Will the US$5 million onasemnogene abeparvosec treatment for spinal muscular atrophy represent 'value for money' for the NHS? A rapid inquiry into suggestions that it may be cost-effective

Gene Therapy for Neuromuscular Diseases: Health Economic Challenges and Future Perspectives

Highly efficacious, potentially curative gene therapies holds immense clinical promise, but also present complex challenges. At the time of regulatory approval and health technology assessment (HTA), evidence of efficacy and safety of gene therapies is often uncertain. In addition, research, development, and manufacturing costs, small pools of eligible patients, and the fact that many gene therapies are administered only once means that they frequently are associated with very high “one-off” price points. Although only a limited number of products have been brought to market globally, hundreds of clinical trials of gene therapies, including several of monogenetic neuromuscular diseases, are currently ongoing. Over time, as more and more conditions become amendable to gene therapy, the number of transformative, high-cost treatments is likely to increase considerably. For these reasons, concerns have been raised regarding the suitability of current health policy systems, including HTA frameworks, in ensuring appropriate access to these therapeutic innovations while simultaneously safeguarding value for taxpayers’ money, as well as affordability and sustainability. This review provides a summary overview of current challenges and future perspectives of gene therapies for neuromuscular diseases from a health economic point of view.

Critical Reflections on Reimbursement and Access of Advanced Therapies

Background: The health economic literature has questioned the cost-effectiveness and affordability of advanced therapies, proposed adjustments to value assessment frameworks, and discussed the use of outcome-based managed entry agreements and staggered payments in the last few years. The aim of this manuscript is to conduct a critical reflection on assessment criteria and access conditions for reimbursement of advanced therapies.

Methods: A narrative review of the peer-reviewed literature and grey literature was conducted in April 2021 by searching PubMed; Google Scholar; policy and legislative documents; websites of health technology assessment agencies, advanced therapy organisations, governmental advanced therapy innovation programmes, consultancy agencies; ISPOR conference abstracts and presentations.

Results: Based on the available evidence, this manuscript argues that: a) advanced therapies can be cost-effective at high prices set by manufacturers; b) the economic evaluation framework adopted by many payers under-values these products; c) advanced therapies can be affordable and may not require spread payments; d) outcome-based managed entry agreements are theoretically attractive, but challenging in practice; e) the cost-effectiveness of advanced therapies depends on the outcome-based managed entry agreement and payment approach; f) there is a role for multinational collaborations to manage reimbursement and access of advanced therapies.

Conclusions: This manuscript shows that there is no single approach to reimbursement and access of advanced therapies. Instead, we support a more tailored assessment of health economic aspects of advanced therapies, which considers the heterogeneity of these products and their target populations.

Systematic Literature Review of Clinical and Economic Evidence for Spinal Muscular Atrophy

INTRODUCTION

The recent advent of disease-modifying therapies (DMTs) has dramatically changed the treatment landscape of spinal muscular atrophy (SMA), and the multifaceted impact of this advancement has not been assessed thoroughly in the growing body of literature. We sought to summarize the literature on the natural history of SMA and the impact of SMA DMTs, including health-related quality of life (HRQOL) and utilities, clinical efficacy and safety, and economic impact.

METHODS

Systematic literature reviews were conducted following PRISMA guidelines with no inclusive dates. Relevant studies were identified by searching full-text databases on November 12-13, 2020, including MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, and EconLit, conference proceedings, health technology assessment databases, and clinical trial registries. All searches used a combination of MeSH and key terms. Studies were screened according to criteria based upon population, intervention, outcomes, and study design structure.

RESULTS

Findings from 17, 23, 32, and 42 studies were included for the evaluation of natural history of SMA, HRQOL and utilities, clinical efficacy and safety, and economic impact of DMTs, respectively. Currently available data indicate that untreated SMA is associated with considerable humanistic and economic burden, with estimates of costs varying by treatment. While a variety of interventions have been evaluated in SMA clinical trials, quantitative synthesis of safety and efficacy findings was not feasible because of inconsistencies in reported outcomes. Data assessing impacts of DMTs on HRQOL were also lacking.

CONCLUSIONS

Overall, this systematic literature review highlights a clear need for up-to-date and methodologically rigorous clinical, HRQOL, and economic data to support unbiased assessments of the relative clinical and economic effectiveness of SMA treatments. More research is required to extend our understanding of the burden of SMA on HRQOL utility assessments and the impact of new DMTs on HRQOL and utilities for patients with SMA.

Systematic Literature Review to Assess Economic Evaluations in Spinal Muscular Atrophy (SMA)

BACKGROUND

Spinal muscular atrophy (SMA) is a rare, progressive neuromuscular disease that affects individuals with a broad age range. SMA is typically characterised by symmetrical muscle weakness but is also associated with cardiac defects, life-limiting impairments in respiratory function and bulbar function defects that affect swallowing and speech. Despite the advent of three innovative disease-modifying therapies (DMTs) for SMA, the cost of DMTs in addition to the costs of standard of care can be a barrier to treatment access for patients. Health Technology Assessment (HTA) decision makers evaluate the cost effectiveness of a new treatment before making a reimbursement decision.

OBJECTIVE

The primary objective was to conduct a systematic literature review (SLR) to identify the modelling approaches used in economic evaluations that assess current approved treatments in SMA, with a secondary objective to widen the scope and identify economic evaluations assessing other (non-SMA) neuromuscular disorders.

METHODS

An SLR was performed to identify available economic evaluations associated with any type of SMA (Type 1, 2, 3 and/or 4). Economic evaluations associated with other (non-SMA) neuromuscular disorders were identified but not further analysed. Electronic searches were conducted in Embase, MEDLINE, Evidence-Based Medicine Reviews and EconLit via the Ovid platform in August 2019, and were supplemented by searches of the grey literature (reference lists, conference proceedings, global HTA body websites and other relevant sources). Eligibility criteria were based on the population, interventions, comparators and outcomes (PICO) framework. Quality assessment of full publications was conducted with reference to a published checklist.

RESULTS

Nine publications covering eight unique studies met all eligibility criteria for inclusion in the SLR, including four conference abstracts, two peer-reviewed original research articles and three HTA submissions (conducted in Canada, the US and the UK). Evaluations considered patients with early infantile-onset (most likely to develop Type 1 or Type 2 SMA), later-onset SMA and both infantile- and later-onset SMA. Data for the identified economic models were collected from literature reviews and relatively short-term clinical trials. Several intent-to-treat clinical trial populations were used in the studies, which resulted in variation in cycle length and different outcome measures to determine clinical efficacy. The results of the quality assessment on the five full-text, peer-reviewed publications found that they generally provided clear descriptions of objectives, modelling methods and results. However, key decisions, such as choice of economic evaluation, model type and choice of variables for sensitivity analysis, were often not adequately justified.

CONCLUSIONS

This SLR highlights the need for economic evaluations in SMA to better align in modelling approaches with respect to (i) consistency in model structure and use of motor function milestones as health states; (ii) consensus on measuring quality of life to estimate utilities; (iii) consistency in data collection by registries; and (iv) consensus on SMA-type classification and endpoints that determine intervention efficacy. Future economic evaluations should also incorporate the review group critiques of previous HTA submissions relating to data inputs and approaches to modelling and should include patient data reflective of the SMA population being modelled. Economic evaluations would also be improved with inclusion of long-term efficacy and safety data from clinical trials and valid patient and caregiver utility data.

Economic Evidence on Potentially Curative Gene Therapy Products: A Systematic Literature Review

OBJECTIVE

The aim of this review was to summarize all available evidence on the cost effectiveness of potentially curative gene therapies and identify challenges that economic evaluations face in this area.

METHODS

We conducted a systematic review of four databases (PubMed/MEDLINE, Embase, CINAHL, EconLit) and grey literature sources. We conducted the search on August 23, 2019 and updated it on November 26, 2020. We included all English, French and Spanish language studies that addressed a gene therapy that had received regulatory approval or had entered a phase III trial, and also reported on costs related to the therapy. Critical appraisal was conducted to assess quality of reporting in included studies.

RESULTS

Fifty-six studies were identified. Of the 42 full economic evaluations, 71% (n = 30) evaluated chimeric antigen receptor T-cell therapies, most used either a Markov model (n = 17, 40%) and/or a partitioned survival model (n = 17, 40%), and 76% (n = 32) adopted a public or private payer perspective. The model characteristics with the greatest impact on cost effectiveness included assumptions about the efficacy of the treatment and the comparators used.

CONCLUSION

All gene therapies in this review were shown to be more effective than their comparators, although due to high costs not all were considered cost effective at standard cost-effectiveness thresholds. Despite their high cost, some gene therapies have the potential to dominate the alternatives in conditions with high mortality/disability. The choice of comparator and assumptions regarding long-term effectiveness had substantial impacts on cost-effectiveness estimates and need to be carefully considered. Both the quality of inputs and the quality of reporting were highly variable.

Recent Advances in Stimulus-Responsive Nanocarriers for Gene Therapy

Gene therapy provides a promising strategy for curing monogenetic disorders and complex diseases. However, there are challenges associated with the use of viral delivery vectors. The advent of nanomedicine represents a quantum leap in the application of gene therapy. Recent advances in stimulus-responsive nonviral nanocarriers indicate that they are efficient delivery systems for loading and unloading of therapeutic nucleic acids. Some nanocarriers are responsive to cues derived from the internal environment, such as changes in pH, redox potential, enzyme activity, reactive oxygen species, adenosine triphosphate, and hypoxia. Others are responsive to external stimulations, including temperature gradients, light irradiation, ultrasonic energy, and magnetic field. Multiple stimuli-responsive strategies have also been investigated recently for experimental gene therapy.

Dravet Syndrome: Novel Approaches for the Most Common Genetic Epilepsy

Dravet syndrome (DS) is a severe developmental and epileptic encephalopathy that is mainly associated with variants in SCN1A. While drug-resistant epilepsy is the most notable feature of this syndrome, numerous symptoms are present that have significant impact on patients' quality of life. In spite of novel, third-generation anti-seizure treatment options becoming available over the last several years, seizure freedom is often not attained and non-seizure symptoms remain. Precision medicine now offers realistic hope for seizure freedom in DS patients, with several approaches demonstrating preclinical success. Therapeutic approaches such as antisense oligonucleotides (ASO) and adeno-associated virus (AAV)-delivered gene modulation have expanded the potential treatment options for DS, with some of these approaches now transitioning to clinical trials. Several of these treatments may risk the exacerbation of gain-of-function variants and may not be reversible, therefore emphasizing the need for functional testing of new pathogenic variants. The current absence of treatments that address the overall disease, in addition to seizures, exposes the urgent need for reliable, valid measures of the entire complement of symptoms as outcome measures to truly know the impact of treatments on DS. Additionally, with so many treatment options on the horizon, there will be a need to understand how to select appropriate patients for each treatment, whether treatments are complementary or adverse to each other, and long-term risks of the treatment. Nevertheless, precision therapeutics hold tremendous potential to provide long-lasting seizure freedom and even complete cures for this devastating disease.

New Treatments in Spinal Muscular Atrophy: Positive Results and New Challenges

Spinal muscular atrophy (SMA) is one of the most common autosomal recessive diseases with progressive weakness of skeletal and respiratory muscles, leading to significant disability. The disorder is caused by mutations in the survival motor neuron 1 (SMN1) gene and a consequent decrease in the SMN protein leading to lower motor neuron degeneration. Recently, Food and Drug Administration (FDA) and European Medical Agency (EMA) approved the antisense oligonucleotide nusinersen, the first SMA disease-modifying treatment and gene replacement therapy by onasemnogene abeparvovec. Encouraging results from phase II and III clinical trials have raised hope that other therapeutic options will enter soon in clinical practice. However, the availability of effective approaches has raised up ethical, medical and financial issues that are routinely faced by the SMA community. This review covers the available data and the new challenges of SMA therapeutic strategies.