Abstract: A 1,4-dihydropyridine derivative having the formula (I): wherein, R1 represents a substituted or unsubstituted phenyl or pyridyl group, R2 represents a C1 to C5 lower alkyl group, R3 represents a substituted or unsubstituted C1 to C8 alkyl, alkenyl, alkynyl or substituted or unsubstituted C3 to C7 cycloalkyl or cycloalkenyl group, R4 represents —A—R5, wherein A represents a C3 to C5 alkynylene group having one triple bond, and R5 represents a substituted or unsubstituted pyridyl, quinolyl, isoquinolyl or pyrimidyl group and a drug for overcoming resistance to an anti-cancer drug or a drug increasing the effect of an anti-cancer drug containing as an effective ingredient the derivative or its pharmacologically acceptable salt or hydrate.

Abstract: An imidazothiazole compound having the formula (A): ##STR1## wherein R.sub.1 is a phenyl or napthyl which may have a substituent, R.sub.2 is an acyl, and the two bonds at dotted line portions may or may not exist simultaneously, or a pharmacologically acceptable salt thereof and an agent for overcoming resistance to an anti-neoplastic agent or an enhancer for the effect of an anti-neoplastic agent comprising said compound or a pharmacologically acceptable salt thereof as an active ingredient.

Abstract: A 1,4-dihydropyridine compound having the formula (I): ##STR1## wherein, R.sup.1 indicates --COO--A--(3-pyridyl), A indicates a C.sub.3 -C.sub.6 straight chain alkylene group in which one piperazine may be interposed; R.sup.2 indicates a C.sub.2 -C.sub.10 alkyl group, alkenyl group or alkynyl group; a lower alkyl group or lower alkenyl group having a substituent; or a cycloalkyl group which may have a substituent; R.sup.3 indicates the same group as R.sup.1 or --COO--R.sup.4 ; and R.sup.4 indicates a lower alkyl group which may have a substituent or its pharmacologically acceptable salt and an anti-allergenic drug, antiphlogistic, drug for overcoming resistance to anti-cancer drugs, or drug for reinforcing the effect of anti-cancer drugs containing the same as effective ingredients.

Abstract: The present invention relates to novel imidazo-[2,1-b]benzothiazole compounds represented by formula (I) and pharmacological acceptable salts thereof: ##STR1## wherein R.sub.1 represents a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms; R.sub.2 represents a ##STR2## group (wherein X and Y, which may be the same or different, each represents a hydrogen atom, a lower alkyl group having 1 to 4 carbon atoms or a substituted or unsubstituted phenyl group), a --CH.sub.2 --O--Z group (wherein Z represents a lower alkyl group having 1 to 4 carbon atoms or a substituted or unsubstituted benzyl group) or a --CH.sub.2 --O--CO--W group (wherein W represents an alkyl group having 1 to 8 carbon atoms, an alkylamino group having 1 to 8 carbon atoms, a substituted or unsubstituted phenyl group or a thienyl group); and R.sub.3 ; R.sub.4 and R.sub.