In vitro and in vivo pharmacokinetics, disposition, and drug-drug interaction potential of tinengotinib (TT-00420), a promising investigational drug for treatment of cholangiocarcinoma and other solid tumors.

Early-stage clinical evaluation of tinengotinib (TT-00420) demonstrated encouraging preliminary efficacies in multiple types of refractory cancers, including fibroblast growth factor receptors (FGFR) inhibitors relapsed cholangiocarcinoma (CCA), castrate-resistant prostate cancer (CRPC), and HR+/HER2- breast cancer and triple negative breast cancer (TNBC). To further evaluate drug-like properties of the drug candidate, it is imperative to understand its metabolism and pharmacokinetic properties. This manuscript presented the investigation results of in vitro permeability, plasma protein binding, metabolic stability, metabolite identification, and drug-drug interaction of tinengotinib. Preclinical ADME (absorption, distribution, excretion, and metabolism) studies in rats and dogs was also conducted using a radioactive labeled tinengotinib, [14C]tinengotinib. Tinengotinib was found to have high permeability and high plasma protein binding and equally distributed between blood and plasma. There were no unique metabolites in human liver microsomes and tinengotinib showed moderate hepatic clearance. Tinengotinib is neither a potential inhibitor nor an inducer of P450 enzymes at clinically relevant concentrations, and unlikely to cause drug-drug interactions when used in combination with other drugs mediated by a key transporter, either as victim or perpetrator. Taken together, tinengotinib demonstrated a minimal risk of clinically relevant drug-drug interactions. Tinengotinib showed good oral bioavailability and dose-dependent exposures in both rat and dog after oral administration. The total radioactivity was largely distributed in the gastrointestinal system and liver, and tinengotinib could not easily pass through the blood-brain barrier. The major drug-related component in rat and dog plasma was unchanged drug (>89 %) with primary route of elimination via feces (>93 % of the dose) and minor via renal excretion (<4 % of the dose). Tinengotinib metabolism is mediated largely by CYP3A4, with minor contributions from CYP2D6 and CYP2C8. Major metabolic pathways include oxidation, oxidative cleavage of the morpholine ring, glucuronide and glutathione conjugations. The overall preclinical pharmacokinetics profile supported the selection and development of tinengotinib as a clinical candidate.

Appropriate in vivo follow-up assays to an in vitro bacterial reverse mutation (Ames) test positive investigational drug candidate (active pharmaceutical ingredient), drug-related metabolite, or drug-related impurity.

Kirkland et al. [Mutation Research/Genetic Toxicology and Environmental Mutagenesis 847 (2019) 403035, https://doi.org/10.1016/j.mrgentox.2019.03.008; Mutation Research/Genetic Toxicology and Environmental Mutagenesis 839 (2019): 21-35, https://doi.org/10.1016/j.mrgentox.2019.01.007] made recommendations on the use of the in vivo comet and transgenic rodent (TGR) gene mutation assays to screen for in vivo mutagenicity. Although it is not directly stated in either of these publications, we are concerned that the reports could potentially be used to support assertions that it is equally acceptable to follow up a positive bacterial reverse mutation (Ames) finding for an investigational drug with either the in vivo TGR mutation assay or an in vivo comet assay. For regulatory genotoxicity assessment, the in vivo follow-up for an in vitro bacterial mutation-positive drug, drug-related metabolite, or impurity should be based upon evaluating a similar endpoint (i.e., mutagenicity) as the intent is to determine if the findings of in vitro gene mutation correlate with findings of in vivo gene mutation (i.e., biologically relevant to the in vitro results). Thus, the most scientifically appropriate in vivo assays would be the TGR mutation assay or, in some circumstances, the in vivo Pig-a assay. An in vivo rodent comet assay or combination of the in vivo micronucleus and in vivo rodent comet assays would generally not be an appropriate follow-up test.

Futibatinib Is a Novel Irreversible FGFR 1-4 Inhibitor That Shows Selective Antitumor Activity against FGFR-Deregulated Tumors.

FGFR signaling is deregulated in many human cancers, and FGFR is considered a valid target in FGFR-deregulated tumors. Here, we examine the preclinical profile of futibatinib (TAS-120; 1-[(3S)-[4-amino-3-[(3,5-dimethoxyphenyl)ethynyl]-1H-pyrazolo[3, 4-d] pyrimidin-1-yl]-1-pyrrolidinyl]-2-propen-1-one), a structurally novel, irreversible FGFR1-4 inhibitor. Among a panel of 296 human kinases, futibatinib selectively inhibited FGFR1-4 with IC50 values of 1.4 to 3.7 nmol/L. Futibatinib covalently bound the FGFR kinase domain, inhibiting FGFR phosphorylation and, in turn, downstream signaling in FGFR-deregulated tumor cell lines. Futibatinib exhibited potent, selective growth inhibition of several tumor cell lines (gastric, lung, multiple myeloma, bladder, endometrial, and breast) harboring various FGFR genomic aberrations. Oral administration of futibatinib led to significant dose-dependent tumor reduction in various FGFR-driven human tumor xenograft models, and tumor reduction was associated with sustained FGFR inhibition, which was proportional to the administered dose. The frequency of appearance of drug-resistant clones was lower with futibatinib than a reversible ATP-competitive FGFR inhibitor, and futibatinib inhibited several drug-resistant FGFR2 mutants, including the FGFR2 V565I/L gatekeeper mutants, with greater potency than any reversible FGFR inhibitors tested (IC50, 1.3-50.6 nmol/L). These results indicate that futibatinib is a novel orally available, potent, selective, and irreversible inhibitor of FGFR1-4 with a broad spectrum of antitumor activity in cell lines and xenograft models. These findings provide a strong rationale for testing futibatinib in patients with tumors oncogenically driven by FGFR genomic aberrations, with phase I to III trials ongoing. SIGNIFICANCE: Preclinical characterization of futibatinib, an irreversible FGFR1-4 inhibitor, demonstrates selective and potent antitumor activity against FGFR-deregulated cancer cell lines and xenograft models, supporting clinical evaluation in patients with FGFR-driven tumors. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/22/4986/F1.large.jpg.

Drug-drug interactions of newly approved small molecule inhibitors for acute myeloid leukemia.

Several small molecule inhibitors (SMIs) have been recently approved for AML patients. These targeted therapies could be more tolerable than classical antineoplastics, but potential drug-drug interactions (DDI) are relatively frequent. Underestimation or lack of appropriate awareness and management of DDIs with SMIs can jeopardize therapeutic success in AML patients, which often require multiple concomitant medications in the context of prior comorbidities or for the prevention and treatment of infectious and other complications. In this systematic review, we analyze DDIs of glasdegib, venetoclax, midostaurin, quizartinib, gilteritinib, enasidenib, and ivosidenib. CYP3A4 is the main enzyme responsible for SMIs metabolism, and strong CYP3A4 inhibitors, such azoles, could increase drug exposure and toxicity; therefore dose adjustments (venetoclax, quizartinib, and ivosidenib) or alternative therapies or close monitoring (glasdegib, midostaurin, and gilteritinib) are recommended. Besides, coadministration of strong CYP3A4 inducers with SMIs should be avoided due to potential decrease of efficacy. Regarding tolerability, QTc prolongation is frequently observed for most of approved SMIs, and drugs with a potential to prolong the QTc interval and CYP3A4 inhibitors should be avoided and replaced by alternative treatments. In this study, we critically assess the DDIs of SMIs, and we summarize best management options for these new drugs and concomitant medications.

Age-Related Changes in Expression and Activity of Human Hepatic Mitochondrial Glutathione Transferase Zeta1.

Glutathione transferase zeta1 (GSTZ1) catalyzes glutathione (GSH)-dependent dechlorination of dichloroacetate (DCA), an investigational drug with therapeutic potential in metabolic disorders and cancer. GSTZ1 is expressed in both hepatic cytosol and mitochondria. Here, we examined the ontogeny and characterized the properties of human mitochondrial GSTZ1. GSTZ1 expression and activity with DCA were determined in 103 human hepatic mitochondrial samples prepared from livers of donors aged 1 day to 84 years. DNA from each sample was genotyped for three common GSTZ1 functional single nucleotide polymorphisms. Expression of mitochondrial GSTZ1 protein increased in an age-dependent manner to a plateau after age 21 years. Activity with DCA correlated with expression, after taking into account the somewhat higher activity of samples that were homo- or heterozygous for GSTZ1A. In samples from livers with the GSTZ1C variant, apparent enzyme kinetic constants for DCA and GSH were similar for mitochondria and cytosol after correcting for the loss of GSH observed in mitochondrial incubations. In the presence of 38 mM chloride, mitochondrial GSTZ1 exhibited shorter half-lives of inactivation compared with the cytosolic enzyme (P = 0.017). GSTZ1 protein isolated from mitochondria was shown by mass spectrometry to be identical to cytosolic GSTZ1 protein in the covered primary protein sequence. In summary, we report age-related development in the expression and activity of human hepatic mitochondrial GSTZ1 does not have the same pattern as that reported for cytosolic GSTZ1. Some properties of cytosolic and mitochondrial GSTZ1 differed, but these were not related to differences in amino acid sequence or post-translationally modified residues.

The antibacterial prodrug activator Rv2466c is a mycothiol-dependent reductase in the oxidative stress response of Mycobacterium tuberculosis.

The Mycobacterium tuberculosis rv2466c gene encodes an oxidoreductase enzyme annotated as DsbA. It has a CPWC active-site motif embedded within its thioredoxin fold domain and mediates the activation of the prodrug TP053, a thienopyrimidine derivative that kills both replicating and nonreplicating bacilli. However, its mode of action and actual enzymatic function in M. tuberculosis have remained enigmatic. In this study, we report that Rv2466c is essential for bacterial survival under H2O2 stress. Further, we discovered that Rv2466c lacks oxidase activity; rather, it receives electrons through the mycothiol/mycothione reductase/NADPH pathway to activate TP053, preferentially via a dithiol-disulfide mechanism. We also found that Rv2466c uses a monothiol-disulfide exchange mechanism to reduce S-mycothiolated mixed disulfides and intramolecular disulfides. Genetic, phylogenetic, bioinformatics, structural, and biochemical analyses revealed that Rv2466c is a novel mycothiol-dependent reductase, which represents a mycoredoxin cluster of enzymes within the DsbA family different from the glutaredoxin cluster to which mycoredoxin-1 (Mrx1 or Rv3198A) belongs. To validate this DsbA-mycoredoxin cluster, we also characterized a homologous enzyme of Corynebacterium glutamicum (NCgl2339) and observed that it demycothiolates and reduces a mycothiol arsenate adduct with kinetic properties different from those of Mrx1. In conclusion, our work has uncovered a DsbA-like mycoredoxin that promotes mycobacterial resistance to oxidative stress and reacts with free mycothiol and mycothiolated targets. The characterization of the DsbA-like mycoredoxin cluster reported here now paves the way for correctly classifying similar enzymes from other organisms.

Pharmacological efficacy of FGF21 analogue, liraglutide and insulin glargine in treatment of type 2 diabetes.

Fibroblast growth factor 21 (FGF21) is a promising regulator of glucose and lipid metabolism with multiple beneficial effects including hypoglycemic and lipid-lowering. Previous studies have reported that FGF21 is expected to become a new drug for treatment of diabetes. Liraglutide and insulin glargine are the two representative anti-diabetic biological drugs. In the current study, we aim to compare the long-term pharmacological efficacy of mFGF21 (an FGF21 analogue), liraglutide and insulin glargine in type 2 diabetic db/db mice. Db/db mice were initially treated with three kinds of proteins (25nmol/kg/day) by subcutaneous injection once a day for 4weeks, then subsequently be treated with once every two days for next 4weeks. After 8weeks of treatments, the blood glucose levels, body weights, glycosylated hemoglobin levels, fasting insulin levels, serum lipid profiles, hepatic biochemical parameters, oral glucose tolerance tests and hepatic mRNA expression levels of several proteins (GK, G6P, GLUT-1 and GLUT-4) associated with glucose metabolism of the experimental mice were detected. Results demonstrated that three proteins could significantly decrease the fed blood glucose levels of db/db mice. After treatment for 1week, the fed blood glucose levels of db/db mice in liraglutide group were significantly lower than those in mFGF21 and insulin glargine groups. However, after 2weeks of administration, the long-lasting hypoglycemic effect of mFGF21 was superior to liraglutide and insulin glargine up to the end of the experiments. Compared with liraglutide and insulin glargine, mFGF21 significantly reduced the glycosylated hemoglobin levels and improved the ability on glycemic control, insulin resistance, serum lipid and liver function states in db/db mice after 8weeks treatments. In addition, mFGF21 regulated glucose metabolism through increasing the mRNA expression levels of GK and GLUT-1, and decreasing the mRNA expression level of G6P. But liraglutide and insulin glargine could only up-regulate the mRNA expression of GLUT-4. In summary, as a hypoglycemic drug for long-term treatment, mFGF21 has the potential to be an ideal drug candidate for the therapy of type 2 diabetes.

A phase I open-label trial evaluating the cardiovascular safety of regorafenib in patients with advanced cancer.

PURPOSE: To characterize the cardiovascular safety profile of regorafenib in patients with advanced cancer. METHODS: Patients received regorafenib 160 mg/day for 21 days followed by a 7-day break. The primary endpoint was the change from baseline in QTcF at the regorafenib t(max) (Day 21, Cycle 1 or 2) and changes in left ventricular ejection fraction (LVEF) from baseline on Cycle 2, Day 21. Secondary objectives were pharmacokinetics, safety, anti-tumor activity and effects on electrocardiogram intervals. QT intervals were corrected using the methods of Fridericia (QTcF) and Bazett (QTcB). LVEF was assessed by multigated acquisition scanning. RESULTS: Fifty-three patients were enrolled, and all received at least one dose of regorafenib 160 mg. Twenty-five patients received regorafenib for 21 days without dose reduction. The mean change from baseline in QTcF at t(max) was (-)2 ms (90 % CI -8, 3). No patient experienced a change from baseline in QTcF > 60 ms, and two had QTcF changes between 30 and 60 ms. No patient had a QTcF or QTcB > 480 ms. In 27 patients who received at least 80 mg of regorafenib, the mean change from baseline in LVEF% ± SD was 1.7 ± 7.8. In 14 patients without a dose reduction, the mean change from baseline in LVEF% was (-)0.1 ± 8.6 at Cycle 2, Day 21. Four patients experienced a LVEF decrease between 10 and 20 %. CONCLUSION: The effects of regorafenib on the QT/QTc interval and LVEF were modest and unlikely to be of clinical significance in the setting of advanced cancer therapy.

The effects of endoxifen and other major metabolites of tamoxifen on the sulfation of estradiol catalyzed by human cytosolic sulfotransferases hSULT1E1 and hSULT1A1*1.

Tamoxifen is successfully used for both treatment and prevention of estrogen-dependent breast cancer, yet side effects and development of resistance remain problematic. Endoxifen is a major active metabolite of tamoxifen that is being investigated for clinical use. We hypothesized that endoxifen and perhaps other major metabolites of tamoxifen may affect the ability of human estrogen sulfotransferase 1E1 (hSULT1E1) and human phenol sulfotransferase 1A1 isoform 1 (hSULT1A1*1) to catalyze the sulfation of estradiol, an important mechanism in termination of estrogen signaling through loss of activity at estrogen receptors. Our results indicated that endoxifen, N-desmethyltamoxifen (N-desTAM), 4-hydroxytamoxifen (4-OHTAM), and tamoxifen-N-oxide were weak inhibitors of hSULT1E1 with Ki values ranging from 10 µM to 38 µM (i.e., over 1000 times higher than the 8.1 nM Km value for estradiol as substrate for the enzyme). In contrast to the results with hSULT1E1, endoxifen and 4-OHTAM were significant inhibitors of the sulfation of 2.0 µM estradiol catalyzed by hSULT1A1*1, with IC50 values (9.9 µM and 1.6 µM, respectively) that were similar to the Km value (1.5 µM) for estradiol as substrate for this enzyme. Additional investigation of the interaction of these metabolites with the two sulfotransferases revealed that endoxifen, 4-OHTAM, and N-desTAM were substrates for hSULT1E1 and hSULT1A1*1, although the relative catalytic efficiencies varied with both the substrate and the enzyme. These results may assist in future elucidation of cell- and tissue-specific effects of tamoxifen and its metabolites.

Induction of UDP-glucuronosyltransferase 2B15 gene expression by the major active metabolites of tamoxifen, 4-hydroxytamoxifen and endoxifen, in breast cancer cells.

We previously reported upregulation of UGT2B15 by 17ß-estradiol in breast cancer MCF7 cells via binding of the estrogen receptor α (ERα) to an estrogen response unit (ERU) in the proximal UGT2B15 promoter. In the present study, we show that this ERα-mediated upregulation was significantly reduced by two ER antagonists (fulvestrant and raloxifene) but was not affected by a third ER antagonist, 4-hydroxytamoxifen (4-OHTAM), a major active tamoxifen (TAM) metabolite. Furthermore, we found that, similar to 17ß-estradiol, 4-OHTAM and endoxifen (another major active TAM metabolite) elevated UGT2B15 mRNA levels, and that this stimulation was significantly abrogated by fulvestrant. Further experiments using 4-OHTAM revealed a critical role for ERα in this regulation. Specifically; knockdown of ERα expression by anti-ERα small interfering RNA reduced the 4-OHTAM-mediated induction of UGT2B15 expression; 4-OHTAM activated the wild-type but not the ERU-mutated UGT2B15 promoter; and chromatin immunoprecipitation assays showed increased ERα occupancy at the UGT2B15 ERU in MCF7 cells upon exposure to 4-OHTAM. Together, these data indicate that both 17ß-estradiol and the antiestrogen 4-OHTAM upregulate UGT2B15 in MCF7 cells via the same ERα-signaling pathway. This is consistent with previous observations that both 17ß-estradiol and TAM upregulate a common set of genes in MCF7 cells via the ER-signaling pathway. As 4-OHTAM is a UGT2B15 substrate, the upregulation of UGT2B15 by 4-OHTAM in target breast cancer cells is likely to enhance local metabolism and inactivation of 4-OHTAM within the tumor. This represents a potential mechanism that may reduce TAM therapeutic efficacy or even contribute to the development of acquired TAM resistance.

Lenvatinib: first global approval.

Lenvatinib (Lenvima™) is a multitargeted receptor kinase inhibitor that inhibits the kinase activities of vascular endothelial-derived growth factor receptors 1, 2 and 3, fibroblast growth factor receptors 1, 2, 3 and 4, platelet-derived growth factor receptor α, RET and KIT. In addition to their role in normal cellular function, these kinases have been implicated in pathogenic angiogenesis, tumour growth and cancer progression. Lenvatinib is being developed by Eisai Co. Ltd for the treatment of solid tumours, primarily for differentiated thyroid cancer, and other malignancies. A capsule formulation of the drug has received approval in the USA for use in locally recurrent or metastatic, progressive, radioactive iodine-refractory differentiated thyroid cancer. Lenvatinib is in pre-registration for this indication in the EU, Australia, Brazil, Canada, Japan, South Korea, Russia, Singapore and Switzerland, and is in phase 3 development in Argentina, Chile and Thailand. Lenvatinib has orphan designation in the EU and Japan for use in differentiated thyroid cancer. In addition, an ongoing global, phase 3 trial is evaluating the use of lenvatinib as first-line treatment in unresectable hepatocellular carcinoma. This article summarizes the milestones in the development of lenvatinib leading to this first approval in locally recurrent or metastatic, progressive, radioactive iodine-refractory differentiated thyroid cancer.

Helix-constrained nociceptin peptides are potent agonists and antagonists of ORL-1 and nociception.

Nociceptin (orphanin FQ) is a 17-residue neuropeptide hormone with roles in both nociception and analgesia. It is an opioid-like peptide that binds to and activates the G-protein-coupled receptor opioid receptor-like-1 (ORL-1, NOP, orphanin FQ receptor, kappa-type 3 opioid receptor) on central and peripheral nervous tissue, without activating classic delta-, kappa-, or mu-opioid receptors or being inhibited by the classic opioid antagonist naloxone. The three-dimensional structure of ORL-1 was recently published, and the activation mechanism is believed to involve capture by ORL-1 of the high-affinity binding, prohelical C-terminus. This likely anchors the receptor-activating N-terminus of nociception nearby for insertion in the membrane-spanning helices of ORL-1. In search of higher agonist potency, two lysine and two aspartate residues were strategically incorporated into the receptor-binding C-terminus of the nociceptin sequence and two Lys(i)→Asp(i+4) side chain-side chain condensations were used to generate lactam cross-links that constrained nociceptin into a highly stable α-helix in water. A cell-based assay was developed using natively expressed ORL-1 receptors on mouse neuroblastoma cells to measure phosphorylated ERK as a reporter of agonist-induced receptor activation and intracellular signaling. Agonist activity was increased up to 20-fold over native nociceptin using a combination of this helix-inducing strategy and other amino acid modifications. An NMR-derived three-dimensional solution structure is described for a potent ORL-1 agonist derived from nociceptin, along with structure-activity relationships leading to the most potent known α-helical ORL-1 agonist (EC50 40 pM, pERK, Neuro-2a cells) and antagonist (IC50 7 nM, pERK, Neuro-2a cells). These α-helix-constrained mimetics of nociceptin(1-17) had enhanced serum stability relative to unconstrained peptide analogues and nociceptin itself, were not cytotoxic, and displayed potent thermal analgesic and antianalgesic properties in rats (ED50 70 pmol, IC50 10 nmol, s.c.), suggesting promising uses in vivo for the treatment of pain and other ORL-1-mediated responses.

Synthesis and biological activity of small peptides as NOP and opioid receptors' ligands: view on current developments.

The heptadecapeptide nociceptin, also called orphanin FQ (N/OFQ), is the endogenous agonist of the N/OFQ peptide receptor (NOP receptor) and is involved in several central nervous system pathways, such as nociception, reward, tolerance, and feeding. The discovery of small molecule ligands for NOP is being actively pursued for several therapeutic applications. This review presents overview of the several recently reported NOP ligands (agonists and antagonists), with an emphasis of the structural features that may be important for modulating the intrinsic activity of these ligands. In addition, a brief account on the characterization of newly synthesized ligands of NOP receptor with aminophosphonate moiety and ß-tryptophan analogues will be presented.

A phase I, open-label, multicenter study to evaluate the pharmacokinetics and safety of oral panobinostat in patients with advanced solid tumors and varying degrees of renal function.

PURPOSE: This study assessed the pharmacokinetics and safety of oral panobinostat and its metabolite BJB432 in patients with advanced solid tumors and normal to severely impaired renal function. METHODS: Patients with varying degrees of renal impairment, defined by their 24-h baseline urine creatinine clearance (as normal, mild, moderate or severe), received a single oral dose of 30 mg panobinostat. Serial plasma samples were collected pre-dose and up to 96-h post-dose. Serial urine samples were collected for 24-h post-dose. Following the serial PK sampling, patients received 30 mg oral panobinostat thrice weekly for as long as the patient had benefit. Pharmacokinetic parameters were derived using non-compartmental analysis. RESULTS: Thirty-seven patients were enrolled, and median age was 64 (range 40-81) years. Eleven patients had normal renal function; 10, 10, and 6 patients had mild, moderate, and severe renal impairment, respectively. Geometric means of AUC(0-∞) in the normal, mild, moderate, and severe groups were 224.5, 144.3, 223.1, and 131.7 ng h/mL, respectively. Geometric mean ratio of BJB432 to parent drug plasma AUC(0-∞) was 0.64 in the normal group and increased to 0.81, 1.13, and 1.20 in the mild, moderate, and severe groups, respectively. The fraction excreted as unchanged panobinostat was small (<2 %), with a large variability. The renal clearance of panobinostat and tolerability was similar across all four groups. CONCLUSION: Systemic exposure to panobinostat did not increase with severity of renal impairment, and the drug was tolerated equally; thus, patients with renal impairment do not require starting dose adjustments.

Characterization of acute biliary hyperplasia in Fisher 344 rats administered the indole-3-carbinol analog, NSC-743380.

NSC-743380 (1-[(3-chlorophenyl)-methyl]-1H-indole-3-carbinol) is in early stages of development as an anticancer agent. Two metabolites reflect sequential conversion of the carbinol functionality to a carboxaldehyde and the major metabolite, 1-[(3-chlorophenyl)-methyl]-1H-indole-3-carboxylic acid. In an exploratory toxicity study in rats, NSC-743380 induced elevations in liver-associated serum enzymes and biliary hyperplasia. Biliary hyperplasia was observed 2 days after dosing orally for 2 consecutive days at 100mg/kg/day. Notably, hepatotoxicity and biliary hyperplasia were observed after oral administration of the parent compound, but not when major metabolites were administered. The toxicities of a structurally similar but pharmacologically inactive molecule and a structurally diverse molecule with a similar efficacy profile in killing cancer cells in vitro were compared to NSC-743380 to explore scaffold versus target-mediated toxicity. Following two oral doses of 100mg/kg/day given once daily on two consecutive days, the structurally unrelated active compound produced hepatic toxicity similar to NSC-743380. The structurally similar inactive compound did not, but, lower exposures were achieved. The weight of evidence implies that the hepatotoxicity associated with NSC-743380 is related to the anticancer activity of the parent molecule. Furthermore, because biliary hyperplasia represents an unmanageable and non-monitorable adverse effect in clinical settings, this model may provide an opportunity for investigators to use a short-duration study design to explore biomarkers of biliary hyperplasia.

Discovery of allosteric BCR-ABL inhibitors from phenotypic screen to clinical candidate.

The development of imatinib, an ATP-competitive inhibitor of the BCR-ABL oncoprotein, has revolutionized the treatment of chronic myelogenous leukemia (CML). Unfortunately, the leukemia eventually becomes resistant imatinib as a result of emergence of cells expressing drug insensitive BCR-ABL mutant proteins. This has motivated the development of several next-generation ATP-competitive drugs. This chapter describes the discovery and development of a complementary strategy involving inhibiting BCR-ABL by targeting an allosteric binding site. Compounds that bind to the myristate-binding pocket of BCR-ABL are able to induce formation of an "inactive" state and are able to overcome resistance mutations located in the ATP-binding pocket including the recalcitrant T315I "gatekeeper" mutation. Myristate-pocket inhibitors are also able to function synergistically with ATP-competitive inhibitors in cellular and murine models of CML and this dual inhibitory strategy is currently being investigated in the clinic.

Selective cellular uptake and retention of SN 28049, a new DNA-binding topoisomerase II-directed antitumor agent.

PURPOSE: SN 28049 is a new DNA-binding topoisomerase II poison identified by its curative activity against the murine colon 38 carcinoma. Previous studies showed activity to be associated with selective drug accumulation and retention in tumour tissue. Retention varied widely among different tumours and was related to antitumour activity. We determined whether differences in the uptake and retention of SN 28049 could be observed in vitro. METHODS: The Co38P and LLTC lines were derived from the murine colon 38 carcinoma and Lewis lung carcinoma (3LL), respectively. The NZM4, NZM10 and NZM52 human melanoma lines, as well as the CCRF/CEM, CEM/VLB100 and CEM/E1000 human leukaemia lines were also utilised. Cell-associated drug was measured by liquid chromatography-mass spectrometry, laser-scanning confocal microscopy and fluorescence microscopy. Data for SN 28049 were compared for four SN 28049 analogues, for the structurally related drug N-[2-(dimethylamino)-ethyl]acridine-4-carboxamide (DACA) and for doxorubicin. RESULTS: Cellular uptake of SN 28049 was rapid and associated with increased fluorescence in cytoplasmic vesicles or bodies. SN 28049 uptake after an incubation time of 1 h varied widely with different cell lines (2-98 pmol/106 cells) and did not correlate with growth inhibitory concentrations (IC50 values), which also varied widely (1.2-19 nM). Changes in the length of the N-linked side chain of SN 28049 had large effects on drug uptake by Co38P cells. SN 28049 uptake by CCRF/CEM cells was only slightly affected by the expression of P-glycoprotein (CEM/VLB100) or MRP1 protein (CEM/E1000). As measured by cytoplasmic fluorescence, SN 28049 was taken up rapidly and retained strongly by Co38P cells, DACA was taken up rapidly and retained poorly, and doxorubicin was taken up slowly and retained moderately. CONCLUSIONS: The results suggest that SN 28049 is actively transported into cytoplasmic vesicles. While vesicle-associated drug is not important for intrinsic cytotoxicity, it may play a key role as a "slow release" form that modifies pharmacokinetics in multicellular structures such as tumours.

Preclinical pharmacokinetics and disposition of a novel selective VEGFR inhibitor fruquintinib (HMPL-013) and the prediction of its human pharmacokinetics.

PURPOSE: This study evaluated the preclinical pharmacokinetics (PK) and disposition of fruquintinib (HMPL-013), a small molecule vascular endothelial growth factor receptors inhibitor. METHODS: In vitro and in vivo PK/ADME assays were conducted. Allometry and PK modeling/simulation were conducted to predict human PK parameters and the time course profiles. RESULTS: HMPL-013 has high permeability without efflux. It shows moderate oral bioavailability of 42-53 % and Tmax < 4 h in mouse, rat, dog and monkey, with exposure-dose linearity proved in rats and dogs. No significant food effect is on dog PK. HMPL-013 has moderately high tissue distribution. It majorly distributes in gastrointestinal tract, liver, kidney, adrenal and adipose. The plasma protein binding fraction is 88-95 % in mouse, rat, dog and human, invariable up to 10 µM. The in vivo clearance of HMPL-013 is low, consistent with the in vitro scaling. Three major oxidative metabolites were identified in liver microsomes of mouse, rat, dog, monkey and human. Dog is mostly similar to human regarding in vitro metabolism. Demethylation, hydroxylation and sequential glucuronidation are the major in vivo metabolic reactions. Direct urinary and biliary excretion of HMPL-013 is negligible. Metabolizing to M1 (demethylation), sequentially glucuronidating, followed by biliary excretion, and to a less extent, by urinary excretion, are important elimination pathways for HMPL-013 in rats. HMPL-013 has low risk of drug-drug interaction. It is predicted to have favorable human PK properties and low efficacious dose. CONCLUSION: HMPL-013 demonstrates good preclinical PK and enables successful human PK and dose projection. It is valuable for further clinical development.