New FDA Orphan Drugs: IPI-504, Pafuramidine, Preos

Jill Taylor

September 21, 2007

September 21, 2007 — The US Food and Drug Administration (FDA) has granted orphan drug designation for IPI-504 for the treatment of gastrointestinal stromal tumors, pafuramidine for the treatment of African sleeping sickness, and PREOS for the treatment of hypoparathyroidism.

Orphan Drug IPI-504 for Gastrointestinal Stromal Tumors

On August 31, the FDA granted orphan drug designation to IPI-504 (Infinity Pharmaceuticals, Inc, and MedImmune) for the treatment of gastrointestinal stromal tumors (GISTs).

A GIST is a rare tumor that is thought to develop in the interstitial cells of Cajal (ICCs) in the wall of the gastrointestinal tract, usually in the stomach or small intestine, and can be either malignant or benign. Malignancy in the majority of cases occurs when specific mutations in the cellular signaling enzymes, KIT or PDGFRA, cause the growth and survival of the signal cell to become permanently active. Both KIT and PDGFRA are client proteins of HSP90, a molecular chaperone that responds to cell stress caused by heat.

IPI-504 is a small-molecule drug that is administered by intravenous infusion. Preclinical studies have shown IPI-504 to selectively inhibit HSP90 as well as to have broad potential to treat certain cancers when used as monotherapy or in combination with other drugs.

Orphan Drug Pafuramidine for African Sleeping Sickness

On August 31, the FDA granted orphan drug designation to pafuramidine (Immtech Pharmaceuticals, Inc) for the treatment of human African trypanosomiasis (African sleeping sickness), a parasitic infection that is transmitted to humans by tsetse fly bite.

African sleeping sickness is found in sub-Saharan Africa, with an estimated 50,000 to 70,000 people currently infected. The parasites, which multiply in subcutaneous tissues, blood, and lymph, eventually cross the blood—brain barrier to infect the central nervous system and cause systems such as confusion, sensory disturbances, poor coordination, and disturbance of the sleep cycle. The disease is fatal in patients who do not receive treatment.

Pafurmidine is the first orally administered drug for African sleeping sickness and has a favorable toxicity profile, though it is effective only during the first stage of disease—a phase that may extend over a period of years without symptoms.

Orphan Drug Recombinant Parathyroid Hormone (Preos) for Hypoparathyroidism

On September 19, NPS Pharmaceuticals, Inc, announced FDA designation of parathyroid hormone (rDNA origin) for injection ( Preos) as an orphan drug for the treatment of hypoparathyroidism, a rare deficiency of parathyroid hormone.

Hypoparathyroidism can be inherited or caused by injury to the parathyroid gland and is estimated to afflict 65,000 Americans. The parathyroid hormone deficiency compromises the proper absorption of calcium, which can lead to symptoms such as tetany, hair loss, dry skin, or malformed nails; unusual sensations around the mouth and fingers; and candidiasis. Left untreated, the condition may lead to complications, including breathing problems, cataracts, and muscle, ligament, and nervous system disorders.

Recombinant human parathyroid hormone has been approved in Europe under the brand name Preotact. There is currently no FDA-approved treatment for hypoparathyroidism.

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