There is a potential for immunogenicity with therapeutic proteins such as ofatumumab. Serum samples from more than 926 patients with CLL were tested during and after treatment for antibodies to ARZERRA. Formation of anti-ofatumumab antibodies was observed in less than 1% of patients with CLL after treatment with ofatumumab.
Immunogenicity assay results are highly dependent on several factors including assay sensitivity and specificity, assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of incidence of antibodies to ARZERRA with the incidence of antibodies to other products may be misleading.
The following adverse reactions have been identified during post-approval use of ARZERRA. 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.
Infusion-related Cardiac Events
Stevens-Johnson syndrome, porphyria cutanea tarda
ARZERRA may cause fetal B-cell depletion based on findings from animal studies and the drug’s mechanism of action [see Clinical Pharmacology (12.1)]. There are no data on ARZERRA use in pregnant women to inform a drug-associated risk. However, there are clinical considerations [see Clinical Considerations]. No teratogenicity was observed in animal reproduction studies with administration of ARZERRA to pregnant monkeys during organogenesis at doses 0.3 and 2.4 times the maximum recommended human dose (MRHD) of 2000 mg based on monkey geometric mean AUCinf of 213 mg.h/mL and 1646 mg.h/mL, respectively. However, ofatumumab caused depletion of maternal circulating B-cells, depletion of peripheral and splenic fetal B-cells, and decreased fetal spleen weights [see Data].
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population the estimated background risk of major birth defects is 2% to 4% and of miscarriage is 15% to 20% of clinically recognized pregnancies, respectively.
Fetal/neonatal adverse reactions
ARZERRA may cause fetal B-cell depletion [see Data]. Avoid administering live vaccines to neonates and infants exposed to ARZERRA in utero until B-cell recovery occurs [see Warnings and Precautions (5.7) and Clinical Pharmacology (12.2)].
In an embryo-fetal development study, pregnant cynomolgus monkeys received 20 or 100 mg/kg/day of ofatumumab intravenously (30 minute infusion) once weekly during the period of organogenesis [Gestation Days (GD) 20 to 50] with systemic exposure throughout pregnancy due to the long half-life as drug was detected in maternal serum on GD 100 (early fetal period of development). At the end of organogenesis on GD 48, the exposure in pregnant monkeys receiving ofatumumab 20 and 100 mg/kg/day was approximately 0.3 and 2.4 times the human exposure after the 8th infusion of the MRHD of 2,000 mg based on monkey geometric mean AUCinf of 213 mg.h/mL and 1,646 mg.h/mL, respectively. Ofatumumab crossed the placenta, as it was detected in fetal cord blood on GD 100 in both dose groups. There was no maternal toxicity and no effect on pregnancy success. As expected, both dose levels of ofatumumab depleted circulating B cells in the mothers; recovery of B lymphocytes in dosed animals was not observed during the dosing-free period. Following Caesarean section at GD 100, fetuses from treated mothers exhibited decreases in mean peripheral and splenic B-cell counts (decreased to approximately 12% and 15% of control values at both dose levels, respectively and spleen weights (decreased by approximately 15% in low-dose group and by approximately 30% in high-dose group, compared with control values). There was no effect on prenatal survival and no evidence of teratogenicity in this monkey study.
The kinetics of B-lymphocyte recovery and the potential long-term effects of perinatal B-cell depletion in offspring from ofatumumab-treated maternal monkeys have not been studied.
There is no information regarding the presence of ARZERRA in human milk, the effects on the breastfed infant, or the effects on milk production. Human IgG is known to be present in human milk. Published data suggest that antibodies in breast milk do not enter the neonatal and infant circulations in substantial amounts.
The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for ARZERRA and any potential adverse effects on the breastfed infant from ARZERRA or from the underlying maternal condition.
Safety and effectiveness of ARZERRA have not been established in children.
In patients with previously untreated CLL (Study 1), 68% (148/217) receiving ARZERRA plus chlorambucil were 65 years and older. Patients age 65 years and older experienced a higher incidence of the following Grade 3 or greater adverse reactions compared with patients younger than 65 years of age: neutropenia (30% versus 17%) and pneumonia (5% versus 1%) [see Adverse Reactions (6.1)]. In patients 65 years and older, 29% experienced serious adverse events compared with 13% of patients younger than 65 years. No clinically meaningful differences in the effectiveness of ARZERRA plus chlorambucil were observed between older and younger patients [see Clinical Studies (14.1)].
In patients with relapsed CLL (Study 2), 33% (60/181) of patients receiving ARZERRA plus fludarabine and cyclophosphamide were 65 years and older. No clinically meaningful differences in the safety or effectiveness of ARZERRA were observed between patients age 65 years and older, and those younger than 65 years [see Adverse Reactions (6.1), Clinical Studies (14.2)].
With extended treatment in patients with CLL (Study 3), 49% (117/237) receiving ARZERRA were 65 years and older. No clinically meaningful differences in the safety or effectiveness of ARZERRA were observed between patients age 65 years and older and those younger than 65 years of age [see Adverse Reactions (6.1), Clinical Studies (14.3)].
In refractory CLL clinical studies there were insufficient numbers of patients aged 65 years and older to determine whether they respond differently from younger patients [see Clinical Pharmacology (12.3)].
ARZERRA (ofatumumab) is an IgG1κ human monoclonal antibody with a molecular weight of approximately 149 kDa. The antibody was generated via transgenic mouse and hybridoma technology and is produced in a recombinant murine cell line (NS0) using standard mammalian cell cultivation and purification technologies.
ARZERRA is a sterile, clear to opalescent, colorless, preservative-free liquid concentrate for intravenous administration. ARZERRA is supplied at a concentration of 20 mg/mL in single-use vials. Each single-use vial contains either 100 mg ofatumumab in 5 mL of solution or 1,000 mg ofatumumab in 50 mL of solution.
Inactive ingredients include: 10 mg/mL arginine, diluted hydrochloric acid, 0.019 mg/mL edetate disodium, 0.2 mg/mL polysorbate 80, 6.8 mg/mL sodium acetate, 2.98 mg/mL sodium chloride, and Water for Injection, USP. The pH is 5.5.
Ofatumumab binds specifically to both the small and large extracellular loops of the CD20 molecule. The CD20 molecule is expressed on normal B lymphocytes (pre–B- to mature B-lymphocyte) and on B-cell CLL. The CD20 molecule is not shed from the cell surface and is not internalized following antibody binding.
The Fab domain of ofatumumab binds to the CD20 molecule and the Fc domain mediates immune effector functions to result in B-cell lysis in vitro. Data suggest that possible mechanisms of cell lysis include complement-dependent cytotoxicity and antibody-dependent, cell-mediated cytotoxicity.
B-cell Depletion: In patients with previously untreated CLL, at 6 months after the last dose, the median reductions in CD19-positive B cells were >99% (n = 155) for ARZERRA in combination with chlorambucil and 94% (n = 121) for chlorambucil alone.
In patients with relapsed CLL, the proportion of responders in the ofatumumab in combination with fludarabine and cyclophosphamide (O+FC) arm who showed complete or near complete B cell depletion was 39% (n = 59) and 82% (n = 126) , respectively. The proportion of responders in the fludarabine and cyclophosphamide (FC) arm with complete or near complete B cell depletion was 4% (n = 5) and 23% (n = 28), respectively.
In patients treated with extended treatment for CLL after response to therapy for their recurrent or progressive disease, the median decreases in B-cell counts were 61% (n = 168) after the first infusion and 80% (n = 114) prior to the sixth infusion; in the observation arm, the median changes in B-cell counts at the same time points were increases of 32% (n = 148) and 1,328% (n = 95).
In patients with CLL refractory to fludarabine and alemtuzumab, the median decrease in circulating CD19-positive B cells was 91% (n = 50) with the 8th infusion and 85% (n = 32) with the 12th infusion. The time to recovery of lymphocytes, including CD19-positive B cells, to normal levels has not been determined.
Although the depletion of B-cells in the peripheral blood is a measurable pharmacodynamic effect, it is not directly correlated with the depletion of B cells in solid organs or in malignant deposits. B-cell depletion has not been shown to be directly correlated to clinical response.
Cardiac Electrophysiology: The effect of multiple doses of ARZERRA on the QTc interval was evaluated in a pooled analysis of 3 open-label studies in patients with CLL (N = 85). Patients received ARZERRA 300 mg on Day 1 followed by either 1,000 mg or 2,000 mg for subsequent doses. No large changes in the mean QTc interval (i.e., >20 milliseconds) were detected in the pooled analysis.
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