Discovery of potent and selective spiroindolinone MDM2 inhibitor, RO8994, for cancer therapy.

The field of small-molecule inhibitors of protein-protein interactions is rapidly advancing and the specific area of inhibitors of the p53/MDM2 interaction is a prime example. Several groups have published on this topic and multiple compounds are in various stages of clinical development. Building on the strength of the discovery of RG7112, a Nutlin imidazoline-based compound, and RG7388, a pyrrolidine-based compound, we have developed additional scaffolds that provide opportunities for future development. Here, we report the discovery and optimization of a highly potent and selective series of spiroindolinone small-molecule MDM2 inhibitors, culminating in RO8994.

Discovery of Potent and Orally Active p53-MDM2 Inhibitors RO5353 and RO2468 for Potential Clinical Development.

The development of small-molecule MDM2 inhibitors to restore dysfunctional p53 activities represents a novel approach for cancer treatment. In a previous communication, the efforts leading to the identification of a non-imidazoline MDM2 inhibitor, RG7388, was disclosed and revealed the desirable in vitro and in vivo pharmacological properties that this class of pyrrolidine-based inhibitors possesses. Given this richness and the critical need for a wide variety of chemical structures to ensure success in the clinic, research was expanded to evaluate additional derivatives. Here we report two new potent, selective, and orally active p53-MDM2 antagonists, RO5353 and RO2468, as follow-ups with promising potential for clinical development.

Discovery of RG7388, a potent and selective p53-MDM2 inhibitor in clinical development.

Restoration of p53 activity by inhibition of the p53-MDM2 interaction has been considered an attractive approach for cancer treatment. However, the hydrophobic protein-protein interaction surface represents a significant challenge for the development of small-molecule inhibitors with desirable pharmacological profiles. RG7112 was the first small-molecule p53-MDM2 inhibitor in clinical development. Here, we report the discovery and characterization of a second generation clinical MDM2 inhibitor, RG7388, with superior potency and selectivity.

Identification of novel, potent and selective inhibitors of Polo-like kinase 1.

A series of pyrimidodiazepines was identified as potent Polo-like kinase 1 (PLK1) inhibitors. The synthesis and SAR are discussed. The lead compound 7 (RO3280) has potent inhibitory activity against PLK1, good selectivity against other kinases, and excellent in vitro cellular potency. It showed strong antitumor activity in xenograft mouse models.

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.

Preparation of human Melanocortin-4 receptor agonist libraries: linear peptides X-Y-DPhe7-Arg8-Trp(or 2-Nal)9-Z-NH2.

Two libraries of hMC4R agonists, X-Y-DPhe(7)-Arg(8)-2-Nal(9)-Z-NH(2) and X-Y-DPhe(7)-Arg(8)-Trp(9)-Z-NH(2), totaling 185 peptides were prepared using Irori radiofrequency tagging technology and Argonaut Quest 210 Synthesizer, where X stands for N-caps, Y for His(6) surrogates and Z for Gly(10) surrogates. As a result of this study, His-modified pentapeptides with Trp were found to be more hMC4R potent than the corresponding 2-Nal analogs, novel N-caps and Gly surrogates were identified and 19 new peptides which are potent hMC4R agonists (EC(50) 1-15nM) and selective against hMC1R were discovered.

Discovery of 1-amino-4-phenylcyclohexane-1-carboxylic acid and its influence on agonist selectivity between human melanocortin-4 and -1 receptors in linear pentapeptides.

Linear pentapeptides (Penta-cis-Apc-DPhe-Arg-Trp-Gly-NH2) containing 1-amino-4-phenylcyclohexane-1-carboxylic acid (cis-Apc) and substituted Apc are potent hMC4R agonists and they are inactive or weakly active in hMC1R, hMC3R, and hMC5R agonist assays. This study, together with our earlier report on 5-BrAtc, demonstrated the importance of replacing His6 with phenyl-containing rigid templates in achieving good hMC4R agonist potency and selectivity against hMC1R in linear pentapeptides.