Antitumor Agents 253. Design, Synthesis, and Antitumor Evaluation of Novel 9-Substituted Phenanthrene-Based Tylophorine Derivatives as Potential Anticancer Agents

C9-Substituted phenanthrene-based tylophorine derivatives (PBTs) (13 − 36) were synthesized and evaluated as in vitro anticancer agents against the human A549 lung cancer cell line. Twelve active compounds were further examined against DU-145 (prostate), ZR-751 (breast), KB (nasopharyngeal), and KB-Vin (multidrug resistant KB subline) human cancer cell lines. They showed potent cytotoxic activity against both wild type and matched multidrug resistant KB cell lines, and displayed notable selectivity toward DU-145 (prostate) and ZR-751 (breast) cancer cell lines. The mode of action of this class may be distinctly different from that of other cancer chemotherapeutic compounds. Three PBT analogs were also evaluated in a murine model. Compound 24b showed modest in vivo antitumor activity against human A549 xenograft in nude mice as well as potent in vitro cytotoxic activity, and thus, is a promising anticancer lead compound.