2.1 Tests to be Performed Prior to Treatment with KRINTAFEL

All patients must be tested for glucose-6-phosphate dehydrogenase (G6PD) deficiency prior to prescribing KRINTAFEL [see Contraindications (4), Warnings and Precautions (5.1)].

Pregnancy testing is recommended for females of reproductive potential prior to initiating treatment with KRINTAFEL [see Use in Specific Populations (8.1, 8.3)].

2.2 Recommended Dosage and Administration

The recommended dose of KRINTAFEL in patients aged 16 years and older is a single dose of 300 mg administered as two 150-mg tablets taken together. Coadminister KRINTAFEL on the first or second day of chloroquine therapy for acute P. vivax malaria [see Clinical Studies (14)].

Administer KRINTAFEL with food to increase systemic absorption [see Clinical Pharmacology (12.3)].

Swallow tablets whole. Do not break, crush, or chew the tablets.

In the event of vomiting within 1 hour after dosing, a repeat dose should be given. Re-dosing should not be attempted more than once.

5.1 Hemolytic Anemia

Due to the risk of hemolytic anemia in patients with G6PD deficiency, G6PD testing must be performed before prescribing KRINTAFEL [see Dosage and Administration (2.1)]. Due to the limitations of G6PD tests, physicians need to be aware of residual risk of hemolysis and adequate medical support and follow-up to manage hemolytic risk should be available. Treatment with KRINTAFEL is contraindicated in patients with G6PD deficiency or unknown G6PD status [see Contraindications (4)]. Patients were excluded from clinical trials of KRINTAFEL if they had a G6PD enzyme activity level <70% of the site median value for G6PD normal activity [see Clinical Studies (14)]. In clinical trials, declines in hemoglobin levels were reported in some G6PD-normal patients [see Adverse Reactions (6.1)]. Monitor patients for clinical signs or symptoms of hemolysis. Advise patients to seek medical attention if signs of hemolysis occur.

5.2 G6PD Deficiency in Pregnancy or Lactation

Potential Harm to the Fetus

The use of KRINTAFEL during pregnancy may cause hemolytic anemia in a G6PD-deficient fetus. Even if a pregnant woman has normal levels of G6PD, the fetus could be G6PD deficient. Advise females of reproductive potential that treatment with KRINTAFEL during pregnancy is not recommended and to avoid pregnancy or use effective contraception for 3 months after the dose of KRINTAFEL [see Use in Specific Populations (8.1, 8.3)].

Potential Harm to the Breastfeeding Infant

A G6PD-deficient infant may be at risk for hemolytic anemia from exposure to KRINTAFEL through breast milk. Infant G6PD status should be checked before breastfeeding begins. KRINTAFEL is contraindicated in breastfeeding women when the infant is found to be G6PD deficient or the G6PD status of the infant is unknown [see Contraindications (4)]. Advise the woman with a G6PD-deficient infant or if the G6PD status of the infant is unknown not to breastfeed for 3 months after the dose of KRINTAFEL [see Use in Specific Populations (8.2)].

5.3 Methemoglobinemia

Asymptomatic elevations in methemoglobin have been observed in the clinical trials of KRINTAFEL [see Adverse Reactions (6.1)]. Institute appropriate therapy if signs or symptoms of methemoglobinemia occur. Carefully monitor individuals with nicotinamide adenine dinucleotide (NADH)-dependent methemoglobin reductase deficiency. Advise patients to seek medical attention if signs of methemoglobinemia occur.

5.4 Psychiatric Effects

Psychiatric adverse reactions including anxiety (<1%), abnormal dreams (<1%), and insomnia (3%) have been reported in clinical trials of KRINTAFEL [see Adverse Reactions (6.1)]. Two cases of depression and 2 cases of psychosis have occurred primarily in patients with a history of psychiatric disorders following receipt of single doses of tafenoquine that were higher than the approved 300-mg dose (350 mg to 600 mg). Safety and effectiveness of KRINTAFEL have not been established at doses or regimens other than the approved regimen; use of KRINTAFEL at doses or regimens other than a 300-mg single dose is not approved by FDA.

The benefit of treatment with KRINTAFEL must be weighed against the potential risk for psychiatric adverse reactions in patients with a history of psychiatric illness. Due to the long half-life of KRINTAFEL (approximately 15 days), signs or symptoms of psychiatric adverse reactions that may occur could be delayed in onset and/or duration [see Clinical Pharmacology (12.3)].

5.5 Hypersensitivity Reactions

Serious hypersensitivity reactions (e.g., angioedema, urticaria) have been observed with administration of KRINTAFEL [see Adverse Reactions (6.1)]. Institute appropriate therapy if hypersensitivity reactions occur. Do not re-administer KRINTAFEL. KRINTAFEL is contraindicated in patients who develop hypersensitivity to tafenoquine or any component of KRINTAFEL or other 8-aminoquinolines [see Contraindications (4)].

Due to the long half-life of KRINTAFEL (approximately 15 days), signs or symptoms of hypersensitivity adverse reactions that may occur could be delayed in onset and/or duration [see Clinical Pharmacology (12.3)]. Advise patients to seek medical attention if signs of hypersensitivity occur.

5.6 Risk of P. vivax Malaria Recurrence

Lack of efficacy in reducing P. vivax malaria recurrence in patients treated with KRINTAFEL combined with an artemisinin-containing antimalarial was seen in a clinical trial (NCT02802501). In this double-blind, randomized, placebo-controlled trial in which all patients with P. vivax malaria were treated with dihydroartemisinin/piperaquine (not approved artemisinin-containing antimalarial) and were coadministered KRINTAFEL, primaquine, or placebo, lack of efficacy (recurrence rates at 6 months following treatment) was seen in patients treated with KRINTAFEL.

Concomitant administration of KRINTAFEL with antimalarials other than chloroquine is not recommended.

6.1 Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The safety data described below reflect exposure to 4,129 subjects, of whom 810 received a 300-mg single dose of KRINTAFEL. KRINTAFEL was evaluated in patients with P. vivax malaria (n = 483) in 3 randomized, double-blind trials including a placebo-controlled trial comparing KRINTAFEL plus chloroquine (n = 260) with chloroquine alone (Trial 1), a placebo-controlled dose-ranging trial (Trial 2) (n = 57) [see Clinical Studies (14)], and a hematologic safety trial (Trial 3, NCT02216123) (n = 166).

In Trial 1, in patients with P. vivax malaria, the most common adverse reactions reported in ≥5% of patients treated with KRINTAFEL are listed in Table 1. Patients included in the trial had a mean age of 35 (range: 16 to 79 years), were 75% male and from the following regions: 70% Latin America (Brazil and Peru), 19% Southeast (SE) Asia (Thailand, Cambodia, and the Philippines), and 11% Africa (Ethiopia).

Other Adverse Reactions Reported with KRINTAFEL

Clinically significant adverse reactions with KRINTAFEL 300-mg single dose in clinical trials (n = 810) in ≤3% of subjects are listed below:

Psychiatric Disorders: Anxiety, insomnia, abnormal dreams.

Nervous System Disorders: Somnolence.

Laboratory Investigations: Increased blood creatinine, increased blood methemoglobin, increased alanine aminotransferase.

Immune System Disorders: Hypersensitivity reactions (e.g., angioedema, urticaria) [see Contraindications (4), Warnings and Precautions (5.5)].

Eye Disorders: Vortex keratopathy, photophobia.

7.1 Effect of KRINTAFEL on Organic Cation Transporter-2 (OCT2) and Multidrug and Toxin Extrusion (MATE) Substrates

The effect of coadministration of tafenoquine on the pharmacokinetics of OCT2 and MATE substrates in humans is unknown. However, in vitro observations suggest the potential for increased concentrations of these substrates [see Clinical Pharmacology (12.3)] which may increase the risk of toxicity of these drugs.

Avoid coadministration of KRINTAFEL with OCT2 and MATE substrates (e.g., dofetilide, metformin). If coadministration cannot be avoided, monitor for drug-related toxicities and consider dosage reduction if needed based on approved product labeling of the coadministered drug.

8.1 Pregnancy

Risk Summary

The use of KRINTAFEL during pregnancy may cause hemolytic anemia in a fetus who is G6PD deficient. Treatment with KRINTAFEL during pregnancy is not recommended [see Warnings and Precautions (5.2)]. Available data with use of KRINTAFEL in pregnant women are insufficient to establish a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. In animal studies, there were increased abortions, with and without maternal toxicity, when KRINTAFEL was given orally to pregnant rabbits at and above doses equivalent to about 0.4 times the clinical exposure based on body surface area comparisons. No fetotoxicity was observed at doses equivalent to the clinical exposure (based on body surface area comparisons) in a similar study in rats.

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. 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.

Clinical Considerations

Disease-Associated Maternal and/or Embryo/Fetal Risk: Malaria during pregnancy increases the risk for adverse pregnancy outcomes, including maternal anemia, prematurity, spontaneous abortion, and stillbirth.

Data

Animal Data: Tafenoquine resulted in dose-related abortions when given orally to pregnant rabbits during organogenesis (Gestation Days 6 to 18) at doses of 7 mg/kg (about 0.4 times the clinical exposure based on body surface area comparisons) and above. Doses higher than 7 mg/kg were also associated with maternal toxicity (mortality and reduced body weight gain). In a similar study in rats, doses of 3, 10, or 30 mg/kg/day resulted in maternal toxicity (enlarged spleen, reduced body weight, and reduced food intake) but no fetotoxicity at the high dose (equivalent to the clinical exposure based on body surface area comparisons). There was no evidence of malformations in either species. In a pre- and postnatal development study in rats, tafenoquine administered throughout pregnancy and lactation produced maternal toxicity and a reversible decrease in offspring body weight gain and decrease in motor activity at 18 mg/kg/day, which is equivalent to about 0.6 times the clinical dose based on body surface area comparisons.

8.2 Lactation

Risk Summary

A breastfed infant with G6PD deficiency is at risk for hemolytic anemia from exposure to KRINTAFEL. Infant G6PD status should be checked before breastfeeding begins. KRINTAFEL is contraindicated in breastfeeding women when the infant is found to be G6PD deficient or the G6PD status of the infant is unknown [see Contraindications (4), Clinical Considerations].

There is no information regarding the presence of KRINTAFEL in human milk, the effects of the drug on the breastfed infant, or the effects of the drug on milk production. In a breastfed infant with normal G6PD, the developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for KRINTAFEL and any potential effects on the breastfed infant from KRINTAFEL or from the underlying maternal condition.

Clinical Considerations

Check the infant’s G6PD status before maternal breastfeeding commences. If an infant is G6PD deficient, exposure to KRINTAFEL during breastfeeding may result in hemolytic anemia in the infant; therefore, advise the woman with an infant who has G6PD deficiency or whose G6PD status is unknown not to breastfeed for 3 months after the dose of KRINTAFEL.

8.3 Females and Males of Reproductive Potential

Pregnancy Testing

Verify the pregnancy status in females of reproductive potential prior to initiating treatment with KRINTAFEL [see Warnings and Precautions (5.2), Use in Specific Populations (8.1)].

Contraception

KRINTAFEL may cause hemolytic anemia in a G6PD-deficient fetus [see Warnings and Precautions (5.2), Use in Specific Populations (8.1)]. Advise females of reproductive potential that treatment with KRINTAFEL during pregnancy is not recommended and to avoid pregnancy or use effective contraception for 3 months after the dose of KRINTAFEL.

8.4 Pediatric Use

The safety and effectiveness of KRINTAFEL have been established in pediatric patients aged 16 years and older. Use of KRINTAFEL in these pediatric patients is supported by evidence from adequate and well-controlled studies of KRINTAFEL [see Clinical Studies (14)].

Safety and effectiveness of KRINTAFEL in pediatric patients younger than 16 years have not been established.

8.5 Geriatric Use

Clinical trials of KRINTAFEL did not include sufficient numbers of patients aged 65 years and older to determine whether they respond differently from younger patients. Other reported clinical experience has not identified differences in responses between the elderly and younger patients [see Clinical Pharmacology (12.3)].

8.6 Renal Impairment

The pharmacokinetics of KRINTAFEL have not been studied in patients with renal impairment. If KRINTAFEL is administered to such patients, monitoring for adverse reactions associated with KRINTAFEL is needed [see Warnings and Precautions (5), Adverse Reactions (6)].

8.7 Hepatic Impairment

The pharmacokinetics of KRINTAFEL have not been studied in patients with hepatic impairment. If KRINTAFEL is administered to such patients, monitoring for adverse reactions associated with KRINTAFEL is needed [see Warnings and Precautions (5), Adverse Reactions (6)].

12.1 Mechanism of Action

Tafenoquine is an 8-aminoquinoline antimalarial drug [see Microbiology (12.4)].

12.2 Pharmacodynamics

Cardiac Electrophysiology

The effect of tafenoquine on the QTc interval was evaluated in a Phase 1 randomized, single-blind, placebo- and positive-controlled, parallel-group thorough QTc study in 260 healthy adult subjects. At a cumulative dose of 1,200 mg (400 mg/day for 3 days; 4 times the maximum recommended dose), tafenoquine did not prolong the QTc interval to any clinically relevant extent.

Exposure-Response Relationships

A saturable relationship between tafenoquine exposure (AUC) and clinical response (recurrence-free rate at 6 months) was identified. Tafenoquine exposures achieved with doses of 300 mg and higher are on the plateau of the exposure-response curve. Use of KRINTAFEL at doses or regimens other than a 300-mg single dose is not approved by the FDA.

12.3 Pharmacokinetics

Absorption

Maximum plasma concentrations were generally observed 12 to 15 hours following oral administration.

Food Effect: Plasma tafenoquine AUC increased by 41% and Cmax increased by 31% when administered as an investigational capsule formulation with a high-calorie, high-fat meal (approximately 1,000 calories with 15% protein, 25% carbohydrate, and 60% fat) compared with the fasted state.

Distribution

Protein binding of tafenoquine is >99.5%. The apparent oral volume of distribution is ~1,600 L. Following single- and multiple-oral-dose administration, tafenoquine whole blood concentrations were on average 67% higher than corresponding plasma values.

Elimination

The apparent oral clearance of tafenoquine is approximately 3 L/h. The average terminal half-life is approximately 15 days.

Metabolism: Tafenoquine undergoes slow metabolism. Unchanged tafenoquine represented the only notable drug-related component in human plasma after a single oral dose of tafenoquine.

Excretion: The full excretion profile of tafenoquine in humans is unknown. Over a 6-day collection period, renal elimination of unchanged tafenoquine was low.

Specific Populations

Pharmacokinetics of tafenoquine were not significantly impacted by age, sex, ethnicity, and body weight. The effect of renal or hepatic impairment on tafenoquine pharmacokinetics is unknown.

Drug Interaction Studies

Clinical Studies: No clinically significant effects on tafenoquine pharmacokinetics were observed following coadministration with chloroquine, dihydroartemisinin-piperaquine, or artemether-lumefantrine in healthy subjects.

No clinically significant effects on the pharmacokinetics of dihydroartemisinin, piperaquine, artemether, lumefantrine, or substrates of cytochrome P450 isoenzymes (CYP)1A2 (caffeine), CYP2D6 (desipramine), CYP2C8 (chloroquine), CYP2C9 (flurbiprofen), or CYP3A4 (midazolam, chloroquine) were observed following coadministration of tafenoquine in healthy subjects.

In Vitro Studies Where Drug Interaction Potential Was Not Further Evaluated Clinically: Tafenoquine inhibited metformin transport via human OCT2, MATE-1, and MATE2-K transporters. Clinical drug interaction studies with tafenoquine and OCT2 and MATE substrates have not been conducted [see Drug Interactions (7)].

The effect of tafenoquine on substrates of P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and organic anion transporting polypeptides 1B1/1B3 (OATP1B1/OATP1B3) is unknown.

12.4 Microbiology

Mechanism of Action

Tafenoquine, an 8-aminoquinoline antimalarial, is active against the liver stages including the hypnozoite (dormant stage) of P. vivax. In addition to its effect on the parasite, tafenoquine causes red blood cell shrinkage in vitro. The molecular target of tafenoquine is not known.

Antimicrobial Activity

Tafenoquine is active against pre-erythrocytic (liver) and erythrocytic (asexual) forms as well as gametocytes of P. vivax. The activity of tafenoquine against the pre-erythrocytic liver stages of the parasite prevents the development of the erythrocytic forms of the parasite, which are responsible for relapses in P. vivax malaria [see Clinical Studies (14)].

Resistance

A potential for development of resistance of Plasmodium species to tafenoquine was not evaluated.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis

Two-year oral carcinogenicity studies were conducted in rats and mice. Renal cell adenomas and carcinomas were increased in male rats at doses of 1 mg/kg/day and above (3 times the clinical exposure based on AUC comparisons). Tafenoquine was not carcinogenic in mice. Given the single-dose administration of KRINTAFEL, these findings may not represent a carcinogenicity risk to humans.

Mutagenesis

Tafenoquine did not cause mutations or chromosomal damage in 2 definitive in vitro tests (bacterial mutation assay and mouse lymphoma L5178Y cell assay) or in an in vivo oral rat micronucleus test.

Impairment of Fertility

In a rat fertility study, tafenoquine was given orally at 1.5, 5, and 15 mg/kg/day (up to about 0.5 times the human dose based on body surface area comparisons) to males for at least 67 days, including 29 days prior to mating, and to females from 15 days prior to mating through early pregnancy. Tafenoquine resulted in reduced number of viable fetuses, implantation sites, and corpora lutea at 15 mg/kg in the presence of maternal toxicity (mortality, piloerection, rough coat, and reduced body weight).