TGFBR1 and cyst: Treatment with several steroids, coumarins, and flavonoids (spectrum library) exacerbated PKD phenotypes in pkd2−/− zebrafish (tail curvature), and androgen and 5α-androstane 3,17-dione had the strongest effect (independent of canonical androgen signaling). Whereas, treatment with several ALK5 (TGFβR1) kinase inhibitors (PKIS library; diclofenac, dibutylhydroxyanisole, and zinc pyrithione) partially ameliorated PKD phenotypes (tail curvature) in pkd2−/− zebrafish, ultimately validated with the ALK5 inhibitor, SD208. Results verified in 3D cyst cultures