Chen focused on the phase I/II trials underway at Duke with 3 IIa infants. Average age at diagnosis is 5 months and survival thereafter is 3 1/2 months on average, with a range of 0-9 months. Very few baby’s survive a year. Recombinant enzyme from CHO cells (5 mg/kg twice weekly) has been given for more than a year to these 3 infants, now aged 20, 17, and 15 months. Symptoms, signs of allergy, liver/kidney/blood toxicity followed. The only adverse event so far has been an allergic reaction during infusion of the enzyme that was treated with benadryl and did not interfere with the trials.
They have been measuring heart and lung function, muscle strength, motor development, and urine/plasma oligosaccharide levels.
By echocardiogram, the volume of the left ventricle has increased steadily (reflecting smaller muscle size) over three months to normal and stayed normal. The left ventricle mass has fallen steadily over the year in all three babies. The size of the hearts on X-ray has gone from very large to borderline large in two and from moderately large to normal in one. Heart function is normal in all three.
As for muscle strength, two showed improvement to near-normal levels over 3 months, then had declines to previous levels as their bodies made antibodies to the enzyme. The third’s muscle strength climbed into the normal range (to the 50th percentile) and remains there. He has no antibodies and evidence of an enzyme precursor in his cells that may prevent him from responding with antibodies to the administered enzyme.
Microscopic examination of his muscle fibers is normal now.
Response to therapy may depend on stage of the disease and whether or not one makes antibody.
The older brother of the third patient died at nine months of age. This baby walked at 12 months of age, has normal developmental milestones, and was shown riding his toy bike as an active toddler.
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Earlier this year, Genzyme obtained exclusive, worldwide rights from Synpac (North Carolina) Inc. to develop and commercialize the human alpha-Glucosidase product derived from CHO cells, shifting its focus from the development of human alpha-Glucosidase produced in the milk of transgenic rabbits. The decision to pursue the CHO-cell product was based on manufacturing considerations. Genzyme and Pharming believe that the CHO-derived product can be scaled to commercial production levels, qualified for use, and made accessible to patients faster than the transgenic product. This decision was not based on efficacy or safety concerns with either product. Clinical results obtained to date suggest that the CHO-derived and transgenic products show comparable clinical effects.
Genzyme and Pharming plan to initiate a second clinical trial of the CHO-cell product by the end of 2000 in patients with infantile-onset Pompe disease. The companies are currently in discussions with the U.S. Food and Drug Administration on the design of the trial, which is expected to involve medical centers in both the United States and Europe. Further details will be announced later this fall once the trial’s protocol has been finalized . . . . . . . . .