Myogen has announced that the United States Food and Drug Administration has granted orphan drug designation to ambrisentan for the treatment of pulmonary arterial hypertension (PAH). Ambrisentan is currently being evaluated for PAH in two pivotal Phase III trials, ARIES-1 & -2.
"The FDA's grant of orphan drug designation to ambrisentan for PAH strengthens our development program by offering regulatory, clinical development and commercial benefits," said J. William Freytag, Ph.D., President and Chief Executive Officer of Myogen.
The U.S. Orphan Drug Act is intended to assist and encourage companies to develop safe and effective therapies for the treatment of rare diseases and disorders. Under the Orphan Drug Act, upon marketing authorization, the FDA does not accept or approve other applications to market the same medicinal product for the same therapeutic indication for a seven-year period. In addition to potential market exclusivity, orphan drug designation provides protocol assistance, advice on the conduct of clinical trials, tax credits for clinical research expenses, grant funding for research of rare disease treatments and waiver of the Prescription Drug User Fee Act (PDUFA) filing fee.
Ambrisentan is a type-A selective endothelin receptor antagonist and potent inhibitor of endothelin-induced vasoconstriction. Endothelin is a small peptide hormone that is believed to play a critical role in the control of blood flow and cell growth. Elevated endothelin blood levels are associated with several cardiovascular disease conditions, including pulmonary arterial hypertension, chronic kidney disease, hypertension, chronic heart failure, stroke and reclosure of coronary arteries after balloon angioplasty or stent implantation. Therefore, many scientists believe that agents that block the detrimental effects of endothelin will provide significant benefits in the treatment of these conditions. Ambrisentan is selective for the ET(A) receptor versus the ET(B) receptor and demonstrates a half-life that may be suitable for once a day dosing.