Infants Receiving a Single Dose of Nirsevimab to Prevent RSV Do Not Have Evidence of Enhanced Disease in Their Second RSV Season

To characterize nirsevimab in the prevention of RSV, children from the Phase 3 MELODY trial were followed through their second RSV season. No increase in medically attended RSV lower respiratory tract infections or evidence of antibody-dependent enhancement of infection or disease severity was found for nirsevimab vs placebo recipients. Clinical Trial Registration: Clinicaltrials.gov, NCT03979313, https://clinicaltrials.gov/ct2/show/NCT03979313.

Safety of Re-dosing Nirsevimab Prior to RSV Season 2 in Children With Heart or Lung Disease

In children with congenital heart disease and/or chronic lung disease entering their second respiratory syncytial virus (RSV) season, 200 mg nirsevimab had a similar safety profile to that of palivizumab and resulted in nirsevimab serum exposures associated with efficacy in healthy infants, supporting efficacy in this population at risk of severe RSV disease.

Efficacy of nirsevimab against respiratory syncytial virus lower respiratory tract infections in preterm and term infants, and pharmacokinetic extrapolation to infants with congenital heart disease and chronic lung disease: a pooled analysis of randomised controlled trials

BACKGROUND

In a phase 2b trial and the phase 3 MELODY trial, nirsevimab, an extended half-life, monoclonal antibody against respiratory syncytial virus (RSV), protected healthy infants born preterm or at full term against medically attended RSV lower respiratory tract infection (LRTI). In the MEDLEY phase 2-3 trial in infants at higher risk for severe RSV infection, nirsevimab showed a similar safety profile to that of palivizumab. The aim of the current analysis was to assess the efficacy of nirsevimab using a weight-banded dosing regimen in infants born between 29 weeks gestational age and full term.

METHODS

Infants enrolled in the phase 2b and MELODY trials were randomised (2:1) to receive a single intramuscular injection of nirsevimab (infants weighing <5 kg received 50 mg; those weighing ≥5 kg received 100 mg) or placebo before the RSV season. Infants in MEDLEY were randomised (2:1) to receive one dose of nirsevimab (infants weighing <5 kg received 50 mg; those weighing ≥5 kg received 100 mg) followed by four monthly placebo doses, or five once-a-month intramuscular doses of palivizumab. We report a prespecified pooled efficacy analysis assessing the weight-banded dosing regimen proposed on the basis of the phase 2b and MELODY trials, in addition to extrapolated efficacy in infants with chronic lung disease, congenital heart disease, or extreme preterm birth (<29 weeks' gestational age) based on pharmacokinetic data from the phase 2-3 MEDLEY safety trial. For the pooled efficacy analysis, the primary endpoint was incidence of medically attended RSV LRTI through 150 days post-dose. The secondary efficacy endpoint was number of admissions to hospital for medically attended RSV LRTI. The incidence of very severe RSV LRTI was an exploratory endpoint, defined as cases of hospital admission for medically attended RSV LRTI that required supplemental oxygen or intravenous fluids. We also did a prespecified exploratory analysis of medically attended LRTI of any cause (in the investigator's judgement) and hospital admission for respiratory illness of any cause (defined as any upper respiratory tract infection or LRTI leading to hospital admission). Post hoc exploratory analyses of outpatient visits and antibiotic use were also done. Nirsevimab serum concentrations in MEDLEY were assessed using population pharmacokinetic methods and the pooled data from the phase 2b and MELODY trials. An exposure target was defined on the basis of an exposure-response analysis. To successfully demonstrate extrapolation, more than 80% of infants in MEDLEY had to achieve serum nirsevimab exposures at or above the predicted efficacious target.

FINDINGS

Overall, 2350 infants (1564 in the nirsevimab group and 786 in the placebo group) in the phase 2b and MELODY trials were included in the pooled analysis. Nirsevimab showed efficacy versus placebo with respect to the primary endpoint of medically attended RSV LRTI (19 [1%] nirsevimab recipients vs 51 [6%] placebo recipients; relative risk reduction [RRR] 79·5% [95% CI 65·9-87·7]). Consistent efficacy was shown for additional endpoints of RSV LRTI hospital admission (nine [1%] nirsevimab recipients vs 21 [3%] placebo recipients; 77·3% [50·3-89·7]) and very severe RSV (five [<1%] vs 18 [2%]; 86·0% [62·5-94·8]). Nirsevimab recipients had fewer hospital admissions for any-cause respiratory illness (RRR 43·8% [18·8-61·1]), any-cause medically attended LRTI (35·4% [21·5-46·9]), LRTI outpatient visits (41·9% [25·7-54·6]), and antibiotic prescriptions (23·6% [3·8-39·3]). Among infants with chronic lung disease, congenital heart disease, or extreme preterm birth in MEDLEY, nirsevimab serum exposures were similar to those found in the pooled data; exposures were above the target in more than 80% of the overall MEDLEY trial population (94%), including infants with chronic lung disease (94%) or congenital heart disease (80%) and those born extremely preterm (94%).

INTERPRETATION

A single dose of nirsevimab protected healthy infants born at term or preterm from medically attended RSV LRTI, associated hospital admission, and severe RSV. Pharmacokinetic data support efficacy extrapolation to infants with chronic lung disease, congenital heart disease, or extreme prematurity. Together, these data suggest that nirsevimab has the potential to change the landscape of infant RSV disease by reducing a major cause of infant morbidity and the consequent burden on caregivers, clinicians, and health-care providers.

FUNDING

AstraZeneca and Sanofi.

Durability of protection and immunogenicity of AZD1222 (ChAdOx1 nCoV-19) COVID-19 vaccine over 6 months

BackgroundWe report updated safety, efficacy, and immunogenicity of AZD1222 (ChAdOx1 nCoV-19) from an ongoing phase 3 trial.MethodsAdults at increased risk of SARS-CoV-2 infection were randomized (2:1), stratified by age, to receive 2 doses of AZD1222 or placebo. The primary efficacy end point was confirmed SARS-CoV-2 reverse-transcriptase PCR-positive (RT-PCR-positive) symptomatic COVID-19 at 15 or more days after a second dose in baseline SARS-CoV-2-seronegative participants. The 21,634 and 10,816 participants were randomized to AZD1222 and placebo, respectively.FindingsData cutoff for this analysis was July 30, 2021; median follow-up from second dose was 78 and 71 days for the double-blind period (censoring at unblinding or nonstudy COVID-19 vaccination) and 201 and 82 days for the period to nonstudy COVID-19 vaccination (regardless of unblinding) in the AZD1222 and placebo groups, respectively. For the primary efficacy end point in the double-blind period (141 and 184 events; incidence rates: 39.2 and 118.8 per 1,000 person years), vaccine efficacy was 67.0% (P < 0.001). In the period to nonstudy COVID-19 vaccination, incidence of events remained consistently low and stable through 6 months in the AZD1222 group; for the primary efficacy end point (328 and 219 events; incidence rates: 36.4, 108.4) and severe/critical disease (5 and 13 events; incidence rates: 0.6, 6.4), respective vaccine efficacy estimates were 65.1% and 92.1%. AZD1222 elicited humoral immune responses over time, with waning at day 180. No emergent safety issues were seen.ConclusionAZD1222 is safe and well tolerated, demonstrating durable protection and immunogenicity with median follow-up (AZD1222 group) of 6 months.Trial registrationClinicalTrials.gov NCT04516746.FundingAstraZeneca; US government.

Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection and hospitalization in infants. Nirsevimab is a monoclonal antibody to the RSV fusion protein that has an extended half-life. The efficacy and safety of nirsevimab in healthy late-preterm and term infants are uncertain.

METHODS

We randomly assigned, in a 2:1 ratio, infants who had been born at a gestational age of at least 35 weeks to receive a single intramuscular injection of nirsevimab or placebo before the start of an RSV season. The primary efficacy end point was medically attended RSV-associated lower respiratory tract infection through 150 days after the injection. The secondary efficacy end point was hospitalization for RSV-associated lower respiratory tract infection through 150 days after the injection.

RESULTS

A total of 1490 infants underwent randomization: 994 were assigned to the nirsevimab group and 496 to the placebo group. Medically attended RSV-associated lower respiratory tract infection occurred in 12 infants (1.2%) in the nirsevimab group and in 25 infants (5.0%) in the placebo group; these findings correspond to an efficacy of 74.5% (95% confidence interval [CI], 49.6 to 87.1; P<0.001) for nirsevimab. Hospitalization for RSV-associated lower respiratory tract infection occurred in 6 infants (0.6%) in the nirsevimab group and in 8 infants (1.6%) in the placebo group (efficacy, 62.1%; 95% CI, -8.6 to 86.8; P = 0.07). Among infants with data available to day 361, antidrug antibodies after baseline were detected in 58 of 951 (6.1%) in the nirsevimab group and in 5 of 473 (1.1%) in the placebo group. Serious adverse events were reported in 67 of 987 infants (6.8%) who received nirsevimab and in 36 of 491 infants (7.3%) who received placebo.

CONCLUSIONS

A single injection of nirsevimab administered before the RSV season protected healthy late-preterm and term infants from medically attended RSV-associated lower respiratory tract infection. (Funded by MedImmune/AstraZeneca and Sanofi; MELODY ClinicalTrials.gov number, NCT03979313.).

Phase 3 Safety and Efficacy of AZD1222 (ChAdOx1 nCoV-19) Covid-19 Vaccine

BACKGROUND

The safety and efficacy of the AZD1222 (ChAdOx1 nCoV-19) vaccine in a large, diverse population at increased risk for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in the United States, Chile, and Peru has not been known.

METHODS

In this ongoing, double-blind, randomized, placebo-controlled, phase 3 clinical trial, we investigated the safety, vaccine efficacy, and immunogenicity of two doses of AZD1222 as compared with placebo in preventing the onset of symptomatic and severe coronavirus disease 2019 (Covid-19) 15 days or more after the second dose in adults, including older adults, in the United States, Chile, and Peru.

RESULTS

A total of 32,451 participants underwent randomization, in a 2:1 ratio, to receive AZD1222 (21,635 participants) or placebo (10,816 participants). AZD1222 was safe, with low incidences of serious and medically attended adverse events and adverse events of special interest; the incidences were similar to those observed in the placebo group. Solicited local and systemic reactions were generally mild or moderate in both groups. Overall estimated vaccine efficacy was 74.0% (95% confidence interval [CI], 65.3 to 80.5; P<0.001) and estimated vaccine efficacy was 83.5% (95% CI, 54.2 to 94.1) in participants 65 years of age or older. High vaccine efficacy was consistent across a range of demographic subgroups. In the fully vaccinated analysis subgroup, no severe or critical symptomatic Covid-19 cases were observed among the 17,662 participants in the AZD1222 group; 8 cases were noted among the 8550 participants in the placebo group (<0.1%). The estimated vaccine efficacy for preventing SARS-CoV-2 infection (nucleocapsid antibody seroconversion) was 64.3% (95% CI, 56.1 to 71.0; P<0.001). SARS-CoV-2 spike protein binding and neutralizing antibodies increased after the first dose and increased further when measured 28 days after the second dose.

CONCLUSIONS

AZD1222 was safe and efficacious in preventing symptomatic and severe Covid-19 across diverse populations that included older adults. (Funded by AstraZeneca and others; ClinicalTrials.gov number, NCT04516746.).

LB13. The Efficacy and Impact in Heathy Infants of Nirsevimab on Medically Attended RSV Lower Respiratory Tract Infection

Background

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection (LRTI) in infants. Nirsevimab is a single-dose monoclonal antibody with extended half-life that was shown to protect preterm infants 29 to &lt; 35 weeks gestation against RSV LRTI. However, most medically attended (MA) cases occur in otherwise healthy, term infants for whom there is currently no effective RSV prevention strategy. We report the primary analysis of efficacy and safety, along with the impact of nirsevimab in late preterm and term infants (≥ 35 weeks gestation) in the phase 3 MELODY study (NCT03979313).

Methods

Infants were randomized 2:1 to receive one intramuscular injection of nirsevimab (50 mg if &lt; 5 kg; 100 mg if ≥ 5 kg at dosing) or placebo entering their first RSV season. The primary endpoint was the incidence of MA RSV LRTI over 150 days postdose. Cases met predefined clinical criteria of disease severity and were confirmed by real-time reverse-transcriptase PCR. Safety was evaluated through 360 days postdose. Enrollment started on 23 July 2019 and was suspended following the declaration of the COVID-19 pandemic by the WHO on 11 March 2020.

Results

Overall, 1490 infants were randomized and included in the intent-to-treat population; 1465 (98%) completed the 150-day efficacy follow-up, and 1367 (92%) completed the 360-day safety follow-up. The incidence of MA RSV LRTI was 1.2% (n=12/994) in the nirsevimab group and 5.0% (n=25/496) in the placebo group, giving nirsevimab an efficacy of 74.5% (95% confidence interval [CI]: 49.6, 87.1; p&lt; 0.0001). Nirsevimab averted 93.6 (95% CI 63.0, 124.0) MA LRTIs per 1000 infants dosed. Nirsevimab was well tolerated, with similar rates of adverse events (87.4% nirsevimab; 86.8% placebo) and serious adverse events (6.8% nirsevimab; 7.3% placebo) between groups.

Conclusion

In this phase 3 study, a single dose of nirsevimab protected late preterm and term infants against MA RSV LRTI over an RSV season with a favorable safety profile. Approximately 11 infants need to be immunized to prevent 1 case of LRTI; nirsevimab has the potential to be an important intervention to reduce the burden of RSV LRTI in healthy infants.

Disclosures

Laura Hammitt, MD, MedImmune (Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support)Merck & Co., Inc. (Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support)Novavax (Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support)Pfizer (Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support) Laura Hammitt, MD, MedImmune (Individual(s) Involved: Self): Grant/Research Support, Research grant to my institution; Merck (Individual(s) Involved: Self): Grant/Research Support, Research grant to my institution; Pfizer (Individual(s) Involved: Self): Grant/Research Support, Research grant to my institution Ron Dagan, MD, Medimmune/AstraZeneca (Grant/Research Support, Scientific Research Study Investigator, Research Grant or Support)MSD (Consultant, Grant/Research Support, Scientific Research Study Investigator, Advisor or Review Panel member, Research Grant or Support, Speaker’s Bureau)Pfizer (Consultant, Grant/Research Support, Scientific Research Study Investigator, Advisor or Review Panel member, Research Grant or Support, Speaker’s Bureau) Yuan Yuan, PhD, AstraZeneca (Employee, Shareholder) Shabhir A. Mahdi, PhD, BMGF (Research Grant or Support)EDCTP (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melody (Research Grant or Support)Minervax (Research Grant or Support)Novavax (Research Grant or Support)SAMRC (Research Grant or Support) William J. Muller, MD, PhD, Ansun (Scientific Research Study Investigator)Astellas (Scientific Research Study Investigator)AstraZeneca (Scientific Research Study Investigator)Genentech (Scientific Research Study Investigator)Gilead (Scientific Research Study Investigator)Janssen (Scientific Research Study Investigator)Karius (Scientific Research Study Investigator)Melinta (Scientific Research Study Investigator)Merck (Scientific Research Study Investigator)Nabriva (Scientific Research Study Investigator)Seqirus (Scientific Research Study Investigator)Tetraphase (Scientific Research Study Investigator) William J. Muller, MD, PhD, Ansun (Individual(s) Involved: Self): Grant/Research Support; Astellas (Individual(s) Involved: Self): Research Grant or Support; AstraZeneca (Individual(s) Involved: Self): Grant/Research Support; BD (Individual(s) Involved: Self): Research Grant or Support; Eli Lilly (Individual(s) Involved: Self): Grant/Research Support; Gilead (Individual(s) Involved: Self): Grant/Research Support; Karius, Inc. (Individual(s) Involved: Self): Grant/Research Support, Scientific Research Study Investigator; Melinta (Individual(s) Involved: Self): Grant/Research Support; Merck (Individual(s) Involved: Self): Grant/Research Support; Moderna (Individual(s) Involved: Self): Grant/Research Support; Nabriva (Individual(s) Involved: Self): Grant/Research Support; Seqirus (Individual(s) Involved: Self): Consultant; Tetraphase (Individual(s) Involved: Self): Grant/Research Support Heather J. Zar, PhD, AstraZeneca (Grant/Research Support)Novavax (Grant/Research Support)Pfizer (Grant/Research Support, Advisor or Review Panel member) Dennis Brooks, MD, AstraZeneca (Employee) Amy Grenham, MSc, AstraZeneca (Employee, Shareholder) Ulrika Wählby Hamrén, PhD, AstraZeneca R&D (Employee, Shareholder) Vaishali S. Mankad, MD, AstraZeneca (Employee) Therese Takas, BSc, AstraZeneca (Employee, Other Financial or Material Support, Own stock in AstraZeneca) Jon Heinrichs, PhD, AstraZeneca (Shareholder)Bristol Myers Squibb (Shareholder)J&J (Shareholder)Merck (Shareholder)Organon (Shareholder)Procter & Gamble (Shareholder)Sanofi (Shareholder)Sanofi Pasteur (Employee) Amanda Leach, MRCPCH, AstraZeneca (Employee, Shareholder) M. Pamela Griffin, MD, AstraZeneca (Employee) Tonya L. Villafana, PhD, AstraZeneca (Employee)

Single-Dose Nirsevimab for Prevention of RSV in Preterm Infants

BACKGROUND

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants, and a need exists for prevention of RSV in healthy infants. Nirsevimab is a monoclonal antibody with an extended half-life that is being developed to protect infants for an entire RSV season with a single intramuscular dose.

METHODS

In this trial conducted in both northern and southern hemispheres, we evaluated nirsevimab for the prevention of RSV-associated lower respiratory tract infection in healthy infants who had been born preterm (29 weeks 0 days to 34 weeks 6 days of gestation). We randomly assigned the infants in a 2:1 ratio to receive nirsevimab, at a dose of 50 mg in a single intramuscular injection, or placebo at the start of an RSV season. The primary end point was medically attended RSV-associated lower respiratory tract infection through 150 days after administration of the dose. The secondary efficacy end point was hospitalization for RSV-associated lower respiratory tract infection through 150 days after administration of the dose.

RESULTS

From November 2016 through November 2017, a total of 1453 infants were randomly assigned to receive nirsevimab (969 infants) or placebo (484 infants) at the start of the RSV season. The incidence of medically attended RSV-associated lower respiratory tract infection was 70.1% lower (95% confidence interval [CI], 52.3 to 81.2) with nirsevimab prophylaxis than with placebo (2.6% [25 infants] vs. 9.5% [46 infants]; P<0.001) and the incidence of hospitalization for RSV-associated lower respiratory tract infection was 78.4% lower (95% CI, 51.9 to 90.3) with nirsevimab than with placebo (0.8% [8 infants] vs. 4.1% [20 infants]; P<0.001). These differences were consistent throughout the 150-day period after the dose was administered and across geographic locations and RSV subtypes. Adverse events were similar in the two trial groups, with no notable hypersensitivity reactions.

CONCLUSIONS

A single injection of nirsevimab resulted in fewer medically attended RSV-associated lower respiratory tract infections and hospitalizations than placebo throughout the RSV season in healthy preterm infants. (Funded by AstraZeneca and Sanofi Pasteur; ClinicalTrials.gov number, NCT02878330.).

901. MEDI8897 Prevents Serious RSV Disease in Healthy Preterm Infants

Background

RSV is the principal cause of lower respiratory tract infection (LRTI) among infants, and a significant unmet need exists for RSV prevention in healthy infants. We have developed a highly potent, extended half-life monoclonal antibody (mAb), to protect infants for an entire RSV season using a single IM dose. Here we report the efficacy, safety, pharmacokinetics, and anti-drug antibody (ADA) responses for MEDI8897 in palivizumab-ineligible preterm infants born between 29 and 35 weeks gestation.

Methods

A total of 1,453 Infants were randomized 2:1 to receive a single 50 mg IM injection of MEDI8897 (n = 969) or placebo (n = 484) and followed for 360 days. Enrollment occurred just prior to the 2016 and 2017 RSV seasons in 23 northern and southern hemisphere countries. Blood was collected periodically. Infants with a medically attended (MA) LRTI (outpatient or inpatient) had nasal swabs obtained for central RSV testing by RT-PCR. Predefined clinical criteria were used for the case definition.

Results

A total of 1,417 (97.5%) subjects completed the 150-day efficacy follow-up period and 1,367 (94.1%) completed the study. In the MEDI8897 group, a 70.1% (95% CI: 52.3%, 81.2%; P < 0.0001) reduction in the incidence of medically attended RSV LRTI and a 78.4% (95% CI: 51.9%, 90.3%; P = 0.0002) reduction in the incidence of RSV LRTI hospitalization was achieved. These efficacy results were consistent when analyzed by hemisphere, RSV subtype, and subject demographics. Similar proportions of adverse events (86.8% placebo; 86.2% MEDI8897) and serious adverse events (16.9% placebo; 11.2% MEDI8897) were reported in study subjects. There were no significant hypersensitivity reactions with similar proportions reported for both groups (0.6% placebo; 0.5% MEDI8897). The incidence of ADA detected any time post baseline was low (3.8% placebo; 5.6% MEDI8897) with no impact on PK or safety. The occurrence of non-RSV LRTIs was similar for both groups indicating no replacement by other pathogens.

Conclusion

In this large randomized study of RSV prophylaxis in healthy preterm infants, MEDI8897 immunoprophylaxis provided a significant reduction in RSV MA-LRTI and hospitalization. These results have promising implications for the future of RSV prophylaxis for all infants.

This study was funded by AstraZeneca and sanofi pasteur.

Disclosures

All Authors: No reported Disclosures.

Safety, Tolerability and Pharmacokinetics of MEDI8897, an Extended Half-life Single-dose Respiratory Syncytial Virus Prefusion F-targeting Monoclonal Antibody Administered as a Single Dose to Healthy Preterm Infants

BACKGROUND

MEDI8897 is a recombinant human monoclonal antibody being developed for prophylaxis of serious respiratory syncytial virus (RSV) disease in all infants.

METHODS

In this phase 1b/2a dose-escalation study, healthy preterm infants with a gestational age of 32-35 weeks were randomized to receive a single intramuscular injection of MEDI8897 (10, 25 or 50 mg) or placebo. Safety, pharmacokinetics, RSV-neutralizing antibody and antidrug antibody (ADA) assessments were performed during the 360-day follow-up period. Infants who experienced medically attended lower respiratory tract infections (LRTIs) were tested for RSV.

RESULTS

MEDI8897 serum half-life ranged from 62.5-72.9 days. On day 151, 87% of infants in the 50 mg group had serum concentrations above the 90% effective concentration target level of 6.8 µg/mL, and 90% showed a ≥4-fold rise from baseline in serum RSV-neutralizing antibody levels. Adverse events (AEs) were reported in 17 of 18 (94.4%) placebo and 66 of 71 (93.0%) MEDI8897 recipients. Three MEDI8897 recipients experienced 5 serious AEs (3 LRTIs, 2 febrile seizures). ADA was detected at any time postbaseline in 28.2% of MEDI8897 recipients and at day 361 only in 26.5% of subjects. ADA response was not associated with AEs. Five (7%) MEDI8897 recipients experienced medically attended LRTIs through day 150; 1 tested positive for RSV (10 mg group).

CONCLUSIONS

MEDI8897 had a favorable safety profile in healthy preterm infants. The extended half-life of MEDI8897 and demonstrated RSV-neutralizing activity support protection from RSV for the duration of a typical 5-month season after a single 50 mg intramuscular (IM) dose.

An Adjuvanted, Postfusion F Protein-Based Vaccine Did Not Prevent Respiratory Syncytial Virus Illness in Older Adults

Background

Respiratory syncytial virus (RSV) is an important cause of illness in older adults. This study assessed efficacy of a vaccine for prevention of RSV-associated acute respiratory illness (ARI), defined by specified symptoms with virologic confirmation.

Methods

This phase 2b study evaluated RSV postfusion F protein (120 µg) with glucopyranosyl lipid adjuvant (5 µg) in 2% stable emulsion. Subjects aged ≥60 years were randomly assigned at a ratio of 1:1 to receive vaccine or placebo (all received inactivated influenza vaccine). Ill subjects recorded symptoms and provided blood and nasal swab samples.

Results

In the per-protocol population (n = 1894), the incidence of RSV-associated ARI occurring ≥14 days after dosing was 1.7% and 1.6% in the vaccine and placebo groups, respectively, for a vaccine efficacy (VE) of –7.1% (90% confidence interval [CI], –106.9%–44.3%). Efficacy was not observed in secondary analyses that included seroresponse to nonvaccine RSV antigens (VE, 8.9%; 90% CI, –28.5%–35.4%) or symptoms combined with seroresponse (VE, 10.0%; 90% CI, –45.4%–44.4%). On day 29, 92.9% of vaccinees had an anti-F immunoglobulin G antibody seroresponse. Overall, 48.5% and 30.9% of RSV vaccine recipients reported local and systemic solicited symptoms, respectively.

Conclusion

The RSV vaccine was immunogenic but did not protect older adults from RSV illness.

Clinical Trials Registration

NCT02508194.

A Single Dose Monoclonal Antibody (mAb) Immunoprophylaxis Strategy to Prevent RSV Disease in All Infants: Results of the First in Infant Study with MEDI8897

Background

RSV is the most common cause of lower respiratory tract infection (LRTI) among infants making prevention of RSV disease a public health priority. A significant unmet need exists for RSV prevention in healthy infants. Our goal is to develop a mAb with an extended half-life (t_½) capable of protecting infants for an entire RSV season by using a single intramuscular (IM) dose. This study was conducted to evaluate the safety profile, pharmacokinetics (PK), RSV neutralizing antibody titers, and anti-drug antibody (ADA) responses for MEDI8897 in healthy preterm infants born between 32 and 35 weeks gestational age.

Methods

Infants were randomized 4:1 to receive a single IM injection of MEDI8897 10mg (n = 8), 25mg (n = 31), 50mg (n = 32) or placebo (n = 18) and followed for 360 days. Enrollment occurred during the 2,015 RSV seasons in the US, South Africa, and Chile. Blood was collected at multiple timepoints. Infants who met criteria for a medically-attended (MA) LRTI had nasal swabs obtained for RSV testing by RT-PCR.

Results

A total of 85/89 (95.5%) infants completed the study. Adverse events (AEs) were reported in 17/18 (94.4%) placebo and 66/71 (93.0%) MEDI8897 recipients. Five serious AEs (three LRTIs, two febrile seizures) were reported in three MEDI8897 recipients. No events were consistent with hypersensitivity reactions. The estimated MEDI8897 serum t_½ ranged from 62.5 to 72.9 days. On day 151, 87% of the infants who received the 50mg dose of MEDI8897 had serum concentrations above the target EC₉₀ level of 6.8 µg/ml, and 93.3% showed a ≥3-fold rise from baseline in serum anti-RSV neutralizing antibody titers. ADA was detected in 28.2% of MEDI8897 recipients, but when present was not associated with any safety findings. ADA was detected at day 361 only in 26.5% of subjects. MA-LRTI was reported in 5 (7%) MEDI8897 recipients through 150 days after dosing. The one subject with an MA-LRTI caused by RSV had received a 10mg dose of MEDI8897.

Conclusion

In healthy preterm infants, the safety profile of MEDI8897 was favorable. The extended t_½ of MEDI8897 with the corresponding increase in RSV neutralizing antibody levels was confirmed and supports protection from RSV disease during a typical 5-month season with a single 50mg IM dose.

This study was sponsored by MedImmune.

Disclosures

J. B. Domachowske, Medimmune: Investigator, Research grant; Regeneron: Investigator, Research grant; Pfizer: Investigator, Research grant; Glaxo Smith Kline: Investigator, Research grant; Novavax: Investigator, Research grant; Janssen: Investigator, Research grant; A. Khan, MedImmune: Employee and Shareholder, Salary and stock; M. T. Esser, MedImmune: Employee and Shareholder, Salary and stock; K. M. Jensen, MedImmune: Employee and Shareholder, Salary and stock; T. Takas, MedImmune: Employee and Shareholder, Salary and stock; T. Villafana, MedImmune: Employee and Shareholder, Salary and stock; F. Dubovsky, MedImmune: Employee and Shareholder, Salary and stock; M. P. Griffin, MedImmune: Employee and Shareholder, Salary and stock