Pluristem Therapeutics, Inc. (Nasdaq: PSTI) has filed the necessary documents requesting that the U.S. Food and Drug Administration (FDA) grant orphan drug status to its PLacental eXpanded (PLX) cells for the treatment of aplastic anemia.

The filing marks Pluristem's second orphan drug application to the U.S. FDA. The company applied once before, and successfully received in August of 2011, orphan drug status from the FDA for its PLX cell therapy in the treatment of Buerger's disease.

Aplastic anemia is a rare but serious disorder caused by destruction of blood-forming stem cells (Hematopoietic Stem Cells or HSCs) in the bone marrow. While normally HSCs develop into three types of blood cells, red blood cells, white blood cells and platelets, in aplastic anemia all blood types are deficient, a condition also known as pancytopenia. The disease is considered an emergency situation where patients are supported either with blood transfusions in anticipation of a bone marrow transplant (BMT) or with drugs that suppress the immune system. Aplastic anemia patients are included in the bone marrow transplant market estimated at $1.3 billion per year in the U.S. alone.

In May of this year, Pluristem announced that a seven year-old girl in Israel, whose condition was rapidly deteriorating due to aplastic bone marrow, experienced a reversal of her condition with a significant increase in her red blood cells, white blood cells and platelets following the intramuscular injection of the company's PLX cells. Prior bone marrow transplants had failed. The patient has subsequently been released from the hospital and returned home.