Pre-clinical evaluation of a novel class of anti-cancer agents, the Pyrrolo-1, 5-benzoxazepines

Abstract

Microtubules are currently ranked one of the most validated targets for chemotherapy; with clinical use of microtubule targeting agents (MTAs) extending beyond half a century. Recent research has focused on the development of novel MTAs to combat drug resistance and drug associated toxicities. Of particular interest are compounds structurally different to those currently used within the clinic. The pyrrolo-1, 5-benzoxazepines (PBOXs) are a structurally distinct novel group of anti-cancer agents, some of which target tubulin. Herein, we review the chemistry, mechanism of action, preclinical development of the PBOXs and comparisons with clinically relevant chemotherapeutics. The PBOXs induce a range of cellular responses including; cell cycle arrest, apoptosis, autophagy, anti-vascular and anti-angiogenic effects. The apoptotic potential of the PBOXs extends across a wide spectrum of cancer-derived cell lines, by targeting tubulin and multiple molecular pathways frequently deregulated in human cancers. Extensive experimental data suggest that combining the PBOXs with established chemotherapeutics or radiation is therapeutically advantageous. Pre-clinical highlights of the PBOXs include; cancer specificity and improved therapeutic efficacy as compared to some current first line therapeutics.

Keywords: 5-benzoxazepines; Pyrrolo-1; apoptosis; drug resistance and G2/M arrest.; tubulin.

Figure 1

The core structure of PBOX-based compounds and the explored modifications for structure-activity relationship studies.

Figure 2

Chemical structure of representative PBOXs.

Figure 3

Synthesis of the representative PBOXs.

Figure 4

Areas of interaction of the biological target explored by the development of specific PBOX-based analogues.