91. Establishing Proof of Concept for a Bivalent RSVpreF Subunit Vaccine for Maternal Immunization

Background

Respiratory syncytial virus (RSV) is a major cause of infant morbidity and mortality worldwide and could be preventable by vaccination in pregnancy.

Methods

We conducted a randomized, placebo-controlled phase 2b trial evaluating safety, immunogenicity, and potential efficacy of a bivalent RSV prefusion F vaccine (RSVpreF) in pregnant women and their infants. Participants were randomized between 24- and 36-weeks’ gestation to receive 120 or 240 µg RSVpreF, with or without aluminum hydroxide, or placebo.

Results

This final analysis includes 579 women and 572 infants in 4 countries (Argentina, Chile, South Africa, and the US); 462 (79.8%) women received RSVpreF. Postvaccination reactions, most commonly injection site pain, fatigue, and myalgia, were generally mild-to-moderate. Adverse events (AEs) in the month following vaccination (maternal) or birth (infant) were mostly anticipated events in pregnancy and the neonatal period, respectively, and were similar between vaccine and placebo groups. No AEs were considered related to vaccination.

For all RSVpreF groups, 50% neutralizing titers for both RSV-A and RSV-B rose sharply by 2 weeks after vaccination. At delivery occurring a mean of ∼8 weeks later, geometric mean titer (GMT) ratios for combined RSV-A/B between vaccine and placebo recipients’ infants were 10.9 to 13.6. Transplacental transfer ratios (all groups) were 1.39 to 1.83. Infant GMTs were higher in infants whose mothers had received RSVpreF versus placebo through 6 months of life; the estimated half-life of infant combined 50% RSV-A/B neutralizing titers was 41 days. Infants of women immunized across the range of assessed gestational ages had similar cord blood titers and transplacental transfer ratios. Observed efficacy (95% CI) against medically attended and severe medically attended infant RSV lower respiratory tract illness (LRTI) through 180 days in an exploratory analysis was 84.7% (21.5%, 97.6%) and 91.5% (-5.6%, 99.8%), respectively.

Conclusion

RSVpreF was well-tolerated in pregnant women, elicited robust neutralizing responses with efficient transplacental transfer, and has the potential to prevent infant RSV LRTI.

Disclosures

Eric A. F. Simões, MD, M.B., B.S., DCH, Abbvie: DSMB|Astra Zeneca: Grant/Research Support|Bill and Melinda Gates Foundation: Grant/Research Support|Bill and Melinda Gates Foundation: DSMB|GSK Inc.: DSMB|Johnson and Johnson: Grant/Research Support|Merck Inc: Advisor/Consultant|Merck Inc: Grant/Research Support|Nivavax: Grant/Research Support|Pfizer Inc: Advisor/Consultant|Pfizer Inc: Grant/Research Support|Regeneron: Grant/Research Support|Sanofi Pasteur: Advisor/Consultant Shabir A. Madhi, MBBCh, FCPaeds, MMed, PhD, AstraZeneca: Funding to institution for conduct of study Kimberly J. Center, M.D., Pfizer: Employee|Pfizer: Stocks/Bonds Jose M. Novoa Pizarro, MD, AstraZeneca: Grant/Research Support|Medimmune: Grant/Research Support|MSD: Grant/Research Support|Pfizer: Grant/Research Support|Regeneron: Grant/Research Support Kena A. Swanson, Ph.D., Pfizer: employee of Pfizer David Radley, MS, Pfizer: Employee|Pfizer: Stocks/Bonds Stephanie B. McGrory, B.S.N., Pfizer: Employee|Pfizer: Stocks/Bonds Emily A. Gomme, Ph.D., Pfizer: Stocks/Bonds Daniel A. Scott, MD, Pfizer: Employee|Pfizer: Stocks/Bonds Kathrin U. Jansen, PhD, Pfizer Inc: Employee|Pfizer Inc: Stocks/Bonds William C. Gruber, MD, Pfizer Inc: Employee|Pfizer Inc: Stocks/Bonds Alejandra C. Gurtman, M.D., Pfizer: employee of Pfizer.

Suptavumab for the Prevention of Medically Attended Respiratory Syncytial Virus Infection in Preterm Infants

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of childhood medically attended respiratory infection (MARI).

METHODS

We conducted a randomized, double-blind, placebo-controlled phase 3 trial in 1154 preterm infants of 1 or 2 doses of suptavumab, a human monoclonal antibody that can bind and block a conserved epitope on RSV A and B subtypes, for the prevention of RSV MARI. The primary endpoint was proportion of subjects with RSV-confirmed hospitalizations or outpatient lower respiratory tract infection (LRTI).

RESULTS

There were no significant differences between primary endpoint rates (8.1%, placebo; 7.7%, 1-dose; 9.3%, 2-dose). Suptavumab prevented RSV A infections (relative risks, .38; 95% confidence interval [CI], .14-1.05 in the 1-dose group and .39 [95% CI, .14-1.07] in the 2-dose group; nominal significance of combined suptavumab group vs placebo; P = .0499), while increasing the rate of RSV B infections (relative risk 1.36 [95% CI, .73-2.56] in the 1-dose group and 1.69 [95% CI, .92-3.08] in the 2-dose group; nominal significance of combined suptavumab group vs placebo; P = .12). Sequenced RSV isolates demonstrated no suptavumab epitope changes in RSV A isolates, while all RSV B isolates had 2-amino acid substitution in the suptavumab epitope that led to loss of neutralization activity. Treatment emergent adverse events were balanced across treatment groups.

CONCLUSIONS

Suptavumab did not reduce overall RSV hospitalizations or outpatient LRTI because of a newly circulating mutant strain of RSV B. Genetic variation in circulating RSV strains will continue to challenge prevention efforts.

CLINICAL TRIALS REGISTRATION

NCT02325791. https://clinicaltrials.gov/ct2/show/NCT02325791.

Four-year antibody persistence and response to a booster dose of a pentavalent MenABCWY vaccine administered to healthy adolescents and young adults

This open-label, multicenter extension study (NCT02451514) assessed persistence of Neisseria meningitidis serogroups ABCWY antibodies 4 years after primary vaccination. Adolescents and young adults who previously received 2 doses of MenABCWY+OMV (Group III), 1 dose of MenACWY-CRM (Group VI), or newly-recruited vaccine-naïve participants (Group VII) were administered 1 (Group III) or 2 doses (Groups VI and VII) of MenABCWY+OMV, 1 month apart. Immunogenicity was assessed by human serum bactericidal assay (hSBA). Safety and reactogenicity were also evaluated. Percentages of participants with hSBA titers ≥8 (serogroups ACWY), ≥5 (serogroup B) and hSBA geometric mean titers (GMTs) were evaluated in all 129 enrolled participants (Group III: 33; Group VI: 46; Group VII: 50). Anti-ACWY antibody concentrations waned over 4 years post-vaccination, but remained above pre-vaccination concentrations. Similarly, levels of antibodies against serogroup B test strains also waned over 4 years post-vaccination, but remained above pre-vaccination concentrations for some strains. MenABCWY+OMV booster induced a robust anamnestic anti-ACWY response in Group III and VI and a good response against serogroup B test strains (≥82%) in Group III. In serogroup B-naïve participants (Groups VI and VII), anti-B responses to 2 doses of MenABCWY+OMV were less homogenous and lower than in Group III. MenABCWY+OMV was reactogenic, but well-tolerated. No safety concerns were identified. These findings indicate that although antibodies against N. meningitidis serogroups ABCWY waned over 4 years post-vaccination, exposure to a MenABCWY+OMV booster dose elicits an anamnestic response in adolescents previously exposed to the same or another multivalent meningococcal vaccine.