Marathon’s Deflazacort Seen to Prolong Walking Ability in DMD Patients By Slowing Growth, Weight Gain

Numerous studies show that deflazacort substantially prolongs walking ability in boys with Duchenne muscular dystrophy (DMD), allowing them to lead a longer productive life. The drug also causes less weight gain than other similar medications, a factor scientists believe might be key to maintaining ambulation.

Despite its worldwide popularity as a DMD treatment, deflazacort is not approved for this indication — a fact Marathon Pharmaceuticals wishes to change, initiating a process to get the drug approved by the U.S. Food and Drug Administration (FDA) for the treatment of DMD. Patients now have free access to deflazacort through the FDA’s Expanded Access Program.

Both deflazacort and prednisone, the second most frequently used drug for DMD, are corticosteroid glucocorticoids. Although the drugs have been considered equally efficient in delaying disease progression, data presented by Marathon scientists at the MDA Clinical Conference, held March 20–23 in Arlington, Virginia, showed that deflazacort might be superior to prednisone in preserving walking ability.

Data from the DuchenneConnect registry, representative of 1,057 boys with DMD, showed that deflazacort prolonged ambulation to a median of 14 years, while the median time for the prednisone-treated group was 13 years. Another, a prospective study using data from the Cooperative International Neuromuscular Research Group (CINRG) involving 340 patients, again noted that deflazacort-treated boys were able to delay wheelchair reliance and loss of ambulation for a median 13.9 years, compared to 11.2 years in those treated with prednisone.

In direct comparisons, prednisone induced less growth retardation, measured by height and the length of the forearm. Moreover, the treatment was associated with more weight gain. Both growth retardation in children and weight gain are two typical side effects of glucocorticoids, but the extent of side effects may differ between individual drugs in a class.

Since these are the main features distinguishing the two drugs, Marathon researchers speculate that the growth limiting effect of deflazacort might explain the drug’s superiority in prolonging ambulation. They argue that this could be a solely biomechanical effect, allowing more movement in a smaller body with the muscle capacity still present at a certain age.

Scientists, however, point out that so far, there is only circumstantial evidence supporting the idea. More studies are warranted to explore the mechanisms behind the preservation of walking ability of deflazacort treatment.