Development of a novel antibody to calcitonin gene-related peptide for the treatment of osteoarthritis-related pain

OBJECTIVE

Investigate a role for calcitonin gene-related peptide (CGRP) in osteoarthritis (OA)-related pain.

DESIGN

Neutralizing antibodies to CGRP were generated de novo. One of these antibodies, LY2951742, was characterized in vitro and tested in pre-clinical in vivo models of OA pain.

RESULTS

LY2951742 exhibited high affinity to both human and rat CGRP (KD of 31 and 246 pM, respectively). The antibody neutralized CGRP-mediated induction of cAMP in SK-N-MC cells in vitro and capsaicin-induced dermal blood flow in the rat. Neutralization of CGRP significantly reduced pain behavior as measured by weight bearing differential in the rat monoiodoacetate model of OA pain in a dose-dependent manner. Moreover, pain reduction with neutralization of CGRP occurred independently of prostaglandins, since LY2951742 and NSAIDs worked additively in the NSAID-responsive version of the model and CGRP neutralization remained effective in the NSAID non-responsive version of the model. Neutralization of CGRP also provided dose-dependent and prolonged (>60 days) pain reduction in the rat meniscal tear model of OA after only a single injection of LY2951742.

CONCLUSIONS

LY2951742 is a high affinity, neutralizing antibody to CGRP. Neutralization of CGRP is efficacious in several OA pain models and works independently of NSAID mechanisms of action. LY2951742 holds promise for the treatment of pain in OA patients.

A global benchmark study using affinity-based biosensors

To explore the variability in biosensor studies, 150 participants from 20 countries were given the same protein samples and asked to determine kinetic rate constants for the interaction. We chose a protein system that was amenable to analysis using different biosensor platforms as well as by users of different expertise levels. The two proteins (a 50-kDa Fab and a 60-kDa glutathione S-transferase [GST] antigen) form a relatively high-affinity complex, so participants needed to optimize several experimental parameters, including ligand immobilization and regeneration conditions as well as analyte concentrations and injection/dissociation times. Although most participants collected binding responses that could be fit to yield kinetic parameters, the quality of a few data sets could have been improved by optimizing the assay design. Once these outliers were removed, the average reported affinity across the remaining panel of participants was 620 pM with a standard deviation of 980 pM. These results demonstrate that when this biosensor assay was designed and executed appropriately, the reported rate constants were consistent, and independent of which protein was immobilized and which biosensor was used.

Kinetic exclusion assay technology: characterization of molecular interactions

Characterization of intermolecular interactions in terms of affinity, binding kinetics, stoichiometry, specificity, and thermodynamics can facilitate the selection of lead compounds in the discovery and development of protein therapeutics. KinExA (Sapidyne Instruments, Inc., Boise, ID) is a relatively new technology that is gaining use in characterizing molecular interactions, particularly with respect to antibody therapeutics. KinExA offers a platform that allows the measurement of true equilibrium binding affinity and kinetics using unmodified molecules in solution phase. This is accomplished by using a solid-phase immobilized molecule to probe for free concentration of one interaction component after allowing sufficient time to reach equilibrium (affinity measurements), or under pre-equilibrium conditions (kinetics). In this review, the theory behind KinExA technology is discussed, and examples of applying this technology to antibody characterization are provided. Finally, a comparison among KinExA, Biacore (surface plasmon resonance), and isothermal titration calorimetry is presented, and potential future improvements and applications of KinExA are discussed.

Comparative analyses of a small molecule/enzyme interaction by multiple users of Biacore technology

To gauge the experimental variability associated with Biacore analysis, 36 different investigators analyzed a small molecule/enzyme interaction under similar conditions. Acetazolamide (222 g/mol) binding to carbonic anhydrase II (CAII; 30000 Da) was chosen as a model system. Both reagents were stable and their interaction posed a challenge to measure because of the low molecular weight of the analyte and the fast association rate constant. Each investigator created three different density surfaces of CAII and analyzed an identical dilution series of acetazolamide (ranging from 4.1 to 1000 nM). The greatest variability in the results was observed during the enzyme immobilization step since each investigator provided their own surface activating reagents. Variability in the quality of the acetazolamide binding responses was likely a product of how well the investigators' instruments had been maintained. To determine the reaction kinetics, the responses from the different density surfaces were fit globally to a 1:1 interaction model that included a term for mass transport. The averaged association and dissociation rate constants were 3.1+/-1.6 x 10(6)M(-1)s(-1) and 6.7+/-2.5 x 10(-2)s(-1), respectively, which corresponded to an average equilibrium dissociation constant (K(D) of 2.6+/-1.4 x 10(-8)M. The results provide a benchmark of variability in interpreting binding constants from the biosensor and highlight keys areas that should be considered when analyzing small molecule interactions.

Glycosylation of erythropoietin affects receptor binding kinetics: role of electrostatic interactions

Erythropoietin (EPO) is a cytokine produced by the kidney whose function is to stimulate red blood cell production in the bone marrow. Previously, it was shown that the affinity of EPO for its receptor, EPOR, is inversely related to the sialylation of EPO carbohydrate. To better understand the properties of EPO that modulate its receptor affinity, various glycoforms were analyzed using surface plasmon resonance. The system used has been well characterized and is based on previous reports employing an EPOR-Fc chimera captured on a Protein A surface. Using three variants of EPO containing different levels of sialylation, we determined that sialic acid decreased the association rate constant (k(on)) about 3-fold. Furthermore, glycosylated EPO had a 20-fold slower k(on) than nonglycosylated EPO, indicating that the core carbohydrate also negatively impacted k(on). The effect of electrostatic forces on EPO binding was studied by measuring binding kinetics in varying NaCl concentrations. Increasing NaCl concentration resulted in a slower k(on) while having little impact on k(off), suggesting that long-range electrostatic interactions are primarily important in determining the rate of association between EPO and EPOR. Furthermore, the glycosylation content (i.e., nonglycosylated vs glycosylated, sialylated vs desialylated) affected the overall sensitivities of k(on) to [NaCl], indicating that sialic acid and the glycan itself each impact the overall effect of these electrostatic forces.

Nature vs. nurture: two brothers with schizophrenia

TOPIC

The nature vs. nurture argument as it pertains to two brothers.

PURPOSE

To explore the synergistic effects of heritability and environment in the cases of two brothers with schizophrenia.

SOURCES

Review of the literature and the authors' clinical experience.

CONCLUSIONS

The nature vs. nurture dichotomy may not be as relevant as looking at the interaction between these two forces.

Functional contributions of noncysteine residues within the cystine knots of human chorionic gonadotropin subunits

Human chorionic gonadotropin (hCG) is a heterodimeric member of a family of cystine knot-containing proteins that contain the consensus sequences Cys-X(1)-Gly-X(2)-Cys and Cys-X(3)-Cys. Previously, we characterized the contributions that cystine residues of the hCG subunit cystine knots make in folding, assembly, and bioactivity. Here, we determined the contributions that noncysteine residues make in hCG folding, secretion, and assembly. When the X(1), X(2), and X(3) residues of hCG-alpha and -beta were substituted by swapping their respective cystine knot motifs, the resulting chimeras appeared to fold correctly and were efficiently secreted. However, assembly of the chimeras with their wild type partner was almost completely abrogated. No single amino acid substitution completely accounted for the assembly inhibition, although the X(2) residue made the greatest individual contribution. Analysis by tryptic mapping, high performance liquid chromatography, and SDS-polyacrylamide gel electrophoresis revealed that substitution of the central Gly in the Cys-X(1)-Gly-X(2)-Cys sequence of either the alpha- or beta-subunit cystine knot resulted in non-native disulfide bond formation and subunit misfolding. This occurred even when the most conservative change possible (Gly --> Ala) was made. From these studies we conclude that all three "X" residues within the hCG cystine knots are collectively, but not individually, required for the formation of assembly-competent hCG subunits and that the invariant Gly residue is required for efficient cystine knot formation and subunit folding.

Intracellular folding pathway of the cystine knot-containing glycoprotein hormone alpha-subunit

Three of the five disulfide bonds in the glycoprotein hormone alpha-subunit (GPH-alpha) form a cystine knot motif that stabilizes a three-loop antiparallel structure. Previously, we described a mutant (alpha(k)) that contained only the three knot disulfide bonds and demonstrated that the cystine knot was necessary and sufficient for efficient GPH-alpha folding and secretion. In this study, we used alpha(k) as a model to study the intracellular GPH-alpha folding pathway. Cystine knot formation proceeded through a 1-disulfide intermediate that contained the 28-82 disulfide bond. Formation of disulfide bond 10-60, then disulfide bond 32-84, followed the formation of 28-82. Whether the two non-cystine knot bonds 7-31 and 59-87 could form independent of the knot was also tested. Disulfide bond 7-31 formed rapidly, whereas 59-87 did not form when all cysteine residues of the cystine knot were converted to alanine, suggesting that 7-31 forms early in the folding pathway and that 59-87 forms during or after cystine knot formation. Finally, loop 2 of GPH-alpha has been shown to be very flexible, suggesting that loop 2 does not actively drive GPH-alpha folding. To test this, we replaced residues 36-55 in the flexible loop 2 with an artificially flexible glycine chain. Consistent with our hypothesis, folding and secretion were unaffected when loop 2 was replaced with the glycine chain. Based on these findings, we describe a model for the intracellular folding pathway of GPH-alpha and discuss how these findings may provide insight into the folding mechanisms of other cystine knot-containing proteins.

Autonomic nervous system evaluation of patients with vasomotor rhinitis

OBJECTIVE

To demonstrate the utility of quantitative neurological laboratory testing of autonomic nervous system dysfunction and to apply this methodology to further study the relation of chronic vasomotor (nonallergic) rhinitis to the autonomic nervous system.

METHODS

It has been suspected that vasomotor rhinitis is due either to a hyperactive parasympathetic nervous system or an imbalance between it and the sympathetic nervous system. The exact relation has not been determined. Recently neurological laboratories have been developed in which a battery of tests can be performed to determine reactivity of the autonomic nervous system.

RESULTS

Autonomic nervous system testing was performed on 19 patients with symptoms fulfilling the diagnostic criteria for vasomotor rhinitis and the results were compared with 75 sex- and age-matched control subjects. Patients with vasomotor rhinitis had significant abnormalities of their sudomotor, cardiovagal, and adrenergic subscores. Their composite autonomic scale score was significantly impaired at 2.43, as compared with 0.11 for controls (P < .005).

CONCLUSION

Autonomic nervous system dysfunction is significant in patients with vasomotor rhinitis. Possible factors that trigger this dysfunction including nasal trauma and extraesophageal manifestations of gastroesophageal reflux are discussed.

Cystine knot mutations affect the folding of the glycoprotein hormone alpha-subunit. Differential secretion and assembly of partially folded intermediates

The common glycoprotein hormone alpha-subunit (GPH-alpha) contains five intramolecular disulfide bonds, three of which form a cystine knot motif (10-60, 28-82, and 32-84). By converting each pair of cysteine residues of a given disulfide bond to alanine, we have studied the role of individual disulfide bonds in GPH-alpha folding and have related folding ability to secretion and assembly with the human chorionic gonadotropin beta-subunit (hCG-beta). Mutation of non-cystine knot disulfide bond 7-31, bond 59-87, or both (leaving only the cystine knot) resulted in an efficiently secreted folding form that was indistinguishable from wild type. Conversely, the cystine knot mutants were inefficiently secreted (<25%). Furthermore, mutation of the cystine knot disulfide bonds resulted in multiple folding intermediates containing 1, 2, or 4 disulfide bonds. High performance liquid chromatographic separation of intracellular and secreted forms of the folding intermediates demonstrated that the most folded forms were preferentially secreted and combined with hCG-beta. From these studies we conclude that: (i) the cystine knot of GPH-alpha is necessary and sufficient for folding and (ii) there is a direct correlation between the extent of GPH-alpha folding, its ability to be secreted, and its ability to heterodimerize with hCG-beta.