RGene Therapeutics Inc., a startup biotech company in TheWoodlands, Texas, announced today that it has received notice oftwo approved patents from opposite sides of the world.
One, issued by the Australian Patent Office, covers "Methods andCompositions for the Suppression of neu-Mediated Transformation"in solid tumors, specifically, ovarian, breast and lung cancers.
The other, for which the U.S. Patent and Trademark Office has justsent RGene (the R stands for "recombinant") a notice of allowance,deals with "Liposomal Antisense Methyl PhosphonateOligonucleotides, and Methods for Their Preparation and Use." Thisprotects proprietary methods for gene therapy of chronicmyelogenous leukemia (CML).
"The common thread of these two different technologies," saidRGene's president and CEO, Martin Lindenberg, "is that both rely onthe fundamental expertise of RGene, which has to do withmanipulation of nucleic acids on the one hand, and intracellulardelivery using liposomes on the other."
The aforesaid expertise derives mainly from the University of Texas'M.D. Anderson Cancer Center, which has licensed the patents inexclusivity, worldwide, to RGene. Other know-how comes to thecompany from the University of Tennessee and ArgusPharmaceuticals, Inc., a liposome/drug-formulating firm two milesdown the road from RGene. (See BioWorld Today, Dec. 6, 1994, p.1.)
"Argus and RGene signed a three-year, arms-length fee contract lastApril," Lindenberg told BioWorld Today, "under which we payArgus for developing and manufacturing lipid-vector formulations."Argus owns "less than 20 percent of RGene's equity," he said, addingthat since RGene started up in March 1994, it has raised $4 miliionfrom private investors (among them Argus), "enough to last us tillearly 1996."
As for today's announcement, Lindenberg said, "Australia justhappened to be the first patent to issue. "We have other applicationspending in all major markets of Europe, and all patent-treatycountries.
"Of the two technologies," he continued, "the more exciting, in termsof immediate relevance to a large pool of people, is ovarian cancer."With in vitro and preclinical mouse studies of the neu-oncogene-suppressing approach all but completed, he foresees clinical trials ofboth now-patented products _ for ovarian cancer and leukemia,respectively _ beginning "by the end of 1995."
A 'FIrst' for Cationic Lipid Vectors
The therapeutic for solid tumors couples E1A, an adenoviral genethat suppresses the key neu oncogene, to a non-viral gene-therapyvector consisting of a cationic DC-cholesterol-based liposome. Thisconstruct, Lindenberg stated, "is the first non-viral vector shown tobe effective in delivering active genetic material into humans."
He added, "It was used in Gary Nabel's very first study in Septemberof last year, when he put the HLA B7 gene into skin lesions ofmelanoma patients."
RGene's "most probable competitor is Vical, Inc." Lindenbergallowed. That San Diego company's vice-president for businessdevelopment, Robert Zaugg, confirmed to BioWorld Today that "theBC cholesterol vector is the one Gary [Nabel] first used, before hestarted working with us." Zaugg went on, "Then he found thatVical's lipids were able to deliver more DNA to the tumors, andswitched over."
Lindenberg also said that "now Genzyme Corp. is using our vector totreat cystic fibrosis "
Pending FDA approval of Phase I clinical trials for ovarian cancer,Lindenberg said, "We will continue developing toxicology data andformulation research -- although we could go into patientstomorrow with the material we already have." This consists of theE1A DNA complex with the cationic lipid, in a saline carriersolution.
"Cationic," he explained, "means that the liposomes have a netpositive-charge ion on the outside, which presumably gives them anaffinity to plasma DNA, which has an outside net negative charge."
He emphasized that "these are not classic bi-layer, drug-encapsulating liposomes, with the drug inside or between the layers.Rather, strands of DNA aggregate with very small mono-layerliposomes."
The active ingredient these vectors ferry into the tumorous cells isdescribed in the patent texts as an "exciting" and "surprising"discovery. It consists of the "adenovirus early E1A gene for thesuppression of neu-mediated oncogenesis." Neu is a.k.a. HER --human epidermal growth-factor receptor.
The Australian patent suggests that "E1A gene products . . . mayultimately be employed as treatment modalities for neu-mediatedcancers, such as cancers of the female genital tract and breast."
In Belly of Beast, Vector Worked
In pursuit of such solid-tumor gene therapy, RGene has already goneinto mice with this construct material, via injection into theperitoneal cavity. This abdominal hollow, filled with ascites fluid, isthe first port of call for ovarian tumors that metastasize, Lindenbergexplained, and added, "It will be injected into humans in exactly thesame way.
"Normally, if you give these mice human ovarian cancer cells," hecontinued, "they'll all be dead in three or four months. But we havemice still in remission after one year, and no clinical evidence oftumor recurrence, even though we withdrew treatment after montheight."
Squirted into the abdominal cavity, the vector is transferred into bothnormal and malignant cells adhering to the peritoneal wall, orfloating in the ascites fluid. "The good news," Lindenberg observed,"is that if it enters the non-malignant ones, it has no effectswhatsoever."
A clinical oncologist at M. D. Anderson, unaffiliated with RGene, isAndrzej Kudelka, a specialist in gynecological malignancies. "Thebulk of my practise consists of ovarian cancer," he told BioWorldToday, so RGene's results in mice "look very exciting."
But in the same breath he voices the caveat: "We always look toanimal studies to see whether or not there is something potentiallyinteresting. Unfortunately, many of them don't turn out positive inclinical trials."
Just as the gene-therapy package will seek out metastasized ovariancancer cells by infusion into the peritoneum, Kudelka pointed out,for breast cancer, the DNA will go into the pleural cavity, the smallspace in the diaphragm between lung and chest wall. Sometimes, heexplained, the cancer pumps large quantities of fluid into thisenclosure, filling and stretching it to a degree that "compromises thequality of a patient's life."
As a role for RGene's "new and different gene therapy approach,"he suggests, "Even if we could just control the pleural effusion --not even discussing whether we could control the systemic disease -- that, in and of itself, would be very interesting, very beneficial."
Kudelka concluded, "So this could be one such therapeutic modality_ if it turns out that it works."
To treat CML -- chronic myelogenous leukemia _ "it's acompletely different set-up," Lindenberg explained.
For one thing, the transforming payload is not DNA, "but a piece ofmessenger RNA that acts as an antisense nucleotide." This methylphosphonate oligo targets the oncogene that expresses a protein onthe translocated Philadelphia chromosome, which causes the CMLcells to proliferate. It achieved 50 percent inhibition in vitro.
For another, instead of cationic lipid complexes, the CML-targetingvector is based on a traditional, but modified, drug-deliveryliposome. Medical oncologist Gabriel Lopez-Berestein, a scientificfounder and board member of RGene, is the architect of this CML-targeting vector.
A third difference: Instead of infusion into a bodily cavity, thisconstruct makes for the bloodstream by needle injection, to be takenup by the leukemic cells.
Asked to describe the mechanism by which the tumor-suppressingeffect takes place, Lopez-Berestein replied simply, "This is notknown."
As for the new lipid vectors, he stated that these "have probably donethe job better than retroviruses and adenoviruses." But he concedesthat the non-viral delivery systems may have their own limitations:"The liposome," he said, "has more of a transient DNA expressionthan a viral vector, "but sufficient to do the job -- which is theimportant thing." n
-- David N. Leff Science Editor
(c) 1997 American Health Consultants. All rights reserved.