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Individuals are deemed to be at high risk for progressing to severe COVID-19 if they meet at least 1 of the following criteria:

• Elderly (65 years or older)
• Obesity or overweight
  • Body mass index (BMI) greater than 25 kg/m²
  • If age 12 to 17 years, BMI greater than or equal to 85^th percentile for age and gender based on CDC growth charts
• Pregnancy
• Chronic kidney disease
• Diabetes
• Immunosuppressive disease or receiving immunosuppressive therapy
• Cardiovascular disease (including congential heart disease) or hypertension
• Chronic lung disease (e.g., chronic obstructive pulmonary disease, moderate-to-severe asthma, interstitial lung disease, cystic fibrosis, pulmonary hypertension)
• Sickle cell disease
• Neurodevelopmental disorder (e.g., cerebral palsy) or other conditions that confer medical complexity (e.g., genetic or metabolic syndromes, severe congential anomalies)
• Medical-related technological dependency (e.g., tracheostomy, gastrostomy, positive pressure ventilation not related to COVID-19)

In addition, other medical conditions or factors (e.g., race, ethnicity) may also place individual patients at high risk, and authorization of casirivimab and imdevimab under the EUA is not limited to only those medical conditions or factors listed above. Health care providers are advised to consider the benefit-to-risk of an individual patient.[66127]

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 emergency use as a treatment for 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, including hospitalization or death. They are also authorized for use as post-exposure prophylaxis of COVID-19 in persons (12 years and older weighing at least 40 kg) exposed to SARS-CoV-2 who are at high risk for progressing to severe COVID-19 and are not fully vaccinated or are not expected to mount an adequate immune response to the complete COVID-19 vaccination. They are NOT authorized for treatment of 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 these drugs in hospitalized patients with COVID-19 who require high flow oxygen or mechanical ventilation may be associated with worsening clinical outcomes. Additionally, the combination is not authorized for pre-exposure prophylaxis, nor should it be used as a substitute for the COVID-19 vaccines.[66127] The National Institutes of Health (NIH) COVID-19 treatment guidelines recommend individuals who have recently been exposed to SARS-CoV-2 and have symptoms consistent with COVID-19 be evaluated for SARS-CoV-2 infection.

• If test results are positive for SARS-CoV-2, the NIH recommends using anti-SARS-CoV-2 monoclonal antibodies (including casirivimab and imdevimab) to treat nonhospitalized adults with mild to moderate COVID-19 who are at high risk of clinical progression as defined by the Emergency Use Authorization (EUA) criteria. Anti-SARS-CoV-2 antibodies should also be considered for treatment of high risk adults with mild to moderate COVID-19 who are hospitalized for a reason other than COVID-19. While these antibodies are not authorized for use in patients hospitalized due to severe COVID-19, they may be available through expanded access programs for patients who have not developed an antibody response or who are not expected to mount an effective immune response to SARS-CoV-2 infection. Treatment with 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.
• If test results are negative for SARS-CoV-2, consider use of casirivimab and imdevimab as post-exposure prophylaxis in adults who would be at high risk of clinical progression if infected (as defined by the EUA) and who are not fully vaccinated or are fully vaccinated but not expected to mount an adequate immune response. The NIH recommends a single prophylactic dose of casirivimab and imdevimab be administered as soon as possible, and preferably within 7 days of exposure; however, unlike the FDA's EUA, the NIH states there are insufficient data to recommend either for or against repeated dosing every 4 weeks for those who continue to have high risk exposures.

In situations where it is necessary to triage eligible patients (i.e., antibody shortages, logistical constraints), the NIH suggests prioritizing treatment dosing over post-exposure prophylaxis and prioritizing to unvaccinated/incompletely vaccinated high risk individuals or vaccinated individuals not expected to mount an adequate immune response over vaccinated individuals who are expected to have developed an adequate immune response. These considerations should NOT limit the use of anti-SARS-CoV-2 antibodies when there are no logistical constraints. 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.[65314]

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 emergency use as a treatment for 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, including hospitalization or death. They are also authorized for use as post-exposure prophylaxis of COVID-19 in persons exposed to SARS-CoV-2 who are at high risk for progressing to severe COVID-19 and are not fully vaccinated or are not expected to mount an adequate immune response to the complete COVID-19 vaccination. Under the Emergency Use Authorization (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:

• The option to accept or refuse casirivimab and imdevimab
• The significant known and potential risks and benefits of treatment, and the extent to which such potential risks and benefits are unknown
• Available alternative treatments and the risk and benefits of those alternatives
• The need to continue to self-isolate and use infection control measures (e.g., wear mask, isolate, social distance, avoid sharing personal items, clean and disinfect, frequent handwashing) according to CDC guidelines

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.[66127]

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.[66127]

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.[66127][66130]

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 using VSV VLP pseudotyped with spike protein variants identified in circulating SARS-CoV-2, variants with reduced susceptibility to casirivimab alone included those with substitutions E406D (51-fold), V445T (107-fold), E484Q (19-fold), G485D (5-fold), G476S (5-fold), F486L (61-fold), F486S (more than 715-fold), Q493E (446-fold), Q493R (70-fold), and S494P (5-fold). Variants with reduced susceptibility to imdevimab alone included those with substitutions P337L (5-fold), N439K (463-fold), N439V (4-fold), N440K (28-fold), K444L (153-fold), K444M (1,577-fold), G446V (135-fold), N450D (9-fold), Q493R (5-fold), Q498H (17-fold), and P499S (206-fold). The G476D substitution has a 4-fold impact on casirivimab and imdevimab together. 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:

• United Kingdom B.1.1.7 variant (Alpha): All spike protein substitutions found in this variant, including key variant N501Y
• South Africa B.1.351 variant (Beta): All spike protein substitutions found in this variant, including key variants K417N, E484K, and N501Y
• Brazil P.1 variant (Gamma): All spike protein substitutions found in this variant, including K417T, E484K, N501Y
• California B.1.427/B.1.429 variant (Epsilon): L452R
• New York B.1.526 variant (Iota): E484K
• NOTE: Not all New York B.1.526 isolates harbored the E484K substitution
• India B.1.617.1/B.1.617.3 variant (Kappa/no designation): L452R + E484Q
• India B.1.617.2 variant (Delta): L452R + T478K

It is unknown how these data correlate with clinical outcomes.[66127]

Casirivimab and imdevimab are administered together via intravenous infusion or subcutaneous injection. 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.[66127]

Affected cytochrome P450 isoenzymes: none