Physical Compatibility of Y-site Pediatric Drug Administration: A Call for Question of US Pharmacopeia Standards.

OBJECTIVE: To evaluate the physical intravenous Y-site compatibility of 29 combinations of medications at commonly used pediatric concentrations using both existing and novel techniques. METHODS: Medication combinations included were selected by a varied group of pediatric inpatient pharmacists, and then assessed by 3 independent reviewers for existing literature. For each combination, 2 different medications were mixed together in a 1:1 ratio and incubated at room temperature for 4 hours to simulate Y-site administration. Each sample was then analyzed using the US Pharmacopeia (USP) <788> recommended analytical technique of light obscuration (LO) in addition to novel flow imaging (FI) microscopy and backgrounded membrane imaging (BMI). Physical compatibility was determined using USP chapter <788> large volume particle count limits for all techniques. RESULTS: A total of 29 different medication combinations were studied. Five combinations met criteria for compatibility by all 3 techniques. The remaining 24 combinations reached the threshold to be considered incompatible by at least 1 of the 3 techniques. Light obscuration, BMI, and FI identified 14%, 59%, and 76% of combinations as incompatible, respectively. All samples deemed incompatible by LO were also incompatible by at least 1 of the other 2 techniques. Flow imaging and BMI results agreed in 69% of samples tested. CONCLUSIONS: Most combinations tested were found to be incompatible by at least 1 of the 3 instruments used. Light obscuration appears to have reduced accuracy for identifying particulate resulting in physical medication incompatibility when compared with the novel techniques of FI and BMI.

Physical compatibility of medications with concentrated neonatal and pediatric parenteral nutrition: A simulated Y-site drug compatibility study.

BACKGROUND: The physical intravenous Y-site compatibility of 15 different medications with highly concentrated neonatal and pediatric parenteral nutrition (PN) compounds is described, using existing and novel methods. METHODS: PN formulations were developed based on common prescribing practices in a 400+-bed freestanding children's hospital. Medications at commonly used pediatric concentrations were mixed in a 1:1 ratio with both pediatric and neonatal PN formulations and incubated at room temperature for 4 h to simulate Y-site administration. Samples were then analyzed using the light obscuration (LO) technique, as recommended by United States Pharmacopeia (USP) chapter 788, in addition to novel flow imaging (FI) microscopy and backgrounded membrane imaging (BMI). Physical compatibility was determined using USP 788 particle count limits for all techniques. RESULTS: Most combinations were found to be compatible per USP 788 thresholds. Pediatric PN was incompatible by at least two methods with cisatracurium 2 mg/ml, sildenafil 0.8 mg/ml, furosemide 10 mg/ml, and ketamine 10 mg/ml. Neonatal PN was incompatible by at least two methods with cisatracurium 2 mg/ml and furosemide 10 mg/ml. Overall, results for 20 of the 30 combinations (66%) agreed across all three methods. FI and BMI results agreed for 22 of 30 combinations. LO agreed with FI in 25 of 30 combinations, and BMI and LO results agreed in 23 of 30 combinations. CONCLUSION: Most combinations tested were found to be compatible across all methods. Novel methods of FI and BMI seem useful to further evaluate LO findings and improve accuracy of particle counts when assessing PN-medication combinations.

Detection of innate immune response modulating impurities (IIRMI) in therapeutic peptides and proteins: Impact of excipients.

Unintended immunogenicity can affect the safety and efficacy of therapeutic proteins and peptides, so accurate assessments of immunogenicity risk can aid in the selection, development, and regulation of biologics. Product- and process- related impurities can act as adjuvants that activate the local or systemic innate immune response increasing the likelihood of product immunogenicity. Thus, assessing whether products have innate immune response modulating impurities (IIRMI) is a key component of immunogenicity risk assessments. Identifying trace levels of individual IIRMI can be difficult and testing individually for all potential impurities is not feasible. Therefore, to mitigate the risk, cell-based assays that use human blood cells or monocyte-macrophage reporter cell lines are being developed to detect minute quantities of impurities capable of eliciting innate immune activation. As these are cell-based assays, there is concern that excipients could blunt the cell responses, masking the presence of immunogenic IIRMI. Here, we explore the impact of frequently used excipients (non-ionic detergents, sugars, amino acids, bulking agents) on the sensitivity of reporter cell lines (THP-1- and RAW-Blue cells) and fresh human blood cells to detect purified TLR agonists as model IIRMI. We show that while excipients do not modulate the innate immune response elicited by TLR agonists in vivo, they can impact on the sensitivity of cell-based IIRMI assays. Reduced sensitivity to detect LPS, FSL-1, and other model IIRMI was also evident when testing 3 different recombinant drug products, product A (a representative mAb), B (a representative growth factor), C (a representative peptide), and their corresponding formulations. These results indicate that product formulations need to be considered when developing and validating cell-based assays for assessing clinically relevant levels of IIRMI in therapeutic proteins. Optimization of reporter cells, culture conditions and drug product concentration appear to be critical to minimize the impact of excipients and attain sensitive and reproducible assays.

Compatibility of medications with intravenous lipid emulsions: Effects of simulated Y-site mixing.

PURPOSE: To determine the physical intravenous Y-site compatibility of 19 commonly used medications at pediatric concentrations with 3 different types of lipid emulsion. METHODS: Medications at commonly used pediatric concentrations were mixed in a 1:1 ratio with lipid emulsions (Intralipid, Nutrilipid, and Smoflipid) and incubated at room temperature for 4 hours to simulate Y-site administration. Each sample was then diluted with particle-free water and analyzed using the analytical technique of light obscuration recommended in United States Pharmacopeia (USP) general information chapter 729 (USP <729>). Physical compatibility was determined by measuring the percentage of fat residing in globules larger than 5 µm (PFAT5) per USP <729> recommendations. RESULTS: Most combinations tested were physically compatible based on USP <729> regulations. Incompatibilities differed for the different brands of lipid emulsion. The two combinations that met USP <729> criteria for physical incompatibility were cisatracurium 2 mg/mL with Intralipid and gentamicin 2 mg/mL with Smoflipid. CONCLUSION: Three different lipid emulsions were physically compatible at the Y site with the majority of medications tested. Data regarding Y-site compatibility for one lipid emulsion product cannot be safely extrapolated to another without additional testing.

Effects of Tubing Type, Operating Parameters, and Surfactants on Particle Formation During Peristaltic Filling Pump Processing of a mAb Formulation.

Filling pump operation is an important cause of particle formation in therapeutic protein formulations. The goals of the present study were to investigate the impacts of peristaltic filling pump tubing type, pump operating parameters (acceleration and velocity), and formulation on both nanoparticle and microparticle formation in water, placebo, and a 120 mg/mL mAb drug formulation. Microparticles were quantified using flow imaging microscopy and light obscuration, and nanoparticles were counted with nanoparticle tracking analysis. Pumping of all solutions through Pharmed® tubing resulted in much higher particle levels than processing with Accusil™ or Masterflex® tubing. Pump acceleration did not measurably affect particle levels in pumped solutions, but in some cases, a relatively high pumping velocity of 400 rpm enhanced nanoparticle formation. The presence of surfactants reduced pumping-induced particle formation in the mAb solution, and the effects of 4 different surfactants tested were similar. Biophysical properties (secondary and tertiary structure, and thermal stability) of the protein in solution were not altered by pumping. Overall, this study demonstrates that investigations of pumping parameters and formulations using both nanoparticle and microparticle measurement methods are important for understanding pumping-induced particle formation and developing effective control strategies.

Effects of Tubing Type, Formulation, and Postpumping Agitation on Nanoparticle and Microparticle Formation in Intravenous Immunoglobulin Solutions Processed With a Peristaltic Filling Pump.

The main goal of this study was to use state-of-the-art instruments for nanoparticle (nanoparticle tracking analysis and resonant mass measurement) and microparticle counting (flow imaging) to assess the effects of peristaltic filling pump operation on particle formation in formulations of intravenous immunoglobulin. Microparticle levels were also measured with light obscuration. Postpumping agitation was studied as an accelerated degradation method, 3 different commercial peristaltic tubing types were tested, and the effects of formulation pH and inclusion of polysorbate 80 were determined. Overall, the results documented that nanoparticle measurements, as well as microparticle determinations with flow imaging, were essential to gain rigorous insights into impacts of processing and formulation parameters on pumping- and agitation-induced particle formation. In addition, light obscuration was a relatively insensitive method and failed to detect large increases in protein particles caused by pumping and postpumping agitation. Formulation studies showed that the presence of polysorbate 80 or increasing protein colloidal stability with appropriate choice of buffer generally reduced particle formation. The results highlight the need for filling pump assessments in formulation development studies. Combining such assessments with appropriate analytical methods should help assure that particle levels are controlled during filling pump operation and that the highest quality products are manufactured.

DEHP Nanodroplets Leached From Polyvinyl Chloride IV Bags Promote Aggregation of IVIG and Activate Complement in Human Serum.

Concerns regarding the impact of subvisible particulate impurities on the safety and efficacy of therapeutic protein products have led manufacturers to implement strategies to minimize protein aggregation and particle formation during manufacturing, storage, and shipping. However, once these products are released, manufacturers have limited control over product handling. In this work, we investigated the effect of di(2-ethylhexyl) phthalate (DEHP) nanodroplets generated in polyvinyl chloride (PVC) bags of intravenous (IV) saline on the stability and immunogenicity of IV immunoglobulin (IVIG) formulations. We showed that PVC IV bags containing saline can release DEHP droplets into the solution when agitated or transported using a pneumatic tube transportation system in a clinical setting. We next investigated the effects of emulsified DEHP nanodroplets on IVIG stability and immunogenicity. IVIG adsorbed strongly to DEHP nanodroplets, forming a monolayer. In addition, DEHP nanodroplets accelerated IVIG aggregation in agitated samples. The immunogenicity of DEHP nanodroplets and IVIG aggregates generated in these formulations were evaluated using an in vitro assay of complement activation in human serum. The results suggested DEHP nanodroplets shed from PVC IV bags could reduce protein stability and induce activation of the complement system, potentially contributing to adverse immune responses during the administration of therapeutic proteins.

Structural dynamics of calmodulin-ryanodine receptor interactions: electron paramagnetic resonance using stereospecific spin labels.

We have used electron paramagnetic resonance, with rigid and stereospecific spin labels, to resolve structural states in calmodulin (CaM), as affected by binding of Ca and a CaM-binding peptide (RyRp) derived from the ryanodine receptor (RyR), the Ca channel that triggers muscle contraction. CaM mutants containing a pair of cysteines in the N-lobe and/or C-lobe were engineered and labeled with a stereospecifically bound bifunctional spin label (BSL). RyRp was synthesized with and without TOAC (a stereospecifically attached spin-labeled amino acid) substituted for a single amino acid near the N-terminus. Intramolecular DEER distance measurements of doubly-labeled BSL-CaM revealed that CaM exists in dynamic equilibrium among multiple states, consistent with open, closed, and compact structural models. Addition of RyRp shifted the equilibrium partially toward the compact state in the absence of Ca, and completely toward the compact state in the presence of Ca, supporting a conformational selection model. Inter-protein distance measurements show that Ca stabilizes the compact state primarily by inducing ordered binding of the CaM N-lobe to RyRp, while only slightly affecting the C-lobe. The results provide insight into the structural mechanism of CaM-mediated RyR regulation, while demonstrating the power of using two types of rigidly and stereospecifically bound spin labels.

Calcium-Dependent Structural Dynamics of a Spin-Labeled RyR Peptide Bound to Calmodulin.

We have used chemical synthesis, electron paramagnetic resonance (EPR), and circular dichroism to detect and analyze the structural dynamics of a ryanodine receptor (RyR) peptide bound to calmodulin (CaM). The skeletal muscle calcium release channel RyR1 is activated by Ca2+-free CaM and inhibited by Ca2+-bound CaM. To probe the structural mechanism for this regulation, wild-type RyRp and four spin-labeled derivatives were synthesized, each containing the nitroxide probe 2,2,6,6-tetramethyl-piperidine-1-oxyl-4-amino-4-carboxylic acid substituted for a single amino acid. In 2,2,6,6-tetramethyl-piperidine-1-oxyl-4-amino-4-carboxylic acid, the probe is rigidly and stereospecifically coupled to the α-carbon, enabling direct detection by EPR of peptide backbone structural dynamics. In the absence of CaM, circular dichroism indicates a complete lack of secondary structure, while 40% trifluoroethanol (TFE) induces >90% helicity and is unperturbed by the spin label. The EPR spectrum of each spin-labeled peptide indicates nanosecond dynamic disorder that is substantially reduced by TFE, but a significant gradient in dynamics is observed, decreasing from N- to C-terminus, both in the presence and absence of TFE. When bound to CaM, the probe nearest RyRp's N-terminus shows rapid rotational motion consistent with peptide backbone dynamics of a locally unfolded peptide, while the other three sites show substantial restriction of dynamics, consistent with helical folding. The two N-terminal sites, which bind to the C-lobe of CaM, do not show a significant Ca2+-dependence in mobility, while both C-terminal sites, which bind to the N-lobe of CaM, are significantly less mobile in the presence of bound Ca2+. These results support a model in which the interaction of RyR with CaM is nonuniform along the peptide, and the primary effect of Ca2+ is to increase the interaction of the C-terminal portion of the peptide with the N-terminal lobe of CaM. These results provide, to our knowledge, new insight into the Ca2+-dependent regulation of RyR by CaM.

The Charge Properties of Phospholipid Nanodiscs.

Phospholipids (PLs) are a major, diverse constituent of cell membranes. PL diversity arises from the nature of the fatty acid chains, as well as the headgroup structure. The headgroup charge is thought to contribute to both the strength and specificity of protein-membrane interactions. Because it has been difficult to measure membrane charge, ascertaining the role charge plays in these interactions has been challenging. Presented here are charge measurements on lipid Nanodiscs at 20°C in 100 mM NaCl, 50 mM Tris, at pH 7.4. Values are also reported for measurements made in the presence of Ca(2+) and Mg(2+) as a function of NaCl concentration, pH, and temperature, and in solvents containing other types of cations and anions. Measurements were made for neutral (phosphatidylcholine and phosphatidylethanolamine) and anionic (phosphatidylserine, phosphatidic acid, cardiolipin, and phosphatidylinositol 4,5-bisphosphate (PIP2)) PLs containing palmitoyl-oleoyl and dimyristoyl fatty acid chains. In addition, charge measurements were made on Nanodiscs containing an Escherichia coli lipid extract. The data collected reveal that 1) POPE is anionic and not neutral at pH 7.4; 2) high-anionic-content Nanodiscs exhibit polyelectrolyte behavior; 3) 3 mM Ca(2+) neutralizes a constant fraction of the charge, but not a constant amount of charge, for POPS and POPC Nanodiscs; 4) in contrast to some previous work, POPC only interacts weakly with Ca(2+); 5) divalent cations interact with lipids in a lipid- and ion-specific manner for POPA and PIP2 lipids; and 6) the monovalent anion type has little influence on the lipid charge. These results should help eliminate inconsistencies among data obtained using different techniques, membrane systems, and experimental conditions, and they provide foundational data for developing an accurate view of membranes and membrane-protein interactions.

Oxidation increases the strength of the methionine-aromatic interaction.

Oxidation of methionine disrupts the structure and function of a range of proteins, but little is understood about the chemistry that underlies these perturbations. Using quantum mechanical calculations, we found that oxidation increased the strength of the methionine-aromatic interaction motif, a driving force for protein folding and protein-protein interaction, by 0.5-1.4 kcal/mol. We found that non-hydrogen-bonded interactions between dimethyl sulfoxide (a methionine analog) and aromatic groups were enriched in both the Protein Data Bank and Cambridge Structural Database. Thermal denaturation and NMR spectroscopy experiments on model peptides demonstrated that oxidation of methionine stabilized the interaction by 0.5-0.6 kcal/mol. We confirmed the biological relevance of these findings through a combination of cell biology, electron paramagnetic resonance spectroscopy and molecular dynamics simulations on (i) calmodulin structure and dynamics, and (ii) lymphotoxin-α binding toTNFR1. Thus, the methionine-aromatic motif was a determinant of protein structural and functional sensitivity to oxidative stress.

Comparison of the intrinsic dynamics of aminoacyl-tRNA synthetases.

Aminoacyl-tRNA synthetases (AARSs) are an important family of enzymes that catalyze tRNA aminoacylation reaction (Ibba and Soll in Annu Rev Biochem 2000, 69:617-650) [1]. AARSs are grouped into two broad classes (class I and II) based on sequence/structural homology and mode of their interactions with the tRNA molecule (Ibba and Soll in Annu Rev Biochem 2000, 69:617-650) [1]. As protein dynamics play an important role in enzyme function, we explored the intrinsic dynamics of these enzymes using normal mode analysis and investigated if the two classes and six subclasses (Ia-c and IIa-c) of AARSs exhibit any distinct patterns of motion. The present study found that the intrinsic dynamics-based classification of these enzymes is similar to that obtained based on sequence/structural homology for most enzymes. However, the classification of seryl-tRNA synthetase was not straightforward; the internal mobility patterns of this enzyme are comparable to both IIa and IIb AARSs. This study revealed only a few general mobility patterns in these enzymes--(1) the insertion domain is generally engaged in anticorrelated motion with respect to the catalytic domain for both classes of AARSs and (2) anticodon binding domain dynamics are partly correlated and partly anticorrelated with respect to other domains for class I enzymes. In most of the class II AARSs, the anticodon binding domain is predominately engaged in anticorrelated motion with respect to the catalytic domain and correlated to the insertion domain. This study supports the notion that dynamic-based classification could be useful for functional classification of proteins.

Monovalent IgG4 molecules: immunoglobulin Fc mutations that result in a monomeric structure.

Antibodies have become the fastest growing class of biological therapeutics, in part due to their exquisite specificity and ability to modulate protein-protein interactions with a high biological potency. The relatively large size and bivalency of antibodies, however, limits their use as therapeutics in certain circumstances. Antibody fragments, such as single-chain variable fragments and antigen binding-fragments, have emerged as viable alternatives, but without further modifications these monovalent formats have reduced terminal serum half-lives because of their small size and lack of an Fc domain, which is required for FcRn-mediated recycling. Using rational engineering of the IgG4 Fc domain to disrupt key interactions at the CH3-CH3 interface, we identified a number of point mutations that abolish Fc dimerization and created half-antibodies, a novel monovalent antibody format that retains a monomeric Fc domain. Introduction of these mutations into an IgG1 framework also led to the creation of half-antibodies. These half-antibodies were shown to be soluble, thermodynamically stable and monomeric, characteristics that are favorable for use as therapeutic proteins. Despite significantly reduced FcRn binding in vitro, which suggests that avidity gains in a dimeric Fc are critical to optimal FcRn binding, this format demonstrated an increased terminal serum half-life compared with that expected for most alternative antibody fragments.

Significance of Proline Residue on Short Mucin Peptide Interactions with Mouse MUC1 Monoclonal Antibody Studied by Saturation Transfer Difference NMR Spectroscopy.

In this study we investigated to see whether or not a shortened MUC1 mucin peptide epitope with the sequence GVTSAPD containing a single prolyl residue would still bind specific monoclonal antibody as its native sequence (e.g., PDTRP), known to be the specific recognition site on the Variable Number Tandem Repeat (VNTR) region of MUC1 mucin by the immune system. The affinity of GVTSAPD peptide to a mouse Muc1 mucin specific monoclonal antibody (clone 6A4, IgG1 isotype) was investigated by Saturation Transfer Difference NMR spectroscopy (STD NMR). Results showed that the shortened mucin epitope GVTSAPD still retained affinity to Muc1 specific monoclonal antibody (mAb) while one that lacks the prolyl residue at position 6 lost its affinity, which suggests that P6 is necessay for antibody binding. The interactions observed by STD NMR occurred strongest at the P6 side chain 1H's (ßH and γH); the P6Hα showed lower degree of saturation transfer effect. Minor interactions also occurred at the methyl groups of V2' T3 and A5. Mucin peptides derived from the VNTR region have been the target of cancer vaccine research, thus properties associated with mucin peptide structure, conformation and antibody interaction are central to peptide design or engineering towards that end.

"We are out of balance here": a Hmong cultural model of diabetes.

A Hmong cultural model of type 2 diabetes has not been described. We analyzed 20 group discussions during 21 group visits over 1 year with 39 Hmong adults with type 2 diabetes in order to describe a model that underlines their discussions. These Hmong adults attribute their diabetes to their refugee experience. They do not fit with the food, activity, weather, or community in the United States. Consuming sugar, salt, fat, and chemicals and then not sweating them out of the body, combined with emotional losses of being refugees, the participants feel they are out of balance. And being out of balance, they develop diabetes. The participants interpret biomedical information, community experiences, and personal sensations of diabetes in terms of a traditional health model of balance and in the context of refugee loss of place. Throughout their discussions, the shared suffering of their personal experiences of diabetes was evident. This cultural model may help providers implement diabetes treatment and prevention programs.

Risk prevalence for type 2 diabetes mellitus in adult Hmong in Wisconsin: a pilot study.

OBJECTIVE: To quantify the proportion that may be at risk for developing type 2 diabetes among a convenience sample of Hmong adults in Wisconsin using the 2000 American Diabetes Association (ADA) Clinical Practice Recommendations for community screening. METHODS: Design was a cross sectional survey. One hundred forty-four participants completed the survey, which consisted of a demographic questionnaire and the ADA Risk Test. Casual capillary whole blood glucose values, blood pressure, height, weight, and waist and hip circumference measures were also recorded. Predictors of positive casual capillary whole blood glucose value (> 140 mg/dl) were identified using logistic regression. RESULTS: Forty-one percent demonstrated positive blood glucose screens on survey. Waist-to-hip ratio was a stronger predictor of a positive screen (Odds Ratio = 3.2 [95% CI: (1.5, 6.2)]) than the ADA Risk Test (Odds Ratio = 2.7 [95% CI: (1.4, 5.1)]). CONCLUSIONS: Hmong adults in Wisconsin demonstrate an increased risk for type 2 diabetes. Present findings are consistent with studies demonstrating increased disease risk in newly arrived populations of industrialized countries.

Culturally responsive care for Hmong patients. Collaboration is a key treatment component.

Since the end of the Vietnam War, tens of thousands of Hmong refugees have resettled in the United States. This ever-increasing population presents specific challenges to the US healthcare system as Hmong seek to preserve their cultural identity while acclimating to American society. Primary care physicians can enhance their interactions with these patients by seeking to understand various elements of Hmong culture, particularly its approach to medicine and healing. By extension, such knowledge and skills will aid physicians in all encounters with patients who belong to minority cultural groups.