704 The computationally designed human antibody, AU-007, mediates human immune activation by endogenous IL-2, while uniquely breaking the IL-2 auto-inhibitory loop and preventing Treg expansion

Background

IL-2 binds two forms of IL-2 receptor: a high affinity trimeric receptor composed of CD25, CD122, and CD132, and a low affinity dimeric receptor composed of CD122 and CD132. Binding to the dimeric receptors, expressed on effector cells, causes expansion of the effector arm of the immune system including CD8 T-cells, NK-cells and NKT-cells. Binding to the trimeric receptor, expressed on Tregs as well as on pulmonary and vascular epithelium, results in expansion of Treg cells and Vascular Leak Syndrome, both are undesired outcomes of high-dose recombinant IL-2 (Aldesleukin), approved for treatment of Melanoma and Renal-Cell-Carcinoma.

Methods

Flow-cytometry analysis of immune-cell populations of C57BL/6 mice and hPBMCs. Tumor-Growth-Index of murine cancer models.

Results

AU-007, is a computationally designed human antibody that bind the CD25-binding portion on IL-2, preventing binding of IL-2 to the trimeric receptor, but not the dimeric receptor. This leads to immune effector activation while also preventing the Treg expansion via the autoinhibitory loop caused by endogenous IL-2 secreted from activated T effector cells (figure 1). AU-007 binds human IL-2 with picomolar affinity and has excellent biophysical properties with low potential for anti-drug immunogenicity (figure 2). Administration of an AU-007/low dose hIL-2 complex to non-tumor bearing C57BL/6 mice promoted proliferation of effector cells with no effect on Tregs (figure 3). Additionally, an AU-007/low dose hIL-2 complex was highly effective in inhibiting tumor progression in a syngeneic B16F10 melanoma model (figure 4). pSTAT5 analysis of hPBMCs incubated with AU-007 and hIL-2 demonstrated activation of the effector cells and inhibition of Tregs expansion (figure 5). hPBMCs activated with anti-CD3/anti-CD28 and treated with either AU-007 or an isotype control antibody but without exogenous IL-2, showed expansion of effector cells. However, while the isotype control antibody expanded also Tregs , AU-007 inhibited Tregs proliferation, indicating that AU-007 captures endogenous IL-2 and prevents the Treg expansion autoinhibitory loop caused by endogenous IL-2 secreted from activated T effector cells (figure 6).Additionally, following establishment of the IL-2 auto-secretion feedback loop in mice genetically engineered to express hIL-2 instead of murine IL-2, AU-007 treatment significantly inhibited MC38 colorectal-tumor growth for twelve days, in a manner comparable to treatment with anti-PD1 (figure 7).

Conclusions

AU-007 is a human antibody that blocks the CD25-binding epitope on IL-2. It redirects endogenous IL-2 to promote effector cell expansion while simultaneously blocking the Treg expansion autoinhibitory loop, indicating its unique therapeutic profile and high potential as a novel cancer treatment. AU-007 is expected to enter clinical testing in 2021.

Abstract 704 Figure 1

Schematic representation of IL-2 mechanism of action and its dual role in controlling immune response. IL-2 structure consists of three binding epitope sites that interact with different forms of IL-2-R complexes with different affinities (Left Panel). IL-2R complexes expressed on different cell populations and their different affinities to IL-2 allow immunosuppression under conditions of low local concentrations of IL-2 and immune stimulation when IL-2 local concentration rises (middle panel). Au-007 utilize autocrine human IL-2 MOA to promote immune stimulation. Targeting IL-2 to different cell populations can be used to modulate the immune response toward towards immune activation. An anti-human IL-2 antibody tumor clearance while reducing IL-2's undesired interactions with endothelial CD25 expressing cells preventing IL-2 induced pulmonary edema and vascular leaking.

Abstract 704 Figure 2

Au-007 bind human IL-2 with high affinity and inhibits the binding to CD25 while preserving the binding to CD122. Affinity and binding site are demonstrated using Surface Plasmon Resonance. Au-007 was captured on CM5 chip and soluble hIL-2 was injected, forming a complex. Subsequently, soluble CD25 was injected followed by injection of soluble CD122 (A). SPR trace of complex formation of Ab/IL-2/IL-2R arrows indicate where Au-007 (17.069), hIL-2, CD25 and CD122 were injected (B). SPR trace and calculated binding kinetics of chip bound Au-007 with hIL-2 serving as analyte (C). Biophysical profile of Au-007. Au-007 was subjected to five freeze thaw cycles, agitation for 3 days and incubation at 40°C for 1 week. Post treatment Au-007 integrity and indicated biophysical properties were measured (D).

Abstract 704 Figure 3

Au-007 demonstrated in-vivo potent immune stimulating effects in a dose depended manner, with no observed effect on Tregs. C57BL/6 healthy mice were administered daily with Au-007/hIL-2 complex for four days. On day five splenocytes were isolated and immune cells populations were analyzed using flow cytometry. (A) Dosing regimen outline. (B–E) Mean values of immune cells calculated as a percentage from parent population of each experimental group (n=6 per group)

Abstract 704 Figure 4

Au-007 inhibits tumor growth in an I/O resistant tumor model with a tolerable profile. C57BL/6 healthy mice were inoculated with B16F10 melanoma tumor cells (day 0), at day 5 mice were randomized to experimental groups (n=10 per group) and administered daily, with single injection per day of Ab/hIL-2 mix (20 ug/1 ug respectively) or with PBS for four days. From the end of schedule administration at day 8 until experiment endpoint, mice were monitored daily for tumor volume (A) and for mean percent of body weight change for each experimental group (B).

Abstract 704 Figure 5

AU-007 inhibits the effect of IL-2 on Tregs while preserving its effect on Teffs and NKs. (A and B) Phosphorylated STAT5 levels of human immune cell subsets responding to various concentrations of hIL-2 with and without 200 nM AU-007. Total naïve hPBMC culture were incubated with increasing doses of hIL-2 or with increasing doses of hIL-2 + 200nM AU-007 for 15 min. Immune cells subpopulations were analyzed by flow cytometry, gating was defined based on FMOs. (C–F) Phosphorylated STAT5 levels of human immune cell subsets responding to titrated AU-007 or isotype control. Total naïve hPBMC culture were incubated with hIL-2 and with increasing doses of indicated antibody for 15 min. Data presented is an average of 3 biological repeats from 3 human PBMC donors.

Abstract 704 Figure 6

Au-007 can rely on endogenous IL-2 to break auto-inhibitory loop in human PBMCs. Total hPBMCs were stimulated for 24h with anti-CD3/anti-CD28 (stimulation only, green) or stimulated with anti-CD3/anti-CD28 in the presence of: 200 nM of Au-007 mAb (red) or with 200 nM of isotype control mAb (blue). No exogenous IL-2 was added. Immune cells subpopulations were analyzed by flow cytometry. Percentage of immune cell sub-populations demonstrate exclusive inhibition of Tregs (A–E). Au-007 downregulate the suppressive markers of CD4+ regulatory Tregs from panel A, as defined by significant reduction in MFI of CD25 and FoxP3 (F and G). Gating was defined based on FMOs. Data presented is an average of 3 biological repeats from 3 human PBMC donors.

Abstract 704 Figure 7

Au-007 captures endogenous hIL-2 and inhibits tumor growth in colorectal cancer model (MC38). Genetically modified C57BL/6 mice, engineered to express human IL-2 in the background of complete knock-out of mouse IL-2, were inoculated with MC38 colorectal tumor cells. All animals treated with Au-007 showed significant inhibition in tumor growth with no observed significant adverse effects. (A) Administration outline: PBS (black), anti-mouse-PD-1 antibody (yellow), Au-007 pre-complexed with low dose IL-2 (blue) and Au-007 alone every three days followed with a single immune kick start with IL-2 (green, IL-2 single dose is marked in red). (B) Tumor growth progression of the four groups treated. (C) Percent of body weight changes per treatment.

Vedolizumab Immunogenicity With Long-Term or Interrupted Treatment of Patients With Inflammatory Bowel Disease

Patients in the GEMINI 1 or 2 study (NCT00790933; Eudra CT2008‐002784‐14) with ulcerative colitis or Crohn disease had low immunogenicity rates after vedolizumab treatment for up to 52 weeks. We report immunogenicity rates from the GEMINI long‐term safety (LTS) study using a new drug‐tolerant electrochemiluminescence assay, including analyses in patients who received continuous vedolizumab induction and maintenance in GEMINI 1 or 2 and long term safety, or vedolizumab induction and placebo maintenance in GEMINI 1 or 2 followed by re‐treatment in long term safety (treatment interruption). Patients were enrolled in GEMINI long term safety from GEMINI 1, 2, or 3, or as de novo vedolizumab‐treated patients; all received vedolizumab 300 mg intravenously every 4 weeks. Vedolizumab antidrug antibody (ADA) status was determined by electrochemiluminescence assay; ADA‐positive samples were characterized by neutralizing activity. Vedolizumab ADA data were available for 1753 patients: 1513 continuously treated with vedolizumab before/during GEMINI long term safety, 240 re‐treated after treatment interruption. Among continuously treated patients, 36 (2.4%) were ADA positive (15 persistently, 20 neutralizing ADA positive). Among re‐treated patients, 53 (22.1%) were ADA positive (42 persistently, 40 neutralizing ADA positive). Longitudinal immunogenicity rates increased during placebo maintenance (19.4% at week 52), then decreased in GEMINI long term safety to rates (0 at the final visit) similar to continuously treated patients. ADA positivity was 1.1% vs 2.5% (continuous treatment) and 23.1% vs 22.0% (re‐treatment) among patients with and without infusion‐related reactions, respectively. Long‐term vedolizumab treatment was associated with generally low immunogenicity rates; vedolizumab–re‐treated patients had higher rates during placebo maintenance, which decreased during re‐treatment. No relationship was observed between immunogenicity and infusion‐related reactions.

Comparison of the ELISA and ECL Assay for Vedolizumab Anti-drug Antibodies: Assessing the Impact on Pharmacokinetics and Safety Outcomes of the Phase 3 GEMINI Trials

Vedolizumab immunogenicity has been assessed using an enzyme-linked immunosorbent assay (ELISA) with a ~ 0.5 μg/mL drug interference, which may underestimate on-drug immunogenicity. We aimed to compare immunogenicity results between ELISA and the new drug-tolerant electrochemiluminescence (ECL) assay (and the two versions of neutralizing assays, drug-sensitive versus drug-tolerant). The ECL assay drug tolerance is ~ 100 times higher than that of the ELISA (≥ 50 μg/mL vs. 0.5 μg/mL with a 500 ng/mL positive control), and assay sensitivity is < 5 ng/mL for both assays. Vedolizumab immunogenicity was assessed in 2000 GEMINI 1 and 2 patients originally tested by ELISA and retested by ECL assay. Anti-drug antibody (ADA) impact on infusion-related reactions and pharmacokinetics (PK) was examined using descriptive statistics and population PK analyses. By ECL assay, 6% (86/1427) of patients treated with vedolizumab as induction and maintenance therapy tested ADA-positive. Of these, 20 patients were persistently positive and 56 had neutralizing antibodies. By ELISA, 4% (56/1434) of these patients were ADA-positive, 9 were persistently positive, and 33 had neutralizing antibodies. Among 61 patients with infusion-related reactions, 6 (10%) were ADA-positive (2 persistently positive) by ECL assay. By ELISA, 3 (5%) patients were both ADA-positive and persistently positive. Most results (96%) were similar with both assays. In the updated population PK model, ADA-positive status was estimated to increase vedolizumab linear clearance by a factor of 1.10 (95% credible interval 1.03-1.17), which is consistent with previous reports. The impact of ADA on safety and PK modeling remained generally consistent using either ELISA or ECL assay. ClinicalTrials.gov: NCT00783718 and NCT00783692.

Characterization of BDG8: An antibody-human IL-2 complex that selectively activates the effector arm of the immune system

e15004

Background: Interleukin 2 is a 15.4 kDa type I cytokine of the four helix bundle structure. IL-2 signaling has two opposite effects, it can enhance immune response by activation of effector cells and regulate immune response by activation proliferation of regulatory T cells (Tregs). IL-2 mediates its effect by binding to two forms of IL-2 receptor: i) trimeric receptors made of IL-2Rα (CD25), IL-2Rβ (CD122), and a common IL-2Rγ (γc, CD132) chains or ii) a dimeric receptor of only the IL-2Rβ and IL-2Rγ subunits. In Tregs, activation of the trimeric receptor is associated with FoxP3 mediated transcription leading to the production of suppression factors. Tregs express higher levels of the αβγ trimeric IL-2 receptor than effector cells. However binding of IL-2 to the βγ dimer is associated with activation of effector cells expressing relatively high levels of the βγ dimer and express low levels of trimer. High dose IL-2 therapy is used in melanoma and metastatic renal cell carcinoma with response rates 10%-15%. While efficacious, this approach has several disadvantages: 1) IL-2 dependent adverse effects such as Vascular Leak Syndrome (VLS) excluding many patients from being considered 2) The short half-life of IL-2 requires frequent administration, resulting in repeated spikes in the level of circulating IL-2. 3) Administered IL-2 is not selective and enhances a non-desired activation of Tregs. Methods: Antibodies were computational designed to bind to a specific epitope on Il-2 allowing for the binding to the CD122/CD132 complex and exclude the CD122/CD132/CD25 complex. Results: Here we show that we specifically designed and tested a humanized antibody (BD8) that: i) binds tightly the human IL-2 (hIL-2) and ii) the antibody- hIL-2 complex preferentially to bind the IL-2Rβ sub-unit and blocks the IL-2Rα subunit. We show administering the BD8 Ab-IL-2 complex to C57BL/6 mice has a profound effect on activation of MP CD8+, NK and NKT effector cells with minimal effect on Tregs. In mice the antibody-hIL-2 complex serum half -life is much longer then the half-life of hIL-2. In the B16-F10 Melanoma model, BD8-hIL2 resulted in robust effect compared to hIL-2 alone. Conclusions: BD8 is a computationally designed antibody specifically binds to IL-2 inducing the activation of effector cells without stimulating Tregs and demonstrates efficacy in animal cancer models.

Novel tetravalent bispecific T-cell engaging antibodies for cancer immunotherapy

e12513

Background: Current immunotherapy involves redirection of T cells against tumor either by chimeric antigen receptors (CAR-T) or bispecific T-cell engagers (BiTEs). These T cell-engaging technologies have been enabled by engineering single-chain variable fragment (scFv). Most BiTEs are designed as heterodimers, with monovalent binding to tumor cell surface antigens and to CD3+ T cells. Here, we describe a novel tetravalent bispecific (TetraBi) platform: a tumor associated antigen specific, T-cell engaging antibody that provides significant advantages over traditional BiTEs. Specifically, we showcase three unique TetraBi antibodies targeted for various cancers. Methods: ABP-100 was engineered by fusing CD3-binding scFv to the c-terminus of anti-HER2 IgG1 light chain, resulting in two binding sites each for HER2 and CD3. In preclinical studies, ABP-100 was compared with a clinical-stage heterodimeric antibody that is monovalent for HER2 and CD3. We also built TetraBi for anti-Glypican 3 (GPC3, ABP-110) and Claudin 18.2 (CLDN18.2, ABP-150) for gastric cancer therapy. Results: We observed bivalent binding to the tumor antigens (HER2, GPC3, CLDN18.2) on tumor cells like the monoclonal antibodies do. Interestingly, the CD3-binding domains in our TetraBi format showed functionally monovalent binding to CD3. ABP-100 displayed comparable cytokine release to the heterodimer molecule both in vitro and in vivo. In HER2+ cancer models, ABP-100 showed highly potent antitumor activity, resulting in complete responses in tumor bearing mice at doses as low as 0.1 mg/kg with no evidence of tumor relapse. ABP110 and ABP-150 also demonstrated potent cancer cell killing in vitro. Conclusions: This novel TetraBi antibody format enables concurrent bivalent and monovalent co-engagement of distinct target antigens in tumor microenvironment with promising therapeutic implications. Furthermore, it provides a potentially larger therapeutic index than more traditional bispecific formats that feature monovalent recognition of tumor antigens.

Consistent expression of guanylyl cyclase-C in primary and metastatic gastrointestinal cancers

BACKGROUND

The transmembrane receptor guanylate cyclase-C (GCC) has been found to be expressed in colorectal cancers. However, limited data are available on GCC protein expression in non-colorectal gastrointestinal tumors and few studies have reported whether GCC protein expression was consistently preserved in synchronous primary and metastatic cancer tissues.

METHODS

GCC protein status was assessed by immunohistochemistry in tumor specimens from individuals (n = 627) with gastrointestinal tumors, including esophageal (n = 130), gastric (n = 276), pancreatic (n = 136), and colorectal (n = 85) primary and metastatic tumors. Tissue specimens consisted of tissue microarrays containing esophageal, gastric, pancreatic tumors, and whole-slide tissue sections from colorectal cancer patients with matching primary and metastatic tumors.

RESULT

Among the evaluated esophageal, gastric, and pancreatic tumors, the frequency of GCC positivity at the protein level ranged from 59% to 68%. GCC was consistently expressed in primary and matched/synchronous metastatic lesions of colorectal cancer tissues derived from the same patients.

CONCLUSION

This observational study demonstrated the protein expression of GCC across various gastrointestinal malignancies. In all cancer histotypes, GCC protein localization was observed predominantly in the cytoplasm compared to the membrane region of tumor cells. Consistent immunohistochemistry detection of GCC protein expression in primary colorectal cancers and in their matched liver metastases suggests that the expression of GCC is maintained throughout the process of tumor progression and formation of metastatic disease.

Phase 1 trial of CA-170, a novel oral small molecule dual inhibitor of immune checkpoints PD-1 and VISTA, in patients (pts) with advanced solid tumor or lymphomas

TPS3099

Background: Programmed-death 1 (PD-1) and V-domain Ig suppressor of T-cell activation (VISTA) are independent immune checkpoints that negatively regulate T-cell function and are implicated in various malignancies. Preclinical studies have demonstrated that dual blockade of these pathways is synergistic. CA-170 is a first-in-class oral small molecule that directly targets both PD-1/PD-L1 and VISTA pathways and has shown anti-tumor activity in multiple preclinical models. Methods: The dose escalation phase has a target enrollment of 50 pts with advanced solid tumors or lymphomas onto escalating doses; the first four single-pt cohorts are accelerated titration but then switch to 3+3 design. The dose expansion phase has a target enrollment of 250 pts with select tumor types known to be responsive to anti-PD-1/L1 inhibitors and/or known to express PD-L1 or VISTA. Key eligibility criteria include: age ≥ 18 years, ECOG ≤1, adequate organ function, and ineligible for/did not respond to standard therapy including anti-PD-1/L1 inhibitors, where available. Primary objectives of this first-in-human study: safety, maximum tolerated dose, and recommended phase 2 dose. Secondary objectives: pharmacokinetics (PK) and anti-tumor activity. Exploratory endpoints: biomarkers and pharmacodynamic (PD) effects, which include changes in immune cell and peripheral cytokine populations in tumor (IHC/mRNA) and blood (flow cytometry/mRNA). Oral CA-170 is administered once daily in 21-day cycles. Response will be evaluated every other cycle per RECIST (v1.1) and Immune-related Response Criteria or by Cheson criteria (2007). Patients who discontinue treatment for reasons other than progressive disease will be followed for progression-free survival. Serial plasma, blood, and tumor samples will be collected for PK and PD evaluation. Clinical trial identifier: Clinical trial information: NCT02812875.

Vedolizumab Pharmacokinetics, Pharmacodynamics, Safety, and Tolerability Following Administration of a Single, Ascending, Intravenous Dose to Healthy Volunteers

BACKGROUND AND OBJECTIVES

Vedolizumab, a humanized monoclonal antibody against the α₄β₇ integrin, is indicated for treatment of moderately to severely active ulcerative colitis or Crohn's disease. In this placebo-controlled, double-blind, randomized, single ascending-dose study, the pharmacokinetics, pharmacodynamics, safety, and tolerability of vedolizumab were evaluated in healthy volunteers.

METHODS

Forty-nine participants (in five cohorts) were randomly assigned in a 4:1 ratio to receive a single intravenous infusion of either vedolizumab (0.2, 0.5, 2.0, 6.0, or 10.0 mg/kg) or placebo. Blood samples were collected for measurement of vedolizumab serum concentrations and α₄β₇ saturation on peripheral blood lymphocytes by vedolizumab. Pharmacokinetic parameters were computed using a non-compartmental approach. Adverse events were monitored.

RESULTS

Vedolizumab maximum observed serum concentration (C _max) demonstrated dose proportionality over the dose range tested. Greater than dose-proportional increases in area under the serum concentration-time curve from time 0 to infinity (AUC_0-inf) and shorter terminal elimination half-life (t _1/2) were observed from 0.2 to 2.0 mg/kg, suggestive of nonlinear pharmacokinetics at lower doses. At doses higher than 2.0 mg/kg, these parameters increased dose proportionally. Saturation of α₄β₇ was at or near maximal levels (>90 %) at all doses and time points when vedolizumab was measurable in serum. A total of 21 of 39 (54 %) vedolizumab-treated participants were anti-drug antibody (ADA) positive, and 11 (28 %) were persistently ADA positive. Overall, no adverse event signals, including serious infections or malignancies, were apparent.

CONCLUSIONS

Vedolizumab exhibited target-mediated disposition, characterized by a rapid, saturable, nonlinear elimination process at low concentrations and a slower linear elimination process at higher concentrations. Nearly complete α₄β₇ saturation was observed at all doses. A single intravenous infusion of vedolizumab was well tolerated by healthy volunteers.

Population pharmacokinetics-pharmacodynamics of vedolizumab in patients with ulcerative colitis and Crohn's disease

BACKGROUND

Vedolizumab, an anti-α(4)β(7) integrin monoclonal antibody (mAb), is indicated for treating patients with moderately to severely active ulcerative colitis (UC) and Crohn's disease (CD). As higher therapeutic mAb concentrations have been associated with greater efficacy in inflammatory bowel disease, understanding determinants of vedolizumab clearance may help to optimise dosing.

AIMS

To characterise vedolizumab pharmacokinetics in patients with UC and CD, to identify clinically relevant determinants of vedolizumab clearance, and to describe the pharmacokinetic-pharmacodynamic relationship using population modelling.

METHODS

Data from a phase 1 healthy volunteer study, a phase 2 UC study, and 3 phase 3 UC/CD studies were included. Population pharmacokinetic analysis for repeated measures was conducted using nonlinear mixed effects modelling. Results from the base model, developed using extensive phase 1 and 2 data, were used to develop the full covariate model, which was fit to sparse phase 3 data.

RESULTS

Vedolizumab pharmacokinetics was described by a 2-compartment model with parallel linear and nonlinear elimination. Using reference covariate values, linear elimination half-life of vedolizumab was 25.5 days; linear clearance (CL(L)) was 0.159 L/day for UC and 0.155 L/day for CD; central compartment volume of distribution (V(c)) was 3.19 L; and peripheral compartment volume of distribution was 1.66 L. Interindividual variabilities (%CV) were 35% for CLL and 19% for V(c); residual variance was 24%. Only extreme albumin and body weight values were identified as potential clinically important predictors of CL(L).

CONCLUSIONS

Population pharmacokinetic parameters were similar in patients with moderately to severely active UC and CD. This analysis supports use of vedolizumab fixed dosing in these patients. Clinicaltrials.gov Identifiers: NCT01177228; NCT00783718 (GEMINI 1); NCT00783692 (GEMINI 2); NCT01224171 (GEMINI 3).

In vitro assessment of the effects of vedolizumab binding on peripheral blood lymphocytes

Vedolizumab (VDZ) is a humanized monoclonal antibody in development for the treatment of inflammatory bowel disease. VDZ binds to the α4β7 integrin complex and inhibits its binding to mucosal addressin cell adhesion molecule-1 (MAdCAM-1), thus preventing lymphocyte extravasation to gut mucosal tissues. To understand whether VDZ has additional effects that may affect its overall safety as a therapeutic molecule, we examined other potential actions of VDZ. In vitro assays with human peripheral blood lymphocytes demonstrated that VDZ fails to elicit cytotoxicity, lymphocyte activation, and cytokine production from memory T lymphocytes and does not interfere with the suppressive ability of regulatory T cells. Furthermore, we demonstrated that VDZ induces internalization of α4β7 and that the integrin is rapidly re-expressed and fully functional after VDZ withdrawal. These studies provide insight into the mechanisms underlying the observed safety profile of VDZ in clinical trials.

Validation of a flow cytometry based chemokine internalization assay for use in evaluating the pharmacodynamic response to a receptor antagonist

Pharmacodynamic assays are important in clinical trial design to investigate the relationship between drug concentration (pharmacokinetics) and drug "effect' or biological activity. Increasingly flow cytometry is being used to examine the pharmacodynamic effect of new drug entities. However, to date, the analytical validation of cytometry based assays is limited and there is no suitable guidance for method validation of flow cytometry-based pharmacodynamic assays. Here we report the validation of a flow cytometry-based chemokine internalization assay for use in evaluating the effect of a receptor antagonist in clinical trials. The assay method was validated by examining the stability of the reagent, assay robustness, sensitivity, repeatability and reproducibility precision. Experimental results show the assay reagent was stable over 26 weeks. The assay demonstrated a sensitivity to distinguish 0.005 μg/ml of a CCR2 antagonist with a %CV of 13.3%. The intra-assay repeatability was less than 15% with an inter-assay repeatability of less than 20%. In vivo study results demonstrated that the assay was consistent and a reliable measure of antagonist activity.

Posttranslational changes in band 3 in adult and aging brain following treatment with ergoloid mesylates, comparison to changes observed in Alzheimer's disease

Band 3, the most heavily used anion transport system in vertebrates, ages as cells and tissues age. Posttranslational changes in band 3 in adult and aging brain were investigated following treatment with ergoloid mesylates and compared to changes observed in Alzheimer's disease (AD). The study was conducted in a double blind fashion and was decoded only after the study was completed. The following posttranslational changes in brain band 3 occur with age: increased breakdown of band 3; decreased phosphorylation; and decreased anion transport. Autoantibodies to senescent cell antigen (SCA) synthetic peptides residue 538-554 and 812-827 increase with age, but antibodies to the former peptide are significantly reduced in ergoloid mesylate treated old mice. This is a critical transport region of band 3. Results showed the aged/altered band 3 increased in Alzheimer's disease (AD) as determined by quantitative antibody binding. Ergoloid mesylates altered the age-related posttranslational changes as follows: the observed age-related decrease in brain band 3 was partially reversed and anion transport was increased. This is consistent with the data indicating decreased autoantibodies to a critical anion transport segment of band 3. Aging appears to result in damage to a critical transport region of the anion transporter which is reflected by decreased anion transport, increased breakdown, alteration of the molecule itself, and an increase in autoantibodies to the region. Ergoloid mesylates seem to protect against this damage.

Autoantibodies to band 3 during aging and disease and aging interventions

An aging antigen, senescent cell antigen, resides on the 911-amino acid membrane protein band 3. It marks cells for removal by initiating specific IgG autoantibody binding. Band 3 is a ubiquitous membrane transport protein found in the plasma membrane of diverse cell types and tissues, and in nuclear, mitochondrial, and golgi membranes. Band 3 in tissues such as brain performs the same functions as it does in red cells. Senescent cell antigen is generated on brain menbranes. Oxidation is a mechanism for generating senescent cell antigen. Neither cross-linking nor hemoglobin appears to play a role in generating senescent cell antigen. Although storage is the only in vitro model that mimics cellular aging in situ, we have discovered three alterations/mutations of band 3 that permit insight into aging in situ. One mutation with an addition to band 3 has normal or decelerated red cell aging. In contrast, another band 3 alteration with a suspected deletion or substitution that renders band 3 more susceptible to proteolysis, shows accelerated aging. The third alteration, which is also more susceptible to proteolysis, is associated with neurologic defects. Peptide technology was used to map the aging antigenic sites and anion transport sites on band 3 using a competitive inhibition assay and immunoblotting with IgG directed against the aging antigen on old cells. Results indicate that: a) aging antigenic sites reside on human band 3 residues 538-554, and 812-830; b) a putative ankyrin binding region peptide is not involved in senescent cell antigen activity; and (c) carbohydrate moieties are not required for the antigenicity or recognition of senescent cell antigen since synthetic peptides alone abolish binding of senescent cell IgG to erythrocytes. Peptide residues 588-594 (a 7-amino acid peptide), 822-839, and 869-883 were the most active inhibitors of anion transport (p < or = 0.001 compared to control without peptide). Localization of the active antigenic and transport sites on band 3 molecule facilitates definition of the molecular changes occurring during aging that initiate molecular as well as cellular degeneration. The role of senescent cell antigen and band 3 in brain aging and Alzheimer's disease is discussed. Antibodies to one component of synthetic senescent cell antigen distinguish between Alzheimer's and normal tissue.