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Adding Sickle Cell Disease To FDA’s Priority Review Voucher List Of Neglected Tropical Diseases


On July 16th, Putting Rare Diseases Patients First!® filed a citizen’s petition to add sickle cell disease to the Food and Drug Administration’s priority review voucher list of neglected tropical diseases. Dr. Lorna Speid, founder and president of the non-profit that supports patients with rare and neglected diseases, says her organization took the action because sickle cell disease is the only tropical disease that afflicts a majority African American population in the U.S.

Priority review vouchers for neglected tropical diseases are aimed to incentivize pharmaceutical companies to develop drugs and vaccines for such diseases. Priority reviews of new drug applications take six months to complete, rather than the standard review period of 10 months. Typically, the priority review designation is given to drugs that treat serious diseases and provide a significant improvement compared to existing therapies.

To qualify for a priority review voucher, a sponsor’s application must be for a drug, biologic, or vaccine for the prevention or treatment of a neglected tropical disease. Sickle cell disease fits the bill of a neglected tropical disease.

Sickle cell disease constitutes a group of congenital red blood cell disorders, named sickle cell for the crescent shape of red blood cells. Sickle cell disease alters the structure of hemoglobin, the molecule in red blood cells that delivers oxygen to organs and tissue throughout the body. The most common disorder type is sickle cell anemia. Sickle cell disease causes significant morbidity, including severe pain, anemia, organ damage, and infections. The disease also leads to premature mortality.

In the U.S., approximately 100,000 patients are living with the congenital disease. The disease predominantly impacts people of sub-Saharan African descent.

Of the 20 million patients suffering from sickle cell disease worldwide, most reside in Africa. Many of these patients lack newborn screening for the disease, and access to even the most basic of treatments, such as hydroxyurea. 

For a sponsor, a neglected tropical disease priority review voucher offers a six-month expedited review of another drug in the sponsor’s development pipeline if it gains approval for a drug with a neglected disease indication. Alternatively, the voucher can be sold to another company. Though critics have claimed that the program doesn’t require treatments to be novel or affordable, the program has been successful in ensuring development and launch of a number of important, new medications for neglected tropical diseases.

High-profile examples include the artemether/lumefantrine (Coartem) combination product targeting malaria. Artemether/lumefantrine was in use in a number of developing nations in the 1990s, and approved by FDA in 2009. Also, the drug benznidazole was in use worldwide as an agent for Chagas disease as early as the 1970s, before it was approved by FDA in 2017. And, the drug miltefosine was in use as an anti-cancer agent in the 1990s, and approved by FDA for leishmaniasis in 2014.

Until now, perhaps the most innovative approval driven by the priority review voucher program was the drug bedaquiline, indicated for multi-drug-resistant tuberculosis. Following a fast-track, accelerated approval process, FDA gave the nod to the drug in 2012. Bedaquiline became the first novel treatment in 40 years for pulmonary multi-drug resistant tuberculosis. The sponsor, Janssen, was awarded a priority review voucher for its efforts, which it used to expedite review of the psoriasis drug, guselkumab (Tremfya).

Sickle cell disease is in need of a bedaquiline-like innovation. Despite the recent uptick in interest in sickle cell disease, it is well documented that it still lags behind other neglected diseases in terms of investment and output of new medicines. Dr. Speid maintains that by adding sickle cell disease to the FDA’s priority review voucher list of neglected tropical diseases, pharmaceutical companies will be incentivized to increase their investment in R&D.


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