Gene therapy work races clock Research: A long-awaited trial drug for cystic fibrosis patients nearly failed this year. Only 11th-hour changes avoided a delay in testing.


PHILADELPHIA -- None of the half-dozen people gathered around the conference table at the Institute for Human Gene Therapy dared say a word. They just looked at institute director Dr. James M. Wilson and waited.

Wilson took off his glasses, closed his eyes and pinched the bridge of his nose. Wilson never did this unless he was very displeased. Wilson had just asked Colleen Baker, the manager of the institute's Human Applications Laboratory, how her work on a new gene drug was progressing, and she said the laboratory was having trouble making it.

It was mid-August. Trials with cystic fibrosis (CF) patients were supposed to start in a month at the University of Pennsylvania Medical Center, and this was the first he had heard that the drug would not be ready. Wilson put his glasses back on and said quietly, "I can't believe that."

For six years, researchers throughout the world had been conducting human trials trying to develop the first effective gene drug, a breakthrough that could revolutionize medical care by correcting the genetic defects that cause some diseases. But so far no one had succeeded, as one research problem after another cropped up in the unexplored territory of gene therapy research.

But this latest news jeopardized the cystic fibrosis trials as well as the development of gene drugs for several other diseases.

By August, Wilson thought he had solved the most vexing problems preventing successful therapy and was anxious to test this new drug his laboratory had developed. But now production problems were thwarting him.

At stake was a drug that might prolong or save the lives of patients with cystic fibrosis, the most common fatal genetic defect. In the United States, 30,000 people have the lung disease, which kills most victims by their 30s.

Racing to be the first with a successful gene therapy, Wilson started testing a first-generation CF drug in 1993. But he stopped the trial in the spring of 1994 when animal studies indicated that the drug would be toxic at high doses.

Wilson decided to wait for a second-generation drug on which they were running final tests. But the second-generation drug was also abandoned when an even better drug looked possible.

Patients were desperate for effective treatment -- a gene drug that could produce the protein they needed to help thin the mucus choking their lungs. And other laboratories conducting human trials for a host of other diseases were pushing ahead with first-generation drugs, like the one Wilson had abandoned.

He was concerned that they would make discoveries he could have made sooner if he had continued the CF trial. But as time passed and no significant discoveries were reported, he was reassured that he had made the right decision to wait.

Wilson was angry at himself for underestimating how difficult it was to grow viruses in the quantities needed for human trials.

Armed with the gene that CF patients lack, the viruses (called vectors) are, in fact, the drug. They deliver the missing CF genes to the patient's lung cells by infecting them.

The viruses are grown in cell lines, composed of human cells that have been engineered to provide special protein the vectors need for growth. Scientists needed a million cells to make the billion vectors required for animal studies. But for human trials, a trillion vectors would be needed.

A few hours after learning that the laboratory couldn't make the CF vector in large enough quantities, Wilson dropped by the lab bench of Guangping Gao, a 39-year-old molecular biologist, who was particularly gifted in making cell lines. He had discovered the cell line for the CF vector, but he wasn't involved in its production.

Wilson asked Gao if he thought he could solve the production problems. Gao said yes.

After talking with Gao about producing the vector, Wilson went home convinced that the laboratory had to be restructured. With only four people working there, it was clearly overwhelmed by more than a dozen different projects, each requiring a different gene drug. He resolved to hire two more lab technicians, increase the space of HAL, and put the best vector grower he could find in charge: Guangping Gao.

The next day Gao reported to the laboratory, a collection of super-sterile rooms in the University of Pennsylvania hospital.

Donning a sterile gown, booties and cap, Gao started from scratch, making the cell line to grow the virus.

That day, he thawed cells stored in a freezer, distributed them among five covered plates, and waited for the 10 million cells to multiply. Four days later, he distributed the cells that now filled the five plates, to 25 plates.

He waited another three days and redistributed the cells to 100 plates. By Day 10, he had a billion cells.

On Day 11, after the cells had multiplied until they covered precisely 90 percent of the surface of each plate, Gao infected them with adenoviruses. Normally, adenoviruses cause colds, but these had been disabled and armed with the gene that cystic fibrosis patients lack.

Not until Gao had harvested the virus would he know if all his work had been worthwhile.

Gao was so excited on the day of the harvest that he woke up at 5: 30 a.m., well ahead of his alarm. All night long, the viruses had been spinning at 20,000 revolutions per minute, as a centrifuge separated them from broken up bits of cells and other debris.

Inside the centrifuge, which looked like a top-loading washing machine, were six plastic tubes, each filled with a whitish fluid and a thin band of bluish material in the center. The bands were about as thick as the width of a matchstick. This was the concentration of viruses the centrifuge had separated from other material in the tube.

There would have been no blue line if no virus had been produced or the line would have been much thinner if only small amounts had been made.

Using a spectrometer, Gao determined that more than a trillion viruses had been made -- more than enough to restart the human cystic fibrosis trial.

One hour later, Gao was sitting at the small wooden table in Wilson's office. Before him was the printout of all the numbers generated by the spectrometer.

"You believe these figures?" Wilson asked, looking at Gao's printout.

Gao said he thought that the first attempts had failed because the cells were either too tightly or loosely packed in the lab dishes when they were infected with the virus.

"So we're swimming in the stuff," Wilson said finally. "That's fantastic."

Gao spent the next four weeks going through the final stages of preparing the drug for the federal approval needed to resume the trials on volunteers.

Finally, on Oct. 7, the data were sent to the Food and Drug Administration.

Approval was given in 16 days.

The word immediately went out to cystic fibrosis patients for volunteers to restart the trial.

Wilson hoped to sign up 15 patients over the next year for the toxicity trial. If the drug proved safe, a second trial would be undertaken to see if it could control cystic fibrosis. It will be another year before Wilson knows if he has something that might work.

Pub Date: 12/25/96

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