I feel like jumping into Phase 2 study is interpreted that we...

I feel like jumping into Phase 2 study is interpreted that we know how the drug works and we have solid formulation and dose but there may remain still some unknowns and human studies are expensive. There are several mouse models that other similar products have reported that would be useful
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC153305/ to see how formulation and drug perform. Looks like the in vitro models for protein binding are less than ideal so doing mouse model we could get better information on that as well.
https://www.nature.com/articles/nrd3287 Maybe they have done this already and just not published results yet, UQ seems to know what they are doing.

I think the idea for companies is to derisk the development as much as possible, certainly acknowledge that there will alway be some risk though.