Role of follow‐on drugs and indications on the WHO Essential Drug List

Summary Introduction:  The World Health Organization's Essential Drug List (EDL) contains first‐in‐class drugs and subsequent class entrants (follow‐on drugs) deemed necessary to combat diseases prevalent throughout the world, with a special emphasis on developing nations. The EDL also includes originally approved and follow‐on indications. There are opposing views regarding the value of follow‐on drugs and indications. Critics suggest many follow‐on drugs and indications offer little or no benefit to patients. Advocates counter that follow‐on drugs offer advantages in terms of improved effectiveness, compliance and patient satisfaction. Objective:  In order to inform this debate on the value of follow‐on drugs and indications we examined the numbers of follow‐on drugs on the EDL and the extent to which follow‐on indications are recommended. Methods:  We identified all 312 drugs on the 14th edition of the EDL, omitting 72 non‐pharmaceutical entities. For the 240 pharmaceutical entities we ascertained whether the Food and Drug Administration (FDA) had approved them, and, if so, when each was approved. We chose a validated therapeutic classification system – the United States Pharmacopeia's Model Guidelines for Medicare formulary management – in order to distinguish first‐in‐class and follow‐on drugs on the EDL. Specifically, we selected the formulary key drug type as our benchmark therapeutic class. We assigned each EDL drug to a formulary key drug type. We defined first‐in‐class drugs as the first in each formulary key drug type, and follow‐on drugs as all other drugs in each formulary key drug type. We identified follow‐on indications by comparing WHO‐listed indications with the original approved indication(s) by the FDA. Finally, we examined the therapeutic rating (priority vs. standard) given by the FDA to follow‐on drugs on the EDL. Results:  Sixty‐three per cent of the EDL drugs were follow‐ons; 15% of the indications were follow‐on indications. Fourteen drugs were listed in multiple WHO (sub) groupings; and 49% of follow‐on drugs were given a priority rating by the FDA. Conclusions:  In light of the fact that the EDL only includes drugs and indications deemed essential, the large number of follow‐on drugs, follow‐on indications, and priority‐rated follow‐on drugs on the EDL suggest their importance. From a public policy perspective, it may prove counterproductive to erect hurdles that impede follow‐on research and development.