Assessing Squarates as Amine-Reactive Probes.

Probes that covalently label protein targets facilitate the identification of ligand-binding sites. Lysine residues are prevalent in the proteome, making them attractive substrates for covalent probes. However, identifying electrophiles that undergo amine-specific, regioselective reactions with binding site lysine residues is challenging. Squarates can engage in two sequential conjugate addition-elimination reactions with amines. Nitrogen donation reduces the second reaction rate, making the mono squaramide a mild electrophile. We postulated that this mild electrophilicity would demand a longer residence time near the amine, affording higher selectivity for binding site lysines. Therefore, we compared the kinetics of squarate and monosquaramide amine substitution to alternative amine bioconjugation handles. The data revealed that N-hydroxy succinimidyl esters react 4 orders of magnitude faster, consistent with their labeling promiscuity. Squarate reactivity can be tuned by a substitution pattern. Electron-withdrawing groups on the vinylogous ester or amide increase reaction rates. Dithionosquarates react more rapidly than squarates, while vinylogous thioester analogs, dithiosquarates, react more slowly. We assessed squarate selectively using the UDP-sugar processing enzyme GlfT2 from Mycobacterium tuberculosis, which possesses 21 surface-exposed lysines. The reaction predominately modified one lysine proximal to a binding site to afford covalent inhibition. These findings demonstrate the selectivity of squaric esters and squaramides, which is a critical feature for affinity-based chemoproteomic probes.

Insulin Concentration in Vials Randomly Purchased in Pharmacies in the United States: Considerable Loss in the Cold Supply Chain.

The insulin content in vials/cartridges should be 95 U/ml upon release. No independent confirmation of insulin concentration is available when purchased in the pharmacy (end of the cold supply chain). We quantitatively measured intact insulin in randomly acquired multidose human insulin vials by standard analytical methods. Eighteen 10 ml vials from two manufacturers (M1 and M2) were randomly acquired. The intact insulin concentration ranged from 13.9 to 94.2 U/ml, mean 40.2 U/ml. No vial met the minimum standard of 95 U/ml. These results imply the cold supply chain impacts insulin concentrations to a larger extent than anticipated. Patients are paying high prices for insulin and should expect to receive insulin vials with adequate insulin content in return.

If PBMs Guard Access to Drugs, Then Quis Custodiet Ipsos Custodies? (Who Will Guard the Guardians?).

Insulin prices in the United States have risen dramatically in recent years, yet pharmacies cannot provide a stable price for a given insulin due to factors that are not widely understood. This commentary discusses the complex and obscure factors that drive today's insulin prices with a discussion of the other players, besides the insulin manufacturer, who benefit from higher prices. An open discussion is critical regarding this drug and others that are essential to the lives of millions of people with diabetes. We'll also explore whether the market introduction of biosimilar insulin will impact insulin prices.

In the Biosimilar Marketplace Will There Be 50 Ways to Leave Your Insulin?

The future biosimilar insulin marketplace could be a bane, benefit, or something in between, to patients under our care in the United States. Formulary preferred product status, with or without FDA interchangeability designation, coupled with current and proposed state pharmacy substitution laws may lead to an environment with as many as 50 different substitution guidelines depending on in which state a patient presents his or her prescription to be filled. If online global prescription supply options, often referred to as "Canada Drug," are utilized, other country substitution guidelines come into play, which may yield a recipe for confusion, if not disaster.

FDA-approved biosimilar insulin: good enough for critical care, adulterated, or counterfeit? How can we tell?

If a biosimilar insulin is discovered postmarketing to be subpotent, superpotent, or contaminated or the contents mislabeled, it is an adulterated product and must be quarantined for removal including from a patient's home. Adulterated products could be considered "counterfeit" since they do not meet the original standards established by the FDA. The FDA must establish a method of regularly assaying samples of biosimilar insulin drawn directly from the supply pipeline to help ensure patient safety and evaluate clinical performance. Independent groups without conflict of interest would perform confidential comparison assay. For less than 5 cents per vial/pen, manufacturers could easily support an independent, FDA-recognized, random sample program and create a functional postmarket surveillance system that better protects the public and the manufacturer from undesired outcomes.

Analysis of the injection force of solostar® compared with other disposable insulin pen devices at constant volume flow rates.

Insulin pen devices have greatly enhanced the portability and accessibility to insulin therapy for millions of people with diabetes. Comparison research data should be reviewed thoroughly. In this issue of Journal of Diabetes Science and Technology, the study presented by Thomas van der Burg is balanced in number of samples tested, same tensile meter, and identical units per second delivery rate into an open beaker. Mean plateau force of SoloSTAR® and KwikPen™ were significantly lower. KwikPen and SoloSTAR utilized 5-mm length 31-gauge (G) needles vs 6-mm 31G needles for FlexPen® and Next Generation FlexPen®, perhaps skewing results in favor of shorter needles instead of device design. Individual understanding of correct insulin use, appropriate self-monitoring of blood glucose, vision and dexterity capability, and affordability of therapy must be considered first. SoloSTAR holds one unique market advantage, delivery of up to 80 units of insulin per injection.

An analysis of the assessment of glycated hemoglobin using A1cNow+ point-of-care device compared to central laboratory testing--an important addition to pharmacist-managed diabetes programs?

The diabetes epidemic is accelerating rapidly. If no progress is made in early detection, then early intervention and treatment-to-goal diabetes care will become an overwhelming burden on our health care system. Better utilization of self-monitoring of blood glucose in patients with type 2 diabetes not on insulin could be achieved with regular review of hemoglobin A1c (A1C) values. Educating patients about the importance of diet, exercise, and medication compliance is enhanced when evidence of average blood glucose control can be presented to the patient directly. Affordable, accurate point-of-care testing of A1C with A1cNow+ (Bayer HealthCare, Terrytown, NY) utilized in pharmacist-managed outpatient diabetes programs may prove to be an important clinical tool for improving patient outcomes and reducing the cost of the expanding diabetes epidemic.

A prospective, randomized, multicentered controlled trial to compare the annual glycemic and quality outcomes of patients with diabetes mellitus monitored with weekly fructosamine testing versus usual care.

Fructosamine is an indicator of overall glycemic control for a 10-14-day time frame, medium-term marker, versus the 90-day average indicated by the hemoglobin A1c (A1C) test. The utility of the home fructosamine test for management of persons with diabetes remains undefined. The primary objectives of this study were (1) to compare the annual A1C results of subjects monitoring weekly fructosamine with those receiving usual care, (2) to identify the number of subjects achieving goal A1C, and (3) to determine if the addition of a weekly fructosamine test changed a subject's quality of life. This was a prospective, randomized, multicenter, controlled trial. Subjects were recruited from three sites and randomly assigned to collect weekly fructosamine in addition to daily glucose (Group 1) or to receive usual care of daily glucose collection (Group 2). Follow-up occurred at 3-month intervals for a year. Baseline and quarterly A1C tests were collected. Quality of life assessment was conducted at baseline and at the final study visit. Seventy-two subjects were randomized. Demographic and whole blood assessments were similar between the two groups at baseline. The mean percent change of A1C from baseline to final study visit in Group 1 (-0.52 +/- 1.5) was not statistically different than Group 2 (-0.86 +/- 1.4) (P = 0.320). Seven subjects in each group achieved A1C of less than 7% (P = 0.532). No change in quality of life between or within the two groups was observed (P > 0.05) for each area of concern. Blood glucose monitoring alone was shown to be superior to the additional fructosamine testing after 1 year of treatment; however, weekly fructosamine testing demonstrated a decrease in A1C earlier and more consistently throughout the study. Despite glycemic improvement, the number of subjects attaining American Diabetes Association-defined A1C goals was not different between the treatment groups. Quality of life did not change with the addition of a weekly fructosamine test.

A prospective, randomized, multicentered controlled trial to compare the annual outcomes of patients with diabetes mellitus monitored with weekly fructosamine testing versus usual care: a 3-month interim analysis.

The recent introduction of a home monitoring system that measures whole blood glucose and whole blood fructosamine values by fingerstick blood drop adds a previously unavailable estimate of overall glycemic control via the fructosamine component. Fructosamine serves as an indicator of overall glycemic control for a 10-14-day time frame versus the 90-day average indicated by the hemoglobin A1c (A1C) test. The utilization of the fructosamine test for management of patients with diabetes mellitus remains unclear. The primary objectives of this study are to compare the quarterly A1C results of subjects monitoring weekly fructosamine with those receiving usual care, to identify the number of patients achieving goal A1C, and to determine if the addition of a weekly fructosamine test changes a patient's quality of life. Secondary objectives include determining if specific patient demographics predict success or difficulty in achieving improved A1C. This is a prospective, randomized, multicenter controlled trial. Patients were randomly assigned to collect weekly fructosamine in addition to daily glucose (Group 1) or usual care of daily glucose (Group 2) and had study visits every 3 months. Baseline and quarterly A1C tests were collected. Quality of life assessment was conducted at baseline and will be evaluated at the final study visit. Sixty subjects have been randomized into the study since May 2001 with enrollment ongoing. Baseline demographics, glucose, fructosamine, and A1C were similar between the two groups. The 3-month interim analysis demonstrated no statistically significant difference in fructosamine (p = 0.265) between Group 1 (293.00 +/- 111.22 micromol/L) and Group 2 (336.69 +/- 111.12 micromol/L), respectively. No statistical difference at 3 months (p = 0.676) in A1C values for Group 1 (7.921 +/- 1.848% vs. 7.755 +/- 1.408%) and Group 2 (7.800 +/- 1.505% vs. 7.971 +/- 1.797%) were noted when compared with baseline. The interim data suggest that the fructosamine group has had a net decrease in A1C over the 3-month time frame, whereas the control group has had a net increase in A1C values. Ongoing follow-up will determine if this trend continues and becomes statistically and clinically significant.