By Randall Osborne
With a marketing deal in place and a supply ready to ship, Genzyme Corp. has received an approvable letter from the FDA for Thyrogen (thyrotropin alpha), its thyroid cancer-screening drug.
The company still has a few questions to answer, though.
"It's pretty simple," said Bo Piela, spokesman for Cambridge, Mass.-based Genzyme. "They want us to refine one of the methods we use to determine the bioactivity of a reference standard we use."
The reference standard is used as a "measuring rod" for quality control, ensuring the bioactivity of Thyrogen, Piela said.
"One of our drug assays measures against the reference standard," he said. "We have to submit a protocol for doing the [refinement], and a time line for completing it. At that point, we're expecting to receive an approval letter."
Genzyme expects to draw up the protocol in a few weeks, and plans to get approval of Thyrogen by the end of the year.
The FDA said Genzyme may use a different reference standard, established by the World Health Organization, for its existing supply of Thyrogen.
"We have enough [drug] to keep us going for a quite a while, beyond the time it will take us to complete this other work," Piela said.
Genzyme last month entered an agreement with Knoll Pharmaceutical Co., of Mount Olive, N.J., a unit of Ludwigshafen, Germany-based BASF AG, giving Knoll exclusive worldwide rights for five years to market Thyrogen. Knoll also manufactures and markets Synthroid (levothyroxine sodium), the leading thyroid replacement therapy in the U.S.
Thyrogen offers an alternative way of testing thyroid cancer patients for metastases, after their thyroid glands have been removed.
The current method is a full-body radioactive iodine screen, which requires that patients quit taking their synthetic hormone supplements for three weeks before testing. The hormone withdrawl can lead to hypothyroidism, with its symptoms of fatigue, weight gain, constipation, mental dullness, lethargy and depression. Using injected Thyrogen, patients may keep taking their supplements.
In May, an FDA advisory panel unanimously recommended approval of Thyrogen. (See BioWorld Today, May 18, 1998, p. 1.)
Piela said Genzyme also expects FDA approval by the end of the year of RenaGel, a non-absorbed phosphate binder for controlling elevated phosphate levels in dialysis patients.
Genzyme's stock (NASDAQ:GENZ) closed Wednesday at $29.687, up $1.125. *