Validation of a clinically relevant humanized mouse model for the safety assessment of 4-1BB agonists utomilumab and urelumab

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Background: Immunotherapy is proven to be powerful and effective in treating cancer. One of the strategies for the therapy is to boost a patient’s immune system by stimulating tumor necrosis factor receptors via the activation of 4-1BB (CD137) costimulatory molecule. Urelumab was the first 4-1BB agonist investigated in clinical trials and showed clinical promise but doses were limited by severe liver toxicity. Preclinical assessment of toxicity failed to predict the clinical safety outcome. Methods: To address the critical needs of in vivo evaluation of toxicity in a preclinical setting, we have developed an animal model using PBMC humanized mice to assess the safety of immunotherapy. In this model, agents targeting human immune system including monoclonal and bispecific antibodies can induce an acute response of cytokine release within hours of treatment and with some therapies a systemic response can manifest in tissue damage and lethality of mice days later. Results: The potential clinical relevance of the PBMC humanized mouse model was demonstrated using 4-1BB agonists urelumab and utomilumab. The antibody-treated PBMC humanized mice were evaluated daily for clinical score and assessed for clinical chemistry and liver histopathology at study terminus. Animals dosed with urelumab at 10 mg/kg exhibited body weight loss and underwent early euthanasia, while animals dosed with utomilumab survived to scheduled euthanasia with minimum body weight loss. Urelumab showed marked liver toxicity relative to utomilumab and controls with more necrosis in the tissue and higher mean ALT, AST and GLDH activities, and the tolerability of urelumab was increased by lowering the dose to 1 mg/kg. The differences captured by the humanized mouse model presented a safety profile similar to the findings about urelumab and utomilumab from the clinical trials. Utomilumab was well tolerated at the dose that caused severe toxicity for urelumab in patients, and the toxicity of urelumab could be reduced by lowering the dose. Conclusions: Our data suggest that the PBMC humanized mouse model could identify human 4-1BB agonists that caused potentially severe liver toxicity. Preclinical safety assessment using humanized mouse models as used for these studies could be an important step in the course of the development of novel immunotherapy for the safety of patients as well as mitigating drug development cost.

Microphysiological systems in early stage drug development: Perspectives on current applications and future impact

Microphysiological systems (MPS) are making advances to provide more standardized and predictive physiologically relevant responses to test articles in living tissues and organ systems. The excitement surrounding the potential of MPS to better predict human responses to medicines and improving clinical translation is overshadowed by their relatively slow adoption by the pharmaceutical industry and regulators. Collaboration between multiorganizational consortia and regulators is necessary to build an understanding of the strengths and limitations of MPS models and closing the current gaps. Here, we review some of the advances in MPS research, focusing on liver, intestine, vascular system, kidney and lung and present examples highlighting the context of use for these systems. For MPS to gain a foothold in drug development, they must have added value over existing approaches. Ideally, the application of MPS will augment in vivo studies and reduce the use of animals via tiered screening with less reliance on exploratory toxicology studies to screen compounds. Because MPS support multiple cell types (e.g. primary or stem-cell derived cells) and organ systems, identifying when MPS are more appropriate than simple 2D in vitro models for understanding physiological responses to test articles is necessary. Once identified, MPS models require qualification for that specific context of use and must be reproducible to allow future validation. Ultimately, the challenges of balancing complexity with reproducibility will inform the promise of advancing the MPS field and are critical for realization of the goal to reduce, refine and replace (3Rs) the use of animals in nonclinical research.

Phenotypic Characterization of Targeted Knockdown of Cyclin-Dependent Kinases in the Intestinal Epithelial Cells

Cyclin-dependent kinases (CDKs) are serine/threonine kinases that regulate cell cycle and have been vigorously pursued as druggable targets for cancer. There are over 20 members of the CDK family. Given their structural similarity, selective inhibition by small molecules has been elusive. In addition, collateral damage to highly proliferative normal cells by CDK inhibitors remains a safety concern. Intestinal epithelial cells are highly proliferative and the impact of individual CDK inhibition on intestinal cell proliferation has not been well studied. Using the rat intestinal epithelial (IEC6) cells as an in vitro model, we found that the selective CDK4/6 inhibitor palbociclib lacked potent anti-proliferative activity in IEC6 relative to the breast cancer cell line MCF7, indicating the absence of intestinal cell reliance on CDK4/6 for cell cycle progression. To further illustrate the role of CDKs in intestinal cells, we chose common targets of CDK inhibitors (CDK 1, 2, 4, 6, and 9) for targeted gene knockdown to evaluate phenotypes. Surprisingly, only CDK1 and CDK9 knockdown demonstrated profound cell death or had moderate growth effects, respectively. CDK2, 4, or 6 knockdowns, whether single, double, or triple combinations, did not have substantial impact. Studies evaluating CDK1 knockdown under various cell seeding densities indicate direct effects on viability independent of proliferation state and imply a potential noncanonical role for CDK1 in intestinal epithelial biology. This research supports the concept that CDK1 and CDK9, but not CDKs 2, 4, or 6, are essential for intestinal cell cycle progression and provides safety confidence for interphase CDK inhibition.

Pharmacologic Properties and Preclinical Activity of Sasanlimab, A High-affinity Engineered Anti-Human PD-1 Antibody

Development of antagonistic mAbs that specifically target the immune checkpoint receptor, programmed cell death protein-1 (PD-1), is of great interest for cancer immunotherapy. Here, we report the biophysical characteristics and nonclinical antagonistic activities of sasanlimab (PF-06801591), a humanized anti-PD-1 antibody of IgG4 isotype. We show that sasanlimab binds selectively and with similar high potency to human and cynomolgus monkey PD-1 receptor and blocks its interaction with PD-L1 and PD-L2, with no detectable Fc-dependent effector function. The binding of sasanlimab to human and cynomolgus PD-1 is associated with the formation of a stable complex, which is likely to be the main driver of this high-affinity interaction. In vitro, sasanlimab significantly augmented T-cell proliferation and cytokine production in mixed lymphocyte reaction and superantigen stimulation assays. In vivo, sasanlimab accelerated the incidence of GvHD by enhancing T-cell proliferation and cytokine secretion in a xenogeneic model of acute GvHD and halted the growth of MC-38 colon adenocarcinoma tumors in human PD-1 knock-in mice. Pharmacokinetic and toxicokinetic findings from cynomolgus monkey showed that sasanlimab was active and well-tolerated. Taken together, the data presented here support the clinical development of sasanlimab for the treatment of patients with advanced cancers as a single agent or in combination with other immunotherapies.

Abstract 99: Phenotypic characterization of knockdown of CDKs in the intestinal epithelial cells

Cyclin-dependent kinases (CDKs) are serine/threonine kinases that bind to cyclins and together act as regulators of cell cycle progression. CDK inhibitors have various therapeutic potentials including cancer (e.g. CDK4/6 inhibitors). Intestinal epithelial cells are highly proliferative; however, the impact of individual CDK inhibition on intestinal cell proliferation has not been well studied. The IEC6 cell line, a non-transformed rat small intestinal epithelial cell line with characteristics of crypt epithelial cells, was utilized in the current study to understand the role of CDKs in the proliferation and survival of intestinal cells. In the initial experiment CDK4/6 inhibitor palbociclib treatment demonstrated a lack of potent toxicity in the IEC6 in comparison with MCF7 (breast cancer cell line), indicating the absence of intestinal cell reliance on CDK4 or CDK6 for cell cycle progression. To further illustrate the role of CDKs in intestinal cells, targeted gene knockdown experiments using CDK1, 2, 4, and 6 siRNA and lipofectamine-mediated transfection were conducted. Surprisingly, only CDK1 knockdown causes profound cell death. CDK2, 4, or 6 knockdowns, whether single, double or triple combinations, did not have significant impact on IEC6 cells, as measured by multiple endpoints including impedance, ATP viability, and caspase activity. To further understand the role of CDK1 in cell cycle, various seeding densities of IEC6 cells were used with CDK1 siRNA. Although the impact of CDK1 knockdown on IEC6 cells decreased at the initial proliferation phase with the higher seeding density, there was still a decrease of viability observed at the later time point (when cells reached proliferation plateau), indicating a non-canonical role of CDK1 that is not related to cell cycle. This research supports the concept that CDK1, but not CDKs 2, 4, or 6, is essential for intestinal cell cycle progression and explains the lack of GI toxicity observed with palbociclib.

Citation Format: Shuyan Lu, Wenyue Hu, Tae Sung, Brad Hirakawa, Marina Amaro, Bart Jessen. Phenotypic characterization of knockdown of CDKs in the intestinal epithelial cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 99.

Validation of the Hygicult® E Dipslides Method in Surface Hygiene Control: A Nordic Collaborative Study

A collaborative study with Enterobacteriaceae was conducted to validate Hygicult® E dipslides by comparison with violet red bile glucose agar (VRBGA) contact plates and swabbing, using stainless steel surfaces artificially contaminated with microbes at various levels. Twelve laboratories participated in the validation procedure. The total number of collaborative samples was 108. The microbial level in each sample was assessed in triplicate by using the 3 above-mentioned methods. No Enterobacteriaceae were used at the low inoculation level. At the middle inoculation level, the percentages detached from the test surfaces were 16.6 with the Hygicult E method, 15.3 with the contact plate method, and 14.6 with swabbing; at the high innoculation level, the percentages were 14.5, 15.8, and 9.8, respectively. The percentage of acceptable results after the removal of outliers was 97.2. Repeatability relative standard deviations ranged from 33.4 to 44.9%; reproducibility relative standard deviations ranged from 45.2 to 77.1%. The Hygicult E dipslide, VRBGA contact plate, and swabbing methods gave similar results at all 3 microbial levels tested: <1.0 colony-forming units (CFU)/cm2 at the low level, 1.2–1.3 CFU/cm2 at the middle level (theoretical yield 8.0 CFU/cm2), and 1.2–2.0 CFU/cm2 at the high level (theoretical yield 12.5 CFU/cm2).

Validation of the Microbiological Methods Hygicult Dipslide, Contact Plate, and Swabbing in Surface Hygiene Control: A Nordic Collaborative Study

A collaborative study on total aerobic bacterial count was conducted to validate the Hygicult® TPC dipslide against contact plates and swabbing, using stainless-steel surfaces artificially contaminated with different microbes at various levels. Twelve laboratories took part in the validation procedure. The total number of collaborative samples was 108. The microbial level in each sample was assessed in triplicate using the 3 above-mentioned methods under 3 different incubation conditions (at 25 ± 1°C for 48 and 72 h and at 30 ± 1°C for 48 h). Surface sampling methods detached 25–30% at the lowest (theoretical yield, 1.4 cfu/cm2), 18–20% at the middle (theoretical yield, 10.7 cfu/cm2), and 16–21% at the highest (theoretical yield, 43.6 cfu/cm2) levels of microbes from the test surfaces. The percentage of acceptable results after removing outliers was 89%. Repeatability standard deviations ranged from 27.2 to 74.6% and reproducibility standard deviations ranged from 42.1 to 97.5%. There were no significant differences between results obtained at different incubation temperatures (25 and 30°C) or incubation times (48 and 72 h) for all 3 methods. The Hygicult TPC dipslide, contact plate, and swabbing methods gave similar results at all 3 microbial levels tested: 0.35–0.43 cfu/cm2 at the lowest level, 1.9–2.2 cfu/cm2 at the middle level, and 7.1–9.1 cfu/cm2 at the highest level.

Abstract P6-20-06: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Dann S, Chionis J, Eisele K, Zhang Q, Liu C, Yuan J, Miller N, Murray B, Xu M, Solowiej J, Wei P, Weinrich S, Sutton S, Behenna D, Ninkovic S, Hoffman R, Freeman-Cook K, Jessen B, Huser N, Zhang C, Visswanathan R, Boras B, VanArsdale T, White MA. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-20-06.

Validation of Cross-Species Reactivity of the VEGF-A/PDGFRβ Bifunctional Antibody PF-06653157

PURPOSE

PF-06653157 is a bifunctional antagonist monoclonal antibody (mAb) that targets human VEGF-A ligand and PDGF-Rβ. With the advent of PF-06653157 as an angiogenesis inhibitor and potential treatment for angiogenesis deregulation diseases, a relevant toxicology species is needed for toxicity and efficacy studies. Investigative studies were conducted to validate the mAb dual antagonist properties in a human system and determine its cross-reactive pharmacology in nonhuman cells.

METHODS

Sequence alignment was used to determine percent sequence identity of VEGF and PDGF receptors and ligands; qualitative reverse transcription polymerase chain reaction (qRT-PCR) was used to determine the presence of PDGF-Rβ on cells of interest. The functional activity of PF-06653157 antibody was assessed in human, dog, porcine, rabbit, rat, mouse, and cynomolgus monkey cells treated with VEGF and PDGF ligands through cell proliferation assays and western blot analysis of AKT and p44/p42 (ERK1/2) protein phosphorylation and enzyme-linked immunosorbent assay.

RESULTS

PF-06653157 attenuated phosphorylation of AKT and p44/p42 proteins in human and cynomolgus monkey cells. The antibody did not attenuate AKT nor p44/p42 phosphorylation in any other species tested. PDGFR signaling could not be activated with human PDGF ligand in the porcine cells, so PF-06653157 activity in porcine remains inconclusive.

CONCLUSION

The PF-06653157 mAb cross-reacts with cynomolgus monkey cells in a similar manner to human cells. Therefore, cynomolgus monkeys are considered the appropriate species for efficacy and regulatory toxicology studies in PF-06653157 development.

Increase in thyroid follicular cell tumors in nelfinavir-treated rats observed in a 2-year carcinogenicity study is consistent with a rat-specific mechanism of thyroid neoplasia

The carcinogenic potential of nelfinavir mesylate (nelfinavir) was evaluated in a 2-year oral (gavage) study on Sprague-Dawley rats at dose levels of 0 (control), 0 (vehicle control), 100, 300 and 1000 mg/kg per day. At the end of the treatment, increased incidences of thyroid follicular cell hyperplasia and neoplasms were observed at 300 (males) and 1000 mg/kg per day (both sexes). There were no other treatment-related effects and no tumors at other sites. Results from previous studies indicated a number of effects in the liver and thyroid, as well as metabolic profiles that suggested nelfinavir might cause thyroid hyperplasia/neoplasia secondary to hormone imbalance by altering thyroid hormone disposition. To investigate this hypothesis, the effects of nelfinavir on gene expression in rat hepatocytes and liver slices (in vitro), thyroxine plasma clearance, and thyroid gland function were evaluated. Compared to controls, gene expression analyses demonstrated an increased expression of glucuronyltransferase (UDPGT) and CYP450 3A1 in nelfinavir-treated rat hepatocytes and liver slices. In rats treated with nelfinavir (1000 mg/kg per day) for 4 weeks, liver weights and centrilobular hepatocellular hypertrophy were increased and minimal to mild diffuse thyroid follicular cell hypertrophy and follicular cell hyperplasia were evident in the thyroid gland. Thyroid-stimulating hormone (TSH) levels were significantly increased (three-fold), while tri-iodothyronine (T3)/tetraiodothyronine (T4) and reverse T3(rT3) levels were unchanged, indicating that a compensated state to maintain homeostasis of T3/T4 had been achieved. Plasma 125I-thyroxine clearance was increased and the plasma thyroxine AUC0 48 was decreased (24%) compared to control. In conclusion, these data indicate that thyroid neoplasms observed in the nelfinavir-treated rats were secondary to thyroid hormone imbalance. Increased thyroxine clearance contributes to the effects of nelfinavir on thyroid gland function and is probably a result of UDPGT induction that leads to elevated TSH levels in the rat and eventual thyroid neoplasia. These results are consistent with a well-recognized rat-specific mechanism for thyroid neoplasms.

Contribution of membrane trafficking perturbation to retinal toxicity

The retina is a highly structured tissue that is formed by layers containing 7 different cell types. The photoreceptor cell is a specialized type of neuron in the retina that is capable of absorbing and converting light into electrophysiological signals. There is a constant renewal process for photoreceptors consisting of intermittent shedding of the distal tips of the photosensitive outer segment and subsequent phagocytosis (uptake, degradation and recycling) by retinal pigmented epithelial (RPE) cells. This rebuilding process is essential for vision and the survival of photoreceptors and RPE cells. Drugs with a basic moiety have the potential to accumulate in the lysosome and impair its functions including the phagocytosis process, which could hinder clearance of outer segments and ultimately induce retinopathy. To determine the prevalence of this cellular mechanism in retinal toxicity, a collection of proprietary compounds associated with retinal toxicity were subjected to a battery of in vitro tests using the human adult retinal pigmented epithelium cell line, ARPE-19. The tests included a phagocytosis assay, and lysosomal and autophagosomal staining. The compounds that induced retinopathy clustered in the basic and lipophilic region, which drives lysosomal sequestration. This accumulation coincided with phagocytosis inhibition and an increase in autophagosome staining, suggesting a blockage of the membrane trafficking process. A correlation between the physicochemical properties and in vitro lysosomal pathway effects was established. These data reveal the importance of physicochemical properties of compounds and lysosome accumulation as a potential mechanism for drug-induced retinopathy and demonstrate the usefulness of in vitro screening in predicting this liability.

Combination of 4-1BB agonist and PD-1 antagonist promotes antitumor effector/memory CD8 T cells in a poorly immunogenic tumor model

Immunotherapies targeting the programmed death 1 (PD-1) coinhibitory receptor have shown great promise for a subset of patients with cancer. However, robust and safe combination therapies are still needed to bring the benefit of cancer immunotherapy to broader patient populations. To search for an optimal strategy of combinatorial immunotherapy, we have compared the antitumor activity of the anti-4-1BB/anti-PD-1 combination with that of the anti-PD-1/anti-LAG-3 combination in the poorly immunogenic B16F10 melanoma model. Pronounced tumor inhibition occurred only in animals receiving anti-PD-1 and anti-4-1BB concomitantly, while combining anti-PD-1 with anti-LAG-3 led to a modest degree of tumor suppression. The activity of the anti-4-1BB/anti-PD-1 combination was dependent on IFNγ and CD8(+) T cells. Both 4-1BB and PD-1 proteins were elevated on the surface of CD8(+) T cells by anti-4-1BB/anti-PD-1 cotreatment. In the tumor microenvironment, an effective antitumor immune response was induced as indicated by the increased CD8(+)/Treg ratio and the enrichment of genes such as Cd3e, Cd8a, Ifng, and Eomes. In the spleen, the combination treatment shaped the immune system to an effector/memory phenotype and increased the overall activity of tumor-specific CD8(+) CTLs, reflecting a long-lasting systemic antitumor response. Furthermore, combination treatment in C57BL/6 mice showed no additional safety signals, and only minimally increased severity of the known toxicity relative to 4-1BB agonist alone. Therefore, in the absence of any cancer vaccine, anti-4-1BB/anti-PD-1 combination therapy is sufficient to elicit a robust antitumor effector/memory T-cell response in an aggressive tumor model and is therefore a candidate for combination trials in patients.

The contribution of lysosomotropism to autophagy perturbation

Autophagy refers to the catabolic process in eukaryotic cells that delivers cytoplasmic material to lysosomes for degradation. This highly conserved process is involved in the clearance of long-lived proteins and damaged organelles. Consequently, autophagy is important in providing nutrients to maintain cellular function under starvation, maintaining cellular homeostasis, and promoting cell survival under certain conditions. Several pathways, including mTOR, have been shown to regulate autophagy. However, the impact of lysosomal function impairment on the autophagy process has not been fully explored. Basic lipophilic compounds can accumulate in lysosomes via pH partitioning leading to perturbation of lysosomal function. Our hypothesis is that these types of compounds can disturb the autophagy process. Eleven drugs previously shown to accumulate in lysosomes were selected and evaluated for their effects on cytotoxicity and autophagy using ATP depletion and LC3 assessment, respectively. All eleven drugs induced increased staining of endogenous LC3 and exogenous GFP-LC3, even at non toxic dose levels. In addition, an increase in the abundance of SQSTM1/p62 by all tested compounds denotes that the increase in LC3 is due to autophagy perturbation rather than enhancement. Furthermore, the gene expression profile resulting from in vitro treatment with these drugs revealed the suppression of plentiful long-lived proteins, including structural cytoskeletal and associated proteins, and extracellular matrix proteins. This finding indicates a retardation of protein turnover which further supports the notion of autophagy inhibition. Interestingly, upregulation of genes containing antioxidant response elements, e.g. glutathione S transferase and NAD(P)H dehydrogenase quinone 1 was observed, suggesting activation of Nrf2 transcription factor. These gene expression changes could be related to an increase in SQSTM1/p62 resulting from autophagy deficiency. In summary, our data indicate that lysosomal accumulation due to the basic lipophilic nature of xenobiotics could be a general mechanism contributing to the perturbation of the autophagy process.

A tyrosine kinase inhibitor-induced myocardial degeneration in rats through off-target phosphodiesterase inhibition

PF-04254644 is a selective kinase inhibitor of mesenchymal epithelial transition factor/hepatocyte growth factor receptor with known off-target inhibitory activity against the phosphodiesterase (PDE) family. Rats given repeated oral doses of PF-04254644 developed a mild to moderate myocardial degeneration accompanied by sustained increase in heart rate and contractility. Investigative studies were conducted to delineate the mechanisms of toxicity. Microarray analysis of Sprague-Dawley rat hearts in a 6 day repeat dose study with PF-04254644 or milrinone, a selective PDE3 inhibitor, revealed similar perturbation of the cyclic adenosine monophosphate (c-AMP) pathway. PDE inhibition and activation of c-AMP were further substantiated using PDE3B immunofluorescence staining and through a c-AMP response element reporter gene assay. The intracellular calcium and oxidative stress signaling pathways were more perturbed by treatment with PF-04254644 than milrinone. The rat cardiomyocytes calcium assay found a dose-dependent increase in intracellular calcium with PF-04254644 treatment. These data suggest that cardiotoxicity of PF-04254644 was probably due to activation of c-AMP signaling, and possibly subsequent disruption of intracellular calcium and oxidative stress signaling pathways. The greater response with PF-04254644 as compared with milrinone in gene expression and micro- and ultrastructural changes is probably due to the broader panel of PDEs inhibition.

Off-target immune cell toxicity caused by AG-012986, a pan-CDK inhibitor, is associated with inhibition of p38 MAPK phosphorylation

AG-012986 is a pan-CDK (cyclin-dependent kinase) inhibitor that has in vitro and in vivo antitumor properties but was stopped in development due in part to rapid bone-marrow-independent white blood cell toxicity in preclinical studies and the potential for acute and delayed immunosuppression in humans. Because peripheral lymphocytes are largely nonproliferating, it was hypothesized the toxicity of AG-012986 was due to an off-target mechanism and not driven by the intended pharmacology. We show the toxicity mechanism in primary human immune cells is caspase driven. T-cells treated with AG-012986 and acutely stimulated through the T-cell receptor exhibited decreased toxicity while still maintaining cell division inhibition. This indicated that the pharmacology of AG-012986 functioned as expected but the toxicity had now been decoupled through activation. Induced phosphorylation of p38 and IL-2 production was impaired with AG-012986. Thus, AG-012986 could cause apoptosis of T-cells by targeting upstream kinases in the p38 Mitogen-activated protein kinase (MAPK) pathway and impairing cellular survival.

Evaluation of the effects of a VEGFR-2 inhibitor compound on alanine aminotransferase gene expression and enzymatic activity in the rat liver

BACKGROUND

Traditional assessment of drug-induced hepatotoxicity includes morphological examination of the liver and evaluation of liver enzyme activity in serum. The objective of the study was to determine the origin of drug-related elevation in serum alanine aminotransferase (ALT) activity in the absence of morphologic changes in the liver by utilizing molecular and immunohistochemical techniques.

METHODS

Sixteen female Sprague-Dawley rats were divided into 2 groups (control and treated, n = 4 per group) and treated rats were dosed orally twice daily (400 mg/kg/day) for 7 days with a VEGFR-2 compound (AG28262), which in a previous study caused ALT elevation without morphological changes. Serum of both treated and control animals were evaluated on day 3 of treatment and at day 8. Three separate liver lobes (caudate, right medial, and left lateral) were examined for determination of ALT tissue activity, ALT gene expression and morphological changes.

RESULTS

ALT activity was significantly (p < 0.01) elevated on day 3 and further increased on day 8. Histologic changes or increase in TUNEL and caspase3 positive cells were not observed in the liver lobes examined. ALT gene expression in the caudate lobe was significantly up-regulated by 63%. ALT expression in the left lateral lobe was not significantly affected. Statistically significant increased liver ALT enzymatic activity occurred in the caudate (96%) and right medial (41%) lobes but not in the left lateral lobe.

CONCLUSIONS

AG28262, a VEFG-r2 inhibitor, causes an increase in serum ALT, due in part to both gene up-regulation. Differences between liver lobes may be attributable to differential distribution of blood from portal circulation. Incorporation of molecular data, such as gene and protein expression, and sampling multiple liver lobes may shed mechanistic insight to the evaluation of hepatotoxicity.

Case reports: hyperbaric oxygen therapy for the treatment of cerebral air embolism

Cerebral air embolism is one of the most deleterious disorders that may affect divers, but it is also a possible complication of surgeries and medical procedures. We report our experience with iatrogenic cerebral air embolism and hyperbaric oxygen treatment.

Lack of evidence for a link between latanoprost use and malignant melanoma: an analysis of safety databases and a review of the literature

AIM

To determine if there is an association between the use of latanoprost ophthalmic solution and malignant melanoma and to assess the evidence of a plausible biological mechanism.

METHODS

Two safety databases were reviewed: one representing all latanoprost (n=24) and fixed-combination latanoprost/timolol (n=16) clinical trials conducted from November 1992 through November 2007 and a global safety database of all spontaneous non-trial-related clinical reports spanning 13 and 9 years for latanoprost and for latanoprost/timolol, respectively. A systematic PubMed search for studies evaluating potential mechanisms was conducted.

RESULTS

Amongst 12,880 latanoprost-treated subjects in clinical trials, no reported cases of ocular melanoma and three cases of cutaneous melanoma were identified. Of 19,940 cases recorded in the global safety database, 22 reports of ocular/cutaneous neoplasms were identified. Of these neoplasms, 11 were ocular and six were cutaneous melanomas. Possible association with latanoprost use could not be excluded in three ocular and one periorbital report. In vitro and in vivo data were consistent with a mechanism whereby the increased iris pigmentation results from stimulation of melanin synthesis by induction of tyrosinase transcription without increasing mitotic activity.

CONCLUSION

There is no evidence at present that establishes a link between latanoprost use and either ocular or cutaneous melanoma.

Abstract A10: Off-target toxicity in white blood cells by AG-012986, a pan-CDK inhibitor, is mediated through inhibition of p38 MAPK signaling pathway

Cyclin-dependent kinases (CDKs) have been an attractive target for cancer research because these kinases are predominantly active during cell division. AG-012986 is a small molecule pan-CDK inhibitor that has in vitro and in vivo antitumor properties. This compound was stopped during development due in part to rapid bone-marrow independent white blood cell toxicity in non-human primate and rodent species, and the potential for acute and delayed immunosuppression in humans. Because peripheral leukocytes are largely nonproliferating cells, it was hypothesized that the effects of AG-012986 was due to an off-target mechanism and not driven by the intended pharmacology. Using primary human peripheral blood mononuclear cells (PBMCs) and T-cells, we show that AG-012986 has a toxicity profile with greater specificity and more rapid cell death compared to the prototypical ATP-competitive kinase inhibitor, staurosporine. The cell toxicity mechanism was caspase-dependent and contained the hallmarks of apoptosis as indicated by cells staining double positive for propidium iodide and annexin-V. PBMCs or T-cells treated with AG-012986 and acutely stimulated either pharmacologically or through the T-cell receptor (TCR), exhibited decreased cellular toxicity compared to non-stimulated control cells. Interestingly under activating conditions with the pan-CDK compound, T-cells did not undergo significant cell division, as measured by BrdU incorporation, and were also rescued from apoptosis. This indicates that the pharmacology of AG-012986 was functioning as expected but that the toxicity due to its off-target effect had now been decoupled through cellular activation. Investigating the downstream signaling network showed that phosphorylation of p38 MAP kinase was impaired in the presence of AG-012986. Thus we hypothesize that AG-012986 may target the upstream kinase MKK3 and/or MKK6 for inhibition under basal conditions, leading to cell death in T cells and perhaps other white blood cells.

Citation Information: Clin Cancer Res 2010;16(14 Suppl):A10.

Corneal neovascularization and ocular irritancy responses in dogs following topical ocular administration of an EP4-prostaglandin E2 agonist

Prostaglandin receptor agonists have intraocular pressure-lowering effects in humans and are of interest in the treatment of glaucoma. The prostanoid receptor agonist PF-04475270 is a potent and selective agonist of the prostaglandin E(2) receptor EP4. This paper characterizes the toxicity associated with topical ocular administration of PF-04475270 in beagles. Dogs were given PF-04475270 topically to the eye on a consecutive daily dosing schedule for one or four weeks followed by a one-or four-week reversal period, respectively. Clinical observations, ophthalmic, and laboratory parameters were recorded. Necropsies were conducted at the end of the dosing and recovery phases, and histologic examinations performed. Corneal neovascularization that was considered adverse was observed at doses of >or=1.0 microg/eye and was not reversed by the end of the recovery phase. Dogs dosed with >or=0.25 microg/eye developed a dose-related conjunctival hyperemia that persisted throughout the reversal period. Corneal neovascular cells stained positive with EP4 and the endothelial biomarker Factor VIII-vWF. Other histopathology findings observed at doses of >or=1.0 microg included single-cell necrosis and neutrophils in the cornea, inflammatory cell infiltrates in the iris/ciliary body, and iridal endothelial cell hypertrophy. A resolving acute to subacute inflammation in the iris/ciliary body was observed after the four-week recovery period.

Antisense inhibition of 11betahydroxysteroid dehydrogenase type 1 improves diabetes in a novel cortisone-induced diabetic KK mouse model

The inhibition of 11betahydroxysteroid dehydrogenase 1 (11betaHSD1), an enzyme that catalyzes the conversion of inactive cortisone to active cortisol, is an attractive target to treat diabetes by suppressing hepatic gluconeogenesis. To test this hypothesis, we developed a novel glucocorticoid-induced diabetic KK mouse model and used 11betaHSD1 antisense oligonucleotide (ASO) as an inhibitory tool. KK mice were treated with 25 or 50mg/kg/day of 11betaHSD1 ASO for 28 days. On day 25, cortisone pellets were surgically implanted to induce diabetes. In the ASO-treated mice, plasma blood glucose levels were significantly reduced by up to 54%. In parallel, cortisol and other diabetes endpoints were also significantly reduced. Hepatic 11betaHSD1 mRNA was suppressed by up to 84% with a concomitant respective decrease of up to 49% in the expression of PEPCK. The results suggest that inhibition of 11betaHSD1 activity reduces the availability of cortisol to activate the glucocorticoid receptor, down regulates gluconeogenesis and thus reduces plasma glucose levels in cortisone-induced diabetic KK mice.

Assessment of the human risk associated with use of pork with possible presence of Salmonella typhimurium DT104 for dry-cured sausages

We examined whether pork with suspected content of Salmonella Typhimurium DT104 (DT104) could be used for production of dry-cured sausages without jeopardizing consumer safety. The results of the risk assessment showed, that if Salmonella is present in raw pork, it is usually in low numbers. Additionally, during processing, an eventual presence of Salmonella will be reduced with at least two log units. The simulations showed that only 1-2 DT104 would be present in dry-cured sausages made by Danish pork, and this extremely seldom. Likewise, up to 4 DT104 would be present in dry-cured sausages made by foreign pork. It is not clear whether these low numbers of DT104 are capable of producing disease at all. However, if higher numbers are present, disease might occur. Therefore, we set up a monitoring and managing program, including a list with demands to processing in order to achieve minimum two-log reduction of any DT104 bacteria. The suggested scheme implies a far better and more systematic monitoring than the current system, ensuring the consumer a higher degree of food safety.

[Treatment of carbon monoxide poisoning. Background and guidelines for oxygen therapy]

Treatment of carbon monoxide (CO) poisoning is still controversial. Standard treatment is pure oxygen either by means of a nasal catheter or oral-facial mask (normobaric oxygen treatment). Since 1960, hyperbaric oxygen (HBO) therapy has been applied in various centres, i.e. treatment in hyperbaric chambers with 100% O2 at 2-2.8 bars absolute pressure. Physically dissolved oxygen at this pressure is sufficient to maintain normal life functions at rest. HBO causes fast reoxygenation of tissues and accelerates the elimination of CO. In this paper, two cases treated with hyperbaric oxygen are reported. Aetiology, pathogenesis and possible sequelae of CO poisoning are reviewed. It is recommended, that all CO-victims, who have been or are unconscious at admission to the emergency ward, should be treated with HBO. In spite of there being comprehensive clinical literature concerning treatment of CO poisoning, there is still a great need for clinically controlled studies.

Motion sickness susceptibility in student navigators

Identification of individuals highly susceptible to motion sickness could be of significant benefit in managing flying personnel in training. Several studies in the past four decades with this end have been primarily aimed at pilot trainees. The following study is a prospective evaluation of airsickness in Air Force navigation students. Motion Sickness Questionnaires and Minnesota Multiphasic Personality Inventories were given to the students at the beginning of navigator training. Airsickness was assessed by means of questionnaires and evaluation by a flight surgeon. Motion sickness among navigation trainees was found to be quite common. However, prediction of susceptible individuals by methods used was not reliable. Further investigation of airsickness susceptibility in navigation students by means of physiologic techniques is suggested.

A control, double-blind comparison of mepivacaine injection versus saline injection for myofascial pain

In a double-blind study 28 patients with acute, localised muscle pain received four local injections of mepivacaine 0.5%, and 25 patients with the same type of pain received local injections of an equivalent volume of physiological saline. The group receiving saline tended to have more relief of pain, especially after the first injection. The results thus show that pain relief is not due merely to the local anaesthetic. The study therefore raises questions about the mechanism by which local injections into muscle relieves pain, since there is the possibility that a similar effect might also be achieved by merely inserting a needle into the trigger point. Physiological saline is considered to be a more appropriate fluid for injection therapy than local anaesthetics since it is less likely to produce side-effects.

Radioimmunoassay, enzyme immunoassay, spectrophotometry, and gas-liquid chromatography compared for determination of phenobarbital and diphenylhydantoin

Sera from epileptic patients were assayed for phenobarbital and diphenylhydantoin by four different analytical procedures. Quantitative results obtained by radioimmunoassay (I) and enzyme immunoassay (II) were compared to each other and to the results obtained on aliquots of the same sample by gas-liquid chromatography (III) and ultraviolet spectrophotometry (IV). For phenobarbital the correlation coefficients were I vs. II, 0.909; I vs. III, 0.947; II vs. III, 0.917; I vs. IV, 0.950; II vs. IV, 0.953. For diphenylhydantoin the correlation coefficients were I vs. II, 0.953; I vs. III, 0.951; II vs. III, 0.957; I vs. IV, 0.862; II vs. IV, 0.898. The immunoassays can be substituted for liquid chromatography or ultraviolet spectrophotometry without changing the resulting clinical interpretations.

Radioimmunoassay, enzyme immunoassay, spectrophotometry, and gas-liquid chromatography compared for determination of phenobarbital and diphenylhydantoin

Sera from epileptic patients were assayed for phenobarbital and diphenylhydantoin by four different analytical procedures. Quantitative results obtained by radioimmunoassay (I) and enzyme immunoassay (II) were compared to each other and to the results obtained on aliquots of the same sample by gas-liquid chromatography (III) and ultraviolet spectrophotometry (IV). For phenobarbital the correlation coefficients were I vs. II, 0.909; I vs. III, 0.947; II vs. III, 0.917; I vs. IV, 0.950; II vs. IV, 0.953. For diphenylhydantoin the correlation coefficients were I vs. II, 0.953; I vs. III, 0.951; II vs. III, 0.957; I vs. IV, 0.862; II vs. IV, 0.898. The immunoassays can be substituted for liquid chromatography or ultraviolet spectrophotometry without changing the resulting clinical interpretations.

Radioimmunoassay, enzyme immunoassay, spectrophotometry, and gas-liquid chromatography compared for determination of phenobarbital and diphenylhydantoin

Sera from epileptic patients were assayed for phenobarbital and diphenylhydantoin by four different analytical procedures. Quantitative results obtained by radioimmunoassay (I) and enzyme immunoassay (II) were compared to each other and to the results obtained on aliquots of the same sample by gas-liquid chromatography (III) and ultraviolet spectrophotometry (IV). For phenobarbital the correlation coefficients were I vs. II, 0.909; I vs. III, 0.947; II vs. III, 0.917; I vs. IV, 0.950; II vs. IV, 0.953. For diphenylhydantoin the correlation coefficients were I vs. II, 0.953; I vs. III, 0.951; II vs. III, 0.957; I vs. IV, 0.862; II vs. IV, 0.898. The immunoassays can be substituted for liquid chromatography or ultraviolet spectrophotometry without changing the resulting clinical interpretations.