Use of the dTAG system in vivo to degrade CDK2 and CDK5 in adult mice and explore potential safety liabilities

The degradation tag (dTAG) system for target protein degradation can remove proteins from biological systems without the drawbacks of some genetic methods, such as slow kinetics, lack of reversibility, low specificity, and the inability to titrate dosage. These drawbacks can make it difficult to compare toxicity resulting from genetic and pharmacological interventions, especially in vivo. Because the dTAG system has not been studied extensively in vivo, we explored the use of this system to study the physiological sequalae resulting from CDK2 or CDK5 degradation in adult mice. Mice with homozygous knock-in of the dTAG sequence onto CDK2 and CDK5 were born at Mendelian ratios despite decreased CDK2 or CDK5 protein levels in comparison to wild-type mice. In bone marrow cells and duodenum organoids derived from these mice, treatment with the dTAG degrader dTAG-13 resulted in rapid and robust protein degradation but caused no appreciable change in viability or the transcriptome. Repeated delivery of dTAG-13 in vivo for toxicity studies proved challenging; we explored multiple formulations in an effort to maximize degradation while minimizing formulation-related toxicity. Degradation of CDK2 or CDK5 in all organs except the brain, where dTAG-13 likely did not cross the blood brain barrier, only caused microscopic changes in the testis of CDK2dTAG mice. These findings were corroborated with conditional CDK2 knockout in adult mice. Our results suggest that the dTAG system can provide robust protein degradation in vivo and that loss of CDK2 or CDK5 in adult mice causes no previously unknown phenotypes.

Scientific and Regulatory Policy Committee Points to Consider: Integration of Clinical Pathology Data With Anatomic Pathology Data in Nonclinical Toxicology Studies

Integrating clinical pathology data with anatomic pathology data is a common practice when reporting findings in the context of nonclinical toxicity studies and aids in understanding and communicating the nonclinical safety profile of test articles in development. Appropriate pathology data integration requires knowledge of analyte and tissue biology, species differences, methods of specimen acquisition and analysis, study procedures, and an understanding of the potential causes and effects of a variety of pathophysiologic processes. Neglecting these factors can lead to inappropriate data integration or a missed opportunity to enhance understanding and communication of observed changes. In such cases, nonclinical safety information relevant to human safety risk assessment may be misrepresented or misunderstood. This "Points to Consider" manuscript presents general concepts regarding pathology data integration in nonclinical studies, considerations for avoiding potential oversights and errors in data integration, and focused discussion on topics relevant to data integration for several key organ systems, including liver, kidney, and cardiovascular systems.

Scientific and Regulatory Policy Committee Points to Consider: Integration of Clinical Pathology Data With Anatomic Pathology Data in Nonclinical Toxicology Studies

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POS1195 ASSESSING ANTIBODY STATUS FOR SARS-CoV-2 IN PEOPLE WITH CORONAVIRUS INFECTION: A TIME COURSE STUDY IN PEOPLE WITH AUTOIMMUNE CONDITIONS

Background:

With the emergence of the global coronavirus pandemic, increasing concerns have been raised about the course of SARS-CoV-2 infection in people with immune-mediated disorders.

Objectives:

In this study we aimed to assess the time course of proven SARS-CoV-2 infection, development of humoral immunity with detectable antibodies to the virus and evaluate any changes in antibody titres over time.

Methods:

We recruited 114 participants in total who had potential symptoms of Covid-19 infection. Participants were recruited from rheumatology or inflammatory bowel disease (IBD) clinics from their records who attended a London Teaching hospital for care. Ethical Approval was in place for the study. Age- and gender- matched control participants without any underlying rheumatological condition/IBD were recruited as a comparator group. Clinical symptoms for Covid-19 infection were assessed using the Covid-19 Rheumatology Global Alliance assessment criteria (https://rheum-covid.org/). Information about Disease Modifying Anti-Rheumatic Drug (DMARD) drug use was also recorded. Participants’ serum samples were collected for quantitative serological assessment of antibodies to SARS-CoV-2 using the Mologic Enzyme-Linked ImmunoSorbent Assay (ELISA) IgG kit. The optical density values were plotted aganist time using a normalisation as previously described (1). A cut-off above 0 indicated positive serology.

Results:

A total of 114 subjects were recruited into the study. Subjects were recruited if they had suspected Covid symptoms. Of the population recruited, the total number subsequently testing positive for SARS-CoV-2 was n=59 (either on serology or PCR). The number of subjects with autoimmune conditions diagnosed with Covid-19 was 32, with 30 subjects being symptomatic (the asymptomatic 2 subjects were excluded from further analyses). Of the 30 symptomatic subjects, the average age was 56, with a female to male ratio of 19:11. The most prevalent diagnoses were RA (30%), Psoriatic Arthritis (16.7%), SLE (10%), sarcoidosis 10%), Ulcerative Colitis (10%), Crohn’s disease (10%), seronegative inflammatory arthritis (6.7%), Sjogren’s (3.3%) and Juvenile Idiopathic Arthritis (3.3%). The majority were on csDMARDs (60%), biologic DMARDs (20%), tacrolimus (3.3%) and the remaining 16.7% were not on DMARDs. Most subjects required treatment in hospital (56.7%), a smaller number required high dependency care (6.7%) and the rest were treated at home (36.6%). The majority required no oxygen (63.3%), with a further 30% requiring oxygen and 6.7% needed more supportive care i.e. CPAP/ventilation. We also had a matched control group (n=29) of subjects who developed SARS-CoV-2 but had no underlying autoimmune conditions. These subjects had a mean age of 55, female: male ratio 18: 11. Of these 31% had home management, 55.2% had ward level treatments and 13.8% had intensive care treatment. Of the controls, 48.3% did not require oxygen, 37.9% needed simple oxygen and 13.8% were on CPAP. A total of 35 subjects from the original study have attended for follow-up visits. Antibody titres for IgG using the Mologic ELISA detection assay were compared at two visits for the control and autoimmune group. Results showed that subjects with autoimmune conditions and those without who developed SARS-CoV-2 showed very similar antibody titres by optical density (OD) (Figure 1) and maintained antibody responses beyond 6 months in most cases.

Conclusion:

Serological assays can assist in the understanding of disease severity of SAR-CoV-2 infection. They can be a useful tool for patient surveillance, especially in people who are on immunomodulatory drugs and are being seen in Rheumatology services. Future work is needed to assess the duration and potential protective nature of humoral antibody responses to SARS-CoV-2.

References:

[1]Staines HM, Kirwan D, Clark DJ et al. Dynamics of IgG seroconversion and pathophysiology of COVID:19 infections. medRxiv preprint doi: https://doi.org/10.1101/2020.06.07.20124636.

Disclosure of Interests:

Kathryn Biddle: None declared, Soraya Koushesh: None declared, Anna Blundell: None declared, David Clark: None declared, Sanjeev Krishna: None declared, Nidhi Sofat Consultant of: Advisory work for Pfizer and Eli Lilly, Grant/research support from: Received grants from Bristol Myers Squibb and Pfizer for Investigator Initiated Studies.

A Diagnostic Approach for Rodent Progressive Cardiomyopathy and Like Lesions in Toxicology Studies up to 28 Days in the Sprague Dawley Rat (Part 2 of 2)

To test the diagnostic approach described in part 1 of this article, 2 exercises were completed by pathologists from multiple companies/agencies. Pathologist's examination of whole slide image (WSI) heart sections from rats using personal diagnostic approaches (exercise #1) corroborated conclusions from study #1. Using the diagnostic approach described in part 1, these pathologists examined the same WSI heart sections (exercise #2) to determine whether that approach increased consistency of diagnosis of rodent progressive cardiomyopathy (PCM) lesions. In exercise #2, there was improved consistency of categorization of small borderline morphologies and mild lesions, but a decrement in consistency of categorizing minimal lesions. Exercises 1 and 2 suggest the described diagnostic approach is representative of that in use by the majority of toxicologic pathologists across companies/agencies and that application by all may improve diagnostic consistency of PCM/like lesions. Additionally, a criterion of approximately 5% heart section involvement is suggested for separating mild from moderate or greater severity. While evidence is not absolute, until further investigation shows otherwise, microscopic changes resembling PCM, but located in the epicardial and subepicardial region of the right ventricle, may be considered as part of the spectrum of PCM.

A Diagnostic Approach for Rodent Progressive Cardiomyopathy and Like Lesions in Toxicology Studies up to 28 Days in the Sprague Dawley Rat (Part 1 of 2)

Spontaneous rodent progressive cardiomyopathy (PCM) in the Sprague Dawley rat may confound identification and/or interpretation of potential test article (TA)-related cardiotoxicity. Pathologists apply diagnostic term(s) and thresholds for diagnosing and assigning severity grades for PCM and/or PCM-like (PCM/like) lesions consistently within a study, which is necessary to identify and interpret TA-related findings. Due to differences in training and/or experiences, diagnostic terms and thresholds may vary between pathologists. Harmonized terminology and thresholds across studies will generate better historical control data, will likely enhance interpretation of study data, and may further enhance our understanding of the spontaneous change. An assessment of the diagnostic approaches of a group of 37 pathologists identified an approach that is relatively easily applied; and if adopted, it could enhance diagnostic consistency across studies. This approach uses the single "slash" term "necrosis/inflammatory cell infiltrate (NICI)" as the diagnosis for the spectrum of lesions seen in younger rats, uses no threshold for diagnosis (e.g., diagnose all lesions clearly identifiable as PCM/like), and uses aggregate lesion size of approximately ≥45% of the field of view (FOV) using a 10×/22 eyepiece and the 40× objective or approximately ≥100% of the FOV using the 60× objective as the criterion separating minimal from mild severities.

Liver Microvascular Injury and Thrombocytopenia of Antibody-Calicheamicin Conjugates in Cynomolgus Monkeys-Mechanism and Monitoring

Purpose: Adverse reactions reported in patients treated with antibody-calicheamicin conjugates such as gemtuzumab ozogamicin (Mylotarg) and inotuzumab ozogamicin include thrombocytopenia and sinusoidal obstruction syndrome (SOS). The objective of this experimental work was to investigate the mechanism for thrombocytopenia, characterize the liver injury, and identify potential safety biomarkers.Experimental Design: Cynomolgus monkeys were dosed intravenously at 6 mg/m²/dose once every 3 weeks with a nonbinding antibody-calicheamicin conjugate (PF-0259) containing the same linker-payload as gemtuzumab ozogamicin and inotuzumab ozogamicin. Monkeys were necropsied 48 hours after the first administration (day 3) or 3 weeks after the third administration (day 63).Results: PF-0259 induced acute thrombocytopenia (up to 86% platelet reduction) with nadirs on days 3 to 4. There was no indication of effects on megakaryocytes in bone marrow or activation of platelets in peripheral blood. Microscopic evaluation of liver from animals necropsied on day 3 demonstrated midzonal degeneration and loss of sinusoidal endothelial cells (SECs) associated with marked platelet accumulation in sinusoids. Liver histopathology on day 63 showed variable endothelial recovery and progression to a combination of sinusoidal capillarization and sinusoidal dilation/hepatocellular atrophy, consistent with early SOS. Among biomarkers evaluated, there were early and sustained increases in serum hyaluronic acid (HA) that correlated well with serum aspartate aminotransferase and liver microscopic changes, suggesting that HA may be a sensitive diagnostic marker of the liver microvascular injury.Conclusions: These data support the conclusion that target-independent damage to liver SECs may be responsible for acute thrombocytopenia (through platelet sequestration in liver sinusoids) and development of SOS. Clin Cancer Res; 23(7); 1760-70. ©2016 AACR.

Abstract LB-202: Liver microvascular injury and thrombocytopenia of antibody-calicheamicin conjugates: mechanism and monitoring

Gemtuzumab ozogamicin (Mylotarg, GO) and inotuzumab ozogamicin (IO) are antibody-drug conjugates (ADCs) comprised of different humanized monoclonal antibodies (against CD33 and CD22 antigen, respectively) and of the same acid-labile linker and calicheamicin payload. GO and IO are developed for the treatment of acute myeloid leukemia and acute lymphoblastic leukemia, respectively. Adverse events reported with these 2 drugs in patients include thrombocytopenia and liver toxicity, which is characterized by increases in serum aminotransferases and bilirubin along with occasional cases of sinusoidal obstruction syndrome (SOS). The platelet and liver effects were seen in patients with conjugates targeting unrelated antigens and are likely target-independent. Since the specific mechanisms of these toxicities remain elusive, an investigative study was performed in cynomolgus monkeys with a non-binding ADC containing the same linker and payload as GO and IO, PF-0259, with the objectives to investigate the mechanism for thrombocytopenia, characterize the liver injury and identify potential safety biomarkers. Cynomolgus monkeys were dosed intravenously with PF-0259 at 6 mg/m2/dose once every 3 weeks for up to 3 doses and were necropsied 48 hours after the 1st administration (Day 3) or 3 weeks after the 3rd administration (Day 63). PF-0259 induced acute thrombocytopenia (up to 86% reduction in platelet count) in monkeys with nadirs on Days 3-4. There was no indication of effects on megakaryocytes in bone marrow or activation of platelets in peripheral blood. Microscopic evaluation of liver samples from animals necropsied on Day 3 demonstrated midzonal degeneration and loss of sinusoidal endothelial cells (SECs) associated with marked platelet accumulation in sinusoids. Liver histopathology on Day 63 showed variable endothelial cell recovery and progression to a combination of sinusoidal capillarization and sinusoidal dilation/hepatocellular atrophy, consistent with early SOS. Among biomarkers evaluated, there were early and sustained increases in serum hyaluronic acid (HA) that correlated well with AST levels and liver microscopic changes, suggesting that HA could be a sensitive diagnostic marker of the liver microvascular injury. In conclusion, this work has demonstrated that target-independent damage to liver SECs was responsible for acute thrombocytopenia (through platelet sequestration in the liver) and development of early SOS in monkeys. The translation of these observations to humans has not been evaluated. We further hypothesize that this toxicity mechanism may operate for other types of non-calicheamicin based ADCs in patients where adverse events of thrombocytopenia, increased liver enzymes and liver microvascular disorders (including nodular regenerative hyperplasia) have been observed.

Citation Format: Magali Guffroy, Hadi Falahatpisheh, Kathleen Biddle, John Kreeger, Leslie Obert, Karen Walters, Richard Goldstein, Germaine Boucher, Timothy Coskran, William Reagan, Danielle Sullivan, Sharon Sokolowski, Richard Giovanelli, Hans-Peter Gerber, Martin Finkelstein, Nasir Khan. Liver microvascular injury and thrombocytopenia of antibody-calicheamicin conjugates: mechanism and monitoring. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-202.

Naming-speed processes, timing, and reading: a conceptual review

This article integrates the findings in the special issue with a comprehensive review of the evidence for seven central questions about the role of naming-speed deficits in developmental reading disabilities. Cross-sectional, longitudinal, and cross-linguistic research on naming-speed processes, timing processes, and reading is presented. An evolving model of visual naming illustrates areas of difference and areas of overlap between naming speed and phonology in their underlying requirements. Work in the cognitive neurosciences is used to explore two nonexclusive hypotheses about the putative links between naming speed and reading processes and about the sources of disruption that may cause subtypes of reading disabilities predicted by the double-deficit hypothesis. Finally, the implications of the work in this special issue for diagnosis and intervention are elaborated.