The U.S. Food and Drug Administration has approved Pfizer Inc and partner OPKO Health Inc's treatment for growth hormone deficiency in children, the companies said on Wednesday.

The drug, which will be sold under brand name Ngenla, is expected to become available in the U.S. in August, the companies said.

Growth hormone deficiency is a rare disease that affects one in about 4,000 to 10,000 children, and is characterized by inadequate secretion of the growth hormone, resulting in very short height in adulthood and delayed puberty.

The drug's approval follows an initial rejection from the FDA last year, the reason for which was not specified by the companies then.