Real-World Experience of Adalimumab Biosimilar (ABP 501) Use in Patients with Inflammatory Bowel Disease in Europe.

INTRODUCTION: Approval of adalimumab biosimilar ABP 501 (Amgevita®) for inflammatory bowel disease (IBD) was based upon the principle of extrapolation. Real-world experience of ABP 501 utilization in IBD can provide useful information to healthcare providers and patients. METHODS: Data were drawn from the 2020-2021 Adelphi IBD Disease Specific Programme™ conducted in five major European countries. Participating gastroenterologists completed a point-in-time survey to provide patient medical record data, and patients voluntarily completed questionnaires to report health-related quality of life (HRQoL). Descriptive analyses were conducted for "ABP 501 initiators" (received ABP 501 as first advanced therapy) and "RP-ABP 501 switchers" (switched to ABP 501 from reference product [RP; Humira®] as first advanced therapy). RESULTS: This analysis included 239 ABP 501 initiators and 136 RP-ABP 501 switchers. At consultation, initiators had been on ABP 501 treatment for a median of 7.5 months and switchers had received ABP 501 for a median of 7.7 months following the switch from a median of 14.0 months treatment with RP. About 74% of initiators and 89% of switchers were reported by their treating physicians as being in clinical remission. Physicians and patients reported satisfaction with ABP 501 in the range of 92-99% across both groups. Patient self-assessment, including EuroQol visual analogue scale, Short IBD Questionnaire, and Work Productivity and Activity Impairment scores, suggested minimal impairment of HRQoL while on ABP 501. The most common reason for RP to ABP 501 switch was lower healthcare costs. CONCLUSION: Both patients with IBD and treating physicians reported high levels of satisfaction with ABP 501 among initiators and switchers.

ABP 501 (Amgevita^®) is the first approved biosimilar to adalimumab originator (Humira^®), referred to here as the reference product. A biosimilar is a biological product that is highly similar to its reference product in terms of safety, purity, and effectiveness. ABP 501 has been approved for the treatment of certain chronic inflammatory diseases. The approval of ABP 501 for inflammatory disease is based upon the principle of extrapolation, with no clinical trial being conducted in patients with inflammatory bowel disease. Therefore, in this current study, we evaluated the utilization experience of biosimilar ABP 501 in the real-world setting from both physicians' and patients' perspectives. We reported that patients with inflammatory bowel disease who initiated ABP 501 as the first advanced therapy as well as patients who continued therapy on ABP 501 after a switch from the adalimumab reference product both had a high level of satisfaction when using the biosimilar ABP 501. Treating physicians also reported that most of their patients were in clinical remission while on treatment with ABP 501, and patients themselves reported minimal impairment of health-related quality of life.

A randomised phase II study evaluating the efficacy and safety of subcutaneously administered ustekinumab and guselkumab in patients with active rheumatoid arthritis despite treatment with methotrexate.

OBJECTIVE: Interleukin (IL)-12 and IL-23 have been implicated in the pathogenesis of rheumatoid arthritis (RA). The safety and efficacy of ustekinumab, a human monoclonal anti-IL-12/23 p40 antibody, and guselkumab, a human monoclonal anti-IL-23 antibody, were evaluated in adults with active RA despite methotrexate (MTX) therapy. METHODS: Patients were randomly assigned (1:1:1:1:1) to receive placebo at weeks 0, 4 and every 8 weeks (n=55), ustekinumab 90 mg at weeks 0, 4 and every 8 weeks (n=55), ustekinumab 90 mg at weeks 0, 4 and every 12 weeks (n=55), guselkumab 50 mg at weeks 0, 4 and every 8 weeks (n=55), or guselkumab 200 mg at weeks 0, 4 and every 8 weeks (n=54) through week 28; all patients continued a stable dose of MTX (10-25 mg/week). The primary end point was the proportion of patients with at least a 20% improvement in the American College of Rheumatology criteria (ACR 20) at week 28. Safety was monitored through week 48. RESULTS: At week 28, there were no statistically significant differences in the proportions of patients achieving an ACR 20 response between the combined ustekinumab group (53.6%) or the combined guselkumab group (41.3%) compared with placebo (40.0%) (p=0.101 and p=0.877, respectively). Through week 48, the proportions of patients with at least one adverse event (AE) were comparable among the treatment groups. Infections were the most common type of AE. CONCLUSIONS: Treatment with ustekinumab or guselkumab did not significantly reduce the signs and symptoms of RA. No new safety findings were observed with either treatment. TRIAL REGISTRATION NUMBER: NCT01645280.

Toreforant, A Histamine H4 Receptor Antagonist, in Patients with Active Rheumatoid Arthritis Despite Methotrexate Therapy: Results of 2 Phase II Studies.

OBJECTIVE: To assess toreforant (selective histamine H4 receptor antagonist) in active rheumatoid arthritis (RA). METHODS: In a phase IIa, double-blind, placebo-controlled test, 86 patients were randomized (2:1) to once-daily toreforant 100 mg or placebo for 12 weeks. In phase IIb, double-blind, placebo-controlled, dose-range-finding evaluations, 272 patients were randomized (1:1:1:1) to once-daily placebo or toreforant 3/10/30 mg. Primary efficacy endpoints for both studies were Week 12 changes in 28-joint Disease Activity Score-C-reactive protein (DAS28-CRP). RESULTS: Phase IIa testing was terminated prematurely (patient fatality; secondary hemophagocytic lymphohistiocytosis). Posthoc analyses indicated toreforant 100 mg/day reduced RA signs/symptoms through Week 12. Phase IIb testing, however, showed no significant Week 12 improvement in DAS28-CRP with toreforant. CONCLUSION: Toreforant was not effective in phase IIb testing.

The effects of laropiprant on the antiplatelet activity of co-administered clopidogrel and aspirin.

Laropiprant is an antagonist of the prostaglandin PGD2 receptor DP1. Laropiprant has a weak affinity for the thromboxane A2 receptor TP. Two double-blinded, randomized, placebo-controlled, crossover studies evaluated the effects of multiple-dose laropiprant at steady state on the antiplatelet effects of multiple-dose aspirin and clopidogrel. Study 1 had two treatment periods, in which each healthy subject received laropiprant 40 mg, clopidogrel 75 mg, and aspirin 80 mg (Treatment A), or placebo, clopidogrel 75 mg, and aspirin 80 mg (Treatment B) once daily for 7 days. Study 2 consisted of three treatment periods. In the first two, each patient with hypercholesterolemia or mixed dyslipidemia received laropiprant 40 mg, clopidogrel 75 mg, and aspirin 81 mg (Treatment A), or placebo, clopidogrel 75 mg, and aspirin 81 mg (Treatment B) once daily for 7 days. In period 3, patients received a single dose of two tablets of extended release nicotinic acid 1 g/laropiprant 20 mg (Treatment C). In both studies, pharmacodynamic endpoints included bleeding time at 24 (primary) and 4 hours (secondary) post-dose following 7 days of once-daily laropiprant in combination with clopidogrel and aspirin, and platelet aggregation in platelet-rich plasma at 4 and 24 hours post-dose on day 7 (secondary). After 7 days, increased bleeding time of 27% (Study 1) and 23% (Study 2) at 24 hours post-dose was observed with laropiprant compared to placebo (both combined with clopidogrel and aspirin), with corresponding upper bounds of the 90% CI marginally exceeding the prespecified upper comparability bound of 1.50 in both studies. The GMR and 90% CI for bleeding time of laropiprant compared to placebo (both combined with clopidogrel and aspirin) at 4 hours post-dose on day 7 was 0.92 (0.70, 1.21) in Study 1, and 1.46 (1.20, 1.78) in Study 2. Compared with placebo, laropiprant (both combined with clopidogrel and aspirin) increased the inhibition of collagen- and ADP-induced platelet aggregation, respectively, by ∼2.4% and ∼8.1% in Study 1 and by ∼4% and ∼5.4% in Study 2, at 24 hours post-dose on day 7. The inhibition of collagen- and ADP-induced platelet aggregation, respectively, was increased by ∼0.1% and ∼5.0% in Study 1, and by ∼5% and ∼12% in Study 2, at 4 hours post-dose on day 7. In conclusion, co-administration of multiple doses of laropiprant with aspirin and clopidogrel induced a prolongation of bleeding time and an inhibitory effect on platelet aggregation ex vivo in healthy subjects and patients with dyslipidemia.

Haemodynamic effects, safety, and pharmacokinetics of human stresscopin in heart failure with reduced ejection fraction.

AIMS: Human stresscopin is a corticotropin-releasing factor (CRF) type 2 receptor (CRFR2) selective agonist and a member of the CRF peptide family. Stimulation of CRFR2 improves cardiac output and left ventricular ejection fraction (LVEF) in patients with stable heart failure (HF) with reduced LVEF. We examined the safety, pharmacokinetics, and effects on haemodynamics and serum biomarkers of intravenous human stresscopin acetate (JNJ-39588146) in patients with stable HF with LVEF ≤ 35% and cardiac index (CI) ≤ 2.5 L/min/m(2). METHODS AND RESULTS: Sixty-two patients with HF and LVEF ≤ 35% were instrumented with a pulmonary artery catheter and randomly assigned (ratio 3:1) to receive an intravenous infusion of JNJ-39588146 or placebo. The main study was an ascending dose study of three doses (5, 15, and 30 ng/kg/min) of study drug or placebo administered in sequential 1 h intervals (3 h total). Statistically significant increases in CI and reduction in systemic vascular resistance (SVR) were observed with both the 15 ng/kg/min (2 h time point) and 30 ng/kg/min (3 h time point) doses of JNJ-39588146 without significant changes in heart rate (HR) or systolic blood pressure (SBP). No statistically significant reductions in pulmonary capillary wedge pressure (PCWP) were seen with any dose tested in the primary analysis, although a trend towards reduction was seen. CONCLUSION: In HF patients with reduced LVEF and CI, ascending doses of JNJ-39588146 were associated with progressive increases in CI and reductions in SVR without significant effects on PCWP, HR, or SBP. TRIAL REGISTRATION: NCT01120210.

A randomized clinical trial comparing point-of-care platelet function assays and bleeding time in healthy subjects treated with aspirin or clopidogrel.

Traditional assays of the coagulation status of patients, bleeding time assessment (BT) and light transmission aggregometry (LTA), are useful in clinical drug development. However, these assays are both labor intensive and expensive. BT results can be operator dependent and by its nature can inhibit subject enrollment in a clinical trial. The preparation of platelet-rich plasma necessary for LTA requires specialized training and laboratory support. Alternatives to these methods are desirable. The goal of this study was identification of a quantitative, easy-to-use, point-of-care device with minimal technical variables that could facilitate assessment of platelet aggregation in clinical drug development. This was a double-blind, placebo-controlled, randomized, three-period cross-over study in healthy volunteers designed to compare the abilities of BT, LTA, and three point-of-care devices, Multiplate®, Platelet Function Analyzer-100®, and VerifyNow® to quantitate the effects on platelet function of 3 days of treatment with aspirin, clopidogrel, or placebo. The effect size (difference in treatment means divided by the pooled standard deviations [SD]) of the three point-of-care devices was greater than or similar to BT and LTA for all treatment comparisons examined. VerifyNow® had the highest effect size comparing ASA to placebo. Multiplate® had the highest effect size comparing clopidogrel to placebo. From this study, we conclude that any one of the three simple-to-use point-of-care devices can reliably assess the treatment effect of ASA and CLP on platelet function in comparison with BT or LTA at the study population level

Development and validation of a LC/MS/MS method for 6-keto PGF1α, a metabolite of prostacyclin (PGI2).

A sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the quantitation of 6-keto PGF(1α) in human urine and plasma. Prostacyclin (PGI(2)) is a locally acting prostanoid, which mediates vasorelaxation and inhibition of platelet aggregation. 6-Keto PGF(1α) is the most-immediate metabolite of PGI(2). Samples were spiked with an internal standard (6-keto PGF(1α)-d(4)), purified by immuno-affinity chromatography and selected reaction monitoring (SRM) was performed. Analytical validation of the 6-keto PGF(1α) assay was performed in urine. This included an assessment of assay precision, recovery, stability, sensitivity and linearity. Urinary 6-keto PGF(1α) concentrations were also correlated to urinary 2,3-dinor-6-keto PGF(1α) (PGIM) concentrations using urine samples collected from 16 healthy volunteers. The mean concentration of 6-keto PGF(1α) in urine (mean ± SD) was 92 ± 51 pg/ml or 168 ± 91 pg/mg creatinine. Overall, there was a statistically significant correlation between urinary 6-keto PGF(1α) and PGIM (r(2)=0.55, p ≤ 0.001; slope=2.7; y-intercept=130). However, PGIM was approximately 3-fold more abundant than 6-keto PGF(1α) in urine. In addition, 6-keto PGF(1α) concentrations were measured in EDTA plasma samples obtained from 7 healthy donors. The mean concentration of 6-keto PGF(1α) in plasma was 1.9 ± 0.8 pg/ml (± SD).

The effects of laropiprant, a selective prostaglandin D2 receptor 1 antagonist, on the antiplatelet activity of clopidogrel or aspirin.

Laropiprant (LRPT) is being developed in combination with Merck's extended-release niacin (ERN) formulation for the treatment of dyslipidemia. LRPT, an antagonist of the prostaglandin PGD2 receptor DP1, reduces flushing symptoms associated with ERN. LRPT also has affinity for the thromboxane A2 receptor TP (approximately 190-fold less potent at TP compared with DP1). Aspirin and clopidogrel are two frequently used anti-clotting agents with different mechanisms of action. Since LRPT may potentially be co-administered with either one of these agents, these studies were conducted to assess the effects of steady-state LRPT on the antiplatelet activity of steady-state clopidogrel or aspirin. Bleeding time at 24 h post-dose (trough) was pre-specified as the primary pharmacodynamic endpoint in both studies. Two separate, double-blind, randomized, placebo-controlled, crossover studies evaluated the effects of multiple-dose LRPT on the pharmacodynamics of multiple-dose clopidogrel or aspirin. Healthy subjects were randomized to once-daily oral doses of LRPT 40 mg or placebo to LRTP co-administered with clopidogrel 75 mg or aspirin 81 mg for 7 days with at least a 21-day washout between treatments. In both studies, bleeding time and platelet aggregation were assessed 4 and 24 hours post-dose on Day 7. Comparability was declared if the 90% confidence interval for the estimated geometric mean ratio ([LRPT+clopidogrel]/clopidogrel alone or [LRPT+aspirin]/aspirin alone) for bleeding time at 24 hours post-dose on Day 7 was contained within (0.66, 1.50). Concomitant daily administration of LRPT 40 mg with clopidogrel 75 mg or aspirin 81 mg resulted in an approximate 4-5% increase in bleeding time at 24 hours after the last dose vs. bleeding time after treatment with clopidogrel or aspirin alone, demonstrating that the treatments had comparable effects on bleeding time. Percent inhibition of platelet aggregation was not significantly different between LRPT co-administered with clopidogrel or aspirin vs. clopidogrel or aspirin alone at 24 hours post-dose at steady state. At 4 hours after the last dose, co-administration of LRPT 40 mg resulted in 3% and 41% increase in bleeding time vs. bleeding time after treatment with aspirin or clopidogrel alone, respectively. Co-administration of LPRT with clopidogrel or aspirin was generally well tolerated in healthy subjects. Co-administration of multiple doses of LRPT 40 mg and clopidogrel 75 mg or aspirin 81 mg had no clinically important effects on bleeding time or platelet aggregation.

Effects of extended release niacin/laropiprant, laropiprant, extended release niacin and placebo on platelet aggregation and bleeding time in healthy subjects.

Laropiprant (LRPT) has been shown to reduce flushing symptoms induced by niacin and has been combined with niacin for treatment of dyslipidemia. LRPT, a potent PGD(2) receptor (DP1) antagonist that also has modest activity at the thromboxane receptor (TP), may have the potential to alter platelet function either by enhancing platelet reactivity through DP1 antagonism or by inhibiting platelet aggregation through TP antagonism. Studies of platelet aggregation ex vivo and bleeding time have shown that LRPT, at therapeutic doses, does not produce clinically meaningful alterations in platelet function. The present study was conducted to assess platelet reactivity to LRPT using methods that increase the sensitivity to detect changes in platelet responsiveness to collagen and ADP. The responsiveness of platelets was quantified by determining the EC(50) of collagen to induce platelet aggregation ex vivo. At 24 hours post-dose on Day 7, the responsiveness of platelets to collagen-induced aggregation was similar following daily treatment with extended-release niacin (ERN) 2 g/LRPT 40 mg or ERN 2 g. At 2 hours post-dose on Day 7, the EC(50) for collagen-induced platelet aggregation was approximately two-fold higher in the presence of LRPT, consistent with a small, transient inhibition of platelet responsiveness to collagen. There was no clinical difference between treatments for bleeding time, suggesting that this small effect on collagen EC(50) does not result in a clinically meaningful alteration of platelet function in vivo. The results of this highly sensitive method demonstrate that LRPT does not enhance platelet reactivity when given alone or with ERN.

A single supratherapeutic dose of rolofylline does not prolong the QTcF interval in healthy volunteers.

Rolofylline is a potent, selective adenosine A1 receptor antagonist that was under development for the treatment of patients with acute decompensated heart failure and renal function impairment. The 30-mg dose of rolofylline administered by intravenous infusion over 4 hours for 3 days represented the anticipated recommended clinical regimen of rolofylline. This was a randomized, double-blind, double-dummy, placebo-controlled, three-period crossover study performed with a single 2-hour intravenous infusion of 60 mg rolofylline, placebo, or oral moxifloxacin in healthy subjects. Plasma samples were collected for determination of rolofylline, M1-trans, and M1-cis pharmacokinetic parameters. The upper limit of the two-sided 90% confidence interval for the placebo-adjusted least squares mean change from baseline in QTcF interval for rolofylline was less than 5 msec at every time point. Moxifloxacin demonstrated an increase in QTcF of greater than 10 msec at 2, 2.5, and 3 hours postdose, thus establishing the sensitivity of the assay to detect modest increases in QTcF interval. Mean Cmax values of 1947.4, 739.2, and 54.8 nM were attained for rolofylline and its metabolites M1-trans and M1-cis, respectively, which were 2.2- to 3.1-fold higher than historic Cmax values seen at the anticipated clinical dose and regimen. Adenosine A1 receptor antagonism from a single supratherapeutic intravenous dose of 60 mg rolofylline over 2 hours was generally well tolerated and did not prolong the QTcF interval relative to placebo.

The effects of multiple doses of rolofylline on the single-dose pharmacokinetics of midazolam in healthy subjects.

Rolofylline is a potent, selective adenosine A1 receptor antagonist that was under development for the treatment of patients with acute decompensated heart failure and renal function impairment. This was a phase I, randomized, open-label, 2-period, fixed-sequence study in 19 healthy adult volunteers to examine the effect of multiple intravenous rolofylline doses on the single-dose pharmacokinetics of midazolam, a sensitive CYP3A4 substrate. In period 1, subjects received a single oral dose of midazolam 7.5 mg on day 1. In period 2, subjects received 30 mg, 4-hour infusions of rolofylline (intended clinical dose and duration) once daily for 4 consecutive days; midazolam 7.5 mg was coadministered on day 4. The geometric mean ratios and 90% confidence intervals for AUC0-infinity and Cmax of midazolam in the presence/absence of rolofylline were 1.20 (1.12-1.29) and 1.17 (1.03-1.32), respectively. The apparent terminal half-life (t1/2) for midazolam was similar in the presence/absence of rolofylline (4.31 and 4.27 hours, respectively). The geometric mean ratios (90% confidence intervals) for AUC0-infinity and Cmax of 1'-hydroxymidazolam in the presence/absence of rolofylline were 1.04 (0.96-1.13) and 0.98 (0.84-1.14), respectively. The t1/2 for 1'-hydroxymidazolam was slightly higher in the presence relative to absence of rolofylline (4.24 and 3.17 hours, respectively). Multiple doses of intravenous rolofylline 30 mg for 4 days were generally well tolerated and did not result in clinically important inhibition of CYP3A4 as indicated by little or no change in the pharmacokinetics of midazolam.

Effects of a niacin receptor partial agonist, MK-0354, on plasma free fatty acids, lipids, and cutaneous flushing in humans.

BACKGROUND: Development of niacin-like agents that favorably affect lipids with an improved flushing profile would be beneficial. OBJECTIVE: To evaluate a niacin receptor partial agonist, MK-0354, in Phase I and II studies. METHODS: The pharmacokinetic/pharmacodynamic effects of single and multiple doses (7 days) of MK-0354 (300-4000 mg) were evaluated in two Phase I studies conducted in healthy men. A Phase II study assessed the effects of MK-0354 2.5 g once daily on lipids during 4 weeks in 66 dyslipidemic patients. RESULTS: MK-0354 single doses up to 4000 mg and multiple doses (7 days) up to 3600 mg produced robust dose-related reductions in free fatty acid (FFA) over 5 hours. Single doses of MK-0354 300 mg and extended release-niacin (Niaspan) 1 g produced comparable reductions in FFA. Suppression of FFA following 7 daily doses of MK-0354 was similar to that after a single dose. In the Phase II study, MK-0354 2.5 g produced little flushing but no clinically meaningful effects on lipids (placebo-adjusted percent change: high-density lipoprotein cholesterol, 0.4%, 95% confidence interval -5.2 to 6.0; low-density lipoprotein cholesterol, -9.8%, 95% confidence interval -16.8 to -2.7; triglyceride, -5.8%, 95% confidence interval -22.6 to 11.9). CONCLUSION: Treatment with MK-0354 for 7 days resulted in plasma FFA suppression with minimal cutaneous flushing. However, 4 weeks of treatment with MK-0354 failed to produce changes in high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, or triglycerides.

Histological spectrum of cutaneous reactions to aspirin in chronic idiopathic urticaria.

BACKGROUND: During a clinical trial, we obtained 16 biopsies of skin eruptions induced by aspirin in patients with chronic idiopathic urticaria (CIU). In this setting, aspirin triggers skin eruptions through a well-established non-immunological mechanism involving the inhibition of cyclooxygenase type I. This presented the rare opportunity to evaluate histological features of a series of skin eruptions induced by a drug acting through a defined mechanism in a controlled experimental setting. OBJECTIVE: Histological analysis of 16 biopsies of skin eruptions induced by oral aspirin challenge in patients with CIU. DESIGN: Microscopic analysis of tissue sections. PATIENTS: 16 patients with CIU. RESULTS: Aspirin (up to 500 mg) induced a restricted range of histological responses with a classic pattern of urticarial tissue reaction occurring in the majority of (12 of 16) cases. Two biopsies showed an interstitial fibrohistiocytic (granuloma annulare-like) reaction pattern. One case showed only a sparse perivascular lymphocytic infiltrate, and paucicellular dermal mucinosis was observed in one case. CONCLUSIONS: Polymorphism of histological patterns induced by aspirin suggests that in addition to the drug-specific mechanisms triggering drug eruptions, individual factors also play a role in determining the ultimate histological phenotype of a drug response.

Safety of cyclooxygenase 2 inhibitors and increased leukotriene synthesis in chronic idiopathic urticaria with sensitivity to nonsteroidal anti-inflammatory drugs.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) exacerbate various forms of urticaria by a nonallergic mechanism involving inhibition of cyclooxygenases. OBJECTIVES: To assess safety of cyclooxygenase inhibitors in patients with chronic idiopathic urticaria (CIU) and NSAID sensitivity and to evaluate a role of cysteinyl leukotriene metabolism and mast cell activation in sensitivity to NSAIDs in CIU. DESIGN: Aspirin challenge test followed by randomized, prospective, double-blind, placebo-controlled crossover trial with cyclooxygenase 2 inhibitors. SETTING: Tertiary referral center of a university hospital. PATIENTS: Thirty-six patients with CIU. INTERVENTIONS: Aspirin challenge test (up to 500 mg); randomized trial with rofecoxib (up to 37.5 mg) and celecoxib (up to 300 mg) in aspirin-sensitive patients. After completion of the trial, 7 patients received naproxen sodium (500 mg) as a positive control. MAIN OUTCOME MEASURES: Standardized skin examination, skin biopsy with mast cell count, urinary levels of leukotriene E4 (LTE4), and serum levels of mast cell tryptase. RESULTS: Aspirin induced skin eruption in 18 patients. Rofecoxib or celecoxib did not elicit skin eruption in any of the aspirin-sensitive patients. Patients with CIU had higher urinary excretion of LTE4 than healthy control subjects. Basal urinary levels of LTE4 and serum mast cell tryptase were increased in aspirin-sensitive compared with aspirin-tolerant patients. Severity and duration of aspirin-induced urticaria showed a positive correlation with urinary LTE4 excretion. Naproxen precipitated urticaria in 5 of 7 aspirin-sensitive patients and caused further increase in urinary LTE4. CONCLUSIONS: Cyclooxygenase 2 inhibitors do not induce urticaria in patients with CIU sensitive to NSAIDs. Sensitivity to NSAIDs in CIU is associated with overproduction of cysteinyl leukotrienes and mast cell activation and most likely depends on inhibition of cyclooxygenase 1.