Evaluation of recombinant platelet-activating factor acetylhydrolase for reducing the incidence and severity of post-ERCP acute pancreatitis.

BACKGROUND: Pancreatitis is the most common major complication of diagnostic and therapeutic ERCP. Platelet-activating factor (PAF) has been implicated in the pathophysiologic events associated with acute pancreatitis. Animal and human studies suggested that recombinant PAF acetylhydrolase (rPAF-AH) might ameliorate the severity of acute pancreatitis. OBJECTIVE: Our purpose was to determine whether prophylactic rPAF-AH administration reduces the frequency or severity of post-ERCP pancreatitis in high-risk patients. DESIGN: Randomized, multicenter, double-blind, placebo-controlled study. INTERVENTIONS: Patients received rPAF-AH at a dose of either 1 or 5 mg/kg or placebo. Patients were administered a single intravenous infusion over 10 minutes of study drug or placebo <1 hour before ERCP. MAIN OUTCOME MEASUREMENTS: Standardized criteria were used to diagnose and grade the severity of post-ERCP pancreatitis. Adverse events were prospectively recorded. RESULTS: A total of 600 patients were enrolled. There were no statistically significant differences among the treatment groups with respect to patient demographics, ERCP indications, and patient and procedure risk factors for post-ERCP pancreatitis with the following exceptions: the rPAF-AH 5 mg/kg group had significantly fewer patients younger than 40 years old and scheduled to undergo a therapeutic ERCP involving the pancreatic sphincter or duct. Post-ERCP pancreatitis occurred in 17.5%, 15.9%, and 19.6% of patients receiving rPAF-AH (1 mg/kg), rPAF-AH (5 mg/kg), and placebo, respectively (P = .59 for rPAF-AH 1 mg/kg vs placebo and P = .337 for rPAF-AH 5 mg/kg vs placebo). There was no statistically significant difference between the groups with regard to the severity of pancreatitis, frequency of amylase/lipase elevation more than 3 times normal, or abdominal pain. CONCLUSIONS: There was no apparent benefit of rPAF-AH treatment compared with placebo in reducing the incidence of post-ERCP pancreatitis in subjects at increased risk.

Characterization of the inflammatory response to a highly selective PDE4 inhibitor in the rat and the identification of biomarkers that correlate with toxicity.

The primary toxicity associated with repeated oral administration of the PDE4 inhibitor IC542 to the rat is an inflammatory response leading to tissue damage primarily in the gastrointestinal tract and mesentery. Although necrotizing vasculitis is frequently seen with other PDE4 inhibitors, blood vessel injury was rare following IC542 administration and was always associated with inflammation in the surrounding tissue. The incidence and severity of the histologic changes in these studies correlated with elevated peripheral blood leukocytes, serum IL-6, haptoglobin, and fibrinogen, and with decreased serum albumin. By monitoring haptoglobin, fibrinogen and serum albumin changes in IC542-treated rats, it was possible to identify rats with early histologic changes that were reversible. Since PDE4 inhibition is generally associated with anti-inflammatory activity, extensive inflammation in multiple tissues was unexpected with IC542. Co-administration of dexamethasone completely blocked IC542-induced clinical and histologic changes in the rat, confirming the toxicity resulted from inflammatory response. In addition, IC542 augmented release of the proinflammatory cytokine IL-6 in LPS-activated whole blood from rats but not monkeys or humans. The effect of IC542 on IL-6 release from rat leukocytes in vitro is consistent with the proinflammatory response observed in vivo and demonstrates species differences to PDE4 inhibition.