Economic modeling in rare diseases can be challenging owing to limitations in data availability. This is true for spinal muscular atrophy (SMA), where there are no existing economic models. There is very little information on how these patients spend money on their treatment over the course of a lifetime, data gaps for disease natural history and data on the cost-effectiveness of treatment.
This is particularly applicable to two patient populations, infantile-onset and later-onset SMA patients. Both groups see significant effects upon being treated with Spinraza, which has been approved by the U.S. Food and Drug Administration and the European Medicines Agency for the treatment of SMA.
In the ENDEAR clinical trial (NCT02193074), infantile-onset patients who received Spinraza showed major advances in motor milestones, event-free survival, overall survival, motor function, and motor neuron health.
Researchers from RTI Health Solutions and Biogen studied Spinraza’s cost-effectiveness. Their objective was to develop two separate economic models to gauge the cost-effectiveness of Spinraza in patients with infantile- and later-onset spinal muscular atrophy compared to standard care.
“The current economic analysis presents the first cost-effectiveness models in the treatment of spinal muscular atrophy,” the researchers said.
The models represent the societal perspective in Sweden, where the study was conducted. The researchers modeled the cost-effectiveness of Spinraza over the course of 40 years in the infantile-onset model and 80 years in the later-onset model.
Their main measurements were for quality-adjusted life-year — a generic measure of disease burden including both the quality and the quantity of life lived used in economic evaluation to assess the value for money of medical interventions — and how much this increase cost.
Spinraza treatment led to a 3.86 increase in quality-adjusted life years for infantile-onset spinal muscular atrophy patients and 9.54 quality-adjusted life-years for later-onset SMA patients compared to standard of care.
Treatment also affected caregiver quality-adjusted life-years, with 0.02 and 2.39 incremental quality-adjusted life-years for infantile-onset and later-onset spinal muscular atrophy caregivers.
Treatment with Spinraza per quality-adjusted life-years gained cost, including caregiver expenditures, approximately 5.64 million SEK ($625,275) and 3.19 million SEK ($353,638) for infantile-onset and later-onset SMA, respectively, in comparison to the standard of care.
These models are affected by changes in Spinraza’s vial price and patient health-state utilities, specifically walking without assistance. This means that when the cost of Spinraza’s vial price or patient health-state utilities increases, so does the cost per quality-adjusted life-years.
These values were quite like those for other rare diseases. However, Spinraza was not cost effective in the infantile-onset and later-onset populations when using a willingness-to-pay threshold (2 million SEK/$221,862) that the TLV has considered reasonable for some rare diseases. Nevertheless, Spinraza gained reimbursement in Sweden in 2017 for patients with SMA types I–IIIa.
“The models can be adapted to evaluate the cost-effectiveness of nusinersen in other countries,” the researchers said.
The researchers recommend compiling more data to improve cost-effectiveness analysis for the treatment of spinal muscular atrophy in Sweden.
“Further evaluation of the cost-effectiveness of nusinersen is recommended when longer-term data are available from the ongoing open-label SHINE extension study (NCT02594124), into which patients from ENDEAR and CHERISH were moved, to incorporate additional evidence on treatment benefit into the economic model,” the researchers said.