Synthesis of N4-(substituted phenyl)-N4-alkyl/desalkyl-9H-pyrimido[4,5-b]indole-2,4-diamines and identification of new microtubule disrupting compounds that are effective against multidrug resistant cells

Abstract

A series of fourteen N4-(substituted phenyl)-N4-methyl/desmethyl-9H-pyrimido[4,5-b]indole-2,4-diamines was synthesized as potential microtubule targeting agents. The synthesis involved a Fisher indole cyclization of 2-amino-6-hydrazinylpyrimidin-4(3H)-one with cyclohexanone, followed by oxidation, chlorination and displacement with appropriate anilines. Compounds 6, 14 and 15 had low nanomolar potency against MDA-MB-435 tumor cells and depolymerized microtubules. Compound 6 additionally had nanomolar GI50 values against 57 of the NCI 60-tumor panel cell lines. Mechanistic studies showed that 6 inhibited tubulin polymerization and [3H]colchicine binding to tubulin. The most potent compounds were all effective in cells expressing P-glycoprotein or the βIII isotype of tubulin, which have been associated with clinical drug reisistence. Modeling studies provided the potential interactions of 6, 14 and 15 within the colchicine site.

Discovery and preclinical evaluation of 7-benzyl-N-(substituted)-pyrrolo[3,2-d]pyrimidin-4-amines as single agents with microtubule targeting effects along with triple-acting angiokinase inhibition as antitumor agents

“…However, compound 8 with added conformational restriction via a N5-methyl over 5 was highly potent and only 2-fold less potent than the most potent analog 7 . As with previously described pyrimidine fused bicyclic and tricyclic compounds, 15, 34, 48–50 the methyl group attached to the 4-nitrogen bridge is crucial for inhibition of tubulin assembly. Removal of this N -methyl group ( 6 compared with 7 ) resulted in significant loss of tubulin inhibitory activity.…”

Design, synthesis, and structure–activity relationships of pyrimido[4,5- b ]indole-4-amines as microtubule depolymerizing agents that are effective against multidrug resistant cells

“…26, 27 Development of MTAs that circumvent Pgp and/or βIII-tubulin-mediated resistance 28 could have advantages in patients who fail to respond to current MTAs. Most of the colchicine site agents circumvent Pgp and βIII-tubulin mediated resistance 28, 29 and could be beneficial. However, thus far, no colchicine site agent has been approved as an anticancer agent.…”

“…Gangjee et al 29 reported pyrimido[4,5- b ]indole 1 (Figure 2) as a potent microtubule depolymerizer (EC 50 of 133 nM) with potent in vitro cytotoxic activity in MDA-MB-435 cells (IC 50 of 14.7 nM). Compound 1 is a colchicine site agent and it also circumvents clinically relevant Pgp and βIII-tubulin mediated resistance.…”

“…Displacement of the 4-Cl group of 20 29 (Scheme 3) with 6-methoxy-1,2,3,4-tetrahydroquinoline 21 and concomitant deprotection of the pivaloyl group from the 2-NH 2 group afforded target compound 6 in 26% yield. Treatment of 19 (Scheme 2) with 21 , followed by base-mediated deprotection of the 2-NH 2 group, provided target compound 7 in 52% yield.…”

“…Treatment of 19 (Scheme 2) with 21 , followed by base-mediated deprotection of the 2-NH 2 group, provided target compound 7 in 52% yield. Compound 8 was obtained by treating 20 29 with 4-thiomethyl- N -methylaniline 22 34 in BuOH at reflux.…”