Assessing the need for routine safety testing for patients being treated with dupilumab for moderate-to-severe atopic dermatitis.

Atopic dermatitis (also known as AD or eczema) is a common skin disease that can cause intense and persistent itching and rashes. Skin creams or ointments are not suitable or effective for some patients with moderate-to-severe AD. In these patients, oral (taken by mouth) or injected medications may be required. Some of those oral or injected treatments could be toxic and often have unwanted side effects, especially when used for a longer period of time, so patients must be regularly tested to see whether those treatments are harming their blood or organs. Dupilumab is a newer injectable drug for treating moderate-to-severe AD. Dupilumab specifically targets key molecules in the body that cause AD. Dupilumab has been tested for up to one year in more than 2000 patients enroled in placebo-controlled clinical trials. During those trials, patients provided blood and urine samples for laboratory testing while they were being treated with dupilumab or placebo (dummy drug). In this paper, the authors from Germany and the U.S.A, analysed how blood cells, blood chemistry, and urine chemistry changed during treatment, to check whether dupilumab is safe to use without the need for regular laboratory tests. After performing many routine laboratory tests on patients' blood and urine, they found that there were no clinically important changes in test results that could be linked to dupilumab. They concluded that patients using dupilumab for moderate-to-severe AD do not need routine laboratory testing. This is a summary of the study: Laboratory safety of dupilumab in moderate-to-severe atopic dermatitis: results from three phase III trials (LIBERTY AD SOLO 1, LIBERTY AD SOLO 2, LIBERTY AD CHRONOS).

Laboratory safety of dupilumab in moderate-to-severe atopic dermatitis: results from three phase III trials (LIBERTY AD SOLO 1, LIBERTY AD SOLO 2, LIBERTY AD CHRONOS).

BACKGROUND: Dupilumab [a monoclonal antibody blocking the shared receptor subunit for interleukin (IL)-4 and IL-13] is approved for patients aged ≥ 12 years with inadequately controlled, moderate-to-severe atopic dermatitis (AD). Dupilumab trials of up to 52 weeks demonstrated efficacy and a favourable safety profile in patients with moderate-to-severe AD inadequately controlled with topical medications. OBJECTIVES: To further characterize the safety of dupilumab by evaluating clinical laboratory findings from three randomized, double-blinded, placebo-controlled phase III trials (LIBERTY AD SOLO 1 & 2 and LIBERTY AD CHRONOS). METHODS: Patients were randomized 1 : 1 : 1 (SOLO 1 & 2) or 3 : 1 : 3 (CHRONOS) for 16 and 52 weeks, respectively, to dupilumab weekly, every 2 weeks or placebo. CHRONOS patients received a standardized concomitant topical corticosteroid regimen. Laboratory outcomes were summarized descriptively in 1376 patients from SOLO 1 & 2 and 740 from CHRONOS. RESULTS: Treatment groups had similar results in baseline laboratory parameters. Platelets and neutrophils showed mild decreases from baseline in dupilumab vs. placebo groups. Some dupilumab-treated patients had small transient increases in eosinophils. Grade 3 eosinophilia was reported in < 1% of dupilumab-treated and placebo-treated patients; no adverse events were associated with eosinophilia. Lactate dehydrogenase levels decreased from baseline during dupilumab treatment in all trials. No clinically meaningful changes were observed between treatment groups in other haematology, chemistry or urinalysis parameters. CONCLUSIONS: There were no clinically important changes in routine laboratory parameters that could be attributed to dupilumab. This study supports the use of dupilumab as a systemic treatment for moderate-to-severe AD that does not require laboratory monitoring. What's already known about this topic? Long-term treatment of atopic dermatitis (AD) with conventional immunosuppressive agents is limited by the risk of significant side-effects and a need for repeated tests to monitor haematological and/or organ (e.g. liver, kidney) toxicities. Dupilumab [a monoclonal antibody blocking the shared receptor subunit for interleukin (IL)-4 and IL-13] is approved for the treatment of patients with inadequately controlled, moderate-to-severe AD. In 16-week and 52-week studies, dupilumab demonstrated a positive risk/benefit profile in moderate-to-severe AD. What does this study add? This study is the first comprehensive analysis of dupilumab laboratory safety data of the 16-week SOLO 1 & 2 (pooled N = 1376) and 52-week CHRONOS (N = 740) trials, demonstrating an absence of clinically important changes in haematology, serum chemistry and urinalysis parameters in patients with moderate-to-severe AD treated with dupilumab. Our data support the use of dupilumab as a systemic treatment for the long-term management of moderate-to-severe AD without routine laboratory monitoring in clinical practice.

Dupilumab in adolescents with uncontrolled moderate-to-severe atopic dermatitis: results from a phase IIa open-label trial and subsequent phase III open-label extension.

BACKGROUND: Dupilumab (monoclonal antibody inhibiting IL-4/IL-13 signalling) is approved for use in adolescents aged ≥ 12 years with inadequately controlled moderate-to-severe atopic dermatitis (AD). Dupilumab significantly improved AD signs/symptoms in a 16-week, randomised, placebo-controlled phase III trial in adolescents (NCT03054428). OBJECTIVES: To characterize the pharmacokinetics of dupilumab, and long-term safety and efficacy in adolescents. METHODS: This was a global, multicentre, phase IIa, open-label, ascending-dose, sequential cohort study with a phase III open-label extension (OLE) in adolescents with moderate-to-severe AD. In the phase IIa study, patients received one dupilumab dose (2 mg kg-1 or 4 mg kg-1 ) and 8 weeks of pharmacokinetic sampling. Thereafter, patients received the same dose weekly for 4 weeks, with 8-week safety follow-up. Patients then enrolled in the OLE, continuing 2 mg kg-1 or 4 mg kg-1 dupilumab weekly. Primary end points were dupilumab concentration-time profile and incidence of treatment-emergent adverse events (TEAEs). Secondary outcomes included Eczema Area and Severity Index (EASI). RESULTS: Forty adolescents received dupilumab in the phase IIa study; 36 enrolled in the OLE. Dupilumab showed nonlinear, target-mediated pharmacokinetics. Mean ± SD trough dupilumab concentrations in serum at week 48 (OLE) were 74 ± 19 mg L-1 and 161 ± 60 mg L-1 for 2 mg kg-1 and 4 mg kg-1 , respectively. Dupilumab was well tolerated over 52 weeks; the most common TEAEs were nasopharyngitis (week 52: 41% [2 mg kg-1 ], 47% [4 mg kg-1 ]) and AD exacerbation (29%, 42%). After one dupilumab dose in the phase IIa study, EASI improved from baseline to week 2 [mean ± SD reduction -34% ± 20% (2 mg kg-1 ) and -51% ± 29% (4 mg kg-1 )]. With continuing treatment, EASI scores improved further [week 52: -85% ± 12% (2 mg kg-1 ) and -84% ± 20% (4 mg kg-1 )]. CONCLUSIONS: In adolescents with moderate-to-severe AD, dupilumab's pharmacokinetic profile was similar to that in adults. These 52-week safety and efficacy data support long-term use of dupilumab in this patient population. What's already known about this topic? Adolescents with moderate-to-severe atopic dermatitis (AD) have high unmet medical need, with significant disease burden and limited treatment options. Dupilumab (monoclonal antibody against interleukin-4 receptor α) is approved for the treatment of adolescents with moderate-to-severe AD who are inadequately responsive to standard of care (U.S.A.) or candidates for systemic therapy (European Union). A 16-week, randomized, placebo-controlled phase III trial in adolescents demonstrated significant improvements in AD signs/symptoms with an acceptable safety profile. What does this study add? These studies demonstrate the long-term safety and efficacy of dupilumab in adolescents with moderate-to-severe AD for up to 52 weeks of treatment, thus extending and reinforcing the findings from the 16-week dupilumab phase III trial. The data from these studies also support the use of dupilumab in combination with current standard of care (topical corticosteroids), which was not evaluated in the 16-week phase III monotherapy trial.

Conjunctivitis in dupilumab clinical trials.

BACKGROUND: Dupilumab blocks the shared receptor component for interleukin (IL)-4 and IL-13. It is approved in the U.S.A. for patients aged ≥ 12 years with moderate-to-severe atopic dermatitis (AD) uncontrolled by topical prescription medicines or who cannot use topical medicines, for patients in Japan whose AD is uncontrolled with existing therapies, for patients with moderate-to-severe AD in Europe who are candidates for systemic therapy and for patients aged ≥ 12 years for maintenance treatment of moderate-to-severe asthma uncontrolled with their current medicines. AD trials have reported increased incidence of conjunctivitis for dupilumab vs. placebo. OBJECTIVES: To characterize further the occurrence and risk factors of conjunctivitis in dupilumab clinical trials. METHODS: We evaluated randomized placebo-controlled trials of dupilumab in AD (n = 2629), asthma (n = 2876), chronic rhinosinusitis with nasal polyps (CRSwNP) (n = 60) and eosinophilic oesophagitis (EoE) (n = 47). RESULTS: In most AD trials, dupilumab-treated patients had higher conjunctivitis incidence than placebo controls. Higher baseline AD severity and previous history of conjunctivitis were associated with increased conjunctivitis incidence. Conjunctivitis was mostly mild to moderate. Most cases recovered or resolved during the treatment period; two patients permanently discontinued dupilumab due to conjunctivitis or keratitis. Common treatments included ophthalmic corticosteroids, antibiotics, and antihistamines or mast cell stabilizers. Most cases were diagnosed by the investigators. In asthma and CRSwNP trials, the incidence of conjunctivitis was lower for both dupilumab and placebo than in AD trials; dupilumab did not increase the incidence compared with placebo. In the EoE trial, no patients had conjunctivitis. CONCLUSIONS: Conjunctivitis was more frequent with dupilumab treatment in most AD trials. In dupilumab trials in other type 2 diseases, incidence of conjunctivitis was overall very low, and was similar for dupilumab and placebo. In AD, the incidence of conjunctivitis was associated with AD severity and prior history of conjunctivitis. The aetiology and treatment of conjunctivitis in dupilumab-treated patients require further study. What's already known about this topic? Ocular disorders, including allergic conjunctivitis, are common in patients with atopic dermatitis (AD). In most dupilumab AD trials, dupilumab-treated patients had higher conjunctivitis incidence than those receiving placebo. Most cases were mild to moderate and recovered or were recovering during study treatment; study treatment discontinuation due to conjunctivitis was rare. Conjunctivitis incidence was very low and similar for dupilumab and placebo in clinical trials in asthma, chronic rhinosinusitis with nasal polyps and eosinophilic oesophagitis. What does this study add? This analysis confirms and extends the results of the individual clinical trials. Baseline disease-related factors, including AD severity, prior conjunctivitis history and certain biomarkers (thymus and activation-regulated chemokine, IgE, eosinophils), were associated with increased incidence of conjunctivitis. Patients who responded well to dupilumab had reduced incidence of conjunctivitis. Further study is needed to elucidate the aetiology and treatment of conjunctivitis in dupilumab-treated patients with AD.

Dupilumab provides important clinical benefits to patients with atopic dermatitis who do not achieve clear or almost clear skin according to the Investigator's Global Assessment: a pooled analysis of data from two phase III trials.

BACKGROUND: In the U.S.A., an Investigator's Global Assessment (IGA) score of ≤ 1 (clear or almost clear skin) has been the standard measure in regulatory outcomes for registration clinical trials in atopic dermatitis (AD), including those supporting the recent approval of dupilumab. OBJECTIVES: To evaluate the treatment effect of dupilumab in patients with IGA > 1 at the end of treatment, using other validated outcome measures for AD signs, symptoms and quality of life. METHODS: LIBERTY AD SOLO 1 and 2 were two 16-week, randomized, double-blind trials enrolling adult patients with moderate-to-severe AD (IGA ≥ 3) inadequately controlled with topical treatment. We performed a post hoc analysis in patients receiving dupilumab 300 mg every 2 weeks (q2w) or placebo. Outcome measures in patients with IGA > 1 included Eczema Area and Severity Index (EASI), pruritus numerical rating scale (NRS), affected body surface area (BSA), Patient-Oriented Eczema Measure (POEM) and Dermatology Life Quality Index (DLQI). The trials were registered at ClinicalTrials.gov: NCT02277743 and NCT02277769. RESULTS: At week 16, 278 of 449 dupilumab q2w-treated patients (median age 36·0 years) and 396 of 443 placebo-treated patients had IGA > 1. Among patients with IGA > 1 at week 16, dupilumab significantly improved several outcome measures compared with placebo: EASI (-48·9% vs. -11·3%, P < 0·001), pruritus NRS (-35·2% vs. -9·1%, P < 0·001), affected BSA (-23·1% vs. -4·5%, P < 0·001), POEM score ≥ 4-point improvement (57·4% vs. 21·0%, P < 0·001) and DLQI score ≥ 4-point improvement (59·3% vs. 24·4%, P < 0·001). CONCLUSIONS: In patients with IGA > 1 at week 16, dupilumab induced statistically significant benefits in multiple validated outcome measures compared with placebo. The IGA ≤ 1 end point significantly underestimates clinically relevant dupilumab treatment effects.

Dupilumab with concomitant topical corticosteroid treatment in adults with atopic dermatitis with an inadequate response or intolerance to ciclosporin A or when this treatment is medically inadvisable: a placebo-controlled, randomized phase III clinical trial (LIBERTY AD CAFÉ).

BACKGROUND: Atopic dermatitis is a chronic inflammatory skin disease that may require systemic therapy. Ciclosporin A (CsA) is a widely used, potent immunosuppressant but it is not effective in all patients with atopic dermatitis, and side-effects limit its use. Dupilumab, a fully human anti-interleukin 4 receptor-alpha monoclonal antibody, inhibits signaling of IL-4 and IL-13, key drivers of Type 2/Th2-mediated inflammation, and is approved in the U.S.A. and the European Union for the treatment of inadequately-controlled moderate-to-severe atopic dermatitis in adults. OBJECTIVES: To evaluate efficacy and safety of dupilumab with concomitant topical corticosteroids (TCS) in adults with atopic dermatitis with inadequate response to/intolerance of CsA, or for whom CsA treatment was medically inadvisable. METHODS: In this 16-week, double-blind, randomized, placebo-controlled, phase III trial, patients were randomized 1 : 1 : 1 to subcutaneous dupilumab 300 mg weekly (qw) or every 2 weeks (q2w) or placebo. All received concomitant medium-potency TCS from Week -2 through Week 16; dosage could be tapered if lesions cleared, or stopped for adverse reactions to TCS. RESULTS: In total, 390 patients were screened, 325 were randomized, and 318 completed the trial. Treatment groups had similar baseline characteristics. Significantly more patients in the dupilumab qw + TCS and q2w + TCS groups achieved ≥ 75% improvement from baseline in the Eczema Area and Severity Index at Week 16 vs. the placebo + TCS group (primary end point) (59·1% and 62·6% vs. 29·6%, respectively; P < 0·001 vs. placebo + TCS, both doses). Other clinical outcomes and atopic dermatitis symptoms were significantly improved in the dupilumab qw + TCS and q2w + TCS groups, including pruritus, pain, sleep disturbance, symptoms of anxiety and depression, and quality of life (QoL). Treatment groups had similar overall rates of adverse events (qw + TCS, q2w + TCS and placebo + TCS groups: 69·1%, 72·0% and 69·4%, respectively) and serious adverse events (1·8%, 1·9% and 1·9%, respectively). Conjunctivitis was more frequent with dupilumab + TCS; skin infections were more frequent with placebo + TCS. CONCLUSIONS: Dupilumab + TCS significantly improved signs and symptoms of atopic dermatitis and QoL in adults with a history of inadequate response to/intolerance of CsA, or for whom CsA treatment was medically inadvisable. No new safety signals were identified.

Effects of pimecrolimus cream 1% in the treatment of patients with atopic dermatitis who demonstrate a clinical insensitivity to topical corticosteroids: a randomized, multicentre vehicle-controlled trial.

BACKGROUND: Colonization with Staphylococcus aureus in atopic dermatitis (AD) is often associated with worsening of clinical symptoms. Staphylococcus aureus produces superantigens that contribute to cutaneous inflammation and corticosteroid (CS) resistance. OBJECTIVES: To investigate the relationship between CS insensitivity, S. aureus colonization and superantigen production in AD, and to explore the efficacy of pimecrolimus cream in CS-insensitive AD. METHODS: This was a randomized, double-blind, vehicle-controlled, multicentre, parallel-group study. Seventy-three patients with AD, aged 2-49 years, who had a documented clinical insensitivity to topical CS, were recruited. The primary efficacy parameters combined laboratory (including S. aureus colonization, superantigens) and clinical assessments [including Eczema Area and Severity Index (EASI), whole body Investigator's Global Assessment (IGA), pruritus assessment score, patient's assessment score of disease control]. RESULTS: An increase in S. aureus counts correlated with worsening of clinical score (week 6 vs. baseline) when assessed by IGA, pruritus severity and patient assessment. The presence of superantigens correlated with this worsening. During the 6-week double-blind phase, disease improvement in the pimecrolimus cream group was demonstrated by decreasing EASI scores compared with vehicle. Mean EASI scores for the head and neck showed greater improvement in the pimecrolimus cream group than in the vehicle group at all observed time points. CONCLUSIONS: In a cohort of patients with clinical insensitivity to CS there was a significant positive correlation between S. aureus and disease severity. Results suggest that for some of these patients, treatment with pimecrolimus cream 1% is useful, especially in the head/neck area.

The treatment of facial atopic dermatitis in children who are intolerant of, or dependent on, topical corticosteroids: a randomized, controlled clinical trial.

BACKGROUND: Atopic dermatitis (AD) is most prevalent in areas of reduced skin barrier reserve, like face and neck, especially in children. Treatment with topical corticosteroids (TCS) is limited due to heightened risk of treatment-associated side-effects, thus necessitating alternative AD therapies. OBJECTIVES: The primary study objective was to determine the efficacy of pimecrolimus cream 1% in children with mild-moderate facial AD dependent on/intolerant of TCS. Secondary objectives included effects on overall Eczema Area and Severity Index (EASI), head/neck EASI, pruritus severity and time to clearance of facial AD. METHODS: A multicentre, double-blind (DB) study of < or = 6 weeks, followed by a 6-week, open-label (OL) phase was conducted. Two hundred patients (aged 2-11 years) were randomized 1:1 to pimecrolimus cream 1% (n = 99) or vehicle (n = 101) twice daily until clearance of facial AD or for a maximum of 6 weeks (DB phase). Sixteen patients receiving vehicle were allowed to switch to the OL phase at day 22. RESULTS: Significantly more pimecrolimus-treated vs. vehicle-treated patients were cleared/almost cleared of facial AD (Investigators' Global Assessment 0/1): 74.5% vs. 51.0%, P < 0.001 (day 43) [57.1% vs. 36.0%, P = 0.004 (day 22)]. Median time to clearance was 22.0 vs. 43.0 days (pimecrolimus vs. vehicle, respectively). Statistically significant differences for pimecrolimus vs. vehicle were also seen on head/neck EASI, overall EASI, and head/neck pruritus scores. Adverse events were mainly mild-moderate, occurring with similar frequency in both treatment groups. CONCLUSIONS: In children with facial dermatitis intolerant of/dependent on TCS, pimecrolimus cream 1% effectively controls eczema and pruritus and is well tolerated.

Addition of topical pimecrolimus to once-daily mid-potent steroid confers no short-term therapeutic benefit in the treatment of severe atopic dermatitis; a randomized controlled trial.

BACKGROUND: Combination therapy with pimecrolimus cream 1%, a topical calcineurin inhibitor (TCI), and fluticasone propionate cream 0.05% (FP), a mid-potency topical corticosteroid, may have a synergistic effect for treatment of atopic dermatitis (AD) because their mechanism of action differs. OBJECTIVES: To assess the efficacy of concomitant pimecrolimus twice daily/FP once daily vs. vehicle twice daily/FP once daily in patients with severe AD. METHODS: An exploratory, 2-week, double-blind, randomized, within-patient study was conducted (n = 45). Two target areas of similar severity, size and location were assessed. Assessments included the modified Eczema Area and Severity Index (0-12 scale) (primary variable), localized investigator global assessment (0-4 scale) and Patients' Self-Assessment of Disease Severity (0-4 scale). RESULTS: Data for all variables were similar for the TCI/FP and vehicle/FP treatments. CONCLUSIONS: The efficacy observed for treatment of severe AD flares with this TCI/FP combination regimen was equivalent to that of vehicle/FP.

A novel anti-inflammatory drug, SDZ ASM 981, for the treatment of skin diseases: in vitro pharmacology.

SDZ ASM 981, a novel ascomycin macrolactam derivative, has high anti-inflammatory activity in animal models of allergic contact dermatitis and shows clinical efficacy in atopic dermatitis, allergic contact dermatitis and psoriasis, after topical application. Here we report on the in vitro activities of this promising new drug. SDZ ASM 981 inhibits the proliferation of human T cells after antigen-specific or non-specific stimulation. It downregulates the production of Th1 [interleukin (IL)-2, interferon-gamma] and Th2 (IL-4, IL-10) type cytokines after antigen-specific stimulation of a human T-helper cell clone isolated from the skin of an atopic dermatitis patient. SDZ ASM 981 inhibits the phorbol myristate acetate/phytohaemagglutinin-stimulated transcription of a reporter gene coupled to the human IL-2 promoter in the human T-cell line Jurkat and the IgE/antigen-mediated transcription of a reporter gene coupled to the human tumour necrosis factor (TNF)-alpha promoter in the murine mast-cell line CPII. It does not, however, affect the human TNF-alpha promoter controlled transcription of a reporter gene in a murine dendritic cell line (DC18 RGA) after stimulation via the FcgammaRIII receptor. SDZ ASM 981 also prevents the release of preformed pro-inflammatory mediators from mast cells, as shown in the murine cell line CPII after stimulation with IgE/antigen. In summary, these results demonstrate that SDZ ASM 981 is a specific inhibitor of the production of pro-inflammatory cytokines from T cells and mast cells in vitro.

Decreased release of histamine and sulfidoleukotrienes by human peripheral blood leukocytes after wasp venom immunotherapy is partially due to induction of IL-10 and IFN-gamma production of T cells.

BACKGROUND: Recent studies provide evidence that venom immunotherapy (VIT) alters the pattern of cytokine production by inducing an allergen-specific T-cell shift in cytokine expression from TH2 (IL-4, IL-5) to TH1 (IFN-gamma) cytokines and also inducing the production of IL-10. OBJECTIVE: This study was carried out to analyze whether these changes in cytokine production of T cells already observed 1 week after the initiation of VIT in subjects with wasp venom allergy also influence the reactivity of effector cells, such as mast cells and basophils. METHODS: All subjects included in this study had a history of severe systemic allergic reactions to wasp stings and positive skin test responses with venom and venom-specific IgE in the sera. Peripheral blood leukocytes were isolated before and after the initiation of VIT (rush therapy reaching a maintenance dose of 100 microg venom injected subcutaneously within 1 week) and preincubated with or without addition of IL-10, IFN-gamma, IL-10 + IFN-gamma, anti-IL-10, or anti-IFN-gamma. After stimulation with wasp venom, histamine and sulfidoleukotriene release were assessed by ELISA and compared with spontaneous release and total histamine content. RESULTS: After the induction of VIT, venom-induced absolute and relative histamine and sulfidoleukotriene release were reduced. This was at least partially due to the induction of IFN-gamma and IL-10 production, because (1) neutralization of IL-10 and IFN-gamma by mAbs partially restored the release after the initiation of VIT and (2) the addition of exogenous IFN-gamma and IL-10 caused a statistically significant diminution of the venom-induced histamine and sulfidoleukotriene release before VIT. Depletion of CD2(+) T cells also restored the releasability after VIT. CONCLUSION: These data indicate that T cells (producing IL-10 and IFN-gamma after VIT) play a key role for the inhibition of histamine and sulfidoleukotriene release of effector cells.

Ascomycin macrolactam derivative SDZ ASM 981 inhibits the release of granule-associated mediators and of newly synthesized cytokines in RBL 2H3 mast cells in an immunophilin-dependent manner.

Mast cells play an important role in the pathological development of many inflammatory and allergic diseases and inhibition of mast cell activation is a potential target for therapeutic intervention. Therefore, the effect of the novel ascomycin macrolactam derivative SDZ ASM 981 on Fc epsilonRI-mediated activation of rat basophilic leukemia (RBL) cells, as a model for mast cell activation, was investigated. First, the ability to inhibit different mast cell immunophilins in vitro was tested. Using recombinant macrophilin-12 (FKBP-12), inhibition of rotamase activity with an IC50 of approximately 6 nM was observed. The rotamase activity of cyclophilin A (18 kDa) was not affected. Secondly, the effect of SDZ ASM 981 on Fc epsilonRI-mediated mast cell activation was investigated in the RBL cell model. SDZ ASM 981 inhibited exocytosis of preformed mediators (e.g. serotonin) with an IC50 of approximately 30 nM. Transcription and release of newly synthesized mediators (e.g. TNF-alpha) was inhibited with an IC50 of approximately 100 nM. The inhibitory effect of SDZ ASM 981 was antagonized by rapamycin. We conclude that SDZ ASM 981 is a potent inhibitor of Fc epsilonRI-mediated activation of mast cells in vitro. The mechanism of action involves formation of (calcineurin) inhibitory complexes with macrophilins. We suggest that this inhibitory action on mast cells might contribute to the antiinflammatory effect of SDZ ASM 981 observed in vivo (e.g. in aptopic dermatitis and psoriasis).

Direct evidence that FK506 inhibition of FcepsilonRI-mediated exocytosis from RBL mast cells involves calcineurin.

FcepsilonRI-mediated exocytosis of preformed mediators from mast cells and basophils (e.g. histamine, serotonin, beta-hexosaminidase) is sensitive to the immunosuppressants cyclosporin A and FK506 (IC50 200 and 4 nM, respectively) but not rapamycin. The mechanism of inhibition does not appear to involve tyrosine phosphorylation, hydrolysis of inositol phosphates or calcium flux. Here we report experiments using a molecular approach to assess the role of calcineurin, a serine/threonine phosphatase thought to be the primary pharmacological target of these drugs. Calcineurin's activity requires association of its catalytic (A) subunit with an intrinsic regulatory (B) subunit. We hypothesized that calcineurin-sensitive signalling events should be affected by the depletion of calcineurin B subunits, thereby reducing the number of active A:B complexes. We therefore transfected rat basophilic leukemia (RBL) cells with an inhibitory (dominant negative) form of the calcineurin A subunit, which binds the calcineurin B subunit with high affinity but does not possess catalytic activity (B subunit knock-out, BKO). In these transfected cells, the dose-response curve for the inhibition of FcepsilonRI-mediated exocytosis by FK506 was shifted to the left, indicating an increased drug sensitivity of BKO-transfected cells. We conclude that FK506 inhibition of FcepsilonRI-mediated exocytosis in mast cells specifically targets calcineurin activity.

Eosinophils, pruritus and psoriasis: effects of treatment with etretinate or cyclosporin-A.

BACKGROUND: The antipsoriatic drugs cyclosporin A (CyA) and etretinate have been found to influence proinflammatory eosinophilic leukocytes and pruritus. AIM: We compared the number of blood eosinophils, concentration of serum eosinophil cationic protein (ECP), and pruritus in patients with psoriasis treated with either CyA or etretinate. STUDY DESIGN: Patients with psoriasis vulgaris were randomly assigned to treatment for 10 weeks with either CyA (n = 21) or etretinate (n = 10). The psoriasis area-and-severity index (PASI-score) and pruritus (according to a 0-3 scale) served as clinical parameters, the blood esosinophil counts (Coulter Counter) and the serum ECP (RIA, Pharmacia) as laboratory parameters. RESULTS: After CyA treatment the PASI-score amounted to 24 +/- 4%, after etretinate to 56 +/- 6% of the initial values (mean +/- SEM). One week after CyA treatment, esosinophils dropped from 190 +/- 21 to 137 +/- 16/microliter (P = 0.038, Wilcoxon test), after 10 weeks to 127 +/- 18/microliter (P = 0.006). By contrast, under etretinate blood eosinophil counts only changed marginally. Before treatment, ECP concentrations of 15.71 +/- 1.30 (CyA) and 15.3 +/- 5.53 micrograms/l (etretinate) were measured (normal range 3-16 micrograms/l), ECP remained constant under both CyA and etretinate or tended to increase after 10 weeks; about 50% of the patients exhibited elevated ECP concentrations. Pruritus diminished more with CyA than etretinate therapy. PASI-scores and pruritus were directly proportional. OUTCOME: We conclude that treatment of psoriasis with CyA leads to a rapid drop of blood eosinophils and that the activation state of eosinophils does not decrease after antipsoriatic treatment. Pruritus in psoriasis is coupled to disease severity. The underlying antipsoriatic mechanisms of CyA may be linked to lowering the number of blood eosinophils.

Enhanced expression of IL-8 in normal human keratinocytes and human keratinocyte cell line HaCaT in vitro after stimulation with contact sensitizers, tolerogens and irritants.

To investigate the interleukin-8 production of keratinocytes after stimulation in vitro we have used various agents: (i) contact sensitizer (2,4-dinitrofluorobenzene, 3-n-pentadecylcatechol); (ii) tolerogen (5-methyl-3-n-pentadecylcatechol); (iii) irritant (sodium lauryl sulfate). Interleukin-8 gene expression was assessed by northern blot hybridization of the total cytoplasmic RNA extracted from subconfluent normal human keratinocyte cultures and the keratinocyte cell line HaCaT using a radiolabeled DNA probe specific for human interleukin-8. Interleukin-8 gene expression was markedly increased upon in vitro stimulation after 1-6 h with contact sensitizers, tolerogen and the irritant. In contrast, interleukin-8 production was not detectable in unstimulated normal human keratinocytes or the HaCaT keratinocyte cell line. These results suggest that the induction and production of interleukin-8 is a response to nonspecific stimuli and may play a critical role in the early response to immunogenic or inflammatory signals in man.

The effect of the immunophilin ligands rapamycin and FK506 on proliferation of mast cells and other hematopoietic cell lines.

The immunosuppressive drugs FK506 and cyclosporin A have an identical spectrum of activities with respect to IgE receptor (Fc epsilon RI)-mediated exocytosis from mast cells and T cell receptor-mediated transcription of IL-2. These findings suggest a common step in receptor-mediated signal transduction leading to exocytosis and transcription and imply that immunosuppressive drugs target specific signal transduction pathways, rather than specific cell types. This hypothesis is supported by studies on the effect of rapamycin on IL-3 dependent proliferation of the rodent mast cell line PT18. Rapamycin inhibits proliferation of PT18 cells, achieving a plateau of 80% inhibition at 1 nM. This inhibition is prevented in a competitive manner by FK506, a structural analogue of rapamycin. Proliferation of rat basophilic leukemia cells and WEHI-3 cells was also inhibited, at doses comparable to those shown previously to inhibit IL-2-dependent proliferation of cytotoxic T lymphocyte line (CTLL) cells. In contrast, proliferation of A-431 cells, a epidermoid cell line, was not affected by rapamycin. DNA histograms indicate that complexes formed between the rapamycin-FK506-binding protein (FKBP) and rapamycin arrest-proliferating PT18 cells in the G0/G1-phase. It is concluded that FKBP-rapamycin complexes may inhibit proliferative signals emanating from IL-3 receptors, resulting in growth arrest of cytokine-dependent, hematopoietic cells.

Immunophilin ligands demonstrate common features of signal transduction leading to exocytosis or transcription.

Investigations of the actions and interactions of the immunophilin ligands FK506, cyclosporin A (CsA), rapamycin, and 506BD suggest that complexes of FK506 with an FK506-binding protein or of CsA with a cyclophilin (CsA-binding protein) inhibit the T-cell receptor-mediated signal transduction that results in the transcription of interleukin 2. Now we report an identical spectrum of activities of FK506, CsA, rapamycin, and 506BD on IgE receptor-mediated signal transduction that results in exocytosis of secretory granules from the rat basophilic leukemia cell line RBL-2H3, a mast cell model. Both FK506 and CsA inhibit receptor-mediated exocytosis (CsA IC50 = 200 nM; FK506 IC50 = 2 nM) without affecting early receptor-associated events (hydrolysis of phosphatidylinositol, synthesis and release of eicosanoids, uptake of Ca2+). In contrast, rapamycin and 506BD, which share common structural elements with FK506, by themselves have no effect on IgE receptor-mediated exocytosis. Both compounds, however, prevent inhibition by FK506 but not by CsA. Affinity chromatography with FK506, CsA, and rapamycin matrices indicates that the same set of immunophilins present in RBL-2H3 cells have been found in Jurkat T cells and calf thymus; however, the relative amounts of these proteins differ in the two cell types. These results suggest the existence of a common step in cytoplasmic signaling in T cells and mast cells that may be part of a general signaling mechanism.