Important note: Information in this article was accurate in 1997. The state of the art may have changed since the publication date.
Important note: Information in this article was accurate in 1997. The state of the art may have changed since the publication date.
Reuters NewMedia, Inc. - Monday July 21 6:01 PM EDT
Ransdell Pierson
Ribozyme chief executive Ralph Christoffersen said three adult males had been injected with ribozymes, a form of RNA molecule designed to kill the HIV virus by slicing it in half, since trials began in March at City of Hope National Medical Center in Los Angeles.
"Three patients have been tested with no side effects. We're very pleased because it represents a new class of therapy with no adverse effects we know of," Christoffersen told Reuters in a telephone interview.
He said two types of ribozymes created by his company, each targeting a different part of the HIV virus, were encased in a harmless retrovirus supplied by collaborator Chiron Corp (CHIR).
The retrovirus was then allowed to infect CD34+ blood "stem cells" previously drawn from patients, with the aim of delivering ribozymes into the stem cells.
Stem cells mature into a variety of blood cell types that make up a healthy immune system.
"These transduced CD34+ cells were then put back in the three patients," Christoffersen said. He said the next step will be to measure over the next six to 12 months the degree to which the cells get re-engrafted into the bone marrow.
He said that ribozyme therapy was unique and had never been tested before in humans.
"If the (the altered stem cells) are re-engrafted, they will produce daughter cells containing the ribozymes," he said, with future descendants of the altered CD34+ cells also inheriting genes to make their own HIV-fighting ribozymes.
Christoffersen said two other patients in the trial had not yet received treatment, adding Phase II initial efficacy trials would be designed only after Phase I safety and engraftment data were compiled.
Future Phase I trials might use three or four ribozymes instead of two, he said, in order to prevent the fast-mutating HIV virus from developing resistance to the gene therapy.
Ribozyme, based in Boulder, Colorado, had a net loss in 1996 of $15.3 million.
Christoffersen said the company hopes to defray its drug-development costs and become profitable in the next few years by forming "target validation" collaborations with bigger drug companies.
In effect, the company would use its propietary ribozyme technology to zero in among countless known gene fragments to find those most likely to become good targets for new drugs.
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