Bamlanivimab is a recombinant neutralizing human IgG1K monoclonal antibody (mAb) to the spike protein of SARS-CoV-2 and is unmodified in the Fc region. Bamlanivimab binds the spike protein with a dissociation constant KD = 0.071 nM and blocks spike protein attachment to the human ACE2 receptor with an IC50 value of 0.17 nM (0.025 μg/mL).
Etesevimab is a recombinant neutralizing human IgG1K mAb to the spike protein of SARS-CoV-2, with amino acid substitutions in the Fc region (L234A, L235A) to reduce effector function. Etesevimab binds the spike protein with a dissociation constant KD = 6.45 nM and blocks spike protein attachment to the human ACE2 receptor with an IC50 value of 0.32 nM (0.046 μg/mL).
Bamlanivimab and etesevimab bind to different but overlapping epitopes in the receptor binding domain (RBD) of the S-protein. Using both antibodies together is expected to reduce the risk of viral resistance.
A flat exposure-response relationship for efficacy was identified for bamlanivimab and etesevimab administered together within the dose range of 700 mg bamlanivimab and 1,400 mg etesevimab to 2,800 mg bamlanivimab and 2,800 mg etesevimab (4 and 2 times the authorized dose, respectively). This flat exposure-response relationship was assessed using available clinical data and pharmacokinetic/pharmacodynamic modeling [see Clinical Trial Results and Supporting Data for EUA (18.2)].
Pharmacokinetic profiles of bamlanivimab and etesevimab are linear and dose-proportional between 700 mg and 7000 mg following a single IV administration. There were no differences in PK of bamlanivimab between severe/moderate participants who were hospitalized and mild/moderate ambulatory participants. There were no differences in PK of etesevimab between mild/moderate ambulatory participants and healthy participants. There is no change in PK of bamlanivimab or etesevimab administered alone or together suggesting there is no interaction between the two antibodies.
The mean maximum concentration (Cmax) of 700 mg bamlanivimab was 196 μg/mL (90% CI: 102 to 378 μg/mL) following approximately 1 hour 700 mg IV infusion.
The mean maximum concentration (Cmax) of 1400 mg etesevimab is estimated to be 504 μg/mL (90% CI: 262 to 974 μg/mL) following approximately 1 hour IV infusion.
Bamlanivimab mean volume of distribution (V) was 2.87 L and 2.71 L for the central and peripheral compartments, respectively. The between subject variability was 23.2% CV.
Etesevimab mean volume of distribution (V) was 2.38 L and 1.98 L for the central and peripheral compartments, respectively. The between subject variability was 27.8% CV.
Bamlanivimab and etesevimab are expected to be degraded into small peptides and component amino acids via catabolic pathways in the same manner as endogenous IgG antibodies.
Bamlanivimab clearance (CL) was 0.27 L/hr (between subject variability 22.3% CV) and the mean apparent terminal elimination half-life was 17.6 days (between subject variability 15.8% CV). Following a single 700 mg IV dose, bamlanivimab was quantifiable for at least 29 days. The mean concentration was 22 μg/mL (90% CI: 10.7 to 41.6 μg/mL) on Day 29.
Etesevimab clearance (CL) was 0.128 L/hr (between subject variability 33.8% CV) and the mean apparent terminal elimination half-life was 25.1 days (between subject variability 29.2% CV). Following a single 1,400 mg IV dose, etesevimab was quantifiable for at least 29 days. The mean concentration was 111 μg/mL (90% CI: 57.4 to 199 μg/mL) on Day 29.
The PK profiles of bamlanivimab and etesevimab were not affected by age, sex, race, or disease severity based on a population PK analysis. Body weight had no clinically relevant effect on the PK of bamlanivimab or etesevimab in adults with COVID-19 over the body weight range of 41 kg to 173 kg [see Use in Specific Populations (11.4, 11.7)].
The PK of bamlanivimab and etesevimab in pediatric patients have not been evaluated.
Using modeling and simulation, the recommended dosing regimen is expected to result in comparable plasma exposures of bamlanivimab and etesevimab in pediatric patients ages 12 years of age or older who weigh at least 40 kg as observed in adult patients [see Use in Specific Populations (11.3)].
Bamlanivimab and etesevimab are not eliminated intact in the urine. Renal impairment is not expected to impact the PK of bamlanivimab and etesevimab, since mAbs with molecular weight >69 kDa are known not to undergo renal elimination. Similarly, dialysis is not expected to impact the PK of bamlanivimab and etesevimab [see Use in Specific Populations (11.5)].
Based on population PK analysis, there is no significant difference in PK of bamlanivimab or etesevimab in patients with mild hepatic impairment compared to patients with normal hepatic function. Bamlanivimab and etesevimab have not been studied in patients with moderate or severe hepatic impairment [see Use in Specific Populations (11.6)].
Bamlanivimab and etesevimab are not renally excreted or metabolized by cytochrome P450 enzymes; therefore, interactions with concomitant medications that are renally excreted or that are substrates, inducers, or inhibitors of cytochrome P450 enzymes are unlikely.
Prophylactic administration of bamlanivimab to female Rhesus macaques (n=3 or 4 per group) resulted in 1 to 4 log10 decreases in viral genomic RNA and viral replication (sub-genomic RNA) in bronchoalveolar lavage samples relative to control animals, but less of an impact on viral RNA in throat and nasal swabs following SARS-CoV-2 inoculation.
Prophylactic or therapeutic administration of etesevimab to male Rhesus macaques (n=3 per group) resulted in approximately 4 or 3 log10 average decreases, respectively, in viral genomic RNA in oropharyngeal swabs at Day 4 post infection relative to control animals.
The applicability of these findings to a prophylaxis or treatment setting is not known.
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