U.S. drug pricing watchdog Institute for Clinical and Economic Review said Sarepta Therapeutics Inc.'s gene therapies Exondys 51 and golodirsen are not cost-effective in treating Duchenne muscular dystrophy.

Duchenne muscular dystrophy, or DMD, is a genetic disorder caused by the absence of a protein called dystrophin, and is characterized by progressive muscle degeneration and weakness. The disorder primarily affects boys.

In 2016, Exondys 51, or eteplirsen, was approved as the first drug ever to treat DMD. Meanwhile, golodirsen is under priority review by the U.S. Food and Drug Administration with a regulatory deadline of August.

Sarepta's Exondys 51 and golodirsen work by skipping over certain genetic mutations in a DNA sequence known as exon 51 and exon 53, respectively. Exon 51 mutations affect 13% of boys diagnosed with DMD, while exon 53 mutations are found in 8% of the patients.

The agency known as ICER assessed the health and economic outcomes of the Sarepta drugs together with PTC Therapeutics Inc.'s Emflaza, another DMD treatment. Emflaza, or deflazacort, belongs in the class of medicines known as corticosteroids which work by reducing inflammation and modifying the immune system's functions.

In its May 22 draft evidence report, ICER said data on patient-important outcomes for Exondys 51 and golodirsen are insufficient. The pricing institution mentioned the lack of high- or moderate-quality evidence that Exondys 51 helped improve functions, as the available limited randomized data for the drug did not show improvements in the six-minute walking test compared to placebo.

The available limited randomized data for Exondys 51 did not exhibit improvements in the six minute walking test compared to placebo. Studies on the dystrophin levels in patients treated with Exondys 51 show increases that are of uncertain clinical or biologic importance, while golodirsen data demonstrated only small increases in dystrophin levels, ICER added.

Exondys 51 and golodirsen — assuming that the two Sarepta drugs will have the same price — were not cost-effective at a willingness-to-pay threshold of $150,000 per quality-adjusted life years, even if the drugs have extremely favorable treatment effects.

An October 2016 Reuters report said that at least one U.S. health insurer has refused to cover Exondys 51 while another has indicated that it will conduct a full clinical review before including it in its coverage policy.

The institute noted that in DMD, the potential health effects would have to be substantial and beyond any current projections from available evidence for the treatments to be cost-effective.

ICER will accept public comments on the draft report until June 18 and will publish an evidence report July 11. The report will be the subject of a July 25 meeting of the New England Comparative Effectiveness Public Advisory Council.