Follow-on products now make up 63% of the medicines on the World Health Organisation’s (WHO) essential drug list (EDL), compared with 47% in 1977, the Tufts Center for the Study of Drug Development has found.

In its latest study, published in the July/August Tufts CSDD Impact Report, the US-based Center also noted that the Food and Drug Administration had assigned a priority rating to 49% of the follow-on products on the EDL approved since 1962, “further highlighting the therapeutic value accorded these medicines.”

The number of follow-on drugs in each WHO-defined category appeared to be a function of the category’s age, the Tufts Center said – in other words, the more mature the category, the more follow-on products were included. The Center also pointed out that, while the percentage of follow-on drugs on the EDL had risen sharply since 1977, the share of follow-on indications had actually fallen, from 19% to 15% now.

The central role of follow-on medicines in WHO drug policy suggested that initiatives to curb research and development for ‘me-toos’ could have a detrimental effect on public health, the Tufts Center maintained. “Growing reliance on follow-on drugs by the World Health Organization reflects the role of incremental improvement on first-in-class drugs as a critical mechanism of pharmaceutical innovation,” commented research fellow Joshua Cohen, who conducted the analysis.

Providing back-up

Follow-on products “provide back-up if the first-in-class drug is withdrawn, and also enhance choice for patients who may not respond well to other similar medicines,” Cohen added. “If development of follow-on drugs were curtailed, many people, especially in poorer regions of the world, would likely suffer.”

He also noted that more than 90% of products on the EDL were drugs whose patents had expired, lowering their cost and enhancing their affordability in developing markets.

The Tufts Center is, by its own description, an “independent, academic, non-profit research group” affiliated with Tufts University in Boston. It receives unrestricted grants from pharmaceutical and biopharmaceutical companies, contract research organisations, trade associations, niche providers and other corporate entities, which cover around 55% of the Center’s operating expenses.