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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
Clin Cancer Res. Author manuscript; available in PMC 2017 May 1.
Published in final edited form as:
PMCID: PMC5111620
NIHMSID: NIHMS747613

Defining the value of a comparative approach to cancer drug development

Abstract

Comparative oncology as a tool in drug development requires a deeper examination of the value of the approach and examples of where this approach can satisfy unmet needs. This review seeks to demonstrate types of drug development questions that are best answered by the comparative oncology approach. We believe common perceived risks of the comparative approach relate to uncertainty of how regulatory bodies will prioritize or react to data generated from these unique studies conducted in diseased animals, and how these new data will affect ongoing human clinical trials. We contend that it is reasonable to consider these data as potentially informative and valuable to cancer drug development, but as supplementary to conventional preclinical studies and human clinical trials particularly as they relate to the identification of drug-associated adverse events.

Introduction

The study of naturally occurring cancer in companion animals, known as comparative oncology, forms the basis of a translational drug development strategy that primarily includes tumor-bearing pet dogs in clinical trials of novel cancer therapies destined for use in human cancer patients.(15) The recognition of spontaneous cancer development in companion animals, and potential for inclusion of such animals in drug development studies, is based upon observations of canine malignancies that share morphologic, histologic and biologic characteristics with human cancers. Dogs’ physical size, amenability to serial biologic sample collections, compressed survival compared to humans, comparable tumor biology, intact immunity and relevant responses to cytotoxic therapies provide clear support to their inclusion as a complementary animal model. (4,5)

Currently the field of comparative oncology is focused on tumor-bearing dogs as they comprise the majority of those presented to veterinarians for cancer diagnosis and management, which is in turn facilitated by scientific knowledge of malignancies they develop, the collective veterinary clinical experience with anticancer therapies such as chemotherapy and radiation, and availability of basic annotation of the canine genome and immune system. A major milestone was establishment of the National Cancer Institute’s Comparative Oncology Program (NCI-COP) at the National Institutes of Health in 2004. A component of this program is the Comparative Oncology Trials Consortium (NCI-COTC; http://ccr.cancer.gov/resources/cop/COTC.asp), an infrastructure uniting study sponsors, such as pharmaceutical and biotechnology companies, with 21 academic veterinary centers within North America to support multicenter clinical trials of investigational therapeutics, wherein centralized trial support and data management is provided by the NCI.(6,7) This mechanism provides access to a clinical trial infrastructure that delivers trial results in a facile manner, considerate of timelines generally required in drug development strategies. Further, a body of published work now exists to demonstrate the feasibility and applicability of the dog cancer model in drug development to ensure data that is both scientifically sound and robust, thus supporting inclusion into FDA applications. Although not formal FDA guidance, direction for clinical trial conduct and data reporting exists for drugs evaluated in comparative oncology studies in the pre and post-Investigational New Drug (IND) settings, and has been used effectively by groups actively involved in these efforts. (8)

Methods

Today’s challenge is how to best capture and convey the value of these studies, given the timeline for drug development and the diversity of data that collectively informs decisions in the development path. Various attempts at defining value have been made, including a financial model that proposes savings of billions of research and development dollars, achieved primarily through the effective design of better phase II human studies.(9) We propose that the value of the comparative approach lies in the answers to critical drug development questions that are not answered in human trials or conventional preclinical models. Herein we present a summary of the types of questions that are best asked and answered by comparative oncology studies (Table 1), along with a discussion of selected studies that generated answers to such questions, thus are demonstrative of the value of the comparative oncology approach.

Results

Small molecules and the relationship of pharmacokinetics, pharmacodynamics, and clinical assessment of tolerability and efficacy

A highly soluble prodrug of ganetespib, STA-1474, was studied in dogs with cancer to establish clinical toxicity, to identify surrogate biomarkers of response and pharmacokinetics between two proposed dosing schedules, and to provide evidence of biologic activity. This study met all defined objectives, and assisted in devising a dosing strategy to provide prolonged drug exposure to support efficient inhibition of drug target via modulation of a surrogate biomarker in blood (HSP70 upregulation in peripheral blood mononuclear cells (PBMCs)) and tumor levels of c-kit (an HSP90 client protein). Collectively, this data informed the design of human clinical trials of ganetespib and demonstrates the strengths of a naturally-occurring canine model by highlighting the ease of serial biopsy procurement, rapid assessment of differential dose and schedule, and correlative assessment of multiple clinical parameters.(10) In another similar example, an orally-bioavailable XPO1 inhibitor verdinexor, a companion agent to a lead human compound KPT-330 (Selinexor, Karyopharm Therapeutics), was studied in tumor-bearing dogs. Based upon profound clinical benefit observed in dogs with non-Hodgkin’s lymphoma (NHL) and the marked similarities between canine and human NHL, the data generated within this study provided critical new information in support of related compounds in humans with hematologic malignancies.(11) Selinexor is currently being evaluated in Phase I and II clinical trials for a variety of human cancers.

Biomarker validation and optimization of pharmacodynamics (PD) assays within the context of drug exposure in tumor-bearing dogs

The irreversible inhibitor of Bruton tyrosine kinase (Btk), ibrutinib, was studied in dogs with B-cell lymphoma to establish tolerability, preliminary efficacy data, and to validate a pharmacodynamic (PD) assay within PBMCs and tumor tissue. Validation of the fluorescently labeled derivative of ibrutinib to monitor occupancy of Btk by the drug has led to adoption of this approach as PD readout in subsequent human trials, while also supporting the use of ibrutinib in humans with B cell malignancies.(12,13)

Another valuable example is study of hydroxychloroquine, an autophagy inhibitor, given to dogs with NHL. The PD response evaluated in both PBMCs and tumor tissue, obtained via serial peripheral lymph node biopsies, demonstrated that reliance on surrogate PBMC for demonstration of sufficient drug levels for effective autophagy inhibition within tumor tissue cannot always be inferred, thus underscoring the strength of the canine cancer model.(14)

Immune-modulating agents for cancer therapy

A comparative oncology study of an immunocytokine, NHS-IL12, administered subcutaneously to dogs with malignant melanoma was conducted to identify tolerability and immunologic activity of this agent across a range of doses.(15) Pharmacokinetic and pharmacodynamic endpoints, in the form of serum IFN-gamma, IL-10 levels and intratumoral CD8+ lymphocytes, were assessed alongside clinical measures of response and toxicity. This study provided data that directly informed the design of the ongoing Phase 1 human trial of this agent (NCT01417546). The study demonstrated both initial safety and efficacy signals in a relevant species bearing a naturally arising tumor. This data was crucial to the rigorous scientific review of the clinical trial at the National Cancer Institute Center for Cancer Research (NCI/CCR) and facilitated the CCR holding the IND for this agent at a time when the study sponsor had deprioritized this compound. This currently is now a high priority agent for planned combination studies in man.(James Gulley MD, personal communication).

Comparative cancer genomics

The use of dogs in cross-species genomics studies provides a unique opportunity to identify regions of potentially shared and clinically relevant genomic changes. In one such example, candidate genes IL-8 and SLC1A3 were identified in canine osteosarcoma as overexpressed; these same genes had variable expression in human OS but nevertheless were associated with a poor clinical outcome.(16) Additional studies adopting this line of investigation could help identify yet-characterized candidate genes and/or pathways for future application to human cancer genomic studies.

Pre-clinical assessment of cancer imaging agents in tumor-bearing dogs

Dogs with measurable malignancies that are considered surgical candidates represent a unique opportunity to assess intraoperative imaging agents to provide, in real time, an assessment of surgical margins to inform on the extent of resection and thus optimize outcome. BLZ-100, a near-infrared imaging agent currently in Phase I human studies, is a peptide-fluorophore conjugate that was evaluated in a comparative oncology study of dogs with a variety of cancer histologies.(17; Blaze Bioscience, Inc.) Canine tissues were imaged both in vivo and ex vivo to identify an efficacious dose of BLZ-100. This data provided a foundation and rationale to assess performance of this agent in human patients with soft-tissue sarcomas.

Challenges and Perceived Risks to Comparative Oncology Studies

Perspectives from those within the pharmaceutical industry against using a comparative oncology approach generally include the relatively higher cost of comparative oncology trials compared to other conventional animal models, the greater amount of drug needed for dosing of dogs, and the time needed to complete such trials from inception to analysis of data. Responses to these points must include consideration of the uniqueness of the data generated within heterogeneous, spontaneous cancer that develops within an immune-competent host, which is not generated with the intent of describing toxicity as a primary endpoint. The amount of drug and time to execute the studies should be considered in context of when the data is desired within an individual drug’s development. Good Manufacturing Practices (GMP)-level material is not generally needed for comparative oncology clinical studies, although basic purity and release criteria have been previously described.(7, 18). Capitalization on a multi-center clinical trial consortium such as the NCI-COTC can assist in hastening the conduct of a trial, but interim analyses will introduce natural and important pauses within the study timeline. Nevertheless, the timeline for comparative oncology studies are much shorter than typical Phase I/II human trials and are conducted at a much lower cost, while providing data that can directly inform the design of human trials, representing a valuable return on investment.

Similarly important to consider are questions that cannot be effectively asked within a dog model. It is important to note that prior to initiation of comparative oncology drug trials in dogs, consideration of existing normal dog toxicology data, generated in most cases by the study sponsor during toxicological assessment, is important to proper and ethical design of the trial. In cases where the dog is a known sensitive species for severe toxicity, and no reasonable margin of safety can be applied to demonstrate therapeutic efficacy, the tumor-bearing dog would not be appropriate for exploration of potential PK/PD relationships and how they correlate to clinical efficacy and tolerability.

The field of cancer genetics and genomics is rapidly evolving, with particular emphasis on specific knowledge of druggable pathways that are critically linked to malignant behavior, supporting the ongoing development of targeted therapies. Indeed, a deeper knowledge of the naturally occurring canine cancer genomic landscape is crucial to defining the pertinent questions that can be asked within canine cancer patients, and how relatable canine cancers are to human cancers on the genomic level. The comparative chromosome alignment technique and the differential organization of the dog genome may narrow key regions of the genome associated with cancers. Recent work in this area demonstrates that recurrent aberrations correlate with cancer subtype, and that corresponding cytogenetic lesions may exist in human patients.(16, 1922) Several examples of where the value of a cross-species approach to cancer genomics has been demonstrated exist in the literature. For example, recent work in canine melanoma demonstrates that although canine tumors possess rare mutations in BRAF and NRAS, they exhibit similar differential gene expression changes to human melanoma within downstream MAPK and PI3K/AKT pathways.(25) Thus, although the driving mutations between human and canine melanoma may differ, similar activation and sensitivity to inhibition of such shared signaling pathways underscores the translational value of studying comparative melanoma biology. This aspect of comparative oncology will continue to develop and could support initiation of so-called ‘basket’ trials wherein response of tumors with shared, credentialed biology to a specific targeted therapy are assessed, agnostic of histologic diagnosis. In order to facilitate future studies in this area, high-quality biologic samples from dogs with various malignancies are available via the Pfizer-Canine Comparative Oncology and Genomics Consortium (CCOGC) biospecimen repository (www.ccogc.net). (26, 27) This resource is uniquely suited to provide the necessary molecular background that is currently missing from the comparative oncology armamentarium. CCOGC samples are treatment-naïve, clinically annotated, and include both tumor and matched normal tissues, including peripheral blood, urine, plasma and serum. Seven histologies were selected based upon their translational relevance at the time the resource was populated (2007–2011), totaling 1800 individual patients and approximately 60,000 samples.

A rapidly growing field in cancer drug development is the conception and creation of biologic agents that affect an antitumor response via immune response manipulation and/or reprogramming within individual patients. For such an approach, the type of the agent may critically influence the applicability of the dog model for ongoing development. Incomplete knowledge of shared tumor antigens between humans and dogs may limit the questions that can be asked of such agents that are destined for human use. Further, even with successful targeting of a specific tumor-associated antigen shared between humans and dogs, immune-competent canine cancer patients will effectively clear any foreign (human or murine) antibodies, thus potentially limiting use of a dog model for evaluation of monoclonal antibodies intended for repeated therapeutic dosing schemes unless an equivalent canin-ized or canine chimeric product is manufactured alongside the parent compound. Tumor vaccines, particularly those which rely on a shared tumor antigen(s) may be viable candidates for validation studies in a dog model.(28, 29) Success in autologous tumor cell lysate vaccination strategies in canine meningioma, melanoma, and lymphoma and others have provided insight for comparative human trials.(3032). Similarly, oncolytic viruses, which capitalize on malignant cells’ defects in viral response gene pathways, may be effectively translated between dogs and humans.(33, 34)

A path forward: a reasonable regulatory response has been provided

During discussion at an Institute of Medicine (IOM) meeting on June 9, 2015, which included individuals from FDA, NIH, and various academic and industry stakeholders in cancer drug development, Dr. John Leighton of the FDA’s Center for Drug Evaluation and Research (CDER) provided public insight into regulatory review of comparative oncology data, of which a summary is available within the IOM proceedings (http://www.nap.edu/catalog/21830/the-role-of-clinical-studies-for-pets-with-naturally-occurring-tumors-in-translational-cancer-research). Although these comments are not considered formal regulatory guidance, their importance is underscored here:

  • The FDA is aware of the role of pet dogs may play as research subjects in human drug development settings. Such data collected in dogs is expected to be filed under the IND as it becomes available. A New Animal Drug (NAD) application is not needed for clinical studies evaluating drugs in this specific research setting.
  • Data collected in the context of a comparative oncology clinical trial setting would be viewed in context. The FDA is aware that companion dogs are housed and treated in the home environment and may have comorbidities reflective of their age and naturally occurring malignancies.
  • Data collected from tumor-bearing pet dogs would never “trump” human data, particularly with respect to drug tolerability and clinical response.
  • Over the past 15 years, safety signals have never been identified in tumor-bearing pet dogs that have resulted in a clinical hold for an existing human IND study.

Conclusions

The questions asked and answered within comparative oncology studies are informative, unique, and not easily provided by conventional preclinical models or by most human trials. These data do not replace controlled toxicokinetic studies in purpose-bred dogs and other laboratory animal species. Regulatory review of these data would include consideration of context and the recognized complexities of working within a naturally-occurring disease model system. It is imperative that investigators actively engaged in comparative oncology studies both report and characterize unexpected adverse events they observe so as to understand and attribute these events fully.

Acknowledgments

This work was supported in part by the Intramural Research Program of the NIH, National Cancer Institute. The authors wish to thank Drs. James Gulley, Michael Henson, Doug Thamm, and Tim Fan for their contributions to this manuscript.

References

1. Paoloni M, Khanna C. Translation of new cancer treatments from pet dogs to humans. Nat Rev Cancer. 2008;8:147–156. [PubMed]
2. Rowell JL, McCarthy DO, Alvarez CE. Dog models of naturally occurring cancer. Trends Mol Med. 2011;17:380–388. [PMC free article] [PubMed]
3. Hansen K, Khanna C. Spontaneous and genetically engineered animal models; use in preclinical cancer drug development. Eur J Cancer. 2004;40(6):858–80. [PubMed]
4. Vail DM, MacEwen EG. Spontaneously occurring tumors of companion animals as models for human cancer. Cancer Invest. 2000;18:781–792. [PubMed]
5. Lairmore MD, Khanna C. Naturally occurring diseases in animals: contributions to translational medicine. ILAR J. 2014;55(1):1–3. [PubMed]
6. Gordon I, Paoloni M, Mazcko C, Khanna C. The Comparative Oncology Trials Consortium: using spontaneously occurring cancers in dogs to inform the cancer drug development pathway. PLoS Med. 2009 Oct;6(10) doi: 10.1371/journal.pmed.1000161. [PMC free article] [PubMed] [Cross Ref]
7. Paoloni MC, Tandle A, Mazcko C, Hanna E, Kachala S, LeBlanc A, et al. Launching a novel preclinical infrastructure: comparative oncology trials consortium directed therapeutic targeting of TNFalpha to cancer vasculature. PLoS One. 2009;4:e4972. [PMC free article] [PubMed]
8. Khanna C, London C, Vail D, Mazcko C, Hirschfeld S. Guiding the optimal translation of new cancer treatments from canine to human cancer patients. Clin Cancer Res. 2009;15(18):5671–7. doi: 10.1158/1078-0432.CCR-09-0719. [PMC free article] [PubMed] [Cross Ref]
9. Gordon I, Khanna C. Modeling opportunities in comparative oncology for drug development. ILAR J. 2010;51(3):214–20. [PubMed]
10. London CA, Bear MD, McCleese J, Foley KP, Paalangara R, Inoue T, et al. Phase I evaluation of STA-1474, a prodrug of the novel HSP90 inhibitor ganetespib, in dogs with spontaneous cancer. PLoS One. 2011;6(11):e27018. [PMC free article] [PubMed]
11. London CA, Bernabe LF, Barnard S, Kisseberth WC, Borgatti A, Henson M, et al. Evaluation of the novel, orally bioavailable selective inhibitor of nuclear export (SINE) KPT-335 in spontaneous canine cancer: results of a Phase I study. PLoS One. 2014;9(2):e87585. [PMC free article] [PubMed]
12. Honigberg LA, Smith AM, Sirisawad M, Verner E, Loury D, Chang B, et al. The Bruton tyrosine kinase inhibitor PCI-32765 blocks B-cell activation and is efficacious in models of autoimmune disease and B-cell malignancy. Proc Natl Acad Sci USA. 2010;107(29):13075–80. [PubMed]
13. Smith MR. Ibrutinib in B lymphoid malignancies. Expert Opin Pharmacother. 2015;16(12):1879–87. doi: 10.1517/14656566.2015.1067302. Epub 2015 Jul 13. [PubMed] [Cross Ref]
14. Barnard RA, Wittenberg LA, Amaravadi RK, Gustafson DL, Thorburn A, Thamm DH. Phase I clinical trial and pharmacodynamic evaluation of combination hydroxychloroquine and doxorubicin treatment in pet dogs treated for spontaneously occurring lymphoma. Autophagy. 2014;10(8):1–11. [PMC free article] [PubMed]
15. Paoloni M, Mazcko C, Selting K, Lana S, Barber L, Phillips J, et al. Defining the Pharmacodynamic Profile and Therapeutic Index of NHS-IL12 Immunocytokine in Dogs with Malignant Melanoma. PLoS One. 2015 Jun 19;10(6):e0129954. doi: 10.1371/journal.pone.0129954. [PMC free article] [PubMed] [Cross Ref]
16. Paoloni M, Davis S, Lana S, Withrow S, Sangiorgi L, Picci P, et al. Canine tumor cross-species genomics uncovers targets linked to osteosarcoma progression. BMC Genomics. 2009;10:625. [PMC free article] [PubMed]
17. Fidel J, Kennedy KC, Dernell WS, Hansen S, Wiss V, Stroud MR, et al. Preclinical Validation of the Utility of BLZ-100 in Providing Fluorescence Contrast for Imaging Spontaneous Solid Tumors. Cancer Res. 2015 Oct 15;75(20):4283–91. doi: 10.1158/0008-5472.CAN-15-0471. [PMC free article] [PubMed] [Cross Ref]
18. Paoloni MC, Mazcko C, Fox E, Fan T, Lana S, Kisseberth W, et al. Rapamycin pharmacokinetic and pharmacodynamic relationships in osteosarcoma: a comparative oncology study in dogs. PLoS One. 2010;5(6):e11013. [PMC free article] [PubMed]
19. Richards KL, Motsinger-Reif AA, Chen HW, Fedoriw Y, Fan C, Nielsen DM, et al. Gene profiling of canine B-cell lymphoma reveals germinal center and postgerminal center subtypes with different survival times, modeling human DLBCL. Cancer Res. 2013 Aug 15;73(16):5029–39. doi: 10.1158/0008-5472.CAN-12-3546. [PMC free article] [PubMed] [Cross Ref]
20. Mochizuki H, Kennedy K, Shapiro SG, Breen M. BRAF mutations in canine cancers. PLoS One. 2015 Jun 8;10(6):e0129534. doi: 10.1371/journal.pone.0129534. [PMC free article] [PubMed] [Cross Ref]
21. Roode SC, Rotroff D, Avery AC, Suter SE, Bienzle D, Schiffman JD, et al. Genome-wide assessment of recurrent genomic imbalances in canine leukemia identifies evolutionarily conserved regions for subtype differentiation. Chromosome Res. 2015 Jun 3; Epub ahead of print. [PubMed]
22. Schiffman JD, Breen M. Comparative oncology: what dogs and other species can teach us about humans with cancer. Philos Trans R Soc Lond B Biol Sci. 2015 Jul 19;370(1673) pii: 20140231. [PMC free article] [PubMed]
23. Pryer NK, Lee LB, Zadovaskaya R, Yu X, Sukbuntherng J, Cherrington JM, et al. Proof of target for SU11654: inhibition of KIT phosphorylation in canine mast cell tumors. Clin Cancer Res. 2003 Nov 15;9(15):5729–34. [PubMed]
24. London CA, Malpas PB, Wood-Follis SL, Boucher JF, Rusk AW, Rosenberg MP, et al. Multi-center, placebo-controlled, double-blind, randomized study of oral toceranib phosphate (SU11654), a receptor tyrosine kinase inhibitor, for the treatment of dogs with recurrent (either local or distant) mast cell tumor following surgical excision. Clin Cancer Res. 2009;15(11):3856–65. doi: 10.1158/1078-0432.CCR-08-1860. [PubMed] [Cross Ref]
25. Fowles JS, Denton CL, Gustafson DL. Comparative analysis of MAPK and PI3K/AKT pathway activation and inhibition in human and canine melanoma. Vet Comp Oncol. 2013 doi: 10.1111/vco.12044. [PubMed] [Cross Ref]
26. Mazcko CM, Thomas R. The establishment of the Pfizer-Canine Comparative Oncology and Genomics Consortium Biospecimen Repository. Vet Sci. 2015;2:127–130. doi: 10.3390/vetsci2030127. [Cross Ref]
27. Webster JD, Simpson ER, Michalowski AM, Hoover SB, Simpson RM. Quantifying Histological Features of Cancer Biospecimens for Biobanking Quality Assurance Using Automated Morphometric Pattern Recognition Image Analysis Algorithms. J Biomol Tech. 2011;22(3):108–118. [PMC free article] [PubMed]
28. Liao JC, Gregor P, Wolchok JD, Orlandi F, Craft D, Leung C, et al. Vaccination with human tyrosinase DNA induces antibody responses in dogs with advanced melanoma. Cancer Immun. 2006;21(6):8. [PMC free article] [PubMed]
29. Grosenbaugh DA, Leard AT, Bergman PJ, Klein MK, Meleo K, Susaneck S, et al. Safety and efficacy of a xenogeneic DNA vaccine encoding for human tyrosinase as adjunctive treatment for oral malignant melanoma in dogs following surgical excision of the primary tumor. Am J Vet Res. 2011;72(12):1631–8. [PubMed]
30. Andersen BM, Pluhar GE, Seiler CE, Goulart MR, SantaCruz KS, Schutten MM, et al. Vaccination for invasive canine meningioma induces in situ production of antibodies capable of antibody-dependent cell-mediated cytoxicity. Cancer Res. 2013;73(10):2987–2997. [PMC free article] [PubMed]
31. Turek MM, Thamm DH, Mitzey A, Kurzman ID, Huelsmeyer MK, Dubielzig RR, et al. Human granulocyte-macrophage colony-stimulating factor DNA cationic-lipid complexed autologous tumour cell vaccination in the treatment of canine B-cell multicentric lymphoma. Vet Comp Oncol. 2007;5(4):219–31. [PubMed]
32. U’Ren LW, Biller BJ, Elmslie RE, Thamm DH, Dow SW. Evaluation of a novel tumor vaccine in dogs with hemangiosarcoma. J Vet Intern Med. 2007;21(1):113–20. [PubMed]
33. Laborda E, Puig-Saus C, Rodriguez-García A, Moreno R, Cascalló M, Pastor J, et al. A pRb-responsive, RGD-modified, and hyaluronidase-armed canine oncolytic adenovirus for application in veterinary oncology. Mol Ther. 2014;22(5):986–98. [PubMed]
34. Gentschev I, Patil SS, Petrov I, Cappello J, Adelfinger M, Szalay AA. Oncolytic virotherapy of canine and feline cancer. Viruses. 2014;6(5):2122–37. [PMC free article] [PubMed]
35. Nguyen SM, Thamm DH, Vail DM, London CA. Response evaluation criteria for solid tumours in dogs (v1.0): a Veterinary Cooperative Oncology Group (VCOG) consensus document. Vet Comp Oncol. 2013 Mar 28; doi: 10.1111/vco.12032. Epub ahead of print. [PubMed] [Cross Ref]
36. Vail DM, Michels GM, Khanna C, Selting KA, London CA. Veterinary Cooperative Oncology Group. Response evaluation criteria for peripheral nodal lymphoma in dogs (v1.0)--a Veterinary Cooperative Oncology Group (VCOG) consensus document. Vet Comp Oncol. 2010;8(1):28–37. [PubMed]
37. Veterinary cooperative oncology group - common terminology criteria for adverse events (VCOG-CTCAE) following chemotherapy or biological antineoplastic therapy in dogs and cats v1.1. Vet Comp Oncol. 2011 doi: 10.1111/j.1476-5829.2011.00283.x. [PubMed] [Cross Ref]
38. Thamm DH, Vail DM, Kurzman ID, Babusis D, Ray AS, Sousa-Powers N, et al. GS-9219/VDC-1101--a prodrug of the acyclic nucleotide PMEG has antitumor activity in spontaneous canine multiple myeloma. BMC Vet Res. 2014;10:30. doi: 10.1186/1746-6148-10-30. [PMC free article] [PubMed] [Cross Ref]
39. Vail DM, Thamm DH, Reiser H, Ray AS, Wolfgang GH, Watkins WJ, et al. Assessment of GS-9219 in a pet dog model of non-Hodgkin’s lymphoma. Clin Cancer Res. 2009;15(10):3503–10. [PubMed]
40. LeBlanc AK, Miller AN, Galyon GD, Moyers TD, Long MJ, Stuckey AC, et al. Preliminary evaluation of serial 18FDG-PET/CT to assess response to toceranib phosphate therapy in canine cancer. Vet Rad Ultrasound. 2012;53:348–357. [PubMed]
41. Wittenburg LA, Gustafson DL, Thamm DH. Phase I pharmacokinetic and pharmacodynamic evaluation of combined valproic acid/doxorubicin treatment in dogs with spontaneous cancer. Clin Cancer Res. 2010;16(19):4832–42. [PMC free article] [PubMed]
42. London CA, Gardner HL, Mathie T, Stingle N, Portela R, Pennell ML, et al. Impact of Toceranib/Piroxicam/Cyclophosphamide Maintenance Therapy on Outcome of Dogs with Appendicular Osteosarcoma following Amputation and Carboplatin Chemotherapy: A Multi-Institutional Study. PLoS One. 2015;10(4):e0124889. doi: 10.1371/journal.pone.0124889. eCollection 2015. [PMC free article] [PubMed] [Cross Ref]
43. Thamm DH, Kurzman ID, Clark MA, Ehrhart EJ, Kraft SL, Gustafson DL, et al. Preclinical investigation of PEGylated tumor necrosis factor alpha in dogs with spontaneous tumors: Phase I evaluation. Clin Cancer Res. 2010;16(5):1498–508. [PubMed]
44. Selting KA, Wang X, Gustafson DL, Henry CJ, Villamil JA, McCaw DL, et al. Evaluation of satraplatin in dogs with spontaneously occurring malignant tumors. J Vet Intern Med. 2011;25(4):909–15. [PubMed]
45. Rutteman GR, Erich SA, Mol JA, Spee B, Grinwis GC, Fleckenstein L, et al. Safety and efficacy field study of artesunate for dogs with non-resectable tumours. Anticancer Res. 2013;33(5):1819–27. [PubMed]
46. Peterson QP, Hsu DC, Novotny CJ, West DC, Kim D, Schmit JM, et al. Discovery and canine preclinical assessment of a nontoxic procaspase-3-activating compound. Cancer Res. 2014;70(18):7232–41. [PMC free article] [PubMed]
47. Sarver AL, Thayanithy V, Scott MC, Cleton-Jansen AM, Hogendoorn PC, Modiano JF, et al. MicroRNAs at the human 14q32 locus have prognostic significance in osteosarcoma. Orphanet Journal of Rare Diseases. 2013;8:7. [PMC free article] [PubMed]
48. Stratham-Ringen KA, Selting KA, Lattimer JC, Henry CJ, Green JA, Bryan JN, et al. Evaluation of a B-cell leukemia-lymphoma 2-specific radiolabeled peptide nucleic acid-peptide conjugate for scintigraphic detection of neoplastic lymphocytes in dogs with B-cell lymphoma. Am J Vet Res. 2012;73:681–688. [PubMed]
49. Zwingenberger AL, Kent MS, Liu R, Kukis DL, Wisner ER, DeNardo SJ, et al. In-vivo biodistribution and safety of 99mTc-LLP2A-HYNIC in canine non-Hodgkin lymphoma. PLoS One. 2012;7(4):e34404. doi: 10.1371/journal.pone.0034404. Epub 2012 Apr 24. [PMC free article] [PubMed] [Cross Ref]
50. Bradshaw TJ, Bowen SR, Jallow N, Forrest LJ, Jeraj R. Heterogeneity in intratumor correlations of 18F-FDG, 18F-FLT, and 61Cu-ATSM PET in canine sinonasal tumors. J Nucl Med. 2013;54:1931–7. [PMC free article] [PubMed]
51. Hansen AE, Kristensen AT, Law I, McEvoy FJ, Kjaer A, Engelholm SA. Multimodality functional imaging of spontaneous canine tumors using 64Cu-ATSM and 18FDG PET/CT and dynamic contrast enhanced perfusion CT. Radiother Oncol. 2012;102:424–428. [PubMed]
52. Hansen AE, Kristensen AT, Jorgensen JT, McEvoy FJ, Busk M, van der Kogel AJ, et al. 64Cu-ATSM and 18FDG PET uptake and 64Cu-ATSM autoradiography in spontaneous canine tumors: comparison with pimonidazole hypoxia immunohistochemistry. Radiat Oncol. 2012;7:89. [PMC free article] [PubMed]
53. Black NF, McJames S, Kadrmas DJ. Rapid multi-tracer PET tumor imaging with 18F-FDG and secondary short-lived tracers. IEEE Trans Nucl Sci. 2009;56:2750–2758. [PMC free article] [PubMed]
54. Black NF, McJames S, Rust TC, Kadrmas DJ. Evaluation of rapid dual-tracer 62Cu-PTSM + 62Cu-ATSM PET in dogs with spontaneously-occurring tumors. Phys Med Biol. 2008;53:217–232. [PMC free article] [PubMed]
55. Khanna C, Fan TM, Gorlick R, Helman LJ, Kleinerman ES, Adamson PC, et al. Toward a drug development path that targets metastatic progression in osteosarcoma. Clin Cancer Res. 2014 Aug 15;20(16):4200–9. doi: 10.1158/1078-0432.CCR-13-2574. [PMC free article] [PubMed] [Cross Ref]
56. Paoloni M, Webb C, Mazcko C, Cherba D, Hendricks W, Lana S, et al. Prospective molecular profiling of canine cancers provides a clinically relevant comparative model for evaluating personalized medicine (PMed) trials. PLoS One. 2014 Mar 17;9(3):e90028. doi: 10.1371/journal.pone.0090028. eCollection 2014. [PMC free article] [PubMed] [Cross Ref]
57. Modiano JF, Bellgrau D, Cutter GR, Lana SE, Ehrhart NP, Ehrhart E, et al. Inflammation, apoptosis, and necrosis induced by neoadjuvant Fas ligand gene therapy improves survival of dogs with spontaneous bone cancer. Mol Ther. 2012;20(12):2234–43. [PubMed]