Introducción: Recientemente se ha aprobado en Europa y en España el uso de nirsevimab, un anticuerpo monoclonal (AcM) para la prevención de la enfermedad por virus respiratorio sincitial (VRS). Objetivos: Facilitar unas recomendaciones para la administración de nirsevimab para la prevención de la enfermedad por VRS. Métodos: Para la elaboración de estas recomendaciones, se decidió realizar una revisión crítica de la literatura, utilizando la metodología Delphi y la metodología GRADE. Se definió un grupo de expertos. Se realizaron tres rondas para definir las preguntas, manifestarse a favor o en contra, graduar la recomendación, y definir el acuerdo o el desacuerdo con las conclusiones. Resultados: En la población general de recién nacidos, se recomienda administrar rutinariamente nirsevimab para reducir la enfermedad y la hospitalización por bronquiolitis y enfermedad de vías bajas por VRS. Se recomienda administrar nirsevimab a todos los lactantes que nazcan en la estación de alta incidencia de VRS y aquellos que cuando esta comience, tengan menos de seis meses de edad. En los pacientes prematuros de 29 a 35 semanas de edad gestacional, en los lactantes con cardiopatía hemodinámicamente significativa y lactantes con enfermedad pulmonar crónica se recomienda rutinariamente administrar nirsevimab para reducir la enfermedad y la hospitalización por bronquiolitis y enfermedad de vías bajas por VRS. En los pacientes con indicación actual de palivizumab, se recomienda sustituir palivizumab por nirsevimab para reducir la carga de enfermedad de bronquiolitis. Conclusiones: Se recomienda administrar rutinariamente nirsevimab a todos los recién nacidos menores de seis meses nacidos en la estación de VRS o que tengan menos de seis meses cuando entran en la estación invernal, para reducir la carga de enfermedad y la hospitalización por bronquiolitis. (AU)

Nirsevimab (Beyfortus(®)), a long-acting intramuscular recombinant neutralising
human IgG1ĸ monoclonal antibody to the prefusion conformation of the respiratory
syncytial virus (RSV) F protein that has been modified with a triple amino acid
substitution in the Fc region to extend the serum half-life, is being jointly
developed by AstraZeneca and Sanofi for the prevention of RSV disease. The
extended serum half-life allows administration of nirsevimab as a single dose to
cover the RSV season. Nirsevimab was approved in the EU on 3 November 2022 and in
the UK on 7 November 2022 for the prevention of RSV lower respiratory tract
disease in neonates and infants during their first RSV season. This article
summarizes the milestones in the development of nirsevimab leading to this first
approval for the prevention of RSV disease in all infants.

BACKGROUND:

Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis, resulting in 3 million hospitalizations each year worldwide. Nirsevimab is a monoclonal antibody against RSV that has an extended half-life. Its postlicensure real-world effectiveness against RSV-associated bronchiolitis is unclear.

METHODS:

We conducted a prospective, multicenter, matched case-control study to analyze the effectiveness of nirsevimab therapy against hospitalization for RSV-associated bronchiolitis in infants younger than 12 months of age. Case patients were infants younger than 12 months of age who were hospitalized for RSV-associated bronchiolitis between October 15 and December 10, 2023. Control patients were infants with clinical visits to the same hospitals for conditions unrelated to RSV infection. Case patients were matched to control patients in a 2:1 ratio on the basis of age, date of hospital visit, and study center. We calculated the effectiveness of nirsevimab therapy against hospitalization for RSV-associated bronchiolitis (primary outcome) by means of a multivariate conditional logistic-regression model with adjustment for confounders. Several sensitivity analyses were performed.

RESULTS:

The study included 1035 infants, of whom 690 were case patients (median age, 3.1 months; interquartile range, 1.8 to 5.3) and 345 were matched control patients (median age, 3.4 months; interquartile range, 1.6 to 5.6). Overall, 60 case patients (8.7%) and 97 control patients (28.1%) had received nirsevimab previously. The estimated adjusted effectiveness of nirsevimab therapy against hospitalization for RSV-associated bronchiolitis was 83.0% (95% confidence interval [CI], 73.4 to 89.2). Sensitivity analyses gave results similar to those of the primary analysis. The effectiveness of nirsevimab therapy against RSV-associated bronchiolitis resulting in critical care was 69.6% (95% CI, 42.9 to 83.8) (27 of 193 case patients [14.0%] vs. 47 of 146 matched control patients [32.2%]) and against RSV-associated bronchiolitis resulting in ventilatory support was 67.2% (95% CI, 38.6 to 82.5) (27 of 189 case patients [14.3%] vs. 46 of 151 matched control patients [30.5%]).

CONCLUSIONS:

In a real-world setting, nirsevimab therapy was effective in reducing the risk of hospitalized RSV-associated bronchiolitis. (Funded by the National Agency for AIDS Research-Emerging Infectious Disease and others; ENVIE ClinicalTrials.gov number, NCT06030505.).

BACKGROUND:

In 2023, nirsevimab, a monoclonal antibody against respiratory syncytial virus (RSV), was approved in the United States to be given to infants to prevent bronchiolitis, a leading cause of pediatric hospitalizations. We sought to better understand how parents of otherwise healthy newborns would respond to this recommendation.

METHODS:

We conducted semistructured interviews of purposefully sampled parents of newborns admitted to the well newborn unit between November 2023 and February 2024. Interviews were performed in a constant comparative manner until thematic sufficiency was reached using the Health Beliefs Model as a conceptual framework.

RESULTS:

We conducted 28 interviews: 38% of participants planned to give nirsevimab to their newborn, 25% did not plan to, and 38% were unsure. Four major themes emerged: (1) Major knowledge gaps existed about RSV prophylaxis; (2) trust in pediatrician's recommendation and fear of RSV infection contributed to uptake; (3) parents deferring RSV prophylaxis were concerned about side effects, wanted more time to decide, felt the maternal RSV vaccine was sufficient, and trusted their own prevention measures; and (4) there was misinformation about nirsevimab among parents including a perception that nirsevimab is a new understudied vaccine with similarities to the COVID-19 vaccine. Application of the Health Beliefs Model highlighted actionable opportunities to positively influence decision making around perceived susceptibility and RSV disease severity, benefits, barriers, self-efficacy, and cues to action.

CONCLUSIONS:

Increasing overall awareness of both nirsevimab and RSV in infants, starting conversations during pregnancy to combat misinformation, leveraging trusting relationships with pediatricians and prenatal clinicians can help with future uptake.

BACKGROUND AND OBJECTIVES:

Immunocompromised children may have increased risk for severe respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI), potentially leading to prolonged hospitalization, intensive care, and death. The open-label phase II MUSIC trial evaluated the safety and pharmacokinetics of nirsevimab, an extended half-life monoclonal antibody against RSV, in immunocompromised children aged ≤24 months.

METHODS:

Participants received a single intramuscular injection of nirsevimab (first RSV season: 50 mg if <5 kg/100 mg if $5 kg; second season: 200 mg). Safety, antidrug antibodies, and pharmacokinetics were evaluated to day 361.

RESULTS:

Participants (n = 100) had $1 immunocompromising conditions: primary immunodeficiency (n = 33), previous transplantation (n = 16), HIV infection (n = 8) or treatment with high-dose systemic corticosteroids (n = 29), immunosuppressive chemotherapy (n = 20), or other immunosuppressive therapies (n = 15). Six children experienced eight treatment-related adverse events (none categorized as serious). Three deaths occurred, all were unrelated to treatment. Eleven children, developed antidrug antibodies, with minimal effects on pharmacokinetics and no apparent impact on safety. Nirsevimab serum concentrations at day 151 were similar to those effective in preventing medically attended RSV LRTI in healthy infants. Fourteen children had increased nirsevimab clearance. No protocol-defined medically attended RSV LRTIs occured through day 151.

CONCLUSIONS:

Among immunocompromised children aged ≤24 months, nirsevimab was well tolerated with no safety concerns and serum concentrations were supportive of efficacy. A subset of children with increased nirsevimab clearance, had conditions potentially associated with protein loss; however, the impact on efficacy is unknown.

Abstract Background The safety of the monoclonal antibody nirsevimab and the effect of nirsevimab on hospitalizations for respiratory syncytial virus (RSV)-associated lower respiratory tract infection when administered in healthy infants are unclear. Methods In a pragmatic trial, we randomly assigned, in a 1:1 ratio, infants who were 12 months of age or younger, had been born at a gestational age of at least 29 weeks, and were entering their first RSV season in France, Germany, or the United Kingdom to receive either a single intramuscular injection of nirsevimab or standard care (no intervention) before or during the RSV season. The primary end point was hospitalization for RSV-associated lower respiratory tract infection, defined as hospital admission and an RSV-positive test result. A key secondary end point was very severe RSV-associated lower respiratory tract infection, defined as hospitalization for RSV-associated lower respiratory tract infection with an oxygen saturation of less than 90% and the need for supplemental oxygen. Results A total of 8058 infants were randomly assigned to receive nirsevimab (4037 infants) or standard care (4021 infants). Eleven infants (0.3%) in the nirsevimab group and 60 (1.5%) in the standard-care group were hospitalized for RSV-associated lower respiratory tract infection, which corresponded to a nirsevimab efficacy of 83.2% (95% confidence interval [CI], 67.8 to 92.0; P<0.001). Very severe RSV-associated lower respiratory tract infection occurred in 5 infants (0.1%) in the nirsevimab group and in 19 (0.5%) in the standard-care group, which represented a nirsevimab efficacy of 75.7% (95% CI, 32.8 to 92.9; P=0.004). The efficacy of nirsevimab against hospitalization for RSV-associated lower respiratory tract infection was 89.6% (adjusted 95% CI, 58.8 to 98.7; multiplicity-adjusted P<0.001) in France, 74.2% (adjusted 95% CI, 27.9 to 92.5; multiplicity-adjusted P=0.006) in Germany, and 83.4% (adjusted 95% CI, 34.3 to 97.6; multiplicity-adjusted P=0.003) in the United Kingdom. Treatment-related adverse events occurred in 86 infants (2.1%) in the nirsevimab group. Conclusions Nirsevimab protected infants against hospitalization for RSV-associated lower respiratory tract infection and against very severe RSV-associated lower respiratory tract infection in conditions that approximated real-world settings. (Funded by Sanofi and AstraZeneca; HARMONIE ClinicalTrials.gov number, NCT05437510). © 2023 Massachusetts Medical Society.; Nirsevimab for Prevention of RSV Hospitalization in Infants Nirsevimab, a monoclonal antibody targeting RSV, led to decreased hospitalizations for RSV-associated lower respiratory tract infection in infants during their first RSV season, in an open-label, pragmatic trial. © 2023 Massachusetts Medical Society.

Study D5290C00008 is a Phase 2, open-label, uncontrolled, single-dose study to evaluate the safety and tolerability, pharmacokinetic(s) (PK), occurrence of antidrug antibody (ADA), and efficacy of nirsevimab in immunocompromised children who are ≤ 24 months of age at the time of dose administration. Approximately 100 subjects will be enrolled. Subjects will be followed for approximately 1 year after dose administration.

Respiratory tract infections caused by respiratory syncytial virus (RSV) are a worldwide burden and represent a major public health issue. In France, bronchiolitis is responsible for around 100,000 emergency room visits and 50,000 hospital admissions every year; 75% of infants hospitalised for RSV bronchiolitis are healthy full-term children.

Recent discoveries concerning the specific viral epitopes of RSV have made it possible to move from an empirical approach to a targeted preventive or curative approach (monoclonal antibodies, vaccines, anti-viral drugs).

Nirsevimab is a monoclonal antibody against RSV with enhanced neutralising activity and a prolonged half-life. A randomised, placebo-controlled phase III trial demonstrated the effectiveness of nirsevimab in reducing lower respiratory tract infections caused by RSV requiring medical management in healthy premature and term infants, with a favourable safety profile. The US Food and Drug Administration (FDA) approved the first RSV vaccine on May 3, 2023, and the second was approved on May 31, 2023. Nirsevimab was approved by the European Medicines Agency (EMA) on November 4, 2022.

The Nirse-CL study is a collaborative effort between the Ministry of Health of Chile, Instituto Sistemas Complejos de Ingeniería (ISCI), and the Faculty of Medicine of the University of Chile. The primary aim is to determine the effectiveness of the monoclonal antibody nirsevimab in preventing RSV infection in infants based on the integrated analysis of several national databases before, during, and after the implementation of a universal immunization program. The impact of the program on RSV-related health outcomes will also be determined.

BACKGROUND:

Data describing respiratory syncytial virus (RSV) neutralizing antibody (nAb) levels for nirsevimab, a recently approved, extended half-life, anti-RSV fusion protein (F protein) monoclonal antibody, relative to the previous standard of care, palivizumab, have not been reported.

METHODS:

MEDLEY was a randomized, palivizumab-controlled, phase 2/3 study of nirsevimab during 2 RSV seasons (season 1 and 2) in infants born preterm (≤35 weeks' gestational age; dosed season 1 only) or with congenital heart disease or chronic lung disease of prematurity (dosed seasons 1 and 2). Participants were randomly assigned to receive a single dose of nirsevimab followed by 4 monthly placebo doses, or 5 once-monthly doses of palivizumab. Anti-RSV F protein serology (ie, levels of prefusion [pre-F]/postfusion [post-F] conformation antibodies), nirsevimab and palivizumab concentrations, and RSV nAbs were measured in participant serum collected at baseline (pre-dose) and days 31, 151, and 361.

RESULTS:

Serologic data were similar in seasons 1 and 2. Nirsevimab predominately conferred pre-F antibodies, whereas palivizumab conferred pre-F and post-F antibodies. Nirsevimab and palivizumab serum concentrations highly correlated with nAb levels in both seasons. In season 1, nAb levels in nirsevimab recipients were highest in day 31 samples and gradually declined but remained 17-fold above baseline at day 361. nAb levels in palivizumab recipients increased incrementally with monthly doses to day 151. nAb levels followed similar patterns in season 2. nAb levels were ~10-fold higher with nirsevimab compared with palivizumab across both seasons.

CONCLUSIONS:

Nirsevimab prophylaxis confers ~10-fold higher and more sustained RSV nAb levels relative to palivizumab.