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September 28, 2021 10:49 AM EDT
R&DCell/Gene Tx
Safety fears force Pfizer to change pivotal DMD gene therapy trial protocol
Kyle Blankenship
Managing Editor
As one of the biggest players in an increasingly packed gene therapy space, Pfizer has taken an early lead over specialists like Sarepta in taking a Duchenne muscular dystrophy (DMD) candidate into late-stage testing. But new safety fears have led Pfizer to scale back that trial, cutting out patients with certain genetic mutations.
Pfizer has amended its enrollment protocol for a Phase III test for gene therapy fordadistrogene movaparvovec in DMD after investigators flagged severe side effects tied to specific mutations, according to a letter the drugmaker sent to Parent Project Muscular Dystrophy, a patient advocacy group.
The amended CIFFREO study plans to enroll 99 DMD patients without any mutations affecting exons 9 through 13, or a deletion that affects both exon 29 and exon 30. Exons are portions of a gene that code for specific amino acids.
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In its letter, Pfizer estimated those mutations cover around 15% of the treatable patient population with DMD, a rare muscle-wasting caused by an abnormal production of the dystrophin protein.
Pfizer said three cases of muscle weakness, two of which included heart inflammation, forced the trial amendment. The drugmaker said the proposed changes are currently being reviewed by regulators and ethics committees, with trial site-specific changes set to roll out on a country-by-country basis.
“We know this change will be very difficult news for the community,” Pfizer wrote in the letter. “However, once the new safety findings and risk information were known, it was necessary to take this step to protect the safety of study participants.”
This isn’t the first time fordadistrogene movaparvovec has hit a roadblock on its late-stage path, with the company reporting in May that it was meeting headwinds from the FDA on the quality of its potency assays. That hurdle appears to be in the past, but given how closely watched safety data are in the gene therapy space, this may not be the last hiccup for Pfizer’s plans in DMD.
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