior to initiating therapy, patients should be evaluated for hepatic and renal function, particularly assessing estimated creatinine clearance.
- Not recommended for patients with severe renal impairment (eGFR <30 mL/min) or those requiring dialysis without specific clinical judgment.
- Pediatric dosing adjustments are not established for children under 12 years or less than 35 kg.
- Liver function should be closely monitored in patients with a history of hepatitis B virus infection since exacerbations may occur upon discontinuation.
- The formulation is designed as a complete regimen and should not be co-administered with other antiretroviral combination therapies containing overlapping components to avoid toxicity or resistance.

Mechanism Of Action

Genvoya combines four active components that act synergistically to inhibit the replication of HIV-1, targeting different stages of the viral life cycle.

Elvitegravir is an integrase strand transfer inhibitor (INSTI) that blocks the catalytic activity of HIV integrase enzyme, which is essential for the integration of viral DNA into the host genome. By binding to the integrase active site, elvitegravir prevents the insertion of viral DNA, thereby blocking the formation of proviral DNA and halting viral replication.

Cobicistat serves as a pharmacokinetic enhancer rather than a direct antiviral agent. It selectively inhibits the cytochrome P450 3A (CYP3A) enzyme system primarily responsible for the metabolism of elvitegravir, resulting in increased plasma concentration and extended half-life of elvitegravir. This boosting effect enables once-daily dosing and maintains effective therapeutic levels.

Emtricitabine is a nucleoside reverse transcriptase inhibitor (NRTI) that acts as a cytidine analog. Inside infected cells, it is phosphorylated to its active form, emtricitabine triphosphate, which competes with natural nucleotides for incorporation into viral DNA by the reverse transcriptase enzyme. Its incorporation causes premature termination of DNA synthesis, inhibiting viral replication.

Tenofovir alafenamide (TAF) is a prodrug of tenofovir, a nucleotide reverse transcriptase inhibitor (NtRTI). It is converted intracellularly to tenofovir diphosphate, a potent inhibitor of HIV reverse transcriptase enzyme. This metabolite competitively inhibits the incorporation of natural deoxynucleotides into viral DNA and causes chain termination. The use of TAF rather than tenofovir disoproxil fumarate reduces systemic exposure to tenofovir, minimizing renal and bone toxicities.

Collectively, these agents disrupt critical enzymes required for viral replication at complementary stages: integration (elvitegravir), and reverse transcription (emtricitabine and tenofovir), with cobicistat enhancing bioavailability of elvitegravir. This multi-targeted approach improves antiviral potency, reduces resistance development, and allows for a simplified once-daily regimen crucial in HIV treatment.

Pharmacological Actions

Inhibition of HIV-1 integrase enzyme by elvitegravir, preventing integration of viral DNA into host genome.
Pharmacokinetic enhancement by cobicistat via selective CYP3A inhibition, increasing elvitegravir plasma concentrations.
Inhibition of HIV-1 reverse transcriptase enzyme by emtricitabine, causing DNA chain termination.
Inhibition of HIV-1 reverse transcriptase enzyme by tenofovir diphosphate derived from tenofovir alafenamide, causing DNA chain termination.
Collective blockade of essential enzymatic steps in the HIV replication cycle, resulting in suppression of viral replication.
Reduced systemic toxicity due to use of tenofovir alafenamide prodrug allowing enhanced intracellular delivery.
Once-daily dosing regimen enabled through enzyme inhibition and boosting effects promoting patient adherence.
Minimal off-target effects improving tolerability compared to older antiretroviral therapies.
Reduced potential for resistance development due to combination targeting multiple viral enzymes.
Synergistic antiviral activity leading to durable viral suppression with optimized pharmacokinetics.

Therapeutic Or Clinical Uses

Treatment of human immunodeficiency virus type 1 (HIV-1) infection in adults and pediatric patients 12 years and older weighing at least 35 kg.
Recommended as a complete antiretroviral regimen for treatment-naïve patients with no known resistance to individual components.
Alternative regimen for virologically suppressed patients switching from stable antiretroviral therapy with no history of treatment failure.
Treatment option to manage HIV-1 infection with improved renal and bone safety profile compared to tenofovir disoproxil fumarate-based therapies.
Utilized to achieve and maintain viral suppression with once-daily oral dosing improving patient adherence.
Not indicated for HIV pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis.
Part of initial antiretroviral treatment recommended by multiple HIV treatment guidelines for eligible patients.
Employed in combination therapies to prevent development of drug resistance in HIV treatment.
Potential use in patients co-infected with hepatitis B virus, though requires monitoring due to reactivation risk upon discontinuation.
Effective in reducing HIV viral load and improving immune function as measured by CD4+ T-cell counts.

Side Or Adverse Effects

Nausea and gastrointestinal discomfort are common mild side effects.
Diarrhea has been reported in some patients during therapy.
Potential for kidney-related adverse events including decreased urine output, swelling, or signs of renal impairment.
Risk of lactic acidosis characterized by muscle pain, difficulty breathing, and profound weakness—an uncommon but serious side effect requiring immediate medical attention.
Hepatotoxicity including elevated liver enzymes, jaundice, and hepatitis-like symptoms, especially in patients with pre-existing liver disease.
Hypersensitivity reactions manifesting as rash, hives, facial swelling, or anaphylaxis requiring urgent discontinuation.
Immune reconstitution inflammatory syndrome (IRIS) may occur in some patients starting antiretroviral therapy.
Potential for redistribution or increase in body fat and weight gain, possibly related to integrase inhibitors.
Headache, fatigue, or dizziness reported infrequently.
Alterations in laboratory parameters such as increased serum creatinine due to inhibition of renal transporters by cobicistat.
Rare cases of arrhythmias or QT prolongation reported in patients with underlying risk factors.
Exacerbation of hepatitis B infection upon abrupt cessation due to viral rebound.
Possible interactions leading to increased side effects from concomitant medications.
Renal tubular dysfunction and decrease in bone mineral density linked to tenofovir component, though less common with TAF.
Potential for decreased effectiveness of hormonal contraceptives and interactions with other drugs.

Precautions

Monitor liver function closely in patients with a history or concurrent hepatitis B or liver disease.
Assess renal function prior to and during therapy due to risk of nephrotoxicity and adjust treatment accordingly.
Advise patients to take Genvoya with food to enhance drug absorption and efficacy.
Avoid co-administration with drugs highly dependent on CYP3A for clearance as it may lead to serious adverse reactions.
Do not discontinue therapy without consulting a healthcare provider to prevent viral rebound and resistance.
Inform patients on the risks of lactic acidosis and advise immediate medical attention if symptoms occur.
Screen for HBV infection before initiation due to risk of exacerbation upon discontinuation.
Use caution in pregnant women; consider alternative regimens as efficacy may be reduced during pregnancy.
Recommend non-hormonal contraceptive methods as Genvoya can reduce effectiveness of hormonal contraceptives.
Advise against breastfeeding as HIV transmission risk exists via breast milk.
Use caution in patients with pre-existing renal impairment, monitor urinary glucose and protein.
Avoid use with certain seizure, antipsychotic, and cholesterol-lowering agents due to significant drug interactions.
Inform patients about the importance of adherence to prevent resistance and therapeutic failure.
Evaluate potential for immune reconstitution inflammatory syndrome in severely immunocompromised patients.
Advise patients about the avoidance of antacids within 2 hours before or after taking Genvoya as they reduce absorption.

Warnings

Severe hepatotoxicity leading to liver failure may occur; symptoms include jaundice, dark urine, abdominal pain, and should prompt immediate evaluation.
Potential for lactic acidosis and severe hepatomegaly with steatosis, a life-threatening mitochondrial toxicity.
Risk of renal toxicity, including acute renal failure and Fanconi syndrome, especially in patients with pre-existing renal impairment.
Do not use Genvoya concomitantly with drugs highly dependent on CYP3A for clearance due to risk of serious adverse effects or loss of efficacy.
Abrupt discontinuation may result in HIV viral rebound and emergence of resistance.
Genvoya is not approved for HIV pre-exposure or post-exposure prophylaxis.
Use caution in patients with known bone density disorders due to potential bone mineral loss.
Efficacy may be reduced in pregnancy; alternative antiretroviral regimens should be considered.
Patients with a history of hypersensitivity to any component should not use Genvoya.
Genvoya may interact adversely with other antiviral drugs and overlapping regimens should be avoided.
Risk of immune reconstitution inflammatory syndrome in patients with advanced HIV disease after starting therapy.
Severe allergic reactions including anaphylaxis and Stevens-Johnson syndrome, although rare, warrant immediate discontinuation.
May cause elevations in serum creatinine due to inhibition of renal tubular transporters without actual renal dysfunction.
Potential for drug-induced arrhythmias, especially in patients with prolonged QT interval or on other QT-prolonging drugs.
Use with hormonal contraceptives may increase side effects and decrease contraceptive efficacy.

Contraindication

Known hypersensitivity or allergy to cobicistat, elvitegravir, emtricitabine, tenofovir alafenamide, or any component of the formulation.
Concomitant use with drugs highly dependent on CYP3A for clearance, such as alfuzosin, cisapride, oral midazolam, triazolam, rifampin, and St. John's wort.
Use with ergot derivatives including dihydroergotamine, ergotamine, and methylergonovine due to risk of serious and life-threatening reactions.
Concurrent administration with certain antipsychotics like lurasidone or pimozide that are contraindicated due to increased plasma levels.
Simultaneous use with cholesterol-lowering agents such as lomitapide, lovastatin, and simvastatin that may lead to severe toxicity.
Co-administration with seizure medications including carbamazepine, phenobarbital, and phenytoin that may reduce antiretroviral effectiveness.
Patients with severe renal impairment (eGFR <30 mL/min) or end-stage renal disease on dialysis without dose adjustment or specialist recommendation.
Current or past history of lactic acidosis or severe hepatic dysfunction.
Use with other antiretroviral medications containing overlapping active agents like adefovir, lamivudine, ritonavir, or tenofovir disoproxil fumarate to avoid toxicity.
Pregnancy, unless no suitable alternatives are available due to limited efficacy and safety data in this population.
Breastfeeding mothers due to risk of HIV transmission through breast milk.
Known resistance to any of the individual components of Genvoya in treatment-experienced patients.
Severe hypersensitivity to any NRTI or integrase inhibitor class agents.
Concomitant use with antacids within 2 hours before or 2 hours after dosing as it reduces absorption.
Patients taking hormonal contraceptives that may have reduced efficacy without additional contraception.

Drug Interactions

Cobicistat strongly inhibits CYP3A enzymes, increasing plasma concentrations of drugs metabolized by CYP3A and risking toxicity.
Co-administration with rifampin is contraindicated due to loss of efficacy of elvitegravir and cobicistat.
Concomitant use with St. John's Wort reduces elvitegravir and cobicistat blood levels, impairing efficacy.
Interactions with cholesterol-lowering agents such as simvastatin and lovastatin increase risk of myopathy and rhabdomyolysis.
Drugs such as carbamazepine, phenytoin, and phenobarbital induce CYP3A and reduce concentrations of elvitegravir and cobicistat.
Antipsychotics like lurasidone and pimozide have increased plasma levels leading to potential cardiac arrhythmias.
Use with ergot derivatives increases risk of severe vasospasm and ischemia.
Midazolam and triazolam levels increase significantly when given orally with Genvoya, enhancing sedation and respiratory depression.
Sildenafil used for pulmonary arterial hypertension (Revatio) may have increased plasma levels, requiring dose adjustment.
Genvoya may reduce effectiveness of hormonal contraceptives; additional non-hormonal contraception advised.
Concurrent use with other antiretrovirals containing cobicistat or elvitegravir may lead to overdose or increased toxicity.
Antacids containing aluminum, magnesium, or calcium can interfere with absorption if taken concomitantly.
Interaction with nephrotoxic drugs may exacerbate renal adverse effects.
Cobicistat may increase levels of drugs prolonging QT interval leading to arrhythmias.
Potential interaction with immunosuppressants like tacrolimus or cyclosporine increasing toxicity risk.

Preparations Of The Drug

Genvoya is supplied as a fixed-dose combination oral tablet.
Each tablet contains cobicistat 150 mg, elvitegravir 150 mg, emtricitabine 200 mg, and tenofovir alafenamide 10 mg.
Packaged in bottles with child-resistant caps to maintain safety.
Storage recommended at controlled room temperature, protected from moisture and heat.
Provided as a prescription medication requiring medical supervision.
Available in single-dose bottles or multi-tablet bottles depending on manufacturer packaging.
Formulation designed for once-daily oral administration with food to enhance absorption.
Contains inactive ingredients to stabilize the tablet and improve bioavailability.
Not available in alternative dosage forms such as liquids or injectables.
Supplied with patient information leaflets detailing dosing, contraindications, and side effects.
Manufactured under GMP standards ensuring consistent potency and purity.
Packaging includes medication guides emphasizing adherence and potential drug interactions.
Distributed through specialized pharmacies with secure handling due to antiviral combination.
Approved by regulatory authorities for treatment of HIV-1 in indicated populations.
Periodic updates in labeling based on post-marketing surveillance and new clinical data.