Comments on palivizumab (Synagis)

Palivizumab in preventing respiratory syncytial virus-related hospitalization in high-risk infants

Respiratory syncytial virus (RSV) causes seasonal epidemics (winter or wet-season) of serious lower respiratory tract infections in young infants with subsequent increased frequency of recurrent wheezing during early childhood. Palivizumab is a humanized monoclonal antibody that provides immunoprophylaxis against RSV when administered monthly over the RSV season. It significantly reduced hospitalizations in high-risk infants including preterm infants with and without bronchopulmonary dysplasia and infants with hemodynamically significant congenital heart disease. Since its license in 1998, approximately 36 methodologically different economic studies have been performed to prove cost-effectiveness of the product. The majority of cost-effectiveness analyses revealed costs of palivizumab exceeding anticipated savings from reduced RSV hospitalizations. A minority of studies performed cost-effectiveness analyses using incremental cost-effectiveness ratios as costs per quality-adjusted life-year gained. The wide variability in the results of economic studies with estimates ranging from cost savings to incremental costs of a high order of magnitude with its use is discussed, in the light of the continuing burden of RSV disease, the limited treatment modalities, and the continuing research for a vaccine.

Use of palivizumab in primary practice

OBJECTIVE

To describe the implementation of a program for the use of palivizumab in a general pediatrics office and evaluate adherence to the 2009 American Academy of Pediatrics (AAP) guidelines.

METHODS

Pediatricians in a large practice were educated in the diagnosis and management of bronchiolitis, with specific attention to the AAP's palivizumab administration guidelines. During the 2009-2010 and 2010-2011 respiratory syncytial virus seasons, children were systematically identified and enrolled for palivizumab administration. Indication for administration was determined by gestational age, age at the beginning of the respiratory syncytial virus season, pertinent diagnoses, and presence of risk factors.

RESULTS

In the 2009-2010 season, 161 children were enrolled to receive palivizumab, 86 of whom (53%) conformed with AAP guidelines. In contrast, in 2010-2011, a total of 85 children were enrolled to receive palivizumab, and 73 (86%) conformed with the guidelines. As a consequence, the total cost of palivizumab (US $: 511 559 vs 1 500 670) and the cost per child (US $: 6018 vs 9438) were lower in 2010-2011 than in 2009-2010. However, of the children selected within the AAP guidelines, only 29% received the appropriate number of doses, whereas 62% and 9% received fewer or excessive doses, respectively; these findings were similar for the 2 seasons.

CONCLUSIONS

In a primary practice, use of palivizumab outside of the AAP guidelines was frequent and manifested as inadequate indications or inadequate number of doses. The former improved with education and standardization of care (suggesting provider problems), while the latter did not (suggesting system problems). Additional interventions are required.

Identification of broad-spectrum antiviral compounds and assessment of the druggability of their target for efficacy against respiratory syncytial virus (RSV)

The search for novel therapeutic interventions for viral disease is a challenging pursuit, hallmarked by the paucity of antiviral agents currently prescribed. Targeting of viral proteins has the inextricable challenge of rise of resistance. Safe and effective vaccines are not possible for many viral pathogens. New approaches are required to address the unmet medical need in this area. We undertook a cell-based high-throughput screen to identify leads for development of drugs to treat respiratory syncytial virus (RSV), a serious pediatric pathogen. We identified compounds that are potent (nanomolar) inhibitors of RSV in vitro in HEp-2 cells and in primary human bronchial epithelial cells and were shown to act postentry. Interestingly, two scaffolds exhibited broad-spectrum activity among multiple RNA viruses. Using the chemical matter as a probe, we identified the targets and identified a common cellular pathway: the de novo pyrimidine biosynthesis pathway. Both targets were validated in vitro and showed no significant cell cytotoxicity except for activity against proliferative B- and T-type lymphoid cells. Corollary to this finding was to understand the consequences of inhibition of the target to the host. An in vivo assessment for antiviral efficacy failed to demonstrate reduced viral load, but revealed microscopic changes and a trend toward reduced pyrimidine pools and findings in histopathology. We present here a discovery program that includes screen, target identification, validation, and druggability that can be broadly applied to identify and interrogate other host factors for antiviral effect starting from chemical matter of unknown target/mechanism of action.

The cost and safety of multidose use of palivizumab vials

Palivizumab is an antirespiratory syncytial virus humanized murine monoclonal antibody that has been shown to reduce the frequency of hospitalization rates of preterm infants infected with respiratory syncytial virus. The United States Food and Drug Administration has approved palivizumab for single-vial dosage; however, if multidose use of single-use vials is proven safe, significant cost savings for respiratory syncytial virus prophylaxis would result. A total of 446 palivizumab vials administered to patients during the respiratory syncytial virus seasons of 2004-2006 were examined for bacterial contamination. One single-use vial showed growth of multiple organisms, and all multidose-use vials were culture negative. The cost benefits of multidose palivizumab vials netted a potential average savings of $37 410 per year in this institution. This study suggests that multidose distribution is a possible solution for cost savings with no increased risk to patients. Secondary to the low incidence of complications, the safety of this practice will require a larger study.

Hospital admission of high risk infants for respiratory syncytial virus infection: implications for palivizumab prophylaxis

OBJECTIVES

To determine the rates of hospital admission for respiratory syncytial virus (RSV) infection among children born at different gestational ages. To assess the theoretical impact of palivizumab prophylaxis on admissions for RSV infection.

DESIGN

Retrospective cohort study of children born in 1991-2000.

SETTING

Tertiary care university hospital.

METHODS

Data on all children born during the 10 year period were combined with information on laboratory confirmed RSV infections in these children until the end of 2002. The theoretical impact of palivizumab on RSV associated admissions was estimated by applying the current recommendations for prophylaxis to the study population and using the observed rates of admission in the calculations.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Rates of RSV infection and hospital admission in different subgroups of children.

RESULTS

Children with chronic lung disease (CLD) were admitted for RSV infection at a rate of 12.0%. The corresponding rates in children born at </=28 or 29-32 weeks gestation were 7.1% and 6.8% respectively. Children born at </=32 weeks gestation accounted for 6.6% of all admissions due to RSV. Of 586 children who would have met the criteria for palivizumab prophylaxis, 27 (4.6%) were admitted with RSV during the presumed prophylactic period. The number needed to treat to prevent one admission for RSV infection was 15 for children with CLD (with a total cost of 75 000) and 43 for children without CLD born at </=32 weeks gestation (with a total cost of 215 000).

CONCLUSIONS

The rates of hospital admission for RSV infection in premature infants were substantially lower than those in most previous reports from other countries. Determination of the local rates of RSV admissions in different groups of children would be useful in making decisions about the use of palivizumab.

Anticipated costs of hospitalization for respiratory syncytial virus infection in young children at risk

BACKGROUND

Reliable estimates of hospitalization costs for severe respiratory syncytial virus (RSV) infection are necessary to perform economic analyses of preventive strategies of severe RSV disease. We aimed to develop a model that predicts anticipated mean RSV hospitalization costs of groups of young children at risk for hospitalization, but not yet hospitalized, based on readily available child characteristics.

METHODS

We determined real direct medical costs of RSV hospitalization from a societal perspective, using a bottom-up strategy, in 3458 infants and young children hospitalized for severe RSV disease during the RSV seasons 1996-1997 to 1999-2000 in the Southwest of the Netherlands. We used a linear regression model to predict anticipated mean RSV hospitalization costs of groups of children at risk, based on 4 child characteristics [age, gestational age, birth weight and bronchopulmonary dysplasia (BPD)], expressed in EC Euros as of the year 2000.

FINDINGS

The mean RSV hospitalization costs of all patients were 3110 Euros. RSV hospitalization costs were higher for patients with lower gestational age (5555 Euros; gestational age, </=28 weeks), lower birth weight (3895 Euros; birth weight </=2500 g), BPD (5785 Euros; with BPD) and young age (4730 Euros; first month of life). The linear regression model had an adjusted R of 0.08. This indicates a low explanatory ability for hospitalization costs of individual children. However, the model could accurately estimate the anticipated mean hospitalization costs of groups of children with the same characteristics.

INTERPRETATION

RSV hospitalization costs were substantial, especially of specific high risk groups. Anticipated mean hospitalization costs of groups of children at risk for RSV hospitalization, but not yet hospitalized, could well be estimated with 4 child characteristics (age, gestational age, birth weight and BPD). These estimated costs can be used for economic analyses of preventive strategies for severe RSV disease.

Rehospitalization for respiratory syncytial virus infection in infants with extremely low gestational age or birthweight in Denmark

AIM

To determine the risk of rehospitalization for respiratory syncytial virus (RSV) infection during the first 2 y of life in extremely preterm infants.

METHODS

Records on all rehospitalizations during the first 2 living years of all infants born with gestational age <28 wk or birthweight <1,000g during 1994 and 1995 in Denmark were retrospectively reviewed.

RESULTS

Among 240 eligible infants, 43 (18%) had been rehospitalized 48 times owing to RSV. In infants (n = 210) without CLD the risk of rehospitalization for RSV was 16%, whereas in infants with CLD (n = 30) it was 30% (p = 0.065). Eighteen infants (38%) required respiratory support (supplemental oxygen only 3, continuous positive airway pressure 14, mechanical ventilation 1). Apart from CLD the only factor that could be associated with increased risk of hospitalization for RSV was discharge during autumn (p = 0.05). No infant died from RSV infection.

CONCLUSION

The high rate of rehospitalization for RSV in extremely preterm infants in Denmark, especially in infants with CLD, should lead to considerations concerning more widespread use of prophylaxis against RSV in these infants.

Impact of palivizumab prophylaxis on respiratory syncytial virus hospitalizations in high risk Alaska Native infants

BACKGROUND

Alaska Native children experience extremely high rates of hospitalization for respiratory syncytial virus (RSV) infection. We evaluated the effect of palivizumab prophylaxis on the incidence of RSV hospitalizations in high risk Alaska Native children.

METHODS

We analyzed two retrospective cohorts. The first analysis, of southwest Alaska Native children hospitalized with acute respiratory infections during 1993 to 1996 and 1998 to 2001, compared RSV hospitalization rates among premature and nonpremature infants born before (1993 to 1996) and after (1998 to 2001) palivizumab use. The second analysis, of Alaska Native infants with a history of prematurity or lung disease during 1998 through 2001, compared RSV hospitalization among children receiving palivizumab during protected periods (within 32 days after a dose of palivizumab) and unprotected periods.

RESULTS

First RSV hospitalizations in premature infants from southwest Alaska meeting criteria for palivizumab prophylaxis decreased from 439 per 1000 births before to 150 per 1000 births after palivizumab (relative rate, 0.34; 95% confidence interval, 0.17 to 0.68), whereas the rate in nonpremature infants remained stable (148 per 1000 births compared with 142 per 1000). Among high risk Alaska Native children during 1998 through 2001, the rate of first RSV hospitalization was 0.55 per 1000 protected days and 1.07 per 1000 unprotected days (relative rate, 0.52; 95% confidence interval, 0.28 to 0.93).

CONCLUSIONS

Palivizumab reduced RSV hospitalizations in high risk infants in a region with high rates of RSV hospitalization.

Parental emotional and time costs predict compliance with respiratory syncytial virus prophylaxis

BACKGROUND

Two agents are effective in preventing respiratory syncytial virus (RSV) hospitalization in premature infants: RSV immune globulin (RSV-IG) and palivizumab. RSV-IG is associated with greater parental emotional and time costs, which may account for the more limited adherence to recommended monthly treatment with this agent.

OBJECTIVES

To compare the emotional distress and time costs associated with RSV-IG and palivizumab treatments and to determine the influence of these costs on treatment adherence.

METHODS

We surveyed parents of 82 infants who received RSV-IG (90% of eligible) and parents of 61 infants who received palivizumab (87% of eligible) at Arkansas Children's Hospital by telephone. We measured infant distress during treatment, parental distress, parental time costs, and adherence with recommended monthly prophylaxis.

RESULTS

Half of parents of RSV-IG recipients witnessed their infant in distress during infusion, over half (61%) were upset by observing the needle stick, and 22% observed infusion in the scalp. Fewer than 5% of parents of palivizumab recipients observed their infant in distress or were themselves distressed during treatment. A quarter of parents took time off from work for RSV-IG or palivizumab treatment. RSV-IG recipients completed 62% of recommended monthly treatments compared with 86% completed by palivizumab recipients. Increased parental distress and time costs largely accounted for the reduction in adherence to monthly treatment among RSV-IG recipients.

CONCLUSIONS

The emotional and time costs of RSV-IG treatment far exceed those of palivizumab and predict substantial differences in treatment adherence between the 2 agents. The impact of hidden costs on treatment adherence should be included in economic evaluations of medical procedures.

Treatment and Prevention of RSV Bronchiolitis

Respiratory syncytial virus is a leading cause of bronchiolitis and pneumonia in children worldwide, resulting in significant morbidity and mortality in high-risk individuals. The pediatric populations at high risk for severe RSV infections include patients with cardiac disease, lung disease, immunosuppression, premature birth or healthy infants less than six months of age. Supportive care is the primary treatment of RSV lower respiratory tract infections. Other treatment regimens include the use of bronchodilators and anti-inflammatory agents; however, the use of these agents is controversial due to lack of evidence of efficacy in all studies. Ribavirin, an antiviral agent, has been administered for the treatment of RSV lower respiratory tract infections, but its efficacy has been questioned due to flawed study designs. RSV-IVIG and palivizumab are approved for the prevention of RSV infection in selected children at high risk for serious disease. These agents are equally efficacious and expensive; however, the cost-effectiveness of prophylaxis is unclear. Currently, no vaccines for RSV are available for general use, but research in the area continues. Until a safe, effective and relatively inexpensive method for prophylaxis is available, RSV infections will continue to cause significant morbidity and mortality in children.

Palivizumab for respiratory syncytial virus prophylaxis in high-risk infants: a cost-effectiveness analysis

BACKGROUND

Prophylactic therapy with palivizumab, a humanized monoclonal antibody, has been shown to reduce the number of respiratory syncytial virus (RSV)-related hospitalizations in preterm infants. The cost-effectiveness of this therapy has not been evaluated from the provider's perspective using cost data.

OBJECTIVES

The objectives of this study were to determine the cost per RSV infection episode avoided by using prophylactic palivizumab therapy in a high-risk infant population and to determine whether certain subgroups of infants derived greater benefit from prophylactic therapy.

METHODS

A decision-analytic model simulating an RSV infection episode was developed to evaluate the cost-effectiveness of palivizumab prophylaxis from the perspective of the health care system (provider). Data to populate the model were gathered from the medical literature (identified through a MEDLINE search of studies on the incidence of RSV infection) and the IMpact-RSV clinical trial. Data included incidence of RSV infection and the associated health care resource use and costs. Costs to the provider were determined using a university-affiliated hospital cost-accounting system. Cost-effectiveness ratios were calculated over a range of RSV infection incidence rates in a control population. Sensitivity analyses were performed for the cost of palivizumab therapy, the cost of RSV-related hospitalization, and the number of emergency department, physician office, and home health care visits. For the subgroup analysis, infants were classified by gestational age (<32 and > or = 32 weeks) and stratified by severity of chronic lung disease.

RESULTS

The cost per additional RSV infection episode avoided ranged from dollars 0 (cost savings) to dollars 39,591 for palivizumab prophylaxis costs of dollars 2500 and from dollars 2702 to dollars 79,706 for palivizumab prophylaxis costs of dollars 4500. The model was insensitive to changes in the number of emergency department, physician office, and home health care visits. The difference in RSV incidence between the treatment and control groups was greater among infants > or = 32 weeks' gestational age than among infants <32 weeks' gestational age. onclusions: The incremental cost-effectiveness of palivizumab compared with no prophylactic therapy was sensitive to changes in the incidence of RSV infection in control infants, the average cost of RSV hospitalization, and the cost of palivizumab. Clinicians may use this information along with additional factors to determine whether palivizumab is cost-effective in their clinical setting and geographic area.

Antibodies for the prevention and treatment of viral diseases

This paper reviews current use and evolving role of polyclonal and monoclonal antibody products for the prevention and treatment of viral diseases. Antibodies continue to be indicated for prophylaxis either prior to an anticipated exposure especially in situations of travel, or more commonly following an exposure. The predominant indication for use of antibody products is to prevent infection. With the availability of vaccines for the prevention of chickenpox, hepatitis A, hepatitis B, measles, rabies and smallpox, the role of passive immunization is reserved for susceptible individuals and those at high risk for complications of infection. Risks of transmission of infections associated with use of human plasma-derived products have been reduced by improvements in donor screening and virus removal and inactivation procedures. An additional safety concern has been addressed by the removal of thimerosal as a preservative. Within the last 5 years, two antibodies have been licensed for a viral indication, RespiGam and Synagis both for prevention of respiratory syncytial virus infection. RespiGam is a human plasma derived antibody and Synagis is a humanized monoclonal antibody, the first such antibody to be licensed for an infectious disease indication. CytoGam for prevention of cytomegalovirus infection in kidney transplant patients has recently been granted an expanded indication to include use in lung, liver, pancreas and heart transplant patients. As the use of therapeutics becomes more sophisticated, researchers may find better ways of using antibody products.