leflunomide

1 INDICATIONS AND USAGE Leflunomide tablets is indicated for the treatment of adults with active rheumatoid arthritis (RA). Leflunomide tablets are a pyrimidine synthesis inhibitor indicated for the treatment of adults with active rheumatoid arthritis.

2 DOSAGE AND ADMINISTRATION Loading dosage for patients at low risk for leflunomide-associated hepatotoxicity and leflunomide-associated myelosuppression: 100 mg daily for 3 days. ( 2.1 ) Maintenance dosage: 20 mg daily. ( 2.1 ) Maximum recommended daily dosage: 20 mg once daily. ( 2.1) If 20 mg once daily is not tolerated, may decrease dosage to 10 mg once daily. ( 2.1 ) Screen patients for active and latent tuberculosis, pregnancy test (females), blood pressure, and laboratory tests before starting leflunomide tablets. ( 2.2 ) 2.1 Recommended Dosage The recommended dosage of leflunomide is 20 mg once daily. Treatment may be initiated with or without a loading dose, depending upon the patient's risk of leflunomide-associated hepatotoxicity and leflunomide-associated myelosuppression. The loading dose provides steady-state concentrations more rapidly. •For patients who are at low risk for leflunomide-associated hepatotoxicity and leflunomide-associated myelosuppression, the recommended leflunomide loading dose is 100 mg once daily for 3 days. Subsequently administer 20 mg once daily. •For patients at high risk for leflunomide-associated hepatotoxicity (e.g., those taking concomitant methotrexate) or leflunomide-associated myelosuppression (e.g., patients taking concomitant immunosuppressants), the recommended leflunomide dosage is 20 mg once daily without a loading dose [see Warnings and Precautions( 5.2 , 5.4 )]. The maximum recommended daily dose is 20 mg once per day. Consider dosage reduction to 10 mg once daily for patients who are not able to tolerate 20 mg daily (i.e., for patients who experience any adverse events listed in Table 1). Monitor patients carefully after dosage reduction and after stopping therapy with leflunomide, since the active metabolite of leflunomide, teriflunomide, is slowly eliminated from the plasma [see Clinical Pharmacology (12.3) ] . After stopping leflunomide treatment, an accelerated drug elimination procedure is recommended to reduce the plasma concentrations of the active metabolite, teriflunomide [see Warnings and Precautions (5.3) ] . Without use of an accelerated drug elimination procedure, it may take up to 2 years to reach undetectable plasma teriflunomide concentrations after stopping leflunomide [see Clinical Pharmacology (12.3) ] . 2.2 Evaluation and Testing Prior to Starting leflunomide tablets Prior to starting leflunomide treatment, the following evaluations and tests are recommended: •Evaluate patients for active tuberculosis and screen patients for latent tuberculosis infection [see Warnings and Precautions (5.4) ] •Laboratory tests including serum alanine aminotransferase (ALT); and white blood cell, hemoglobin or hematocrit, and platelet counts [see Warnings and Precautions ( 5.2 , 5.4 )] •For females of reproductive potential, pregnancy testing [see Warnings and Precautions (5.1) ] •Check blood pressure [see Warnings and Precautions (5.11) ]

5 WARNINGS AND PRECAUTIONS After stopping leflunomide, it is recommended that an accelerated drug elimination procedure be used to reduce the plasma concentrations of the active metabolite, teriflunomide. (5.3) Severe infections (including sepsis), pancytopenia, agranulocytosis, and thrombocytopenia: Stop leflunomide and use accelerated elimination procedure. Do not start leflunomide in patients with active infection. Monitor CBCs during treatment with leflunomide. (5.4) Stevens-Johnson syndrome and toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (DRESS): Stop leflunomide and use accelerated elimination procedure. (5.5) Skin ulcers: If skin ulcer is suspected, discontinue leflunomide treatment and consider an accelerated drug elimination procedure. (5.6) Peripheral neuropathy: If patient develops symptoms consistent with peripheral neuropathy, evaluate patient and consider discontinuing leflunomide. (5.8) Interstitial lung disease: May be fatal. New onset or worsening symptoms may necessitate discontinuation of leflunomide and initiation of accelerated elimination procedure. (5.9) Increased blood pressure: Monitor and treat. (5.11) 5.1 Embryo-Fetal Toxicity Leflunomide may cause fetal harm when administered to a pregnant woman. Teratogenicity and embryo-lethality occurred in animal reproduction studies with leflunomide at doses lower than the human exposure level [see Use in Specific Populations (8.1) ] . Leflunomide is contraindicated for use in pregnant women [see Contraindications (4) ] . Exclude pregnancy before starting treatment with leflunomide in females of reproductive potential [see Dosage and Administration (2.2) ] . Advise females of reproductive potential to use effective contraception during leflunomide treatment and during an accelerated drug elimination procedure after leflunomide treatment [see Use in Specific Populations (8.3) ]. If a woman becomes pregnant while taking leflunomide, stop treatment with leflunomide, apprise the patient of the potential risk to a fetus, and perform an accelerated drug elimination procedure to achieve nondetectable plasma concentrations of teriflunomide, the active metabolite of leflunomide [see Warnings and Precautions (5.3) ] . Upon discontinuing leflunomide, it is recommended that all females of reproductive potential undergo an accelerated drug elimination procedure. Women receiving leflunomide treatment who wish to become pregnant must discontinue leflunomide and undergo an accelerated drug elimination procedure, which includes verification that plasma concentrations of the active metabolite of leflunomide, teriflunomide, are less than 0.02 mg/L (0.02 mcg/mL). Based on animal data, human plasma concentrations of teriflunomide of less than 0.02 mg/L (0.02 mcg/mL) are expected to have minimal embryo-fetal risk [see Contraindications (4) , Warnings and Precautions (5.3) , and Use in Specific Populations (8.1) ] . 5.2 Hepatotoxicity Severe liver injury, including fatal liver failure, has been reported in some patients treated with leflunomide. Patients with pre-existing acute or chronic liver disease, or those with serum alanine aminotransferase (ALT) of greater than twice the upper limits of normal (>2 x ULN) before initiating treatment, should not be treated with leflunomide. Use caution when leflunomide is given with other potentially hepatotoxic drugs. Monitoring of ALT levels is recommended at least monthly for six months after starting leflunomide, and thereafter every 6 to 8 weeks. If ALT elevation > 3 fold ULN occurs, interrupt leflunomide therapy and investigate the cause. If likely leflunomide-induced, perform the accelerated drug elimination procedure and monitor liver tests weekly until normalized [see Warnings and Precautions (5.3) ]. If leflunomide-induced liver injury is unlikely because some other cause has been found, resumption of leflunomide therapy may be considered. If leflunomide and methotrexate are given concomitantly, f…

4 CONTRAINDICATIONS Leflunomide tablets are contraindicated in: •Pregnant women. Leflunomide may cause fetal harm. If a woman becomes pregnant while taking this drug, stop leflunomide, apprise the patient of the potential hazard to the fetus, and begin a drug elimination procedure [see Warnings and Precautions ( 5.1 , 5.3 ) and Use in Specific Populations (8.1) ]. •Patients with severe hepatic impairment [see Warnings and Precautions (5.2) ] . •Patients with known hypersensitivity to leflunomide or any of the other components of leflunomide tablets. Known reactions include anaphylaxis [see Adverse Reactions (6.1) ] . •Patients being treated with teriflunomide [see Drug Interactions (7) ] . Pregnancy. ( 4 , 5.1 , 8.1 ) Severe hepatic impairment. ( 4 , 5.2 ) Hypersensitivity to leflunomide tablet or any of its inactive components. ( 4 ) Current teriflunomide treatment. (4 )

7 DRUG INTERACTIONS Following oral administration, leflunomide is metabolized to an active metabolite, teriflunomide, which is responsible for essentially all of leflunomide's in vivo activity. Drug interaction studies have been conducted with both leflunomide and with its active metabolite, teriflunomide, where the metabolite was directly administered to the test subjects. Effect of Potent CYP and Transporter Inducers Leflunomide is metabolized by CYP450 metabolizing enzymes. Concomitant use of leflunomide and rifampin, a potent inducer of CYP and transporters, increased the plasma concentration of teriflunomide by 40%. However, when coadministered with the metabolite, teriflunomide, rifampin did not affect its pharmacokinetics. No dosage adjustment is recommended for leflunomide when coadministered with rifampin. Because of the potential for leflunomide concentrations to continue to increase with multiple dosing, caution should be used if patients are to be receiving both leflunomide and rifampin [see Clinical Pharmacology (12.3) ] . Effect on CYP2C8 Substrates Teriflunomide is an inhibitor of CYP2C8 in vivo . In patients taking leflunomide, exposure of drugs metabolized by CYP2C8 (e.g., paclitaxel, pioglitazone, repaglinide, rosiglitazone) may be increased. Monitor these patients and adjust the dose of the concomitant drug(s) metabolized by CYP2C8 as required [see Clinical Pharmacology (12.3) ] . Effect on Warfarin Coadministration of leflunomide with warfarin requires close monitoring of the international normalized ratio (INR) because teriflunomide, the active metabolite of leflunomide, may decrease peak INR by approximately 25%. Effect on Oral Contraceptives Teriflunomide may increase the systemic exposures of ethinylestradiol and levonorgestrel. Consideration should be given to the type or dose of contraceptives used in combination with leflunomide [see Clinical Pharmacology (12.3) ] . Effect on CYP1A2 Substrates Teriflunomide, the active metabolite of leflunomide, may be a weak inducer of CYP1A2 in vivo . In patients taking leflunomide, exposure of drugs metabolized by CYP1A2 (e.g., alosetron, duloxetine, theophylline, tizanidine) may be reduced. Monitor these patients and adjust the dose of the concomitant drug(s) metabolized by CYP1A2 as required [see Clinical Pharmacology (12.3) ] . Effect on Organic Anion Transporter 3 (OAT3) Substrates Teriflunomide inhibits the activity of OAT3 in vivo . In patients taking leflunomide, exposure of drugs which are OAT3 substrates (e.g., cefaclor, cimetidine, ciprofloxacin, penicillin G, ketoprofen, furosemide, methotrexate, zidovudine) may be increased. Monitor these patients and adjust the dose of the concomitant drug(s) which are OAT3 substrates as required [see Clinical Pharmacology (12.3) ] . Effect on BCRP and Organic Anion Transporting Polypeptide B1 and B3 (OATP1B1/1B3) Substrates Teriflunomide inhibits the activity of BCRP and OATP1B1/1B3 in vivo . For a patient taking leflunomide, the dose of rosuvastatin should not exceed 10 mg once daily. For other substrates of BCRP (e.g., mitoxantrone) and drugs in the OATP family (e.g., methotrexate, rifampin), especially HMG-Co reductase inhibitors (e.g., atorvastatin, nateglinide, pravastatin, repaglinide, and simvastatin), consider reducing the dose of these drugs and monitor patients closely for signs and symptoms of increased exposures to the drugs while patients are taking leflunomide [see Clinical Pharmacology (12.3) ] . Drugs metabolized by CYP2C8 and OAT3 transporters: Monitor patients because teriflunomide may increase exposure of these drugs. ( 7 ) Teriflunomide may increase exposure of ethinylestradiol and levonorgestrel. Choose an appropriate oral contraceptive. ( 7 ) Drugs metabolized by CYP1A2: Monitor patients because teriflunomide may decrease exposure of these drugs. ( 7 ) Warfarin: Monitor INR as teriflunomide may decrease INR. ( 7 ) Drugs metabolized by BCRP and OATP1B1/B3 transporters: Monitor patients because te…

8.1 Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to leflunomide during pregnancy. Health care providers and patients are encouraged to report pregnancies by calling 1-877-311-8972 or visit http://www.pregnancystudies.org/participate-in-a-study/. Risk Summary Leflunomide is contraindicated for use in pregnant women because of the potential for fetal harm. In animal reproduction studies, oral administration of leflunomide during organogenesis at a dose of 1/10 of, and equivalent to, the maximum recommended human dose (MRHD) based on AUC, respectively, in rats and rabbits, caused teratogenicity (rats and rabbits), and embryo-lethality (rats) [see Data] . Pregnancy exposure registry data are not available at this time to inform the presence or absence of drug-associated risk with the use of leflunomide during pregnancy. The background risk of major birth defects and miscarriage for the indicated populations is unknown. The background risk in the U.S. general population of major birth defects is 2% to 4% and of miscarriage is 15% to 20% of clinically recognized pregnancies. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, stop treatment with leflunomide, apprise the patient of the potential hazard to a fetus, and perform the accelerated drug elimination procedure to achieve teriflunomide concentrations of less than 0.02 mg/L (0.02 mcg/mL) [see Warnings and Precautions (5.3) ] . Clinical Considerations Fetal/Neonatal adverse reactions Lowering the plasma concentration of the active metabolite, teriflunomide, by instituting an accelerated drug elimination procedure as soon as pregnancy is detected may decrease the risk to the fetus from leflunomide. The accelerated drug elimination procedure includes verification that the plasma teriflunomide concentration is less than 0.02 mg/L. [see Warnings and Precautions (5.3) and Clinical Pharmacology (12.3) ] . Data Animal data In an embryo-fetal development study, pregnant rats administered leflunomide during organogenesis from gestation days 7 to 19 at a dose approximately 1/10 of the MRHD (on an AUC basis at a maternal oral dose of 15 mg/kg), teratogenic effects, most notably anophthalmia or microphthalmia and internal hydrocephalus, were observed. Under these exposure conditions, leflunomide also caused a decrease in the maternal body weight and an increase in embryolethality with a decrease in fetal body weight for surviving fetuses. In an embryo-fetal development study, pregnant rabbits administered leflunomide during organogenesis from gestation days 6 to 18 at a dose approximately equivalent to the MRHD (on an AUC basis at a maternal oral dose of 10 mg/kg), a teratogenic finding of fused, dysplastic sternebrae was observed. Leflunomide was not teratogenic in rats and rabbits at doses approximately 1/150 and 1/10 of the MRHD, respectively (on an AUC basis at maternal oral dose of 1 mg/kg in both rats and rabbits). In a pre and postnatal development study, when female rats were treated with leflunomide at a dose that was approximately 1/100 of the MRHD (on an AUC basis at a maternal dose of 1.25 mg/kg) beginning 14 days before mating and continuing until the end of lactation, the offspring exhibited marked (greater than 90%) decreases in postnatal survival.

6 ADVERSE REACTIONS Hepatotoxicity [see Warnings and Precautions (5.2)] Immunosuppression [see Warnings and Precautions (5.4)] Bone marrow suppression [see Warnings and Precautions (5.4)] Serious infections [see Warnings and Precautions (5.4)] Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reactions with eosinophilia and systemic symptoms [see Warnings and Precautions (5.5)] Skin ulcers [see Warnings and Precautions (5.6)] Peripheral neuropathy [see Warnings and Precautions (5.8)] Interstitial lung disease [see Warnings and Precautions (5.9)] The most commonly reported adverse reactions (≥10%) regardless of relation to leflunomide treatment were diarrhea, respiratory infection, nausea, headache, rash, abnormal liver enzymes, and dyspepsia. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Avet Pharmaceuticals Inc. at 1-800-901-DRUG (3784) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in practice. In clinical studies (Trials 1, 2, and 3), 1,865 patients were treated with leflunomide as either monotherapy or in combination with methotrexate or sulfasalazine. Patients ranged in age from 19 to 85 years, with an overall median age of 58 years. The mean duration of RA was 6 years ranging from 0 to 45 years. Elevation of Liver Enzymes Treatment with leflunomide was associated with elevations of liver enzymes, primarily ALT and AST, in a significant number of patients; these effects were generally reversible. Most transaminase elevations were mild (≤2-fold ULN) and usually resolved while continuing treatment. Marked elevations (>3-fold ULN) occurred infrequently and reversed with dose reduction or discontinuation of treatment. Table 1 shows liver enzyme elevations seen with monthly monitoring in clinical trials Trial 1 and Trial 2. It was notable that the absence of folate use in Trial 3 was associated with a considerably greater incidence of liver enzyme elevation on methotrexate. Table 1: Liver Enzyme Elevations >3-fold Upper Limits of Normal (ULN) in Patients with RA in Trials 1, 2, and 3* Trial 1 Trial 2 Trial 3* LEF PL MTX LEF PL SSZ LEF MTX 20 mg/day (n=118) 7.5-15 mg/wk 20mg/day (n=92) 2 g/day 20 mg/day 7.5 -15 mg/wk (n=182) (n=182) (n=133) (n=133) (n=501) (n=498) ALT(SGPT)>3-fold ULN (n%) 8(4.4) 3(2.5) 5(2.7) 2(1.5) 1(1.1) 2(1.5) 13(2.6) 83(16.7) Reversed to ≤2-fold ULN: 8 3 5 2 1 2 12 82 Timing of Elevation 0-3 Months 4-6 Months 7-9 Months 10-12 Months 6 1 1 - 1 1 1 - 1 3 1 - 2 - - - 1 - - - 2 - - - 7 1 - 5 27 34 16 6 LEF = leflunomide, MTX = methotrexate, PL = placebo, SSZ = sulfasalazine, ULN = Upper limit of normal *Only 10% of patients in Trial 3 received folate. All patients in Trial 1 received folate. In a 6-month study of 263 patients with persistent active rheumatoid arthritis despite methotrexate therapy, and with normal LFTs, leflunomide was administered to a group of 130 patients starting at 10 mg per day and increased to 20 mg as needed. An increase in ALT greater than or equal to three times the ULN was observed in 3.8% of patients compared to 0.8% in 133 patients continued on methotrexate with placebo. Most Common Adverse Reactions The most common adverse reactions in leflunomide-treated patients with RA include diarrhea, elevated liver enzymes (ALT and AST), alopecia, and rash. Table 2 displays the most common adverse reactions in the controlled studies in patients with RA at one year (≥5% in any leflunomide treatment group). Table 2: Percentage Of Patients With Adverse Events ≥ 5% In Any Leflunomide Treated Group in all RA Studies in Patients with RA Placebo-Controlled Trials Active-Controlled Trials All RA Studies Trial 1 and 2 Trial 3 1 LEF PL (n=210) SSZ MTX 7.5 - 15 LEF MTX 7.5 - 15 LEF (n=1339) 2 20 m…