belotecan belotecan belotecan is a drug used in chemotherapy. it is a semi-synthetic camptothecin analogue indicated for small-cell lung cancer and ovarian cancer, approved in south korea under the trade name camtobell, presented in 2 mg vials for injection. the drug has been marketed by chongkundang pharmaceuticals since 2003. belotecanclinical dataatc codel01ce04 (who) identifiers iupac name (4s)-4-ethyl-4-hydroxy-11--1h-pyranoindolizinoquinoline-3,14(4h,12h)-dione cas number256411-32-2pubchem cid6456014drugbankdb12459 ychemspider4958253 yunii27z82m2g1nkeggd03225chemblchembl2107315comptox dashboard (epa)dtxsid60180332 chemical and physical dataformulac25h27n3o4molar mass433.508 g·mol−13d model (jsmol)interactive image smiles o=c\1n4\c(=c/c2=c/1coc(=o)2(o)cc)c3nc5c(c(c3c4)ccnc(c)c)cccc5 inchi inchi=1s/c25h27n3o4/c1-4-25(31)19-11-21-22-17(12-28(21)23(29)18(19)13-32-24(25)30)15(9-10-26-14(2)3)16-7-5-6-8-20(16)27-22/h5-8,11,14,26,31h,4,9-10,12-13h2,1-3h3/t25-/m0/s1 ykey:lnhwxbunxoxmrl-vwlotqadsa-n y (verify) mechanism of action belotecan blocks topoisomerase i with a pic50 of 6.56, stabilizing the cleavable complex of topoisomerase i-dna, which inhibits the religation of single-stranded dna breaks generated by topoisomerase i; lethal double-stranded dna breaks occur when the topoisomerase i-dna complex is encountered by the dna replication machinery, dna replication is disrupted, and the tumor cell undergoes apoptosis. topoisomerase i is an enzyme that mediates reversible single-strand breaks in dna during dna replication.