In the pivotal toxicity studies in rat and monkey, the exposure ratios were at
least 1 or higher, with the exception of the low dose in monkeys where an
exposure ratio of 0.6 was calculated. At the MTD or highest dose tested
(monkey) the exposure ratios were between 1 and 2. Even taking into
account the possible overestimation of the AUC of abiraterone – in the 28-
day and 13-week toxicity studies- due to co-elution of the isobaric
metabolite, still an exposure ratio slightly above 1 was calculated in both rat
and monkey. This is acceptable as for anticancer agents animal to human
exposure ratios of less than 1 are not uncommon.

Судя по всему, это показатель, означающий, во сколько раз уровень воздействия (ППК - AUC) у животных превосходит таковой у человека. Но как его правильно называют - "кратность превосходства воздействия", "отношение воздействия" или, возможно, еще как-нибудь (?).