Immunogenicity assay development and validation for biological therapy as exemplified by ustekinumab.

Introduction of biotherapeutics has been a major milestone in the treatment of different chronic diseases. Nevertheless, the immune system can recognize the administered biological as non-self and respond with generation of anti-drug antibodies (ADA), including neutralizing ADA (nADA). Immunogenic responses may result in altered drug dynamics and kinetics leading to changes in safety and efficacy. However, there are several challenges with standard techniques for immunogenicity testing. Ustekinumab (UST), used in different inflammatory diseases, is a therapeutic antibody directed against the shared p40 subunit of interleukin (IL)-12 and IL-23, interfering in the pathogenically crucial T helper type 1 (Th1)/Th17 pathway. We established and validated different approaches for detection and quantitation of UST, UST-specific ADA and nADA. Addressing the obstacle of complex formation of UST with nADA, we developed an acidification assay to approach the total amount of nADA. Validated methods were based on surface plasmon resonance spectroscopy (SPR), enzyme-linked immunosorbent assay (ELISA) and a cell-based approach to characterize neutralizing capacity of nADA. Parameters assessed were determination and quantitation limits, linearity, range, precision, accuracy and selectivity. Quantitation of ADA and UST was feasible at lower concentrations using ELISA, whereas SPR showed a wider linear range for determination of ADA and UST. Accuracy, precision and linearity for quantitation were comparable using ELISA, SPR and the cell-based approach. All validated parameters fulfill the requirements of regulatory agencies. A combination of the testing approaches could address the increasing demand of precision medicine as it can be suitable for capturing the whole spectrum of immunogenicity and is transferable to other biologicals.

A machine-learned analysis of human gene polymorphisms modulating persisting pain points to major roles of neuroimmune processes.

BACKGROUND: Human genetic research has implicated functional variants of more than one hundred genes in the modulation of persisting pain. Artificial intelligence and machine-learning techniques may combine this knowledge with results of genetic research gathered in any context, which permits the identification of the key biological processes involved in chronic sensitization to pain. METHODS: Based on published evidence, a set of 110 genes carrying variants reported to be associated with modulation of the clinical phenotype of persisting pain in eight different clinical settings was submitted to unsupervised machine-learning aimed at functional clustering. Subsequently, a mathematically supported subset of genes, comprising those most consistently involved in persisting pain, was analysed by means of computational functional genomics in the Gene Ontology knowledgebase. RESULTS: Clustering of genes with evidence for a modulation of persisting pain elucidated a functionally heterogeneous set. The situation cleared when the focus was narrowed to a genetic modulation consistently observed throughout several clinical settings. On this basis, two groups of biological processes, the immune system and nitric oxide signalling, emerged as major players in sensitization to persisting pain, which is biologically highly plausible and in agreement with other lines of pain research. CONCLUSIONS: The present computational functional genomics-based approach provided a computational systems-biology perspective on chronic sensitization to pain. Human genetic control of persisting pain points to the immune system as a source of potential future targets for drugs directed against persisting pain. Contemporary machine-learned methods provide innovative approaches to knowledge discovery from previous evidence. SIGNIFICANCE: We show that knowledge discovery in genetic databases and contemporary machine-learned techniques can identify relevant biological processes involved in Persitent pain.

Dysregulation of lysophosphatidic acids in multiple sclerosis and autoimmune encephalomyelitis.

Bioactive lipids contribute to the pathophysiology of multiple sclerosis. Here, we show that lysophosphatidic acids (LPAs) are dysregulated in multiple sclerosis (MS) and are functionally relevant in this disease. LPAs and autotaxin, the major enzyme producing extracellular LPAs, were analyzed in serum and cerebrospinal fluid in a cross-sectional population of MS patients and were compared with respective data from mice in the experimental autoimmune encephalomyelitis (EAE) model, spontaneous EAE in TCR1640 mice, and EAE in Lpar2 -/- mice. Serum LPAs were reduced in MS and EAE whereas spinal cord LPAs in TCR1640 mice increased during the 'symptom-free' intervals, i.e. on resolution of inflammation during recovery hence possibly pointing to positive effects of brain LPAs during remyelination as suggested in previous studies. Peripheral LPAs mildly re-raised during relapses but further dropped in refractory relapses. The peripheral loss led to a redistribution of immune cells from the spleen to the spinal cord, suggesting defects of lymphocyte homing. In support, LPAR2 positive T-cells were reduced in EAE and the disease was intensified in Lpar2 deficient mice. Further, treatment with an LPAR2 agonist reduced clinical signs of relapsing-remitting EAE suggesting that the LPAR2 agonist partially compensated the endogenous loss of LPAs and implicating LPA signaling as a novel treatment approach. Graphical summary of lysophosphatidic signaling in multiple sclerosis.

Multiple rodent models and behavioral measures reveal unexpected responses to FTY720 and DMF in experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a widely-used rodent model for multiple sclerosis (MS), but a single model can hardly capture all features of MS. We investigated whether behavioral parameters in addition to clinical motor function scores could be used to assess treatment efficacy during score-free intervals in the relapsing-remitting EAE model in SJL/J mice. We studied the effects of the clinical reference compounds FTY720 (fingolimod, 0.5mg/kg/day) and dimethyl fumarate (DMF, 20-30 mg/kg/day) on clinical scores in several rodent EAE models in order to generate efficacy profiles. SJL/J mice with relapsing-remitting EAE were studied using behavioral tests, including rotarod, gait analysis, locomotor activity and grip strength. SJL/J mice were also examined according to Crawley's sociability and preference for social novelty test. Prophylactic treatment with FTY720 prevented clinical scores in three of the four EAE rodent models: Dark Agouti (DA) and Lewis rats and C57BL/6J mice. Neither prophylactic nor late-therapeutic treatment with FTY720 reduced clinical scores or reversed deficits in the rotarod test in SJL/J mice, but we observed effects on motor functions and sociability in the absence of clinical scores. Prophylactic treatment with FTY720 improved the gait of SJL/J mice whereas late-therapeutic treatment improved manifestations of reduced social (re)cognition or preference for social novelty. DMF was tested in three EAE models and did not improve clinical scores at the dose used. These data indicate that improvements in behavioral deficits can occur in absence of clinical scores, which indicate subtle drug effects and may have translational value for human MS.

Azithromycin distinctively modulates classical activation of human monocytes in vitro.

BACKGROUND AND PURPOSE: Azithromycin has been reported to modify activation of macrophages towards the M2 phenotype. Here, we have sought to identify the mechanisms underlying this modulatory effect of azithromycin on human monocytes, classically activated in vitro. EXPERIMENTAL APPROACH: Human blood monocytes were primed with IFN-γ for 24 h and activated with LPS for 24 h. Azithromycin, anti-inflammatory and lysosome-affecting agents were added 2 h before IFN-γ. Cytokine and chemokine expression was determined by quantitative PCR and protein release by ELISA. Signalling molecules were determined by Western blotting and transcription factor activation quantified with a DNA-binding ELISA kit. KEY RESULTS: Azithromycin (1.5-50 µM) dose-dependently inhibited gene expression and/or release of M1 macrophage markers (CCR7, CXCL 11 and IL-12p70), but enhanced CCL2, without altering TNF-α or IL-6. Azithromycin also enhanced the gene expression and/or release of M2 macrophage markers (IL-10 and CCL18), and the pan-monocyte marker CD163, but inhibited that of CCL22. The Toll-like receptor (TLR) 4 signalling pathway was modulated, down-regulating NF-κB and STAT1 transcription factors. The inhibitory profile of azithromycin differed from that of dexamethasone, the phosphodiesterase-4 inhibitor roflumilast and the p38 kinase inhibitor SB203580 but was similar to that of the lysosomotropic drug chloroquine. Effects of concanamycin and NH4Cl, which also act on lysosomes, differed significantly. CONCLUSIONS AND IMPLICATIONS: Azithromycin modulated classical activation of human monocytes by inhibition of TLR4-mediated signalling and possible effects on lysosomal function, and generated a mediator expression profile that differs from that of monocyte/macrophage phenotypes so far described.

Macrolides for the treatment of chronic bacterial prostatitis: an effective application of their unique pharmacokinetic and pharmacodynamic profile (Review).

Chronic bacterial prostatitis (CBP) is a persistent infection of the prostate characterized by poor quality of life mainly due to frequent relapse episodes caused by incomplete eradication of causative pathogens. Aggressive antibacterial therapy is required to attenuate the severe symptoms of CBP and to achieve a permanent cure. Although fluoroquinolones are currently recommended as first-choice agents, macrolide antibiotics are emerging as a noteworthy option for the treatment of CBP. Macrolide antibiotics are characterized by an impressive array of distinct pharmacokinetic (PK) and pharmacodynamic (PD) properties. These properties include high intracellular accumulation in phagocytes and at sites of infection, including the prostate; broad antibiotic but also biofilm-inhibiting properties; immunomodulating and inflammation-resolving activities. These features offer particular advantages for the treatment of chronic infections of the prostate gland, which are not easily amenable to drug therapy. Macrolides may be exploited to counteract the unsatisfactory rates of clinical symptom improvement and pathogen eradication. The results of a number of clinical trials support this proposal.

Antibiotic therapy for exacerbations of chronic obstructive pulmonary disease (COPD).

Chronic obstructive pulmonary disease (COPD) is already the world's fourth most common cause of mortality and likely to become the third in a few year's time. Because it is an inflammatory airway disease with altered host immune response, infectious complications are frequent. Acute exacerbations of COPD (AECOPD) significantly worsen the patient's general health, accelerating disability. Each exacerbation leads progressively to further deterioration of lung function. Among the various causes of AECOPD, including viruses, bacteria and air pollution, a bacterial etiology is most common (50-69%). The management of AECOPD remains extremely challenging and places a heavy economic burden on health care institutions. The decision to administer antibiotics in AECOPD is multifactorial, the most important considerations being severity of the COPD stage and patient performance status, clinical symptoms (increased dyspnea, sputum volume and sputum purulence), severity of current and previous exacerbations, comorbidity and current smoking. Exacerbations which require hospital admission are associated with significant in-patient mortality. AECOPD patients presenting with worsening dyspnea, increased sputum volume and purulence should be offered antimicrobial therapy. If treating with antibiotics, treatment must include coverage for Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis in all cases, but other bacteria (such as Gram-negatives) may need to be covered depending on the condition of the patient. Antibiotics, particularly macrolides and fluoroquinolones, when administered under suitable conditions, shorten the clinical course and prevent severe deterioration. possible complications resulting from untreated severe AECOPD surpass the potential risks from the use of antibiotic therapy. Additional anti-inflammatory and immunomodulatory actions of some antibiotics may contribute to their efficacy in AECOPD.

Accelerated healing of excisional skin wounds by PL 14736 in alloxan-hyperglycemic rats.

PL 14736 is a synthetic peptide, originally isolated from human gastric juice, that has anti-inflammatory and tissue-protective actions in experimental models of gastrointestinal inflammation. To investigate its possible benefit in poorly healing skin wounds, the effects of the topical application of PL 14736 in a gel formulation have been studied on full-thickness excisional wounds in rats, either healthy or made hyperglycemic by alloxan (175 mg/kg s.c.) 5 days previously. The effects of becaplermin gel (platelet-derived growth factor, PDGF-BB, Regranex, a standard therapy for diabetic foot ulcers, were investigated for comparison. Healing was evaluated for up to 7 days after wounding, using digital planimetry analysis, macroscopic scoring and histology. While healing was too rapid in healthy rats to observe enhancement by either treatment, in the hyperglycemic rats which exhibited delayed healing, PL 14736 (10-1,000 microg/wound) produced a dose-dependent acceleration of wound healing (determined by macroscopic scoring) equivalent at the highest doses to that observed with becaplermin. The beneficial effect on healing was associated with increased deposition of organized granulation tissue by day 7 for both PL 14736 and becaplermin, as determined histologically. PL 14736 tended to have a greater effect than becaplermin on the formation of granulation tissue containing mature collagen. Wound contraction, as measured by planimetry, was not significantly affected. In conclusion, topical PL 14736 produces a dose-dependent acceleration of deficient skin wound healing in hyperglycemic rats by facilitating granulation tissue formation, similar to the response seen with topical becaplermin, the standard therapy for diabetic skin wounds. PL 14736 may represent an alternative therapy for delayed wound healing, such as that seen with diabetic foot ulcers, without the proliferative concerns or immunogenicity associated with growth factors.

The novel antifungal agent PLD-118 is neither metabolized by liver microsomes nor inhibits cytochrome P450 in vitro.

PLD-118 is a novel, oral antifungal drug, under development for the treatment of Candida infections. Possible metabolism of PLD-118 by rat, dog and human S9 liver homogenates and inhibition of human cytochrome P450 (CYP) enzymes were investigated. PLD-118 (10 and 100 microM) incubated for 0-60 min with S9 fractions and NADPH was determined by HPLC, using the Waters AccQ.Tag method after derivatization of amino acids to stable, fluorescent derivatives. CYP assays were performed using pooled human liver microsomes with substrates, selective towards human CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A, incubated at concentrations around the Km. Incubation mixtures were preincubated with PLD-118 (0.1-100 microM) or control inhibitor for 5 min. No metabolism of PLD-118 was detected with rat and dog S9 fractions. A small (8%) decrease in PLD-118 at 100 microM (not detected at 10 microM) with human microsomes was considered to be biologically irrelevant. PLD-118 did not inhibit any of the tested CYPs. PLD-118, at concentrations up to 100 microM, is not metabolized by rat, dog or human liver S9 homogenates and does not inhibit human CYPs in vitro, suggesting little likelihood for interaction of PLD-118 with drugs metabolized by these enzymes.

Anti-inflammatory effects of macrolide antibiotics.

Macrolides are widely used as antibacterial drugs. Clinical and experimental data, however, indicate that they also modulate inflammatory responses, both contributing to the treatment of infective diseases and opening new opportunities for the therapy of other inflammatory conditions. Considerable evidence, mainly from in vitro studies, suggests that leukocytes and neutrophils in particular, are important targets for modulatory effects of macrolides on host defense responses. This underlies the use of the 14-membered macrolide erythromycin for the therapy of diffuse panbronchiolitis. A variety of other inflammatory mediators and processes are also modulated by macrolides, suggesting that the therapeutic indications for these drugs may be extended significantly in future.

Ebselen: prospective therapy for cerebral ischaemia.

Stroke occurs due to haemorrhage or occlusive injury and results in ischaemia and reperfusion injury. A variety of destructive mechanisms are involved including oxygen radical generation, calcium overload, cytotoxicity and apoptosis as well as the generation of inflammatory mediators. Ebselen, 2-phenyl-1, 2-benzisoselenazol-3(2H)-one (PZ 51, DR3305), is a mimic of GSH peroxidase which also reacts with peroxynitrite and can inhibit enzymes such as lipoxygenases, NO synthases, NADPH oxidase, protein kinase C and H(+)/K(+)-ATPase. Ebselen is in a late stage of development for the treatment of stroke. The molecular actions of ebselen contribute to its anti-inflammatory and anti-oxidant properties, which have been demonstrated in a variety of in vivo models. Numerous in vitro experiments using isolated LDL, liposomes, microsomes, isolated cells and organs have established that ebselen protects against oxidative challenge. Unlike many inorganic and aliphatic selenium compounds, ebselen has low toxicity as metabolism of the compound does not liberate the selenium moiety, which remains within the ring structure. Subsequent metabolism involves methylation, glucuronidation and hydroxylation. Experimental studies in rats and dogs have revealed that ebselen is able to inhibit both vasospasm and tissue damage in stroke models, which correlates with its inhibitory effects on oxidative processes. Results from randomised, placebo-controlled, double-blind clinical studies on the neurological consequences of acute ischaemic stroke, subarachnoid haemorrhage and acute middle cerebral artery occlusion, have revealed that ebselen significantly enhances outcome in patients who have experienced occlusive cerebral ischaemia of limited duration. The benefit achieved with ebselen is closely related to the rapidity with which the treatment is initiated, following the onset of the stroke attack. Safety and tolerability are good and no adverse effects have become apparent. Ebselen is currently at the pre-registration stage for subarachnoid haemorrhage and stroke in Japan.

Oxaceprol is a well-tolerated therapy for osteoarthritis with efficacy equivalent to diclofenac.

The therapeutic equivalence and safety of treatment for 21 days with 400 mg t.i.d. oxaceprol (n = 132) and 50 mg t.i.d. diclofenac (n = 131) were assessed in a multicentre, randomised, double-blind study of a mixed population of patients with osteoarthritis of the knee and/or hip. In a per-protocol analysis of efficacy, the mean Lequesne index decreased by 2.5 points in the oxaceprol group (n = 109) and by 2.8 points in the diclofenac group (n = 109). The 95% confidence interval for the end-point difference revealed therapeutic equivalence. This was confirmed by assessments (visual analogue scale) of pain at rest, weight-bearing pain, pain on standing and pain on movement, all of which decreased to a similar extent under both treatments. The pain-free walking time increased in both groups from 10 min to 25 min by the end of the treatment period. Mobility was also increased to a similar extent by both drugs. The physicians assessed treatment as good or very good in 45-46% of patients in both groups. In all patients who received treatment, 28 and 37 adverse events were reported by 25 out of 132 (18.9%) and 33 out of 131 (25.2%) patients treated with oxaceprol and diclofenac, respectively. In 15 patients (11.4%) with 15 adverse events in the oxaceprol group and 25 patients (19.1%) with 27 adverse events in the diclofenac group, a relation to the medication was considered probable. The difference between the groups was statistically significant (p = 0.04106) for the number of these adverse events. Oxaceprol is therapeutically equivalent to diclofenac, but better tolerated than diclofenac in the treatment of osteoarthritis.

Antirheumatic agents and leukocyte recruitment. New light on the mechanism of action of oxaceprol.

Most anti-inflammatory agents used in the treatment of joint diseases exert inhibitory effects on leukocyte infiltration. Methotrexate, a disease-modifying drug, and corticosteroids also inhibit leukocyte accumulation during inflammation. However, the mechanisms of action of these different compounds on leukocytes vary and in the case of non-steroidal anti-inflammatory drugs (NSAIDs) the mechanism(s) may be indirect. No current drug for inflammatory or degenerative joint disease has been proposed to act specifically by an inhibitory action on neutrophilic leukocytes. Oxaceprol is an amino acid derivative that has been used for several years for the treatment of osteoarthritis and rheumatoid arthritis, ameliorating pain and stiffness and showing good gastrointestinal safety, particularly in comparison with NSAIDs. Recent experimental studies have shown that oxaceprol does not inhibit the synthesis of prostaglandins in vitro, but markedly inhibits neutrophil infiltration into the joints of rats with adjuvant arthritis. These results support earlier screening data showing inhibition by oxaceprol of leukocyte infiltration into sites of acute inflammation. In studies on surgical ischemia reperfusion in hamsters in vivo, oxaceprol was an effective inhibitor of leukocyte adhesion and extravasation. It is proposed that oxaceprol represents a therapeutic agent for degenerative and inflammatory joint diseases, which acts predominantly by inhibiting leukocyte adhesion and migration.

Inflammation: from molecular biology to clinic.

The 3rd World Congress on Inflammation reflected an emphasis on cytokines and cell signaling, but also provided an overview of some of the current hot topics in inflammation research. The chemokines are an exponential growth area for researchers in several fields, and chemokine antagonists are under study for potential use in inflammatory disease. The use of soluble receptors, antibodies and gene deletion has already validated a number of new approaches, notably those targeted at TNF-alpha, IL-8 and, as revealed at this meeting, IL-6, NFkappaB and AP-1. The pharmacological regulation of apoptosis for disease therapy is also becoming a possibility. It is probable that within the next 12 months a number of small-molecule synthetic compounds will be reported as likely candidates for future antiinflammatory agents. The marketing of specific COX-2 inhibitors is likely to provide a significant step forward in therapeutic tolerability. Gene therapy for inflammation still lies several years in the future, but initial clinical studies are under way.

COX-2 inhibitors at the 8th International Conference of the Inflammation Research Association.

An intensive search is underway for novel selective inhibitors of cyclo-oxygenase (COX)-2. These compounds promise to be potent anti-inflammatory agents with little gastrointestinal intolerance. Meloxicam, with some selectivity for COX-2, is already marketed, and at least two companies are carrying out clinical studies with selective inhibitors. A variety of potential successor compounds were presented at the 8th International Conference of the Inflammation Research Association (IRA) in Hershey, PA on 27-31 October 1996.

Aceclofenac in rheumatoid arthritis: a useful and novel anti-inflammatory.

The efficacy and safety of 100 mg aceclofenac twice daily was investigated in 73 patients with active rheumatoid arthritis in a multi-centre, double blind, randomised, parallel group, placebo controlled study over a period of 4 weeks. Treatment with aceclofenac was effective in improving the Ritchie articular index (predetermined primary end point), duration of morning stiffness, joint swelling, ARA functional class, patient's and physician's global assessments, and pain. All these improved to a significantly (P < 0.05) greater extent than in placebo-treated patients. Grip strength showed a significant improvement from baseline in the aceclofenac-treated group and this was greater than the improvement measured in placebo treated patients. No significant difference was detected between the treatment groups for the number of subjects reporting an adverse event. Aceclofenac administered orally at 100 mg twice daily for four weeks thus produced significant improvements in patients with active rheumatoid arthritis. This treatment was well tolerated with an adverse event profile similar to that of placebo.

Stimulation of cytokine production via a special standardized mistletoe preparation in an in vitro human skin bioassay.

The mistletoe preparation Lektinol is standardized with respect to bioactive mistletoe lectin, the active component of mistletoe. This standardized mistletoe preparation and its active components (mistletoe lectins) were compared in the skin2 bioassay in vitro for their capacity to stimulate interleukin 1 alpha and interleukin 6 release from skin analogue tissue, composed of human cells in their naturally secreted matrix. The standardized mistletoe preparation, its basic ingredient, aqueous mistletoe extract, and pure mistletoe lectins all stimulated IL-1 alpha and IL-6 release from skin2 tissues during 24 h incubation. The amounts of cytokines released from various skin2 tissue lots by mistletoe lectin I (ML I) (0.75-8.0 ng/ml) and by the standardized mistletoe preparation remained relatively constant across a series of different batches. Concentration-response curves to the standardized mistletoe preparation and ML I were similar for IL-1 alpha and IL-6 release. The importance of the concentration of mistletoe lectins for the cytokine-releasing action of the standardized mistletoe preparation was confirmed using a neutralizing anti-mistletoe lectin antiserum. CONCLUSIONS. Using the skin2 method it was shown that reproducible stimulation of cytokine release by a standardized mistletoe preparation from batch to batch is one of the notable features of its pharmaceutical quality. This standardized mistletoe preparation therefore represents a preparation with constant immunobiological effects. Mistletoe lectins of the standardized mistletoe preparation are the active substances in the skin2 bioassay. The skin2 method is a reliable quantitative bioassay for determination of immunopharmacological effects.

Oxaceprol, an atypical inhibitor of inflammation and joint damage.

Oxaceprol, an established therapeutic agent for osteoarthritis, had no effect on macrophage prostaglandin E2 release in vitro and inhibited carrageenan paw oedema at high doses (18-150 mg/kg p.o.). In the same dose range, oxaceprol was comparable to indomethacin (3 mg/kg p.o.) as an inhibitor of yeast hyperalgaesia and at 6-50 mg/kg/day p.o. had a mild, variable inhibitory effect on cotton pellet granuloma formation. In adjuvant arthritic rats, oxaceprol (6-54 mg/kg/day p.o.) given therapeutically had no effect on the primary paw oedema response, but inhibited secondary lesions in the ears and tail. Histologically, oxaceprol markedly inhibited inflammatory cell infiltration and bone damage in the adjuvant-injected paw. In contrast to indomethacin, oxaceprol was more effective at inhibiting periarticular soft tissue inflammation but did not affect cartilage breakdown in this model. Oxaceprol has a clearly different spectrum of action to NSAIDs such as indomethacin and may act by inhibiting leucocyte infiltration and late connective tissue changes during inflammatory joint disease.

Clinical pharmacokinetics of molsidomine.

Molsidomine is a prodrug for the formation of nitric oxide (NO). Its pharmacokinetics are characterised by rapid absorption and hydrolysis, taking a short time to achieve maximal systemic concentrations of both the parent compound and its active metabolite, SIN-1. The time to peak plasma drug concentration (tmax) is 1 to 2 hours. The bioavailability of the parent compound after oral administration in tablet form is 44 to 59%, but further metabolism to release NO and form polar metabolites is rapid; the half-life (t-1/2) of SIN-1 is 1 to 2 hours. Urinary excretion accounts for more than 90% of the part of the administered dose of molsidomine which is not excreted unchanged. Protein binding of the parent compound is very low (3 to 11%) and its volume of distribution (Vd) corresponds to the range of bodyweight. Single-dose studies (1, 2 and 4 mg) have revealed linear pharmacokinetics, and multiple dose studies in healthy individuals (2 mg 3 times daily for 7 days) and coronary artery disease (CAD) patients (4 mg 4 times daily for 4 weeks) do not show any accumulation of the drug. A study in young and elderly individuals indicated that the first-pass effect is decreased and t-1/2 prolonged with age, resulting in an increased area under the concentration-time curve (AUC) of molsidomine and SIN-1. In patients with liver disease and congestive heart failure similar changes were observed, but much less so in patients with CAD. Clearance was also impaired in patients with liver disease, but the pharmacokinetics of molsidomine were not markedly altered by impaired renal function. In general, due to a large therapeutic dose range, dosage adjustments are not required on the basis of clinical experience. In certain patients a lower starting dose may be recommended, such as in those with impaired liver or kidney function, in congestive heart failure or in the presence of concomitant treatment with other vasoactive compounds. A linear dose-effect relationship is observed with counterclockwise hysteresis, i.e. a greater effect associated with the decrease of plasma concentrations than during their increase, which may be at least partly due to the metabolic delay in the formation of NO from SIN-1. Accordingly, the duration of action of molsidomine is longer than would be expected on the basis of the elimination half-life. The pharmacokinetics of molsidomine support the recommended dosages for use in angina pectoris.