Biomedical subjects

Bradford Graves

Publications and source records attributed to Bradford Graves.

4 recordsLinked to original sources

PubMed2006

Discovery of [4-Amino-2-(1-methanesulfonylpiperidin-4-ylamino)pyrimidin-5-yl](2,3-difluoro-6- methoxyphenyl)methanone (R547), a potent and selective cyclin-dependent kinase inhibitor with significant in vivo antitumor activity.

The cyclin-dependent kinases (CDKs) and their cyclin partners are key regulators of the cell cycle. Since deregulation of CDKs is found with high frequency in many human cancer cells, pharmacological inhibition of CDKs with small molecules has the potential to provide an effective strategy for the treatment of cancer. The 2,4-diamino-5-ketopyrimidines 6 reported here represent a novel class of potent and ATP-competitive inhibitors that selectively target the cyclin-dependent kinase family. This diaminopyrimidine core with a substituted 4-piperidine moiety on the C2-amino position and 2-methoxybenzoyl at the C5 position has been identified as the critical structure responsible for the CDK inhibitory activity. Further optimization has led to a good number of analogues that show potent inhibitory activities against CDK1, CDK2, and CDK4 but are inactive against a large panel of serine/threonine and tyrosine kinases (K(i) > 10 microM). As one of these representative analogues, compound 39 (R547) has the best CDK inhibitory activities (K(i) = 0.001, 0.003, and 0.001 microM for CDK1, CDK2, and CDK4, respectively) and excellent in vitro cellular potency, inhibiting the growth of various human tumor cell lines including an HCT116 cell line (IC(50) = 0.08 microM). An X-ray crystal structure of 39 bound to CDK2 has been determined in this study, revealing a binding mode that is consistent with our SAR. Compound 39 demonstrates significant in vivo efficacy in the HCT116 human colorectal tumor xenograft model in nude mice with up to 95% tumor growth inhibition. On the basis of its superior overall profile, 39 was chosen for further evaluation and has progressed into Phase I clinical trial for the treatment of cancer.

Animals↗

PubMed2005

Development of E3-substrate (MDM2-p53)-binding inhibitors: structural aspects.

Inhibition of E3 ligase-substrate binding is the most direct approach for blocking protein ubiquitylation and degradation. However, protein-protein interactions have proven to be difficult targets for discovery of small molecules that bind at the interface and modulate protein activity in a selective manner. Recently, we developed the first potent and selective small-molecule inhibitors of the binding between MDM2 E3 ligase and its substrate p53 (Vassilev et al., 2004). This process was aided significantly by the acquisition and use of structural information. We describe herein how such information was obtained and used at various stages in the program. These applications included assessment of MDM2 as a target, evaluation of hits from high-throughput screening and the selection of lead molecules, and analysis of binding strategies used by the inhibitors as a basis for guiding studies of similar systems. These tools are likely to be useful in any attempt to find and develop druglike compounds that modulate the function of a protein-protein interaction.

Crystallography, X-Ray↗

PubMed2005

Small molecule inhibitors of p53/MDM2 interaction.

The discovery of the key negative regulator MDM2 (mouse double minute 2, also termed HDM2 for its human equivalent) provided a great opportunity to manipulate the levels of the tumor suppressor p53 in cancer cells. Activation of p53 in tumor cells by inhibiting the interaction of MDM2 with p53 has therefore been the focus of a large effort in drug discovery. The modulation of protein-protein interactions, however, has historically been very difficult to achieve owing to the large surface area of interaction. In this article, we review the recent accomplishments in this area and our quest for a clinically viable MDM2 inhibitor.

Animals↗

PubMed2004

In vivo activation of the p53 pathway by small-molecule antagonists of MDM2.

MDM2 binds the p53 tumor suppressor protein with high affinity and negatively modulates its transcriptional activity and stability. Overexpression of MDM2, found in many human tumors, effectively impairs p53 function. Inhibition of MDM2-p53 interaction can stabilize p53 and may offer a novel strategy for cancer therapy. Here, we identify potent and selective small-molecule antagonists of MDM2 and confirm their mode of action through the crystal structures of complexes. These compounds bind MDM2 in the p53-binding pocket and activate the p53 pathway in cancer cells, leading to cell cycle arrest, apoptosis, and growth inhibition of human tumor xenografts in nude mice.

Animals↗