In a final order issued August 20, 2015, FDA updated the list of tropical disease products eligible to receive a priority review voucher ("PRV"), an incentive to encourage the development of new drugs for the prevention or treatment of certain diseases by providing priority review of a subsequent human drug application. While the Federal Food, Drug, and Cosmetic Act (the "FDCA") lists 17 eligible diseases, it also authorizes FDA to expand the list to include "[a]ny other infectious disease for which there is no significant market in developed nations and that disproportionately affects poor and marginalized populations." Under criteria established in the order, FDA determined that Chagas disease, a potentially life-threatening illness caused by the protozoan parasite T. cruzi, and neurocysticercosis, a parasitic infection caused by larval cysts of pork tapeworms, satisfy the definition of "tropical diseases," and FDA added them to the list of designated tropical diseases. FDA also explained the criteria it applied, and will apply in the future, when expanding the list.

FDA's criteria for expanding the list of tropical diseases include:

  • The agency proposes to rely predominantly on a country's presence on the World Bank's list of "low income economies" as evidence the country should not be considered a "developed nation."
  • FDA will take a two-pronged approach when considering the significance of the market. FDA will use a disease prevalence rate of 0.1 percent of developed nation population as a factor in determining whether a "significant market" may exist. FDA will also consider whether governmental and nongovernmental organizations would purchase the product for distribution or stockpiling purposes.
  • When considering whether a disease "disproportionately affects poor and marginalized countries," FDA will look at the proportion of global-disability adjusted life years attributable to developing countries; the relative burden of the disease in the most impoverished populations within the countries in which it is found; the relative burden of the disease in infants, children, or other marginalized segments within the countries in which it is found; and designation by the World Health Organization as a neglected tropical disease.

FDA's approach takes into consideration stakeholder feedback received in a December 2008 public meeting, during which participants requested FDA establish a flexible approach to the criteria it would apply when determining eligibility of an infectious disease, the process for making tropical disease designations, and recommendations for specific diseases to designate. FDA has established a docket (FDA-2008-N-0567) for tropical disease designation suggestions. The docket will remain continuously open and FDA will periodically review its contents.

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