Eli Lilly and Company Insulins - A Century of Innovation.

Eli Lilly and Company has played a pivotal role in the development of insulin products since its discovery in 1921. Through their dedication to pharmaceutical innovation, Josiah K. Lilly Sr. and George HA Clowes, in close collaborations with the University of Toronto, made insulin commercially available in 1923. Other innovations include the development and commercialization of the first biosynthetic human insulin, a rapid-acting insulin analog and analog mixtures. Lilly has advanced the field of knowledge with significant efforts toward developing a hepatic preferential basal insulin. Other important insulin projects include the first concentrated rapid-acting insulin analog, clinical studies supporting the use of highly concentrated human insulin, and an advanced clinical development program for an ultra-rapid insulin analog. Lilly's commitment to people affected with diabetes remains strong and will continue into the future through collaborative research, innovative product development and investing in advanced technologies.

Characteristics of insulin-Naïve people with type 2 diabetes who successfully respond to insulin glargine U100 after 24 weeks of treatment: a meta-analysis of individual participant data from 3 randomized clinical trials.

BACKGROUND: To identify baseline/clinical characteristics associated with clinically meaningful responses to insulin glargine 100 U/mL (IGlar) in insulin-naive people with type 2 diabetes mellitus (T2DM). METHODS: Individual participant data were pooled from 3 randomized trials to compare baseline characteristics and clinical outcomes associated with 24-week response to IGlar in combination with non-insulin antihyperglycemic agents in participants with T2DM. Responders were defined as achieving endpoint HbA1c target < 53 mmol/mol (< 7%) and/or ≥ 11 mmol/mol (≥ 1%) HbA1c reduction from baseline. RESULTS: Differences in baseline characteristics for responders versus nonresponders were higher HbA1c (99 vs 91 mmol/mol [9.1 vs 8.3%]; P < 0.001), higher fasting blood glucose (FBG; 10.4 vs 8.8 mmol/L [187 vs 159 mg/dL; P < 0.001), and fewer participants (94% vs 98%; P = 0.006) taking oral medications targeting postprandial blood glucose (BG). Most participants (80%) achieved one or both components of composite endpoint. 12-week response was a strong predictor of subsequent 24-week response (sensitivity, 85.9%; predictive positive value, 91.4%). At both 12 and 24 weeks, < 40% of responders and nonresponders reached target FBG ≤ 5.6 mmol/L (≤ 100 mg/dL). Responders at 24 weeks had higher incidence of hypoglycemia (total, 82.5% vs 70.4%; P < 0.001; nocturnal, 60.3% vs 50.5%; P = 0.002; documented symptomatic, 65.8% vs 55.6%; P < 0.001) than nonresponders. CONCLUSIONS: Baseline characteristics associated with response were identified. The strong predictability of 12-week response suggests that the magnitude of early HbA1c reduction should be considered when assessing response to IGlar. More aggressive IGlar titration may be reasonable for nonresponders and responders who have not reached FBG and HbA1c targets, taking into account other BG timepoints.

Efficacy and safety of LY2963016 insulin glargine in patients with type 1 and type 2 diabetes previously treated with insulin glargine.

The safety and efficacy of LY2963016 insulin glargine (LY IGlar) and Lantus insulin glargine (IGlar), products with identical primary amino acid sequences, were assessed in subgroups of patients with type 1 (T1D, n = 452) or type 2 diabetes (T2D, n = 299) reporting prestudy IGlar treatment in 52-week open-label (ELEMENT-1) and 24-week double-blind (ELEMENT-2) studies. At randomization, patients transitioned from their prestudy IGlar to equivalent doses of LY IGlar or IGlar. Primary efficacy (change in glycated haemoglobin from baseline to 24 weeks), other efficacy and select safety outcomes of LY IGlar were compared with those of IGlar. Continuous data were analysed using analysis of covariance, categorical data by Fisher's exact test, and treatment comparisons for hypoglycaemia by Wilcoxon test. No statistically significant treatment differences were identified for efficacy and safety outcomes except for weight change (T1D), overall incidence of detectable insulin antibodies (T2D), and serious adverse events (T2D). These differences were neither consistently observed across both studies nor observed in the total study populations, and their magnitude suggests they were not clinically meaningful. LY IGlar and IGlar show similar efficacy and safety profiles in patients reporting prestudy IGlar treatment.

Evaluation of immunogenicity of LY2963016 insulin glargine compared with Lantus® insulin glargine in patients with type 1 or type 2 diabetes mellitus.

AIMS: To compare the immunogenicity profiles and the potential effects on clinical outcomes of LY2963016 insulin glargine (LY IGlar) and Lantus® insulin glargine (IGlar), products with identical primary amino acid sequences, in patients with type 1 or type 2 diabetes mellitus (T1DM or T2DM). METHODS: To assess immunogenicity, anti-insulin glargine antibodies (measured as percent binding) were compared between treatments in 52-week (open-label) and 24-week (double-blind) randomized studies in total study populations of patients with T1DM (N = 535) and T2DM (N = 756), respectively, and two subgroups of patients with T2DM: insulin-naïve patients and those reporting prestudy IGlar treatment (prior IGlar). Relationships between insulin antibody levels and clinical outcomes were assessed using analysis of covariance and partial correlations. Insulin antibody levels were assessed using Wilcoxon rank sum. Treatment comparisons for treatment-emergent antibody response (TEAR) and incidence of detectable antibodies were analysed using Fisher's exact test. RESULTS: No significant treatment differences were observed for insulin antibody levels, incidence of detectable anti-insulin glargine antibodies, or incidence of TEAR [overall and endpoint, by last-observation-carried-forward (LOCF)] in patients with T1DM or patients with T2DM, including the insulin-naïve subgroup. A statistically significant difference was noted in the overall incidence of detectable antibodies but not at endpoint (LOCF) nor in TEAR for the prior IGlar subgroup of patients with T2DM. Insulin antibody levels were low (<5%) in both treatment groups. Insulin antibody levels or developing TEAR was not associated with clinical outcomes. CONCLUSIONS: LY IGlar and IGlar have similar immunogenicity profiles; anti-insulin glargine antibody levels were low for both treatments, with no observed effect on efficacy and safety outcomes.

Similar efficacy and safety of LY2963016 insulin glargine and insulin glargine (Lantus®) in patients with type 2 diabetes who were insulin-naïve or previously treated with insulin glargine: a randomized, double-blind controlled trial (the ELEMENT 2 study).

AIMS: To compare the efficacy and safety of LY2963016 insulin glargine (LY IGlar) and the reference product (Lantus(®)) insulin glargine (IGlar) in combination with oral antihyperglycaemic medications in patients with type 2 diabetes (T2D). METHODS: This phase III, randomized, double-blind, 24-week study enrolled patients with T2D who were insulin-naïve [glycated haemoglobin (HbA1c) ≥7 and ≤11.0%] or previously on IGlar (HbA1c ≤11%) and treated with ≥2 oral antihyperglycaemic medications. Patients were randomized to receive once-daily LY IGlar (n = 376) or IGlar (n = 380) for 24 weeks. The primary efficacy outcome was to test the non-inferiority (0.4% and then 0.3% margin) of LY IGlar to IGlar, as measured by change in HbA1c from baseline to 24 weeks. RESULTS: Both treatment groups had similar and significant (p < 0.001) within-group decreases in mean HbA1c values from baseline. LY IGlar met non-inferiority criteria compared with IGlar for change in HbA1c from baseline [-1.29 vs -1.34%; respectively, least-squares mean difference 0.052% (95% confidence interval -0.070 to 0.175); p > 0.05]. There were no treatment differences (p > 0.05) in fasting plasma glucose, proportion of patients reaching HbA1c <7% or insulin dose at 24 weeks. Adverse events, allergic reactions, weight change, hypoglycaemia and insulin antibodies were similar between treatment groups. Similar findings were observed in patients who were insulin-naïve or previously treated with IGlar at baseline. CONCLUSIONS: Both LY IGlar and IGlar, when used in combination with oral antihyperglycaemic medications, provided effective and similar glucose control with similar safety profiles in patients with T2D.

Efficacy and safety of LY2963016 insulin glargine compared with insulin glargine (Lantus®) in patients with type 1 diabetes in a randomized controlled trial: the ELEMENT 1 study.

AIMS: To compare the efficacy and safety of LY2963016 insulin glargine (LY IGlar) and the reference product (Lantus®) insulin glargine (IGlar) in patients with type 1 diabetes (T1D). METHODS: This phase III, randomized, open-label, 52-week study enrolled patients with T1D [glycated haemoglobin (HbA1c) ≤11%] being treated with basal (once-daily) and bolus insulin. Patients were randomized to receive once-daily LY IGlar (n = 268) or IGlar (n = 267) in combination with mealtime insulin lispro for 52 weeks. The primary efficacy outcome was to test the non-inferiority (0.4% and then 0.3% margin) of LY IGlar to IGlar as measured by change in HbA1c from baseline to 24 weeks. RESULTS: Both treatment groups had similar and significant (p < 0.001) within-group decreases in mean HbA1c values from baseline. LY IGlar met the non-inferiority criteria compared with IGlar for change in HbA1c from baseline to 24 weeks [-0.35 vs -0.46%, least-squares mean difference 0.108% (95% confidence interval -0.002 to 0.219), p > 0.05]. There were no significant (p > 0.05) treatment differences in other efficacy measures, including proportion of patients reaching HbA1c <7%, daily mean blood glucose, and insulin dose at 24 and 52 weeks. At 52 weeks, similar findings were observed between LY IGlar and IGlar for safety outcomes, including adverse events, allergic reactions, hypoglycaemia, weight change and insulin antibodies. CONCLUSIONS: Both LY IGlar and IGlar, when used in combination with mealtime insulin lispro, provided effective and similar glucose control and similar safety profiles.

Prandial-basal insulin regimens plus oral antihyperglycaemic agents to improve mealtime glycaemia: initiate and progressively advance insulin therapy in type 2 diabetes.

AIMS: To compare two progressive approaches [once-daily insulin glargine plus ≤3 mealtime lispro (G+L) vs. insulin lispro mix 50/50 (LM50/50) progression once up to thrice daily (premix progression, PP)] of beginning and advancing insulin in patients with type 2 diabetes (T2D) and inadequate glycaemic control on oral therapy, with the aim of showing non-inferiority of PP to G+L. METHODS: Patients were randomized to PP (n = 242) or G+L (n = 242) in a 36-week, multinational, open-label trial. Dinnertime insulin LM 50/50 could be replaced with insulin lispro mix 75/25 if needed for fasting glycaemic control. RESULTS: Baseline haemoglobin A1c (HbA1c) were 9.5% (PP) and 9.3% (G+L); p = 0.095. Change in A1C (baseline to endpoint) was -1.76% (PP) and -1.93% (G+L) (p = 0.097) [between-group difference of 0.17 (95% confidence interval: -0.03, 0.37)]. Non-inferiority of PP to G+L was not shown based on the prespecified non-inferiority margin of 0.3%. A1C was lower with G+L at weeks 12 (7.8 vs. 7.9%; p = 0.042), 24 (7.4 vs. 7.6%; p = 0.046), but not at week 36 (7.5 vs. 7.6%; p = 0.405). There were no significant differences in percentages of patients achieving A1C ≤7%, overall hypoglycaemia incidence and rate or weight change. Total daily insulin dosages at endpoint were higher with PP vs. G+L (0.57 vs. 0.51 U/kg; p = 0.017), likely due to more injections (1.98 vs. 1.79; p = 0.011). CONCLUSIONS: Both treatments progressively improved glycaemic control in patients with T2D on oral therapy, although non-inferiority of PP to G+L was not shown. Higher insulin doses were observed with PP with no between-treatment differences in overall hypoglycaemia or weight gain.

Comparison of insulin lispro protamine suspension and insulin detemir in basal-bolus therapy in patients with Type 1 diabetes.

AIMS: The efficacy of two basal insulins, insulin lispro protamine suspension (ILPS) and insulin detemir, was compared in basal-bolus regimens in Type 1 diabetes. METHODS: In this 32-week, multinational, parallel-group, randomized, controlled trial, adult patients with Type 1 diabetes received ILPS or insulin detemir, injected twice daily (before breakfast and bedtime) and prandial insulin lispro three times daily. The primary outcome was change in glycated haemoglobin (HbA(1c)) from baseline to endpoint. RESULTS: Least squares mean (+/-se) changes in HbA(1c) were similar between groups, meeting non-inferiority (margin, 0.4%): -0.69 +/- 0.07% for ILPS and -0.59 +/- 0.07% for insulin detemir [between-treatment difference -0.10%; 95% confidence interval (CI) -0.29, 0.10]. Standard deviation of fasting blood glucose was similar (non-inferiority margin 0.8 mmol/l): 2.74 +/- 0.14 mmol/l for ILPS and 2.38 +/- 0.14 mmol/l for insulin detemir (CI -0.03, 0.75). Patients on ILPS gained more weight (1.59 +/- 0.23 kg vs. 0.62 +/- 0.24 kg; CI 0.34, 1.60; margin 1.5 kg). Weight-adjusted daily total and prandial insulin doses were lower for ILPS (prandial insulin, 0.38 +/- 0.01 U/kg/day for ILPS, 0.44 +/- 0.01 U/kg/day for insulin detemir; P = 0.004); daily basal insulin dose was similar. All hypoglycaemia incidence and rate and nocturnal hypoglycaemia incidence were similar between groups; nocturnal hypoglycaemia rate was lower for insulin detemir (mean +/- sd 0.79 +/- 1.23 for ILPS, 0.49 +/- 0.85 for insulin detemir; P = 0.001). Severe hypoglycaemia rate was 0.03 +/- 0.11 for ILPS and 0.02 +/- 0.10 for insulin detemir (P = 0.37). CONCLUSIONS: ILPS-treated patients with Type 1 diabetes achieved similar glycaemic control as insulin detemir-treated patients after 32 weeks. Glucose variability was similar. While weight gain and nocturnal hypoglycaemia rate were statistically higher with ILPS, the clinical relevance is unclear.

The relationship between self-monitored blood glucose values and glycated haemoglobin in insulin-treated patients with Type 2 diabetes.

AIMS: Self-monitoring of blood glucose (SMBG) is an important self-management tool for insulin-treated patients with Type 2 diabetes mellitus (T2DM). Its value in estimating glycaemic control in insulin-treated T2DM patients remains unclear. The relationship between glycated haemoglobin (HbA(1c)) and SMBG measures in T2DM patients treated with premixed insulin lispro mixtures or basal insulin glargine was examined. METHODS: HbA(1c) and plasma equivalent glucose (PGe) data derived from SMBG profiles were pooled from five randomized clinical trials of patients with T2DM on one or more oral glucose-lowering medication +/- 0-2 insulin injections per day switching to insulin lispro mixtures (N = 317) or glargine (N = 306). Patients generated seven-point SMBG profiles three times in a 2-week period prior to each HbA(1c) measurement. Pearson's correlation coefficients (r) were calculated for PGe values and HbA(1c). Receiver-operating characteristic (ROC) curves determined the ability of sets of PGe to estimate HbA(1c) (< or > 7.0%). RESULTS: Mean +/- standard deviation age was 57.5 +/- 9.5 years, body mass index 31.3 +/- 5.6 kg/m(2), 52.5% were male and HbA(1c) overall was 7.4 +/- 1.0% at end-point. Among individual SMBG measures, r for HbA(1c) ranged from 0.34 to 0.49. For means of two or more PGe measures, r for HbA(1c) ranged from 0.51 to 0.59. Correlations were similar for either regimen. ROC curves were consistent with the correlation data. CONCLUSIONS: These data provide patients and clinicians information on the relationship between HbA(1c) and SMBG measurements in patients with T2DM, and support the value of frequent blood glucose measurements for assessing overall glycaemic control.

Autocrine semaphorin 3A signaling promotes glioblastoma dispersal.

Glioblastoma multiforme (GBM) is the most malignant glioma type with diffuse borders due to extensive tumor cell infiltration. Therefore, understanding the mechanism of GBM cell dispersal is critical for developing effective therapies to limit infiltration. We identified neuropilin-1 as a mediator of cancer cell invasion by a functional proteomic screen and showed its role in GBM cells. Neuropilin-1 is a receptor for semaphorin3A (Sema3A), a secreted chemorepellent that facilitates axon guidance during neural development. Although neuropilin-1 expression in GBMs was previously shown, its role as a Sema3A receptor remained elusive. Using fluorophore-assisted light inactivation and RNA interference , we showed that neuropilin-1 is required for GBM cell migration. We also showed that GBM cells secrete Sema3A endogenously, and RNA interference-mediated downregulation of Sema3A inhibits migration and alters cell morphology that is dependent on Rac1 activity. Sema3A depletion also reduces dispersal, which is recovered by supplying Sema3A exogenously. Extracellular application of Sema3A decreases cell-substrate adhesion in a neuropilin-1-dependent manner. Using immunohistochemistry, we showed that Sema3A is overexpressed in a subset of human GBMs compared with the non-neoplastic brain. Together, these findings implicate Sema3A as an autocrine signal for neuropilin-1 to promote GBM dispersal by modulating substrate adhesion and suggest that targeting Sema3A-neuropilin-1 signaling may limit GBM infiltration.

Does microalbuminuria predict diabetic nephropathy?

OBJECTIVE: To describe risk factors associated with microalbuminuria (MA) in subjects with diabetes, investigate the predictive value of MA as a marker of risk for diabetic nephropathy (DN), and define risk factors associated with the development and progression of MA. RESEARCH DESIGN AND METHODS: We conducted a prospective longitudinal study of 23 diabetic subjects with persistent MA and 209 diabetic subjects without MA who attended diabetes clinics at the University of Michigan Medical Center in 1989 and 1990. Both groups were examined at baseline and after 7 years. At baseline, urinary albumin-to-creatinine ratios were studied in random, first morning, and 24-h urine samples. At follow-up, a 12-h overnight urine sample was collected and analyzed for albumin and creatinine. At baseline, MA was defined by at least two separate urine specimens with albumin-to-creatinine ratios between 30 and 299 microg albumin per milligram of creatinine. RESULTS: MA regressed in 56% of subjects with baseline MA without systematic application of corrective measures and developed in 16% of subjects without baseline MA. The predictive value positive of MA as a marker of risk for DN was 43%, and the predictive value negative was 77%. In the combined cohort, the incidence and progression of MA were significantly associated with poor glycemic control and duration of diabetes between 10 and 14 years. CONCLUSIONS: MA may not be as sensitive and specific a predictor of DN as previously suggested. Other markers of risk for DN are needed for optimal clinical management.

Isolation and characterization of disease resistance gene homologues from rice cultivar IR64.

We initiated a search for disease resistance (R) gene homologues in rice cultivar IR64, one of the most agronomically important rice varieties in the world, with the assumption that some of these homologues would correspond to previously identified disease resistance loci. A family of rice R gene homologues was identified using the Arabidopsis NBS-LRR disease resistance gene RPS2 as a hybridization probe. Because member genes of this rice R gene family exhibit features characteristic of the NBS-LRR class of resistance genes, the family was given the name NRH (for NBS-LRR resistance gene homologues). Three members of the NRH family, NRH1, NRH2, and NRH3, were cloned and studied in detail. In IR64, NRH1 and NRH2 appear to encode full-length polypeptides, whereas NRH3 is prematurely truncated with a stop codon generated by a frameshift. NRH1 maps on chromosome 5, and NRH2 and NRH3 are less than 48kb apart on chromosome 11. Although NRH1, NRH2, and NRH3 map to regions of the rice genome where disease resistance loci to Xanthomonas oryzae pv. oryzae (Xoo) have been identified, susceptible rice varieties transformed with either NRH1 or NRH2 failed to exhibit increased resistance to a set of well-characterized Xoo strains.

Reduced pancreatic polypeptide response to hypoglycemia and amylin response to arginine in subjects with a mutation in the HNF-4alpha/MODY1 gene.

Subjects with the Q268X mutation in the hepatocyte nuclear factor (HNF)-4alpha gene (RW pedigree/maturity-onset diabetes of the young [MODY]-1) have diminished insulin and glucagon secretory responses to arginine. To determine if pancreatic polypeptide (PP) secretion is likewise involved, we studied PP responses to insulin-induced hypoglycemia in 17 RW pedigree members: 6 nondiabetic mutation-negative [ND(-)], 4 nondiabetic mutation-positive [ND(+)], and 7 diabetic mutation-positive [D(+)]. Subjects received 0.08 U/kg body wt human regular insulin as an intravenous bolus to produce moderate self-limited hypoglycemia. PP areas under the curve (PP-AUCs) were compared among groups. With hypoglycemia, the PP-AUC was lower in the D(+) group (14,907 +/- 6,444 pg/ml, P = 0.03) and the ND(+) group (14,622 +/- 6,015 pg/ml, P = 0.04) compared with the ND(-) group (21,120 +/- 4,158 pg/ml). In addition, to determine if the beta-cell secretory defect in response to arginine involves amylin in addition to insulin secretion, we analyzed samples from 17 previously studied RW pedigree subjects. We compared the AUCs during arginine infusions for the 3 groups both at euglycemia and hyperglycemia as well as their C-peptide-to-amylin ratios. The D(+) and ND(+) groups had decreased amylin AUCs during both arginine infusions compared with the ND(-) group, but had similar C-peptide-to-amylin ratios. These results suggest that the HNF-4alpha mutation in the RW/MODY1 pedigree confers a generalized defect in islet cell function involving PP cells in addition to beta- and alpha-cells, and beta-cell impairment involving proportional deficits in insulin and amylin secretion.

Functional genomics with protein-protein interactions.

Knowing the sequence of a gene does not mean knowing its function. Although, information stored at the DNA level can be used to predict biological processes, proteins are the final executors of the various response programs of a cell. Transient information, like posttranslational modifications or interactions among proteins, cannot be deduced from DNA sequences. The rapid accumulation of large amounts of DNA sequence data in genomics projects has led to an increasing demand for powerful tools to analyze proteins and their behaviour at a large scale. This review aims to compare different technologies used for identification of interacting proteins and discusses recent developments in the field of high-throughput protein-protein interaction mapping.

Selection of a peptide ligand to the p75 neurotrophin receptor death domain and determination of its binding sites by NMR.

The p75 neurotrophin receptor (p75(NTR)) contains a conserved death domain module similar to that of the cytotoxic receptors Fas and TNFR-1. Here, we describe the selection of peptide ligands from a combinatorial library using a variation of the selectively-infective phage (SIP) method directed to the death domain of p75(NTR). The binding sites on the death domain of p75(NTR) were identified for a 15 amino acid residue peptide by nuclear magnetic resonance (NMR) spectroscopy. The selected peptides may be useful for probing the function of the p75(NTR) death domain and aid in defining its downstream signalling mechanism.

A phage-based system to select multiple protein-protein interactions simultaneously from combinatorial libraries.

Selectively infective phage (SIP) can be used to identify protein-protein interactions. SIP was modified to facilitate the simultaneous selection of interacting protein pairs from large combinatorial libraries. An interference-resistant phage was constructed which non-covalently, but stably links the genetic information of an interacting pair, encoded separately on phage and phagemid vectors, by co-packaging into heteropolyphages. In a model system, the interaction between a SIP-selected peptide and the intracellular domain of the p75 neurotrophin receptor was detected in the presence of a 10(4)-fold excess of a non-interacting control pair (jun leucine zipper and p75 intracellular domain) via SIP hetero-polyphage transductants. To minimize the redundancy of transductants and to minimize possible ligand exchange generated in a solution-based SIP screening, a filter-based in situ infectivity screening was developed. The combination of the above techniques may provide a powerful system for rapid screening of very large sequence spaces.

Structure of a viral procapsid with molecular scaffolding.

The assembly of a macromolecular structure proceeds along an ordered morphogenetic pathway, and is accomplished by the switching of proteins between discrete conformations as they are added to the nascent assembly. Scaffolding proteins often play a catalytic role in the assembly process, rather like molecular chaperones. Although macromolecular assembly processes are fundamental to all biological systems, they have been characterized most thoroughly in viral systems, such as the icosahedral Escherichia coli bacteriophage phiX174. The phiX174 virion contains the proteins F, G, H and J. During assembly, two scaffoldingproteins B and D are required for the formation of a 108S, 360-A-diameter procapsid from pentameric precursors containing the F, G and H proteins. The procapsid contains 240 copies of protein D, forming an external scaffold, and 60 copies each of the internal scaffolding protein B, the capsid protein F, and the spike protein G. Maturation involves packaging of DNA and J proteins and loss of protein B, producing a 132S intermediate. Subsequent removal of the external scaffold yields the mature virion. Both the F and G proteins have the eight-stranded antiparallel beta-sandwich motif common to many plant and animal viruses. Here we describe the structure of a procapsid-like particle at 3.5-A resolution, showing how the scaffolding proteins coordinate assembly of the virus by interactions with the F and G proteins, and showing that the F protein undergoes conformational changes during capsid maturation.

NMR structure of the death domain of the p75 neurotrophin receptor.

The intracellular domain of the p75 neurotrophin receptor (p75ICD) lacks catalytic activity but contains a motif similar to death domains found in the cytoplasmic regions of members of the tumor necrosis factor receptor family and their downstream targets. Although some aspects of the signaling pathways downstream of p75 have been elucidated recently, mechanisms of receptor activation and proximal signaling events are unknown. Here we report the nuclear magnetic resonance (NMR) structure of the 145 residue long p75ICD. The death domain of p75ICD consists of two perpendicular sets of three helices packed into a globular structure. The polypeptide segment connecting the transmembrane and death domains as well as the serine/threonine-rich C-terminal end are highly flexible in p75ICD. Unlike the death domains involved in signaling by the TNF receptor and Fas, p75ICD does not self-associate in solution. A surface area devoid of charged residues in the p75ICD death domain may indicate a potential site of interaction with downstream targets.

Multivalent antibody fragments with high functional affinity for a tumor-associated carbohydrate antigen.

We report in this work a human-derived self-assembling polypeptide based on the tetramerization domain of the human transcription factor p53, which can be fused to single-chain Fv Ab (scFv) fragments via a long and flexible hinge sequence of human origin, allowing exploitation of the functional affinity increase of binding to a ligand or cell surface with multimeric binding sites. We have demonstrated the use of this polypeptide by applying it to the construction of a tetrameric scFv against the tumor-associated carbohydrate Ag Lewis Y (Fuc alpha 1-->2Gal beta 1-->4[Fuc alpha 1-->3] GlcNAc beta 1-->3R). For comparison purposes, the corresponding scFv and dimeric mini-antibody, comprising the scFv fused via a flexible murine hinge to an artificial dimerization domain, were also created. The recombinant mini-antibody proteins were expressed in functional form in Escherichia coli and showed the expected m.w. of a dimer and tetramer, respectively. Analysis of Lewis Y-binding behavior by surface plasmon resonance revealed specific but very weak binding of the scFv fragment. In contrast, both dimeric and tetrameric scFv fusion proteins exhibited an enormous gain in functional affinity that was greatest in the case of the tetrameric mini-antibody.