Cobicistat

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 in adults and in pediatric patients weighing at least 14 kg. ( 1.1 ) 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. ( 1.2 , 5.4 ) 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. ( 1.2 , 5.3 , 7 , 12.3 )

1.1 Indications Adult Patients: 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 in adults [see Dosage and Administration (2.1) ]. Pediatric Patients: 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 in pediatric patients weighing at least 14 kg [see Dosage and Administration (2.2) , and Drug Interactions (7.3) ].

1.2 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 (5.4) ]. 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 (5.3) , Drug Interactions (7) , and Clinical Pharmacology (12.3) ].

TYBOST, 150 mg: Orange, round, biconvex, film-coated tablets debossed with "GSI" on one side and plain faced on the other side of the tablet. TYBOST, 90 mg: White, round, biconvex, film-coated tablets debossed with "TYB" on one side and "90" on the other side of the tablet. Tablets: 150 mg and 90 mg. ( 3 )

The concomitant use of TYBOST with atazanavir or darunavir and the following drugs is contraindicated due to the potential for serious and/or life-threatening events or loss of therapeutic effect [see Drug Interactions (7.3) and Clinical Pharmacology (12.3) ] . Alpha 1-adrenoreceptor antagonist: alfuzosin Antianginal: ranolazine Antiarrhythmic: dronedarone Anticonvulsants: carbamazepine, phenobarbital, phenytoin Anti-gout: colchicine Antimycobacterial: rifampin Antineoplastics: irinotecan These contraindications apply only to TYBOST coadministered with atazanavir Antipsychotics: lurasidone, pimozide Ergot Derivatives: dihydroergotamine, ergotamine, methylergonovine Herbal Products: St. John's wort ( Hypericum perforatum ) Hormonal Contraceptives: drospirenone/ ethinyl estradiol Lipid-modifying Agents: lomitapide, lovastatin, simvastatin Non-nucleoside Reverse Transcriptase Inhibitor: nevirapine Phosphodiesterase-5 (PDE-5) Inhibitor: sildenafil when administered as Revatio ® for the treatment of pulmonary arterial hypertension Protease Inhibitor: indinavir Sedative/hypnotics triazolam, orally administered midazolam Coadministration with certain drugs for which altered plasma concentrations are associated with serious and/or life-threatening events or loss of therapeutic effect. ( 4 )

Assess creatinine clearance (CLcr) before initiating treatment. ( 5.1 ) When TYBOST is used in combination with a TDF-containing regimen, cases of acute renal failure and Fanconi syndrome have been reported. ( 5.2 ) Use with TDF: Assess urine glucose and urine protein at baseline and monitor CLcr, urine glucose, and urine protein. Monitor serum phosphorus in patients with or at risk for renal impairment. ( 5.2 ) TYBOST in combination with more than one antiretroviral that requires pharmacokinetic enhancement (i.e., two protease inhibitors or elvitegravir in combination with a protease inhibitor) is not recommended. ( 5.4 ) Use with HIV-1 protease inhibitors other than atazanavir or darunavir administered once daily is not recommended. ( 5.4 ) Coadministration with drugs or regimens containing ritonavir is not recommended. ( 5.4 )

5.1 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 (2.3) ] . Dosage recommendations are not available for drugs that require dosage adjustments in TYBOST-treated patients with renal impairment [see Adverse Reactions (6.1) , Drug Interactions (7.3) , and Clinical Pharmacology (12.2) ] . 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.

5.2 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 TDF. Coadministration of TYBOST and TDF is not recommended in patients who have an estimated creatinine clearance below 70 mL/min because dose adjustment of TDF is required below 50 mL/min and such dose adjustments have not been established for coadministration with TYBOST [see Dosage and Administration (2.3 , 2.4) ] . Document urine glucose and urine protein at baseline [see Dosage and Administration (2.3) ] and perform routine monitoring of estimated creatinine clearance, urine glucose, and urine protein during treatment when TYBOST is used with TDF. Measure serum phosphorus in patients with or at risk for renal impairment when used with TDF. Coadministration of TYBOST and TDF 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%) participants treated with TYBOST coadministered with atazanavir and TRUVADA ® and 11 (3.2%) participants treated with ritonavir coadministered with atazanavir and TRUVADA discontinued study drug due to a renal adverse event. Seven of the 10 participants (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 participants (2.0% overall) in the ritonavir group. One participant 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 participants with evidence of proximal tubulopathy improved but did not completely resolve in all participants upon discontinuation of TYBOST coadministered with atazanavir and TRUVADA. Renal replacement therapy was not required in any participant.

5.3 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 and reduce plasma concentrations of active metabolite(s) formed by CYP3A. Initiation of medications that inhibit or induce CYP3A may respectively increase or decrease concentrations of TYBOST with atazanavir or darunavir. These interactions 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. These interactions may lead to: loss of therapeutic effect of TYBOST with atazanavir or darunavir and possible development of resistance. loss of therapeutic effect of the concomitant medications from lower exposures of active metabolite(s). See Table 7 for steps to prevent or manage these possible and known significant drug interactions, including dosing recommendations [see Drug Interactions (7) ] . 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 (4) and Drug Interactions (7) ] . 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 (7) and Clinical Pharmacology (12.3) ].

5.4 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.

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 (5.2) ]. The most common adverse drug reactions observed with TYBOST in combination with atazanavir (incidence greater than 5%, Grades 2−4) are jaundice and rash. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Gilead Sciences, Inc. at 1-800-GILEAD-5 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .

6.1 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. Adverse Reactions from Clinical Trials Experience in Adults The safety of TYBOST is based on Week 144 data from a Phase 3 trial, Trial 114, in which 692 antiretroviral treatment-naïve participants with HIV-1 received: TYBOST coadministered with atazanavir and TDF/emtricitabine (administered as TRUVADA) (N=344) or ritonavir coadministered with atazanavir and TDF/emtricitabine (administered as TRUVADA) (N=348). The most common adverse reactions (Grades 2−4) and reported in >5% of participants in the TYBOST group were jaundice (6%) and rash (5%). The proportion of participants who discontinued study treatment due to adverse events, regardless of severity, was 11% in both the TYBOST and ritonavir groups. Table 4 displays the frequency of adverse reactions (Grades 2−4) occurring in at least 2% of participants in the TYBOST group in Trial 114. Table 4 Selected Adverse Reactions Frequencies of adverse reactions are based on Grades 2–4 adverse events attributed to study drugs. (Grades 2−4) Reported in ≥2% of Treatment-Naïve Adults with HIV-1 in the TYBOST Coadministered with Atazanavir Group in Trial 114 (Week 144 Analysis) TYBOST Coadministered with Atazanavir + TRUVADA N=344 Ritonavir Coadministered with Atazanavir + TRUVADA N=348 Jaundice 6% 3% Rash 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. 5% 4% Ocular icterus 4% 2% Nausea 2% 2% Diarrhea 2% 1% Headache 2% 1% Less Common Adverse Reactions Selected adverse reactions of at least moderate severity (≥Grade 2) occurring in less than 2% of participants 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 participants in the TYBOST group in Trial 114 is presented in Table 5 . Table 5 Laboratory Abnormalities (Grades 3−4) in ≥2% of Treatment-Naïve Adults with HIV-1 in the TYBOST Coadministered with Atazanavir Group in Trial 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 Amylase For participants with serum amylase >1.5 × 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. (>2.0 × ULN) 4% 2% Urine Glucose (Glycosuria) (≥1000 mg/dL) 3% 3% Neutrophils (<750/mm 3 ) 3% 2% Serum Glucose (Hyperglycemia) (>250 mg/dL) 2% 2% 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 (5.1) and Clinical Pharmacology (12.2) ] . In Trial 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 6 . 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 6 Lipid Values, Mean Change from Baseline, Reported in Treatment-Naïve Adults with HIV-1 Receiving TYBOST Coadministered with Atazanavir + TRUVADA or Ritonavir Coadministered with Atazanavir + TRUVADA in Trial 114 (Week 144 Analysis) TYBOST + Atazanavir + TRUVADA Ritonavir + Atazanavir + TRUVADA Baseline Week 144 Baseline Week 144 mg/dL Change from baseline The change from baseline is the mean of within-patient changes from baseline for patients with both baseline and Week 144 values. Analysis excludes participants receiving an HMG-CoA reductase inhibitor drug. mg/dL Change from baseline 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] Adverse Reactions from Clinical Trials Experience in Pediatric Participants The safety of TYBOST was evaluated in an open-label clinical trial (Trial 128) of pediatric participants with HIV-1 administered TYBOST-boosted atazanavir or darunavir plus two nucleoside reverse transcriptase inhibitors; this study included 22 virologically-suppressed participants between the ages of 12 to less than 18 years (weighing ≥35 kg) administered atazanavir (N=14) or darunavir (N=7) through Week 48; 9 virologically-suppressed pediatric participants between the ages of 6 to less than 12 years weighing at least 25 kg to less than 40 kg administered darunavir (N=9) through Week 48; and 11 virologically-suppressed participants at least 2 years of age (weighing ≥14 kg to <25 kg) administered darunavir through Week 48 [see Drug Interactions (7.3) , Use in Specific Populations (8.4) , Clinical Studies (14.2) ] . In this trial, the safety profile of TYBOST was similar to that in adults.

TYBOST, in combination with atazanavir or darunavir, can alter the concentration of drugs metabolized by CYP3A or CYP2D6. Drugs that induce CYP3A can alter the concentrations of TYBOST, atazanavir and darunavir. Consult the full prescribing information prior to and during treatment for potential drug interactions. ( 4 , 5.3 , 7 , 12.3 )

7.1 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 drugs that have active metabolite(s) formed by CYP3A may result in reduced plasma concentrations of these active metabolite(s). Coadministration with other CYP3A substrates may require a dose adjustment or additional monitoring as shown in Table 7 .

7.2 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 7 ). 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 7 ).

7.3 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. Table 7 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 [see Contraindications (4) , Warnings and Precautions (5.3 , 5.4) , and Clinical Pharmacology (12.3) ]. In Table 7 , if not specifically stated, the drug interaction information applies to both coadministered agents: TYBOST coadministered with atazanavir or darunavir [see Clinical Pharmacology (12.3) ] . In addition to the drug interactions noted in Table 7 , 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 (5.4) ]. 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 TDF or rilpivirine are coadministered with TYBOST and atazanavir or darunavir. Table 7 Established and Other Potentially Significant This table is not all inclusive. Drug Interactions: Alteration in Dose or Regimen May Be Recommended Based on Drug Interaction Studies or Predicted Interaction Concomitant Drug Class: Drug Name Potential Effect ↑ = Increase, ↓ = Decrease, ↔ = No change Clinical Comment Antiretroviral Agents: Nucleotide Reverse Transcriptase Inhibitor (NRTI) tenofovir alafenamide ↔tenofovir alafenamide ↑tenofovir alafenamide TYBOST coadministered with darunavir in pediatric patients weighing at least 15 kg: No dose adjustment. TYBOST coadministered with atazanavir in pediatric patients weighing 14 to less than 35 kg: Coadministration is not recommended [see Use in Specific Populations (8.4) ]. 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 adult 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 adult 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 ↓ atazanavir ↑ nevirapine ↓ cobicistat darunavir: effect unknown Contraindicated with TYBOST coadministered with atazanavir only: Coadministration of atazanavir with nevirapine is contraindicated due to potential for loss of atazanavir therapeutic effect and development of resistance, and potential for nevirapine-associated adverse reactions. 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, adult patients should receive maraviroc 150 mg twice daily. Antiretroviral Agents: Protease Inhibitors indinavir Contraindicated with TYBOST coadministered with atazanavir only: Both atazanavir and indinavir are associated with indirect (unconjugated) hyperbilirubinemia. Other Agents: Alpha 1- adrenoreceptor antagonist: alfuzosin ↑ alfuzosin Coadministration with alfuzosin is contraindicated due to potential for serious and/or life-threatening reactions such as hypotension. Antianginal ranolazine ↑ ranolazine Coadministration with ranolazine is contraindicated due to potential for serious and/or life-threatening reactions. 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. […]

Pregnancy: TYBOST coadministered with darunavir or atazanavir is not recommended during pregnancy. TYBOST coadministered with darunavir or atazanavir should not be initiated in pregnant individuals. ( 2.5 , 8.1 , 12.3 ) Pediatrics: Not recommended for patients weighing less than 14 kg. ( 8.4 )

8.1 Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors fetal outcomes in individuals exposed to TYBOST during pregnancy. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) 1-800-258-4263. Risk Summary TYBOST coadministered with darunavir or atazanavir is not recommended during pregnancy [see Dosage and Administration (2.5) ] . In a clinical trial of individuals taking cobicistat coadministered with darunavir, exposures of cobicistat and darunavir were substantially lower during the second and third trimesters of pregnancy [see Data and Clinical Pharmacology (12.3) ] . TYBOST use during pregnancy has been evaluated in a limited number of individuals as reported by the APR, and available data show no significant difference in the rate of overall birth defects for cobicistat compared with the background rate for major defects of 2.7% in a U.S. reference population of the Metropolitan Atlanta Congenital Defects Program (MACDP) ( see Data ). The rate of miscarriage is not reported in the APR. The estimated background rate of miscarriage in clinically recognized pregnancies in the U.S. general population is 15−20%. 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 ). 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 Human Data Cobicistat coadministered with darunavir as a fixed dose combination, in combination with a background regimen, was evaluated in a clinical trial of 7 pregnant individuals taking darunavir/cobicistat prior to enrollment and who were willing to remain on darunavir/cobicistat throughout the study. The study period included the second and third trimesters, and through 12 weeks postpartum. Six pregnant individuals completed the trial. Exposure to darunavir and cobicistat as part of an antiretroviral regimen was substantially lower during the second and third trimesters of pregnancy compared with postpartum [see Clinical Pharmacology (12.3) ] . One out of 6 individuals who completed the study experienced virologic failure with HIV-1 RNA >1,000 copies/mL from the third trimester visit through the postpartum period. Five individuals had sustained virologic response (HIV-1 RNA <50 copies/mL) throughout the study period. There are no clinical data on the virologic response when darunavir/cobicistat is initiated during pregnancy. There were no new clinically relevant safety findings compared with the known safety profile of darunavir/cobicistat in adult participants with HIV-1. The APR has received prospective reports of live births following exposure to cobicistat-containing regimens during pregnancy, including over 600 exposures in the first trimester and over 90 exposures in the second/third trimester. The prevalence of birth defects in live births was 3.5% (95% CI: 2.2% to 5.3%) and 3.2% (95% CI: 0.7% to 9.1%) following first trimester and second/third trimester exposure, respectively, to cobicistat-containing regimens. Methodological limitations of the APR include the use of MACDP as the external comparator group. The MACDP population is not disease-specific, evaluates women and infants from a limited geographic area, and does not include outcomes for births that occurred at <20 weeks gestation. 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 were 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.

8.2 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. Cobicistat is present in rat milk (see Data ) . Potential risks of breastfeeding include: (1) HIV-1 transmission to HIV-1–negative infants; (2) developing viral resistance in HIV-1–positive infants; and (3) adverse reactions in a breastfed infant similar to those seen in adults. Animal Data During the prenatal and postnatal development toxicology study at doses up to 75 mg/kg/day, mean cobicistat milk to plasma ratio of up to 1.9 was measured 2 hours after administration to rats on lactation Day 10.

8.3 Females and Males of Reproductive Potential Contraception TYBOST interacts with certain oral contraceptives [see Drug Interactions (7.3) ].

8.4 Pediatric Use The safety and effectiveness of TYBOST coadministered with atazanavir or darunavir and two nucleoside reverse transcriptase inhibitors for the treatment of HIV-1 infection have been established in pediatric patients weighing at least 14 kg [see Indications and Usage (1.1) and Dosage and Administration (2.2) ]. Use of TYBOST and Darunavir Adolescent Patients Weighing at Least 40 kg Use of TYBOST and darunavir for this indication is supported by evidence from adequate and well-controlled studies in adults, and by pharmacokinetic, safety, and virologic data from an open-label trial (Trial 128; cohort 1 [Part A]) in virologically suppressed pediatric participants with HIV-1 aged 12 years and older (n=7). The safety, pharmacokinetics, and effectiveness in these participants were similar to that in adults [see Adverse Reactions (6.1) , Clinical Pharmacology (12.3) , and Clinical Studies (14.2) ]. Pediatric Patients Weighing at Least 15 kg to Less than 40 kg: Use of TYBOST and darunavir in combination with other ARVs is supported by evidence from adequate and well-controlled studies in adults, and by pharmacokinetic, safety, and efficacy data from an open-label trial (Trial 128; cohorts 2 and 3) in pediatric participants with HIV-1 at least 2 years of age and weighing at least 15 kg to less than 40 kg (n=20, all of whom were virologically suppressed at baseline). The safety, pharmacokinetics, and effectiveness of TYBOST when administered with darunavir in pediatric patients weighing at least 15 kg to less than 40 kg were similar to that in adults [see Adverse Reactions (6.1) , Clinical Pharmacology (12.3) , and Clinical Studies (14.2) ] . Pediatric Patients Weighing Less than 15 kg: Safety, pharmacokinetics, and effectiveness of TYBOST in combination with darunavir in pediatric patients weighing less than 15 kg have not been established. […]

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.