Effect of a new oral somatostatin analog (SDZ CO 611) on gastric emptying, mouth to cecum transit time, and pancreatic and gut hormone release in normal male subjects

Orally Absorbed Cyclic Peptides

Peptides and proteins are not orally bioavailable in mammals, although a few peptides are intestinally absorbed in small amounts. Polypeptides are generally too large and polar to passively diffuse through lipid membranes, while most known active transport mechanisms facilitate cell uptake of only very small peptides. Systematic evaluations of peptides with molecular weights above 500 Da are needed to identify parameters that influence oral bioavailability. Here we describe 125 cyclic peptides containing four to thirty-seven amino acids that are orally absorbed by mammals. Cyclization minimizes degradation in the gut, blood, and tissues by removing cleavable N- and C-termini and by shielding components from metabolic enzymes. Cyclization also folds peptides into bioactive conformations that determine exposure of polar atoms to solvation by water and lipids and therefore can influence oral bioavailability. Key chemical properties thought to influence oral absorption and bioavailability are analyzed, including molecular weight, octanol-water partitioning, hydrogen bond donors/acceptors, rotatable bonds, and polar surface area. The cyclic peptides violated to different degrees all of the limits traditionally considered to be important for oral bioavailability of drug-like small molecules, although fewer hydrogen bond donors and reduced flexibility generally favored oral absorption.

[Dumping syndrome: Diagnostics and therapeutic options]

BACKGROUND

Dumping syndrome is a common complication after surgery of the upper gastrointestinal tract with symptoms ranging from mild gastrointestinal discomfort and moderate vasomotor disturbances, to severe hyperinsulinemic hypoglycemia. Due to the increasing number of bariatric procedures being performed worldwide, bariatric surgery has become the most common cause for this disease entity.

OBJECTIVE

The aim of this review is to highlight the evidence for the physiological mechanisms contributing to dumping syndrome after the two most common bariatric surgery procedures, Roux-en-Y gastric bypass and sleeve gastrectomy, to discuss technical aspects of the procedures underlying the development of the syndrome, patient-related predictive factors and other differential diagnoses, together with diagnostic and therapeutic algorithms.

[Prevention of gastrostasis after pancreaticoduodenal resection: new technique of gastroenterostomy]

It was performed a retrospective comparative analysis of treatment results of 113 patients with pancreatic head and periampular cancer. The main group consisted of 58 patients in whom pancreaticoduodenal resection was performed according to an original technique of Russian Scientific Center of Surgery. Control group included 55 patients who underwent end-to-side gastrojejunostomy reconstruction. We have analyzed immediate postoperative complications in 2 groups without taking into consideration nosological forms of the disease. Pancreaticojejunostomy failure was diagnosed postoperatively in 5 (8.6%) patients in main group and in 10 (18.2%) patients in control group. There was no hepaticoentero- and gastroenterostomy failure in patients who underwent new technique of gastrojejunostomy while these events were observed in 8 (14.5%) and 3 (5.5%) patients respectively in control group. Mortality was 1.7% (n=1) in main group and 5.5% (n=3) in control group (p=0.29). Mild degree of gastrostasis (A class) was observed in 54 (93.7%) patients of main group and in 34 (61.8%) patients of control group (p=0.0004). There was B class of gastrostasis in 4 (6.9%) patients of main group. Severe gastrostasis (C class) was not revealed in any observation. In control group B class of gastrostasis was diagnosed in 14 (25.5%) patients, severe degree - in 7 (12.7%) patients. Univariant analysis showed hemotransfusion (p=0.037), pancreatic fistula (p=0.001), enteric fistula (p=0.005) and reconstruction technique (p=0.00004) as predictors of gastrostasis. Multivariant analysis defined pancreatic fistula (p=0.01), enteric fistula (p=0.04) and reconstruction technique (p=0.001) as significant predictors of gastrostasis. Thus, our study revealed significant decreasing gastrostasis incidence in case of original technique in comparison with conventional anastomosis, as well as demonstrated effect of anastomoses failure on augmentation of gastrostasis frequency after pancreaticoduodenal resection. Further randomized investigations are necessary to confirm our results.

Novel exenatide analogs with peptidic albumin binding domains: potent anti-diabetic agents with extended duration of action

The design, synthesis and pharmacology of novel long-acting exenatide analogs for the treatment of metabolic diseases are described. These molecules display enhanced pharmacokinetic profile and potent glucoregulatory and weight lowering actions compared to native exenatide. [Leu(14)]exenatide-ABD is an 88 residue peptide amide incorporating an Albumin Binding Domain (ABD) scaffold. [Leu(14)]exenatide-ABP is a 53 residue peptide incorporating a short Albumin Binding Peptide (ABP). [Leu(14)]exenatide-ABD and [Leu(14)]exenatide-ABP exhibited nanomolar functional GLP-1 receptor potency and were metabolically stable in vitro in human plasma and in a pancreatic digestive enzyme mixture. Both molecules displayed picomolar and nanomolar binding association with albumin across multiple species and circulating half lives of 16 and 11 hours, respectively, post a single IV dose in rats. Unlike exenatide, both molecules elicited robust glucose lowering when injected 1 day prior to an oral glucose tolerance test, indicative of their extended duration of action. [Leu(14)]exenatide-ABD was compared to exenatide in a Lep (ob/ob) mouse model of diabetes. Twice-weekly subcutaneously dosed [Leu(14)]exenatide-ABD displayed superior glucose lowering and weight loss in diabetic mice when compared to continuously infused exenatide at the same total weekly dose. A single oral administration of each molecule via an enteric coated capsule to cynomolgus monkeys showed superior pharmacokinetics for [Leu(14)]exenatide-ABD as compared to [Leu(14)]exenatide-ABP with detectable exposure longer than 14 days. These studies support the potential use of these novel long acting exenatide analogs with different routes of administration for the treatment of type 2 diabetes.

Chronic Intestinal Pseudo-obstruction

For many patients, nutritional support and relief of symptoms remain the primary management goal of pseudo-obstruction. Specific pharmacological agents for this disorder are, in general, lacking. Given that the efficacy of many of the individual available agents is far from excellent, several centers have turned to combination therapy. Though there is at present no evidence from controlled studies to support this strategy, it is, at the very least, theoretically attractive as these agents act through a number of separate mechanisms. The combination of a prokinetic and an emetic may prove especially useful. As the pseudo-obstruction syndromes are, individually, rare, and experience with any given prokinetic agent in these disorders limited, it is difficult to develop strict guidelines for their use in this context. It stands to reason that a response to a prokinetic agent would seem unlikely in a patient with an advanced myopathic process; anecdotal evidence suggests, however, that some patients with severe scleroderma may derive some symptomatic improvement. Where oral therapy is tolerated, cisapride would appear the best choice among available agents. When this fails, subcutaneous octreotide may be added or substituted. In the acute situation, intravenous erythromycin may alleviate gastroparesis, but probably exerts little beneficial effect beyond the pylorus; parenteral metoclopramide may be tried, but, here again, convincing evidence of efficacy is lacking. The roles of endoscopy and surgery are largely confined to facilitating nutrition and providing decompression.