Risdiplam, sold under the brand name Evrysdi, is the oral pill that effectively replaced Zolgensma, the one-time gene therapy injection that carried a staggering $2.125 million price tag and held the record as the most expensive drug in the world. Approved by the FDA in August 2020, risdiplam gave families dealing with spinal muscular atrophy something that had never existed before: a treatment you could take at home, by mouth, every single day, without a hospital visit, without an IV, and without a bill that could bankrupt a small insurance company. For a child like those enrolled in the FIREFISH trial, many of whom achieved the ability to sit independently and some of whom learned to walk, this pill represented a genuine shift in how SMA could be managed across a lifetime. But calling risdiplam a simple “replacement” for Zolgensma oversimplifies a complicated treatment landscape.
These two therapies work through entirely different biological mechanisms, target different patient populations at different stages, and carry different risk profiles. Some neurologists now use them in combination. The cost comparison alone, while dramatic, does not capture the full picture of what each drug does and does not do. This article covers how risdiplam works, who it is best suited for, how it stacks up against both Zolgensma and the earlier injection nusinersen (Spinraza), and what families and caregivers should realistically expect from oral SMA therapy, including its limitations.
Table of Contents
- How Did a Daily Pill Replace a $2 Million Injection for Spinal Muscular Atrophy?
- Who Benefits Most from Risdiplam, and Where Does It Fall Short?
- Risdiplam Versus Spinraza — The Other Injection It Competed Against
- Understanding the Real Costs — One-Time Payment Versus Lifelong Therapy
- Newborn Screening and the Race Against Motor Neuron Loss
- The Impact on Caregivers and Daily Life
- Where SMA Treatment Goes from Here
- Conclusion
- Frequently Asked Questions
How Did a Daily Pill Replace a $2 Million Injection for Spinal Muscular Atrophy?
Spinal muscular atrophy is caused by mutations in the SMN1 gene, which leads to a shortage of survival motor neuron protein. Without enough SMN protein, motor neurons in the spinal cord degenerate, causing progressive muscle weakness that in its most severe form, Type 1, is fatal before age two without treatment. For decades, there was nothing to offer these families. Then three therapies arrived in rapid succession: nusinersen (Spinraza) in 2016, onasemnogene abeparvovec (Zolgensma) in 2019, and risdiplam (Evrysdi) in 2020. Each attacks the same underlying protein deficiency, but through very different routes.
Zolgensma works by delivering a functional copy of the SMN1 gene directly into motor neuron cells using an adeno-associated virus vector. It is a one-time intravenous infusion, typically given to children under two years old, and its $2.125 million cost reflected both the gene therapy’s complexity and Novartis’s argument that a single dose replaces a lifetime of treatment. Risdiplam, developed by Roche and Genentech, takes a fundamentally different approach. It is a small molecule that modifies how the backup gene, SMN2, splices its messenger RNA, coaxing it to produce more full-length, functional SMN protein. Because it is an oral liquid taken daily, it can be administered at home without any medical infrastructure. The initial annual cost of risdiplam was approximately $100,000 to $340,000 depending on the patient’s age and weight, a fraction of Zolgensma’s price, though it is a lifelong, ongoing expense rather than a one-time payment.
Who Benefits Most from Risdiplam, and Where Does It Fall Short?
Risdiplam’s broadest advantage is its indication range. It is FDA-approved for patients two months of age and older with all types of SMA, including adults, making it the only approved SMA therapy without an upper age limit. This matters enormously because Zolgensma is only approved for children under two, and nusinersen, while approved for all ages, requires repeated intrathecal injections directly into the spinal fluid, a procedure that becomes increasingly difficult in patients with severe scoliosis or spinal fusion, which are common in older SMA patients. For a 35-year-old with Type 3 SMA who has a fused spine and cannot safely undergo lumbar puncture, risdiplam may be the only viable disease-modifying treatment available. However, risdiplam is not a cure, and it does not work the same way in every patient.
Clinical trial data from SUNFISH, which studied patients aged 2 to 25 with Types 2 and 3, showed statistically significant improvements in motor function scores compared to placebo, but the gains were modest for many participants, particularly older patients with long-established disease. The drug cannot reverse motor neuron death that has already occurred. It can only increase SMN protein production going forward, which may slow or stabilize decline rather than restore lost function. Families who expect a child or adult to regain abilities lost years ago are likely to be disappointed, and neurologists have an obligation to set those expectations clearly. There is also the commitment factor: because risdiplam does not permanently alter the genome the way Zolgensma aims to, stopping the medication means SMN protein levels drop again, making this a lifelong daily therapy with no defined stopping point.
Risdiplam Versus Spinraza — The Other Injection It Competed Against
Before risdiplam arrived, the primary alternative to Zolgensma was nusinersen, branded as Spinraza, which Biogen launched in 2016 as the first-ever approved SMA treatment. Spinraza is an antisense oligonucleotide that also targets the SMN2 gene’s splicing, but it must be delivered by intrathecal injection, meaning a needle into the spinal canal. The loading dose schedule requires four injections over two months, followed by maintenance doses every four months, indefinitely. At roughly $750,000 for the first year and $375,000 per year after that, Spinraza’s cumulative lifetime cost can rival or exceed Zolgensma’s single payment.
For many families, the practical burden of Spinraza was as significant as the financial one. Each injection requires a hospital or clinic visit, sedation for young children, and carries procedural risks including headache, back pain, and in rare cases, infection or bleeding at the injection site. A specific example illustrates the shift well: at Boston Children’s Hospital, clinicians reported that some adolescent patients with moderate SMA who had been stable on Spinraza chose to transition to risdiplam during the early pandemic months of 2020 and 2021, in part because traveling to the hospital every four months for spinal injections during COVID posed unacceptable risk. Risdiplam offered disease management from home with a strawberry-flavored liquid measured by syringe, a vastly simpler routine. Published transition studies have generally shown that patients switching from nusinersen to risdiplam maintained their motor function, though the data on whether one is clinically superior to the other in head-to-head terms remains limited.
Understanding the Real Costs — One-Time Payment Versus Lifelong Therapy
The price tag comparison between Zolgensma and risdiplam is frequently cited but frequently misunderstood. Zolgensma’s $2.125 million is a one-time charge, and Novartis even offered outcomes-based payment plans where portions would be refunded if the therapy failed to meet specified milestones. Risdiplam’s annual cost, while much lower per year, accumulates. For an infant started on risdiplam at two months old who takes it for an expected lifespan of, say, 50 to 70 years, the total expenditure could reach $5 million to $24 million at current pricing, depending on dosing and price adjustments over time. Insurers and health systems must weigh an enormous upfront cost against a lower but perpetual one, and there is no consensus on which model is more sustainable.
The tradeoff extends beyond dollars. Zolgensma carries a known risk of serious liver toxicity, requiring monitoring of liver enzymes and a course of corticosteroids around the infusion. Rare cases of thrombotic microangiopathy, a dangerous blood-clotting condition, have also been reported post-marketing. Risdiplam’s side effect profile in trials included fever, diarrhea, and rash, but long-term safety data beyond five to six years does not yet exist because the drug is simply too new. For a parent deciding between a single high-risk event and decades of daily medication with unknown very-long-term effects, neither option is uncomplicated. Many pediatric neurologists now discuss both therapies as complementary rather than competitive, and a growing number of children receive Zolgensma first and are then maintained on risdiplam or nusinersen afterward, though this combination approach is still being studied in formal trials and is not part of any standard guideline.
Newborn Screening and the Race Against Motor Neuron Loss
The single most important variable in SMA treatment outcomes is not which drug is chosen but when treatment begins. Motor neurons, once dead, cannot be replaced by any of these therapies. Studies have consistently shown that presymptomatic infants, those identified through newborn screening before they show any muscle weakness, have dramatically better outcomes than those treated after symptoms appear. In the STR1VE trial for Zolgensma and the RAINBOWFISH trial for risdiplam, presymptomatic infants achieved motor milestones like sitting and walking at rates approaching those of unaffected children. This creates an urgent public health issue.
As of early 2025, SMA has been added to the Recommended Uniform Screening Panel in the United States, and most states now screen for it at birth. But globally, the picture is very different. Many countries in Africa, South Asia, and South America have no newborn screening for SMA, meaning children are typically diagnosed only after significant motor neuron loss has already occurred, often months or years into decline. For these patients, risdiplam’s oral formulation offers a distinct logistical advantage over both Zolgensma, which requires sophisticated infusion centers and cold-chain transport, and Spinraza, which demands access to specialists trained in intrathecal injection. However, the limitation remains stark: risdiplam given late cannot undo the damage already done, and in a child with Type 1 SMA diagnosed at 18 months who has already lost the ability to swallow safely, the drug may stabilize but will not restore that function. Families in this situation need honest guidance about what stabilization means versus what recovery means.
The Impact on Caregivers and Daily Life
One dimension of risdiplam that clinical trials rarely capture is what it means for the daily lives of caregivers. Administering a flavored liquid once a day at home, typically after a meal, is a fundamentally different experience from managing quarterly hospital visits for spinal injections or coordinating a gene therapy infusion that may require weeks of pre- and post-treatment monitoring. For a single parent managing a child with SMA alongside work and other children, this difference is not trivial. Roche has reported that in post-marketing surveys, caregiver burden scores improved meaningfully in families who transitioned from nusinersen to risdiplam, with particular reductions in time lost from work and anxiety related to medical procedures.
There is a practical caveat, though. Because risdiplam must be taken every day without interruption, adherence becomes its own challenge over years and decades. A teenager with SMA who feels stable may question why they need to keep taking a daily medication, a scenario familiar to clinicians managing any chronic condition from epilepsy to HIV. Missed doses lead to drops in SMN protein levels, and there is not yet good data on what intermittent adherence means for long-term motor neuron health. This is a challenge that Zolgensma, by design, sidesteps entirely.
Where SMA Treatment Goes from Here
The SMA treatment landscape is no longer a story of one breakthrough drug but of a maturing field with multiple options, unanswered questions, and active research. Combination therapy trials, evaluating Zolgensma followed by risdiplam or nusinersen, are underway at several major centers and may eventually establish whether layering treatments produces better outcomes than any single approach. Next-generation molecules targeting other aspects of motor neuron biology, including muscle-directed therapies like apitegromab, are in clinical trials and could complement existing SMN-boosting drugs. For the brain health and neurodegeneration community more broadly, the SMA story offers both hope and caution.
It demonstrates that genetic neurodegenerative diseases once considered untreatable can be meaningfully altered by pharmacological intervention, a principle that researchers working on conditions from Huntington’s disease to ALS are actively pursuing. But it also illustrates that “treated” is not the same as “cured.” Children who received these therapies earliest are still young, and the first generation of treated SMA patients is, in effect, writing the long-term outcome data in real time. What their motor function, respiratory health, and quality of life look like at 20 or 40 years old remains unknown. The honest answer to many families’ most urgent questions is: we do not know yet, and anyone who claims certainty is overstepping the evidence.
Conclusion
Risdiplam changed the SMA treatment conversation by proving that a daily oral medication could meaningfully increase survival motor neuron protein, improve or stabilize motor function across all ages and SMA types, and do so without hospital visits, spinal injections, or a multimillion-dollar single payment. It did not make Zolgensma or Spinraza obsolete. Instead, it expanded the options available to families and clinicians, particularly for older patients, those in resource-limited settings, and those who cannot tolerate the procedural demands of the alternatives. The choice among these therapies is not a simple ranking but a nuanced decision that depends on age, disease severity, insurance coverage, access to medical infrastructure, and family circumstances.
For caregivers and families navigating an SMA diagnosis, the most critical steps remain early detection through newborn screening, prompt consultation with a neuromuscular specialist, and an honest conversation about what each therapy can and cannot do. The existence of three mechanistically distinct treatments for a disease that had zero approved therapies a decade ago is genuinely remarkable. But the work is not finished. Long-term outcome data, combination therapy results, and equitable global access are the challenges that will define whether this progress translates into a fundamentally different life trajectory for people born with SMA in the coming decades.
Frequently Asked Questions
Is risdiplam a cure for spinal muscular atrophy?
No. Risdiplam increases production of SMN protein by modifying how the SMN2 gene is read, but it does not fix or replace the mutated SMN1 gene. It must be taken daily for life, and stopping treatment allows SMN protein levels to fall. It can slow progression and improve or stabilize motor function, but it cannot reverse motor neuron death that has already occurred.
Can a patient take both Zolgensma and risdiplam?
Some patients have received Zolgensma as infants and been placed on risdiplam or nusinersen afterward. This combination approach is increasingly used in clinical practice, particularly when Zolgensma alone did not produce the expected level of motor function. However, formal combination therapy guidelines do not yet exist, and this remains an area of active research.
What are the most common side effects of risdiplam?
In clinical trials, the most frequently reported side effects included fever, diarrhea, rash, upper respiratory infections, and mouth sores. Because the drug has only been available since 2020, long-term safety data beyond approximately five years is still being collected.
How much does risdiplam cost compared to Zolgensma?
Risdiplam costs approximately $100,000 to $340,000 per year depending on the patient’s weight and age. Zolgensma is a single infusion priced at $2.125 million. Over a full lifetime of treatment, risdiplam’s cumulative cost can potentially exceed Zolgensma’s one-time price, making the financial comparison more complex than the headline numbers suggest.
Does risdiplam work for adults with SMA?
Yes. Risdiplam is the only SMA therapy approved without an upper age limit. The SUNFISH trial included patients up to age 25 and showed statistically significant improvements in motor function scores. However, the magnitude of benefit tends to be more modest in older patients with longer disease duration and more established motor neuron loss.
Why is newborn screening so important for SMA treatment outcomes?
All three SMA therapies work best when given before significant motor neuron loss has occurred. Presymptomatic infants treated within weeks of birth have achieved milestones like independent sitting and walking at rates approaching those of unaffected children. Once motor neurons die, no current therapy can replace them, making early detection the single greatest predictor of treatment success.
