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Mechanism of Action
NOTE: Patients are deemed to be at high risk for progressing to severe COVID-19 or requiring hospitalization if they meet at least 1 of the following criteria:
NOTE: Casirivimab and imdevimab are not authorized for use in patients who are hospitalized due to COVID-19, who require oxygen therapy for COVID-19, or who require an increase in baseline oxygen flow rate due to COVID-19 if already on chronic oxygen therapy for an underlying condition. Use of the drug in hospitalized patients with COVID-19 who require high flow oxygen or mechanism ventilation may be associated with worsening clinical outcomes.
The optimal dosing regimen has not yet been established, and the recommended dose may be updated as data from clinical trials become available. Administer 2,400 mg (1,200 mg of casirivimab and 1,200 mg of imdevimab) as a single intravenous infusion over at least 60 minutes. Administer the infusion as soon as possible after the positive test for SARS-CoV-2 and within 10 days of symptom onset.
40 kg or more: 2,400 mg (1,200 mg casirivimab and 1,200 mg imdevimab) IV.
less than 40 kg: Use not authorized.
12 years and weighing 40 kg or more: 2,400 mg (1,200 mg casirivimab and 1,200 mg imdevimab) IV.
12 years and weighing less than 40 kg: Use not authorized.
1 to 11 years: Use not authorized.
Use not authorized.
Specific guidelines for dosage adjustments in hepatic impairment are not available; it appears that no dosage adjustments are needed.
No dosage adjustments are needed.
Casirivimab and imdevimab are investigational neutralizing human immunoglobulin G-1 (IgG1) monoclonal antibodies with activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). They are not an FDA-approved treatment; however, they have been authorized for use under an Emergency Use Authorization (EUA) to treat mild to moderate COVID-19 in patients (12 years and older weighing at least 40 kg) with positive SARS-CoV-2 viral testing who are at high risk for progressing to severe COVID-19 or hospitalization. The drug is NOT authorized for use in patients who are hospitalized due to COVID-19, who require oxygen therapy for COVID-19, or who require an increase in baseline oxygen flow rate due to COVID-19 if already on chronic oxygen therapy for an underlying condition. Use of the drug in hospitalized patients with COVID-19 who require high flow oxygen or mechanism ventilation may be associated with worsening clinical outcomes. The National Institutes of Health (NIH) COVID-19 treatment guidelines recommend using combination anti-SARS-CoV-2 monoclonal antibodies (including casirivimab and imdevimab) to treat outpatients with mild to moderate COVID-19 who are at high risk of clinical progression as defined by the EUA criteria. The NIH emphasizes that anti-SARS-CoV-2 antibodies should NOT be used to treat patients hospitalized due to COVID-19, except in a clinical trial; however, their use should be considered for high risk persons with mild to moderate COVID-19 who are hospitalized for a reason other than COVID-19. Anti-SARS-CoV-2 antibodies should be started as soon as possible after positive test results for SARS-CoV-2 and within 10 days of symptom onset. For patients who receive anti-SARS-CoV-2 antibodies, defer administration of the COVID-19 vaccination for at least 90 days as a precaution to avoid interference with vaccine-induced immune responses. Conversely, the use and timing of treatment with anti-SARS-CoV-2 antibodies should not be affected by prior vaccinations in patients who develop COVID-19 after receiving the vaccine.
For storage information, see the specific product information within the How Supplied section.
NOTE: Casirivimab and imdevimab are not FDA-approved medications; however, they have been authorized for use under an Emergency Use Authorization (EUA) to treat mild to moderate COVID-19 in patients with positive SARS-CoV-2 viral testing who are at high risk for progressing to severe COVID-19 or hospitalization. Under the EUA, health care providers are required to communicate to the patient, parent, or caregiver information consistent with the "Fact Sheet for Patients, Parents and Caregivers" prior to the patient receiving treatment; such information includes the following:
NOTE: Under the EUA, health care providers are required to report all medication errors and serious adverse events potentially related to casirivimab and imdevimab therapy within 7 calendar days from the onset of the event.
Preparation and Dilution:
The safety of casirivimab and imdevimab were evaluated in a phase 1/2 trial involving non-hospitalized patients with mild to moderate COVID-19. In this study, patients were randomized to receive single infusions of 2,400 mg (1,200 mg casirivimab and 1,200 mg imdevimab) (n = 258), 8,000 mg (4,000 mg casirivimab and 4,000 mg of imdevimab) (n = 518), or a placebo (n = 262). Serious adverse events were reported in 4 patients (1.6%) in the 2,400 mg group, 2 patients (less than 1%) in the 8,000 mg group, and 6 patients (2.3%) in the placebo group. None of the serious adverse events were considered to be related to the study drug. However, 4 patients in the 8,000 mg group developed infusion-related reactions of grade 2 or higher severity. There reactions were moderate in severity and included abdominal pain, flushing, fever, chills, pruritus, and urticaria. In 2 of the patients, the adverse reactions resulted in permanent discontinuation of the infusion. All events resolved upon treatment discontinuation. Note, the 8,000 mg dose (4,000 mg casirivimab and 4,000 mg imdevimab) is not authorized for use by the EUA. No infusion-related adverse events were reported in the 2,400 mg group, but 1 patient in the placebo group reported nausea.
Anaphylactic or anaphylactoid reactions have been reported in 1 patient treated with casirivimab and imdevimab during the clinical program. This adverse event began within 1 hour of the completed infusion, and required treatment with epinephrine which resolved the event.
Monoclonal antibodies, such as casirivimab and imdevimab, may be associated with worsening clinical outcomes when administered to hospitalized patients with COVID-19 who require high flow oxygen or mechanical ventilation. Therefore, the drug is not authorized for use in patients who are hospitalized due to COVID-19, who require oxygen therapy for COVID-19, or who require an increase in baseline oxygen flow rate due to COVID-19 if already on chronic oxygen therapy for an underlying condition.
Infusion-related reactions have been observed during treatment with casirivimab and imdevimab; these reactions may be severe or life-threatening. Signs and symptoms of these reactions include fever, chills, nausea, headache, bronchospasms, dyspnea, reduced oxygen saturation, fatigue, arrhythmia exacerbation (e.g., atrial fibrillation, sinus tachycardia, bradycardia), chest pain or discomfort, weakness, altered mental status, hypotension, hypertension, angioedema, throat irritation, rash, urticaria, pruritus, myalgia, dizziness, and diaphoresis. If an infusion-related reaction develops, consider slowing or stopping the infusion and administer appropriate medications and supportive care. Similarly, serious hypersensitivity reactions, including anaphylaxis, have been observed with casirivimab and imdevimab. If signs and symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, immediately discontinue treatment and initiate appropriate medications and supportive care.
There are insufficient data regarding the use of casirivimab and imdevimab during pregnancy to determine a drug-associated risk for major birth defects, miscarriages, or adverse maternal or fetal outcomes. Human immunoglobulin G1 (IgG1) antibodies are known to cross the placental barrier; therefore, casirivimab and imdevimab have the potential to be transferred from the mother to the developing fetus. It is unknown if this potential in utero transfer provides any therapeutic benefit or risk to the fetus. According to the manufacturer, casirivimab and imdevimab should be administered during pregnancy only if the potential benefit outweighs the potential risk for the mother and fetus. The National Institutes of Health (NIH) COVID-19 treatment guidelines recommend that the drug not be withheld from a pregnant woman at high risk of progressing to severe COVID-19 if the clinician thinks that the potential benefit outweighs potential risk.
There are no data regarding the presence of casirivimab or imdevimab in human milk, the effects on the breast-fed infant, or the effects on milk production; however, maternal immunoglobulin G (IgG) is known to be present in human milk. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, the potential for viral transmission to SARS-CoV-2-negative infants, and the risk of an untreated or inadequately treated condition. Lactating mothers are advised to follow practices according to clinical guidelines to avoid exposing the infant to COVID-19. If a breast-feeding infant experiences an adverse effect related to a maternally administered drug, health care providers are encouraged to report the adverse effect to the FDA.
Casirivimab and imdevimab are recombinant human immunoglobulin G-1 (IgG1) monoclonal antibodies used in combination as an antiviral medication to target severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The antibodies bind to non-overlapping epitopes of the spike protein receptor binding domain (RBD) of SARS-CoV-2, which prevents the virus from interacting with the human ACE2 receptor. In Jurkat target cells expressing SARS-CoV-2 spike proteins, the combination of casirivimab plus imdevimab elicited antibody-dependent cell-mediated cytotoxicity (ADCC) with human natural killer (NK) effector cells and antibody-dependent cellular phagocytosis (ADCP) with human macrophages. However, the combination did not mediate complement-dependent cytotoxicity in cell-based assays. The estimated 50% effective concentration (EC50) of casirivimab plus imdevimab in neutralizing SARS-CoV-2 in Vero cells is 0.005 mcg/mL.
There is a potential for treatment failure due to the development of viral variants that are resistant to the combination of casirivimab and imdevimab. Health care providers are advised to consider the prevalence of SARS-CoV-2 variants in their area when considering treatment options. In cell culture studies, spike protein amino acid substitutions in variants showing reduced susceptibility to casirivimab alone include K417E (182-fold), K417N (7-fold), K417R (61-fold), Y453F (more than 438-fold), L455F (80-fold), E484K (25-fold), F486V (more than 438-fold), and Q493K (more than 438-fold). Variants showing reduced susceptibility to imdevimab alone include substitutions K444N (more than 755-fold), K444Q (more than 548-fold), K444T (more than 1,033-fold), and V445A (548-fold). Casirivimab and imdevimab together show reduced susceptibility to variants with substitutions K444T (6-fold) and V445A (5-fold). In neutralization assays of 39 different spike protein variants identified in circulating SARS-CoV-2, variants with reduced susceptibility to casirivimab alone included those with substitutions Q409E (4-fold), G476S (5-fold), S494P (5-fold), E484Q (9-fold), and Q493E (446-fold). Variants with reduced susceptibility to imdevimab alone included 1 with N439K (463-fold) substitution. Casirivimab and imdevimab together retained activity against all variants tested. Neutralization data for SARS-CoV-2 variant substitutions identified through global surveillance have found no change in susceptibility (i.e., less than 2-fold reduction) to casirivimab and imdevimab together. The variants and key substitutions are as follows:
It is unknown how these data correlate with clinical outcomes.
Casirivimab and imdevimab are administered via intravenous infusion. Data regarding the pharmacokinetics of casirivimab and imdevimab are limited; however, the pharmacokinetic profiles are expected to be consistent with the profile of other IgG1 monoclonal antibodies. Casirivimab and imdevimab are not metabolized by cytochrome P450 enzymes, nor are they renally excreted.
Affected cytochrome P450 isoenzymes: none
Monoclonal antibodies with a molecular weight greater than 69 kDa are known not to undergo renal elimination; therefore, renal impairment and dialysis are not expected to impact the pharmacokinetics of casirivimab (145.23 kDa) or imdevimab (144.14 kDa).
The recommended dosing regimen is expected to result in comparable serum exposures of casirivimab and imdevimab in pediatric patients (12 years and older weighing at least 40 kg) as observed in adults.
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