Patent ID: 8858911

Claim:
A radiolabeled phosphodiesterase 1 (PDE1) inhibitor for use in gamma radiation-based diagnostic imaging, wherein the PDE1 inhibitor has low nanomolar potency versus PDE1 and greater than 10-fold selectivity to PDE1 as compared to other PDE enzyme families, and wherein the PDE1 inhibitor is in free or salt form and contains chemically bound radionuclide, and wherein the PDE1 inhibitor is selected from: i) 7,8-dihydro-[1H or 2H]-imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-one; ii) 7,8,9-trihydro-[1H or 2H]-pyrimido[1,2-a]pyrazolo[4,3-e]pyrimidin-4(5H)-one; iii) 3-(optionally hetero)arylamino-[2H]-pyrazolo[3,4-d]pyrimidine-4,6(5H, 7H)-dione; and iv) (6aR*,9aS*)-3-(phenylamino)-5-6a,7,8,9,9a-hexahydro-5-methylcyclopent-[4,5]imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(1H or 2H)-one; wherein each of (i), (ii), (iii) and (iv) are substituted at the 1- or 2-position with C2-9 alkyl, C3-9 cycloalkyl, heteroarylalkyl, or substituted arylalkyl.