Interim Phase III data of Gynex Pharmaceuticals Inc.’s ethinyl estradiol showedthat the compound increased breast development in Turner’s syndrome girls withoutadversely affecting their growth rate or causing bones to age too quickly.

Turner’s syndrome occurs when a girl is born with only one healthy X chromosomeinstead of two, resulting in short stature and a lack of sexual development. There is noapproved therapy for the condition.

Gynex’s ongoing Phase III study of the estrogen compound, a synthetic analog ofestradiol, is focusing on whether feminization of adolescent girls with the syndrome canbe achieved without compromise in final height.

In the study, presented Wednesday at the American Pediatric Society meeting inBaltimore, Turner’s syndrome girls received growth hormone each day in conjunctionwith either placebo or one of two dosage amounts of ethinyl estradiol (EE).

Of 28 patients completing six months of treatment, significant breast developmentoccurred in one of seven on placebo, four of nine on a 25 nanogram dose of EE and 11 of 12on a 100 ng dose. Growth rates and bone age advancement didn’t differ among the threegroups.

The study, under the direction of doctors E. Kirk Neely and Ron Rosenfeld of StanfordUniversity, received the Pediatric Society’s 1992 Fellow’s Basic and ClinicalResearch Award.

Gynex (NASDAQ:GYNX) of Vernon Hills, Ill., plans to seek marketing approval in 1993.The drug has orphan designation.

Gynex stock closed at $2.69, up 25 cents.