Mechanism of first-dose cytokine-release syndrome by CAMPATH 1-H: involvement of CD16 (FcgammaRIII) and CD11a/CD18 (LFA-1) on NK cells

Alemtuzumab induction of intracellular signaling and apoptosis in malignant B lymphocytes

The molecular changes induced by alemtuzumab following binding of CD52 on B tumor cells were investigated. Alemtuzumab alone had no detectable impact on cell signaling but cross-linking of alemtuzumab on the surface of B tumor lines with anti-human Fc antibodies induced a transient Ca(2+) flux followed by phosphorylation of several kinases involved in stress and survival pathways, and expression of associated proteins including TNF-α. Cross-linking of alemtuzumab also induced capping and caspase-dependent apoptosis of the tumor lines. When using primary cells from B-CLL patients, alemtuzumab alone was capable of inducing protein phosphorylation and apoptosis through the cross-linking of alemtuzumab by FcγRIIb receptors on B-CLL cells. Apoptosis was prevented by blocking of FcγRIIb receptors with anti-CD32 antibody. Overall, our results indicate that cross-linking of alemtuzumab on B tumor cells can occur naturally through Fc receptor interaction and leads to the activation of specific cellular pathways and induction of apoptosis.

A predictive biomimetic model of cytokine release induced by TGN1412 and other therapeutic monoclonal antibodies

Human peripheral blood mononuclear cells (PBMC) are routinely used in vitro to detect cytokine secretion as part of preclinical screens to delineate agonistic and antagonistic action of therapeutic monoclonal antibodies (mAbs). Preclinical value of standard human PBMC assays to detect cytokine release syndrome (CRS) has been questioned, as they did not predict the "cytokine storm" that occurred when healthy human volunteers were given a CD28-specific super-agonist mAb, TGN1412. In this article, we describe a three-dimensional biomimetic vascular test-bed that can be used as a more physiologically relevant assay for testing therapeutic Abs. For developing such a system, we used TGN1412 as a model mAb. We tested soluble TGN1412 on various combinations of human blood components in a module containing endothelial cells grown on a collagen scaffold and measured cytokine release using multiplex array. Our system, consisting of whole leukocytes, endothelial cells, and 100% autologous platelet-poor plasma (PPP) consistently produced proinflammatory cytokines in response to soluble TGN1412. In addition, other mAb therapeutics known to induce CRS or first infusion reactions, such as OKT3, Campath-1H, or Herceptin, generated cytokine profiles in our model system consistent with their in vivo responses. As a negative control we tested the non-CRS mAbs Avastin and Remicade and found little difference between these mAbs and the placebo control. Our data indicate that this novel assay may have preclinical value for predicting the potential of CRS for mAb therapeutics.

Innovative monoclonal antibody therapies in multiple sclerosis

The recent years have witnessed great efforts in establishing new therapeutic options for multiple sclerosis (MS), especially for relapsing-remitting disease courses. In particular, the application of monoclonal antibodies provide innovative approaches allowing for blocking or depleting specific molecular targets, which are of interest in the pathogenesis of MS. While natalizumab received approval by the US Food and Drug Administration and the European Medicines Agency in 2006 as the first monoclonal antibody in MS therapy, rituximab, alemtuzumab, and daclizumab were successfully tested for relapsing-remitting MS in small cohorts in the meantime. Here, we review the data available from these recent phase II trials and at the same time critically discuss possible pitfalls which may be relevant for clinical practice. The results of these studies may not only broaden our therapeutic options in the near future, but also provide new insights into disease pathogenesis.

Development of a human whole blood assay for prediction of cytokine release similar to anti-CD28 superagonists using multiplex cytokine and hierarchical cluster analysis

Anti-CD28 superagonist (SA) mediated cytokine release syndrome (CRS), an adverse event resulting in systemic release of cytokines, is an emergent issue in drug development. CRS is of potential concern for all monoclonal antibodies (mAbs) particularly those directed against cell surface targets on lymphocytes. Concern regarding patient safety requires development of novel methods to predict these adverse reactions. Due to the inability of animal studies to predict CRS, we have developed a whole blood in vitro screen to support First in Human studies and assess the potential for mAbs to cause anti-CD28 SA-like CRS. For this purpose we have immobilized marketed mAbs, whose potential for causing CRS and milder infusion reactions is known, on Protein A beads and used these beads to stimulate cytokine release. After culture, supernatants are harvested and frozen for later multiplex analysis of cytokines using Searchlight™ technology. We have employed hierarchicalluster analysis (HCA) to allow comparison of 12 different cytokine levels across numerous donors, treatments, and experiments. Results conclusively distinguish test mAb responses from an anti-CD28 superagonist mAb response. As part of a global analysis of preclinical data, the results of this assay can facilitate entry into First in Human clinical trials, help with selection of starting doses and may allow more rapid dose escalation using smaller cohorts.

Monoclonal antibody TGN1412 trial failure explained by species differences in CD28 expression on CD4+ effector memory T-cells

BACKGROUND AND PURPOSE

In 2006, a life-threatening 'cytokine storm', not predicted by pre-clinical safety testing, rapidly occurred in all six healthy volunteers during the phase I clinical trial of the CD28 superagonist monoclonal antibody (mAb) TGN1412. To date, no unequivocal explanation for the failure of TGN1412 to stimulate profound cytokine release in vitro or in vivo in species used for pre-clinical safety testing has been established. Here, we have identified a species difference almost certainly responsible for this disparate immunopharmacology.

EXPERIMENTAL APPROACH

Polychromatic flow cytometry and intracellular cytokine staining were employed to dissect the in vitro immunopharmacology of TGN1412 and other therapeutic mAbs at the cellular level to identify differences between humans and species used for pre-clinical safety testing.

KEY RESULTS

In vitro IL-2 and IFN-γ release from CD4+ effector memory T-cells were key indicators of a TGN1412-type response. This mechanism of cytokine release differed from that of other therapeutic mAbs, which can cause adverse reactions, because these other mAbs stimulate cytokine release primarily from natural killer cells. In contrast to humans, CD28 is not expressed on the CD4+ effector memory T-cells of all species used for pre-clinical safety testing, so cannot be stimulated by TGN1412.

CONCLUSIONS AND IMPLICATIONS

It is likely that activation of CD4+ effector memory T-cells by TGN1412 was responsible for the cytokine storm. Lack of CD28 expression on the CD4+ effector memory T-cells of species used for pre-clinical safety testing of TGN1412 offers an explanation for the failure to predict a 'cytokine storm' in humans.

Activating and inhibitory Fcgamma receptors in immunotherapy: being the actor or being the target

Membrane Fcgamma receptors (FcgammaRs) can act either as potent activators of effector cell functions or as inhibitors of receptor-mediated cell activation following engagement by IgG antibodies bound to their target molecules. The remarkable ability of activating FcgammaRs to trigger antibody-dependent cellular cytotoxicity, cytokine release and phagocytosis/endocytosis followed by antigen presentation has stimulated the development of a number of therapeutic monoclonal antibodies whose Fc regions have been engineered to optimize their effector functions, mostly their killing activities. Conversely, the demonstration that inhibitory FcgammaRs can block or downmodulate effector functions has led to the concept that targeting these receptors is of interest in a number of pathologies. The use of bispecific antibodies leading to the crosslinking of FcgammaRIIB with activating receptors could induce immunomodulation in autoimmune or allergic diseases. Alternatively, the use of cytotoxic/antagonist anti-FcgammaRIIB antibodies could kill FcgammaRIIB-positive tumor cells or prevent the downmodulation of activating receptors. Thus, antibodies engineered to preferentially target activating or inhibitory FcgammaRs are currently being designed for therapeutic use.

Monoclonal antibody-induced cytokine-release syndrome

Monoclonal antibodies (mAbs) are widely used in anti-inflammatory and tumor therapy. Although effective, mAbs can cause a variety of adverse effects. An important toxicity seen with a few mAbs is cytokine-release syndrome (CRS). These mAbs include: alemtuzumab, muromonab-CD3, rituximab, tosituzumab, CP-870,893, LO-CD2a/BTI-322 and TGN1412. By contrast, over 30 mAbs used clinically are not associated with CRS. In this review, the clinical aspects of CRS, the mAbs associated with CRS, the cytokines involved and putative mechanisms mediating cytokine release will be discussed. This will be followed by a discussion of the poor predictive value of studies in animals and the prospects for creating in vitro screens. Finally, approaches to decreasing the probability of CRS, decreasing the severity or treating CRS, should it occur, will be described.

The safety and side effects of monoclonal antibodies

Monoclonal antibodies (mAbs) are now established as targeted therapies for malignancies, transplant rejection, autoimmune and infectious diseases, as well as a range of new indications. However, administration of mAbs carries the risk of immune reactions such as acute anaphylaxis, serum sickness and the generation of antibodies. In addition, there are numerous adverse effects of mAbs that are related to their specific targets, including infections and cancer, autoimmune disease, and organ-specific adverse events such as cardiotoxicity. In March 2006, a life-threatening cytokine release syndrome occurred during a first-in-human study with TGN1412 (a CD28-specific superagonist mAb), resulting in a range of recommendations to improve the safety of initial human clinical studies with mAbs. Here, we review some of the adverse effects encountered with mAb therapies, and discuss advances in preclinical testing and antibody technology aimed at minimizing the risk of these events.

Opportunistic autoimmune disorders: from immunotherapy to immune dysregulation

Rapid advances in our understanding of the immune network have led to treatment modalities for malignancies and autoimmune diseases based on modulation of the immune response. Yet therapeutic modulation has resulted in immune dysregulation and opportunistic autoimmune sequelae, despite prescreening efforts in clinical trials. This review focuses on recent clinical data on opportunistic autoimmune disorders arising from three immunotherapeutic modalities: (1) systemic immunomodulators, including interferon-alpha (also used to treat hepatitis C patients) and interferon-beta; (2) monoclonal antibodies to CTLA-4 and CD52, and (3) hematopoietic stem cell transplantation. Uncategorized predisposing factors in these patients include major histocompatibility complex and gender genetics, prevalence of different autoimmune diseases, prior chemotherapy, underlying disorder (e.g., hepatitis C), and preconditioning regimens as part of organ and stem cell transplants. Not unexpectedly, the prevalent autoimmune thyroid disease surfaced frequently. Our combination models to study the balance between thyroid autoimmunity and tumor immunity upon regulatory T-cell perturbation are briefly described.

Mechanisms of adverse drug reactions to biologics

Biologics encompass a broad range of therapeutics that include proteins and other products derived from living systems. Although the multiplicity of target organs often seen with new chemical entities is generally not seen with biologics, they can produce significant adverse reactions. Examples include IL-12 and an anti-CD28 antibody that resulted in patient deaths and/or long stays in intensive care units. Mechanisms of toxicities can be categorized as pharmacological or nonpharmacological, with most, excepting hypersensitivity reactions, associated with the interaction of the agent with its planned target. Unexpected toxicities generally arise as a result of previously unknown biology. Manufacturing quality is a significant issue relative to the toxicity of biologics. The development of recombinant technology represented the single biggest advance leading to humanized products with minimal or no contaminants in comparison to products purified from animal tissues. Nevertheless, the type of manufacturing process including choice of cell type, culture medium, and purification method can result in changes to the protein. For example, a change to the closure system for erythropoietin led to an increase in aplastic anemia as a result of changing the immunogenicity characteristics of the protein. Monoclonal antibodies represent a major class of successful biologics. Toxicities associated with these agents include those associated with the binding of the complementary determining region (CDR) with the target. First dose reactions or infusion reactions are generally thought to be mediated via the Fc region of the antibody activating cytokine release, and have been observed with several antibodies. Usually, these effects (flu-like symptoms, etc.) are transient with subsequent dosing. Although biologics can have nonpharmacologic toxicities, these are less common than with small molecule drugs.

[Toxic effects and use of therapeutic monoclonal antibodies]

The extensive use of therapeutic monoclonal antibodies in clinic has shown that toxic effects may occur in patients. Examples such as muromonab (anti-CD3) and recently TGN1412 (anti-CD28) clearly establish that prediction of toxic effects for these targeted therapies is still complex. These undesirable effects can be classified in four categories: cytokine release syndrome, auto-immune diseases, organ toxicity and opportunistic infections. Immunogenicity, which is highly variable depending on the degree of humanization, could also potentially lead to adverse effects due to immune-complexes formation. The recent accident observed with the anti-CD28 TGN1412 has led to the conclusion that the relative confidence in the safety of monoclonal antibodies should be revised. In addition, the prediction of non-clinical models is rather limited and extrapolation of animal results to the human situation should be performed with caution. A better knowledge of the cellular target of the antibodies and of their mechanisms of action and the identification of risk factors (immune cell activation, wide expression of the target...) should improve the clinical safety of these products. .

Investigation of the mechanism of action of alemtuzumab in a human CD52 transgenic mouse model

Alemtuzumab is a humanized monoclonal antibody against CD52, an antigen found on the surface of normal and malignant lymphocytes. It is approved for the treatment of B-cell chronic lymphocytic leukaemia and is undergoing Phase III clinical trials for the treatment of multiple sclerosis. The exact mechanism by which alemtuzumab mediates its biological effects in vivo is not clearly defined and mechanism of action studies have been hampered by the lack of cross-reactivity between human and mouse CD52. To address this issue, a transgenic mouse expressing human CD52 (hCD52) was created. Transgenic mice did not display any phenotypic abnormalities and were able to mount normal immune responses. The tissue distribution of hCD52 and the level of expression by various immune cell populations were comparable to those seen in humans. Treatment with alemtuzumab replicated the transient increase in serum cytokines and depletion of peripheral blood lymphocytes observed in humans. Lymphocyte depletion was not as profound in lymphoid organs, providing a possible explanation for the relatively low incidence of infection in alemtuzumab-treated patients. Interestingly, both lymphocyte depletion and cytokine induction by alemtuzumab were largely independent of complement and appeared to be mediated by neutrophils and natural killer cells because removal of these populations with antibodies to Gr-1 or asialo-GM-1, respectively, strongly inhibited the activity of alemtuzumab whereas removal of complement by treatment with cobra venom factor had no impact. The hCD52 transgenic mouse appears to be a useful model and has provided evidence for the previously uncharacterized involvement of neutrophils in the activity of alemtuzumab.

CD52 expression in non-mycotic T- and NK/T-cell lymphomas

CD52 antigen (Campath-1) is expressed in high density by lymphocytes and monocytes. Campath-1H or alemtuzumab, a human anti-CD52, has been shown to be effective in T-cell malignancies; however, there is very limited information on CD52 expression in T-cell lymphoma (TCL). This study retrospectively investigated 97 TCL cases by immunohistochemistry using paraffin sections to elucidate the CD52 expression rates in various TCL sub-types. Fourteen cases of angioimmunoblastic T-cell lymphoma (AITL) were excluded as there were no reliable criteria to differentiate whether the CD52-positive cells were neoplastic T-cells, which are usually small-sized, or the usually abundant, small-to-large residual/reactive B-cells in this lymphoma sub-type. In the remaining 83 tumors, CD52 was expressed in 29 (35%) tumors including 8/17 (47%) NK/T-cell lymphomas, 14/35 (40%) unspecified peripheral TCLs and 4/18 (22%) anaplastic large cell lymphomas. There was no statistical significance in CD52 expression in terms of patient age, gender, nodal vs extra-nodal presentation or tumor sub-types. The authors recommend performing CD52 immunostaining for future clinical trials of alemtuzumab on TCL patients and to correlate the staining results with treatment outcome.

Pathogenic study of anti-CD20 infusion-related severe refractory shock in diffuse large B-cell lymphoma

Although rituximab is an effective and safe therapy for B-cell lymphoid malignancies, a few cases of severe infusion-related reactions have been reported. Severe refractory distributive shock is an infrequent side-effect of treatment with rituximab and, to our knowledge, there are no reports describing its pathogenesis in a case of fatal outcome in detail. We present for the first time a case of fatal rituximab infusion-related refractory distributive shock in a patient with CD5+ diffuse large B-cell lymphoma (DLBCL) and analyse the pathogenic mechanisms involved. We have compared measurements obtained from the patient that experienced lethal refractory shock with the four subsequent DLBCL patients treated with rituximab, either at diagnosis or upon relapse, at our center. Serum cytokines [interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70] and complement components C3 and C4 were analysed, both pretreatment, and 3 h and 9 h after the onset of infusion. When compared with the control subjects, the potential risk factors for rituximab toxicity displayed by the patient that suffered refractory shock included C4 hypercomplementemia, IFN-gamma and IL-10 hypercytokinemia, as well as a high tumor burden. The refractory shock was distributive with most cytokines (IFN-gamma, TNF-alpha, IL-2, IL-4, IL-6 and IL-8) peaking 3 h after infusion and coinciding with the onset of the shock. Furthermore, the concentrations of IL-10 were persistently elevated. In conclusion, the cytokine pattern was similar to that observed in patients with rapid onset septic shock and serum cytokines reached levels markedly higher than previously described in other cases of severe rituximab infusion-related toxicity.

[Possibilities and risks of the monoclonal antibody alemtuzumab as a new treatment option for multiple sclerosis]

Monoclonal antibodies are of growing interest as treatment options for immune-mediated diseases in neurology. As our knowledge of immunological principals increases, we learn to modulate specifically mechanisms of pathogenesis by the use of monoclonal antibodies. It is clearly desirable to improve efficacy in disease treatment without increasing toxicity by using drugs with more specific modes of action. Natalizumab was the first monoclonal antibody approved in the field of neurology for treatment of relapsing remitting multiple sclerosis (MS). Several other monoclonal antibodies are currently under investigation. Alemtuzumab, a monoclonal antibody targeting CD52, is a highly promising agent currently being studied in two phase III clinical trials. In this review, data from the recently published phase II clinical trial in the treatment of early relapsing remitting MS is summarized and analyzed in light of the development of alemtuzumab for MS and its potential role in treating this disease is discussed.

Targeting of natural killer cells by rabbit antithymocyte globulin and campath-1H: similar effects independent of specificity

T cell depleting strategies are an integral part of immunosuppressive regimens widely used in the hematological and solid organ transplant setting. Although it is known to induce lymphocytopenia, little is known about the effects of the polyclonal rabbit antithymocyte globulin (rATG) or the monoclonal anti-CD52 antibody alemtuzumab on Natural Killer (NK) cells in detail. Here, we demonstrate that induction therapy with rATG following kidney/pancreas transplantation results in a rapid depletion of NK cells. Treatment of NK cells with rATG and alemtuzumab in vitro leads to impairment of cytotoxicity and induction of apoptosis even at a 10-fold lower concentration (0.1 microg/ml) compared with T and B cells. By generating Fc-parts of rATG and alemtuzumab we illustrate that their ligation to FcgammaRIII (CD16) is sufficient for the significant induction of degranulation, apoptosis and inflammatory cytokine release (FasL, TNFalpha and IFNgamma) exclusively in CD3(-)CD56(dim) NK cells whereas application of rATG and alemtuzumab F(ab) fragments abolishes these effects. These findings are of general importance as our data suggest that NK cells are also mediators of the clinically relevant cytokine release syndrome and that their targeting by therapeutic antibodies should be considered as they are functionally relevant for the effective clearance of opportunistic viral infections and anti-tumor activity posttransplantation.

Monoclonal antibody first dose cytokine release syndromes-mechanisms and prediction

Acute cytokine release syndromes are associated with some therapeutic antibodies in man, leading to a spectrum of clinical signs from nausea, chills and fever to more serious dose limiting hypotension and tachycardia. When anticipated this syndrome is typically manageable, however this adverse reaction recently became headline news when a massive and unexpected cytokine release syndrome occurred within a few hours of dosing six healthy volunteers with a therapeutic antibody, putting their lives at risk due to multiple organ failure. Preclinical studies did not predict this adverse event, emphasising the need to compare the relative potency of the product in man and the chosen toxicology species, so that additional margins of safety can be applied when conducting first in man (FIM) studies if there is uncertainty over the predictability of the toxicology species. In vitro human PBMC and whole blood cultures may be useful for predicting cytokine release. However since cytokine release arises through at least two distinct mechanisms, it should be emphasised that the utility of these in vitro methods needs to be established for each antibody product.

Membrane-tethered proteins for basic research, imaging, and therapy

Secreted and intracellular proteins including antibodies, cytokines, major histocompatibility complex molecules, antigens, and enzymes can be redirected to and anchored on the surface of mammalian cells to reveal novel functions and properties such as reducing systemic toxicity, altering the in vivo distribution of drugs and extending the range of useful drugs, creating novel, specific signaling receptors and reshaping protein immunogenicity. The present review highlights progress in designing vectors to target and retain chimeric proteins on the surface of mammalian cells. Comparison of chimeric proteins indicates that selection of the proper cytoplasmic domain and introduction of oligiosaccharides near the cell surface can dramatically enhance surface expression, especially for single-chain antibodies. We also describe progress and limitations of employing surface-tethered proteins for preferential activation of prodrugs at cancer cells, imaging gene expression in living animals, performing high-throughput screening, selectively activating immune cells in tumors, producing new adhesion molecules, creating local immune privileged sites, limiting the distribution of soluble factors such as cytokines, and enhancing polypeptide immunogenicity. Surface-anchored chimeric proteins represent a rich source for developing new techniques and creating novel therapeutics.

Successful treatment of stem cell graft failure in pediatric patients using a submyeloablative regimen of campath-1H and fludarabine

Graft failure is a significant cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT). We used a nonmyeloablative conditioning regimen consisting of the lympho-depleting humanized CD52-antibody Campath-1H and fludarabine to rescue 12 consecutive children age 9 months to 17 years with engraftment failure after initial myeloablative HSCT. Primary diagnoses included lymphohematologic malignancies (n=6), severe combined immunodeficiency syndrome (SCID) (n=4), and metabolic diseases (n=2). The same stem cell donor was used as for the primary graft: mismatched family member (n=7), matched unrelated donor (n=4), or matched related donor (n=1). The patients received doses of CD34+ cells that did not significantly differ from those used in the initial, failed transplant. At a median follow-up of 51 months (range, 4 to 84 months), 6 of 6 patients with nonmalignant diseases and 4 of 6 patients with malignancy were alive. Two patients died, 1 patient from pulmonary toxicity and 1 from relapse, at 51 days and 8 months posttransplantation, respectively. All 12 patients initially achieved sustained neutrophil engraftment and complete donor chimerism by day 28. Six patients received donor lymphocyte infusion (DLI) after "rescue" therapy to maintain donor chimerism. At 6 months, 4 patients had complete donor cell engraftment, 4 had 15% to 89% stable donor chimerism, and 3 had developed secondary graft failure. This conditioning regimen was generally well tolerated; 4 of the 12 patients never became neutropenic, and 9 never became thrombocytopenic. Only 1 patient developed graft-versus-host disease (GVHD; grade 1), and none had chronic GVHD. Thus, the regimen that we describe can be used with minimal toxicity to effectively overcome graft failure after myeloablative HSCT in children.

Identification and development of new therapeutics for multiple sclerosis

In recent years, large efforts have been undertaken to establish new therapeutic options for the treatment of multiple sclerosis (MS). So far, all of these strategies more or less specifically target subsets of the immune response in MS, including not only activation and expansion of T cells, their circulation and transmigration over the blood-brain barrier but also other cell types such as B cells and probably also natural killer cells. Here, we review available data on the most promising (at present) new therapeutic approaches. These involve the orally available compounds cladribine, FTY720, fumaric-acid esters, laquinimod and teriflunomide in addition to the monoclonal antibodies alemtuzumab, daclizumab, natalizumab and rituximab. After successful completion of Phase III studies, these compounds might have the potential to add to the current therapeutic armentarium especially for relapsing remitting disease courses in the near future, possibly opening the way to a more individualized treatment.

When binding is enough: nonactivating antibody formats

Most therapeutic antibodies currently used in the clinic are based on the human IgG1 format, which is a bivalent molecule that efficiently interacts with the immune system's effector functions. In clinical applications where binding to the target alone is sufficient for therapeutic efficacy; however, engagement of the immune system is not required and may even cause unwanted side-effects. Likewise, bivalent binding to the target may negatively influence the therapeutic efficacy of an antibody. Here we discuss the state of the art for antibody-based therapeutics, designed to be nonactivating (i.e. do not engage the innate immune system's effector functions), in both monovalent and bivalent formats.

Cardiac toxicity: old and new issues in anti-cancer drugs

Although rare, cardiotoxicity is a significant complication of cancer treatment. The incidence and severity of cardiovascular side effects are dependent on the type of drugs used, dose and schedule employed, and age of patients, as well as the presence of coexisting cardiac diseases and previous mediastinal irradiation. Classically, anthracyclines are among one of the most active agents in oncology, but their use is often hampered by their cumulative dose-limiting cardiotoxicity. In the past decade, combination therapy with new drugs such as taxanes or anti- EGFR, and Her-2 therapy as a single agent have also resulted in unexpected cardiotoxicity. Cardiac damage can be secondary to an alteration of cardiac rhythm, changes in blood pressure and ischaemia, and can also alter the ability of the heart to contract and/or relax. The clinical spectrum of these toxicities can range from subclinical abnormalities to being catastrophic, life-threatening and sometimes fatal. Knowledge of this toxicity can aid clinicians to choose the optimal and least toxic regimen suitable for an individual patient. In this work we present an exhaustive review of the cardiovascular side effects associated to new anticancer drugs, from new formulations of anthracyclines to tyrosine kinase inhibitors and monoclonal antibodies.

Alemtuzumab in the treatment of chronic lymphocytic lymphoma

Alemtuzumab was the first monoclonal antibody to be humanized, a process which embeds rodent sequence fragments in a human IgG framework. The antibody target is CD52, an antigen expressed on normal lymphocytes as well as many T- and B-cell neoplasms. It therefore has a potential broad application across a spectrum of B- and T-cell malignancies as well as use as an immunosuppressant drug in, for example, bone marrow transplantation. The original licensing in the USA and Europe was for the treatment of fludarabine-refractory chronic lymphocytic leukemia (CLL). However, recent trials using alemtuzumab as a first-line agent for CLL have shown superior response rates compared with traditional alkylator therapy and this has led to US FDA approval for first-line treatment for CLL. It seems to be particularly useful in patients with CLL who have deletion of the TP53 tumor suppressor gene, a subset of disease that responds poorly to other currently available chemotherapeutics.

Non-infectious causes of elevated procalcitonin and C-reactive protein serum levels in pediatric patients with hematologic and oncologic disorders

BACKGROUND

Procalcitonin (PCT) is considered a sensitive and specific diagnostic and prognostic marker of systemic bacterial infection, but its value is questionable in certain clinical conditions, particularly in hemato-oncological patients.

MATERIALS AND METHODS

We analyzed PCT and C-reactive protein (CRP) levels in 56 patients of a pediatric hematology-oncology unit during 110 consecutive non-infectious febrile episodes related to administration of T-cell antibodies (group A; n = 22), alemtuzumab (monoclonal CD52 antibody, CAMPATH-1H/group B; n = 8), interleukin-2 (IL-2/group C; n = 41), prophylactic donor granulocyte transfusions (group D; n = 9), or to acute graft-versus-host disease (aGvHD/group E; n = 10) and compared the results with 20 episodes of Gram-negative sepsis (group F).

MAIN RESULTS

In the majority of the non-infectious episodes PCT and CRP increased to serum levels statistically indistinguishable from Gram-negative sepsis. Median peak levels of PCT (normal < 0.5 ng/ml)/CRP (normal < 8 mg/l) for groups A-F were 4.34/59.0 (A), 10.14/93.5 (B), 1.11/175.0 (C), 1.43/164 (D), 0.96/34.0 (E), and 8.14 ng/ml /126.0 mg/l (F). Highest single levels were observed in groups A and F.

CONCLUSIONS

PCT and CRP are of limited value as diagnostic markers of sepsis during T-cell-directed immunomodulatory treatment, granulocyte support, or acute GvHD.

Cytokine-Release Syndrome: Overview and Nursing Implications

Cytokine-release syndrome is a symptom complex associated with the use of many monoclonal antibodies. Commonly referred to as an infusion reaction, it results from the release of cytokines from cells targeted by the antibody as well as immune effector cells recruited to the area. When cytokines are released into the circulation, systemic symptoms such as fever, nausea, chills, hypotension, tachycardia, asthenia, headache, rash, scratchy throat, and dyspnea can result. In most patients, the symptoms are mild to moderate in severity and are managed easily. However, some patients may experience severe, life-threatening reactions that result from massive release of cytokines. Severe reactions occur more commonly during the first infusion in patients with hematologic malignancies who have not received prior chemotherapy; severe reactions are marked by their rapid onset and the acuity of associated symptoms. Massive cytokine release is an oncologic emergency, and special precautions must be taken to prevent life-threatening complications. This article will present an overview of the etiology and management of cytokine-release syndrome in patients receiving monoclonal antibodies to better prepare oncology nurses to safely care for such patients.

Immunostimulatory antibodies: Challenging the drug testing paradigm

The recently failed first-in-man clinical trial of TGN1412 raises concerns about whether the existing drug testing paradigm is suited to the safety assessment of drugs based on immunostimulatory antibodies that have complex and novel mechanisms of action. In particular, there is a need to consider whether animal studies are relevant and, if so, how the resulting information can be used to best inform clinical studies. The preclinical testing of TGN1412 is considered in relation to the selection of a suitable test species, deficiencies in an understanding of the similarities and differences between human and other primate immune functioning and species extrapolation. It is concluded that more emphasis should be placed on the development and use of in vitro and computational methods to identify potentially important species differences in the activity of immunostimulatory antibodies. Such approaches are useful with regards to species extrapolation, mechanistic studies and the design of both preclinical tests in animals and clinical studies in humans.

Adoptive therapy of head and neck squamous cell carcinoma with antibody coated immune cells: a pilot clinical trial

BACKGROUND

Catumaxomab is an antibody that binds with one arm epithelial cell adhesion molecule (EpCAM) positive tumors and with the other arm CD3+ T cells. Intravenous application of therapeutic antibodies may result in intravascular cytokine release.

AIM

In this pilot trial we assessed whether cytokine release can be controlled by ex vivo cell opsonization and cytokine wash-out before administration of catumaxomab, preserving its anti-cancer activity. In addition, preliminary data on safety of and clinical response to catumaxomab coated autologous immune cells were acquired.

METHODS

Peripheral blood mononuclear cells (PBMNC) of four patients with recurrent head and neck carcinoma were collected by leukapheresis, incubated ex vivo with catumaxomab for 24 h and cleared from released cytokines. Each patient received an escalated number of antibody-coated PBMNC equivalent to 1 x 10(4), 1 x 10(5), 1 x 10(6) and 1 x 10(7) CD3(+) cells/kgBW intravenously at bi-weekly intervals.

RESULTS

After opsonization, PBMNC released substantial amounts of interferon gamma (IFNgamma) and tumor necrosis factor alpha (TNFalpha) in vitro, which were removed before administration. Catumaxomab up-regulated CD25, CD69, and CD83 on PBMNC, and catumaxomab loaded PBMNC released IFNgamma and granzyme B when coincubated with EpCAM(+) BHY cells, suggesting cell activation and target directed biological activity. During the study period, one patient died of aspiration pneumonia and one patient needed a tracheotomy. Treatment related adverse events (AE) occurred at the highest cell dose in two patients, whereas 1 x 10(6) loaded CD3(+) cells/kgBW were well tolerated by all patients. One patient showed stable disease for 6 months and one patient is in complete remission for 27 months.

CONCLUSION

Ex vivo opsonization of PBMNC with catumaxomab provided biologically active, tumor targeting cells. Extracorporeal PBMNC coating may be an option to control intravascular cytokine release induced by therapeutic antibodies.

Drug insight: using monoclonal antibodies to treat multiple sclerosis

Multiple sclerosis (MS) is an immunopathological, presumably autoimmune, disease of the CNS. Several immunomodulatory treatments, including various preparations of interferon-beta, glatiramer acetate and mitoxantrone, have been approved for MS therapy. Because these agents are only partially effective, the search for better therapies continues. Therapeutic monoclonal antibodies (mAbs), a class of biotechnological agents, allow the precise targeting of molecules involved in pathological processes. Therapeutic mAbs have shown much promise in the treatment of many disorders, including inflammatory and putative autoimmune diseases such as MS. These agents have intrinsic limitations, however, such as induction of neutralizing 'anti-antibodies', systemic inflammatory reactions and severe adverse effects, some of which remain to be explained. Most notably, natalizumab (Tysabri), a mAb against alpha4 integrin, was very effective in suppressing MS activity, but had to be withdrawn from the market because several treated patients developed progressive multifocal leukoencephalopathy. This article reviews the state of development of various therapeutic mAbs for MS treatment.

Toxicity as a result of immunostimulation by biologics

The immune system has evolved highly effective mechanisms of surveillance and defense against foreign pathogens, and is also thought to act in surveillance and suppression of cancer. Thus, a predominant goal of immune system-based therapies is to normalize or enhance the host immune response in the areas of infectious disease and oncology. This review considers general approaches used for therapeutic immunostimulation, alterations in immune response mechanisms that occur with these treatments and the syndromes that commonly arise as a result of these changes. Because nonclinical studies of these therapies are conducted in animal models as the basis for predicting potential human toxicities, this review also considers the value of nonclinical testing to predict human toxicity.

Alemtuzumab (Campath-1H) in the treatment of chronic lymphocytic leukemia

Alemtuzumab (Campath-1H) is a humanized IgG1 monoclonal antibody that targets the human CD52 antigen. CD52 is expressed by a variety of lymphoid neoplasms and most human mononuclear cell subsets. In 2001, alemtuzumab was approved for marketing in the United States and Europe for use in patients with fludarabine-refractory chronic lymphocytic leukemia (CLL). In heavily pretreated patients with CLL, the overall response rate (ORR) is approximately 35%, and in previously untreated patients the ORR is greater than 80%, with a recent randomized study suggesting it is superior to alkylator-based therapy. Importantly, alemtuzumab is effective in patients with high-risk del(17p13.1) and del(11q22.3) CLL. Alemtuzumab combination studies with fludarabine and/or monoclonal antibodies such as rituximab have demonstrated promising results. Alemtuzumab is also being studied in CLL patients as consolidation therapy for treatment of minimal residual disease, in preparation for stem cell transplantation and to prevent acute and chronic graft versus host disease. Alemtuzumab is frequently associated with acute 'first-dose' reactions when administered intravenously, but is much better tolerated when administered subcutaneously without loss of therapeutic efficacy. Additional potential adverse events associated with alemtuzumab administration include myelosuppression as well as profound cellular immune dysfunction with the associated risk of viral reactivation and other opportunistic infections. Additional studies detailing the mechanism of action of alemtuzumab as well as new strategies for prevention of opportunistic infections will aid in the future therapeutic development of this agent.

Sodium channels and multiple sclerosis: roles in symptom production, damage and therapy

Our understanding of the potential role of sodium channels in multiple sclerosis (MS) has grown substantially in recent years. The channels have long had a recognized role in the symptomatology of the disease, but now also have suspected roles in causing permanent axonal destruction, and a potential role in modulating the intensity of immune activity. Sodium channels might also provide an avenue to achieve axonal and neuronal protection in MS, thereby impeding the otherwise relentless advance of permanent neurological deficit. The symptoms of MS are largely determined by the conduction properties of axons and these, in turn, are largely determined by sodium channels. The number, subtype and distribution of the sodium channels are all important, together with the way that channel function is modified by local factors, such as those resulting from inflammation (eg, nitric oxide). Suspicion is growing that sodium channels may also contribute to the axonal degeneration primarily responsible for permanent neurological deficits. The proposed mechanism involves intra-axonal sodium accumulation which promotes reverse action of the sodium/calcium exchanger and thereby a lethal rise in intra-axonal calcium. Partial blockade of sodium channels protects axons from degeneration in experimental models of MS, and therapy based on this approach is currently under investigation in clinical trials. Some recent findings suggest that such systemic inhibition of sodium channels may also promote axonal protection by suppressing inflammation within the brain.

Biologic therapies in rheumatology: lessons learned, future directions

During the past decade biologic therapies such as monoclonal antibodies and fusion proteins have revolutionized the management of rheumatic disease. By targeting key cytokines and immune cells biologics have provided more specific therapeutic interventions with less immunosuppression. Clinical use, however, has revealed that their theoretical simplicity hides a more complex reality. Efficacy, toxicity and even pharmacodynamic effects can deviate from those predicted, as poignantly illustrated by the catastrophic effects witnessed during the first-into-human administration of TGN1412. This review summarizes lessons gleaned from practical experience and discusses how these can inform future discovery and development of new biologic therapies for rheumatology.

Common variants in genes that mediate immunity and risk of multiple myeloma

Multiple myeloma (MM) is a B-cell malignancy characterized by aberrant immune function. Using genomic DNA extracted from 127 MM cases aged 21-84 years and 545 population-based controls, we examined the risk of MM associated with 82 common variants in 45 genes that mediate immunity among women of European American descent. Genotyping was determined using validated and optimized TaqMan assays. We estimated haplotype frequencies from unphased genotype data for 20 of these genes using the expectation-maximization progressive insertion algorithm. Compared with controls, MM risk was positively associated with homozygotes of single loci, IL4R (-28120T, rs2107356) and FCGR2A (-120G, rs1801274) (OR = 1.91, 95% CI 1.08-3.38 and 1.95, 95% CI 1.06-3.60, respectively). For genes in which linkage disequilibrium was observed between multiple loci, MM risk was positively associated with the haplotype block covering part of the LTA*TNF complex (LTA -82C/-90G *TNF -1036C/-487G/-417G, OR = 1.63, 95% CI 1.02-2.16) compared with the most frequently occurring haplotype observed among controls (LTA -82A/-90A *TNF -1036C/-487G/-417G). Our findings provide preliminary evidence that common genetic variants in specific immune-mediated pathways could influence the risk of MM.

Emerging monoclonal antibody therapies for multiple sclerosis

BACKGROUND

Monoclonal antibodies constitute a relatively new class of therapeutic agent designed to interact with specific target antigens. Monoclonal antibodies can be created to deplete cell lineages or antagonize receptors for which small molecule drugs are not available. Because of their accessibility, proteins expressed on the surface of immune system cell lineages are appealing targets for monoclonal antibody therapies.

REVIEW SUMMARY

To review monoclonal antibodies currently under investigation for treatment of multiple sclerosis (MS). This was a review of the literature and ongoing clinical trials. Alemtuzumab, daclizumab, rituximab, and natalizumab are monoclonal antibodies at different stages of clinical development that show promise as MS disease modifying therapies.

CONCLUSIONS

Several monoclonal antibodies directed against antigens present on the cell surface of immune system cell lines are promising candidates for immune suppression therapies in MS. Because these drugs are still in development, their clinical benefits and safety profiles are not fully established. Nevertheless, it seems possible that their specificity will offer advantages over broad-spectrum immune suppressing therapies.

Cytokine storm in a phase 1 trial of the anti-CD28 monoclonal antibody TGN1412

Six healthy young male volunteers at a contract research organization were enrolled in the first phase 1 clinical trial of TGN1412, a novel superagonist anti-CD28 monoclonal antibody that directly stimulates T cells. Within 90 minutes after receiving a single intravenous dose of the drug, all six volunteers had a systemic inflammatory response characterized by a rapid induction of proinflammatory cytokines and accompanied by headache, myalgias, nausea, diarrhea, erythema, vasodilatation, and hypotension. Within 12 to 16 hours after infusion, they became critically ill, with pulmonary infiltrates and lung injury, renal failure, and disseminated intravascular coagulation. Severe and unexpected depletion of lymphocytes and monocytes occurred within 24 hours after infusion. All six patients were transferred to the care of the authors at an intensive care unit at a public hospital, where they received intensive cardiopulmonary support (including dialysis), high-dose methylprednisolone, and an anti-interleukin-2 receptor antagonist antibody. Prolonged cardiovascular shock and acute respiratory distress syndrome developed in two patients, who required intensive organ support for 8 and 16 days. Despite evidence of the multiple cytokine-release syndrome, all six patients survived. Documentation of the clinical course occurring over the 30 days after infusion offers insight into the systemic inflammatory response syndrome in the absence of contaminating pathogens, endotoxin, or underlying disease.

Vasculitis and Biologic Infusion Therapies

Vasculitis is a heterogeneous group of uncommon, complex rheumatologic diseases. These diseases are known for their high mortality and morbidity rates due to the underlying disorders themselves, as well as complications of their conventional treatments. Oral and intravenous glucocorticosteroids and other immunosuppressive agents such as cyclophosphamide, methotrexate, and azathioprine are used to manage these diseases. These therapies are effective, but they have a global impact (often negative) on patients' immune systems and cause a number of nonimmunologic toxicities. They also are ineffective in inducing long-term remissions. Novel biologic infusion agents such as rituximab and infliximab are being prescribed off-label for some patients with vasculitis who have failed to respond to conventional therapy or because there are contraindications to standard-of-care treatments. This article provides an orientation to vasculitis, its standard of care, infusion biologics under investigation in these diseases, and the nursing implications for infusion professionals.

Strategies in the management of alemtuzumab-related side effects

B-cell chronic lymphocytic leukemia has traditionally been treated with alkylating agents and purine analogues. The introduction of alemtuzumab, a CD52 monoclonal antibody with significant clinical activity in chemotherapy refractory B-cell chronic lymphocytic leukemia, is accompanied by a side effect profile different from that resulting from chemotherapy. The intravenous administration of alemtuzumab is usually accompanied by transient infusion-related side effects manifesting primarily as flu-like symptoms. These reactions can be reduced by use of corticosteroid prophylaxis, and will subside gradually during continued treatment. Alternatively, administration of alemtuzumab subcutaneously may markedly reduce the occurrence of general side effects but results in limited transient local skin reactions in most patients. Neutropenia (grade 4) may occur in approximately 20% of patients, but is usually transient and/or responds promptly to colony stimulating factor therapy; episodes of febrile neutropenia are infrequent. The major side effect of alemtuzumab is T-cell depletion, leading to an increased risk of infection, in particular reactivation of cytomegalovirus. This event typically occurs 3 to 8 weeks after initiation of therapy, coinciding with the T-cell nadir. With vigilance and early detection, these infections are usually manageable and do not cause organ failure. Preliminary data indicate that other infections following alemtuzumab therapy do not seem to occur at a frequency that is higher than expected, probably because of the general prophylactic use of cotrimoxazole (trimethoprim and sulfamethoxazole) and valacyclovir in combination with clinical tumor regressions. The overall safety profile of alemtuzumab appears to be beneficial in relation to disease severity and prognosis in patients with fludarabine-refractory B-cell chronic lymphocytic leukemia.

Cancer immunotherapy

Cancer is the second leading cause of death in the industrialized world. Most cancer patients are treated by a combination of surgery, radiation and/or chemotherapy. Whereas the primary tumor can, in most cases, be efficiently treated by a combination of these standard therapies, preventing the metastatic spread of the disease through disseminated tumor cells is often not effective. The eradication of disseminated tumor cells present in the blood circulation and micro-metastases in distant organs therefore represents another promising approach in cancer immunotherapy. Main strategies of cancer immunotherapy aim at exploiting the therapeutic potential of tumor-specific antibodies and cellular immune effector mechanisms. Whereas passive antibody therapy relies on the repeated application of large quantities of tumor antigen-specific antibodies, active immunotherapy aims at the generation of a tumor-specific immune response combining both humoral and cytotoxic T cell effector mechanisms by the host's immune system following vaccination. In the first part of this review, concurrent developments in active and passive cancer immunotherapy are discussed. In the second part, the various approaches for the production of optimized monoclonal antibodies used for anti-cancer vaccination are summarized.

Development of Antibodies and Chimeric Molecules for Cancer Immunotherapy

Monoclonal antibodies are among the most rapidly expanding class of therapeutics for cancer treatment. Monoclonal antibodies targeting non-Hodgkin's lymphoma (NHL), Her-2/neu highly expressing metastatic breast cancer, colorectal cancer, acute myelogenous leukemia, and B-cell chronic lymphocytic leukemia (CLL) have received FDA approval. Promising new targets for antibody therapy include cellular growth factor receptors, mediators of tumor-driven neo-angiogenesis, as well as host negative immunoregulatory checkpoints that impede an effective immune response to neoplasia. Antibody efficacy has been increased by genetic engineering to humanize the antibodies and to increase their effector functions including antibody dependent cellular cytotoxicity. Furthermore, antibodies have been armed with cytokines, chemotherapeutic agents, toxins, and radionuclides to augment their efficacy as tumor cytotoxic agents. As a consequence of these advances, 30 years after their first development, monoclonal antibodies have become an important standard approach for the therapy of neoplasia with 19 therapeutic monoclonal antibodies now approved by the FDA including 8 for the treatment of cancer.

Antitumor Activity in Melanoma and Anti-Self Responses in a Phase I Trial With the Anti-Cytotoxic T Lymphocyte–Associated Antigen 4 Monoclonal Antibody CP-675,206

Purpose

Cytotoxic T lymphocyte–associated antigen 4 (CTLA4) blockade with CP-675,206, a fully human anti-CTLA4 monoclonal antibody, may break peripheral immunologic tolerance leading to effective immune responses to cancer in humans. A phase I trial was conducted to test the safety of CP-675,206.

Patients and Methods

Thirty-nine patients with solid malignancies (melanoma, n = 34; renal cell, n = 4; colon, n = 1) received an intravenous (IV) infusion of CP-675,206 at seven dose levels. The primary objective was to determine the maximum-tolerated dose and the recommended phase II dose.

Results

Dose-limiting toxicities and autoimmune phenomena included diarrhea, dermatitis, vitiligo, panhypopituitarism and hyperthyroidism. Two patients experienced complete responses (maintained for 34+ and 25+ months), and there were two partial responses (26+ and 25+ months) among 29 patients with measurable melanoma. There have been no relapses thus far after objective response to therapy. Four other patients had stable disease at end of study evaluation (16, 7, 7, and 4 months). Additionally, five patients had extended periods without disease progression (36+, 35+, 26+, 24+, and 23+ months) after local treatment of progressive metastases. Longer systemic exposure to CP-675,206 achieved in higher dose cohorts predicted for a higher probability of response.

Conclusion

CP-675,206 can be administered safely to humans as a single IV dose up to 15 mg/kg, resulting in breaking of peripheral immune tolerance to self-tissues and antitumor activity in melanoma.

Tolerability and safety of rituximab (MabThera)

Rituximab, a human/mouse chimeric anti-CD20 antibody, has become part of standard therapy for patients with CD20-expressing B-cell lymphoma, and is currently under investigation for other indications including autoimmune diseases, in particular rheumatoid arthritis (RA). Its characteristic tolerability profile was established soon after clinical testing began and compares favourably with chemotherapy. The majority of patients experience mild to moderate infusion-related reactions (IRRs) during the first administration of rituximab, but the incidence decreases markedly with subsequent infusions. Current data suggest that the type of adverse events in patients with RA are similar to those in lymphoma, but that adverse events related to the rituximab infusions are less severe and less frequent. Rituximab induces a rapid depletion of normal CD20-expressing B-cells in the peripheral blood, and levels remain low or undetectable for 2-6 months before returning to pretreatment levels, generally within 12 months. Serum immunoglobulin levels remain largely stable, although a reduction in IgM has been described. T-cells are unaffected by rituximab and consequently opportunistic infections rarely occur in association with rituximab therapy. When used in combination with a variety of chemotherapeutic regimens, rituximab does not add to the toxicity of chemotherapy, with the exception of a higher rate of neutropenia. However, this does not translate into a higher infection rate. Over 540,000 patients worldwide have now received rituximab and serious adverse reactions have occurred in a small minority of patients, but for the great majority of patients, rituximab is safe and well tolerated.

Fatal intra-alveolar hemorrhage after rituximab in a patient with non-Hodgkin lymphoma

A 65-year-old male developed progressive dry cough and digital clubbing after starting rituximab-CHOP chemotherapy for non-Hodgkin lymphoma. A lung biopsy showed loose non-necrotic granulomas in a background of mild fibrosis and rare eosinophils, compatible with a drug-induced hypersensitivity pneumonia. Associated manifestations of this hypersensitivity reaction were a high eosinophil count, elevated serum levels of immunoglobulin E, and a skin rash consistent with pigmented purpuric dermatitis (Schamberg disease). Corticosteroids were marginally efficacious in treating this reaction. Few similar reactions have since been described, 2 of them ultimately fatal, but none was associated with pulmonary hemorrhage. A 2.5:1 ratio between the interstitial alveolar T4/T8 lymphocytes in our case is similar to the findings in methotrexate-induced pneumonitis and farmer lung disease. This report documents the serologic and immunohistologic findings associated with a pulmonary interstitial reaction to rituximab. A review of the pertinent literature is provided. The possible pathogenetic mechanisms, including the role of cytokines, cytotoxic T-lymphocytes and CD 20 positive T-cells in relation to the administration of rituximab are discussed.

In Vitro Depletion of Tissue-Derived Dendritic Cells by CMRF-44 Antibody and Alemtuzumab: Implications for the Control of Graft-Versus-Host Disease

Graft-versus-host disease (GvHD), a life-threatening complication of bone marrow transplantation, is initiated by donor T cells reacting to recipient dendritic cells (DC). GvHD can be controlled by attenuating donor T cells, but few strategies exist to target DC, particularly resident tissue DC, despite recent evidence of their importance. In this report, CMRF-44, a mouse monoclonal IgM reactive to human DC, is tested against human Langerhans cells (LC) in vitro. CMRF-44 antigen is expressed at low level on fresh LC but is up-regulated 40-60-fold during migration. CMRF-44 and complement kill more than 97% of migratory LC in vitro and inhibit allostimulation by LC up to 95%. In comparison, alemtuzumab, which binds CD52, reacts weakly with primary LC and fails to induce significant lysis with complement (less than 5%). These results highlight the potential of new therapeutic antibodies active against tissue DC to control graft-versus-host reactions.

Alemtuzumab in the Treatment of Chronic Lymphocytic Leukemia

Alemtuzumab is a humanized therapeutic monoclonal antibody (MAb) that recognizes the CD52 antigen, expressed on normal and neoplastic lymphocytes, monocytes, and natural killer cells. In 2001, alemtuzumab was approved in the US and Europe to treat B-cell chronic lymphocytic leukemia (CLL) that had been treated previously with alkylating agents and was refractory to fludarabine. In heavily pretreated patients this MAb is able to produce response rates of about 40%, and in symptomatic, previously untreated patients response rates of more than 80% can be achieved. Alemtuzumab can also be used in patients with CLL as a preparative regimen for stem cell transplantation (SCT) and to prevent graft versus host disease. Moreover its in vivo use before or after SCT may also potentially result in depletion of residual leukemia cells, especially in the autologous setting. Adverse events associated with alemtuzumab include acute first-dose reaction, hematologic toxicity, and infectious complications. Usually they are predictable, manageable, and acceptable in the context of CLL. However, in a significant percentage of patients, cytomegalovirus reactivation occurs during alemtuzumab therapy, and routine weekly monitoring with the polymerase chain reaction methodology is indicated. Moreover, antiviral and antibacterial prophylaxis is mandatory.