The incidence of Type 1 diabetes is growing yearly. Worryingly, the aetiology of the disease is inconclusive. What is known is that the total number of affected individuals, as well as the severity and number of associated complications are growing for this chronic disease. With increasing complications due to severity, length of exposure, and poor control, the disease is beginning to consume an increasingly major portion of healthcare costs to the extent that it poses major economic risks in several nations. Research has shown that intensive insulin therapy aimed at certain minimum glycosylated haemoglobin threshold levels reduces the incidence of complications by up to 76% compared to conventional insulin therapy. Moreover, the effects of such intensive therapy regimes over a 6.5y duration persists for at least 10y after, a so called metabolic memory. Thus, early intervention can slow the momentum of complications far more easily than later intervention. Early, safe, intensive therapy protocols offer potential solutions to the growing social and economic effects of diabetes. Since the 1970s, the artificial endocrine pancreas has been heralded as just this type of solution. However, no commercial product currently exists, and ongoing limitations in sensors and pumps have resulted in, at best, modest clinical advantages over conventional methods of insulin administration or multiple daily injection. With high upfront costs, high costs of consumables, significant complexity, and the extensive infrastructure and support required, these systems and devices are only used by 2-15% of individuals with Type 1 diabetes. Clearly, there is an urgent need to address the large majority of the Type 1 diabetes population using conventional glucose measurement and insulin administration. For these individuals, current conventional or intensive therapies are failing to deliver recommended levels of glycaemic control. This research develops an understanding of clinical glycaemic control using conventional insulin administration and glucose measurement techniques in Type 1 diabetes based on a clinically validated in silico virtual patient simulation. Based on this understanding, a control protocol for Type 1 diabetes that is relatively simple and clinically practical is developed. The protocol design incorporates physiological modelling and engineering techniques to adapt to individual patient clinical requirements. By doing so, it produces accurate, patient-specific recommendations for insulin interventions. Initially, a simple, physiological compartmental model for the pharmacokinetics of subcutaneously injected insulin is developed. While the absorption process itself is subject to significant potential variability, such models enable a real-time estimation of plasma insulin concentration. This information would otherwise be lacking in the clinical environment of outpatient Type 1 diabetes treatment due to the inconvenience, cost, and laboratory turnaround for plasma insulin measurements. Hence, this validated model offers significant opportunity to optimise therapy selection. An in silico virtual patient simulation tool is also developed. A virtual patient cohort is developed on patient data from a representative cohort of the broad diabetes population. The simulation tool is used to develop a robust, adaptive protocol for prandial insulin dosing against a conventional intensive insulin therapy, as well as a controls group representative of the general diabetes population. The effect on glycaemic control of suboptimal and optimal, prandial and basal insulin therapies is also investigated, with results matching clinical expectations. To gauge the robustness of the developed adaptive protocol, a Monte Carlo analysis is performed, incorporating realistic and physiological errors and variability. Due to the relatively infrequent glucose measurement in outpatient Type 1 diabetes, a method for identifying the diurnal cycle in effective insulin sensitivity and modelling it in retrospective patient data is also presented. The method consists of identifying deterministic and stochastic components in the patient effective insulin sensitivity profile. Circadian rhythmicity and sleep-wake phases have profound effects on effective insulin sensitivity. Identification and prediction of this rhythm is of utmost clinical relevance, with the potential for safer and more effective glycaemic control, with less frequent measurement. It is thus a means of further enhancing any robust protocol and making it more clinically practical to implement. Finally, this research presents an entire framework for the realistic, and rapid development and testing of clinical glycaemic control protocols for outpatient Type 1 diabetes. The models and methods developed within this framework allow rapid and physiological identification of time-variant, patient-specific, effective insulin sensitivity profiles. These profiles form the responses of the virtual patient and can be used to develop and robustly test clinical glycaemic control protocols in a broad range of patients. These effective insulin sensitivity profiles are also rich in dynamics, specifically those circadian in nature which can be identified, and used to provide more accurate glycaemic prediction with the potential for safer and more effective control.

Over the last several years, injectable drugs have been a growing area for the treatment of various therapeutic conditions and they are projected to comprise an even larger proportion among the drugs that will be available in the years to come. The injectable drugs are administered by various routes such as intramuscular (IM), intravenous (IV), subcutaneous (SC) and others, however, the majority of these drugs are administered subcutaneously. Even though subcutaneous delivery has been utilized for a number of years, very little is known about the processes governing the absorption of macromolecules from the interstitial space; and the resulting impact of these processes on the bioavailability (BA) and pharmacokinetic (PK) profiles. Also, there is no established In vitro - In vivo correlation (IVIVC) for subcutaneously administered immediate release (IR) peptide based drugs in a biorelevant manner. The contribution of IVIVC in drug development of orally administered drugs is very well known. For oral drugs, the in vivo process of drug absorption is often rate limited by the rate at which drug dissolves in the gastrointestinal tract. This can be simulated by measuring the rate of dissolution in an in vitro apparatus, which can be correlated with the in vivo absorption rate to produce an IVIVC. This research program involved efforts to develop biorelevant IVIVC methods and model for subcutaneously administered peptide based drugs. The in vivo component of this Program involves the use of clinical data from a bioequivalence (BE) study of Iplex™ [(IGF-I (Insulin like growth factor-I)/IGFBP-3 (Insulin like growth factor binding protein-3)], administered subcutaneously, that was conducted at the Center for Drug Studies (CDS), VCU School of Pharmacy in the year 2005 (Barr et. al., 2005). The PK parameters for Increlex™ (IGF-I) are calculated from the clinical data obtained from another study (Rabkin et. al., 1996). Literature research and molecular modeling research formed the basis of our hypotheses that unbound and bound IGF-I are absorbed from the blood capillaries and lymphatic capillaries respectively and that simulation of these physiologic variables is possible with the use of the modified Hanson Microette® device. The Hanson Microette® device is a vertical diffusion cell system that has been modified to simulate the pores in the capillaries with the use of a synthetic membrane. The flow and composition of circulatory fluid was simulated by the use of modified Hanks balanced salts solution (HBSS). A validated RP-HPLC (reversed-phase high performance liquid chromatography) method has been used for the analysis of IGF-1/IGFBP-3 in the in vitro samples. The in vitro permeation/release results gave the in vitro component to conduct IVIVC analysis. The General Electric (GE) healthcare sourced polycarbonate nucleopore track etched membranes were the only set of membranes that resulted in significant permeation in the in vitro experiments. IVIVC results demonstrated high inter and intra-membrane variability for the membranes (available from today’s technology) that were used to simulate the in vivo membrane characteristics. Currently, there are no validated biorelevant IVIVC methods for SC formulations. The methods described here are the basis for future in vitro method development that will be of significant value for (a) predicting the in vivo performance of SC formulations based on the in vitro data, and (b) provide a reproducible in vitro method as the basis of developing an IVIVC for other subcutaneously administered drugs. This will provide an important tool for both development and regulation of this growing class of drugs.

Résumé: Comparées aux classiques insulines humaines régulières (IHR), les insulines analogues ultrarapides (IAUR) ont été conçues pour mieux synchroniser le pic insulinémique avec l’absorption du repas. Le progrès a été démontré chez les patients diabétiques de type 1, mais le contrôle glycémique s’est peu ou pas amélioré chez les patients diabétiques de type 2 (DT2), qu’ils soient sous IAUR ou IHR. Or ces patients constituent 75 % des utilisateurs d’insuline. L’utilité des IAUR est donc toujours débattue. La dose (donc le volume) injectée et le flot sanguin dans le tissu adipeux sous-cutané (FSTA) sont les facteurs majeurs de l’absorption de l’insuline. Les patients DT2, résistants à l’insuline, s’injectent des doses importantes et leur FSTA est de 50 à 70 % plus faible que celui des sujets sains de poids normal (PN). Nous avons montré que l’absorption sous-cutanée des IAUR est diminuée chez les sujets obèses et DT2 (ODT2) par rapport aux sujets PN, que le volume injecté avait un effet délétère additionnel et que le FSTA peut être augmenté de façon pharmacologique avec un agent vasoactif (AV) chez des sujets résistants à l’insuline. Nous suggérons que l’ajout d’un AV à une IAUR va augmenter le FSTA au site d’injection et donc améliorer sa pharmacocinétique (PK) et sa pharmacodynamie (PD). Pour vérifier cette hypothèse, nous avons 1) évalué la réponse du FSTA à 4 AV chez des sujets PN, obèses non-diabétiques et ODT2; 2) évalué la PK/PD et la biodisponibilité de l’IAUR lispro ± AV chez des sujets ODT2; et 3) caractérisé l’expression des cibles des AV dans le tissu adipeux sous-cutané chez les sujets énumérés en 1). Les 4 AV ont augmenté le FSTA des sujets ODT2, mais moins que celui des autres sujets. L’occurrence de la raréfaction et/ou dysfonction microvasculaire chez les sujets ODT2 pourrait expliquer l’hyporéactivité vasculaire aux AV testés. Le plus actif des AV chez les sujets ODT2 a été ajouté à l’IAUR lispro pour améliorer sont absorption sc. Les PK/PD ont été améliorées seulement chez les sujets ODT2 avec une hémoglobine glycosylée A1c ≥ 8 %; c’est-à-dire 4 sujets sur 8. Chez ces derniers, l’absorption de 30 U + AV a été plus rapide de 14 et 71 min à 20 et 80 % de l’aire sous la courbe totale de la lispro plasmatique, respectivement. Chez les 4 autres sujets ODT2, l’absorption de la lispro semble s’être détériorée avec l’AV. Une interaction chimique a peut-être eu lieu entre l’AV et la lispro, ce qui aurait perturbé son absorption. Selon nos résultats, le niveau de contrôle du diabète, le volume d’injection et les caractéristiques chimiques de l’AV seraient des modulateurs de l’efficacité du concept IAUR + AV. Il nous faut maintenant déterminer l’impact de ces facteurs sur la capacité d’un AV à améliorer l’absorption sc de l’IAUR chez les sujets ODT2. / Abstract: Compared to classic regular human insulin (RHI), short-acting insulin analogues were designed to better synchronize plasma insulin increase to food absorption. Although improvements were noted in subjects with type 1 diabetes, slight to no improvement in glycemic control were observed in subjects with type 2 diabetes (T2D) using SAIA instead of RHI. Nevertheless, they represent 75 % of all insulin users. Consequently, the relative useful-ness of SAIA in T2D patients is currently hotly debated. Injected volume and subcutaneous (sc) adipose tissue blood flow (ATBF) are two main factors involved in insulin absorption. In fact, T2D patients use large doses of insulin because of their resistance to insulin and have an ATBF 50 to 70 % lower than lean healthy subjects. We already showed that SAIA absorption is decreased in obese T2D (OT2D) subjects compared to normal weight healthy subjects and that volume has additional detrimental effects. We also showed that ATBF can be increased pharmacologically with vasoactive agents (VA) in healthy and insulin-resistant subjects. Then we suggest that in OT2D subjects, addition of VA to SAIA preparations will locally increase ATBF, improve insulin sc absorption (Pharmacokinetic - PK) and bioavailability, thus insulin hypoglycemic effect (Pharmacodynamic - PD). To test this hypothesis, we 1) assessed ATBF response of 4 selected VA within three experimental groups (normal weight, obese non-diabetic and OT2D subjects); 2) evaluated insulin PK/PD and bioavailability improvement in OT2D subjects after the addition of the best VA to SAIA lispro and 3) characterized expression of selected VA targets in sc adipose tissue biopsies, within equivalent experimental groups, and compared results with ATBF responses. All 4 VA were able to increase ATBF of OT2D subjects but in a less extend than other subjects. The occurrence of microvascular rarefaction and/or dysfunction in OT2D subjects can explain the hyporeactivity to tested VA. Nevertheless, one VA among others was shown more effective to increase ATBF in OT2D subjects and was then tested (mixed) with SAIA lispro. With the AV, PK/PD were improved only in OT2D subjects with A1c glycated hemoglobin ≥ 8 %; 4 subjects on 8. The sc absorption of 30 U + VA was faster by 14 and 71 min for respectively 20 and 80 % of the total area under the lispro plasmatic curve. But the sc absorption with VA appeared blunted with the other subjects. Maybe detrimental chemical interactions occurred between the VA and lispro, which could impede absorption. Our results suggest that diabetes control state, injection volume, and VA chemical characteristics influence the efficacy of our SAIA + VA concept. Further tests are needed to seize the impact of these factors on VA effectiveness in sc absorption improvement of SAIA in OT2D subjects.