PHA-848125

PHA-848125 is a potent and ATP-competitive Cdk2/cyclin A inhibitor with an IC50 value of 45 nM. PHA-848125 also inhibited Cdk7/cyclin H, Cdk4/cyclin D1, Cdk5/p35, Cdk2/cyclin E and Cdk1/cyclin B with less potency (IC50= 0.15 µM, 0.16 µM, 0.265 µM, 0.363 µM and 0.398 µM, respectively). [1]

CDK (cyclin-dependent kinase) is a group of serine/threonine kinases. It is activated by binding to cyclin and participates in the regulation of cell cycle.

In cells treated with PHA-848125, hyperphosphorylated form of CDK substrate—retinoblastoma protein (pRb) was reduced and hypophosporylated from of pRb was accumulated. It further indicated inhibition effect of PHA-848125 on CDK2 activity. [1]

In human ovarian A2780 xenogaft mouse model, 20, 30 and 40mg/kg of PHA-848125 were each administrated orally twice a day for 10 days. PHA-848125 inhibited A2780 tumor growth up to 91% at 40 mg/kg dose. [1]

Reference:
1. Brasca MG, Amboldi N, Ballinari D et al.  Identification of N,1,4,4-tetramethyl-8-{[4-(4-methylpiperazin-1-yl)phenyl]amino}-4,5-dihydro-1H-pyrazolo[4,3-h]quinazoline-3-carboxamide (PHA-848125), a potent, orally available cyclin dependent kinase inhibitor. J Med Chem. 2009 Aug 27;52(16):5152-63.

Efficacy of PHA-848125, a cyclin-dependent kinase inhibitor, on the K-Ras(G12D)LA2 lung adenocarcinoma transgenic mouse model: evaluation by multimodality imaging.[Pubmed:20197397]

Mol Cancer Ther. 2010 Mar;9(3):673-81.

K-ras is the most frequently mutated oncogene in non-small cell lung cancer (NSCLC), the most common form of lung cancer. Recent studies indicate that NSCLC patients with mutant K-ras do not respond to epidermal growth factor receptor inhibitors. In the attempt to find alternative therapeutic regimes for such patients, we tested PHA-848125, an oral pan cyclin-dependent kinase inhibitor currently under evaluation in phase II clinical trial, on a transgenic mouse model, K-Ras(G12D)LA2, which develops pulmonary cancerous lesions reminiscent of human lung adenocarcinomas. We used magnetic resonance imaging and positron emission tomography to follow longitudinally disease progression and evaluate therapeutic efficacy in this model. Treatment of K-Ras(G12D)LA2 mice with 40 mg/kg twice daily for 10 days with PHA-848125 induced a significant tumor growth inhibition at the end of treatment (P < 0.005) and this was accompanied by a reduction in the cell membrane turnover, as seen by 11C-Choline-positron emission tomography (P < 0.05). Magnetic resonance imaging data were validated versus histology and the mechanism of action of the compound was verified by immunohistochemistry, using cyclin-dependent kinase-related biomarkers phospho-Retinoblastoma and cyclin A. In this study, multimodality imaging was successfully used for the preclinical assessment of PHA-848125 therapeutic efficacy on a lung adenocarcinoma mouse model. This compound induced a volumetric and metabolic anticancer effect and could represent a valid therapeutic approach for NSCLC patients with mutant K-ras.

Anti-tumour efficacy on glioma models of PHA-848125, a multi-kinase inhibitor able to cross the blood-brain barrier.[Pubmed:23347136]

Br J Pharmacol. 2013 May;169(1):156-66.

BACKGROUND AND PURPOSE: Malignant gliomas, the most common primary brain tumours, are highly invasive and neurologically destructive neoplasms with a very bad prognosis due to the difficulty in removing the mass completely by surgery and the limited activity of current therapeutic agents. PHA-848125 is a multi-kinase inhibitor with broad anti-tumour activity in pre-clinical studies and good tolerability in phase 1 studies, which could affect two main pathways involved in glioma pathogenesis, the G1-S phase progression control pathway through the inhibition of cyclin-dependent kinases and the signalling pathways mediated by tyrosine kinase growth factor receptors, such as tropomyosin receptors. For this reason, we tested PHA-848125 in glioma models. EXPERIMENTAL APPROACH: PHA-848125 was tested on a panel of glioma cell lines in vitro to evaluate inhibition of proliferation and mechanism of action. In vivo efficacy was evaluated on two glioma models both as single agent and in combination with standard therapy. KEY RESULTS: When tested on a subset of representative glioma cell lines, PHA-848125 blocked cell proliferation, DNA synthesis and inhibited both cell cycle and signal transduction markers. Relevantly, PHA-848125 was also able to induce cell death through autophagy in all cell lines. Good anti-tumour efficacy was observed by oral route in different glioma models both with s.c. and intracranial implantation. Indeed, we demonstrate that the drug is able to cross the blood-brain barrier. Moreover, the combination of PHA-848125 with temozolomide resulted in a synergistic effect, and a clear therapeutic gain was also observed with a triple treatment adding PHA-848125 to radiotherapy and temozolomide. CONCLUSIONS AND IMPLICATIONS: All the pre-clinical data obtained so far suggest that PHA-848125 may become a useful agent in chemotherapy regimens for glioma patients and support its evaluation in phase 2 trials for this indication.

Dual targeting of CDK and tropomyosin receptor kinase families by the oral inhibitor PHA-848125, an agent with broad-spectrum antitumor efficacy.[Pubmed:20682657]

Mol Cancer Ther. 2010 Aug;9(8):2243-54.

Altered expression and activity of cyclin-dependent kinase (CDK) and tropomyosin receptor kinase (TRK) families are observed in a wide variety of tumors. In those malignancies with aberrant CDK activation, the retinoblastoma protein (pRb) pathway is deregulated, leading to uncontrolled cell proliferation. Constitutive activation of TRKs is instead linked to cancer cell survival and dissemination. Here, we show that the novel small-molecule PHA-848125, a potent dual inhibitor of CDKs and TRKs, possesses significant antitumor activity. The compound inhibits cell proliferation of a wide panel of tumoral cell lines with submicromolar IC(50). PHA-848125-treated cells show cell cycle arrest in G(1) and reduced DNA synthesis, accompanied by inhibition of pRb phosphorylation and modulation of other CDK-dependent markers. The compound additionally inhibits phosphorylation of TRKA and its substrates in cells, which functionally express this receptor. Following oral administration, PHA-848125 has significant antitumor activity in various human xenografts and carcinogen-induced tumors as well as in disseminated primary leukemia models, with plasma concentrations in rodents in the same range as those found active in inhibiting cancer cell proliferation. Mechanism of action was also confirmed in vivo as assessed in tumor biopsies from treated mice. These results show that the dual CDK-TRK inhibitor PHA-848125 has the potential for being a novel and efficacious targeted drug for cancer treatment.

Down-regulation of the PTTG1 proto-oncogene contributes to the melanoma suppressive effects of the cyclin-dependent kinase inhibitor PHA-848125.[Pubmed:22704958]

Biochem Pharmacol. 2012 Sep 1;84(5):598-611.

We previously demonstrated that PHA-848125, a cyclin-dependent kinase inhibitor presently under Phase II clinical investigation, impairs melanoma cell growth. In this study, gene expression profiling showed that PHA-848125 significantly modulated the expression of 128 genes, predominantly involved in cell cycle control, in the highly drug-sensitive GL-Mel (p53 wild-type) melanoma cells. Up-regulation of 4 selected genes (PDCD4, SESN2, DDIT4, DEPDC6), and down-regulation of 6 selected genes (PTTG1, CDC25A, AURKA, AURKB, PLK1, BIRC5) was confirmed at protein levels. The same protein analysis performed in PHA-848125-treated M10 melanoma cells - p53 mutated and less sensitive to the drug than GL-Mel cells - revealed no DEPDC6 expression and no changes of PTTG1, PDCD4 and BIRC5 levels. Upon PHA-848125 treatment, a marked PTTG1 down-modulation was also observed in A375 cells (p53 wild-type) but not in CN-Mel cells (p53 mutated). PTTG1 silencing significantly inhibited melanoma cell proliferation and induced senescence, with effects less pronounced in p53 mutated cells. PTTG1 silencing increased PHA-848125 sensitivity of p53 mutated cells but not that of A375 or GL-Mel cells. Accordingly, in M10 but not in A375 cells a higher level of senescence was detected in PHA-848125-treated/PTTG1-silenced cells with respect to PHA-848125-treated controls. In A375 and GL-Mel cells, TP53 silencing attenuated PHA-848125-induced down-modulation of PTTG1 and decreased cell sensitivity to the drug. These findings indicate that PHA-848125-induced down-regulation of PTTG1 depends, at least in part, on p53 function and contributes to the antiproliferative activity of the drug. Our study provides further molecular insight into the antitumor mechanism of PHA-848125.

Milciclib (PHA-848125) is a potent, dual inhibitor of CDK and Tropomyosin receptor kinase (TRK), with IC50s of 45, 150, 160, 363, 398 nM and 53 nM for cyclin A/CDK2, cyclin H/CDK7, cyclin D1/CDK4, cyclin E/CDK2, cyclin B/CDK1 and TRKA, respectively.

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