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We have developed a workflow to extract, separate, and semi-quantify bioactive oxysterols from mouse colon tissues and fecal matters using solid- and liquid-phase extractions, enzymatic and chemical modifications, and stable-isotope dilution LC/MS/MS. The method was applied to a dextran sodium sulphate (DSS)-induced mouse colitis model, which revealed that one particular dihydroxycholesterol (diOHC), 7α,25-diOHC, was significantly elevated in both colon tissue and fecal matters of mice with colitis compared to that in naive mice. The extent of 7α,25-diOHC elevation was positively correlated with colitis severity.

Deregulation of the phosphoinositide 3-kinase (PI3K) signaling pathway such as by PTEN loss or PIK3CA mutation occurs frequently in human cancer and contributes to resistance to antitumor therapies. Inhibition of key signaling proteins in the pathway therefore represents a valuable targeting strategy for diverse cancers. PF-04691502 is an ATP-competitive PI3K/mTOR dual inhibitor, which potently inhibited recombinant class I PI3K and mTOR in biochemical assays and suppressed transformation of avian fibroblasts mediated by wild-type PI3K γ, δ, or mutant PI3Kα. In PIK3CA-mutant and PTEN-deleted cancer cell lines, PF-04691502 reduced phosphorylation of AKT T308 and AKT S473 (IC50 of 7.5–47 nmol/L and 3.8–20 nmol/L, respectively) and inhibited cell proliferation (IC50 of 179–313 nmol/L). PF-04691502 inhibited mTORC1 activity in cells as measured by PI3K-independent nutrient stimulated assay, with an IC50 of 32 nmol/L and inhibited the activation of PI3K and mTOR downstream effectors including AKT, FKHRL1, PRAS40, p70S6K, 4EBP1, and S6RP. Short-term exposure to PF-04691502 predominantly inhibited PI3K, whereas mTOR inhibition persisted for 24 to 48 hours. PF-04691502 induced cell cycle G1 arrest, concomitant with upregulation of p27 Kip1 and reduction of Rb. Antitumor activity was observed in U87 (PTEN null), SKOV3 (PIK3CA mutation), and gefitinib- and erlotinib-resistant non–small cell lung carcinoma xenografts. In summary, PF-04691502 is a potent dual PI3K/mTOR inhibitor with broad antitumor activity. PF-04691502 has entered phase I clinical trials. Mol Cancer Ther; 10(11); 2189–99. ©2011 AACR.

PF04942847 [2-amino-4-{4-chloro-2-[2-(4-fluoro-1H-pyrazol-1-yl)ethoxy]-6-methylphenyl}-N-(2,2-difluoropropyl)-5,7-dihydro-6H-pyrrolo[3,4-d]pyrimidine-6-carboxamide] was identified as an orally available, ATP-competitive, small-molecule inhibitor of heat shock protein 90 (HSP90). The objectives of the present study were: 1) to characterize the pharmacokinetic-pharmacodynamic relationship of the plasma concentrations of PF04942847 to the inhibition of HSP90-dependent protein kinase, AKT, as a biomarker and 2) to characterize the relationship of AKT degradation to tumor growth inhibition as a pharmacological response (antitumor efficacy). Athymic mice implanted with MDA-MB-231 human breast cancer cells were treated with PF04942847 once daily at doses selected to encompass ED(50) values. Plasma concentrations of PF04942847 were adequately described by a two-compartment pharmacokinetic model. A time delay (hysteresis) was observed between the plasma concentrations of PF04942847 and AKT degradation; therefore, a link model was used to account for the hysteresis. The model reasonably fit the time courses of AKT degradation with the estimated EC(50) of 18 ng/ml. For tumor growth inhibition, the signal transduction model reasonably fit the inhibition of individual tumor growth curves with the estimated EC(50) of 7.3 ng/ml. Thus, the EC(50) for AKT degradation approximately corresponded to the EC(50) to EC(80) for tumor growth inhibition, suggesting that 50% AKT degradation was required for significant antitumor efficacy (50-80%). The consistent relationship between AKT degradation and antitumor efficacy was also demonstrated by applying an integrated signal transduction model for linking AKT degradation to tumor growth inhibition. The present results will be helpful in determining the appropriate dosing regimen and guiding dose escalation to achieve efficacious systemic exposure in the clinic.

Hsp90 is required for conformational maturation and stability of numerous key signaling proteins (clients) involved in cell proliferation and transformation. Here we describe two novel Hsp90 inhibitors, PF-4470296 and PF-3823863, demonstrate a differential sensitivity in B-Raf mutant (V600E) versus wild-type protein degradation. These two inhibitors inhibit proliferation and anchorage-independent growth, and abolish in vivo xenograft tumor growth in melanoma cells regardless of B-Raf mutation status. Mutant B-Raf protein and other Hsp90 clients, such as cMet, ErbB2, C-Raf, and AKT, are degraded in cells and xeno- graft tumors. Our results indicate that Hsp90 inhibitors induce anti-tumor activity in mel- anoma cells and are likely to show therapeutic benefit in melanoma patients by collaboratively targeting multiple pathways.

Phase II attrition of clinical candidates in the drug development cycle is currently a major issue facing the pharmaceutical industry. To decrease phase II attrition, there is an increased emphasis on validation of mechanism of action, development of efficacy models and measurement of drug levels at the site of action. PD 0332991, a highly specific inhibitor of cyclin-dependent kinase 4 (CDK-4) is currently in clinical development for the treatment of solid tumor. A clinical presurgical study will be required to better understand how PD 0332991 affects signaling pathways and how the intratumoral concentration of PD 0332991 correlates with plasma PK parameters and molecular alterations in breast cancer tissues after PD 0332991 treatment. Before conducting such a clinical study, it is important to evaluate PD 0332991 levels in tumor tissue samples from a xenograft mouse model for the determination of drug exposure at the site of action. Therefore, the objectives of this study were (1) to develop and validate a sensitive LC-MS/MS method to quantify PD 0332991 in mouse tumor tissues from MDA-MB-231-Luc human breast tumor xenografts in SCID-beige mice; (2) to quantify PD 0332991 levels in mouse tumor tissues after oral administration of PD 0332991 at 10 and 100mg/kg using the validated LC-MS/MS method. Both liquid-liquid extraction (LLE) and supported liquid extraction (SLE) in a 96-well format were developed and evaluated to achieve optimal extraction recovery with minimal matrix effects. The newly developed SLE method is more efficient (speed and ease) and demonstrates comparable recovery (93.1-100% at three different concentrations) compared to the traditional LLE method. The validated LC-MS/MS for PD 032291 in mouse tumor tissue homogenate method exhibited a linear dynamic range of 0.1-100 ng/mL with inter-day accuracy and precision within 15%. The validated method was successfully applied to measure PD 0332991 levels in tumor tissues in MDA-MB-231-Luc human breast tumor xenografts in SCID beige mice. The mean tumor concentrations at 6h post-oral PD 0332991 administration at 10 and 100mg/kg were 1793 (+/-1008) and 25,163 (+/-3959) ng/g, respectively.

NMDA receptor antagonists, particularly these targeting the GluN2B subunit are of therapeutic interest for the treatment of severe mood disorders. The receptor occupancy profiles of several NMDA receptor antagonists (30 mg/kg, s.c.) were compared in mouse hippocampus by ex vivo autoradiography using [(3)H]MK-801, a non-selective NMDA channel blocker, and [(3)H]ifenprodil a selective GluN2B antagonist. Subcutaneous administration of ketamine ((RS)-2-(2-Chlorophenyl)-2-(methylamino)cyclohexanone) and memantine (3,5-dimethyladamantan-1-amine) inhibited [(3)H]MK-801 but not [(3)H]ifenprodil binding in mouse hippocampus. Ketamine reached maximal occupancy of [(3)H]MK-801 binding sites after 15 min and rapidly cleared from the brain with no significant level of occupancy measured at the 1h time point. Memantine significantly occupied [(3)H]MK-801 binding sites throughout the 6h time course. The selective GluN2B antagonist CP101,606 ((1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol) and Ro 25-6981 ((αR,βS)-α-(4-Hydroxyphenyl)-β-methyl-4-(phenylmethyl)-1-piperidinepropanol maleate) inhibited [(3)H]ifenprodil but not [(3)H]MK-801 binding and significant levels of occupancy (above 50%) were measured throughout the 6h time course. These data highlight the unique quick pulse target engagement profile of ketamine compared to other NMDA receptor antagonists.

Background: Initial pharmacokinetic (PK) studies of discovery compounds are conducted in mice to demonstrate exposure prior to conducting efficacy studies. PK information obtained from a single mouse by serial blood microsampling, dried blood spot collection and analyses using microbore (1 mm internal diameter column) LC–MS/MS is presented. Ex vivo blood to plasma concentration ratios (BPRs) from mouse PK studies were compared with in vitro BPRs for 15 compounds. Results: Two compounds were orally dosed and blood was collected at time points via serial blood sampling. The calculated PK parameters (AUC, Tmax and Cmax) were comparable across liquid blood, dried blood spot and plasma matrices. The BPR results from both methods were comparable. Conclusion: Serial blood microsampling has led to reduced animal and compound usage with improved PK data. Ex vivo BPR is suitable in a discovery setting. Microbore LC–MS/MS is well suited in instances where sample volume is limited, and enables faster analyses, reduced solvent use, and less frequent MS source cleaning.