Sterling Drug Inc.

James B Rake

Mark P Wentland

George Y Lesher, Deceased

Susan Coughlin

A method of inhibiting mammalian topoisomerase II and inhibiting the growth and inducing the regression of malignant cells in mammals by the action of a (S)-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine or -benzothiazine of the formula ##STR1## wherein R.sub.1 is hydrogen or fluoro, R.sub.2 and R.sub.3 each independently is hydrogen or alkyl having 1 to 4 carbon atoms, and X is O, S or S=O; a pharmaceutically acceptable acid-addition salt thereof; or a salt thereof with a pharmaceutically acceptable cation; and certain novel compounds of formula I.

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Halfmoon, NY, United States of America

James B Rake