Human Antichimeric Antibodies Research Articles

Abstract PO2-06-13: Promising clinical performance of 89Zirconium-labelled Girentuximab PET-CT for imaging metastatic triple negative breast cancer patients (OPALESCENCE)

Abstract Aim: Triple Negative Breast Cancer (TNBC) is aggressive, often with a metastatic evolution and drug-resistant with limited therapeutic options. Evaluating new markers is an unmet need. Recently, the combination of anti-angiogenic and targeted hypoxia effectors agents proved to enhance therapy response. Indeed, anhydrase Carbonic-IX (CA-IX), a hypoxia-mediated breast tumor growth regulator, is important for the BC stem cells maintenance within hypoxic region and is highly overexpressed in TNBC. This pilot prospective study “OPALESCENCE” (NCT04758780) aimed at assessing PET/CT with 89Zr-labeled girentuximab (89Zr-TLX250) targeting CA-IX in 12 metastatic TNBC patients. Methods: Patients underwent FDG and 89Zr-TLX250 PET-CT and conventional imaging (CI) if needed (CT, US, mammography, brain MRI). Without any premedication or dietary preparation, patients received a single slow intravenous administration of 37±10% MBq 89Zr-TLX250 (10 mg). Day 3 or 5 post injection, a skull to mid-thigh PET/CT was acquired with 10 minutes acquisition time per bed position. The gold standard was determined by FDG PET/CT, CI and follow-up; lesion detected at least by 2 modalities was considered as true positive. Immunohistochemistry (IHC) was performed with Bond RX fully automated research stainer with CA-IX antibody (Leica, clone TH22). Staining was evaluated with semi-quantitative analysis (percentage and intensity of tumor cells expression). Human anti-chimeric antibody (HACA) were sampled but will be determined at study end. Results: Enrolment has been completed, a total of 273 lesions confirmed by gold standard as shown on table 1 were detected in 12 patients (231 by 89Zr-TLX250 and 264 by FDG PET/CT). Overall sensitivity of 89Zr-TLX250 PET/CT was 87.5%, with 100% sensitivity for breast, skin, adrenal gland and brain and 88.0%, 91.9% for nodes and bone respectively. Overall sensitivity for FDG-PET/CT was 96.7%. According to table 2, 6 patients had 100% of their lesions highlighted by 89Zr-TLX250 PET. In addition, for 2 other patients only one of the lesions was not detected by immunoPET. 89Zr-TLX250 PET therefore detected almost all of the metastatic lesions in 67% of the patients. For 8/12 patients, IHC was analysed and for 6 patients, CA-IX expression lesions was from 100% to 10% with an intensity from 3+ to 2+, whereas two patients presented no Ca-IX expression on tumour lesions. No 89Zr-TLX250 safety issue was reported. Conclusion: 89Zr-TLX250 PET/CT seems very promising because it allows the CA IX status lesions knowledge on whole body scale with a minimally invasive way, unlike the information provided by biopsies corresponding to only 1 or 2 lesions studied. Moreover, these results illustrated interest of 89Zr-TLX250 PET/CT as targeting agent for TNBC patients leading above all to a theranostic approach possibility. Study analysis (specially IHC, HACA and semi-quantitative PET/CT analysis) is ongoing and supplementary data will be presented during the congress. This is an investigator initiated trial. Investigational medicinal product was provided by Telix Pharmaceuticals. Table 1: Sensitivity of 89Zr-TLX250 PET, FDG PET, and conventional imaging (US, brain MRI and Mammography). Table 2: Number of confirmed lesions according to Gold Standard detected by 89Zr-TLX250 PET/CT (iPET), FDG PET/CT and CI for each patients. Citation Format: Caroline Rousseau, Marie Francoise Heymann, Jean Sebastien FRENEL, Elise Picot-Dilly, Maelle Le Thiec, Manon Taupin, Alexis Mouton, Emmanuelle Bourbouloux, Agnès Morel, Nadia Allam, Amélie Mallet, Mario Campone, Ludovic Ferrer, Françoise Kraeber-Bodéré. Promising clinical performance of 89Zirconium-labelled Girentuximab PET-CT for imaging metastatic triple negative breast cancer patients (OPALESCENCE) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-06-13.

Rituximab Resistance in Glomerular Diseases: A GlomCon Mini Review

Resistance to rituximab B-cell depletion therapy is a clinically pertinent adverse sequela, which can have significant implications for the treatment of immune-mediated glomerular diseases. The true incidence of rituximab resistance remains unknown, however, it is an increasingly recognized treatment complication. Resistance typically presents with suboptimal treatment response, rapid B-cell reconstitution, and a relapsing disease course. While the diverse mechanisms resulting in rituximab resistance are ongoing topics of research, both primary and secondary mechanisms have been identified as key catalysts.The emergence of human anti-chimeric antibodies (HACA) is a major cause of secondary resistance to rituximab therapy and typically appears following repeated drug exposure. Frequently, HACA develop in the setting of underlying autoimmune disease and contribute to poor B-cell depletion, reduced rituximab therapeutic efficacy, and enhanced drug clearance.The clinical challenge of rituximab resistance necessitates heightened awareness among clinicians. Screening for HACA should be considered in individuals with poor clinical response to rituximab, more rapid B-cell reconstitution, and relapsing disease. Detection of HACA may guide treatment alterations, including addition of further immunosuppressive therapy and transitioning to a humanized B-cell depleting monoclonal antibody.

Lack of B-cell Depletion with Ocrelizumab (P7-3.006)

Lack of B-cell Depletion with Ocrelizumab (P7-3.006)

Rituximab Chimeric Anti-CD20 Monoclonal Antibody Therapy for Relapsed Indolent Lymphoma: Half of Patients Respond to a Four-Dose Treatment Program.

The CD20 antigen is expressed on more than 90% of B-cell lymphomas. It is appealing for targeted therapy, because it does not shed or modulate. A chimeric monoclonal antibody more effectively mediates host effector functions and is itself less immunogenic than are murine antibodies. This was a multiinstitutional trial of the chimeric anti-CD20 antibody, IDEC-C2B8. Patients with relapsed low grade or follicular lymphoma received an outpatient treatment course of IDEC-C2B8 375 mg/m2 intravenously weekly for four doses. From 31 centers, 166 patients were entered. Of this intent-to-treat group, 48% responded. With a median follow-up duration of 11.8 months, the projected median time to progression for responders is 13.0 months. Serum antibody levels were sustained longer after the fourth infusion than after the first, and were higher in responders and in patients with lower tumor burden. The majority of adverse events occurred during the first infusion and were grade 1 or 2; fever and chills were the most common events. Only 12% of patients had grade 3 and 3% grade 4 toxicities. A human antichimeric antibody was detected in only one patient. The response rate of 48% with IDEC-C2B8 is comparable to results with single-agent cytotoxic chemotherapy. Toxicity was mild. Attention needs to be paid to the rate of antibody infusion, with titration according to toxicity. Further investigation of this agent is warranted, including its use in conjunction with standard chemotherapy.

Sequential rituximab therapy sustains remission of nephrotic syndrome but carries high risk of adverse effects.

Sequential rituximab (RTX) administration has emerged as an important strategy to sustain remission of disease in patients with difficult-to-treat nephrotic syndrome. We report the efficacy and safety of sequential therapy with two or more courses of intravenous RTX in 250 patients with difficult-to-treat steroid dependence (n=127) and calcineurin inhibitor (CNI)-dependent or CNI-refractory steroid resistance (n=123) managed at one center during 2015-2021. Subsets of patients were cross-sectionally tested for hypogammaglobulinemia, seroprotection against and hyporesponsiveness to vaccines for hepatitis B and tetanus, BK/JC viruria and human antichimeric antibodies (HACAs). Sequential RTX therapy, initiated at a median of 10years [interquartile range (IQR) 7.3-14.4], was administered for 1.8courses/person-year [95% confidence interval (CI) 1.7-2.0] over 2.0years (95% CI 1.2-3.0). Therapy was associated with postponement of relapses by a median of 3years in patients with steroid-sensitive disease and 2years in those with steroid resistance. Relapses were reduced by a mean of 2.0relapses/person-year (95% CI 1.8-2.2), enabling a reduction in prednisolone dose to 0.04mg/kg/day (95% CI 0.01-0.11) and withdrawal of additional immunosuppression in 154 (62%) patients. RTX-associated adverse events, occurring at 0.20events/person-year (95% CI 0.17-0.23), were chiefly comprised of infusion reactions (n=108) and infections (n=46); serious adverse events were observed in 10.8% patients, at 0.03events/person-year (95% CI 0.02-0.05). Hypogammaglobulinemia was observed in 35% of 177 patients and was moderate to severe in 8.5% of cases. Rates of seroprotection at baseline and response following vaccination were lower for hepatitis B [1.9% and 29.4% (n=52)] than tetanus [65.5% and 34.5% (n=58)]. BK/JC viruria, without viremia, was observed in 7.3% of 109 cases. A total of 19 of 107 patients (17.8%) had HACAs, which were associated with B cell nondepletion and serum sickness. Age at therapy of <9-10years was associated with a risk of early relapse, treatment failure and hypogammaglobulinemia following RTX therapy. Sequential therapy with RTX effectively reduces relapses in patients with difficult-to-treat steroid- and/or CNI-dependent or CNI-refractory nephrotic syndrome. Therapy is associated with high rates of hypogammaglobulinemia and infusion reactions.

Outcomes Following GD2-Directed Postconsolidation Therapy for Neuroblastoma After Cessation of Random Assignment on ANBL0032: A Report From the Children's Oncology Group.

Postconsolidation immunotherapy including dinutuximab, granulocyte-macrophage colony-stimulating factor, and interleukin-2 improved outcomes for patients with high-risk neuroblastoma enrolled on the randomized portion of Children's Oncology Group study ANBL0032. After random assignment ended, all patients were assigned to immunotherapy. Survival and toxicities were assessed. Patients with a pre-autologous stem cell transplant (ASCT) response (excluding bone marrow) of partial response or better were eligible. Demographics, stage, tumor biology, pre-ASCT response, and adverse events were summarized using descriptive statistics. Event-free survival (EFS) and overall survival (OS) from time of enrollment (up to day +200 from last ASCT) were evaluated. From 2009 to 2015, 1,183 patients were treated. Five-year EFS and OS for the entire cohort were 61.1 ± 1.9% and 71.9 ± 1.7%, respectively. For patients ≥ 18 months old at diagnosis with International Neuroblastoma Staging System stage 4 disease (n = 662) 5-year EFS and OS were 57.0 ± 2.4% and 70.9 ± 2.2%, respectively. EFS was superior for patients with complete response/very good partial response pre-ASCT compared with those with PR (5-year EFS: 64.2 ± 2.2% v 55.4 ± 3.2%, P = .0133); however, OS was not significantly different. Allergic reactions, capillary leak, fever, and hypotension were more frequent during interleukin-2-containing cycles than granulocyte-macrophage colony-stimulating factor-containing cycles (P < .0001). EFS was superior in patients with higher peak dinutuximab levels during cycle 1 (P = .034) and those with a high affinity FCGR3A genotype (P = .0418). Human antichimeric antibody status did not correlate with survival. Analysis of a cohort assigned to immunotherapy after cessation of random assignment on ANBL0032 confirmed previously described survival and toxicity outcomes. EFS was highest among patients with end-induction complete response/very good partial response. Among patients with available data, higher dinutuximab levels and FCGR3A genotype were associated with superior EFS. These may be predictive biomarkers for dinutuximab therapy.

Low-dose methotrexate as rescue therapy in patients with hidradenitis suppurativa and pyoderma gangrenosum developing human antichimeric antibodies to infliximab: A retrospective chart review

Low-dose methotrexate as rescue therapy in patients with hidradenitis suppurativa and pyoderma gangrenosum developing human antichimeric antibodies to infliximab: A retrospective chart review

Only Follow-Up of Memory B Cells Helps Monitor Rituximab Administration to Patients with Neuromyelitis Optica Spectrum Disorders.

IntroductionNeuromyelitis optica spectrum disorders (NMOSD) are identified as a spectrum of inflammatory demyelinating disorders involving the brain, spinal cord and optic nerves. These disorders require early diagnosis and highly active immunosuppressive treatment. Rituximab (RTX) has demonstrated efficacy in limiting relapse in NMOSD when using several administration schedules. We questioned if the CD19+ CD27+ memory B cell count was a more reliable marker to monitor RTX administration than the RTX plasma level and CD19+ B cell count.MethodsWe analyzed 125 blood samples from 17 NMOSD patients treated with RTX and also measured the level of anti-aquaporine-4 antibodies (anti-AQP-4 Abs), human anti-chimeric antibodies to the murine fragment of RTX (HACA-RTX Abs), and the RTX concentration.ResultsThe mean follow-up time of the cohort was 7.4 (2–16) years. All patients improved with a mean EDSS going from 4 (1–8.5) to 2.7 (1–5.5). The mean interval between RTX infusions was 9.6 months with identification of prolonged responders. Total CD19+ B cell detection with the routine technique did not correlate to re-emergence of CD19+ CD27+ memory B cells. The RTX residual concentration did not correlate with the CD19+ CD27+ memory B cell count or with anti-RTX antibody production.ConclusionIn contrast to total CD19+ cell, detected with the routine technique, CD19+ CD27+ memory B cells are a reliable marker for biological relapse and allow a decrease in the frequency of infusions.

Serum sickness with refractory nephrotic syndrome following treatment with rituximab.

Rituximab (RTX) is effective for treating childhood refractory nephrotic syndrome (NS), such as steroid-dependent (SD), frequently relapsing (FR), and steroid-resistant (SR) NS. While RTX has been proven to be effective in treating SDNS, FRNS, and SRNS, it may cause serum sickness, a rare illness characterized by fever, rash, and arthralgia, 10-14days after primary antigen exposure or within a few days after secondary antigen exposure, by producing human anti-chimeric antibodies (HACAs). A 17-year-old girl with refractory SDNS treated with RTX and oral cyclosporine A was admitted with fever and arthralgia 10days after the fifth RTX dose was administered. After RTX was started when she was 14-years-old, SDNS remission was then achieved, and prednisolone was discontinued. Although antibiotics and non-steroidal anti-inflammatory agents were administered, fever and arthralgia continued. After various inspections and clinical course, we considered her as RTX-induced serum sickness (RISS). The patient had an elevated HACA level and was diagnosed with RISS. Fever and arthralgia disappeared 5days after onset. To the best of our knowledge, this is the first reported case of RISS with NS. Fever, rash, and arthralgia after RTX administration can be the initial symptoms.

The Pharmacodynamic Effects of Rituximab at Very Low Doses

No dose-finding trials are available for rituximab that could guide dosing in non-malignant diseases. We hypothesized that currently used doses (≥375mg/m2) exceed several hundred-fold the half-maximal effective dose, which is most sensitive for detecting putative differences between biosimilars and important for dose-finding. In an exploratory, dose-finding, trial healthy volunteers received single infusions of 0.1 (n=4), 0.3 (n=4) and 1 mg/m2 (n=8) rituximab. Subsequently, in a randomized, double-blind trial, healthy volunteers received single infusions of 0.1 (n=24) or 0.3 mg/m2 (n=12) of two rituximab products. CD19/20+ cell counts were measured, pharmacokinetics and, immunogenicity were assessed. Single infusions of 0.1, 0.3 and 1 mg/m2 rituximab transiently depleted CD20+ cells by a mean 68% (95%CI: 24-100%), 74% (95%CI: 59-84%) and 97% (95%CI: 95-99%), respectively. In the randomized trial infusion of 0.1mg/m2 or 0.3mg/m2 proposed biosimilar or reference rituximab decreased CD20+cells by 45% (95%CI: 32-58%) - 55% (95%CI: 45-66%) and 81 (95%CI: 73-87%) – 87% (95%CI: 74-100%), respectively. In the randomized trial, 26 of 36 patients developed human anti-chimeric antibodies and 9 of 36 patients developed neutralizing anti-drug antibodies. Pharmacokinetic analyses were limited by the assay sensitivity and the very low rituximab doses. However, there was a clear pharmacokinetic signal during the first 24 hours in the 1mg/m2 group. It is important to understand that <1% of the authorized rituximab doses depletes all circulating B lymphocytes in healthy volunteers. This will help particularly countries struggling to meet the financial burden of therapy with biologics.

Retrospective Study on the Use of Infliximab and Adalimumab Drug and Antibody Levels for Clinical Decision Making in IBD Patients at a University-Based Single-Center Practice

Introduction: Anti TNF agents are now first line medications to treat moderate to severe Crohn's disease (CD) and Ulcerative colitis (UC). However, primary and secondary treatment failure still frequently occur due to immunogenicity1,2. Antibodies to infliximab (ATIs), also known as human anti-chimeric antibodies (HACAs), form immune complexes with the drug and are associated with decreased infliximab levels, shorter duration of response, and higher risk of infusion reactions3-5. Assays developed to detect anti-drug antibodies and drug levels for both infliximab and adalimumab were initially used for research but several commercially available tests are now on the market for clinical use6. Individualized therapy based on antibody and drug level testing has been found to be more cost effective than empiric dose escalation in patients with Crohns disease who lost response to infliximab7,8. However, data on utilization of testing in routine clinical practice is newly emerging. We present the outcomes of drug and antibody testing for 80 patients on anti TNF therapy at a single center gastroenterology practice within a university hospital setting. Methods: All patients that had infliximab and adalimumab drug level and antibody testing using the AnserTM assay by Prometheus laboratories between August 2012 and March 2015 were identified and their charts were retrospectively reviewed. Demographic characteristics, disease activity, current therapy, serum drug and antibody levels, and management after testing were recorded and analyzed. Results: Drug and antibody tests were obtained from 80 patients. The majority of patients had IBD for over 2 years. Sixity one percent had Crohn's disease with a mean age of 37.2. The most common reason for checking levels was loss of response (63.8%). 61.3% of patients were secondary nonresponders to anti TNF, and 35% of patients were responding. Therapeutic drug levels were found in 76.3% of patients and antibodies were detected in 20% of patients. Dose changes and anti TNF discontinuation occurred in 29% and 30% of patients, respectively while 41.3 % had no change to the anti TNF regimen. Conclusion: Serum infliximab and adalimumab drug and antibody level testing frequently aids clinical decision making in the real world setting resulting in medication changes in a majority of cases.Table 1Table 2: Testing results n =80

Validated detection of human anti-chimeric immune responses in serum of neuroblastoma patients treated with ch14.18/CHO

Human/mouse chimeric monoclonal antibody (mAb) ch14.18/CHO is directed against disialoganglioside GD2. Activity and efficacy of this mAb are currently determined in ongoing clinical Phase II and -III studies in high-risk neuroblastoma (NB). Based on the chimeric nature of this mAb, some patients may develop a human anti-chimeric immune response (Mirick et al., 2004) which impacts on pharmacokinetics and may induce anti-anti-idiotype (Id) mAb with a potential survival benefit. Therefore, a validated method of quantitative detection of human anti-chimeric antibodies (HACA) in serum samples of NB patients treated with ch14.18/CHO is an important tool for monitoring of clinical trials.Here, we report a validated sandwich enzyme-linked immunosorbent assay (ELISA) according to the one arm binding principle using ch14.18/CHO as a capture mAb and biotinylated ch14.18/CHO mAb for detection. Ganglidiomab, a monoclonal anti-Id Ab to ch14.18/CHO (Lode et al., 2013), was used as a standard for assay validation and HACA quantification. Systematic evaluation of the established ELISA procedure revealed an optimal serum sample dilution factor of 1:160. Assay validation was accomplished with a set of tailored quality controls (QC) containing distinct concentrations of ganglidiomab (3 and 15μg/ml). The coefficients of variation (CV) for all within-assay and inter-assay measurements using QCs were under 20% and the limit of detection (LOD) was 1.1μg/ml. Three patients (P1, P2, P3) treated with a 10day continuous infusion of 100mg/m2 of ch14.18/CHO were selected for analysis with this assay. Selection was based on ch14.18/CHO drug level on day 8 in cycle 2 of >10μg/ml (expected) (P1) and of <2μg/ml (unexpected) (P2 and P3). Both patients with unexpected low ch14.18/CHO levels revealed a strong signal in the HACA ELISA.Interestingly, ch14.18/CHO-mediated complement-dependent cytotoxicity (CDC) could not be detected in P2 in contrast to P3 suggesting anti-NB activity even in the presence of HACA. We showed that neither eight freeze–thaw cycles nor storage at room temperature for up to 168h affected HACA stability in serum. In summary, we describe a validated ELISA method suitable for the assessment of HACA in NB patients treated with ch14.18/CHO.

Utilidad clínica de la cuantificación de infliximab y anticuerpos antiquiméricos humanos

Introductioninfliximab (IFX), a chimeric antibody against tumour necrosis factor-alpha, is used in the treatment of patients with several inflammatory diseases, but it can lead to the formation of human anti-chimeric antibodies (HACA). HACA and low IFX serum levels have been associated with lack or loss of response, and infusion reactions. The usefulness of measuring the IFX and HACA concentrations is evaluated. Material and methodsIFX and HACA were measured using a relatively new ELISA technique in a cohort of 110 patients treated with IFX. Serum samples were collected immediately before patients were given the next drug infusion. The patients had received a median dose of 5mg/kg, with dose intervals adjusted to the patient's disease activity, usually every 8 weeks. The median number of infusions was 17. ResultsHACA were identified in 10 patients, and therapeutic IFX concentrations were observed in 37 patients. Eight out of 10 positive HACA patients had gastrointestinal disorders, and the therapy was discontinued in 9 of them. The concomitant use of immunosuppressants did not reduce the risk of HACA formation. Among 100 patients with no HACA, 79 continued on the same dose, 16 required a dose adjustment, 2 discontinued treatment, and 3 were switched to another biological agent. ConclusionsBlood IFX and HACA concentrations should be monitored in patients receiving IFX, as it may be useful to optimize dose regimens or avoid use of inadequate therapy.

Development of antirituximab antibodies in children with nephrotic syndrome

Rituximab is actively used as a rescue therapy for nephrotic syndrome (NS). The development of antidrug antibodies, including antirituximab antibodies (ARA) and human antichimeric antibodies (HACA), is reported with rituximab treatment in various diseases. Here we report two pediatric patients with NS who developed ARA. Rituximab was given as a rescue therapy for two patients with steroid-dependent NS. Both patients had been treated orally with glucocorticosteroid, methylprednisolone, and calcineurin inhibitors but experienced frequent relapses. With rituximab treatment, the patients remained in remission for several months. After the B-cell count recovered, the patients received a second course of rituximab administration and experienced a hypersensitivity reaction during drug infusion. CD19 cell counts rose despite treatment with rituximab. ARA titers were monitored before and after rituximab treatment, and the development of ARA after the second course of rituximab administration was confirmed. We report the development of HACA in two patients with NS who did not achieve B-cell depletion after repeated administration of rituximab. This report suggests that additional studies are needed to determine the incidence of ARA in patients with NS, and its clinical significance.

FRI0088 Effect of body mass index on clinical response to anti-tnf therapy in rheumatoid arthritis

BackgroundRheumatoid Arthritis is the commonest inflammatory arthritis. Improved understanding of its pathogenesis has led to targeted therapies like TNF inhibitors. With more emphasis on personalised treatment of RA, a better...

Phase II study of low-dose methotrexate to reduce the incidence of human anti-mouse antibodies in patients receiving I-131 tositumomab as first-line treatment for follicular lymphoma.

e19519 Background: I-131 tositumomab is a radiolabeled murine anti-CD20 antibody. In a frontline phase II follicular lymphoma (FL) trial, treatment with I-131 tositumomab produced a 95% ORR with 75% CR (NEJM 352:441, 2005). Median PFS was 6.1 yrs. However, 30% of patients (pts) developed high levels of human anti-mouse antibodies (HAMA) and a serum sickness syndrome within 7 weeks of treatment (early onset HAMA). The 5-yr PFS for this group was 35% compared to 70% for the others (p = 0.003). Low-dose oral methotrexate (mtx) reduces the incidence of human anti-chimeric antibody (HACA) formation in rheumatoid arthritis pts receiving infliximab. We hypothesized that low-dose mtx would likewise reduce the incidence of early onset HAMA when given in combination with I-131 tositumomab. Methods: This is a single arm, phase II study in pts with FL, grade 1-2, stage III or IV disease without limits on marrow involvement, and ≥ 1 of the GELF criteria. Prior therapy, other than focal radiotherapy, is not allowed. Pts must have adequate hematologic, hepatic and renal function, and serum HAMA levels ≤ ULN. I-131 tositumomab is given as a dosimetric dose followed within 1-2 weeks by a therapeutic dose of 75cGy of total body radiation. Pts take mtx 7.5 mg orally once weekly for 3 weeks prior to their dosimetric dose, followed by 7 additional weekly doses. The primary endpoint is the rate of HAMA formation within 7 wks of I-131 tositumomab treatment. Secondary endpoints are overall HAMA incidence, ORR, CR, PFS OS, and safety. Results: Between 8/2011 and 10/2012, 15 pts were enrolled. Median age was 56 (39-83); 11 were male. Three pts had serum HAMA levels &gt;ULN at baseline. One pt had a spontaneous remission prior to starting treatment, leaving 11 evaluable pts. One pt developed early onset HAMA (9%). ORR = 82%, CR = 64%. Two pts progressed with DLBCL. Grade 3 or 4 toxicities included thrombocytopenia n = 3, neutropenia n = 2 and pain n = 3. Conclusions: These preliminary results show that concurrent low-dose oral mtx appears to reduce the incidence of early onset HAMA in FL patients receiving first- line I-131 tositumomab (9% vs. 30% in historical controls) while preserving efficacy. Clinical trial information: NCT01389076.

B-Cell Depletion With Rituximab in Patients With Primary Biliary Cirrhosis Refractory to Ursodeoxycholic Acid

Rituximab, an anti-CD20 monoclonal antibody that selectively depletes B cells, has shown promise in autoantibody-associated, immune-mediated disorders. As ursodeoxycholic acid (UDCA) is not successful in all patients with primary biliary cirrhosis (PBC), additional treatment options are necessary. The objective of this study was to assess the safety and efficacy of rituximab in patients with PBC refractory to UDCA. Fourteen PBC patients refractory to UDCA received two rituximab infusions (1,000 mg) 2 weeks apart. The primary efficacy outcome was normalization and/or 25% improvement in serum alkaline phosphatase (ALP) concentration at 6 months. The median age was 53 years, and 92% were female and antimitochondrial antibody (AMA) positive. The median UDCA dosage was 15.3 mg/kg/day (interquartile range 14.5-17.8). Although rituximab was well tolerated, one patient withdrew due to an asthma exacerbation during the first infusion. Effective B-cell depletion was observed in the remaining 13 patients, including three that developed human anti-chimeric antibodies. ALP normalization and/or ≥ 25% improvement was observed in three patients (23%) at 6, 12, and 18 months. Significant reductions in median ALP (from 259 U/l at baseline to 213 U/l at 6 months; median decrease 16%), and serum IgM and AMA levels were observed at 6 months. Although fatigue was stable, pruritus improved in 60% of patients at 12 months (vs. 8% with worsening pruritus). Selective B-cell depletion with rituximab was safe and associated with a significant decrease in autoantibody production, but had limited biochemical efficacy in PBC patients with an incomplete response to UDCA.

P544 Does measuring IFX and human anti-chimeric antibody concentrations in patients with inflammatory bowel disease impact clinical management? A Canadian experience

Background: For over thirty years high dose steroids followed by colectomy if required has been the mainstay of treatment for active ulcerative colitis (UC). Recently we have seen the introduction of second-line medical therapies such as anti-TNFa and cyclosporin with the hope of avoiding the need for surgery if first line medical therapy fails. Methods: Using a cohort of UC patients from round two (2008) and three (2010) of the UK inflammatory bowel disease (IBD) audit respectively we aim to assess the outcomes of patients receiving second-line medical therapies. We audited 3049 patients with UC from the 2010 round of the UK IBD audit of which 1071 were considered to have acute severe UC (ASUC). 202 Sites audited a median of 18 UC patients per site that were admitted with IBD between 1/09/09 and 31/08/10. The results of this were compared against the results from the 2008 UK IBD audit which collected data on 2981 UC patients of which there were 863 with ASUC. 209 sites audited a median of 17 UC patients per site that were admitted with IBD between 1/09/07 and 31/08/08. Results: Between rounds there was no significant change in mortality in the ASUC population, 1.2% (10/863) in 2008 vs 0.7% (7/1071) in 2010 (p < 0.3) additionally response rates to first line steroids were similar between rounds 61.1% (498/815) in 2008 vs 58.8% (602/1024) in 2010 (p < 0.4). Significantly more patients are receiving second-line medical therapy 47.3% (150/317) in 2008 vs 57.6% (243/422) in 2010 (p < 0.01). Of the patients failing first line therapy significantly less underwent surgery in 2010: 51.4% (163/317) vs 41.0% (173/422) (p < 0.005). The response rates to anti-TNFa were significantly better than to cyclosporin in both rounds: 75% (39/52) vs 45.9% (45/98) in 2008 (p < 0.005); 81.4% (79/97) vs 60.3% (88/146) in 2010 (p < 0.005). There was a significant difference in response rates to cyclosporin between rounds 45.9% (45/98) in 2008 vs 60.3% (88/146) in 2010 (p < 0.03). Among patients receiving secondline medical therapies there was no significant difference in mortality either between treatments or rounds. Conclusions: In this unselected population, patients consistently respond significantly better to anti-TNFa than cyclosporin. There has been a significant increase in the number of patients receiving rescue medical therapy and an overall decrease in the number of patients receiving rescue surgery. Interestingly, response rates to cyclosporin are improving which could be a reflection of more established protocols for its use.

Does Measuring Infliximab and Human Anti-Chimeric Antibody Concentrations in Patients With Inflammatory Bowel Disease Impact Clinical Management? A Canadian Experience.

Does Measuring Infliximab and Human Anti-Chimeric Antibody Concentrations in Patients With Inflammatory Bowel Disease Impact Clinical Management? A Canadian Experience.

Clinical Implications of Measuring Infliximab Levels and Human Anti-Chimeric Antibodies in Patients with Inflammatory Bowel Disease

Purpose: Infliximab is a chimeric anti-tumor necrosis factor (TNF) agent, and repeated administration can result in development of antibodies in patients with inflammatory bowel disease (IBD). Utility of measuring infliximab levels and human anti-chimeric antibodies (HACA) to infliximab in routine clinical practice is not validated. The aim of this study is to establish the utility of measuring these levels to optimize treatment in IBD patients. Methods: 40 patients with IBD who underwent testing for HACA and infliximab levels from 2009-2011 were included. We documented disease activity, primary reason for measuring these levels and subsequent changes made in the therapeutic management. Results: Forty patients (20 males, 50%) with median age 23 years were included. The cohort included 25 patients (62.5%) with Crohn's disease and 12 patients (30%) with Ulcerative Colitis. In addition to infliximab, 16 patient were treated with concomitant steroids and 10 were on immunomodulator therapy. The most common reason for testing was secondary response failure (50%) followed by hypersensitivity reaction (17.5%). In 6 out of 7 patients with positive HACA, infusion was stopped. Four out of these 6 experienced a further decline in disease activity. One patient in whom the drug therapy was intensified, an improvement in the disease activity was noted. Eighteen patients had subtherapeutic infliximab level. Six out of 9 patients in whom infusion was subsequently stopped noted worsening in disease activity. Four out of 6 patients in whom infusion was continued without any modification had better outcome and all 3 patients with increase in dosing or frequency of infliximab noticed marked improvement in symptoms. Conclusion: Our study suggests that in IBD patients with loss of response to infliximab, measurement of infliximab level and HACA can be considered. Clinical improvement may occur upon intensification of infliximab therapy in patients with either subtherapeutic serum concentration or presence of antibodies.Table 1: Baseline characteristics of inflammatory bowel disease patients who underwent testing for human anti-chimeric antibodies or subtherapeutic infliximab concentrationsTable 2: Clinical outcomes of patients with detectable human anti-chimeric antibodies or subtherapeutic infliximab concentrations