Part I. Design, synthesis and biological evaluation of novel 2,5,6-trisubstituted benzimidazoles targeting FtsZ as antitubercular agents. Part II. Development of novel taxoid-based drug conjugates and theranostic imaging agents towards tumor-targeted chemotherapy.

摘要

Part I. Design, synthesis and biological evaluation of novel 2,5,6-trisubstituted benzimidazoles targeting FtsZ as antitubercular agents: Filamenting temperature-sensitive protein Z (FtsZ), an essential cell division protein, is a promising target for the drug discovery of new-generation antibacterial agents against various bacterial pathogens. As a part of SAR studies on benzimidazoles, we have synthesized a library of 376 novel 2,5,6-trisubstituted benzimidazoles, bearing ether or thioether linkage at the 6-position. In a preliminary HTP screening against Mtb H37Rv, 108 compounds were identified as hits at a cut off values of 5 microg/mL. Among those hits, 10 compounds exhibited MIC values in the range of 0.63-12.5 microg/mL. Light scattering assay and TEM analysis with the most potent compound clearly indicate that its molecular target is Mtb FtsZ. In addition, we have identified number of hits against M. Smeg. Further optimization of the lead compound is currently on going in our lab based on rational drug design.;Part II. Development of novel taxoid-based drug conjugates and theranostic imaging agents towards tumor-targeted chemotherapy: The second part of my dissertation pertains to development of new generation of taxoids and taxoid-based imaging probes for tumor-targeted drug delivery. The folate-linker-taxoid (FLT) conjugate which contains spacers to promote aqueous solubility and promote tumor-specific uptake and a mechanism-based self-immolative disulfide linker for site-specific prodrug activation was designed and synthesized. The conjugate was evaluated in vitro against a series of FR-positive cancer cell lines, L1210FR, MX-1, and ID8 and FR-negative cell line, WI-38. Folate conjugate demonstrated almost equally high potency against FR-positive cell lines as the parent taxoid, indicating rapid internalization and efficient drug release. However, against FR- normal lung fibroblast cell line WI-38, the folate conjugate was virtually non-toxic (IC50 > 5 microM).;In addition, we have identified a novel class of 3'-vinyliodo taxoids to develop a better understanding of their biodistribution and PK profiles since radioactive isotopes of 123I and 124I can be used for PET and SPECT studies. 3'-Vinyliodo taxoid has been evaluated in vitro against various cancer cell lines, ID8, NCI/ADR-RES, HCT-116, MX-1 and MCF-7 with high potency. We also have developed conditions for their synthesis via site-specific iodination amenable to radiolabeling.;Furthermore, we have been exploring synergistic combinations between new-generation taxoids and other drugs, i.e. CMC2.24, EGCG, MMP inhibitors, against various cell lines including cancer stem cells (CSCs). Preliminary screening showed very promising results.