Mathematical Model-Based Accelerated Development of Extended-release Metformin Hydrochloride Tablet Formulation.

A computational fluid dynamic (CFD) model was developed to predict metformin release from a hydroxypropylmethylcellulose (HPMC) matrix-based extended-release formulation that took into consideration the physical and chemical properties of the drug substance, composition, as well as size and shape of the tablet. New high dose strength (1000 mg) tablet geometry was selected based on the surface area/volume (SA/V) approach advocated by Lapidus/Lordi/Reynold to obtain the desired equivalent metformin release kinetics. Maintaining a similar SA/V ratio across all extended-release metformin hydrochloride (Met XR) tablet strengths that had different geometries provided similar simulations of dissolution behavior. Experimental dissolution profiles of three lots of high-strength tablets agreed with the simulated release kinetics. Additionally, a pharmacokinetic absorption model was developed using GastroPlus™ software and known physicochemical, pharmacokinetic, and in vitro dissolution properties of metformin to predict the clinical exposure of the new high strength (1000 mg) tablet prior to conducting a human clinical bioequivalence study. In vitro metformin release kinetics were utilized in the absorption model to predict exposures in humans for new 1000-mg Met XR tablets, and the absorption model correctly projected equivalent in vivo exposure across all dose strengths. A clinical bioequivalence study was pursued based on the combined modeling results and demonstrated equivalent exposure as predicted by the simulations.

Impact of the counterion on the solubility and physicochemical properties of salts of carboxylic acid drugs.

AIM: Salt formation is a widely used approach to improve the physicochemical and solid state properties of an active pharmaceutical ingredient. In order to better understand the relationships between the active drug, the selected counterion and the resultant salt form, crystalline salts were formed using four different carboxylic acid drugs and a closely related series of amine counterions. Thirty-six related crystalline salts were prepared, characterized and the relationship between solubility and dissolution behaviour and other properties of the salt and the counterion studied. METHODS: Salts of four model acid drugs, gemfibrozil, flurbiprofen, ibuprofen and etodolac were prepared using the counterions butylamine, hexylamine, octylamine, benzylamine, cyclohexylamine, tert-butylamine, 2-amino-2-methylpropan-1-ol, 2-amino-2-methylpropan-1,3-diol and tris(hydroxymethyl)aminomethane. Salt formation was confirmed, the salts were characterized and their corresponding solubilities determined and rationalized with respect to the counterions' properties. RESULTS AND CONCLUSION: The properties of the salt highly dependent on the nature of the counterion and, although there is considerable variation, some general conclusion can be drawn. For the alkyl amines series, increasing chain length leads to a reduction in solubility across all the acidic drugs studied and a reduction in melting point, thus contradicting simplistic relationships between solubility and melting point. Small, compact counterions consistently produce crystalline salts with high melting point accompanied with a modest improvement in solubility and the nature of hydrogen bonding between the ions has a major impact on the solubility.

Investigation of gammaE-crystallin target protein binding to bovine lens alpha-crystallin by small-angle neutron scattering.

alpha-Crystallin, one of the main constituent proteins in the crystalline lens, is an important molecular chaperone both within and outside the lens. Presently, the structural relationship between alpha-crystallin and its target proteins during chaperone action is poorly understood. It has been hypothesised that target proteins bind within a central cavity. Small-angle neutron-scattering (SANS) experiments in conjunction with isotopic substitution were undertaken to investigate the interaction of a target lens protein (gammaE-crystallin) with alpha-crystallin (alpha(H)) and to measure the radius of gyration (Rg) of the proteins and their binary complexes in solution under thermal stress. The size of the alpha(H) in D(2)O incubated at 65 degrees C increased from 69+/-3 to 81+/-5 A over 40 min, in good agreement with previously published small-angle X-ray scattering (SAXS) and SANS measurements. Deuterated gammaE-crystallin in H(2)O buffer (gammaE(D)/H(2)O) and hydrogenous gammaE-crystallin in D(2)O buffer (gammaE(H)/D(2)O) free in solution were of insufficient size and/or too dilute to provide any measurable scattering over the angular range used, which was selected primarily to investigate gammaE:alpha(H) complexes. The evolution of the aggregation size/shape as an indicator of alpha(H) chaperone action was monitored by recording the neutron scattering in different H:D solvent contrasts under thermally stressed conditions (65 degrees C) for binary mixtures of alpha(H), gammaE(H), and gammaE(D). It was found that Rg(alpha(H):gammaE(D)/D(2)O)>Rg(alpha(H):gammaE(H)/D(2)O)>Rg(alpha(H)/D(2)O) and that Rg(alpha(H):gammaE(H)/D(2)O) approximately Rg(alpha(H)/D(2)O). The relative sizes observed for the complexes weighted by the respective scattering powers of the various components imply that gammaE-crystallin binds in a central cavity of the alpha-crystallin oligomer, during chaperone action.

Optimizing ophthalmic delivery of a poorly water soluble drug from an aqueous in situ gelling system.

Poorly soluble drugs are often unsuitable to incorporate in ocular in situ gelling systems due to the aqueous based gelling formulations and low volumes administered. For such formulations to be successful, the administered drug must have sufficient solubility to diffuse from the formulation to the eye and should not affect the gelation of the in situ gelling material. Drug salt forms can improve the solubility of poorly soluble drugs, however, as in situ gel forming formulations are often designed to be crosslinked by salts (present the lacrimal fluid) it can make salt forms difficult to formulate. The aim of this study was to develop an in situ gel forming ophthalmic formulation of a poorly soluble drug flurbiprofen (FBP) through cyclodextrin complex formation and to analyse the impact on gelation, release and permeation through the cornea. Hydroxypropyl-beta-cyclodextrin (HßCD) was used as a complexing agent and low acyl gellan gum was added to the FBP- HßCD complex as a water soluble in situ gelling polymer. Measurements were performed using rheo-dissolution, which utilises a rheometer with a modified lower plate that has the unique ability to allow rheological measurement and analysis of drug release simultaneously. An ex-vivo permeation study was also performed using porcine cornea. Rheological measurements in terms of elastic (G') and viscous (G″) modulus showed rapid gelation of the formulation upon contact with simulated lacrimal fluid (SLF). Approximately, 97% FBP was released when 10% HßCD was used and release was decreased to 79% when the amount of HßCD was increased to 20%. The percentage of drug permeation through the cornea was 55% in 300 min whereas the marketed non gelling eye drop formulation containing FBP sodium showed only 37% permeation. The data presented here, revealed that not only could a poorly soluble drug be complexed with cyclodextrin and loaded into an in situ gelling system without interfering with the gelation, but also permeability the of the drug improved.

The location of bound lipid in the lipovitellin complex.

The location of the bound lipid in the soluble lipoprotein lipovitellin has been determined by neutron crystallographic techniques. With the use of the contrast variation method, whereby the crystals are soaked in different H2O-D2O mixtures, the lipid has been found to occupy a large cavity in the protein whose structure had previously been determined by x-ray crystallography. The lipid appears to be bound in the form of a bilayer with the major protein-lipid interactions being hydrophobic and with the lipid headgroups projecting into the bulk solvent and into a solvent-filled space in the cavity.

Structure of collagen in cartilage of intervertebral disk.

Small-angle x-ray and neutron diffraction patterns have been obtained from the annulus fibrosus of porcine intervertebral disk. These show that the collagen in this tissue is modified compared with that in tendon.

A survey on IVIVC/IVIVR development in the pharmaceutical industry - Past experience and current perspectives.

The present work aimed to describe the current status of IVIVC/IVIVR development in the pharmaceutical industry, focusing on the use and perception of specific approaches as well as successful and failed case studies. Two questionnaires have been distributed to 13 EFPIA partners of the Oral Biopharmaceutics Tools Initiative and to the Pharmacokinetics Working Party of the European Medicines Agency in order to capture the perspectives and experiences of industry scientists and agency members, respectively. Responses from ten companies and three European Agencies were received between May 21st 2014 and January 19th 2016. The majority of the companies acknowledged the importance of IVIVC/IVIVR throughout the drug development stages and a well-balanced rate of return on investment. However, the IVIVC/IVIVR approach seemed to be underutilized in regulatory submissions. Four of the ten companies stated to have an internal guidance related to IVIVC/IVIVR modelling, whereas three felt that an overall strategy is not necessary. Successful models mainly served to support formulation development and to provide a better mechanistic understanding. There was not yet much experience with safe-space IVIVRs as well as the use of physiologically based modelling in the field of IVIVC. At the same time, the responses from both industry and agencies indicated that there might be a need for a regulatory framework to guide the application of these novel approaches. The relevance of IVIVC/IVIVR for oral IR drug products was recognized by most of the companies. For IR formulations, relationships other than Level A correlation were more common outcomes among the provided case studies, such as multiple Level C correlation or safe-space IVIVR, which could be successfully used for requesting regulatory flexibility. Compared to the responses from industry scientists, there was a trend towards a higher appreciation of the BCS among the regulators, but a less positive attitude towards the utility of non-compendial dissolution methods for establishing a successful IVIVC/IVIVR. The lack of appropriate in vivo data and regulatory uncertainty were considered the major difficulties in IVIVC/IVIVR development. The results of this survey provide unique insights into current IVIVC/IVIVR practices in the pharmaceutical industry. Pursuing an IVIVC/IVIVR should be generally encouraged, considering its high value from both industry and regulators' perspective.

The three-dimensional distribution of RNA and protein in the interior of tomato bushy stunt virus: a neutron low-resolution single-crystal diffraction study.

BACKGROUND: The published high-resolution model of the isometric T = 3 plant virus tomato bushy stunt virus (TBSV) shows the packing in three different environments (A, B, C) of the 180 coat protein subunits of the capsid. It does not, however, account for the localization of either the viral RNA or approximately 25% of the amino acids of the protein subunits, although at least the RNA is rigidly linked to the viral capsid. Solution studies have shown that most of the missing protein is located in an inner shell, and that most of the RNA is sandwiched between the two protein shells. RESULTS: We have determined the organization of TBSV at 16 A resolution, using neutron single-crystal diffraction. Connections between the two protein shells are confined to the 20 three-fold axes of the virion, where three C-type subunits meet. Much more RNA density is located under the 30 C-C dimers than under the 60 A-B dimers, where we could even identify lagoons of solvent. CONCLUSIONS: Our results emphasize the importance of the amino termini of the 60 C-type protein subunits not only in the RNA-protein interactions but also in the organization of the coat protein, and, probably, in the assembly of the virion. The lack of equivalence between subunits of classes A or B and subunits of class C is even more pronounced in the interior of the virion than in the outer shell, which possesses icosahedral symmetry.

Detergent structure in tetragonal crystals of OmpF porin.

BACKGROUND: The high-resolution structures of five porins have been solved by X-ray crystallography including the trigonal crystal form of the trimeric OmpF porin from Escherichia coli. In an accompanying article, the structure of the tetragonal form of OmpF porin is presented. In contrast to the trigonal crystal form, the protein surfaces normally in contact with lipids in the membrane are exposed and interact with amphiphiles in the tetragonal crystal. Thus, the tetragonal form can be used to investigate protein-detergent interactions. RESULTS: Using single-crystal neutron diffraction studies and two different detergents (one of them deuterated in its hydrophobic moiety), details of the amphiphile-protein interactions are revealed. Detergent molecules bind to the so-called hydrophobic zone that surrounds the OmpF porin trimer and which is exposed to lipid in the native environment. The aromatic rings on both sides of the hydrophobic zone coincide with the boundary between non-polar and polar moieties of the detergents. CONCLUSIONS: In the tetragonal crystal form of OmpF porin, the membrane-exposed area is accessible from the aqueous solution. It is coated by a film of detergent molecules, which presumably mimics the interactions of the protein with lipids in the biological membrane. In the trigonal form, protein-protein interactions predominate in the hydrophobic zone. These may reflect the tight interactions between trimers that are observed in the biological membrane.

Neutron and X-ray scattering by ox corneal stroma differentially loaded with bound anions.

Ox corneas at near physiological hydration were subjected to two variables: the amount of chloride ions bound to them and exposure of various mixtures of H(2)O/D(2)O as solvent. The preparations were then exposed to a neutron beam and the contrast match points, at which the collagen fibrils of the corneal stroma most nearly matched the scattering density of the various H(2)O/D(2)O mixtures, were measured. In both cases of high and low bound chloride, the contrast match points of the collagen fibril were equal, indicating that there were no significant changes in the water of electrostriction at the fibril surface when chloride ions bind to the stroma. The data suggest that the ligands which bind anions to corneal stroma are not located at the collagen fibril surface. When the chloride binding ligands were extracted from the corneal stroma there were significant changes in the structure of the fibrils. We suggest that the chloride binding ligands may be located within the collagen fibril.

Structural studies of adenovirus type 2 by neutron and X-ray scattering.

Small-angle neutron and X-ray scattering have been used to investigate various aspects of the structural organization of adenovirus type 2. Neutron scattering allows the determination of the radial distribution of DNA and protein, which because of the highly icosahedral form of the virus allows it to be described in terms of three icosahedral shells. X-ray scattering shows that the distance between the major coat proteins (hexons) in the capsid is 100 +/- A. Evidence was also observed for an organization in the nucleoprotein core that gives rise to a maximum in the X-ray scattering at 1/29 A-1.

Structural parameters of the Pf1 gene 5 protein-DNA complex in solution by neutron scattering.

Neutron-scattering experiments have been performed on the intracellular complex formed by the gene 5 protein and single-stranded DNA in cells infected by filamentous bacteriophage Pf1. The contrast matched point of the complex (37% 2H2O) is lower than expected and implies that a substantial fraction of potentially labile hydrogen atoms are unable to exchange with the solvent. The mass/length ratio of the complex (3270 daltons/A) indicates an axial subunit repeat of 5.1 A, a value much larger than the subunit repeat previously determined in fibres. The measured value of the cross-sectional radius of gyration at infinite contrast (Rc = 43.3 A) indicates an outer radius of 60 to 63 A for the complex. The variation in Rc with contrast shows that regions of higher scattering density are located, on average, towards the outside of the complex. The high-angle region of the intensity curve (measured in 2H2O) reveals a clear subsidiary maximum at 0.105 A-1 arising from the 60 A helical pitch of the nucleoprotein complex. The structural parameters of the Pf1 gene 5 protein-DNA complex in solution are compared with those of the fd gene 5 protein-DNA complex.

Membrane-bound form of the pore-forming domain of colicin A. A neutron scattering study.

The ion-channel forming C-terminal fragment of colicin A binds to negatively charged lipid vesicles and provides an example of the insertion of a soluble protein into a lipid bilayer. The soluble structure is known and consists of a ten-helix bundle containing a hydrophobic helical hairpin. This fragment forms a well-defined complex with dimyristoylphosphatidyl-glycerol which is thus amenable to neutron scattering studies. Neutron scattering experiments in the Guinier range (low angles) provided the mass and the stoichiometry of the complex (290,000 (+/- 10,000) M(r), 8.2 (+/- 0.5)), in fair agreement with previous determinations. By varying the neutron scattering length density of the solvent with 2H2O/H2O mixtures and therefore the contrast of the different components, the radial distribution of the protein and of the lipids was determined. Finally, an attempt was made to fit various models to the wider angle scattering data. This study suggests that the pore-forming fragment of colicin A lies mostly at the surface of the membrane, with the lipids arranged in a bilayer organization.

Crystal packing and stoichiometry of the fibre protein of adenovirus type 2.

Crystals of the fibre protein of adenovirus type 2 have been grown and studied by electron microscopy and X-ray powder diffraction. The molecular packing and density of the crystals suggest that the fibre is dimeric.

Activation of recA protein. The open helix model for LexA cleavage.

RecA protein is induced by the binding of DNA and ATP to become active in the hydrolysis of ATP and the cleavage of repressors. These reactions appear to depend on the structural state of the protein polymerized along the DNA, i.e. a helical coat of six RecA per turn of 95 to 100 A pitch. In support of this model of the active conformation, it was shown that high concentrations of salt also induce this helical polymerized state as well as the enzymatic activities. Here, we describe that, in vitro and with the non-hydrolyzable analogue ATP gamma S, RNA and heparin can also induce both the structural transition and the enzymatic activation of RecA to LexA cleavage in accordance with the model. RNA and heparin do not support the reaction in the presence of ATP, and they do not induce the hydrolysis of ATP either, suggesting that, in contrast to ATP gamma S, the nucleotide is not bound stably enough, and that the combined affinities of polynucleotide and ATP actually modulate the discrimination of RecA for the various possible inducers in vivo.

Effects of ligand binding on the association properties and conformation in solution of retinoic acid receptors RXR and RAR.

In higher eukaryotes, vitamin A derived metabolites such as 9-cis and all-trans retinoic acid (RA), are involved in the regulation of several essential physiological processes. Their pleiotropic physiological effects are mediated through direct binding to cognate nuclear receptors RXRs and RARs that act as regulated transcription factors belonging to the superfamily of nuclear hormone receptors. Hormone binding to the structurally conserved ligand-binding domain (LBD) of these receptors triggers a conformational change that principally affects the conserved C-terminal transactivation helix H12 involved in transcriptional activation. We report an extensive biophysical solution study of RAR alpha, RXR alpha LBDs and their corresponding RXR alpha/RAR alpha LBD heterodimers combining analytical ultracentrifugation (AUC), small-angle X-ray and neutron scattering (SAXS and SANS) and ab initio three-dimensional shape reconstruction at low resolution. We show that the crystal structures of RXRs and RARs LBDs correlate well with the average conformations observed in solution. Furthermore we demonstrate the effects of 9-cisRA and all-transRA binding on the association properties and conformations of RXR alpha and RAR alpha LBDs in solution. The present study shows that in solution RAR alpha LBD behaves as a monomer in both unliganded and liganded forms. It confirms the existence in solution of a ligand-induced conformational change towards a more compact form of the LBD. It also confirms the stability of the predicted RXR alpha/RAR alpha LBD heterodimers in solution. SAS measurements performed on three different types of RXR alpha/RAR alpha LBD heterodimers (apo/apo, apo/holo and holo/holo) with respect to their ligand-binding site occupancy show the existence of three conformational states depending on the progressive binding of RA stereoisomers on RAR alpha and RXR alpha LBD subunits in the heterodimeric context. These results suggest that the subunits are structurally independent within the heterodimers. Our study also underlines the particular behaviour of RXR alpha LBD. In solution unliganded RXR alpha LBD is observed as two species that are unambiguously identified as homotetramers and homodimers. Molecular modelling combined with SAS data analysis allows us to propose a structural model for this autorepressed apo-tetramer. In contrast to the monomeric state observed in the crystal structure, our data show that in solution active holo-RXR alpha LBD bound to 9-cisRA is a homodimer regardless of the protein concentration. This study demonstrates the crucial role of ligands in the regulation of homodimeric versus heterodimeric association state of RXR in the NR signalling pathways.

Complexes of RecA protein in solution. A study by small angle neutron scattering.

RecA complexes on DNA and self-polymers were analysed by small-angle neutron scattering in solution. By Guinier analysis at small angles and by model analysis of a subsidiary peak at wider angles, we find that the filaments fall into two groups: the DNA complex in the presence of ATP gamma S, an open helix with pitch 95 A, a cross-sectional radius of gyration of 33 A and a mass per length of about six RecA units per turn, which corresponds to the state of active enzyme; and the compact form (bound to single-stranded DNA in the absence of ATP, or binding ATP gamma S in the absence of DNA, or just the protein on its own), a helical structure with pitch 70 A, cross-sectional radius of gyration 40 A and mass per length about five RecA units per turn, which corresponds to the conditions of inactive enzyme. The results are discussed in the perspective of unifying previous conflicting structural results obtained by electron microscopy.

The effect of regulatory Ca2+ on the in situ structures of troponin C and troponin I: a neutron scattering study.

The effects of regulatory amounts of Ca2+ on the in situ structures of troponin C (TnC) and troponin I (TnI) in whole troponin have been investigated by neutron scattering. In separate difference experiments, 97% deuterated TnC and TnI within whole troponin were studied +/-Ca2+ in 41.6% 2H2O buffers in which protonated subunits were rendered "invisible". We found that the radius of gyration (Rg) of TnI decreased by approximately 10% upon addition of regulatory Ca2+ indicating that it was significantly more compact in the presence of Ca2+. The apparent cross-sectional radius of gyration (Rc) of TnI increased by about 9% when regulatory Ca2+ was bound to TnC. Modeling studies showed that the high-Q scattering patterns of TnI could be fit by a TnI which consisted of two subdomains: one, a highly oblate ellipsoid of revolution containing about 65% of the mass and the other, a highly prolate ellipsoid of revolution consisting of about 35% of the mass. No other fits could be found with this class of models. Best fits were achieved when the axes of revolution of these ellipsoids were steeply inclined with respect to each other. Ca2+ addition decreased the center of mass separation by about 1.5 nm. The Rg of TnI, its high-Q scattering pattern, and the resultant structure were different from previous results on neutron scattering by TnI in the (+Ca2+) TnC.TnI complex. The Rg of TnC indicated that it was elongate in situ. The Rg of TnC was not sensitive to the Ca2+ occupancy of its regulatory sites. However, Rc increased upon Ca2+ addition in concert with expectations from NMR and crystallography of isolated TnC. The present observations indicate that TnI acts like a molecular switch which is controlled by smaller Ca2+-induced changes in TnC.

Studies on the structure and mechanism of a bacterial protein toxin by analytical ultracentrifugation and small-angle neutron scattering.

Pneumolysin, an important virulence factor of the human pathogen Streptococcus pneumoniae, is a pore-forming toxin which also possesses the ability to activate the complement system directly. Pneumolysin binds to cholesterol in cell membrane surfaces as a prelude to pore formation, which involves the oligomerization of the protein. Two important aspects of the pore-forming activity of pneumolysin are therefore the effect of the toxin on bilayer membrane structure and the nature of the self-association into oligomers undergone by it. We have used analytical ultracentrifugation (AUC) to investigate oligomerization and small-angle neutron scattering (SANS) to investigate the changes in membrane structure accompanying pore formation. Pneumolysin self-associates in solution to form oligomeric structures apparently similar to those which appear on the membrane coincident with pore formation. It has previously been demonstrated by us using site-specific chemical derivatization of the protein that the self-interaction preceding oligomerization involves its C-terminal domain. The AUC experiments described here involved pneumolysin toxoids harbouring mutations in different domains, and support our previous conclusions that self-interaction via the C-terminal domain leads to oligomerization and that this may be related to the mechanism by which pneumolysin activates the complement system.SANS data at a variety of neutron contrasts were obtained from liposomes used as model cell membranes in the absence of pneumolysin, and following the addition of toxin at a number of concentrations. These experiments were designed to allow visualization of the effect that pneumolysin has on bilayer membrane structure resulting from oligomerization into a pore-forming complex. The structure of the liposomal membrane alone and following addition of pneumolysin was calculated by the fitting of scattering equations directly to the scattering curves. The fitting equations describe scattering from simple three-dimensional scattering volume models for the structures present in the sample, whose dimensions were varied iteratively within the fitting program. The overall trend was a thinning of the liposome surface on toxin attack, which was countered by the formation of localized structures thicker than the liposome bilayer itself, in a manner dependent on pneumolysin concentration. At the neutron contrast match point of the liposomes, pneumolysin oligomers were observed. Inactive toxin appeared to bind to the liposome but not to cause membrane alteration; subsequent activation of pneumolysin in situ brought about changes in liposome structure similar to those seen in the presence of active toxin. We propose that the changes in membrane structure on toxin attack which we have observed are related to the mechanism by which pneumolysin forms pores and provide an important perspective on protein/membrane interactions in general. We discuss these results in the light of published data concerning the interaction of gramicidin with bilayers and the hydrophobic mismatch effect.

Low incidence of port-site metastasis after robotic assisted surgery for endometrial cancer staging: descriptive analysis.

The purpose of this study was to evaluate the incidence and characteristics of patients with port-site metastasis following robotic assisted surgery for gynecological malignancies. Patients who underwent robotic assisted total laparoscopic hysterectomy and surgical staging at a single institution from November 2006 through November 2011 were retrospectively identified. Medical records were reviewed and the following information was extracted: diagnosis, histology, tumor extension, procedure, complications and post-surgical intervention. Port-site metastases were differentiated between isolated and not isolated. All metastases were confirmed with biopsy and treated with chemotherapy and radiotherapy as indicated. Four hundred forty-six patients with endometrial carcinoma were identified who had undergone robotic assisted hysterectomy and staging. Eight patients were converted to laparotomy and excluded from the study. Of 438 patients, 384 patients were diagnosed with early stages (stages 1 and 2), and 54 were diagnosed with advanced stages (stages 3 and 4). A total of 332 patients underwent pelvic lymphadenectomy regardless of the endometrial cancer stage; of those, 283 with early stage disease underwent pelvic lymphadenectomy, while 49 with advanced stage disease underwent pelvic lymphadenectomy. One hundred seventy-six patients received adjuvant treatment after surgical staging. Four patients were identified with port-site metastases (0.9 %), two patients were reported as isolated metastases. The mean patient age was 63 and mean BMI was 37 kg/m(2). The incidence of port-site metastasis is low after robotic assisted surgery for treatment of endometrial cancer (0.9 %). There is no clear risk factor for development of port-site metastasis or easily identifiable prevention.