AMERSHAM’s METASTRON (STRONTIUM-89) APPROVED FOR BONE PAIN RELIEF

Executive Summary

AMERSHAM's METASTRON (STRONTIUM-89) APPROVED FOR BONE PAIN RELIEF in cancer patients with painful skeletal metastases on June 18. Metastron is "not indicated for use in patients with cancer not involving bone," the precautions section of approved labeling states. The injectable radiopharmaceutical was designated a "1P" approval (priority review) by FDA. The NDA (20-135) was filed on Nov. 30, 1990 by Medi-Physics, Amersham's U.S. radiopharmacy unit based in Arlington Heights, Ill. FDA sent the firm refusal to file and refusal to file over protest letters dated Feb. 4, 1991 and Sept. 11, 1991 before commencing with its review of the new molecular entity. Zeneca and Amersham will comarket Metastron under a worldwide agreement formed at the close of Amersham's fiscal year (ended March 31). Zeneca plans to market the drug initially to physicians who treat prostate cancer patients, the firm said in a May 12 public offering prospectus. Amersham's responsibilities under the deal include the manufacture and distribution of the drug, Zeneca said. The recommended dose of the radiopharmaceutical is 148 megabecquerels (4 mu Ci), or, alternatively 1.5 to 2.2 MBq (40-60 mu Ci)/kg body weight, given as a one- to two-minute I.V. injection. Repeated doses "should be based on an individual patient's response to therapy, current symptoms, and hematological status, and are generally not recommended at intervals of less than 90 days," labeling counsels. "In view of the delayed onset of pain relief, typically 7 to 20 days post-injection, administration of Metastron to patients with very short life expectancy is not recommended," the precautions section adds. The warning section of approved labeling states that Metastron use in patients "with evidence of seriously compromised bone marrow from previous therapy or disease infiltration is not recommended unless the potential benefit of the treatment outweighs the risks. Bone marrow toxicity is to be expected following the administration of Metastron, particularly white blood cells and platelets. The extent of toxicity is variable." Labeling adds that "verification of dose and patient identification is necessary prior to administration because Metastron delivers a relatively high dose of radioactivity." Metastron has been approved in 11 countries for the relief of bone pain associated with prostate cancer, Amersham reported in a June 9 financial release. In the U.K. and France, Metastron's indication has been extended to cover use as an adjunct or alternative to radiotherapy, the U.K.-based firm added. Cytogen is also developing a radiopharmaceutical for the alleviation of bone pain associated with metastatic cancer. The company acquired Samarium-153 EDTMP, which is currently in advanced Phase III trials, from Dow Chemicals in May. The firm reported on clinical results June 8 at the 40th Annual Meeting of Nuclear Medicine in Toronto. "In studies performed to date, pain palliation has been observed in 70%-80% of patients who received the radiotherapeutic product, with an onset of pain relief typically seen in four to seven days," Cytogen said.