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Background CD73 upregulation in tumors leads to local immunosuppression. This phase I, first-in-human study evaluated oleclumab (MEDI9447), an anti-CD73 human IgG1λ monoclonal antibody, alone or with durvalumab in patients with advanced colorectal cancer (CRC), pancreatic ductal adenocarcinoma (PDAC), or epidermal growth factor receptor-mutant non-small-cell lung cancer (NSCLC). Methods Patients received oleclumab 5–40 mg/kg (dose-escalation) or 40 mg/kg (dose-expansion) intravenously every 2 weeks (Q2W), alone (escalation only) or with durvalumab 10 mg/kg intravenously Q2W. Results 192 patients were enrolled, 66 during escalation and 126 (42 CRC, 42 PDAC, 42 NSCLC) during expansion. No dose-limiting toxicities occurred during escalation. In the monotherapy and combination therapy escalation cohorts, treatment-related adverse events (TRAEs) occurred in 55 and 54%, respectively, the most common being fatigue (17 and 25%). In the CRC, PDAC, and NSCLC expansion cohorts, 60, 57, and 45% of patients had TRAEs, respectively; the most common were fatigue (15%), diarrhea (9%), and rash (7%). Free soluble CD73 and CD73 expression on peripheral T cells and tumor cells showed sustained decreases, accompanied by reduced CD73 enzymatic activity in tumor cells. Objective response rate during escalation was 0%. Response rates in the CRC, PDAC, and NSCLC expansion cohorts were 2.4% (1 complete response [CR]), 4.8% (1 CR, 1 partial response [PR]), and 9.5% (4 PRs), respectively; 6-month progression-free survival rates were 5.4, 13.2, and 16.0%. Conclusions Oleclumab ± durvalumab had a manageable safety profile, with pharmacodynamic activity reflecting oleclumab’s mechanism of action. Evidence of antitumor activity was observed in tumor types that are generally immunotherapy resistant. Clinical trial registration Clinicaltrials.gov, NCT02503774; date of registration, July 17, 2015.

Expression of cell surface Fc gamma receptors on human cells

Supplementary Methods

Ligation of OX40 (CD134, TNFRSF4) on activated T cells by its natural ligand (OX40L, CD252, TNFSF4) enhances cellular survival, proliferation, and effector functions such as cytokine release and cellular cytotoxicity. We engineered a recombinant human OX40L IgG4P Fc fusion protein termed MEDI6383 that assembles into a hexameric structure and exerts potent agonist activity following engagement of OX40. MEDI6383 displayed solution-phase agonist activity that was enhanced when the fusion protein was clustered by Fc gamma receptors (FcγRs) on the surface of adjacent cells. The resulting costimulation of OX40 on T cells induced NFκB promoter activity in OX40-expressing T cells and induced Th1-type cytokine production, proliferation, and resistance to regulatory T cell (Treg)-mediated suppression. MEDI6383 enhanced the cytolytic activity of tumor-reactive T cells and reduced tumor growth in the context of an alloreactive human T cell:tumor cell admix model in immunocompromised mice. Consistent with the role of OX40 costimulation in the expansion of memory T cells, MEDI6383 administered to healthy nonhuman primates elicited peripheral blood CD4 and CD8 central and effector memory T-cell proliferation as well as B-cell proliferation. Together, these results suggest that OX40 agonism has the potential to enhance antitumor immunity in human malignancies. Mol Cancer Ther; 17(5); 1024–38. ©2018 AACR.

Supplementary Figure 5. Lack of NK cell mediated ADCC and complement protein C1q binding by MEDI6383. Supplementary Figure 6. MEDI6383 mediated release of cytokines from primary human T cells.

The 15th edition of the Workshop on Recent Issues in Bioanalysis (15th WRIB) was held on 27 September to 1 October 2021. Even with a last-minute move from in-person to virtual, an overwhelmingly high number of nearly 900 professionals representing pharma and biotech companies, contract research organizations (CROs), and multiple regulatory agencies still eagerly convened to actively discuss the most current topics of interest in bioanalysis. The 15th WRIB included three Main Workshops and seven Specialized Workshops that together spanned 1 week in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on biomarker assay development and validation (BAV) (focused on clarifying the confusion created by the increased use of the term “context of use” [COU]); mass spectrometry of proteins (therapeutic, biomarker and transgene); state-of-the-art cytometry innovation and validation; and critical reagent and positive control generation were the special features of the 15th edition. This 2021 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop, and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2021 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 2) covers the recommendations on ISR for Biomarkers, Liquid Biopsies, Spectral Cytometry, Inhalation/Oral & Multispecific Biotherapeutics, Accuracy/LLOQ for Flow Cytometry. Part 1A (Endogenous Compounds, Small Molecules, Complex Methods, Regulated Mass Spec of Large Molecules, Small Molecule, PoC), Part 1B (Regulatory Agencies' Inputs on Bioanalysis, Biomarkers, Immunogenicity, Gene & Cell Therapy and Vaccine) and Part 3 (TAb/NAb, Viral Vector CDx, Shedding Assays; CRISPR/Cas9 & CAR-T Immunogenicity; PCR & Vaccine Assay Performance; ADA Assay Comparability & Cut Point Appropriateness) are published in volume 14 of Bioanalysis, issues 9 and 11 (2022), respectively.

Figure S5: Dual MoA of MEDI0562

Purpose:Immune checkpoint blockade has demonstrated clinical benefits across multiple solid tumor types; however, resistance and relapse often occur. New immunomodulatory targets, which are highly expressed in activated immune cells, are needed. MEDI0562, an agonistic humanized mAb, specifically binds to the costimulatory molecule OX40. This first-in-human study evaluated MEDI0562 in adults with advanced solid tumors.Patients and Methods:In this phase I, multicenter, open-label, single-arm, dose-escalation (3+3 design) study, patients received 0.03, 0.1, 0.3, 1.0, 3.0, or 10 mg/kg MEDI0562 through intravenous infusion every 2 weeks, until confirmed disease progression or unacceptable toxicity. The primary objective evaluated safety and tolerability. Secondary endpoints included antitumor activity, pharmacokinetics, immunogenicity, and pharmacodynamics.Results:In total, 55 patients received ≥1 dose of MEDI0562 and were included in the analysis. The most common tumor type was squamous cell carcinoma of the head and neck (47%). Median duration of treatment was 10 weeks (range, 2–48 weeks). Treatment-related adverse events (TRAEs) occurred in 67% of patients, most commonly fatigue (31%) and infusion-related reactions (14%). Grade 3 TRAEs occurred in 14% of patients with no apparent dose relationship; no TRAEs resulted in death. Two patients had immune-related partial responses per protocol and 44% had stable disease. MEDI0562 induced increased Ki67+ CD4+ and CD8+ memory T-cell proliferation in the periphery and decreased intratumoral OX40+ FOXP3+ cells.Conclusions:MEDI0562 was safely administered at doses up to 10 mg/kg in heavily pretreated patients. On-target pharmacodynamic effects were suggested in this setting. Further evaluation with immune checkpoint inhibitors is ongoing.

The 15th edition of the Workshop on Recent Issues in Bioanalysis (15th WRIB) was held on 27 September to 1 October 2021. Even with a last-minute move from in-person to virtual, an overwhelmingly high number of nearly 900 professionals representing pharma and biotech companies, contract research organizations (CROs), and multiple regulatory agencies still eagerly convened to actively discuss the most current topics of interest in bioanalysis. The 15th WRIB included three Main Workshops and seven Specialized Workshops that together spanned 1 week in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on biomarker assay development and validation (BAV) (focused on clarifying the confusion created by the increased use of the term "context of use" [COU]); mass spectrometry of proteins (therapeutic, biomarker and transgene); state-of-the-art cytometry innovation and validation; and critical reagent and positive control generation were the special features of the 15th edition. This 2021 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop, and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2021 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 2) covers the recommendations on ISR for Biomarkers, Liquid Biopsies, Spectral Cytometry, Inhalation/OralMultispecific Biotherapeutics, Accuracy/LLOQ for Flow Cytometry. Part 1A (Endogenous Compounds, Small Molecules, Complex Methods, Regulated Mass Spec of Large Molecules, Small Molecule, PoC), Part 1B (Regulatory Agencies' Inputs on Bioanalysis, Biomarkers, Immunogenicity, GeneCell Therapy and Vaccine) and Part 3 (TAb/NAb, Viral Vector CDx, Shedding Assays; CRISPR/Cas9CAR-T Immunogenicity; PCRVaccine Assay Performance; ADA Assay ComparabilityCut Point Appropriateness) are published in volume 14 of Bioanalysis, issues 9 and 11 (2022), respectively.

The 14th edition of the Workshop on Recent Issues in Bioanalysis (14th WRIB) was held virtually on June 15-29, 2020 with an attendance of over 1000 representatives from pharmaceutical/biopharmaceutical companies, biotechnology companies, contract research organizations, and regulatory agencies worldwide. The 14th WRIB included three Main Workshops, seven Specialized Workshops that together spanned 11 days in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy and vaccine. Moreover, a comprehensive vaccine assays track; an enhanced cytometry track and updated Industry/Regulators consensus on BMV of biotherapeutics by LCMS were special features in 2020. As in previous years, this year's WRIB continued to gather a wide diversity of international industry opinion leaders and regulatory authority experts working on both small and large molecules to facilitate sharing and discussions focused on improving quality, increasing regulatory compliance and achieving scientific excellence on bioanalytical issues. This 2020 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop, and is aimed to provide the Global Bioanalytical Community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2020 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication covers the recommendations on (Part 2A) BAV, PK LBA, Flow Cytometry Validation and Cytometry Innovation and (Part 2B) Regulatory Input. Part 1 (Innovation in Small Molecules, Hybrid LBA/LCMS & Regulated Bioanalysis), Part 3 (Vaccine, Gene/Cell Therapy, NAb Harmonization and Immunogenicity) are published in volume 13 of Bioanalysis, issues 4, and 6 (2021), respectively.

The current consensus recommendation papers dealing with the unique requirements for the analytical validation of assays performed by flow cytometry address the validation of sensitivity (both analytical and functional) only in general terms. In this paper, a detailed approach for designing and validating the sensitivity of rare event methods is described. The impact of panel design and optimization on the lower limit of quantification (LLOQ) and suggestions for reporting data near, or below, the LLOQ are addressed. This paper serves to provide best practices for the development, optimization, and analytical validation of flow cytometric assays designed to assess rare events. Note that this paper does not discuss clinical sensitivity validation, which addresses the positive and negative predictive value of the test result.

Background: IL-12 is a key mediator of antitumor immune response. In preclinical models, IT IL-12 mRNA led to IFNγ release and CD8+ T cell-dependent tumor regression and potentiated PD-L1 blockade. MEDI1191, a lipid nanoparticle-formulated mRNA encoding IL-12 delivered by IT injection, drives IL-12 production and enhances antitumor immune response with improved tolerability. We hypothesized that combining MEDI1191 with PD-L1 blockade would augment antitumor immunity in vivo. Here we report updated results from the dose-escalation phase of the first-in-human study of IT MEDI1191 and IV durvalumab (D; anti-PD-L1) for advanced/metastatic solid tumors (NCT03946800). Methods: In this multicenter, open-label study, MEDI1191 was dosed sequentially (seq, Part 1A) or concurrently (conc, Part 1B) with D. In Part 1A, MEDI1191 was given IT on Days 1 and 22 followed by D 1500 mg on day 43 and then Q4W IV. In Part 1B, MEDI1191 was given IT on Days 1, 29, 57 and then Q8W, along with D on Day 1 and then Q4W. Treatment continued until progression or unacceptable toxicity for up to 2 years. Eligible adult pts had any solid tumor with cutaneous or subcutaneous lesions suitable for IT injection and progression on standard therapy for recurrent/metastatic disease. Primary objectives were safety and tolerability and determination of maximum tolerated dose (MTD); secondary objectives included preliminary antitumor activity by RECIST v1.1. Results: Starting in May 2019, 31 pts received seq MEDI1191 with D (Part 1A cohorts 0.1-12 μg; n=20) or conc MEDI1191 with D (Part 1B cohorts 1.0-3.0 μg; n=11); 23 pts had received prior anti-PD-1/PD-L1 therapy. Most common tumor types were melanoma, n=8; head and neck cancer, n=4; and breast cancer, n=4. At the data cutoff of Dec 7, 2021, there were no dose-limiting toxicities and no MTD was identified. One pt (3.2%) had a Gr ≥3 MEDI1191-related AE (Gr 3 pyrexia, resolved within 24 hr) and 1 (3.2%) had a MEDI1191-related serious AE (SAE; Gr 2 confusion). Two pts had Gr 3 D-related AEs (6.5%, pyrexia also related to MEDI1191 and pruritus; each n=1); none had a D-related SAE. There were no Gr 4 related AEs. 3 pts had partial responses (PR): 1 with head and neck cancer (unconfirmed, off study) and 2 with anti-PD-1 resistant melanoma (1 confirmed, >12 months on treatment; 1 unconfirmed, off study); 10 pts had stable disease (including the 2 unconfirmed PRs). Among pts with available biomarker data (up to 3 μg in Part 1A and 1 μg in Part 1B), MEDI1191 increased serum IL-12 in 15/17 pts, increased CD8+ T cell tumor infiltration by >2-fold in 8/14 pts and increased tumor PD-L1 expression in 6/14 pts. Conclusions: IT MEDI1191 plus systemic anti-PD-L1 was safe and feasible. Preliminary antitumor efficacy and pharmacodynamics, including tumor CD8+ T cell recruitment, were consistent with expected mechanism of action. Pts with injectable deep visceral and superficial lesions are being recruited. Citation Format: Benedito A. Carneiro, Dmitriy Zamarin, Thomas Marron, Inderjit Mehmi, Sandip P. Patel, Vivek Subbiah, Anthony El-Khoueiry, David Grand, Kirema Garcia-Reyes, Sanjay Goel, Phillip Martin, Jixin Wang, Yuling Wu, Steven Eck, Benjamin Ridgway, Nairouz Elgeioushi, Jim Eyles, Nicholas Durham, Analia Azaro, Omid Hamid. First-in-human study of MEDI1191 (mRNA encoding IL-12) plus durvalumab in patients (pts) with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT183.

ObjectiveImmune complexes (ICs) play a critical role in the pathology of autoimmune diseases. The aim of this study was to generate and characterise a first-in-class anti-FcγRIIA antibody (Ab) VIB9600 (previously known as MEDI9600) that blocks IgG immune complex-mediated cellular activation for clinical development.MethodsVIB9600 was humanised and optimised from the IV.3 Ab. Binding affinity and specificity were determined by Biacore and ELISA. Confocal microscopy, Flow Cytometry-based assays and binding competition assays were used to assess the mode of action of the antibody. In vitro cell-based assays were used to demonstrate suppression of IC-mediated inflammatory responses. In vivo target suppression and efficacy was demonstrated in FcγRIIA-transgenic mice. Single-dose pharmacokinetic (PK)/pharmacodynamic study multiple dose Good Laboratory Practice (GLP) toxicity studies were conducted in non-human primates.ResultsWe generated a humanised effector-deficient anti-FcγRIIA antibody (VIB9600) that potently blocks autoantibody and IC-mediated proinflammatory responses. VIB9600 suppresses FcγRIIA activation by blocking ligand engagement and by internalising FcγRIIA from the cell surface. VIB9600 inhibits IC-induced type I interferons from plasmacytoid dendritic cells (involved in SLE), antineutrophil cytoplasmic antibody (ANCA)-induced production of reactive oxygen species by neutrophils (involved in ANCA-associated vasculitis) and IC-induced tumour necrosis factor α and interleukin-6 production (involved in rheumatoid arthritis). In FcγRIIA transgenic mice, VIB9600 suppressed antiplatelet antibody-induced thrombocytopaenia, acute anti-GBM Ab-induced nephritis and anticollagen Ab-induced arthritis. VIB9600 also exhibited favourable PK and safety profiles in cynomolgus monkey studies.ConclusionsVIB9600 is a specific humanised antibody antagonist of FcγRIIA with null effector function that warrants further clinical development for the treatment of IC-mediated diseases.

The 14

Chimeric Antigen Receptor (CAR) T cells are recognized as efficacious therapies with demonstrated ability to produce durable responses in blood cancer patients. Regulatory approvals and acceptance of these unique therapies by patients and reimbursement agencies have led to a significant increase in the number of next generation CAR T clinical trials. Flow cytometry is a powerful tool for comprehensive profiling of individual CAR T cells at multiple stages of clinical development, from product characterization during manufacturing to longitudinal evaluation of the infused product in patients. There are unique challenges with regard to the development and validation of flow cytometric methods for CAR T cells; moreover, the assay requirements for manufacturing and clinical monitoring differ. Based on the collective experience of the authors, this recommendation paper aims to review these challenges and present approaches to address them. The discussion focuses on describing key considerations for the design, optimization, validation and implementation of flow cytometric methods during the clinical development of CAR T cell therapies.

Ligation of OX40 (CD134, TNFRSF4) on activated T cells by its natural ligand (OX40L, CD252, TNFSF4) enhances cellular survival, proliferation, and effector functions such as cytokine release and cellular cytotoxicity. We engineered a recombinant human OX40L IgG4P Fc fusion protein termed MEDI6383 that assembles into a hexameric structure and exerts potent agonist activity following engagement of OX40. MEDI6383 displayed solution-phase agonist activity that was enhanced when the fusion protein was clustered by Fc gamma receptors (FcγRs) on the surface of adjacent cells. The resulting costimulation of OX40 on T cells induced NFκB promoter activity in OX40-expressing T cells and induced Th1-type cytokine production, proliferation, and resistance to regulatory T cell (Treg)-mediated suppression. MEDI6383 enhanced the cytolytic activity of tumor-reactive T cells and reduced tumor growth in the context of an alloreactive human T cell:tumor cell admix model in immunocompromised mice. Consistent with the role of OX40 costimulation in the expansion of memory T cells, MEDI6383 administered to healthy nonhuman primates elicited peripheral blood CD4 and CD8 central and effector memory T-cell proliferation as well as B-cell proliferation. Together, these results suggest that OX40 agonism has the potential to enhance antitumor immunity in human malignancies. Mol Cancer Ther; 17(5); 1024–38. ©2018 AACR.

Purpose: Immune checkpoint blockade has demonstrated clinical benefits across multiple solid tumor types; however, resistance and relapse often occur. New immunomodulatory targets, which are highly expressed in activated immune cells, are needed. MEDI0562, an agonistic humanized mAb, specifically binds to the costimulatory molecule OX40. This first-in-human study evaluated MEDI0562 in adults with advanced solid tumors. Patients and Methods: In this phase I, multicenter, open-label, single-arm, dose-escalation (3+3 design) study, patients received 0.03, 0.1, 0.3, 1.0, 3.0, or 10 mg/kg MEDI0562 through intravenous infusion every 2 weeks, until confirmed disease progression or unacceptable toxicity. The primary objective evaluated safety and tolerability. Secondary endpoints included antitumor activity, pharmacokinetics, immunogenicity, and pharmacodynamics. Results: In total, 55 patients received ≥1 dose of MEDI0562 and were included in the analysis. The most common tumor type was squamous cell carcinoma of the head and neck (47%). Median duration of treatment was 10 weeks (range, 2–48 weeks). Treatment-related adverse events (TRAEs) occurred in 67% of patients, most commonly fatigue (31%) and infusion-related reactions (14%). Grade 3 TRAEs occurred in 14% of patients with no apparent dose relationship; no TRAEs resulted in death. Two patients had immune-related partial responses per protocol and 44% had stable disease. MEDI0562 induced increased Ki67+ CD4+ and CD8+ memory T-cell proliferation in the periphery and decreased intratumoral OX40+ FOXP3+ cells. Conclusions: MEDI0562 was safely administered at doses up to 10 mg/kg in heavily pretreated patients. On-target pharmacodynamic effects were suggested in this setting. Further evaluation with immune checkpoint inhibitors is ongoing.

The CD40/CD40L axis plays a central role in the generation of humoral immune responses and is an attractive target for treating autoimmune diseases in the clinic. Here, we report the generation and clinical results of a CD40L binding protein, VIB4920, which lacks an Fc domain, therefore avoiding platelet-related safety issues observed with earlier monoclonal antibody therapeutics that targeted CD40L. VIB4920 blocked downstream CD40 signaling events, resulting in inhibition of human B cell activation and plasma cell differentiation, and did not induce platelet aggregation in preclinical studies. In a phase 1 study in healthy volunteers, VIB4920 suppressed antigen-specific IgG in a dose-dependent fashion after priming and boosting with the T-dependent antigen, KLH. Furthermore, VIB4920 significantly reduced circulating Ki67+ dividing B cells, class-switched memory B cells, and a plasma cell gene signature after immunization. In a phase 1b proof-of-concept study in patients with rheumatoid arthritis, VIB4920 significantly decreased disease activity, achieving low disease activity or clinical remission in more than 50% of patients in the two higher-dose groups. Dose-dependent decreases in rheumatoid factor autoantibodies and Vectra DA biomarker score provide additional evidence that VIB4920 effectively blocked the CD40/CD40L pathway. VIB4920 demonstrated a good overall safety profile in both clinical studies. Together, these data demonstrate the potential of VIB4920 to significantly affect autoimmune disease and humoral immune activation and to support further evaluation of this molecule in inflammatory conditions.

Background Collectively, the cell surface Fc region of IgG receptors (FcγRs) engage soluble IgG and IgG containing immune complexes and trigger activation or inhibtory signals that play a critical role in the regulation of immune responses. The low affinity FcγRIIA (CD32A) is the most widely expressed activating FcγR in humans and appears to drive autoantibody and immune complex mediated autoimmune disorders. So far a therapeutic targeting this receptor has not been developed. Objectives To generate and characterize a novel humanized effector-deficient FcγRIIA antibody (MEDI9600) for clinical development. Methods The mode of action of MEDI9600 was assessed by confocal microscopy, whole blood internalization, and binding competition assays. Multiple cell based assays were used to measure autoantibody and immune complex mediated responses. The safety of MEDI9600 was assessed in in vitro by neutrophil migration, activation and opsonophagocytic killing assays. Safety and pharmacokinetics were examined in vivo in a single-dose PK/PD study in cynomolgus monkey. Results We generated a humanized effector-deficient FcγRIIA antibody (MEDI9600) that potently blocks both autoantibody and immuno complex-mediated proinflammatory responses from a variety of cell types. This includes the inhibition of Toll-like receptor stimulatory immune complexes that induce type I Interferons from pDC, and the inhibition of anti-neutrophil cytoplasmic antibody (ANCA) induced production of reactive oxygen species from neutrophils, which are associated with the pathogenesis of systemic lupus and ANCA vasculitis respectively. MEDI9600 specifically binds FcγRIIA and its suppressive activity is attributed to its capacity to block ligand engagement and to internalize the receptor from the cell surface. Moreover, in vivo studies indicate that MEDI9600 has a favorable pharmacokinetic and safety profile. Conclusions We have generated MEDI9600, a specific humanized antibody antagonist of FcγRIIA with null effector function that may provide a novel therapeutic approach in the treatment of immune complex mediated diseases. Disclosure of Interest None declared

Analytical method validation provides a means to ensure that data are credible and reproducible. This unit will provide a brief introduction to analytical method validation as applied to cellular analysis by flow cytometry. In addition, the unit will provide practical procedures for three different types of validation. The first is a limited validation protocol that is applicable for research settings and non-regulated laboratories. The second is validation protocol that presents the minimum validation requirements in regulated laboratories. The third is a transfer validation protocol to be used when methods are transferred between laboratories. The recommendations presented in this unit are consistent with the white papers published by the American Association of Pharmaceutical Scientists and the International Clinical Cytometry Society, as well as with Clinical Laboratory Standards Institute Guideline H62: Validation of Assays Performed by Flow Cytometry (currently in preparation). © 2018 by John Wiley & Sons, Inc.

and 13 had stable disease. Commonly reported adverse events (AEs) in MEDI-551 pts were infusion-related reactions (IRRs; 62%), nausea (23%), pyrexia (23%), and neutropenia (23%) in the 26 ph 1/2 pts; in the 29 ph 2 pts, they were nausea (62%), IRRs (31%), pyrexia (28%), chills (28%), and fatigue (28%). 11 pts had ≥ grade 3 AEs in the ph 1/2 study and 16 in the ph 2. Common treatmentrelated AEs: IRRs (58%) and nausea (12%) in the ph 1/2; nausea (52%), IRRs (28%), chills (24%), and fatigue (24%) in the ph 2. Three treatment-unrelated AEs of general health deterioration (ph 1/2), subarachnoid hemorrhage (ph 1/2), and sepsis (ph 2), resulted in death. Conclusions MEDI-551 as a single agent demonstrated B-cell depletion, increased serum BAFF levels, clinical activity, and an acceptable risk-benefit profile in relapsed/refractory CLL pts. Preliminary results of the ongoing ph 2 study of MEDI-551+bendamustine demonstrated an acceptable safety profile.

3052 Background: MEDI6383 is a human OX40 ligand fusion protein currently in clinical development for the treatment of advanced solid malignancies. In vitro, this OX40 agonist binds and activates t...

3056 Background: OX40 is a tumor necrosis factor receptor found primarily on activated T effector (Teff) cells and regulatory T (Treg) cells including lymphocytes infiltrating mouse and human tumor...

7045 Background: Anti-CD20 mAb therapy has provided survival advantage to patients (pts) with CLL; but pts invariably relapse after anti-CD20 therapy and new approaches are needed. The CLL cells of most pts express CD19, which are upregulated following anti-CD20 therapy. MEDI-551, an affinity-optimized anti-CD19 antibody, destroys malignant cells by Ab-dependent cellular cytotoxicity (ADCC) once bound to CD19. Methods: The activity and toxicity of single-agent MEDI-551 in CLL pts with prior rituximab administration was assessed in a phase 1/2, open-label, dose-escalation and expansion study (NCT00983619). Response was assessed using the 2008 Intl Working Group criteria. B-cell depletion was assessed with flow cytometry and confirmed with biomarker analyses (BAFF). Safety assessments included laboratory parameters and adverse events (AEs and serious AEs [SAEs]). Results: Of 91 pts with refractory B-cell malignancies included in the study, 26 had CLL. CLL pts had received a median of 6 prior therapies: 89% with chemotherapy, 27% with single-agent biologics. Within 3 cycles of MEDI-551 (3 mos), >60% of assessable pts achieved CD20+ B-cell depletion to + and CD22+B cells were associated with concomitant increases in serum BAFF concentrations. Of 20 pts evaluable for response, 4 achieved partial response and 13 had stable disease. Commonly reported AEs were generally grade 1/2 and included infusion reactions (62%), nausea (23%), pyrexia (23%), and neutropenia (23%). Six SAEs were noted in 3 pts: 1 had infusion reaction and general health deterioration, another had subarachnoid hemorrhage (SAH), and a third had dyspnea, pyrexia, and back pain. Only infusion reaction was considered treatment related. Two treatment-unrelated events of general health deterioration and SAH resulted in death. Conclusions: Single-agent activity with a manageable toxicity profile was seen in CLL pts treated in this phase 1/2 study of MEDI-551. An ongoing phase 2 study of MEDI-551 in combination with bendamustine in relapsed CLL patients (NCT01466153) is evaluating clinical response to MEDI-551 and chemotherapy. This study was sponsored by MedImmune, LLC.