Roland Repp

Clinical significance of IgG Fc receptors and FcγR-directed immunotherapies

Abstract Fc receptors for IgG (FcγRs) can trigger the inflammatory, cytotoxic and hypersensitivity functions of immune effector cells. Activation or deactivation of effector cells via FcγRs can be exploited to develop novel therapies for cancer, infectious diseases and autoimmune disorders. Initial results of clinical trials for several FcγR-directed immunotherapies show the potential promise of this approach.

Potent In vitro and In vivo Activity of an Fc-Engineered Anti-CD19 Monoclonal Antibody against Lymphoma and Leukemia

CD19 is a pan B-cell surface receptor expressed from pro-B-cell development until its down-regulation during terminal differentiation into plasma cells. CD19 represents an attractive immunotherapy target for cancers of lymphoid origin due to its high expression levels on the vast majority of non-Hodgkins lymphomas and some leukemias. A humanized anti-CD19 antibody with an engineered Fc domain (XmAb5574) was generated to increase binding to Fcgamma receptors on immune cells and thus increase Fc-mediated effector functions. In vitro, XmAb5574 enhanced antibody-dependent cell-mediated cytotoxicity 100-fold to 1,000-fold relative to an anti-CD19 IgG1 analogue against a broad range of B-lymphoma and leukemia cell lines. Furthermore, XmAb5574 conferred antibody-dependent cell-mediated cytotoxicity against patient-derived acute lymphoblastic leukemia and mantle cell lymphoma cells, whereas the IgG1 analogue was inactive. XmAb5574 also increased antibody-dependent cellular phagocytosis and apoptosis. In vivo, XmAb5574 significantly inhibited lymphoma growth in prophylactic and established mouse xenograft models, and showed more potent antitumor activity than its IgG1 analogue. Comparisons with a variant incapable of Fcgamma receptor binding showed that engagement of these receptors is critical for optimal antitumor efficacy. These results suggest that XmAb5574 exhibits potent tumor cytotoxicity via direct and indirect effector functions and thus warrants clinical evaluation as an immunotherapeutic for CD19(+) hematologic malignancies.

Definition of risk factors for death, end stage renal disease, and thromboembolic events in a monocentric cohort of 338 patients with systemic lupus erythematosus

Background: The survival rate in patients with systemic lupus erythematosus (SLE) has improved dramatically during the past four decades to 96.6% (five year) in the Erlangen cohort, but it is nearly three times as high as in an age and sex matched control population. Reasons for death are mainly cardiovascular diseases (37%) and infections (29%). Objective: To find risk factors existing at disease onset for a severe outcome in the Erlangen cohort. Patients and methods: By using a database of 338 patients with SLE from a single centre, documented at least one to 15 years and including Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) damage score data and index (SDI) and an activity score (European Consensus Lupus Activity Measurement (ECLAM)), a retrospective search was made for risk factors for a severe outcome like death, end stage renal disease (ESRD), and thromboembolic events (TE) in SLE. For this purpose, multivariable Cox regression models were analysed using the statistical package SPSS 10.0 for Windows. Results: The following were defined as risk factors for death at disease onset: male sex (p<0.001, relative risk (RR)=3.5), age >40 at disease onset (p<0.0001, RR=19.9), nephritis (p<0.05, RR=1.6), a reduction of creatinine clearance (p<0.001, RR=1.8), heart disease (p=0.05, RR=1.5), and central nervous system (CNS) disease (p=0.06, RR=1.6). An increase in the SDI of two or more points from the first to the third year of disease was the worst prognostic factor (p<0.0001, RR=7.7). The existence of Ro or nRNP antibodies, or both, was protective (p<0.05, RR =0.1). A low C3 (p<0.01 RR=3.0) and splenomegaly (p<0.01 RR=2.7) at disease onset turned out to be risk factors for ESRD besides a nephritis. In patients with hypertension (p<0.05) and/or high titres of dsDNA antibodies (>70 U/l) (p<0.01) and/or a mean ECLAM score of 4 (p<0.01) in the course of disease, a prevalence of ESRD was recorded in 9% (p<0.05) and 10% (p<0.01), and 8% (p<0.01) v 4% in the whole group. Analysis of risk factors at disease onset for TE identified positive lupus anticoagulant (p=0.17, RR=1.6), cryoglobulins (p<0.05, RR=1.8), and nephritis (p=0.05, RR=1.4), in addition to an age >40 at disease onset. Conclusions: A subgroup of patients in the Erlangen cohort with a typical clinical and serological phenotype at disease onset that is at high risk for a worse outcome was identified. Identification of these white patients at risk at disease onset will enable treatment to be intensified and thereby possibly prevent or better control late stage manifestations.

Multicenter Phase II Trial of Immunotherapy With the Humanized Anti-CD22 Antibody, Epratuzumab, in Combination With Rituximab, in Refractory or Recurrent Non-Hodgkin's Lymphoma

PURPOSE A multicenter, single-arm study examining efficacy and toxicity of epratuzumab combined with rituximab was conducted in patients with recurrent or refractory non-Hodgkins lymphoma. PATIENTS AND METHODS Sixty-five patients were enrolled; 34 patients with follicular lymphoma (FL), 15 patients with diffuse large B-cell lymphoma (DLBCL), and 16 patients with other lymphomas. The patients had received a median of two prior therapies (range, 1 to 4); 23% had received rituximab. Epratuzumab was given at 360 mg/m2 intravenously over 60 minutes followed by infusion of 375 mg/m2 rituximab, weekly for 4 consecutive weeks. RESULTS Combination therapy was well tolerated without greater toxicity than rituximab alone. The objective response (OR) rate was 47% (30 of 64) in assessable patients (46%; 30 of 65 in all patients), being highest in FL (64%; 21 of 33) and DLBCL (47%; seven of 15), and with 24% (eight of 33) and 33% (five of 15) achieving complete response (CR) or complete response unconfirmed (CRu) in these two groups, respectively. Two of six patients with marginal zone lymphoma responded to treatment (one CR). There was a trend for the response rates to be higher in patients with low prognostic index scores (statistically significant with respect to the Follicular Lymphoma International Prognostic Index score in FL patients), with 12 FL patients and three DLBCL patients in groups 0 to 1 having OR (CR/CRu) rates of 83% (33%) and 100% (100%), respectively. The median duration of response was 16 months for FL, with five patients currently progression free for 18 months to 30 months, and 6 months for DLBCL, with two patients currently progression free for 12 months and 18 months. CONCLUSION Epratuzumab combined with rituximab was well tolerated, demonstrating promising antilymphoma activity that warrants additional study.

Clinical Relevance of Fcγ Receptor Polymorphisms

: Human IgG receptors are very heterogeneous and we currently distinguish three Fc gamma receptor classes specifying at least 12 receptor isoforms. On top of this complexity, Fc gamma R are further found to differ between different individuals. Polymorphisms have been identified for all three Fc gamma R classes. The best-studied ones represent allelic variation of Fc gamma RIIa (CD32) and Fc gamma RIIIb (CD16). The Fc gamma RIIa polymorphism is now considered to be a heritable risk factor for autoimmune and infectious diseases, and support for a relevant role of the IIIb polymorphism has also been obtained. A detailed analysis of the exact contribution of each of these Fc gamma R polymorphisms in relation to previously implicated risk factors should unravel the pathophysiological importance of Fc gamma R polymorphisms in the near future.

Triggering FCα-Receptor I (CD89) Recruits Neutrophils as Effector Cells for CD20-Directed Antibody Therapy

CD20 Abs induce clinical responses in lymphoma patients, but there are considerable differences between individual patients. In 51Cr release assays with whole blood as effector source, RAJI cells were effectively killed by a mouse/human chimeric IgG1 construct of CD20 Ab 1F5, whereas ARH-77 proved resistant to killing by this Ab. When whole blood was fractionated into plasma, mononuclear cells, or granulocytic effector cells, RAJI cells were effectively killed in the presence of complement-containing plasma, whereas the mature B cell line ARH-77 proved complement resistant. However, with a bispecific Ab (BsAb) against the myeloid receptor for IgA (CD89; FcαRI) and CD20, a broad range of B cell lines were effectively killed. FcαRI is expressed on monocytes/macrophages, neutrophils, and eosinophils. As the numbers of these effector cells and their functional activity can be enhanced by application of G-CSF or GM-CSF, lysis via (FcαRI × CD20) BsAb was significantly enhanced in blood from patients during therapy with these myeloid growth factors. Interestingly, the major effector cell population for this BsAb were polymorphonuclear neutrophils, which proved ineffective in killing malignant B cells with murine, chimeric IgG1, or FcγRI- or FcγRIII-directed BsAbs against CD20. Experiments with blood from human FcαRI/FcγRI double-transgenic mice showed corresponding results, allowing the establishment of relevant syngenic animal models in these mice. In conclusion, the combination of myeloid growth factors and an (FcαRI × CD20) BsAb may represent a promising approach to improve effector cell recruitment for CD20-directed lymphoma therapy.

Fcγ receptor IIa polymorphism in caucasian patients with systemic lupus erythematosus: Association with clinical symptoms

OBJECTIVE The class II human leukocyte Fcy receptor for IgG (FcgammaRIIa) occurs in 2 codominantly expressed allelic forms (R131 and H131). Cells expressing IIa-H131 interact much more effectively with complexed IgG2 and IgG3 than do cells with IIa-R131. This might be linked to variability in immune complex handling, and therefore related to disease pathogenesis. The present study examines these possibilities in a cohort of Caucasian patients with systemic lupus erythematosus (SLE). METHODS One hundred eight Caucasian patients were diagnosed with SLE according to the American College of Rheumatology criteria. The SLE patients and 187 Caucasian controls were genotyped for the FcgammaRIIa polymorphism, and associations between FcgammaRIIa genotypes, selected HLA haplotypes, and clinical as well as laboratory features were analyzed. RESULTS No significant skewing of the FcgammaRIIa polymorphism was observed in the SLE cohort. Various clinical and serologic parameters were found more frequently or at a younger age in patients homozygous for the genotype IIa-R/R131 compared with those with the genotype IIa-H/H131. In patients with the genotype IIa-R/R131, significantly higher frequencies of proteinuria, hemolytic anemia, anti-nuclear RNP antibodies, and hypocomplementemia were found. The only clinical symptom observed more frequently in patients homozygous for IIa-H/H131 was livedo. Patients with the IIa-R/R131 genotype were significantly younger at disease onset and had an earlier incidence of arthritis, sicca syndrome, nephritis, lymphadenitis, hematologic abnormalities, immunologic abnormalities, lupus anticoagulant, cryoglobulinemia, and hypocomplementemia. HLA-DR3 was found in 41.7% of SLE patients, but was not associated with clinical symptoms, serologic abnormalities, or the homozygous genotypes of the FcgammaRIIa, although an association with a significantly later onset of SLE was found. CONCLUSION The FcgammaRIIa polymorphism constitutes an additional factor that might influence the clinical manifestations and course of SLE, but does not represent a genetic risk factor for the occurrence of SLE.

Addition of sorafenib versus placebo to standard therapy in patients aged 60 years or younger with newly diagnosed acute myeloid leukaemia (SORAML): a multicentre, phase 2, randomised controlled trial

BACKGROUND Preclinical data and results from non-randomised trials suggest that the multikinase inhibitor sorafenib might be an effective drug for the treatment of acute myeloid leukaemia. We investigated the efficacy and tolerability of sorafenib versus placebo in addition to standard chemotherapy in patients with acute myeloid leukaemia aged 60 years or younger. METHODS This randomised, double-blind, placebo-controlled, phase 2 trial was done at 25 sites in Germany. We enrolled patients aged 18-60 years with newly diagnosed, previously untreated acute myeloid leukaemia who had a WHO clinical performance score 0-2, adequate renal and liver function, no cardiac comorbidities, and no recent trauma or operation. Patients were randomly assigned (1:1) to receive two cycles of induction therapy with daunorubicin (60 mg/m(2) on days 3-5) plus cytarabine (100 mg/m(2) on days 1-7), followed by three cycles of high-dose cytarabine consolidation therapy (3 g/m(2) twice daily on days 1, 3, and 5) plus either sorafenib (400 mg twice daily) or placebo on days 10-19 of induction cycles 1 and 2, from day 8 of each consolidation, and as maintenance for 12 months. Allogeneic stem-cell transplantation was scheduled for all intermediate-risk patients with a sibling donor and for all high-risk patients with a matched donor in first remission. Computer-generated randomisation was done in blocks. The primary endpoint was event-free survival, with an event defined as either primary treatment failure or relapse or death, assessed in all randomised patients who received at least one dose of study treatment. We report the final analysis. This trial is registered with ClinicalTrials.gov, number NCT00893373, and the EU Clinical Trials Register (2008-004968-40). FINDINGS Between March 27, 2009, and Nov 28, 2011, 276 patients were enrolled and randomised, of whom nine did not receive study medication. 267 patients were included in the primary analysis (placebo, n=133; sorafenib, n=134). With a median follow-up of 36 months (IQR 35·5-38·1), median event-free survival was 9 months (95% CI 4-15) in the placebo group versus 21 months (9-32) in the sorafenib group, corresponding to a 3-year event-free survival of 22% (95% CI 13-32) in the placebo group versus 40% (29-51) in the sorafenib group (hazard ratio [HR] 0·64, 95% CI; 0·45-0·91; p=0·013). The most common grade 3-4 adverse events in both groups were fever (71 [53%] in the placebo group vs 73 [54%] in the sorafenib group), infections (55 [41%] vs 46 [34%]), pneumonia (21 [16%] vs 20 [14%]), and pain (13 [10%] vs 15 [11%]). Grade 3 or worse adverse events that were significantly more common in the sorafenib group than the placebo group were fever (relative risk [RR] 1·54, 95% CI 1·04-2·28), diarrhoea (RR 7·89, 2·94-25·2), bleeding (RR 3·75, 1·5-10·0), cardiac events (RR 3·46, 1·15-11·8), hand-foot-skin reaction (only in sorafenib group), and rash (RR 4·06, 1·25-15·7). INTERPRETATION In patients with acute myeloid leukaemia aged 60 years or younger, the addition of sorafenib to standard chemotherapy has antileukaemic efficacy but also increased toxicity. Our findings suggest that kinase inhibitors could be a useful addition to curative treatment for acute myeloid leukaemia. Overall survival after long-term follow-up and strategies to reduce toxicity are needed to determine the future role of sorafenib in treatment of this disease. FUNDING Bayer HealthCare.

Chimeric IgA antibodies against HLA class II effectively trigger lymphoma cell killing

Antibodies against human leukocyte antigen (HLA) class II, such as 1D10 or Lym-1, are currently being evaluated for the treatment of B-cell lymphomas. Previous studies have demonstrated that, in addition to IgG Fc receptors, the human myeloid IgA receptor (Fc(alpha)RI, CD89) also effectively triggered tumor cell killing. Therefore, we used the variable light and heavy chain sequences from another murine anti-HLA class II hybridoma, F3.3, to generate a panel of chimeric human/mouse antibodies, including human immunoglobulin A1 (IgA1), IgA2, IgG1, IgG2, IgG3, and IgG4. Antibody production was accomplished by stable transfection of baby hamster kidney cells, and binding activity and specificity were confirmed by enzyme-linked immunosorbent assay (ELISA) and Western blotting. All constructs demonstrated similar binding to HLA class II. Functional studies revealed that chimeric IgG1, IgA1, and IgA2 triggered similar levels of tumor cell lysis. Analyses of effector populations, however, demonstrated that killing by chimeric IgG1 constructs was triggered mainly by human mononuclear cells and complement, while IgA1 and IgA2 mediated effective lysis by polymorphonuclear neutrophils. Importantly, IgG1 and both IgA isotypes were equally effective at killing freshly isolated human chronic lymphocytic leukemia cells. Chimeric IgA antibodies against HLA class II may constitute attractive reagents for lymphoma therapy.

Fcγ receptor IIa, IIIa, and IIIb polymorphisms in German patients with systemic lupus erythematosus: association with clinical symptoms

Background: Receptors for IgG play an important part in immune complex clearance. Several studies have identified polymorphisms of receptors for the Fc fragment of IgG (FcγR) as genetic factors influencing susceptibility to disease or disease course of systemic lupus erythematosus (SLE). Objective: To examine these possibilities by evaluating a panel of clinical parameters in a cohort of 140 German patients with SLE for correlations with the FcγRIIa, IIIa, and IIIb polymorphisms in an explorative study. Methods: 140 German patients with SLE according to American College of Rheumatology (ACR) criteria and 187 German controls were genotyped for the FcγRIIa, IIIa, and IIIb polymorphisms. Associations between FcγR genotypes, combined genotypes and clinical as well as laboratory features were analysed. Results: No significant skewing of any of the three FcγR polymorphisms was seen in the German SLE cohort studied. Various clinical and serological parameters were found more frequently and at younger age in homozygous patients with the genotypes IIA-R/R131 or IIIA-F/F158 than in patients with IIA-H/H131 or IIIA-V/V158. These effects were even more pronounced in patients with the low binding combined phenotypes of the FcγRIIa, IIIa (double negative phenotypes) and FcγRIIa, IIIa, and IIIb (triple negative phenotypes). In patients with the double negative IIA and IIIA genotypes significantly higher frequencies of nephritis (63% v 33%) and proteinuria according to ACR criteria (58% v 11%), anaemia (84% v 55%), and anticardiolipin antibodies (63% v 22%) were found than in patients with the double positive genotypes. Patients with the IIA-R/R131 genotype and the double negative homozygous genotype had an earlier incidence of clinical symptoms, haematological and immunological abnormalities. Accordingly, SLE is diagnosed earlier in these patients, the difference reaching statistical significance only in the double negative v the double positive genotype (26.3 v 39.5 years) and the IIIA-F/F158 genotype v the rest (26.7 v 32.0 years). Most relevant is the fact that a higher median disease activity (ECLAM score) was demonstrated, both in the IIA-R/R131 homozygous (3.3 v 2.7) and the double negative (3.4 v 2.3) patients, reaching statistical significance in the first group. Conclusion: The results of this explorative study support the view that the FcγRIIa/IIIa and IIIb polymorphisms constitute factors influencing clinical manifestations and the disease course of SLE but do not represent genetic risk factors for the occurrence of SLE. Higher frequencies of clinical symptoms, haematological and immunological abnormalities as well as an earlier onset of clinical symptoms, haematological and immunological markers of active disease were found in patients with the IIA-R/R131 genotype and the double negative and triple negative genotypes.