Abstract The remarkable cytostatic activity of 1-substituted indazolols 2a, b, condensed indazolinones 4a–c and indoxyl derivatives 5a, b against HeLa cells is reported. Three different approaches to the synthesis of indazolophthalazinone 4a, representing alternatives to those previously reported, were studied. Several compounds related to the mentioned indazolols and indazolinones were obtained and their cytostatic activity against HeLa ...