THE future of at least four children with a rare but deadly genetic disorder
has been thrown into uncertainty.
The lives of the children, who have Pompe鈥檚 disease, depend on an
experimental enzyme obtained from the milk of genetically engineered rabbits.
But the companies involved have decided to try to make it using cultured cells
instead.
Pompe鈥檚 disease destroys muscles. Infants born with it are never able to roll
over or even sit up, and usually die within a year. The disease is caused by
lack of the enzyme alpha-glucosidase, which converts stored glycogen into
glucose.
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In 1995, Ans van der Ploeg of the University Hospital Rotterdam in the
Netherlands and her colleagues managed to produce this enzyme using modified
Chinese hamster ovary (CHO) cells. But they could not find any companies to help
them make it this way. Eventually, Pharming of Leiden agreed to help them
produce the enzyme in transgenic rabbits.
In clinical trials, two children who began receiving the enzyme when they
were as young as two-and-a-half months have shown a vast improvement.
One child can sit up on her own. The other can walk and even ride a tricycle.
Two children who began treatment later are dependent on respirators, but they
can sit up and grab at things with their hands.
鈥淲e, and in particular the parents and the families, have experienced great
joy,鈥� says van der Ploeg. Twenty infants who did not receive the enzyme all
died.
Now Pharming and its partner Genzyme have decided to abandon transgenic
production in favour of CHO cells. They believe this is the quickest way to get
a treatment to market, because there will be fewer regulatory hurdles.
But van der Ploeg is worried. 鈥淲hat if the process fails?鈥� she asks. 鈥淚 am
called almost daily by parents who are in despair.鈥�
Rick Moscicki, Genzyme鈥檚 chief medical officer, says there鈥檚 no need for
concern. 鈥淕enzyme is committed to ensuring that these patients will be treated
and cared for.鈥� There will not be a treatment gap, he says.
Moscicki says that a researcher at Duke University has produced the protein
using CHO cells and successfully treated three infants with it. 鈥淚f CHO didn鈥檛
work, then we would seek a programme that would work,鈥� he adds.
But van der Ploeg says the enzyme produced from milk and the one from Duke
are slightly different. She thinks both production methods should be pursued
simultaneously. Moscicki says the companies don鈥檛 have the resources to do
this.
