Ten years with biologics: to whom do data on effectiveness and safety apply?

During the past decade, the position of biologics in the therapeutic armamentarium, the number of approved indications and the number of available biologics have changed. Available data on (long-term) safety might thus pertain to patient populations not comparable with contemporary patients. The aim of this study was to assess the extent to which contemporary patients who start or switch biologic therapies are comparable with those patients who gave rise to the currently available data on effectiveness and safety.

We identified all adult patients with RA (n=9612), PsA (n=1417) and other SpA (n=1652) initiating a first biologic therapy between 1 January 1999 and 31 December 2008, registered in the Swedish Biologics Register (ARTIS), including information on demographics, disease characteristics and 1-year risk of first-line treatment discontinuation.

Over calendar time, measures of disease activity at start declined substantially for all indications, and diminished between first-, second- and third-line therapy starts. One-year risks of first-line therapy discontinuation increased. Switchers to anti-TNF and non-TNF biologics had different comorbidities. Despite <50% drug retention at 5 years, most patients remained exposed to some biologic.

The trends in baseline characteristics and drug retention underscores that any effects of biologics, including comparison between different biologics, must be interpreted in light of the characteristics of the population treated. The observed differences further call for continued vigilance to properly evaluate the safety profiles of biologic treatments as they are currently used. Exposure to multiple biologics presents a challenge for attribution of long-term effects.