Role of tyrosine kinase inhibitors in cancer therapy

Quantum dots for molecular pathology: their time has arrived

Assessing malignant tumors for expression of multiple biomarkers provides data that are critical for patient management. Quantum dot-conjugated probes to specific biomarkers are powerful tools that can be applied in a multiplex manner to single tissue sections of biopsies to measure expression levels of multiple biomarkers.

Profiling of CD4+, CD8+, and CD4+CD25+CD45RO+FoxP3+ T cells in patients with malignant glioma reveals differential expression of the immunologic transcriptome compared with T cells from healthy volunteers

PURPOSE

Analyses of T-cell mRNA expression profiles in glioblastoma multiforme has not been previously reported but may help to define and characterize the immunosuppressed phenotype in patients with this type of cancer.

EXPERIMENTAL DESIGN

We did microarray studies that have shown significant and fundamental differences in the expression profiles of CD4(+) and CD8(+) T cells and immunosuppressive CD4(+)CD25(+)CD45RO(+)FoxP3(+) regulatory T cells (T(reg)) from normal healthy volunteers compared with patients with newly diagnosed glioblastoma multiforme. For these investigations, we isolated total RNA from enriched CD4(+) and CD8(+) T cell or T(reg) cell populations from age-matched individuals and did microarray analyses.

RESULTS

ANOVA and principal components analysis show that the various T cell compartments exhibit consistently similar mRNA expression profiles among individuals within either healthy or brain tumor groups but reflect significant differences between these groups. Compared with healthy volunteers, CD4(+) and CD8(+) T cells from patients with glioblastoma multiforme display coordinate down-regulation of genes involved in T cell receptor ligation, activation, and intracellular signaling. In contrast, T(regs) from patients with glioblastoma multiforme exhibit increased levels of transcripts involved in inhibiting host immunity.

CONCLUSION

Our findings support the notion that key differences between expression profiles in T-cell populations from patients with glioblastoma multiforme results from differential expression of the immunologic transcriptome, such that a limited number of genes are principally important in producing the dysregulated T-cell phenotype.

Interplay of distinct growth factors during epithelial mesenchymal transition of cancer progenitor cells and molecular targeting as novel cancer therapies

In this review, we describe the critical functions assumed by the interplay of epidermal growth factor, hedgehog, Wnt/beta-catenin, tumor growth factor-beta and integrin signaling cascades in tumorigenic and migrating cancer progenitor cells and activated stromal cells during carcinogenesis. These growth factors provide an important role for the sustained growth and survival of tumorigenic cancer progenitor cells and their progeny by up-regulating numerous mitotic and antiapoptotic signaling cascades. Furthermore, these potent morphogens may cooperate for inducing the molecular events associated with the epithelial-mesenchymal program in cancer cells including the alterations in epithelial cell shape and motility through the dissociation of intercellular adherens junctions. Of therapeutic interest, new strategies for the development of more effective clinical treatments against the locally aggressive and invasive cancers based on the molecular targeting of deregulated signaling elements in tumorigenic and migrating cancer cells and their local microenvironment are also described.

VEGF-specific Short Hairpin RNA–expressing Oncolytic Adenovirus Elicits Potent Inhibition of Angiogenesis and Tumor Growth

RNA interference is being developed to treat cancer. Although highly target specific, its use has been limited by its short duration of expression. To overcome this shortcoming, we constructed an oncolytic adenovirus (Ad)-based short hairpin RNA (shRNA) expression system (Ad-DeltaB7-shVEGF) against vascular endothelial growth factor (VEGF), a key mediator in angiogenesis. To demonstrate the VEGF-specific nature of this Ad-based shRNA, replication-incompetent Ad expressing VEGF-specific shRNA (Ad-DeltaE1-shVEGF) was also generated. Ad-DeltaE1-shVEGF was highly effective in reducing VEGF expression, and elicited an antiangiogenic effect in vitro and in vivo. Similarly, Ad-DeltaB7-shVEGF exhibited potent antiangiogenic effects in the matrigel plug assay. Moreover, Ad-DeltaB7-shVEGF demonstrated a greater antitumor effect and enhanced survival compared to the cognate control oncolytic Ad, Ad-DeltaB7. Ad-DeltaB7-shVEGF induced significant reduction in tumor vasculature, verifying the antiangiogenic mechanism. Furthermore, both the duration and magnitude of gene silencing by Ad-DeltaB7-shVEGF was greater than Ad-DeltaE1-shVEGF. These results suggest that the combined effects of oncolytic viral therapy and cancer cell-specific expression of VEGF-targeted shRNA elicits greater antitumor effect than an oncolytic Ad alone.

Genomics of Renal Cell Cancer: The Biology Behind and the Therapy Ahead

Renal cell cancer (RCC) is the most lethal of the urological cancers and accounts for 3% of all adult malignancies. Despite numerous recent advances in diagnostic imaging, surgical therapy, and basic molecular understanding, many patients still experience metastatic disease. For metastatic disease patients, response rates to conventional therapies rarely exceed 15% to 25% and are associated with serious adverse effects. The recent development of novel targeted therapies based on the precise biological pathways deregulated in a particular patient has paved the way for individualized, targeted patient management. Nevertheless, to achieve this goal, it is important to delineate the molecular mechanisms underlying cancer development and progression. Genomic approaches have revolutionized the field of cancer research and have led to the rapid discovery of multiple, parallel disease hypotheses, which ultimately have to be validated in large cohorts of patients and in downstream biological experiments for translation into clinical applications. The variable course of RCC and, until recently, a paucity of therapeutic options in the event of metastasis have led to the search for diagnostic and prognostic markers. We and others have used transcriptional profiling to classify different subtypes of RCC and to identify subtype- and metastasis-specific gene signatures predictive for outcome. We discuss herein recent genomic approaches to RCC and the emerging biological pathways underlying RCC development and progression. We also speculate how genomics may affect drug development and the management of patients with RCC.

Multitarget-directed drug design strategy: a novel molecule designed to block epidermal growth factor receptor (EGFR) and to exert proapoptotic effects

The multifactorial mechanistic nature of cancer calls for the development of multifunctional therapeutic tools, i.e., single compounds able to interact with multiple altered pathogenetic pathways. Following this rationale, we designed compounds able to irreversibly block epidermal growth factor receptor (EGFR), and to induce apoptosis in tumor cell lines. The novel molecules were synthesized by combining the structural features of the EGFR inhibitor PD153035 (1) and lipoic acid, which among other therapeutic effects triggers apoptosis in human cancer cells.

Utilization of achiral alkenyl amines for the preparation of high affinity Grb2 SH2 domain-binding macrocycles by ring-closing metathesis

A family of previously reported ring-closing metathesis (RCM)-derived macrocycles that exhibit potent Grb2 SH2 domain-binding affinity is characterized by stereoselectively-introduced upper ring junctions that bear bicyclic aryl substituents. However, the synthetic complexity of these macrocycles presents a potential limit to their therapeutic application. Therefore, the current study was undertaken to simplify these macrocycles through the use of achiral 4-pentenylamides as ring-forming components. A series of macrocycles (5a-f) was prepared bearing both open and cyclic constructs at the upper ring junction. The Grb2 SH2 domain-binding affinities of these macrocycles varied, with higher affinities being obtained with cyclo-substituents. The most potent analogue (5d) contained a cyclohexyl group and exhibited Grb2 SH2 domain-binding affinity (K(D) = 1.3 nM) that was nearly equal to the parent macrocycle (2), which bore a stereoselectively-introduced naphthylmethyl substituent at the upper ring junction (K(D) = 0.9 nM). The results of this study advance design considerations that should facilitate the development of Grb2 SH2 domain-binding antagonists.

Synthesis and anti-tumor activities of novel pyrazolo[1,5-a]pyrimidines

A series of novel pyrazolo[1,5-a]pyrimidines were designed and synthesized in order to find novel potent anti-tumor compounds. The structures of all the compounds were confirmed by IR, (1)H-NMR, elemental analysis, and MS. Their anti-tumor activities against cancer cell lines were tested by the MTT method in vitro. Compound 19 displayed potent anti-tumor activity.

Surviving cell death through epidermal growth factor (EGF) signal transduction pathways: Implications for cancer therapy

There is a balance between cell death and survival in living organisms. The ability of cells to sense their environment and decide to survive or die is dependent largely upon growth factors. Epidermal growth factor (EGF) is a key growth factor regulating cell survival. Through its binding to cell surface receptors, EGF activates an extensive network of signal transduction pathways that include activation of the PI3K/AKT, RAS/ERK and JAK/STAT pathways. These pathways predominantly lead to activation or inhibition of transcription factors that regulate expression of both pro- and anti-apoptotic proteins effectively blocking the apoptotic pathway. In cancer, EGF signaling pathways are often dysfunctional and targeted therapies that block EGF signaling have been successful in treating cancers. In this review, we will discuss the EGF survival signaling network, how it cross-talks with the apoptotic signaling pathways and the therapeutic drugs targeting the EGF survival pathway used to treat cancers.

Cutaneous side effects of epidermal growth factor receptor inhibitors: clinical presentation, pathogenesis, and management

The growing investigation and use of epidermal growth factor receptor (EGFR) inhibitors in anticancer therapy has been motivated by their specificity for EGFR, which improves their ability to target cancer cells and enhances their safety profile compared with many other conventional chemotherapeutic agents. However, their growing use has been accompanied by an increasing incidence of cutaneous toxicities, which can cause serious discomfort and be disabling. This review illustrates the common cutaneous side effects seen in patients receiving EGFR inhibitors and discusses various options for management. With effective management of these side effects, dermatologists can play an integral role in facilitating compliance with anti-EGFR therapy and aid with effective oncologic management.

Profile and Molecular Modeling of 3-(Indole-3-yl)-4-(3,4,5-trimethoxyphenyl)-1H-pyrrole-2,5dione (1) as a Highly Selective VEGF-R2/3 Inhibitor

We report on selectivity profiling of 1 in a panel of 20 protein kinases and molecular modeling indicating 1 to be highly active and selective for VEGF-R2/3. Sequence alignment analysis and detailed insights into the ATP binding pockets of targeted protein kinases from the panel result in a unique structural architecture of VEGF-R2 mainly caused by the hydrophobic pocket I, determining the molecular basis for activity and selectivity of 1.

Small molecule tyrosine kinase inhibitors in the treatment of solid tumors: an update of recent developments

Small molecule tyrosine kinase inhibitors (TKIs) are developed to block intracellular signaling pathways in tumor cells, leading to deregulation of key cell functions such as proliferation and differentiation. Over 25 years ago, tyrosine kinases were found to function as oncogenes in animal carcinogenesis; however, only recently TKIs were introduced as anti cancer drugs in human cancer treatment. Tyrosine kinase inhibitors have numerous good qualities. First, in many tumor types they tend to stabilize tumor progression and may create a chronic disease state which is no longer immediately life threatening. Second, side effects are minimal when compared to conventional chemotherapeutic agents. Third, synergistic effects are seen in vitro when TKIs are combined with radiotherapy and/or conventional chemotherapeutic agents. In this article, we will give an update of the tyrosine kinase inhibitors that are currently registered for use or in an advanced stage of development, and we will discuss the future role of TKIs in the treatment of solid tumors. The following TKIs are reviewed: Imatinib (Gleevec/Glivec), Gefitinib (Iressa), Erlotinib (OSI-774, Tarceva), Lapatinib (GW-572016, Tykerb), Canertinib (CI-1033), Sunitinib (SU 11248, Sutent), Zactima (ZD6474), Vatalanib (PTK787/ZK 222584), Sorafenib (Bay 43-9006, Nexavar), and Leflunomide (SU101, Arava).

Characterization and development of a peptide substrate-based phosphate transfer assay for the human vascular endothelial growth factor receptor-2 tyrosine kinase

Vascular endothelial growth factor (VEGF), a critical regulator in angiogenesis, exerts its angiogenic effect via binding to its receptor, VEGF receptor-2 tyrosine kinase (VEGFR2) or kinase insert domain-containing receptor (Kdr), on the surface of endothelial cells. Kdr-mediated signaling plays an important role in the proliferation, migration, differentiation, and survival of endothelial cells. Therefore, the inhibition of this signaling pathway represents a promising therapeutic approach for the discovery of novel anticancer agents by destabilizing the progression of solid tumors via abrogating tumor-induced angiogenesis. To explore Kdr as an anticancer target and further characterize the enzyme, we purified a cytoplasmic domain of human Kdr (Kdr-CD) and characterized its autophosphorylation activity. We also designed and synthesized peptides containing amino acid sequences corresponding to the autophosphorylation sites of Kdr and developed a simple, robust, high-throughput assay for measuring the phosphate transfer activity of the enzyme. This assay was validated by the experiments showing that the phosphate transfer activity of the purified Kdr-CD required Mg2+ or Mn2+ and preactivation by adenosine 5'-triphosphate (ATP) and was inhibited by known Kdr inhibitors. Using this assay, we examined effects of Mg2+ and Mn2+ on the enzyme activity; optimized the concentrations of Kdr-CD, peptide and ATP substrates, and metal ions in the assay; and determined the kinetic properties of the enzyme for the peptide and ATP as well as IC50 values of two known Kdr inhibitors. Thus, the results of these studies have validated the utilities of this assay for biochemical characterizations of the enzyme and its inhibitors. This approach of designing peptides corresponding to the autophosphorylation sites of Kdr as substrates for the enzyme has general practical implications to other kinases.

Epigenetic regulation of immune escape genes in cancer

According to the concept of immune surveillance, the appearance of a tumor indicates that it has earlier evaded host defenses and subsequently must have escaped immunity to evolve into a full-blown cancer. Tumor escape mechanisms have focused mainly on mutations of immune and apoptotic pathway genes. However, data obtained over the past few years suggest that epigenetic silencing in cancer may be as frequent a cause of gene inactivation as are mutations. Here, we discuss the evidence that tumor immune evasion is mediated by non-mutational epigenetic events involving chromatin and that epigenetics collaborates with mutations in determining tumor progression. Since epigenetic changes are potentially reversible, the relative contribution of mutations and epigenetics, to the gene defects in any given tumor, may be a factor in determining the efficacy of treatments. We review new developments in basic chromatin mechanisms and in this context describe the rationale for the current use of epigenetic agents in cancer therapy and for a novel epigenetically generated tumor vaccine model. We emphasize that epigenetic cancer treatments are currently a 'blunt-sword' and suggest future directions for designing chromatin-based programs of potential value in the diagnosis and treatment of cancer.

Sorafenib for the Treatment of Renal Cell Carcinoma

Objective:

To summarize the pharmacology, development, and clinical application of sorafenib, a specific tyrosine kinase and vascular growth factor inhibitor, for the treatment of renal cell carcinoma (RCC).

Data Sources:

Clinical literature, including both primary studies and review articles, was obtained by searching MEDLINE (1966–May 2006), using the search terms BAY 43-9006, sorafenib, renal cell carcinoma, and tyrosine kinase inhibitor. Additional information was supplied by the manufacturer, Bayer HealthCare Pharmaceuticals.

Study Selection and Data Extraction:

Review articles, abstracts, and clinical studies related to sorafenib were analyzed. An evaluation of the research exploring sorafenib as a potential therapy for RCC was conducted. Relevant information was then selected and is reviewed in this article.

Data Synthesis:

Knowledge of the cellular abnormalities that can cause solid tumors has led to the development of medications that block these pathways. Sorafenib is an oral tyrosine kinase inhibitor that both blocks the Raf kinase pathway and inhibits vascular growth factors. Phase I and II trials have demonstrated that sorafenib has activity against RCC. Dermatologic reactions (rash, desquamation), fatigue, and hypertension have been the most commonly seen treatment-related adverse events. Sorafenib received FDA approval in December 2005 for treatment of advanced RCC.

Conclusions:

Sorafenib is a novel oral tyrosine kinase inhibitor effective in the treatment of RCC.

Comparing antibody and small-molecule therapies for cancer

The 'magic bullet' concept of specifically targeting cancer cells at the same time as sparing normal tissues is now proven, as several monoclonal antibodies and targeted small-molecule compounds have been approved for cancer treatment. Both antibodies and small-molecule compounds are therefore promising tools for target-protein-based cancer therapy. We discuss and compare the distinctive properties of these two therapeutic strategies so as to provide a better view for the development of new drugs and the future direction of cancer therapy.

New treatment approaches in metastatic renal cell carcinoma

PURPOSE OF REVIEW

Recent developments in the understanding of the molecular biology of renal cell carcinoma have led to the development of several biologic agents with different mechanisms of action. In 2005, promising results have been observed especially in second-line therapy following cytokine failures and in 2006 more mature data with regard to time to progression and overall survival should be available. This review, analyzing basic translational research principles, will summarize the available evidence with a glimpse of the future therapeutic approaches in renal cell carcinoma.

RECENT FINDINGS

Vascular endothelial growth factor- and platelet-derived growth factor receptor-inhibiting drugs (SU11248, Bay 43-9006, Bevacizumab, AG-013736, etc.) report time to progression ranging between 4 and 9 months and variable benefits in overall survival. Confirmatory studies are ongoing regarding other novel treatments (CCI-779, Infliximab, PTK-787).

SUMMARY

In renal cell carcinoma, there is a strong rationale for targeting multiple pathways and particularly angiogenesis. Vascular endothelial growth factor- and platelet-derived growth factor receptor-inhibiting drugs have been rapidly approved in the second-line setting and will soon be used as first-line therapy. In the next years, translational/clinical research will provide evidence for combination strategies to improve upon the results of the biologic agents and hopefully offer more hope to patients with renal cell carcinoma.

kinDOCK: a tool for comparative docking of protein kinase ligands

KinDOCK is a new web server for the analysis of ATP-binding sites of protein kinases. This characterization is based on the docking of ligands already co-crystallized with other protein kinases. A structural library of protein kinase–ligand complexes has been extracted from the Protein Data Bank (PDB). This library can provide both potential ligands and their putative binding orientation for a given protein kinase. After protein–protein structural superposition, the ligands are transferred from the template complexes to the target protein kinase. The resulting complexes are evaluated using the program SCORE to compute a theoretical affinity. They can be dynamically visualized to allow a rapid mapping of important steric clashes and potential substitutions relevant for specificity and affinity. These characteristics allow a quick characterization of protein kinase active sites including conformation changes potentially required to accommodate particular ligands. Additionally, promising pharmacophores can be identified in the focussed library. These features will help to rationalize or optimize virtual screening (VS) on larger chemical compound libraries. The server and its documentation are freely available at .

Low dose leflunomide activates PI3K/Akt signalling in erythroleukemia cells and reduces apoptosis induced by anticancer agents

Rheumatoid arthritis (RA) is characterized by persistent joint synovial tissue inflammation. Leflunomide is an immunomodulatory agent that has been approved for treatment of active RA. In the past few years, uses other than RA treatment have appeared. Leflunomide has been reported to show antitumor potential through inhibition of cancer cell proliferation. We thus tested the antiproliferative potential of leflunomide on HEL and K562 erythroleukemia cells. The findings summarized in this report demonstrate for the first time that low dose leflunomide prolonged survival and reduced apoptosis induced by several anticancer agents in erythroleukemia cells. We showed that in treated cells, leflunomide reduced the signalling pathways involved in promoting apoptosis by reducing p38 MAPK and JNK basal activity. On the other hand, leflunomide transiently activated the ERK signalling pathway and induced a sustained activation of Akt. We also showed that leflunomide reduced caspase-3 activity and DNA fragmentation induced by anticancer agents. By using an inhibitory strategy, we showed that inhibition of Akt activation but not ERK abolished the protective effect of leflunomide. Thus our findings suggested that leflunomide reduced apoptosis induced by anticancer agents through PI3K/Akt signalling activation.

A CSF‐1 receptor kinase inhibitor targets effector functions and inhibits pro‐inflammatory cytokine production from murine macrophage populations

CSF-1 regulates macrophage differentiation, survival, and function, and is an attractive therapeutic target for chronic inflammation and malignant diseases. Here we describe the effects of a potent and selective inhibitor of CSF-1R-CYC10268-on CSF-1R-dependent signaling. In in vitro kinase assays, CYC10268 was active in the low nanomolar range and showed selectivity over other kinases such as Abl and Kit. CYC10268 blocked survival mediated by CSF-1R in primary murine bone marrow-derived macrophages (BMM) and in the factor-dependent cell line Ba/F3, in which the CSF-1R was ectopically expressed. CYC10268 also inhibited CSF-1 regulated signaling (Akt, ERK-1/2), gene expression (urokinase plasminogen activator, toll-like receptor 9, and apolipoprotein E), and priming of LPS-inducible cytokine production in BMM. In thioglycollate-elicited peritoneal macrophages (TEPM), which survive in the absence of exogenous CSF-1, CYC10268 impaired LPS-induced cytokine production and regulated expression of known CSF-1 target genes. These observations support the conclusion that TEPM are CSF-1 autocrine and that CSF-1 plays a central role in macrophage effector functions during inflammation. CSF-1R inhibitors such as CYC10268 provide a powerful tool to dissect the role of the CSF-1/CSF-1R signaling system in a range of biological systems and have potential for a number of therapeutic applications.

Readout Technologies for Highly Miniaturized Kinase Assays Applicable to High-Throughput Screening in a 1536-Well Format

This article discusses the development of homogeneous, miniaturized assays for the identification of novel kinase inhibitors from very large compound collections. In particular, the suitability of time-resolved fluorescence resonance energy transfer (TR-RET) based on phospho-specific antibodies, an antibody-independent fluorescence polarization (FP) approach using metal-coated beads (IMAP™ technology), and the determination of adenosine triphosphate consumption through chemiluminescence is evaluated. These readouts are compared with regard to assay sensitivity, compound interference, reagent consumption, and performance in a 1536-well format, and practical considerations for their application in primary screening or in the identification of kinase substrates are discussed. All of the tested technologies were found to be suitable for miniaturized high-throughput screening (HTS) in principle, but each of them has distinct limitations and advantages. Therefore, the target-specific selection of the most appropriate readout technology is recommended to ensure maximal relevance of HTS campaigns.

Multiple targeted tyrosine kinase inhibition in the clinic: all for one or one for all?

Recent insight into the role of receptor tyrosine kinase function in cancer cells culminated in the design of highly selective tyrosine kinase inhibitors. After proof of concept for the clinical efficacy and tolerability of selective tyrosine kinase inhibitors, it was conceived that most tumours will depend on more than one signalling pathway for their growth and survival. As a consequence, different strategies were pursued to inhibit multiple signalling pathways or multiple steps in the same pathway either by the development of multi-targeted agents or the combination of single targeted drugs. The use of a combination of different compounds will be less convenient to the patient, may result in dosing mistakes and drug-drug interaction should be anticipated. However, this approach will enable the titration of the dose of either agent to optimize target inhibition. The use of multi-targeted agents will circumvent several of the problems of combination therapy. Clinical activity resulting in FDA approval for both BAY 43-9006 and SU11248 has been noted. However, optimal inhibition of several targets might not be feasible at a dose with acceptable toxicity.

Early renal cell cancer

Renal cell cancer (RCC) mostly arises from the proximal renal tubules and is classified as an adenocarcinoma. The most reliable treatment for RCC is surgical excision; chemotherapy or radiotherapy does not have a practical effect on RCC. In selected patients, immunotherapy, including cytokine administration, has survival benefits. There is no established definition of early RCC. Surgical removal of organ-confined disease (T1 and T2) is likely to achieve tumor-free status leading to good prognosis. Possible definitions, diagnosis and treatment options for T1 and T2 disease are discussed.

Inhibitors of signal transduction protein kinases as targets for cancer therapy

Cancer development requires that tumour cells attain several capabilities, including increased replicative potentials, anchorage and growth-factor independency, evasion of apoptosis, angiogenesis and metastasis. Many of these processes involve the actions of protein kinases, which have emerged as key regulators of all aspects of neoplasia. Perturbed protein kinase activity is repeatedly found to be associated with human malignancies, making these proteins attractive targets for anti-cancer therapy. The last decade has witnessed an exponential increase in the development of specific small protein kinase inhibitors. Many of them are in clinical trials in patients with different types of cancer and some are successfully used in clinic. This review describes different approaches that are currently applied to develop such specific protein kinase inhibitors and provides an overview of protein kinase inhibitors that are currently in clinical trials or are administered in the clinic. Focus is directed on inhibitors against receptor tyrosine kinases and protein kinases participating in the signalling cascades.

A high-throughput, fully automated liquid/liquid extraction liquid chromatography/mass spectrometry method for the quantitation of a new investigational drug ABT-869 and its metabolite A-849529 in human plasma samples

ABT-869 is a novel ATP-competitive inhibitor for all the vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) receptor tyrosine kinases (RTKs). It is one of the oncology drugs in development at Abbott Laboratories and has great potential for enhanced anti-tumor efficacy as well as activity in a broad range of human cancers. We report here an accurate, precise and rugged liquid chromatography/mass spectrometry (LC/MS/MS) assay for the quantitative measurement of ABT-869 and its acid metabolite A-849529. A fully automated 96-well liquid/liquid extraction method was achieved utilizing a Hamilton liquid handler. The only manual intervention required prior to LC/MS/MS injection is to transfer the 96-well plate to a drying rack to dry the extracts then transfer the plate back to the Hamilton for robotic reconstitution. The linear dynamic ranges were from 1.1 to 598.8 ng/mL for ABT-869 and from 1.1 to 605.8 ng/mL for A-849529. The coefficient of determination (r2) for all analytes was greater than 0.9995. For the drug ABT-869, the intra-assay coefficient of variance (CV) was between 0.4% and 3.7% and the inter-assay CV was between 0.9% and 2.8%. The inter-assay mean accuracy, expressed as percent of theoretical, was between 96.8% and 102.2%. For the metabolite A-849529, the intra-assay CV was between 0.5% and 5.1% and the inter-assay CV was between 0.8% and 4.9%. The inter-assay mean accuracy, expressed as percent of theoretical, was between 96.9% and 100.6%.

A high-throughput liquid chromatography/tandem mass spectrometry method for simultaneous quantification of a hydrophobic drug candidate and its hydrophilic metabolite in human urine with a fully automated liquid/liquid extraction

ABT-869 (A-741439) is an investigational new drug candidate under development by Abbott Laboratories. ABT-869 is hydrophobic, but is oxidized in the body to A-849529, a hydrophilic metabolite that includes both carboxyl and amino groups. Poor solubility of ABT-869 in aqueous matrix causes simultaneous analysis of both ABT-869 and its metabolite within the same extraction and injection to be extremely difficult in human urine. In this paper, a high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) method has been developed and validated for high-speed simultaneous quantitation of the hydrophobic ABT-869 and its hydrophilic metabolite, A-849529, in human urine. The deuterated internal standards, A-741439D(4) and A-849529D(4), were used in this method. The disparate properties of the two analytes were mediated by treating samples with acetonitrile, adjusting pH with an extraction buffer, and optimizing the extraction solvent and mobile phase composition. For a 100 microL urine sample volume, the lower limit of quantitation was approximately 1 ng/mL for both ABT-869 and A-849529. The calibration curve was linear from 1.09 to 595.13 ng/mL for ABT-869, and 1.10 to 600.48 ng/mL for A-849529 (r2 > 0.9975 for both ABT-869 and A-849529). Because the method employs simultaneous quantification, high throughput is achieved despite the presence of both a hydrophobic analyte and its hydrophilic metabolite in human urine.