Preclinical Efficacy Studies Research Articles

Abstract 229: Utilizing a mouse cross-reactive model system to better understand antibody-drug conjugate pharmacokinetics, biodistribution and efficacy

Abstract Antibody-drug conjugates (ADCs) are designed to deliver a potent cytotoxic payload directly to tumors, thus limiting exposure in normal tissues. However, target antigen expression on normal tissues can lead to lower systemic ADC exposures, resulting in sub-efficacious concentrations at the tumor site as well as heterogeneous distribution within tumors. Traditional preclinical efficacy studies performed in rodent models using ADCs with non-cross-reactive antibodies have been of limited translational relevance, and a better understanding of the factors that impact ADC dose and activity remains to be elucidated. To examine relationships between variables that could influence ADC efficacy, we generated a cross-reactive model system that utilized a chimeric anti-murine folate receptor α (FRα) antibody (designated rmFR1-12) that binds both mouse and human FRα, and can be conjugated to either maytansinoid (DM) or indolinobenzodiazepine (IGN) payloads. This model system was predicted to have substantial target-mediated drug disposition (TMDD) due to normal tissue expression of FRα. An rmFR1-12-s-SPDB-DM4 ADC was made using tritium-labeled DM4 and administered to tumor-bearing mice in order to assess ADC pharmacokinetics (PK), biodistribution, and efficacy. This approach allowed tracking of the ADC at multiple levels – whole animal, organ, tumor, and cell. Studies were undertaken that assessed the impact of xenograft antigen expression, ADC dose, and ADC drug-to-antibody ratio (DAR) on the PK, biodistribution, and efficacy of the rmFR1-12-s-SPDB-DM4 conjugate. The results showed that TMDD significantly impacted the PK, biodistribution, and activity of the conjugate relative to a non-cross-reactive ADC, with lower ADC doses being more severely impacted than higher doses. Antigen expression positively correlated with local ADC exposure and efficacy. Decreasing the DAR (by co-dosing naked antibody with the ADC) increased systemic exposure. A positive correlation between systemic exposure and dose of naked antibody was observed. Factors that impacted local exposure included: the type of tissue (normal vs tumor), presence or absence of FRα expression on normal tissue, and dose of naked antibody. Of note, in the naked antibody plus ADC study, efficacy did not correlate with local exposure - suggesting that ADC distribution within tumors is of similar importance as the amount of ADC delivered. Overall, these findings underscore the importance of accounting for site, and extent of, normal tissue target expression with respect to ADC PK/PD, and the data generated from these studies are currently being used to build a multiscale physiologically based PK model of a cross-reactive ADC. Citation Format: Leanne Lanieri, Rassol Laleau, Bahar Matin, Jenny Lee, Steven Boule, Paulin Salomon, Luke Harris, Michael Miller, Nicholas C. Yoder, Yulius Setiady, Neeraj Kohli, Thomas A. Keating, Jan Pinkas, Richard Gregory. Utilizing a mouse cross-reactive model system to better understand antibody-drug conjugate pharmacokinetics, biodistribution and efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 229.

Abstract 90: The “reproducibility crisis” of animal studies in oncology - How did we get here, and how can we resolve it

Abstract Historically, a large majority of clinical phase III trials fail to gain regulatory approval due primarily to a lack of demonstrated efficacy, demonstrating the challenge of conducting clinically relevant efficacy studies in laboratory animals. In 2012, Amgen researchers published their finding that an astoundingly-high proportion (90%) of more than 50 republished in vivo studies in oncology was not reproducible. This sparked an intense debate about data validity in preclinical sciences, and several reviews have been published in the last two years analysing this issue. A number of best-practice initiatives and resources have since been created along with the development of animal study workflow software applications and databases to address the causes of this significant, global problem in cancer research. Major sources of irreproducibility in animal research such as bias, suboptimal disease models, lack of controls, and most importantly bad documentation practices will be discussed. Several initiatives have resulted in practically-applicable concepts and publicly-available resources to address this issue, such as ARRIVE guidelines, PHISPS protocols and the N3R Design Assistant, will be described. Electronic spreadsheets have been the most prevalently-used tool to plan and conduct preclinical efficacy studies in oncology. The advent of animal study workflow software and database technology, designed specifically for in vivo oncology research, has seen increasingly widespread adoption in recent years in both academia and industry. By employing standardized and more detailed approaches to the processes documenting highly detailed study design, data collection, method and procedure descriptions and adherence, real-time monitoring of animal welfare parameters, standardized graphing, data analyses and report generation, measurement and task scheduling, as well as data preservation approaches, will be explored. Using some real-life examples, the advantages and disadvantages of preclinical study automation and the use of electronic spreadsheets will be discussed in the context of helping to resolve the animal study “Reproducibility Crisis”. Citation Format: Hannes Hentze, Eric Ibsen. The “reproducibility crisis” of animal studies in oncology - How did we get here, and how can we resolve it [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 90.

How well are Phase 2 cancer trial publications supported by preclinical efficacy evidence?

Major ethics policies require that human studies be preceded by animal experiments. We probed the extent to which trials testing efficacy of cancer drugs cited preclinical efficacy studies testing the same drug and disease indication. Using a sample of Phase 2 trial publications for novel cancer monotherapies approved by Food and Drug Administration 2005-2007, we conducted a systematic analysis of citations to preclinical efficacy evidence within trial publications. Citations were classified based on whether they "matched" the drug and indication of the trial. Our sample included 179 Phase 2 publications published 2004-2016. At least one preclinical study was cited for 113 of 179 publications (63%); 56 (31%) cited matching preclinical studies, and 74 (41%) did not cite either matching preclinical or matching clinical trial evidence. When excluding evidence that would likely not have been available to investigators before trial launch, 45 trials (25%) cited matching preclinical studies; 91 (51%) did not cite any matched preclinical or clinical, preceding evidence. No relationship between citation of matching and preceding preclinical evidence and trial outcomes was observed (28.4% of nonpositive trials vs. 26.9% of positive trials, p ~ 1). This suggests that many Phase 2 trial publications do not cite matching preclinical efficacy studies. Limited citation either suggests its absence or its exclusion from a publication. To ensure trials rest on a sound ethical basis and that publications support valid inference, journal editors and referees might encourage more complete descriptions of preclinical evidence or, where appropriate, active disclosure of its absence.

H3B-6527 clinical biomarker assay development and characterization of HCC patient samples.

4121 Background: FGFR4/FGF19 signaling axis is a novel therapeutic target in HCC. Multiple covalent FGFR4 inhibitors, including H3B-6527, are under clinical development. Preclinical efficacy studies in mice (including PDX) have shown that FGF19 expression (FGF19+) is a predictive biomarker for FGFR4 inhibitor response. The mechanisms driving FGF19 expression in HCC is largely unknown however, in some cases, focal amplification of ch11q13.3 containing FGF19 gene is thought to drive the FGF19 expression. Consistent with the preclinical observations, clinical studies have also shown that FGF19+is a predictive biomarker for FGFR4 inhibitor response. However, these trials have also reported a large number of FGF19+patients failing to respond to FGFR4 inhibitors necessitating refinement of patient selection strategies. In an attempt to obtain deeper insights into the role of FGF19+as a predictive biomarker and potentially uncover additional biomarkers that will enable improvement in patient selection strategies, we have characterized a set of 258 HCC patient samples Methods: Samples were acquired from biobanks and utilized to qualify clinical assays including FGF19 copy number (FISH), mRNA expression (qRT-PCR), FGF19 protein (IHC), and a focused NGS panel for assessing both mutations and copy number. A multiplexed protein and mRNA platform enabled assessment of p-ERK and Ki67 (protein) and Cyp7A1 (mRNA) amongst other exploratory PD biomarkers from two FFPE slides. Results: FGF19 positivity rates for IHC and qRT-PCR were 18% (41/225) and 42% (87/209), respectively. The overall correlation was 60%, with 63% (22/235) IHC positive cases also being positive by qRT-PCR. For IHC+/qRT-PCR (-) cases, RNA quality may have impacted assay sensitivity. 4% (9/244) of samples were positive for FGF19 copy number. Among samples with FGF19 copy number gains, 22% (2/9) did not show positive FGF19 expression. Conclusions: Based on our data, FGF19 mRNA is a more inclusive selection strategy and offers an approach to further refine thresholds for efficacy as determined in the clinic. Multiplexed protein-mRNA assays were also validated and implemented to enable a more comprehensive clinical biomarker program.

Integrative analyses of signaling and DNA damage repair pathways in patient-derived xenograft (PDX) models from NCI’s patient-derived models repository (PDMR).

3111 Background: Patient-derived xenografts (PDXs) are increasingly being used in translational cancer research for preclinical drug efficacy studies. The National Cancer Institute (NCI) has developed a Patient-Derived Models Repository (NCI PDMR; pdmr.cancer.gov ) of PDXs with clinical annotation, proteomics, and comprehensive genomic datasets to facilitate these studies. Here, we present an integrative genomic, transcriptomic, and proteomic analysis of critical signaling and DNA damage repair pathways in these PDX models, which represent 9 common and multiple rare tumor histologies. Methods: 304 PDX models from 294 patients were established from various solid tumor histologies from patients with primary or metastatic cancer. Whole Exome Sequencing, RNA-Seq and Reverse Phase Protein Array (RPPA) were performed on 2-9 PDXs per model across multiple passages. An integrative workflow was applied on multiple data sets to detect pathway activation. Results: We profiled 10 signaling and 5 DNA repair pathways in the PDMR dataset. We observed that: (i) a large fraction (40%) of PDX models have at least 1 targetable mutation in the RTK/RAS and/or PIK3CA pathways; (ii) 131 models (45%) have putative driver and oncogenic mutations and copy number variants (CNVs) in the WNT, TGFRb , NRF2 and NOTCH pathways. In addition, 17% of PDX models have targetable mutations in DNA damage repair pathways and 20 PDMR models have a DNA mismatch repair defect (MSI-H). We confirmed activation of the signaling pathways in a subset of PDX models by pathway enrichment analysis on gene expression data from RNASeq and phosphoprotein-specific antibody binding data from RPPA. Activation of DNA repair processes was confirmed by enrichment of relevant mutational signatures and loss of heterozygosity in these PDX models. Conclusions: Genomic analysis of NCI PDMR models revealed that a large fraction have clinically relevant somatic alterations in key signaling and DNA damage repair pathways. Further integrative analyses with matched transcriptomic and proteomic profiles confirmed pathway activation in a subset of these models, which may prioritize them for preclinical drug studies.

CNS penetration of the CDK4/6 inhibitor ribociclib in non-tumor bearing mice and mice bearing pediatric brain tumors.

Ribociclib, an orally bioavailable small-molecule CDK4/6 inhibitor is currently undergoing evaluation to treat pediatric central nervous system (CNS) tumors. However, it is crucial that it penetrates the brain and tumor. Thus, the objectives of the present study were to derive a clinically relevant mouse dosage for cerebral microdialysis studies, and to characterize ribociclib CNS penetration in non-tumor bearing mice and in mice bearing DIPGx7 (glioma) cortical allograft tumors. A plasma pharmacokinetic study of ribociclib (100mg/kg, orally) was performed in CD1 nude mice bearing glioma cortical allografts to obtain initial plasma pharmacokinetic parameters and to derive D-optimal plasma sampling time-points for microdialysis studies. Using a cerebral microdialysis technique, the extracellular fluid (ECF) disposition of ribociclib was evaluated after a single oral ribociclib dose (100mg/kg) in non-tumor bearing mice and in mice bearing glioma cortical allografts. A one-compartment plasma model with absorption and ECF compartments were fit to plasma and ECF concentration-time data using a nonlinear mixed effects modeling approach (NONMEM 7.2). The mean unbound ribociclib plasma exposure (6812ng/ml*h) was similar to that observed clinically at recommended dosages in adults. The median ribociclib ECF to plasma partition coefficient (Kp,uu) in non-tumor bearing and glioma mice was 0.10 and 0.07, respectively, and was not statistically different (t test, p = 0.19). The CNS penetration observed was encouraging enough to move ribociclib forward with preclinical efficacy studies in models of pediatric brain tumors.

Investigational RNAi Therapeutic Targeting C5 Is Efficacious in Pre-clinical Models of Myasthenia Gravis

Complement-mediated damage to the neuromuscular junction (NMJ) is a key mechanism of pathology in myasthenia gravis (MG), and therapeutics inhibiting complement have shown evidence of efficacy in the treatment of MG. In this study, we describe the development of a subcutaneously administered N-acetylgalactosamine (GalNAc)-conjugated small interfering RNA (siRNA) targeting the C5 component of complement that silences C5 expression in the liver (ALN-CC5). Treatment of wild-type rodents with ALN-CC5 resulted in robust and durable suppression of liver C5 expression. Dose-dependent serum C5 suppression was observed in non-human primates, with a lowering of serum C5 of up to 97.5% and the concomitant inhibition of serum complement activity. C5 silencing was efficacious in ameliorating disease symptoms in two standard rat models of MG, demonstrating the key role of circulating C5 in pathology at the NMJ. Improvement in disease activity scores and NMJ pathology was observed at intermediate levels of complement activity inhibition, suggesting that complete ablation of complement activity may not be required for efficacy in MG. The pre-clinical studies of ALN-CC5 and efficacy of C5 silencing in rat models of MG support further clinical development of ALN-CC5 as a potential therapeutic for the treatment of MG and other complement-mediated disorders.

Arylsulfonamide 64B Inhibits Hypoxia/HIF-Induced Expression of c-Met and CXCR4 and Reduces Primary Tumor Growth and Metastasis of Uveal Melanoma.

Uveal melanoma (UM) is the most prevalent and lethal intraocular malignancy in adults. Here, we examined the importance of hypoxia in UM growth and tested the antitumor effects of arylsulfonamide 64B, an inhibitor of the hypoxia-induced factor (HIF) pathway in animal models of UM and investigated the related mechanisms. UM cells were implanted in the uvea of mice eyes and mice systemically treated with 64B. Drug effect on primary eye tumor growth, circulating tumor cells, metastasis formation in liver, and survival were examined. 64B effects on UM cell growth, invasion and hypoxia-induced expression of C-X-C chemokine receptor type 4 (CXCR4) and mesenchymal-epithelial transition factor (c-Met) were measured. Luciferase reporter assays, chromatin immunoprecipitation, co-immunoprecipitation, and cellular thermal shift assays were used to determine how 64B interferes with the HIF transcriptional complex. Systemic administration of 64B had potent antitumor effects against UM in several orthotopic mouse models, suppressing UM growth in the eye (∼70% reduction) and spontaneous liver metastasis (∼50% reduction), and extending mice survival (P < 0.001) while being well tolerated. 64B inhibited hypoxia-induced expression of CXCR4 and c-Met, 2 key drivers of tumor invasion and metastasis. 64B disrupted the HIF-1 complex by interfering with HIF-1α binding to p300/CBP co-factors, thus reducing p300 recruitment to the MET and CXCR4 gene promoters. 64B could thermostabilize p300, supporting direct 64B binding to p300. Our preclinical efficacy studies support the further optimization of the 64B chemical scaffold toward a clinical candidate for the treatment of UM.

The potential use of oncolytic viruses in breast cancer: historical aspects and future prospects (literature review)

Viral oncolysis, an approach to cancer therapy that emerged in the XX century and based on the natural ability of viruses to kill (lyse) cells in which it multiplies, has been developed in recent years by identifying viruses or their engineering variants with selective tumor replication. Over the past decades, a number of specific interactions of oncolytic viruses (both RNA and IDNA-containing) with malignant tumor cells have been described, individual candidate viruses and the types of tumors that they lase have been detected. The therapeutic efficacy of oncolytic viruses is achieved through a combination of selective destruction of tumor cells through a direct cytotoxic effect and activation of antitumor immunity; In addition, oncolytic viruses can affect abberant signaling pathways followed by blockade of tumor cell apoptosis, which gives the virus more time to complete its life cycle. A number of oncolytic viruses have shown promising therapeutic efficacy in preclinical studies in breast cancer; thus, the herpes simplex virus has a high selectivity for replication in tumor cells, which contributes to the death and the formation of infiltration of CD8+ and CD4+ T cells around tumor islands. The ability of reoviruses to enhance the expression of PD-L1 protein in cells was found, and the measles virus armed with the BNiP3 proapoptosis gene is more active in the cell lines of triple negative breast cancer. Improved viruses, from the point of view of the effectiveness and selectivity of effects on the tumor, as well as optimized combinations with other "standard" types of systemic therapy, are very promising, especially in patients with developed drug resistance.

ARV-110: An oral androgen receptor PROTAC degrader for prostate cancer.

259 Background: The Androgen Receptor (AR) remains the principal driver of castration-resistant prostate cancer during the transition from a localized to metastatic disease. Most patients initially respond to inhibitors of the AR pathway, but the response is often relatively short-lived. The majority of patients progressing on enzalutamide or abiraterone exhibit genetic alterations in the AR locus, either in the form of amplifications or point mutations in the AR gene. Given these mechanisms of resistance, our goal is to eliminate the AR protein using the PROteolysis TArgeting Chimera (PROTAC) technology. Methods: Here we report an orally bioavailable small molecule AR PROTAC degrader, ARV-110, that promotes ubiquitination and degradation of AR. This molecule has been characterized in in vitro degradation and functional assays, and DMPK, toxicology and preclinical efficacy studies. Results: ARV-110 robustly degrades AR in all cell lines tested, with an observed half-maximal degradation concentration (DC50) of ~1 nM. ARV-110 treatment leads to highly selective AR degradation, as demonstrated by proteomic studies. In VCaP cells, PROTAC-mediated AR degradation suppresses the expression of the AR-target gene PSA, inhibits AR-dependent cell proliferation, and induces apoptosis at low nanomolar concentrations. Further, ARV-110 degrades clinically relevant mutant AR proteins and retains activity in a high androgen environment. In mouse xenograft studies, greater than 90% AR degradation is observed at a 1 mg/kg PO QD dose. Significant inhibition of tumor growth and AR signaling has been achieved in LNCaP, VCaP and prostate cancer patient derived xenograft (PDX) models. Notably, ARV-110 demonstrates in vivo efficacy and reduction of AR-target gene expression in a long term, castrate, enzalutamide-resistant VCaP tumor model. Conclusions: In summary, we report preclinical data on an orally bioavailable AR PROTAC degrader, ARV-110, that demonstrates efficacy in multiple prostate cancer models. ARV-110 has completed IND-enabling studies and FIH studies are planned for 1Q2019.

Organoids Increase the Predictive Value of in vitro Cancer Chemoprevention Studies for in vivo Outcome.

Epidemiological and preclinical data suggest that antioxidants are protective against prostate cancer whose pathogenesis has been linked to oxidative stress. However, the selenium and vitamin E Cancer Prevention Trial (SELECT), found no efficacy for selenium in reducing prostate cancer incidence while vitamin E was associated with an increased risk of the disease. These results have called in to question the models used in preclinical chemoprevention efficacy studies and their ability to predict in vivo outcomes. Chemoprevention agents have traditionally been tested on two dimensional monolayer cultures of cell lines derived from advanced prostate cancers. But as SELECT demonstrates, results from advanced disease models were not predictive of the outcome of a primary chemoprevention trial. Additionally, lack of cell-matrix interactions in two dimensional cultures results in loss of biochemical and mechanical cues relevant for native tissue architecture. We use recent findings in three dimensional organoid cultures that recapitulated the SELECT trial results to argue that the organoid model could increase the predictive value of in vitro studies for in vivo outcomes.

Abstract P1-06-03: A selective Cdk12/13 non-covalent inhibitor with potent anti-breast cancer activity

Abstract Cyclin-dependent kinases 12 and 13 (CDK12 and CDK13) are Ser/Thr protein kinase members of the CDK family. CDKs are regulated by cyclins and members of the family are key regulators of the cell cycle. Other members of this family—CDK7, CDK8, CDK9, CDK12 and CDK13—have been described as transcription-regulating kinases. CDK12 and CDK13 phosphorylate the C-terminal domain (CTD) of rpb1 the largest subunit of RNA polymerase II and interact with RNA processing factors, playing pivotal roles controlling transcription initiation and elongation, as well as posttranscriptional RNA processing. Specifically, CDK12 acts as the limiting factor for the transcription of a small subset of genes that are involved in the DNA damage response pathway and CDK13 affects expression of genes involved in growth signaling pathways. Importantly, like their cell cycle family members CDK12 and CDK13 have also been shown to be promising therapeutic targets for several cancer types. We have generated a novel, selective, and orally bioavailable, small molecule inhibitor of CDK12 and CDK13. Our lead molecule downregulates key DNA damage repair proteins including ATM, ATR, Brca1 and Rad51 leading to induction of apoptotic cell death in all triple negative breast cancer (TNBC) cell lines tested. We have confirmed the selectivity of our compound by kinase profiling and by comparing the gene expression profile by RNA-seq of cells treated with compound or infected with CRISPR sgRNA targeting Cdk12 and/or Cdk13. Importantly, our compound acts in synergy with the chemotherapeutic agents Cisplatin, Irinotecan and Olaparib. Finally, in preclinical efficacy studies, our lead compound blocked tumor progression in two different PDX models of TNBC and demonstrated tumor regression and enhanced efficacy over single treatment when dosed in combination with selected chemotherapeutic agents. Citation Format: Quereda V, Bayle S, Francesca V, Andrii M, William R, Derek D. A selective Cdk12/13 non-covalent inhibitor with potent anti-breast cancer activity [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 P1-06-03.

Abstract OT1-02-02: A phase 1, first-in-human, multi-part study of RAD140, an oral nonsteroidal selective androgen receptor modulator, in postmenopausal women with hormone receptor positive breast cancer

Abstract Background: Hormone receptor-positive (HR+) breast cancer accounts for about 75% of breast cancer cases. Despite initial response to ER-targeted therapies, subsequent tumor progression remains an important clinical problem, highlighting the need for new therapies with activity in endocrine-resistant tumors. The androgen receptor (AR) is expressed in up to 90% of ER+ breast cancers, and until the 1970s, breast cancer was commonly treated with androgens with single-agent response rates ranging from 20% to 25%. However, androgen-based therapy for breast cancer declined due to lack of tissue selectivity, potential for aromatization to estrogen, and the emergence of ER-targeted agents such as tamoxifen. RAD140 is an oral nonsteroidal selective androgen receptor modulator (SARM) that cannot be converted to estrogen by aromatase. RAD140 has high AR affinity and target selectivity, demonstrating marked tissue-selective AR agonist activity comparable to natural androgens in breast cancer cells, but lacking agonist activity in prostate cancer cells. Preclinical efficacy studies in multiple in vivo and in vitro models of AR+/ER+ breast cancer demonstrate potent anti-tumor activity of RAD140 as a single agent and in combination with a CDK4/6 inhibitor. This first-in-human study will evaluate the safety, tolerability, pharmacokinetics (PK) and clinical activity of RAD140 in patients with HR+ breast cancer. Trial Design and Specific Aims: This is a Phase I, open-label dose escalation and safety expansion study of RAD140 in postmenopausal patients (pts) with advanced HR+ breast cancer for whom no standard therapy is available. During dose escalation (Part A), pts are assigned sequentially to escalating doses of RAD140 using a standard 3+3 design to establish a maximum tolerated dose (MTD) and/or recommended dose (RD) based on safety, PK and preliminary clinical activity. The Safety Expansion (Part B) will further evaluate the safety, tolerability and clinical activity of the RD. Eligibility Criteria: Pts must be post-menopausal females ≥18 years old with locally advanced or metastatic ER+/HER2- (Part A) or ER+/AR+/HER2- (Part B) breast cancer and ECOG 0 or 1. Part A pts must not be eligible for standard therapy. Pts in Part B must have had at least 1 line of prior systemic therapy in the metastatic setting and at least 6 months of prior endocrine therapy in the metastatic setting and progressed on the most recent endocrine therapy. Measurable disease by RECIST 1.1 is also required for enrollment in Part B. Statistical Methods: Descriptive statistics (including mean, standard deviation, median for continuous variables; frequency counts and percentages for categorical variables) will be presented by dose. Plasma or serum PK parameters for RAD140 will be estimated using non-compartmental methods. Present Accrual and Target Accrual: The study will enroll up to 40 pts, including up to approximately 24 pts enrolled in cohorts of 3 to 6 in Part A, and another 15 pts enrolled in Part B. As of June 2018, 11 pts have enrolled at 5 sites. (NCT03088527) Citation Format: Hamilton E, Vidula N, Ma C, LoRusso P, Saeh J, Reichert V, Yu Z, Annett M, Weitzman A, Hattersly G, O'Neill A, Weise A. A phase 1, first-in-human, multi-part study of RAD140, an oral nonsteroidal selective androgen receptor modulator, in postmenopausal women with hormone receptor positive breast cancer [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 OT1-02-02.

Evaluation of a Fully Human, Hepatitis B Virus-Specific Chimeric Antigen Receptor in an Immunocompetent Mouse Model.

Chimeric antigen receptor (CAR) Tcell therapy is a promising novel therapeutic approach for cancer but also for chronic infection. We have developed a fully human, second-generation CAR directed against the envelope protein of hepatitis B virus on the surface of infected cells (S-CAR). The S-CAR contains a human B cell-derived single-chain antibody fragment and human immunoglobulin G (IgG) spacer, CD28- and CD3-signaling domains that may be immunogenic in mice. Because immunosuppression will worsen the clinical course of chronic hepatitis B, we aimed at developing a preclinical mouse model that is immunocompetent and mimics chronic hepatitis B but nevertheless allows evaluating efficacy and safety of a fully human CAR. The S-CAR grafted on Tcells triggered antibody responses in immunocompetent animals, and a co-expressed human-derived safeguard, the truncated epidermal growth factor receptor (EGFRt), even induced B and Tcell responses, both limiting the survival of S-CAR-grafted Tcells. Total body irradiation and transfer of Tcells expressing an analogous, signaling-deficient S-CAR decoy and the safeguard induced immune tolerance toward the human-derived structures. S-CAR Tcells transferred after immune recovery persisted and showed long-lasting antiviral effector function. The approach we describe herein will enable preclinical studies of efficacy and safety of fully human CARs in the context of a functional immune system.

Pathology Approaches to Determine Safety and Efficacy of Cardiac Ablation Catheters.

Cardiac electrophysiology utilizes nonimplantable, catheter-based devices for diagnosis and treatment of arrhythmias as well as electroanatomical mapping of cardiac chambers. Gross pathology and histopathological assessments in preclinical studies play critical roles in determining the safety and efficacy of cardiac ablation systems used to treat tachyarrhythmias. The pathologist must assess ablation sites, adjacent structures and organs, and downstream organs to characterize the effects of the ablation treatment and determine whether adverse local reactions, collateral injury, or downstream thromboembolism are present. Histopathological assessment serves as an adjunct to electroanatomical data in determining efficacy in preclinical studies. Histopathology is the standard in definitively demonstrating transmurality of ablation lesions, which is necessary for complete conduction block, as well as showing the linear or circumferential distribution of a contiguous, transmural ablation lesion necessary for electroanatomical isolation of entire target structures such as pulmonary veins and the cavotricuspid isthmus, which are involved in propagating certain arrhythmias. This article will detail gross and histological methods for the pathology assessment of preclinical studies evaluating the safety and/or efficacy of cardiac ablation catheter systems as well as discuss correlation of pathology data with other supporting evidence for safety and efficacy such as acute, electroanatomical data.

The Binding of Human IgG to Minipig Fc\u03b3Rs \u2013 Implications for Preclinical Assessment of Therapeutic Antibodies

PurposeThe Göttingen minipig is a relevant non-rodent species for regulatory toxicological studies. Yet, its use with therapeutic antibodies has been limited by the unknown binding properties of human immunoglobulins (huIgG) to porcine Fc gamma receptors (poFcγR) influencing safety and efficacy readouts. Therefore, knowing IgG-FcγR interactions in the animal model is a prerequisite for the use of minipigs in preclinical safety and efficacy studies with therapeutic antibodies.MethodsHere, we describe the cloning and expression of poFcγRs and their interactions with free and complexed human therapeutic IgG1 by surface plasmon resonance and flow cytometry.ResultsWe show here that poFcγRIa, poFcγRIIa, and poFcγRIIb bind huIgG1 antibodies with comparable affinities as corresponding huFcγRs. Importantly, poFcγRs bind huIgG immune complexes with high avidity, thus probably allowing human-like effector functions. However, poFcγRIIIa binds poIgG1a but not to huIgG1.ConclusionsThe lack of binding of poFcγRIIIa to huIgG1 might cause underestimation of FcγRIIIa-mediated efficacy or toxicity as mediated by porcine natural killer cells. Therefore, the suitability of minipigs in preclinical studies with human therapeutic antibodies has to be assessed case by case. Our results facilitate the use of Göttingen minipigs for assessment of human therapeutic antibodies in preclinical studies.

Cloning of carrier cells infected with oncolytic adenovirus driven by midkine promoter and biosafety studies.

BackgroundA549 carrier cells infected with oncolytic adenovirus can induce complete tumor reduction of subcutaneous ovarian tumors but not intraperitoneal disseminated ovarian tumors. This appears to be a result of the insufficient antitumor effect of A549 carrier cells. Therefore, in the present study, we cloned a novel carrier cell with the aim of improving the antitumor effects.MethodsCarrier cells infected with oncolytic adenovirus AdE3‐midkine with a midkine promoter were cloned by limiting dilution. We examined the antitumor effects of these cells on subcutaneous and intraperitoneal OVHM ovarian tumors in a syngeneic mouse model. Biosafety tests were conducted in beagle dogs and rabbits.ResultsWe cloned EHMK‐51‐35 carrier cells with 10‐fold higher antitumor effects compared to A549 carrier cells in vitro. EHMK‐51‐35 carrier cells co‐infected with AdE3‐midkine and Ad‐mGM‐CSF induced a 100% complete tumor reduction in subcutaneous tumors and a 60% reduction of intraperitoneal disseminated tumors. Single‐dose acute toxicity test on beagle dogs with EHMK‐51‐35 carrier cells co‐infected with AdE3‐midkine and Ad‐cGM‐CSF showed no serious side effects. Biologically active adenoviruses were not detected in the blood, saliva, feces, urine or whole organs. In a chronic toxicity test, VX2 tumors in rabbits were injected five times with EHMK‐51‐35 carrier cells infected with AdE3‐midkine and these rabbits showed no serious side effects.ConclusionsSignificant antitumor effects and safety of cloned EHMK‐51‐35 carrier cells were confirmed in intraperitoneal ovarian tumors and toxicity tests, respectively. These findings will be extended to preclinical efficacy studies using dogs and cats, with the aim of conducting human clinical trials on refractory solid tumors.

Preclinical toxicity and pharmacokinetics of a new orally bioavailable flubendazole formulation and the impact for clinical trials and risk/benefit to patients.

BackgroundFlubendazole, originally developed to treat infections with intestinal nematodes, has been shown to be efficacious in animal models of filarial infections. For treatment of filarial nematodes, systemic exposure is needed. For this purpose, an orally bioavailable amorphous solid dispersion (ASD) formulation of flubendazole was developed. As this formulation results in improved systemic absorption, the pharmacokinetic and toxicological profile of the flubendazole ASD formulation have been assessed to ensure human safety before clinical trials could be initiated.Methods & findingsSafety pharmacology, toxicity and genotoxicity studies have been conducted with the flubendazole ASD formulation.In animals, flubendazole has good oral bioavailability from an ASD formulation ranging from 15% in dogs, 27% in rats to more than 100% in jirds. In in vivo toxicity studies with the ASD formulation, high systemic exposure to flubendazole and its main metabolites was reached. Flubendazole, up to high peak plasma concentrations, does not induce Cmax related effects in CNS or cardiovascular system. In repeated dose toxicity studies in rats and dogs, flubendazole-induced changes were observed in haematological, lymphoid and gastrointestinal systems and in testes. In dogs, the liver was an additional target organ. Upon treatment cessation, at least partial recovery was observed for these changes in dogs. In rats, the No Observed Adverse Effect Level (NOAEL) was 5 mg (as base)/kg body weight/day (mg eq./kg/day) in males and 2.5 mg eq./kg/day in females. In dogs, the NOAEL was lower than 20 mg eq./kg/day. Regarding genotoxicity, flubendazole was negative in the Ames test, but positive in the in vivo micronucleus test.ConclusionsBased on these results, in combination with previously described genotoxicity and reproductive toxicity data and the outcome of the preclinical efficacy studies, it was concluded that no flubendazole treatment regimen can be selected that would provide efficacy in humans at safe exposure.

Combination of Sunitinib and PD-L1 Blockade Enhances Anticancer Efficacy of TLR7/8 Agonist-Based Nanovaccine.

Cancer vaccines composed of tumor-associated antigens (TAAs) and toll-like receptor (TLR) agonists have shown promising antitumor efficacy in preclinical studies by generating antigen-specific CD8 T cells, but translation of cancer vaccines to the clinic has been limited due to variables responses and development of resistance. The tumor microenvironment deploys various immune escape mechanisms that neutralize CD8 T cell-mediated tumor rejection. Therefore, we hypothesized that modulation of the tumor microenvironment can augment CD8 T cell activation and enhance therapeutic efficacy of cancer vaccines. To accomplish this, we aimed to eliminate immune suppressive cells and block their inhibitory signaling. Combination of the tyrosine kinase inhibitor (TKI) sunitinib with a nanoparticle-based cancer vaccine (nanovaccine) resulted in the reduction of immune-suppressive myeloid-derived suppressive cells (MDSCs) and regulatory T cells (Tregs). Blockade of programmed death-ligand 1 (PD-L1) using anti-PD-L1 antibody was used to reduce CD8 T cell exhaustion. Combination of nanovaccine+sunitinib+PD-L1 antibody treatment reduced PD-L1high M2 macrophages and MDSCs and upregulated activation of CD8 T cells in the tumor. Nanovaccine+sunitinib+PD-L1 antibody treatment also stimulated antigen-specific CD8 T cell response, which led to improved therapeutic efficacy in MB49 and B16F10 murine tumor models. These results suggest that modulation of tumor microenvironment using sunitinib and PD-L1 blockade can significantly enhance the antitumor efficacy of cancer nanovaccine.

The Endothelin-A Receptor Antagonist Zibotentan Induces Damage to the Nasal Olfactory Epithelium Possibly Mediated in Part through Type 2 Innate Lymphoid Cells.

Zibotentan, an endothelin-A receptor antagonist, has been used in the treatment of various cardiovascular disorders and neoplasia. Castrated athymic nude mice receiving zibotentan for a preclinical xenograft efficacy study experienced weight loss, gastrointestinal bloat, and the presence of an audible respiratory click. Human side effects have been reported in the nasal cavity, so we hypothesized that the nasal cavity is a target for toxicity in mice receiving zibotentan. Lesions in the nasal cavity predominantly targeted olfactory epithelium in treated mice and were more pronounced in castrated animals. Minimal lesions were present in vehicle control animals, which suggested possible gavage-related reflux injury. The incidence, distribution, and morphology of lesions suggested direct exposure to the nasal mucosa and a possible systemic effect targeting the olfactory epithelium, driven by a type 2 immune response, with group 2 innate lymphoid cell involvement. Severe nasal lesions may have resulted in recurrent upper airway obstruction, leading to aerophagia and associated clinical morbidity. These data show the nasal cavity is a target of zibotentan when given by gavage in athymic nude mice, and such unanticipated and off-target effects could impact interpretation of research results and animal health in preclinical studies.