Monoclonal antibody therapy for B-cell lymphoma

Treatment strategies and outcomes for patients with non-Hodgkin's lymphoma (NHL) are undergoing rapid and important evolution. We have recently witnessed the advent of novel targeted therapies, such as gene therapies, active immunotherapies, antisense therapies, new small molecules and biologicals, and monoclonal antibodies (MoAbs). The first MoAb approved for the treatment of cancer, rituximab, was approved in 1997 and has been rapidly incorporated into treatment regimens for NHL. In a randomized trial in combination with CHOP chemotherapy (cyclophosphamide, hydroxydaunomycin, vincristine, and prednisone), rituximab showed superiority to CHOP for patients with diffuse large cell NHL (DLCL).The rituximab + CHOP combination has become the gold standard for frontline therapy for DLCL and has shown significant activity in the management of follicular NHL. In February 2002, the first radioimmunotherapeutic agent for the treatment of cancer, ibritumomab tiuxetan (Zevalin), was approved. Ibritumomab tiuxetan, an yttrium-labeled antibody used in conjunction with rituximab, has significant activity in follicular and transformed NHL. Use of rituximab has proved that antibodies are safe and active even as single agents. The results have helped dispel the negativity and biases resulting from many years of disappointing results in this important area of research. Results with rituximab have opened the doors to continued research and have provided the impetus necessary for renewed enthusiasm and optimism in continuing the search for curative regimens for patients with NHL.     

Combination immunotherapy with rituximab and interleukin 2 in patients with relapsed or refractory follicular non-Hodgkin's lymphoma

Rituximab has significant activity as a single agent in the treatment of follicular non-Hodgkin's lymphoma (NHL). Interleukin 2 (IL-2) is a lymphokine that increases effector cell number. In an effort to augment antibody-dependent cell-mediated cytotoxicity (ADCC) associated with rituximab therapy, low-dose IL-2 was added to a standard rituximab regimen and patients were evaluated for safety and efficacy. Twenty patients with relapsed or refractory follicular NHL were treated with IL-2 (1.2 MIU/m(2)/d for 56 d subcutaneously) as outpatients. Rituximab (375 mg/m(2)) was given on d 15, 22, 29 and 36. The regimen was well tolerated and only three patients required dose adjustments in IL-2. Infusional toxicity associated with rituximab was not exacerbated by IL-2. Peripheral blood immunophenotyping demonstrated significant increases in circulating CD8+ and CD56+ lymphocytes in all evaluable patients (P = 0.0002). Increases in total eosinophil number were observed in all patients. Eleven patients responded to therapy, for an overall response rate of 55%. Four additional patients had stable disease. For these 15 patients, the median time to progression exceeded 13 months. We conclude concomitant cytokine therapy to enhance ADCC with monoclonal antibody therapy was well tolerated and did not exacerbate antibody-related infusional toxicity. Further studies of this rational combination are warranted and ongoing.     

Rituximab therapy in Waldenstrom's macroglobulinemia: Preliminary evidence of clinical activity

To assess the preliminary efficacy of rituximab therapy in Waldenstrom's macroglobulinemia (WM), we examined the clinical and laboratory data for all patients with WM treated on IDEC Pharmaceuticals sponsored trials and one patient treated at Walter Reed Army Medical Center. Seven symptomatic patients with WM were treated with four (n = 6) or eight (n = 1) weekly infusions of rituximab (375 mg/m²). Patients had received a median of three prior therapies (range 1–4) which included alkylator therapy in all (five patients refractory) and fludarabine in four (all refractory). Therapy was tolerated well in all patients without decrement in cellular immune function or significant infectious morbidity. Partial responses were noted in three of these patients, including two with fludarabine-refractory disease. The median progression-free survival for these patients was 6.6 months (range 2.2–29+ months). These data suggest that rituximab has clinical activity in heavily pre-treated patients with Waldenstrom's macroglobulinemia. Based on these data, clinical studies of Rituximab in previously untreated and treated WM appear indicated.     

Current approaches to treatment of antibody-mediated rejection

Antibody-mediated rejection (AMR) has recently been recognized as a significant and unique form of rejection that is not amenable to treatment with standard immunosuppressive medications aimed at modification of T-cell function. Recent interest in AMR and the role of B cells in rejection has been aided by the concomitant discovery that C4d staining of renal biopsy tissue is strongly associated with AMR and a poor prognosis, and the emergence of desensitization protocols for treatment of highly human leukocyte antigen (HLA)-sensitized patients. Treatment options include: (i) the use of high-dose intravenous immunoglobulin (IVIG) which works by blocking anti-HLA antibody activity and through complement inhibition, (ii) the use of Rituxan (anti-CD20 chimeric antibody) to deplete B cells and interfere with antigen-presenting cell (APC) activity of B cells subsequently decreasing T-cell activation, and (iii) the use of plasmapheresis (PE) + anti-cytomegalovirus (CMV) immunoglobulin G (IgG) or IVIG in lower doses. This protocol removes deleterious anti-HLA antibodies and may also allow complexing of anti-HLA with anti-idiotypes in the anti-CMV IgG. Although early, data support the efficacy of all three approaches. Many centers are now designing protocols that utilize a combination of all three agents. In summary, recent advances in the diagnosis and treatment of AMR has allowed for significant improvements in outcomes of a condition usually associated with rapid graft failure. However, much work needs to be done to better understand the immunologic processes leading to AMR and how current therapies can be best used to effectively prevent and treat it.     

Immunotherapy of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is typically an indolent B-cell malignancy, primarily affecting the aging population. Standard cytotoxic treatment with alkylating agents or purine analogs is very effective at inducing remission. However, curative treatment is not yet available. Immunotherapy is emerging as an exciting modality with significant potential to advance the treatment of this disease. This review discusses the different modalities of immunotherapy under investigation for the treatment of CLL. These modalities include passive immunotherapy with monoclonal antibodies against antigens on CLL B-cells including CD52 and CD20. Active immunotherapy by vaccination with genetically modified autologous leukemia cells is being evaluated in clinical trials. Allogeneic stem cell transplant for adoptive immunotherapy of CLL is yet another modality being investigated. While this modality may have limited application due to morbidity in older patients, it may result in improved survival and possibly cure. The use of immunotherapy in CLL is in the early stages of development. It is likely that this approach will significantly improve the treatment of CLL and possibly contribute to the cure of this disease.     

Stopping oral steroid-sparing agents at initiation of rituximab in myasthenia gravis

Rituximab is a chimeric monoclonal antibody that binds CD20 and causes the depletion of B-cell subsets. Although initially designed to treat lymphoma, it has found wide use in the management of various autoimmune conditions, including myasthenia gravis (MG), an autoimmune disorder of the neuromuscular junction. Treated myasthenia patients are often on an oral steroid-sparing agent. To determine the safety of stopping oral steroid-sparing agents at the initiation of rituximab therapy and its effectiveness we reviewed the records of 27 MG patients with rituximab, including 13 with anti-MuSK+ MG, 10 with anti-AChR+ MG, and 4 double seronegative MG patients. All patients that were on an oral steroid-sparing agent (21 of 27) were able to stop it, and they did not require re-introduction of the medication. Also, the daily prednisone dosage was significantly decreased in 20/24 patients across all three serotype groups. MGFA post intervention status analysis also showed 15/27 of all patients achieved minimal manifestation status or remission across all groups. Antibody titers decreased dramatically and promptly in anti-MuSK+ MG patients. Our data suggests that stopping oral steroid-sparing agents at initiation of rituximab therapy is safe. Also, our data indicates that rituximab is highly effective in the management of seropositive MG patients.     

小剂量利妥昔单抗对难治性免疫性血小板减少症患者凝血功能及预后的影响

目的研究小剂量利妥昔单抗对难治性免疫性血小板减少症(r ITP)患者凝血功能及预后的影响。方法选取我院2010年12月至2014年12月r ITP患者78例,抽签随机分为观察组和对照组两组,每组39例,对照组患者给予常规剂量利妥昔单抗375 mg/m~2,观察组患者给予小剂量利妥昔单抗100 mg/m~2,比较两组患者临床疗效、复发率,治疗前后血小板计数(PLT)、凝血酶原时间(PT)、部分凝血活酶时间(a PTT)变化情况,血清免疫球蛋白Ig A、Ig M、Ig G和淋巴细胞CD3~+、CD4~+的水平变化及不良反应发生率。结果观察组治疗有效率为64.10%、复发率为5.13%与对照组比较53.85%、7.69%无统计学意义(P0.05);与治疗前比较两组患者的PLT水平较治疗前显著较高(P0.05),PT、a PTT水平较治疗前显著较低(P0.05);观察组Ig M水平较对照组显著较低(P0.05),Ig A、Ig G、CD3~+、CD4~+水平较对照组显著较高(P0.05);观察组患者的不良反应发生率为10.26%较对照组28.21%显著较低(P0.05)。结论常规剂量和小剂量利妥昔单抗治疗r ITP患者均有显著疗效,复发率低,有利于凝血功能的恢复,小剂量给予利妥昔单抗治疗安全性更高。     

Rituxan (anti-CD20 antibody)-induced translocation of CD20 into lipid rafts is crucial for calcium influx and apoptosis

Rituxan, a chimeric anti-CD20 antibody, is the first antibody approved for immunotherapy in non-Hodgkin's B-cell lymphoma and other B-cell lymphoproliferative disorders. Additionally, efficacy of Rituxan treatment has been reported in nonmalignant autoimmune diseases such as rheumatoid arthritis. Crosslinking of CD20 molecules by Rituxan induces therapeutic B-cell depletion. CD20 is a B-lymphocyte specific integral membrane protein, proposed to function as a store-operated calcium channel, which is activated upon receptor-stimulated calcium depletion of intracellular stores. Crosslinking of CD20 by antibodies has been reported to induce a redistribution of CD20 molecules to specialized microdomains at the plasma membrane known as lipid rafts. Here, we report that in the absence of Rituxan, CD20 exhibits a low affinity to lipid rafts. However, binding of Rituxan significantly increases the affinity of CD20 for lipid rafts resulting in its redistribution to a fraction resistant to Triton X-100 solubilization. Furthermore, we demonstrate that disturbing the raft integrity by cholesterol extraction results in dissociation of CD20 from a Triton X-100 resistant fraction followed by complete inhibition of Rituxan-induced calcium entry and apoptosis. The integrity of lipid rafts seems to play a crucial role for CD20-induced caspase activation. These data show, for the first time, that Rituxan-induced translocation of CD20 to lipid rafts is important for increased intracellular Ca(2+) levels and downstream apoptotic signalling.     

Antibody-based therapeutics in oncology

The recent clinical and commercial success of anticancer antibodies, such as rituximab (Rituxan®) and trastuzumab (Herceptin®) has created great interest in antibody-based therapeutics for hematopoietic malignancies and solid tumors. Given the likely lower toxicity for antibodies versus small molecules, the potential increase in efficacy by conjugation to radioisotopes and other cellular toxins and the ability to characterize the target with clinical laboratory diagnostics to improve the drug's clinical performance, it is anticipated that current and future antibody therapeutics will find substantial roles alone and in combination therapy strategies for the treatment of patients with cancer. It is also likely that conjugation strategies will add new radiolabeled and toxin-linked products to the market to complement the recent approvals of ibritumomab tiuxetan (Zevalin?) and gemtuzumab ozogamycin (Mylotarg®). However, although there are a large number of agents in both early and later stages of clinical development, only a handful will make it through regulatory approval and become successful products. This review considers the structure of anticancer therapeutic antibodies, the techniques used to reduce their antigenicity, factors that influence efficacy and toxicity, conjugation with isotopes and toxins and antibody target validation.     

Radiation-guided drug delivery systems

A primary limiting factor for cancer treatment is normal tissue toxicity. Targeted cancer treatment can potentially maximize cancer cure and minimize normal tissue toxicity. Physical energy can be used to activate inert oncologic drugs. X-rays have an advantage over other forms of physical energy because tissue penetration and precise localization can be achieved. Radiation can be used to control drug delivery through radiation-inducible gene therapy. Radiation-guided drug delivery systems involve the targeting of immunoconjugates to radiation-inducible neoantigens induced by irradiation of neoplasms. Magnetic fields can compliment these technologies by drawing magnetic particles containing oncologic drugs toward an externally applied magnetic field. The field of targeted drug delivery by use of external radiation fields will ultimately bring new delivery systems into clinical trials. This review highlights radiation-guided cancer drug delivery systems, at preclinical and clinical stages of development, to tumors and tumor blood vessels.