If you're honestly interested in the history of Osimertinib (Tagrisso) then this article has a good overview. It specifies the studies involved so that you can dig into funding sources. Generally for drug development, public funding only covers basic science and maybe early-stage trials. The majority of the expense is in phase 3 clinical trials which pharmaceutical companies pay for.

https://doi.org/10.1093/annonc/mdw129