2023 White Paper on Recent Issues in Bioanalysis: ISR for ADA Assays, the Rise of dPCR vs qPCR, International Reference Standards for Vaccine Assays, Anti-AAV TAb Post-Dose Assessment, NanoString Validation, ELISpot as Gold Standard (Part 3 - Recommendations on Gene Therapy, Cell Therapy, Vaccines Immunogenicity & Technologies; Biotherapeutics Immunogenicity & Risk Assessment; ADA/NAb Assay/Reporting Harmonization).

The 17th Workshop on Recent Issues in Bioanalysis (17th WRIB) took place in Orlando, FL, USA on June 19-23, 2023. Over 1000 professionals representing pharma/biotech companies, CROs, and multiple regulatory agencies convened to actively discuss the most current topics of interest in bioanalysis. The 17th WRIB included 3 Main Workshops and 7 Specialized Workshops that together spanned 1 week to allow an exhaustive and thorough coverage of all major issues in bioanalysis of biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on "EU IVDR 2017/746 Implementation and impact for the Global Biomarker Community: How to Comply with these NEW Regulations" and on "US FDA/OSIS Remote Regulatory Assessments (RRAs)" were the special features of the 17th edition. As in previous years, WRIB continued to gather a wide diversity of international, industry opinion leaders and regulatory authority experts working on both small and large molecules as well as gene, cell therapies and vaccines to facilitate sharing and discussions focused on improving quality, increasing regulatory compliance, and achieving scientific excellence on bioanalytical issues. This 2023 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 2023 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 3) covers the recommendations on Gene Therapy, Cell therapy, Vaccines and Biotherapeutics Immunogenicity. Part 1A (Mass Spectrometry Assays and Regulated Bioanalysis/BMV), P1B (Regulatory Inputs) and Part 2 (Biomarkers, IVD/CDx, LBA and Cell-Based Assays) are published in volume 16 of Bioanalysis, issues 8 and 9 (2024), respectively.

Analytical assay validation for acute myeloid leukemia measurable residual disease assessment by multiparametric flow cytometry.

BACKGROUND: Measurable residual disease (MRD) assessed by multiparametric flow cytometry (MFC) has gained importance in clinical decision-making for acute myeloid leukemia (AML) patients. However, complying with the recent In Vitro Diagnostic Regulations (IVDR) in Europe and Food and Drug Administration (FDA) guidance in the United States requires rigorous validation prior to their use in investigational clinical trials and diagnostics. Validating AML MRD-MFC assays poses challenges due to the unique underlying disease biology and paucity of patient specimens. In this study, we describe an experimental framework for validation that meets regulatory expectations. METHODS: Our validation efforts focused on evaluating assay accuracy, analytical specificity, analytical and functional sensitivity (limit of blank (LoB), detection (LLoD) and quantitation (LLoQ)), precision, linearity, sample/reagent stability and establishing the assay background frequencies. RESULTS: Correlation between different MFC methods was highly significant (r = 0.99 for %blasts and r = 0.93 for %LAIPs). The analysis of LAIP specificity accurately discriminated from negative control cells. The assay demonstrated a LoB of 0.03, LLoD of 0.04, and LLoQ of 0.1%. Precision experiments yielded highly reproducible results (Coefficient of Variation <20%). Stability experiments demonstrated reliable measurement of samples up to 96 h from collection. Furthermore, the reference range of LAIP frequencies in non-AML patients was below 0.1%, ranging from 0.0% to 0.04%. CONCLUSION: In this manuscript, we present the validation of an AML MFC-MRD assay using BM/PB patient specimens, adhering to best practices. Our approach is expected to assist other laboratories in expediting their validation activities to fulfill recent health authority guidelines.

Role of Tumor-Infiltrating B Cells in Clinical Outcome of Patients with Melanoma Treated With Dabrafenib Plus Trametinib.

PURPOSE: Although patients with unresectable or metastatic melanoma can experience long-term survival with BRAF- and MEK-targeted agents or immune checkpoint inhibitors over 5 years, resistance develops in most patients. There is a distinct lack of pretherapeutic biomarkers to identify which patients are likely to benefit from each therapy type. Most research has focused on the predictive role of T cells in antitumor responses as opposed to B cells. PATIENTS AND METHODS: We conducted prespecified exploratory biomarker analysis using gene expression profiling and digital pathology in 146 patients with previously untreated BRAF V600-mutant metastatic melanoma from the randomized, phase III COMBI-v trial and treated with dabrafenib plus trametinib who had available tumor specimens from screening. RESULTS: Baseline cell-cycle gene expression signature was associated with progression-free survival (P = 0.007). Patients with high T-cell/low B-cell gene signatures had improved median overall survival (not reached [95% confidence interval (CI), 33.8 months-not reached]) compared with patients with high T-cell/high B-cell signatures (19.1 months; 95% CI, 13.4-38.6 months). Patients with high B-cell signatures had high B-cell infiltration into the tumor compartment, corresponding with decreased MAPK activity and increased expression of immunosuppressive markers. CONCLUSIONS: B cells may serve as a potential biomarker to predict clinical outcome in patients with advanced melanoma treated with dabrafenib plus trametinib. As separate studies have shown an opposite effect for B-cell levels and response to immunotherapy, B cells may serve as a potential biomarker to facilitate treatment selection. Further validation in a larger patient cohort is needed.

2020 White Paper on Recent Issues in Bioanalysis: Vaccine Assay Validation, qPCR Assay Validation, QC for CAR-T Flow Cytometry, NAb Assay Harmonization and ELISpot Validation (Part 3 - Recommendations on Immunogenicity Assay Strategies, NAb Assays, Biosimilars and FDA/EMA Immunogenicity Guidance/Guideline, Gene & Cell Therapy and Vaccine Assays).

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 (Part 3) covers the recommendations on Vaccine, Gene/Cell Therapy, NAb Harmonization and Immunogenicity). Part 1 (Innovation in Small Molecules, Hybrid LBA/LCMS & Regulated Bioanalysis), Part 2A (BAV, PK LBA, Flow Cytometry Validation and Cytometry Innovation) and Part 2B (Regulatory Input) are published in volume 13 of Bioanalysis, issues 4 and 5 (2020), respectively.

Multimarker scores of Th1 and Th2 immune cellular profiles in peripheral blood predict response and immune related toxicity with CTLA4 blockade and IFNα in melanoma.

Neoadjuvant therapy with ipilimumab in combination with high dose IFNα was evaluated in patients with locally/regionally advanced melanoma in a previously reported clinical trial [NCT01608594]. In this study, peripheral immune cell profiling was performed in order to investigate the underlying mechanisms of tumor immune susceptibility and resistance. Peripheral blood mononuclear cells (PBMCs) from treated patients (N = 28) were collected at baseline and then at 6-weeks, 3-months and 12-months. High complexity (14-color) flow cytometry, designed to detect key immunological biomarkers was used to evaluate the frequencies of immune cell subsets. Statistical significance was determined using R-package employing Kruskal's test. We found that higher levels of Th1 cells at baseline (defined as CD45RA- CCR6- CXCR3+ CCR4-) correlated with the preoperative radiological response (p = 0.007) while higher Th2 cells (defined as CD45RA- CCR6- CXCR3- CCR4+) were associated with progressive disease (p = 0.009). A multimarker score consisting of higher levels of Th1 cells and CD8+ central memory T-cells was associated with pathologic complete response (pCR) (p = 0.041) at surgical resection. On the other hand, high TIM3 expression on T-cells correlated with gross viable tumor (p = 0.047). With regard to immune related toxicity, higher levels of phenotypically naive (defined as CCR7+CD45RA+) and effector memory (defined as CCR7-CD45RO+) CD8+ T-cells (p = 0.014) or lower levels of Th2 cells were associated with lower toxicity (p = 0.024). Furthermore, a multimarker score consisting of higher CD19+ and CD8+ cells was associated with lower toxicity (p = 0.0014). In conclusion, our study yielded mechanistic insights related to the immune impact of CTLA4 blockade and IFNα and potential biomarkers of immune response and toxicity.

2020 White Paper on Recent Issues in Bioanalysis: BAV Guidance, CLSI H62, Biotherapeutics Stability, Parallelism Testing, CyTOF and Regulatory Feedback (Part 2A - Recommendations on Biotherapeutics Stability, PK LBA Regulated Bioanalysis, Biomarkers Assays, Cytometry Validation & Innovation Part 2B - Regulatory Agencies' Inputs on Bioanalysis, Biomarkers, Immunogenicity, Gene & Cell Therapy and Vaccine).

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.

Monitoring CAR-T cell kinetics in clinical trials by multiparametric flow cytometry: Benefits and challenges.

Exceptional clinical responses produced by the first chimeric antigen receptor T [CAR-T] cell therapies, and their entry into commercial markets prompted a logarithmic increase in the number of next generation CAR-T clinical trials. As a result, there is a growing interest in understanding the analytical approaches utilized for reliable monitoring of these "living" drugs, and the challenges encountered during their clinical development. Multiparametric flow cytometry (MFC) assays have played a crucial role in understanding the phenotype and function of first approved CAR-T therapies. Herein, three main areas for monitoring CAR-T therapies in clinical trials are discussed: (1) analytical considerations critical for development of MFC assays for the reliable enumeration of CAR-T levels, (2) operational challenges associated with clinical trial sampling and transportation, and (3) differential cellular kinetics observed by MFC and qPCR analyses and their relationship with efficacy (measurable residual disease levels). Initial experiences described here may enable design of fit-for-purpose tools and help to more rapidly advance the development of next generation CAR-T therapies.

Best practices for the development, analytical validation and clinical implementation of flow cytometric methods for chimeric antigen receptor T cell analyses.

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.

Impact of minimal residual disease status in patients with relapsed/refractory acute lymphoblastic leukemia treated with inotuzumab ozogamicin in the phase III INO-VATE trial.

Minimal residual disease (MRD) negativity is a key prognostic indicator of outcome in acute lymphocytic leukemia. In the INO-VATE trial (clinicaltrials.gov identifier: NCT01564784), patients with relapsed/refractory acute lymphocytic leukemia who received inotuzumab versus standard chemotherapy achieved greater remission and MRD-negativity rates as well as improved overall survival: hazard ratio 0.75, one-sided P = 0.0105. The current analysis assessed the prognostic value of MRD negativity at the end of inotuzumab treatment. All patients who received inotuzumab (n = 164) were included. Among patients with complete remission/complete remission with incomplete hematologic response (CR/CRi; n = 121), MRD-negative status (by multiparametric flow cytometry) was defined as <1 × 10-4 blasts/nucleated cells. MRD negativity was achieved in 76 patients at the end of treatment. Compared with MRD-positive, MRD-negative status with CR/CRi was associated with significantly improved overall survival and progression-free survival, respectively: hazard ratio (97.5% confidence interval; one-sided P-value) 0.512 (97.5% CI [0.313-0.835]; P = 0.0009) and 0.423 (97.5% CI [0.256-0.699]; P < 0.0001). Median overall survival was 14.1 versus 7.2 months, in the MRD-negative versus MRD-positive groups. Patients in first salvage who achieved MRD negativity at the end of treatment experienced significantly improved survival versus that seen in MRD-positive patients, particularly for those patients who proceeded to stem cell transplant. Among patients with relapsed/refractory acute lymphocytic leukemia who received inotuzumab, those with MRD-negative CR/CRi had the best survival outcomes.

2019 White Paper on Recent Issues in Bioanalysis: FDA Immunogenicity Guidance, Gene Therapy, Critical Reagents, Biomarkers and Flow Cytometry Validation (Part 3 - Recommendations on 2019 FDA Immunogenicity Guidance, Gene Therapy Bioanalytical Challenges, Strategies for Critical Reagent Management, Biomarker Assay Validation, Flow Cytometry Validation & CLSI H62).

The 2019 13th Workshop on Recent Issues in Bioanalysis (WRIB) took place in New Orleans, LA, USA on April 1-5, 2019 with an attendance of over 1000 representatives from pharmaceutical/biopharmaceutical companies, biotechnology companies, contract research organizations and regulatory agencies worldwide. WRIB was once again a 5-day, week-long event - a full immersion week of bioanalysis, biomarkers, immunogenicity and gene therapy. As usual, it was specifically designed to facilitate sharing, reviewing, discussing and agreeing on approaches to address the most current issues of interest including both small- and large-molecule bioanalysis involving LCMS, hybrid LBA/LCMS, LBA cell-based/flow cytometry assays and qPCR approaches. This 2019 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 2019 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 3) covers New Insights in Biomarker Assay Validation, Current & Effective Strategies for Critical Reagent Management, Flow Cytometry Validation in Drug Discovery & Development & CLSI H62, Interpretation of the 2019 FDA Immunogenicity Guidance and Gene Therapy Bioanalytical Challenges. Part 1 (Innovation in Small Molecules and Oligonucleotides & Mass Spectrometry Method Development Strategies for Large Molecule Bioanalysis) and Part 2 (Recommendations on the 2018 FDA BMV Guidance, 2019 ICH M10 BMV Draft Guideline and regulatory agencies' input on bioanalysis, biomarkers, immunogenicity and gene therapy) are published in volume 11 of Bioanalysis, issues 22 and 23 (2019), respectively.

PD-1/PD-L1 expression and interaction by automated quantitative immunofluorescent analysis show adverse prognostic impact in patients with diffuse large B-cell lymphoma having T-cell infiltration: a study from the International DLBCL Consortium Program.

Programmed cell death protein 1/programmed cell death protein ligand1 (PD-1/PD-L1) interaction is an important immune checkpoint targeted by anti-PD-1/PD-L1 immunotherapies. However, the observed prognostic significance of PD-1/PD-L1 expression in diffuse large B-cell lymphoma treated with the standard of care has been inconsistent and even contradictory. To clarify the prognostic role of PD-1/PD-L1 expression and interaction in diffuse large B-cell lymphoma, in this study we used 3-marker fluorescent multiplex immunohistochemistry and Automated Quantitative Analysis Technology to assess the CD3+, PD-L1+, and PD-1+CD3+ expression in diagnostic samples and PD-1/PD-L1 interaction as indicated by presence of PD-1+CD3+ cells in the vicinity of PD-L1+ cells, analyzed their prognostic effects in 414 patients with de novo diffuse large B-cell lymphoma, and examined whether PD-1/PD-L1 interaction is required for the prognostic role of PD-1+/PD-L1+ expression. We found that low T-cell tissue cellularity, tissue PD-L1+ expression (irrespective of cell types), PD-1+CD3+ expression, and PD-1/PD-L1 interaction showed hierarchical adverse prognostic effects in the study cohort. PD-1/PD-L1 interaction showed higher sensitivity and specificity than PD-1+ and PD-L1+ expression in predicting inferior prognosis in patients with high CD3+ tissue cellularity ("hot"/inflammatory tumors). However, both PD-1+ and PD-L1+ expression showed adverse prognostic effects independent of PD-1/PD-L1 interaction, and PD-1/PD-L1 interaction showed favorable prognostic effect in PD-L1+ patients without high CD3+ tissue cellularity. Macrophage function and tumor-cell MYC expression may contribute to the PD-1-independent adverse prognostic effect of PD-L1+ expression. In summary, low T-cell tissue cellularity has unfavorable prognostic impact in diffuse large B-cell lymphoma, and tissue PD-L1+ expression and T-cell-derived PD-1+ expression have significant adverse impact only in patients with high T-cell infiltration. PD-1/PD-L1 interaction in tissue is essential but not always responsible for the inhibitory effect of PD-L1+/PD-1+ expression. These results suggest the benefit of PD-1/PD-L1 blockade therapies only in patients with sufficient T-cell infiltration, and the potential of immunofluorescent assays and Automated Quantitative Analysis in the clinical assessment of PD-1/PD-L1 expression and interaction.

Quantitative Spatial Profiling of PD-1/PD-L1 Interaction and HLA-DR/IDO-1 Predicts Improved Outcomes of Anti-PD-1 Therapies in Metastatic Melanoma.

Purpose: PD-1/L1 axis-directed therapies produce clinical responses in a subset of patients; therefore, biomarkers of response are needed. We hypothesized that quantifying key immunosuppression mechanisms within the tumor microenvironment by multiparameter algorithms would identify strong predictors of anti-PD-1 response.Experimental Design: Pretreatment tumor biopsies from 166 patients treated with anti-PD-1 across 10 academic cancer centers were fluorescently stained with multiple markers in discovery (n = 24) and validation (n = 142) cohorts. Biomarker-positive cells and their colocalization were spatially profiled in pathologist-selected tumor regions using novel Automated Quantitative Analysis algorithms. Selected biomarker signatures, PD-1/PD-L1 interaction score, and IDO-1/HLA-DR coexpression were evaluated for anti-PD-1 treatment outcomes.Results: In the discovery cohort, PD-1/PD-L1 interaction score and/or IDO-1/HLA-DR coexpression was strongly associated with anti-PD-1 response (P = 0.0005). In contrast, individual biomarkers (PD-1, PD-L1, IDO-1, HLA-DR) were not associated with response or survival. This finding was replicated in an independent validation cohort: patients with high PD-1/PD-L1 and/or IDO-1/HLA-DR were more likely to respond (P = 0.0096). These patients also experienced significantly improved progression-free survival (HR = 0.36; P = 0.0004) and overall survival (HR = 0.39; P = 0.0011). In the combined cohort, 80% of patients exhibiting higher levels of PD-1/PD-L1 interaction scores and IDO-1/HLA-DR responded to PD-1 blockers (P = 0.000004). In contrast, PD-L1 expression was not predictive of survival.Conclusions: Quantitative spatial profiling of key tumor-immune suppression pathways by novel digital pathology algorithms could help more reliably select melanoma patients for PD-1 monotherapy. Clin Cancer Res; 24(21); 5250-60. ©2018 AACR.

Deep exploration of the immune infiltrate and outcome prediction in testicular cancer by quantitative multiplexed immunohistochemistry and gene expression profiling.

Platinum-based chemotherapy is usually curative for patients with testicular germ cell tumors (TGCT), but a subset of patients experience disease progression and poor clinical outcomes. Here, we tested whether immune profiling of TGCT could identify novel prognostic markers and therapeutic targets for this patient cohort. We obtained primary and metastatic TGCT samples from one center. We performed immune profiling using multiplexed fluorescence immunohistochemistry (FIHC) for T-cell subsets and immune checkpoints, and targeted gene expression profiling (Nanostring nCounter Immune panel). Publically available data sets were used to validate primary sample analyses. Nearly all samples had some degree of T-cell infiltration and immune checkpoint expression. Seminomas were associated with increased CD3+ T-cell infiltration, decreased Regulatory T-cells, increased PD-L1, and increased PD-1/PD-L1 spatial interaction compared with non-seminomas using FIHC. Gene expression profiling confirmed these findings and also demonstrated increased expression of T-cell markers (e.g., IFNγ, and LAG3) and cancer/testis antigens (e.g., PRAME) in seminomas, whereas non-seminomas demonstrated high neutrophil and macrophage gene signatures. Irrespective of histology, advanced TGCT stage was associated with decreased T-cell and NK-cell signatures, while Treg, neutrophil, mast cell and macrophage signatures increased with advanced stage. Importantly, cancer/testis antigen, neutrophil, and CD8+/regulatory T-cell signatures correlated with recurrence free survival. Thus, deep immune characterization of TGCT using IHC and gene expression profiling identified activated T-cell infiltration which correlated with seminoma histology and good prognosis. These results may provide a rationale for testing of anti-PD-1/PD-L1 agents and suggest prognostic markers.

Recommendations for clinical biomarker specimen preservation and stability assessments.

With the wide use of biomarkers to enable critical drug-development decisions, there is a growing concern from scientific community on the need for a 'standardized process' for ensuring biomarker specimen stability and hence, a strong desire to share best practices on preserving the integrity of biomarker specimens in clinical trials and the design of studies to evaluate analyte stability. By leveraging representative industry experience, we have attempted to provide an overview of critical aspects of biomarker specimen stability commonly encountered during clinical development, including: planning of clinical sample collection procedures, clinical site training, selection of sample preservation buffers, shipping logistics, fit-for-purpose stability assessments in the analytical laboratory and presentation of case studies covering widely utilized biomarker specimen types.

Phase I study of BIIB028, a selective heat shock protein 90 inhibitor, in patients with refractory metastatic or locally advanced solid tumors.

PURPOSE: Heat shot protein 90 (Hsp90) is a ubiquitous molecular chaperone involved in protein folding, activation, and assembly, including key mediators of signal transduction, cell-cycle control, and transcriptional regulation. We conducted a phase I dose-finding and pharmacokinetic/pharmacodynamic study of BIIB028, a prodrug designed to inhibit Hsp90 activity. EXPERIMENTAL DESIGN: Patients with advanced solid tumors were enrolled and received escalating doses of BIIB028 intravenously twice a week in 21-day cycles (3+3 design). Response was evaluated after two cycles. RESULTS: Forty-one patients received doses of 6 to 192 mg/m2. The maximum tolerated dose was 144 mg/m2. Dose-limiting toxicities were syncope (n=1) and fatigue (n=1). Common toxicities at least possibly related to drug were grades 1 to 2, including fatigue (46%), diarrhea (44%), nausea (44%), vomiting (29%), hot flushes (29%), and abnormal dreams (17%). The concentration-time curves for day 1 and day 18 for both prodrug and active metabolite (CF2772) showed a negligible difference. There was a dose-dependent increase in plasma exposure for BIIB028 (CF3647) and CF2772 with plasma half-life of 0.5 and 2.1 hours, respectively. Pharmacodynamic analyses showed significant increases in Hsp70 in peripheral blood mononuclear cells and significantly decreased circulating human EGF receptor-2 extracellular domain in all patients who received BIIB028 at dose levels of 48 mg/m2 or more. Stable disease for at least eight cycles (24 weeks) was achieved in 5 (12%) patients (for durations of 6, 6, 8, 12.5, and 19 months). CONCLUSION: BIIB028 is a well-tolerated molecule that showed target impact and was associated with prolonged stable disease in two patients.

CD80 (B7.1) is expressed on both malignant B cells and nonmalignant stromal cells in non-Hodgkin lymphoma.

BACKGROUND: CD80 is a member of the B7 family of immune coregulatory proteins that mediate both immune activation and suppression. CD80 in particular has recently been shown to play an important role in supporting immune suppression through interactions with B7-H1. CD80 has been identified as a therapeutic target in non-Hodgkin lymphoma (NHL) based on limited immunohistochemical studies of CD80 expression. Clinical studies have shown that the anti-CD80 antibody galiximab is safe and clinically efficacious in follicular NHL. However, the mechanisms through which targeting CD80 inhibits tumor progression remain poorly understood. METHODS: To further define the potential of CD80 as a therapeutic target in NHL, CD80 expression was evaluated by multicolor flow cytometric analysis of primary lymphoma cell suspensions generated from 241 diagnostic biopsies of patients with NHL. RESULTS: CD80 was expressed on malignant B cells in essentially all cases of follicular lymphoma (97%; n = 115), the majority of cases of diffuse large B-cell lymphoma (90%; n = 69), marginal zone lymphoma (91%; n = 22), mantle cell lymphoma (75%; n = 12), and in about half of small lymphocytic lymphoma cases (43%; n = 23). CD80 was also present on tumor-infiltrating T lymphocytes in nearly all cases. Additionally, CD80 was expressed by non-B, non-T cells in 68 and 44% of cases of follicular and diffuse large B-cell NHL, respectively. CONCLUSIONS: CD80 is expressed on both malignant cells and the nonmalignant cells in NHL. Therapeutic targeting of CD80 will therefore modulate the complex intercellular interactions that define the tumor microenvironment in NHL.

An investigation into the potential use of serum Hsp70 as a novel tumour biomarker for Hsp90 inhibitors.

Hsp90 inhibitors are under investigation in multiple human clinical trials for the treatment of cancers, including myeloma, breast cancer, prostate, lung, melanoma, gastrointestinal stromal tumour and acute myeloid leukaemia. The pharmacodynamic activity of Hsp90 inhibitors in the clinic is currently assessed by Hsp70 induction in peripheral blood mononuclear cells using Western blot analysis, a method that is laborious, semiquantitative and difficult to implement in the clinic. Since Hsp70 was reported to be secreted by tumour cells and elevated in sera of cancer patients, serum Hsp70 has been evaluated as a potentially more robust, easily and reproducibly measured biomarker of Hsp90 inhibition as an alternative to cytosolic Hsp70. A highly sensitive and specific electrochemiluminescent ELISA was developed to measure serum Hsp70 and employed to evaluate Hsp70 levels in both ex vivo and xenograft samples. In ex vivo studies, maximal secretion of Hsp70 by tumour cells was observed between 48 and 72 h after exposure to Hsp90 inhibitors. In in vivo studies a 3-4-fold increase in serum Hsp70 was observed following treatment with BIIB021 in tumour-bearing mice. Strikingly, secreted Hsp70 was detectable in mice transplanted with human tumours but not in naive mice indicating a direct origination from the transplanted tumours. Analysis of clinical samples revealed low baseline levels (2 - 15 ng ml(-1)) of Hsp70 in the serum of cancer patients and normal donors. Together these findings in laboratory studies and archived cancer patient sera suggest that serum Hsp70 could be a novel biomarker to assess reliably the pharmacological effects of Hsp90 inhibitors in clinical trials, especially under conditions where collection of tumour biopsies is not feasible.

Blockade of CD200 in the presence or absence of antibody effector function: implications for anti-CD200 therapy.

CD200 is an immunosuppressive molecule overexpressed in multiple hematologic malignancies such as B cell chronic lymphocytic leukemia, multiple myeloma, and acute myeloid leukemia. We previously demonstrated that up-regulation of CD200 on tumor cells suppresses antitumor immune responses and that antagonistic anti-human CD200 mAbs enabled human PBMC-mediated tumor growth inhibition in xenograft NOD/SCID human (hu)-mouse models. Ab variants with effector function (IgG1 constant region (G1)) or without effector function (IgG2/G4 fusion constant region (G2G4)) exhibited high antitumor activity in a human tumor xenograft model in which CD200 was expressed. In this report, we seek to select the best candidate to move forward into the clinic and begin to decipher the mechanisms of tumor cell killing by comparing anti-CD200-G1 vs anti-CD200-G2G4 in two related animal models. In a CD200-expressing xenograft NOD/SCID hu-mouse model where CD200 ligand/receptor interactions are already established before initiating treatment, we find that anti-CD200-G1 is a less effective Ab compared with anti-CD200-G2G4. Separately, in a model that evaluates the effect of the Abs on the immune cell component of the xenograft NOD/SCID hu-mouse model distinctly from the effects of binding to CD200 on tumor cells, we find that the administration of anti-CD200-G1 Abs completely abolished human PBMC-mediated tumor growth inhibition. Along with supporting in vitro studies, our data indicate that anti-CD200-G1 Abs efficiently mediate Ab-dependent cellular cytotoxicity of activated T cells, critical cells involved in immune-mediated killing. These studies suggest important implications regarding the selection of the constant region in anti-CD200 immunotherapy of cancer patients.

In vivo targeting of antigens to human dendritic cells through DC-SIGN elicits stimulatory immune responses and inhibits tumor growth in grafted mouse models.

Multiple cancer vaccine trials have been carried out using ex vivo generated autologous dendritic cells (DCs) loaded with tumor antigen before readministration into patients. Though promising, overall immunologic potency and clinical efficacy might be improved with more efficient DC-based therapies that avoid ex vivo manipulations, but are instead based on in vivo targeting of DCs. For initial in vivo proof of concept studies, we evaluated targeting of proteins or peptides to DCs through DC-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN). Because the biology of DC-SIGN is different between mice and humans, we assess human DC-SIGN targeting in the setting of elements of a human immune system in a mouse model. Administration of anti-DC-SIGN antibodies carrying either tetanus toxoid peptides or keyhole limpet hemocyanin (KLH) to Rag2gammaC mice reconstituted with human immune cells raised stimulatory human T-cell responses to the respective antigen without additional adjuvant requirements. Furthermore, administration of anti-DC-SIGN antibody-KLH conjugate enhanced the adjuvant properties of KLH resulting in inhibition of RAJI (Human Burkitt's Lymphoma Cell Line) cell tumor growth in Nonobese Diabetic/Severe Combined Immunodeficient mice transplanted with human immune cells. Thus, mouse models reconstituted with human immune cells seem to be suitable for evaluating DC-targeted vaccines, and furthermore, targeting to DCs in situ via DC-SIGN may provide a promising vaccine platform for inducing strong immune responses against cancer and infectious disease agents.

CD200 expression on tumor cells suppresses antitumor immunity: new approaches to cancer immunotherapy.

Although the immune system is capable of mounting a response against many cancers, that response is insufficient for tumor eradication in most patients due to factors in the tumor microenvironment that defeat tumor immunity. We previously identified the immune-suppressive molecule CD200 as up-regulated on primary B cell chronic lymphocytic leukemia (B-CLL) cells and demonstrated negative immune regulation by B-CLL and other tumor cells overexpressing CD200 in vitro. In this study we developed a novel animal model that incorporates human immune cells and human tumor cells to address the effects of CD200 overexpression on tumor cells in vivo and to assess the effect of targeting Abs in the presence of human immune cells. Although human mononuclear cells prevented tumor growth when tumor cells did not express CD200, tumor-expressed CD200 inhibited the ability of lymphocytes to eradicate tumor cells. Anti-CD200 Ab administration to mice bearing CD200-expressing tumors resulted in nearly complete tumor growth inhibition even in the context of established receptor-ligand interactions. Evaluation of an anti-CD200 Ab with abrogated effector function provided evidence that blocking of the receptor-ligand interaction was sufficient for control of CD200-mediated immune modulation and tumor growth inhibition in this model. Our data indicate that CD200 expression by tumor cells suppresses antitumor responses and suggest that anti-CD200 treatment might be therapeutically beneficial for treating CD200-expressing cancers.