'Anti-gene' therapy shows promise....

Scientists are expanding the meaning of gene therapy to include treatments that thwart gene expression. Using gene-like material, these researchers target not the genes themselves, but messenger RNA, the intermediary that passes a cell's genetic information along and makes possible the production of proteins.

One approach involves small pieces of synthetic DNA, called antisense (SN: 6/10/89, p. 360). Chemical differences in the structure of antisense make this form of nucleic acid more resistant than normal DNA to being broken down by cells.

Like DNA, antisense molecules carry much more information than a typical drug molecule, says Stanley T. Crooke of Isis Pharmaceuticals in Carlsbad, Calif. This extra information enables them to home in on specific tumor targets better than traditional cancer treatments: Scientists design each antisense molecule to bind to and disarm or destroy a particular RNA.

At the University of Nebraska Medical Center in Omaha, Eliel Bayever and his colleagues have conducted a preliminary evaluation of one type of antisense in 11 people suffering from either an acute or premalignant form of myelogenous leukemia. In contrast to conventional chemotherapy for the disease, the antisense drug so far seems safe enough for patients to take in a doctor's office rather than in the hospital, says Bayever.

Another antisense molecule, this one directed against the RNA involved in the synthesis of a growth-regulating hormone, may prove useful against chronic myelogenous leukemia, says Alan M. Gerwirtz of the University of Pennsylvania School of Medicine in Philadelphia. He is seeking permission from the U.S. Food and Drug Administration to test this molecule in patients.

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