Last reviewed 2026-04-20 · How we verify

Tybost (COBICISTAT)

Tybost works by blocking the enzyme Cytochrome P450 3A, which is responsible for breaking down many other medications.

Tybost (Cobicistat) is a small molecule Cytochrome P450 3A inhibitor originally developed by Gilead Sciences Inc and currently owned by the same company. It is used to treat human immunodeficiency virus infection and malignant melanoma with BRAF V600E mutation. Tybost works by inhibiting the enzyme Cytochrome P450 3A, which is involved in the metabolism of other drugs. It is FDA approved and has a commercial status of patented, with one generic manufacturer available. Key safety considerations include its potential to interact with other medications.

At a glance

Mechanism of action

Cobicistat is mechanism-based inhibitor of cytochrome P450 3A (CYP3A). Inhibition of CYP3A-mediated metabolism by cobicistat increases the systemic exposure of CYP3A substrates atazanavir and darunavir.

Approved indications

• Human immunodeficiency virus infection
• Malignant Melanoma with BRAF V600E Mutation

Common side effects

• Jaundice
• Rash
• Ocular icterus
• Nausea
• Diarrhea
• Headache
• Vomiting
• Upper abdominal pain
• Fatigue
• Rhabdomyolysis
• Depression
• Abnormal dreams

Drug interactions

• alfentanil
• alfuzosin
• amprenavir
• atazanavir
• axitinib
• boceprevir
• bosentan
• cabozantinib
• clarithromycin
• colchicine
• conivaptan
• crizotinib

Key clinical trials

• A Study of the Effects of Food and Cobicistat on Plixorafenib Pharmacokinetics in Healthy Participants. (PHASE1)
• Study of Cobicistat-Boosted Atazanavir (ATV/co), Cobicistat-Boosted Darunavir (DRV/co) and Emtricitabine/Tenofovir Alafenamide (F/TAF) in Children With HIV (PHASE2,PHASE3)
• A Study of Revumenib in R/R Leukemias Including Those With an MLL/KMT2A Gene Rearrangement or NPM1 Mutation (PHASE1,PHASE2)
• A Study to Provide Continued Access to Study Drug to Children and Adolescents Who Have Completed Clinical Studies Involving Gilead HIV Treatments (PHASE4)
• KF2025#1 Trial: Ketamine, Cannabidiol and Cobicistat Interaction Study (PHASE1)
• KF2024#1-trial: Esketamine Interaction Study (PHASE1)
• Study to Evaluate the Pharmacokinetics, Safety, and Antiviral Activity of the Elvitegravir/Cobicistat/Emtricitabine/Tenofovir Alafenamide (E/C/F/TAF) Single Tablet Regimen (STR) in HIV-1 Infected Antiretroviral Treatment-Naive Adolescents and Virologically Suppressed Children (PHASE2,PHASE3)
• Trial to Evaluate the Interest of a Reductive Anti Retroviral Strategy Using Dual Therapy Inspite of Triple Therapy (PHASE3)

Patents

Primary sources

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