To be frank, I don't know. My work with mice was rather limited so I don't have the depth of knowledge of mice as a model organism that I would need to answer this good question.
In general, toxicities are identified in humans that weren't observed in mice, the delivery mechanism may be intrinsically unsafe or unknown to be safe, the genetic architecture differs in a way that changes expression of relevant genes, or the metabolism differs in some way.
In general, toxicities are identified in humans that weren't observed in mice, the delivery mechanism may be intrinsically unsafe or unknown to be safe, the genetic architecture differs in a way that changes expression of relevant genes, or the metabolism differs in some way.