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Idebenone Reduces Respiratory Function Loss in Duchenne Muscular Dystrophy

SYROS study data showed that switching to and maintaining long-term treatment with idebenone was associated with a 50% reduction in the annual rate of decline in forced vital capacity percent of predicted.

Kristina Sjolblom Nygren, MD

The recently reported results of the SYROS study have shown that long-term treatment of Duchenne muscular dystrophy (DMD) with idebenone (Raxone) can consistently slow the rate of respiratory function loss.1

Santhera Pharmaceuticals, the manufacturer of the synthetic short-chain benzoquinone and NAD(P)H quinone oxidoreductase (NQO1) cofactor, announced that the study data revealed that switching to and maintaining long-term treatment with idebenone was associated with a 50% reduction in the annual rate of decline in forced vital capacity percent of predicted (FVC%p).

“We are very excited to see that the significant treatment effect with idebenone observed in our 52-week phase 3 DELOS study is maintained over the long-term,” said Kristina Sjöblom Nygren, MD, the chief medical officer and head of development at Santhera, in a statement. “The new findings are highly relevant for DMD patients in respiratory decline who have an urgent need for a therapy to modify the declining course of respiratory function decline and ultimately delay the need for assisted ventilation.”

Additionally, the results showed that the treatment effect of idebenone was found to be maintained year-on-year for up to 6 years. As well, the findings were further supported by consistent reductions in the rate of both inspiratory and expiratory respiratory function loss over the same period.

Notably, continued treatment with idebenone also reduced the risk of important patient relevant outcomes, such as bronchopulmonary adverse events (AEs) and hospitalizations due to respiratory causes.

The SYROS study was a prospectively planned collection of retrospective real-world, long-term data from the patients who completed the DELOS study (n = 18) that were subsequently treated with 900 mg/day of idebenone. Patients were treated for an average of 4.2 years (range, 2.4 to 6.1 years) under Expanded Access Programs. In the United States, the treatment is available through the FDA-authorized EAP BreatheDMD.

Currently, patients are being recruited for the SIDEROS-E phase 3 study (NCT03603288), which is aiming to determine the long-term safety and efficacy of the therapy in patients with DMD who have completed the SIDEROS study (NCT02814019), another phase 3 trial of the therapy in patients with DMD who are taking glucocorticoid steroids.

In the DELOS study (NCT01027884), a total of 64 patients were randomized to either idebenone (n = 31) or placebo (n = 33) thrice daily for 1 year. The results showed that the study treatment reduced the loss of respiratory function, delaying the need for assisted ventilation by 3 years. The fall in peak expiratory flow (PEF) as percentage predicted (PEF%p) was —3.05%p (95% CI, –7.08 to 0.97; P = .134) in the modified intention to treat group, compared to placebo which observed a drop of —9.01%p (95% CI, –13.18 to –4.84; P =.0001) for a difference of 5.96%p (95% CI, 0.16 to 11.76; P = .044). In the intent to treat populations, the fall was —2.57%p (95% CI, –6.68 to 1.54; P = .215) compared to a drop of —8.84%p (95% CI, –12.73 to –4.95; P <.0001) with placebo, for a difference 6.27%p [95% CI, 0.61 to 11.93; P = .031).2

Idebenone, according to Santhera, is capable of stimulating mitochondrial electron transport, thereby reducing and scavenging reactive oxygen species and supplementing cellular energy levels. It was originally developed by Takeda Pharmaceuticals for the treatment of cognitive defects and Alzheimer disease.

Santhera announced that the SYROS data have been accepted for presentation at the 2019 MDA Clinical & Scientific Conference, which will be held from April 13 to 17, 2019, in Orlando, Florida, and will be submitted for publication in a peer-reviewed journal.


1. Santhera’s SYROS Study Shows Long-term Efficacy with Idebenone in Slowing Respiratory Function Loss in Patients with Duchenne Muscular Dystrophy [press release]. Pratteln, Switzerland: Santhera Pharmaceuticals; Published February 25, 2019. santhera.com/assets/files/press-releases/2019-02-25_SYROS_e_final.pdf. Accessed March 21, 2019.

2. Buyse GM, Voit T, Schara U, et al. Efficacy of idebenone on respiratory function in patients with Duchenne muscular dystrophy not using glucocorticoids (DELOS): a double-blind


placebo-controlled phase 3 trial. Lancet. 2015;385(9979):1748-1757.


: 10.1016/S0140-6736(15)60025-3.