Structure-activity relationships of new chemical entities based on the anti-tumor and anti-angiogenic agent 2-methoxyestradiol

4085 2-Methoxyestradiol (2ME2) is an endogenous metabolite of estradiol that exhibits potent anti-proliferative activity against a wide range of tumor and non-tumor cell types in vitro , as well as significant anti-angiogenic and anti-tumor activities in vivo with minimal toxicity at pharmacologically active doses. The anti-proliferative activity of 2ME2 is independent of estrogen receptors, and while all mechanistic actions are not fully defined, 2ME2 has been shown to disrupt microtubule polymerization and to inhibit HIF activity. 2ME2 is currently in clinical trials for oncology under the name Panzem®. Pre-clinical studies in murine models and clinical studies in humans demonstrated that, as reported for estradiol, 2ME2 undergoes significant oxidation at the 17-position to form 2-methoxyestrone (2ME1) as well as extensive conjugation at the 3- and 17-positions. To get a better understanding of the structure-activity relationships and metabolism of 2ME2, we have designed and synthesized several series of new chemical entities (NCEs) modified at position 3 on the A-ring, at position 17 on the D-ring or at both positions simultaneously. Hundreds of NCEs have been generated with a range of activities. These NCEs are screened for anti-proliferative activity in vitro using tumor and endothelial cell types. In vitro estrogenicity is tested by the ability of these NCEs to support the proliferation of an estrogen-dependent cell line. Several NCEs with single or combined substitutions at positions 3 and/or 17 show similar or improved anti-proliferative activities and further reduced estrogenicity as compared to 2ME2. Additionally, many of these molecules demonstrate improved pharmacokinetic (PK) parameters in rodents. Several of the NCEs showing acceptable responses in the in vitro screening assays and having a good PK profile after oral administration are being tested for efficacy in animal tumor models. Their mechanism of action is also being investigated.