Summary Genomic screening is routinely used to guide the treatment of cancer patients in many countries. However, several multi-layered factors make this effort difficult to deliver within a clinically relevant timeframe. Here we share the learnings from the CRUK-funded Stratified Medicine Programme for advanced NSCLC patients, which could be useful to better plan future studies.

Introduction: The availability of high-quality, rigorously validated diagnostic tests that can be broadly implemented is necessary to efficiently identify patients with anaplastic lymphoma kinase (ALK)-positive NSCLC who can potentially benefit from treatment with crizotinib. Here we present data on the recently approved Ventana ALK (D5F3) CDx Assay (Ventana Medical Systems, Tucson, AZ), the only immunohistochemistry (IHC)-based assay linked to treatment outcome.Methods: NSCLC specimens prospectively tested for anaplastic lymphoma receptor tyrosine kinase gene (ALK) status by flourescent in situ hybridization (FISH) in the PROFILE 1014 clinical trial of crizotinib versus chemotherapy (N = 1018, including 179 ALK-positive and 754 ALK-negative specimens) were evaluated using the ALK (D5F3) CDx assay. Hazard ratios for progression-free survival comparing crizotinib and chemotherapy for ALK IHC-positive patients and ALK FISH-positive patients, as well as for concordance with the enrollment ALK FISH assay, were determined.Results: Results from both assays were obtained for 933 cases. Percent positive, negative, and overall agreement rates were 86.0%, 96.3%, and 94.3%, respectively. There were 53 discrepant cases, of which 25 were ALK FISHpositive/ALK IHC-negative and 28 were ALK FISHnegative/ALK IHC-positive. The hazard ratios using observed outcomes were 0.401 for ALK FISH-positive/ALK IHC-positive cases and 0.407 for all ALK FISH-positive cases tested with ALK IHC versus 0.454 for all ALK FISH positive cases enrolled in the trial. Outcome data for ALK FISH-negative/ALK IHC-positive cases were not available for analysis. Between-reader agreement rates for ALK IHC involving three independent laboratories exceeded 98%.Conclusions: The ALK (D5F3) CDx assay is a stand-alone companion diagnostic test for identification of patients for treatment with crizotinib. This automated assay provides an effective option to accurately and rapidly identify patients with ALK-positive NSCLC. The simple binary scoring algorithm results in high reader-to-reader precision. (C) 2017 International Association for the Study of Lung Cancer. Published by Elsevier Inc.

Crizotinib (XALKORI®) is a small molecule ALK, ROS1, and c-MET tyrosine kinase inhibitor approved for the treatment of patients with ALK-positive or ROS1-positive metastatic NSCLC. PROFILE 1005 was a single arm phase 2 study of the safety and efficacy of crizotinib in previously treated patients with advanced NSCLC that is ALK-positive as determined by the investigational use only FISH test or on a case-by-case basis using a local FISH, IHC or RT-PCR laboratory developed test. In this study 54.1% of patients exhibited a confirmed complete or partial response to crizotinib (responders) by investigator assessment, while 9.9% had a best overall tumor response of progressive disease (progressors).

Introduction: This phase I trial was conducted to determine the safety, maximum tolerated dose (MTD)/recommended phase II dose, and efficacy of crizotinib plus erlotinib in patients with advanced NSCLC.Methods: Patients with NSCLC and an Eastern Cooperative Oncology Group performance status of 0 to 2 after failure of one or two prior chemotherapy regimens were eligible. Erlotinib, 100 mg, was given continuously once daily starting between day 14 and 7; crizotinib, 200 mg twice daily (dose level 1) or 150 mg twice daily (dose level 1), was added continuously beginning on day 1 of treatment cycle 1. Potential pharmacokinetic interactions between crizotinib and erlotinib were evaluated.Results: Twenty-seven patients received treatment; 26 received crizotinib plus erlotinib. Frequent adverse events were diarrhea, rash, decreased appetite, and fatigue. Dose-limiting toxicities were dehydration, diarrhea, dry eye, dysphagia, dyspepsia, esophagitis and vomiting. The MTD was crizotinib, 150 mg twice daily, with erlotinib, 100 mg once daily. Crizotinib increased the erlotinib area under the concentration-time curve 1.5-fold (dose level 1) and 1.8-fold (dose level 1). The plasma level of crizotinib appeared to be unaffected by coadministration of erlotinib. Two patients whose tumors harbored activating EGFR mutations achieved confirmed partial responses, one at each crizotinib dose level.Conclusions: The MTD of the combination of crizotinib and erlotinib in patients with advanced NSCLC was crizotinib, 150 mg twice daily, with erlotinib, 100 mg once daily, which is less than the approved dose of either agent. The phase II portion of the study was not initiated. (C) 2016 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.

9062 Background: Crizotinib trials provide a large dataset to evaluate the distribution of % ALK+ cells by FISH in ALK+ NSCLC and the association between degree of ALK positivity and clinical outcome. Methods: Data were pooled from 3 ongoing crizotinib trials in ALK+ NSCLC: a large single-arm trial in the ≥ 2nd-line (NCT00932451) and 2 phase 3 trials vs. chemotherapy in the 1st- (NCT01154140) and 2nd-line (NCT00932893) settings. Prospective screening was performed at central laboratories using Vysis ALK Break Apart FISH and a cutoff of ≥ 15% ALK+ cells to define ALK positivity. Association between % ALK+ cells by FISH and clinical outcome in ALK+ pts was assessed using logistic regression for objective response (OR) and proportional hazards regression for PFS. Results: Screening of tumor samples from 11,081 pts identified 1958 (18%) ALK+ and 7512 (68%) ALK− pts, with 1540 (14%) undetermined. The median % ALK+ cells was 58% in ALK+ pts and 2% in ALK− pts, with 11% of ALK+ pts and 2% of ALK− pts near the 15% ALK+ cell cutoff (15−24% and 10−14% ALK+ cells, respectively). 1357 ALK+ pts received crizotinib initially or on crossover from chemotherapy. Only small differences in mean/median % ALK+ cells were seen across best response categories (CR, PR, SD, PD). ORs were seen across the range of % ALK+ cells, including 7/19 (37%) at 15% ALK+ cells (ORR for all crizotinib-treated pts: 54%). Using % ALK+ cells as a continuous variable, higher percentages of ALK+ cells were associated with larger differences between crizotinib and chemotherapy in OR and PFS, but the treatment by % ALK+ interaction tests were not significant (OR: P = 0.07; PFS: P = 0.16). Conclusions: These results indicate that among ALK+ pts as defined by ≥ 15% ALK+ cells by FISH, differences in OR or PFS outcomes for crizotinib vs chemotherapy as a function of % ALK+ cells were not statistically significant. The non-significant trend to greater benefit at higher ALK+ cell percentages may reflect the greater impact of technical or biologic false-positive signals at lower ALK+ cell percentages. Given that borderline ALK− pts (10−14% ALK+ cells) comprised 2% of all ALK− pts and that ORs were observed even at 15% ALK+ cells, further diagnostic evaluation of borderline cases may be in order.

Introduction: The demonstration of anaplastic lymphoma kinase (ALK) positivity in non–small-cell lung cancer (NSCLC) has been hindered by the technical complexity and interpretative challenges of fluorescence in situ hybridization methods for detection of ALK gene rearrangement and by the inadequate sensitivity of existing immunohistochemistry (IHC) methods for ALK protein detection. In this study, we sought to increase the sensitivity of ALK IHC detection and to develop a brightfield assay for concurrent detection of ALK protein expression and ALK gene rearrangement. Methods: We developed a horseradish peroxidase–based IHC detection system using the novel, nonendogenous hapten 3-hydroxy-2-quinoxaline (HQ) and tyramide. We also developed a dual gene protein ALK assay combining a brightfield break-apart in situ hybridization ALK assay with another sensitive IHC method using the novel, nonendogenous hapten 5-nitro-3-pyrazole. We examined the sensitivity and accuracy of these methods using surgically resected NSCLC cases examined with ALK fluorescence in situ hybridization. Results: The new HQ-tyramide IHC detection system offered readily interpretable staining with substantially greater sensitivity than conventional ALK IHC, and produced heterogeneous and homogeneous patterns of ALK protein staining among ALK-positive NSCLC surgical cases. The new 5-nitro-3-pyrazole–based IHC detection system was similar in ALK detection sensitivity to the HQ-tyramide IHC system and was compatible with the brightfield in situ hybridization assay. Conclusion: The new HQ-tyramide IHC reagent system allows more sensitive assessment of ALK protein status in NSCLC cases. The new ALK gene-protein assay allows the concurrent visualization of ALK gene and ALK protein status in single cells, allowing more accurate ALK status determination even in heterogeneous specimens.

Gene Splicing by Overlap Extension or "gene SOEing" is a PCR-based method of recombining DNA sequences without reliance on restriction sites and of directly generating mutated DNA fragments in vitro. By modifying the sequences incorporated into the 5'-ends of the primers, any pair of polymerase chain reaction products can be made to share a common sequence at one end. Under polymerase chain reaction conditions, the common sequence allows strands from two different fragments to hybridize to one another, forming an overlap. Extension of this overlap by DNA polymerase yields a recombinant molecule. This powerful and technically simple approach offers many advantages over conventional approaches for manipulating gene sequences.

Galiximab is a primatized monoclonal antibody that targets CD80 expressed on malignant B cells and is being studied in the clinic as a potential treatment for follicular NHL. We have recently reported that galiximab signals B-NHL cells in vitro and inhibits cell growth and sensitizes resistant tumor cells to apoptosis by chemotherapeutic drugs. This study was designed to validate the in vitro findings in in vivo in mice. Thus, we examined in vivo the antitumor activity of galiximab used alone and in combination with chemotherapeutic agents in SCID mice bearing human lymphoma xenografts. The in vivo antitumor effects of galiximab used alone and in combination with fludarabine or doxorubicin were determined in solid and disseminated human B-lymphoma tumors grown in SCID mice. Galiximab monotherapy in vivo demonstrated significant antitumor activity in a Raji lymphoma solid tumor model and in an SKW disseminated lymphoma tumor model. There was significant inhibition in tumor growth and prolongation of survival. In vitro, galiximab sensitized Raji cells to apoptosis by both fludarabine and doxorubicin. Tumor growth inhibition was significantly enhanced when the mice were treated with the combination of galiximab and fludarabine. These findings support the potential clinical application of galiximab in combination with chemotherapeutic drugs for the treatment of CD80-expressing hematological malignancies.

The recently approved ALK kinase inhibitor crizotinib has demonstrated successful treatment of metastatic and late stage ALK fusion positive non-small cell lung cancer (NSCLC). However, the median duration of clinical benefit is ~10-11months due to the emergence of multiple and simultaneous resistance mechanisms in these tumors. Mutations in the ALK kinase domain confer resistance to crizotinib in about one-third of these patients. We developed a multiplex deep sequencing method using semiconductor sequencing technology to quickly detect resistance mutations within the ALK kinase domain from tumor biopsies. By applying a base-pair specific error-weighted mutation calling algorithm (BASCA) that we developed for this assay, genomic DNA analysis from thirteen relapsed patients revealed three known crizotinib resistance mutations, C1156Y, L1196M and G1269A. Our assay demonstrates robust and sensitive detection of ALK kinase mutations in NSCLC tumor samples and aids in the elucidation of resistance mechanisms pertinent to the clinical setting.

The TWEAK receptor Fn14 (TNFRSF12), a member of the TNF Receptor superfamily, can mediate many processes, including apoptosis. Fn14 agonists have therefore been the subject of interest as potential cancer therapeutics. In cell culture experiments, interferon gamma (IFNγ) is typically required for induction of apoptotic activity by either TWEAK or Fn14 agonistic antibodies in most cell lines. We have investigated the mechanism of IFNγ signaling and the role of JAK–STAT signaling in TWEAK/Fn14-mediated tumor cell killing. We found that IFNγ-mediated enhancement of tumor cell killing is JAK–STAT dependent, as JAK inhibitors block IFNγ−dependent TWEAK induced apoptosis. Exposure of tumor cells to IFNγ results in an increase in Fn14 expression on the cell surface, which may be a mechanism by which IFNγ induces sensitivity to TWEAK. In a reciprocal fashion, we observed that IFNγ receptor levels increase in response to TWEAK treatment in WiDr cells. Significantly, we found that TWEAK alone can induce STAT1 phosphorylation in WiDr tumor cells. Moreover, TWEAK induction of tumor cell apoptosis in WiDr cells in the absence of IFNγ is mediated by the JAK–STAT pathway. Correspondingly, we show that treatment of tumor bearing mice with mBIIB036, an Fn14 agonistic antibody, results in STAT1 phosphorylation in the tumors. Notably, the level of STAT1 phosphorylation appears to correlate with the degree of tumor growth inhibition by BIIB036 in vivo. Additionally, in WiDr cells, TWEAK induces a soluble factor, which we have identified as IFNβ, capable of independently inducing STAT1 phosphorylation when transferred to naïve cells. Finally, either IFNα or IFNβ can partially substitute for IFNγ in sensitizing tumor cells to Fn14 agonists. In summary, we show that TWEAK/Fn14 can signal through the JAK–STAT pathway to induce IFNβ, and that the ability of TWEAK to induce tumor cell apoptosis is mediated by JAK-STAT signaling. We also demonstrate that IFNγ enhancement of TWEAK/FN14-mediated tumor cell death is JAK-dependent and may occur by IFNγ-dependent upregulation of Fn14 on tumor cells. These findings may have implications for the appropriately targeted clinical development of Fn14 agonists as anti-cancer therapy.

Abstract Abstract 4873 The non-Hodgkin's lymphomas (NHLs) are a group of lymphoproliferative malignancies with divergent clinical courses. Although the NHLs have historically been treated with radiation therapy and/or chemotherapy, the standard of care has evolved to incorporate the use of rituximab, a mAb that is directed against the CD20 antigen expressed on the surface of transformed B-lymphocytes. However, there are subsets of patients who do not initially respond or become refractory to further treatments. Hence, there is a need for new therapeutic strategies for these patients. CD80 is constitutively expressed on the surface of many B-cell lymphomas. When cell-surface CD80 is cross-linked with anti-CD80 antibodies, cell proliferation is inhibited, proapoptotic molecules are upregulated and antibody-dependent cell cytotoxicity (ADCC) is induced. These findings provide the rationale for using an anti-CD80 mAb to treat lymphoma. Galiximab is a primatized monoclonal antibody that targets CD80 expressed on malignant B cells and is being studied in the clinic as a potential treatment for follicular NHL. Galiximab is a primatized anti-CD80 mAb that has been tested as monotherapy in phase I/II clinical trials involving patients with relapsed/refractory follicular lymphoma (FL), producing an overall response rate of 11% and tumor reductions in 46% of patients. In a recent phase I/II clinical trial involving patients with relapsed or refractory FL, combined therapy with galiximab and rituximab yielded an overall response rate of 66% and a median progression-free survival of 12.1 months at the recommended phase II dose of galiximab (500 mg/m2). We have recently reported that galiximab signals B-NHL cells in vitro and inhibits cell growth and sensitizes resistance tumor cells to apoptosis by chemotherapeutic drugs. The present finding was designed to validate the in vitro findings in in vivo in mice. Thus, we examined in vivo the anti-tumor activity of galiximab used alone and in combination with chemotherapeutic agents in SCID mice bearing human lymphoma xenografts. The in vivo anti-tumor effects of galiximab used alone and in combination with fludarabine or doxorubicin were determined in solid and disseminated human B-lymphoma tumors grown in SCID mice. Galiximab monotherapy in vivo demonstrated significant anti-tumor activity in a Raji lymphoma solid tumor model and in an SKW disseminated lymphoma tumor model. There was significant inhibition in tumor growth and prolongation of survival in both models. In vitro, galiximab sensitized Raji cells to apoptosis by both fludarabine and doxorubicin. Tumor growth inhibition was significantly enhanced when the mice were treated with the combination of galiximab and fludarabine. These findings support the potential clinical application of galiximab in combination with chemotherapeutic drugs for the treatment of CD80-expressing hematologic malignancies. Disclosures: No relevant conflicts of interest to declare.

The epidermal growth factor receptor (EGFR) and the type I insulin-like growth factor receptor (IGF-1R) are two cell surface receptor tyrosine kinases known to cooperate to promote tumor progression and drug resistance. Combined blockade of EGFR and IGF-1R has shown improved anti-tumor activity in preclinical models. Here, we report the characterization of a stable IgG-like bispecific antibody (BsAb) dual-targeting EGFR and IGF-1R that was developed for cancer therapy. The BsAb molecule (EI-04), constructed with a stability-engineered single chain variable fragment (scFv) against IGF-1R attached to the carboxyl-terminus of an IgG against EGFR, displays favorable biophysical properties for biopharmaceutical development. Biochemically, EI-04 bound to human EGFR and IGF-1R with sub nanomolar affinity, co-engaged the two receptors simultaneously, and blocked the binding of their respective ligands with similar potency compared to the parental monoclonal antibodies (mAbs). In tumor cells, EI-04 effectively inhibited EGFR and IGF-1R phosphorylation, and concurrently blocked downstream AKT and ERK activation, resulting in greater inhibition of tumor cell growth and cell cycle progression than the single mAbs. EI-04, likely due to its tetravalent bispecific format, exhibited high avidity binding to BxPC3 tumor cells co-expressing EGFR and IGF-1R, and consequently improved potency at inhibiting IGF-driven cell growth over the mAb combination. Importantly, EI-04 demonstrated enhanced in vivo anti-tumor efficacy over the parental mAbs in two xenograft models, and even over the mAb combination in the BxPC3 model. Our data support the clinical investigation of EI-04 as a superior cancer therapeutic in treating EGFR and IGF-1R pathway responsive tumors.

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. (C) 2011 International Clinical Cytometry Society

Objective. This phase II, multicenter, single-arm, two-stage study in platinum-resistant, advanced epithelial ovarian or primary peritoneal cancer evaluated the efficacy, safety, and tolerability of weekly single-agent volociximab. Pharmacokinetic/pharmacodynamic (PK/PD) studies were also performed.Methods. Sixteen patients were enrolled in Stage 1. Volociximab was administered at 15 mg/kg IV qwk until progression of disease or drug intolerability. Tumor response was assessed every 8 weeks. Serum samples for PK or whole blood for the evaluation of circulating tumor cells, endothelial cells, and endothelial progenitor cells were obtained on Days 1, 8, 15, 29, and 50. Ascites from one patient was collected for volociximab concentration analysis. Archived tumor tissue was analyzed by immunohistochemistry (IHC) for alpha 5 integrin expression.Results. Safety data are available on all 16 patients; 14 were evaluable for efficacy. One patient had stable disease at 8 weeks. The remaining 13 progressed on treatment. Twelve patients (75%) experienced study-related adverse events (AEs); the most common (>= 20%) were headache and fatigue. Three patients experienced possible study-related serious AEs (SAEs): reversible posterior leukoencephalopathy syndrome, pulmonary embolism, and hyponatremia. Peak serum concentrations of volociximab increased 2-3 fold from Day 1 to Day 50. Clinically relevant trough levels were achieved (> 150 mu g/mL). IHC analysis of archived tumor sections showed low-to-moderate expression of alpha 5 integrin on all ovarian cancer tissue evaluated.Conclusion. Despite insufficient clinical activity in this refractory patient population to continue the study, weekly volociximab was well tolerated, and the gained understanding of the mechanism of action of volociximab will inform future development efforts. (C) 2011 Elsevier Inc. All rights reserved.

TonEBP (tonicity-responsive enhancer binding protein) is a transcription factor that promotes cellular accumulation of organic osmolytes in the hypertonic renal medulla by stimulating expression of its target genes. Genetically modified animals with deficient TonEBP activity in the kidney suffer from severe medullary atrophy in association with cell death, demonstrating that TonEBP is essential for the survival of the renal medullary cells. Using both TonEBP knockout cells and RNA interference of TonEBP, we found that TonEBP promoted cellular adaptation to hypertonic stress. Microarray analyses revealed that the genetic response to hypertonicity was dominated by TonEBP in that expression of totally different sets of genes was increased by hypertonicity in those cells with TonEBP vs. those without TonEBP activity. Of over 100 potentially new TonEBP-regulated genes, we selected seven for further analyses and found that their expressions were all dependent on TonEBP. RNA interference experiments showed that some of these genes, asporin, insulin-like growth factor-binding protein-5 and -7, and an extracellular lysophospholipase D, plus heat shock protein 70, a known TonEBP target gene, contributed to the adaptation to hypertonicity without promoting organic osmolyte accumulation. We conclude that TonEBP stimulates multiple cellular pathways for adaptation to hypertonic stress in addition to organic osmolyte accumulation.

A sample preparation procedure has been developed to prepare Formalin-Fixed Paraffin-Embedded (FFPE) tissues for proteomic profiling. Protocols have been established for processing FFPE sections on slides, including deparaffinization, rehydration, protein extraction, and enzymatic digestion, all using in-house developed and optimized buffers and techniques. These methods are practical and allow for parallel sample processing. The efficiency of protein extraction from FFPE tissue is comparable to the results from fresh or frozen tissue. The prepared samples can be directly coupled to a wide range of proteomic technologies, including isobaric labeling and on-line multidimensional chromatography. Comprehensive proteomic profiling of prepared FFPE tissue was performed using a fully automated tandem multidimensional liquid chromatography (LC) system coupled with on-line electrospray ionization (ESI) tandem mass spectrometry (MS): LC/LC-MS/MS. Routinely around 4,000 unique proteins of high confidence could be identified from 100 mu g of extracted protein. The method presented here will be valuable for others who plan to analyze FFPE tissues.

Abstract The insulin-like growth factor-I receptor (IGF-IR) is a cell surface receptor tyrosine kinase that mediates cell survival signaling and supports tumor progression in multiple tumor types. We identified a spectrum of inhibitory IGF-IR antibodies with diverse binding epitopes and ligand-blocking properties. By binding distinct inhibitory epitopes, two of these antibodies, BIIB4 and BIIB5, block both IGF-I and IGF-II binding to IGF-IR using competitive and allosteric mechanisms, respectively. Here, we explored the inhibitory effects of combining BIIB4 and BIIB5. In biochemical assays, the combination of BIIB4 and BIIB5 improved both the potency and extent of IGF-I and IGF-II blockade compared with either antibody alone. In tumor cells, the combination of BIIB4 and BIIB5 accelerated IGF-IR downregulation and more efficiently inhibited IGF-IR activation as well as downstream signaling, particularly AKT phosphorylation. In several carcinoma cell lines, the antibody combination more effectively inhibited ligand-driven cell growth than either BIIB4 or BIIB5 alone. Notably, the enhanced tumor growth–inhibitory activity of the BIIB4 and BIIB5 combination was much more pronounced at high ligand concentrations, where the individual antibodies exhibited substantially reduced activity. Compared with single antibodies, the BIIB4 and BIIB5 combination also significantly further enhanced the antitumor activity of the epidermal growth factor receptor inhibitor erlotinib and the mTOR inhibitor rapamycin. Moreover, in osteosarcoma and hepatocellular carcinoma xenograft models, the BIIB4 and BIIB5 combination significantly reduced tumor growth to a greater degree than each single antibody. Taken together, our results suggest that targeting multiple distinct inhibitory epitopes on IGF-IR may be a more effective strategy of affecting the IGF-IR pathway in cancer. Mol Cancer Ther; 9(9); 2593–604. ©2010 AACR.

Therapeutic antibodies directed against the type 1 insulin-like growth factor receptor (IGF-1R) have recently gained significant momentum in the clinic because of preliminary data generated in human patients with cancer. These antibodies inhibit ligand-mediated activation of IGF-1R and the resulting down-stream signaling cascade. Here we generated a panel of antibodies against IGF-1R and screened them for their ability to block the binding of both IGF-1 and IGF-2 at escalating ligand concentrations (>1 μm) to investigate allosteric versus competitive blocking mechanisms. Four distinct inhibitory classes were found as follows: 1) allosteric IGF-1 blockers, 2) allosteric IGF-2 blockers, 3) allosteric IGF-1 and IGF-2 blockers, and 4) competitive IGF-1 and IGF-2 blockers. The epitopes of representative antibodies from each of these classes were mapped using a purified IGF-1R library containing 64 mutations. Most of these antibodies bound overlapping surfaces on the cysteine-rich repeat and L2 domains. One class of allosteric IGF-1 and IGF-2 blocker was identified that bound a separate epitope on the outer surface of the FnIII-1 domain. Using various biophysical techniques, we show that the dual IGF blockers inhibit ligand binding using a spectrum of mechanisms ranging from highly allosteric to purely competitive. Binding of IGF-1 or the inhibitory antibodies was associated with conformational changes in IGF-1R, linked to the ordering of dynamic or unstructured regions of the receptor. These results suggest IGF-1R uses disorder/order within its polypeptide sequence to regulate its activity. Interestingly, the activity of representative allosteric and competitive inhibitors on H322M tumor cell growth in vitro was reflective of their individual ligand-blocking properties. Many of the antibodies in the clinic likely adopt one of the inhibitory mechanisms described here, and the outcome of future clinical studies may reveal whether a particular inhibitory mechanism leads to optimal clinical efficacy.

Abstract Abstract 1953 Poster Board I-976 CD80 is a member of the B7/CD28 family of regulatory proteins. B7/CD28 proteins are expressed on the surface of cells of the adaptive and innate immune system (i.e. lymphocytes, monocyte/macrophages, dendritic cells, myeloid-derived suppressor cells). These proteins function to establish a biologically optimal and dynamic balance between immune activation and inhibition or self-tolerance. Interactions between CD80 and its receptors, which include CD28, CTLA4 and PD-L1, contribute to both stimulatory as well as inhibitory or homeostatic regulation. Galiximab, an antibody directed against CD80, is currently under investigation for the treatment of follicular NHL. Initial clinical trials demonstrated that galiximab is well tolerated and suggest that combining galiximab with rituximab may provide clinical benefit. While expression of CD80 by malignant B cells in non-Hodgkin's lymphoma (NHL) has been reported, these studies utilized poorly quantitative immunohistochemical methods. To gain further understanding of the potential role of CD80 as a therapeutic target in NHL, CD80 expression was evaluated by six-color flow cytometric analysis of primary lymphoma cell suspensions generated from diagnostic biopsies of patients presenting with lymphadenopathy. Results obtained to date confirm that CD80 is uniformly expressed by malignant cells in a large majority of cases of follicular lymphoma (N=63), diffuse large B cell lymphoma (N=38), mantle cell lymphoma (n=7), marginal zone lymphoma (n=12) and small lymphocytic lymphoma (n=9). Furthermore, CD80 expression was also observed on tumor-infiltrating, non-malignant T cells. These results confirm the nearly ubiquitous expression of CD80 by malignant B cells in follicular, diffuse and other low grade NHL. Furthermore, these data demonstrate expression of CD80 by non-malignant cells (e.g. T cells) that define the tumor microenvironment. Further work to expand this dataset and to evaluate the expression of CD80 in non-T, non-B cells is ongoing. The expression of CD80 by malignant cells as well as non-malignant cells in NHL provides an opportunity to not only employ therapeutic antibodies to direct anti-tumor effector function such as antibody-dependent cellular cytotoxicity, but to also potentially interfere with interactions involving CD80 that might be involved in establishing an immune suppressive microenvironment supportive of tumor growth. Disclosures: No relevant conflicts of interest to declare.