Pfizer pauses trial for experimental gene therapy drug after child participant dies suddenly
Pfizer has halted a trial of a drug for a rare muscle wasting disease after a child died suddenly.
The boy, who was between two and four years old, suffered a cardiac arrest last year after receiving the one-off gene therapy.
Pfizer has not determined exactly what happened or whether the death was caused by the treatment, called fordadistrogene movaparvovec.
The New York pharmaceutical giant said the pause would allow the death to be investigated “while protecting the safety of participants, which is our top priority.”
Pfizer has halted its trial of a drug for a rare muscle wasting disease after a child died suddenly (stock)
The victim was part of a mid-stage study involving children between two and four years old with Duchenne muscular dystrophy.
The rare disease mainly affects boys – about one in 3,500 male births – and patients usually do not live beyond the age of 25.
Three serious side effects occurred during the study, but all children recovered within two weeks.
Pfizer has stopped administering the same gene therapy in a separate latest study involving boys up to eight years old.
That study compared whether the drug could slow the progression of the disease compared to a placebo.
If the trials went well, it would become one of the most expensive drugs ever.
A competing gene therapy from Sarepta Therapeutics Inc. received accelerated approval from the FDA last year, becoming the only approved treatment for children with DMD.
A single dose costs about $3 million.
DMD is caused by a genetic mutation that means the body does not produce enough of the protein dystrophin, which maintains muscle strength.
Without this system, the muscles gradually break down, leading to problems walking, sitting and speaking, and eventually affecting the muscles around the lungs and heart.
By age 11, most patients usually require a wheelchair.
Pfizer’s drug works by introducing a shortened but functional dystrophin protein directly into patients’ muscle cells, slowing their breakdown.
It is given as a one-time infusion.
Historically, the only medications used to treat DMD were steroids such as prednisone or deflazacort.
They dampen inflammation – a major problem in Duchenne – which slows down the decline in muscle strength and mobility and can delay heart and lung complications.
But these can cause serious side effects, such as weight gain, stunted growth, delayed puberty and a reduction in bone density, which can increase the risk of fractures.