The pK(a), log P, and intestinal transport mechanisms should be considered when determining which drugs may have altered pharmacokinetics in patients who have undergone RYGB.

Solid lipid nanoparticles (SLNs) are gaining importance due to numerous advantages they offer as a drug delivery system. SLN incorporate poorly soluble drugs, proteins, biologicals, etc. SLN are prepared by techniques like high-pressure homogenization, sonication and employs a wide range of lipids and surfactants. Physicochemical characterization techniques include particle size analysis, zeta potential and determination of crystallinity/polymorphism. Furthermore, drug loading and drug entrapment efficiency are common parameters used to test the efficiency of SLN. Most importantly, the functionality assay of SLN is essential to predict the activity and performance in vivo. The review presented discusses the importance of SLN in drug delivery with emphasis on principles and limitations associated with their physicochemical characterization.

Isoprenylcysteine carboxylmethyltransferase (Icmt) is an integral membrane protein localized to the endoplasmic reticulum of eukaryotic cells that catalyzes the post-translational alpha-carboxylmethylesterification of CAAX motif proteins, including the oncoprotein Ras. Prior to methylation, these protein substrates all contain an isoprenylcysteine residue at the C terminus. In this study, we developed a variety of substrates and inhibitors of Icmt that vary in the isoprene moiety in order to gain information about the nature of the lipophilic substrate binding site. These isoprenoid-modified analogs of the minimal Icmt substrate N-acetyl-S-farnesyl-L-cysteine (AFC) were synthesized from newly and previously prepared farnesol analogs. Using both yeast and human Icmt enzymes, these compounds were found to vary widely in their ability to act as substrates, supporting the isoprenoid moiety as a key substrate recognition element for Icmt. Compound 3 is a competitive inhibitor of overexpressed yeast Icmt (K(I) = 17.1 +/- 1.7 microm). Compound 4 shows a mix of competitive and uncompetitive inhibition for both the yeast and the human Icmt proteins (yeast K(IC) = 35.4 +/- 3.4 microm, K(IU) = 614.4 +/- 148 microm; human K(IC) = 119.3 +/- 18.1 microm, K(IU) = 377.2 +/- 42.5 microm). These data further suggest that differences in substrate specificity exist between the human and yeast enzymes. Biological studies suggest that inhibition of Icmt results in Ras mislocalization and loss of cellular transformation ability, making Icmt an attractive and novel anticancer target. Further elaboration of the lead compounds synthesized and assayed here may lead to clinically useful higher potency inhibitors.

Prenylcysteine derivatives are of interest for a variety of different biological reasons, including probing the CaaX protein processing pathway. A solid-phase synthesis protocol for the preparation of prenylcysteines using 2-chlorotrityl chloride resin as a solid support has been developed. A series of novel amide-modified farnesylcysteine analogs were synthesized in both high purity and yield under mild conditions. The farnesylcysteine analogs were evaluated using human isoprenylcysteine carboxyl methyltransferase (Icmt) as a biological target, and several new inhibitors, one with significantly enhanced potency, were identified.

N-acetyl-S-farnesyl-L-cysteine (AFC) is the minimal substrate for the enzyme isoprenylcysteine carboxyl methyltransferase (Icmt). A series of amide-modified farnesylcysteine analogs were synthesized and screened against human Icmt. From a 23-member library of compounds, six inhibitors were identified and evaluated further. The adamantyl derivative 7c was the most potent inhibitor with an IC 50 of 12.4 μM.Numerous proteins are initially synthesized with a C-terminal -CaaX box motif, where -C is cysteine, -aa are generally two aliphatic residues, and -X is typically S, M, F, Q, or L. This motif labels the protein for a series of sequential post-translational modifications ( Figure 1). First, either a 15-carbon farnesyl or 20-carbon geranylgeranyl group is added via a thioether linkage to the cysteine by one of two soluble isoprenyltransferases (proteinfarnesyltransferase, FTase, or protein-geranylgeranyltransferase I, GGTase I). Following the attachment of the prenyl group, the three -aaX residues are cleaved by the endoprotease Ras-converting enzyme 1 (Rce1), and subsequently the newly exposed cysteine carboxyl group is methylated by isoprenylcysteine carboxyl methyltransferase (Icmt). It is estimated that at least 120 mammalian proteins undergo this sequential three step post-translational modification sequence, 1 the sum of which typically results in increased hydrophobicity and enhanced membrane association of an initially cytosolic protein.This post-translational pathway became the subject of intense scrutiny as a target for cancer therapies, as it was determined that the oncogenic Ras family of GTPases must be farnesylated in order to properly function. Importantly, mutations in this family of proteins are responsible for approximately 20-30% of all human cancers and 90% of pancreatic cancers. A number of farnesyltransferase inhibitors (FTIs) are currently undergoing evaluation in clinical trials. 2,3 However, these agents have not exhibited significant activity in most patients with Ras-driven tumors 4 due to alternative geranylgeranylation of Ras in FTI treated cells. 5,6 Rce1 and Icmt have been recognized for a number of years as potential alternative anticancer targets to FTase. 7 Although originally thought to be too important for cell viability due to the embryonic lethal phenotype of Rce1 −/− and Icmt −/− mice, 8 10 We have therefore initiated an effort to generate Icmt inhibitors based on the structure of the minimal Icmt substrate N-acetyl-S-farnesyl-Lcysteine (AFC, Figure 2, 1) in hopes of developing potent anticancer agents as well as molecular tools to study the structure and mechanism of Icmt.Recently reported work from our laboratories has shown that selective changes in the farnesyl group of AFC can afford effective inhibitors of yeast Icmt ( The biochemical and cellular effects of other FC analogs have been previously reported. Farnesyl thiosalicylic acid (FTS) has been shown to inhibit the growth of H-Ras-driven Rat1 cells, though it is believed this effect is not solely due to inhib...

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N-Acetyl-S-farnesyl cysteine (AFC) is the minimal synthetic substrate for the enzyme Icmt, which methylates prenylated proteins. The desthio-AFC isostere 2 has been synthesized in racemic form. This analog was not an Icmt substrate, but instead a weak inhibitor with an IC50 of approximately 325 microM.

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