Intestinally Targeted Diacylglycerol Acyltransferase 1 (DGAT1) Inhibitors Robustly Suppress Postprandial Triglycerides

Abstract

High DGAT1 expression levels in the small intestine highlight the critical role this enzyme plays in nutrient absorption. Identification of inhibitors which predominantly inhibit DGAT1 in the gut is an attractive drug discovery strategy with anticipated benefits of reduced systemic toxicity. In this report we describe our discovery and optimization of DGAT1 inhibitors whose plasma exposure is minimized by the action of transporters, including the P-glycoprotein transporter. The impact of this unique absorption profile on efficacy in rat and dog efficacy models is presented. KEYWORDS: DGAT1, triglyceride synthesis, efflux O rally ingested triglycerides (TG) undergo hydrolysis and then are reassembled within enterocytes into TG-rich chylomicrons destined for systemic circulation. The final committed step in triglyceride biosynthesis is known to be mediated by at least two distinct intracellular acyl-coA diacylglycerol acyltransferases (DGATs), namely DGAT1 1 and DGAT2. 2 Since the development of whole-body knockout models of these enzymes, there has been intense evaluation of pharmacological approaches to modulate their activity. 3−8 For DGAT1, this interest is inspired by the favorable metabolic phenotype of DGAT1 −/− mice, 9 which are resistant to dietinduced body weight gain, 10 are more insulin-sensitive relative to wild-type littermates, 11 and exhibit a reduced rate of chylomicrons formation when challenged with lipid nutrients. 12 Interestingly, all aspects of this phenotype are lost when DGAT1 is reintroduced via a tissue-specific promoter into the intestines of female DGAT1 −/− mice, implying that intestinal DGAT1 plays a crucial role in the effects observed in the whole-body knockout model. 13 Indeed, DGAT1 mRNA expression levels have been shown to be high in regions of the small intestine in mice and humans. 14,15 Selective inhibition of intestinal DGAT1 therefore becomes an intriguing drug discovery approach to recapitulate aspects of the DGAT1 −/− mouse, especially if this gut-specific inhibition reduces the potential risk of on-and off-target activity for candidate molecules. Particularly relevant for DGAT1 pharmacological inhibition is the observation of functional and morphological abnormalities in the fur and sebaceous glands of DGAT1 −/− mice. 16 In this report we describe a novel approach to specifically inhibit intestinal DGAT1, and demonstrate the potential viability of this strategy with regard to efficacy and safety in multiple preclinical models.High-throughput screening efforts using recombinant human DGAT1 enzyme identified the benzimidazole 1 (DGAT1 IC 50 = 1.3 μM; DGAT2 IC 50 > 20 μM; Figure 1) as a potential starting point for optimization. Initial structural modifications demonstrated that both the ethyl carbamate and the 2,6-dichlorophenyl substituents on the benzimidazole core could be replaced without substantial loss of activity (i.e., 2, DGAT1 IC 50 = 1.4 μM), and in fact introducing an additional substituent at the 4-position of the 2,6-dimethylphenyl ring led to an im...

Identification of a botanical inhibitor of intestinal diacylglyceride acyltransferase 1 activity via in vitro screening and a parallel, randomized, blinded, placebo-controlled clinical trial

“…Intestinal DGAT1 is positioned at a site that makes it a good candidate for impacting the postprandial TG response. Pharmacological inhibitors of DGAT1 have been shown to effectively reduce the postprandial TG response to an HFM challenge [ 36 , 37 , 40 , 41 ], but not without significant and intolerable gastrointestinal side effects in humans like nausea, diarrhea and vomiting. This indicates that intestinal DGAT1 is a good target to reduce postprandial TG levels.…”

Chemical Genetic Approaches for the Investigation of Neutral Lipid Metabolism

“…[147] Serrano-Wu of Novartis presented 37,w hich is an anomolar inhibitor of DGAT1 and has been characterizedi nr ats and in dogs. [148] Pradigastat( 38,f ormerlyL CQ-908) has been tested in healthy human subjects, in which it suppressed postprandial TGs in ad ose-dependentmanner,w ith maximum suppression of % 90 %, [149] and provede ffective in patients with familialc hylomicronemia syndrome (FCS). [150] Although 38 is the clinically most advanced compound, no IC 50 and selectivity data have so far been published, and this makesi ts use as at ool compound problematic.T wo new compounds that have not yet enteredc linical trials but exhibit very high activity against DGAT1 have recently been reported:M erck presented inhibitor 39,w hich has been profiled against ap anel of more than 100 other targets,i nw hich it showed > 10 mm against all protein targets with the exception of A2A receptor (K i = 4.6 mm), which makes it the best-characterized tool compound for DGAT1.…”

“…of Astra–Zeneca introduced the reversible arylpyrazine‐based inhibitor AZD7687 ( 36 ), which showed 400× selectivity towards DGAT1 versus acyl‐coenzyme A:cholesterol acyltransferase 1 (ACAT1), and was entered into Phase I clinical trials, in which it showed the expected reduction of triglycerides in plasma, but intolerable side effects in the form of severe diarrhea . Serrano‐Wu of Novartis presented 37 , which is a nanomolar inhibitor of DGAT1 and has been characterized in rats and in dogs . Pradigastat ( 38 , formerly LCQ‐908) has been tested in healthy human subjects, in which it suppressed postprandial TGs in a dose‐dependent manner, with maximum suppression of ≈90 %, and proved effective in patients with familial chylomicronemia syndrome (FCS) .…”

Discovery and optimization of adamantane carboxylic acid derivatives as potent diacylglycerol acyltransferase 1 inhibitors for the potential treatment of obesity and diabetes

“…To investigate PK and PD correlation, we examined intestinal disposition of 43c. DGAT1 is mainly expressed in intestine [18]. Whole mouse small intestine was collected to estimate the total intestinal concentration of 43c could represent total amount in the intestinal area including lumen.…”