R547

R547 is a novel, selective inhibitor of cell cycle and transcriptional cyclin dependent kinases with a Ki of median 2 nM for CDK1/cyclin B, CDK2/cyclin E, and CDK4/cyclin D1((Ki=0.001,0.003,and 0.001 μM for CDK1,CDK2, and CDK4,respectively).[1]
Cyclin-dependent kinases (CDKs) are a family of protein kinases regulating the cell cycle, transcription, mRNA processing, and the differentiation of nerve cells which considered a potential anticancer target. CDK inhibitors such as Seliciclib are undergoing clinical trials. Although it was originally developed as a potential anti-cancer drug, in recent laboratory tests Seliciclib has also proven to induce apoptosis in neutrophil granulocytes, which mediate inflammation.[2].
R547 inhibited the proliferation of tumor cell lines and is active in all 19 cell lines tested irrespective of tissue of origin, multidrug resistance (MDR), p53, or retinoblastoma status. R547 possessing both 5-and 6-fluoro substitution culminated in an Inhibitor with low, single-digit nanomolar potency against the CDKs and excellent cellular potency (IC50=0.08 μM,HCT116 cell line). R547 administered orally at dose of 40 mg/kg daily in colon, lung, breast, prostate, and melanoma human tumor xenograft models shows significant TGI (79-99%). R547 is equally efficacious (TGI, 61-95%) when dosed with 40 mg/kg i.v. once weekly. These doses of R547 are not toxic and did not result in body weight loss. R547 does not show signs of overt toxicity during the course of the 3-week study and any gross pathology at necropsies done at the end of the studies. [3]R547 inhibits tumor growth up to 95% in the HCT116 human colorectal tumor xenograft model in nude mice . R547 causes significant TGI in all of the models tested when dosed orally and i.v. at or below the maximum tolerated dose. R547 inhibits phosphorylation of retinoblastoma protein in tumors at the efficacious exposures in tumor xenograft models, providing a pharmacodynamic biomarker for clinical use. R547 reported here suggests that this is a promising molecule for evaluation in the treatment of solid tumors. [4]
References:
1. Davis MI1, Hunt JP, Herrgard S, Ciceri P, Wodicka LM, Pallares G, Hocker M, Treiber DK, Zarrinkar PP. “Comprehensive analysis of kinase inhibitor selectivity.” Nat Biotechnol. 2011, 29(11):1046-51.
2. Rossi, Adriano G. “Cyclin-dependent kinase inhibitors enhance the resolution of inflammation by promoting inflammatory cell apoptosis.” 2006. Nature Medicine 12 .
3. Rodriguez A , et al. Mol Cancer Ther, 2006, 5(11), 2644-2658.
4. Chu XJ, et al. J Med Chem, 2006, 49(22), 6549-6560.

In vitro and in vivo activity of R547: a potent and selective cyclin-dependent kinase inhibitor currently in phase I clinical trials.[Pubmed:17121911]

Mol Cancer Ther. 2006 Nov;5(11):2644-58.

The cyclin-dependent protein kinases are key regulators of cell cycle progression. Aberrant expression or altered activity of distinct cyclin-dependent kinase (CDK) complexes results in escape of cells from cell cycle control, leading to unrestricted cell proliferation. CDK inhibitors have the potential to induce cell cycle arrest and apoptosis in cancer cells, and identifying small-molecule CDK inhibitors has been a major focus in cancer research. Several CDK inhibitors are entering the clinic, the most recent being selective CDK2 and CDK4 inhibitors. We have identified a diaminopyrimidine compound, R547, which is a potent and selective ATP-competitive CDK inhibitor. In cell-free assays, R547 effectively inhibited CDK1/cyclin B, CDK2/cyclin E, and CDK4/cyclin D1 (K(i) = 1-3 nmol/L) and was inactive (K(i) > 5,000 nmol/L) against a panel of >120 unrelated kinases. In vitro, R547 effectively inhibited the proliferation of tumor cell lines independent of multidrug resistant status, histologic type, retinoblastoma protein, or p53 status, with IC(50)s R547 reduced phosphorylation of the cellular retinoblastoma protein at specific CDK phosphorylation sites at the same concentrations that induced cell cycle arrest, suggesting a potential pharmacodynamic marker for clinical use. In vivo, R547 showed antitumor activity in all of the models tested to date, including six human tumor xenografts and an orthotopic syngeneic rat model. R547 was efficacious with daily oral dosing as well as with once weekly i.v. dosing in established human tumor models and at the targeted efficacious exposures inhibited phosphorylation of the retinoblastoma protein in the tumors. The selective kinase inhibition profile and the preclinical antitumor activity of R547 suggest that it may be promising for development for use in the treatment of solid tumors. R547 is currently being evaluated in phase I clinical trials.

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.[Pubmed:17064073]

J Med Chem. 2006 Nov 2;49(22):6549-60.

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.

R547 is a potent, selective and oral orally bioavailable ATP-competitive CDK inhibitor, with Kis of 2 nM, 3 nM and 1 nM for CDK1/cyclin B, CDK2/cyclin E and CDK4/cyclin D1, respectively.

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