Meaningful score changes for SF-36v2, FACIT-fatigue, and RASIQ in rheumatoid arthritis.

BACKGROUND: Interpretation thresholds for patient-reported outcome (PRO) scores are of crucial importance, particularly when interpreting treatment benefit. This study was designed to determine the within-patient meaningful improvement (WPMI) thresholds for the Short-Form 36 Health Survey version 2 (SF-36v2), the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue), and the novel Rheumatoid Arthritis Symptoms and Impact Questionnaire (RASIQ) among patients with rheumatoid arthritis (RA). METHODS: In this post-hoc analysis, anchor-based and supportive distribution-based methods were used to derive WPMI based on blinded data from all treatment arms in two Phase 2 RA trials with otilimab. Patient's Global Assessment of Disease Activity (PtGA) was the general anchor for all SF-36v2 scales. SF-36 Patient's Global Impression of Status (PGIS), PtGA, and VT03 (an SF-36v2 item) were used as anchors for FACIT-Fatigue. SF-36 PGIS, PtGA, and Patient's Assessment of Arthritis Pain (PAIN) were anchors for RASIQ. Mean change was calculated for the anchor category associated with minimal meaningful improvement from baseline to Week 24 for SF-36v2 and FACIT-Fatigue, and to Week 12 for RASIQ. Sensitivity and specificity were used to evaluate the accuracy of estimated WPMI values. RESULTS: For the SF-36v2 physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional, and mental health domains, anchor-based estimates of WPMI based on 0-100 scores were 24.5, 24.5, 25.4, 13.6, 21.5, 20.5, 16.9, and 14.3, respectively. Anchor-based WPMI estimates were 9.7 for the Physical Component Summary score and 7.6 for the Mental Component Summary score (using norm-based T-score metric). For FACIT-Fatigue (range 0-52), WPMI estimates ranged from 9.7 to 11.3 points. For RASIQ (range 0-100), anchor-based WPMI was determined as a change between -32.7 and -21.7 points for the Joint Pain scale, -26.7 to -23.7 for the Joint Stiffness scale, and -21.1 to -17.4 for the Impact scale. CONCLUSIONS: This study derived WPMI thresholds for SF-36v2, FACIT-Fatigue, and RASIQ among patients with RA, using multiple anchors. Derivation of WPMI thresholds for these PRO instruments will enable their broader use in evaluating and interpreting treatment benefit in future RA studies.

When assessing medical treatments in clinical trials, it is important to understand whether the treatment improves symptoms or impacts of a disease to an extent which is meaningful for patients. Patients are often asked to complete questionnaires about their symptoms throughout clinical trials to measure if and how symptoms change. Questionnaire responses are used to calculate a score that is compared before and after treatment. This study was designed to investigate how much scores in three questionnaires (SF-36v2, FACIT-Fatigue, and RASIQ) changed for patients with rheumatoid arthritis who reported experiencing meaningful symptom improvement based on data from two clinical trials. As the RASIQ is a new questionnaire that was designed specifically for rheumatoid arthritis, this research is particularly important for interpretation of RASIQ results.

A concept elicitation study to understand the relationship between sleep and pain in rheumatoid arthritis and axial spondyloarthritis.

PURPOSE: This qualitative study (GSK study: 213635) was designed to better understand sleep disturbance as experienced by individuals with rheumatoid arthritis (RA) or axial spondyloarthritis (axSpA), and the relationship between sleep disturbance and pain and other aspects of the disease and disease activity. METHODS: Sixty-minute, one-on-one, concept elicitation interviews were conducted with 30 participants (15 with RA and 15 with axSpA) from the US. Interviews were audio-recorded and transcribed verbatim. Interview transcripts were coded and analyzed to explore themes related to pain and sleep disturbance, and relationships among those themes. RESULTS: Pain was a prominent driver of sleep disturbance; 12 participants with RA (80%) and 14 with axSpA (93%) reported that pain impacted their ability to fall asleep, while all 15 with RA (100%) and 14 with axSpA (93%) reported that pain impacted their ability to stay asleep. Two-thirds of participants with RA (67%) or axSpA (60%) described a bi-directional relationship, whereby pain worsened sleep disturbance and sleep disturbance further aggravated pain. Factors other than pain, such as fatigue and emotional health, were also reported as important contributors to sleep disturbance (RA: n = 12/15, 80%; axSpA: n = 14/15, 93%). Participants with RA or axSpA described complex interconnections between fatigue, emotional health, pain, and sleep, often labeling these relationships as "vicious cycles". Notably, half of all participants reported sleep disturbance occurring without pain or other understood causes. CONCLUSION: These perspectives collected from people with RA or axSpA suggest that reducing sleep disruption directly may offer clinically relevant benefits.

Anti-GM-CSF otilimab versus tofacitinib or placebo in patients with active rheumatoid arthritis and an inadequate response to conventional or biologic DMARDs: two phase 3 randomised trials (contRAst 1 and contRAst 2).

OBJECTIVES: To investigate the efficacy and safety of otilimab, an antigranulocyte-macrophage colony-stimulating factor antibody, in patients with active rheumatoid arthritis. METHODS: Two phase 3, double-blind randomised controlled trials including patients with inadequate responses to methotrexate (contRAst 1) or conventional synthetic/biologic disease-modifying antirheumatic drugs (cs/bDMARDs; contRAst 2). Patients received background csDMARDs. Through a testing hierarchy, subcutaneous otilimab (90/150 mg once weekly) was compared with placebo for week 12 endpoints (after which, patients receiving placebo switched to active interventions) or oral tofacitinib (5 mg two times per day) for week 24 endpoints. PRIMARY ENDPOINT: proportion of patients achieving an American College of Rheumatology response ≥20% (ACR20) at week 12. RESULTS: The intention-to-treat populations comprised 1537 (contRAst 1) and 1625 (contRAst 2) patients. PRIMARY ENDPOINT: proportions of ACR20 responders were statistically significantly greater with otilimab 90 mg and 150 mg vs placebo in contRAst 1 (54.7% (p=0.0023) and 50.9% (p=0.0362) vs 41.7%) and contRAst 2 (54.9% (p<0.0001) and 54.5% (p<0.0001) vs 32.5%). Secondary endpoints: in both trials, compared with placebo, otilimab increased the proportion of Clinical Disease Activity Index (CDAI) low disease activity (LDA) responders (not significant for otilimab 150 mg in contRAst 1), and reduced Health Assessment Questionnaire-Disability Index (HAQ-DI) scores. Benefits with tofacitinib were consistently greater than with otilimab across multiple endpoints. Safety outcomes were similar across treatment groups. CONCLUSIONS: Although otilimab demonstrated superiority to placebo in ACR20, CDAI LDA and HAQ-DI, improved symptoms, and had an acceptable safety profile, it was inferior to tofacitinib. TRIAL REGISTRATION NUMBERS: NCT03980483, NCT03970837.

Anti-GM-CSF otilimab versus sarilumab or placebo in patients with rheumatoid arthritis and inadequate response to targeted therapies: a phase III randomised trial (contRAst 3).

OBJECTIVES: To investigate the efficacy and safety of otilimab, an anti-granulocyte-macrophage colony-stimulating factor antibody, in patients with active rheumatoid arthritis and an inadequate response to conventional synthetic (cs) and biologic disease-modifying antirheumatic drugs (DMARDs) and/or Janus kinase inhibitors. METHODS: ContRAst 3 was a 24-week, phase III, multicentre, randomised controlled trial. Patients received subcutaneous otilimab (90/150 mg once weekly), subcutaneous sarilumab (200 mg every 2 weeks) or placebo for 12 weeks, in addition to csDMARDs. Patients receiving placebo were switched to active interventions at week 12 and treatment continued to week 24. The primary end point was the proportion of patients achieving an American College of Rheumatology ≥20% response (ACR20) at week 12. RESULTS: Overall, 549 patients received treatment. At week 12, there was no significant difference in the proportion of ACR20 responders with otilimab 90 mg and 150 mg versus placebo (45% (p=0.2868) and 51% (p=0.0596) vs 38%, respectively). There were no significant differences in Clinical Disease Activity Index, Health Assessment Questionnaire-Disability Index, pain Visual Analogue Scale or Functional Assessment of Chronic Illness Therapy-Fatigue scores with otilimab versus placebo at week 12. Sarilumab demonstrated superiority to otilimab in ACR20 response and secondary end points. The incidence of adverse or serious adverse events was similar across treatment groups. CONCLUSIONS: Otilimab demonstrated an acceptable safety profile but failed to achieve the primary end point of ACR20 and improve secondary end points versus placebo or demonstrate non-inferiority to sarilumab in this patient population. TRIAL REGISTRATION NUMBER: NCT04134728.

Qualitative concept elicitation and cognitive debriefing interviews of symptoms, impacts and selected customized PROMIS® Short Forms: a study in patients with axial spondyloarthritis.

BACKGROUND: Sleep disturbance, pain, and fatigue are key symptoms/impacts of axial spondyloarthritis (axSpA). Three customized Patient-Reported Outcomes Measurement Information System (PROMIS®) Short Forms (Sleep Disturbance, Pain Interference, and Fatigue) have been proposed for use in axSpA to assess these key disease concepts. This study was designed to further understand the patient experience of axSpA and evaluate the content validity of the three customized PROMIS® Short Forms to support their use in axSpA clinical trials. METHODS: Non-interventional, cross-sectional, qualitative (concept elicitation [CE] and cognitive debriefing [CD]) study. Participants took part in 90-min telephone interviews. The CE section used open-ended questions to elicit information about axSpA symptoms and impacts. The CD section involved a 'think-aloud' exercise where participants read out each instruction, item, and response option for the customized PROMIS® Short Forms and shared their feedback. Participants also discussed the relevance of the items, response options and recall period. Verbatim interview transcripts were subject to thematic and content analysis. RESULTS: In total, there were 28 participants (non-radiographic axSpA, n = 12; ankylosing spondylitis, n = 16), from the US (n = 20) and Germany (n = 8). Mean age was 52.8 years, and 57% were male; mean time since diagnosis was 9.5 years. The CE section identified 12 distinct symptoms that characterized axSpA: pain, sleep problems, fatigue/tiredness, stiffness, swelling, vision/eye issues, restricted body movements, headache/migraine, spasms, change in posture/stature, balance/coordination problems, and numbness. Pain, sleep problems, and fatigue/tiredness were experienced by ≥ 90% of participants, occurring simultaneously and exacerbating one another. Participants reported axSpA impacted their lives across six domains of health-related quality of life (HRQoL): physical functioning (100%), emotional wellbeing (89%), work/volunteering (79%), social functioning (75%), activities of daily living (61%) and cognitive functioning (54%). Impacts were most frequently associated with pain, stiffness, and fatigue. CD showed the PROMIS® instruments were conceptually comprehensive and well understood, with all items relevant to ≥ 50% of participants. CONCLUSIONS: Pain, sleep problems and fatigue are pivotal symptoms of axSpA and associated with HRQoL impacts. These results were used to update a conceptual model of axSpA which was originally developed based on a targeted literature review. Interpretability and content validity of the customized PROMIS® Short Forms were confirmed, with each deemed to adequately assess key impacts associated with axSpA, making them suitable for use in axSpA clinical trials.

A qualitative study to explore the symptoms and impacts of Crohn's disease and to develop the Crohn's Disease Diary.

PURPOSE: To explore symptoms and disease impacts of Crohn's disease and to develop a new patient-reported outcomes (PRO) measure according to industry best practices. METHODS: A conceptual model of relevant symptoms experienced by patients with Crohn's disease was developed following a literature review. Three rounds of combined qualitative semi-structured concept elicitation and cognitive debriefing interviews with 36 patients (≥ 16 years) with Crohn's disease and 4 clinicians were conducted to further explore the most commonly reported and most bothersome symptoms to patients. Interview results were used to update the conceptual model as well as items and response options included in The Crohn's Disease Diary, a new PRO measure. RESULTS: All patients (N = 36) reported abdominal pain, loose or liquid bowel movements, and high or increased frequency of bowel movements, with most reporting these symptoms spontaneously (100%, 92%, and 75%, respectively). All patients reported bowel movement urgency, but 61% reported this symptom only when probed. Most also reported that symptoms impacted activities of daily living, work/school, and emotional, social, and physical functioning (overall, 78%-100%; spontaneously, 79% - 92%). Data regarding core symptoms of Crohn's disease from clinician concept elicitation interviews supported patient data. The 17-item Crohn's Disease Diary assesses core symptoms and impacts of Crohn's disease over 24 h, and extraintestinal manifestations over 7 days. The content validity of the diary was confirmed during cognitive debriefing interviews. CONCLUSION: The Crohn's Disease Diary is a new PRO measure for the assessment of Crohn's disease symptoms and impacts, developed according to industry best practices.

Development, psychometric evaluation and cognitive debriefing of the rheumatoid arthritis symptom and impact questionnaire (RASIQ).

BACKGROUND: Rheumatoid arthritis (RA) is a chronic inflammatory disease often associated with persistent pain. There is a need for a patient-reported outcome measure (PROM) that is rooted in the patient experience and psychometrically validated. We describe the development of the Rheumatoid Arthritis Symptom and Impact Questionnaire (RASIQ), a novel PROM with potential to record key symptoms and impacts of RA with a 24-h recall period. RESULTS: A literature review identified RA concepts that patients considered most important to their disease experience, including pain, fatigue, joint swelling and stiffness. From this, an initial item pool (33 items; 27 related to symptoms, 6 related to impacts) was developed with a recall period of 24 h. Two rheumatologists evaluated each item's relevance, and the second version of the RASIQ was refined (29 items; 21 related to symptoms, 8 related to impacts). Next, three rounds of cognitive debriefing interviews were conducted with patients with RA (n = 15 overall). The RASIQ was revised to remove items deemed irrelevant or redundant, leaving 16 items measuring symptoms (joint pain, energy/tiredness, joint stiffness) and impacts (rest, sleep). A parallel series of semi-structured concept elicitation interviews (n = 30) facilitated the design of a conceptual model of RA symptoms, impacts and treatment experiences. Post-hoc comparison of the model with RASIQ revealed that all items selected were among the most important and relevant symptoms and impacts for patients. A final round of cognitive debriefing interviews (n = 12) confirmed that the final 16-item RASIQ was relevant and easy to understand, with no further changes recommended. Psychometric evaluation using data from two Phase II RA clinical trials confirmed a 3-factor structure, as well as the reliability and validity of the scale scores, and the ability of RASIQ to detect changes in symptoms and impacts when administered at specific study timepoints, using a 24-h recall period. CONCLUSIONS: RASIQ is a novel, 16-item PROM developed with substantial patient input. Results from concept elicitation, cognitive debriefing, and psychometric evaluation confirmed the validity of the instrument, which has the potential to measure symptoms and impacts through a 24-h recall period and complement existing disease activity instruments with longer recall periods.

Discovery and Toxicological Profiling of Aminopyridines as Orally Bioavailable Selective Inhibitors of PI3-Kinase γ.

Using a novel physiologically relevant in vitro human whole blood neutrophil shape change assay, an aminopyrazine series of selective PI3Kγ inhibitors was identified and prioritized for further optimization. Severe solubility limitations associated with the series leading to low oral bioavailability and poor exposures, especially at higher doses, were overcome by moving to an aminopyridine core. Compound 33, with the optimal balance of on-target activity, selectivity, and pharmacokinetic parameters, progressed into in vivo studies and demonstrated good efficacy (10 mg/kg) in a rat model of airway inflammation. Sufficient exposures were achieved at high doses to support toxicological studies, where unexpected inflammatory cell infiltrates in cardiovascular tissue prevented further compound development.

Efficacy of an Inhaled IL-13 Antibody Fragment in a Model of Chronic Asthma.

RATIONALE: IL-13 is an important cytokine implicated in the pathogenesis of allergic asthma and is an attractive target for an inhaled therapeutic. OBJECTIVE: To investigate the efficacy of CDP7766, a nebulized inhaled anti-IL-13 monoclonal antibody Fab fragment, in a model of allergic asthma in cynomolgus macaques naturally sensitized to Ascaris suum. METHODS: CDP7766 was nebulized using a vibrating-membrane nebulizer on the basis of eFlow technology. The aerosol generated was analyzed to determine the particle size profile and the biophysical and functional properties of CDP7766. Nebulized CDP7766 (0.1-60 mg/animal, once daily for 5 d) was delivered via the inhaled route. MEASUREMENTS AND MAIN RESULTS: The investigational eFlow nebulizer used in this study generated a respirable aerosol of CDP7766 with no evidence of degradation, loss of potency, aggregation, or formation of particulates. Inhaled CDP7766 was well tolerated in the model (no adverse effects related to local irritation) and significantly inhibited BAL allergen-induced cytokine and chemokine upregulation (60 mg vs. vehicle: eotaxin-3, P < 0.0008; MIP [macrophage inflammatory protein]-1ß, IL-8, IFN-γ, P ≤ 0.01). CDP7766 significantly inhibited the increase in pulmonary resistance stimulated by inhaled allergen, measured 15 minutes and 24 hours after allergen challenge. CONCLUSION: Inhaled CDP7766 potently inhibited the function of IL-13 generated during the airway response to inhaled allergen in cynomolgus macaques, demonstrating the potential of inhaled anti-IL-13 therapeutics for the treatment of allergic asthma.

Anti-Folate Receptor-α IgE but not IgG Recruits Macrophages to Attack Tumors via TNFα/MCP-1 Signaling.

IgE antibodies are key mediators of antiparasitic immune responses, but their potential for cancer treatment via antibody-dependent cell-mediated cytotoxicity (ADCC) has been little studied. Recently, tumor antigen-specific IgEs were reported to restrict cancer cell growth by engaging high-affinity Fc receptors on monocytes and macrophages; however, the underlying therapeutic mechanisms were undefined and in vivo proof of concept was limited. Here, an immunocompetent rat model was designed to recapitulate the human IgE-Fcε receptor system for cancer studies. We also generated rat IgE and IgG mAbs specific for the folate receptor (FRα), which is expressed widely on human ovarian tumors, along with a syngeneic rat tumor model expressing human FRα. Compared with IgG, anti-FRα IgE reduced lung metastases. This effect was associated with increased intratumoral infiltration by TNFα+ and CD80+ macrophages plus elevated TNFα and the macrophage chemoattractant MCP-1 in lung bronchoalveolar lavage fluid. Increased levels of TNFα and MCP-1 correlated with IgE-mediated tumor cytotoxicity by human monocytes and with longer patient survival in clinical specimens of ovarian cancer. Monocytes responded to IgE but not IgG exposure by upregulating TNFα, which in turn induced MCP-1 production by monocytes and tumor cells to promote a monocyte chemotactic response. Conversely, blocking TNFα receptor signaling abrogated induction of MCP-1, implicating it in the antitumor effects of IgE. Overall, these findings show how antitumor IgE reprograms monocytes and macrophages in the tumor microenvironment, encouraging the clinical use of IgE antibody technology to attack cancer beyond the present exclusive reliance on IgG. Cancer Res; 77(5); 1127-41. ©2017 AACR.

The discovery, engineering and characterisation of a highly potent anti-human IL-13 fab fragment designed for administration by inhalation.

We describe the discovery, engineering and characterisation of a highly potent anti-human interleukin (IL)-13 Fab fragment designed for administration by inhalation. The lead candidate molecule was generated via a novel antibody discovery process, and the selected IgG variable region genes were successfully humanised and reformatted as a human IgG γ1 Fab fragment. Evaluation of the biophysical properties of a selection of humanised Fab fragments in a number of assays allowed us to select the molecule with the optimal stability profile. The resulting lead candidate, CA652.g2 Fab, was shown to have comparable activity to the parental IgG molecule in a range of in vitro assays and was highly stable. Following nebulisation using a mesh nebuliser, CA652.g2 Fab retained full binding affinity, functional neutralisation potency and structural integrity. Epitope mapping using solution nuclear magnetic resonance confirmed that the antibody bound to the region of human IL-13 implicated in the interaction with IL-13Rα1 and IL-13Rα2. The work described here resulted in the discovery and design of CA652.g2 human γ1 Fab, a highly stable and potent anti-IL-13 molecule suitable for delivery via inhalation.

Attenuation of IgE affinity for FcepsilonRI radically reduces the allergic response in vitro and in vivo.

The high affinity of IgE for its receptor, FcepsilonRI (K(a) approximately 10(10) M(-1)), is responsible for the persistence of mast cell sensitization. Cross-linking of FcepsilonRI-bound IgE by multivalent allergen leads to cellular activation and release of pro-inflammatory mediators responsible for the symptoms of allergic disease. We previously demonstrated that limiting the IgE-FcepsilonRI interaction to just one of the two Cepsilon3 domains in IgE-Fc, which together constitute the high affinity binding site, results in 1000-fold reduced affinity. Such attenuation, effected by a small molecule binding to part of the IgE:FcepsilonRI interface or a distant allosteric site, rather than complete blocking of the interaction, may represent a viable approach to the treatment of allergic disease. However, the degree to which the interaction would need to be disrupted is unclear, because the importance of high affinity for immediate hypersensitivity has never been investigated. We have incorporated into human IgE a mutation, R334S, previously characterized in IgE-Fc, which reduces its affinity for FcepsilonRI approximately 50-fold. We have compared the ability of wild type and R334S IgE to stimulate allergen-induced mast cell activation in vitro and in vivo. We confirmed the expected difference in affinity between wild type and mutant IgE for FcepsilonRI (approximately 50-fold) and found that, in vitro, mast cell degranulation was reduced proportionately. The effect in vivo was also marked, with a 75% reduction in the passive cutaneous anaphylaxis response. We have therefore demonstrated that the high affinity of IgE for FcepsilonRI is critical to the allergic response, and that even moderate attenuation of this affinity has a substantial effect in vivo.

Role of IgE receptors in IgE antibody-dependent cytotoxicity and phagocytosis of ovarian tumor cells by human monocytic cells.

Antibodies directed against tumor-associated antigens are emerging as effective treatments for a number of cancers, although the mechanism(s) of action for some are unclear and still under investigation. We have previously examined a chimeric IgE antibody (MOv18 IgE), against the ovarian tumor-specific antigen, folate binding protein (FBP), and showed that it can direct human PBMC to kill ovarian cancer cells. We have developed a three-color flow cytometric assay to investigate the mechanism by which IgE receptors on U937 monocytes target and kill ovarian tumor cells. U937 monocytes express three IgE receptors, the high-affinity receptor, FcepsilonRI, the low-affinity receptor, CD23, and galectin-3, and mediate tumor cell killing in vitro by two mechanisms, cytotoxicity, and phagocytosis. Our results suggest that CD23 mediates phagocytosis, which is enhanced by upregulation of CD23 on U937 cells with IL-4, whereas FcepsilonRI mediates cytotoxicity. We show that effector : tumor cell bridging is associated with both activities. Galectin-3 does not appear to be involved in tumor cell killing. U937 cells and IgE exerted ovarian tumor cell killing in vivo in our xenograft model in nude mice. Harnessing IgE receptors to target tumor cells suggests the potential of tumor-specific IgE antibodies to activate effector cells in immunotherapy of ovarian cancer.

IgE-antibody-dependent immunotherapy of solid tumors: cytotoxic and phagocytic mechanisms of eradication of ovarian cancer cells.

Abs have a paramount place in the treatment of certain, mainly lymphoid, malignancies, although tumors of nonhemopoietic origin have proved more refractory ones. We have previously shown that the efficacy of immunotherapy of solid tumors, in particular ovarian carcinoma, may be improved by the use of IgE Abs in place of the conventional IgG. An IgE Ab (MOv18 IgE) against an ovarian-tumor-specific Ag (folate binding protein), in combination with human PBMC, introduced into ovarian cancer xenograft-bearing mice, greatly exceeded the analogous IgG1 in promoting survival. In this study, we analyzed the mechanisms by which MOv18 IgE may exert its antitumor activities. Monocytes were essential IgE receptor-expressing effector cells that mediated the enhanced survival of tumor-bearing mice by MOv18 IgE and human PBMC. Monocytes mediated MOv18 IgE-dependent ovarian tumor cell killing in vitro by two distinct pathways, cytotoxicity and phagocytosis, acting respectively through the IgE receptors FcepsilonRI and CD23. We also show that human eosinophils were potent effector cells in MOv18 IgE Ab-dependent ovarian tumor cell cytotoxicity in vitro. These results demonstrate that IgE Abs can engage cell surface IgE receptors and activate effector cells against ovarian tumor cells. Our findings offer a framework for an improved immunotherapeutic strategy for combating solid tumors.

Three-colour flow cytometric method to measure antibody-dependent tumour cell killing by cytotoxicity and phagocytosis.

We have developed a three-colour flow cytometric method to assay the contributions of cytotoxicity and phagocytosis to antibody-dependent cell-mediated tumour cell killing. In this assay, tumour target cells are pre-labelled with CFSE, and mixed with effector cells and a tumour antigen-specific monoclonal antibody. After incubation of the cells with the antibody, effector cells are labelled with PE and dead cells with PI. Using flow cytometry, dead and phagocytosed tumour cells can be quickly and easily counted and the numbers summed to determine the total number of killed cells. One can thereby measure the phagocytic aspect of antibody-dependent cell-mediated tumour cell killing, otherwise only revealed by microscopic examination. The failure to detect phagocytosed, in addition to live and dead target cells, by standard assays may result in an underestimation of tumour cell killing and hence the potential of an antibody for immunotherapy of cancer. We illustrate the new method by analysing human monocyte-mediated cytotoxic and phagocytic cell killing of IGROV1 ovarian tumour cells by the ovarian tumour antigen-specific anti-folate binding protein monoclonal antibody, MOv18 IgE.

Activity of human monocytes in IgE antibody-dependent surveillance and killing of ovarian tumor cells.

We have previously shown that a chimeric IgE antibody against the folic acid receptor (MOv18 IgE) inhibits tumor growth in a SCID mouse model of ovarian carcinoma. MOv18 IgE gave greater protection than the corresponding chimeric MOv18 IgG1. We have now confirmed these effects in a nude-mouse model of ovarian carcinoma and have demonstrated for the first time that human monocytes are active in IgE antibody-dependent cell-mediated cytotoxicity. Injection of tumor-bearing mice with PBMC and MOv18 IgE led to infiltration of monocytes into the tumors and prolonged survival of the mice. Incubation of PBMC or purified monocytes and MOv18 IgE with ovarian tumor cells in vitro resulted in tumor cell killing proportional to the expression of unoccupied FcepsilonRI on monocytes.We observed phagocytosis of tumor cells by the monocytes in vitro. Our results suggest that tumor-specific IgE antibodies may be exploited for immunotherapy of cancer.