Kathleen McKeever

B-cell targeted therapeutics in clinical development

B lymphocytes are the source of humoral immunity and are thus a critical component of the adaptive immune system. However, B cells can also be pathogenic and the origin of disease. Deregulated B-cell function has been implicated in several autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis. B cells contribute to pathological immune responses through the secretion of cytokines, costimulation of T cells, antigen presentation, and the production of autoantibodies. DNA-and RNA-containing immune complexes can also induce the production of type I interferons, which further promotes the inflammatory response. B-cell depletion with the CD20 antibody rituximab has provided clinical proof of concept that targeting B cells and the humoral response can result in significant benefit to patients. Consequently, the interest in B-cell targeted therapies has greatly increased in recent years and a number of new biologics exploiting various mechanisms are now in clinical development. This review provides an overview on current developments in the area of B-cell targeted therapies by describing molecules and subpopulations that currently offer themselves as therapeutic targets, the different strategies to target B cells currently under investigation as well as an update on the status of novel therapeutics in clinical development. Emerging data from clinical trials are providing critical insight regarding the role of B cells and autoantibodies in various autoimmune conditions and will guide the development of more efficacious therapeutics and better patient selection.

The Plasma Cell Signature in Autoimmune Disease

Production of pathogenic autoantibodies by self‐reactive plasma cells (PCs) is a hallmark of autoimmune diseases. We undertook this study to investigate the prevalence of PCs and their relationship to known pathogenic pathways to increase our understanding of the role of PCs in disease progression and treatment response.

Nonclinical safety of mavrilimumab, an anti-GMCSF receptor alpha monoclonal antibody, in cynomolgus monkeys: relevance for human safety.

Mavrilimumab (CAM-3001) is an investigational human IgG4 monoclonal antibody (MAb) targeting GM-CSF receptor alpha which is currently being developed for the treatment of RA. GM-CSF plays a central role in the pathogenesis of rheumatoid arthritis (RA) through the activation, differentiation, and survival of macrophages and neutrophils. To support clinical development, the nonclinical safety of mavrilimumab was evaluated in several studies with cynomolgus monkeys as the pharmacologically relevant species. Comprehensive toxicity parameters were assessed in each study, and treatment duration ranged from 4 to 26weeks. Mavrilimumab has an acceptable safety profile in monkeys with no changes in any parameters other than microscopic findings in lung. In several studies, minimal accumulation of foamy alveolar macrophages was observed. This finding was only seen in studies of at least 11weeks duration, was reversible following a dose-free recovery period and was considered non-adverse. At higher dose levels (≥30mg/kg/week), in a 26-week repeat-IV dose study, the presence of lung foreign material, cholesterol clefts, and granulomatous inflammation was also observed in a few animals and was considered adverse. The dose- and time-related accumulation of foamy macrophages in lung following exposure to mavrilimumab observed in several NHP studies was expected based upon the known role of GM-CSFRα signaling in the function of alveolar macrophages. Overall, a clean no-observed-adverse-effect-level (NOAEL) without any effects in lung was established and provided adequate clinical safety margins. In clinical studies in RA patients, mavrilimumab has demonstrated good clinical activity with adequate safety to support further clinical development. A Phase 2b study of mavrilimumab in subjects with RA is in progress.

Choice of Starting Dose for Biopharmaceuticals in First-in-Human Phase I Cancer Clinical Trials

BACKGROUND First-in-human (FIH) trials of low-molecular-weight anticancer agents conventionally derive a safe start dose (SD) from one-tenth the severely toxic dose in 10% of rodents or one-sixth the highest nonseverely toxic dose (HNSTD) in nonrodent species. No consensus has been reached on whether this paradigm can be safely applied to biotechnology-derived products (BDPs). MATERIALS AND METHODS A comprehensive search was conducted to identify all BDPs (excluding immune checkpoint inhibitors and antibody drug conjugates) with sufficient nonclinical and clinical data to assess the safety of hypothetical use of one-sixth HNSTD in an advanced cancer FIH trial. RESULTS The search identified 23 BDPs, of which 21 were monoclonal antibodies. The median ratio of the maximum tolerated or maximum administered dose (MTD or MAD) to the actual FIH SD was 36 (range, 8-500). Only 2 BDPs reached the MTD. Hypothetical use of one-sixth HNSTD (allometrically scaled to humans) would not have exceeded the MTD or MAD for all 23 BDPs and would have reduced the median ratio of the MTD or MAD to a SD to 6.1 (range, 3.5-55.3). Pharmacodynamic (PD) markers were included in some animal toxicology studies and were useful to confirm the hypothetical SD of one-sixth HNSTD. CONCLUSION One-sixth HNSTD would not have resulted in unacceptable toxicities in the data available. Supporting its use could reduce the number of dose escalations needed to reach the recommended dose. A low incidence of toxicities in animals and humans underscores the need to identify the pharmacokinetic and PD parameters to guide SD selection of BDPs for FIH cancer trials. IMPLICATIONS FOR PRACTICE Start dose (SD) for biotechnology-derived products (BDPs) can be safely derived from one-sixth the highest nonseverely toxic dose in nonrodent species and may reduce the number of dose escalations needed to reach the recommended dose in first-in-human studies while limiting unnecessary exposure to high drug levels in humans. The use of this type of SD could improve the design of phase I studies of BDPs by making them more efficient. The role of preclinical pharmacodynamic markers was useful in confirming the hypothetical SD, and attempts should be explored in future animal studies to identify such parameters.

Challenges of general safety evaluations of biologics compared to small molecule pharmaceuticals in animal models

Importance of the field: The prediction of human toxicity by employing animal models for nonclinical safety evaluation of pharmaceuticals poses numerous challenges. Each type, biologics, vaccines and small molecules, has unique features, which may impact the ability to effectively assess safety. Areas covered in this review: The importance of taking a case-by-case approach is highlighted in this review of the challenges encountered in general safety evaluations for biologics and vaccines compared to small molecules. What the reader will gain: The reader will gain insights in specific issues related to building a successful predictive nonclinical safety program for biologics. Take home message: While there is fair concordance for small molecules, animal models used for the safety evaluation of biologics may have limitations with regard to human relevance. For small molecules, this is commonly because of differences in metabolism profiles or off-target effects. For biologics, which are highly targeted molecules, it may be because of differences in physiological processes or biologic pathways that limit pharmacologic relevance. For vaccines or immunomodulatory biologics, it may be related to the complexities of modeling the human immune system in a nonhuman species. While international guidances are available to govern the nonclinical safety assessment process for human pharmaceuticals (such as ICH M3), in many instances a case-by-case approach is employed for novel agents.

Effects of ICOS+ T cell depletion via afucosylated monoclonal antibody MEDI-570 on pregnant cynomolgus monkeys and the developing offspring

MEDI-570 is a fully human afucosylated monoclonal antibody (MAb) against Inducible T-cell costimulator (ICOS), highly expressed on CD4+ T follicular helper (TFH) cells. Effects of MEDI-570 were evaluated in an enhanced pre-postnatal development toxicity (ePPND) study in cynomolgus monkeys. Administration to pregnant monkeys did not cause any abortifacient effects. Changes in hematology and peripheral blood T lymphocyte subsets in maternal animals and infants and the attenuated infant IgG immune response to keyhole limpet hemocyanin (KLH) were attributed to MEDI-570 pharmacology. Adverse findings included aggressive fibromatosis in one dam and two infant losses in the high dose group with anatomic pathology findings suggestive of atypical lymphoid hyperplasia. The margin of safety relative to the no observed adverse effect level (NOAEL) for the highest planned clinical dose in the Phase 1a study was 7. This study suggests that women of child bearing potential employ effective methods of contraception while being treated with MEDI-570.

THU0005 Investigating the Plasma Cell Signature in Autoimmune Disease

Background Production of pathogenic autoantibodies by self-reactive plasma cells (PC) is a hallmark of autoimmune diseases; thus, PC levels could be associated with efficacy of B-cell depleting therapies. Additionally, investigating the prevalence of PC in autoimmune disease and their relationship with known pathogenic pathways may increase our understanding of the role of PC in disease progression and treatment response. Objectives Flow cytometry methods that are commonly used to enumerate and describe PC are difficult to implement routinely in the clinic and almost impossible in large clinical trials because of the fragility of PC. This difficulty has hampered thorough assessment of the effect of therapeutics on PC. For this reason, we first developed a highly sensitive and specific gene expression signature that can be easily implemented in the clinic, and then applied this signature to assess the impact of a novel therapeutic on PC and the prevalence of PC in different autoimmune diseases. Methods Whole genome microarray analysis of sorted cellular fractions identified a panel of genes, IGHA, IGJ, IGKC, IGKV, and TNFRSF17, whose expression is highly significantly enriched in PC. We combined expression levels of these genes to create a signature score that estimates PC counts in blood and tissue. The sensitivity of this PC signature score was assessed through ex vivo experiments with sorted cells. The PC signature was used to monitor changes in PC levels following anti-CD19 therapy; evaluate the relationship between PC and other autoimmune disease-related genes; and estimate PC levels in affected blood and tissue from multiple autoimmune diseases. Results Results indicated that the PC signature was highly sensitive and capable of detecting as few as 300 PCs. In scleroderma patients enrolled in a Phase I trial with MEDI-551, an anti-CD19 antibody with enhanced effector function, the PC signature was reduced over 90% following MEDI-551 treatment and this reduction was highly correlated (r=0.72, p=0.002) between blood and skin. Comparing the distribution of the PC signature in tissue and whole blood of patients with various autoimmune diseases revealed 30-35% of systemic lupus erythematosus, rheumatoid arthritis, and scleroderma patients with increased PC levels. Conclusions Our results demonstrate the utility of this newly developed gene expression-based PC signature. In addition to providing a robust and straightforward way to accurately measure PC levels in the clinic, the signature may be especially useful to tailor the treatment of autoimmune diseases by identifying those patients who may most benefit from PC-targeted therapies. Disclosure of Interest K. Streicher Shareholder of: MedImmune; AstraZeneca, C. Morehouse Shareholder of: MedImmune; AstraZeneca, C. Groves Shareholder of: MedImmune; AstraZeneca, B. Rajan Shareholder of: MedImmune; AstraZeneca, F. Pilataxi Shareholder of: MedImmune; AstraZeneca, K. Lehmann Shareholder of: MedImmune; AstraZeneca, P. Brohawn Shareholder of: MedImmune; AstraZeneca, B. Higgs Shareholder of: MedImmune; AstraZeneca, K. McKeever Shareholder of: MedImmune; AstraZeneca, S. Greenberg: None Declared, D. Fiorentino: None Declared, L. Richman: None Declared, B. Jallal Shareholder of: MedImmune; AstraZeneca, R. Herbst Shareholder of: MedImmune; AstraZeneca, Y. Yao Shareholder of: MedImmune; AstraZeneca, K. Ranade Shareholder of: MedImmune; AstraZeneca

FRI0482 Safety and Tolerability of MEDI-551 in Subjects with Systemic Sclerosis (SSC): Results from A Phase 1 Randomized, Placebo-Controlled Escalating Single-Dose Study

Background CD19+ B cells may play a role in the pathogenesis of SSc. MEDI-551 is a humanized afucosylated IgG1κ monoclonal antibody that binds to CD19 and depletes B cells. Therefore, MEDI-551 may show activity in patients with SSc. Objectives Safety and tolerability of escalating single IV doses of MEDI-551 in adults with SSc who have moderate skin thickening. PK, PD, immunogenicity, and disease activity are also assessed. Methods A phase 1, randomized, placebo-controlled study in adults with SSc with moderate skin thickening (modified Rodnan Skin Score [mRSS] ≥2) in an area suitable for repeat biopsy. Subjects received 1 of 5 single IV doses of MEDI-551 (0.1, 0.3, 1.0, 3.0, or 10.0 mg/kg) or placebo (PBO). Cohort 1 (0.1 mg/kg; n=1) received MEDI-551 in an open-label manner; cohort 2 (0.3 mg/kg; n=5) was randomized 4:1 to receive MEDI-551 or PBO; cohorts 3 and 4 (1.0, 3.0 mg/kg; n=7) were randomized 6:1; and cohort 5 (10 mg/kg; n=8) was randomized 7:1. AEs were monitored. Blood was collected for PK, PD, and anti-drug antibodies (ADAs). All subjects were followed until the B-cell count in peripheral blood returned to baseline (BL). Results All subjects (MEDI-551 n=24; PBO n=4) completed primary follow up period (Day 85) of the study; there were no discontinuations for any reason. Most subjects were white (86%) and female (68%); median age 48.5y and median disease duration 4.65y from first non-Raynauds symptoms. 86% subjects had diffuse cutaneous SSc; median mRSS was 22 (range 9–43). Follow-up is ongoing. As of 31Dec13, median duration in study ranged from 401d–1364d for MEDI-551 subjects and was 622d for PBO. Related AEs occurred only with MEDI-551; most were single events except infusion-related reaction (n=4; only observed in subjects without pre-medication) and cough (n=2). No serious AEs occurred in the PBO group. 15 SAEs occurred in 6 subjects in the MEDI-551 group; 2 (supraventricular tachycardia, subclavian vein thrombosis) were considered possibly related to MEDI-551. 1 subject in the 3.0 mg/kg group died due to worsening of scleroderma renal disease (not considered MEDI-551 related). PK was nonlinear after MEDI-551 administration (0.1–10.0 mg/kg). The t1/2 were similar (11.2–13.5d) for doses ≥1.0 and shorter for doses <1.0 mg/kg (6.8–7.1d). ADAs were detected in 4 subjects who received MEDI-551; all had reduced serum MEDI-551 levels compared to those without ADAs in the same dose group. Following MEDI-551 infusion, B-cell counts were depleted ∼90% from BL in all dose groups by Day 57. B-cell depletion was maintained for ≥6mos in 1 (17%) subject in the 1.0 mg/kg group, 3 (50%) in the 3.0 mg/kg group, and 6 (86%) in the 10 mg/kg group. Median mRSS decreased from BL (-5; range -14 to 2) with MEDI-551 by Day 85 but increased with PBO (2.5; range -4 to 8) suggesting clinical activity on skin thickness by MEDI-551. Conclusions The safety profile of MEDI-551 at single IV doses ranging from 0.1 to 10.0 mg/kg supports further clinical development. Rapid sustained B-cell depletion was observed following single IV infusion with 3.0 and 10.0 mg/kg MEDI-551. Clinical activity was suggested by decreased mRSS with MEDI-551. Acknowledgements This study was sponsored by MedImmune. Disclosure of Interest E. Schiopu Grant/research support: Actelion, InterMune, MedImmune, Pfizer, United Therapeutics, Consultant for: Sobi, Inc., Paid instructor for: United Therapeutics, Speakers bureau: United Therapeutics, Actelion, S. Chatterjee Grant/research support: MedImmune, V. Hsu Grant/research support: MedImmune, A. Flor Shareholder of: AstraZeneca, Employee of: MedImmune, D. Pavlovic Shareholder of: AstraZeneca, Employee of: MedImmune, K. Patra Shareholder of: AstraZeneca, Employee of: MedImmune, J. Li Shareholder of: AstraZeneca, Employee of: MedImmune, K. McKeever Shareholder of: AstraZeneca, Employee of: MedImmune, R. Herbst Shareholder of: AstraZeneca, Employee of: MedImmune DOI 10.1136/annrheumdis-2014-eular.5908

Abstract 4424: Nonclinical safety evaluation of MEDI0639 (Anti-DLL4 Mab) to support first time In human: linking DLL4-notch signaling blockade to exaggerated pharmacology effects in cynomolgus monkeys.

Delta-like ligand 4 (DLL4)-Notch signaling regulates several key stages of angiogenesis. MEDI0639 is a human IgG1 antibody that blocks the binding of DLL4 to the Notch receptor and is being developed as a potential anticancer therapy for patients with solid tumors. Cynomolgus monkeys were selected as a pharmacologically relevant species for toxicologic evaluations of MEDI0639. The results of these studies showed dose-dependent MEDI0639-related serious adverse effects associated with possible gastrointestinal bleeding and heart failure. In general, these adverse effects were monitorable, reversible and consistent with the likely pharmacologic effects on vascular homeostasis. Pathologic changes were observed in liver, heart, lung, and thymus. Changes in clinical pathology parameters, such as decreased red blood cell (RBC) mass, were consistent with possible blood loss and responsive erythropoiesis. Elevations in levels of liver enzymes were indicative of hepatocellular injury and were consistent with histopathologic findings in liver. Due to the adverse cardiovascular (CV) findings from repeat-dose toxicity studies, the effects of MEDI0639 on the CV system were characterized in a dedicated CV safety pharmacology study in cynomolgus monkeys. Notable findings from this study were increased levels of C-reactive protein (CRP), blood pressure (BP), and heart rate (HR) which tended to return to baseline levels during an 8-week dose-free recovery period. In addition to the evaluation of these toxicity parameters, the potential pharmacodynamic (PD) effects of MEDI0639 on circulating endothelial cells (CECs) in whole blood and on RNA expression levels of selected genes in the DLL4 and angiogenesis pathways in samples of colon tissue were assessed. Results showed that mRNA expressions levels of DLL4 and Notch4 were up-regulated when normalized to housekeeping genes while expression levels of Jagged1, Hey1, and Hes1 were down regulated when normalized to the EC surface marker PECAM (CD31) in all MEDI0639-treated groups. The effects of MEDI0639 on EC were confirmed by the observed increase in expression of PECAM in colon tissue and the increased numbers of total, proliferating, and apoptotic CECs in whole blood of MEDI0639-treated animals. Overall, MEDI0639-related adverse effects were monitorable, reversible and consistent with exaggerated pharmacology effects - that is DLL4 blockade is expected to lead to the formation of immature, disorganized blood vessels with inadequate mural cell coverage. This data was used to determine an appropriate starting dose for a FTIH Phase 1 clinical study of MEDI0639 in cancer patients. Citation Format: Patricia C. Ryan, Jiaqi Huang, Haifeng Bao, Song Cho, Philip Brohawn, Patricia Burke, Kim Lehmann, Fernanda Pilataxi, Yihong Yao, Kathleen McKeever, Rakesh Dixit. Nonclinical safety evaluation of MEDI0639 (Anti-DLL4 Mab) to support first time In human: linking DLL4-notch signaling blockade to exaggerated pharmacology effects in cynomolgus monkeys. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4424. doi:10.1158/1538-7445.AM2013-4424

OP0255 Inhibition of the Plasma Cell Signature Correlates with Reduced Collagen Expression in Systemic Sclerosis

Background Systemic sclerosis (SSc) is characterized by excessive extracellular matrix (ECM) deposition in the skin, as well as autoantibody production, release of various cytokines, and T-cell activation. Several lines of evidence indicate a potential role for B cells in the pathogenesis of SSc through effects on autoantibody production, T-cell activation, and fibrosis, among others. Accordingly, targeting B cells could effectively reduce ECM deposition and the inflammatory background of this disease. Objectives In animal models of SSc, decreased B-cell function following CD19 inhibition led to reduced skin thickness and a reduction in autoantibody production, which is consistent with the expression of CD19 on plasma cells (PC), the major source of antibody production. Therefore, our goal was to investigate the effect of CD19 inhibition on PC levels and collagen expression in the skin of SSc patients. Methods We evaluated skin biopsies obtained from a Phase I clinical trial of MEDI-551, an anti-CD19 antibody expected to deplete PC and B cells. Skin biopsies were collected pre-treatment (baseline) and at 29 days post-treatment with either MEDI-551 or placebo. To evaluate PC, we used whole genome microarray analysis of sorted cellular fractions to identify a panel of genes expressed predominantly in PC. To account for the multiple collagen types involved in skin fibrosis, a collagen score was calculated as the median expression of three collagen genes, COL1A1, COL3A1, and COL5A1. Results In patients with SSc, the collagen score was positively correlated with the modified Rodnan skin score (mRSS) disease activity measure at baseline (r=0.67, p=0.004), highlighting the role of collagen expression in SSc disease severity. Additionally, we identified a positive correlation between the PC signature and the collagen score at baseline (r=0.60, p=0.001). Following anti-CD19 treatment, the collagen score and the PC signature were both inhibited in skin as much as 90%, with a median inhibition of 35% and 50%, respectively. No change in the PC signature or collagen score was observed following placebo treatment. Interestingly, the inhibition of the PC signature was positively correlated with inhibition of the collagen score in all patients (r=0.80, p=0.001). Conclusions The positive correlation observed between inhibition of the PC signature and inhibition of this collagen score in scleroderma skin supports a role for PC in the pathogenic mechanism of this disease. These preliminary results need to be validated in a larger cohort of patients to determine if changes in PC signature and the collagen score could predict those who respond to treatment with PC-depleting therapeutics. Disclosure of Interest K. Streicher Shareholder of: MedImmune; AstraZeneca, C. Morehouse Shareholder of: MedImmune; AstraZeneca, C. Groves Shareholder of: MedImmune; AstraZeneca, B. Rajan Shareholder of: MedImmune; AstraZeneca, F. Pilataxi Shareholder of: MedImmune; AstraZeneca, K. Lehmann Shareholder of: MedImmune; AstraZeneca, P. Brohawn Shareholder of: MedImmune; AstraZeneca, B. Higgs Shareholder of: MedImmune; AstraZeneca, K. McKeever Shareholder of: MedImmune; AstraZeneca, L. Richman: None Declared, B. Jallal Shareholder of: MedImmune; AstraZeneca, R. Herbst Shareholder of: MedImmune; AstraZeneca, Y. Yao Shareholder of: MedImmune; AstraZeneca, K. Ranade Shareholder of: MedImmune; AstraZeneca