Cytogen Corp. is seeking FDA approval of a radiopharmaceuticaldrug aimed at alleviating severe pain associated with cancers thathave metastasized in bone, such as prostate, breast and lung cancers.

The Princeton, N.J.-based company Tuesday filed a new drugapplication (NDA) for Quadramet, boosting the company's stock(NASDAQ:CYTO) 22.5 percent. Cytogen closed at $4.75, up 87cents.

The anti-pain drug combines the radioisotope samarium-153 with thephosphonate EDTMP, to attack newly formed cancerous tissue onbone. The isotope has a short half-life of 46 hours and is delivered byEDTMP, which has an affinity for skeletal tissue.

Quadramet, which Cytogen acquired from Midland, Mich.-basedDow Chemical Corp. in 1993, apparently is able to reduce canceroustissue around the bone, but researchers have not determined how itworks. The isotope emits beta radiation to attack the cancer cells aswell as gamma radiation for imaging.

Cytogen's NDA is supported by data from more than 500 patients,including those who participated in Phase III studies showing thedrug achieved statistical significance in relieving pain.

In addition to filing the NDA, Cytogen spokeswoman ColleenTeschko said the company intends to begin Phase II/III trials ofQuadramet as a treatment for cancer. She said the National CancerInstitute already has a Phase I study under way targeting bone tumorsin children.

Cytogen licensed rights to manufacture and market Quadramet to theBillerica, Mass.-based radiopharmaceuticals division of DupontMerck Pharmaceutical Co.

Cytogen's only product on the U.S. market is OncoScint, which is amonoclonal antibody imaging agent used to detect colon and ovariancancers. The company also has an application pending with the FDAfor approval of another diagnostic, ProstaScint, an antibody used todetect prostate cancer. _ Charlie Craig

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