Cladribine

12.1 Mechanism of Action The mechanism by which cladribine exerts its therapeutic effects in patients with multiple sclerosis has not been fully elucidated but is thought to involve cytotoxic effects on B and T lymphocytes through impairment of DNA synthesis, resulting in depletion of lymphocytes.

1 INDICATIONS AND USAGE Cladribine tablets are indicated for the treatment of relapsing form of multiple sclerosis (MS), to include relapsing-remitting disease in adults. Because of its safety profile, use of cladribine tablets is generally recommended for patients who have had an inadequate response to, or are unable to tolerate, an alternate drug indicated for the treatment of MS [ see Warnings and Precautions (5) ]. Limitations of Use Cladribine tablets are not recommended for use in patients with clinically isolated syndrome (CIS) because of its safety profile [ see Warnings and Precautions (5) ]. Cladribine tablets are purine antimetabolite indicated for the treatment of relapsing form of multiple sclerosis (MS), to include relapsing-remitting disease in adults. Because of its safety profile, use of cladribine tablets are generally recommended for patients who have had an inadequate response to, or are unable to tolerate, an alternate drug indicated for the treatment of MS. ( 1 , 5 ) Limitations of Use Cladribine tablets are not recommended for use in patients with clinically isolated syndrome (CIS) because of its safety profile. ( 1 , 5 )

2 DOSAGE AND ADMINISTRATION Assessments are required prior to starting each cladribine treatment course. (2.1) Cumulative dosage of 3.5 mg/kg administered orally and divided into 2 treatment courses (1.75 mg/kg per treatment course). Each treatment course is divided into 2 treatment cycles. (2.2) Cladribine tablets are a cytotoxic drug. (2.4) Separate administration from any other oral drug by at least 3 hours. (2.4) 2.1 Assessments Prior to Starting Each Cladribine Treatment Course Cancer Screening Follow standard cancer screening guidelines because of the risk of malignancies [ see Boxed Warning and Warnings and Precautions (5.1) ]. Pregnancy Exclude pregnancy prior to treatment with cladribine tablets in females of reproductive potential [ see Contraindications (4) , Warnings and Precautions (5.2) , and Use in Specific Populations (8.1, 8.3) ]. Complete Blood Count (CBC) Obtain a CBC with differential including lymphocyte count [ see Dosage and Administration (2.5) and Warnings and Precautions (5.3) ]. Lymphocytes must be: within normal limits before initiating the first treatment course at least 800 cells per microliter before initiating the second treatment course If necessary, delay the second treatment course for up to 6 months to allow for recovery of lymphocytes to at least 800 cells per microliter. If this recovery takes more than 6 months, the patient should not receive further treatment with cladribine tablets. Infections [ see Warnings and Precautions (5.4) ] Exclude HIV infection. Perform tuberculosis screening. Screen for hepatitis B and C. Evaluate for acute infection. Consider a delay in cladribine treatment until any acute infection is fully controlled. Vaccination of patients who are seronegative for VZV is recommended prior to initiation of cladribine tablets. Vaccination of patients who are seropositive to VZV is recommended with zoster vaccine recombinant, adjuvanted. Patients may be administered zoster vaccine recombinant, adjuvanted at any time prior to or during the year 1 or year 2 course of cladribine treatment. These patients may also be administered the vaccine if their lymphocyte counts are ≤ 500 cells per microliter. Administer all immunizations (except as noted for VZV) according to immunization guidelines prior to starting cladribine tablets. Administer live-attenuated or live vaccines at least 4 to 6 weeks prior to starting cladribine tablets. Obtain a baseline (within 3 months) magnetic resonance imaging prior to the first treatment course because of the risk of progressive multifocal leukoencephalopathy (PML). Liver Injury Obtain serum aminotransferase, alkaline phosphatase, and total bilirubin levels prior to each treatment cycle and course [ see Warnings and Precautions (5.7) ]. 2.2 Recommended Dosage The recommended cumulative dosage of cladribine tablets is 3.5 mg per kg body weight administered orally and divided into 2 yearly treatment courses (1.75 mg per kg per treatment course) (see Table 1). Each treatment course is divided into 2 treatment cycles: Administration of First Treatment Course First Course/First Cycle: start any time. First Course/Second Cycle: administer 23 to 27 days after the last dose of First Course/First Cycle. Administration of Second Treatment Course Second Course/First Cycle: administer at least 43 weeks after the last dose of First Course/Second Cycle. Second Course/Second Cycle: administer 23 to 27 days after the last dose of Second Course/First Cycle. Table 1 Dose of Cladribine tablets per Cycle by Patient Weight in Each Treatment Course Weight Range Dose in mg (Number of 10 mg Tablets) per Cycle kg First Cycle Second Cycle 40* to less than 50 40 mg (4 tablets) 40 mg (4 tablets) 50 to less than 60 50 mg (5 tablets) 50 mg (5 tablets) 60 to less than 70 60 mg (6 tablets) 60 mg (6 tablets) 70 to less than 80 70 mg (7 tablets) 70 mg (7 tablets) 80 to less than 90 80 mg (8 tablets) 70 mg (7 tablets) 90 to less than 100 90 mg (9 tablets) 80 mg (8 tablets) 100 to less than 110 100 mg (10 tablets) 90 mg (9 tablets) 110 and above 100 mg (10 tablets) 100 mg (10 tablets) *The use of cladribine tablets in patients weighing less than 40 kg has not been investigated. Administer the cycle dosage as 1 or 2 tablets once daily over 4 or 5 consecutive days [ see How Supplied/Storage and Handling (16.1) ]. Do not administer more than 2 tablets daily. Following the administration of 2 treatment courses, do not administer additional cladribine treatment during the next 2 years. Treatment during these 2 years may further increase the risk of malignancy [ see Warnings and Precautions (5.1) ]. The safety and efficacy of reinitiating cladribine tablets more than 2 years after completing 2 treatment courses has not been studied. 2.3 Missed Dose If a dose is missed, patients should not take double or extra doses. If a dose is not taken on the scheduled day, then the patient must take the missed dose on the following day and extend the number of days in that treatmen

6 ADVERSE REACTIONS The following serious adverse reactions and potential risks are discussed, or discussed in greater detail, in other sections of the labeling: Malignancies [ see Warnings and Precautions (5.1) ] Risk of Teratogenicity [ see Warnings and Precautions (5.2) ] Lymphopenia [ see Warnings and Precautions (5.3)] Infections [ see Warnings and Precautions (5.4) ] Hematologic Toxicity [ see Warnings and Precautions (5.5) ] Graft-Versus-Host Disease With Blood Transfusion [ see Warnings and Precautions (5.6) ] Liver Injury [ see Warnings and Precautions (5.7) ] Hypersensitivity [ see Warnings and Precautions (5.8) ] Cardiac Failure [ see Warnings and Precautions (5.9) ] Most common adverse reactions (incidence > 20%) are upper respiratory tract infection, headache, and lymphopenia. (6.1) To report SUSPECTED ADVERSE REACTIONS, contact Apotex Corp. at 1-800-706-5575 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 trials 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 the clinical trial program of cladribine in MS, 1,976 patients received cladribine for a total of 9,509 patient years. The mean time on study including follow-up was approximately 4.8 years, and approximately 24% of cladribine-treated patients had approximately 8 years of time on study including follow-up. Of these, 923 patients aged 18 to 66 years received cladribine as monotherapy at a cumulative dose of 3.5 mg per kg. Table 2 shows adverse reactions in Study 1 [ see Clinical Studies (14) ] with an incidence of at least 5% for cladribine and higher than placebo. The most common (> 20%) adverse reactions reported in Study 1 are upper respiratory tract infection, headache, and lymphopenia. Table 2 Adverse Reactions in Study 1 with an Incidence of at Least 5% for Cladribine tablets and Higher than Placebo Cladribine (N=440) % Placebo (N=435) % Upper respiratory tract infection 38 32 Headache 25 19 Lymphopenia 24 2 Nausea 10 9 Back pain 8 6 Arthralgia and arthritis 7 5 Insomnia 6 4 Bronchitis 5 3 Hypertension 5 3 Fever 5 3 Depression 5 3 Hypersensitivity In clinical studies, 11% of cladribine patients had hypersensitivity adverse reactions, compared to 7% of placebo patients [see Warnings and Precautions ( 5.8 )]. Alopecia Alopecia occurred in 3% of cladribine-treated patients compared to 1% of placebo patients. Myelodysplastic Syndrome Cases of myelodysplastic syndrome have been reported in patients that had received parenteral cladribine at a higher dosage than that approved for cladribine. These cases occurred several years after treatment. Herpes Meningoencephalitis Fatal herpes meningoencephalitis occurred in one cladribine-treated patient, at a higher dosage and longer duration of therapy than the approved cladribine dosage and in combination with interferon beta-1a treatment. Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) SJS and TEN are identified risks of parenteral cladribine for the treatment of oncologic indications. Seizures In clinical studies, serious events of seizure occurred in 0.3% of cladribine-treated patients compared to 0 placebo patients. Serious events included generalized tonic-clonic seizures and status epilepticus. It is unknown whether these events were related to the effects of multiple sclerosis alone, to cladribine, or to a combination of both. 6.2 Postmarketing Experience The following adverse reactions have been identified during postapproval use of cladribine. 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. Infections and Infestations: nocardiosis, varicella zoster, histoplasmosis, cryptococcosis, and toxoplasmosis [see Warnings and Precautions ( 5.4 )]. Hepatobiliary Disorders: liver injury [see Warnings and Precautions ( 5.7 )]

7 DRUG INTERACTIONS Table 3 Drug Interactions with cladribine tablets 7.1 Immunomodulatory, Immunosuppressive, or Myelosuppressive Drugs Clinical Impact Concomitant use of cladribine with immunomodulatory, immunosuppressive, or myelosuppressive drugs may increase the risk of adverse reactions because of the additive effects on the immune system [see Warnings and Precautions ( 5.4 )]. Prevention or Management Concomitant use with myelosuppressive or other immunosuppressive drugs is not recommended. Acute short-term therapy with corticosteroids can be administered. In patients who have previously been treated with immunomodulatory or immunosuppressive drugs, consider potential additive effect, the mode of action, and duration of effect of the other drugs prior to initiation of cladribine. 7.2 Interferon-Beta Clinical Impact Concomitant use of cladribine with interferon-beta did not change the exposure of cladribine to a clinically significant effect; however, lymphopenia risk may be increased [ see Warnings and Precautions (5.3) ]. Prevention or Management Concomitant use is not recommended. 7.3 Hematotoxic Drugs Clinical Impact Concomitant use of cladribine with hematotoxic drugs may increase the risk of adverse reactions because of the additive hematological effects [ see Warnings and Precautions (5.5) ]. Prevention or Management Monitor hematological parameters. 7.4 Antiviral and Antiretroviral Drugs Clinical Impact Compounds that require intracellular phosphorylation to become active (e.g., lamivudine, zalcitabine, ribavirin, stavudine, and zidovudine) could interfere with the intracellular phosphorylation and activity of cladribine. Prevention or Management Avoid concomitant use. 7.5 Potent ENT, CNT and BCRP Transporter Inhibitors Clinical Impact Cladribine is a substrate of breast cancer resistance protein (BCRP), equilibrative nucleoside (ENT1), and concentrative nucleoside (CNT3) transport proteins. The bioavailability, intracellular distribution, and renal elimination of cladribine may be altered by potent ENT1, CNT3, and BCRP transporter inhibitors. Prevention or Management Avoid co-administration of potent ENT1, CNT3, or BCRP transporter inhibitors (e.g., ritonavir, eltrombopag, curcumin, cyclosporine, dilazep, nifedipine, nimodipine, cilostazol, sulindac, dipyridamole, or reserpine) during the 4 to 5 day cladribine treatment cycles. If this is not possible, consider selection of alternative concomitant drugs with no or minimal ENT1, CNT3, or BCRP transporter inhibiting properties. If this is not possible, dose reduction to the minimum mandatory dose of drugs containing these compounds, separation in the timing of administration, and careful patient monitoring is recommended. 7.6 Potent BCRP and P-gp Transporter Inducers Clinical Impact Possible decrease in cladribine exposure if potent BCRP or P-gp transporter inducers are co-administered. Prevention or Management Consider a possible decrease in cladribine efficacy if potent BCRP (e.g., corticosteroids) or P-gp (e.g., rifampicin, St. John's Wort) transporter inducers are co-administered. Immunosuppressive drugs: Consider overlapping effects on immune system, when used sequentially. Concomitant use not recommended. (7.1) Hematotoxic drugs: Monitor patients for additive effects on the hematological profile. (7.3) Antiviral and antiretroviral drugs: Avoid concomitant use. (7.4) BCRP or ENT/CNT inhibitors: May alter bioavailability of cladribine. Avoid concomitant use. (7.5)