Multiple studies of vaccinated and convalescent cohorts have demonstrated that serum neutralizing antibody (nAb) titers correlate with protection against coronavirus disease 2019 (COVID-19). However, the induction of multiple layers of immunity after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure has complicated the establishment of nAbs as a mechanistic correlate of protection (CoP) and hindered the definition of a protective nAb threshold. Here, we show that a half-life–extended monoclonal antibody (adintrevimab) provides about 50% protection against symptomatic COVID-19 in SARS-CoV-2–naïve adults at serum nAb titers on the order of 1:30. Vaccine modeling results support a similar 50% protective nAb threshold, suggesting that low titers of serum nAbs protect in both passive antibody prophylaxis and vaccination settings. Extrapolation of adintrevimab pharmacokinetic data suggests that protection against susceptible variants could be maintained for about 3 years. The results provide a benchmark for the selection of next-generation vaccine candidates and support the use of broad, long-acting monoclonal antibodies as alternatives or supplements to vaccination in high-risk populations.

Multiple studies of vaccinated and convalescent cohorts have demonstrated that serum neutralizing antibody (nAb) titers correlate with protection against COVID-19. However, the induction of multiple layers of immunity following SARS-CoV-2 exposure has complicated the establishment of nAbs as a mechanistic correlate of protection (CoP) and hindered the definition of a protective nAb threshold. Here, we show that a half-life extended monoclonal antibody (adintrevimab) provides approximately 50% protection against symptomatic COVID-19 in SARS-CoV-2-naive adults at low serum nAb titers on the order of 1:30. Vaccine modeling supports a similar 50% protective nAb threshold, suggesting low levels of serum nAb can protect in both monoclonal and polyclonal settings. Extrapolation of adintrevimab pharmacokinetic data suggests that protection against susceptible variants could be maintained for approximately 3 years. The results provide a benchmark for the selection of next-generation vaccine candidates and support the use of broad, long-acting monoclonal antibodies as an alternative or supplement to vaccination in high-risk populations.

Background ADG20 is a fully human IgG1 monoclonal antibody engineered to have high potency and broad neutralization against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other SARS-like CoVs with pandemic potential by binding to a highly conserved epitope in the receptor-binding domain (RBD) of the spike protein. The Fc region of ADG20 has been modified to provide an extended half-life. ADG20 is in clinical development for the treatment and prevention of COVID-19. Methods This is an ongoing Phase 1, randomized, placebo (PBO)-controlled, single ascending-dose study of ADG20 administered intramuscularly (IM) or intravenously (IV) to healthy adults aged 18–50 years with no evidence of prior or current SARS-CoV-2 infection. Participants were randomized 8:2 in 3 cohorts (N=10/cohort: n=8 ADG20, n=2 PBO): ADG20 300 mg IM, 500 mg IV, and 600 mg IM. Safety, tolerability, PK, and sVNA titers were assessed up to 3 months post dose. Serum ADG20 concentrations were measured with a validated hybrid ligand binding liquid chromatography–mass spectrometry (MS)/MS assay. sVNA titers against authentic SARS-CoV-2 were determined by a plaque reduction neutralization assay. Results Overall, 30 participants received ADG20 (n=24) or PBO (n=6). Blinded safety data for all cohorts and PK/sVNA titer data for the 300 mg IM cohort are reported. Through a minimum of 10 weeks post dose, no study drug-related adverse events (AEs), serious AEs, injection site reactions, or hypersensitivity reactions were reported. The observed preliminary PK profile was dose proportional, consistent with an extended half-life monoclonal antibody, and well predicted by translational physiologically-based PK modeling. The measured 50% sVNA titer (MN50; geometric mean [coefficient of variation, %]) was 1382 (32.7%) 13 days after a single 300 mg IM dose. These values are within the range of peak serum neutralizing antibody titers reported for COVID-19 mRNA vaccines. Conclusion A single dose of ADG20, up to 600 mg IM, was well tolerated. Preliminary PK and sVNA titer profiles support the ongoing Phase 2/3 trials of ADG20 at a 300 mg IM dose for the prevention of COVID-19 (EVADE: NCT04859517) and treatment of ambulatory patients with mild to moderate COVID-19 (STAMP: NCT04805671). Disclosures Helen Paguntalan, MD, Adagio Therapeutics, Inc. (Scientific Research Study Investigator) Zoltán Magyarics, MD, PhD, Adagio Therapeutics, Inc. (Consultant) Lynn E. Connolly, MD, PhD, Adagio Therapeutics, Inc. (Employee) Ellie Hershberger, PharmD, Adagio Therapeutics, Inc. (Employee) Kristin Narayan, PhD, Adagio Therapeutics, Inc. (Employee) Deepali Gupta, BS, Adagio Therapeutics, Inc. (Employee) Paul G. Ambrose, PharmD, Adagio Therapeutics, Inc. (Employee) Frank Engler, PhD, Adagio Therapeutics, Inc. (Independent Contractor) Ed Campanaro, BSN, MSHS, Adagio Therapeutics, Inc. (Employee) Anita F. Das, PhD, Adagio Therapeutics, Inc. (Consultant) Pete Schmidt, MD, Adagio Therapeutics, Inc. (Employee)

Introduction Adintrevimab is a fully human immunoglobulin G1 extended half-life monoclonal antibody that was developed to have broad neutralization against SARS-CoV, SARS-CoV-2, and other SARS-like CoVs with pandemic potential. Here we report the safety, pharmacokinetics (PK), serum viral neutralizing antibody (sVNA) titers, and immunogenicity results of the first three cohorts evaluated in the first-in-human study of adintrevimab in healthy adults. Methods This is a phase 1, randomized, placebo-controlled, single ascending-dose study of adintrevimab administered intramuscularly (IM) or intravenously (IV) to healthy adults aged ≥ 18–55 years with no current or prior SARS-CoV-2 infection. Participants were randomized 8:2 to adintrevimab or placebo in each of three dose cohorts: adintrevimab 300 mg IM (cohort 1), 500 mg IV (cohort 2), and 600 mg IM (cohort 3). Follow-up was 12 months. Blood samples were taken predose and at multiple time points postdose up to month 12 to assess sVNA, PK, and antidrug antibodies (ADAs). Results Thirty participants received a single dose of adintrevimab ( n = 24; 8 per cohort) or placebo ( n = 6). All except one adintrevimab participant in cohort 1 completed the study. No participants in any treatment arm experienced a study drug-related adverse event. Across adintrevimab-treated participants, 11 (45.8%) experienced at least one TEAE. All but one TEAE were mild in severity, and all were either viral infection or respiratory symptoms. There were no serious adverse events, discontinuations due to adverse events, or deaths. Adintrevimab exhibited a linear and dose-proportional PK profile and extended serum half-life (mean 96, 89, and 100 days in cohorts 1, 2, and 3, respectively). Participants receiving adintrevimab demonstrated dose-dependent increased sVNA titers and breadth across multiple variants. Conclusion Adintrevimab at doses of 300 mg IM, 500 mg IV, and 600 mg IM was well tolerated in healthy adults. Adintrevimab demonstrated dose-proportional exposure, rapid development of neutralizing antibody titers, and an extended half-life. Supplementary Information The online version contains supplementary material available at 10.1007/s40121-023-00794-1.

Background Peak SARS-CoV-2 viral replication occurs in the upper respiratory tract in presymptomatic and early symptomatic phases. Administration of a monoclonal antibody may be most beneficial in the early time period immediately after symptom onset. Here we describe the effect of early therapy on efficacy in patients receiving ADI. Methods High risk patients with mild or moderate COVID-19 were enrolled in the ADI treatment study (STAMP), with primary endpoint of COVID-19 related hospitalization or all-cause death through Day 29 in patients with disease due to confirmed or suspected SARS-CoV-2 variants other than Omicron. Patients were randomized 1:1 to receive ADI or placebo administered by a single intramuscular (IM) injection. For this subgroup analysis, patients that had received therapy within 3 days of symptom onset were evaluated. Results In the overall population, the study met the primary endpoint demonstrating 66% relative risk reduction of COVID-19 hospitalization or all cause death in 336 patients. Among 261 patients receiving therapy within 3 days of symptom onset (n=133 ADI, n=128 placebo), ADI was associated with a statistically significant reduction in the risk of COVID-19-related hospitalization or all-cause death through Day 29 compared with placebo (4 [3%] vs. 15 [11.7%], standardized risk difference -8%, 95% CI: -14.11, -1.86, p=0.0106), demonstrating a 72% standardized relative risk reduction in favor of ADI. When given as early therapy, ADI provided a greater reduction in viral load from baseline to Day 5 compared with placebo as assessed by saliva samples, with an adjusted least-squares mean difference of -0.97 log10 copies/mL (95% CI: -1.540, -0.391; p=0.0011). No study drug related SAEs, including deaths, and no hypersensitivity reactions were reported. Conclusion Early therapy with a single dose of ADI 300 mg IM provided a 72% reduction in the risk of COVID-19 related hospitalization and all-cause death compared to placebo in high-risk ambulatory patients with mild to moderate COVID-19. Therapy within the first 3 days also led to a greater reduction in viral load compared to placebo and favorable outcomes in patients who are at high risk for progression of disease. Disclosures Kathryn Mahoney, PharmD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Kristin Narayan, PhD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Natalia Betancourt, MS, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Yong Li, PhD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Deepali Gupta, B.Sc, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Pamela Hawn, PharmD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Pete Schmidt, MD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds Myra Popejoy, PharmD, Adagio Therapeutics: Employee|Adagio Therapeutics: Stocks/Bonds.