Acute toxicity "six-pack" studies supporting approved new drug applications in the U.S., 2015-2018

The acute toxicity "six-pack" is a battery of animal tests used to evaluate acute systemic toxicity by three routes of exposure, skin and eye irritation/corrosion, and skin sensitization. A perception exists that these tests are not required for pharmaceuticals. For the four years from 2015 through 2018, we tallied the number of corresponding tests submitted by sponsors in approved, original new drug applications, as reported by the U.S. Food and Drug Administration (FDA) in publicly available reviews. In 125 reviews, we identified 228 single dose acute toxicity studies, 62 in vivo local tolerance studies, and 32 in vivo skin sensitization studies, as well as 37 in vitro or ex vivo local tolerance studies. A total of 4798 animals were used in these studies; however, FDA's reporting was inconsistent, and we estimate the actual number of animals used to be 8998. For the evaluation of single dose acute toxicity, we accessed two guidance documents with conflicting recommendations regarding routes of administration and number of species to be used. For the evaluation of local tolerance and skin sensitization, most studies examined were conducted by routes other than that intended for human administration. Non-animal methods used to evaluate skin sensitization were not reported.