Current opinion in investigational drugs最新文献

Since the development of the first vaccines, modern medicine has been consistently aiming to improve the efficacy of immune responses. Traditionally, adjuvants have been used as non-specific immune modulators to enhance recognition and activation against a desired antigen. By providing 'danger' signals to the immune system, adjuvants activate innate immunity, which enhances the development of protective and therapeutic adaptive immune responses. The newest class of immune modulators bypasses the innate response and targets cells of the adaptive response directly. Targeted immunomodulatory therapy is focused primarily on the activation of costimulatory receptors (eg, 4-1BB, OX40 and GITR [glucocorticoid-induced TNF receptor-related gene]) or the blockade of co-inhibitory receptors (eg, CTLA-4, PD-1 and PD-L1) on T-cells during activation and/or effector responses. With promising clinical results obtained to date, immunomodulatory therapy is becoming an integral part of immunotherapeutic approaches. The modulation of GITR is listed as one of the top 25 most promising research areas by the NCI, and has demonstrated potential in both antitumor and vaccine settings. This review discusses the role of GITR as a potential target for immunomodulatory therapy, as well as the research involved in understanding the mechanisms of anti-GITR therapy and current progress in translation into the clinic.

Considerable research in the field of immunotherapy for melanoma has demonstrated that this tumor type can be responsive to therapeutic immune activation strategies. In early clinical trials, vaccine strategies using dendritic cells (DCs) and adenovirus (Ad) vectors (AdVs) were safe and immunogenic, and induced clinical responses in a minority of patients. Research from the past several years has yielded an improved mechanistic understanding of DC biology, AdV effects on DCs and the crosstalk that occurs between antigen-loaded DCs and specific lymphocyte subsets. This knowledge base is being combined with technological advances in cytokine delivery, AdV design and in vivo DC targeting. These developments are leading to novel AdV-transduced DC-based therapeutic modalities that may further advance melanoma immunotherapy. Interactions between AdVs and DCs, initial clinical trial results, and new developments in DC engineering and in AdV biology are reviewed.

Necitumumab (IMC-11F8), under development by ImClone Systems in collaboration with Bristol-Myers Squibb, is a fully human IgG1 mAb targeting the epidermal growth factor receptor (EGFR), for the potential intravenous treatment of cancer, in particular NSCLC. In vitro studies demonstrate that necitumumab inhibits downstream targets in the EGFR pathway (eg, MAPK), which are important for cellular proliferation, differentiation, invasion and metastasis. Furthermore, because necitumumab is an IgG1 construct, it has the potential to induce antibody-dependent cell-mediated cytotoxicity against tumor cells. Preclinical studies indicated that the antitumor activity of necitumumab is either comparable with or superior to that of ImClone's chimeric anti-EGFR mAb cetuximab. In a phase I clinical trial in patients with advanced solid malignancies, necitumumab displayed nonlinear pharmacokinetic behavior. The toxicity profile of necitumumab is acceptable, with skin toxicity being the most frequently reported adverse event in the phase I and II clinical trials conducted to date. Preliminary data from a phase II clinical trial of necitumumab in combination with chemotherapy for the first-line treatment of advanced colon cancer are promising. Success in the ongoing phase III clinical trials in patients with advanced NSCLC would lead to necitumumab becoming a valuable addition to future therapeutic strategies in oncology.

Mammalian target of rapamycin (mTOR) complex 1 (mTORC1) is a multicomponent, nutrient-sensitive protein that is implicated in a wide range of major human diseases. mTORC1 responds to both growth factors and changes in local amino acid levels. Until recently, the intracellular amino acid-sensing mechanism that regulates mTORC1 had remained unexplored. However, studies in human cells in culture have demonstrated that in response to amino acid stimulation, mTOR (a conserved member of the PI3K superfamily) is shuttled to late endosomal and lysosomal compartments, where it binds the Ragulator-Rag complex and is assembled into active mTORC1. Members of the proton-assisted amino acid transporter (PAT/SLC36) family have been identified as critical components of the amino acid-sensing system that regulates mTORC1 present in endosomal and lysosomal membranes. These discoveries not only highlight several new potential drug targets that could impact selectively on mTORC1 activity in cancer cells, but also provide novel insights into the strategies used by such cells to outcompete their neighbors in growth factor- and nutrient-depleted conditions. In this review, recent mechanistic insights into how mTORC1 activity is controlled by amino acids and the potential for the selective targeting this regulatory input are discussed.

Infection with HBV and HCV are considered the most important etiological factors for hepatocellular carcinoma (HCC). Current treatment options are insufficient, creating an urgent need for new therapeutic strategies that inhibit disease progression and improve survival in patients with HCC. A promising strategy for the treatment of HCC is gene therapy (GT), which is characterized by the transduction of tumor cells with genes displaying antitumor properties, such as pro-apoptotic, suicide, anti-angiogenic and immunomodulatory genes, as well as siRNAs. Other GT strategies have investigated oncolytic viral vectors that propagate specifically in tumor cells and, subsequently, kill these malignant cells. Furthermore, GT strategies directed toward halting virus proliferation, such as genetic vaccines or genetic interference with viral replication, as well as strategies that prevent viral induced pre-carcinogenic changes, represent the most efficient strategies to prevent HCC development. These GT approaches are promising alternatives to, and could complement or substitute, current treatment options for HCC. This review summarizes trends in GT during the past decade, including investigations in animal models and patients for the prevention and treatment of hepatitis virus-induced HCC.

Recent evidence has demonstrated that aberrant reactivation of the Hedgehog signaling pathway contributes to tumor initiation and progression in various human malignancies, including pancreatic cancer; therefore, the Hedgehog pathway has emerged as a promising novel therapeutic target. Initial translational studies conducted using cyclopamine, a small-molecule inhibitor of the Smoothened (SMO) component of the Hedgehog pathway, demonstrated that pharmacological blockade of aberrant Hedgehog signaling has the potential to inhibit tumor initiation, progression and metastatic spread. This concept has been corroborated using different compounds in various preclinical models of pancreatic cancer and other malignancies; several of these studies suggest possible therapeutic synergisms of Hedgehog inhibitors with established antineoplastic agents. This review provides a concise overview of translational studies assessing the use of Hedgehog inhibitors as novel therapeutic strategy for cancer, particularly pancreatic cancer.

More than 50 years after the introduction of the dihydrofolate reductase inhibitor, methotrexate, new antifolates have emerged and have been incorporated into the chemotherapeutic armamentarium. These include pralatrexate, with the same target as methotrexate, but with enhanced properties, and pemetrexed, with different enzyme targets and properties. Current synthetic efforts are focused on developing antifolates that are selectively delivered to cancer cells, but not to normal proliferating cells, exploiting the different properties of folate transporters. In another novel approach, drugs structurally and mechanistically unrelated to folates are linked to and use folic acid as a carrier to be endocytosed by folate receptors and then released to inhibit their cellular targets. This review describes the evolution and current status of antifolate pharmacology and prospects for the development of the next generation of folate analogs.

There is considerable evidence suggesting that a variety of malignancies utilize the TGFβ cytokine to evade immune surveillance mechanisms to facilitate tumor growth and metastatic progression. The recently developed large- and small-molecule TGFβ inhibitors have demonstrated antitumor efficacy in several preclinical tumor models. Further investigation has revealed these agents to be critically dependent upon the host's immune system, suggesting that the inhibition of TGFβ may overcome the immunosuppressive tumor microenvironment and, ultimately, augment the antitumor immune response. These findings strongly support combining this strategy with other immunotherapeutic approaches for the treatment of metastatic cancer. This review discusses the immunoregulatory and antitumor properties of these pharmacological inhibitors of TGFβ signaling as either independent agents or in combination with various immunotherapeutic strategies, their potential side effects, as well as additional avenues of research that may be necessary for their eventual clinical application.

Tumor antigen-specific T-cell function is regulated by both positive and negative costimulatory signals, which are received in the secondary lymphoid organs and within the tumor microenvironment. Tumor-induced T-cell dysfunction results from a lack of positive costimulatory signals, combined with a predominance of negative immunoregulatory mechanisms. The engagement of the protein programmed death 1 (PD1), expressed on activated T-cells, by programmed death ligand 1 (PD-L1)/B7H1 within tumor cells or other host-derived cells results in the downregulation of T-cell function, and represents an important negative regulatory pathway. Preclinical cancer models suggest that interruption of PD1/PD-L1 interactions leads to improved antitumor T-cell responses and tumor control. mAbs developed against both PD1 and PD-L1/B7H1 are being evaluated in phase I/II clinical trials in patients with a variety of cancers. The uncoupling of negative immune regulatory pathways therefore represents an exciting and potentially highly valuable new modality for cancer immunotherapy.

Crizotinib (PF-02341066), under development by Pfizer, is an orally bioavailable, ATP-competitive, small-molecule inhibitor of the receptor tyrosine kinases (RTKs) c-Met (also known as hepatocyte growth factor receptor) and anaplastic lymphoma kinase (ALK), for the potential treatment of cancers dependent on these oncogenic kinases for growth and survival. Since the first published characterizations of crizotinib only a few years ago, the drug has been extensively validated as a highly specific inhibitor of c-Met and ALK among > 120 different RTKs surveyed. In preclinical tumor xenograft studies, crizotinib inhibited the growth and survival of cell lines dependent upon c-Met or ALK enzymatic activity. Crizotinib has been particularly effective against anaplastic large cell lymphoma and non-small cell lung cancer (NSCLC) cell lines that harbor ALK translocations resulting in expression of oncogenic ALK fusion proteins. During early-stage clinical testing, crizotinib was well tolerated and produced dramatic antitumor activity in patients with ALK-rearranged NSCLC. At the time of publication, an ongoing phase III clinical trial is comparing crizotinib with standard second-line chemotherapy in previously treated patients with NSCLC harboring ALK rearrangement, and a phase III trial comparing crizotinib with standard chemotherapy in the first-line setting in non-squamous lung cancer is planned. Thus, in the future, crizotinib is expected to become a highly used therapeutic for the treatment of ALK-rearranged tumors.