Pharmacokinetic parameters and biodistribution of soluble cytokine receptors

Under the Umbrella of Clinical Pharmacology: Inflammatory Bowel Disease, Infliximab and Adalimumab, and a Bridge to an Era of Biosimilars

Monoclonal antibodies (MAbs) have revolutionized the treatment of many chronic inflammatory diseases, including inflammatory bowel disease (IBD). IBD is a term that comprises two quite similar, yet distinctive, disorders-Crohn's disease (CD) and ulcerative colitis (UC). Two blockbuster MAbs, infliximab (IFX) and adalimumab (ADL), transformed the pharmacological approach of treating CD and UC. However, due to the complex interplay of pharmacology and immunology, MAbs face challenges related to their immunogenicity, effectiveness, and safety. To ease the burden of IBD and other severe diseases, biosimilars have emerged as a cost-effective alternative to an originator product. According to the current knowledge, biosimilars of IFX and ADL in IBD patients are shown to be as safe and effective as their originators. The future of biosimilars, in general, is promising due to the potential of making the health care system more sustainable. However, their use is accompanied by misconceptions regarding their effectiveness and safety, as well as by controversy regarding their interchangeability. Hence, until a scientific consensus is achieved, scientific data on the long-term effectiveness and safety of biosimilars are needed.

A Mechanistic Site-Of-Action Model: A Tool for Informing Right Target, Right Compound, And Right Dose for Therapeutic Antagonistic Antibody Programs

Quantitative modeling is increasingly utilized in the drug discovery and development process, from the initial stages of target selection, through clinical studies. The modeling can provide guidance on three major questions–is this the right target, what are the right compound properties, and what is the right dose for moving the best possible candidate forward. In this manuscript, we present a site-of-action modeling framework which we apply to monoclonal antibodies against soluble targets. We give a comprehensive overview of how we construct the model and how we parametrize it and include several examples of how to apply this framework for answering the questions postulated above. The utilities and limitations of this approach are discussed.

Intraperitoneal Route of Drug Administration: Should it Be Used in Experimental Animal Studies?

Intraperitoneal (IP) route of drug administration in laboratory animals is a common practice in many in vivo studies of disease models. While this route is an easy to master, quick, suitable for chronic treatments and with low impact of stress on laboratory rodents, there is a common concern that it may not be an acceptable route for drug administration in experimental studies. The latter is likely due to sparsity of information regarding pharmacokinetics of pharmacological agents and the mechanisms through which agents get systemic exposure after IP administration. In this review, we summarize the main mechanisms involved in bioavailability of IP administered drugs and provide examples of pharmacokinetic profiles for small and large molecules in comparison to other routes of administration. We conclude with a notion that IP administration of drugs in experimental studies involving rodents is a justifiable route for pharmacological and proof-of-concept studies where the goal is to evaluate the effect(s) of target engagement rather than properties of a drug formulation and/or its pharmacokinetics for clinical translation.

Effects of atorvastatin and aspirin combined therapy on inflammatory responses in patients undergoing coronary artery bypass grafting

This study was conducted to compare the effects of atorvastatin plus aspirin combined therapy on inflammatory responses, endothelial cell function, and blood coagulation system in patients undergoing coronary artery bypass grafting (CABG) to aspirin monotherapy. The patients were randomized into atorvastatin plus aspirin combined therapy group and aspirin monotherapy group. Reduced total cholesterol in the combined therapy group was found in a short term of medication for 14 days. On postoperative day (POD)-14, inhibitory effects of the combined therapy on whole blood aggregation as well as platelet activation assessed by flow cytometry were stronger than those of the monotherapy. Furthermore, cytokine, cytokine receptors, c-reactive protein and alpha1-acid glycoprotein in the combined therapy group were down-regulated on POD-14. At the same time, circulating levels of thromboxane A(2), vascular endothelial growth factor and thrombin-antithrombin III complex as well as P-selectin, L-selectin and intercellular adhesion molecule-1 were down-regulated, while E-selectin and transforming growth factor-beta1 was up-regulated. Atorvastatin plus aspirin combined therapy may improve inflammatory responses, accelerated platelet function, vascular endothelial cell function, blood coagulation system at the early stage such as 14th day after CABG. In conclusion, atorvastatin and aspirin combined therapy may bring beneficial effects to the patient after CABG.

AntiTNF-alpha agents in the treatment of inflammation

Tumour necrosis factor/cachecin (TNF-alpha) and lymphotoxin (LTalpha / TNF-alpha), 2 members of the TNF family of cytokines, have numerous biological functions, such as induction of apoptosis, cytotoxicity, inflammation, immunoregulation, proliferation and antiviral responses. Although TNF-alpha is produced by many cell types, the majority comes from activated macrophages. The related molecule, LT-alpha is produced mainly by activated lymphocytes and shares many of TNF's properties. TNF-alpha is active in both of its molecular forms, a secreted 17 kDa mature form and a transmembrane 26 kDa precursor. It induces activity by stimulating 2 distinct receptor subtypes, TNFR1 (55 kDa) and TNFR2 (75 kDa). The activation of TNFR1 is generally thought to trigger the majority of inflammatory and apoptotic effects, although TNFR2 has recently been shown to play more of a role in signal transduction than was initially thought. TNF-alpha is responsible for the induction of apoptosis in certain cell types, where it plays a pivotal role in the induction of cytotoxicity, killing of neoplastic cells and deletion of autoreactive T-cell clones. This cytokine, and in particular, its overproduction, has been implicated in the pathogenesis of a variety of immunologically mediated inflammatory diseases, including endotoxic shock, inflammatory bowel disease (IBD), multiple sclerosis (MS) and rheumatoid arthritis (RA). Currently, there is an intense effort underway to regulate TNF-alpha production and activity, in order to treat diseases where TNF-alpha is thought to be pathologically indicated. To achieve this goal, the pharmaceutical industry is currently pursuing a 2 pronged strategy: a) testing biological agents such as antibodies against TNF-alpha or soluble TNF-alpha receptor constructs, and b) identifying small molecular inhibitors directed against targets such as phosphodiesterase-IV (PDE-IV) and TNF-alpha converting enzyme (TACE), a subgroup of the matrix metalloproteinases (MMP). The main difficulties in the clinical implementation of the biological agents are: development of immunogenicity, lack of oral availability and the high cost of production. The currently available small molecular compounds exhibit poor bio-availability and low selectivity, resulting in unacceptable side effects and a low therapeutic index. Despite these hurdles, numerous companies are actively pursuing agents that inhibit TNF-alpha.

Interferon-gamma therapy: evaluation of routes of administration and delivery systems

Although different routes and delivery systems have been used to deliver interferon-gamma (IFN-gamma) for the treatment of a variety of viral and neoplastic diseases, little has been reported regarding the most efficient and least toxic routes and drug delivery modes required to achieve these goals. To have a greater understanding of the best strategies to use to administer this cytokine in an efficient, stable, and safe manner, this review details aspects of IFN-gamma concerning its mechanism of action, physical properties, and pharmacokinetics. One important conclusion that is drawn from this analysis is that a consistent, local concentration of IFN-gamma is necessary to achieve an optimal therapeutic response. A critical discussion covering the advantages and limitations of the currently used methodologies to deliver IFN-gamma in such a fashion is presented.

Inflammatory cytokines and soluble receptors after coronary artery bypass grafting

Much interest has been focused on the overexpression of proinflammatory cytokines, but studies on their soluble receptors are rare. For a comprehensive picture of cytokine activation in cardiac surgery, a combination of cytokines and the corresponding soluble receptor concentration should be determined. Blood samples were collected from the radial artery and coronary sinus perioperatively in ten patients undergoing coronary artery bypass grafting with cardiopulmonary bypass. TNF-alpha, IL-6, sTNFRI, sTNFRII, and sIL-6R levels in the plasma were determined. Systemic TNFRI, TNFRII and IL-6 increased significantly after reperfusion to the myocardium, while perioperative systemic sIL-6r levels were similar. Arterial and sinus levels of TNFRI, TNFRII and sIL-6r were similar before cardiopulmonary bypass. Five minutes after reperfusion to the myocardium, higher sinus TNFRI and TNFRII and lower sinus sIL-6R levels were observed as compared to the arterial levels. The myocardium release of sTNFRI (r=0.57, P=0.089) and sTNFRII (r=0.64, P=0.047) positively correlated with the change of cardiac index after cardiopulmonary bypass. Myocardium releases sTNFRI and sTNFRII after ischaemic-reperfusion injury, and this may be of benefit to cardiac performance. sIL-6R is constantly being produced in areas other than the myocardium, while sIL-6R levels are reduced by consumption in the myocardium after ischaemic-reperfusion injury.

Old and new drugs used in rheumatoid arthritis: a historical perspective. Part 2: the newer drugs and drug strategies

After a 20-year hiatus, drug development for rheumatoid arthritis resumed in the early 1980s with cyclosporine, continuing in the 1990s with minocycline, leflunomide, and the tumor necrosis factor-alpha antagonists, infliximab and etanercept. Unlike the older disease-modifying antirheumatic drugs (apart from the cytotoxics), the newer drugs were designed with strict reference to proven pathophysiology in rheumatoid arthritis and, apart from minocycline, the intended action of these agents is highly likely the explanation for the observed efficacy. The evidence for the evolution of more rational drug development in rheumatoid arthritis has not altered the fact that efficacy versus toxicity still remains the major determinant in the practical use of these agents, as well as in the use of other, experimental agents briefly discussed. Action, efficacy, and toxicity also determine the rational chronologic use of these drugs alone and, in particular, in combination.

Cortical interleukin-1 beta elevation after traumatic brain injury in the rat: no effect of two selective antagonists on motor recovery

Interleukin-1 is an inflammatory cytokine implicated in secondary responses to traumatic brain injury. We utilized a specific IL-beta enzyme-linked immunoadsorbant assay to examine the expression of IL-beta after lateral fluid percussion brain injury in the rat. IL-beta was significantly elevated in the ipsilateral injured cortex at 4 h after injury. Increased levels of IL-beta were also observed at 12, 24 and 72 h after injury, although such changes did not reach statistical significance. To determine whether injury-induced IL-beta expression may contribute to subsequent neurological impairment, we treated rats with either of two structurally different, selective IL-1 antagonists and monitored neurological recovery 1, 7 and 14 days later. Intracerebroventricular treatment with either the endogenous interleukin-1 receptor antagonist (10 microg) at 15 min, 2, 4, 6, and 8 h after injury or soluble IL-1 receptors (10 microg) at 15 min, 4 and 8 h after injury did not significantly alter outcome in a series of motor tasks. These data suggest that cortical elevations of IL-beta follow traumatic brain injury, but they may not contribute to subsequent neurological impairment.

Anti-TNF agents in Crohn's disease

The current treatment of Crohn's disease is limited by a lack of long-term efficacy of corticosteroid therapy and the associated side effects. Biological treatment strategies aimed at neutralising immune responses, offer new opportunities for the management of chronic inflammatory disorders. In Crohn's disease, anti-TNF agents have taken the lead in development of immune-modulating drugs since TNF is known to be a pivotal cytokine in this illness. Different strategies have been explored aimed at inhibiting TNF but at present, the majority of clinical data have been obtained with monoclonal antihuman TNF antibodies. The chimeric anti-TNF IgG1 antibody infliximab (cA2, Remicade, Centocor) has been proven, in multiple clinical trials, to be an effective and well tolerated therapy for the management of acute Crohn's disease and recently this compound has obtained FDA and European Medicines Evaluation Agency approval. Although there are some concerns about immunogenicity of the anti-TNF antibody resulting in the formation of human antichimeric antibodies (HACA) as well as lymphoproliferative disorders, the clinical benefit in the treatment of refractory Crohn's disease is a major therapeutic breakthrough. Further studies will be needed to establish the role and optimal dosing scheme of anti-TNF antibodies in maintenance of remission, monitor safety in the long run and to evaluate the effectiveness of alternative anti-TNF agents such as the TNF receptor/Fc fusion protein etanercept (Enbrel, Immunex) and TNF synthesis inhibitor thalidomide.

Etanercept: a review of its use in rheumatoid arthritis

Etanercept, a fusion protein consisting of the extracellular ligand-binding domain of the 75kD receptor for tumour necrosis factor-alpha and the constant portion of human IgG1, is administered by subcutaneous injection and is the first specific anti-cytokine therapy approved for rheumatoid arthritis. In patients with active rheumatoid arthritis [American College of Rheumatology (ACR) functional class I to III] who had failed to respond to previous treatment with > or = 1 disease-modifying antirheumatic drug (DMARD), etanercept, alone or in combination with methotrexate, produced improvements in all components included in the ACR core set of disease activity measures. A dose-response effect was apparent with etanercept 0.25 to 16 mg/m2 twice weekly in a randomised, double-blind study in 180 patients. The mean number of swollen or tender joints at the end of the 12-week study decreased by >50% in patients treated with etanercept 16 mg/m2 twice weekly and by <25% in patients treated with placebo. In a 24-week multicentre, randomised, double-blind study in 234 patients who were not allowed to use DMARDs, etanercept 10 or 25mg twice weekly had a rapid onset of effect. Significantly more patients treated with etanercept 25mg twice weekly than placebo experienced 20 (ACR 20), 50 (ACR 50) or 70% (ACR 70) improvement in ACR criteria after 3 and 6 months. Limited evidence suggests that the therapeutic effects of etanercept are maintained for up to 2 years. Etanercept 25mg twice weekly produced significant improvement in patients receiving oral or subcutaneous methotrexate 10 to 25 mg/week in a multicentre, randomised, double-blind, placebo-controlled study. A significantly greater proportion of patients treated with etanercept plus methotrexate (71%) than placebo plus methotrexate (27%) achieved the ACR 20 criteria after 6 months. Moreover, 39 and 15% of patients treated with etanercept plus methotrexate, but no placebo plus methotrexate recipients, had achieved the ACR 50 and ACR 70 criteria at this time. Etanercept 0.4 mg/kg twice weekly reduced disease activity in a preliminary, noncomparative study in 69 children aged > or =4 years with refractory juvenile rheumatoid arthritis. Although the overall frequency of infections was similar in patients treated with etanercept or placebo, upper respiratory tract infections were more common in patients treated with etanercept (29%) than placebo (16%). Injection site reactions occurred more frequently in etanercept- than placebo-treated patients, but did not bias the results of any study.

CONCLUSIONS

When etanercept is administered alone or in combination with methotrexate in patients with refractory rheumatoid arthritis, significant reductions in disease activity occur within 2 weeks and are sustained for at least 6 months. Thus, etanercept appears to be particularly well suited for use in patients who fail to respond to treatment with DMARDs.

Antitumor necrosis factor therapy for inflammatory bowel disease: a review of agents, pharmacology, clinical results, and safety

Tumor necrosis factor-alpha (TNFalpha), a proinflammatory cytokine, plays an important role in the pathogenesis of inflammatory bowel disease (IBD). Biotechnology agents including a chimeric monoclonal anti-TNF antibody (infliximab), a humanized monoclonal anti-TNF antibody (CDP571), and a recombinant TNF receptor fusion protein (etanercept) have been used to inhibit TNFalpha activity. Controlled trials have demonstrated efficacy for infliximab in moderately to severely active Crohn's disease (CD) and fistulizing CD sufficient to justify recent U.S. Food and Drug Administration (FDA) approval. Additional trials have been completed in rheumatoid arthritis (RA). Similarly, preliminary controlled trials have suggested efficacy for CDP571 in active CD and RA. Larger controlled trials have demonstrated efficacy for etanercept in RA patients who have failed disease modifying antirheumatic drug (DMARD) therapy leading to FDA approval for RA. Toxicities observed with anti-TNF therapies have included formation of human antichimeric antibodies (HACA) with associated acute and delayed hypersensitivity infusion reactions, human antihuman antibodies (HAHAs), and formation of autoantibodies with rare instances of drug-induced lupus. Several cases of non-Hodgkin's lymphoma also has been described. Future studies should evaluate optimal timing and duration of anti-TNF therapy, the utility of adjuvant medical treatments during anti-TNF therapy, and evaluate long-term safety and efficacy of the various anti-TNF agents.

Recombinant human tumor necrosis factor receptor (p75) Fc fusion protein (TNFR:Fc) in rheumatoid arthritis

BACKGROUND

Tumor necrosis factor (TNF) is the dominant mediator of the cytokine cascade that causes inflammation and joint destruction in rheumatoid arthritis. A new class of agents under investigation, the biologic TNF inhibitors, inhibits the activity of TNF. Recombinant human TNF receptor p75 Fc fusion protein (TNFR:Fc; Enbrel) blocks the activity of the cytokine TNF. The preclinical, Phase I, and Phase II data of TNFR:Fc in rheumatoid arthritis are reviewed in this article.

METHODS

All available data on TNFR:Fc in rheumatoid arthritis were reviewed. These data included published literature and data on file at the manufacturer.

RESULTS

TNFR:Fc has been effective in many models of inflammation, including animal models of rheumatoid arthritis and in clinical rheumatoid arthritis trials. Conclusions from a study with TNFR "knockout" mice (genetically altered mice incapable of producing TNFR proteins) demonstrated that p75 TNFR is a natural antagonist of TNF-mediated inflammation. A placebo-controlled, dose-escalation, Phase I trial evaluated the safety and efficacy of TNFR:Fc in patients with rheumatoid arthritis. There were no serious adverse effects reported. A Phase II, randomized, double-blind, placebo-controlled trial evaluated 180 patients with active rheumatoid arthritis whose previous therapy had failed. A dose-response relationship was observed in the number of tender and swollen joints; patients who received the highest dose (16 mg/m2) of TNFR:Fc had the greatest improvement. Treatment was generally well tolerated. TNFR:Fc is nonimmunogenic; no antibodies to TNFR:Fc have been detected thus far in human studies.

CONCLUSIONS

Preliminary data indicate that TNFR:Fc is an excellent candidate for future long-term studies in the treatment of rheumatoid arthritis.

Circulating tumor necrosis factor (TNF)-alpha and soluble TNF-alpha receptors in patients with Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an inflammatory disorder that may implicate proinflammatory cytokines such as TNF-alpha in its pathogenesis. We determined serum levels of TNF-alpha and the specific antagonists sTNF-Rs p55 and p75 in 24 patients with GBS at days 1, 15 and 30 of hospitalization. Patients were in the progression phase of the disease at day 1, and in the recovery phase at day 30. They were classified as able to walk (stage A), confined to bed (B), or under assisted ventilation (C). All patients underwent plasma exchange within day 1-12. At day 1, TNF-alpha levels were elevated in 15/24 patients, and sTNF-Rs were elevated in 21/23. TNF-alpha levels had not decreased at day 15, and dropped at day 30 (p < 0.04), whereas sTNF-R p55 remained elevated at day 15 and day 30. The TNF-alpha/sTNF-Rs ratio, estimating active TNF-alpha unbound to sTNF-Rs, decreased from day 1 to day 30 (p < 0.05). A positive correlation was found between disease severity and sTNF-R serum levels (p < 0.01). In conclusion, elevated circulating sTNF-Rs assesses activation of the TNF-alpha system in almost all patients with GBS and correlates positively with disease severity. Drop of TNF-alpha contrasting with sustained elevation of sTNF-R p55 during recovery suggests that sTNF-R p55 may be important in the fading of the neural inflammatory effect of TNF-alpha in GBS.

ICAM-1 and VCAM-1 expression in accelerated cardiac allograft arteriopathy and myocardial rejection are influenced differently by cyclosporine A and tumour necrosis factor-alpha blockade

Expression of the vascular cell adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) occurs in allograft myocardium and in coronary arteries, promoting adhesion and transendothelial migration of inflammatory cells. We therefore investigated, in cholesterol-fed rabbits 9-10 days following heterotopic cardiac transplantation, whether the reduction of both myocardial rejection and graft arteriopathy with cyclosporine A (CsA) or graft arteriopathy alone with tumour necrosis factor-alpha soluble receptor (TNFsr) was associated with suppression of ICAM-1 and VCAM-1 expression. Host hearts showed negative immunostaining for these adhesion molecules, whereas donor specimens from untreated (control) rabbits showed moderate immunostaining for ICAM-1 and weaker immunostaining for VCAM-1 in the coronary arteries, myocardium (cardiac myocytes), and perivenular regions. The selective reduction of the coronary arteriopathy with TNFsr was associated with somewhat reduced expression of these adhesion molecules in the arteries, whereas CsA also suppressed myocardial rejection and markedly decreased both vascular and myocyte expression of ICAM-1 and VCAM-1.

Molecular and biological properties of an interleukin-1 receptor immunoadhesin

Overproduction of the cytokine interleukin 1 (IL-1) is an important factor in the pathogenesis of several autoimmune and inflammatory disease. To develop a recombinant inhibitor of IL-1 with an extended pharmacologic half-life, we constructed an IL-1 receptor immunoadhesin (IL-1R-IgG), by fusing the extracellular domain of the type IL-1 receptor with the hinge and Fc regions of human IgG1 heavy chain. Transfected human 293 cells express IL-1R-IgG as a secreted, disulfide-bonded homodimer. The secreted protein contains an intact antibody Fc region, as indicated by immunoblotting, and a functional IL-1 receptor region, as indicated by ligand-blotting. Saturation binding analysis indicates an equilibrium dissociation constant (KD) of 350 pM for the binding of IL-1R-IgG to its ligand, IL-1 beta. Kinetic analysis of the binding reveals an off rate of 0.1 min-1 and an on rate of 1.5 x 10(8) min-1 M-1, yielding a calculated KD of 770 pM. These binding properties are similar to those of cell-surface type I IL-1 receptor. IL-1R-IgG is capable of inhibiting the biological activity of IL-1 beta in vitro, as evidenced in a thymocyte proliferation assay. Pharmacokinetic analysis in mice indicates that IL-1R-IgG has a terminal half-life of 91 hr in the blood circulation. This half-life is markedly longer than the values reported for other recombinant inhibitors of IL-1 such as the IL-1 receptor antagonist or soluble IL-1 receptor. Thus, IL-1R-IgG may be useful for investigating the interaction of IL-1 with its receptor and the role of IL-1 in disease, as well as for potential intervention in pathological situations involving overproduction of IL-1.

Protective effect of 55- but not 75-kD soluble tumor necrosis factor receptor-immunoglobulin G fusion proteins in an animal model of gram-negative sepsis

The aim of this study was to compare the ability of both a 55- and 75-kD soluble tumor necrosis factor receptor immunoglobulin G fusion protein (sTNFR-IgG) in protecting against death in a murine model of gram-negative sepsis. Pretreatment with 250 micrograms of the p75 construct delayed but did not avert death in this model, reducing peak bioactive TNF-alpha levels after infection from 76.4 ng ml-1 in control mice to 4.7 ng ml-1 in the treated group (p < 0.05, two-sample t test). However, these low levels of bioactive TNF-alpha persisted in the p75 fusion protein-treated animals compared with the controls and were sufficient to mediate delayed death. In contrast, pretreatment with 200 micrograms of the p55 sTNFR-IgG gave excellent protection against death with complete neutralization of circulating TNF. Studies of the binding of TNF-alpha with the soluble TNFR fusion proteins showed that the p75 fusion construct exchanges bound TNF-alpha about 50-100-fold faster than the p55 fusion protein. Thus, although both fusion proteins in equilibrium bind TNF-alpha with high affinity, the TNF-alpha p55 fusion protein complex is kinetically more stable than the p75 fusion construct, which thus acts as a TNF carrier. The persistent release of TNF-alpha from the p75 fusion construct limits its therapeutic effect in this model of sepsis.