Relevant Ligands Research Articles

Enhancing the antitumor efficacy of a cell-surface death ligand by covalent membrane display

TNF superfamily death ligands are expressed on the surface of immune cells and can trigger apoptosis in susceptible cancer cells by engaging cognate death receptors. A recombinant soluble protein comprising the ectodomain of Apo2 ligand/TNF-related apoptosis-inducing ligand (Apo2L/TRAIL) has shown remarkable preclinical anticancer activity but lacked broad efficacy in patients, possibly owing to insufficient exposure or potency. We observed that antibody cross-linking substantially enhanced cytotoxicity of soluble Apo2L/TRAIL against diverse cancer cell lines. Presentation of the ligand on glass-supported lipid bilayers enhanced its ability to drive receptor microclustering and apoptotic signaling. Furthermore, covalent surface attachment of Apo2L/TRAIL onto liposomes--synthetic lipid-bilayer nanospheres--similarly augmented activity. In vivo, liposome-displayed Apo2L/TRAIL achieved markedly better exposure and antitumor activity. Thus, covalent synthetic-membrane attachment of a cell-surface ligand enhances efficacy, increasing therapeutic potential. These findings have translational implications for liposomal approaches as well as for Apo2L/TRAIL and other clinically relevant TNF ligands.

Synthesis and structures of cadmium carboxylate and thiocarboxylate compounds with a sulfur-rich coordination environment: carboxylate exchange kinetics involving tris(2-mercapto-1-t-butylimidazolyl)hydroborato cadmium complexes, [Tm(Bu(t))]Cd(O2CR).

A series of cadmium carboxylate compounds in a sulfur-rich environment provided by the tris(2-tert-butylmercaptoimidazolyl)hydroborato ligand, namely, [TmBut]CdO2CR, has been synthesized via the reactions of the cadmium methyl derivative [TmBut]CdMe with RCO2H. Such compounds mimic aspects of cadmium-substituted zinc enzymes and also the surface atoms of cadmium chalcogenide crystals, and have therefore been employed to model relevant ligand exchange processes. Significantly, both 1H and 19F NMR spectroscopy demonstrate that the exchange of carboxylate groups between [TmBut]Cd(κ2-O2CR) and the carboxylic acid RCO2H is facile on the NMR time scale, even at low temperature. Analysis of the rate of exchange as a function of concentration of RCO2H indicates that reaction occurs via an associative rather than dissociative pathway. In addition to carboxylate compounds, the thiocarboxylate derivative [TmBut]Cd[κ1-SC(O)Ph] has also been synthesized via the reaction of [TmBut]CdMe with thiobenzoic acid. The molecular structure of [TmBut]Cd[κ1-SC(O)Ph] has been determined by X-ray diffraction, and an interesting feature is that, in contrast to the carboxylate derivatives [TmBut]Cd(κ2-O2CR), the thiocarboxylate ligand binds in a κ1 manner via only the sulfur atom.

Optical and analytical investigations on dengue virus rapid diagnostic test for IgM antibody detection.

Evaluation of binding between analytes and its relevant ligands on surface plasmon resonance (SPR) biosensor is of considerable importance for accurate determination and screening of an interference in immunosensors. Dengue virus serotype 2 was used as a case study in this investigation. This research work compares and interprets the results obtained from analytical analysis with the experimental ones. Both the theoretical calculations and experimental results are verified with one sample from each category of dengue serotypes 2 (low, mid, and high positive), which have been examined in the database of established laboratorial diagnosis. In order to perform this investigation, the SPR angle variations are calculated, analyzed, and then validated via experimental SPR angle variations. Accordingly, the error ratios of 5.35, 6.54, and 3.72% were obtained for the low-, mid-, and high-positive-specific immune globulins of patient serums, respectively. In addition, the magnetic fields of the biosensor are numerically simulated to show the effect of different binding mediums.

Surface Enhanced Raman Spectroscopy of Organic Molecules on Magnetite (Fe3O4) Nanoparticles.

Surface-enhanced Raman spectroscopy (SERS) of species bound to environmentally relevant oxide nanoparticles is largely limited to organic molecules structurally related to catechol that facilitate a chemical enhancement of the Raman signal. Here, we report that magnetite (Fe3O4) nanoparticles provide a SERS signal from oxalic acid and cysteine via an electric field enhancement. Magnetite thus likely provides an oxide substrate for SERS study of any adsorbed organic molecule. This substrate combines benefits from both metal-based and chemical SERS by providing an oxide surface for studies of environmentally and catalytically relevant detailed chemical bonding information with fewer restrictions of molecular structure or binding mechanisms. Therefore, the magnetite-based SERS demonstrated here provides a new approach to establishing the surface interactions of environmentally relevant organic ligands and mineral surfaces.

Selectivity of odorant-binding proteins from the southern house mosquito tested against physiologically relevant ligands.

As opposed to humans, insects rely heavily on an acute olfactory system for survival and reproduction. Two major types of olfactory proteins, namely, odorant-binding proteins (OBPs) and odorant receptors (ORs), may contribute to the selectivity and sensitivity of the insects' olfactory system. Here, we aimed at addressing the question whether OBPs highly enriched in the antennae of the southern house mosquito, Culex quinquefasciatus, contribute at least in part to the selective reception of physiologically relevant compounds. Using a fluorescence reporter and a panel of 34 compounds, including oviposition attractants, human-derived attractants, and repellents, we measured binding affinities of CquiOBP1, CquiOBP2, and CquiOBP5. Based on dissociation constants, we surmised that CquiOBP2 is a carrier for the oviposition attractant skatole, whereas CquiOBP1 and CquiOBP5 might transport the oviposition pheromone MOP, a human-derived attractant nonanal, and the insect repellent picardin. Binding of these three ligands to CquiOBP1 was further analyzed by examining the influence of pH on apparent affinity as well as by docking these three ligands into CquiOBP1. Our findings suggest that CquiOBP1 might discriminate MOP from nonanal/picaridin on the basis of the midpoint transition of a pH-dependence conformational change, and that MOP is better accommodated in the binding cavity than the other two ligands. These findings, along with previous experimental evidence suggesting that CquiOBP1 does not detect nonanal in vivo, suggest that OBP selectivity may not be clearly manifested in their dissociation constants.

FARNESOID X RECEPTOR AND REPRODUCTION

Farnesoid X alpha receptors (FXRα or NR1H4) are present in male and female reproductive tissues. The aim of the present review is to describe those actions of the most relevant ligands of FXRα on reproduction and the interaction of this receptor with other nuclear receptors, for understanding the possible role of FXRα in reproductive events. Thus, although the relevance of the FXRα on reproduction is widely unknown, its endogenous ligands like farnesol, chenodeoxycholic acid (CDCA), and cholate acid (CA) participate in proliferation, apoptosis, differentiation, and steroidogenesis in reproductive tissues. In these tissues FXRα modulates estrogen and androgen actions. Since FXRα is stretched related to other nuclear receptors, also present in reproductive tissues, such as the liver X receptors (LXR), peroxisome proliferation-activated receptor (PPAR), liver receptors homolog-1 (LRH-1), small heterodimer partner (SHP), and dosage-sensitive sex reversal (DAX1), the FXRα actions on reproductive tissues might be directly or indirectly mediated by its interaction with these nuclear receptors.

Exploring the conformational variability in the heme b propionic acid side chains through the effect of a biological probe: a study of the isolated ions.

The iron(III) protoporphyrin IX complex with imidazole, a biologically relevant ligand, occupying an axial position, has been studied by infrared multiple photon dissociation (IRMPD) spectroscopy. The complex has been delivered in gas-phase by electrospray ionization (ESI), mass selected in an ion trap, and assayed by IRMPD spectroscopy in two complementary frequency regions. The fingerprint range (900-1900 cm(-1)) has been scanned using the Orsay free-electron laser beamline (CLIO), while the X-H (X = C,N,O) stretching region (3000-3600 cm(-1)) has been inspected using a tabletop IR optical parametric oscillator/amplifier (OPO/OPA) laser source. DFT calculations have been performed to obtain a comprehensive pattern of the various potential conformers yielding optimized geometries, relative thermodynamic parameters, and respective IR spectra. The comparison between the IR spectra for representative conformers and the experimental IRMPD features suggests the coexistence of two families of conformers involving different degrees of folding and hydrogen bonding between the two propionic acid functionalities on the periphery of the protoporphyrin IX macrocycle in a ratio depending on environmental conditions such as ESI solvent and temperature. The observed conformational variability of the porphyrin substituents in the naked heme-imidazole complex is consistent with the fine-tuning of the reactivity properties of this important prosthetic group by the specific surroundings in the protein core.

WW Domains of the Yes-Kinase-Associated-Protein (YAP) Transcriptional Regulator Behave as Independent Units with Different Binding Preferences for PPxY Motif-Containing Ligands

YAP is a WW domain-containing effector of the Hippo tumor suppressor pathway, and the object of heightened interest as a potent oncogene and stemness factor. YAP has two major isoforms that differ in the number of WW domains they harbor. Elucidating the degree of co-operation between these WW domains is important for a full understanding of the molecular function of YAP. We present here a detailed biophysical study of the structural stability and binding properties of the two YAP WW domains aimed at investigating the relationship between both domains in terms of structural stability and partner recognition. We have carried out a calorimetric study of the structural stability of the two YAP WW domains, both isolated and in a tandem configuration, and their interaction with a set of functionally relevant ligands derived from PTCH1 and LATS kinases. We find that the two YAP WW domains behave as independent units with different binding preferences, suggesting that the presence of the second WW domain might contribute to modulate target recognition between the two YAP isoforms. Analysis of structural models and phage-display studies indicate that electrostatic interactions play a critical role in binding specificity. Together, these results are relevant to understand of YAP function and open the door to the design of highly specific ligands of interest to delineate the functional role of each WW domain in YAP signaling.

Acute neuroinflammation in a clinically relevant focal cortical ischemic stroke model in rat: longitudinal positron emission tomography and immunofluorescent tracking.

Adequate estimation of neuroinflammatory processes following ischemic stroke is essential for better understanding of disease mechanisms, and for the development of treatment strategies. With the TSPO (18 kDa translocator protein) positron emission tomography (PET) radioligand [(11)C]PBR28, we monitored longitudinally the inflammatory response post-transient cerebral ischemia in rats, using a recently developed rat stroke model that produces isolated focal cortical infarcts with clinical relevance in size and pathophysiology. Six Sprague-Dawley rats were subjected to 90 min transient endovascular occlusion of the M2 segment of the middle cerebral artery (M2CAO). Animals were imaged with a nanoScan(®) PET/MRI system at 1, 4, 7 and 14 days after M2CAO with a bolus injection of [(11)C]PBR28. In the infarct region, we found a significantly increased uptake of [(11)C]PBR28 on day 4, 7 and 14 compared to day 1 as well as compared to the contralateral cortex. No significant increase was detected in the contralateral cortex during the 14 days of imaging. The activation in the infarct region gradually decreased between day 4 and day 14. In an additional group of animals (n = 26), immunofluorescence studies were performed with antibodies for activated microglia/monocytes (Cd11b), phagocytes (Cd68), astrocytes (glial fibrillary acidic protein) and TSPO. The TSPO immunofluorescence signal indicated reactive microgliosis post injury, corresponding to PET findings. The present clinically relevant animal model and TSPO PET ligand appear to be well suited for studies on neuroinflammation after ischemic stroke.

The Role of Cellular Mechanical Properties in Microenvironment-Dependent Behavior

Understanding the role of mechanics in cell behavior is necessary for effective development of tissue engineering therapies. This study observed how cellular mechanical phenotype influenced cell morphology and actin organization on substrates coated with different extracellular matrix ligands. Inherent cell stiffness, represented by Young's modulus, for MG-63 (osteosarcoma) and SH-SY5Y (neuroblastoma) cells was mechanically determined using atomic force microscopy. These cells have dissimilar moduli when probed over the nucleus (1.3±0.5 and 0.26±0.15 kPa for MG-63 and SH-SY5Y cells, respectively). To investigate the effect of substrate compliance, cells were cultured on polyacrylamide gels ranging from 0.3 to 12 kPa and functionalized with fibronectin, laminin, or collagen-1. We hypothesized that cells would spread and attach more successfully to substrates with an elastic modulus equal to or greater than that of the cell, provided physiologically relevant ligands are present. Cellular responses were captured daily over 4 days using fluorescent microscopy. MG-63 cells showed two different organizational phenotypes: a multi-cell, spheroid-like structure and a spread monolayer. The threshold substrate compliance required for MG-63 cells to organize into either phenotype was designated by the cells’ own stiffness, most clearly observed on collagen-1 coated gels. While SH-SY5Y cells exhibited similar phenotypic organizations when plated on varying substrates, no mechanical compliance threshold was observed. However, SH-SY5Y cells exhibited greater tendencies toward forming spheroids when plated on fibronectin. These morphological changes show a possible correlation between the cells’ characteristic mechanical phenotypes and their relationship to the microenvironment. Cells exhibiting less compliant phenotypes may have more substrate stiffness-dependent behavior, whereas more compliant cell types may have more ligand-dependent behavior. These findings indicate that cellular mechanosensing is influenced not only by the mechanical and biological characteristics of the microenvironment but also by the inherent mechanical phenotype of cells comprising a population.

Late Alk4/5/7 signaling is required for anterior skeletal patterning in sea urchin embryos.

Skeletal patterning in the sea urchin embryo requires a conversation between the skeletogenic primary mesenchyme cells (PMCs) and the overlying pattern-dictating ectoderm; however, our understanding of the molecular basis for this process remains incomplete. Here, we show that TGF-β-receptor signaling is required during gastrulation to pattern the anterior skeleton. To block TGF-β signaling, we used SB431542 (SB43), a specific inhibitor of the TGF-β type I receptor Alk4/5/7. Treatment with SB43 during gastrulation blocks anterior PMC positioning and the formation of the anterior skeleton, but does not perturb general ectoderm specification or development. This is the first example of a signaling event required for patterning of a specific part of the skeleton. Alk4/5/7 inhibition does not prevent the formation of a mouth, although SB43-treated plutei display reduced feeding ability, presumably due to the loss of the structural support for the mouth conferred by the anterior skeleton. Both Univin and Nodal are potential ligands for Alk4/5/7; however, Nodal is unilaterally expressed on only the right side, whereas Univin is bilaterally expressed in the ectoderm adjacent to the anterior skeleton during the relevant time period. Our results demonstrate that Univin is both necessary and sufficient for secondary skeletal development in a control background, consistent with the hypothesis that Univin is a relevant Alk4/5/7 ligand for anterior skeletal patterning. Taken together, our data demonstrate that Alk4/5/7 signaling during gastrulation is required to direct PMCs to the oral hood, and suggest that Univin is a relevant ligand for this signaling event.

Localization of Small Ligands in a Metabolic Protein Complex using Cryo-Electron Microscopy

Revolutionary advances in cryo-electron microscopy are rapidly driving the determination of structures of small protein complexes to near-atomic resolution. Automation of image acquisition together with streamlined image processing pipelines now offer the opportunity to localize the binding of ligands with low molecular weight to their target proteins using largely automated procedures that could be useful for pharmaceutical drug development. To test the practicality of this approach, we used automated procedures and advances with direct electron detectors to localize ADP (427 Da) and other small ligands on glutamate dehydrogenase, a clinically significant 365 kDa enzyme that is a relevant pharmaceutical target for cancer and diabetes.Data from 385 images from a single specimen in a single session recorded on a Falcon II detector using EPU data collection software provided enough information to localize ADP in the ligand-protein complex at ∼ 4.5 A resolution. The validity of the results was confirmed by comparison with the crystallographic coordinates of the GDH-ADP complex. Using these methods we were able to localize the binding site of other physiologically relevant ligands in different conformations of the enzyme. These methods thus provide a streamlined path to localize nucleotides and other low molecular weight.

Bias analyses of preclinical and clinical D2 dopamine ligands: studies with immediate and complex signaling pathways.

G protein-coupled receptors (GPCRs) often activate multiple signaling pathways, and ligands may evoke functional responses through individual pathways. These unique responses provide opportunities for biased or functionally selective ligands to preferentially modulate one signaling pathway over another. Studies with several GPCRs have suggested that selective activation of signaling pathways downstream of a GPCR may lead to safer and more effective drug therapies. The dopamine D2 receptor (D2R) is one of the main drug targets in the therapies for Parkinson's disease and schizophrenia. Recent studies suggest that selective modulation of individual signaling pathways downstream of the D2R may lead to safer antipsychotic drugs. In the present study, immediate effectors of the D2R (i.e., Gαi/o, Gβγ, β-arrestin recruitment) and more complex signaling pathways (i.e., extracellular signal-regulated kinase phosphorylation, heterologous sensitization, and dynamic mass redistribution) were examined in response to a series of D2R ligands. This was accomplished using Chinese hamster ovary cells stably expressing the human D2L dopamine receptor in the PathHunter β-Arrestin GPCR Assay Platform. The use of a uniform cellular background was designed to eliminate potential confounds associated with cell-to-cell variability, including expression levels of receptor as well as other components of signal transduction, including G protein subunits. Several well characterized and clinically relevant D2R ligands were evaluated across each signaling pathway in this cellular model. The most commonly used methods to measure ligand bias were compared. Functional selectivity analyses were also used as tools to explore the relative contribution of immediate D2R effectors for the activation of more complex signaling pathways.

Arteries are formed by vein-derived endothelial tip cells.

Tissue vascularization entails the formation of a blood vessel plexus, which remodels into arteries and veins. Here we show, by using time-lapse imaging of zebrafish fin regeneration and genetic lineage tracing of endothelial cells in the mouse retina, that vein-derived endothelial tip cells contribute to emerging arteries. Our movies uncover that arterial-fated tip cells change migration direction and migrate backwards within the expanding vascular plexus. This behaviour critically depends on chemokine receptor cxcr4a function. We show that the relevant Cxcr4a ligand Cxcl12a selectively accumulates in newly forming bone tissue even when ubiquitously overexpressed, pointing towards a tissue-intrinsic mode of chemokine gradient formation. Furthermore, we find that cxcr4a mutant cells can contribute to developing arteries when in association with wild-type cells, suggesting collective migration of endothelial cells. Together, our findings reveal specific cell migratory behaviours in the developing blood vessel plexus and uncover a conserved mode of artery formation.

Promiscuity and the conformational rearrangement of drug-like molecules: insight from the protein data bank.

Selectivity is a central aspect of lead optimization in the drug discovery process. Medicinal chemists often try to decrease molecular flexibility to improve selectivity, given the common belief that the two are interdependent. To investigate the relationship between polypharmacology and conformational flexibility, we mined the Protein Data Bank and constructed a dataset of pharmaceutically relevant ligands that crystallized in more than one protein target while binding to each co-crystallized receptor with similar in vitro affinities. After analyzing the molecular conformations of these 100 ligands, we found that 59 ligands bound to different protein targets without significantly changing conformation, suggesting that there is no distinct correlation between conformational flexibility and polypharmacology within our dataset. Ligands crystallized in similar proteins and highly ligand-efficient compounds with five or fewer rotatable bonds were less likely to adjust conformation when binding.

Aryl hydrocarbon receptor ligands in cancer: friend and foe.

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that is best known for mediating the toxicity and tumour-promoting properties of the carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin, commonly referred to as ‘dioxin’. AHR influences the major stages of tumorigenesis — initiation, promotion, progression and metastasis — and physiologically relevant AHR ligands are often formed during disease states or during heightened innate and adaptive immune responses. Interestingly, ligand specificity and affinity vary between rodents and humans. Studies of aggressive tumours and tumour cell lines show increased levels of AHR and constitutive localization of this receptor in the nucleus. This suggests that the AHR is chronically activated in tumours, thus facilitating tumour progression. This Review discusses the role of AHR in tumorigenesis and the potential for therapeutic modulation of its activity in tumours.

Gold nanoparticles functionalization notably decreases radiosensitization through hydroxyl radical production under ionizing radiation

The purpose of this work was to study the influence of gold nanoparticles (GNP) coating on hydroxyl radical (HO) production under ionizing radiation. Though radiosensitizing mechanisms are still unknown, radical oxygen species are likely to be involved, especially HO. We synthesized six different types of GNP, choosing relevant ligands such as polyethylene glycol or human serum albumin. A great attention was paid to characterize these GNP in terms of size, charge and number of atoms in the coating. Our results show that functionalization dramatically decreases HO production, which is correlated to reduced plasmidic DNA damages. These findings are of high importance as GNP translation from fundamental research to applied medicine requires their functionalization to increase blood circulation time and specific cancerous cells addressing. We suggest that to keep GNP efficient for radiotherapy, a wispy coating is required.

Interaction of Chromium(III) with a N,N′-Disubstituted Hydroxylamine-(diamido) Ligand: A Combined Experimental and Theoretical Study

Reaction of hydroxylamine hydrochloride with prop-2-enamide in dichloromethane in the presence of triethylamine resulted in the isolation of the N,N'-disubstituted hydroxylamine-(diamido) ligand, 3,3'-(hydroxyazanediyl)dipropanamide (Hhydia). The ligand Hhydia was characterized by multinuclear NMR, high-resolution electrospray ionization mass spectrometry (ESI-MS), and X-ray structure analysis. Interaction of Hhydia with trans-[Cr(III)Cl2(H2O)4]Cl·2H2O in ethanol yields the ionization isomers [Cr(III)(Hhydia)2]Cl3·2H2O(1·2H2O) and cis/trans-[Cr(III)Cl2(Hhydia)2]Cl·2H2O (2·2H2O). The X-ray structure analysis of 1 revealed that the chromium atom in [Cr(III)(Hhydia)2](3+) is bonded to two neutral tridentate O,N,O-Hhydia ligands. The twist angle, θ, in [Cr(III)(Hhydia)2](3+) is 54.5(6)(0), that is, very close to an ideal octahedron. The intramolecular hydrogen bonds developed between the N-OH group of the first ligand and the amidic oxygen atom of the second ligand and vice versa contribute to the overall stability of the cation [Cr(III)(Hhydia)2](3+). The reaction rate constant of the formation of Cr(III) complexes 1·2H2O and 2·2H2O was found to be 8.7(±0.8) × 10(-5) M(-1) s(-1) at 25 °C in methyl alcohol and follows a first-order law kinetics based on the biologically relevant ligand Hhydia. The reaction rate constant is considerably faster in comparison with the corresponding water exchange rate constant for the hydrated chromium(III). The modification of the kinetics is of fundamental importance for the chromium(III) chemistry in biological systems. Ultraviolet-visible and electron paramagnetic resonance studies, both in solution and in the solid state, ESI-MS, and conductivity measurements support the fact that, irrespective of the solvent used in the interaction of Hhydia with trans-[Cr(III)Cl2(H2O)4]Cl·2H2O, the ionization isomers[Cr(III)(Hhydia)2]Cl3·2H2O (1·2H2O) and cis/trans-[Cr(III)Cl2(Hhydia)2]Cl·2H2O (2·2H2O) are produced.The reaction medium affects only the relevant percentage of the isomers in the solid state. The thermodynamic stability of the ionization isomers 1·2H2O and cis/trans-2·2H2O, their molecular structures as well as the vibrational spectra and the energetics of the Cr(III)- Hhydia/hydia(-) were studied by means of density functional theory calculations and found to be in excellent agreement with our experimental observations.

Synthesis, DNA binding and complex formation reactions of 3-amino-5,6-dimethyl-1,2,4-triazine with Pd(II) and some selected biorelevant ligands

With the purpose of studying the binding behavior of Pd(II) complexes with DNA as the main biological target, and their ability to penetrate reasonably into tumour cells and destroy their replication ability, Pd(ADT)Cl2 complex was synthesized and characterized, where ADT is 3-amino-5,6-dimethyl-1,2,4-triazine. Stoichiometry and stability constants of the complexes formed between various biologically relevant ligands (amino acids, amides, DNA constituents, and dicarboxylic acids) and [Pd(ADT)(H2O)2]2+ were investigated at 25°C and at constant 0.1moldm−3 ionic strength. The concentration distribution diagrams of the various species formed are evaluated. Further investigation of the binding properties of the diaqua complex [Pd(ADT)(H2O)2]2+ with calf thymus DNA (CT-DNA) was investigated by UV–vis spectroscopy. The intrinsic binding constants (Kb) calculated from UV–vis absorption studies was calculated to be 2.00×103moldm−3. The calculated (Kb) value was found to be of lower magnitude than that of the classical intercalator EB (Ethidium bromide) (Kb=1.23(±0.07)×105moldm−3) suggesting an electrostatic and/or groove binding mode for the interaction with CT-DNA. Thermal denaturation has been systematically studied by spectrophotometric method and the calculated ΔTm was nearly 5°C, supporting the electrostatic and/or groove binding mode for the interaction between the complex and CT-DNA

457P - A First-In-Human Study Evaluating the Safety and Pharmacology of Mm-151, a Novel Oligoclonal Anti-Egfr Antibody Combination in Patients with Refractory Solid Tumors

ABSTRACT Aim: MM-151 is an oligoclonal combination of three IgG1, anti-EGFR antibodies designed to bind distinct non-overlapping EGFR epitopes and inhibit ligand-mediated signal amplification. MM-151's molecular composition enables antagonism of clinically relevant EGFR ligand mixtures, EGFR down-regulation and immune effector function (ADCC, CDC). A Phase 1 study was initiated to assess the safety, tolerability, PK, immunogenicity and preliminary clinical activity of MM-151. Methods: 69 patients were enrolled on 3 schedules (QW, Q2W, and Q3W) at escalating doses using standard 3 + 3 design. Response was assessed per RECIST criteria every 8 weeks. Patients continued on study until disease progression or unacceptable toxicity. Results: Results presented are based on preliminary data as of Apr. 25, 2014. 69 patients (median age 63 years; 33 male, 36 female) have been enrolled across 3 dosing schedules. 69 patients were evaluable for safety and 46 evaluable for efficacy. The most common tumor types were CRC (28 [41%]), NSCLC (9 [13%]), SCCHN (5 [7%]), and pancreatic (5 [7%]). An MTD has not been reached and dose escalation continues. Most adverse events were CTCAE grades 1 and 2. Infusion related reaction (IRR) was the most common AE (47 [68.1%]); however, this was managed with premedication and an optimized infusion schedule. The most common non-IRR AEs were comprised of EGFR-pathway toxicities, including rash (54 [78%]), hypomagnesemia (17 [25%]), mucositis (8 [12%]) and diarrhea (15 [22%]). Initial biomarker data in a subset of patients suggest that IRR relates to engagement of the innate immune system, shown in pre- and post - dose cytokine and peripheral blood flow cytometry data. Partial responses were observed in 2 CRC patients and a total of 8 (29% of mCRC) patients had SD for > 4 months (2 of the 8 had SD for 20.1 and 19.8 months). At doses > 9 mg/kg QW, trough total antibody levels at steady state were in expected therapeutic range. Conclusions: Results to date show that MM-151 has an acceptable safety profile and objective clinical activity in CRC. Updated safety, efficacy and preliminary biomarker data will be presented. Disclosure: C. Lieu: Consultant for Sanofi Aventis; L. Power, C. Sloss, J. Kearns, R. Nering, V. Moyo and B. Wolf: employee of Merrimack Pharmaceuticals, stock ownership. All other authors have declared no conflicts of interest.