Indole derivative having heterocycle and mono- or diazaindole derivative

A compound according to formula (1):

• Wherein Het represents an optionally substituted heterocyclic group selected from the group consisting of oxetane, furan, dihydrofuran;
• tetrahydrofuran;
• pyran;
• dihydropyran;
• tetrahydropyran;
• dioxole;
• thiophene;
• dihydrothiophene;
• tetrahydrothiophene;
• thiopyran;
• dihydrothiopyran;
• tetrahydrothiopyran;
• pyrrole;
• dihydropyrrole;
• pyrrolidine;
• pyridine;
• dihydropyridine;
• tetrahydropyridine;
• piperidine;
• pyrazole;
• 2-pyrazoline;
• pyrazolidine;
• imidazole;
• imidazolidine;
• pyrimidine;
• pyrazine;
• oxazoline;
• piperazine;
• 1,2,3-triazole;
• 1,2,4-triazole;
• tetrazole;
• isoxazole;
• 1,3-oxadiazole;
• 1,2,3-oxadiazole;
• 1,2,4-oxadiazole;
• 1,2,5-oxadiazole;
• 1,3,4-oxadiazole;
• 1,2-thiazole;
• 1,3-thiazole;
• 1,2,3-thiadiazole;
• 1,2,4-thiadiazole;
• 1,2,5-thiadiazole;
• 1,3,4-thiadiazole;
• 1,3-dioxolan, oxazolidine, and morpholine;
• Wherein A1 and A2 each represents —N═;
• A3 represents —CH2—, —(C═O)—, or —SO2—;
• R1 represents a group selected from the following formulae:
• Wherein A4 represents —O—, —S—, or —NH—;
• R2 represents a straight or branched alkyl group having 1 to 3 carbon atoms;
• n is 0, 1, or 2;
• Or an addition salt thereof with a pharmaceutically acceptable acid or base.