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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

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% (P0.001). 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.

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.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.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]; P0.001) 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]; P0.001). 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.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.).

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

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 < 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 < 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< 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)

MEDI8852 is an IgG1 kappa monoclonal antibody that is being developed to treat patients hospitalized with influenza A. We evaluated the safety and tolerability, pharmacokinetics, and anti-drug antibodies (ADA) of a single intravenous dose of MEDI8852 in healthy adult volunteers (NCT02350751). Forty subjects were randomized to receive either MEDI8852 (250, 750, 1,500, or 3000 mg) (n = 32) or placebo (n = 8) on day 1. Dose escalation was based on cumulative safety data through day 8. Subjects were followed through day 101 for safety, pharmacokinetics, and ADA. Treatment-emergent adverse events (TEAEs) were comparable (37.5%; 37.5%); all TEAEs were mild (grade 1) or moderate (grade 2) in severity. The most frequently reported TEAEs were headache (9.4%, 12.5%) and hypoglycemia (12.5%, 12.5%); all subjects with hypoglycemia were asymptomatic and did not require treatment. No subjects discontinued the study due to a TEAE. Mean area under the curve from time 0 to last sampling time point, area under the curve from time 0 to infinity, and observed maximum concentration for MEDI8852 were dose proportional. The terminal half-life ranged from 19.4 to 22.6 days. No ADAs were detected. A population pharmacokinetic model demonstrated good concentration separation between the 750- and 3000-mg dose groups.

We evaluated MEDI8852, a human IgG1 monoclonal antibody that binds a highly conserved influenza A hemagglutinin stalk epitope, in outpatients with uncomplicated influenza A infection. A total of 126 subjects aged 18 to 65 years were enrolled during the 2015 to 2016 Northern and 2016 Southern Hemisphere seasons. Subjects with symptom onset ≤5 days before dosing were randomized to four cohorts: 750 mg (cohort 1) or 3,000 mg (cohort 2) MEDI8852 (single intravenous infusion) plus 75 mg oseltamivir, placebo plus 75 mg oseltamivir (cohort 3), and 3,000 mg MEDI8852 alone (cohort 4). Subjects were monitored through day 10 for solicited influenza symptoms, day 28 for adverse events (AEs), and day 101 for serious AEs and AEs of special interest. Nasopharyngeal samples were collected through day 7 for confirmation of influenza A infection, viral shedding, and oseltamivir and MEDI8852 susceptibility. Slightly more AEs were reported in subjects receiving MEDI8852 (cohorts 1, 2, and 4 combined: 39/93, 41.9%) than oseltamivir only (cohort 3: 10/32, 31.3%). Most AEs were mild or moderate. The most common AE was bronchitis (11/93, 11.8%; 1/32, 3.1%). The median (range) decrease in viral shedding (log(10) virus genome copies/ml) was similar between the two groups (−3.58 [−6.2. 0.5]; −3.43 [−5.9, 0.9]). Genotypic analyses found a limited number of hemagglutinin and neuraminidase amino acid changes between viruses isolated before and after therapy; however, none appeared within a known oseltamivir-resistant site or MEDI8852-binding region. The safety profile of MEDI8852 supports its continued development for treatment of patients hospitalized with influenza A infection. (This study has been registered at ClinicalTrials.gov under identifier NCT02603952.)

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

This is the second phase 1 study of a respiratory syncytial virus (RSV) vaccine containing RSV fusion protein (sF) adjuvanted with glucopyranosyl lipid A (GLA) in a squalene-based 2% stable emulsion (GLA-SE). In this randomized, double-blind study, 261 subjects aged ≥60 years received inactivated influenza vaccine (IIV), a vaccine containing 120 μg sF with escalating doses of GLA (1, 2.5, or 5 μg) in SE, or a vaccine containing 80 μg sF with 2.5 μg GLA in SE. Subjects receiving 120 μg sF with 2.5 or 5 μg GLA were also randomized to receive IIV or placebo. Immunity to RSV was assessed by detection of microneutralizing, anti-F immunoglobulin G, and palivizumab-competitive antibodies and F-specific gamma interferon enzyme-linked immunosorbent spot assay T-cell responses. Higher adjuvant doses increased injection site discomfort, but at the highest dose, the reactogenicity was similar to that of IIV. Significant humoral and cellular immune responses were observed. The 120 μg sF plus 5.0 μg GLA formulation resulted in the highest responses in all subjects and in older subjects. These results confirm previous observations of vaccine tolerability, safety, and immunogenicity and were used to select the 120 μg sF plus 5.0 μg GLA formulation for phase 2 evaluation. (This study has been registered at ClinicalTrials.gov under registration no. NCT02289820.)

Prevention of respiratory syncytial virus (RSV) illness in infants is a major public health priority, but there is no approved vaccine. Palivizumab is a monoclonal antibody that provides RSV prophylaxis but requires 5 monthly injections and is approved only for infants who experience the greatest morbidity and mortality from RSV. Thus, there remains a significant unmet medical need for prevention of RSV disease in healthy infants. MEDI8897 is a recombinant human RSV monoclonal antibody with a modified Fc region that extends its half-life and is being developed as RSV prophylaxis for all infants. In this phase 1, first-in-human, placebo-controlled study, 136 healthy adults were randomized to receive a single dose of MEDI8897 ( n = 102) or placebo ( n = 34) in 1 of 5 cohorts (300, 1,000, or 3,000 mg intravenously or 100 or 300 mg intramuscularly [i.m.]) and were monitored for 360 days. The mean half-life of MEDI8897 was 85 to 117 days across dose groups, and bioavailability after 300-mg i.m. dose administration was 77%. Time to maximum concentration following i.m. dosing was 5 to 9 days. Antidrug antibody (ADA) responses were detected in a similar proportion of placebo (15.2%) and MEDI8897 (13.7%) recipients. The safety profile of MEDI8897 was similar to that of the placebo. These results support clinical studies of the i.m. administration of a single dose of MEDI8897 in the target population of infants to provide protection for the duration of the RSV season. (This study has been registered at ClinicalTrials.gov under identifier NCT02114268.)

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.

Purpose: RSV is the most common cause of lower respiratory tract infection (LRTI) among infants. A significant unmet need exists for RSV prevention in healthy infants. Our goal is to develop a monoclonal antibody with an extended half-life (t½) to protect infants through an entire RSV season with a single intramuscular (IM) dose. This study was conducted …

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 (t½) 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 t½ 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 t½ 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

Background Respiratory syncytial virus (RSV) causes significant illness in older adults resulting in substantial health and economic impact. A successful vaccine would reduce morbidity in this growing segment of the population. Methods In this double-blind phase 1 study, subjects 60 years of age and older were enrolled by cohort and randomized to receive vaccines containing escalating doses (20, 50, or 80 μg) of soluble RSV fusion protein (sF) alone or adjuvanted with 2.5 μg of glucopyranosyl lipid A, a toll-like receptor-4 agonist, in 2% stable emulsion (GLA-SE). Each cohort included 20 vaccine and 4 placebo recipients. Immune responses were evaluated using assays for RSV microneutralizing, anti-F IgG, and palivizumab competitive antibodies and for F-specific interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) responses. Results The inclusion of adjuvant increased local reactogenicity, with the majority of subjects who received sF and adjuvant reporting low-grade injection site pain or tenderness. At all doses, the safety profile was acceptable for further development. Immune responses were antigen dose-dependent, and the inclusion of adjuvant increased both humoral and cellular immune responses, with responses statistically higher than for placebo recipients in all 4 assays. At the highest dosage level with adjuvant, half of the subjects had a ≥3-fold rise from day 0 in RSV neutralizing antibody titers, and all had a ≥3-fold rise in antibody levels by anti-F IgG and palivizumab competitive antibody assays on day 29. For the day 8 IFNγ ELISPOT assay, 74% of subjects in the highest dosing cohort had a ≥3-fold rise from baseline. Conclusions The safety and immunogenicity results from this study support inclusion of the GLA-SE adjuvant in this RSV vaccine for older adults and also support assessment of the efficacy of the vaccine in a larger clinical trial. Clinicaltrials.gov NCT02115815 .