High-dose bovine transforming growth factor-B2 (bTGF-B2),dribbled surgically onto the edges of tiny holes or tears in themiddle of the retina, has enabled 10 of 11 patients to read twomore lines down an eye chart, improved their vision from20/200 to 20/25, and averted the onset of legal blindness.
Celtrix Pharmaceuticals Inc. of Santa Clara, Calif., supplied thegrowth factor, trademarked BetaKine, to The Retina Center atSt. Joseph Hospital in Baltimore. Results from this 60-patientclinical trial are described in this month's issue ofOphthalmology as "the first use of a growth factor ... to alter theoutcome of a retinal disorder."
Eye surgeon Bert M. Glaser, The Retina Center's director, toldBioWorld that results of the experimental procedure are dose-related. He obtained the best eyesight-salvaging response -- 10of 11 eyes treated, or 91 percent -- with 1,330 nanograms ofbTGF-B2. Fewer eyes -- four of 12, or 33 percent -- improvedwith 330 ng infusions of the protein.
Recruitment is completed for a 90-patient, Celtrix-sponsoredPhase II trial in Baltimore and at the retina center of theUniversity of Miami.
"To date, over 250 macular-hole patients have receivedBetaKine, and we remain enthusiastic," said Bruce B. Pharriss,Celtrix chairman and chief executive. He expects Phase IIItrials to begin next year, subject to FDA approval.
Holes in the retina usually occur when the jelly-like vitreousfluid inside the eyeball starts to shrink and pulls away fromthe retinal wall. This is often a prelude to detachment, as fluidleaks into the wound behind the retina. When the damagestrikes the macula, a pinhead-size spot of maximum fine-visionsensitivity at the retina's center, need for repair is particularlyurgent.
"The only (existing) recourse is vitrectomy -- removing thevitreous fluid -- in an effort to prevent further destruction,"Pharriss said.
"Adding transforming growth factor-beta is a new approachthat from a theoretical aspect is an attractive idea," saidChicago ophthalmologist Serge Debustros, an investigator in anationwide collaborative trial sponsored by 20ophthalmological center across the U.S. to gauge theeffectiveness of vitrectomy alone. "The factor causes fibrosis,which should tack the macular hole down better." Moreover,it's non-toxic at the doses Dr. Glaser is trying."
Celtrix is now synthesizing in Chinese hamster ovary cells arecombinant bTGFB2 for experimental use, Pharriss said. "Weare building a $13 million plan to manufacture this geneticallyengineered version of the growth factor," he said.
-- David Leff Science Editor
(c) 1997 American Health Consultants. All rights reserved.