Symbollon Pharmaceuticals Inc. began a Phase III trial of its iodine-based IoGen, designed to treat patients suffering pain associated with fibrocycstic breast disease.

The multicenter trial will involve about 175 euthyroid premenopausal women who are unresponsive to conservative treatment, the company said.

Representatives of the Framingham, Mass.-based company could not be reached for comment.

Symbollon said previous Phase II trials evaluating IoGen in FBD showed a significant reduction of pain and tenderness for the patients taking the oral drug, compared to placebo.

Patients in the Phase III will receive one 6-mg tablet of IoGen or placebo, daily, for six months, and researchers will evaluate the efficacy of IoGen comparing the proportion of patients that experience a clinically meaningful reduction in breast pain and tenderness. Pain will be measured through patient self-assessment reported in daily diaries. Nodularity will be used as a secondary efficacy endpoint and be evaluated by physicians.

Symbollon expects the trial to last about 12 months and cost about $1.25 million.

The company said certain sites included in the trial also will test for the presence of iodinated arachidonic acid derivatives in the breast duct of patients, which might help explain how IoGen can eliminate benign excess cell growth and possibly expand to serve as a treatment or preventive product.

In July, Symbollon acquired assets related to iodine drug development from Memetix Inc. and other related parties.

IoGen is a solid oral dosage form that delivers molecular iodine when dissolved in gastric fluid. Symbollon has completed Phase I and II trials to evaluate the product as a possible treatment for moderate to severe cyclic pain and tenderness - clinical mastalgia - associated with FBD. The company also said IoGen might be useful in treating or preventing other conditions, including endometriosis, ovarian cysts and premenopausal breast cancer.

Earlier this year, Symbollon announced plans to seek regulatory approval for IoGen in Canada, and Canadian authorities advised the company to file an application following product exposure in at least 500 patients, less than the usually required 1,500 patients.