The FDA has approved a Sarepta Therapeutics drug for Duchenne muscular dystrophy, clearing the best way for the corporate to commercialize its third remedy for the uncommon, muscle-wasting illness.
Thursday’s resolution covers sufferers with a specific genetic mutation that impacts an estimated 8% of Duchenne sufferers. The drug, casimersen, will likely be marketed underneath the title Amondys 45.
Duchenne is genetic dysfunction that renders sufferers unable to supply dystrophin, a key muscle protein. With out it, sufferers develop progressive muscle weak spot, beginning with their legs. Cambridge, Massachusetts-based Sarepta developed Amondys 45 to assist restore cells’ capability to supply dystrophin. Cells make proteins from items of DNA referred to as exons. However typically this string of genetic materials is lacking items, which might cease manufacturing of that protein altogether.
The Sarepta remedy, a kind of drug referred to as an antisense oligonucleotide, is an “exon skipper.” Within the numbered string of exons that code for dystrophin, the drug will get the cell’s protein-making equipment to skip exon 45. Doing so is meant to get the cell to supply a truncated however nonetheless practical model of dystrophin.
The FDA’s approval was based mostly on the outcomes of a placebo-controlled research enrolling 43 sufferers, all males, who had a genetically confirmed mutation that might be addressed by exon 45 skipping. Within the research, sufferers handled with the Sarepta drug confirmed a “considerably larger improve in dystrophin protein ranges” after 48 weeks of therapy, in comparison with these given a placebo, the company mentioned.
It’s vital to notice that rising dystrophin manufacturing has not but been demonstrated as translating into medical profit, equivalent to improved motor perform. The choice for Amondys 45 was an accelerated approval, a speedier resolution based mostly on thinner proof than is often required for a drug evaluate. These quicker approvals are reserved for illnesses which have few, if any, therapy choices.
“In making this resolution, the FDA thought-about the potential dangers related to the drug, the life-threatening and debilitating nature of the illness, and the shortage of accessible remedy,” the company mentioned.
In accordance with the FDA, the commonest unintended effects noticed in sufferers handled with Amondys 45 have been higher respiratory tract infections, cough, fever, headache, joint ache, and throat ache. Kidney toxicity was not noticed within the Amondys 45 medical research, although such toxicity was noticed in nonclinical research. Kidney issues have been related to some antisense oligonucleotides and the regulator cautions that perform of those organs must be monitored in sufferers taking the Sarepta drug.
Corporations granted accelerated approval are required to conduct extra medical assessments to verify a drug’s profit. Such testing has not but been accomplished for Exondys 51, which became Sarepta’s first FDA-approved medicine in 2016. That drug treats the estimated 13% of Duchenne sufferers whose illness is amenable to exon 51 skipping. The second Sarepta Duchenne remedy, Vyondys 53, was approved in 2019 for the 8% of sufferers whose illness will be addressed by skipping exon 53.
A confirmatory research for Amondys 45 is underway and Sarepta expects to complete that medical trial in 2024. The corporate mentioned its new drug could be priced consistent with its two different Duchenne therapies. Exondys 51, which is dosed in line with a affected person’s weight, can price between $750,000 and $1.5 million annually.
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