Pharmacokinetics and biodistribution of the cyclin-dependent kinase inhibitor -CR8- in mice

Preclinical Toxicity and Safety of MM-129-First-in-Class BTK/PD-L1 Inhibitor as a Potential Candidate against Colon Cancer

MM-129 is a novel inhibitor targeting BTK/PI3K/AKT/mTOR and PD-L1, as it possesses antitumor activity against colon cancer. To evaluate the safety profile of MM-129, we conducted a toxicity study using the zebrafish and rodent model. MM-129 was also assessed for pharmacokinetics features through an in vivo study on Wistar rats. The results revealed that MM-129 exhibited favorable pharmacokinetics with quick absorption and 68.6% of bioavailability after intraperitoneal administration. No serious adverse events were reported for the use of MM-129, confirming a favorable safety profile for this compound. It was not fatal and toxic to mice at an anticancer effective dose of 10 μmol/kg. At the end of 14 days of administering hematological and biochemical parameters, liver and renal functions were all at normal levels. No sublethal effects were either detected in zebrafish embryos treated with a concentration of 10 μM. MM-129 has the potential as a safe and well-tolerated anticancer formulation for future treatment of patients with colon cancer.

Systemic Administration of the Cyclin-Dependent Kinase Inhibitor (S)-CR8 Selectively Reduces Escalated Ethanol Intake in Dependent Rats

BACKGROUND

Chronic exposure to ethanol (EtOH) and other drugs of abuse can alter the expression and activity of cyclin-dependent kinase 5 (CDK5) and its cofactor p35, but the functional implication of CDK5 signaling in the regulation of EtOH-related behaviors remains unknown. In the present study, we sought to determine whether CDK5 activity plays a role in the escalation of EtOH self-administration triggered by dependence.

METHODS

We tested the effect of systemically administered (S)-CR8, a nonselective CDK inhibitor, on operant responding for EtOH or saccharin, a highly palatable reinforcer, in adult male Wistar rats. Half of the rats were made EtOH-dependent via chronic intermittent EtOH inhalation (CIE). We then sought to identify a possible neuroanatomical locus for the behavioral effect of (S)-CR8 by quantifying protein levels of CDK5 and p35 in subregions of the extended amygdala and prefrontal cortex from EtOH-naïve, nondependent, and dependent rats at the expected time of EtOH self-administration. We also analyzed the phosphorylation of 4 CDK5 substrates and of the CDK substrate consensus motif.

RESULTS

(S)-CR8 dose-dependently reduced EtOH self-administration in dependent rats. It had no effect on water or saccharin self-administration, nor in nondependent rats. The abundance of CDK5 or p35 was not altered in any of the brain regions analyzed. In the bed nucleus of the stria terminalis, CDK5 abundance was negatively correlated with intoxication levels during EtOH vapor exposure but there was no effect of dependence on the phosphorylation ratio of CDK5 substrates. In contrast, EtOH dependence increased the phosphorylation of low-molecular-weight CDK substrates in the basolateral amygdala (BLA).

CONCLUSIONS

The selective effect of (S)-CR8 on excessive EtOH intake has potential therapeutic value for the treatment of alcohol use disorders. Our data do not support the hypothesis that this effect would be mediated by the inhibition of up-regulated CDK5 activity in the extended amygdala nor prefrontal cortex. However, increased activity of CDKs other than CDK5 in the BLA may contribute to excessive EtOH consumption in alcohol dependence. Other (S)-CR8 targets may also be implicated.

LC-MS/MS method for determination of cyclin-dependent kinase inhibitors, BP-14 and BP-20, and its application in pharmacokinetic study in rat

N²-(4-Amino-cyclohexyl)-9-cyclopentyl-N⁶-(6-furan-2-yl-pyridine-3-ylmethyl)-9H-purine-2,6-diamine (BP-14) and 2-(5-{[2-(4-amino-cyclohexylamino)-9-cyclopentyl-9H-purine-6-ylamino]-methyl}-pyridine-2-yl)-phenol (BP-20) are novel cyclin-dependent kinase inhibitors, structurally related to roscovitine, with significant biological activity. A simple, selective and sensitive liquid chromatography - tandem mass spectrometry method for determining them in rat plasma, using roscovitine as an internal standard, was developed and validated. Chromatographic separation was performed in reversed phase mode on Acquity BEH C18 column (100 × 2.1 mm, 1.7 μm) by gradient elution with mobile phases composed of 15 mM ammonium formate pH 4.0 and methanol at flow rate 0.25 mL/min at 40 °C. The analytes were detected based on their characteristic multiple reaction monitoring transitions in positive electrospray ionization mode m/z 473.07 > 157.93 for BP-14, m/z 499.62 > 184.2 for BP-20 and m/z 355.5 > 90.86 for internal standard. In plasma the method provided good linearity within the entire concentration range: 1-10,000 nmol/L (r² = 0.9989) for BP-14 and 10-25,000 nmol/L (r² = 0.9994) for BP-20; the limit of detection was 0.6 nmol/L for BP-14 and 6.1 nmol/L for BP-20. Validation was also performed in bile and urine. The results of validation fit within the acceptance limits following European Medicines Agency guidelines. The method was applied in a pharmacokinetic study of BP-14 and BP-20 in vivo in rats following intravenous and intraduodenal administration including plasma pharmacokinetics, tissue distribution and excretion (renal and biliary). Both compounds showed low bioavailability after intraduodenal administration (0.630 and 1.58% for BP-14 and BP-20, respectively). Distribution into all the analyzed tissues (brain, lungs, liver, kidney, spleen, muscle, adipose tissue) was observed 3 h after single dose administration, the highest and lowest concentrations being reached in the adipose tissue and brain, respectively. The biliary excretion of the parent BP-14 and BP-20 compounds accounted for 4.81% and 10.6% of the doses, respectively, and renal excretion for <0.5% in both cases. The obtained results represent pilot knowledge for further development of a new generation of compounds with strong anticancer activities.

Pharmacokinetics, biodistribution and antitumour effects of Sclerotium rolfsii lectin in mice

Sclerotium rolfsii lectin (SRL) is a lectin isolated from the fungus Sclerotium rolfsii and has exquisite binding specificity towards the oncofetal Thomsen-Friedenreich antigen (TF-Ag; Galβ1-3GalNAcα-O-Ser/Thr) and its derivatives. Previous studies have shown that SRL inhibits the proliferation of human colon, breast and ovarian cancer cells in vitro and suppresses tumour growth in mice when introduced intratumourally. The present study assessed the effect of SRL on tumour growth when introduced intraperitoneally in BALB/c nude mice and investigated the pharmacokinetics and biodistribution of SRL in Swiss albino mice. When 9 doses of SRL (30 mg/kg body weight/mice) was administered to BALB/c nude mice bearing human colon cancer HT-29 xenografts, a substantial reduction in tumour size was observed. A 35.8% reduction in tumour size was noted in the treated animals after 17 days. SRL treatment also inhibited angiogenesis, and the tumours from the treated animals were observed to carry fewer blood vessels and express less angiogenesis marker protein CD31, than that from the control animals. Pharmacokinetics and biodistribution analysis revealed that SRL was detected in the serum after 1 h and its level peaked after 24 h. SRL was not detected in any of the organs apart from the kidney where a trace amount was detected after 24 h of SRL injection. No significant changes were observed in any of the biochemical parameters tested including SGOT, SGPT, LDH, CREAT and BUN in the SRL-treated mice compared to these levels in the controls. This suggests that SRL has good potential to be developed as a therapeutic agent for cancer treatment and warrant further investigations in vivo and subsequent clinical trials.

Reduction of ciliary length through pharmacologic or genetic inhibition of CDK5 attenuates polycystic kidney disease in a model of nephronophthisis

Polycystic kidney diseases (PKDs) comprise a subgroup of ciliopathies characterized by the formation of fluid-filled kidney cysts and progression to end-stage renal disease. A mechanistic understanding of cystogenesis is crucial for the development of viable therapeutic options. Here, we identify CDK5, a kinase active in post mitotic cells, as a new and important mediator of PKD progression. We show that long-lasting attenuation of PKD in the juvenile cystic kidneys (jck) mouse model of nephronophthisis by pharmacological inhibition of CDK5 using either R-roscovitine or S-CR8 is accompanied by sustained shortening of cilia and a more normal epithelial phenotype, suggesting this treatment results in a reprogramming of cellular differentiation. Also, a knock down of Cdk5 in jck cells using small interfering RNA results in significant shortening of ciliary length, similar to what we observed with R-roscovitine. Finally, conditional inactivation of Cdk5 in the jck mice significantly attenuates cystic disease progression and is associated with shortening of ciliary length as well as restoration of cellular differentiation. Our results suggest that CDK5 may regulate ciliary length by affecting tubulin dynamics via its substrate collapsin response mediator protein 2. Taken together, our data support therapeutic approaches aimed at restoration of ciliogenesis and cellular differentiation as a promising strategy for the treatment of renal cystic diseases.

Cyclin-Dependent Kinase Inhibitor AT7519 as a Potential Drug for MYCN-Dependent Neuroblastoma

PURPOSE

MYCN-dependent neuroblastomas have low cure rates with current multimodal treatment regimens and novel therapeutic drugs are therefore urgently needed. In previous preclinical studies, we have shown that targeted inhibition of cyclin-dependent kinase 2 (CDK2) resulted in specific killing of MYCN-amplified neuroblastoma cells. This study describes the in vivo preclinical evaluation of the CDK inhibitor AT7519.

EXPERIMENTAL DESIGN

Preclinical drug testing was performed using a panel of MYCN-amplified and MYCN single copy neuroblastoma cell lines and different MYCN-dependent mouse models of neuroblastoma.

RESULTS

AT7519 killed MYCN-amplified neuroblastoma cell lines more potently than MYCN single copy cell lines with a median LC50 value of 1.7 compared to 8.1 μmol/L (P = 0.0053) and a significantly stronger induction of apoptosis. Preclinical studies in female NMRI homozygous (nu/nu) mice with neuroblastoma patient-derived MYCN-amplified AMC711T xenografts revealed dose-dependent growth inhibition, which correlated with intratumoral AT7519 levels. CDK2 target inhibition by AT7519 was confirmed by significant reductions in levels of phosphorylated retinoblastoma (p-Rb) and nucleophosmin (p-NPM). AT7519 treatment of Th-MYCN transgenic mice resulted in improved survival and clinically significant tumor regression (average tumor size reduction of 86% at day 7 after treatment initiation). The improved efficacy of AT7519 observed in Th-MYCN mice correlated with higher tumor exposure to the drug.

CONCLUSIONS

This study strongly suggests that AT7519 is a promising drug for the treatment of high-risk neuroblastoma patients with MYCN amplification.

The effect of circadian rhythm on pharmacokinetics and metabolism of the Cdk inhibitor, roscovitine, in tumor mice model

Roscovitine is a selective Cdk-inhibitor that is under investigation in phase II clinical trials under several conditions, including chemotherapy. Tumor growth inhibition has been previously shown to be affected by the dosing time of roscovitine in a Glasgow osteosarcoma xenograft mouse model. In the current study, we examined the effect of dose timing on the pharmacokinetics, biodistribution and metabolism of this drug in different organs in B6D2F1 mice. The drug was orally administered at resting (ZT3) or activity time of the mice (ZT19) at a dose of 300 mg/kg. Plasma and organs were removed at serial time points (10, 20 and 30 min; 1, 2, 4, 6, 8, 12 and 24 h) after the administration. Roscovitine and its carboxylic metabolite concentrations were analyzed using HPLC-UV, and pharmacokinetic parameters were calculated in different organs. We found that systemic exposure to roscovitine was 38% higher when dosing at ZT3, and elimination half-life was double compared to when dosing at ZT19. Higher organ concentrations expressed as (organ/plasma) ratio were observed when dosing at ZT3 in the kidney (180%), adipose tissue (188%), testis (132%) and lungs (112%), while the liver exposure to roscovitine was 120% higher after dosing at ZT19. The metabolic ratio was approximately 23% higher at ZT19, while the intrinsic clearance (CLint) was approximately 67% higher at ZT19, indicating faster and more efficient metabolism. These differences may be caused by circadian differences in the absorption, distribution, metabolism and excretion processes governing roscovitine disposition in the mice. In this article, we describe for the first time the chronobiodistribution of roscovitine in the mouse and the contribution of the dosing time to the variability of its metabolism. Our results may help in designing better dosing schedules of roscovitine in clinical trials.