The Office of Orphan Products Development of the US Food and Drug Administration (FDA) has granted orphan drug designation to Immunomedics, Inc's IMMU-132, an antibody-drug conjugate for solid cancer therapy, for the treatment of small cell lung cancer (SCLC).

“We are pleased to receive the orphan designation for IMMU-132 from the FDA,” remarked Cynthia L Sullivan, president and chief executive officer. “In addition to small cell lung cancer, the agent is currently in phase II clinical development focusing on a few select types of solid cancers,” Sullivan added.

In an early phase I clinical study, IMMU-132 has produced partial responses in patients with small cell lung cancer, colorectal cancer, and triple negative breast cancer. IMMU-132 is an active antibody-drug conjugate containing the humanized anti-TROP-2 antibody, hRS7, conjugated by a pH sensitive linker to SN-38. TROP-2 is expressed by many human tumours, such as cancers of the breast, cervix, colon and rectum, kidney, liver, lung, ovary, pancreas, and prostate, but with only limited  expression in normal human tissues.

hRS7 internalizes into cancer cells following binding to TROP-2, making it a suitable candidate for the delivery of cytotoxic drugs.

SN-38 is the active metabolite of irinotecan, which is a standard therapy for patients with metastatic colorectal cancer, but has major gastrointestinal and hematologic toxicity. By attaching SN-38 to tumour-targeting antibodies, delivery of SN-38 to the tumor may be increased several-fold while mitigating systemic toxicity.

Orphan drug status is granted by the FDA to a drug or biological product to treat a rare disease or condition upon request of a sponsor. Orphan drug designation qualifies the Company for various development incentives, including tax credits for qualified clinical testing, a waiver from the FDA’s application User Fee for marketing application, and a seven-year period of marketing exclusivity in the United States for IMMU-132, if it is approved by the FDA for the treatment of patients with SCLC.

The granting of an orphan designation request does not alter the standard regulatory requirements and process for obtaining marketing approval. Safety and effectiveness of a drug must be established through adequate and well-controlled studies.

Immunomedics is primarily focused on the development of monoclonal antibody-based products for the targeted treatment of cancer, autoimmune and other serious diseases.