A combination of the vasopressin type 2 receptor antagonist tolvaptan and the somatostatin analogue pasireotide synergistically reduces cyst progression in a PKD1 mutant mouse model of autosomal dominant polycystic kidney disease (ADPKD). Both drugs indirectly inhibit adenylyl cyclase 6 activity, leading to a reduction in levels of 3', 5'-cAMP, which are decreased to those of wild-type controls by combination therapy. The dual therapy also results in smaller cystic and fibrotic volume, suggesting that it might be an effective treatment for ADPKD.
Coming off the stinging results of dual ACEi/ARB therapy that were so promising in theory, I would be very cautious extrapolating from animal data and mouse models. If it hasn't been tested in humans we should probably restrict it to protocols.