Current Drug Targets - Volume 18, Issue 3, 2017

Despite great progress in the curative treatment of acute leukemia, outcomes for those with relapsed and/or chemotherapy-refractory disease remain poor. Current intensive cytotoxic therapies can be associated with significant morbidity and novel therapies are needed to improve outcomes. Immunotherapy based approaches provide an alternative mechanism of action in the treatment of acute leukemia. Due to cell surface antigen expression, leukemia in particular is amenable to targeted therapies, such as antibody-based therapy. Based on the potential for non-overlapping toxicity, the possibility of synergistic action with standard chemotherapy, and by providing a novel method to overcome chemotherapy resistance, antibody-based therapies have shown potential for benefit. Modifications to standard monoclonal antibodies, including drug conjugation and linkage to T-cells, may further enhance efficacy of antibody-based therapies. Identifying the ideal timing for incorporation of antibody-based therapies, within standard regimens, may lead to improvement in overall outcomes. This article will provide an overview of antibody-based therapies in clinical development for the treatment of acute leukemia in children and adults, with a particular focus on the current strategies and future developments.

The development of novel T cell therapies to target leukemia has facilitated the translation of this approach for hematologic malignancies. Different methods of manufacturing leukemia-specific T cells have evolved, along with additional measures to increase the safety of this therapy. This is an overview of expanded T cell therapeutics with a focus on how the manufacturing strategies have been refined, and where the research is heading.

"Alloreactive cell therapy without substantial engraftment" (ACT-WiSE) refers to adoptive transfer of natural (“non-engineered”) human leukocyte antigen-mismatched lymphocytes to mediate anti-neoplastic alloreactivity in recipients without employing pharmacologic immunosuppression. By definition, ACT-WiSE entails subsequent rejection of most, if not all, donor cells. Macrochimerism is transient and microchimerism may be either short-lived or persistent. This strategy harnesses the anticancer potency of alloreactivity without incurring significant risk of graft-versus-host disease. "Microtransplantation" refers to a form of ACT-WiSE where the donor cell product contains hematopoietic progenitor cells. Microtransplantation therefore accelerates hematopoietic recovery and its immunomodulatory effects may differ from other forms of ACT-WiSE. Recent studies suggest that various forms of ACT-WiSE, including microtransplantation, may improve chemosensitivity in patients with myeloid malignancies, resulting in higher complete remission rates and increased survival. Microtransplantation has also demonstrated promising pilot results in relapsed or refractory Non-Hodgkin and Hodgkin lymphoma. ACT-WiSE and microtransplantation may establish a new class of allogeneic cell therapy of particular relevance to persons not considered candidates for traditional allogeneic hematopoietic cell transplantation (AHCT). Open questions include the optimal timing and cell dose of ACT-WiSE, which donor factors contribute to efficacy, and whether these remissions are durable after eradication of donor cells. We extrapolate from lessons learned in the course of traditional and haploidentical AHCT to propose ways of optimizing ACT-WiSE. We divide these into donor-related strategies (including rational donor selection and boosting NK-cell and T-cell alloreactivity) and patient- related strategies (that may favor development of autologous NK-cell and T-cell mediated anticancer cytotoxicity in the post-ACT-WiSE window).

Acute myeloid leukemia (AML) was the first malignancy for which immunotherapy, in the form of allogeneic hematopoietic stem cell transplantation (allo-HSCT), was integrated into the standard of care. Allo-HSCT however is an imperfect therapy associated with significant morbidity and mortality while offering only incomplete prevention of AML clinical relapse. These limitations have motivated the search for AML-related antigens that might be used as more specific and effective targets of immunotherapy. While historically such investigations have focused on protein targets expressed uniquely in AML or at significantly higher levels than in normal tissues, this article will review recent discoveries which have identified a novel selection of potential antigen targets for AML immunotherapy, such as non-protein targets including lipids and carbohydrates, neo-antigens created from genetic somatic mutations or altered splicing and post-translational modification of protein targets, together with innovative ways to target overexpressed protein targets presented by cell surface peptide-MHC complexes. These novel antigens represent promising candidates for further development as targets of AML immunotherapy.

AML patients have an aberrant and dysfunctional immune state, paving the way for novel agents targeting pathways that integrate with immune signaling, function, and response. Small molecule immunomodulatory drugs (IMiDs) represent a class of agents derived from the parent compound, thalidomide. There are currently 3 IMiDs approved for a variety of malignancies: thalidomide, lenalidomide, and the newest agent, pomalidomide. IMiDs lead to a multitude of immunobiologic effects such as cytokine modulation, co-stimulation of T cells, down-regulation of co-inhibitory molecules, enhancing natural killer cell activity, inhibition of regulatory T cells, and repairing perturbed synapse formation on T cells. IMiDs have been extensively studied in various AML settings with promising clinical activity. This review discusses the immunologic effects of IMiDs, the rationale for studying IMiDs in AML, and the published and ongoing clinical trials investigating IMiD activity in AML.

Intrinsic immune responses to acute leukemia are inhibited by a variety of mechanisms, such as aberrant antigen expression by leukemia cells, secretion of immunosuppressive cytokines and expression of inhibitory enzymes in the tumor microenvironment, expansion of immunoregulatory cells, and activation of immune checkpoint pathways, all leading to T cell dysfunction and/or exhaustion. Leukemic cells, similar to other tumor cells, hijack these inhibitory pathways to evade immune recognition and destruction by cytotoxic T lymphocytes. Thus, blockade of immune checkpoints has emerged as a highly promising approach to augment innate anti-tumor immunity in order to treat malignancies. Most evidence for the clinical efficacy of this immunotherapeutic strategy has been seen in patients with metastatic melanoma, where anti-CTLA-4 and anti-PD-1 antibodies have recently revolutionized treatment of this lethal disease with otherwise limited treatment options. To meet the high demand for new treatment strategies in acute leukemia, clinical testing of these promising therapies is commencing. Herein, we review the biology of multiple inhibitory checkpoints (including CTLA-4, PD-1, TIM-3, LAG-3, BTLA, and CD200R) and their contribution to immune evasion by acute leukemias. In addition, we discuss the current state of preclinical and clinical studies of immune checkpoint inhibition in acute leukemia, which seek to harness the body's own immune system to fight leukemic cells.

The chimeric antigen receptor (CAR) technology started out as a tool to understand lymphocyte biology but rapidly developed into a T cell therapeutic agent for the treatment of cancers. Here, we describe the technological advances in the field of CARs and highlight critical components of its success. Additionally, we describe how various laboratories have worked toward developing new, safer, and more potent CARs for cancer.

Small cell lung cancer is a highly aggressive, difficult to treat neoplasm. Among all lung tumors, small cell lung cancers account for about 20%. Patients typically include heavy smokers in 70s age group, presenting with symptoms such as intrathoracic tumors growth, distant spread or paraneoplastic syndromes at the time of diagnosis. A useful and functional classification divides small cell lung cancers into limited disease and extensive disease. Concurrent chemo-radiotherapy is the standard treatment for limited disease, with improved survival when combined with prophylactic cranial irradiation. Platinum compounds (cisplatin/carboplatin) plus etoposide remain the cornerstone for extensive disease. Nevertheless, despite high chemo- and radio-sensitivity of this cancer, nearly all patients relapse within the first two years and the prognosis is extremely poor. A deeper understanding about small cell lung cancer carcinogenesis led to develop and test a considerable number of new and targeted agents but the results are currently weak or insufficient. To date, small cell lung cancer is still a challenge for researchers. In this review, key aspects of small cell lung cancer management and controversial points of standard and new treatments will be discussed.

Escalating resistance to almost every class of antibiotics is reducing the utility of currently available antimicrobial drugs. A part of this menace is attributed to poor pharmacokinetics and pharmacodynamics of the drug. Improvement in drug delivery is the most challenging task encountered by the pharmaceutical industries; however nanotechnology can bring a revolution in drug delivery design. Nano-antimicrobials (NAMs) have their own intrinsic antimicrobial activity (nanoparticles) or augment overall efficacy of enclosed antibiotics (nano-carriers), thus contribute in mitigating or reversing the resistance phenomenon. Nano-particles (NPs) having their own intrinsic antimicrobial activity kill microbes by mimicking natural course of killing by phagocytic cells i.e., by producing large quantity of Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS). It is believed that NPs kill microbes by simultaneously acting on many essential life processes or metabolic routes of microbes; that as many genetic mutations to develop resistance against them seems to be impossible. Nano carriers improve the pharmacokinetics of the enclosed drug. Moreover, one of the major techniques by which NAMs can overcome resistance is targeted drug delivery to the site of disease. In this review, a comprehensive detail about the mechanism of action of NAMs are presented in context to multi drug resistance phenomenon.