Atazanavir

• Atazanavir capsules must be taken with food.
• Do not open the capsules.
• The recommended oral dosage of atazanavir capsules depends on the treatment history of the patient and the use of other coadministered drugs. When coadministered with H ₂-receptor antagonists or proton-pump inhibitors, dose separation may be required [see Dosage and Administration ( 2.3, 2.4, and 2.6) and Drug Interactions ( 7)] .
• Atazanavir capsules without ritonavir are not recommended for treatment-experienced adult or pediatric patients with prior virologic failure [see Clinical Studies ( 14)] .
• Efficacy and safety of atazanavir capsules with ritonavir when ritonavir is administered in doses greater than 100 mg once daily have not been established. The use of higher ritonavir doses may alter the safety profile of atazanavir (cardiac effects, hyperbilirubinemia) and, therefore, is not recommended. Prescribers should consult the complete prescribing information for ritonavir when using ritonavir.

Renal laboratory testing should be performed in all patients prior to initiation of atazanavir capsules and continued during treatment with atazanavir capsules. Renal laboratory testing should include serum creatinine, estimated creatinine clearance, and urinalysis with microscopic examination [see Warnings and Precautions ( 5.5, 5.6)] .
Hepatic laboratory testing should be performed in patients with underlying liver disease prior to initiation of atazanavir capsules and continued during treatment with atazanavir capsules [see Warnings and Precautions ( 5.4)] .

Table 1 displays the recommended dosage of atazanavir capsules in treatment-naive and treatment-experienced adults. Table 1 also displays recommended dosage of atazanavir capsules and ritonavir when given concomitantly with other antiretroviral drugs and H ₂-receptor antagonists (H2RA). Ritonavir is required with several atazanavir capsule dosage regimens (see the ritonavir complete prescribing information about the safe and effective use of ritonavir). The use of atazanavir capsules in treatment-experienced adult patients without ritonavir is not recommended.

Table 1: Recommended Atazanavir Capsules  and Ritonavir Dosage in Adults ^a

^a See Drug Interactions ( 7) for instructions concerning coadministration of acid-reducing medications (eg, H2RA or proton pump inhibitors [PPIs]), and other antiretroviral drugs (eg, efavirenz, tenofovir DF, and didanosine).

The recommended daily dosage of atazanavir capsules and ritonavir in pediatric patients (6 years of age to less than 18 years of age) is based on body weight (see Table 2).
Table 2: Recommended Dosage of Atazanavir Capsules and Ritonavir in Pediatric  Patients (6 to less than 18 years of age) ^a,b

^aAdminister atazanavir capsules and ritonavir simultaneously with food. 

^bThe same recommendations regarding the timing and maximum doses of concomitant PPIs and H2RAs in adults also apply to pediatric patients. See Drug Interactions ( 7) for instructions concerning coadministration of acid-reducing medications (eg, H2RA or PPIs), and other antiretroviral drugs (eg, efavirenz, tenofovir DF, and didanosine). 
^cIn treatment-experienced patients, atazanavir capsules must be administered with ritonavir. 
When transitioning between formulations, a change in dose may be needed. Consult the dosing table for the specific formulation.

Table 4 includes the recommended dosage of atazanavir capsules and ritonavir in treatment-naive and treatment-experienced pregnant patients. In these patients, atazanavir capsules must be administered with ritonavir. There are no dosage adjustments for postpartum patients (see Table 1 for the recommended atazanavir capsules dosage in adults) [see Use in Specific Populations ( 8.1)] .
Table 4: Recommended Dosage of Atazanavir Capsules and Ritonavir in Pregnant Patients ^a

^aSee Drug Interactions (7)for instructions concerning coadministration of acid-reducing medications (eg, H2RA or PPIs), and other antiretroviral drugs (eg, efavirenz, tenofovir DF, and didanosine). 
^bAtazanavir capsules are not recommended for treatment-experienced pregnant patients during the second and third trimester taking atazanavir capsules with  BOTHtenofovir DF and H2RA.

For patients with renal impairment, including those with severe renal impairment who are not managed with hemodialysis, no dose adjustment is required for atazanavir capsules. Treatment-naive patients with end-stage renal disease managed with hemodialysis should receive atazanavir capsules 300 mg with ritonavir 100 mg. Atazanavir capsules are not recommended in treatment-experienced patients with HIV-1 who have end-stage renal disease managed with hemodialysis  [see Use in Specific Populations ( 8.7)] .

Table 5 displays the recommended atazanavir capsule dosage in treatment-naive patients with hepatic impairment. The use of atazanavir capsules in patients with severe hepatic impairment (Child-Pugh Class C) is not recommended. The coadministration of atazanavir capsules with ritonavir in patients with any degree of hepatic impairment is not recommended.
Table 5: Recommended Dosage of Atazanavir Capsules in Treatment-Naïve Adults with Hepatic Impairment

Atazanavir has been shown to prolong the PR interval of the electrocardiogram in some study participants. In healthy participants and in participants with HIV-1 treated with atazanavir, abnormalities in atrioventricular (AV) conduction were asymptomatic and generally limited to first-degree AV block. There have been reports of second-degree AV block and other conduction abnormalities [see Adverse Reactions ( 6.2) and Overdosage ( 10)] . In clinical trials that included electrocardiograms, asymptomatic first-degree AV   block   was   observed   in 5.9% of atazanavir-treated participants (n=920), 5.2% of lopinavir/ritonavir-treated participants (n=252), 10.4% of nelfinavir-treated participants (n=48), and 3.0% of efavirenz-treated participants (n=329). In Study AI424-045, asymptomatic first-degree AV block was observed in 5% (6/118) of atazanavir with ritonavir-treated participants and 5% (6/116) of lopinavir/ritonavir-treated participants who had on-study electrocardiogram measurements. Because of limited clinical experience in those with preexisting conduction system disease (eg, marked first-degree AV block or second- or third-degree AV block), ECG monitoring should be considered in these patients [see Clinical Pharmacology ( 12.2)] .

In controlled clinical trials, rash (all grades, regardless of causality) occurred in approximately 20% of participants with HIV-1 treated with atazanavir. The median time to onset of rash in clinical studies was 7.3 weeks and the median duration of rash was 1.4 weeks. Rashes were generally mild-to-moderate maculopapular skin eruptions. Treatment-emergent adverse reactions of moderate or severe rash (occurring at a rate of ≥2%) are presented for the individual clinical studies [see Adverse Reactions ( 6.1)] . Dosing with atazanavir was often continued without interruption in patients who developed rash. The discontinuation rate for rash in clinical trials was <1%. Cases of Stevens-Johnson syndrome, erythema multiforme, and toxic skin eruptions, including drug rash, eosinophilia, and systemic symptoms (DRESS) syndrome, have been reported in patients receiving atazanavir [see Contraindications ( 4) and Adverse Reactions ( 6.1)] . Atazanavir should be discontinued if severe rash develops.

Patients with underlying hepatitis B or C virus or marked elevations in transaminases before treatment may be at increased risk for developing further transaminase elevations or hepatic decompensation. In these patients, hepatic laboratory testing should be conducted prior to initiating therapy with atazanavir and during treatment [see Dosage and Administration ( 2.2), Adverse Reactions ( 6.1), and Use in Specific Populations ( 8.8)] .

Chronic kidney disease in patients with HIV-1 treated with atazanavir, with or without ritonavir, has been reported during postmarketing surveillance. Reports included biopsy-proven cases of granulomatous interstitial nephritis associated with the deposition of atazanavir drug crystals in the renal parenchyma. Consider alternatives to atazanavir in patients at high risk for renal disease or with preexisting renal disease. Renal laboratory testing (including serum creatinine, estimated creatinine clearance, and urinalysis with microscopic examination) should be conducted in all patients prior to initiating therapy with atazanavir and continued during treatment with atazanavir. Expert consultation is advised for patients who have confirmed renal laboratory abnormalities while taking atazanavir. In patients with progressive kidney disease, discontinuation of atazanavir may be considered [see Dosage and Administration ( 2.2and 2.7) and Adverse Reactions ( 6.2)] .

Cases of nephrolithiasis and/or cholelithiasis have been reported during postmarketing surveillance in patients with HIV-1 receiving atazanavir therapy. Some patients required hospitalization for additional management, and some had complications. Because these events were reported voluntarily during clinical practice, estimates of frequency cannot be made. If signs or symptoms of nephrolithiasis and/or cholelithiasis occur, temporary interruption or discontinuation of therapy may be considered [see Adverse Reactions ( 6.2)] .

Initiation of atazanavir with ritonavir, a CYP3A inhibitor, in patients receiving medications metabolized by CYP3A or initiation of medications metabolized by CYP3A in patients already receiving atazanavir with ritonavir, may increase plasma concentrations of medications metabolized by CYP3A. Initiation of medications that inhibit or induce CYP3A may increase or decrease concentrations of atazanavir with ritonavir, respectively. These interactions may lead to:
•  clinically significant adverse reactions potentially leading to severe, life-threatening, or fatal events from greater exposures of concomitant medications.
•  clinically significant adverse reactions from greater exposures of atazanavir with ritonavir.
•  loss of therapeutic effect (virologic response) of atazanavir with ritonavir and possible development of resistance.
See Table 16 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 therapy containing atazanavir with ritonavir; and monitor for the adverse reactions associated with concomitant medications [see Contraindications ( 4) and Drug Interactions ( 7)] .

Most patients taking atazanavir experience asymptomatic elevations in indirect (unconjugated) bilirubin related to inhibition of UDP-glucuronosyl transferase (UGT). This hyperbilirubinemia is reversible upon discontinuation of atazanavir. Hepatic transaminase elevations that occur with hyperbilirubinemia should be evaluated for alternative etiologies. No long-term safety data are available for patients experiencing persistent elevations in total bilirubin >5 times the upper limit of normal (ULN). Alternative antiretroviral therapy to atazanavir may be considered if jaundice or scleral icterus associated with bilirubin elevations presents cosmetic concerns for patients. Dose reduction of atazanavir is not recommended since long-term efficacy of reduced doses has not been established [see Adverse Reactions ( 6.1)] .

New-onset diabetes mellitus, exacerbation of preexisting diabetes mellitus, and hyperglycemia have been reported during postmarketing surveillance in patients with HIV-1 receiving protease inhibitor therapy. Some patients required either initiation or dose adjustments of insulin or oral hypoglycemic agents for treatment of these events. In some cases, diabetic ketoacidosis has occurred. In those patients who discontinued protease inhibitor therapy, hyperglycemia persisted in some cases. Because these events have been reported voluntarily during clinical practice, estimates of frequency cannot be made and a causal relationship between protease inhibitor therapy and these events has not been established [see Adverse Reactions ( 6.2)].

Immune reconstitution syndrome has been reported in patients treated with combination antiretroviral therapy, including atazanavir. During the initial phase of combination antiretroviral treatment, patients whose immune system responds may develop an inflammatory response to indolent or residual opportunistic infections (such as Mycobacterium avium, cytomegalovirus, Pneumocystis jiroveciipneumonia, or tuberculosis), which may necessitate further evaluation and treatment.
Autoimmune disorders (such as Graves’ disease, polymyositis, Guillain-Barré syndrome, and autoimmune hepatitis) have also been reported to occur in the setting of immune reconstitution; however, the time to onset is more variable, and can occur many months after initiation of treatment.

Redistribution/accumulation of body fat including central obesity, dorsocervical fat enlargement (buffalo hump), peripheral wasting, facial wasting, breast enlargement, and “cushingoid appearance” have been observed in patients receiving antiretroviral therapy. The mechanism and long-term consequences of these events are currently unknown. A causal relationship has not been established.

There have been reports of increased bleeding, including spontaneous skin hematomas and hemarthrosis, in patients with hemophilia type A and B treated with protease inhibitors. In some patients, additional factor VIII was given. In more than half of the reported cases, treatment with protease inhibitors was continued or reintroduced. A causal relationship between protease inhibitor therapy and these events has not been established.

Various degrees of cross-resistance among protease inhibitors have been observed. Resistance to atazanavir may not preclude the subsequent use of other protease inhibitors [see Microbiology ( 12.4)] .

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 in Treatment-Naive Adult Participants
The safety profile of atazanavir in treatment-naive adults is based on 1625 participants with HIV-1 in clinical trials. 536 participants received atazanavir 300 mg with ritonavir 100 mg and 1089 participants received atazanavir 400 mg or higher (without ritonavir).
The most common adverse reactions were nausea, jaundice/scleral icterus, and rash.
Selected clinical adverse reactions of moderate or severe intensity reported in > 2% of treatment- naive participants receiving combination therapy including atazanavir 300 mg with ritonavir 100 mg and atazanavir 400 mg (without ritonavir) are presented in Tables 7 and 8, respectively.
Table 7: Selected Adverse Reactions ^aof Moderate or Severe Intensity Reported in >2% of Adult Treatment-Naive Participants with HIV-1, ^bStudy AI424-138

* None reported in this treatment arm.

^a Includes events of possible, probable, certain, or unknown relationship to treatment regimen.
^b Based on the regimen containing atazanavir.
^c Median time on therapy.
^d Administered as a fixed-dose.
^e As a fixed-dose product: 300 mg tenofovir DF, 200 mg emtricitabine once daily.
Table 8: Selected Adverse Reactions ^aof Moderate or Severe Intensity Reported in ≥2% of Adult Treatment-Naive Participants with HIV-1, ^b Studies AI424-034, AI424-007, and AI424-008

* None reported in this treatment arm.
^a Includes events of possible, probable, certain, or unknown relationship to treatment regimen.
^b Based on regimens containing atazanavir.
^c Median time on therapy.
^d Includes long-term follow-up.
^e As a fixed-dose product: 150 mg lamivudine/300 mg zidovudine twice daily.
Adverse Reactions in Treatment-Experienced Adult Participants
The safety profile of atazanavir in treatment-experienced adults with HIV-1 is based on 119 participants with HIV-1 in clinical trials.
The most common adverse reactions are jaundice/scleral icterus and myalgia.
Selected clinical adverse reactions of moderate or severe intensity reported in ≥2% of treatment- experienced participants receiving atazanavir with ritonavir are presented in Table 9.
Table 9: Selected Adverse Reactions ^aof Moderate or Severe Intensity Reported in ≥2% of Adult Treatment-Experienced Participants with HIV-1, ^bStudy AI424-045

* None reported in this treatment arm.
^a Includes events of possible, probable, certain, or unknown relationship to treatment regimen.
^b Based on the regimen containing atazanavir.
^c Median time on therapy.
^d As a fixed-dose product.

Laboratory Abnormalities in Treatment-Naive Participants
The percentages of adult treatment-naive participants with HIV-1 treated with combination therapy, including atazanavir 300 mg with ritonavir 100 mg or atazanavir 400 mg (without ritonavir) with Grade 3 to 4 laboratory abnormalities, are presented in Tables 10 and 11, respectively.

The following events have been identified during postmarketing use of atazanavir. Because these reactions are reported voluntarily from a population of unknown size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Body as a Whole:edema

Cardiovascular System: second-degree AV block, third-degree AV block, left bundle branch block, QTc prolongation [see Warnings and Precautions ( 5.1)]

Gastrointestinal System:pancreatitis

Hepatic System:hepatic function abnormalities

Hepatobiliary Disorders:cholelithiasis [see Warnings and Precautions ( 5.6)] , cholecystitis, cholestasis

Metabolic System and Nutrition Disorders:diabetes mellitus, hyperglycemia [see Warnings and Precautions ( 5.9)]

Musculoskeletal System:arthralgia

Renal System:nephrolithiasis [see Warnings and Precautions ( 5.6)] , interstitial nephritis, granulomatous interstitial nephritis, chronic kidney disease [see Warnings and Precautions ( 5.5)]

Skin and Appendages:alopecia, maculopapular rash [see Contraindications ( 4) and Warnings and Precautions ( 5.2)] , pruritus, angioedema

Atazanavir is an inhibitor of CYP3A and UGT1A1. Coadministration of atazanavir and drugs primarily metabolized by CYP3A or UGT1A1 may result in increased plasma concentrations of the other drug that could increase or prolong its therapeutic and adverse effects.
Atazanavir is a weak inhibitor of CYP2C8. Use of atazanavir without ritonavir is not recommended when coadministered with drugs highly dependent on CYP2C8 with narrow therapeutic indices (eg, paclitaxel, repaglinide). When atazanavir with ritonavir is coadministered with substrates of CYP2C8, clinically significant interactions are not expected [see Clinical Pharmacology, Table 22 ( 12.3)].
The magnitude of CYP3A-mediated drug interactions on coadministered drug may change when atazanavir is coadministered with ritonavir. See the complete prescribing information for ritonavir for information on drug interactions with ritonavir.

Atazanavir is a CYP3A4 substrate; therefore, drugs that induce CYP3A4 may decrease atazanavir plasma concentrations and reduce atazanavir therapeutic effect  (see Table 16).
Atazanavir solubility decreases as pH increases. Reduced plasma concentrations of atazanavir are expected if proton-pump inhibitors, antacids, buffered medications, or H ₂-receptor antagonists are administered with atazanavir [see Dosage and Administration ( 2.3, 2.4, and 2.6)] .

Table 16 provides dosing recommendations in adults as a result of drug interactions with atazanavir. These recommendations are based on either drug interaction studies or predicted interactions due to the expected magnitude of interaction and potential for serious events or loss of efficacy.
Table 16: Established and Other Potentially Significant Drug Interactions: Alteration in Dose or Regimen May Be Recommended Based on Drug Interaction Studies ^aor Predicted Interactions (Information in the table applies to atazanavir with or without ritonavir, unless otherwise indicated)

^a  For magnitude of interactions

see Clinical Pharmacology, Tables 21and 22 ( 12.3) .
^b   See Contraindications (4), Table 6for orally administered midazolam.
^c  In combination with atazanavir 300 mg with ritonavir 100 mg once daily.
^d  In combination with atazanavir 400 mg once daily.

No clinically significant drug interactions were observed when atazanavir was coadministered with methadone, fluconazole, acetaminophen, atenolol, or the nucleoside reverse transcriptase inhibitors lamivudine or zidovudine [see Clinical Pharmacology, Tables 21 and 22 ( 12.3)].

Pregnancy Exposure Registry

There is a pregnancy exposure registry that monitors pregnancy outcomes in patients exposed to atazanavir during pregnancy. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) at 1-800-258-4263.

Risk Summary
Atazanavir has been evaluated in a limited number of women during pregnancy. Available human and animal data suggest that atazanavir does not increase the risk of major birth defects overall compared to the background rate [see Data].In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. No treatment-related malformations were observed in rats and rabbits, for which the atazanavir exposures were 0.7 to 1.2 times of those at the human clinical dose (300 mg/day atazanavir boosted with 100 mg/day ritonavir). When atazanavir was administered to rats during  pregnancy  and  throughout  lactation,  reversible  neonatal  growth  retardation  was observed [see Data].
Clinical Considerations
Dose Adjustments during Pregnancy and the Postpartum Period
•  Atazanavir must be administered with ritonavir in pregnant patients.
•  For pregnant patients, no dosage adjustment is required for atazanavir with the following exceptions:
•  For treatment-experienced pregnant women during the second or third trimester, when atazanavir is coadministered with either an H ₂-receptor antagonist ortenofovir DF, atazanavir 400 mg with ritonavir 100 mg once daily is recommended. There are insufficient data to recommend a atazanavir dose for use with both an H ₂-receptor antagonist andtenofovir DF in treatment-experienced pregnant patients.
•  No dosage adjustment is required for postpartum patients. However, patients should be closely monitored for adverse events because atazanavir exposures could be higher during the first 2 months after delivery [see Dosage and Administration ( 2.6) and Clinical Pharmacology ( 12.3)].
Maternal Adverse Reactions
Cases of lactic acidosis syndrome, sometimes fatal, and symptomatic hyperlactatemia have occurred in pregnant women using atazanavir in combination with nucleoside analogues, which are associated with an increased risk of lactic acidosis syndrome.
Hyperbilirubinemia occurs frequently in patients who take  atazanavir [see  Warnings  and Precautions ( 5.8)] , including those who are pregnant [see Data].
Advise pregnant women of the potential risks of lactic acidosis syndrome and hyperbilirubinemia.
Fetal/Neonatal Adverse Reactions
All infants, including neonates exposed to atazanavir in utero, should be monitored for the development of severe hyperbilirubinemia during the first few days of life [see Data].
Data
Human Data
In Study AI424-182, atazanavir with ritonavir (300/100 mg or 400/100 mg) coadministered with lamivudine/zidovudine (150 mg/ 300 mg, as fixed-dose product) was administered to 41 pregnant women with HIV-1, during the second or third trimester. Among the 39 women who completed the study, 38 women achieved an HIV-1 RNA less than 50 copies/mL at time of delivery. Six of 20 (30%) women on atazanavir with ritonavir 300/100 mg and 13 of 21 (62%) women on atazanavir with ritonavir 400/100 mg experienced hyperbilirubinemia (total bilirubin greater than or equal to 2.6 times ULN). There were no cases of lactic acidosis observed in clinical trial AI424-182.
Atazanavir drug concentrations in fetal umbilical cord blood were approximately 12% to 19% of maternal concentrations. Among the 40 infants born to 40 pregnant women with HIV-1, all had test results that were negative for HIV-1 DNA at the time of delivery and/or during the first 6 months postpartum. All 40 infants received antiretroviral prophylactic treatment containing zidovudine. No evidence of severe hyperbilirubinemia (total bilirubin levels greater than 20 mg/dL) or acute or chronic bilirubin encephalopathy was observed among neonates in this study. However, 10/36 (28%) infants (6 greater than or equal to 38 weeks gestation and 4 less than 38 weeks gestation) had bilirubin levels of 4 mg/dL or greater within the first day of life.
Lack of ethnic diversity was a study limitation. In the study population, 33/40 (83%) infants were Black/African American, who have a lower incidence of neonatal hyperbilirubinemia than Caucasians and Asians. In addition, women with Rh incompatibility were excluded, as well as women who had a previous infant who developed hemolytic disease and/or had neonatal pathologic jaundice (requiring phototherapy).
Additionally, of the 38 infants who had glucose samples collected in the first day of life, 3 had adequately collected serum glucose samples with values of less than 40 mg/dL that could not be attributed to maternal glucose intolerance, difficult delivery, or sepsis.
Based on prospective reports from the APR of approximately 1600 live births following exposure to atazanavir-containing regimens (including 1037 live births in infants exposed in the first trimester and 569 exposed in second/third trimesters), there was no difference between atazanavir, and overall birth defects compared with the background birth defect rate. In the U.S. general population, the estimated background risk of major birth defects in clinically recognized pregnancies is 2 to 4%.
Animal Data
In animal reproduction studies, there was no evidence of mortality or teratogenicity in offspring
born to animals at systemic drug exposure levels (AUC) 0.7 (in rabbits) to 1.2 (in rats) times those observed at the human clinical dose (300 mg/day atazanavir boosted with 100 mg/day ritonavir). In pre- and postnatal development studies in the rat, atazanavir caused neonatal growth retardation during lactation that reversed after weaning. Maternal drug exposure at this dose was 1.3 times the human exposure at the recommended clinical exposure. Minimal maternal toxicity occurred at this exposure level.

Risk Summary
Atazanavir has been detected in human milk. No data are available regarding atazanavir effects on milk production. Atazanavir was present in the milk of lactating rats and was associated with neonatal growth retardation that reversed after weaning.
Potential risks of breastfeeding include: (1) HIV-1 transmission (in infants without HIV-1), (2) developing viral resistance (in infants with HIV-1), and (3) adverse reactions in a breastfed infant similar to those seen in adults.

Atazanavir is indicated in combination with other antiretroviral agents for the treatment of pediatric patients with HIV-1, 6 years of age and older weighing at least 15 kg. Atazanavir is not recommended for use in pediatric patients below the age of 3 months due to the risk of kernicterus [see Indications and Usage ( 1)]. All atazanavir contraindications, warnings, and precautions apply to pediatric patients [see Contraindications ( 4) and Warnings and Precautions ( 5)].
The safety, pharmacokinetic profile, and virologic response of atazanavir in pediatric patients at least 6 years of age and older weighing at least 15 kg were established in three open-label, multicenter clinical trial: PACTG 1020A, AI424-451, and AI424-397  [see Clinical Pharmacology ( 12.3) and Clinical Studies ( 14.3)]. The safety profile in pediatric patients was generally similar to that observed in adults [see Adverse Reactions ( 6.1)] . See Dosage and Administration ( 2.4) for dosing recommendations for the use of atazanavir capsules.

Clinical studies of atazanavir did not include sufficient numbers of patients aged 65 and over to determine whether they respond differently from younger patients. Based on a comparison of mean single-dose pharmacokinetic values for C _maxand AUC, a dose adjustment based upon age is not recommended. In general, appropriate caution should be exercised in the administration and monitoring of atazanavir in elderly patients reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

A study of the pharmacokinetics of atazanavir was performed in young (n=29; 18 to 40 years) and elderly (n=30; >65 years) healthy participants.  There were no clinically significant pharmacokinetic differences observed due to age or gender.

Atazanavir is not recommended for use in treatment-experienced patients with HIV-1, who have end-stage renal disease managed with hemodialysis [see Dosage and Administration ( 2.7) and Clinical Pharmacology ( 12.3)].

Atazanavir is not recommended for use in patients with severe hepatic impairment. Atazanavir with ritonavir is not recommended in patients with any degree of hepatic impairment [see Dosage and Administration ( 2.8) and Clinical Pharmacology ( 12.3)] .

Atazanavir is an HIV-1 antiretroviral drug [see Microbiology ( 12.4)].

Cardiac Electrophysiology
Concentration- and dose-dependent prolongation of the PR interval in the electrocardiogram has been observed in healthy participants receiving atazanavir. In placebo-controlled Study AI424-076, the mean (±SD) maximum change in PR interval from the predose value was 24 (±15) msec following oral dosing with 400 mg of atazanavir (n=65) compared to 13 (±11) msec following dosing with placebo (n=67). The PR interval prolongations in this study were asymptomatic. There is limited information on the potential for a pharmacodynamic interaction in humans between atazanavir and other drugs that prolong the PR interval of the electrocardiogram [see Warnings and Precautions ( 5.1)].
Electrocardiographic effects of atazanavir were determined in a clinical pharmacology study of 72 healthy participants. Oral doses of 400 mg (maximum recommended dosage) and 800 mg (twice the maximum recommended dosage) were compared with placebo; there was no concentration- dependent effect of atazanavir on the QTc interval (using Fridericia’s correction). In 1793 participants with HIV-1, receiving antiretroviral regimens, QTc prolongation was comparable in the atazanavir and comparator regimens. No atazanavir-treated healthy participant or participant with HIV-1 in clinical trials had a QTc interval >500 msec [see Warnings and Precautions ( 5.1)].

The pharmacokinetics of atazanavir were evaluated in adult participants who either were healthy, or with HIV, after administration of atazanavir 400 mg once daily and after administration of atazanavir 300 mg with ritonavir 100 mg once daily (see Table 17).

Table 17: Steady-State Pharmacokinetics of Atazanavir in Healthy Participants or Participants  with HIV-1 in the Fed State

^a n=26.
^b n=12.
Figure 1 displays the mean plasma concentrations of atazanavir at steady state after atazanavir 400 mg once daily (as two 200 mg capsules) with a light meal and after atazanavir 300 mg (as two 150 mg capsules) with ritonavir 100 mg once daily with a light meal in adult participants with HIV-1. 
Figure 1: Mean (SD) Steady-State Plasma Concentrations of Atazanavir 400 mg (n=13) and 300 mg with Ritonavir (n=10) for Adult Participants with HIV-1 

 
Absorption
Atazanavir is rapidly absorbed with a T _maxof approximately 2.5 hours. Atazanavir demonstrates nonlinear pharmacokinetics with greater than dose-proportional increases in AUC and C _maxvalues over the dose range of 200 to 800 mg once daily. Steady state is achieved between Days 4 and 8, with an accumulation of approximately 2.3 fold.
Food Effect
Administration of atazanavir with food enhances bioavailability and reduces pharmacokinetic variability. Administration of a single 400 mg dose of atazanavir with a light meal (357 kcal, 8.2 g fat, 10.6 g protein) resulted in a 70% increase in AUC and 57% increase in C _maxrelative to the fasting state. Administration of a single 400 mg dose of atazanavir with a high-fat meal (721 kcal, 37.3 g fat, 29.4 g protein) resulted in a mean increase in AUC of 35% with no change in C _maxrelative to the fasting state. Administration of atazanavir with either a light meal or high-fat meal decreased the coefficient of variation of AUC and C _maxby approximately one-half compared to the fasting state.
Coadministration of a single 300 mg dose of atazanavir and a 100 mg dose of ritonavir with a light meal (336 kcal, 5.1 g fat, 9.3 g protein) resulted in a 33% increase in the AUC and a 40% increase in both the C _maxand the 24-hour concentration of atazanavir relative to the fasting state. Coadministration with a high-fat meal (951 kcal, 54.7 g fat, 35.9 g protein) did not affect the AUC of atazanavir relative to fasting conditions and the C _maxwas within 11% of fasting values. The 24-hour concentration following a high-fat meal was increased by approximately 33% due to delayed absorption; the median T _maxincreased from 2.0 to 5.0 hours. Coadministration of atazanavir with ritonavir with either a light or a high-fat meal decreased the coefficient of variation of AUC and C _maxby approximately 25% compared to the fasting state.
Distribution
Atazanavir is 86% bound to human serum proteins and protein binding is independent of concentration. Atazanavir binds to both alpha-1-acid glycoprotein (AAG) and albumin to a similar extent (89% and 86%, respectively). In a multiple-dose study in participants with HIV-1 dosed with atazanavir 400 mg once daily with a light meal for 12 weeks, atazanavir was detected in the cerebrospinal fluid and semen. The cerebrospinal fluid/plasma ratio for atazanavir (n=4) ranged between 0.0021 and 0.0226 and seminal fluid/plasma ratio (n=5) ranged between 0.11 and 4.42.
Metabolism
Atazanavir is extensively metabolized in humans. The major biotransformation pathways of atazanavir in humans consisted of monooxygenation and dioxygenation. Other minor biotransformation pathways for atazanavir or its metabolites consisted of glucuronidation, N-dealkylation, hydrolysis, and oxygenation with dehydrogenation. Two minor metabolites of atazanavir in plasma have been characterized. Neither metabolite demonstrated in vitroantiviral activity. In vitrostudies using human liver microsomes suggested that atazanavir is metabolized by CYP3A.
Elimination
Following a single 400 mg dose of ¹⁴C-atazanavir, 79% and 13% of the total radioactivity was recovered in the feces and urine, respectively. Unchanged drug accounted for approximately 20% and 7% of the administered dose in the feces and urine, respectively. The mean elimination half-life of atazanavir in healthy participants (n=214) and adult participants with HIV-1 (n=13) was approximately 7 hours at steady state following a dose of 400 mg daily with a light meal.
Specific Populations
Renal Impairment
In healthy participants, the renal elimination of unchanged atazanavir was approximately 7% of the administered dose. Atazanavir has been studied in adult participants with severe renal impairment (n=20), including those on hemodialysis, at multiple doses of 400 mg once daily. The mean atazanavir C _maxwas 9% lower, AUC was 19% higher, and C _minwas 96% higher in participants with severe renal impairment not undergoing hemodialysis (n=10), than in age-, weight-, and gender-matched participants with normal renal function. In a 4-hour dialysis session, 2.1% of the administered dose was removed. When atazanavir was administered either prior to, or following hemodialysis (n=10), the geometric means for C _max, AUC, and C _minwere approximately 25% to 43% lower compared to participants with normal renal function. The mechanism of this decrease is unknown. Atazanavir is not recommended for use in treatment-experienced patients with HIV-1 who have end-stage renal disease managed with hemodialysis [ see Dosage and Administration (2.7)].
Hepatic Impairment
Atazanavir has been studied in adult participants with moderate-to-severe hepatic impairment (14 with Child-Pugh B and 2 with Child-Pugh C participants) after a single 400 mg dose. The mean AUC(0 to ∞ ) was 42% greater in participants with impaired hepatic function than in healthy participants. The mean half-life of atazanavir in hepatically impaired participants was 12.1 hours compared to 6.4 hours in healthy participants. A dose reduction to 300 mg is recommended for patients with moderate hepatic impairment (Child-Pugh Class B) who have not experienced prior virologic failure as increased concentrations of atazanavir are expected. Atazanavir is not recommended for use in patients with severe hepatic impairment. The pharmacokinetics of atazanavir in combination with ritonavir has not been studied in participants with hepatic impairment; thus, coadministration of atazanavir with ritonavir is not recommended for use in patients with any degree of hepatic impairment [see Dosage and Administration (2.8)].
Pediatrics 
The pharmacokinetic parameters for atazanavir at steady state in pediatric participants taking the capsule formulation were predicted by a population pharmacokinetic model and are summarized in Table 19 by weight ranges that correspond to the recommended doses [see Dosage and Administration (2.4)]. 
Table 19: Predicted Steady-State Pharmacokinetics of Atazanavir (capsule formulation) with Ritonavir in Pediatric Participants with HIV-1

Pregnancy
The pharmacokinetic data from pregnant women with HIV-1 receiving atazanavir capsules with ritonavir are presented in Table 20.

 ^a  Available data during the 2nd trimester are limited.
^b  Atazanavir peak concentrations and AUCs were found to be approximately 28% to 43% higher during the postpartum period (4 to 12 weeks) than       those observed historically in, non-pregnant patients with HIV-1. Atazanavir plasma trough concentrations were approximately 2.2-fold higher during the postpartum period when compared to those observed historically in non-pregnant patients with HIV-1.
^c  C _minis concentration 24 hours post-dose.
Drug Interaction Data
Atazanavir is a metabolism-dependent CYP3A inhibitor, with a K _inactvalue of 0.05 to 0.06 min ^-1and K _ivalue of 0.84 to 1.0 µM. Atazanavir is also a direct inhibitor for UGT1A1 (K _i=1.9 µM) and CYP2C8 (K _i=2.1 µM).
Atazanavir has been shown in vivonot to induce its own metabolism nor to increase the biotransformation of some drugs metabolized by CYP3A. In a multiple-dose study, atazanavir decreased the urinary ratio of endogenous 6β-OH cortisol to cortisol versus baseline, indicating that CYP3A production was not induced.
Clinically significant interactions are not expected between atazanavir and substrates of CYP2C19, CYP2C9, CYP2D6, CYP2B6, CYP2A6, CYP1A2, or CYP2E1. Clinically significant interactions are not expected between atazanavir when administered with ritonavir and substrates of CYP2C8. See the complete prescribing information for ritonavir for information on other potential drug interactions with ritonavir.
Based on known metabolic profiles, clinically significant drug interactions are not expected between atazanavir and dapsone, trimethoprim/sulfamethoxazole, azithromycin, or erythromycin. Atazanavir does not interact with substrates of CYP2D6 (eg, nortriptyline, desipramine, metoprolol).
Drug interaction studies were performed with atazanavir and other drugs likely to be coadministered and some drugs commonly used as probes for pharmacokinetic interactions. The effects of coadministration of atazanavir on the AUC, C _max, and C _minare summarized in Tables 21 and 22. Neither didanosine EC nor diltiazem had a significant effect on atazanavir exposures (see Table 22 for effect of atazanavir on didanosine EC or diltiazem exposures). Atazanavir did not have a significant effect on the exposures of didanosine (when administered as the buffered tablet), stavudine, or fluconazole. For information regarding clinical recommendations, see Drug Interactions ( 7) .
Table 21: Drug Interactions: Pharmacokinetic Parameters for Atazanavir in the Presence of Coadministered Drugs ^a

 ^a Data provided are under fed conditions unless otherwise noted.
^b All drugs were given under fasted conditions.
^c  Atazanavir 300 mg with ritonavir 100 mg once daily coadministered with famotidine 40 mg twice daily resulted in atazanavir geometric mean               C _maxthat was similar and AUC and C _minvalues that were 1.79- ­and 4.46-fold higher relative to atazanavir 400 mg once daily alone.
^d  Similar results were noted when famotidine 20 mg BID was administered 2 hours after and 10 hours before atazanavir 300 mg and ritonavir               100 mg and tenofovir DF 300 mg.
^e  Coadministration of atazanavir with ritonavir and tenofovir DF was administered after a light meal.
f  Study was conducted in participants with HIV-1.
^g  Compared with atazanavir 400 mg historical data without nevirapine (n=13), the ratio of geometric means (90% confidence intervals)  for                     C _max, AUC, and C _min were 1.42  (0.98, 2.05), 1.64 (1.11, 2.42), and  1.25 (0.66, 2.36), respectively, for atazanavir with ritonavir 300/100 mg;               and 2.02 (1.42, 2.87), 2.28 (1.54, 3.38), and 1.80 (0.94, 3.45), respectively, for atazanavir with ritonavir 400/100 mg.
^h  Parallel group design; n=23 for atazanavir with ritonavir and nevirapine, n=22 for atazanavir 300 mg/ritonavir 100 mg without nevirapine.                     Participants were treated with nevirapine prior to study entry.
ⁱ  Omeprazole 40 mg was administered on an empty stomach 2 hours before atazanavir.
^j  Omeprazole 20 mg was administered 30 minutes prior to a light meal in the morning and atazanavir 300 mg with ritonavir 100 mg in the                       evening after a light meal, separated by 12 hours from omeprazole.
^k  Atazanavir 300 mg with ritonavir 100 mg once daily separated by 12 hours from omeprazole 20 mg daily resulted in increases in atazanavir                 geometric mean AUC (10%) and C _min(2.4-fold), with a decrease in C _max(29%) relative to atazanavir 400 mg once daily in the absence of                   omeprazole (study days 1 to 6).
^l  Omeprazole 20 mg was given 30 minutes prior to a light meal in the morning and atazanavir 400 mg with ritonavir 100 mg once daily after a                 light meal, 1 hour after omeprazole. Effects on atazanavir concentrations were similar when atazanavir 400 mg with ritonavir 100 mg was                   separated from omeprazole 20 mg by 12 hours.
^m  Atazanavir 400 mg with ritonavir 100 mg once daily administered with omeprazole 20 mg once daily resulted in increases in atazanavir geometric     mean AUC (32%) and C _min(3.3-fold), with a decrease in C _max(26%) relative to atazanavir 400 mg once daily in the absence of omeprazole                (study days 1–6).
ⁿ  Compared with atazanavir 400 mg QD historical data, administration of atazanavir with ritonavir 300/100 mg QD increased the atazanavir                    geometric mean values of C _max, AUC, and C _minby 18%, 103%, and 671%, respectively.
^o  Note that similar results were observed in studies where administration of tenofovir DF and atazanavir was   separated by 12 hours.
^p  Ratio of atazanavir with ritonavir with tenofovir DF to atazanavir with ritonavir. Atazanavir 300 mg with ritonavir 100 mg results in higher atazanavir     exposure than atazanavir 400 mg (see footnote ^o). The geometric mean values of atazanavir pharmacokinetic parameters when coadministered         with ritonavir and tenofovir DF were: C _max= 3190 ng/mL, AUC = 34459 ng•h/mL, and Cmin = 491 ng/mL. Study was conducted in participants with       HIV-1.
 NA = not available.

Table 22: Drug Interactions: Pharmacokinetic Parameters for Coadministered Drugs in the Presence of Atazanavir ^a

^a Data provided are under fed conditions unless otherwise noted.
^b 400 mg ddI EC and atazanavir were administered together with food on Days 8 and 19.
^c Upon further dose normalization of ethinyl estradiol 25 mcg with atazanavir relative to ethinyl estradiol 35 mcg without atazanavir, the ratio of geometric means (90% confidence intervals) for C _max, AUC, and C _minwere 0.82 (0.73, 0.92), 1.06 (0.95, 1.17), and 1.35 (1.11, 1.63), respectively.
^d Upon further dose normalization of ethinyl estradiol 35 mcg with atazanavir with ritonavir relative to ethinyl estradiol 25 mcg without atazanavir with ritonavir, the ratio of geometric means (90% confidence intervals) for C _max, AUC, and C _minwere 1.17 (1.03, 1.34), 1.13 (1.05, 1.22), and 0.88 (0.77, 1.00), respectively.
^e All participants were on a 28-day lead-in period; one full cycle of Ortho Tri-Cyclen ^®. Ortho Tri-Cyclen ^®contains 35 mcg of ethinyl estradiol. Ortho Tri-Cyclen ^®LO contains 25 mcg of ethinyl estradiol. Results were dose normalized to an ethinyl estradiol dose of 35 mcg.
^f 17-deacetyl norgestimate is the active component of norgestimate.
^g Effect of atazanavir with ritonavir on the first dose of glecaprevir and pibrentasvir is reported.
^h (R)-methadone is the active isomer of methadone.
ⁱ Study was conducted in participants with HIV-1.
^j Participants were treated with nevirapine prior to study entry.
^k Omeprazole was used as a metabolic probe for CYP2C19. Omeprazole was given 2 hours after atazanavir on Day 7; and was given alone 2 hours after a light meal on Day 20.
^l Not the recommended therapeutic dose of atazanavir.
^m When compared to rifabutin 150 mg QD alone d1–10 (n=14). Total of rifabutin + 25-O-desacetyl-rifabutin: AUC 2.19 (1.78, 2.69).
ⁿ Rosiglitazone used as a probe substrate for CYP2C8.
^o Mean ratio (with/without coadministered drug). ↑ indicates an increase in rosuvastatin exposure.
^p The combination of atazanavir and saquinavir 1200 mg QD produced daily saquinavir exposures similar to the values produced by the standard therapeutic dosing of saquinavir at 1200 mg TID. However, the C _maxis about 79% higher than that for the standard dosing of saquinavir (soft gelatin capsules) alone at 1200 mg TID.
^q Note that similar results were observed in a study where administration of tenofovir DF and atazanavir was separated by 12 hours.
^r Administration of tenofovir DF and atazanavir was temporally separated by 12 hours.

NA = not available.

Mechanism of Action
Atazanavir (ATV) is an azapeptide HIV-1 protease inhibitor (PI). The compound selectively inhibits the virus-specific processing of viral Gag and Gag-Pol polyproteins in HIV-1-infected cells, thus preventing formation of mature virions.
Antiviral Activity in Cell Culture
Atazanavir exhibits anti-HIV-1 activity with a mean 50% effective concentration (EC ₅₀) in the absence of human serum of 2 to 5 nM against a variety of laboratory and clinical HIV-1 isolates grown in peripheral blood mononuclear cells, macrophages, CEM-SS cells, and MT-2 cells. Atazanavir has activity against HIV-1 Group M subtype viruses A, B, C, D, AE, AG, F, G, and J isolates in cell culture. Atazanavir has variable activity against HIV-2 isolates (1.9-32 nM), with EC ₅₀values above the EC ₅₀values of failure isolates. Two-drug combination antiviral activity studies with atazanavir showed no antagonism in cell culture with PIs (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir), NNRTIs (delavirdine, efavirenz, and nevirapine), NRTIs (abacavir, didanosine, emtricitabine, lamivudine, stavudine, tenofovir DF, and zidovudine), the HIV-1 fusion inhibitor enfuvirtide, and two compounds used in the treatment of viral hepatitis, adefovir and ribavirin, without enhanced cytotoxicity.
Resistance
In Cell Culture:HIV-1 isolates with a decreased susceptibility to atazanavir have been selected in cell culture and obtained from patients treated with atazanavir or atazanavir with ritonavir. HIV-1 isolates with 93- to 183-fold reduced susceptibility to atazanavir from three different viral strains were selected in cell culture by 5 months. The substitutions in these HIV-1 viruses that contributed to atazanavir resistance include I50L, N88S, I84V, A71V, and M46I. Changes were also observed at the protease cleavage sites following drug selection. Recombinant viruses containing the I50L substitution without other major PI substitutions were growth impaired and displayed increased susceptibility in cell culture to other PIs (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir). The I50L and I50V substitutions yielded selective resistance to atazanavir and amprenavir, respectively, and did not appear to be cross-resistant.
Clinical Studies of Treatment-Naïve Participants: Comparison of Ritonavir-Boosted Atazanavir vs Unboosted Atazanavir:Study AI424-089 compared atazanavir 300 mg once daily with ritonavir 100 mg vs atazanavir 400 mg once daily when administered with lamivudine and extended- release stavudine in treatment-naive participants with HIV-1. A summary of the number of virologic failures and virologic failure isolates with atazanavir resistance in each arm is shown in Table 23.
 Table 23:   Summary of Virologic Failures ^aat Week 96 in Study AI424-089: Comparison of Ritonavir Boosted Atazanavir vs Unboosted Atazanavir: Randomized Participants

^a Virologic failure includes participants who were never suppressed through Week 96 and on study at Week 96, had virologic rebound or discontinued due to insufficient viral load response.
^b Percentage of Virologic Failure Isolates with genotypic and phenotypic data.
^cMixture of I50I/L emerged in 2 other atazanavir 400 mg-treated participants. Neither isolate was phenotypically resistant to atazanavir.

Clinical Studies of Treatment-Naive Participants Receiving Atazanavir 300 mg with Ritonavir 100 mg: In Phase 3 Study AI424-138, an as-treated genotypic and phenotypic analysis was conducted on samples from participants who experienced virologic failure (HIV-1 RNA >400 copies/mL) or discontinued before achieving suppression on atazanavir with ritonavir (n=39; 9%) and lopinavir/ritonavir (n=39; 9%) through 96 weeks of treatment. In the atazanavir with ritonavir arm, one of the virologic failure isolates had a 56-fold decrease in atazanavir susceptibility emerge on therapy with the development of PI resistance-associated substitutions L10F, V32I, K43T, M46I, A71I, G73S, I85I/V, and L90M. The NRTI resistance-associated substitution M184V also emerged on treatment in this isolate conferring emtricitabine resistance. Two atazanavir with ritonavir-virologic failure isolates had baseline phenotypic atazanavir resistance and IAS-defined major PI resistance-associated substitutions at baseline. The I50L substitution emerged on study in one of these failure isolates and was associated with a 17-fold decrease in atazanavir susceptibility from baseline and the other failure isolate with baseline atazanavir resistance and PI substitutions (M46M/I and I84I/V) had additional IAS-defined major PI substitutions (V32I, M46I, and I84V) emerge on atazanavir treatment associated with a 3-fold decrease in atazanavir susceptibility from baseline. Five of the treatment failure isolates in the atazanavir with ritonavir arm developed phenotypic emtricitabine resistance with the emergence of either the M184I (n=1) or the M184V (n=4) substitution on therapy and none developed phenotypic tenofovir disoproxil resistance. In the lopinavir/ritonavir arm, one of the virologic failure participant isolates had a 69-fold decrease in lopinavir susceptibility emerge on therapy with the development of PI substitutions L10V, V11I, I54V, G73S, and V82A in addition to baseline PI substitutions L10L/I, V32I, I54I/V, A71I, G73G/S, V82V/A, L89V, and L90M. Six lopinavir/ritonavir virologic failure isolates developed the M184V substitution and phenotypic emtricitabine resistance and two developed phenotypic tenofovir disoproxil resistance.
Clinical Studies of Treatment-Naive Participants Receiving Atazanavir 400 mg without Ritonavir: Atazanavir-resistant clinical isolates from treatment-naive participants who experienced virologic failure on atazanavir 400 mg treatment without ritonavir often developed an I50L substitution (after an average of 50 weeks of atazanavir therapy), often in combination with an A71V substitution, but also developed one or more other PI substitutions (eg, V32I, L33F, G73S, V82A, I85V, or N88S) with or without the I50L substitution. In treatment-naive participants, viral isolates that developed the I50L substitution, without other major PI substitutions, showed phenotypic resistance to atazanavir but retained in cell culture susceptibility to other PIs (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir); however, there are no clinical data available to demonstrate the effect of the I50L substitution on the efficacy of subsequently administered PIs.
Clinical Studies of Treatment-Experienced Participants: In studies of treatment-experienced participants treated with atazanavir or atazanavir with ritonavir, most atazanavir-resistant isolates from participants who experienced virologic failure developed substitutions that were associated with resistance to multiple PIs and displayed decreased susceptibility to multiple PIs. The most common protease substitutions to develop in the viral isolates of participants who failed treatment with atazanavir 300 mg once daily and ritonavir 100 mg once daily (together with tenofovir DF and an NRTI) included V32I, L33F/V/I, E35D/G,   M46I/L,   I50L,   F53L/V,   I54V,   A71V/T/I,   G73S/T/C,   V82A/T/L,   I85V,   and L89V/Q/M/T. Other substitutions that developed on atazanavir with ritonavir treatment including E34K/A/Q, G48V, I84V, N88S/D/T, and L90M occurred in less than 10% of participant isolates. Generally, if multiple PI resistance substitutions were present in the HIV-1 virus of the participant at baseline, atazanavir resistance developed through substitutions associated with resistance to other PIs and could include the development of the I50L substitution. The I50L substitution has been detected in treatment-experienced participants experiencing virologic failure after long-term treatment. Protease cleavage site changes also emerged on atazanavir treatment, but their presence did not correlate with the level of atazanavir resistance.

Clinical Studies of Pediatric Participants in AI424-397 (PRINCE I) and AI424-451 (PRINCE II):Treatment-emergent atazanavir with ritonavir resistance-associated amino acid substitution M36I in the protease was detected in the virus of one participant among treatment failures in AI424-397. In addition, three known resistance-associated substitutions for other PIs arose in the viruses from one participant each (L19I/R, H69K/R, and I72I/V). Reduced susceptibility to atazanavir, ritonavir, or atazanavir with ritonavir was not seen with these viruses. In AI424-451, atazanavir with ritonavir resistance-associated substitutions G16E, V82A/I/T, I84V, and/or L90M arose in the viruses of two participants. The virus population harboring the M46M/V, V82V/I, I84I/V, and L90L/M substitutions acquired phenotypic resistance to ritonavir (ritonavir phenotypic fold-change of 3.5, with a ritonavir cutoff of 2.5-fold change). However, these substitutions did not result in phenotypic resistance to atazanavir (atazanavir phenotypic fold-change of <1.8, with an atazanavir cutoff of 2.2-fold change). Secondary PI resistance-associated amino acid substitutions also arose in the viruses of one participant each, including V11V/I, D30D/G, E35E/D, K45K/R, L63P/S, and I72I/T. Q61D and Q61E/G emerged in the viruses of two participants who failed treatment with atazanavir with ritonavir. Viruses from nine participants in the two studies developed NRTI resistance-associated substitutions: K65K/R (n=1), M184V (n=7), and T215I (n=1).

Cross-Resistance

Cross-resistance among PIs has been observed. Baseline phenotypic and genotypic analyses of clinical isolates from atazanavir clinical trials of PI-experienced participants showed that isolates cross- resistant to multiple PIs were cross-resistant to atazanavir. Greater than 90% of the isolates with substitutions that included I84V or G48V were resistant to atazanavir. Greater than 60% of isolates containing L90M, G73S/T/C, A71V/T, I54V, M46I/L, or a change at V82 were resistant to atazanavir, and 38% of isolates containing a D30N substitution in addition to other changes were resistant to atazanavir. Isolates resistant to atazanavir were also cross-resistant to other PIs with >90% of the isolates resistant to indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir, and 80% resistant to amprenavir. In treatment-experienced participants, PI-resistant viral isolates that developed the I50L substitution in addition to other PI resistance-associated substitution were also cross-resistant to other PIs.

Baseline Genotype/Phenotype and Virologic Outcome Analyses

Genotypic and/or phenotypic analysis of baseline virus may aid in determining atazanavir susceptibility before initiation of atazanavir with ritonavir therapy. An association between virologic response at 48 weeks and the number and type of primary PI resistance-associated substitutions detected in baseline HIV-1 isolates from antiretroviral-experienced participants receiving atazanavir with ritonavir once daily or lopinavir/ritonavir (fixed-dose product) twice daily in Study AI424-045 is shown in Table 24.

Overall, both the number and type of baseline PI substitutions affected response rates in treatment- experienced participants. In the atazanavir with ritonavir group, participants had lower response rates when 3 or more baseline PI substitutions, including a substitution at position 36, 71, 77, 82, or 90, were present compared to participants with 1 to 2 PI substitutions, including one of these substitutions.

Table 24: HIV-1 RNA Response by Number and Type of Baseline PI Substitution, Antiretroviral-Experienced Participants in Study AI424¬-045, As-Treated Analysis

^a Primary substitutions include any change at D30, V32, M36, M46, I47, G48, I50, I54, A71, G73, V77, V82, I84, N88, and L90.
^b Results should be interpreted with caution because the subgroups were small.
^c Administered as a fixed-dose product.
^d There were insufficient data (n<3) for PI substitutions V32I, I47V, G48V, I50V, and F53L.
The response rates of antiretroviral-experienced participants in Study AI424-045 were analyzed by baseline phenotype (shift in susceptibility in cell culture relative to reference, Table 25). The analyses are based on a select population with 62% of participants receiving an NNRTI-based regimen before study entry compared to 35% receiving a PI-based regimen. Additional data are needed to determine clinically relevant break points for atazanavir.
Table 25: Baseline Phenotype by Outcome, Antiretroviral-Experienced Participants in Study AI424-045, As-Treated Analysis 

 
^a  Fold change susceptibility in cell culture relative to the wild-type reference.

^b Results should be interpreted with caution because the subgroups were small.
^c Administered as a fixed-dose product.

Carcinogenesis
Long-term carcinogenicity studies in mice and rats were carried out with atazanavir for two years. In the mouse study, drug-related increases in hepatocellular adenomas were found in females at 360 mg/kg/day. The systemic drug exposure (AUC) at the NOAEL (no observable adverse effect level) in females, (120 mg/kg/day) was 2.8 times and in males (80 mg/kg/day) was 2.9 times higher than those in humans at the clinical dose (300 mg/day atazanavir boosted with 100 mg/day ritonavir, non-pregnant patients). In the rat study, no drug-related increases in tumor incidence were observed at doses up to 1200 mg/kg/day, for which AUCs were 1.1 (males) or 3.9 (females) times those measured in humans at the clinical dose.
Mutagenesis 
Atazanavir tested positive in an in vitroclastogenicity test using primary human lymphocytes, in the absence and presence of metabolic activation. Atazanavir tested negative in the in vitroAmes reverse-mutation assay, in vivomicronucleus and DNA repair tests in rats, and in vivoDNA damage test in rat duodenum (comet assay). 
Impairment of Fertility 
At the systemic drug exposure levels (AUC) 0.9 (in male rats) or 2.3 (in female rats) times that of the human clinical dose, (300 mg/day atazanavir boosted with 100 mg/day ritonavir) significant effects on mating, fertility, or early embryonic development were not observed.

Study AI424-138: a 96-week study comparing the antiviral efficacy and safety of either atazanavir or lopinavir/ritonavir, each in combination with fixed-dose tenofovir DF-emtricitabine in treatment-naive participants with HIV-1.Study AI424-138 (NCT00272779)was a 96-week, open-label, randomized, multicenter study, comparing atazanavir (300 mg once daily) with ritonavir (100 mg once daily) to lopinavir/ritonavir (400/100 mg twice daily as fixed-dose product), each in combination with the fixed-dose product, tenofovir DF/emtricitabine (300/200 mg once daily), in 878 antiretroviral treatment-naive participants. Participants had a mean age of 36 years (range: 19 to 72), 49% were Caucasian, 18% Black, 9% Asian, 23% Hispanic/Mestizo/mixed race, and 68% were male. The median baseline plasma CD4+ cell count was 204 cells/mm ³(range: 2 to 810 cells/mm ³) and the mean baseline plasma HIV-1 RNA level was 4.94 log ₁₀copies/mL (range: 2.60 to 5.88 log ₁₀copies/mL). Treatment response and outcomes through Week 96 are presented in Table 26.
Table 26: Outcomes of Treatment Through Week 96 in Treatment-Naive Adults (Study AI424-138)

^a As a fixed-dose product: 300 mg tenofovir DF/200 mg emtricitabine once daily.
^b As a fixed-dose product: 400 mg lopinavir/100 mg ritonavir (twice daily).
^c Participants achieved HIV-1 RNA <50 copies/mL at Week 96. Roche Amplicor®, v1.5 ultra-sensitive assay.
^d Pre-specified ITT analysis at Week 48 using as-randomized cohort: atazanavir with ritonavir 78% and lopinavir/ritonavir 76% (difference estimate: 1.7% [95% confidence interval: −3.8%, 7.1%]).
^e Pre-specified ITT analysis at Week 96 using as-randomized cohort: atazanavir with ritonavir 74% and lopinavir/ritonavir 68% (difference estimate: 6.1% [95% confidence interval: 0.3%, 12.0%]).
f Includes viral rebound and failure to achieve confirmed HIV-1 RNA <50 copies/mL through Week 96.
^g Includes lost to follow-up, participant's withdrawal, noncompliance, protocol violation, and other reasons.
Through 96 weeks of therapy, the proportion of responders among participants with high viral loads (ie, baseline HIV-1 RNA >100,000 copies/mL) was comparable for the atazanavir with ritonavir (165 of 223 participants, 74%) and lopinavir/ritonavir (148 of 222 participants, 67%) arms. At 96 weeks, the median increase from baseline in CD4+ cell count was 261 cells/mm3 for the atazanavir with ritonavir arm and 273 cells/mm ³for the lopinavir/ritonavir arm.
Study AI424-034: Atazanavir once daily compared to efavirenz once daily, each in combination with fixed-dose lamivudine/zidovudine twice daily.Study AI424-034 (NCT00013897) was a randomized, double-blind, multicenter trial comparing atazanavir (400 mg once daily) to efavirenz (600 mg once daily), each in combination with the fixed-dose product of lamivudine/zidovudine (150 mg/300 mg) given twice daily, in 810 antiretroviral treatment-naive participants. Participants had a mean age of 34 years (range: 18 to 73), 36% were Hispanic, 33% were Caucasian, and 65% were male. The mean baseline CD4+ cell count was 321 cells/mm ³(range: 64 to 1424 cells/mm ³) and the mean baseline plasma HIV-1 RNA level was 4.8 log ₁₀copies/mL (range: 2.2 to 5.9 log ₁₀copies/mL). Treatment response and outcomes through Week 48 are presented in Table 27.
Table 27: Outcomes of Randomized Treatment Through Week 48 in Treatment-Naive Adults (Study AI424-034) 

^a Participants achieved and maintained confirmed HIV-1 RNA <400 copies/mL (<50 copies/mL) through Week 48. Roche Amplicor® HIV-1 Monitor ^TMAssay, test version 1.0 or 1.5 as geographically appropriate. 
^b Includes viral rebound and failure to achieve confirmed HIV-1 RNA <400 copies/mL through Week 48.
^c Includes lost to follow-up, participants withdrawal, noncompliance, protocol violation, and other reasons.
^d As a fixed-dose product: 150 mg lamivudine/300 mg zidovudine twice daily.
Through 48 weeks of therapy, the proportion of responders among participants with high viral loads (ie, baseline HIV-1 RNA ≥100,000 copies/mL) was comparable for the atazanavir and efavirenz arms. The mean increase from baseline in CD4+ cell count was 176 cells/mm ³for the atazanavir arm and 160 cells/mm ³for the efavirenz arm.
Study AI424-008: Atazanavir 400 mg once daily compared to atazanavir 600 mg once daily, and compared to nelfinavir 1250 mg twice daily, each in combination with stavudine and lamivudine twice daily.Study AI424-008 (NCT identifier not available) was a 48-week, randomized, multicenter trial, blinded to dose of atazanavir, comparing atazanavir at two dose levels (400 mg and 600 mg once daily) to nelfinavir (1250 mg twice daily), each in combination with stavudine (40 mg) and lamivudine (150 mg) given twice daily, in 467 antiretroviral treatment-naive participants. Participants had a mean age of 35 years (range: 18 to 69), 55% were Caucasian, and 63% were male. The mean baseline CD4+ cell count was 295 cells/mm ³(range: 4 to 1003 cells/mm ³) and the mean baseline plasma HIV-1 RNA level was 4.7 log ₁₀copies/mL (range: 1.8 to 5.9 log ₁₀copies/mL). Treatment response and outcomes through Week 48 are presented in Table 28.
Table 28: Outcomes of Randomized Treatment Through Week 48 in Treatment-Naive Adults (Study AI424-008)

a Participants achieved and maintained confirmed HIV-1 RNA <400 copies/mL (<50 copies/mL) through Week 48. Roche Amplicor ^®HIV-1 Monitor™ Assay, test version 1.0 or 1.5 as geographically appropriate.
b Includes viral rebound and failure to achieve confirmed HIV-1 RNA <400 copies/mL through Week 48.
c Includes lost to follow-up, participants withdrawal, noncompliance, protocol violation, and other reasons.
Through 48 weeks of therapy, the mean increase  from  baseline  in  CD4+  cell  count  was 234 cells/mm ³for the atazanavir 400 mg arm and 211 cells/mm ³for the nelfinavir arm.

Study AI424-045: Atazanavir once daily with ritonavir once daily compared to atazanavir once daily and saquinavir (soft gelatin capsules) once daily, and compared to lopinavir/ritonavir twice daily, each in combination with tenofovir DF and one NRTI.Study AI424-045 (NCT00035932):was a randomized, multicenter trial comparing atazanavir (300 mg once daily) with ritonavir (100 mg once daily) to atazanavir (400 mg once daily) with saquinavir soft gelatin capsules (1200 mg once daily), and to lopinavir/ritonavir (400/100 mg twice daily as fixed-dose product), each in combination with tenofovir DF and one NRTI, in 347 (of 358 randomized) participants who experienced virologic failure on highly active antiretroviral therapy regimens containing PIs, NNRTIs, and NRTIs. The mean time of prior exposure to antiretrovirals was 139 weeks for PIs, 85 weeks for NNRTIs, and 283 weeks for NRTIs. The mean age was 41 years (range: 24 to 74); 60% were Caucasian, and 78% were male. The mean baseline CD4+ cell count was 338 cells/mm ³(range: 14 to 1543 cells/mm ³) and the mean baseline plasma HIV-1 RNA level was 4.4 log ₁₀copies/mL (range: 2.6 to 5.88 log ₁₀copies/mL).

Treatment outcomes through Week 48 for the atazanavir with ritonavir and lopinavir/ritonavir treatment arms are presented in Table 29. Atazanavir with ritonavir and lopinavir/ritonavir were similar for the primary efficacy outcome measure of time-averaged difference in change from baseline in HIV-1 RNA level. Study AI424-045 was not large enough to reach a definitive conclusion that atazanavir with ritonavir and lopinavir/ritonavir are equivalent on the secondary efficacy outcome measure of proportions below the HIV-1 RNA lower limit of quantification [see Microbiology, Tables 24 and 25 ( 12.4)].
Table 29: Outcomes of Treatment Through Week 48 in Study AI424-045 (Participants with Prior Antiretroviral Experience)

^a Time-averaged difference through Week 48 for HIV-1 RNA; Week 48 difference in HIV-1 RNA percentages and CD4+ mean changes, atazanavir with ritonavir vs lopinavir/ritonavir; CI = 97.5% confidence interval for change in HIV-1 RNA; 95% confidence interval otherwise.

^b Administered as a fixed-dose product.
^c Roche Amplicor ^®HIV-1 Monitor ^TMAssay, test version 1.5.
^d Protocol-defined primary efficacy outcome measure.
^e Based on participants with baseline and Week 48 CD4+ cell count measurements (atazanavir with ritonavir, n=85; lopinavir/ritonavir, n=93).
^f Participants achieved and maintained confirmed HIV-1 RNA <400 copies/mL (<50 copies/mL) through Week 48.
No participants in the atazanavir with ritonavir treatment arm and three participants in the lopinavir/ritonavir treatment arm experienced a new-onset CDC Category C event during the study.
In Study AI424-045, the mean change from baseline in plasma HIV-1 RNA for atazanavir 400 mg with saquinavir (n=115) was −1.55 log ₁₀copies/mL, and the time-averaged difference in change in HIV-1 RNA levels versus lopinavir/ritonavir was 0.33. The corresponding mean increase in CD4+ cell count was 72 cells/mm ³. Through 48 weeks of treatment, the proportion of participants in this treatment arm with plasma HIV-1 RNA <400 (<50) copies/mL was 38% (26%). In this study, coadministration of atazanavir and saquinavir did not provide adequate efficacy [see Drug Interactions ( 7)] .
Study AI424-045 also compared changes from baseline in lipid values. [See Adverse Reactions ( 6.1).]
Study AI424-043 (NCT00028301):Study AI424-043 was a randomized, open-label, multicenter trial comparing atazanavir (400 mg once daily) to lopinavir/ritonavir (400/100 mg twice daily as fixed-dose product), each in combination with two NRTIs, in 300 participants who experienced virologic failure to only one prior PI-containing regimen. Through 48 weeks, the proportion of participants with plasma HIV-1 RNA <400 (<50) copies/mL was 49% (35%) for participants randomized to atazanavir (n=144) and 69% (53%) for participants randomized to lopinavir/ritonavir (n=146). The mean change from baseline was −1.59 log ₁₀copies/mL in the atazanavir treatment arm and −2.02 log ₁₀copies/mL in the lopinavir/ritonavir arm. Based on the results of this study, atazanavir without ritonavir was inferior to lopinavir/ritonavir in PI-experienced participants with prior virologic failure and is not recommended for such patients.

Pediatric Trials with Atazanavir Capsules 
Study AI424-040; PACTG 1020A (NCT00006604):Assessment of the pharmacokinetics, safety, tolerability, and virologic response of atazanvir capsules was based on data from this open-label, multicenter clinical trial which included participants from 6 years to 21 years of age. In this study, 105 participants (43 antiretroviral-naive and 62 antiretroviral-experienced) received once daily atazanvir capsule formulation, with or without ritonavir, in combination with two NRTIs. 
One-hundred five (105) participants (6 to less than 18 years of age) treated with the atazanvir capsule formulation, with or without ritonavir, were evaluated. Using an intent-to-treat (ITT) analysis, the overall proportions of antiretroviral-naive and -experienced participants with HIV-1 RNA <400 copies/mL at Week 96 were 51% (22/43) and 34% (21/62), respectively. The overall proportions of antiretroviral-naive and -experienced participants with HIV-1 RNA <50 copies/mL at Week 96 were 47% (20/43) and 24% (15/62), respectively. The median increase from baseline in absolute CD4 count at 96 weeks of therapy was 335 cells/mm ³in antiretroviral-naive participants and 220 cells/mm ³in antiretroviral-experienced participants.