VIRACEPT (nelfinavir mesylate 250 mg) Dailymed

Recent Major Changes Section

Contraindications ( 4)

9/2016

1indications And Usage

VIRACEPT in combination with other antiretroviral agents is indicated for the treatment of HIV-1 infection.


VIRACEPT is a protease inhibitor indicated for the treatment of HIV-1 infection in combination with other antiretroviral agents. ( 1)

2dosage And Administration

• See full prescribing information for administration instructions ( 2)
• Adults and adolescents 13 years and older (tablets): 1250 mg twice daily or 750 mg three times daily with a meal ( 2.1)
• Children 2 to less than 13 years (oral powder or 250 mg tablets): 45 to 55 mg/kg twice daily or 25 to 35 mg/kg three times daily with a meal. Refer to Tables 1 and 2 of the full prescribing information for specific dosing guidelines based on age and body weight ( 2.2)

2.1Adults and Adolescents (13 years and older)

The recommended dose is 1250 mg (five 250 mg tablets or two 625 mg tablets) twice daily or 750 mg (three 250 mg tablets) three times daily. VIRACEPT should be taken with a meal. Patients unable to swallow the 250 or 625 mg tablets may dissolve the tablets in a small amount of water [see Dosage and Administration (2.3)] .

2.2Pediatric Patients (2 to less than 13 years)

In children 2 years of age and older, the recommended oral dose of VIRACEPT Oral Powder or 250 mg tablets is 45 to 55 mg/kg twice daily or 25 to 35 mg/kg three times daily. All doses should be taken with a meal. Doses higher than the adult maximum dose of 2500 mg per day have not been studied in children.

For children unable to swallow tablets, VIRACEPT 250 mg tablet(s) may be dissolved in a small amount of water or, VIRACEPT Oral Powder may be administered [see Dosage and Administration (2.3)] .

The healthcare provider should assess appropriate formulation and dosage for each patient. Tables 1 and 2 provide dosing guidelines for VIRACEPT tablets and powder based on age and body weight.

Table 1: Dosing Table for Children 2 to less than 13 years of age (tablets)

Body weight	Twice daily (BID) 45 – 55 mg/kg ≥2 years	Three times daily (TID) 25 – 35 mg/kg ≥2 years
	Number of tablets (250 mg)	Number of tablets (250 mg)
Kg
10 – 12	2	1
13 – 18	3	2
19 – 20	4	2
≥21	4 – 5 For BID dosing, the maximum dose per day is 5 tablets BID	3 For TID dosing, the maximum dose per day is 3 tablets TID

Table 2: Dosing Table for Children 2 to less than 13 years of age (powder)

Body weight	Twice daily (BID) 45 – 55 mg/kg		Three times daily (TID) 25 – 35 mg/kg
Kg	Scoops of powder (50 mg/1 g)	Teaspoons If a teaspoon is used to measure VIRACEPT oral powder, 1 level teaspoon contains 200 mg of VIRACEPT (4 level scoops equals 1 level teaspoon) of powder	Scoops of powder (50 mg/1 g)	Teaspoons of powder
9.0 to <10.5	10	2½	6	1½
10.5 to <12	11	2¾	7	1¾
12 to <14	13	3¼	8	2
14 to <16	15	3¾	9	2¼
16 to <18	Not recommended Use VIRACEPT 250 mg tablet	Not recommended	10	2½
18 to <23	Not recommended	Not recommended	12	3
≥23	Not recommended	Not recommended	15	3¾

2.3Method of Administration

For Patients Unable to Swallow Viracept Tablets

• Place VIRACEPT tablet(s) in small amount of water.
• Once dissolved, mix the cloudy liquid well, and consume it immediately.
• The glass should be rinsed with water and the rinse swallowed to ensure the entire dose is consumed.

Viracept Oral Powder

• Mix VIRACEPT Oral Powder with a small amount of water, milk, formula, soy formula, soy milk, or dietary supplements
• Once mixed, the entire contents must be consumed in order to obtain the full dose.
• If the mixture is not consumed immediately, it must be stored under refrigeration, but storage must not exceed 6 hours.
• Acidic food or juice (e.g., orange juice, apple juice, or apple sauce) are not recommended for mixing VIRACEPT Oral Powder because the combination may result in a bitter taste.
• VIRACEPT Oral Powder should not be reconstituted with water in its original container.

2.4Hepatic Impairment

VIRACEPT can be used in patients with mild hepatic impairment without any dose adjustment. VIRACEPT should not be used in patients with either moderate or severe hepatic impairment [see Warnings and Precautions (5.2), Use in Specific Populations (8.6), and Clinical Pharmacology (12.3)] .

Coadministration of VIRACEPT is contraindicated with drugs that are highly dependent on CYP3A for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events. These drugs and other contraindicated drugs (which may lead to reduced efficacy of nelfinavir) are uled in Table 3 ]. Coadministration of VIRACEPT is contraindicated with drugs that are highly dependent on CYP3A for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events. These drugs and other contraindicated drugs (which may lead to reduced efficacy of nelfinavir) are uled in Table 3 [also see Drug Interactions (7), Table 6 ].

Table 3: Drugs That Are Contraindicated With VIRACEPT

Drug Class	Drugs Within Class That Are Contraindicated With VIRACEPT	Clinical Comment
Alpha 1-adrenoreceptor antagonist	Alfuzosin	Potentially increased alfuzosin concentrations can result in hypotension.
Antiarrhythmics	Amiodarone, quinidine	Potential for serious and/or life-threatening cardiac arrhythmia.
Antimycobacterial Agents	Rifampin	Plasma concentrations of nelfinavir can be reduced by concomitant use of rifampin. This may lead to loss of therapeutic effect and possible development of resistance to VIRACEPT or other coadministered antiretroviral agents.
Antipsychotics	Lurasidone Pimozide	Potential for serious and/or life-threatening reactions. Potential for serious and/or life threatening reactions such as cardiac arrhythmias.
Ergot Derivatives	Dihydroergotamine, ergotamine, methylergonovine	Potential for serious and/or life threatening reactions such as ergot toxicity characterized by peripheral vasospasm and ischemia of the extremities and other tissues.
GI Motility Agent	Cisapride	Potential for serious and/or life threatening reactions such as cardiac arrhythmias.
Herbal products	St. John's wort ( Hypericum perforatum)	Plasma concentrations of nelfinavir can be reduced by concomitant use of the herbal preparation St. John's wort. This may lead to loss of therapeutic effect and possible development of resistance to VIRACEPT or other coadministered antiretroviral agents.
HMG-CoA Reductase Inhibitors	Lovastatin, Simvastatin	Potential for serious reactions such as myopathy including rhabdomyolysis.
PDE5 Inhibitors	Sildenafil (Revatio ®) [for treatment of pulmonary arterial hypertension] See Drug Interactions, Table 6 for coadministration of sildenafil and tadalafil when dosed for erectile dysfunction.	A safe and effective dose has not been established when used with nelfinavir. There is increased potential for sildenafil-associated adverse events (which include visual disturbances, hypotension, prolonged erection, and syncope).
Sedative/Hypnotics	Triazolam, oral midazolam	Potential for serious and/or life threatening reactions such as prolonged or increased sedation or respiratory depression.

Coadministration with drugs that are highly dependent on CYP3A for clearance and which elevated concentrations are associated with serious and/or life-threatening events ( 4)

5warnings And Precautions

ALERT: Find out about medicines that should not be taken with VIRACEPT. This statement is included on the product's bottle label.


ALERT: Find out about medicines that should not be taken with VIRACEPT.

• The concomitant use of VIRACEPT and certain other drugs may result in known or potentially significant drug interactions. Consult the full prescribing information prior to and during treatment for potential drug interactions ( 5.1, 7.3)
• Hepatic impairment: should not be used in patients with either moderate or severe hepatic impairment ( 2.4, 5.2)
• Phenylketonuria: the oral powder contains 11.2 mg phenylalanine per gram of powder ( 5.3)
• Diabetes mellitus/hyperglycemia: new onset or exacerbation of pre-existing diabetes mellitus and hyperglycemia reported with protease inhibitors. In some cases after treatment discontinuation, hyperglycemia persisted ( 5.4)
• Hemophilia: increased bleeding, including spontaneous skin hematomas and hemarthrosis reported with protease inhibitors. In more than half of the cases, protease inhibitors was continued or reintroduced ( 5.5)
• Fat redistribution: observed with antiretroviral therapy ( 5.6)
• Immune reconstitution syndrome: reported with combination antiretroviral therapy, including VIRACEPT. Patients may develop an inflammatory response to indolent or residual opportunistic infections ( 5.7)

5.1Risk of Serious Adverse Reactions Due to Drug Interactions

Initiation of VIRACEPT, a CYP3A inhibitor, in patients receiving medications metabolized by CYP3A or initiation of medications metabolized by CYP3A in patients already receiving VIRACEPT, may increase plasma concentrations of medications metabolized by CYP3A. Initiation of medications that inhibit or induce CYP3A may increase or decrease concentrations of VIRACEPT, 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 VIRACEPT.
• Loss of therapeutic effect of VIRACEPT and possible development of resistance.

See Table 6 for steps to prevent or manage these possible and known significant drug interactions, including dosing recommendations [see Drug Interactions (7)] . Consider the potential for drug interactions prior to and during VIRACEPT therapy; review concomitant medications during VIRACEPT therapy; and monitor for the adverse reactions associated with the concomitant medications [see Contraindications (4) and Drug Interactions (7)] .

5.2Hepatic Impairment

VIRACEPT should not be used in patients with either moderate or severe hepatic impairment (Child-Pugh B or C, score greater than or equal to 7) [see Dosage and Administration (2.4)and Clinical Pharmacology (12.3)].

5.3Phenylketonurics

Viracept Oral Powder contains phenylalanine, a component of aspartame. Each gram of VIRACEPT powder contains 11.2 mg phenylalanine. Phenylalanine can be harmful to patients with phenylketonuria.

5.4Diabetes Mellitus/Hyperglycemia

New onset diabetes mellitus, exacerbation of pre-existing diabetes mellitus and hyperglycemia have been reported during post-marketing surveillance in HIV-infected patients 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.

5.5Hemophilia

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 has not been established.

5.6Fat Redistribution

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.

5.7Immune Reconstitution Syndrome

Immune reconstitution syndrome has been reported in patients treated with combination antiretroviral therapy, including VIRACEPT. 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 infection, cytomegalovirus, Pneumocystis jiroveci pneumonia (PCP), or tuberculosis], which may necessitate further evaluation and treatment.

Autoimmune disorders (such as Graves' disease, polymyositis, and Guillain-Barré syndrome) 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.

6adverse Reactions

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.

• Most common adverse reactions (≥2%) of moderate or severe intensity in adults and adolescents (13 years and older) are diarrhea, nausea, rash, and flatulence ( 6.1).
• Most common adverse reactions in pediatric patients (2 to less than 13 years) are diarrhea, leukopenia/neutropenia, rash, anorexia, and abdominal pain. ( 6.2)

To report SUSPECTED ADVERSE REACTIONS, contact Pfizer Inc at 1-800-438-1985 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

6.1Clinical Trials Experience: Adults and Adolescents (13 years and older)

The safety of VIRACEPT was studied in over 5000 patients who received drug either alone or in combination with nucleoside analogues. The majority of adverse events were of mild intensity. The most frequently reported adverse event among patients receiving VIRACEPT was diarrhea, which was generally of mild to moderate intensity.

Drug-related clinical adverse experiences of moderate or severe intensity in ≥2% of patients treated with VIRACEPT coadministered with d4T and 3TC (Study 542) for up to 48 weeks, or with ZDV plus 3TC (Study 511) for up to 24 weeks are presented in Table 4.

Table 4: Percentage of Patients with Treatment-Emergent Includes those adverse events at least possibly, probably or definitely related to study drug or of unknown relationship and excludes concurrent HIV conditions Adverse Events of Moderate or Severe Intensity Reported in ≥ 2% of Adult and Adolescent Patients

	Study 511			Study 542
	24 weeks			48 weeks
  Adverse Events	Placebo + ZDV/3TC (n=101)	500 mg TID VIRACEPT + ZDV/3TC (n=97)	750 mg TID VIRACEPT + ZDV/3TC (n=100)	1250 mg BID VIRACEPT + d4T/3TC (n=344)	750 mg TID VIRACEPT + d4T/3TC (n=210)
Digestive System
  Diarrhea	3%	14%	20%	20%	15%
  Nausea	4%	3%	7%	3%	3%
  Flatulence	0	5%	2%	1%	1%
Skin/Appendages
  Rash	1%	1%	3%	2%	1%

Adverse events occurring in less than 2% of patients receiving VIRACEPT in all phase 2 and 3 clinical trials and considered at least possibly related or of unknown relationship to treatment and of at least moderate severity are uled below.

Body as a Whole: abdominal pain, accidental injury, allergic reaction, asthenia, back pain, fever, headache, malaise, pain, and redistribution/accumulation of body fat [see Warnings and Precautions (5.7)] .

Digestive System: anorexia, dyspepsia, epigastric pain, gastrointestinal bleeding, hepatitis, mouth ulceration, pancreatitis, and vomiting.

Hemic/Lymphatic System: anemia, leukopenia, and thrombocytopenia.

Metabolic/Nutritional System: increases in alkaline phosphatase, amylase, creatine phosphokinase, lactic dehydrogenase, SGOT, SGPT, and gamma-glutamyl transpeptidase; hyperlipemia, hyperuricemia, hyperglycemia, hypoglycemia, dehydration, and liver function tests abnormal.

Musculoskeletal System: arthralgia, arthritis, cramps, myalgia, myasthenia, and myopathy.

Nervous System: anxiety, depression, dizziness, emotional lability, hyperkinesia, insomnia, migraine, paresthesia, seizures, sleep disorder, somnolence, and suicide ideation.

Respiratory System: dyspnea, pharyngitis, rhinitis, and sinusitis.

Skin/Appendages: dermatitis, folliculitis, fungal dermatitis, maculopapular rash, pruritus, sweating, and urticaria.

Special Senses: acute iritis and eye disorder.

Urogenital System: kidney calculus, sexual dysfunction, and urine abnormality.

Laboratory Abnormalities

The percentage of patients with marked laboratory abnormalities in Studies 542 and 511 are presented in Table 5. Marked laboratory abnormalities are defined as a Grade 3 or 4 abnormality in a patient with a normal baseline value, or a Grade 4 abnormality in a patient with a Grade 1 abnormality at baseline.

Table 5: Percentage of Patients by Treatment Group With Marked Laboratory Abnormalities Marked laboratory abnormalities are defined as a shift from Grade 0 at baseline to at least Grade 3 or from Grade 1 to Grade 4 in >2% of Patients

	Study 511			Study 542
	Placebo + ZDV/3TC (n=101)	500 mg TID VIRACEPT + ZDV/3TC (n=97)	750 mg TID VIRACEPT + ZDV/3TC (n=100)	1250 mg BID VIRACEPT + d4T/3TC (n=344)	750 mg TID VIRACEPT + d4T/3TC (n=210)
Hematology
  Hemoglobin	6%	3%	2%	0	0
  Neutrophils	4%	3%	5%	2%	1%
  Lymphocytes	1%	6%	1%	1%	0
Chemistry
  ALT (SGPT)	6%	1%	1%	2%	1%
  AST (SGOT)	4%	1%	0	2%	1%
  Creatine Kinase	7%	2%	2%	NA	NA

6.2Clinical Trials Experience: Pediatrics (2 to less than 13 years of age)

VIRACEPT has been studied in approximately 400 pediatric patients in clinical trials from birth to 13 years of age. The adverse event profile seen during pediatric clinical trials was similar to that for adults.

The most commonly reported drug-related, treatment-emergent adverse events reported in the pediatric studies included: diarrhea, leukopenia/neutropenia, rash, anorexia, and abdominal pain. Diarrhea, regardless of assigned relationship to study drug, was reported in 39% to 47% of pediatric patients receiving VIRACEPT in 2 of the larger treatment trials. Leukopenia/neutropenia was the laboratory abnormality most commonly reported as a significant event across the pediatric studies.

6.3Postmarketing Experience

The following adverse reactions have been identified during post-approval use of VIRACEPT. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Body as a Whole: hypersensitivity reactions (including bronchospasm, moderate to severe rash, fever, and edema).

Cardiovascular System: QTc prolongation, torsades de pointes.

Digestive System: jaundice.

Metabolic/Nutritional System: bilirubinemia, metabolic acidosis.

7drug Interactions

• Co-administration of VIRACEPT with other drugs (CYP3A substrates) can alter the concentration of these other drugs, and other drugs (inhibitors and/or inducers of CYP3A or CYP2C19) may alter the concentrations of nelfinavir. The potential drug-drug concentrations must be considered prior to and during therapy ( 4, 7, 12.3)
• VIRACEPT should be given with food one hour after or more than 2 hours before didanosine ( 7)

7.1Potential for VIRACEPT to Affect Other Drugs

Nelfinavir is an inhibitor of CYP3A. Coadministration of VIRACEPT and drugs primarily metabolized by CYP3A (e.g., dihydropyridine calcium channel blockers, HMG-CoA reductase inhibitors, immunosuppressants and PDE5 inhibitors) may result in increased plasma concentrations of such drugs that could increase or prolong both its therapeutic and adverse effects. (see Tables 3and 6).

7.2Potential for Other Drugs to Affect VIRACEPT

Nelfinavir is metabolized by CYP3A and CYP2C19. Coadministration of VIRACEPT and drugs that induce CYP3A or CYP2C19, such as rifampin, may decrease nelfinavir plasma concentrations and reduce its therapeutic effect. Coadministration of VIRACEPT and drugs that inhibit CYP3A or CYP2C19 may increase nelfinavir plasma concentrations.

7.3Established and Other Potentially Significant Drug Interactions

Table 6 provides the effect on concentrations of VIRACEPT or concomitant drug as a result of coadministration with VIRACEPT. These recommendations are based on either drug interaction studies or predicted interactions due to the expected magnitude of interaction and potential for serious adverse events or loss of efficacy.

Table 6: Established and Other Potentially Significant Drug Interactions: Alteration in Dose or Regimen May Be Recommended Based on Drug Interaction Studies [see Clinical Pharmacology (12.3)( Tables 12and 13) for magnitude of interaction]

Concomitant Drug Class: Drug Name	Effect on Concentration	Clinical Comment
HIV Antiviral Agents: Reverse Transcriptase Inhibitors
Delavirdine	↑ nelfinavir (C min) ↓ delavirdine	Concentrations of nelfinavir were increased while concentrations of delavirdine were decreased when the two agents were coadministered. Appropriate doses of the combination, with respect to safety and efficacy, have not been established.
Nevirapine	↓ nelfinavir (C min)	Concentrations of nelfinavir were decreased when coadministered with nevirapine. An appropriate dose of nelfinavir with respect to safety and efficacy has not been established.
Didanosine	↔ nelfinavir	There was no change in nelfinavir concentration when coadministered with didanosine. However, it is recommended that didanosine be administered on an empty stomach; therefore, didanosine should be given one hour before or two hours after VIRACEPT (given with food).
HIV Antiviral Agents: Protease Inhibitors
Indinavir	↑ nelfinavir ↑ indinavir	Concentrations of both indinavir and nelfinavir were increased when the two agents were coadministered. Appropriate doses for these combinations, with respect to safety and efficacy, have not been established.
Ritonavir	↑ nelfinavir ↔ ritonavir	Concentrations of nelfinavir were increased when coadministered with ritonavir. An appropriate dose of nelfinavir for this combination, with respect to safety and efficacy, has not been established.
Saquinavir	↑ nelfinavir ↑ saquinavir	Concentrations of both saquinavir and nelfinavir were increased when the two agents were coadministered. Appropriate doses for these combinations, with respect to safety and efficacy, have not been established.
ANTICOAGULANT
Warfarin	Warfarin	Coadministration of warfarin and VIRACEPT may affect concentrations of warfarin. It is recommended that the INR (international normalized ratio) be monitored carefully during treatment with VIRACEPT, especially when commencing therapy.
ANTICONVULSANTS
Carbamazepine Phenobarbital Phenytoin	↓ nelfinavir ↓ phenytoin	Concentrations of nelfinavir may be decreased. VIRACEPT may not be effective due to decreased nelfinavir plasma concentrations in patients taking these agents concomitantly. Phenytoin plasma/serum concentrations should be monitored; phenytoin dose may require adjustment to compensate for altered phenytoin concentration.
ANTIDEPRESSANT
Trazodone	↑ trazodone	Concomitant use of trazodone and VIRACEPT may increase plasma concentrations of trazodone. Adverse events of nausea, dizziness, hypotension and syncope have been observed following coadministration of trazodone and ritonavir. If trazodone is used with a CYP3A4 inhibitor such as VIRACEPT, the combination should be used with caution and a lower dose of trazodone should be considered.
ANTIGOUT
Colchicine	↑ colchicines	Patients with renal or hepatic impairment should not be given colchicine with VIRACEPT due to the risk of colchicine toxicity. Treatment of gout flares – co- administration of colchicine in patients on VIRACEPT: 0.6 mg (1 tablet) × 1 dose, followed by 0.3 mg (half tablet) 1 hour later. Dose to be repeated no earlier than 3 days. Prophylaxis of gout-flares – coadministration of colchicine in patients on VIRACEPT: If the original colchicine regimen was 0.6 mg twice a day, the regimen should be adjusted to 0.3 mg once a day. If the original colchicine regimen was 0.6 mg once a day, the regimen should be adjusted to 0.3 mg once every other day. Treatment of familial Mediterranean fever (FMF)– coadministration of colchicine in patients on VIRACEPT: Maximum daily dose of 0.6 mg (may be given as 0.3 mg twice a day).
ANTIMYCOBACTERIAL
Rifabutin	↑ rifabutin ↓ nelfinavir   (750 mg TID) ↔ nelfinavir   (1250 mg BID)	It is recommended that the dose of rifabutin be reduced to one-half the usual dose when administered with VIRACEPT; 1250 mg BID is the preferred dose of VIRACEPT when coadministered with rifabutin.
ENDOTHELIN RECEPTOR ANTAGONIST
Bosentan	↑ bosentan	Concentrations of bosentan may be increased when coadministered with VIRACEPT. Coadministration of bosentan in patients on VIRACEPT or coadministration of VIRACEPT in patients on bosentan: Start at or adjust bosentan to 62.5 mg once daily or every other day based upon individual tolerability.
HMG-CoA REDUCTASE INHIBITORS
Atorvastatin Rosuvastatin	↑ atorvastatin ↑ rosuvastatin	Titrate atorvastatin dose carefully and use the lowest necessary dose; do not exceed atorvastatin 40 mg/day.
IMMUNOSUPPRESSANTS
Cyclosporine Tacrolimus Sirolimus	↑ immuno-suppressants ↑ nelfinavir	Concentrations of these immunosuppressants and nelfinavir may be increased by coadministration of these agents with nelfinavir.
INHALED BETA AGONIST
Salmeterol	↑ salmeterol	Concurrent administration of salmeterol with VIRACEPT is not recommended. The combination may result in increased risk of cardiovascular adverse events associated with salmeterol, including QT prolongation, palpitations and sinus tachycardia.
INHALED/NASAL STEROID
Fluticasone	↑ fluticasone	Concomitant use of fluticasone propionate and VIRACEPT may increase plasma concentrations of fluticasone propionate. Use with caution. Consider alternatives to fluticasone propionate, particularly for long-term use.
MACROLIDE ANTIBIOTIC
Azithromycin	↑ azithromycin	Dose adjustment of azithromycin is not recommended, but close monitoring for known side effects such as liver enzyme abnormalities and hearing impairment is warranted.
NARCOTIC ANALGESIC
Methadone	↓ methadone	Concentrations of methadone were decreased when coadministered with VIRACEPT. Dosage of methadone may need to be increased when coadministered with VIRACEPT.
HORMONAL CONTRACEPTIVES
Ethinyl estradiol Norethindrone	↓ ethinyl estradiol ↓ norethindrone	Concentrations of ethinyl estradiol and norethindrone were decreased when coadministered with VIRACEPT. Alternative or additional contraceptive measures should be used when oral contraceptives containing ethinyl estradiol or norethindrone and VIRACEPT are coadministered.
PDE5 INHIBITORS
Sildenafil Vardenafil Tadalafil	↑ PDE5 Inhibitors	Concomitant use of PDE5 inhibitors and VIRACEPT should be undertaken with caution. May result in an increase in PDE5 inhibitor-associated adverse events, including hypotension, syncope, visual disturbances, and priapism. Use of PDE5 inhibitors for pulmonary arterial hypertension (PAH): • Use of sildenafil (REVATIO) is contraindicated when used for the treatment of pulmonary arterial hypertension (PAH) [see Contraindications (4)] . • The following dose adjustments are recommended for use of tadalafil (ADCIRCA™) with VIRACEPT: Coadministration of ADCIRCA in patients on VIRACEPT or coadministration of VIRACEPT in patients on ADCIRCA: Start at or adjust ADCIRCA to 20 mg once daily. Increase to 40 mg once daily based upon individual tolerability. Use of PDE5 inhibitors for erectile dysfunction: Sildenafil at a single dose not exceeding 25 mg in 48 hours, vardenafil at a single dose not exceeding 2.5 mg in 24 hours, or tadalafil at a single dose not exceeding 10 mg dose in 72 hours, is recommended. Use with increased monitoring for adverse events.
PROTON PUMP INHIBITORS
Omeprazole	↓ nelfinavir	Omeprazole decreases the plasma concentrations of nelfinavir. Concomitant use of proton pump inhibitors and VIRACEPT may lead to a loss of virologic response and development of resistance.
ANTIPSYCHOTICS
Quetiapine	↑ quetiapine	Initiation of VIRACEPT in patients taking quetiapine: Consider alternative antiretroviral therapy to avoid increases in quetiapine drug exposures. If coadministration is necessary, reduce the quetiapine dose to 1/6 of the current dose and monitor for quetiapine-associated adverse reactions. Refer to the quetiapine prescribing information for recommendations on adverse reaction monitoring. Initiation of quetiapine in patients taking VIRACEPT: Refer to the quetiapine prescribing information for initial dosing and titration of quetiapine.

8use In Specific Populations

• Use during pregnancy if the potential benefit justifies the potential risk to the fetus ( 8.1)
• Nursing mothers: should not breast-feed their infants ( 8.3)

8.1Pregnancy

TERATOGENIC EFFECTS SECTION

Pregnancy Category B

VIRACEPT should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. There are no adequate and well-controlled studies in pregnant women taking VIRACEPT.

There were no effects on fetal development or maternal toxicity when nelfinavir was administered to pregnant rats at systemic exposures (AUC) comparable to human exposure. Administration of nelfinavir to pregnant rabbits resulted in no fetal development effects up to a dose at which a slight decrease in maternal body weight was observed; however, even at the highest dose evaluated, systemic exposure in rabbits was significantly lower than human exposure. Additional studies in rats indicated that exposure to nelfinavir in females from mid-pregnancy through lactation had no effect on the survival, growth, and development of the offspring to weaning. Subsequent reproductive performance of these offspring was also not affected by maternal exposure to nelfinavir.

Antiretroviral Pregnancy Registry (APR): To monitor maternal-fetal outcomes of pregnant women exposed to VIRACEPT and other antiretroviral agents, an Antiretroviral Pregnancy Registry has been established. Physicians are encouraged to register patients by calling (800) 258-4263.

8.3Nursing Mothers

The Centers for Disease Control and Prevention recommends that HIV-infected mothers not breast-feed their infants to avoid risking postnatal transmission of HIV. Studies in lactating rats have demonstrated that nelfinavir is excreted in milk. Because of both the potential for HIV transmission and the potential for serious adverse reactions in nursing infants, mothers should be instructed not to breast-feed if they are receiving VIRACEPT.

8.4Pediatric Use

The safety, tolerability, pharmacokinetic profile and efficacy of VIRACEPT were evaluated in HIV infected pediatric patients from 2 to 13 years of age in multicenter clinical trials, Study 556 and PACTG 337 [see Clinical Pharmacology (12.3)and Clinical Studies (14.3)] . In patients less than 2 years of age, VIRACEPT was found to be safe at the doses studied, but a reliably effective dose could not be established [see Dosage and Administration (2.2), Adverse Reactions (6.2), and Clinical Pharmacology (12.3)] . The pharmacokinetic profile, safety and antiviral activity of VIRACEPT in adolescent patients 13 years and older is supported by data from the adult clinical trials where some trials allowed enrolment of subjects 13 years and older. Thus, the data for adolescents and adults were analyzed collectively. [see Adverse Reactions (6.1)] .

8.5Geriatric Use

Clinical studies of VIRACEPT did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.

8.6Hepatic Impairment

VIRACEPT should not be used in patients with either moderate or severe hepatic impairment (Child-Pugh B or C, score greater than or equal to 7) [see Warnings and Precautions (5.2) and Clinical Pharmacology (12.3)] . No dose adjustment of VIRACEPT is necessary for patients with mild hepatic impairment (Child-Pugh A, score 5–6).

8.7Renal Impairment

The safety and efficacy of VIRACEPT have not been established in patients with renal impairment.

12.1Mechanism of Action

Nelfinavir is an inhibitor of the HIV-1 protease [see Microbiology (12.4)] .

12.2Pharmacodynamics

Effects on Electrocardiogram

The effect of Viracept at the recommended dose of 1250 mg twice daily on the QTcF interval administered with a low fat meal (20% fat) was evaluated in a randomized, placebo and active (moxifloxacin 400 mg once daily) controlled, crossover study in 66 healthy subjects. The maximum mean time-matched (95% upper confidence bound) differences in QTcF interval from placebo after baseline-correction was below 10 milliseconds, the threshold of clinical concern. This finding was unchanged when a single supratherapeutic dose of Viracept 3125 mg was administered following a 3-day administration of Viracept 1250 mg twice daily. The exposure at 3125 mg was 1.4-fold that at 1250 mg. The dose of 3125 mg in this study did not achieve the anticipated exposures in patients taking a high fat meal (50% fat) or with concomitant administration of drugs that could increase nelfinavir exposure [see Pharmacokinetics (12.3)] .

No subject in any group had an increase in QTcF of ≥60 milliseconds from baseline. No subject experienced an interval exceeding the potentially clinically relevant threshold of 500 milliseconds.

12.3Pharmacokinetics

The pharmacokinetic properties of nelfinavir were evaluated in healthy volunteers and HIV-infected patients; no substantial differences were observed between the two groups.

Absorption

Pharmacokinetic parameters of nelfinavir (area under the plasma concentration-time curve during a 24-hour period at steady-state [AUC ₂₄], peak plasma concentrations [C _max], morning and evening trough concentrations [C _trough]) from a pharmacokinetic study in HIV-positive patients after multiple dosing with 1250 mg (five 250 mg tablets) twice daily (BID) for 28 days (10 patients) and 750 mg (three 250 mg tablets) three times daily (TID) for 28 days (11 patients) are summarized in Table 7.

Table 7: Summary of a Pharmacokinetic Study in HIV-positive Patients With Multiple Dosing of 1250 mg (Five 250 mg Tablets) BID for 28 Days and 750 mg (Three 250 mg Tablets) TID for 28 Days

Regimen	AUC 24 mg∙h/L	C max mg/L	C trough Morning mg/L	C trough Afternoon or Evening mg/L
Data are mean ± SD
1250 mg BID	52.8±15.7	4.0±0.8	2.2±1.3	0.7±0.4
  750 mg TID	43.6±17.8	3.0±1.6	1.4±0.6	1.0±0.5

The difference between morning and afternoon or evening trough concentrations for the TID and BID regimens was also observed in healthy volunteers who were dosed at precisely 8- or 12-hour intervals.

In healthy volunteers receiving a single 1250 mg dose, the 625 mg tablet was not bioequivalent to the 250 mg tablet formulation. Under fasted conditions (n=27), the AUC and C _max were 34% and 24% higher, respectively, for the 625 mg tablets. In a relative bioavailability assessment under fed conditions (n=28), the AUC was 24% higher for the 625 mg tablet; the C _max was comparable for both formulations. In HIV-1 infected subjects (N=21) receiving multiple doses of 1250 mg BID under fed conditions, the 625 mg formulation was bioequivalent to the 250 mg formulation based on similarity in steady state exposure (C _max and AUC).

Table 8 shows the summary of the steady state pharmacokinetic parameters (mean ± SD) of nelfinavir after multiple dose administration of 1250 mg BID (2 × 625 mg tablets) to HIV-infected patients (N=21) for 14 days.

Table 8: Summary of the Steady State Pharmacokinetic Parameters (Mean ± SD) of Nelfinavir After Multiple Dose Administration of 1250 mg BID (2 × 625 mg Tablets) to HIV-infected Patients (N=21) for 14 Days.

Regimen	AUC 12 mg∙h/L	C max mg/L	C min mg/L
AUC 12: Steady state AUC
C max: Maximum plasma concentration at steady state
C min: Minimum plasma concentration at steady state
1250 mg BID	35.3 (16.4)	4.7 (1.9)	1.5 (1.0)

In healthy volunteers receiving a single 750 mg dose under fed conditions, nelfinavir concentrations were similar following administration of the 250 mg tablet and oral powder.

Effect of Food on Oral Absorption

Food increases nelfinavir exposure and decreases nelfinavir pharmacokinetic variability relative to the fasted state. In one study, healthy volunteers received a single dose of 1250 mg of VIRACEPT 250 mg tablets (5 tablets) under fasted or fed conditions (three different meals). In a second study, healthy volunteers received single doses of 1250 mg VIRACEPT (5 × 250 mg tablets) under fasted or fed conditions (two different fat content meals). The results from the two studies are summarized in Table 9 and Table 10, respectively.

Table 9: Increase in AUC, C _max and T _max for Nelfinavir in Fed State Relative to Fasted State Following 1250 mg VIRACEPT (5 × 250 mg Tablets)

Number of Kcal	% Fat	Number of subjects	AUC fold increase	C max fold increase	Increase in T max (hr)
125	20	n=21	2.2	2.0	1.00
500	20	n=22	3.1	2.3	2.00
1000	50	n=23	5.2	3.3	2.00

Table 10: Increase in Nelfinavir AUC, C _max and T _max in Fed Low Fat (20%) versus High Fat (50%) State Relative to Fasted State Following 1250 mg VIRACEPT (5 × 250 mg Tablets)

Number of Kcal	% Fat	Number of subjects	AUC fold increase	C max fold increase	Increase in T max (hr)
500	20	n=22	3.1	2.5	1.8
500	50	n=22	5.1	3.8	2.1

Nelfinavir exposure can be increased by increasing the calorie or fat content in meals taken with VIRACEPT.

A food effect study has not been conducted with the 625 mg tablet. However, based on a cross-study comparison (n=26 fed vs. n=26 fasted) following single dose administration of nelfinavir 1250 mg, the magnitude of the food effect for the 625 mg nelfinavir tablet appears comparable to that of the 250 mg tablets. VIRACEPT should be taken with a meal.

Distribution

The apparent volume of distribution following oral administration of nelfinavir was 2–7 L/kg. Nelfinavir in serum is extensively protein-bound (>98%).

Metabolism

Unchanged nelfinavir comprised 82–86% of the total plasma radioactivity after a single oral 750 mg dose of ¹⁴C-nelfinavir. In vitro, multiple cytochrome P-450 enzymes including CYP3A and CYP2C19 are responsible for metabolism of nelfinavir. One major and several minor oxidative metabolites were found in plasma. The major oxidative metabolite has in vitro antiviral activity comparable to the parent drug.

Elimination

The terminal half-life in plasma was typically 3.5 to 5 hours. The majority (87%) of an oral 750 mg dose containing ¹⁴C-nelfinavir was recovered in the feces; fecal radioactivity consisted of numerous oxidative metabolites (78%) and unchanged nelfinavir (22%). Only 1–2% of the dose was recovered in urine, of which unchanged nelfinavir was the major component.

Specific Populations

Hepatic Impairment

The steady-state pharmacokinetics of nelfinavir (1250 mg BID for 2 weeks) was studied in HIV-seronegative subjects with mild (Child-Pugh Class A; n=6) or moderate (Child-Pugh Class B; n=6) hepatic impairment. When compared with subjects with normal hepatic function, the C _max and AUC of nelfinavir were not significantly different in subjects with mild hepatic impairment but were increased by 22% and 62%, respectively, in subjects with moderate hepatic impairment. The steady-state pharmacokinetics of nelfinavir has not been studied in HIV-seronegative subjects with severe hepatic impairment.

The steady-state pharmacokinetics of nelfinavir has not been studied in HIV-positive patients with any degree of hepatic impairment.

Renal Impairment

The pharmacokinetics of nelfinavir have not been studied in patients with renal impairment.

Gender and Race

No significant pharmacokinetic differences have been detected between males and females. Pharmacokinetic differences due to race have not been evaluated.

Pediatrics

The pharmacokinetics of nelfinavir have been investigated in 5 studies in pediatric patients from birth to 13 years of age either receiving VIRACEPT three times or twice daily. The dosing regimens and associated AUC ₂₄ values are summarized in Table 11.

Table 11: Summary of Steady-state AUC ₂₄ of Nelfinavir in Pediatric Studies

Protocol number	Dosing regimen Protocol specified dose (actual dose range)	N N: number of subjects with evaluable pharmacokinetic results	Age	AUC 24 (mg∙hr/L) arithmetic mean ± SD
C trough values are not presented in the table because they are not available for all studies
AG1343-524	20 (19–28) mg/kg TID	14	2–13 years	56.1±29.8
PACTG-725	55 (48–60) mg/kg BID	6	3–11 years	101.8±56.1
PENTA 7	40 (34–43) mg/kg TID	4	2–9 months	33.8±8.9
PENTA 7	75 (55–83) mg/kg BID	12	2–9 months	37.2±19.2
PACTG-353	40 (14–56) mg/kg BID	10	6 weeks	44.1±27.4
			1 week	45.8±32.1

Pharmacokinetic data are also available for 86 patients (age 2 to 12 years) who received VIRACEPT 25–35 mg/kg TID in Study AG1343-556. The pharmacokinetic data from Study AG1343-556 were more variable than data from other studies conducted in the pediatric population; the 95% confidence interval for AUC ₂₄ was 9 to 121 mg∙hr/L.

Overall, use of VIRACEPT in the pediatric population is associated with highly variable drug exposure. The high variability may be due to inconsistent food intake in pediatric patients [see Dosage and Administration (2.2)] .

Geriatric Patients

The pharmacokinetics of nelfinavir have not been studied in patients over 65 years of age.

Drug Interactions

CYP3A and CYP2C19 appear to be the predominant enzymes that metabolize nelfinavir in humans. The potential ability of nelfinavir to inhibit the major human cytochrome P450 enzymes (CYP3A, CYP2C19, CYP2D6, CYP2C9, CYP1A2 and CYP2E1) has been investigated in vitro. Only CYP3A was inhibited at concentrations in the therapeutic range. Specific drug interaction studies were performed with nelfinavir and a number of drugs. Table 12 summarizes the effects of nelfinavir on the geometric mean AUC, C _max and C _min of coadministered drugs. Table 13 shows the effects of coadministered drugs on the geometric mean AUC, C _max and C _min of nelfinavir.

Table 12: Drug Interactions: Changes in Pharmacokinetic Parameters for Coadministered Drug in the Presence of VIRACEPT

			% Change of Coadministered Drug Pharmacokinetic Parameters ↑ Indicates increase; ↓ Indicates decrease; ↔ Indicates no change (geometric mean exposure increased, or decreased <10%) (90% CI)
Coadministered Drug	Nelfinavir Dose	N	AUC	C max	C min
NA: Not relevant for single-dose treatment; ND: Cannot be determined
HIV-Protease Inhibitors
Indinavir 800 mg Single Dose	750 mg q8h × 7 days	6	↑51% (↑29–↑77%)	↓10% (↓28–↑13%)	NA
Ritonavir 500 mg Single Dose	750 mg q8h × 5 doses	10	↔	↔	NA
Saquinavir 1200 mg Single Dose Using the soft-gelatin capsule formulation of saquinavir 1200 mg	750 mg TID × 4 days	14	↑392% (↑291–↑521%)	↑179% (↑117–↑259%)	NA
Amprenavir 800 mg TID × 14 days	750 mg TID × 14 days	6	↔	↓14% (↓38–↑20%)	↑189% (↑52–↑448%)
Nucleoside Reverse Transcriptase Inhibitors
Lamivudine 150 mg Single Dose	750 mg q8h × 7–10 days	11	↑10% (↑2–↑18%)	↑31% (↑9–↑56%)	NA
Zidovudine 200 mg Single Dose	750 mg q8h × 7–10 days	11	↓35% (↓29–↓40%)	↓31% (↓13–↓46%)	NA
Non-nucleoside Reverse Transcriptase Inhibitors
Efavirenz 600 mg qd × 7 days	750 mg q8h × 7 days	10	↓12% (↓31–↑12%)	↓12% (↓29–↑8%)	↓22% (↓54–↑32%)
Delavirdine 400 mg q8h × 14 days	750 mg q8h × 7 days	7	↓31% (↓57–↑10%)	↓27% (↓49–↑4%)	↓33% (↓70–↑49%)
Anti-infective Agents
Rifabutin 150 mg qd × 8 days Rifabutin 150 mg qd changes are relative to Rifabutin 300 mg qd × 8 days without coadministration with nelfinavir	750 mg q8h × 7–8 days Comparable changes in rifabutin concentrations were observed with VIRACEPT 1250 mg q12h × 7 days	12	↑83% (↑72–↑96%)	↑19% (↑11–↑28%)	↑177% (↑144–↑215%)
Rifabutin 300 mg qd × 8 days	750 mg q8h × 7–8 days	10	↑207% (↑161–↑263%)	↑146% (↑118–↑178%)	↑305% (↑245–↑375%)
Azithromycin 1200 mg Single Dose	750 mg TID × 11 days	12	↑112% (↑80–↑150%)	↑136% (↑77–↑215%)	NA
HMG-CoA Reductase Inhibitors
Atorvastatin 10 mg qd × 28 days	1250 mg BID × 14 days	15	↑74% (↑41–↑116%)	↑122% (↑68–↑193%)	↑39% (↓21–↑145%)
Simvastatin 20 mg qd × 28 days	1250 mg BID × 14 days	16	↑505% (↑393–↑643%)	↑517% (↑367–↑715%)	ND
Other Agents
Ethinyl estradiol 35 µg qd × 15 days	750 mg q8h × 7 days	12	↓47% (↓42–↓52%)	↓28% (↓16–↓37%)	↓62% (↓57–↓67%)
Norethindrone 0.4 mg qd × 15 days	750 mg q8h × 7 days	12	↓18% (↓13–↓23%)	↔	↓46% (↓38–↓53%)
Methadone 80 mg ± 21 mg qd Changes are reported for total plasma methadone; changes for the individual R-enantiomer and S-enantiomer were similar >1 month	1250 mg BID × 8 days	13	↓47% (↓42–↓51%)	↓46% (↓42–↓49%)	↓53% (↓49–↓57%)
Phenytoin 300 mg qd × 14 days Phenytoin exposure measures are reported for total phenytoin exposure. The effect of nelfinavir on unbound phenytoin was similar	1250 mg BID × 7 days	12	↓29% (↓17–↓39%)	↓21% (↓12–↓29%)	↓39% (↓27–↓49%)

Table 13: Drug Interactions: Changes in Pharmacokinetic Parameters for Nelfinavir in the Presence of the Coadministered Drug

			% Change of Nelfinavir Pharmacokinetic Parameters ↑ Indicates increase; ↓ Indicates decrease; ↔ Indicates no change (geometric mean exposure increased or decreased <10%) (90% CI)
Coadministered Drug	Nelfinavir Dose	N	AUC	C max	C min
NA: Not relevant for single-dose treatment
HIV-Protease Inhibitors
Indinavir 800 mg q8h × 7 days	750 mg Single Dose	6	↑83% (↑42–↑137%)	↑31% (↑16–↑48%)	NA
Ritonavir 500 mg q12h × 3 doses	750 mg Single Dose	10	↑152% (↑96–↑224%)	↑44% (↑28–↑63%)	NA
Saquinavir 1200 mg TID × 4 days Using the soft-gelatin capsule formulation of saquinavir 1200 mg	750 mg Single Dose	14	↑18% (↑7–↑30%)	↔	NA
Nucleoside Reverse Transcriptase Inhibitors
Didanosine 200 mg Single Dose	750 mg Single Dose	9	↔	↔	NA
Zidovudine 200 mg + Lamivudine 150 mg Single Dose	750 mg q8h × 7–10 days	11	↔	↔	↔
Non-nucleoside Reverse Transcriptase Inhibitors
Efavirenz 600 mg qd × 7 days	750 mg q8h × 7 days	7	↑20% (↑8–↑34%)	↑21% (↑10–↑33%)	↔
Nevirapine 200 mg qd × 14 days followed by 200 mg BID × 14 days	750 mg TID × 36 days	23	↔	↔	↓32% (↓50–↑5%)
Delavirdine 400 mg q8h × 7 days	750 mg q8h × 14 days	12	↑107% (↑83–↑135%)	↑88% (↑66–↑113%)	↑136% (↑103–↑175%)
Anti-infective Agents
Ketoconazole 400 mg qd × 7 days	500 mg q8h × 5–6 days	12	↑35% (↑24–↑46%)	↑25% (↑11–↑40%)	↑14% (↓23–↑69%)
Rifabutin 150 mg qd × 8 days	750 mg q8h × 7–8 days	11	↓23% (↓14–↓31%)	↓18% (↓8–↓27%)	↓25% (↓8–↓39%)
	1250 mg q12h × 7–8 days	11	↔	↔	↓15% (↓43–↑27%)
Rifabutin 300 mg qd × 8 days	750 mg q8h × 7–8 days	10	↓32% (↓15–↓46%)	↓24% (↓10–↓36%)	↓53% (↓15–↓73%)
Rifampin 600 mg qd × 7 days	750 mg q8h × 5–6 days	12	↓83% (↓79–↓86%)	↓76% (↓69–↓82%)	↓92% (↓86–↓95%)
Azithromycin 1200 mg Single Dose	750 mg tid × 9 days	12	↓15% (↓7–↓22%)	↓10% (↓19–↑1%)	↓29% (↓19–↓38%)
Other Agents
Phenytoin 300 mg qd × 7 days	1250 mg BID × 14 days	15	↔	↔	↓18% (↓45–↑23%)
Omeprazole 40 mg qd × 4 days administered 30 minutes before nelfinavir	1250 mg BID × 4 days	19	↓36% (↓20–↓49%)	↓37% (↓23–↓49%)	↓39% (↓15–↓57%)

12.4Microbiology

Mechanism of Action

Nelfinavir is an inhibitor of the HIV-1 protease. Inhibition of the viral protease prevents cleavage of the gag and gag-pol polyprotein resulting in the production of immature, non-infectious virus.

Antiviral Activity in Cell Culture

The antiviral activity of nelfinavir has been demonstrated in both acute and/or chronic HIV infections in lymphoblastoid cell lines, peripheral blood lymphocytes, and monocytes/macrophages. Nelfinavir was found to be active against several laboratory strains and clinical isolates of HIV-1, and the HIV-2 strain ROD. The EC ₉₅ (95% effective concentration) of nelfinavir ranged from 7 to 196 nM. Drug combination studies with other HIV-1 protease inhibitors showed nelfinavir had antagonistic interactions with indinavir, additive interactions with ritonavir or saquinavir, and synergistic interactions with amprenavir and lopinavir. Minimal to no cellular cytotoxicity was observed with any of these protease inhibitors alone or in combination with nelfinavir. In combination with reverse transcriptase inhibitors, nelfinavir demonstrated additive (didanosine or stavudine) to synergistic (abacavir, delavirdine, efavirenz, emtricitabine, lamivudine, nevirapine, tenofovir, zalcitabine, or zidovudine) antiviral activity without enhanced cytotoxicity. Nelfinavir's anti-HIV activity was not antagonized by the anti-HCV drug ribavirin.

Resistance

HIV-1 isolates with reduced susceptibility to nelfinavir have been selected in cell culture. HIV-1 isolates from selected patients treated with nelfinavir alone or in combination with reverse transcriptase inhibitors were monitored for phenotypic (n=19) and genotypic (n=195, 157 of which were evaluable) changes in clinical trials over a period of 2 to 82 weeks. One or more viral protease mutations at amino acid positions 30, 35, 36, 46, 71, 77, and 88 were detected in the HIV-1 of >10% of patients with evaluable isolates. The overall incidence of the D30N substitution in the viral protease of evaluable isolates (n=157) from patients receiving nelfinavir monotherapy or nelfinavir in combination with zidovudine and lamivudine or stavudine was 54.8%. The overall incidence of other substitutions associated with primary protease inhibitor resistance was 9.6% for the L90M substitution, whereas substitutions at 48, 82, or 84 were not observed. Of the 19 clinical isolates for which both phenotypic and genotypic analyses were performed, 9 showed reduced susceptibility (5- to 93-fold) to nelfinavir in cell culture. All 9 isolates possessed one or more mutations in the viral protease gene. Amino acid position 30 appeared to be the most frequent mutation site.

Cross-resistance

Non-clinical Studies: Patient-derived recombinant HIV-1 isolates containing the D30N substitution (n=4) and demonstrating high-level (>10-fold) nelfinavir-resistance remained susceptible (<2.5-fold resistance) to amprenavir, indinavir, lopinavir, and saquinavir in cell culture. Patient-derived recombinant HIV-1 isolates containing the L90M substitution (n=8) demonstrated moderate to high-level resistance to nelfinavir and had varying levels of susceptibility to amprenavir, indinavir, lopinavir, and saquinavir in cell culture. Most patient-derived recombinant isolates with phenotypic and genotypic evidence of reduced susceptibility (>2.5-fold) to amprenavir, indinavir, lopinavir, and/or saquinavir demonstrated high-level cross-resistance to nelfinavir. Amino acid substitutions associated with resistance to other protease inhibitors (e.g., G48V, V82A/F/T, I84V, L90M) appeared to confer high-level cross-resistance to nelfinavir. Following ritonavir therapy 6 of 7 clinical isolates with decreased ritonavir susceptibility (8- to 113-fold) compared to baseline also exhibited decreased susceptibility to nelfinavir (5- to 40-fold). Cross-resistance between nelfinavir and reverse transcriptase inhibitors is unlikely because different enzyme targets are involved. Clinical isolates (n=5) with decreased susceptibility to lamivudine, nevirapine, or zidovudine remain fully susceptible to nelfinavir.

Clinical Studies: There have been no controlled or comparative studies evaluating the virologic response to subsequent protease inhibitor-containing regimens in subjects who have demonstrated loss of virologic response to a nelfinavir-containing regimen. However, virologic response was evaluated in a single-arm prospective study of 26 subjects with extensive prior antiretroviral experience with reverse transcriptase inhibitors (mean 2.9) who had received nelfinavir for a mean duration of 59.7 weeks and were switched to a ritonavir (400 mg BID)/saquinavir hard-gel (400 mg BID)-containing regimen after a prolonged period of nelfinavir failure (median 48 weeks). Sequence analysis of HIV-1 isolates prior to switch demonstrated a D30N or an L90M substitution in 18 and 6 subjects, respectively. Subjects remained on therapy for a mean of 48 weeks (range 40 to 56 weeks) where 17 (65%) and 13 (50%) of the 26 subjects were treatment responders with HIV-1 RNA below the assay limit of detection (<500 HIV-1 RNA copies/mL, Chiron bDNA) at 24 and 48 weeks, respectively.