Noninvasive Blood-Based Cancer Detection in Veterinary Medicine.

The past decade has seen incredible advances in blood-based cancer detection in people and in dogs - yet this represents only a glimpse of the benefits these tests can provide to patients. The clinical uses of this technology range from screening asymptomatic individuals for early detection to use as an aid in diagnosis when cancer is suspected, to cancer monitoring both during and after treatment. This article summarizes the benefits of early cancer detection and examines use cases and methods of blood-based cancer detection in dogs, including quantitative, qualitative, and alternative approaches.

Monitoring plasma nucleosome concentrations to measure disease response and progression in dogs with hematopoietic malignancies.

BACKGROUND: Hematopoietic malignancies are extremely common in pet dogs and represent nearly 30% of the malignancies diagnosed in this population each year. Clinicians commonly use existing tools such as physical exam findings, radiographs, ultrasound and baseline blood work to monitor these patients for treatment response and remission. Circulating biomarkers, such as prostate specific antigen or carcinoembryonic antigen, can be useful tools for monitoring treatment response and remission status in human cancer patients. To date, there has a been a lack of useful circulating biomarkers available to veterinary oncology patients. METHODS: Circulating plasma nucleosome concentrations were evaluated at diagnosis, throughout treatment and during remission monitoring for 40 dogs with lymphoma, acute myelogenous leukemia and multiple myeloma. Additionally, C-reactive protein and thymidine kinase-1 levels were recorded. RESULTS: Plasma nucleosome concentrations were significantly higher at diagnosis and progressive disease than they were when dogs were in remission. All but two dogs had plasma nucleosome concentrations that returned to the low range during treatment. These two dogs had the shortest progression free and overall survival times. Dogs with the highest plasma nucleosome concentrations had a significantly shorter first progression free survival than dogs with lower plasma nucleosome concentrations at diagnosis. Plasma nucleosome concentrations correlated better with disease response and progression than either thymidine kinase or C reactive protein. CONCLUSIONS: Plasma nucleosome concentrations can be a useful tool for treatment monitoring and disease progression in dogs with hematopoietic malignancies.

Esomeprazole induces structural changes and apoptosis and alters function of in vitro canine neoplastic mast cells.

Histamine-2 receptor antagonists such as famotidine and proton pump inhibitors such as esomeprazole are commonly used in canine MCT disease, but direct effects on dog MCs have not been evaluated. Omeprazole is a proton pump inhibitor which has been demonstrated to cause structural and functional changes to in vitro murine mast cells (MCs). It has not yet been determined if esomeprazole, the commercially available and commonly prescribed S-isomer of omeprazole, has similar effects. Our primary study objective was to evaluate and compare the effects of acid suppressants (esomeprazole and famotidine) on MC ultrastructure, viability, and function in vitro using both healthy and neoplastic MCs. Murine bone marrow derived mast cells (BMMC), human LAD2, and canine C2 and BR cells, were used for these studies, representing a single healthy (i.e., BMMCs) MC model and multiple neoplastic MC models (i.e., LAD2, C2, BR), respectively. The rat basophilic leukemic (RBL-2H3) and canine B cell lymphoma 17-71 cell lines served as granulocytic and agranulocytic control lines for experiments, respectively. The treatment effect of acid suppressants on MC ultrastructure was assessed via both light and transmission electron microscopy. Differences in MC viability was assessed between groups via MTS-based, colorimetric assays and flow cytometry. Degranulation was assessed by quantification of ß-hexosaminidase (i.e., LAD2 and RBL-2H3). Esomeprazole-treated MCs of all lines exhibited dramatic time and concentration-dependent alterations in ultrastructure (i.e., increased vacuolization, compromise of cell membrane), increased apoptosis, and altered degranulation responses in comparison to famotidine and vehicle-treated cells. The canine B cell lymphoma cells consistently exhibited either no significant (i.e., cytotoxicity assays) or greatly diminished treatment responses (i.e., apoptosis) compared to MCs. Esomeprazole, but not famotidine, induces significant cytotoxicity, as well as alterations to cell structure and function to multiple lines of in vitro neoplastic MCs. Continued in vitro work investigating the specific mechanisms by which proton pump inhibitors induce these effects, as well as prospective, in vivo work comparing the treatment effects of acid suppressants on canine MCTs, are warranted.

Anti-tumor effects of cryptotanshinone (C19H20O3) in human osteosarcoma cell lines.

Osteosarcoma is the most prevalent malignant bone tumor and occurs most commonly in the adolescent and young adult population. Despite the recent advances in surgeries and chemotherapy, the overall survival in patients with resectable metastases is around 20%. This challenge in osteosarcoma is often attributed to the drastic differences in the tumorigenic profiles and mutations among patients. With diverse mutations and multiple oncogenes, it is necessary to identify the therapies that can attack various mutations and simultaneously have minor side-effects. In this paper, we constructed the osteosarcoma pathway from literature and modeled it using ordinary differential equations. We then simulated this network for every possible gene mutation and their combinations and ranked different drug combinations based on their efficacy to drive a mutated osteosarcoma network towards cell death. Our theoretical results predict that drug combinations with Cryptotanshinone (C19H20O3), a traditional Chinese herb derivative, have the best overall performance. Specifically, Cryptotanshinone in combination with Temsirolimus inhibit the JAK/STAT, MAPK/ERK, and PI3K/Akt/mTOR pathways and induce cell death in tumor cells. We corroborated our theoretical predictions using wet-lab experiments on SaOS2, 143B, G292, and HU03N1 human osteosarcoma cell lines, thereby demonstrating the potency of Cryptotanshinone in fighting osteosarcoma.

Feasibility and safety of whole lung irradiation in the treatment of canine appendicular osteosarcoma.

Whole lung irradiation (WLI) has been used successfully in humans as an adjuvant treatment for osteosarcoma. The aim of this study is to describe the feasibility and safety of WLI in dogs with appendicular osteosarcoma. Twelve client-owned dogs with appendicular osteosarcoma that had successfully completed amputation and four doses of carboplatin without evidence of gross metastasis were enrolled in this prospective clinical trial. Ten once-daily fractions of 1.75 Gy were administered to the planning target volume encompassing the lungs. Overall, WLI was well tolerated in these patients. No dogs developed symptoms of pneumonitis or pulmonary fibrosis. Haematopoietic toxicity evaluated during radiation therapy was found to be mild. The median disease free interval for WLI treated dogs was not significantly different than the median DFI for a group of historic control dogs (376 days for WLI treated dogs versus 304.5 days for control dogs; p = 0.5461). Although no significant improvement in outcome was observed with this study, WLI appears to be safe in dogs and warrants further investigation to characterize the efficacy and toxicity.

In Silico Modeling of the Induction of Apoptosis by Cryptotanshinone in Osteosarcoma Cell Lines.

Osteosarcoma (OS) is the most common primary malignant bone tumor of both children and pet canines. Its characteristic genomic instability and complexity coupled with the dearth of knowledge about its etiology has made improvement in the current treatment difficult. We use the existing literature about the biological pathways active in OS and combine it with the current research involving natural compounds to identify new targets and design more effective drug therapies. The key components of these pathways are modeled as a Boolean network with multiple inputs and multiple outputs. The combinatorial circuit is employed to theoretically predict the efficacies of various drugs in combination with Cryptotanshinone. We show that the action of the herbal drug, Cryptotanshinone on OS cell lines induces apoptosis by increasing sensitivity to TNF-related apoptosis-inducing ligand (TRAIL) through its multi-pronged action on STAT3, DRP1 and DR5. The Boolean framework is used to detect additional drug intervention points in the pathway that could amplify the action of Cryptotanshinone.

Characterizing circulating nucleosomes in the plasma of dogs with lymphoma.

BACKGROUND: Nucleosomes consist of DNA wrapped around a histone octamer core like beads on a string so that DNA can be condensed as chromatin into chromosomes. Diseases such as cancer or inflammation lead to cell death where chromatin is fragmentated and released as mononucleosomes into the blood. The Nu.Q™ H3.1 assay measures total nucleosome concentration in plasma of humans and has been used to detect and identify cancer even at early stages. The objectives of this study were to determine if nucleosome levels could be used to distinguish between healthy dogs and dogs with various stages of lymphoma (LSA) using the Nu.Q™ H3.1 assay. A total of 126 dogs diagnosed with LSA and 134 healthy controls were recruited for this study. Plasma was collected from each dog and stored in K2-EDTA tubes. The LSA patient samples were recruited from TAMU or purchased from various biobanks. All control cases were recruited from TAMU. RESULTS: Dogs with LSA had an approximately 7-fold increase in their plasma nucleosome concentrations compared to controls (AUC 87.8%). Nucleosome concentrations increased with cancer stage and dogs with B cell lymphomas had significantly higher nucleosome concentrations than dogs with T cell lymphomas. CONCLUSIONS: The Nu.Q™ H3.1 assay was able to reliably detect elevated nucleosome concentrations in the plasma of dogs with LSA. Furthermore, it appears that nucleosomes are useful for differentiating cancer from healthy individuals in canines.

Enhancer reprogramming in PRC2-deficient malignant peripheral nerve sheath tumors induces a targetable de-differentiated state.

Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas that frequently harbor genetic alterations in polycomb repressor complex 2 (PRC2) components-SUZ12 and EED. Here, we show that PRC2 loss confers a dedifferentiated early neural-crest phenotype which is exclusive to PRC2-mutant MPNSTs and not a feature of neurofibromas. Neural crest phenotype in PRC2 mutant MPNSTs was validated via cross-species comparative analysis using spontaneous and transgenic MPNST models. Systematic chromatin state profiling of the MPNST cells showed extensive epigenomic reprogramming or chromatin states associated with PRC2 loss and identified gains of active enhancer states/super-enhancers on early neural crest regulators in PRC2-mutant conditions around genomic loci that harbored repressed/poised states in PRC2-WT MPNST cells. Consistently, inverse correlation between H3K27me3 loss and H3K27Ac gain was noted in MPNSTs. Epigenetic editing experiments established functional roles for enhancer gains on DLX5-a key regulator of neural crest phenotype. Consistently, blockade of enhancer activity by bromodomain inhibitors specifically suppressed this neural crest phenotype and tumor burden in PRC2-mutant PDXs. Together, these findings reveal accumulation of dedifferentiated neural crest like state in PRC2-mutant MPNSTs that can be targeted by enhancer blockade.

Characterizing circulating nucleosomes in the plasma of dogs with hemangiosarcoma.

BACKGROUND: Nucleosomes consist of DNA wrapped around a histone octamer core like thread on a spool to condense DNA as chromatin into chromosomes. Diseases such as cancer or inflammation lead to cell death, chromatin fragmentation and release of nucleosomes into the blood. The Nu.Q™ platform measures circulating nucleosomes in the blood of humans that result from disease and has been used to detect and identify cancer even at early stages. The objectives of this study are to quantify and better characterize nucleosomes in dogs with various stages of hemangiosarcoma (HSA) using this ELISA-based assay. Samples from 77 dogs with a confirmed diagnosis of hemangiosarcoma and 134 healthy controls were utilized for this study. The HSA samples were recruited from the Texas A&M University Small Animal Clinic (TAMU-SAC) or purchased from biobanks. All control samples were recruited from the TAMU-SAC. RESULTS: Dogs with hemangiosarcoma had a 6.6-fold increase in their median plasma nucleosome concentrations compared to controls (AUC 92.9 %). Elevated nucleosome concentrations were seen at all stages of disease and nucleosome concentrations increased with the stage of the disease. CONCLUSIONS: Plasma nucleosome concentrations are a reliable way to differentiate dogs with hemangiosarcoma from healthy dogs. Further testing is underway to better characterize cancer associated HSA circulating nucleosomes and optimize future diagnostics for canine HSA detection.

Adjuvant Sirolimus Does Not Improve Outcome in Pet Dogs Receiving Standard-of-Care Therapy for Appendicular Osteosarcoma: A Prospective, Randomized Trial of 324 Dogs.

PURPOSE: The mTOR pathway has been identified as a key nutrient signaling hub that participates in metastatic progression of high-grade osteosarcoma. Inhibition of mTOR signaling is biologically achievable with sirolimus, and might slow the outgrowth of distant metastases. In this study, pet dogs with appendicular osteosarcoma were leveraged as high-value biologic models for pediatric osteosarcoma, to assess mTOR inhibition as a therapeutic strategy for attenuating metastatic disease progression. PATIENTS AND METHODS: A total of 324 pet dogs diagnosed with treatment-naïve appendicular osteosarcoma were randomized into a two-arm, multicenter, parallel superiority trial whereby dogs received amputation of the affected limb, followed by adjuvant carboplatin chemotherapy ± oral sirolimus therapy. The primary outcome measure was disease-free interval (DFI), as assessed by serial physical and radiologic detection of emergent macroscopic metastases; secondary outcomes included overall 1- and 2-year survival rates, and sirolimus pharmacokinetic variables and their correlative relationship to adverse events and clinical outcomes. RESULTS: There was no significant difference in the median DFI or overall survival between the two arms of this trial; the median DFI and survival for standard-of-care (SOC; defined as amputation and carboplatin therapy) dogs was 180 days [95% confidence interval (CI), 144-237] and 282 days (95% CI, 224-383) and for SOC + sirolimus dogs, it was 204 days (95% CI, 157-217) and 280 days (95% CI, 252-332), respectively. CONCLUSIONS: In a population of pet dogs nongenomically segmented for predicted mTOR inhibition response, sequentially administered adjuvant sirolimus, although well tolerated when added to a backbone of therapy, did not extend DFI or survival in dogs with appendicular osteosarcoma.

Comprehensive live-cell imaging analysis of cryptotanshinone and synergistic drug-screening effects in various human and canine cancer cell lines.

BACKGROUND: Several studies have highlighted both the extreme anticancer effects of Cryptotanshinone (CT), a Stat3 crippling component from Salvia miltiorrhiza, as well as other STAT3 inhibitors to fight cancer. METHODS: Data presented in this experiment incorporates 2 years of in vitro studies applying a comprehensive live-cell drug-screening analysis of human and canine cancer cells exposed to CT at 20 µM concentration, as well as to other drug combinations. As previously observed in other studies, dogs are natural cancer models, given to their similarity in cancer genetics, epidemiology and disease progression compared to humans. RESULTS: Results obtained from several types of human and canine cancer cells exposed to CT and varied drug combinations, verified CT efficacy at combating cancer by achieving an extremely high percentage of apoptosis within 24 hours of drug exposure. CONCLUSIONS: CT anticancer efficacy in various human and canine cancer cell lines denotes its ability to interact across different biological processes and cancer regulatory cell networks, driving inhibition of cancer cell survival.

Evaluation of nucleosome concentrations in healthy dogs and dogs with cancer.

INTRODUCTION: Nucleosomes consist of small fragments of DNA wrapped around a histone octamer core. Diseases such as cancer or inflammation lead to cell death, which causes fragmentation and release of nucleosomes into the blood. The Nu.Q™ technology measures circulating nucleosome levels and exploits the different compositions of cancer derived nucleosomes in blood to detect and identify cancer even at early stages. The objectives of this study are to identify the optimal sample type for the Nu.Q™ H3.1 assay and to determine if it can accurately detect nucleosomes in the blood of healthy canines as well as those with cancer. MATERIALS AND METHODS: Blood samples from healthy canine volunteers as well as dogs newly diagnosed with lymphoma were used. The blood was processed at a variety of times under a variety of conditions to determine the most reliable sample type and conditions, and to develop an appropriate processing strategy to ensure reliably accurate results. RESULTS: Nucleosomes could be detected using a variety of sample collection and processing protocols. Nucleosome signals were highest in EDTA plasma and serum samples and most consistent in plasma. Samples should be processed within an hour of collection. Experiments showed that samples were able to withstand several freeze thaw cycles. Processing time and tcollection tube type did affect nucleosome detection levels. Finally, significantly elevated concentrations of nucleosomes were seen in a small cohort of dogs that had been newly diagnosed with lymphoma. CONCLUSIONS: When samples are collected and processed appropriately, the Nu.Q™ platform can reliably detect nucleosomes in the plasma of dogs. Further testing is underway to validate and optimize the Nu.Q™ platform for veterinary use.

Treatment of feline injection-site sarcoma with surgery and iridium-192 brachytherapy: retrospective evaluation of 22 cats.

OBJECTIVES: The aim of this retrospective descriptive study was to determine the effectiveness of using iridium implants in addition to surgery in cats with feline injection-site sarcomas (FISSs) in terms of time to progression and disease-specific survival and to identify prognostic factors for patient outcome. METHODS: Medical records of cats presented at our institution with FISS were reviewed. Inclusion criteria included histologic diagnosis of a tumor type associated with post-injection neoplastic development, tumor located at a site associated with vaccination, no other therapies prior to the administration of brachytherapy with the exception of surgery and adequate follow-up data. RESULTS: Twenty-two cats with FISS were treated with surgery and brachytherapy delivered by postoperative iridium-192 interstitial implants. Radiation doses ranged from 4000 to 6000 cGy (median dose 5079.55 cGy), with most doses delivered over 7 days. The median number of surgeries prior to brachytherapy was one (range 1-4). The complications associated with postoperative brachytherapy were typically mild, although four cats developed more severe complications. The median time to progression for all cats was 619 days and disease-specific survival time for all cats was 1242 days. The 1 and 2 year tumor-free rates in these cats were 63.6% and 40.9%, respectively. The local failure rate was 54.5% and the distant failure rate was 13.6% due to lung metastasis. There was a significant difference in time to progression of cats that had a single surgery performed prior to brachytherapy and those that had multiple surgeries (undefined vs 310 days; P = 0.01). There were no other statistically significant identified prognostic factors. CONCLUSIONS AND RELEVANCE: These data suggest that the addition of brachytherapy postoperatively in cats with FISS was well tolerated and is comparable to other forms of adjuvant therapy.

Characterization of five newly derived canine osteosarcoma cell lines.

BACKGROUND: Canine and human osteosarcomas (OS) are notably similar and have a high rate of metastasis. There is a poor understanding of the tumor development process, predisposing causes, and varying levels of aggression among different cell lines. By characterizing newly developed canine osteosarcoma cell lines, treatments for people and pets can be developed. Of the seven subtypes of OS, three are represented in this group: osteoblastic (the most common), fibroblastic, and giant cell variant. To our knowledge, there are no other giant cell variant canine OS cell lines in the published literature and only one canine fibroblastic osteosarcoma cell line. Understanding the differences between the histologic subtypes in dogs will help to guide comparative research. RESULTS: Alkaline phosphatase expression was ubiquitous in all cell lines tested and invasiveness was variable between the cell lines tested. Invasiveness and oxidative damage were not correlated with in vivo growth rates, where TOT grew the fastest and had the higher percentage of mice with metastatic lesions. TOL was determined to be the most chemo-resistant during cisplatin chemotherapy while TOM was the most chemo-sensitive. CONCLUSIONS: Further comparisons and studies using these cell lines may identify a variety of characteristics valuable for understanding the disease process and developing treatments for osteosarcoma in both species. Some of this data was presented as a poster by KMF at the August 5th, 2017 National Veterinary Scholars Program in Bethesda, MA. Characterization of 5 newly generated canine osteosarcoma cell lines. Kelli Franks, Tasha Miller, Heather Wilson-Robles.

Long-term postoperative effects of administration of allogeneic blood products in 104 dogs with hemangiosarcoma.

OBJECTIVE: To determine the influence of administering allogeneic blood products (ABP) on the progression of hemangiosarcoma in dogs. STUDY DESIGN: Multi-institutional, retrospective study. SAMPLE POPULATION: One hundred four dogs with hemangiosarcoma that survived until postoperative discharge from the hospital. METHODS: Medical records of dogs that had been operated on for hemoangiosarcoma were reviewed for signalment, presence of a hemoabdomen, presence of metastatic disease, and whether the dog had received chemotherapy or Yunnan Baiyao. Data that were collected were compared between dogs that received perioperative ABP and those that did not. Disease-free interval was compared between groups. The Kaplan-Meier method was used to obtain univariate descriptive statistics for time to clinical decline. A multivariable Cox regression model was used to analyze association or effect of potential predictor variables. RESULTS: The median disease-free interval (DFI) was shorter in the 67 dogs that received a blood transfusion (76 days; range, 1-836) than in the 37 dogs that did not receive a blood transfusion (120 days; range, 38-916). According to the multivariable Cox regression model, administration of blood products (P = .04) and the presence of gross metastatic disease at the time of surgery (P < .01) shortened the DFI, whereas administration of Yunnan Baiyao (P = .01) prolonged the DFI. CONCLUSION: Allogeneic blood product administration was associated with a shorter disease-free interval in this population. However, we could not demonstrate the association between blood products and shorter DFI because of confounding factors. CLINICAL SIGNIFICANCE: Dogs that receive ABP at the time of surgical therapy for hemangiosarcoma may have accelerated disease progression compared with dogs that do not receive ABP.

NCI Comparative Oncology Program Testing of Non-Camptothecin Indenoisoquinoline Topoisomerase I Inhibitors in Naturally Occurring Canine Lymphoma.

PURPOSE: Only one chemical class of topoisomerase I (TOP1) inhibitors is FDA approved, the camptothecins with irinotecan and topotecan widely used. Because of their limitations (chemical instability, drug efflux-mediated resistance, and diarrhea), novel TOP1 inhibitors are warranted. Indenoisoquinoline non-camptothecin topoisomerase I (TOP1) inhibitors overcome chemical instability and drug resistance that limit camptothecin use. Three indenoisoquinolines, LMP400 (indotecan), LMP776 (indimitecan), and LMP744, were examined in a phase I study for lymphoma-bearing dogs to evaluate differential efficacy, pharmacodynamics, toxicology, and pharmacokinetics. EXPERIMENTAL DESIGN: Eighty-four client-owned dogs with lymphomas were enrolled in dose-escalation cohorts for each indenoisoquinoline, with an expansion phase for LMP744. Efficacy, tolerability, pharmacokinetics, and target engagement were determined. RESULTS: The MTDs were 17.5 mg/m2 for LMP 776 and 100 mg/m2 for LMP744; bone marrow toxicity was dose-limiting; up to 65 mg/m2 LMP400 was well-tolerated and MTD was not reached. None of the drugs induced notable diarrhea. Sustained tumor accumulation was observed for LMP744; γH2AX induction was demonstrated in tumors 2 and 6 hours after treatment; a decrease in TOP1 protein was observed in most lymphoma samples across all compounds and dose levels, which is consistent with the fact that tumor response was also observed at low doses LMP744. Objective responses were documented for all indenoisoquinolines; efficacy (13/19 dogs) was greatest for LMP744. CONCLUSIONS: These results demonstrate proof-of-mechanism for indenoisoquinoline TOP1 inhibitors supporting their further clinical development. They also highlight the value of the NCI Comparative Oncology Program (https://ccr.cancer.gov/Comparative-Oncology-Program) for evaluating novel therapies in immunocompetent pets with cancers.

Removal of hemangiosarcoma cells from canine blood with a cell salvage system and leukocyte reduction filter.

OBJECTIVE: To determine the ability of an intraoperative cell salvage (IOCS) system and a leukocyte reduction filter (LRF) to remove hemangiosarcoma (HSA) cells from canine blood. STUDY DESIGN: Cultured HSA cells were added to canine blood to simulate intraoperative hemorrhage and address hemoabdomen from ruptured splenic HSA. The blood/HSA cell mixture was processed through an IOCS, followed by LRF processing. SAMPLE POPULATION: Whole blood from 3 healthy dogs combined with cultured HSA cells. METHODS: The ability of quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), multiparameter flow cytometry, and cytologic examination to detect 50 HSA cells per milliliter of culture media was confirmed. RT-PCR, multiparameter flow cytometry, and cytologic examination were used to determine the presence of cultured HSA cells at 4 points during processing. RESULTS: HSA cells were found in all control samples and in all samples after IOCS but prior to LRF processing with all 3 cell detection methods. HSA cells were not found after IOCS/LRF processing with all 3 cell detection methods. CONCLUSION: IOCS combined with LRF processing is able to remove cultured HSA cells from canine blood. The addition of LRF to IOCS may allow application of IOCS in dogs with HSA. CLINICAL SIGNIFICANCE: A combination of IOCS and LRF processing may provide an alternative to allogeneic blood transfusion in dogs with hemoabdomen due to HSA.

Oncology of Reptiles: Diseases, Diagnosis, and Treatment.

Based on necropsy review, neoplasia in reptiles has a comparable frequency to that of mammals and birds. Reptile neoplasia is now more frequently diagnosed in clinical practice based on increased use of advanced diagnostic techniques and improvements in reptilian husbandry allowing greater longevity of these species. This article reviews the current literature on neoplasia in reptiles, and focuses on advanced diagnostics and therapeutic options for reptilian patientssuffering neoplastic disease. Although most applied clinical reptile oncology is translated from dog and cat oncology, considerations specific to reptilian patients commonly encountered in clinical practice (turtles, tortoises, snakes, and lizards) are presented.

A Comparative Oncology Study of Iniparib Defines Its Pharmacokinetic Profile and Biological Activity in a Naturally-Occurring Canine Cancer Model.

Development of iniparib as an anti-cancer agent was hindered in part by lingering questions regarding its mechanism of action, the activity of its metabolites, and their potential accumulation in tumors. Due to strong similarities in metabolism of iniparib between humans and dogs, a veterinary clinical trial in pet dogs with spontaneous cancers was designed to answer specific questions pertaining to pharmacokinetic exposures and tolerability of iniparib. Dogs were treated with iniparib alone and in combination with carboplatin chemotherapy. Iniparib doses ranged between 10-70 mg/kg intravenously (IV). Plasma, tumor and normal tissue samples were collected before and at various time points scheduled after exposure for pharmacokinetic and biologic analysis. The primary endpoints included characterization of dose-limiting toxicities (DLT) and determination of the drug exposures that could be achieved in both normal and tumor tissues. Nineteen dogs were treated. DLT included fever, anorexia, diarrhea, neutropenia, and thrombocytopenia; most effects were attributable to carboplatin based on the timing of adverse event onset. The maximum tolerated dose (MTD) of iniparib was not identified. Moderate to high variability in plasma exposure was noted for iniparib and all metabolites between animals. When quantifiable, iniparib and metabolite plasma:tumor ratios were < 0.088 and <1.7, respectively. In this study, iniparib was well tolerated as a single agent and in combination with carboplatin over a range of doses. However, clinically relevant concentrations of the parent drug and selected metabolites were not detectable in canine tumor tissues at any studied dose, thus eliminating expectations for clinical responses in dogs or humans. Negative clinical trials in humans, and the uncertainties of its mechanism of action, ultimately led to the decision to stop clinical development of the drug. Nevertheless, the questions that can be asked and answered within the comparative oncology approach are evident from this successfully executed comparative clinical trial and exemplify the value of such studies in drug development.