Current Drug Discovery Technologies - Volume 6, Issue 4, 2009

Chronic inflammatory and autoimmune diseases are a major cause of morbidity and mortality in the industrialized world, affecting 3 to 8 % of the population. The wide spectrum of these diseases includes rheumatoid arthritis, systemic lupus erythematosus, psoriasis, multiple sclerosis, type-1 diabetes, Crohn's disease, and systemic sclerosis. Besides apparent clinical differences, there are also many clinical and pathogenic overlaps supported by the fact that they co-occur in a significant number of patients. For example, co-occurrence of type-1 diabetes, autoimmune thyroiditis, rheumatoid arthritis, coeliac disease and multiple sclerosis has been described. Furthermore, there is compelling evidence for a central role of so-called Th17 T cells in the immunopathogenesis of these diseases. Th17 cells have been recently identified as effector CD4+ Th cells, defined by their production of IL-17A and IL-17F, two inflammatory cytokines which are normally not produced by Th1 or Th2 cells. After IL-23 stimulation, this new type of T cells produces a range of further inflammatory mediators such TNF-α, IL-6, IL-21, IL-22 and CCL20. Recent genetic studies have shown that many of the mentioned diseases have a strong genetic background with some overlapping genetic patterns. Systematic genome-wide association studies have been performed to test common genetic variants (e.g., single nucleotide polymorphisms) for association to disease risk of the mentioned diseases. Independent risk alleles were identified at the IFN regulatory factor 5 (IRF5) locus for systemic lupus erythematosus and at the IL23R locus for Crohn's disease. Single nucleotide polymorphisms in the STAT4 (signal transducer and activator of transcription 4) gene were described to be associated with rheumatoid arthritis and systemic lupus. Treatment of autoimmune diseases has long been based on non-specific anti-inflammatory drugs. This has changed dramatically in recent years with the development of neutralizing antibodies and soluble receptor molecules targeting inflammatory cytokines or immune cell receptors, and the use of tolerizing autoantigens, all of which specifically downmodulate immune responses. Historically, a major breakthrough was the observation that the expression of major pro-inflammatory cytokines IL- 1, IL-6, IL-8, and GM-CSF, produced by synoviocytes from RA patients, could be blocked by addition of a TNF-neutralizing antibody. This observation laid the foundation for the development of TNF-neutralizing biological agents, which were applied soon thereafter in humans for variety of chronic inflammatory and autoimmune diseases. In this issue of the journal, we will give an overview of current treatment of autoimmune diseases such as psoriasis, bullous autoimmune diseases, Crohn's disease, lupus erythematosus and autoimmune vasculitides, with a special emphasis on biologics. This includes recent progresses in treatment of bullous autoimmune diseases using immune absorption combined with biological agents. Moreover, we present the current status of experimental mouse models of autoimmunity with a focus on mouse genetics. Finally, we will describe the potential of current metabolomics technologies for disease and treatment monitoring. Taken together, treatment modalities of chronic inflammatory and autoimmune diseases have dramatically improved in recent years, but there is still a plethora of new targets for further innovative treatment approaches.

Psoriasis is a chronic inflammatory skin disease with a significant number of patients suffering from additional joint involvement and other co-morbidities. The precise pathomechanisms of this disease are still unknown. But based on recent findings a picture emerges putting a new subset of inflammatory T cells, so-called Th17 T cells, into the centre of psoriasis pathogenesis. These cells secrete interleukin (IL)-17 and a further set of so-called Th17 cytokines such as IL-21 and IL-22, the latter of which appears to significantly contribute to the epidermal changes observed in this disease. Differentiation and maintenance of Th17 cells depends on IL-23 and transforming growth factor (TGF)-β, secreted by activated monocytes or macrophages within the dermal compartment. In recent years, a plethora of new treatment approaches was introduced using antibodies or small molecule inhibitors specifically targeting inflammatory cytokines, cellular receptors or signalling mechanisms. Based on current results from large clinical trials, a more individualized treatment for affected patients may be achieved in the near future. In this review, we summarize the current knowledge about treatment of psoriasis with biological agents targeting inflammatory mechanisms.

Anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides (AAV) comprise the most common group of primary systemic vasculitides and include Wegener's granulomatosis (WG), microscopic polyangiitis (MPA), Churg-Strauss syndrome (CSS), and renal-limited vasculitis (RLV). AAV share the feature of necrotizing predominantly small vessel vasculitis, but are otherwise distinct diseases with differences in the genetic background, epidemiological and exogenous factors, immune and pathologic features, preferences of organ involvement, and frequencies of ANCAassociation. MPA and RLV display solely vasculitic features, whereas WG and CSS are characterized by both granulomatous disease and a systemic vasculitis. Chronic inflammation and neoformation of tertiary lymphoid tissue appear to initiate and maintain the break of tolerance and induction of ANCA in AAV. A number of mechanisms are implied in this process, e.g., nasal S. aureus carriage suggestive of a potential link to infection in WG, danger-signals, neutrophil extracellular traps (NETs), the protease-activated receptor (PAR)-2, cytokines (Th1/Th2-type, IL-15, IL-17), and NK-like Tcells. The outcome of AAV has greatly improved since the introduction of immunosuppressive therapy. Still, the prognosis is impaired by high relapse rates and side effects of immunosuppressive therapy. Biologicals emerged as a new class of drugs that may help to improve outcome and reduce side effects of conventional treatments. So far, anti-CD20 therapy (rituximab) and TNF-α-antagonists represent strategies for refractory disease, but evidence from controlled trials is still lacking. Controlled trials for “routine” remission induction with these biological are also pending. New therapy principles hold further promise for the future.

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by specific organ manifestations and the production of autoantibodies to nuclear antigens. SLE can induce severe organ damage and carries the risk of fatal outcome. During recent years, no major progress has been made regarding new treatment options except for the introduction of mycophenolate mofetil. Therefore, the results of several large clinical trials using biological agents for treatment of SLE were hopefully awaited. Yet, the application of abatacept, belimumab and rituximab, respectively, to non-renal or renal lupus patients surprisingly has not been successful. Other studies using different agents have not been completed yet. Nevertheless, the results available so far will have a significant impact on the design of future clinical trials and will stimulate the debate on new targets for treatment of SLE.

Metabolomics is a recently emerging member of the “omics” technologies. It aims at detecting and quantifying all detectable small molecules, the so-called metabolites, present in a biological sample. Because of the lower number of metabolites compared with the number of genes and proteins identified in genomics and proteomics approaches, data of metabolic studies are less complex and may therefore be more informative. Metabolomics may thus significantly contribute to our understanding of disease mechanisms. Autoimmune diseases are of growing clinical relevance, and due to the chronic nature of these diseases successful treatment is often challenging. In the past years, a variety of studies have been published about the metabolome of autoimmune diseases such as Crohn’s disease and rheumatoid arthritis. However, our understanding of the role of different metabolites in the pathogenesis of autoimmune diseases is still far from being complete.

Significant progress has been made in past decades in our understanding of the basic mechanisms underlying autoimmune diseases. Nevertheless, many questions remain unanswered, in particular regarding the mechanisms at very early stages of these diseases. Reliable animal models are of crucial importance in basic research and may help us to understand central disease pathways. They are also indispensable for pre-clinical drug testing. Here we present and discuss two mouse models of rheumatoid arthritis and multiple sclerosis, respectively. In experimental studies using the models of collagen-induced arthritis and experimental autoimmune encephalomyelitis, the efficacy of new biological agents has been tested, which paved the way for clinical trials. A further interesting field where mouse models may provide valuable informations, is the identification of susceptibility genes for autoimmune diseases. Overall, in some instances studies with inbred strains may have an advantage over human studies, because environmental factors may easily be controlled and the genetic differences between different mouse strains are better characterized.

Autoimmune bullous diseases are a heterogeneous group of disorders that can be subdivided according to the level of split formation in the intraepidermal blistering pemphigus diseases and subepidermal bullous disorders, latter including pemphigoid diseases, epidermolysis bullosa acquisita, and dermatitis herpetiformis. In the majority of autoimmune bullous disorders, disease activity can be sufficiently controlled by systemic corticosteroids in combination with further immunosuppressants/immunomodulants such as dapsone, doxycycline, methotrexate, azathioprine, or mycophenolate mofetil. In contrast, in pemphigus, mucous membrane pemphigoid, and epidermolysis bullosa acquisita, treatment is challenging and only in a minority of patients, conventional immunosuppressive therapy induces clinical remission. Since only a few years ago, only cyclophosphamide and high-dose intravenous immunoglobulin were available as potent second-line therapies. Meanwhile, immunoadsorption and the monoclonal anti-CD20 antibody rituximab have been established as further therapeutic options. Here, both conventional therapies and novel treatment regimens for autoimmune blistering diseases are discussed.

Heparin has been used as an anticoagulant for decades. Recently, attention has been drawn to the nonanticoagulant activities of heparin. Experimentally and clinically those non-anticoagulant properties of heparin inhibit inflammation and metastatic spread of tumor cells. On the molecular level, heparin inhibits the function, expression and/or synthesis of adhesion molecules, cytokines, angiogenic factors and complement. However, despite a similar anticoagulant activity, those non-anticoagulant effects of heparin differ greatly among the different heparin preparations. The same holds true for the most common adverse events of heparin treatment. The incidence of immune mediated heparin-induced thrombocytopenia and cutaneous hypersensitivity responses is greatly, but not exclusively, influenced by the heparin preparation used. As the structure-function relationship of the anti-inflammatory and anti-metastatic effects of heparins are understood in more detail, and as the risk profile of different heparin preparations regarding the induction of adverse events have been identified, we propose to use the different heparin preparations according to the individual needs of each patient.

The broad spectrum of chronic inflammatory bowel diseases encompasses the two main entities Crohn's disease (CD) and ulcerative colitis (UC). Rapid action and long-term duration is the superordinate goal in most therapeutic approaches facing chronic inflammation including inflammatory bowel diseases (IBD) for induction and maintenance of remission. The availability of antibodies targeting TNF-α or alpha 4 integrin has recently offered new opportunities apart from classical remedies for the treatment of CD, a major challenge for future therapeutic concepts. Classical way of treating CD is an escalation scheme (“step-up”) whereas the novel and still controverse approach (“top-down”) favors a biological as initial drug. Today, four biologicals have proven efficacy and safety in CD treatment strategies and have received approval by FDA and, with the exception of natalizumab and certolizumab, by EMEA. Infliximab was the first TNF-α blocker and extended the care in CD. Adalimumab and certolizumab pegol followed as humanized second generation TNF-α blockers. Another targeted therapy option is natalizumab, an alpha 4 integrin monoclonal antibody, which blocks the migration of leukocytes into inflamed gut tissue. Nevertheless, a considerable number of patients remain refractory, lose response or render intolerant to these biologicals. An overall long lasting remission of less than 30% with scheduled administration of TNF-α blockers in patients with steroid dependent or refractory CD seems to be lifelike and alternative therapeutic options are warranted. Broad acting antimetabolites come into focus again and recent data provide substantial evidence for the efficacy and safety of cyclophosphamide pulse therapy in ileocolonic, refractory CD. This therapeutic option should be kept in mind as a reasonable agent to target the inflammatory process in severely disabled patients. Hence, targeted therapy in CD seems to be still a myth at present owing to the complex nature of disease.

The core-in-cup matrix tablets of Metoprolol succinate were prepared by wet granulation technique. Of all the investigated formulations, the optimized formulation of MS-09 followed zero-order kinetics of drug release. Trail on MS- 09 was formulated using 7.5% hydrogenated castor-oil (HCO) and 4% of hydroxyl propyl methylcellulose (HPMC K15M) with an objective to achieve a linear release profile for 24 h. There is no initial burst release, with 16.17% of drug released during the first hour and release was extended up to 24 hrs. Study of drug release kinetics was performed by application of dissolution data to various kinetic equations like zero-order; first order, Higuchi and Korsmeyer-Peppas, from R2 value (0.9975) it was concluded that the drug release followed zero order kinetics with both erosion and diffusion as the release mechanisms.

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