Late, never or non-existent: the inaccessibility of preclinical evidence for new drugs.

Abstract

Animal studies establish much of the evidence used to support clinical development of new drugs. Recent studies suggest that many preclinical investigations are withheld from publication, leading to exaggerated estimates of clinical utility. We sought to estimate the volume and properties of all published animal efficacy studies for a cohort of novel drugs. We searched biomedical databases to identify 47 novel drugs whose first trials were reported between 2000 and 2003, inclusive. Next, we searched for all published animal studies testing the same drug, regardless of publication date. We then extracted items from titles and abstracts of eligible studies. We identified 2462 efficacy studies, representing an average of 52 studies per drug. No published efficacy studies were available for three drugs in our sample. The volume of efficacy studies was related to how far the drug had progressed in clinical development (Spearman's correlation coefficient = 0.66, P < 0.0001). Most (87%) accessible animal efficacy studies were reported after publication of the first trial, and for 17% of the drugs in our sample, no efficacy studies were published before the first trial report. Disease indications used in trials often did not match those modelled in efficacy studies; for 35% of indications tested in trials, we were unable to identify any published efficacy studies in models of the same indication. The volume of published efficacy studies is large, although numerous gaps reflect non-publication, publication delay or non-performance of efficacy studies supporting trials.