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Mechanism Of Action

The pancreatic enzymes in ZENPEP catalyze the hydrolysis of fats to monoglycerides, glycerol, and free fatty acids, protein into peptides and amino acids, and starch into dextrins and short chain sugars such as maltose and maltriose in the duodenum and proximal small intestine, thereby acting like digestive enzymes physiologically secreted by the pancreas.


The pancreatic enzymes in ZENPEP are enteric-coated to minimize destruction or inactivation in gastric acid. ZENPEP is designed to release most of the enzymes in vivo at pH greater than 5.5. Pancreatic enzymes are not absorbed from the gastrointestinal tract in any appreciable amount.

Clinical Studies

The short-term safety and efficacy of ZENPEP were evaluated in 2 studies conducted in 53 patients, ages 1 to 23 years, with exocrine pancreatic insufficiency (EPI) associated with cystic fibrosis (CF).

Study 1, was a randomized, double-blind, placebo-controlled, crossover study of 34 patients, ages 7 to 23 years, with EPI due to CF. The final analysis population was limited to 32 patients, who completed both double-blind treatment periods, and were included in the efficacy analysis population. Patients were randomized to receive ZENPEP or matching placebo for 6 to 7 days of treatment, followed by crossover to the alternate treatment for an additional 6 to 7 days. The mean dose during the controlled treatment periods ranged from a mean dose of 3,900 lipase units per kilogram per day to 5,700 lipase units per kilogram per day. All patients consumed a high-fat diet (greater than or equal to 100 grams of fat per day) during the treatment period.

The primary efficacy endpoint was the mean difference in the coefficient of fat absorption (CFA) between ZENPEP and placebo treatment. The CFA was determined by a 72-hour stool collection during both treatments, when both fat excretion and fat ingestion were measured. Each patient's CFA during placebo treatment was used as their no-treatment CFA value.

Mean CFA was 88% with ZENPEP treatment compared to 63% with placebo treatment. The mean difference in CFA was 26 percentage points in favor of ZENPEP treatment with 95% Confidence Interval of (19, 32) and p < 0.001.

Subgroup analyses of the CFA results showed that mean change in CFA was greater in patients with lower no-treatment (placebo) CFA values than in patients with higher no-treatment (placebo) CFA values. There were similar responses to ZENPEP by age and gender.

Study 2, was an open-label, uncontrolled study of 19 patients, ages 1 to 6 years (mean age 4 years), with EPI due to CF. Approximately half of the patients were ages 1 to 3 years. Study 2 compared a measurement of fat malabsorption, spot fecal fat testing, before (while receiving therapy with another commercial PEP) and after oral administration of Zenpep capsules with each meal or snack.

All patients in Study 2 were transitioned to ZENPEP from their usual PEP treatment. After a 4-14 days screening period on the current PEP, patients in Study 2 received ZENPEP at individually titrated doses ranging between 2,300 and 10,000 lipase units per kg body weight per day, with a mean of approximately 5,000 lipase units per kg body weight per day (not to exceed 2,500 lipase units per kilogram per meal) for 14 days. There was no wash-out period. Overall, patients showed similar control of fat malabsorption by spot fecal fat testing when switched to ZENPEP treatment at similar doses.


1. Borowitz DS, Grand RJ, Durie PR, et al. Use of pancreatic enzyme supplements for patients with cystic fibrosis in the context of fibrosing colonopathy. Journal of Pediatrics. 1995; 127: 681-684.

2. Borowitz DS, Baker RD, Stallings V. Consensus report on nutrition for pediatric patients with cystic fibrosis. Journal of Pediatric Gastroenterology Nutrition. 2002 Sep; 35: 246-259.

3. Stallings VA, Start LJ, Robinson KA, et al. Evidence-based practice recommendations for nutrition-related management of children and adults with cystic fibrosis and pancreatic insufficiency: results of a systematic review. Journal of the American Dietetic Association. 2008; 108: 832-839.

4. Smyth RL, Ashby D, O'Hea U, et al. Fibrosing colonopathy in cystic fibrosis: results of a case-control study.9 Lancet. 1995; 346: 1247-1251.

5. FitzSimmons SC, Burkhart GA, Borowitz DS, et al. High-dose pancreatic-enzyme supplements and fibrosing colonopathy in children with cystic fibrosis. New England Journal of Medicine. 1997; 336: 1283-1289.

Last reviewed on RxList: 4/4/2014
This monograph has been modified to include the generic and brand name in many instances.

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