**5. Conclusions**

Our studies showed for the first time that anticancer drugs ixazomib, oprozomib, and delanzomib had a critical role in upregulating OAT3 transport activity and expression, suggesting their potential impact on the OAT3-mediated drug disposition and clinical drug–drug interactions during combination therapies of proteasome inhibitor drugs and other types of drugs (Figure 11).

**Author Contributions:** Conceptualization, Y.F. and G.Y.; methodology, Y.F.; software, Y.F.; validation, Y.F.; formal analysis, Y.F.; investigation, Y.F., Z.L., J.Z.; resources, Y.F.; data curation, Y.F.; writing—original draft preparation, Y.F.; writing—review and editing, G.Y.; supervision, G.Y.; project administration, G.Y.; funding acquisition, G.Y. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by grants (to Guofeng You) from National Institute of General Medical Sciences (R01-GM079123 and R01-GM127788).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
