Ibritumomab tiuxetan

12.1 Mechanism of Action Ibritumomab tiuxetan binds specifically to the CD20 antigen (human B-lymphocyte-restricted differentiation antigen, Bp35). The apparent affinity (K D ) of ibritumomab tiuxetan for the CD20 antigen ranges between approximately 14 to 18 nM. The CD20 antigen is expressed on pre-B and mature B lymphocytes and on > 90% of B-cell non-Hodgkin’s lymphomas (NHL). The CD20 antigen is not shed from the cell surface and does not internalize upon antibody binding. The chelate tiuxetan, which tightly binds Y-90, is covalently linked to ibritumomab. The beta emission from Y-90 induces cellular damage by the formation of free radicals in the target and neighboring cells. Ibritumomab tiuxetan binding was observed in vitro on lymphoid cells of the bone marrow, lymph node, thymus, red and white pulp of the spleen, and lymphoid follicles of the tonsil, as well as lymphoid nodules of other organs such as the large and small intestines.

1 INDICATIONS AND USAGE Zevalin is a CD20-directed radiotherapeutic antibody administered as part of the Zevalin therapeutic regimen indicated for the treatment of adult patients with: relapsed or refractory, low-grade or follicular B-cell non-Hodgkin's lymphoma (NHL) ( 1.1 ). previously untreated follicular NHL who achieve a partial or complete response to first-line chemotherapy ( 1.2 ). 1.1 Relapsed or Refractory, Low-grade or Follicular NHL Zevalin is indicated for the treatment of adult patients with relapsed or refractory, low-grade or follicular B-cell non-Hodgkin's lymphoma (NHL). 1.2 Previously Untreated Follicular NHL Zevalin is indicated for the treatment of previously untreated follicular NHL in adult patients who achieve a partial or complete response to first-line chemotherapy.

2 DOSAGE AND ADMINISTRATION Day 1 : Administer rituximab 250 mg/m 2 intravenous infusion. ( 2.2 ) Day 7, 8, or 9 : Administer rituximab 250 mg/m 2 intravenous infusion. ( 2.2 ) If platelets at least 150,000/mm 3 : Within 4 hours after rituximab infusion, administer 0.4 mCi/kg (14.8 MBq per kg) Y-90 Zevalin intravenous infusion. If platelets 100,000 to 149,000/mm 3 in relapsed or refractory patients: Within 4 hours after rituximab infusion, administer 0.3 mCi/kg (11.1 MBq per kg) Y-90 Zevalin intravenous infusion. 2.1 Recommended Dosing Schedule Administer the Zevalin therapeutic regimen as outlined below. Initiate the Zevalin therapeutic regimen following recovery of platelet counts to 150,000/mm 3 or more at least 6 weeks, but no more than 12 weeks, following the last dose of first-line chemotherapy. Only administer rituximab/Zevalin in facilities where immediate access to resuscitative measures is available. Overview of Dosing Schedule Zevalin Dosing Schedule 2.2 Zevalin Therapeutic Regimen Dosage and Administration Day 1: Premedicate with acetaminophen 650 mg orally and diphenhydramine 50 mg orally prior to rituximab infusion. Administer rituximab 250 mg/m 2 intravenously at an initial rate of 50 mg/hr. In the absence of infusion reactions, escalate the infusion rate in 50 mg/hr increments every 30 minutes to a maximum of 400 mg/hr. Do not mix or dilute rituximab with other drugs. Immediately stop the rituximab infusion for serious infusion reactions and discontinue the Zevalin therapeutic regimen [ see Boxed Warning and Warnings and Precautions ( 5.1 ) ]. Temporarily slow or interrupt the rituximab infusion for less severe infusion reactions. If symptoms improve, continue the infusion at one-half the previous rate. Day 7, 8 or 9: Premedicate with acetaminophen 650 mg orally and diphenhydramine 50 mg orally prior to rituximab infusion. Administer rituximab 250 mg/m 2 intravenously at an initial rate of 100 mg/hr. Increase rate by 100 mg/hr increments at 30 minute intervals, to a maximum of 400 mg/hr, as tolerated. If infusion reactions occurred during rituximab infusion on Day 1 of treatment, administer rituximab at an initial rate of 50 mg/hr and escalate the infusion rate in 50 mg/hr increments every 30 minutes to a maximum of 400 mg/hr. Administer Y-90 Zevalin injection through a free flowing intravenous line within 4 hours following completion of rituximab infusion. Use a 0.22 micron low-protein-binding in-line filter between the syringe and the infusion port. After infusion, flush the line with at least 10 mL of normal saline. If platelet count at least 150,000/mm 3 , administer Y-90 Zevalin over 10 minutes as an intravenous infusion at a dose of Y-90 0.4 mCi per kg (14.8 MBq per kg) actual body weight. If platelet count 100,000 to 149,000/mm 3 , in relapsed or refractory patients, administer Y-90 Zevalin over 10 minutes as an intravenous infusion at a dose of Y-90 0.3 mCi per kg (11.1 MBq per kg) actual body weight. Do not administer more than 32 mCi (1184 MBq) Y-90 Zevalin dose regardless of the patient’s body weight. Monitor patients closely for evidence of extravasation during the infusion of Y-90 Zevalin. Immediately stop infusion and restart in another limb if any signs or symptoms of extravasation occur [ see Warnings and Precautions ( 5.5 ) ]. 2.3 Directions for Preparation of Radiolabeled Y-90 Zevalin Doses A clearly-labeled kit is required for preparation of Yttrium-90 (Y-90) Zevalin. Follow the detailed instructions for the preparation of radiolabeled Zevalin [ see Dosage and Administration ( 2.4 ) ]. Required materials not supplied in the kit: Yttrium-90 Chloride Sterile Solution Three sterile 1 mL plastic syringes One sterile 3 mL plastic syringe Two sterile 10 mL plastic syringes with 18-20 G needles ITLC silica gel strips 0.9% Sodium Chloride aqueous solution for the chromatography solvent Developing chamber for chromatography Suitable radioactivity counting apparatus Filter, 0.22 micrometer, low-protein-binding Appropriate acrylic shielding for reaction vial and syringe for Y-90 Method: Allow contents of the refrigerated Y-90 Zevalin kit (Zevalin vial, 50 mM sodium acetate vial, and formulation buffer vial) to reach room temperature. Place the empty reaction vial in an appropriate acrylic shield. Determine the amount of each component needed: Calculate volume of Y-90 Chloride equivalent to 40 mCi based on the activity concentration of the Y-90 Chloride stock. The volume of 50 mM Sodium Acetate solution needed is 1.2 times the volume of Y-90 Chloride solution determined in step 3.a, above. Calculate the volume of formulation buffer needed to bring the reaction vial contents to a final volume of 10 mL. Transfer the calculated volume of 50 mM Sodium Acetate to the empty reaction vial. Coat the entire inner surface of the reaction vial by gentle inversion or rolling. Transfer 40 mCi of Y-90 Chloride to the reaction vial using an acrylic shielded syringe. Mix the two solutions by gentle i

6 ADVERSE REACTIONS The following serious adverse reactions are discussed in greater detail in other sections of the label: Serious Infusion Reactions [ see Boxed Warning and Warnings and Precautions ( 5.1 ) ] . Prolonged and Severe Cytopenias [ see Boxed Warning and Warnings and Precautions ( 5.2 ) ]. Severe Cutaneous and Mucocutaneous Reactions [ see Boxed Warning and Warnings and Precautions ( 5.3 ) ]. Leukemia and Myelodysplastic Syndrome [ see Warnings and Precautions ( 5.4 ) ]. Common adverse reactions ( > 10%) in clinical trials were: cytopenias, fatigue, nasopharyngitis, nausea, abdominal pain, asthenia, cough, diarrhea, and pyrexia. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Acrotech Biopharma Inc. at 1-866-298-8433 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch 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 to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The reported safety data reflects exposure to Zevalin in 349 patients with relapsed or refractory, low-grade, follicular or transformed NHL across 5 trials (4 single arm and 1 randomized) and in 206 patients with previously untreated follicular NHL in a randomized trial (FIT study) who received any portion of the Zevalin therapeutic regimen. The safety data reflect exposure to Zevalin in 270 patients with relapsed or refractory NHL with platelet counts ≥150,000/ mm 3 who received 0.4 mCi/kg (14.8 MBq/kg) of Y-90 Zevalin (Group 1 in Table 4 ), 65 patients with relapsed or refractory NHL with platelet counts of ≥ 100,000 but ≤ 149,000 /mm 3 who received 0.3 mCi/kg (11.1 MBq/kg) of Y-90 Zevalin (Group 2 in Table 4 ), and 204 patients with previously untreated NHL with platelet counts ≥150,000/ mm 3 who received 0.4 mCi/kg (14.8 MBq/kg) of Y-90 Zevalin; all patients received a single course of Zevalin. The most common adverse reactions of Zevalin are cytopenias, fatigue, nasopharyngitis, nausea, abdominal pain, asthenia, cough, diarrhea, and pyrexia. The most serious adverse reactions of Zevalin are prolonged and severe cytopenias (thrombocytopenia, anemia, lymphopenia, neutropenia) and secondary malignancies. Because the Zevalin therapeutic regimen includes the use of rituximab, see prescribing information for rituximab. Table 2 displays selected adverse reaction incidence rates in patients who received any portion of the Zevalin therapeutic regimen (n=206) or no further therapy (n=203) following first-line chemotherapy (FIT study). Table 2. Per-Patient Incidence (%) of Selected Between-group difference of ≥5% Adverse Reactions Occurring in ≥ 5% of Patients with Previously Untreated Follicular NHL Treated with the Zevalin Therapeutic Regimen Zevalin (n=206) Observation (n=203) All Grades NCI CTCAE version 2.0 Grade 3-4 All Grades Grade 3-4 % % % % Gastrointestinal Disorders Abdominal pain 17 2 13 <1 Diarrhea 11 0 3 0 Nausea 18 0 2 0 Body as a Whole Asthenia 15 1 8 <1 Fatigue 33 1 9 0 Influenza-like illness 8 0 3 0 Pyrexia 10 3 4 0 Musculoskeletal Myalgia 9 0 3 0 Metabolism Anorexia 8 0 2 0 Respiratory, Thoracic & Media Cough 11 <1 5 0 Pharyngolaryngeal pain 7 0 2 0 Epistaxis 5 2 <1 0 Nervous System Dizziness 7 0 2 0 Vascular Hypertension 7 3 2 <1 Skin & Subcutaneous Night sweats 8 0 2 0 Petechiae 8 2 0 0 Pruritus 7 0 1 0 Rash 7 0 <1 0 Infections & Infestations Bronchitis 8 0 3 0 Nasopharyngitis 19 0 10 0 Rhinitis 8 0 2 0 Sinusitis 7 <1 <1 0 Urinary tract infection 7 <1 3 0 Blood and Lymphatic System Thrombocytopenia 62 51 1 0 Neutropenia 45 41 3 2 Anemia 22 5 4 0 Leukopenia 43 36 4 1 Lymphopenia 26 18 9 5 Table 3 shows hematologic toxicities in 349 Zevalin-treated patients with relapsed or refractory, low-grade, follicular or transformed B-cell NHL. Grade 2-4 hematologic toxicity occurred in 86% of Zevalin-treated patients. Table 3. Per-Patient Incidence (%) of Hematologic Adverse Reactions in Patients with Relapsed or Refractory Low-grade, Follicular or Transformed B-cell NHL Occurring within the 12 weeks following the first rituximab infusion of the Zevalin therapeutic regimen (N = 349) All Grades % Grade 3-4 % Thrombocytopenia 95 63 Neutropenia 77 60 Anemia 61 17 Ecchymosis 7 <1 Prolonged and Severe Cytopenias Patients in clinical studies were not permitted to receive hematopoietic growth factors beginning 2 weeks prior to administration of the Zevalin therapeutic regimen. The incidence and duration of severe hematologic toxicity in previously treated NHL patients (N=335) and in previously untreated patients (FIT study) receiving Y-90 Zevalin are shown in Table 4 . Table 4. Severe Hematologic Toxicity in Patients Receiving Zevalin Baseline Platelet Count Group 1 (n=270) ≥ 150,000/mm 3 Group 2 (n=65 ) ≥ 100,000 but ≤ 149,000/mm 3 FIT study (n=204) ≥ 150,000/mm 3 Y-90 Zevalin Dose 0.4 mCi/kg (14.8 MBq/kg) 0.3 mCi/kg (11.1 MBq/kg) 0.4 mCi/kg

7 DRUG INTERACTIONS Patients receiving medications that interfere with platelet function or coagulation should have more frequent laboratory monitoring for thrombocytopenia. No formal drug interaction studies have been performed with Zevalin. Monitor patients receiving medications that interfere with platelet function or coagulation more frequently for thrombocytopenia. ( 7 )