Gene therapy may be equitable therapeutic option for sickle cell disease in US
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Gene therapy could represent an equitable therapeutic strategy for sickle cell disease in the United States, according to study results presented at ASH Annual Meeting and Exposition.
Researchers reached this conclusion that accounted for the projected cost of sickle cell gene therapy — more than $2 million — while accounting for the impact of health inequities.
Background
Individuals with sickle cell disease are at considerable risk for mortality, with continued declines in quality of life over time.
Gene therapy — which may be approved for this indication in the United States as early as 2023 — could offer the potential for lifelong remission without the risks associated with allogeneic transplantation, including an estimated 5% risk for death.
Gene therapy pricing varies by indication, ranging from $2.1 million for spinal muscular atrophy and $2.8 million for thalassemia to a recently announced $3.5 million for hemophilia B.
“The question becomes, what would be a fair price to put on gene therapy specifically for patients with sickle cell disease, knowing this is a particularly unique population that has been historically marginalized in our country?” George Goshua, MD, MSc, assistant professor of medicine (hematology) at Yale School of Medicine, said during a press conference.
Prior projections using traditional criteria classified gene therapy as cost-ineffective in the United States. However, conventional cost-effectiveness analysis does not capture the impact of health inequities.
Methodology
Goshua and colleagues performed what they believe is the first distributional cost-effectiveness analysis (DCEA) in hematology/oncology, evaluating gene therapy vs. standard of care for individuals in the United States with sickle cell disease.
The method quantifies the tradeoff between traditional cost-effectiveness outcomes and health equity.
Researchers built and validated a Markov simulation model to evaluate the cost-effectiveness of gene therapy compared with standard of care for patients with mild, moderate or severe sickle cell disease.
They used Optum claims data from 2007 to 2017 to inform age-, sex- and disease severity-specific annual costs, as well as the probabilities of transition between disease severities. Investigators defined disease severity based on annual number of hospitalizations.
Standard-of-care options included hydroxyurea, antibiotics, opioid therapy, blood transfusions, vaccinations and stem cell transplantation.
Published lifetime simulation of patients living with sickle cell disease and matched controls informed quality-adjusted life-years. Researchers also employed age-, sex- and disease-specific background mortality probabilities.
Goshua and colleagues quantified traditional cost-effectiveness using an incremental cost-effectiveness ratio and cost-effectiveness threshold of $100,000 per quality-adjusted life-year.
Based on other approved indications, researches assumed gene therapy would cost $2.1 million.
They also assumed gene therapy would be 100% effective for achieving disease remission — meaning mortality would be brought back to age-, sex- and race/ethnicity-adjusted background mortality — and that the treatment modality would be applicable to patients aged 12 years or older, per the demographics of randomized controlled trials that studied the approach.
Results
Researchers conducted a DCEA — which applies an inequality aversion parameter to the distribution of outcomes across relevant subgroups — to account for health inequities in sickle cell disease.
“Epsilon of 0 implies no weight on equity, meaning we really don’t care about equity considerations,” Goshua said. “We know from income studies in the 1970s and 1980s that prior U.S. estimates put this value at roughly 0.5 to 3.”
Using an epsilon threshold of 2 implies that 1 quality-adjusted life-year gained by a person with sickle cell disease is equivalent to 2.91 quality-adjusted life years gained by a person without sickle cell disease, Goshua said.
Using an epsilon threshold of 1 implies that 1 quality-adjusted life-year gained by a person with sickle cell disease is equivalent to 1.68 quality-adjusted life-years gained by a person without sickle cell disease, he added.
Results showed base-case gene therapy starting at age 12 years yielded 25.5 discounted lifetime quality-adjusted life-years at a cost of $2.4 million, whereas standard of care yielded 16 discounted lifetime quality-adjusted life-years at a cost of $1.1 million.
The incremental cost-effectiveness ratio of $144,000 per quality-adjusted life-year “is not good value for money” using traditional cost-effectiveness methods and a $100,000 per quality-adjusted life-year cost-effectiveness threshold, Goshua and colleagues wrote.
However, a DCEA two-way sensitivity analysis that used the established inequality aversion parameter — or inequity weight — showed the price point for gene therapy for sickle cell disease “can go just a little bit north of $3 million,” Goshua said.
“Although gene therapy may exceed conventional cost-effectiveness standards, if we actually care about equity, we can see this truly could be an equitable therapy for our patients,” Goshua said. “If we care about equity and this is how we want to move forward in clinical medicine, these kinds of studies that can help inform equitable and value-based price benchmarks going decades into the future.”
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Goshua G, et al. Abstract 581. Presented at: ASH Annual Meeting and Exposition; Dec. 10-13, 2022; New Orleans.
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