Available data suggest a positive relationship between serum neutralizing antibody titers and COVID-19 pre-exposure-prophylactic efficacy using clinical data (completed prior to the emergence of Omicron and Omicron lineage VOCs) and drug concentration data of neutralizing human monoclonal antibodies against SARS-CoV-2.
Following single-dose administration of pemivibart 4500 mg IV, calculated geometric mean titer values (pemivibart concentration divided by the authentic virus neutralization assay EC50 value against JN.1) [see Microbiology] range from 3451 (on Day 90) to 22552 (end of infusion on Day 1). After the repeat dose of pemivibart 4500 mg IV every 3 months, it is anticipated that the range of titers at steady-state will be approximately 33% higher than those observed following the first dose administration.
A summary of PK parameters of pemivibart following administration of a single 4500 IV dose of pemivibart to adults based on population PK modeling is provided in Table 1.
The PK of pemivibart was not substantially affected by age, sex, or race based on a population PK analysis to the pooled data from VYD222-1-001 and Phase 3 CANOPY. Body weight is not expected to have a clinically relevant effect on the PK of pemivibart in individuals with body weights ranging from 43 to 190 kg through 3 months postdose.
Population PK analysis showed immune compromise status had no clinically relevant effect on the PK of pemivibart.
The PK of pemivibart in pediatric individuals has not been evaluated. The dosing regimen is expected to result in comparable plasma exposures of pemivibart in pediatric individuals 12 years of age or older who weigh at least 40 kg as observed in adult individuals [see Use In Specific Populations].
Renal impairment is not expected to impact the PK of pemivibart since mAbs with molecular weight >69 kDa are known not to undergo renal elimination. Similarly, dialysis is not expected to impact the PK of pemivibart.
Pemivibart is not anticipated to be impacted by hepatic impairment. Pemivibart is expected to be degraded into small peptides and amino acids via catabolic pathways in the same manner as other IgG mAbs and human endogenous IgG antibodies.
Pemivibart is a recombinant human monoclonal IgG1λ antibody that targets the SARS-CoV-2 spike protein receptor binding domain (RBD), thereby inhibiting virus attachment to the human ACE2 receptor on host cells. Amino acid substitutions in the Fc region (M435L/N441A) of pemivibart extend serum half-life. Pemivibart binds the spike RBD proteins of ancestral SARS-CoV-2 B.1 (D614G) and Omicron variants BA.1, BA.2, and BA.4/5 with equilibrium dissociation constants (KD) of 2.1 nM, 18 nM, 13.5 nM, and 15.9 nM, respectively, and blocks attachment of ancestral SARS-CoV-2 and BA.2.86 variant RBD proteins to the human ACE2 receptor with IC50 values of 0.068 nM (10 ng/mL) and 23 nM (3370 ng/mL), respectively.
Pemivibart neutralized authentic SARS-CoV-2 isolates in Vero E6 or Vero E6-TMPRSS2 cells with EC50 values of 0.165-0.230 nM (24.3-34 ng/mL) against B.1, and 0.075 nM (11 ng/mL) against B.1.617.2 (Delta). For Omicron variants, EC50 values were 0.096 nM (14.2 ng/mL) against BA.1, 0.039 nM (5.8 ng/mL) against BA.2, 0.175 nM (25.8 ng/mL) against BA.4.1, 0.80-4.48 nM (118-661.2 ng/mL) against XBB.1.16, 1.97-3.25 nM (290-479.9 ng/mL) against XBB.1.5, 9.8 nM (1,445 ng/mL) against EG.5.1, 3.59 nM (529.4 ng/mL) against HV.1, and 0.43 nM (63.6 ng/mL) against JN.1.
Pemivibart has not been directly evaluated for Fc-mediated effector functions or antibody-dependent enhancement (ADE) of infection. The parent antibody of pemivibart, which contains an identical Fc region and targets an overlapping epitope, exhibited antibody-dependent cellular phagocytosis (ADCP) and antibody-dependent complement deposition (ADCD), but failed to exhibit detectable ADE in cell culture.
There is a potential risk of prophylaxis failure due to the emergence of a pemivibart-resistant SARS-CoV-2 variant. Prescribing healthcare providers should consider the prevalence of SARS-CoV-2 variants in their area, where data are available, when considering prophylactic treatment options.
Data are limited regarding the scope of spike substitutions in Omicron-lineage variants that may confer significantly reduced susceptibility to pemivibart. Escape variants were identified following serial passage of SARS-CoV-2 (Omicron XBB.1.5.6) in cell culture in the presence of pemivibart that contained a T500N spike substitution or a combination of Q489R, N501Y, and Y505H spike substitutions. Each of these substitutions is within 5 Ã… of the pemivibart binding interface.
Pemivibart neutralization susceptibility of recent and historic SARS-CoV-2 variants was evaluated using a pseudotyped, luciferase-expressing, lentivirus virus-like particle (VLP) assay. Pemivibart neutralized SARS-CoV-2 spike protein-pseudotyped VLPs representing B.1 and pre-Omicron variants with EC50 values ranging from 0.022 to 0.083 nM (3.2 to 12.2 ng/mL), and Omicron-lineage variants with EC50 values ranging from 0.198 to 14.3 nM (29.2 to 2,112 ng/mL) (Table 2).
| Pango lineage |
RBD substitutions relative to B.1 present in pseudotyped VLPs |
Pemivibart |
| Mean EC50 values ng/mL (SD / range)a |
Fold-change from B.1 |
| B.1 |
|
8.4 (3) |
1.0 |
| B.1.1.7 |
N501Y |
11.4 |
1.4 |
| B.1.351 |
K417N, E484K, N501Y |
9 |
1.1 |
| P.1 |
K417T, E484K, N501Y |
12.2 |
1.5 |
| B.1.617.2 |
L452R, T478K |
5.2
(4.2-6.2) |
0.6 |
| B.1.427 |
L452R |
3.2 |
0.4 |
| P.2 |
E484K |
9.3 |
1.1 |
| B.1.526 |
E484K |
8.6 |
1.0 |
| B.1.621 |
R346K, E484K, N501Y |
9.5 |
1.1 |
| BA.1 |
G339D, S371L, S373P, S375F, K417N, N440K, G446S, S477N, T478K, E484A, Q493R, G496S, Q498R, N501Y, Y505H |
121.4 |
14.5 |
| BA.2 |
G339D, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, S477N, T478K, E484A, Q493R, Q498R, N501Y, Y505H |
44.6 (6.5) |
5.3 |
| BA.4/BA.5 |
G339D, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, L452R, S477N, T478K, E484A, F486V, Q498R, N501Y, Y505H |
47.9 (29.7-66.2) |
5.7 |
| BA.4.6 |
G339D, R346T, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, L452R, S477N, T478K, E484A, F486V, Q498R, N501Y, Y505H |
29.2 |
3.5 |
| BF.7 |
G339D, R346T, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, L452R, S477N, T478K, E484A, F486V, Q498R, N501Y, Y505H |
72.7 |
8.7 |
| BQ.1 |
G339D, R346T, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, K444T, L452R, S477N, T478K, E484A, F486V, Q498R, N501Y, Y505H |
164.6 |
19.6 |
| BQ.1.1 |
G339D, R346T, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, K444T, L452R, N460K, S477N, T478K, E484A, F486V, Q498R, N501Y, Y505H |
102.1 |
12.2 |
| BA.2.75 |
G339H, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, G446S, N460K, S477N, T478K, E484A, Q498R, N501Y, Y505H |
1,364.6 |
162.5 |
| BN.1 |
G339H, R346T, K356T, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, G446S, N460K, S477N, T478K, E484A, F490S, Q498R, N501Y, Y505H |
2,112 |
251.4 |
| XBB |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, N460K, S477N, T478K, E484A, F486S, F490S, Q493R, Q498R, N501Y, Y505H |
152.2 |
18.1 |
| XBB.1 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, N460K, S477N, T478K, E484A, F486S, F490S, Q493R, Q498R, N501Y, Y505H |
121.1 |
14.4 |
| XBB.1.5 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, N460K, S477N, T478K, E484A, F486P, F490S, Q498R, N501Y, Y505H |
104.3 |
12.4 |
| XBB.1.16 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, N460K, S477N, T478R, E484A, F486P, F490S, Q498R, N501Y, Y505H |
77.6 (18.1) |
9.2 |
| XBB.1.5.10 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, F456L, N460K, S477N, T478K, E484A, F486P, F490S, Q498R, N501Y, Y505H |
108.1 (35.5) |
12.9 |
| XBB.1.5.1 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, N460K, S477N, T478K, E484A, F486P, F490S, Q498R, N501Y, Y505H |
80 (8.9) |
9.5 |
| XBB.2.3 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, N460K, S477N, T478K, E484A, F486P, F490S, Q498R, N501Y, Y505H, P521S |
87 (15.5) |
10.4 |
| EU.1.1 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, I410V, K417N, N440K, V445P, G446S, N460K, S477N, T478K, E484A, F486P, F490S, Q498R, N501Y, Y505H, P521S |
52.1 (10.6) |
6.2 |
| FL.1.5.1 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, F456L, N460K, S477N, T478R, E484A, F486P, F490S, Q498R, N501Y, Y505H |
102.1 (8.8) |
12.2 |
| HV.1 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, L452R, F456L, N460K, S477N, T478K, E484A, F486P, F490S, Q498R, N501Y, Y505H |
41.2 (9.2) |
4.9 |
| HK.3 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, L455F, F456L, N460K, S477N, T478K, E484A, F486P, F490S, Q498R, N501Y, Y505H |
72.3 (7.7) |
8.6 |
| JD.1.1 |
G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, L455F, F456L, N460K, A475V, S477N, T478K, E484A, F486P, F490S, Q498R, N501Y, Y505H |
101.9 (4.9) |
12.3 |
| BA.2.86 |
I332V, G339H, K356T, S371F, S373P, S375F, T376A, R403K, D405N, R408S, K417N, N440K, V445H, G446S, N450D, L452W, N460K, S477N, T478K, N481K, del483, E484K, F486P, Q498R, N501Y, Y505H |
167.7 (4.4) |
20.0 |
| JN.1 |
I332V, G339H, K356T, S371F, S373P, S375F, T376A, R403K, D405N, R408S, K417N, N440K, V445H, G446S, N450D, L452W, L455S, N460K, S477N, T478K, N481K, del483, E484K, F486P, Q498R, N501Y, Y505H |
74.6 (5.8) |
8.9 |
EC50=half-maximal inhibitory concentration; Pango=Phylogenetic Assignment of Named Global Outbreak; RBD=receptor binding domain; SARS-CoV-2=severe acute respiratory syndrome coronavirus 2; WT=wild-type.
a EC50 values are reported as the mean along with range when data were obtained from 2 independent experiments or as mean and standard deviation when data were obtained from 3 or more independent experiments. 5,000 ng/mL was the upper concentration tested. |
Evaluations are ongoing of the pemivibart neutralization susceptibility of variants that have been identified through global surveillance.
Cross-resistance is not expected between pemivibart and currently approved/authorized COVID-19 therapies, including remdesivir, nirmatrelvir, or molnupiravir, since pemivibart has a distinct mechanism of action and targets a different viral protein than these drugs.
There are no immunogenicity data available for the currently authorized dosing regimen of PEMGARDA 4500 mg IV administered every 3 months.
In a toxicology study in rats, pemivibart had no adverse effects when administered intravenously.
In tissue cross-reactivity studies with pemivibart using human adult and fetal tissues, no off-target binding was detected.
To support this EUA, an immunobridging approach was used to determine if PEMGARDA may be effective for pre-exposure prophylaxis of COVID-19. Immunobridging is based on the serum neutralization titer-efficacy relationships identified with other neutralizing human monoclonal antibodies against SARS-CoV-2. This includes adintrevimab, the parent mAb of pemivibart, and other mAbs that were previously authorized for EUA. To support immunobridging, serum neutralization titer was utilized to compare PEMGARDA to previous mAbs [see CLINICAL PHARMACOLOGY].
CANOPY [NCT06039449] is an ongoing clinical trial evaluating PEMGARDA for the pre-exposure prophylaxis of COVID-19 in adults ≥18 years of age in two cohorts.
A total of 623 participants, 306 in Cohort A and 317 in Cohort B, received at least one dose of PEMGARDA 4500 mg in the trial. In Cohort A, 296 participants received a second dose of PEMGARDA 4500 mg at Month 3. In Cohort B, 162 participants received at least one dose of placebo, and a total of 450 participants received a second dose of either PEMGARDA 4500 mg or placebo (blinded) at Month 3. The trial excluded participants with known or suspected SARS-CoV-2 infection within 120 days before randomization or a positive SARS-CoV-2 antigen test or RT-PCR at the time of screening. The primary data to support this EUA comes from Cohort A and is summarized below.
Participants in Cohort A were mostly female (61%), White (86%) or Black/African American (12%), and not Hispanic or Latino (94%). The median age was 59 years, with 31% aged 65 years or older. All participants had underlying moderate-to-severe immune compromise, including:
The primary efficacy objective of Cohort A was to evaluate protection against symptomatic COVID-19 based on calculated titers against SARS-CoV-2 following PEMGARDA administration by immunobridging to historical data from the EVADE study, which provided evidence of clinical efficacy of adintrevimab, the parent mAb of pemivibart. The primary immunobridging endpoint for Cohort A compared the ratio of the geometric mean titers between pemivibart against the relevant variant (JN.1) at Day 28 to the reference titer at Day 28. The reference titer at Day 28 was the extrapolated titer from the Day 90 adintrevimab titer [which was calculated based on Day 90 concentration of adintrevimab divided by the EC50 value against the B.1.617.2 (Delta) variant determined in an authentic virus neutralization assay] using the half-life of pemivibart. Immunobridging would be established if the lower limit of the 2-sided 90% CI of the ratio of the geometric mean titer value is greater than 0.8.
The primary immunobridging results are as follows: the geometric mean ratio between the calculated titer for pemivibart against JN.1 (based on an authentic virus neutralization assay EC50 value of 63.6 ng/mL) and the calculated titer for adintrevimab against Delta (based on a similar authentic virus neutralization assay EC50 value of 7 ng/mL) was 0.82 (90% CI: 0.80-0.85). However, there are limitations of this analysis, including differences in the methodologies of the assays used to determine the EC50 values for pemivibart and adintrevimab against the respective variants. In a sensitivity analysis using an identical cell-based assay (a pseudotyped VLP neutralization assay), for the calculated titer comparison between pemivibart against JN.1 (based on an EC50 value of 74.6 ng/mL) and adintrevimab against Delta (based on an EC50 value of 3.5 ng/mL), the geometric mean ratio was 0.35 (90% CI: 0.34-0.36). This sensitivity analysis highlights the impact of even modest differences in EC50 values on the results of the primary endpoint.
Based on the totality of scientific evidence available, it is reasonable to believe that PEMGARDA may be effective for pre-exposure prophylaxis of COVID-19 in the authorized population. The calculated pemivibart serum neutralizing antibody titers were consistent with the titer levels associated with efficacy in prior clinical trials of adintrevimab and certain other monoclonal antibody products previously authorized for the prevention of COVID-19.
There are limitations of the data supporting the benefits of PEMGARDA. Evidence of clinical efficacy for other neutralizing human monoclonal antibodies against SARS-CoV-2 was based on different populations and SARS-CoV-2 variants that are no longer circulating. Additionally, the variability associated with cell-based EC50 value determinations, along with limitations related to PK data and efficacy estimates for the mAbs in prior clinical trials, impact the ability to precisely estimate protective titer ranges.