Leflunomide

12.1 Mechanism of Action Leflunomide is an isoxazole immunomodulatory agent that inhibits dihydroorotate dehydrogenase (a mitochondrial enzyme involved in de novo pyrimidine synthesis) and has antiproliferative activity. Several in vivo and in vitro experimental models have demonstrated an anti-inflammatory effect.

1 INDICATIONS AND USAGE Leflunomide Tablets, USP are 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. ( 1 )

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 dosage 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 dosage 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 dosage 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 (5.10) ]

6 ADVERSE REACTIONS The following serious adverse reactions are described elsewhere in the labeling: Hepatotoxicity [see Warnings and Precautions (5.2) ] Immunosuppression [see Warnings and Precautions (5.4) ] Bone marrow suppression [see Warnings and Precautions (5.4) ] Stevens-Johnson syndrome and toxic epidermal necrolysis [see Warnings and Precautions (5.5) ] Peripheral neuropathy [see Warnings and Precautions (5.7) ] Interstitial lung disease [see Warnings and Precautions (5.8) ] The most commonly reported adverse reactions (≥10%) regardless of relation to leflunomide treatment were diarrhea, respiratory infection, nausea, headache, rash, abnormal liver enzymes, dyspepsia. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Chartwell RX, LLC. at 1-845-232-1683 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 administered 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 20 mg/day (n=182) PL (n=118) MTX 7.5-15 mg/wk (n=182) LEF 20mg/day (n=133) PL (n=92) SSZ 2.0 g/day LEF 20 mg/day (n=501) MTX 7.5-15 mg/wk (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 20 mg/day (N=315) PL (N=210) SSZ 2.0g/day (N=133) MTX 7.5-15 mg/wk (N=182) LEF 20 mg/day (N=501) MTX 7.5–15 mg/wk (N=498) LEF (N=1339) 2 Diarrhea 27% 12% 10% 20% 22% 10% 17% Headache 13% 11% 12% 21% 10% 8% 7% Nausea 13% 11% 19% 18% 13% 18% 9% Rash 12% 7% 11% 9% 11% 10% 10% Abnormal Liver Enzymes 10% 2% 4% 10% 6% 17% 5% Alopecia 9% 1% 6% 6% 17% 10% 10% Hypertension 3 9% 4% 4% 3% 10% 4% 10% Asthenia 6% 4% 5% 6% 3% 3% 3% Back Pain 6% 3% 4% 9% 8% 7% 5% GI/Abdominal Pain 6% 4% 7% 8% 8% 8% 5% Abdominal Pain 5% 4% 4% 8% 6% 4% 6% Allergic Reaction 5% 2% 0% 6% 1% 2% 2% Bronchitis 5% 2% 4% 7% 8% 7% 7% Dizziness 5% 3% 6% 5% 7% 6% 4% Mouth Ulcer 5% 4% 3% 10% 3% 6% 3% Pruritus 5% 2% 3% 2% 6% 2% 4% Rhinitis 5% 2% 4% 3% 2% 2% 2% Vomiting 5% 4% 4% 3% 3% 3% 3% Tenosynovitis 2% 0% 1% 2% 5% 1% 3% LEF = leflunomide, MTX = methotrexate, PL = placebo, SSZ = sulfasalazine 1 Only 10% of patients in Trial3 received folate. All patients in Trial 1 received folate; none in Trial 2 received folate. 2 Includes all controlled and uncontrolled trials with leflunomide (duration up to 12 3 Hypertension as a preexisting condition was overrepresented in all l

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 co-administered 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 teriflunomide may increase exposure of these drugs. ( 7 ) Rosuvastatin: The dose of rosuvastatin should not exceed 10 mg once daily in patients taking leflunomide. ( 7 )