Try stuffing a basketball into a wiffle ball.
Fanciful as the notion is, it illustrates a pivotal challenge faced bypioneers of gene therapy. DNA may be minute, but it still takes upspace. Researchers would welcome a way to compress it, so they canguide genes more easily through the narrow receptors of target cells.
Now a pair of biotech entrepreneurs say they are preparing todevelop that technology, and other advances, for the market.
Working with scientists who formulated the new technology at CaseWestern Reserve University in Cleveland, Robert Butz and ChuckNoland have established Copernicus Gene Systems. The company,which is owned in part by Case Western, plans to begin formaloperations in January.
Neither Butz nor Noland are new to the hectic, competitive andinsecure world of biotech start-ups.
Butz, to be named the company's president and CEO, helped foundQuintiles Transnational Corp., of Research Triangle Park, N.C., inthe 1970's to assess the value of new biotech products. Noland, to bedirector of the company, was most recently a biotech analyst at DakinSecurities Corp. in San Francisco.
"This technology is a remarkably rich source for potentialcommercialization," Butz said.
"If we have anything close to what we think we have," said Noland,"it will become the payload delivery technology of choice in a lot ofareas."
Those who have followed gene therapy research know that payloaddelivery poses one of the most challenging scientific obstacles tosuccess. Researchers have spent years experimenting with a range ofpossible vectors _ including, most recently, one which relies on bitsof HIV _ usually with less than optimal results. Some vectors cannotcarry genes into chromosomes. Others splice genes into cells onlywhen the cell divides and the membrane surrounding thechromosomes dissolves. Surmounting these difficulties is a principalgoal of gene therapists everywhere.
Other challenges involve delivering working genes to target cells andthen forcing the genes to replicate often enough to assure that theywill produce enough protein to achieve the desired therapeutic goals.
More than half a dozen scientists at Case Western Reserve have beenworking on these problems, and now they say they have found waysto solve them.
Several preclinical studies, published in the Proceedings of theNational Academy of Sciences and the Journal of ClinicalInvestigation, suggest that the new approach holds promise.
DNA With A Shelf Life
"Our goal really is to make DNA into a drug," said Richard Hanson,chairman of the university's biochemistry department, whose labdeveloped the gene compression technology. "We'll be able tostabilize these condensed DNA complexes, so they can be injectedand so that they'll last on the shelf."
Hanson, Jose Carlos Perales and Thomas Ferkol have succeeded incompressing 5,000 base pairs of DNA into a particle that is just 20nanometers in size, which would allow it to be targeted to receptorsin the liver. With other methods, the best that has been achieved hasbeen 100 to 150 nanometers.
Butz said this promises to make it much easier for cells to integratethe DNA. "The ability of a cell to ingest a particle is directly relatedto size of the particle," he said. "You and I could not eat a rhinocerosbut we could eat a carrot."
The process involves marrying the DNA with a polycation, "so ithooks to the negative charges on DNA's backbone," Hanson said."Then we condense DNA into unimolecular complexes. That'scritical. If you change DNA's ionic strength, two or three rods willfuse together, and the DNA will be digested by macrophages.Condensing it properly is the key to the procedure."
Published animal studies have demonstrated that a single intravenousinjection of this preparation can insert large amounts of compressedDNA into target cells. Butz said: "We can achieve 18 percenttransfection rates into tissue, vs .1 percent to 3 percent with othermethods."
The second major advance involved delivery of the DNA into the cellso that it can manufacture proteins. Many of the researchers whohave wrestled with this problem have focused on finding ways to getDNA into the chromosome of the cell. But Mark Cooper, a CaseWestern Reserve oncologist, approached the problem from adifferent angle.
"The point of DNA is to allow RNA to be made, so it can move intothe cytoplasm and make the desired proteins," Butz said. "Ourscientists asked the question, `What's so magic about inserting DNAinto a chromosome of a target cell?'"
Cooper tried a different strategy. He successfully induced the DNAexpression inside a cell's nucleus but outside the chromosome.Cooper also incorporated gene sequences that enables DNA toreplicate, so that the inserted DNA can divide when the cell divides_ even though the DNA is outside the chromosome. Otherwise, 50percent of the DNA would be lost. This is critical for treating cancer,because cancer cells divide so rapidly.
Preliminary studies indicate that, at least in the lab, the methodworks, Butz said, producing quantities of expressed proteins that are"two to three orders of magnitude higher than anyone else hasachieved."
Hanson demonstrated the effectiveness of the technique using theWatanabe rabbit, which lacks the gene necessary to produce areceptor for low-density lipoprotein (LDL), the so-called badcholesterol. As a result, the rabbits' blood cholesterol levels soar, andthey live just six months.
Hanson gave each rabbit a single injection of compacted DNAcontaining working LDL receptor genes. Within six months, theircholesterol levels had fallen to near normal _ and remained normalfor the six months of the experiment. Giving the rabbits anotherinjection lowered their cholesterol levels even further.
"It was a proof of concept and a good model," Noland said. "With asingle intravenous injection, they were able to insert the gene into theright spot and get it to express."
The National Institutes of Health has awarded Hanson a grant toexplore whether the method works to restore a Factor 9 production inhemophiliacs. That work is being carried out in animals, Hanson said.
Using these techniques, DNA could be packaged in a vector, aliposome _ or simply in a poly-cation complex with a ligand that willbe taken up by cell receptors _ and delivered to the specific sites intarget organs.
Noland said the scientists now are debating what indications offer thebest opportunity for rapid progress. "Our goal is to have an indicationin the clinic in a year and a half," he said. n
-- Steve Sternberg Special To BioWorld Today
(c) 1997 American Health Consultants. All rights reserved.