(MEMPHIS, Tenn. – August 13, 2025) Spinal muscular atrophy (SMA) is a rare genetic condition that causes progressive muscle weakness, which, when untreated, prevents infants with the most severe form from gaining motor development — never gaining the ability to sit — and typically leads to death before 2 years of age. The oral drug risdiplam benefits symptomatic patients with improved motor function and increased survival, but had only been Food and Drug Administration–approved for use in patients aged 2 months and older. An international consortium, co-led by Richard Finkel, MD , of St. Jude Children's Research Hospital, formerly of Nemours Children's Health, reports today that giving risdiplam as early as 16 days of age, before symptoms arise, is safe and effective. The phase 2 clinical trial results were published in the New England Journal of Medicine.
"The impact of giving risdiplam soon after birth is quite dramatic," said co-first and corresponding author Finkel, who is now the Center for Experimental Neurotherapeutics director and Department of Pediatric Medicine member at St. Jude, but started the consortium and participated in the study as a faculty member at Nemours Children's Health. "By age 2, we saw most of the children who we had treated were walking and in good general health."
Babies with the genetic mutations that cause SMA were all started on daily risdiplam in the first six weeks of life, before definitive features of SMA appeared, and were followed for two years. The trial took place at multiple sites worldwide, including Nemours Children's Health in the U.S., with 23 patients completing the study. Of the eight children genetically predisposed to the most severe form of SMA, type 1, seven were able to sit at 12 months, and five could walk by the end of the study's two-year reporting period, with no fatalities. Of the 18 children who had a mutation predicting less severe disease, all achieved sitting by 12 months and walking by 24 months, with most reaching these milestones in timeframes comparable to typically developing children. None of the children experienced any major treatment-related adverse events.
"For families facing a diagnosis of SMA, the results of this study offer real hope. Treating children before symptoms appear — when they are still developing normally — can change the entire trajectory of the disease. We are no longer just managing symptoms; we are preserving strength, function and quality of life from the very start," said contributing author Aledie Navas, MD, FAAP, FCCP, of Nemours Children's Hospital, Orlando.
"We demonstrated in this study that with treatment shortly after birth, risdiplam maintained a good safety profile and generated a favorable clinical response," Finkel said. "I'm pleased to say that data from this study led the FDA to change the label for risdiplam's use, extending it to younger children."
Stopping SMA earlier in life
SMA causes the loss of a specific neuron that activates muscles. Without those neurons, the muscle tissue begins to atrophy. Risdiplam and similar treatments work by preventing the atrophy from accumulating over time. By giving the drug earlier, the researchers hope to avoid more muscle loss and, therefore, delay or prevent disease progression even more than current approaches.
"We've learned that it's crucial to start the drug as soon as possible. Literally every day counts," Finkel said.
While risdiplam slows disease progression, no current pharmaceutical treatment is curative. However, the success of this approach in newborns suggests that early interventions can still be very beneficial. This RAINBOWFISH study is ongoing. It is sponsored by F. Hoffman–LaRoche and continues the path established in their earlier risdiplam studies in older infants, children and adults with SMA, demonstrating a strong safety profile and clinical benefit of this drug, which is taken orally daily.
"The treatment of babies right after birth is an important milestone," Finkel said. "But we will continue to investigate potentially even better ways to give these kids a chance at a normal life."
To that end, Finkel has already begun testing the drug even earlier in life, in the prenatal environment, which showed promising results in a phase 1 clinical trial published earlier this year, also in the New England Journal of Medicine .
Authors and funding
The study's other co-first author is Laurent Servais, University of Oxford and University Hospital Liège & University of Liège. The study's other authors are Dmitry Vlodavets, Veltischev Clinical Pediatrics and Pediatric Surgery Research Institute of Pirogov of the Russian National Research Medical University; Edmar Zanoteli, Faculdade de Medicina, Universidade de São Paulo (FMUSP); Maria Mazurkiewicz-Bełdzińska, Medical University of Gdańsk; Yuh-Jyh Jong, Kaohsiung Medical University Hospital and National Yang Ming Chiao Tung University; Mohammad Al-Muhaizea, King Faisal Specialist Hospital & Research Center-Riyadh; Alexandra PQC Araujo, Federal University of Rio de Janeiro; Leslie Nelson, University of Texas Southwestern Medical Center; Yi Wang, Children's Hospital of Fudan University; Birgit Jaber, Ksenija Gorni, Paulo Fontoura and Kathryn Wagner, F. Hoffmann-La Roche Ltd; Heidemarie Kletzl, Roche Innovation Center Basel; Laura Palfreeman, Dave Summers and Eleni Gaki, Roche Products Ltd; Michelle Farrar, Sydney Children's Hospital Network and UNSW Sydney; and Enrico Bertini, Bambino Gesù Children's Research Hospital IRCCS.
The study was supported by F. Hoffmann–La Roche Ltd.
