Class Of Mimetics Research Articles

Measurements of Mcl-1 protein dependencies using dimerization-specific antibodies as predictive biomarkers for BH-3 mimetic class therapies in AML.

e19505 Background: The anti-apoptotic Bcl-2 family proteins facilitate pro-survival and resistance to anti-cancer therapies. Measuring the function of these proteins has shown utility in predicting response to treatment. A biomarker platform that assesses the functionality of these proteins by measuring BH3 mediated signaling potential in individual patients’ cancers, could provide a potential guiding platform for treating AML. In AML venetoclax is becoming widely prescribed and highly effective in combination with other drugs. Recent data indicate that Mcl-1 dependence is a resistance factor to venetoclax and that methods for identifying this could provide guidance for combination treatments. We are developing a technology to directly measure the occurrence of heterodimers of Mcl-1, or Bcl-xL, bound to pro-apoptotic BH3-only protein Bim. These measurements are combined in algorithms developed to indicate the cancer cell apoptotic priming state and offer great potential for identifying best AML treatment options. Methods: Monoclonal antibodies against conformation-specific epitopes induced in Mcl-1/Bim and Bcl-xL/Bim protein complexes were made. Selective bonding of Heterodimer Specific Mcl-1 Bim (HSMCB) and Heterodimer Specific Bcl-xL Bim (HSBXB) mabs were confirmed using ELISA, fluorescence polarization, immunofluorescence microscopy and flow, and by immunohistochemistry in genetically defined cell lines and in AML patient biopsied samples. Results: We show that HSMCB signal depends on both Mcl-1 and Bim protein levels while HSBXB requires Bc-xL and Bim levels. The relative signals of HSMCB to unbound Mcl-1 signal ([HsMcB]/[Mcl-1]) provide a biomarker for Mcl-1 dependence. We carefully established binding metrics that correlate to drug response in cell lines. The pharmacological disruption of these complexes is monitored by the ratiometric readouts that serve as predictive biomarkers for BH-3 mimetic drugs in AML cells. Conclusions: Mcl-1 dependence is a predictive biomarker for venetoclax resistance and for response to Mcl-1 targeted therapies. Flow cytometric and IHC based measurements of a heterodimer complex offer a direct and simpler approach that harbors potential for use in clinical settings. Additional antibodies targeting Mcl-1/Bak and Bcl-2/Bim complexes are being tested.

Monocarbonyl Curcumin Analogues: Heterocyclic Pleiotropic Kinase Inhibitors That Mediate Anticancer Properties

Curcumin is a biologically active component of curry powder. A structurally related class of mimetics possesses similar anti-inflammatory and anticancer properties. Mechanism has been examined by exploring kinase inhibition trends. In a screen of 50 kinases relevant to many forms of cancer, one member of the series (4, EF31) showed ≥85% inhibition for 10 of the enzymes at 5 μM, while 22 of the proteins were blocked at ≥40%. IC50 values for an expanded set of curcumin analogues established a rank order of potencies, and analyses of IKKβ and AKT2 enzyme kinetics for 4 revealed a mixed inhibition model, ATP competition dominating. Our curcumin mimetics are generally selective for Ser/Thr kinases. Both selectivity and potency trends are compatible with protein sequence comparisons, while modeled kinase binding site geometries deliver a reasonable correlation with mixed inhibition. Overall, these analogues are shown to be pleiotropic inhibitors that operate at multiple points along cell signaling pathways.

Low Immunogenicity to Romiplostim in Clinical Studies with ITP Subjects.

Romiplostim, a member of the thrombopoietin (TPO) mimetic class, is an Fc-peptide fusion protein (peptibody) that activates intracellular transcriptional pathways leading to increased platelet production via the TPO receptor (also known as cMpl). The peptibody molecule contains two identical single-chain subunits each consisting of human immunoglobulin IgG1 Fc domain, covalently linked at the C-terminus to a peptide containing two TPO receptor-binding domains. Due to the general concern regarding the immunogenic potential for all therapeutic proteins and the specific concern for monitoring antibodies capable of neutralizing thrombopoietin (TPO), an extensive immunogenicity assessment program was developed to support romiplostim. Romiplostim has been engineered to have no amino acid sequence homology to endogenous TPO. A low theoretical risk of developing conformational antibodies that cross-react against TPO exists. This risk was addressed by using an immunogenicity assessment strategy that relied upon a surface plasmon resonance based biosensor immunoassay using the Biacore 3000 capable of simultaneously monitoring antibodies that bind to romiplostim, TPO, or the active peptide portion of romiplostim (TMP). Samples that tested positive for binding antibodies in the Biacore immunoassay were then tested in the definitive functional biological assay to identify any antibodies capable of neutralizing the biological effect of romiplostim or TPO. Serum samples from 236 actively treated subjects were obtained both before and after exposure to romiplostim and were tested for romiplostim and TPO antibodies. In baseline samples, seventeen subjects (7.1%) tested romiplostim antibody positive and 12 subjects (5.1%) tested TPO antibody positive for pre-existing binding antibodies. After romiplostim exposure, twenty-five out of 236 (10.5%) subjects with ITP developed binding antibodies against romiplostim (inclusive of antibodies to both peptide and the whole molecule) and 12 out of 236 (5.1%) subjects with ITP developed binding antibodies against TPO. The antibodies that developed against romiplostim did not cross react with TPO and the antibodies that developed against TPO did not cross react with romiplostim. The incidence of anti-romiplostim neutralizing antibodies among 236 subjects with ITP who were treated with romiplostim across 10 clinical studies was 0.4% (1 out of 236). No cases of anti-TPO neutralizing antibodies were detected in romiplostim treated samples. In conclusion, after thorough immunogenicity assessment of all subjects treated with romiplostim using sensitive methods to detect binding and neutralizing antibodies, only one subject was found positive for the presence of antibodies capable of neutralizing romiplostim that was negative at the time of follow up 4 months later. As expected, none of the subjects treated were positive for antibodies capable of neutralizing TPO. No clinical sequelae were observed in association to the presence of antibodies.

Exenatide (Byetta) as a Novel Treatment Option for Type 2 Diabetes Mellitus

Exenatide is the first drug in the incretin mimetic class and is indicated for treatment of type 2 diabetes mellitus. Although structurally similar to the native glucagon-like peptide, this synthetic form has a much longer duration of action. Randomized trials have shown exenatide to be efficacious in improving glycemic control when combined with either metformin or a sulfonylurea. The dose is initially 5 mcg subcutaneously twice daily and may be titrated to 10 mcg subcutaneously twice daily to achieve better diabetes management. Nausea, vomiting, and diarrhea were the most common adverse events reported with exenatide therapy. Exenatide is not associated with hypoglycemia, which may provide advantages over adding insulin to a sulfonylurea or metformin.

Exenatide: NMR/CD evaluation of the medium dependence of conformation and aggregation state.

Exenatide, synthetic exendin-4, is the first member of the incretin mimetic class of potential therapeutic agents. It has been the subject of extensive clinical trials in people with Type 2 diabetes. Results to date indicate that exenatide decreases postmeal blood glucose concentrations and that this effect is associated with weight loss. Prior NMR studies of exendin-4 utilized 30% trifluoroethanol because this medium affords sharp, high-resolution NMR spectra. These studies defined its three-dimensional structure in this medium. The NMR-derived ensemble included a novel tertiary structure motif that has subsequently been optimized, yielding water-soluble Trp-cage miniproteins. Prior to the present study, the structuring propensities (and aggregation/association state) of exendin-4 in strictly aqueous media had not been established. Studies of exendin-4 and N-terminally truncated analogs of exendin have established that the structuring propensities of these species are highly medium dependent. This study extends knowledge of the medium dependence of exendin structure to DMSO-water mixtures and to aqueous media mimicking the formulation conditions for this investigational drug. Exenatide retains a substantial helical propensity from residues 9-27 even in 98% DMSO. The addition of water leads to the appearance of NMR diagnostics of the Trp-cage formation. In strictly aqueous media (pH 4-4.4), exenatide is monomeric only at <10 microM peptide concentrations. Under these conditions the Trp cage is partially formed. NMR and CD data indicate that higher concentrations lead to helix bundle formation and that the helix/helix interactions involve residues 11-26. Both the N- and C-termini of the helix bundle state display rapid segmental motion.

Macrocyclic hairpin mimetics of the cationic antimicrobial peptide protegrin I: a new family of broad-spectrum antibiotics.

The problems associated with increasing antibiotic resistance have stimulated great interest in newly discovered families of naturally occurring cationic antimicrobial peptides. These include protegrin, tachyplesin, and RTD-1, which adopt beta-hairpin-like structures. We report here an approach to novel peptidomimetics based on these natural products. The mimetics were designed by transplanting the cationic and hydrophobic residues onto a beta-hairpin-inducing template, either a D-Pro-L-Pro dipeptide or a xanthene derivative. The mimetics have good antimicrobial activity against Gram-positive and Gram-negative bacteria (minimal inhibitory concentration approximately 6-25 microgram mL(-1)). Analogues with improved selectivity for microbial rather than red blood cells (1 % hemolysis at 100 microgram mL(-1)) were identified from a small library prepared by parallel synthesis. Thus, it is possible to separate the antimicrobial and hemolytic activities in this class of mimetics. NMR studies on one mimetic revealed a largely unordered structure in water, but a transition to a regular beta-hairpin backbone conformation in the presence of dodecylphosphocholine micelles. This family of mimetics may provide a starting point for the optimization of antimicrobial agents of potential clinical value in the fight against multiple-drug-resistant microorganisms.

Associations of co-mimetic ithomiine butterflies on small spatial and temporal scales in a neotropical rainforest

To test whether ithomiine butterfly species within Mullerian mimetic classes are associated in space and time, we sampled a community of ithomiine butterflies at monthly intervals with traps in the canopy and the understory of four forest habitats: primary, higrade, secondary and edge. A species accumulation curve reached an asymptote at 22 species, suggesting that these species have a greater preference for feeding on fruit juices than other ithomiines known to occur at the study site. Species richness and individual abundance showed marked temporal variation, and there were slight differences in the distribution of species richness and individual abundance among the four habitats. The 22 species sampled in this study were not stratified vertically. The five mimetic colour classes of these butterflies were unequally distributed among the four habitats and over the course of the twelve months. There is suggestive evidence that co-mimic species occurred in the same habitats, and strong evidence that they occurred at the same times. Habitat and temporal effects each contributed approximately 10% to the total mimetic class diversity, with the temporal effect being slightly larger than that of habitat. This study demonstrates that Mullerian co-mimic associations can be measured on a much smaller scale than has been done previously.

Associations of co-mimetic ithomiine butterflies on small spatial and temporal scales in a neotropical rainforest

To test whether ithomiine butterfly species within Müllerian mimetic classes are associated in space and time, we sampled a community of ithomiine butterflies at monthly intervals with traps in the canopy and the understory of four forest habitats: primary, higrade, secondary and edge. A species accumulation curve reached an asymptote at 22 species, suggesting that these species have a greater preference for feeding on fruit juices than other ithomiines known to occur at the study site. Species richness and individual abundance showed marked temporal variation, and there were slight differences in the distribution of species richness and individual abundance among the four habitats. The 22 species sampled in this study were not stratified vertically. The five mimetic colour classes of these butterflies were unequally distributed among the four habitats and over the course of the twelve months. There is suggestive evidence that co-mimic species occurred in the same habitats, and strong evidence that they occurred at the same times. Habitat and temporal effects each contributed approximately 10% to the total mimetic class diversity, with the temporal effect being slightly larger than that of habitat. This study demonstrates that Müllerian co-mimic associations can be measured on a much smaller scale than has been done previously.