Diane E. Sutter

Improved genetic immunization via micromechanical disruption of skin-barrier function and targeted epidermal delivery

Skin is an attractive target for delivery of genetic therapies and vaccines. However, new approaches are needed to access this tissue more effectively. Here, we describe a new delivery technology based on arrays of structurally precise, micron-scale silicon projections, which we term microenhancer arrays (MEAs). In a human clinical study, these devices effectively breached the skin barrier, allowing direct access to the epidermis with minimal associated discomfort and skin irritation. In a mouse model, MEA-based delivery enabled topical gene transfer resulting in reporter gene activity up to 2,800-fold above topical controls. MEA-based delivery enabled topical immunization with naked plasmid DNA, inducing stronger and less variable immune responses than via needle-based injections, and reduced the number of immunizations required for full seroconversion. Together, the results provide the first in vivo use of microfabricated devices to breach the skin barrier and deliver vaccines topically, suggesting significant clinical and practical advantages over existing technologies.

Microneedle-Based Intradermal Delivery Enables Rapid Lymphatic Uptake and Distribution of Protein Drugs

ABSTRACTPurposeThe purpose of this research was to examine the pharmacokinetics (PK) of drug uptake for microneedle-based intradermal (ID) delivery of several classes of protein drugs compared to standard subcutaneous (SC) administration.MethodsSystemic absorption kinetics of various proteins were analyzed following microneedle-based ID delivery and standard injection methods in the swine model. Comparative PK data were determined using standard non-compartmental techniques based on blood serum levels.ResultsDelivery of proteins using microneedles resulted in faster systemic availability, measured via tmax, and increased maximal drug concentration, Cmax, over SC delivery for all proteins tested. Some agents also exhibited increased bioavailability for the ID route. Imaging studies using reporter dyes showed rapid lymphatic-mediated uptake.ConclusionsMicroneedle delivery is applicable to a wide variety of protein drugs and is capable of effective parenteral administration of therapeutic drug dosages. This delivery route alters absorption kinetics via targeting a tissue bed better perfused with lymphatic and blood vessels than the SC space. Microneedle delivery may afford various advantages, including a robust method to increase the absorption rate and bioavailability of proteins that have been challenging to deliver at therapeutic levels or with physiologically relevant profiles.

Intradermal Microneedle Delivery of Insulin Lispro Achieves Faster Insulin Absorption and Insulin Action than Subcutaneous Injection

BACKGROUND This study compared insulin lispro (IL) pharmacokinetics (PK) and pharmacodynamics (PD) delivered via microneedle intradermal (ID) injection with subcutaneous (SC) injection under euglycemic glucose clamp conditions. METHODS Ten healthy male volunteers were administered 10 international units (IU) of IL at 3 microneedle lengths (1.25, 1.50, or 1.75 mm) in a randomized, crossover fashion on Days 1-3 followed by a repetitive ID 1.5-mm microneedle dose (Day 4) and an SC dose (Day 5). RESULTS Microneedle ID delivery resulted in more rapid absorption of IL, with decreased time to maximum insulin concentration (ID vs. SC: 36.0-46.4 vs. 64.3 min, P < 0.05) and higher fractional availability at early postinjection times. ID produced more rapid effects on glucose uptake with shorter times to maximal and early half-maximal glucose infusion rates (GIRs) (ID vs. SC: time to maximum GIR, 106-112 vs. 130 min, P < 0.05; early half-maximal GIR, 29-35 vs. 42 min), increased early GIR area under the curve (AUC), and faster offset of insulin action (shorter time to late half-maximal GIR: 271-287 vs. 309 min). Relative total insulin bioavailability (AUC to 360 min and AUC to infinite measurement) did not significantly differ between administration routes. ID PK/PD parameters showed some variation as a function of needle length. Delivery of ID IL was generally well tolerated, although transient, localized wheal formation and redness were observed at injection sites. CONCLUSIONS Microneedle ID insulin lispro delivery enables more rapid onset and offset of metabolic effect than SC therapy and is safe and well tolerated; further study for insulin therapy is warranted.

Microneedle-Based Intradermal Versus Subcutaneous Administration of Regular Human Insulin or Insulin Lispro: Pharmacokinetics and Postprandial Glycemic Excursions in Patients with Type 1 Diabetes

BACKGROUND This study assessed pharmacokinetics (PK) and pharmacodynamic postprandial glycemia (PPG) in patients with type 1 diabetes mellitus (T1DM) after a standardized liquid meal following insulin lispro (IL) or regular human insulin (RHI) given by microneedle-based intradermal (ID) versus subcutaneous (SC) delivery. RESEARCH DESIGN AND METHODS In this randomized, open-label, five-way crossover study, 29 T1DM patients received IL and RHI (0.125 U/kg) at 2 min and 17 min premeal, respectively, by both the SC and ID routes and also received RHI by the ID route at 2 min premeal. Blood glucose was stabilized at 120 mg/dL prior to a standardized 82-g carbohydrate liquid meal. ID delivery used a 34-gauge 1.5-mm steel microneedle, and SC delivery used a 31-gauge 8-mm syringe needle. RESULTS The 90-min PPG (blood glucose area under the curve for 0-1.5 h) for ID RHI was 14% lower than SC RHI at -17 min (P < 0.0001) and 11% lower than ID RHI at -2 min (P = 0.0006). PPG did not differ between ID RHI and SC IL, both at -2 min (P = 0.8345). ID IL PPG was lower than SC, both at -2 min, but not significantly (P = 0.10). Both ID IL and ID RHI PK data showed significantly faster uptake and time to maximum concentration, higher maximum concentration, and shorter systemic circulating duration versus SC dosing. ID IL and RHI delivery was generally well tolerated. CONCLUSIONS PPG with RHI administered ID via microneedle was improved versus SC delivery when dosed 17 min premeal. ID RHI provided similar control of PPG as SC IL immediately premeal. Further studies of ID insulin delivery via steel microneedles are warranted.

Pharmacokinetics and postprandial glycemic excursions following insulin lispro delivered by intradermal microneedle or subcutaneous infusion.

Background: Intradermal (ID) delivery has been shown to accelerate insulin pharmacokinetics (PK). We compared the PK and pharmacodynamic (PD) effects of insulin lispro administered before two daily standardized solid mixed meals (breakfast and lunch), using microneedle-based ID or traditional subcutaneous (SC) delivery. Method: The study included 22 subjects with type 1 diabetes in an eight-arm full crossover block design. One arm established each subjects optimal meal dose. In six additional arms, the optimal, higher, and lower doses (+30%, −30%) were each given ID and SC delivery, in random order. The final arm assessed earlier timing for the ID optimal dose (−12 versus −2 min). The PK/PD data were collected for 6 h following meals. Intravenous basal regular insulin was given throughout, and premeal blood glucose (BG) adjusted to 115 mg/dl. Results: The primary end point, postprandial time in range (70–180 mg/dl), showed no route-based differences with a high level of overall BG control for both SC and ID delivery. Secondary insulin PK end points showed more rapid ID availability versus SC across doses and meals (ΔTmax −16 min, ΔT50rising −7 min, ΔT50falling −30 min, all p < .05). Both intrasubject and intersubject variability for ID Tmax were significantly lower. Intradermal delivery showed modest, statistically significant secondary PD differences across doses and meals, generally within 90–120 min postprandially (Δ12 mg/dl BG at 90 min, Δ7 mg/dl BGmax, Δ7 mg/dl mean BG 0–2 h, all p < .05). Conclusions: This study indicates that ID insulin delivery is superior to SC delivery in speed of systemic availability and PK consistency and may improve postprandial glucose control.

Evaluation of Intradermal and Subcutaneous Infusion Set Performance Under 24-Hour Basal and Bolus Conditions

Background: This study sought to assess the function and delivery reliability of intradermal (ID) infusion sets used with commercial insulin pumps. Method: Healthy subjects (n = 43) were randomized to either ID or subcutaneous (SC) arms, and received basal/bolus placebo delivery for 24 hours. Subjects received 4 of 8 infusion set combinations (ID: microneedle design A or B, with 2 pump brands [Animas or MiniMed]; SC: Teflon Quickset or steel Rapid-D, Animas pump only, with or without overtaping) and were evaluated for pump occlusion alarms, fluid leakage, pain, and tissue tolerability. A novel algorithm was developed to determine flow consistency based on fluid pressure, and the duration and occurrence rate for periods of unalarmed but interrupted flow (“silent occlusions’”) were compared. Results: ID delivery was successfully maintained over the 24-hour infusion period. The number of silent occlusions was lower for ID microneedle cannula design B than A (P < .01) and lower for Rapid-D SC device compared to Quick-set (P = .03). There was no significant difference in the number of occlusion alarms between the ID and SC devices with the Animas pump. However, the pumps tested with ID devices had significantly different alarm rates (MiniMed 29.5%, Animas 0%, P < .001). Leakage and tissue tolerability were comparable across devices. Conclusion: The ID infusion set reliably delivered diluent for an extended 24-hour period in healthy subjects and was well tolerated. Silent occlusion flow interruptions could be detected in both ID and SC infusion sets using a proprietary algorithm. This algorithm is a promising method for quantitatively evaluating infusion set flow performance.