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CLINICAL PHARMACOLOGY Mechanism Of Action Cobicistat is a 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. Pharmacodynamics Effects On Pharmacokinetic Enhancement The effect of TYBOST on atazanavir pharmacokinetics was evaluated in the pharmacokinetic substudy (N=48) of Study 114 in which HIV-1 infected subjects received atazanavir 300 mg coadministered with TYBOST 150 mg or atazanavir 300 mg coadministered with ritonavir 100 mg, both in combination with TRUVADA. The steady-state pharmacokinetic parameters of atazanavir were comparable when coadministered with TYBOST versus ritonavir groups as shown in Table 7 [see Clinical Studies]. Table 7 Pharmacokinetic Parameters (Mean ± SD) of Atazanavir in HIV-1 Infected Treatment-Naive Adults (Pharmacokinetic Substudy of Study 114) Atazanavir Pharmacokinetic Parameters TYBOST + Atazanavir + TRUVADA Once Daily Ritonavir + Atazanavir + TRUVADA Once Daily N=22 N=26 AUCtau (mcg∙hr/mL) 46.13 ± 26.18 47.59 ± 24.38 Cmax (mcg/mL) 3.91 ± 1.94 4.76 ± 1.94 Ctau (mcg/mL) 0.80 ± 0.72 0.85 ± 0.72 The effect of TYBOST on darunavir was evaluated in a clinical study (Study 115) in 31 healthy subjects who received darunavir 800 mg in combination with TYBOST 150 mg or ritonavir 100 mg, all once daily, for 10 days. With the exception of Ctau, the steady-state pharmacokinetic parameters of darunavir were comparable when coadministered with TYBOST versus ritonavir as shown in Table 8, and these results were similar to those reported in previous clinical trials of darunavir 800 mg with ritonavir 100 mg once daily (refer to prescribing information for darunavir). Table 8 Pharmacokinetic Parameters (Mean ± SD) of Darunavir in Healthy Adults (Study 115) Darunavir Pharmacokinetic Parameters TYBOST + Darunavir Once Daily Ritonavir + Darunavir Once Daily N=31 N=31 AUCtau (mcg∙hr/mL) 81.08 ± 25.15 79.99 ± 27.20 Cmax (mcg/mL) 7.74 ± 1.69 7.46 ± 1.52 C0h (mcg/mL) 2.40 ± 1.22 2.48 ± 0.85 Ctau (mcg/mL) 1.33 ± 0.89 1.87 ± 1.56 Cardiac Electrophysiology The effect of a single dose of cobicistat 250 mg and 400 mg (approximately 1.7 and 2.7 times the recommended dose, respectively) on QTc interval was evaluated in a randomized, placebo-and active-controlled (moxifloxacin 400 mg), four-period crossover thorough QT study in 48 healthy subjects. In this study, no significant QTc prolongation effect of cobicistat was detected. The dose of 400 mg TYBOST is expected to cover a high exposure clinical scenario. Prolongation of the PR interval was noted in subjects receiving TYBOST in the same study. The maximum mean (95% upper confidence bound) difference in PR from placebo after baseline-correction was 9.5 (12.1) msec for 250 mg and 20.2 (22.8) msec for 400 mg of cobicistat. Effects On Serum Creatinine The effect of TYBOST on serum creatinine was investigated in a trial in subjects with normal renal function (eGFR ≥80 mL/min, N=12) and mild-to-moderate renal impairment (eGFR 50.79 mL/min, N=18). A statistically significant decrease in the estimated glomerular filtration rate, calculated by Cockcroft-Gault method (eGFRCG) from baseline, was observed after 7 days of treatment with cobicistat 150 mg among subjects with normal renal function (.9.9 ± 13.1 mL/min) and mild-to-moderate renal impairment (.11.9 ± 7.0 mL/min). No statistically significant changes in eGFRCG were observed compared to baseline for subjects with normal renal function or mild-to-moderate renal impairment 7 days after cobicistat was discontinued. The actual glomerular filtration rate, as determined by the clearance of probe drug iohexol, was not altered from baseline following treatment with TYBOST among subjects with normal renal function and mild-to-moderate renal impairment, indicating that cobicistat inhibits tubular secretion of creatinine, reflected as a reduction in eGFRCG, without affecting the actual glomerular filtration rate [see WARNINGS AND PRECAUTIONS]. Pharmacokinetics Absorption In a trial where subjects were instructed to take coadministered TYBOST and darunavir with food, median cobicistat peak plasma concentrations were observed approximately 3.5 hours postdose. Steady-state cobicistat Cmax, AUCtau, and Ctau (mean ± SD) values were 0.99 ± 0.3 mcg/mL (n=60), 7.6 ± 3.7 mcg*hr/mL (n=59), and 0.03 ± 0.1 mcg/mL (n=59), respectively. Effect Of Food On Oral Absorption A food-effect trial was not conducted for TYBOST. In clinical trials, TYBOST was coadministered with other antiretroviral agents [see Clinical Studies] under fed conditions, in accordance with the prescribing information for these agents. It is recommended that TYBOST coadministered with atazanavir or darunavir be administered with food [see DOSAGE AND ADMINISTRATION]. Distribution Cobicistat is 97.98% bound to human plasma proteins and the mean blood-to-plasma ratio was approximately 0.5. Metabolism Cobicistat is metabolized by CYP3A and to a minor extent by CYP2D6 enzymes and does not undergo glucuronidation. Elimination The terminal plasma half-life of cobicistat following administration of TYBOST is approximately 3 to 4 hours. With single dose administration of [14C] cobicistat after multiple dosing of cobicistat for 6 days, the mean percent of the administered dose excreted in feces and urine was 86.2% and 8.2%, respectively. Specific Populations Patients With Hepatic Impairment Cobicistat is primarily metabolized and eliminated by the liver. A study of the pharmacokinetics of cobicistat was performed in non-HIV-1 infected subjects with moderate hepatic impairment. No clinically relevant differences in cobicistat pharmacokinetics were observed between subjects with moderate hepatic impairment (Child-Pugh Class B) and healthy subjects. The effect of severe hepatic impairment (Child-Pugh Class C) on the pharmacokinetics of cobicistat has not been studied [see Use In Specific Populations]. Patients With Renal Impairment A study of the pharmacokinetics of cobicistat was performed in non-HIV-1 infected subjects with severe renal impairment (estimated creatinine clearance below 30 mL/min). No clinically relevant differences in cobicistat pharmacokinetics were observed between subjects with severe renal impairment and healthy subjects [see Use In Specific Populations]. Race Population pharmacokinetic analysis of cobicistat in HIV-1 infected subjects indicated that race had no clinically relevant effect on the exposure of cobicistat. Gender No clinically relevant pharmacokinetic differences have been observed between men and women for cobicistat. Assessment Of Drug Interactions Drug interaction trials were not conducted for TYBOST coadministered with atazanavir or darunavir. Drug interaction trials were conducted with TYBOST (as a single entity) and desipramine, digoxin, and efavirenz. Drug interaction trials of TYBOST coadministered with elvitegravir included rosuvastatin and rifabutin. The effects of cobicistat on the exposure of coadministered drugs are shown in Table 9. Table 9 Drug Interactions: Changes in Pharmacokinetic Parameters for Coadministered Drugs in the Presence of Cobicistata Note: The information listed below is not a comprehensive list of all the available druginteraction data for concomitant medications with cobicistat containing regimens. Please refer to the U.S. prescribing information for antiretroviral medications administered incombination with cobicistat for additional drug interaction information. Coadministered Drug Dose of Coadministered Drug (mg) TYBOST Dose (mg) N Mean Ratio of Coadministered Drug Pharmacokinetic Parameters (90% CI); No effect = 1.00 Cmax AUC Ctau Desipramine 50 single dose 150 once daily 8 1.24 (1.08, 1.44) 1.65 (1.36, 2.02) NCb Digoxin 0.5 single dose 150 once daily 22 1.41 (1.29, 1.55) 1.08 (1.00, 1.17) NCb Efavirenz 600 single dose 150 once daily 17 0.87 (0.80, 0.94) 0.93 (0.89, 0.97) NCb a. All interaction studies conducted in healthy subjects. b. NC = Not Calculated. Microbiology Antiviral Activity Cobicistat does not inhibit recombinant HIV-1 protease in a biochemical assay and has no detectable antiviral activity in cell culture against HIV-1, HBV, or HCV. The antiviral activity in cell culture of selected HIV-1 antiretroviral drugs was not antagonized by cobicistat. Resistance In an analysis of treatment-failure subjects who received TYBOST coadministered with atazanavir and TRUVADA in Study 114 through Week 144, evaluable genotypic data from paired baseline and treatment-failure isolates from subjects who had HIV-1 RNA greater than or equal to 400 copies/mL were available for all 21 virologic failures in the TYBOST group [6%, 21/344]. Among the 21 subjects, 3 developed the emtricitabineassociated resistance substitution M184V. No subject developed the tenofovirassociated resistance substitution K65R or K70E, or any primary resistance substitution associated with protease inhibitors. In the ritonavir group, evaluable genotypic data were available for all 19 virologic failures [5%, 19/348]. Among the 19 patients, 1 developed the emtricitabine-associated resistance substitution M184V with no tenofovir or protease inhibitor associated resistance substitutions. Clinical Studies The activity of TYBOST as a CYP3A inhibitor to increase the systemic exposures of atazanavir or darunavir has been demonstrated in pharmacokinetic trials. In these trials, the exposure of atazanavir or darunavir coadministered with TYBOST 150 mg was consistent with those observed with ritonavir 100 mg [see CLINICAL PHARMACOLOGY]. For clinical efficacy of darunavir/ritonavir 800/100 mg once daily, refer to the prescribing information for darunavir. The safety and efficacy of TYBOST coadministered with atazanavir were evaluated in a randomized, double-blind, active-controlled trial (Study 114) in HIV-1 infected treatment-naive subjects with baseline estimated creatinine clearance above 70 mL/min (N=692). In Study 114, subjects were randomized in a 1:1 ratio to receive either atazanavir 300 mg + TYBOST 150 mg once daily or atazanavir 300 mg + ritonavir 100 mg once daily. All subjects received concomitant treatment with 300 mg of tenofovir DF and 200 mg of emtricitabine once a day administered as single tablet TRUVADA. Randomization was stratified by screening HIV-1 RNA level (≤100,000 copies/mL or >100,000 copies/mL). The mean age of subjects was 37 years (range 19.70); 83% were male, 60% were White, 18% were Black, and 12% were Asian. The mean baseline plasma HIV-1 RNA was 4.8 log10 copies/mL (range 3.2.6.4). Forty percent of patients had baseline viral loads >100,000 copies/mL. The mean baseline CD4+ cell count was 352 cells/mm3 (range 1.1455) and 17% had CD4+ cell counts ≤200 cells/mm3 . Virologic outcomes in Study 114 through Week 144 are presented in Table 10. In Study 114, the mean increase from baseline in CD4+ cell count at Week 144 was 281 cells/mm3 in the TYBOST group and 297 cells/mm3 in the ritonavir group. Table 10 Virologic Outcome of Randomized Treatment of Study 114 in HIV-1 Infected Treatment Naive Adults at Week 144a TYBOST + Atazanavir + TRUVADA (N=344) Ritonavir + Atazanavir + TRUVADA (N=348) HIV-1 RNA <50 copies/mL 72% 74% Treatment Difference −2.1% (95% CI = −8.7%, 4.5%) HIV RNA ≥50 copies/mLb 8% 5% No Virologic Data at Week 144 Window 20% 21% Discontinued Study Drug Due to AE or Deathc 11% 11% Discontinued Study Drug Due to Other Reasons and Last Available HIV-1 RNA <50 copies/mLd 8% 10% Missing Data During W indow but on Study Drug <1% <1% a. Week 144 window was between Day 967 and 1050 (inclusive). b. Included subjects who had ≥50 copies/mL in the Week 144 window; subjects who discontinued early due to lack or loss of efficacy; subjects who discontinued for reasons other than an adverse event (AE), death, or lack or loss of efficacy and at the time of discontinuation had a viral value of ≥50 copies/mL. c. Includes subjects who discontinued due to AE or death at any time point from Day 1 through the time window if this resulted in no virologic data on treatment during the specified window. d. Includes subjects who discontinued for reasons other than an AE, death, or lack or loss of efficacy; e.g., withdrew consent, lost to follow-up, etc.

Find Lowest Prices on TYBOST® (cobicistat) Tablets DESCRIPTION TYBOST (cobicistat) is a mechanism-based CYP3A inhibitor. The chemical name for cobicistat is 1,3-thiazol-5-ylmethyl [(2R,5R)-5-{[(2S)-2[(methyl{[2-(propan-2-yl)-1,3-thiazol-4-yl]methyl}carbamoyl)amino]-4-(morpholin-422 yl)butanoyl]amino}-1,6-diphenylhexan-2-yl]carbamate. It has a molecular formula of C40H53N7O5S2 and a molecular weight of 776.0. It has the following structural formula: Cobicistat is adsorbed onto silicon dioxide. Cobicistat on silicon dioxide is a white to pale yellow solid with a solubility of 0.1 mg/mL in water at 20 °C. TYBOST tablets are for oral administration. Each tablet contains 150 mg of cobicistat. The tablets include the following inactive ingredients: silicon dioxide, microcrystalline cellulose, croscarmellose sodium, and magnesium stearate. The tablets are film-coated with a coating material containing the following inactive ingredients: polyethylene glycol, polyvinyl alcohol, talc, titanium dioxide, sunset yellow FCF (FD&C Yellow #6) aluminum lake, and iron oxide yellow.

INDICATIONS TYBOST is a CYP3A inhibitor indicated to increase systemic exposure of atazanavir or darunavir (once daily dosing regimen) in combination with other antiretroviral agents in the treatment of HIV-1 infection [see DOSAGE AND ADMINISTRATION]. Limitations Of Use TYBOST is not interchangeable with ritonavir to increase systemic exposure of darunavir 600 mg twice daily, fosamprenavir, saquinavir, or tipranavir due to lack of exposure data. The use of TYBOST is not recommended with darunavir 600 mg twice daily, fosamprenavir, saquinavir, or tipranavir [see WARNINGS AND PRECAUTIONS]. Complex or unknown mechanisms of drug interactions preclude extrapolation of ritonavir drug interactions to certain TYBOST interactions. TYBOST and ritonavir when administered with either atazanavir or darunavir may result in different drug interactions when used with concomitant medications [see WARNINGS AND PRECAUTIONS , DRUG INTERACTIONS and CLINICAL PHARMACOLOGY]. DOSAGE AND ADMINISTRATION Recommended Dosage Administer TYBOST in conjunction with atazanavir or darunavir and other antiretroviral agents in the treatment of adults with HIV-1 infection. The recommended dosages of TYBOST and atazanavir or darunavir given with food are presented in Table 1. TYBOST must be coadministered at the same time as atazanavir or darunavir [see DRUG INTERACTIONS]. Consult the prescribing information for atazanavir or darunavir. Table 1 Recommended Dosing Regimens TYBOST Dosage Coadministered Agent Dosage Patient Populations 150 mg orally once daily atazanavir 300 mg orally once daily Treatment-naïve or experienced darunavir 800 mg orally once daily Treatment-naïve Treatment-experienced with no darunavir resistance associated substitutions Testing Prior To Initiation Of TYBOST Prior to starting TYBOST, assess estimated creatinine clearance because TYBOST decreases estimated creatinine clearance due to inhibition of tubular secretion of creatinine without affecting actual renal glomerular function [see WARNINGS AND PRECAUTIONS]. When coadministering TYBOST with tenofovir disoproxil fumarate (tenofovir DF), assess estimated creatinine clearance, urine glucose, and urine protein at baseline [see WARNINGS AND PRECAUTIONS]. Renal Impairment TYBOST coadministered with tenofovir DF is not recommended in patients who have an estimated creatinine clearance below 70 mL/min because dose adjustment of tenofovir DF is required below 50 mL/min and such dose adjustments have not been established for coadministration with TYBOST [see WARNINGS AND PRECAUTIONS and ADVERSE REACTIONS]. HOW SUPPLIED Dosage Forms And Strengths Orange, round, biconvex, film-coated tablets debossed with “GSI” on one side and plain faced on the other side providing 150 mg of cobicistat. Storage And Handling TYBOST tablets, 150 mg, are orange, round, biconvex, film-coated, and debossed with “GSI” on one side and plain faced on the other side. Each bottle contains 30 tablets (NDC 61958-1401-1) and a silica gel desiccant, with a child-resistant closure. Store at 25 °C (77 °F); excursions permitted to 15.30 °C (59.86 °F) (see USP Controlled Room Temperature). Keep container tightly closed. Dispense only in original container. Do not use if seal over bottle opening is broken or missing. Distributed by: Gilead Sciences, Inc. Foster City, CA 94404. Revised: May 2017

PATIENT INFORMATION TYBOST® (TYE-bost) (cobicistat) Tablets Important: Ask your healthcare provider or pharmacist about medicines that should not be taken with TYBOST. For more information, see the section “What should I tell my healthcare provider before taking TYBOST?” Read this Patient Information before you start taking TYBOST and each time you get a refill. There may be new information. This information does not take the place of talking with your healthcare provider about your medical condition or treatment. Also read the Patient Information for atazanavir (REYATAZ®) or darunavir (PREZISTA®) prescribed by your healthcare provider when taking TYBOST. What is TYBOST? TYBOST is a prescription medicine used in adults 1 time each day with the antiretroviral Human Immunodeficiency Virus-1 (HIV-1) medicines atazanavir (REYATAZ®) or darunavir (PREZISTA®) to increase the amount of those medicines in your blood. TYBOST is not an antiretroviral medicine and does not treat the HIV-1 virus. You must also take all the antiretroviral HIV-1 medicines prescribed by your healthcare provider even if you take TYBOST and atazanavir (REYATAZ®) or darunavir (PREZISTA®). TYBOST should not be used if you take darunavir (PREZISTA®) when prescribed by your healthcare provider to be taken 2 times each day, or if you take other HIV-1 protease inhibitor medicines, including fosamprenavir (LEXIVA®), saquinavir (INVIRASE®), or tipranavir (APTIVUS®). It is not known if TYBOST is safe and effective in children under 18 years of age. Do not take TYBOST combined with atazanavir or darunavir if you also take any of the following medicines: alfuzosin hydrochloride (UROXATRAL®) carbamazepine (CARBATROL®, EPITOL®, EQUETRO®, TEGRETOL®) cisapride (PROPULSID®, PROPULSID® QUICKSOLV) colchicine (COLCRYS , MITIGARE™.), if you have liver or kidney problems dronedarone hydrochloride (MULTAQ®) ergot-containing medicines: dihydroergotamine mesylate (D.H.E. 45®, MIGRANAL®) ergotamine tartrate (CAFERGOT®, MIGERGOT®, ERGOSTAT®, MEDIHALER ERGOTAMINE®, WIGRAINE®, WIGRETTES®) methylergonovine maleate (ERGOTRATE®, METHERGINE®) lovastatin (ADVICOR®, ALTOPREV®, MEVACOR®) lurasidone (LATUDA®) midazolam (VERSED®), when taken by mouth phenobarbital (LUMINAL®) phenytoin (DILANTIN®, PHENYTEX®) pimozide (ORAP®) ranolazine (RANEXA®) rifampin (RIFADIN®, RIFAMATE®, RIFATER®, RIMACTANE®) sildenafil (REVATIO®), when used for treating the lung problem pulmonary arterial hypertension (PAH) simvastatin (SIMCOR®, VYTORIN®, ZOCOR®) St. John’s wort (Hypericum perforatum) or a product that contains St. John’s wort triazolam (HALCION®) If you take TYBOST with atazanavir (REYATAZ®), do not take it with any of the following medicines: indinavir (CRIXIVAN®) irinotecan (CAMPTOSAR®) nevirapine (VIRAMUNE®, VIRAMUNE XR®) What should I tell my healthcare provider before taking TYBOST? Before you take TYBOST, tell your healthcare provider if you: have kidney problems have liver problems have any other medical conditions are pregnant or plan to become pregnant. It is not known if TYBOST can harm your unborn baby. Tell your healthcare provider if you become pregnant while taking TYBOST. Pregnancy Registry: There is a pregnancy registry for women who take TYBOST during pregnancy. The purpose of the registry is to collect information about the health of you and your baby. Talk to your healthcare provider about how you can take part in this registry. are breastfeeding or plan to breastfeed. Do not breastfeed if you take TYBOST. You should not breastfeed if you have HIV-1 because of the risk of passing HIV-1 to your baby. It is not known if TYBOST can pass to your baby in your breast milk. Talk to your healthcare provider about the best way to feed your baby. Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. TYBOST with atazanavir or darunavir may affect the way other medicines work, and other medicines may affect how TYBOST with atazanavir or darunavir works. Taking TYBOST with atazanavir or darunavir, along with certain other medicines can lead to severe or life threatening side effects, or could lead to death. Keep a list of your medicines and show it to your healthcare provider and pharmacist when you get a new medicine. You can ask your healthcare provider or pharmacist for a list of medicines that interact when taken with TYBOST with atazanavir or darunavir. Do not start a new medicine without telling your healthcare provider. Your healthcare provider can tell you if it is safe to take TYBOST with atazanavir or darunavir, along with other medicines. How should I take TYBOST? Take TYBOST exactly as your healthcare provider tells you. Do not change your dose or stop taking TYBOST without first talking with your healthcare provider. Stay under the care of your healthcare provider during treatment with TYBOST. See your healthcare provider regularly while taking TYBOST. Take TYBOST 1 time each day at the same time you take atazanavir (REYATAZ®) or darunavir (PREZISTA®). It is important to take these medicines on a regular dosing schedule. . Take TYBOST with atazanavir or TYBOST with darunavir, along with food. If you take too much TYBOST, call your healthcare provider or go to the nearest hospital emergency room right away. Do not run out of TYBOST. The virus in your blood may become resistant to the HIV-1 medicine atazanavir (REYATAZ®) or darunavir (PREZISTA®) if TYBOST is stopped for even a short time. When your supply starts to run low, get more from your healthcare provider or pharmacy. What are the possible side effects of TYBOST? TYBOST when taken with certain other medicines can cause new or worse kidney problems, including kidney failure. Your healthcare provider should check your kidneys before you start and while you are taking TYBOST. The most common side effects of TYBOST with atazanavir (REYATAZ®) include yellowing of the skin and rash. Tell your healthcare provider if you have any side effect that bothers you or that does not go away. These are not all the possible side effects of TYBOST. For more information, ask your healthcare provider or pharmacist. Call your healthcare provider for medical advice about side effects. You may report side effects to FDA at 1-800-FDA1088. How should I store TYBOST? Store TYBOST at room temperature between 68 °F to 77 °F (20 °C to 25 °C). Do not use TYBOST if the seal over the bottle opening is broken or missing. Keep TYBOST in its original container. Keep the container tightly closed. Keep TYBOST and all medicines out of reach of children. General information about TYBOST Medicines are sometimes prescribed for purposes other than those listed in a Patient Information leaflet. Do not use TYBOST for a condition for which it was not prescribed. Do not give TYBOST to other people, even if they have the same symptoms you have. It may harm them. If you would like more information, talk with your healthcare provider. You can ask your healthcare provider or pharmacist for information about TYBOST that is written for health professionals. For more information, call 1-800-445-3235 or go to www.GILEAD.com. What are the ingredients in TYBOST? Active ingredient: cobicistat Inactive ingredients: silicon dioxide, microcrystalline cellulose, croscarmellose sodium, and magnesium stearate. The tablets are film-coated with a coating material containing polyethylene glycol, polyvinyl alcohol, talc, titanium dioxide, sunset yellow FCF (FD&C Yellow #6) aluminum lake, and iron oxide yellow.

OVERDOSE If overdose occurs, the patient must be monitored for evidence of toxicity. Treatment of overdose with TYBOST consists of general supportive measures including monitoring of vital signs, as well as observation of the clinical status of the patient. As cobicistat is highly bound to plasma proteins, it is unlikely that it will be significantly removed by hemodialysis or peritoneal dialysis. CONTRAINDICATIONS The concomitant use of TYBOST with atazanavir or darunavir and the following drugs (see Table 2) is contraindicated due to the potential for serious and/or life-threatening events or loss of therapeutic effect [see DRUG INTERACTIONS]. Table 2 Drugs that are Contraindicated with Concomitant use with TYBOST and Atazanavir or Darunavir Drug Class Drugs within Class that are Contraindicated Clinical Comment Alpha 1-Adrenoreceptor Antagonist alfuzosin Potential for increased alfuzosin concentrations, which can result in serious or life-threatening reactions such as hypotension. Antianginal ranolazine Potential for serious and/or life-threatening reactions. Antiarrhythmic dronedarone Potential for increased dronedarone concentrations. Anticonvulsants carbamazepine, phenobarbital, phenytoin Potential for decreased atazanavir or darunavir plasma concentrations, which may result in loss of therapeutic effect and development of resistance. Anti-gout colchicine Contraindicated in patients with renal and/or hepatic impairment due to potential for serious and/or life-threatening reactions. Antimycobacterial rifampin Rifampin is a potent inducer of CYP metabolism and coadministration may cause a significant decrease in the plasma concentrations of atazanavir or darunavir and result in loss of therapeutic effect and development of resistance. Antineoplastics irinotecan Contraindicated with TYBOST coadministered with atazanavir only: Atazanavir inhibits UGT1A1 and may interfere with the metabolism of irinotecan, resulting in increased irinotecan toxicity. Antipsychotics lurasidone pimozide Potential for serious and/or life-threatening reactions. Potential for serious and/or life-threatening reactions such as cardiac arrhythmias. Ergot Derivatives dihydroergotamine, ergotamine, methylergonovine Potential for serious and/or life-threatening reactions such as acute ergot toxicity characterized by peripheral vasospasm and ischemia of the extremities and other tissues. GI Motility Agent cisapride Potential for serious and/or life-threatening reactions such as cardiac arrhythmias. Herbal Products St. John’s wort (Hypericum perforatum) Products containing St. John’s wort may result in reduced plasma concentrations of atazanavir or darunavir, which may result in loss of therapeutic effect and development of resistance. HMG-CoA Reductase Inhibitors lovastatin, simvastatin Potential for serious reactions such as myopathy including rhabdomyolysis. Non-nucleoside Reverse Transcriptase Inhibitor nevirapine Contraindicated with TYBOST coadministered with atazanavir only: Nevirapine substantially decreases atazanavir exposure which may result in loss of therapeutic effect and development of resistance. Potential risk for nevirapine-associated adverse reactions due to increased nevirapine exposures. Phosphodiesterase-5 (PDE-5) Inhibitor sildenafila when administered as REVATIO® for the treatment of pulmonary arterial hypertension Potential for sildenafil-associated adverse reactions (which include visual disturbances, hypotension, priapism, and syncope). Protease Inhibitor indinavir Contraindicated with TYBOST coadministered with atazanavir only: Both atazanavir and indinavir are associated with indirect (unconjugated) hyperbilirubinemia. Sedative/hypnotics triazolam, orally administered midazolamb Triazolam and orally administered midazolam are extensively metabolized by CYP3A4. Coadministration of triazolam or orally administered midazolam may cause large increases in the concentration of these benzodiazepines. The potential exists for serious and/or life-threatening benzodiazepine reactions such as prolonged or increased sedation or respiratory depression. a. See DRUG INTERACTIONS, Table 6 for sildenafil when dosed as VIAGRA for erectile dysfunction. b. See DRUG INTERACTIONS, Table 6 for parenterally administered midazolam.

SIDE EFFECTS The following adverse reaction is described in greater detail in another section of the labeling: New Onset or Worsening Renal Impairment When Used with Tenofovir Disoproxil Fumarate [see WARNINGS AND PRECAUTIONS] Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The safety of TYBOST is based on Week 144 data from a Phase 3 trial, Study 114, in which 692 HIV-1 infected, antiretroviral treatment-naive subjects received: TYBOST coadministered with atazanavir and tenofovir DF/emtricitabine(administered as TRUVADA) (N=344) or; ritonavir coadministered with atazanavir and tenofovir DF/emtricitabine (administered as TRUVADA) (N=348). The most common adverse reactions (Grades 2-4) and reported in >5% of subjects in the TYBOST group were jaundice (6%) and rash (5%). The proportion of subjects who discontinued study treatment due to adverse events, regardless of severity, was 11% in both the TYBOST and ritonavir groups. Table 3 displays the frequency of adverse reactions (Grades 2-4) occurring in at least 2% of subjects in the TYBOST group in Study 114. Table 3 Selected Adverse Reactionsa (Grades 2-4) Reported in ≥2% of HIV-1 Infected Treatment-Naive Adults in the TYBOST Coadministered with Atazanavir Group in Study 114 (Week 144 Analysis) TYBOST Coadministered with Atazanavir + TRUVADA N=344 Ritonavir Coadministered with Atazanavir + TRUVADA N=348 Jaundice 6% 3% Rashb 5% 4% Ocular icterus 4% 2% Nausea 2% 2% Diarrhea 2% 1% Headache 2% 1% a. Frequencies of adverse reactions are based on Grades 2-4 adverse events attributed to study drugs. b. Rash events include dermatitis allergic, drug hypersensitivity, pruritus generalized, eosinophilic pustular folliculitis, rash, rash generalized, rash macular, rash maculo-papular, rash morbilliform, rash papular, and urticaria. Less Common Adverse Reactions Selected adverse reactions of at least moderate severity (≥Grade 2) occurring in less than 2% of subjects receiving TYBOST coadministered with atazanavir and TRUVADA are listed below. These events have been included because of the investigator’s assessment of potential causal relationship and were considered serious or have been reported in more than one subject treated with TYBOST and with greater frequency compared with ritonavir. Gastrointestinal Disorders: vomiting, upper abdominal pain General Disorders and Administration Site Conditions: fatigue Musculoskeletal and Connective Tissue Disorders: rhabdomyolysis Psychiatric Disorders: depression, abnormal dreams, insomnia Renal and Urinary Disorders: nephropathy, Fanconi syndrome acquired, nephrolithiasis Refer to the prescribing information for atazanavir or darunavir for information regarding adverse reactions with these drugs. Laboratory Abnormalities The frequency of laboratory abnormalities (Grades 3-4) occurring in at least 2% of subjects in the TYBOST group in Study 114 is presented in Table 4. Table 4 Laboratory Abnormalities (Grades 3-4) in ≥2% of HIV-1 Infected Treatment-Naive Adults in the TYBOST Coadministered with Atazanavir Group in Study 114 (Week 144 Analysis) TYBOST + Atazanavir + TRUVADA Ritonavir + Atazanavir + TRUVADA Laboratory Parameter Abnormality N=344 N=348 Total Bilirubin (>2.5 × ULN) 73% 66% Creatine Kinase (≥10.0 × ULN) 8% 9% Urine RBC (Hematuria) (>75 RBC/HPF) 6% 3% ALT (>5.0 × ULN) 6% 3% AST (>5.0 × ULN) 4% 3% GGT (>5.0 × ULN) 4% 2% Serum Amylasea (>2.0 × ULN) 4% 2% Urine Glucose (Glycosuria) (≥1000 mg/dL) 3% 3% Neutrophils (<750/mm3) 3% 2% Serum Glucose (Hyperglycemia) (>250 mg/dL) 2% 2% a. For subjects with serum amylase >1.5 x upper limit of normal, lipase test was also performed. The frequency of increased lipase (Grades 3-4) occurring in the TYBOST (N=46) and ritonavir (N=35) groups was 7% and 3%, respectively. Increase In Serum Creatinine TYBOST causes increases in serum creatinine and decreases in estimated creatinine clearance due to inhibition of tubular secretion of creatinine without affecting actual renal glomerular function [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY]. In Study 114, increases in serum creatinine and decreases in estimated creatinine clearance occurred early in treatment with TYBOST, after which they stabilized. The mean (± SD) change in estimated glomerular filtration rate (eGFR) by Cockcroft-Gault method after 144 weeks of treatment was .15.1 ± 16.5 mL/min in the TYBOST group and .8.0 ± 16.8 mL/min in the ritonavir group. Serum Lipids Changes from baseline in total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides are presented in Table 5. In both groups, mean values for serum lipids remained within the study reference range for each laboratory test. The clinical significance of these changes is unknown. Table 5 Lipid Values, Mean Change from Baseline, Reported in HIV-1 Infected Treatment-Naive Adults Receiving TYBOST Coadministered with Atazanavir + TRUVADA or Ritonavir Coadministered with Atazanavir TYBOST + Atazanavir + TRUVADA Ritonavir + Atazanavir + TRUVADA Baseline Week 144 Baseline Week 144 mg/dL Change from baselinea mg/dL Change from baselinea Total Cholesterol (fasted) 163 [N=219] +11 [N=219] 165 [N=227] +13 [N=227] HDL-cholesterol (fasted) 43 [N=218] +7 [N=218] 43 [N=228] +6 [N=228] LDL-cholesterol (fasted) 102 [N=218] +11 [N=218] 104 [N=228] +16 [N=228] Triglycerides (fasted) 130 [N=219] +14 [N=219] 131 [N=227] +14 [N=227] a. The change from baseline is the mean of within-patient changes from baseline for patients with both baseline and Week 144 values. Analysis excludes subjects receiving an HMG-CoA reductase inhibitor drug. DRUG INTERACTIONS See also DOSAGE AND ADMINISTRATION , CONTRAINDICATIONS , WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY . Potential Effect Of Cobicistat (Coadministered With Atazanavir Or Darunavir) On The Pharmacokinetics Of Concomitant Drugs Cobicistat is an inhibitor of CYP3A and CYP2D6. The transporters that cobicistat inhibits include p-glycoprotein (P-gp), BCRP, OATP1B1, and OATP1B3. The plasma concentration of drugs that are primarily metabolized by CYP3A or CYP2D6, or are substrates of P-gp, BCRP, OATP1B1, or OATP1B3 may be increased if those drugs are coadministered with TYBOST. Based on in vitro data, cobicistat is not expected to induce CYP1A2 or CYP2B6 and based on in vivo data, cobicistat is not expected to induce MDR1 or, in general, CYP3A to a clinically significant extent. The induction effect of cobicistat on CYP2C9, CYP2C19, or UGT1A1 is unknown, but is expected to be low based on CYP3A in vitro induction data. Coadministration of TYBOST with atazanavir or darunavir with drugs highly dependent on CYP3A for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events is contraindicated. Coadministration with other CYP3A substrates may require a dose adjustment or additional monitoring as shown in Table 6. Potential Effect Of Concomitant Drugs On The Pharmacokinetics Of Cobicistat (Coadministered With Atazanavir Or Darunavir) Cobicistat is metabolized by CYP3A, and to a minor extent, by CYP2D6. Atazanavir and darunavir are also metabolized by CYP3A. Coadministration of TYBOST with atazanavir or darunavir in combination with drugs that induce CYP3A activity have the potential to decrease plasma concentrations of cobicistat, atazanavir, and darunavir, which may lead to loss of therapeutic effect and development of resistance (see Table 6). Coadministration of TYBOST with atazanavir or darunavir in combination with other drugs that inhibit CYP3A may further increase the plasma concentrations of cobicistat, atazanavir, and darunavir (see Table 6). Established And Other Potentially Significant Interactions Coadministration of TYBOST with fosamprenavir, saquinavir, or tipranavir is not recommended because pharmacokinetic data are not available to provide appropriate dosing recommendations. Use of TYBOST with lopinavir is not recommended because lopinavir is co-formulated with ritonavir. Drug interaction trials were not conducted for TYBOST in combination with atazanavir or darunavir. As a single entity, drug interaction trials were conducted with TYBOST and desipramine, digoxin, and efavirenz. Table 6 provides dosing recommendations as a result of drug interactions with TYBOST coadministered with atazanavir or darunavir. These recommendations are based on either drug interaction trials or predicted interactions due to the expected magnitude of the interaction and potential for serious adverse events or loss of therapeutic effect. In Table 6, if not specifically stated, the drug interaction information applies to both coadministered agents: TYBOST coadministered with atazanavir or darunavir [see CLINICAL PHARMACOLOGY]. In addition to the drug interactions noted in Table 6, TYBOST is not recommended for use in combination with fixed-dose combination tablets that contain cobicistat, lopinavir/ritonavir or regimens containing ritonavir, or in combination with more than one antiretroviral agent that requires pharmacokinetic enhancement [see WARNINGS AND PRECAUTIONS]. Evaluate whether dosing adjustments of concomitant medications or coadministered antiretroviral drugs are necessary in: Patients on a stable concomitant medication who initiate or switch to a TYBOST-containing regimen Patients on a TYBOST-containing regimen who initiate a new concomitant medication Patients initiating a TYBOST-containing regimen and a new concomitant medication simultaneously Under these circumstances, also monitor for adverse events and/or monitor concentrations of concomitant medications if appropriate. No dose adjustment is required when tenofovir DF or rilpivirine are coadministered with TYBOST and atazanavir or darunavir. Table 6 Established and Other Potentially Significanta Drug Interactions: Alteration in Dose or Regimen May Be Recommended Based on Drug Interaction Studies or Predicted Interaction Concomitant Drug Class: Drug Name Potential Effectb Clinical Comment Antiretroviral Agents: Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) efavirenz ↓ cobicistat ↓ darunavir ↓ atazanavir TYBOST coadministered with darunavir: Coadministration of darunavir and TYBOST with efavirenz is not recommended because it may result in the loss of therapeutic effect and development of resistance to darunavir. TYBOST coadministered with atazanavir: In treatment-naïve patients: Atazanavir 400 mg with TYBOST 150 mg should be coadministered once daily as a single dose with food, and efavirenz 600 mg should be administered once daily on an empty stomach, preferably at bedtime. In treatment-experienced patients: Coadministration of atazanavir and TYBOST with efavirenz in treatment-experienced patients is not recommended because it may result in the loss of therapeutic effect and development of resistance to atazanavir. etravirine ↓ cobicistat darunavir: effect unknown ↓ atazanavir Coadministration with etravirine is not recommended because it may result in the loss of therapeutic effect and development of resistance to atazanavir or darunavir. nevirapine ↓ cobicistat darunavir: effect unknown TYBOST coadministered with atazanavir: TYBOST coadministration with nevirapine and atazanavir is contraindicated [see CONTRAINDICATIONS] TYBOST coadministered with darunavir: TYBOST coadministration with nevirapine and darunavir is not recommended because it may result in the loss of therapeutic effect and development of resistance to darunavir. Antiretroviral Agents: CCR5 Antagonists maraviroc ↑ maraviroc Maraviroc is a substrate of CYP3A. When coadministering with maraviroc, patients should receive maraviroc 150 mg twice daily. Other Agents: Antacids: e.g., aluminum and magnesium hydroxide (please also see H2 Receptor Antagonists and Proton Pump Inhibitors below) ↓ atazanavir TYBOST coadministered with atazanavir: With concomitant use, administer a minimum of 2 hours apart. Antiarrhythmics: e.g., amiodarone disopyramide flecainide mexiletine propafenone quinidine ↑ antiarrhythmics Contraindicated antiarrhythmics [see CONTRAINDICATIONS] Clinical monitoring is recommended upon coadministration with antiarrhythmics. digoxin ↑ digoxin When coadministering with digoxin, titrate the digoxin dose and monitor digoxin concentrations. Antibacterials (macrolide or ketolide antibiotics): clarithromycin erythromycin telithromycin ↑ clarithromycin ↑ erythromycin ↑ telithromycin ↑ cobicistat ↑ atazanavir ↑ darunavir Consider alternative antibiotics with concomitant use of TYBOST coadministered with atazanavir or darunavir. Anticancer Agents: dasatinib nilotinib vinblastine vincristine ↑ anticancer agents A decrease in the dosage or an adjustment of the dosing interval of dasatinib or nilotinib may be necessary upon coadministration with TYBOST coadministered with atazanavir or darunavir. Consult the dasatinib and nilotinib prescribing information for dosing instructions. For vincristine and vinblastine, monitor for hematologic or gastrointestinal side effects. Anticoagulants: warfarin warfarin: effect unknown Monitor the international normalized ratio (INR) when coadministering with warfarin. rivaroxaban ↑ rivaroxaban Avoid coadministration with rivaroxaban which may result in increased exposure of rivaroxaban and increased risk of bleeding. Anticonvulsants: Anticonvulsants with CYP3A induction effects that are NOT contraindicated (e.g., eslicarbazepine, oxcarbazepine) ↓ cobicistat ↓ atazanavir darunavir: effect unknown Contraindicated anticonvulsants [see CONTRAINDICATIONS] Consider alternative anticonvulsant or antiretroviral therapy to avoid potential changes in exposures. If coadministration is necessary, monitor for lack or loss of virologic response. Anticonvulsants that are metabolized by CYP3A (e.g., clonazepam) ↑ clonazepam Clinical monitoring of anticonvulsants is recommended. Antidepressants: Selective Serotonin Reuptake Inhibitors (SSRIs) e.g., paroxetine Tricyclic Antidepressants (TCAs) e.g., amitriptyline desipramine imipramine nortriptyline Other antidepressants: trazodone SSRIs: effects unknown ↑ TCAs ↑ trazodone When coadministering with SSRIs, TCAs, or trazodone, careful dose titration of the antidepressant to the desired effect, including using the lowest feasible initial or maintenance dose, and monitoring for antidepressant response are recommended. Antifungals: itraconazole ketoconazole voriconazole ↑ itraconazole ↑ ketoconazole Voriconazole: effects unknown ↑ cobicistat ↑ atazanavir ↑ darunavir Specific dosing recommendations are not available for coadministration with itraconazole or ketoconazole. Coadministration with voriconazole is not recommended unless the benefit/risk assessment justifies the use of voriconazole. Anti-gout: colchicine ↑ colchicine Coadministration with colchicine in patients with renal or hepatic impairment is contraindicated [see CONTRAINDICATIONS]. Treatment of gout flares – coadministration of colchicine: 0.6 mg (1 tablet) x 1 dose, followed by 0.3 mg (half tablet) 1 hour later. Treatment course to be repeated no earlier than 3 days. Prophylaxis of gout flares – coadministration of colchicine: If the original regimen was 0.6 mg twice a day, the regimen should be adjusted to 0.3 mg once a day. If the original regimen was 0.6 mg once a day, the regimen should be adjusted to 0.3 mg once every other day. Treatment of familial Mediterranean fever – coadministration of colchicine: Maximum daily dose of 0.6 mg (may be given as 0.3 mg twice a day). Antimycobacterial: rifabutin ↑ rifabutin cobicistat: effects unknown darunavir: effects unknown atazanavir: effects unknown Contraindicated antimycobacterials [see CONTRAINDICATIONS] The recommended dosage regimen for rifabutin is 150 mg every other day. Monitor for rifabutin associated adverse reactions including neutropenia and uveitis. Antipsychotics: e.g., perphenazine risperidone thioridazine ↑ antipsychotic Contraindicated antipsychotics [see CONTRAINDICATIONS] A decrease in the dose of antipsychotics that are metabolized by CYP3A or CYP2D6 may be needed upon coadministration. quetiapine ↑ quetiapine Initiation of TYBOST coadministered with atazanavir or darunavir in patients taking quetiapine: Consider alternative antiretroviral therapy to avoid increases in quetiapine exposure. If coadministration is necessary, reduce the quetiapine dose to 1/6 of the current dose and monitor for quetiapine-associated adverse reactions. Refer to the quetiapine prescribing information for recommendations on adverse reaction monitoring. Initiation of quetiapine in patients taking TYBOST coadministered with atazanavir or darunavir: Refer to the quetiapine prescribing information for initial dosing and titration of quetiapine. Beta-Blockers: e.g., metoprolol carvedilol timolol ↑ beta-blockers Clinical monitoring is recommended for coadministration with beta-blockers that are metabolized by CYP2D6. Calcium Channel Blockers: e.g., amlodipine diltiazem felodipine nifedipine verapamil ↑ calcium channel blockers Clinical monitoring is recommended for coadministration with calcium channel blockers metabolized by CYP3A. Systemic/Inhaled/ Nasal/Ophthalmic Corticosteroids: e.g., betamethasone budesonide ciclesonide dexamethasone fluticasone methylprednisolone mometasone prednisone triamcinolone ↓ cobicistat ↓ atazanavir ↓ darunavir ↑ corticosteroids Coadministration with oral dexamethasone or other systemic corticosteroids that induce CYP3A may result in loss of therapeutic effect and development of resistance to atazanavir or darunavir. Consider alternative corticosteroids. Coadministration with corticosteroids whose exposures are significantly increased by strong CYP3A inhibitors can increase the risk for Cushing’s syndrome and adrenal suppression. Alternative corticosteroids including beclomethasone and prednisolone (whose PK and/or PD are less affected by strong CYP3A inhibitors relative to other studied steroids) should be considered, particularly for long-term use [see Drug Interactions (7.4)]. Endothelin Receptor Antagonists: bosentan ↑ bosentan ↓ cobicistat ↓ darunavir ↓ atazanavir Initiation of bosentan in patients taking TYBOST coadministered with atazanavir or darunavir: In patients who have been receiving TYBOST coadministered with atazanavir or darunavir for at least 10 days, start bosentan at 62.5 mg once daily or every other day based upon individual tolerability. Initiation of TYBOST coadministered with atazanavir or darunavir in patients taking bosentan: Discontinue use of bosentan at least 36 hours prior to initiation of TYBOST coadministered with atazanavir or darunavir. After at least 10 days following the initiation of TYBOST combined with atazanavir or darunavir, resume bosentan at 62.5 mg once daily or every other day based upon individual tolerability. Switching from ritonavir to TYBOST coadministered with atazanavir or darunavir Maintain bosentan dose. H2-Receptor Antagonists: e.g., famotidine ↓ atazanavir TYBOST coadministered with atazanavir: Administer atazanavir/TYBOST either at the same time or a minimum of 10 hours after administering H2 receptor antagonists. The dose of the H2-receptor antagonist should not exceed a dose comparable to famotidine 40 mg twice daily in treatment-naïve patients or 20 mg twice daily in treatment-experienced patients. TYBOST coadministered with atazanavir and tenofovir DF: Treatment-experienced patients: The recommended once daily dosage regimen is TYBOST 150 mg coadministered with atazanavir 400 mg with concomitant use of H2-receptor antagonists and tenofovir. HCV Protease Inhibitors: boceprevir darunavir: effects unknown atazanavir: effects unknown No drug interaction data are available. Coadministration with boceprevir or simeprevir is not recommended. boceprevir: effects unknown simeprevir ↑ simeprevir HMG-CoA Reductase Inhibitors: e.g., atorvastatin rosuvastatin ↑ HMG-CoA reductase inhibitors Contraindicated HMG-CoA Reductase Inhibitors [see CONTRAINDICATIONS] For HMG-CoA reductase inhibitors that are not contraindicated with TYBOST coadministered with atazanavir or darunavir, start with the lowest recommended dose and titrate while monitoring for safety. Hormonal Contraceptives: progestin/estrogen progestin: effects unknown estrogen: effects unknown No data are available to make recommendations on the coadministration of TYBOST and atazanavir or darunavir with oral or other hormonal contraceptives. Additional or alternative (non-hormonal) forms of contraception should be considered. Immuno- suppressants: cyclosporine everolimus sirolimus tacrolimus ↑ immuno-suppressants These immunosuppressant agents are metabolized by CYP3A. Therapeutic drug monitoring is recommended if coadministered. Inhaled Beta Agonist: salmeterol ↑ salmeterol Coadministration with salmeterol is not recommended and may result in increased risk of cardiovascular adverse events associated with salmeterol, including QT prolongation, palpitations, and sinus tachycardia. Narcotic Analgesics For treatment of opioid dependence: buprenorphine buprenorphine/ naloxone methadone buprenorphine or buprenorphine/ naloxone: effects unknown methadone: effects unknown Initiation of buprenorphine, buprenorphine/naloxone, or methadone in patients taking TYBOST coadministered with atazanavir or darunavir: Carefully titrate the dose of buprenorphine, buprenorphine/naloxone, or methadone to the desired effect; use the lowest feasible initial or maintenance dose. Initiation of TYBOST coadministered with atazanavir or darunavir in patients taking buprenorphine, buprenorphine/naloxone, or methadone:Ar / dose adjustment for buprenorphine, buprenorphine/naloxone, or methadone may be needed. Monitor clinical signs and symptoms. fentanyl ↑ fentanyl Careful monitoring of therapeutic and adverse effects of fentanyl (including potentially fatal respiratory depression) is recommended with coadministration. tramadol ↑ tramadol A dose decrease may be needed for tramadol with concomitant use. Phosphodiesterase5 (PDE-5) Inhibitors: avanafil sildenafil tadalafil vardenafil ↑ PDE-5 inhibitors Contraindicated PDE-5 Inhibitors [see CONTRAINDICATIONS] Coadministration with avanafil is not recommended because a safe and effective avanafil dosage regimen has not been established. Coadministration with TYBOST coadministered with atazanavir or darunavir may result in an increase in PDE-5 inhibitor associated adverse events, including hypotension, syncope, visual disturbances, and priapism. Use of PDE-5 inhibitors for pulmonary arterial hypertension (PAH): Use of sildenafil is contraindicated when used for the treatment of PAH [see CONTRAINDICATIONS]. The following dose adjustments are recommended for tadalafil concomitant use: Initiation of tadalafil in patients taking TYBOST coadministered with atazanavir or darunavir: In patients taking TYBOST coadministered with atazanavir or darunavir for at least 1 week, start tadalafil at 20 mg once daily. Increase tadalafil dose to 40 mg once daily based upon individual tolerability. Initiation of TYBOST coadministered with atazanavir or darunavir in patients taking tadalafil: Avoid use of tadalafil during the initiation of TYBOST coadministered with atazanavir or darunavir. Stop tadalafil at least 24 hours prior to starting TYBOST coadministered with atazanavir or darunavir. After at least one week following initiation of TYBOST coadministered with atazanavir or darunavir, resume tadalafil at 20 mg once daily. Increase tadalafil dose to 40 mg once daily based upon individual tolerability. Patients switching from ritonavir to TYBOST coadministered with atazanavir or darunavir: Maintain tadalafil dose. Use of PDE-5 inhibitors for erectile dysfunction: Sildenafil at a single dose not exceeding 25 mg in 48 hours, tadalafil at a single dose not exceeding 10 mg in 72 hours, or vardenafil at a single dose not exceeding 2.5 mg in 72 hours can be used with increased monitoring for PDE-5 inhibitor associated adverse events. Proton-pump Inhibitors (PPIs) e.g., omeprazole ↓ atazanavir TYBOST coadministered with atazanavir: In treatment-naïve patients, administer TYBOST with atazanavir a minimum of 12 hours after administering PPIs. The dose of the PPI should not exceed a dose comparable to omeprazole 20 mg daily. In treatment-experienced patients, coadministration with PPIs, with or without tenofovir, is not recommended. Sedative/Hypnotics: e.g., buspirone diazepam parenterally administered midazolam ↑ sedatives/hypnotics Contraindicated Sedative/Hypnotics [see CONTRAINDICATIONS] Coadministration with parenteral midazolam may increase plasma concentrations of midazolam. Coadministration should be done in a setting that ensures close clinical monitoring and appropriate medical management in case of respiratory depression and/or prolonged sedation. Dosing reduction for midazolam should be considered, especially if more than a single dose of midazolam is administered. Concomitant use with oral midazolam is contraindicated [see CONTRAINDICATIONS]. With other sedatives/hypnotics that are CYP3A metabolized, dose reduction may be necessary and clinical monitoring is recommended. a. This table is not all inclusive. b. ↑ = Increase, ↓ = Decrease, ↔ = No change Drugs Without Clinically Significant Interactions With TYBOST No clinically significant drug interactions have been either observed or are expected when TYBOST is combined with the following drugs: beclomethasone and prednisolone.

WARNINGS Included as part of the "PRECAUTIONS" Section PRECAUTIONS Effects On Serum Creatinine TYBOST decreases estimated creatinine clearance due to inhibition of tubular secretion of creatinine without affecting actual renal glomerular function. This effect should be considered when interpreting changes in estimated creatinine clearance in patients initiating TYBOST, particularly in patients with medical conditions or receiving drugs needing monitoring with estimated creatinine clearance. Prior to initiating therapy with TYBOST, assess estimated creatinine clearance [see DOSAGE AND ADMINISTRATION]. Dosage recommendations are not available for drugs that require dosage adjustments in TYBOST-treated patients with renal impairment [see ADVERSE REACTIONS , DRUG INTERACTIONS and CLINICAL PHARMACOLOGY]. Consider alternative medications that do not require dosage adjustments in patients with renal impairment. Although TYBOST may cause modest increases in serum creatinine and modest declines in estimated creatinine clearance without affecting renal glomerular function, patients who experience a confirmed increase in serum creatinine of greater than 0.4 mg/dL from baseline should be closely monitored for renal safety. New Onset Or Worsening Renal Impairment When Used With Tenofovir Disoproxil Fumarate Renal impairment, including cases of acute renal failure and Fanconi syndrome, has been reported when TYBOST was used in an antiretroviral regimen that contained tenofovir DF. Coadministration of TYBOST and tenofovir DF is not recommended in patients who have an estimated creatinine clearance below 70 mL/min because dose adjustment of tenofovir DF is required below 50 mL/min and such dose adjustments have not been established for coadministration with TYBOST [see DOSAGE AND ADMINISTRATION]. Document urine glucose and urine protein at baseline [see DOSAGE AND ADMINISTRATION] and perform routine monitoring of estimated creatinine clearance, urine glucose, and urine protein during treatment when TYBOST is used with tenofovir DF. Measure serum phosphorus in patients with or at risk for renal impairment when used with tenofovir DF. Coadministration of TYBOST and tenofovir DF in combination with concomitant or recent use of a nephrotoxic agent is not recommended. In a clinical trial of TYBOST over 144 weeks (N=692), 10 (2.9%) subjects treated with TYBOST coadministered with atazanavir and TRUVADA® and 11 (3.2%) subjects treated with ritonavir coadministered with atazanavir and TRUVADA discontinued study drug due to a renal adverse event. Seven of the 10 subjects (2.0% overall) in the TYBOST group had laboratory findings consistent with proximal renal tubulopathy leading to study drug discontinuation compared to 7 of 11 subjects (2.0% overall) in the ritonavir group. One subject in the TYBOST group had renal impairment at baseline (i.e., estimated creatinine clearance less than 70 mL/min). The laboratory findings in these 7 subjects with evidence of proximal tubulopathy improved but did not completely resolve in all subjects upon discontinuation of TYBOST coadministered with atazanavir and TRUVADA. Renal replacement therapy was not required in any subject. Risk Of Serious Adverse Reactions Or Loss Of Virologic Response Due To Drug Interactions Initiation of TYBOST, a CYP3A inhibitor, in patients receiving medications metabolized by CYP3A, or initiation of medications metabolized by CYP3A in patients already receiving TYBOST may increase plasma concentrations of medications metabolized by CYP3A. Initiation of medications that inhibit or induce CYP3A may respectively increase or decrease concentrations of TYBOST with atazanavir or darunavir. Increased concentrations may lead to: clinically significant adverse reactions, potentially leading to severe, life-threatening, or fatal events from higher exposures of concomitant medications. Clinically significant adverse reactions from higher exposures of TYBOST and atazanavir or darunavir. Decreased antiretroviral concentrations may lead to: loss of therapeutic effect of TYBOST with atazanavir or darunavir and possible development of resistance. See Table 6 for steps to prevent or manage these possible and known significant drug interactions, including dosing recommendations [see DRUG INTERACTIONS]. Consider the potential for drug interactions prior to and during TYBOST with atazanavir or darunavir therapy; review concomitant medications during TYBOST with atazanavir or darunavir therapy; and monitor for the adverse reactions associated with concomitant medications [see CONTRAINDICATIONS and DRUG INTERACTIONS]. TYBOST or ritonavir when administered with either atazanavir or darunavir may result in different drug interactions when used with concomitant medications. Complex or unknown mechanisms of drug interactions preclude extrapolation of ritonavir drug interactions to certain TYBOST interactions [see DRUG INTERACTIONS and CLINICAL PHARMACOLOGY]. Antiretrovirals That Are Not Recommended In Combination With TYBOST The following antiretrovirals are not recommended in combination with TYBOST because dosing recommendations for such combinations have not been established and coadministration may result in decreased plasma concentrations of the antiretroviral agents, leading to loss of therapeutic effect and development of resistance: More than one antiretroviral that requires pharmacokinetic enhancement (i.e., two protease inhibitors or a protease inhibitor in combination with elvitegravir) Darunavir in combination with efavirenz, nevirapine, or etravirine Atazanavir in combination with etravirine Atazanavir in combination with efavirenz in treatment-experienced patients Darunavir 600 mg twice daily Other HIV-1 protease inhibitors including fosamprenavir, saquinavir, or tipranavir TYBOST in combination with fixed-dose combination tablets that contain cobicistat is not recommended. TYBOST in combination with lopinavir/ritonavir or regimens containing ritonavir is not recommended due to similar effects of TYBOST and ritonavir on CYP3A. Patient Counseling Information Advise the patient to read the FDA-approved patient labeling (Patient Information). Drug Interaction Inform patients that TYBOST coadministered with atazanavir or darunavir may interact with many drugs with potential serious implications and that some drugs are contraindicated with TYBOST coadministered with atazanavir or darunavir. Advise patients to report to their healthcare provider the use of any other prescription or nonprescription medication, including acid-modifying medications or herbal products, including St. John's wort [see CONTRAINDICATIONS , WARNINGS AND PRECAUTIONS and DRUG INTERACTIONS]. New Onset Or Worsening Renal Impairment Inform patients that renal impairment, including cases of acute renal failure and Fanconi syndrome, has been reported when TYBOST is used in combination with a tenofovir DF containing regimen [see WARNINGS AND PRECAUTIONS]. Pregnancy Registry Inform patients that there is a pregnancy exposure registry that monitors fetal outcomes in women exposed to TYBOST during pregnancy [see Use In Specific Populations]. Lactation Instruct women with HIV-1 infection not to breastfeed because HIV-1 can be passed to the baby in breast milk [see Use In Specific Populations]. Dosing Instructions Inform patients that TYBOST must be taken at the same time as atazanavir or darunavir and with food once daily as prescribed. It is important to take TYBOST and atazanavir or darunavir together on a regular dosing schedule and to avoid missing doses. Counsel patients about the risks of developing resistance to their HIV-1 medications. TYBOST, GSI, and TRUVADA are trademarks of Gilead Sciences, Inc., or its related companies. All other trademarks are the property of their respective owners. Nonclinical Toxicology Carcinogenesis, Mutagenesis, Impairment Of Fertility Carcinogenesis In a long-term carcinogenicity study in mice, no drug-related increases in tumor incidence were observed at doses up to 50 and 100 mg/kg/day (males and females, respectively). Cobicistat exposures at these doses were approximately 7 (male) and 16 (females) times, respectively, the human systemic exposure at the therapeutic daily dose. In a long-term carcinogenicity study of cobicistat in rats, an increased incidence of follicular cell adenomas and/or carcinomas in the thyroid gland was observed at doses of 25 and 50 mg/kg/day in males, and at 30 mg/kg/day in females. The follicular cell findings are considered to be rat-specific, secondary to hepatic microsomal enzyme induction and thyroid hormone imbalance, and are not relevant for humans. At the highest doses tested in the rat carcinogenicity study, systemic exposures were approximately 2 times the human systemic exposure at the therapeutic daily dose. Mutagenesis Cobicistat was not genotoxic in the reverse mutation bacterial test (Ames test), mouse lymphoma, or rat micronucleus assays. Impairment Of Fertility Cobicistat did not affect fertility in male or female rats at daily exposures (AUC) approximately 3-fold higher than human exposures at the recommended 150 mg daily dose. Fertility was normal in the offspring of rats exposed daily from before birth (in utero) through sexual maturity at daily exposures (AUC) of approximately similar human exposures at the recommended 150 mg daily dose. Use In Specific Populations Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors fetal outcomes in women exposed to TYBOST during pregnancy. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry 1-800-258-4263. Risk Summary There are no data with TYBOST in pregnant women to inform a drug-associated risk. In animal reproduction studies in rats and rabbits, no evidence of fetal harm was observed with oral administration of cobicistat during organogenesis at doses that produced exposures up to 1.4 and 3.3 times, respectively, the maximal recommended human dose (MRHD) of 150 mg [see Data]. Consider the benefits and risks of TYBOST when prescribing TYBOST to a pregnant woman. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2.4% and 15.20%, respectively. Because TYBOST is coadministered with atazanavir or darunavir and other antiretroviral drugs, also refer to the prescribing information of each drug for information about pregnancy. Data Animal Data Cobicistat was administered orally to pregnant rats at doses of 0, 25, 50, and 125 mg/kg/day on gestation day 6 to 17. Maternal toxicity (adverse clinical signs, decreased body weight and food consumption) was noted at 125 mg/kg/day and was associated with increases in postimplantation loss and decreased fetal weights. No malformations were noted at doses up to 125 mg/kg/day. Systemic exposures (AUC) at 50 mg/kg/day in pregnant females was 1.4-fold higher than the exposures at the MRHD. In pregnant rabbits, cobicistat was administered orally at doses of 0, 20, 50, and 100 mg/kg/day during the gestation days 7 to 20. No maternal or embryo/fetal effects were noted at the highest dose of 100 mg/kg/day. Systemic exposures (AUC) at 100 mg/kg/day were 3.3-fold higher than exposures at the MRHD. In a pre-and postnatal developmental study, cobicistat was administered orally at doses of 0, 10, 30, and 75 mg/kg from gestation day 6 to postnatal day 20, 21, or 22. At doses of 75 mg/kg/day of cobicistat, neither maternal nor developmental toxicity was noted. Systemic exposures (AUC) at this dose were slightly lower than (0.9-fold) the MRHD. Lactation Risk Summary There is no information regarding the presence of cobicistat in human milk, the effects on the breastfed infant, or the effects on milk production. The Centers for Disease Control and Prevention recommend that HIV-infected mothers not breastfeed their infants to avoid risking postnatal transmission of HIV. Pediatric Use Safety and effectiveness of TYBOST in pediatric patients younger than 18 years of age have not been established. Geriatric Use Clinical trials of TYBOST did not include sufficient numbers of subjects aged 65 and older to determine whether they respond differently from younger subjects. Renal Impairment No dosage adjustment of TYBOST is required in patients with renal impairment, including those with severe renal impairment. No clinically relevant differences in cobicistat pharmacokinetics were observed between subjects with severe renal impairment and healthy subjects. TYBOST is coadministered with atazanavir or darunavir; therefore, refer to the prescribing information for atazanavir or darunavir for information regarding dosing recommendations of these drugs in patients with renal impairment [see CLINICAL PHARMACOLOGY]. TYBOST has been shown to decrease estimated creatinine clearance without affecting actual renal glomerular function. Dosing recommendations are not available for drugs that require dosing adjustment for renal impairment when used in combination with TYBOST [see DOSAGE AND ADMINISTRATION , WARNINGS AND PRECAUTIONS , ADVERSE REACTIONS and CLINICAL PHARMACOLOGY]. Hepatic Impairment No dosing adjustment of TYBOST is necessary for patients with mild-to-moderate hepatic impairment. No data are available in patients with severe hepatic impairment. TYBOST is coadministered with atazanavir or darunavir and other antiretroviral drugs; therefore, refer to the prescribing information of these other drugs for information regarding dosing recommendations in patients with hepatic impairment [see CLINICAL PHARMACOLOGY].