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Sigbjørn Berentsen,1 Alexander Röth,2 Ulla Randen,3 Bernd Jilma,4 Geir E Tjønnfjord5–71Department of Research and Innovation, Haugesund Hospital, Haugesund, Norway; 2Department of Hematology, West German Cancer Center, University Hospital Essen, University of Duisburg-Essen, Essen, Germany; 3Department of Pathology, Akershus University Hospital, Lørenskog, Norway; 4Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria; 5Department of Haematology, Oslo University Hospital, Oslo, Norway; 6KG Jebsen’s Center for B-cell Malignancies, University of Oslo, Oslo, Norway; 7Institute of Clinical Medicine, University of Oslo, Oslo, NorwayAbstract: Cold agglutinin disease (CAD) is a complement-dependent, classical pathway-mediated immune hemolytic disease, accounting for 15–25% of autoimmune hemolytic anemia, and at the same time, a distinct clonal B-cell lymphoproliferative disorder of the bone marrow. The disease burden is often high, but not all patients require pharmacological treatment. Several therapies directed at the pathogenic B-cells are now available. Rituximab plus bendamustine or rituximab monotherapy should be considered first-line treatment, depending on individual patient characteristics. Novel treatment options that target the classical complement pathway are under development and appear very promising, and the C1s inhibitor sutimlimab is currently being investigated in two clinical Phase II and III trials. These achievements have raised new challenges and further prospects, which are discussed. Patients with CAD requiring therapy should be considered for clinical trials.Keywords: autoimmune hemolytic anemia, cold agglutinin disease, lymphoproliferative, complement, complement inhibitors, therapy

Background: Cold agglutinin disease (CAD) is a rare autoimmune haemolytic anaemia mediated by the classical complement pathway (CP). Sutimlimab selectively targets complement C1s inhibiting classical CP activation. In CADENZA Part A (26-weeks), a placebo-controlled study in patients without recent transfusion history, sutimlimab reduced haemolysis, anaemia, and fatigue, and was generally well tolerated., Methods: The CADENZA study (NCT03347422) started in March 2018 (Part A) and completed in December 2021 (Part B). All patients in Part B were eligible to receive sutimlimab for up to 1 year after the last patient completed Part A. Efficacy and safety was assessed throughout Part B, until the last on-treatment visit with available assessment (LV), and after a 9-week washout., Findings: In total, 32/39 patients completed Part B; median treatment duration: 99 weeks. Similar sustained improvements in haemolysis, anaemia, and quality of life were observed in patients switching to sutimlimab and those continuing sutimlimab. Mean LV values for the combined group (ie, placebo-to-sutimlimab group and sutimlimab-to-sutimlimab group) improved from baseline for haemoglobin (≥11.0 g/dL on-treatment vs 9.3 g/dL at baseline), bilirubin (≤20.0 μmol/L on-treatment vs 35.0 μmol/L at baseline), and FACIT-Fatigue scores. Following a 9-week washout, inhibition of CP activity was reversed, and haemolytic markers approached baseline levels. Overall, sutimlimab was generally well tolerated throughout the study. No patients developed systemic lupus erythematosus or meningococcal infections. During the 9-week washout, most adverse events could be attributed to recurrence of underlying CAD., Interpretation: The CADENZA Part B results support the sustained efficacy and safety of sutimlimab for treatment of CAD; however, upon discontinuation disease activity reoccurs., Funding: Sanofi., Competing Interests: AR has received consultancy fees from Alexion Pharmaceuticals, Inc, Apellis Pharmaceuticals, Bioverativ, a Sanofi company, Novartis, Roche, and Sanofi; honoraria from Alexion, Amgen, Apellis, Novartis, Roche, Sanofi and Sobi, and advisory board fees from Alexion, Amgen, Apellis, Bioverativ, Novartis, Roche, Sanofi, and Sobi. SB has received research support from Mundipharma; lecture honoraria from Apellis, Bioverativ (a Sanofi company), Janssen-Cilag, Momenta Pharmaceuticals and True North Therapeutics; and consultancy and advisory board honoraria from Apellis, Bioverativ, and Momenta Pharmaceuticals. WB has received research support from Alexion; honoraria from Agios, Alexion, Apellis, Biocryst, Incyte, Janssen, Momenta, Novartis, Sanofi, and Sobi; and advisory board fees from Alexion, Novartis, Roche, Sanofi, and Sobi. SD reports speaker fees and research funding from Janssen, BeiGene and Sanofi. BJ has received reimbursement for travel costs related to scientific advice and scientific presentations from Sanofi. MM has received research support for clinical studies from Roche; received fees from Amgen and GlaxoSmithKline for their participation in scientific advisory boards. ICW has received consultancy fees from Alexion, Apellis, Novartis, and Biocryst; and honoraria from Alexion. MY has no disclosures. JN is a member of the advisory board for Chugai Pharmaceuticals and Alexion Pharmaceuticals and has received research funding and honorarium from Alexion Pharmaceuticals. JMIV has received honoraria from Sanofi, Amgen, and BMS; research support from Beigene and AbbVie/Genmab, and advisory board fees from Sanofi and Janssen; all of these are institutional. JC received research funding from Cerus, Kawasumi Laboratories and Sanofi; he also received speaker or advisory fees from Cerus, Fresenius Kabi, Grifols, MacoPharma, Pharm-Olam, Sanofi and Terumo Blood and Cell Technologies. CMB has received research support from Alexion, Argenx, Electra, Novartis, and Sanofi; honoraria from Alexion, Argenx, and Sanofi; and advisory board fees from Argenx, Novartis, and Sanofi. DJ, FS, ML, MS, MW, NW, RY, SS are Sanofi employees and may hold stock and/or stock options in the company., (© 2024 The Author(s).)

Competing Interests: S.B. has received consultancy and advisory board honoraria from BeiGene, HillStar Bio, Hummingbird Bioscience, Sanofi, and Sobi, and lecture honoraria from BeiGene, Janssen-Cilag, Sanofi, and Sobi. S.S.D. declares no conflicts of interest.

Autoimmune haemolytic anaemia (AIHA) is a common term for several disorders that differ from one another in terms of aetiology, pathogenesis, clinical features, and treatment. Therapy is becoming increasingly differentiated and evidence-based, and several new established and investigational therapeutic approaches have appeared during recent years. While this development has resulted in therapeutic improvements, it also carries increased medical and financial requirements for optimal diagnosis, subgrouping, and individualization of therapy, including the use of more advanced laboratory tests and expensive drugs. In this brief Viewpoint review, we first summarize the diagnostic workup of AIHA subgroups and the respective therapies that are currently considered optimal. We then compare these principles with real-world data from India, the world's largest nation by population and a typical low-to-middle income country. We identify major deficiencies and limitations in general and laboratory resources, real-life diagnostic procedures, and therapeutic practices. Incomplete diagnostic workup, overuse of corticosteroids, lack of access to more specific treatments, and poor follow-up of patients are the rule more than exceptions. Although it may not seem realistic to resolve all challenges, we try to outline some ways towards an improved management of patients with AIHA., Competing Interests: The authors did not receive any funding or writing assistance for this paper. Outside this work, SB has received consultancy and advisory board honoraria from Annexon, BeiGene, Momenta, Sanofi, and Sobi; lecture honoraria from BeiGene, Janssen-Cilag, Sanofi, and Sobi; and royalties from Wolters Kluwer. SSD declares no conflicts of interest., (© 2023 The Author(s).)

Cold agglutinin disease (CAD) is a rare, autoimmune, classical complement pathway (CP)-mediated hemolytic anemia. Sutimlimab selectively inhibits C1s of the C1 complex, preventing CP activation while leaving the alternative and lectin pathways intact. In Part A (26 weeks) of the open-label, single-arm, Phase 3 CARDINAL study in patients with CAD and a recent history of transfusion, sutimlimab demonstrated rapid effects on hemolysis and anemia. Results of the CARDINAL study Part B (2-year extension) study, described herein, demonstrated that sutimlimab sustains improvements in hemolysis, anemia, and quality of life over a median of 144 weeks of treatment. Mean last-available on-treatment values in Part B were improved from baseline for hemoglobin (12.2 g/dL on-treatment versus 8.6 g/dL at baseline), bilirubin (16.5 μmol/L on-treatment versus 52.1 μmol/L at baseline), and FACIT-Fatigue scores (40.5 on-treatment versus 32.4 at baseline). In the 9-week follow-up period after sutimlimab cessation, CP inhibition was reversed, and hemolytic markers and fatigue scores approached pre-sutimlimab values. Overall, sutimlimab was generally well tolerated in Part B. All 22 patients experienced ≥1 treatment-emergent adverse event (TEAE); 12 (54.5%) patients experienced ≥1 serious TEAE, including seven (31.8%) with ≥1 serious infection. Three patients discontinued due to a TEAE. No patients developed systemic lupus erythematosus or meningococcal infections. After cessation of sutimlimab, most patients reported adverse events consistent with recurrence of CAD. In conclusion, the CARDINAL 2-year results provide evidence of sustained sutimlimab effects for CAD management, but that disease activity reoccurs after treatment cessation. NCT03347396. Registered November 20, 2017., (© 2023 The Authors. American Journal of Hematology published by Wiley Periodicals LLC.)

Cold agglutinin disease (CAD) is a rare autoimmune hemolytic anemia and a bone marrow clonal lymphoproliferative disorder. Hemolysis in CAD is complement-dependent and mediated by the classical activation pathway. Patients also frequently suffer from fatigue and cold-induced circulatory symptoms. Although not all patients need treatment, the symptom burden has previously been underestimated. Effective therapies target the clonal lymphoproliferation or the complement activation. Sutimlimab, a humanized monoclonal IgG4 antibody that binds and inactivates complement protein C1s, is the most extensively investigated complement inhibitor for the treatment of CAD. This review addresses the preclinical studies of sutimlimab and the studies of pharmacokinetics and pharmacodynamics. We then describe and discuss the prospective clinical trials that established sutimlimab as a rapidly acting, highly efficacious, and low-toxic therapeutic agent. This complement inhibitor does not improve the cold-induced circulatory symptoms, which are not complement-mediated. Sutimlimab is approved for the treatment of CAD in the US, Japan, and the European Union. A tentative therapeutic algorithm is presented. The choice of therapy for CAD should be based on an individual assessment, and patients requiring therapy should be considered for inclusion in clinical trials., Competing Interests: Outside this work, SB has received advisory board honoraria from Anexon, Momenta Pharmaceuticals, Sanofi-Genzyme, and Sobi, and lecture honoraria from Apellis, BeiGene, Janssen-Cilag, Sanofi-Genzyme, and Sobi. The author has no conflicts of interest to disclose., (Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the European Hematology Association.)

Autoimmune hemolytic anemia (AIHA) is defined by increased erythrocyte turnover mediated by autoimmune mechanisms. While corticosteroids remain first-line therapy in most cases of warm-antibody AIHA, cold agglutinin disease is treated by targeting the underlying clonal B-cell proliferation or the classical complement activation pathway. Several new established or investigational drugs and treatment regimens have appeared during the last 1-2 decades, resulting in an improvement of therapy options but also raising challenges on how to select the best treatment in individual patients. In severe warm-antibody AIHA, there is evidence for the upfront addition of rituximab to prednisolone in the first line. Novel agents targeting B-cells, extravascular hemolysis, or removing IgG will offer further options in the acute and relapsed/refractory settings. In cold agglutinin disease, the development of complement inhibitors and B-cell targeting agents makes it possible to individualize therapy, based on the disease profile and patient characteristics. For most AIHAs, the optimal treatment remains to be found, and there is still a need for more evidence-based therapies. Therefore, prospective clinical trials should be encouraged., Competing Interests: Outside this work, SB has received advisory board honoraria from Annexon, Momenta, Sanofi, and Sobi, and lecture honoraria from Apellis, BeiGene, Janssen-Cilag, Sanofi, and Sobi. BF declares consultancies with Amgen, Alexion, Annexon, Apellis, Momenta, Novartis, and Sobi. WB has received consultancy and advisory board honoraria from Agios, Alexion, Biocryst, Incyte, Novartis, and Sanofi; lecture honoraria and congress support from Alexion, Incyte, Novartis, and Sanofi; and research support from Alexion., (Copyright © 2023 Berentsen, Fattizzo and Barcellini.)

Therapies for cold agglutinin disease have been directed at the pathogenic B-cell clone. Sutimlimab, a monoclonal antibody that targets C1s, is the first complement inhibitor to be extensively studied in cold agglutinin disease. Sutimlimab selectively blocks the classical activation pathway and leaves the alternative and lectin pathways intact. Trials have documented high response rates with rapid improvement in hemolysis, hemoglobin levels and fatigue scores and low toxicity. Sutimlimab was recently approved in the USA. This drug appears to be particularly useful in severely anemic patients who require a rapid response, in acute exacerbations that do not resolve spontaneously and in patients in whom chemoimmunotherapy is contraindicated or has failed. The choice of therapy in cold agglutinin disease should be individualized.

Sutimlimab, a first-in-class humanized immunoglobulin G4 (IgG4) monoclonal antibody that selectively inhibits the classical complement pathway at C1s, rapidly halted hemolysis in the single-arm CARDINAL study in recently transfused patients with cold agglutinin disease (CAD). CADENZA was a 26-week randomized, placebo-controlled phase 3 study to assess safety and efficacy of sutimlimab in patients with CAD without recent (within 6 months prior to enrollment) transfusion history. Forty-two patients with screening hemoglobin ≤10 g/dL, elevated bilirubin, and ≥1 CAD symptom received sutimlimab (n = 22) or placebo (n = 20) on days 0 and 7 and then biweekly. Composite primary endpoint criteria (hemoglobin increase ≥1.5 g/dL at treatment assessment timepoint [mean of weeks 23, 25, 26], avoidance of transfusion, and study-prohibited CAD therapy [weeks 5-26]) were met by 16 patients (73%) on sutimlimab, and 3 patients (15%) on placebo (odds ratio, 15.9 [95% confidence interval, 2.9, 88.0; P < .001]). Sutimlimab, but not placebo, significantly increased mean hemoglobin and FACIT-Fatigue scores at treatment assessment timepoint. Sutimlimab normalized mean bilirubin by week 1. Improvements correlated with near-complete inhibition of the classical complement pathway (2.3% mean activity at week 1) and C4 normalization. Twenty-one (96%) sutimlimab patients and 20 (100%) placebo patients experienced ≥1 treatment-emergent adverse event. Headache, hypertension, rhinitis, Raynaud phenomenon, and acrocyanosis were more frequent with sutimlimab vs placebo, with a difference of ≥3 patients between groups. Three sutimlimab patients discontinued owing to adverse events; no placebo patients discontinued. These data demonstrate that sutimlimab has potential to be an important advancement in the treatment of CAD. This trial was registered at www.clinicaltrials.gov as #NCT03347422., (© 2022 by The American Society of Hematology.)

The last decades have seen great progress in the treatment of cold agglutinin disease (CAD). Comparative trials are lacking, and recommendations must be based mainly on nonrandomized trials and will be influenced by personal experience. Herein, current treatment options are reviewed and linked to 3 cases, each addressing specific aspects of therapy. Two major steps in CAD pathogenesis are identified, clonal B-cell lymphoproliferation and complement-mediated hemolysis, each of which constitutes a target of therapy. Although drug treatment is not always indicated, patients with symptomatic anemia or other bothersome symptoms should be treated. The importance of avoiding ineffective therapies is underscored. Corticosteroids should not be used to treat CAD. Studies on safety and efficacy of relevant drugs and combinations are briefly described. The author recommends that B cell-directed approaches remain the first choice in most patients requiring treatment. The 4-cycle bendamustine plus rituximab combination is highly efficacious and sufficiently safe and induces durable responses in most patients, but the time to response can be many months. Rituximab monotherapy should be preferred in frail patients. The complement C1s inhibitor sutimlimab is an emerging option in the second line and may also find its place in the first line in specific situations., (© 2021 by The American Society of Hematology.)

We retrospectively studied 232 patients with cold agglutinin disease (CAD) at 24 centers in 5 countries. In Norway and a northern region of Italy, the study was close to being population-based. For the first time, we demonstrate fourfold differences between cold and warmer climates regarding prevalence (20 vs 5 cases/million) and incidence (1.9 vs 0.48 cases/million per year). Mean baseline hemoglobin level was 9.3 g/dL, but 27% had hemoglobin <8 g/dL. Identification of typical features of CAD-associated lymphoproliferative disorder in the bone marrow was greatly increased by centralized biopsy assessment. CAD seems to be associated with a slightly increased risk of venous thrombosis. This work includes a follow-up study of therapies, focusing on the long-term outcomes of the rituximab plus bendamustine and rituximab plus fludarabine regimens. Rituximab plus bendamustine therapy resulted in responses in 35 (78%) of 45 patients; 24 (53%) achieved complete response. Interestingly, these rates were still higher than observed in the original (2017) prospective trial, and we also found a shift toward deeper responses with time. This is explained by the prolonged time to response seen in many patients, probably related to long-lived plasma cells. In patients responding to rituximab-bendamustine, median response duration was not reached after 88 months, and estimated 5-year sustained remission was 77%. The regimen appeared safe regarding late-occurring malignancies. Rituximab plus fludarabine therapy seems to carry a higher risk of long-term adverse effects., (© 2020 by The American Society of Hematology.)

Autoimmune hemolytic anemias mediated by cold agglutinins can be divided into cold agglutinin disease (CAD), which is a well-defined clinicopathologic entity and a clonal lymphoproliferative disorder, and secondary cold agglutinin syndrome (CAS), in which a similar picture of cold-hemolytic anemia occurs secondary to another distinct clinical disease. Thus, the pathogenesis in CAD is quite different from that of polyclonal autoimmune diseases such as warm-antibody AIHA. In both CAD and CAS, hemolysis is mediated by the classical complement pathway and therefore can result in generation of anaphylotoxins, such as complement split product 3a (C3a) and, to some extent, C5a. On the other hand, infection and inflammation can act as triggers and drivers of hemolysis, exemplified by exacerbation of CAD in situations with acute phase reaction and the role of specific infections (particularly Mycoplasma pneumoniae and Epstein-Barr virus) as causes of CAS. In this review, the putative mechanisms behind these phenomena will be explained along with other recent achievements in the understanding of pathogenesis in these disorders. Therapeutic approaches have been directed against the clonal lymphoproliferation in CAD or the underlying disease in CAS. Currently, novel targeted treatments, in particular complement-directed therapies, are also being rapidly developed and will be reviewed., (Copyright © 2020 Berentsen.)

Primary cold agglutinin disease (CAD) is characterized by a very indolent bone marrow clonal B-cell lymphoproliferative disorder that initiates an autoimmune hemolytic anemia. The clonal B cells produce a monoclonal autoantibody termed cold agglutinin, most often of the immunoglobulin (Ig) Mκ class. After binding to its antigen, the IgM initiates a complement classical pathway-driven erythrocyte destruction, predominantly mediated by opsonization with complement protein C3b and extravascular hemolysis in the liver. We review the molecular biology, histopathology, clinical features, and diagnostic procedures in CAD. Some patients are only slightly anemic and do not require treatment, but moderate or severe anemia frequently occurs, and the disease burden has been underestimated. CAD should not be treated with corticosteroids. Several B-cell-directed treatment options are available, and complement-directed approaches are being rapidly developed. Current and possible future therapies are reviewed.

Cold agglutinin disease (CAD) is a rare form of autoimmune hemolytic anemia with limited epidemiological and clinical data. We used the Danish National Patient Registries to examine CAD occurrence and risk of thromboembolic events (TEs) and mortality in CAD patients compared with a matched cohort from the general population in Denmark. We identified 72 patients diagnosed with CAD and 720 matched controls between 1999 and 2013. For 2013, the most recent year of study, crude incidence of CAD was 0.18 per 100 000 inhabitants per year and prevalence was 1.26 per 100 000 inhabitants. Risk of TEs was higher in the CAD patient cohort than in the comparison cohort at 1 year (7.2% of CAD patients had TEs vs 1.9% of comparisons), 3 years (9.0% vs 5.3%), and 5 years (11.5% vs 7.8%) after the index date. The median survival was 8.5 years. CAD patients had increased mortality compared with the general population cohort (adjusted hazard ratio [aHR], 1.84; 95% confidence interval [CI], 1.10-3.06; P = .020), with the highest mortality observed during the first 5 years after diagnosis (aHR, 2.27; 95% CI, 1.32-3.89; P = .003). Mortality rates 1 and 5 years after diagnosis were 17% and 39% in the CAD group vs 3% and 18% in the comparison cohort, respectively. CAD is a rare illness characterized by increased risk of TEs and mortality., (© 2019 by The American Society of Hematology.)

Complement-mediated hemolytic anemias can either be caused by deficiencies in regulatory complement components or by autoimmune pathogenesis that triggers inappropriate complement activation. In paroxysmal nocturnal hemoglobinuria (PNH) hemolysis is entirely complement-driven. Hemolysis is also thought to be complement-dependent in cold agglutinin disease (CAD) and in paroxysmal cold hemoglobinuria (PCH), whereas warm antibody autoimmune hemolytic anemia (wAIHA) is a partially complement-mediated disorder, depending on the subtype of wAIHA and the extent of complement activation. The pathophysiology, clinical presentation, and current therapies for these diseases are reviewed in this article. Novel, complement-directed therapies are being rapidly developed. Therapeutic terminal complement inhibition using eculizumab has revolutionized the therapy and prognosis in PNH but has proved less efficacious in CAD. Upstream complement modulation is currently being investigated and appears to be a highly promising therapy, and two such agents have entered phase II and III trials. Of these, the anti-C1s monoclonal antibody sutimlimab has shown favorable activity in CAD, while the anti-C3 cyclic peptide pegcetacoplan appears to be promising in PNH as well as CAD, and may also have a therapeutic potential in wAIHA., Competing Interests: Conflict of interest statement: The authors did not receive any funding for this work. Outside this work, S. Berentsen has received research funding from Mundipharma, consulting fees from Apellis, Bioverativ, Momenta Pharmaceuticals and True North Therapeutics, and travel grants and lecture honoraria from Alexion, Apellis, Bioverativ and Janssen-Cilag. A. Hill has received honoraria from Alexion, Apellis, Bioverativ, and Novartis. Q.A. Hill has received research support from Alexion and honoraria for lecturing or advisory work from Novartis, Shire, and Bioverativ. T.H.A. Tvedt has received advisory board honoraria from Ablynx and Alexion and lecture honoraria from Alexion and Novartis. M. Michel has advisory board honoraria from Alexion, Apellis, and Rigel.

The terminology applied to autoimmune hemolytic anemia (AIHA) seems inconsistent. We aimed to evaluate the consistency of definitions used for diagnosis and treatment. In this systematic review of literature from January 2006 to December 2015, we assessed heterogeneity in the definition of AIHA and its subtypes, refractory disease, disease phase, severity, criteria for treatment response, and response durability. A Medline search for anemia, hemolytic, autoimmune was supplemented with keyword searches. Main exclusions were conference abstracts, animal and non-English studies, and studies with <10 cases. Of 1371 articles retrieved, 1209 were excluded based on titles and abstracts. Two authors independently reviewed 10% and 16% of abstracts and full papers, respectively. After full-paper review, 84 studies were included. AIHA was most frequently (32 [52%] of 61) defined as hemolytic anemia with positive direct antiglobulin test (DAT) and exclusion of alternatives, but 10 of 32 also recognized DAT-negative AIHA. A lower threshold for diagnosis of DAT-negative AIHA was observed in literature on chronic lymphocytic leukemia. Definitions of anemia, hemolysis, and exclusion criteria showed substantial variation. Definitions of primary/secondary cold agglutinin disease/syndrome were not consistent. Forty-three studies provided criteria for treatment response, and other than studies from 1 center, these were almost entirely unique. Other criteria were rarely defined. Only 7, 0, 3, 2, 2, and 3 studies offered definitions of warm AIHA, paroxysmal cold hemoglobinuria, mixed AIHA, AIHA severity, disease phase, and refractory AIHA, respectively. Marked heterogeneity in the time period sampled indicates the need to standardize AIHA terminology., (© 2019 by The American Society of Hematology.)

Cold agglutinin disease (CAD) is an autoimmune hemolytic anemia and a distinct, clonal bone marrow lymphoproliferative disorder, characterized in most cases by a monoclonal IgMκ serum protein. We describe a CAD patient presenting with a monoclonal immunoglobulin of the IgA λ class. For years, she remained asymptomatic apart from the hemolytic anemia until eventually she developed multiple myeloma (MM) of the IgA λ phenotype. Prior to the development of MM, her hemolytic anemia responded to rituximab monotherapy. After she was diagnosed with MM, both conditions responded well to bortezomib-based therapy. We performed further investigations to determine whether her MM represented a progression/transformation of CAD or an independent disease. Flow cytometry and biopsy findings convincingly confirmed two unrelated clonal B-cell disorders. On this background, we also discuss previously published reports on cold agglutinin activity in patients with IgA gammopathy. In conclusion, cold agglutinins of the IgA class do probably not result in CAD. If a monoclonal immunoglobulin other than IgMκ is found in a patient with CAD, the coexistence of two unrelated B-cell clones should be suspected.

Competing Interests: Conflict-of-interest disclosure: S.B. has received research support from Mundipharma, travel support from Alexion, lecture honoraria from Bioverativ and Janssen-Cilag, and has consulted for Apellis, Bioverativ, Momenta Pharmaceuticals, and True North Therapeutics.

Primary chronic cold agglutinin disease (CAD) is a well-defined clinicopathologic entity in which a bone marrow clonal B-cell lymphoproliferation results in autoimmune hemolytic anemia and cold-induced circulatory symptoms. Rituximab monotherapy and fludarabine-rituximab in combination are documented treatment options. In a prospective, nonrandomized multicenter trial, 45 eligible patients received rituximab 375 mg/m 2 day 1 and bendamustine 90 mg/m 2 days 1 and 2 for 4 cycles at a 28-day interval. Thirty-two patients (71%) responded; 18 (40%) achieved complete response (CR) and 14 (31%) partial response (PR). Among 14 patients previously treated with rituximab or fludarabine-rituximab, 7 (50%) responded to bendamustine-rituximab (3 CR and 4 PR). Hemoglobin levels increased by a median of 4.4 g/dL in the complete responders, 3.9 g/dL in those achieving PR, and 3.7 g/dL in the whole cohort. The 10th percentile of response duration was not reached after 32 months. Grade 3-4 neutropenia occurred in 15 patients (33%), but only 5 (11%) experienced infection with or without neutropenia. Thirteen patients (29%) had their dose of bendamustine reduced. In conclusion, bendamustine-rituximab combination therapy is highly efficient, sufficiently safe, and may be considered in first line for patients with CAD requiring therapy. The trial was registered at www.clinicaltrials.gov as #NCT02689986., (© 2017 by The American Society of Hematology.)

Primary chronic cold agglutinin disease (CAD) is an autoimmune haemolytic anaemia in which a specific bone marrow lymphoproliferative disorder causes production of cold agglutinins (CA). Binding of CA to erythrocyte surface antigens results in a predominantly extravascular haemolysis that is entirely complement dependent. Because of complement activation, exacerbations are common during febrile infections, trauma or major surgery. Involvement of the terminal complement pathway with C5-mediated intravascular haemolysis is probably not prominent in stable disease but is supposed to be of importance in exacerbations following acute phase reaction.We report on a patient with CAD prone to exacerbation of haemolysis during acute phase reactions who was scheduled for cardiac surgery. To prevent her having an exacerbation of haemolysis, we chose to treat her prophylactically with eculizumab along with the usual perioperative precautions. Aortic valve replacement was undertaken with full cardiopulmonary bypass at normothermia. The procedure was successful; no exacerbation of haemolysis was observed, and transfusion requirements did not exceed what could be expected., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Primary chronic cold agglutinin disease (CAD) is a well-defined clinicopathologic entity in which a specific, clonal lymphoproliferative B-cell bone marrow disorder results in autoimmune hemolytic anemia. The immune hemolysis is entirely complement-dependent, predominantly mediated by activation of the classical pathway and phagocytosis of erythrocytes opsonized with complement protein C3b. Typical clinical features in CAD have diagnostic and therapeutic implications. Pharmacologic treatment should be offered to patients with symptom-producing anemia or disabling circulatory symptoms. CAD should not be treated with corticosteroids. Based on an individualized approach, rituximab monotherapy or rituximab-fludarabine in combination is recommended as first-line therapy. Rituximab-bendamustine is still an investigational therapy. Although complement-modulating agents are still to be considered experimental in CAD, therapy with the anti-C1s monoclonal antibody TNT009 seems promising., (© 2016 by The American Society of Hematology. All rights reserved.)

The classification of autoimmune hemolytic anemias and the complement system are reviewed. In autoimmune hemolytic anemia of the warm antibody type, complement-mediated cell lysis is clinically relevant in a proportion of the patients but is hardly essential for hemolysis in most patients. Cold antibody-mediated autoimmune hemolytic anemias (primary cold agglutinin disease, secondary cold agglutinin syndrome and paroxysmal cold hemoglobinuria) are entirely complement-mediated disorders. In cold agglutinin disease, efficient therapies have been developed in order to target the pathogenic B-cell clone, but complement modulation remains promising in some clinical situations. No established therapy exists for secondary cold agglutinin syndrome and paroxysmal cold hemoglobinuria, and the possibility of therapeutic complement inhibition is interesting. Currently, complement modulation is not clinically documented in any autoimmune hemolytic anemia. The most relevant candidate drugs and possible target levels of action are discussed.

Autoimmune hemolytic anemia (AIHA) is a collective term for several diseases characterized by autoantibody-initiated destruction of red blood cells (RBCs). Exact subclassification is essential. We provide a review of the respective types of AIHA with emphasis on mechanisms of RBC destruction, focusing in particular on complement involvement. Complement activation plays a definitive but limited role in warm-antibody AIHA (w-AIHA), whereas primary cold agglutinin disease (CAD), secondary cold agglutinin syndrome (CAS), and paroxysmal cold hemoglobinuria (PCH) are entirely complement-dependent disorders. The details of complement involvement differ among these subtypes. The theoretical background for therapeutic complement inhibition in selected patients is very strong in CAD, CAS, and PCH but more limited in w-AIHA. The optimal target complement component for inhibition is assumed to be important and highly dependent on the type of AIHA. Complement modulation is currently not an evidence-based therapy modality in any AIHA, but a number of experimental and preclinical studies are in progress and a few clinical observations have been reported. Clinical studies of new complement inhibitors are probably not far ahead.