Combinatorial Efficacy and Toxicity of an Engineered Toxin Body MT-3724 with Gemcitabine and Oxaliplatin in Relapsed or Refractory Diffuse Large B Cell Lymphoma.

MT-3724 is an engineered direct-kill immunotoxin comprised of a CD20-specific scFv fused to a Shiga-like toxin subunit. In this phase IIa study, eight patients with relapsed diffuse large B-cell lymphoma were treated with MT-3724 combined with gemcitabine and oxaliplatin (GEMOX). The objective response rate was 85.7%, with a median duration of response of 2.2 months. The 12-month overall survival and progression-free survival were 71.4% and 28.6%, respectively. Two patients experienced grade 2 capillary leak syndrome (CLS). Combination therapy with MT-3724 and GEMOX demonstrated an early efficacy signal but was limited by the incidence of CLS.

Safety and Efficacy of Engineered Toxin Body MT-3724 in Relapsed or Refractory B-cell Non-Hodgkin's Lymphomas and Diffuse Large B-cell Lymphoma.

MT-3724, a novel engineered toxin body comprised of an anti-CD20 single-chain variable fragment genetically fused to Shiga-like Toxin A subunit, is capable of binding to and internalizing against CD20, inducing cell killing via permanent ribosomal inactivation. This study evaluated MT-3724 in patients with relapsed/refractory B-cell non-Hodgkin lymphoma (r/rNHL). This open-label, multiple-dose phase Ia/b trial included a dose escalation in patients with r/rNHL according to a standard 3+3 design. Primary objectives were to determine the MTD and pharmacokinetics/pharmacodynamics. In a dose expansion study at MTD in serum rituximab-negative patients with diffuse large B-cell lymphoma (DLBCL), primary objectives were safety, tolerability, and pharmacokinetics/pharmacodynamics. Twenty-seven patients enrolled. MTD was 50 µg/kg/dose with 6,000 µg/dose cap. Thirteen patients experienced at least one grade ≥3 treatment-related adverse events; the most common grade ≥3 event was myalgia (11.1%). Two patients (75 µg/kg/dose) experienced grade 2 treatment-related capillary leak syndrome. Overall objective response rate was 21.7%. In serum rituximab-negative patients with DLBCL or composite DLBCL (n = 12), overall response rate was 41.7% (complete response, n = 2; partial response, n = 3). In patients with detectable baseline peripheral B cells, treatment resulted in dose-dependent B-cell depletion. The proportion of patients with anti-drug antibodies (ADA) increased during treatment and the majority appeared to be neutralizing based on an in vitro assay; nevertheless, tumor regression and responses were observed. MT-3724 demonstrated efficacy at the MTD in this population of previously treated patients with r/rDLBCL, with mild-to-moderate immunogenic safety events. Significance: This work describes the safety and efficacy of a new pharmaceutical pathway that could provide a treatment option for a subset of patients with a critical unmet therapeutic need. The study drug, MT-3724, is capable of targeting B-cell lymphomas via a unique, potent cell-killing mechanism that appears to be promising.

Phase 1 Study of High-Specific-Activity I-131 MIBG for Metastatic and/or Recurrent Pheochromocytoma or Paraganglioma.

Context: No therapies are approved for the treatment of metastatic and/or recurrent pheochromocytoma or paraganglioma (PPGL) in the United States. Objective: To determine the maximum tolerated dose (MTD) of high-specific-activity I-131 meta-iodobenzylguanidine (MIBG) for the treatment of metastatic and/or recurrent PPGL. Design: Phase 1, dose-escalating study to determine the MTD via a standard 3 + 3 design, escalating by 37 MBq/kg starting at 222 MBq/kg. Setting: Three centers. Patients: Twenty-one patients were eligible, received study drug, and were evaluable for MTD, response, and toxicity. Intervention: Open-label use of high-specific-activity I-131 MIBG therapy. Main Outcome Measures: Dose-limiting toxicities, adverse events, radiation absorbed dose estimates, radiographic tumor response, biochemical response, and survival. Results: The MTD was determined to be 296 MBq/kg on the basis of two observed dose-limiting toxicities at the next dose level. The highest mean radiation absorbed dose estimates were in the thyroid and lower large intestinal wall (each 1.2 mGy/MBq). Response was evaluated by total administered activity: four patients (19%), all of whom received >18.5 GBq of study drug, had radiographic tumor responses of partial response by Response Evaluation Criteria in Solid Tumors. Best biochemical responses (complete or partial response) for serum chromogranin A and total metanephrines were observed in 80% and 64% of patients, respectively. Overall survival was 85.7% at 1 year and 61.9% at 2 years after treatment. The majority (84%) of adverse events were considered mild or moderate in severity. Conclusions: These findings support further development of high-specific-activity I-131 MIBG for the treatment of metastatic and/or recurrent PPGL at an MTD of 296 MBq/kg.

Phase 2 Study of 99mTc-Trofolastat SPECT/CT to Identify and Localize Prostate Cancer in Intermediate- and High-Risk Patients Undergoing Radical Prostatectomy and Extended Pelvic LN Dissection.

99mTc-trofolastat (99mTc-MIP-1404), a small-molecule inhibitor of prostate-specific membrane antigen, shows high potential to detect prostate cancer (PCa) noninvasively using SPECT. We therefore wanted to assess the performance of 99mTc-trofolastat SPECT/CT in a phase 2 multicenter, multireader prospective study in patients with intermediate- and high-grade PCa, before radical prostatectomy and extended pelvic lymph node (LN) dissection, with histopathology as the gold standard. Methods: PCa patients (n = 105) with an increased risk of LN involvement (LNI) underwent pelvic 99mTc-trofolastat SPECT/CT before radical prostatectomy with extended pelvic LN dissection. The sensitivity of 99mTc-trofolastat for detection of PCa on a patient and lobe basis, using visual and semiquantitative (tumor-to-background ratio [TBR]) scores, and of LNI was evaluated as well as the correlation of uptake within the gland to Gleason scores (GS) and assessment of the predictive potential of 99mTc-trofolastat uptake for LNI. Results: PCa was detected in 98 patients (94%) with acceptable variability between readers. There was a significantly higher visual score and TBR in positive lobes compared with tumor-negative lobes. Receiver-operating characteristic analysis showed that visual scores more accurately discriminated lobes with GS ≤ 3 + 3 from ≥ 3 + 4, whereas TBRs discriminated high-grade disease from normal lobes better. Visual scores and TBRs correlated significantly with GS. 99mTc-trofolastat SPECT/CT detected LNI with a sensitivity of 50% and specificity of 87%, and TBR values significantly predicted LNI with a sensitivity of 90%. Conclusion:99mTc-trofolastat SPECT/CT detects PCa with high sensitivity in patients with intermediate- and high-risk PCa compared with histology. It has the potential to be used as a surrogate marker for GS and predict LNI.

Synthesis and characterization of rhenium and technetium-99m labeled insulin.

A (99m)Tc-labeled insulin analogue was synthesized through a direct labeling method in which the [(99m)Tc(CO)(3)](+) core was combined with a protected insulin derivative (9) bearing a M(I) chelate linked to the first amino acid of the B-chain (B1). Regioselective labeling was achieved by careful control over the pH and the reaction time. Following a TFA-anisole mediated deprotection step (decay-corrected yield of 30 +/- 11%, n = 4), the identity of the final (99m)Tc-labeled product was confirmed by HPLC. Displacement of (125)I-insulin from the insulin receptor (IR) by the Re analogue 6 was similar to that of native insulin (17.8 nM vs 11.7 nM, respectively). The extent of autophosphorylation and Akt activation, as indicated by production of phospho-Akt (pAkt), showed no statistical difference between 6 and native insulin in both assays. These results support the use of the reported (99m)Tc-insulin derivative as a tracer for studying insulin biochemistry in vivo.

The pharmacokinetics of alternative insulin delivery systems.

Limited progress has been made toward developing safer and more acceptable methods for the administration of insulin treatment, despite several attempts to replace subcutaneous injection with alternate routes of administration. Attempts to develop methods for pulmonary administration have demonstrated promise, but have been met with little patient acceptance thus far, while potentially more attractive routes, such as nasal, oral or transdermal administration, have been mainly unsuccessful in providing sufficiently favorable pharmacokinetics and bioavailability for clinical use. The use of enhancers and/or enzyme inhibitors transiently increases absorption across the epithelia of the oral and nasal cavities and the mucosa of the gastrointestinal tract; however, absorption appears to be highly variable, overall bioavailability remains low, causing the cost of goods to be high, and the long-term safety of additives and insulin as a potential local growth factor is not well characterized. While research in some areas of alternative insulin delivery is ongoing, the continued refinement of subcutaneous injection devices and new pharmacological strategies for patients with type 2 diabetes may reduce the need for delivering exogenous insulin and, thus, for alternate administration routes.

Real-world effectiveness of new medicines should be evaluated by appropriately designed clinical trials.

OBJECTIVES: Health care providers, policy makers, and importantly patients themselves are increasingly interested in the outcomes of clinical trials yet often expect different questions to be addressed than those commonly asked in conventional phase 3 trials. STUDY DESIGN AND SETTING: Review of methodological articles. RESULTS: Conventional randomized controlled trials (RCTs) emphasize internal validity through standardization and control but by design reduce external validity, that is, generalizability of results and conclusions. Ongoing uncertainty about effectiveness or safety of medical interventions in the real world is the major driver for developing improved phase 3b and phase 4 study designs. Factors that should improve the relevance of these real-world trials (RWTs) include choice of endpoints; investigator specialty, appropriate patient selection criteria; emphasis on patient-physician interaction; admittance of relevant interventions in all study groups; and more flexible, simple, and possibly event-driven study visits and procedures, while maintaining randomization as a critical element to address confounders. CONCLUSION: Although we do not believe that RWTs will supplant conventional RCTs, properly designed RWTs will enrich our understanding of the effectiveness of new health care interventions and better inform patients and health care providers alike.

Glycemic exposure is affected favorably by inhaled human insulin (Exubera) as compared with subcutaneous insulin glargine (Lantus) in patients with type 2 diabetes.

BACKGROUND: The objective was to compare the effects on glycemia of adding either inhaled human insulin (Exubera [EXU] [insulin human (recombinant DNA origin) inhalational powder]) or subcutaneous insulin glargine (GLA) to the treatment regimens of patients with type 2 diabetes uncontrolled with oral antidiabetic drugs. METHODS: Forty patients were randomized to receive either EXU three times daily prior to meals or subcutaneous GLA once daily in a crossover design. Interstitial glucose concentrations were monitored using a continuous glucose monitoring system (CGMS) for the final 72-h period of 8 treatment days. RESULTS: Total insulin dosage on the last treatment day was approximately 40.1+/-18.1 units/day EXU compared with 16.4+/-4.8 units/day GLA. Serum insulin levels over the 72-h CGMS period were higher for EXU than for GLA (1,091+/-589 pmol/mL/h vs. 737+/-386 pmol/mL/h; ratio, 148; 95% confidence interval [CI], 130-169). The glucose exposure over this period was lower with EXU than with GLA (380+/-45 mmol/Lh vs. 426+/-89 mmol/Lh; ratio, 88.57; 95% CI, 84-93). The overall hypoglycemic event rate was 8.7 events per subject-month for EXU and 2.4 for GLA. CONCLUSIONS: Prandial insulin therapy with EXU, using a higher daily insulin dose, reduces total daily glucose exposure--in particular postmeal glycemia--more effectively than a basal insulin analog.

Inhaled insulin is associated with prolonged enhancement of glucose disposal in muscle and liver in the canine.

Diabetic patients treated with inhaled insulin exhibit reduced fasting plasma glucose levels. In dogs, insulin action in muscle is enhanced for as long as 3 h after insulin inhalation. This study was designed to determine whether this effect lasts for a prolonged duration such that it could explain the effect observed in diabetic patients. Human insulin was administered via inhalation (Exubera; n = 9) or infusion (Humulin R; n = 9) in dogs using an infusion algorithm that yielded matched plasma insulin kinetics between the two groups. Somatostatin was infused to prevent insulin secretion, and glucagon was infused to replace basal plasma levels of the hormone. Glucose was infused into the portal vein at 4 mg/kg/min and into a peripheral vein to maintain the arterial plasma glucose level at 160 mg/dl. Arterial and hepatic sinusoidal insulin and glucose levels were virtually identical in the two groups. Notwithstanding, glucose utilization was greater when insulin was administered by inhalation. At its peak, the peripheral glucose infusion rate was 4 mg/kg/min greater in the inhalation group, and a 50% difference between groups persisted over 8 h. Inhalation of insulin caused a greater increase in nonhepatic glucose uptake in the first 3 h after inhalation; thereafter, net hepatic glucose uptake was greater. Inhalation of insulin was associated with greater than expected (based on insulin levels) glucose disposal. This may explain the reduced fasting glucose concentrations observed in humans after administration of certain inhaled insulin formulations compared with subcutaneous insulin.

Assessing the impact of a new delivery method of insulin on glycemic control using a novel trial design.

OBJECTIVE: The purpose of the trial was to examine the impact of inhaled human insulin (INH) on patient or physician willingness to adopt insulin after oral diabetes agent failure. RESEARCH DESIGN AND METHODS: The EXPERIENCE trial was a one-year randomized controlled trial conducted at primary, secondary and tertiary care facilities in Europe and North America. The primary study endpoint was difference in glycated hemoglobin (A(1c)) between randomized groups at 26 weeks, and results from that phase have been reported previously. The present report concerns results from the second 26-week extension phase. We also consider the applicability of the design. The trial recruited 727 patients with type 2 diabetes mellitus who, prior to randomization, were using two or more oral diabetes agents and whose A(1c) was ≥ 8.0%. Patients were randomized to two treatment settings: Group 1 (usual care with the option of INH) or Group 2 (usual care only). Usual care included adjusting oral therapy (optimizing current regimen or adding/deleting agents) and/or initiating subcutaneous (SC) insulin. RESULTS: At baseline, insulin was initiated by more (odds ratio [OR] 6.0;95% confidence interval [CI] 4.2 to 8.8; P < 0.0001) patients in Group 1 (86.2%; 76.7% INH plus 9.5% SC) than in Group 2 (50.7%; SC insulin only). The largest reduction from baseline in A(1c) was in Group 1 (-2.0 ± 1.2%) at Week 12 and in Group 2 (-1.8 ± 1.3%) at Week 26 (P = 0.003). At 52 weeks, 79.8% were on insulin in Group 1 (67.4% INH; 12.4% SC) vs 58.1% (SC only) in Group 2, and mean (SD) changes in A(1c) from baseline were -1.9% (1.2%) and -1.8% (1.3%) in Groups 1 and 2, respectively (P = 0.05). Hypoglycemic event rates per patient month were 0.3 and 0.1 in Groups 1 and 2, respectively (P < 0.0001). CONCLUSION: The EXPERIENCE trial showed that novel delivery technology can accelerate the adoption of insulin although some attenuation of differences is observed over time. And further, that this was achieved in a population of patients who appeared more ready to move to insulin therapy than observed in standard clinical practice, and a group of physicians who appeared more ready to adopt INH than the majority of physicians.

Imaging as a tool in drug development.

Medical imaging has experienced a huge increase in exploratory technologies over the past 20 to 30 years. From drug discovery to drug development to routine clinical practice, the advent of functional imaging is about to revolutionize both medicine and pharmaceutical drug development. Currently, a number of technologies are in competition. Positron emission tomography (PET) and magnetic resonance imaging (MRI) have advanced furthest as useful adjuncts to clinical drug development, even though data from both remain, at best, biomarkers that alone will not suffice for regulatory approval. However, the high-risk proof-of-concept and early proof-of-efficacy trial programs can be accelerated with judicious use of PET or MRI. The U.S. Food and Drug Administration (FDA) is currently working to establish guidelines for these new imaging methods, which might accelerate drug development and improve treatment of individual patients.

Inhalation of human insulin (exubera) augments the efficiency of muscle glucose uptake in vivo.

This study assessed the site of increased glucose uptake resulting from insulin inhalation, quantified its effect under steady-state glucose concentrations, and identified the time to onset of effect. Human insulin was administered to 13 beagles via inhalation (Exubera [insulin human (rDNA origin)] Inhalation Powder; n = 7) or infusion into the inferior vena cava (Humulin R; n = 6) using an algorithm to match plasma insulin levels and kinetics for both groups. Somatostatin and glucagon were infused. Glucose was delivered into the portal vein (4 mg x kg(-1) x min(-1)) and a peripheral vein, as needed, to maintain arterial plasma glucose levels at 180 mg/dl. Hepatic exposure to insulin and glucose and liver glucose uptake were similar in both groups. Despite comparable arterial insulin and glucose levels, hind-limb glucose uptake increased 2.4-fold after inhalation compared with infusion due to increased muscle glucose uptake. Glucose infusion rate, nonhepatic glucose uptake, and tracer-determined glucose disposal were about twice as great compared with intravenous insulin. The effect appeared after 1 h, persisting at least as long as arterial insulin levels remained above basal. Pulmonary administration of insulin increases nonhepatic glucose uptake compared with infusion, and skeletal muscle is the likely site of that effect.

Inhalation of human insulin is associated with improved insulin action compared with subcutaneous injection and endogenous secretion in dogs.

This study compared the effects of endogenous (portal) insulin secretion versus peripheral insulin administration with subcutaneous or inhaled human insulin [INH; Exubera, insulin human (rDNA origin) inhalation powder] on glucose disposal in fasted dogs. In the control group, glucose was infused into the portal vein (Endo; n = 6). In two other groups, glucose was infused portally, whereas insulin was administered peripherally by inhalation (n = 13) or s.c. injection (n = 6) with somatostatin and basal glucagon. In the Endo group, over the first 3 h, the arterial insulin concentration was twice that of the peripheral groups, whereas hepatic sinusoidal insulin levels were half as much. Although net hepatic glucose uptake was greatest in the Endo group, the peripheral groups demonstrated larger increases in nonhepatic glucose uptake so that total glucose disposal was greater in the latter groups. Compared with s.c. insulin action, glucose excursions were smaller and shorter, and insulin action was at least twice as great after INH. Thus, at the glucose dose and insulin levels chosen, peripheral insulin delivery was associated with greater whole-body glucose disposal than endogenous (portal) insulin secretion. INH administration resulted in increased insulin sensitivity in nonhepatic but not in hepatic tissues compared with s.c. delivery.

Will availability of inhaled human insulin (Exubera) improve management of type 2 diabetes? The design of the Real World trial.

BACKGROUND: Common deterrents to insulin therapy for both physicians and patients are the complexity and burden of daily injections. In January 2006, the first inhaled human insulin (INH, Exubera (insulinhuman [rDNA origin])InhalationPowder) was approved for use in adult patients with type 1 diabetes mellitus (T1DM) or type 2 diabetes mellitus (T2DM) in the United States and European Union. Results from the INH clinical trial program have shown comparable efficacy of INH to subcutaneous (s.c.) insulin and superior efficacy versus oral antidiabetic agents; thus providing effective glycemic control in adult patients with T2DM without the requirement for preprandial injections. However, because subjects in those trials were randomized to either INH or an alternative, the studies could not estimate the effect of INH on patient acceptance of insulin therapy. Therefore, traditional study designs cannot provide answers to important and practical questions regarding real world effectiveness, which is influenced by psychological and other access barriers. METHODS: To overcome these limitations, the Real World Trial was designed to estimate the effect of the availability of INH as a treatment option for glycemic control. A total of approximately 700 patients from Canada, France, Germany, Italy, Spain, United Kingdom, and the United States with T2DM poorly controlled by oral agent therapy will be randomized to two different treatment settings. Patients and clinicians in both groups (A & B) may choose from all licensed therapies for diabetes including SC insulin delivered by pens; INH will be an additional treatment option only available in Group A. The Real World Trial (Protocol A2171018) has been registered with ClincalTrials.gov, registration id NCT00134147. RESULTS: The primary outcome for the trial will be the difference in mean glycosylated hemoglobin (HbA1c) at 6 months between groups. The design was based on a preceding feasibility study examining the theoretical effects of inhaled insulin availability on treatment choice in 779 patients. In that study, patients were three times more likely to choose insulin therapy when inhaled insulin was available. CONCLUSION: Innovations in study designs may provide an opportunity to reveal unbiased answers to important treatment questions that are more relevant to prescribers, funding agencies, and healthcare policymakers.

Inhaled human insulin.

The benefit of subcutaneous insulin therapy in patients with diabetes is frequently limited due to difficulty in convincing patients of the importance of multiple daily insulin injections to cope effectively with meal-associated glycemic changes. Thus, the aim of achieving tight glycemic control, which is critical for reducing the risk of long-term diabetes-related complications, frequently remains elusive. The successful development of an inhalable insulin as a noninvasive alternative promises to change the management of diabetes. The first product to become available to patients is inhaled human insulin, a dry-powder formulation packaged into discrete blisters containing 1 or 3 mg of dry-powder human insulin and administered via a unique pulmonary inhaler device. It has recently been approved in both the United States and the European Union for the control of hyperglycemia in adult patients with type 1 or type 2 diabetes. The pharmacokinetic profile of inhaled human insulin closely mimics the natural pattern of insulin secretion, and resembles that of rapid-acting subcutaneous analogs. Similarly to rapid-acting subcutaneous analogs, inhaled human insulin has a more rapid onset of glucose-lowering activity compared to subcutaneous regular insulin, allowing it to be administered shortly before meals. It has a duration of glucose-lowering activity comparable to subcutaneous regular insulin and longer than rapid-acting insulin analogs. Inhaled human insulin effectively controls postprandial glucose concentrations in patients with type 1 or type 2 diabetes without increasing the risk of hypoglycemia, and even improves fasting glucose levels compared to subcutaneous insulin. Inhaled human insulin has an overall favorable safety profile. There are small reductions in lung function (1-1.5% of total lung forced expiratory volume in the first second [FEV1] capacity) after onset of treatment that are reversible in most patients if treatment is discontinued. Inhaled human insulin is associated with an increase in insulin antibody titers, especially in patients with type 1 diabetes. These increases are not associated with any clinical sequelae. Patient satisfaction data have shown that inhaled human insulin is associated with greater treatment satisfaction relative to subcutaneous insulin in patients with type 1 or type 2 diabetes. This review summarizes the current data on the clinical efficacy and safety of inhaled human insulin in patients with type 1 or type 2 diabetes.

Synthesis and in vitro evaluation of 18F- and 19F-labeled insulin: a new radiotracer for PET-based molecular imaging studies.

A new and regioselective strategy was developed for the preparation of fluorine-18-labeled insulin as a novel positron emission tomography (PET) tracer. [18F]-4-Fluorobenzoic acid (4-18FBA), which was produced in 83 +/- 8% yield (n = 10), through the use of succinimidyl [18F]-4-fluorobenzoate (4-(18)FSB), was conjugated through a short spacer (6-aminohexanoic acid, AHx) to the PheB1 residue of a protected form of insulin. 18FB-AHx-insulin (8b) was repeatedly prepared in practical quantities (10-20 mCi, 370-740 MBq) in good radiochemical yield (9 +/- 5%, n = 9) and in a specific activity of 7.8 mCi/micromol. The final product was characterized by comparing the radioHPLC and radioTLC of 8b with that of the 19F-analogue (19FB-AHx-insulin, 8a) and by analyzing a carrier-added synthesis by mass spectrometry. Dithiothreitol and endoproteinase Glu-C digestion experiments on 8a confirmed that the prosthetic group was in fact conjugated to the PheB1 residue. An insulin receptor (IR) phosphorylation assay using CHO-hIR cells overexpressing recombinant human insulin receptors indicated no statistical difference in the extent of autophosphorylation stimulated by 8a as compared to that for human insulin (EC50 values of 0.82 nM and 1.0 nM, respectively). The stimulation of 2-deoxyglucose uptake in 3T3-L1 mouse adipocytes utilizing 8a versus unmodified human insulin gave similar EC50 values of 0.68 nM and 0.41 nM, respectively. The IC50 values for 8a versus native insulin for the displacement of 125I-insulin from HEK-293 cells were also the same within experimental error (2.6 nM for 8a versus 2.4 nM for unmodified human insulin). These results support the use of the 18F-insulin analogue as a PET tracer for imaging the distribution of insulin in vivo.

Inhalation of insulin (Exubera) is associated with augmented disposal of portally infused glucose in dogs.

The results of the present study, using the conscious beagle dog, demonstrate that inhaled insulin (INH; Exubera) provides better glycemic control during an intraportal glucose load than identical insulin levels induced by insulin (Humulin) infusion into the inferior vena cava (IVC). In the INH group (n = 13), portal glucose infusion caused arterial plasma glucose to rise transiently (152 +/- 9 mg/dl), before it returned to baseline (65 min) for the next 2 h. Net hepatic glucose uptake was minimal, whereas nonhepatic uptake rose to 12.5 +/- 0.5 mg x kg(-1) x min(-1) (65 min). In the IVC group (n = 9), arterial glucose rose rapidly (172 +/- 6 mg/dl) and transiently fell to 135 +/- 13 mg/dl (65 min) before returning to 165 +/- 15 mg/dl (125 min). Plasma glucose excursions and hepatic glucose uptake were much greater in the IVC group, whereas nonhepatic uptake was markedly less (8.6 +/- 0.9 mg x kg(-1) x min(-1); 65 min). Insulin kinetics and areas under the curve were identical in both groups. These data suggest that inhalation of Exubera results in a unique action on nonhepatic glucose clearance.

Inhalation of insulin in dogs: assessment of insulin levels and comparison to subcutaneous injection.

Pulmonary insulin delivery is being developed as a more acceptable alternative to conventional subcutaneous administration. In 15 healthy Beagle dogs (average weight 9.3 kg), we compared insulin distribution in arterial, deep venous, and hepatic portal circulation. Dogs received 0.36 units/kg s.c. regular human insulin (n = 6) or 1 mg (2.8 units/kg) or 2 mg (5.6 units/kg) dry-powder human inhaled insulin (n = 3 and 6, respectively). Postinhalation of inhaled insulin (1 or 2 mg), arterial insulin levels quickly rose to a maximum of 55 +/- 6 or 92 +/- 9 microU/ml, respectively, declining to typical fasting levels by 3 h. Portal levels were lower than arterial levels at both doses, while deep venous levels were intermediate to arterial and portal levels. In contrast, subcutaneous insulin was associated with a delayed and lower peak arterial concentration (55 +/- 8 microU/ml at 64 min), requiring 6 h to return to baseline. Peak portal levels for subcutaneous insulin were comparable to those for 1 mg and significantly less than those for 2 mg inhaled insulin, although portal area under the curve (AUC) was comparable for the subcutaneous and 2-mg groups. The highest insulin levels with subcutaneous administration were seen in the deep venous circulation. Interestingly, the amount of glucose required for maintaining euglycemia was highest with 2 mg inhaled insulin. We conclude that plasma insulin AUC for the arterial insulin level (muscle) and hepatic sinusoidal insulin level (liver) is comparable for 2 mg inhaled insulin and 0.36 units/kg subcutaneous insulin. In addition, arterial peak concentration following insulin inhalation is two times greater than subcutaneous injection; however, the insulin is present in the circulation for half the time.