Fused tri-cyclic compound as a PDE3/PDE4 dual inhibitor

A compound of formula (I), a stereoisomer or tautomer thereof or a pharmaceutically acceptable salt thereof,

• wherein,
• a ring Cy is selected from the group consisting of 5-membered heterocyclyl containing 1-3 heteroatoms independently selected from the group consisting of sulfur, oxygen or nitrogen and 5-membered heteroaryl containing at least one ring atom selected from the group consisting of N, O and S, wherein the 5-membered heterocyclyl or 5-membered heteroaryl is optionally substituted by one or more of the following groups:
• amino, hydroxy, ═O, halogen, cyano, C1-12 alkyl, —C(O)NH2, —C(O)NH(C1-6 alkyl), —C(O)N(C1-6 alkyl)2, —COOH, —C(O)O(C1-6 alkyl) or C1-12 alkoxy, wherein the C1-12 alkyl or C1-12 alkoxy is optionally substituted by one or more groups selected from the group consisting of halogen, amino and hydroxy;
• ring atoms of the ring Cy comprise at least one nitrogen atom;
• L is selected from the group consisting of —N(R6)—, —N(R6)C(O)—, —C(O)N(R6)—, —O—, —S—, —OC(O)—, —C(O)O—, —CH2N(R6)C(O)—, —CH2C(O)N(R6)—, —S(O)2NH—, —NHS(O)2— and a single bond;
• n is 1, 2, 3 or 4;
• E1 is —(CH2)m—, wherein m is 1, 2 or 3;
• E2 is selected from the group consisting of —O—, —NH—, —S— and a single bond;
• R3, R4 and R5 are each independently selected from the group consisting of hydrogen, halogen and C1-6 alkyl, wherein the C1-6 alkyl is optionally substituted by one or more groups selected from the group consisting of halogen, amino and hydroxy;
• and
• each R6 is independently selected from the group consisting of hydrogen, hydroxy and C1-3 alkyl, wherein the C1-3 alkyl is optionally substituted by one or more groups selected from the group consisting of halogen, amino and hydroxy.