To suppress proliferation of cell in human small cell lung cancer by using a specific serotonin 5-HTID receptor antagonist.

A compound of formula I {R1 is a group of formula II [R11 is H, a 1-10C alkyl or (CH2)m-aryl1 [(m) is 0 or 1-6; aryl1 can be substituted], etc.; R2 is R4, OR4 or OS(O)2R4 (R4 is CF3, a 1-6C alkylaryl, etc.); R3 is H, a halogen, CN, etc.], etc.} or its pharmaceutically permissible salt, e.g. 2-[8-(4- methylpiperazin-1-yl)naphthalen-2-yloxy]nicotinonitrile is administered in an amount required for suppressing proliferation of cells. Furthermore, the compound is preferably obtained by reacting an intermediate of formula III [R8 and R9 are each H or a substituted 1-6C alkyl; (g) is 0 or 1-3] with a compound of formula IV (Y is chloro, bromo, etc.; R6 and R7 are each H or a 1-6C alkyl) in the presence of sodium hydrate in N,N-dimethylformamide at about 25-100°C under 1 atmospheric pressure.