Blog
An update on treatment options and pipeline developments for Duchenne muscular dystrophy
IQVIA Pipeline Intelligence
Sam Lam, Senior Analyst, IQVIA Pipeline Intelligence
Apr 06, 2021

Duchenne muscular dystrophy (DMD) is a rare X-linked progressive genetic disorder and the most common and severe type of dystrophinopathy. It is characterized by mutations in the DMD gene that prevent the production of functional dystrophin, a structural protein involved in maintaining the integrity of muscle cells. The absence of dystrophin in muscles leads to muscle degeneration, loss of ambulation and cardiomyopathy. According to statistics from the National Organization for Rare Disorders (USA), DMD occurs in approximately one out of every 3,500 male infants worldwide. The current therapies alleviate the symptoms and have been shown to slow the progression of the disease. Newer exon skipping therapies can halt the progression of DMD but only work in a subset of DMD patients with certain gene mutations and do not cure the disease. The first phase III DMD gene therapy program commenced patient enrollment in January 2021 and following this milestone, a gene therapy to deliver a healthy copy of the dystrophin gene may provide a cure for this debilitating disease. This article will provide an update on current treatment options for DMD and outline the latest development activities of key experimental drugs with data sourced from IQVIA Pipeline Intelligence, a proprietary drug pipeline database.

CURRENT TREATMENT OPTIONS FOR DMD:

Corticosteroids

Corticosteroids, including prednisone and deflazacort, have been commonly used to treat DMD. Corticosteroids act by delaying the progression of muscle weakness and reducing inflammation by inhibiting the expression of pro-inflammatory genes. While the first corticosteroid won US FDA approval for the treatment of DMD in 2017, the widely available generic prednisone is frequently prescribed for the disease but does not have formal US FDA approval.

Antisense-mediated exon skipping therapies

Gene-targeted treatments have also been investigated for DMD, including exon skipping therapies which mask specific exons in a gene sequence of the DMD gene and gene therapies to deliver a healthy DMD gene directly to a patient. There are currently four antisense-mediated exon skipping therapies approved by the US FDA for DMD.

KEY SELECTED NEXT-GENERATION THERAPEUTICS FOR DMD:

Gene therapies

Recent progress has been made in the development of gene therapies to cover all patients regardless of mutation. Despite the identification of the dystrophin gene in 1986, which is the largest human gene (2,200 kb in size), it has proved a challenge to transfer the gene into adeno-associated viruses (AAV) used to deliver gene therapies due to its size. As the carrying capacity of AAVs is approximately 4.7 kb, instead of utilizing the full dystrophin gene, researchers engineered smaller, modified genes that produce a shortened form of dystrophin: micro-dystrophin (gene size 3.5 to 4 kb) and mini-dystrophin (gene size 6 to 8 kb) that are designed to function like the normal dystrophin protein. There are currently several key gene therapies in clinical development for DMD.

GENOME-EDITING THERAPIES

With the development of genome editing systems, including CRISPR/Cas9 it is now possible to make targeted modifications in the genome. Gene-editing therapies can restore the expression of partially functional dystrophin protein by reframing DMD mutations at the genomic level and potentially provide a cure for the disease. Although no CRISPR-based therapies have entered clinical development yet, several companies are working on CRISPR programs for DMD.

FUTURE DIRECTIONS

Many advances have been made over the last few decades in elucidating the molecular mechanisms of DMD since the discovery of the dystrophin gene, which has aided the emergence of new gene-based therapies. This has opened the door for combination therapies, with the use of gene therapies to stabilize muscle and small molecule drugs such as anti-inflammatory therapies to combat the downstream effects of fibrosis and inflammation. The latest developments could provide DMD patients further treatment options and potentially increased benefit.

Contact Us