Clinical Pharmacology for Xevudy
Mechanism Of Action
Sotrovimab is a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antiviral drug [see Microbiology].
Pharmacokinetics
A summary of pharmacokinetic parameters following a single 500-mg IV infusion is presented in Table 1 based on population pharmacokinetic analyses:
Table 1. Summary of IV Sotrovimab Serum Pharmacokinetic Exposure Parameters
| Parametera |
Sotrovimab (500 mg IV) |
| Cmax, mcg/mL |
170.1 (53.4) |
| CD28, mcg/mL |
39.7 (37.6) |
| AUCD0-28b, day*mcg/mL |
1564 (34.4) |
a Parameters are reported as geometric mean (Geometric %CV).
b Based on a population pharmacokinetic analysis using data from a total of 1984 subjects across 5 clinical trials. |
The primary analysis in the clinical efficacy study COMET-ICE was conducted when the ancestral Wuhan-Hu-1 virus was predominant, with the most common SARS-CoV-2 variants being Alpha and Epsilon among participants in the study population, which was enrolled prior to the emergence of the Delta and Omicron variants (Table 3).
Specific Populations
Based on available population pharmacokinetic analyses of sotrovimab dosages of 500 mg or less, the pharmacokinetics of sotrovimab administered intravenously were not affected by age or sex; body weight was identified as a significant covariate on the pharmacokinetics of sotrovimab, but the impact is not anticipated to be clinically relevant.
Renal impairment is not expected to impact the pharmacokinetics of sotrovimab since mAbs with molecular weight >69 kDa do not undergo renal elimination. Similarly, dialysis is not expected to impact the pharmacokinetics of sotrovimab.
Microbiology
Mechanism Of Action
Sotrovimab is a recombinant human IgG1-kappa mAb that binds to a conserved epitope on the spike protein receptor binding domain of SARS-CoV-2 with a dissociation constant of KD = 0.21 nM but does not compete with human ACE2 receptor binding (IC50 value >33.6 nM [5 μg/mL]). Sotrovimab inhibits an undefined step that occurs after virus attachment and prior to fusion of the viral and cell membranes. The Fc domain of sotrovimab includes M428L and N434S amino acid substitutions (LS modification) that extend antibody half-life, but do not impact wild-type Fc-mediated effector functions in cell culture.
Antiviral Activity
The neutralization activity of sotrovimab against SARS-CoV-2 (isolate WA1/2020) was measured in a concentration response model using cultured Vero E6 cells. Sotrovimab neutralized SARS-CoV-2 with an average EC50 value of 0.67 nM (100.1 ng/mL).
Sotrovimab demonstrated cell culture FcγR activation using Jurkat reporter cells expressing FcγRIIa (low-affinity R131 and high affinity H131 alleles), FcγRIIIa (low-affinity F158 and high-affinity V158 alleles), and FcγRIIb. Sotrovimab exhibited antibody-dependent cell-mediated cytotoxicity (ADCC) in cell culture using isolated human natural killer (NK) cells following engagement with target cells expressing spike protein. Sotrovimab also elicited antibody-dependent cellular phagocytosis (ADCP) in cell-based assays using CD14+ monocytes targeting cells expressing spike protein.
Antibody Dependent Enhancement (ADE) Of Infection
The risk that sotrovimab could mediate viral uptake and replication by immune cells was studied in U937 cells, primary human monocytic dendritic cells, and peripheral blood mononuclear cells. This experiment did not demonstrate productive viral infection in immune cells exposed to SARS-CoV-2 in the presence of concentrations of sotrovimab from 1-fold down to 1000-fold below the EC50 value.
The potential for ADE was also evaluated in a hamster model of SARS-CoV-2 using sotrovimab. Intraperitoneal administration prior to inoculation resulted in a dose-dependent improvement in all measured outcomes (body weight, total viral RNA in the lungs, or infectious virus levels based on TCID50 measurements). No evidence of enhancement of disease was observed at any dose evaluated, including sub-neutralizing doses down to 0.05 mg/kg.
Antiviral Resistance
There is a potential risk of treatment failure due to the development of viral variants that are resistant to sotrovimab.
Cell Culture Studies
Spike protein amino acid substitution E340A emerged in cell culture selection of resistant virus and had a >100-fold reduction in activity in a pseudotyped virus-like particle (VLP) assay. This substitution is in the conserved epitope of sotrovimab, which is comprised of 23 amino acids. Pseudotyped VLP assessments in cell culture were performed using Wuhan-Hu-1, Omicron BA.1, and Omicron BA.2 spike proteins. The epitope amino acid substitutions P337H/K/L/N/R/T, E340A/I/K/G/Q/S/V, T345P, K356T, and L441N in the Wuhan-Hu-1 spike, conferred reduced susceptibility to sotrovimab based on observed fold-increase in EC50 value shown in parentheses: P337H (5.1), P337K (>304), P337L (>192), P337N (5.6), P337R (>192), P337T (10.6), E340A (>100), E340G (18.2), E340I (>190), E340K (>297), E340Q (>50), E340S (68), E340V (>200), T345P (225), K356T (5.9), and L441N (72). Epitope substitutions P337H (>631), K356T (>631), P337S (>609), E340D (>609), and V341F (5.9) in the Omicron BA.1 spike variant, and P337H (>117), P337S (>117), P337T (>117), E340D (>117), E340G (>117), K356T (>117), and K440D (5.1) in the Omicron BA.2 spike variant conferred reduced susceptibility to sotrovimab based on the observed fold-increase in EC50 value shown in parenthesis relative to each spike viral variant.
Table 2 provides cell culture neutralization data for SARS-CoV-2 variants. The clinical relevance of the fold reductions in susceptibility >5 is unknown. There are no data evaluating variants with fold reductions >5 in randomized controlled clinical studies.
Table 2. Sotrovimab Neutralization Data for SARS-CoV-2
| SARS-CoV-2 Variant |
Key Substitutions Testeda |
Fold Reduction in Susceptibilityb |
| Lineage |
WHO Nomenclature |
Pseudotyped VLP |
Authentic Virus |
| B.1.1.7 |
Alpha |
N501Y |
No change |
No change |
| B.1.351 |
Beta |
K417N+E484K+N501Y |
No change |
No change |
| P.1 |
Gamma |
K417T+E484K+N501Y |
No change |
No change |
| B.1.617.2 |
Delta |
L452R+T478K |
No change |
No change |
| AY.1 and AY.2 |
Delta [+K417N] |
K417N+L452R+T478K |
No change |
Not tested |
| AY.4.2 |
Delta [+] |
L452R+T478K |
No change |
Not tested |
| B.1.427/B.1.429 |
Epsilon |
L452R |
No change |
Not tested |
| B.1.526 |
Iota |
E484K |
No change |
Not tested |
| B.1.617.1 |
Kappa |
L452R+E484Q |
No change |
No change |
| C.37 |
Lambda |
L452Q+F490S |
No change |
Not tested |
| B.1.621 |
Mu |
R346K+E484K+N501Y |
No change |
Not tested |
| B.1.1.529/BA.1 |
Omicron |
G339D+S371L+S373P+ S375F+K417N+N440K+ G446S+S477N+T478K+ E484A+Q493R+G496S+ Q498R+N501Y+Y505H |
No change |
No change |
| BA.1.1 |
Omicron |
G339D+R346K+S371L+ S373P+S375F+K417N+ N440K+G446S+S477N+ T478K+E484A+Q493R+ G496S+Q498R+N501Y+ Y505H |
No change |
No change |
| BA.2 |
Omicron |
G339D+S371F+S373P+ S375F+T376A+D405N+ R408S+K417N+N440K+ S477N+T478K+E484A+ Q493R+Q498R+N501Y+ Y505H |
16 |
15.7c |
| BA.2.12.1 |
Omicron |
G339D+S371F+S373P+ S375F+T376A+D405N+ R408S+K417N+N440K+ L452Q+S477N+T478K+ E484A+Q493R+Q498R+ N501Y+Y505H |
16.6 |
25.1c |
| BA.2.75 |
Omicron |
G339H+S371F+S373P+ S375F+T376A+D405N+ R408S+K417N+N440K+ G446S+N460K+S477N+ T478K+E484A+Q498R+ N501Y+Y505H |
8.3 |
Not tested |
| BA.2.75.2 |
Omicron |
G339H+R346T+S371F+ S373P+S375F+T376A+ D405N+R408S+K417N+ N440K+G446S+N460K+ S477N+T478K+E484A+ F486S+Q498R+N501Y+ Y505H |
10 |
Not tested |
| BA.3 |
Omicron |
G339D+S371F+S373P+ S375F+D405N+K417N+ N440K+G446S+S477N+ T478K+E484A+Q493R+ Q498R+N501Y+Y505H |
7.3 |
Not tested |
| BA.4 |
Omicron |
G339D+S371F+S373P+ S375F+T376A+D405N+ R408S+K417N+N440K+ L452R+S477N+T478K+ E484A+F486V+Q498R+ N501Y+Y505H |
21.3 |
48.4c |
| BA.4.6 |
Omicron |
G339D+R346T+S371F+ S373P+S375F+T376A+ D405N+R408S+K417N+ N440K+L452R+S477N+ T478K+E484A+F486V+ Q498R+N501Y+Y505H |
57.9 |
Not tested |
| BA.5 |
Omicron |
G339D+S371F+S373P+ S375F+T376A+D405N+ R408S+K417N+N440K+ L452R+S477N+T478K+ E484A+F486V+Q498R+ N501Y+Y505H |
22.6 |
21.6c |
| BF.7/BA.5.2.6 |
Omicron |
G339D+R346T+S371F+ S373P+S375F+T376A+ D405N+R408S+K417N+ N440K+L452R+S477N+ T478K+E484A+F486V+ Q498R+N501Y+Y505H |
74.2 |
Not tested |
| BN.1 |
Omicron |
G339H+R346T+K356T+ S371F+S373P+S375F+ T376A+D405N+R408S+ K417N+N440K+G446S+ N460K+S477N+T478K+ E484A+F490S+Q498R+ N501Y+Y505H |
778 |
Not tested |
| BQ.1 |
Omicron |
G339D+S371F+S373P+ S375F+T376A+D405N+ R408S+K417N+N440K+ K444T+L452R+N460K+ S477N+T478K+E484A+ F486V+Q498R+N501Y+ Y505H |
28.5 |
Not tested |
| BQ.1.1 |
Omicron |
G339D+R346T+S371F+ S373P+S375F+T376A+ D405N+R408S+K417N+ N440K+K444T+L452R+ N460K+S477N+T478K+ E484A+F486V+Q498R+ N501Y+Y505H |
94 |
Not tested |
| XBB/XBB.1 |
Omicron |
G339H+R346T+L368I+ S371F+S373P+S375F+ T376A+D405N+R408S+ K417N+N440K+V445P+ G446S+N460K+S477N+ T478K+E484A+F486S+ F490S+Q498R+N501Y+ Y505H |
6.5 |
Not tested |
| XBB.1.5 |
Omicron |
G339H+R346T+L368I+ S371F+S373P+S375F+ T376A+D405N+R408S+ K417N+N440K+V445P+ G446S+N460K+S477N+ T478K+E484A+F486P+ F490S+Q498R+N501Y+ Y505H |
11.3 |
33.3c |
| XD |
Noned |
G339D+S371L+S373P+ S375F+K417N+N440K+ G446S+S477N+T478K+ E484A+Q493R+G496S+ Q498R+N501Y+Y505H |
Not tested |
No change |
a Substitutions in the spike receptor binding domain relative to wild-type are listed.
b Based on EC50 fold change compared to wild-type. No change: ≤5-fold change in EC50 value compared to wild-type.
c Sotrovimab inhibited authentic virus isolates of Omicron BA.2, BA.2.12.1, BA.4, BA.5, and XBB.1.5 lineages with maximum percentage inhibition in the range of 80% to 100%.
d Variant has not been named by the WHO. |
Clinical Studies
SARS-CoV-2 variants of concern or variants of interest (VOC/VOI) were detected in participants enrolled in COMET-ICE (Table 3).
Table 3. SARS-CoV-2 VOC/VOI Detected at ≥2% Prevalence in Sotrovimab-Treated Participants
| Clinical Study |
VOC/VOI |
Prevalence, % (n/N)a |
Participants Meeting Primary Clinical Endpointb |
| COMET-ICE |
Alpha (B.1.1.7) |
10% (35/338) |
1 |
| Epsilon (B.1.427/B.1.429) |
5% (16/338) |
1 |
| Gamma (P.1) |
3% (9/338) |
0 |
a n = number of sotrovimab-treated participants with the designated VOC/VOI; N = total number of sotrovimab-treated participants with SARS-CoV-2 spike sequence results.
b The primary clinical endpoint for progression was defined as hospitalization for >24 hours for acute management of any illness or death from any cause through Day 29. |
SARS-CoV-2 viruses with baseline and treatment-emergent substitutions at amino acid positions associated with reduced susceptibility to sotrovimab in cell culture were observed in COMET-ICE (Table 4). Of the 32 sotrovimab-treated participants with a substitution detected at amino acid positions 337 and/or 340 at any visit baseline or post-baseline, only 1 met the primary endpoint for progression of hospitalization for >24 hours for acute management of any illness or death from any cause through Day 29. This participant had E340K detected post-baseline and was infected with the Epsilon variant of SARS-CoV-2.
Table 4. Baseline and Treatment-Emergent Substitutions Detected in Sotrovimab-Treated Participants at Amino Acid Positions Associated with Reduced Susceptibility to Sotrovimab
| Clinical Study |
Baselinea |
Treatment-Emergentb |
| Substitutions |
Frequency, % (n/N) |
Substitutions |
Frequency, % (n/N) |
| COMET-ICE |
P337H, E340A |
1% (4/307) |
P337L/R, E340A/K/V |
14% (24/170)c |
a n = number of sotrovimab-treated participants with a baseline substitution detected at spike amino acid positions 337 or 340; N = total number of sotrovimab-treated participants with baseline sequence results.
b n = number of sotrovimab-treated participants with treatment-emergent substitutions detected at spike amino acid positions 337 or 340; N = total number of sotrovimab-treated participants with paired baseline and post-baseline sequence results.
c Four participants with a post-baseline substitution at P337 or E340 and lacking a baseline sequence are not included. |
Immune Response Attenuation
There is a theoretical risk that antibody administration may attenuate the endogenous immune response to SARS-CoV-2 and make patients more susceptible to re-infection.
Immunogenicity
As with all therapeutic proteins, there is potential for immunogenicity. The detection of antibody formation is highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of antibody (including neutralizing antibody) positivity in an assay may be influenced by several factors including assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of the incidence of antibodies in the studies described below with the incidence of antibodies in other studies may be misleading.
Treatment-emergent anti-drug antibodies (ADAs) to sotrovimab were detected in 13% (65/513) of participants, through week 24, in the COMET-ICE study. None of the participants with confirmed treatment-emergent ADAs had neutralizing antibodies against sotrovimab.
Animal Toxicology And/Or Pharmacology
In a Syrian Golden hamster model of SARS-CoV-2 infection, antiviral activity was demonstrated using a single dose of sotrovimab which was administered intraperitoneally at 24- or 48-hours prior to infection. Animals receiving 5 mg/kg or more of the antibody showed a significant improvement in body weight loss and significantly decreased total lung SARS-CoV-2 viral RNA compared to vehicle only and control antibody-treated animals. Levels of virus in the lung (as measured by TCID50) were significantly decreased versus controls in hamsters receiving 0.5 mg/kg or more of the antibody.
Protection was also observed in the Syrian Golden hamster model using the SARS-CoV-2 B.1.351 (Beta, South Africa origin) variant. Significant reductions in total and replication competent virus were observed on Day 4 post-infection in animals receiving a single intraperitoneal dose of 0.5, 2, 5, or 15 mg/kg sotrovimab compared to isotype control antibody-treated animals.
Clinical Studies
The clinical data supporting this EUA are based on the analysis of the Phase 1/2/3 COMET-ICE trial (NCT04545060) with supporting data from the Phase 3 COMET-TAIL trial (NCT04913675).
COMET-ICE (Study 214367)
COMET-ICE was a randomized, multi-center, double-blind, placebo-controlled trial studying sotrovimab for the treatment of subjects with mild-to-moderate COVID-19 (subjects with COVID-19 symptoms who were not hospitalized). Eligible subjects were 18 years of age and older with at least one of the following comorbidities: diabetes, obesity (BMI >30), chronic kidney disease, congestive heart failure, chronic obstructive pulmonary disease, or moderate to severe asthma; or were 55 years of age and older regardless of comorbidities. The trial included symptomatic subjects with SARS-CoV-2 infection as confirmed by local laboratory tests and/or point of care tests and symptom onset within 5 days of enrollment. The study was conducted when the wild-type Wuhan-Hu-1 virus was predominant, with the highest frequency of variants being Alpha and Epsilon [see Microbiology]. Subjects with severe COVID-19 requiring supplemental oxygen or hospitalization and severely immunocompromised subjects were excluded from the trial.
A total of 1,057 eligible subjects were randomized to receive a single 500-mg infusion of sotrovimab (n = 528) or placebo (n = 529) over 1 hour (Intent to Treat [ITT] population at Day 29). At baseline, the median age was 53 years (range:17 to 96); 20% of subjects were 65 years of age or older and 11% were over 70 years of age; 46% of subjects were male; 87% were White, 8% Black or African American, 4% Asian, 65% Hispanic or Latino. Fifty-nine percent of subjects received sotrovimab or placebo within 3 days of COVID-19 symptom onset and 41% within 4 to 5 days. The four most common pre-defined risk factors or comorbidities were obesity (63%), 55 years of age or older (47%), diabetes requiring medication (22%), and moderate-to-severe asthma (17%). Overall, baseline demographic and disease characteristics were well balanced between the treatment arms.
The primary endpoint, progression of COVID-19 at Day 29, was reduced by 79% (adjusted relative risk reduction) in recipients of sotrovimab versus placebo. Table 5 provides the results for the primary and key secondary endpoint of COMET-ICE.
Table 5. Efficacy Results in Adults with Mild-to-Moderate COVID-19 in COMET-ICE at Day 29
|
Sotrovimab 500 mg
n = 528 |
Placebo
n = 529 |
| Progression of COVID-19 (defined as hospitalization for >24 hours for acute management of any illness or death from any cause) (Day 29)a |
| Proportion (n, %) |
6 (1.1%) |
30 (5.7%) |
Adjusted Relative Risk Reduction
(95% CI) |
79%
(50%, 91%) |
| All-cause mortality (up to Day 29) |
| Proportion (n, %) |
0 |
2 (<1%) |
| a The determination of primary efficacy was based on a planned interim analysis of 583 subjects, which had similar findings to those seen in the full population above. The adjusted relative risk reduction was 85% with a 97.24% CI of (44%, 96%) and p-value = 0.002. |
Within the subset of the ITT population who had a central laboratory confirmed, virologically quantifiable nasopharyngeal swab at Day 1 and Day 8 (n = 639), the mean decline in viral RNA levels from baseline to Day 8 was greater in subjects treated with sotrovimab (-2.610 log10 copies/mL) compared to that in subjects treated with placebo (-2.358); mean difference = -0.251, 95% CI: (-0.415, -0.087).
COMET-TAIL (Study 217114)
COMET-TAIL was a randomized, multi-center, open label trial which evaluated the efficacy, safety, and tolerability of sotrovimab for the treatment of subjects with mild-to-moderate COVID-19 (subjects with COVID-19 symptoms who were not hospitalized). Eligible subjects were 12 years of age or older with at least one of the following comorbidities: diabetes, obesity (BMI ≥85th percentile for age/gender based on Centers for Disease Control and Prevention [CDC] growth charts for adolescents or BMI ≥30 for subjects ≥18 years old), chronic kidney disease, congenital heart disease, congestive heart failure (for subjects ≥18 years old), chronic lung diseases, sickle cell disease, neurodevelopmental disorders, immunosuppressive disease or receiving immunosuppressive medications, or chronic liver disease; or were 55 years of age or older regardless of comorbidities. The trial included symptomatic subjects with SARS-CoV-2 infection as confirmed by local laboratory tests and/or point of care tests and symptom onset within 7 days of enrollment. Subjects with severe COVID-19 requiring supplemental oxygen or hospitalization were excluded from the trial.
The ITT population consisted of 385 subjects randomized to receive a single 500-mg IV infusion of sotrovimab over 15 minutes. The primary analysis population, which excluded 7 subjects because they were fully vaccinated and immunocompetent (key inclusion/exclusion violation), consisted of 378 subjects.
In the primary analysis population at baseline, the median age was 51 years (range:15 to 90, including 2 subjects under 18 years); 25% of subjects were 65 years of age or older and 8% were over 75 years of age; 42% of subjects were male; 96% were White and 4% were Black or African American; 83% were Hispanic or Latino. Forty-eight percent (48%) of subjects received sotrovimab within 3 days of COVID-19 symptom onset, 37% within 4 to 5 days, and 14% within 6 to 7 days. The four most common pre-defined risk factors or comorbidities were obesity (63%), 55 years of age or older (42%), chronic lung disease (16%), and diabetes requiring medication (13%).
In the primary analysis population, 5 (1.3%) of 378 subjects had progression to COVID-19 defined as hospitalization for >24 hours for acute management of any illness or death due to any cause through Day 29. No deaths were reported through Day 29.