Synthesis and antitumor evaluation of 2,5-disubstituted-indazolo[4,3-gh]isoquinolin-6(2H)-ones (9-aza-anthrapyrazoles)

The synthesis and antitumor evaluation of 2,5-disubstituted-indazolo[4,3-gh ]isoquinolin-6-(2H)-ones (9-aza-APs) are described. The key intermediates i n the synthesis are benz[g]isoquinoline-5,10-diones which are substituted a t positions 6 and 9 with groups of different nucleofugacity for SNAr displa cements. The initial displacement of fluoride by a substituted hydrazine le ads to the pyrazole analogues. Substitution of the remaining leaving group by an amine or BOC-protected amines leads to the 9-aza-APs 12. These analog ues were converted into their maleate or hydrochloride salts 13. In two cas es, namely, 13x and 13z, sidearm buildup was also employed in the synthetic pathway. In vitro evaluation of 9-aza-APs against the human colon tumor ce ll line LoVo uncovered for most of the compounds a cytotoxic potency lower than that of DuP-941 or mitoxantrone and comparable to that of doxorubicin. Only analogues 13c, 13n, and 13ff were as cytotoxic as DuP-941. Interestin gly, while DuP-941 was highly cross-resistant in the LoVo cell line resista nt to doxorubicin (LoVo/Dx), the 9-aza-APs carrying a distal lipophilic ter tiary amine moiety in both chains were capable of overcoming the MDR resist ance induced in this cell line. The 9-aza-APs show outstanding in vivo anti tumor activity against both systemic P388 murine leukemia and MX-1 human ma mmary carcinoma transplanted in nude mice. At their optimal dosages, congen ers 13a-c, 13f, 13n, 13q, 13x, and 13dd were highly effective against P388 leukemia with T/C% of 200-381, while the T/C% value of DuP-941 was 147. In the MX-1 tumor model, 24 compounds elicited percentages of tumor weight inh ibitions (TWI) ranging from 50% to 99%. Congeners 13d, 13k, 13l, 13x, 132, and 13ee emerged as the most effective ones, with TWI% 96, simliar to that of DuP-941 (TWI% = 95). On the basis of their efficacy profile in additiona l experimental tumors and lack of cardiotoxicity in preclinical models, two congeners have surfaced as potential clinical candidates.