Phase 1 Study of Lumiliximab with Detailed Pharmacokinetic and Pharmacodynamic Measurements in Patients with Relapsed or Refractory Chronic Lymphocytic Leukemia

Extracellular targeted protein degradation: an emerging modality for drug discovery

Targeted protein degradation (TPD) has emerged in the past decade as a major new drug modality to remove intracellular proteins with bispecific small molecules that recruit the protein of interest (POI) to an E3 ligase for degradation in the proteasome. Unlike classic occupancy-based drugs, intracellular TPD (iTPD) eliminates the target and works catalytically, and so can be more effective and sustained, with lower dose requirements. Recently, this approach has been expanded to the extracellular proteome, including both secreted and membrane proteins. Extracellular targeted protein degradation (eTPD) uses bispecific antibodies, conjugates or small molecules to degrade extracellular POIs by trafficking them to the lysosome for degradation. Here, we focus on recent advances in eTPD, covering degrader systems, targets, molecular designs and parameters to advance them. Now almost any protein, intracellular or extracellular, is addressable in principle with TPD.

Recent Advances in Translational Pharmacokinetics and Pharmacodynamics Prediction of Therapeutic Antibodies Using Modeling and Simulation

Therapeutic monoclonal antibodies (mAbs) have been a promising therapeutic approach for several diseases and a wide variety of mAbs are being evaluated in clinical trials. To accelerate clinical development and improve the probability of success, pharmacokinetics and pharmacodynamics (PKPD) in humans must be predicted before clinical trials can begin. Traditionally, empirical-approach-based PKPD prediction has been applied for a long time. Recently, modeling and simulation (M&S) methods have also become valuable for quantitatively predicting PKPD in humans. Although several models (e.g., the compartment model, Michaelis–Menten model, target-mediated drug disposition model, and physiologically based pharmacokinetic model) have been established and used to predict the PKPD of mAbs in humans, more complex mechanistic models, such as the quantitative systemics pharmacology model, have been recently developed. This review summarizes the recent advances and future direction of M&S-based approaches to the quantitative prediction of human PKPD for mAbs.

Elimination of plasma soluble antigen in cynomolgus monkeys by combining pH-dependent antigen binding and novel Fc engineering

A conventional antibody targeting a soluble antigen in circulation typically requires a huge dosage and frequent intravenous administration to neutralize the antigen. This is because antigen degradation is reduced by the formation of antigen–antibody immune complexes, which escape from lysosomal degradation using neonatal Fc receptor (FcRn)-mediated recycling. To address this, we developed an antigen-sweeping antibody that combines pH-dependent antigen binding and Fc engineering to enhance Fc receptor binding. The sweeping antibody actively eliminates the plasma antigens by increasing the cellular uptake of the immune complex and dissociating the antigens in the acidic endosome for degradation. Strong antigen sweeping can reduce the dosage, potentially achieve higher efficacy, and expand the scope of antigen space available for targeting by antibodies. In this study, to further improve the sweeping efficacy, we developed a novel antibody Fc variant by enhancing Fcγ receptor IIb (FcγRIIb) binding and modulating charge characteristics for increased cellular uptake of the immune complex, together with enhancing FcRn binding for efficient salvage of the antigen-free antibodies. Our Fc variant achieved strong antigen sweeping in cynomolgus monkeys with antibody pharmacokinetics comparable to a wild-type human IgG₁ antibody. The positive-charge substitutions enhanced uptake of the immune complex by FcγRIIb-expressing cells in vitro, which was completely inhibited by an anti-FcγRIIb antibody. This suggests that the strong in vivo sweeping efficacy improved by the charge engineering is more likely achieved by FcγRIIb-dependent uptake of the immune complex rather than nonspecific uptake. We expect this novel Fc engineering can maximize the antigen sweeping efficacy even in humans and create novel therapeutic antibodies that meet unmet medical needs for patients.

pH-responsive antibodies for therapeutic applications

Therapeutic antibodies are instrumental in improving the treatment outcome for certain disease conditions. However, to enhance their efficacy and specificity, many efforts are continuously made. One of the approaches that are increasingly explored in this field are pH-responsive antibodies capable of binding target antigens in a pH-dependent manner. We reviewed suitability and examples of these antibodies that are functionally modulated by the tumor microenvironment. Provided in this review is an update about antigens targeted by pH-responsive, sweeping, and recycling antibodies. Applicability of the pH-responsive antibodies in the engineering of chimeric antigen receptor T-cells (CAR-T) and in improving drug delivery to the brain by the enhanced crossing of the blood-brain barrier is also discussed. The pH-responsive antibodies possess strong treatment potential. They emerge as next-generation programmable engineered biologic drugs that are active only within the targeted biological space. Thus, they are valuable in targeting acidified tumor microenvironment because of improved spatial persistence and reduced on-target off-tumor toxicities. We predict that the programmable pH-dependent antibodies become powerful tools in therapies of cancer.

SKY59, A Novel Recycling Antibody for Complement-mediated Diseases

BACKGROUND

The complement system usually helps protect against microbial infection, but it could also be involved in the onset of various diseases. Inhibition of complement component 5 (C5) with eculizumab has resulted in a significant reduction of hemolysis, reduction of thromboembolic events, and increased survival in patients with Paroxysmal Nocturnal Hemoglobinuria (PNH). However, eculizumab requires frequent intravenous infusions due to the abundance of C5 in plasma and some patients may still experience breakthrough hemolysis. This review introduces the recent body of knowledge on recycling technology and discusses the likely therapeutic benefits of SKY59, a novel recycling antibody, for PNH and complement-mediated disorders.

METHODS

By using recycling technology, we created a novel anti-C5 antibody, SKY59, capable of binding to C5 pH-dependently.

RESULTS

In cynomolgus monkeys, SKY59 robustly inhibited C5 and complement activity for significantly longer than a conventional antibody. SKY59 also showed an inhibitory effect on C5 variant p.Arg885His, whereas eculizumab does not suppress complement activity in patients with this type of mutation.

CONCLUSION

SKY59 is a promising anti-C5 biologic agent that has significant advantages over current therapies such as long duration of action and efficacy against C5 variants.

Strategies for clinical development of monoclonal antibodies beyond first-in-human trials: tested doses and rationale for dose selection

BACKGROUND

Our previous survey on first-in-human trials (FIHT) of monoclonal antibodies (mAbs) showed that, due to their limited toxicity, the recommended phase II dose (RP2D) was only tentatively defined.

METHODS

We identified, by MEDLINE search, articles on single-agent trials of mAbs with an FIHT included in our previous survey. For each mAb, we examined tested dose(s) and dose selection rationale in non-FIHTs (NFIHTs). We also assessed the correlation between doses tested in the registration trials (RTs) of all FDA-approved mAbs and the corresponding FIHT results.

RESULTS

In the 37 dose-escalation NFIHTs, the RP2D indication was still poorly defined. In phase II-III NFIHTs (n=103 on 37 mAbs), the FIHT RP2D was the only dose tested for five mAbs. For 16 mAbs, only doses different from the FIHT RP2D or the maximum administered dose (MAD) were tested and the dose selection rationale infrequently indicated. In the 60 RTs on 27 FDA-approved mAbs with available FIHT, the FIHT RP2D was tested only for two mAbs, and RT doses were much lower than the FIHT MAD.

CONCLUSIONS

The rationale beyond dose selection in phase II and III trials of mAbs is often unclear in published articles and not based on FIHT data.

Neutralization of Botulinum Neurotoxin Type E by a Humanized Antibody

Botulinum neurotoxins (BoNTs) cause botulism and are the deadliest naturally-occurring substances known to humans. BoNTs have been classified as one of the category A agents by the Centers for Disease Control and Prevention, indicating their potential use as bioweapons. To counter bio-threat and naturally-occurring botulism cases, well-tolerated antibodies by humans that neutralize BoNTs are relevant. In our previous work, we showed the neutralizing potential of macaque (Macaca fascicularis)-derived scFv-Fc (scFv-Fc ELC18) by in vitro endopeptidase immunoassay and ex vivo mouse phrenic nerve-hemidiaphragm assay by targeting the light chain of the botulinum neurotoxin type E (BoNT/E). In the present study, we germline-humanized scFv-Fc ELC18 into a full IgG hu8ELC18 to increase its immunotolerance by humans. We demonstrated the protection and prophylaxis capacity of hu8ELC18 against BoNT/E in a mouse model. A concentration of 2.5 ng/mouse of hu8ELC18 protected against 5 mouse lethal dose (MLD) in a mouse protection assay and complete neutralization of 1 LD50 of pure BoNT/E toxin was achieved with 8 ng of hu8ELC18 in mouse paralysis assay. Furthermore, hu8ELC18 protected mice from 5 MLD if injected up to 14 days prior to intraperitoneal BoNT/E administration. This newly-developed humanized IgG is expected to have high tolerance in humans.

Development of Germline-Humanized Antibodies Neutralizing Botulinum Neurotoxin A and B

Botulinum neurotoxins (BoNTs) are counted among the most toxic substances known and are responsible for human botulism, a life-threatening disease characterized by flaccid muscle paralysis that occurs naturally by food poisoning or colonization of the gastrointestinal tract by BoNT-producing clostridia. To date, 7 serologically distinct serotypes of BoNT (serotype A-G) are known. Due to the high toxicity of BoNTs the Centers for Disease Control and Prevention (CDC) have classified BoNTs as category A agent, including the six biological agents with the highest potential risk of use as bioweapons. Well tolerated antibodies neutralizing BoNTs are required to deal with the potential risk. In a previous work, we described the development of scFv and scFv-Fc (Yumab) from macaque origin (Macaca fascicularis) neutralizing BoNT/A and B by targeting the heavy and light chain of each serotype. In the present study, we humanized the macaque antibodies SEM120-IIIC1 (anti-BoNT/A light chain), A1HC38 (anti-BoNT/A heavy chain), BLC3 (anti-BoNT/B light chain) and B2-7 (anti-BoNT/B heavy chain) by germline-humanization to obtain a better potential immunotolerance in humans. We increased the Germinality Index (GI) of SEM120-IIIC1 to 94.5%, for A1HC38, to 95% for BLC3 and to 94.4% for B2-7. Furthermore, the neutralization efficacies of the germline-humanized antibodies were analyzed in lethal and non-lethal in vivo mouse assays as full IgG. The germline-humanized IgGs hu8SEM120-IIIC1, hu8A1HC38, hu8BLC3 and hu8B2-7 were protective in vivo, when anti-heavy and anti-light chain antibodies were combined. The synergistic effect and high humanness of the selected IgGs makes them promising lead candidates for further clinical development.

An update on current and prospective immunotherapies for chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common leukemia. Combined agent chemotherapy is the current standard front-line treatment for physically fit patients with CLL. Use of chemotherapy can be complicated by significant toxicity, especially in patients with advanced age or comorbid conditions. Moreover, patients may relapse and become refractory to further chemotherapy. Immunotherapy targets the aberrant immunological processes in CLL without the toxicity of chemotherapy. Immunotherapeutic strategies can also be combined with chemotherapy to improve response rates in this incurable disease. In this review, we evaluate current and future immune-based options in the treatment of CLL.

Targeted therapies for CLL: Practical issues with the changing treatment paradigm

Chemoimmunotherapy (CIT) such as FCR (fludarabine, cyclophosphamide, rituximab) has been the standard first-line therapy for younger patients with CLL. In the last few years, several novel targeted therapies have been developed for patients with CLL. These include B-cell receptor (BCR) inhibitors such as Bruton tyrosine kinase (BTK) inhibitors, PI3 kinase inhibitors, and Syk inhibitors, novel anti-CD20 monoclonal antibodies such as ofatumumab and obinutuzumab, and Bcl-2 antagonists such as venetoclax (ABT-199). Strategies targeting the immune system such as lenalidomide, chimeric antigen receptor (CAR) T cells, and more recently, checkpoint inhibitors, are in clinical development. Ibrutinib and idelalisib are already approved for patients with relapsed and refractory CLL. Ibrutinib is also approved for first-line treatment of CLL patients with del(17p). Several ongoing phase III clinical trials with novel therapies will further define the role of targeted agents in CLL.

Inhibitory FcγRIIb-Mediated Soluble Antigen Clearance from Plasma by a pH-Dependent Antigen-Binding Antibody and Its Enhancement by Fc Engineering

Fc engineering can modulate the Fc-FcγR interaction and thus enhance the potency of Abs that target membrane-bound Ags, but it has not been applied to Abs that target soluble Ags. In this study, we revealed a previously unknown function of inhibitory FcγRII in vivo and, using an Ab that binds to Ag pH dependently, demonstrated that the function can be exploited to target soluble Ag. Because pH-dependent Ab dissociates Ag in acidic endosome, its Ag clearance from circulation reflects the cellular uptake rate of Ag/Ab complexes. In vivo studies showed that FcγR but not neonatal FcR contributes to Ag clearance by the pH-dependent Ab, and when Fc binding to mouse FcγRII and III was increased, Ag clearance was markedly accelerated in wild-type mice and FcR γ-chain knockout mice, but the effect was diminished in FcγRII knockout mice. This demonstrates that mouse FcγRII efficiently promotes Ab uptake into the cell and its subsequent recycling back to the cell surface. Furthermore, when a human IgG1 Fc variant with selectively increased binding to human FcγRIIb was tested in human FcγRIIb transgenic mice, Ag clearance was accelerated without compromising the Ab half-life. Taken together, inhibitory FcγRIIb was found to play a prominent role in the cellular uptake of monomeric Ag/Ab immune complexes in vivo, and when the Fc of a pH-dependent Ab was engineered to selectively enhance human FcγRIIb binding, the Ab could accelerate soluble Ag clearance from circulation. We assume such a function would enhance the therapeutic potency of Abs that target soluble Ags.

Emerging immunological drugs for chronic lymphocytic leukemia

INTRODUCTION

Over the last few years, several new immunological drugs, particularly monoclonal antibodies (mAbs), immunomodulatory drugs and B-cell receptor (BCR) pathway inhibitors have been developed and investigated in chronic lymphocytic leukemia (CLL). This article summarizes recent discoveries regarding their mechanism of action, pharmacological properties, clinical activity and toxicity, as well as the emerging role of these agents in CLL.

AREAS COVERED

A literature review of mAbs, BCR pathway inhibitors and immunomodulating drugs was conducted of the MEDLINE database via PubMed for articles in English. Publications from 2000 through February 2015 were scrutinized. The search terms used were alemtuzumab, BI 836826, duvelisib ibrutinib, idelalisib, lenalidomide, monoclonal antibodies, MEDI-551, MOR208, obinutuzumab, ocaratuzumab, ofatumumab, ONO-4059, otlertuzumab, spebrutinib, veltuzumab and XmAb5574 in conjunction with CLL. Conference proceedings from the previous 5 years of the American Society of Hematology, European Hematology Association, American Society of Clinical Oncology, and ACR/ARHP Annual Scientific Meetings were searched manually. Additional relevant publications were obtained by reviewing the references from the chosen articles.

EXPERT OPINION

The use of mAbs, BCR inhibitors and immunomodulating drugs is a promising new strategy for chemotherapy-free treatment of CLL. However, definitive data from ongoing and future clinical trials will aid in better defining the status of immunological drugs in the treatment of this disease.

CD30 as a therapeutic target for lymphoma

Hodgkin's lymphoma (HL) and ALK(+) anaplastic large-cell lymphoma (ALCL) have become highly curable due to the success of modern regimens of chemotherapy and radiotherapy. However, up to one-third of the patients experience relapse or do not respond to first-line therapy, and half of them relapse again after secondary therapy with limited options for further treatment. In the last 15 years, monoclonal antibodies (mAbs) directed to surface receptors became a new and valuable therapeutic option in many hematologic malignancies. Due to its restricted expression on normal activated lymphocytes and its high expression on malignant cells, CD30 represents an attractive target molecule for HL and ALCL therapy. However, unconjugated CD30 mAbs have demonstrated a lack of objective clinical responses in patients with recurrent HL. CD30 exhibits complex signaling pathways, and binding of its natural ligand or anti-CD30 mAbs can induce apoptosis but may also promote proliferation and activation depending on the cellular context. Moreover, CD30 rapidly internalizes after crosslinking, which counteracts efficient recruitment of immunologic effectors but also provides the opportunity to transfer cytotoxic payloads coupled to CD30-specific mAbs into the tumor cells. Several tumor targeting approaches have been studied, including radio-immunoconjugates, immunotoxins, immunoRNases, immunokinases, and antibody drug conjugates (ADCs). In 2011, the ADC brentuximab-vedotin, consisting of the CD30-specific chimeric mAb cAC10 and the potent tubulin toxin monomethyl auristatin E, gained regulatory approval as a well tolerated and highly active drug in patients with refractory and relapsed HL and ALCL. SGN-35 is on the way to being incorporated in the standard management of CD30(+) lymphoma with significant therapeutic impact. This review gives a critical overview about anti-CD30 therapies with unconjugated, engineered, and conjugated mAbs and the therapeutic challenges of treatment of CD30(+) lymphoma.

Promising therapies for the treatment of chronic lymphocytic leukemia

INTRODUCTION

The combination schedule of fludarabine, cyclophosphamide and rituximab is the gold standard of therapy for younger, physically fit chronic lymphocytic leukemia (CLL) patients; it allows achieving high and durable complete response rates. Although treatment outcome has considerably improved with chemo-immunotherapy, most patients eventually relapse and CLL is still incurable. Thus, newer and more rationally developed drugs are needed to improve CLL therapy, particularly in cases of relapsed/refractory disease.

AREAS COVERED

The authors review preclinical and clinical data regarding newer CLL agents, currently undergoing examination, such as: signal transduction and cyclin-dependent kinase inhibitors, immunomodulatory agents, B-cell lymphoma 2 inhibitors, next generation mAbs, heat shock protein 90 and histone deacetylase inhibitors, and chimeric antigen receptor T-cell therapy.

EXPERT OPINION

Newer compounds with different mechanisms of action, such as B-cell receptor signal transduction inhibitors, lenalidomide, next generation mAbs and several pro-apoptotic molecules, have shown efficacy in relapsed or refractory CLL patients. Several studies are under way to investigate the efficacy of combinations of these novel drugs. Hopefully, the combined use of these molecules in risk-adapted treatment strategies will change the therapeutic approach in the near future and will pave the way for a long-term control of CLL.

Tailored therapy for severe asthma

Patients with severe asthma or COPD have often a suboptimal symptom control due to inadequate treatment. A better understanding of pathogenetic mechanisms, phenotypes, endotypes and the new technologies available in the fields of molecular biology and immunogenetics have made it possible to synthesize specific monoclonal antibodies virtually able to interact with any target antigen, or to open a way for new therapeutic target options. At the moment, the only biologic drug available in clinical practice is omalizumab. To overcome the limits of omalizumab, the research has focused on new monoclonal antibodies presenting higher avidity for IgE (e.g. ligelizumab and lumiximab) and ability to interact also with low affinity IgE receptor (FcϵRII). At present, many new biological drugs with different mechanisms of action and targets are matter of research. It is very important to identify the asthmatic phenotype in order to select the most appropriate drug for the individual patient. The most promising agents are targeted against cytokines of Th2 pattern and related receptors, such as IL-2 (daclizumab) and IL-13 (lebrikizumab) or IL-5 in patients with hypereosinophilia (mepolizumab, reslizumab and benralizumab). Other interesting drugs have as a target TNF-α or its soluble receptor (infliximab, golimumab and etanercept) or IL-1 (canakinumab), a cytokine with an important systemic proinflammatory action. Finally, the discovery of increased levels of C5a in the airways of asthmatic patients has led to the synthesis of a specific monoclonal antibody (eculizumab). Further help should come from the identification of biomarkers that can guide in choosing the best treatment for the individual patient, such as IgE for omalizumab or periostin for lebrikizumab.

Target Therapy in Hematological Malignances: New Monoclonal Antibodies

Apart from radio- and chemotherapy, monoclonal antibodies (MoAbs) represent a new, more selective tool in the treatment of hematological malignancies. MoAbs bind with the specific antigens of the tumors. This interaction is a basis for targeted therapies which exhibit few side effects and significant antitumor activity. This review provides an overview of the functional characteristics of MoAbs, with some examples of their clinical application. The promising results in the treatment of hematological malignancies have led to the more frequent usage of MoAbs in the therapy. Development of MoAbs is a subject of extensive research. They are a promising method of cancer treatment in the future.

Current and emerging monoclonal antibody treatments for chronic lymphocytic leukemia: state of the art

Anti-CD20 monoclonal antibodies (mAbs), rituximab, ofatumumab and obinutuzumab, have a significant impact in the treatment of chronic lymphocytic leukemia (CLL), particularly in combination with chemotherapy. Over the last few years, several new mAbs have been developed and investigated in CLL. The most promising newer mAbs are directed against CD20, CD19, CD37 and CD40. Combinations of antibodies with targeted drugs like ibrutinib, idelalisib or lenalidomide will probably replace chemotherapy-based combinations in the near future. This review gives a critical overview of established mAbs as well as new antibodies potentially useful in CLL.

A randomized, open-label, multicentre, phase 2/3 study to evaluate the safety and efficacy of lumiliximab in combination with fludarabine, cyclophosphamide and rituximab versus fludarabine, cyclophosphamide and rituximab alone in subjects with relapsed chronic lymphocytic leukaemia

Lumiliximab is a chimeric monoclonal antibody that targets CD23 on the surface of chronic lymphocytic leukaemia (CLL) B-cells. Early phase clinical studies with lumiliximab alone and in combination with fludarabine, cyclophosphamide and rituximab (FCR) established its potential efficacy and tolerability. The 152CL201 trial [Lumiliximab with fludarabine, cyclophosphamide and rituximab (FCR) versus FCR alone in subjects with relapsed CLL; LUCID] was a phase 2/3, randomized (1:1), open-label, multicentre study of lumiliximab in combination with FCR versus FCR alone in patients with relapsed CLL. Six hundred and twenty-seven patients were randomized to either arm. Overall the combination of lumiliximab with FCR was not significantly better than FCR alone (overall response rate 71% vs. 72%, complete response rate 16% vs. 15%, median progression-free survival 24.6 vs. 23.9 months respectively, for FCR with and without lumiliximab). There was a slightly increased incidence of adverse events with lumiliximab but these increases did not appear to lead to differences in eventual outcomes. An interim analysis failed to show sufficient efficacy of the combination of lumiliximab with FCR. The study was therefore stopped early for lack of efficacy. Despite the eventual outcome, the LUCID trial is one of the largest studies that provides valuable insight into the efficacy and tolerability of FCR as a therapeutic option for patients with relapsed CLL.

The role of chemotherapy in managing chronic lymphocytic leukemia: optimizing combinations with targeted therapy

For many years, alkylating agents were the standard treatment for chronic lymphocytic leukemia (CLL). The advent of purine analogs improved response rates, but not overall survival, and although the monoclonal antibody rituximab is generally active against B-cell malignancies, it has demonstrated limited benefits as monotherapy for the treatment of CLL. However, specific combinations of chemotherapy, antibodies and targeted therapies have demonstrated additive or synergistic activity in CLL cells and deliver substantial clinical benefits. A greater understanding of the actions of chemotherapies and targeted agents on cellular pathways will advance the development of rationally designed combinations corresponding to individual patients' disease profiles.

Engineered monoclonal antibody with novel antigen-sweeping activity in vivo

Monoclonal antibodies are widely used to target disease-related antigens. However, because conventional antibody binds to the antigen but cannot eliminate the antigen from plasma, and rather increases the plasma antigen concentration by reducing the clearance of the antigen, some clinically important antigens are still difficult to target with monoclonal antibodies because of the huge dosages required. While conventional antibody can only bind to the antigen, some natural endocytic receptors not only bind to the ligands but also continuously eliminate them from plasma by pH-dependent dissociation of the ligands within the acidic endosome and subsequent receptor recycling to the cell surface. Here, we demonstrate that an engineered antibody, named sweeping antibody, having both pH-dependent antigen binding (to mimic the receptor-ligand interaction) and increased binding to cell surface neonatal Fc receptor (FcRn) at neutral pH (to mimic the cell-bound form of the receptor), selectively eliminated the antigen from plasma. With this novel antigen-sweeping activity, antibody without in vitro neutralizing activity exerted in vivo efficacy by directly eliminating the antigen from plasma. Moreover, conversion of conventional antibody with in vitro neutralizing activity into sweeping antibody further potentiated the in vivo efficacy. Depending on the binding affinity to FcRn at neutral pH, sweeping antibody reduced antigen concentration 50- to 1000-fold compared to conventional antibody. Thereby, sweeping antibody antagonized excess amounts of antigen in plasma against which conventional antibody was completely ineffective, and could afford marked reduction of dosage to a level that conventional antibody can never achieve. Thus, the novel mode of action of sweeping antibody provides potential advantages over conventional antibody and may allow access to the target antigens which were previously undruggable by conventional antibody.

Novel targeted treatment strategies for refractory chronic lymphocytic leukaemia

Patients with refractory chronic lymphocytic leukaemia (CLL) still have an unfavourable prognosis and novel treatment strategies are necessary, preferably adjusted to the patient's individual situation. Refractoriness is no longer limited just to fludarabine (F) but extends to F-combinations with other chemotherapeutic agents (e.g. cyclophosphamide [C] and FC) and antibodies (e.g. rituximab [R], FR, and FCR). Also, refractoriness to alemtuzumab is an increasing problem. New pharmacological developments provide promising approaches. This review focuses on novel therapies such as monoclonal antibodies and small molecules aiming at specific targets of the CLL cell in the refractory situation. Approved therapeutic regimens will be presented as well as investigational approaches. An overview of completed and current clinical trials is offered.

Emerging monoclonal antibodies and related agents for the treatment of chronic lymphocytic leukemia

Monoclonal antibodies (mAbs) – rituximab, ofatumumab and alemtuzumab – have been approved for use in the therapy of chronic lymphocytic leukemia (CLL). Recently, a new generation of anti-CD20 mAbs has become available for preclinical studies and clinical trials. These antibodies were engineered to have augmented antitumor activity by increasing complement-dependent cytotoxicity, antibody-dependent cellular cytotoxicity and Fc-binding affinity for the low-affinity variants of the Fcγ receptor IIIa. The most promising mAb directed against CD20 is obinutuzumab (GA-101). mAbs directed against CD22, CD37 and CD40 have also shown some activity in CLL. In addition, small modular immunopharmaceuticals – TRU-015 (anti-CD20) and TRU-016 (anti-CD37) – that retain Fc-mediated effector functions have been developed and investigated in preclinical studies and clinical trials. Antibody–drug conjugates and recombinant immunotoxins are also being evaluated in lymphoid malignancies. Further studies will elucidate the role of these agents in the treatment of CLL.

Therapeutic advancement of chronic lymphocytic leukemia

Despite the combinations of chemotherapy with monoclonal antibodies have further improved response rates, chronic lymphocytic leukemia (CLL) remains an incurable disease with an extremely variable course. This article reviews the ongoing clinical advances in the treatment of CLL in both previously untreated and relapsed disease and focuses on the benefit of different therapeutic strategies, the most effective therapy combinations and the potential activity of novel agents. Novel agents and combination therapies have been investigated by several studies in both the upfront and relapsed setting, particularly for patients with 17p deletion, TP53 mutation and fludarabine-refractory CLL. While these agents and combination therapies have improved initial response rates, ongoing studies are continued to determine and improve the efficacy and safety. Despite advancements in the treatment of CLL have led to high response rates, allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative option and reduced-intensity conditioning (RIC) allo-HSCT must be strongly considered whenever feasible. As such, ongoing studies of these agents and other novel approaches in clinical development are needed to expand and improve treatment options for CLL patients.

Treatment of relapsed or refractory chronic lymphocytic leukemia

BACKGROUND

Recent advances in the treatment of chronic lymphocytic leukemia (CLL) have moved beyond the traditional use of alkylating agents and purine analogs into regimens combining these two chemotherapy classes with monoclonal antibodies.

METHODS

This article reviews treatments options for patients with relapsed or refractory CLL.

RESULTS

Several studies have investigated novel agents in treating patients with 17p deletion, TP53 mutation, and fludarabine-refractory CLL, as well as patients with suboptimal response to intense treatment. These investigational agents include rituximab, alemtuzumab, ofatumumab, bendamustine, high-dose methylprednisolone, lenalidomide, lumiliximab, cyclin-dependent kinase inhibitors, small modular immunopharmaceuticals, Bcl-2 inhibitors, and histone deacetylase inhibitors. While these newer drugs and combination therapies have shown promise as treatment options for CLL, additional studies are needed to determine the immunosuppression, toxicities, and infections associated with their use.

CONCLUSIONS

Despite improvement in initial overall response rates, most patients relapse and require further treatment. CLL remains incurable with standard therapies due to development of disease refractoriness. As such, novel approaches such as those noted above warrant continued research to improve outcomes for patients with CLL.

Update on novel monoclonal antibodies and immunoconjugates for the treatment of lymphoproliferative disorders

The year 1997 was pivotal in lymphoma research, as it was the year that the US FDA approved rituximab. Rituximab significantly altered clinical management and outcomes of patients with B-cell malignancies. Despite a high initial response rate, the majority of patients subsequently develop variable degrees of therapeutic resistance to rituximab. Research attempting to understand the mechanisms of rituximab resistance and potential ways to overcome them has given rise to the development of novel targeted immunotherapeutics. This article will update the readers on advances in bioengineering of monoclonal antibodies and immunoconjugates that target CD20, as well as other surface antigens. Some additional novel immunotherapeutics, including small modular immunopharmaceuticals, bispecific monoclonal antibodies, T-cell engaging antibodies and immunoconjugates, will also be discussed.

Chronic lymphocytic leukemia

The management of chronic lymphocytic leukemia (CLL) is currently undergoing a profound change. First, several new drugs have been approved (fludarabine, bendamustine and two monoclonal antibodies, alemtuzumab and rituximab). In addition, novel monoclonal antibodies targeting CD20, CD23, CD37 or CD40, as well as drugs designed to interfere with central pathways regulating the cell cycle, the apoptotic machinery, or the leukemic microenvironment (flavopiridol, oblimersen, ABT-263 or lenalidomide) are being tested in clinical trials. Furthermore, improved protocols using reduced-intensity allogeneic progenitor cell transplantation makes it possible to offer this procedure to more patients with CLL. Finally, new prognostic markers that may influence therapeutic decisions have been identified. This review attempts to summarize the current knowledge in this rapidly moving field.

Phase I trial of a novel human monoclonal antibody mAb216 in patients with relapsed or refractory B-cell acute lymphoblastic leukemia

BACKGROUND

This phase I trial was conducted to determine the safety and pharmacokinetics of monoclonal antibody 216, a human monoclonal Immunoglobulin M antibody targeting a linear B-cell lactosamine antigen, administered alone and in combination with vincristine in patients with relapsed or refractory B-cell acute lymphoblastic leukemia, and to preliminarily assess tumor targeting and efficacy.

DESIGN AND METHODS

Three cohorts of patients received escalating doses of monoclonal antibody 216 administered as an intravenous infusion. In the case of poor response to the first dose of monoclonal antibody 216 alone, defined as less than 75% reduction in peripheral blood blast count, a second dose of the antibody with vincristine was given between days 4 and 7. Responses were assessed weekly until day 35. Serum concentration of monoclonal antibody 216 was measured before and after infusion. Monoclonal antibody 216 targeting was determined with an anti-idiotypic antibody to monoclonal antibody 216 and preliminary efficacy was analyzed by changes in peripheral blood blasts.

RESULTS

Thirteen patients were enrolled. One episode of grade 3 epistaxis was the only dose-limiting toxicity observed. All patients showed a poor response to the first monoclonal antibody 216 infusion with a decrease in peripheral blasts from 6-65% in 9 patients. In 8 patients, addition of vincristine to monoclonal antibody 216 resulted in an average reduction of the peripheral blasts of 81%. One patient without peripheral blasts achieved a hypoplastic marrow without evidence of leukemia after one infusion of monoclonal antibody 216 and monoclonal antibody 216/vincristine each. Monoclonal antibody 216 was detected on peripheral blasts in all patients.

CONCLUSIONS

Treatment with monoclonal antibody 216 in combination with vincristine is feasible and well tolerated in patients with relapsed or refractory B-cell acute lymphoblastic leukemia. Binding of monoclonal antibody 216 to leukemic blasts was efficient, and favorable early responses were observed.

Intraclonal complexity in chronic lymphocytic leukemia: fractions enriched in recently born/divided and older/quiescent cells

The failure of chemotherapeutic regimens to eradicate cancers often results from the outgrowth of minor subclones with more dangerous genomic abnormalities or with self-renewing capacity. To explore such intratumor complexities in B-cell chronic lymphocytic leukemia (CLL), we measured B-cell kinetics in vivo by quantifying deuterium ((2)H)-labeled cells as an indicator of a cell that had divided. Separating CLL clones on the basis of reciprocal densities of chemokine (C-X-C motif) receptor 4 (CXCR4) and cluster designation 5 (CD5) revealed that the CXCR4(dim)CD5(bright) (proliferative) fraction contained more (2)H-labeled DNA and hence divided cells than the CXCR4(bright)CD5(dim) (resting) fraction. This enrichment was confirmed by the relative expression of two cell cycle-associated molecules in the same fractions, Ki-67 and minichromosome maintenance protein 6 (MCM6). Comparisons of global gene expression between the CXCR4(dim)CD5(bright) and CXCR4(bright)CD5(dim) fractions indicated higher levels of pro-proliferation and antiapoptotic genes and genes involved in oxidative injury in the proliferative fraction. An extended immunophenotype was also defined, providing a wider range of surface molecules characteristic of each fraction. These intraclonal analyses suggest a model of CLL cell biology in which the leukemic clone contains a spectrum of cells from the proliferative fraction, enriched in recently divided robust cells that are lymphoid tissue emigrants, to the resting fraction enriched in older, less vital cells that need to immigrate to lymphoid tissue or die. The model also suggests several targets preferentially expressed in the two populations amenable for therapeutic attack. Finally, the study lays the groundwork for future analyses that might provide a more robust understanding of the development and clonal evolution of this currently incurable disease.

Pathophysiology of asthma: what has our current understanding taught us about new therapeutic approaches?

Current asthma therapy is based on the use of adrenergic bronchodilator and anti-inflammatory drugs the specificity, efficacy, duration of action, and safety of which have been derived through classical pharmacology and medicinal chemistry. That asthma is a T(H)2-type inflammatory disorder frequently associated with atopy and allergic comorbidities has led to a concentrated effort to find treatments that act selectively on this pathway. A systematic literature review was undertaken, as well as a review of the Web site Clinicaltrials.gov for ongoing trials. Targets have included T cells themselves and their associated cytokines, chemokines, and receptors mostly targeted with biological agents. With the exception of anti-human IgE, none of these have met the expectations predicted from animal models and human in vitro tests. For most of these new therapies, only a very small subpopulation appears to respond. A case is made for a different approach to drug discovery based on acquiring a greater understanding of asthma stratification, the relevant pathways involved, and the development of appropriate diagnostic tests enabling the targeting of selective treatments to those asthmatic phenotypes most likely to respond. The recognition that asthma is more than allergy mandates improved predictive animal models and an appreciation that many of the environmental insults that initiate, consolidate, and exacerbate asthma operate through an epithelium functioning in a disorderly fashion. An integrated model that places the epithelium at the forefront of asthma pathogenesis suggests that greater emphasis should be placed on therapeutics that increase the airways' resistance against the inhaled environment rather than focusing only on suppression of inflammation.

Refractory chronic lymphocytic leukemia--new therapeutic strategies

Treatment outcome of chronic lymphocytic leukemia (CLL) has considerably improved since the introduction of fludarabine (F) as part of the standard therapy. Nevertheless, refractoriness to fludarabine occurs in a significant number of patients and is associated with an unfavorable prognosis. Important risk factors are 17p deletion and/or mutation of TP53. For this subgroup the CD52 antibody alemtuzumab (A) presents a new treatment approach and has already been approved. Meanwhile we have to face also refractoriness to alemtuzumab. Importantly, the monoclonal CD20 antibody ofatumumab has now shown efficacy in F and A double-refractory CLL. The next generation CD20 antibody GA-101 is currently compared to rituximab (R) and will possibly be its more potent successor. Further B-cell antigens are targeted by lumiliximab (CD23), TRU-016 (CD37) and blinatumomab (CD19). Apart from monoclonal antibody therapies, a great number of small molecules are examined for the treatment of refractory and relapsed CLL. Most of these agents aim to overcome apoptosis resistance in CLL cells or influence the microenvironment. Typical targets are regulators of the cell cycle and antiapoptotic molecules like the members of the Bcl-2 family. Up to now the most promising agents appear to be flavopiridol and lenalidomide among others.

Novel antibodies against follicular non-Hodgkin's lymphoma

The anti-CD20 monoclonal antibody rituximab has revolutionized the treatment of patients with follicular B-cell lymphoma. With the combination of chemotherapy and rituximab the overall survival rate has increased with approximately 30%. Unfortunately, there is resistance to rituximab with relapse of the disease in about 60% of the patients during the first five years of treatment and eventually in all patients. To this end, there is a need to develop improved anti-CD20 monoclonal antibodies and antibodies that target other attractive molecules expressed on the follicular lymphoma cell. This review describes the development and clinical achievements so far of next generation anti-CD20 and other antibodies in the treatment of follicular B-cell lymphoma.

In vitro and in vivo model of a novel immunotherapy approach for chronic lymphocytic leukemia by anti-CD23 chimeric antigen receptor

Chronic lymphocytic leukemia (CLL) is characterized by an accumulation of mature CD19(+)CD5(+)CD20(dim) B lymphocytes that typically express the B-cell activation marker CD23. In the present study, we cloned and expressed in T lymphocytes a novel chimeric antigen receptor (CAR) targeting the CD23 antigen (CD23.CAR). CD23.CAR(+) T cells showed specific cytotoxic activity against CD23(+) tumor cell lines (average lysis 42%) and primary CD23(+) CLL cells (average lysis 58%). This effect was obtained without significant toxicity against normal B lymphocytes, in contrast to CARs targeting CD19 or CD20 antigens, which are also expressed physiologically by normal B lymphocytes. Moreover, CLL-derived CD23.CAR(+) T cells released inflammatory cytokines (1445-fold more TNF-β, 20-fold more TNF-α, and 4-fold more IFN-γ). IL-2 was also produced (average release 2681 pg/mL) and sustained the antigen-dependent proliferation of CD23.CAR(+) T cells. Redirected T cells were also effective in vivo in a CLL Rag2(-/-)γ(c)(-/-) xenograft mouse model. Compared with mice treated with control T cells, the infusion of CD23.CAR(+) T cells resulted in a significant delay in the growth of the MEC-1 CLL cell line. These data suggest that CD23.CAR(+) T cells represent a selective immunotherapy for the elimination of CD23(+) leukemic cells in patients with CLL.

Standard of care and novel treatments for chronic lymphocytic leukemia

PURPOSE

The standard of care and novel treatments for chronic lymphocytic leukemia (CLL) are reviewed.

SUMMARY

Recent advances in the treatment of CLL have dramatically changed the therapeutic landscape for both patients and health care professionals. The majority of conventional first-line therapies are noncurative and are only used to treat disease that is symptomatic or progressive and include chlorambucil, monotherapy with purine analogues, and combination chemotherapy. Immunotherapeutic agents such as rituximab and alemtuzumab may be indicated in select patient populations. However, because clinical trials have found that overall survival does not depend on the initial therapy, selection of first-line therapy should be based on patient-specific factors and the patient's goals for therapy with respect to response, survival, and symptom palliation. Progression-free survival time and time to treatment are critical endpoints for CLL treatment. An increasingly important endpoint is minimal residual disease (MRD), as it is considered to be the major cause of relapse in CLL. Finally, comparison of toxicities between different therapies is critical in CLL, as it is in other disease states. Several new agents are currently being evaluated for use in CLL, including alvocidib, oblimersen, and lumiliximab.

CONCLUSION

Chemotherapy remains the mainstay of treatment for the majority of patients with CLL. The introduction of rituximab, alemtuzumab, and bendamustine has improved the current outlook for patients with CLL. As overall survival does not appear to depend on the initial therapy, treatment should be selected based on patient-specific factors and goals. Challenges in CLL include determining when to initiate therapy, eradicating MRD, and managing therapeutic resistance.

Beyond chemotherapy: new agents for targeted treatment of lymphoma

An improved understanding of the molecular biology of cancer cell growth and survival and the role of the microenvironment in supporting the survival of cancer cells, including lymphoma cells, has led to the identification of a number of potential therapeutic targets. Despite these advances, drug development for lymphoma remains slow, inefficient, and frequently unfocused. Future work should focus on identifying 'driver' molecular defects of oncogenic pathways that can be targeted therapeutically, discovering predictive biomarkers for treatment response, and prioritizing promising drugs to accelerate their approval. This Review summarizes the current development status of novel agents for lymphoma and discusses strategies to move the field forward.

CD23 expression in follicular lymphoma: clinicopathologic correlations

Follicular lymphoma (FL) is typically a CD10+/CD5-/FMC-7+ B-cell lymphoma with variable CD23 expression. The clinical significance of CD23 expression in FL is uncertain. We studied the expression of CD23 by flow cytometry in 69 lymph nodes (LNs) and correlated it with pathologic and clinical parameters. Of 69 FLs, 48 (70%) were CD23+. Grade 3 FLs were CD23- more often (12/16 [75%]) than grade 1 and 2 cases (9/53 [17%]; P < .001). CD23 expression was more common in FLs in inguinal LNs than in other sites: 20 of 23 (87%) vs 28 of 46 (61%; P = .029). Overall survival (P = .002) and event-free survival (P < .0001) were longer in the CD23+ group than in the CD23- FLs. Our study shows that grade 3 FLs are more often CD23- than lower grade FLs and that FLs in inguinal LNs are more frequently CD23+ than in LNs from other sites. Furthermore, our findings also indicate that survival is significantly better in CD23+ FLs.

The clinical application of monoclonal antibodies in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) represents the most prevalent adult leukemia. Treatment with chemotherapy over the past 3 decades has been palliative. The introduction of therapeutic antibodies has increased the number of treatment options for this disease. Despite this increase, our true understanding of the mechanism of action of antibody therapy in CLL remains limited. Rituximab, a CD20 antibody, is currently widely used in combination-based strategies for both previously untreated symptomatic CLL and as salvage therapy. Recent data suggest that the addition of rituximab to fludarabine with or without cyclophosphamide prolongs survival in younger patients with CLL. Other improved CD20 antibodies with promising clinical activity, including ofatumumab and GA-101, are coming forward. Alemtuzumab, a CD52 antibody, likewise has demonstrated benefit in both symptomatic, previously untreated CLL and in patients with relapsed disease but has less selectivity. Development of other therapeutic antibodies targeting alternative B-cell-specific antigens in CLL has been less successful, although many promising candidate antibodies and/or small modular immune pharmaceuticals (SMIPs) are coming forward. In addition, recent efforts to combine currently applied therapeutic antibodies with other biologic and targeted therapies with efficacy in CLL offers the potential to move toward alternative non-chemotherapy-based treatment approaches.

Refractory chronic lymphocytic leukemia--new therapeutic strategies

Treatment outcome of chronic lymphocytic leukemia (CLL) has considerably improved since the introduction of fludarabine (F) as part of the standard therapy. Nevertheless, refractoriness to fludarabine occurs in a significant number of patients and is associated with an unfavorable prognosis. Important risk factors are 17p deletion and/or mutation of TP53. For this subgroup the CD52 antibody alemtuzumab (A) presents a new treatment approach and has already been approved. Meanwhile we have to face also refractoriness to alemtuzumab. Importantly, the monoclonal CD20 antibody ofatumumab has now shown efficacy in F and A double-refractory CLL. The next generation CD20 antibody GA-101 is currently compared to rituximab (R) and will possibly be its more potent successor. Further B-cell antigens are targeted by lumiliximab (CD23), TRU-016 (CD37) and blinatumomab (CD19). Apart from monoclonal antibody therapies, a great number of small molecules are examined for the treatment of refractory and relapsed CLL. Most of these agents aim to overcome apoptosis resistance in CLL cells or influence the microenvironment. Typical targets are regulators of the cell cycle and antiapoptotic molecules like the members of the Bcl-2 family. Up to now the most promising agents appear to be flavopiridol and lenalidomide among others.

The lysosomotropic agent, hydroxychloroquine, delivered in a biodegradable nanoparticle system, overcomes drug resistance of B-chronic lymphocytic leukemia cells in vitro

Nonviral delivery systems are relatively easy to produce in the large scale, are safe, and elicit a negligible immune response. Nanoparticles (NPs) offer promise as nonviral vectors as biocompatible and -degradable carriers of drugs with targeting to specific sites by surface receptors of monoclonal antibodies (mAbs). We investigated the effect of four PEG-PLGA (polyethylene glycol-polylactic-co-glycolic acid) NP systems on drug-resistant B-chronic lymphocytic leukemia (B-CLL) cells in vitro, three of them encapsulating the drug, hydroxylchloroquine (HDQ), two with NP surface coatings of mAbs (NP1) CD20, (NP2) CD19, and CD20, and one (NP3) with no mAb, but tagged with the fluorescent marker, fluorescein isothiocyanate. The fourth NP system (NP4) was coated with anti-CD19/FITC and anti-CD20/Alexa-Fluor((R)) antibodies, but did not contain the active drug, HCQ. Our data indicate that PEG-PLGA nanoparticles with surface mAbs are suitable for selective drug delivery to B-CLL cells and produce a strong apoptotic effect when loaded with the lysosomotropic agent, HDQ.

Chronic lymphocytic leukemia: new concepts for future therapy

Over the past several years, we have witnessed rapid advances in our understanding of the biology and treatment of chronic lymphocytic leukemia (CLL). New prognostic factors have been characterized that help identify patients at high risk of rapid disease progression, refractoriness to treatment, and short overall survival (OS). These advances have led to a significant paradigm shift in the management of CLL. Novel therapeutic strategies, including combinations of monoclonal antibodies with conventional chemotherapy, have dramatically improved response rates, remission duration, and recently, OS. However, these benefits do not appear to extend to certain patient subsets, especially those with unfavorable clinical or cytogenetic risk factors. The majority of patients with CLL will invariably relapse following first-line therapy and can acquire high-risk genetic abnormalities. Repeated treatment leads to eventual therapeutic refractoriness and shortened survival compared with age-matched healthy individuals. Several novel agents and strategies, including next-generation anti-CD20 monoclonal antibodies, the alkylating agent bendamustine, the immunomodulatory agent lenalidomide, the cyclin-dependent kinase inhibitor flavopiridol, and small-molecule Bcl2 inhibitors, are currently under clinical investigation as novel agents that will hopefully improve treatment outcomes for CLL. Though allogeneic stem cell transplantation offers curative potential, it also presents clinical challenges in terms of patient appropriateness, donor availability, and timing. The merits and challenges of incorporating these treatment modalities into the treatment algorithm for patients with CLL, as discussed by a panel of experts in CLL, are outlined in this article.