Human Breast Extracellular Matrix Microstructures and Protein Hydrogel 3D Cultures of Mammary Epithelial Cells.

Tissue extracellular matrix (ECM) is a structurally and compositionally unique microenvironment within which native cells can perform their natural biological activities. Cells grown on artificial substrata differ biologically and phenotypically from those grown within their native tissue microenvironment. Studies examining human tissue ECM structures and the biology of human tissue cells in their corresponding tissue ECM are lacking. Such investigations will improve our understanding about human pathophysiological conditions for better clinical care. We report here human normal breast tissue and invasive ductal carcinoma tissue ECM structural features. For the first time, a hydrogel was successfully fabricated using whole protein extracts of human normal breast ECM. Using immunofluorescence staining of type I collagen (Col I) and machine learning of its fibrous patterns in the polymerized human breast ECM hydrogel, we have defined the microstructural characteristics of the hydrogel and compared the microstructures with those of other native ECM hydrogels. Importantly, the ECM hydrogel supported 3D growth and cell-ECM interaction of both normal and cancerous mammary epithelial cells. This work represents further advancement toward full reconstitution of the human breast tissue microenvironment, an accomplishment that will accelerate the use of human pathophysiological tissue-derived matrices for individualized biomedical research and therapeutic development.

Distinct phenotypes of cancer cells on tissue matrix gel.

BACKGROUND: Breast cancer cells invading the connective tissues outside the mammary lobule or duct immerse in a reservoir of extracellular matrix (ECM) that is structurally and biochemically distinct from that of their site of origin. The ECM is a spatial network of matrix proteins, which not only provide physical support but also serve as bioactive ligands to the cells. It becomes evident that the dimensional, mechanical, structural, and biochemical properties of ECM are all essential mediators of many cellular functions. To better understand breast cancer development and cancer cell biology in native tissue environment, various tissue-mimicking culture models such as hydrogel have been developed. Collagen I (Col I) and Matrigel are the most common hydrogels used in cancer research and have opened opportunities for addressing biological questions beyond the two-dimensional (2D) cell cultures. Yet, it remains unclear whether these broadly used hydrogels can recapitulate the environmental properties of tissue ECM, and whether breast cancer cells grown on CoI I or Matrigel display similar phenotypes as they would on their native ECM. METHODS: We investigated mammary epithelial cell phenotypes and metabolic profiles on animal breast ECM-derived tissue matrix gel (TMG), Col I, and Matrigel. Atomic force microscopy (AFM), fluorescence microscopy, acini formation assay, differentiation experiments, spatial migration/invasion assays, proliferation assay, and nuclear magnetic resonance (NMR) spectroscopy were used to examine biological phenotypes and metabolic changes. Student's t test was applied for statistical analyses. RESULTS: Our data showed that under a similar physiological stiffness, the three types of hydrogels exhibited distinct microstructures. Breast cancer cells grown on TMG displayed quite different morphologies, surface receptor expression, differentiation status, migration and invasion, and metabolic profiles compared to those cultured on Col I and Matrigel. Depleting lactate produced by glycolytic metabolism of cancer cells abolished the cell proliferation promoted by the non-tissue-specific hydrogel. CONCLUSION: The full ECM protein-based hydrogel system may serve as a biologically relevant model system to study tissue- and disease-specific pathological questions. This work provides insights into tissue matrix regulation of cancer cell biomarker expression and identification of novel therapeutic targets for the treatment of human cancers based on tissue-specific disease modeling.

Self-Adhesive Microneedles with Interlocking Features for Sustained Ocular Drug Delivery.

The interests in sustained ocular drug delivery have grown rapidly in recent years, with hope to replace repeated intravitreal injections. Microneedles (MNs), which are minimally invasive, have been shown to be a feasible vehicle for sustained drug delivery. However, securing an MN patch in the eye remains challenging. In this study, a new design of hydrogel MNs with interlocking features to achieve self-adhesion is proposed. Upon swelling, the swollen interlocking features help secure the MNs in place. A new molding process is developed to fabricate MNs with interlocking features that can cause issues when demolding using the regular micromolding process. MNs with two different interlocking feature designs are used in this study and are made with polyvinyl alcohol. MNs with the interlocking features show an 80% increase in adhesion strength and a small amount of increase in penetration force, in comparison to MNs without any feature. The experiments are performed using both a sclera-mimicking phantom and ex vivo eyes harvested from rabbits and are shown to have comparable results. This study demonstrates the feasibility of incorporating interlocking features to MNs to achieve self-adhesion that can enable sustained drug delivery via MNs.

A Feasibility Study of an Extrusion-Based Fabrication Process for Personalized Drugs.

Developing a high-efficiency manufacturing system for personalized medicine plays an important role in increasing the feasibility of personalized medication. The purpose of this study is to investigate the feasibility of a new extrusion-based fabrication process for personalized drugs with a faster production rate. This process uses two syringe pumps with a coaxial needle as an extruder, which extrudes two materials with varying ratios into a capsule. The mixture of hydrogel, polyethylene glycol (PEG), hydroxypropyl methylcellulose, poly acrylic acid and the simulated active pharmaceutical ingredient, Aspirin, was used. To validate the method, samples with different ratios of immediate release (IR) and sustained release (SR) mixtures were fabricated. The results of a dissolution test show that it is feasible to control the release profile by changing the IR and SR ratio using this fabrication setup. The fabrication time for each capsule is about 20 seconds, which is significantly faster than the current 3D printing methods. In conclusion, the proposed fabrication method shows a clear potential to step toward the feasibility of personalized medication.

Determination of Tissue Thermal Conductivity as a Function of Thermal Dose and Its Application in Finite Element Modeling of Electrosurgical Vessel Sealing.

OBJECTIVE: Electrosurgical vessel sealing is a process commonly used to control bleeding during surgical procedures. Finite element (FE) modeling is often performed to obtain a better understanding of thermal spread during this process. The accuracy of the FE model depends on the implemented material properties. Thermal conductivity is one of the most important properties that affect temperature distribution. The goal of this study is to determine the tissue thermal conductivity as a function of thermal dose. Methods: We developed an iterative approach to correlating tissue thermal conductivity to more accurately calculated thermal dose, which cannot be experimentally measured. The resulting regression model was then implemented into an electrosurgical vessel sealing FE model to examine the accuracy of this FE model. Results: The results show that with the regression model, more reasonable temperature and thermal dose prediction can be achieved at the center of the sealed vessel tissue. The resulting electrical current and impedance from the FE model match with the experimental results. Conclusion: The developed approach can be used to determine the correlation between thermal dose and thermal conductivity. Describing the thermal conductivity as a function of thermal dose allows modeling of irreversible changes in tissue properties. Significance: By having a more accurate temperature estimation at the center of the sealed vessel, more insight is provided into how the tissue reacts during the vessel sealing process.

Porcine Breast Extracellular Matrix Hydrogel for Spatial Tissue Culture.

Porcine mammary fatty tissues represent an abundant source of natural biomaterial for generation of breast-specific extracellular matrix (ECM). Here we report the extraction of total ECM proteins from pig breast fatty tissues, the fabrication of hydrogel and porous scaffolds from the extracted ECM proteins, the structural properties of the scaffolds (tissue matrix scaffold, TMS), and the applications of the hydrogel in human mammary epithelial cell spatial cultures for cell surface receptor expression, metabolomics characterization, acini formation, proliferation, migration between different scaffolding compartments, and in vivo tumor formation. This model system provides an additional option for studying human breast diseases such as breast cancer.

Characterization and Modeling of Tissue Thermal Conductivity During an Electrosurgical Joining Process.

Electrosurgical vessel joining is commonly performed in surgical procedures to maintain hemostasis. This process requires elevated temperature to denature the tissue and while compression is applied, the tissue can be joined together. The elevated temperature can cause thermal damages to the surrounding tissues. In order to minimize these damages, it is critical to understand how the tissue properties change and how that affects the thermal spread. The purpose of this study is to investigate the changes of tissue thermal conductivity and how the changes correlate to thermal dose during the joining process. We propose a hybrid method combining experimental measurement with inverse heat transfer analysis to determine thermal conductivity of thin tissue sample. Porcine aorta arterial tissues were used to investigate tissue thermal conductivity with variable thermal dose. Different joining times were used to create different amounts of thermal dose. A 36% decrease in tissue thermal conductivity was found when the thermal dose reaches the threshold for second-degree burn. When thermal dose is beyond the threshold of third-degree burn, the tissue thermal conductivity does not decrease significantly. A regression model was also developed and can be used to predict tissue thermal conductivity based on the thermal dose.

An experimental study and finite element modeling of head and neck cooling for brain hypothermia.

Reducing brain temperature by head and neck cooling is likely to be the protective treatment for humans when subjects to sudden cardiac arrest. This study develops the experimental validation model and finite element modeling (FEM) to study the head and neck cooling separately, which can induce therapeutic hypothermia focused on the brain. Anatomically accurate geometries based on CT images of the skull and carotid artery are utilized to find the 3D geometry for FEM to analyze the temperature distributions and 3D-printing to build the physical model for experiment. The results show that FEM predicted and experimentally measured temperatures have good agreement, which can be used to predict the temporal and spatial temperature distributions of the tissue and blood during the head and neck cooling process. Effects of boundary condition, perfusion, blood flow rate, and size of cooling area are studied. For head cooling, the cooling penetration depth is greatly depending on the blood perfusion in the brain. In the normal blood flow condition, the neck internal carotid artery temperature is decreased only by about 0.13°C after 60min of hypothermia. In an ischemic (low blood flow rate) condition, such temperature can be decreased by about 1.0°C. In conclusion, decreasing the blood perfusion and metabolic reduction factor could be more beneficial to cool the core zone. The results also suggest that more SBC researches should be explored, such as the optimization of simulation and experimental models, and to perform the experiment on human subjects.

Bone geometry on the contact stress in the shoulder for evaluation of pressure ulcers: finite element modeling and experimental validation.

This research presents the finite element modeling (FEM) of human-specific computed tomography (CT) data to study the effect of bone prominences on contact stress in the shoulder for prevention of pressure ulcers. The 3D geometry of scapula, skin, and surrounding soft tissues in the shoulder was reconstructed based on the anonymous CT data of a human subject in a prone posture (without loading on the shoulder) for FEM analysis of the contact stress. FEM analysis results show that the maximum stress is located at the prominence of the scapula with sharp bone geometry. This demonstrates that stress concentration at the bone prominence is a significant factor to cause the high contact stress, which is a source for pressure ulcers. For experimental validation, a physical shoulder model manufactured by 3D printing of the bone geometry and the mold for molding of tissue-mimicking silicone was developed. Compression tests of the mattress foam and silicone were conducted to find the nonlinear stress-strain relations as inputs for FEM. Experiments of compressing the shoulder model against the foam were carried out. Three flexible force sensors were embedded inside the model to measure the contact forces and compared to the FEM predictions. Results show that the FEM predicted forces match well with the experimental measurements and demonstrate that FEM can accurately predict the stress distributions in the shoulder to study the effect of bone geometry on the inception of pressure ulcers.

Study of insertion force and deformation for suturing with precurved NiTi guidewire.

This research presents an experimental study evaluating stomach suturing using a precurved nickel-titanium (NiTi) guidewire for an endoscopic minimally invasive obesity treatment. Precise path planning is critical for accurate and effective suturing. A position measurement system utilizing a hand-held magnetic sensor was used to measure the shape of a precurved guidewire and to determine the radius of curvature before and after suturing. Ex vivo stomach suturing experiments using four different guidewire tip designs varying the radius of curvature and bevel angles were conducted. The changes in radius of curvature and suturing force during suturing were measured. A model was developed to predict the guidewire radius of curvature based on the measured suturing force. Results show that a small bevel angle and a large radius of curvature reduce the suturing force and the combination of small bevel angle and small radius of curvature can maintain the shape of guidewire for accurate suturing.

Optimal needle design for minimal insertion force and bevel length.

This research presents a methodology for optimal design of the needle geometry to minimize the insertion force and bevel length based on mathematical models of cutting edge inclination and rake angles and the insertion force. In brachytherapy, the needle with lower insertion force typically is easier for guidance and has less deflection. In this study, the needle with lancet point (denoted as lancet needle) is applied to demonstrate the model-based optimization for needle design. Mathematical models to calculate the bevel length and inclination and rake angles for lancet needle are presented. A needle insertion force model is developed to predict the insertion force for lancet needle. The genetic algorithm is utilized to optimize the needle geometry for two cases. One is to minimize the needle insertion force. Using the geometry of a commercial lancet needle as the baseline, the optimized needle has 11% lower insertion force with the same bevel length. The other case is to minimize the bevel length under the same needle insertion force. The optimized design can reduce the bevel length by 46%. Both optimized needle designs were validated experimentally in ex vivo porcine liver needle insertion tests and demonstrated the methodology of the model-based optimal needle design.

Bipolar electrosurgical vessel-sealing device with compressive force monitoring.

Bipolar electrosurgical vessel sealing is commonly used in surgery to perform hemostasis. The electrode compressive force is demonstrably an important factor affecting the vessel seal burst pressure, an index of the seal quality. Using a piezoresistive force sensor attached to the handle of a laparoscopic surgical device, applied handle force was measured and used to predict the electrosurgical vessel compressive force and the pressure at the electrode. The sensor enables the monitoring of vessel compressive force during surgery. Four levels of compressive force were applied to seal three types of porcine vessels (carotid artery, femoral artery, and jugular vein). The burst pressure of the vessel seal was tested to evaluate the seal quality. Compressive pressure was found to be a statistically significant factor affecting burst pressure for femoral arteries and jugular veins. Vessels sealed with low compressive pressure (<300 kPa) have a higher failure rate (burst pressure<100 mm Hg) than vessels sealed with high compressive pressure. An adequate compressive force is required to generate the compressive pressure needed to form a seal with high burst pressure. A laparoscopic surgical device with compressive force monitoring capability can help ensure adequate compressive pressure, vessel burst pressure, and quality of seal.

Thermoelectrical modeling of bipolar coagulation on posterior spinal artery in a porcine spinal surgery model.

The primary objective of our study was to develop a thermoelectrical model with both solid and liquid phases to calculate tissue temperature during bipolar coagulation of a posterior spinal artery on the spinal cord. Control of thermal spread caused by coagulation is a concern in spinal surgery. This model utilizes a nonisothermal flow to account for the heat transfer due to the movement of cerebrospinal fluid that is induced by electrical field and temperature gradient. The model is validated by in situ temperature measurements on a porcine spinal cord model. The maximum error for tissue temperature of this model is 12.6%, and the overall average error is 4.2%. The lesional region (>50°C) is identified to be as wide as 5 mm, and thermal dose cumulative equivalent minutes at 43°C (CEM 43) is also calculated with this model. The incorporation of nonisothermal flow has been shown to be crucial in order to accurately predict thermal dose in tissue. The developed model can be further used to establish a guideline for the use of bipolar coagulation.

Comparison of thermal coagulation profiles for bipolar forceps with different cooling mechanisms in a porcine model of spinal surgery.

BACKGROUND: Coagulation accomplished using bipolar forceps is common in neurosurgery. Control of thermal spread from the forceps tips into surrounding neural tissues is a persistent concern, as neural tissues are especially vulnerable to heat injury. The purpose of our investigation was to compare the efficacy of cooling mechanisms for four different bipolar forceps and to understand thermal spread when coagulating vessels on the spinal cord. METHODS: Immediately following euthanasia, the dura mater of an ex vivo porcine model was opened to expose vessels on the spinal cord for coagulation. Temperature profiles were measured at generator power of 25 W and at fixed 5-second activation times. The bipolar forceps used in this study included regular stainless steel, titanium, heat-pipe embedded, and SILVERGlide forceps. Temperature was measured by micro-thermistor at the midpoint between the bipolar tips, and 1 and 2 mm away from the midpoint along the centerline. Statistical analysis was performed to evaluate temperature differences. RESULTS: Temperature profiles indicated that heat-pipe embedded forceps create the least amount of temperature increase and the highest normalized temperature decreasing slope after activation. The decreasing slope of SILVERGlide forceps is slightly higher than that of regular stainless steel forceps. CONCLUSIONS: Bipolar forceps incorporating either heat-pipe embedded technology or SILVERGlide coating can effectively limit excessive thermal spread, thus decreasing potential injury to adjacent tissues when compared with standard stainless steel and titanium bipolar forceps. Of the two, heat-pipe embedded technology appeared safest, having better cooling efficiency at higher temperature.

Multi-modality gellan gum-based tissue-mimicking phantom with targeted mechanical, electrical, and thermal properties.

This study develops a new class of gellan gum-based tissue-mimicking phantom material and a model to predict and control the elastic modulus, thermal conductivity, and electrical conductivity by adjusting the mass fractions of gellan gum, propylene glycol, and sodium chloride, respectively. One of the advantages of gellan gum is its gelling efficiency allowing highly regulable mechanical properties (elastic modulus, toughness, etc). An experiment was performed on 16 gellan gum-based tissue-mimicking phantoms and a regression model was fit to quantitatively predict three material properties (elastic modulus, thermal conductivity, and electrical conductivity) based on the phantom material's composition. Based on these material properties and the regression model developed, tissue-mimicking phantoms of porcine spinal cord and liver were formulated. These gellan gum tissue-mimicking phantoms have the mechanical, thermal, and electrical properties approximately equivalent to those of the spinal cord and the liver.

Electrosurgical vessel sealing tissue temperature: experimental measurement and finite element modeling.

The temporal and spatial tissue temperature profile in electrosurgical vessel sealing was experimentally measured and modeled using finite element modeling (FEM). Vessel sealing procedures are often performed near the neurovascular bundle and may cause collateral neural thermal damage. Therefore, the heat generated during electrosurgical vessel sealing is of concern among surgeons. Tissue temperature in an in vivo porcine femoral artery sealed using a bipolar electrosurgical device was studied. Three FEM techniques were incorporated to model the tissue evaporation, water loss, and fusion by manipulating the specific heat, electrical conductivity, and electrical contact resistance, respectively. These three techniques enable the FEM to accurately predict the vessel sealing tissue temperature profile. The averaged discrepancy between the experimentally measured temperature and the FEM predicted temperature at three thermistor locations is less than 7%. The maximum error is 23.9%. Effects of the three FEM techniques are also quantified.

The efficacy and safety of the dipeptidyl peptidase-4 inhibitor saxagliptin in treatment-naïve patients with type 2 diabetes mellitus: a randomized controlled trial.

BACKGROUND: The aim of this study was to assess efficacy and safety of saxagliptin monotherapy for up to 76 weeks in patients with type 2 diabetes mellitus (T2DM) and inadequate glycemic control, with main efficacy assessment at 24 weeks. METHODS: 365 treatment-naïve patients with T2DM (HbA1c 7.0%-10.0%) were treated with saxagliptin 2.5 mg q.A.M., saxagliptin 2.5 mg q.A.M. with possible titration to saxagliptin 5 mg, saxagliptin 5 mg q.A.M., saxagliptin 5 mg q.P.M., or placebo. After week 24, patients in all groups were eligible for titration to saxagliptin 10 mg based on HbA1c ≥7%, and all unrescued placebo patients began blinded metformin 500 mg/day. Rescue with open-label metformin was available for patients with inadequate glycemic control. RESULTS: At week 24, placebo-subtracted mean HbA1c reduction from baseline (LOCF) was significantly greater in the saxagliptin treatment groups vs placebo, and remained greater through week 76. Serious adverse events (AEs) and discontinuations due to AEs were similar in saxagliptin and control groups; incidence of confirmed hypoglycemia was low across all treatment groups (saxagliptin-treated, 2 [0.7]; control, 1 [1.4]). CONCLUSIONS: In treatment-naïve patients with T2DM, saxagliptin monotherapy demonstrated statistically significant improvement in HbA1c compared with placebo at 24 weeks and was generally well tolerated for up to 76 weeks. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00316082.

Effect of saxagliptin as add-on therapy in patients with poorly controlled type 2 diabetes on insulin alone or insulin combined with metformin.

OBJECTIVE: To evaluate efficacy and safety of saxagliptin as add-on therapy in patients with type 2 diabetes (T2D) with inadequate glycemic control on insulin alone or combined with metformin. METHODS: Adults (n = 455) with HbA(1c) 7.5-11% on stable insulin therapy (30-150 U/day ± metformin) for at least 8 weeks were stratified by metformin use and randomly assigned 2:1 to receive saxagliptin 5 mg or placebo once daily for 24 weeks. Patients were to maintain stable insulin doses but these could be decreased to reduce risk of hypoglycemia. Patients with hyperglycemia or substantially increased insulin use were rescued with a flexible insulin regimen and remained in the study. Metformin doses were kept stable. The primary efficacy endpoint was change in HbA(1c) from baseline to week 24 (or rescue). RESULTS: Patients treated with saxagliptin versus placebo had significantly greater reductions in adjusted mean HbA(1c) (difference: -0.41%, p < 0.0001), postprandial glucose (PPG) 180-minute area under the curve (-3829.8 mg·min/dL, p = 0.0011), and 120-minute PPG (-23.0 mg/dL, p = 0.0016) at 24 weeks. Treatment with saxagliptin resulted in similar reductions in HBA(1c) relative to placebo, irrespective of metformin treatment. At 24 weeks, difference in adjusted mean fasting plasma glucose for saxagliptin versus placebo was -4.02 mg/dL (p = 0.3958); 17.3% and 6.7% of patients in the saxagliptin and placebo groups, respectively, achieved HbA(1c) < 7%. Mean change from baseline in body weight at week 24 was 0.39 kg for saxagliptin and 0.18 kg for placebo. Hypoglycemia was reported in 18.4% and 19.9% of patients in the saxagliptin and placebo groups, respectively (confirmed hypoglycemia: 5.3%, 3.3%). Other adverse events reported in at least 5% of patients were urinary tract infection (saxagliptin, placebo: 5.9%, 6.0%), influenza (3.0%, 6.6%), and pain in extremity (1.6%, 6.0%). CONCLUSIONS: Saxagliptin 5-mg once-daily add-on therapy improves glycemic control in T2D patients on insulin alone or combined with metformin and is generally well-tolerated. NCT00757588.

The design and rationale of the saxagliptin assessment of vascular outcomes recorded in patients with diabetes mellitus-thrombolysis in myocardial infarction (SAVOR-TIMI) 53 study.

OBJECTIVES: Saxagliptin, a dipeptidyl peptidase 4 inhibitor, improves glycemic control in patients with type 2 diabetes mellitus (T2DM) by increasing endogenous active, intact glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide in response to food, which augments insulin secretion and decreases glucagon release. RESEARCH DESIGN AND METHODS: SAVOR-TIMI 53 is a phase 4, randomized, double-blind, placebo-controlled trial conducted in 25 countries that is designed to evaluate the safety and efficacy of saxagliptin during long-term treatment of approximately 16,500 patients with T2DM. Eligible patients who are either treatment naive or on any background antidiabetic treatment (except incretin therapy) with history of established cardiovascular (CV) disease or multiple risk factors are randomized 1:1 to saxagliptin 5 mg QD (2.5 mg in subjects with moderate/severe renal impairment) or matching placebo, stratified by qualifying disease state. The primary end point is the composite of CV death, nonfatal myocardial infarction, or nonfatal ischemic stroke. The trial will continue until approximately 1,040 primary end points accrue, providing 85% power to identify a 17% relative reduction of the primary end point with saxagliptin versus placebo and 98% power to test for noninferiority of saxagliptin versus placebo (reject the upper limit of 95% CI for a hazard ratio <1.3 at a 1-sided α of .025). CONCLUSION: SAVOR-TIMI 53 is testing the hypothesis that treatment with saxagliptin is safe and reduces CV events in high-risk patients with T2DM.

Efficacy and safety of saxagliptin combination therapy in US patients with type 2 diabetes.

BACKGROUND: The mechanism of action of dipeptidyl peptidase-4 inhibitors, such as saxagliptin, makes them suitable for combination therapy in type 2 diabetes mellitus (T2DM). Genetic, cultural, and environmental differences in individuals from different regions of the world may result in differences in treatment response to oral antidiabetic drugs (OADs). This post-hoc subanalysis assessed the efficacy and safety of saxagliptin as add-on therapy to metformin, glyburide, or a thiazolidinedione in patients with inadequately controlled T2DM in the United States. METHODS: In 3 phase 3 studies of patients with T2DM uncontrolled on monotherapy, 547 adult US patients were randomized to receive saxagliptin (2.5 or 5 mg/d) or placebo as add-on to metformin, glyburide, or a thiazolidinedione (pioglitazone or rosiglitazone). Efficacy was assessed as the change from baseline to week 24 in glycated hemoglobin (HbA1c), fasting plasma glucose (FPG), and postprandial glucose area under the curve (PPG-AUC) and the proportion of patients achieving HbA1c<7.0%. Pooled safety and tolerability data across trials were also analyzed. RESULTS: Reductions from baseline to week 24 in HbA1c were observed in all saxagliptin treatment groups versus placebo: saxagliptin 2.5 or 5 mg plus metformin (mean difference from placebo, -0.87% and -0.89%, respectively), glyburide (-0.51% and -0.52%), or thiazolidinedione (-0.45% and -0.60%). Improvement was also observed in FPG and PPG-AUC. Adverse events for the US cohort were consistent with previously reported data from the 3 trials. The pooled incidence of reported hypoglycemia was 5.3% and 11.4% with saxagliptin 2.5 and 5 mg/d add-on, respectively, versus 6.8% with placebo add-on. CONCLUSIONS: This post-hoc analysis in a cohort of US patients with T2DM uncontrolled on monotherapy suggests that saxagliptin 2.5 or 5 mg as add-on therapy to OADs results in improvement across key glycemic parameters compared with placebo add-on and was generally safe and well tolerated.