Givinostat (Duvyzat) has demonstrated favorable outcomes in functional tests and histological findings for patients with Duchenne muscular dystrophy (DMD), according to a systematic review of drug trials presented at the Child Neurology Society annual meeting. However, the benefits were less clear in Becker muscular dystrophy (BMD), a less severe form of the disease. The drug, a histone deacetylase (HDAC) inhibitor, received FDA approval in February for DMD patients aged 6 years and older.
EPIDYS Trial Results
The review included three clinical trials, with a total of 250 participants, evaluating givinostat in DMD and BMD. The pivotal phase 3 EPIDYS trial, which led to the drug's approval, revealed that DMD patients treated with givinostat experienced significantly less decline in the standard timed four-stair climb test compared to the placebo group after 18 months. Specifically, the mean change from baseline to month 18 in time to climb four stairs was 1.25 seconds for the givinostat group versus 3.03 seconds for the placebo group. While the givinostat cohort also showed less worsening in physical function as assessed by the North Star Ambulatory Assessment, a secondary efficacy endpoint, this difference did not reach statistical significance.
Mechanism of Action and Histological Impact
Jessica Nance, MD, from Johns Hopkins University, explained that in DMD, the absence of dystrophin protein makes muscle cell membranes vulnerable to injury, leading to inflammation, fat replacement, and fibrosis. "Givinostat is a histone deacetylase inhibitor that appears to target the pathways that promote replacement of muscle with fat and fibrosis in Duchenne muscular dystrophy," she noted.
Additional findings from EPIDYS, including MR spectroscopy studies, showed reduced fat fraction in the vastus lateralis muscle of patients treated with givinostat. This aligns with a 2016 study included in the review, which found that givinostat increased muscle tissue fraction by 29.1 percent and cross-sectional area by 77 percent, while reducing necrosis by 43.5 percent and fatty replacement by 37.5 percent.
Challenges in Becker Muscular Dystrophy
The systematic review also considered a 2023 trial of givinostat in BMD, which found no significant effect on mean total fibrosis. The two groups did not differ at month 12 (least squares mean difference 1.04 percent; p = 0.8282). Dr. Nance suggested this may be due to the slower progression and more variable presentation of BMD. "Because progression of weakness may be slower in Becker, you may not be able to demonstrate efficacy over the same period of time that you can with Duchenne," she stated.
Safety and Cost Considerations
Givinostat has a more limited side effect profile compared to prednisone, with the most common adverse events being gastrointestinal in nature, such as loose stools and diarrhea. These side effects can usually be managed with dose adjustments. Other potential concerns include high triglyceride levels and low platelet counts, requiring close monitoring. However, the average annual cost of givinostat, at $700,000, presents a significant financial challenge.
