New FDA Orphan Drugs: Nitroimidazole PA-824, 3'-deoxyadenosine, Iobenguane I 131

Jill Taylor

August 24, 2007

August 24, 2007 — The US Food and Drug Administration (FDA) has granted orphan drug designation for nitroimidazole PA-824 for the treatment of tuberculosis, 3'-deoxyadenosine for the treatment of TdT-positive acute lymphocytic leukemia, and iobenguane I 131 for the treatment of neuroendocrine tumors.

Orphan Drug Nitroimidazole PA-824 for Tuberculosis

On July 5, the FDA granted orphan drug designation to nitroimidazole PA-824 (The Global Alliance for TB Drug Development) for the treatment of tuberculosis (TB), a bacterial infection of the lungs caused by the organism Mycobacterium tuberculosis.

According to the World Health Organization, TB is the leading killer among infectious diseases, accounting for 1 in 4 preventable deaths among adults. It is estimated that one third of the world's population is infected with TB bacilli.

PA-824 is an antibacterial agent with a mechanism of action not previously used to treat TB. It has demonstrated activity in vitro against all tested drug-resistant clinical isolates, suggesting potential utility in the treatment of drug-resistant strains of TB bacilli. Furthermore, PA-824 has shown no evidence of mutagenicity and no significant cytochrome P450 interactions and has a narrow spectrum of activity.

According to The Global Alliance for TB Drug Development, an initial Phase 2a proof-of-concept trial is planned for PA-824. The study will examine the short-term potency of PA-824 given as a single drug.

Orphan Drug 3'-Deoxyadenosine for Acute Lymphocytic Leukemia

On July 5, the FDA granted orphan drug designation to 3'-deoxyadenosine ( Cordycepin, OncoVista, Inc) for the treatment of acute lymphocytic leukemia (ALL) in patients who express the enzyme terminal deoxynucleotidyl transferase (TdT).

ALL is a fast-growing cancer of the white blood cells in which unformed cells called blasts, which would normally develop into the white blood cells used by the body to fight infections (lymphocytes), are abnormal. These abnormal cells do not develop into lymphocytes but collect in the body and compete with other healthy blood constituents, including red blood cells, other white blood cells, and platelets. According to the National Marrow Donor Program, there are approximately 4000 new cases of ALL annually in the United States.

Cordycepin is a nucleoside analog, a class of drugs with known efficacy against viral infection. It is OncoVista's first clinical-stage development compound.

Orphan Drug Iobenguane I 131 for Neuroendocrine Tumors

On July 5, the FDA granted orphan drug designation to iobenguane I 131 (Draximage) for the treatment of neuroendocrine tumors.

Neuroendocrine tumors represent a diverse class of malignancies, as they are able to arise almost anywhere in the body and can be associated with a broad range of local symptoms. As such, they represent a challenge to clinicians both in terms of diagnosis and treatment.

Iobenguane I 131 is comprised of iobenguane, also known as MIBG, a compound readily absorbed by neuroendocrine tumor cells, and I 131, a radioactive form of iodine. Tumors are subjected to radioactivity when I 131 is absorbed into the tumor with the iobenguane.


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