[Pharmaceutical development concerning diseases predominating in tropical regions: the concept of indigent drugs]

When the WHO certified the eradication of smallpox in 1981, there was a general impression that the fight against infectious diseases which began with Jenner and Pasteur was entering a phase of achievement: poliomyelitis, dracunculasis, leprosy, Chagas' disease and neonatal tetanus were also responding to eradication campaigns. However, in 1995, infectious diseases are still an important cause of mortality and morbidity and the rising incidence of emerging or re-emerging diseases remains a matter of great concern. Although this situation can be explained, at least partly, by the deterioration of health care systems and diverse socio-economic and ecological disorders, important changes occurring in the drug industry since 1980 have also played a role due to changes in pharmaco-epidemiology and new policies of drug development. Among the 1061 new drugs developed from 1975 to 1994, less than 2.7% concern tropical diseases. Since praziquantel, novel drugs have issued from veterinary medicine (ivermectin), military research (halofantrine, mefloquine) or fortuitous analysis of pharmacopoeia (artesunate). The cost of investments and the lack of market potential and market security in developing countries have dampened interest in developing drugs for tropical diseases. Observing the combined effect of deficient pharmaceutical development, drug wear due to chemoresistance (chloroquine, sulfadoxine-pyrimethamine, aminopenicillins), the cost barrier (second generation molecules) and the potential abandon of major drugs (eflornithine, melarsoprol) has led us to establish a classification of these "indigent" drugs (in opposition to "orphan" drugs) into five classes: true indigent drugs (eflornithine), indigent drugs by indication (pentamidine), indigent drugs by function (ceftriaxone), indigent drugs by formulation (melarsoprol) and indigent drugs by default (suramin). This analysis can serve as a basis for a search for solutions (regulatory, administrative and financial incentives) favoring a reactivation of drug development for diseases predominating in intertropical regions.