Abstract 1772: Immunotherapy of colorectal cancer by the T-cell targeted DART® protein MGD007: Cellular mechanisms of action

Introduction

MGD007 (glycoprotein A33 x CD3), a DART protein designed to redirect T cells to target gpA33-expressing colon cancer, is presently undergoing clinical evaluation (NCT02238805). The gpA33 target was selected based on its universal expression profile across primary and metastatic CRC, including expression on putative cancer stem cell (CSC) populations. MGD007 activity in CRC cell cytolysis and its prolonged PK in non-human primates have previously been reported (Cancer Res 2014;74(19 Suppl): Abstract nr 669.1). Here we further characterize MGD007 cellular mechanisms associated with redirected T-cell killing, cytokine responses and modulation with steroids.

Method

Redirected killing assays were performed using luciferase labelled gpA33+ve Colo205 or RECA0201-GF colorectal cancer stem-like cells (CSLC) with freshly isolated PBMC or fractionated T-cell populations; Treg cells (CD4+, CD127lo, CD25+) were expanded for 14 days in presence of IL-2 and rapamycin and confirmed to be suppressive; steroids (budesonide and dexamethasone) were evaluated at pharmacologically relevant concentrations; multi-parameter FACS and ELISA were performed to determine cell surface marker expression and cytokine levels respectively.

Results

MGD007 displays potent redirected T-cell killing of gpA33+ve CRC cells, including complete lysis of CRC stem cell-like models. Importantly, MGD007 mediated cytolysis can be supported by various T-cell populations, including Treg cells. Following prolonged in vitro exposure to MGD007 and gpA33+ve tumor cells, expanded T cells acquire a memory phenotype and retain potent CTL activity when challenged with fresh gpA33+ve target cells; however, much decreased cytokine release was observed compared to that observed following initial T-cell exposure. The addition of dexamethasone or budesonide to freshly isolated effector cells and gpA33+ve target cells also reduces cytokine release levels to baseline in the presence of MGD007, with minimal impact observed on MGD007-mediated killing.

Discussion

MGD007 supports targeted lysis of CRC, including CSC subpopulations, and can leverage suppressive Tregs in addition to conventional T cells for cytolytic activity. Biological activity modulation is also feasible through induction of cytolytic Tmem cells with diminished cytokine release potential via sequential exposure to MGD007 or the simultaneous exposure to low-dose steroids. These data support further clinical development of MGD007 for the treatment of CRC patients.

Citation Format: Paul A. Moore, Yinhua Yang, Kalpana Shah, Daorong Liu, Vatana Long, Douglas H. Smith, Zhuangyu Pan, Ralph Alderson, Liqin Liu, Syd Johnson, Ezio Bonvini. Immunotherapy of colorectal cancer by the T-cell targeted DART® protein MGD007: Cellular mechanisms of action [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1772.

Abstract 820: Preclinical development of MGC018, a duocarmycin-based antibody-drug conjugate targeting B7-H3 for solid cancer

Introduction: B7-H3, a member of the B7 family of immunomodulatory molecules, is overexpressed in a wide range of solid tumors; tumor overexpression has been correlated with disease severity and poor outcome in several cancer types. MGC018 is an antibody-drug conjugate (ADC) targeted against B7-H3 and comprised of the cleavable linker-duocarmycin payload, valine-citrulline-seco DUocarmycin hydroxyBenzamide Azaindole (vc-seco-DUBA), conjugated to an anti-B7-H3 humanized IgG1/kappa monoclonal antibody through reduced interchain disulfides, with an average drug-to-antibody ratio of ~2.7. Previous studies indicated MGC018 exhibited a favorable preclinical profile, with strong reactivity toward tumor cells and tumor-associated vasculature, limited normal tissue reactivity, potent cytotoxicity in vitro and antitumor activity in vivo toward a range of B7-H3-expressing tumor cell lines representing several cancer types. Based on these preliminary results, expanded preclinical development of MGC018 was undertaken to support clinical development.

Methods: vc-seco-DUBA conjugation to obtain MGC018 ADC was performed by Synthon Biopharmaceuticals B.V. Single- and repeat-dose in vivo efficacy studies were conducted in CD-1 nude mice with human tumor xenografts that express B7-H3 to explore the relationship between Cmax, exposure and anti-tumor activity, and to define the minimal efficacious dose in these models. A GLP toxicology study was conducted in cynomolgus monkeys in which MGC018 was administered at dose levels of 1, 3, 6 and 10 mg/kg every three weeks for a total of three doses.

Results: MGC018 demonstrated specific, dose-dependent in vivo antitumor activity toward B7-H3-positive tumor xenografts representing breast, lung and ovarian cancers, and melanoma. Fractionated MGC018 dose studies were consistent with antitumor activity driven by the total exposure (AUC) rather than peak drug exposure (Cmax). MGC018 was tolerated in cynomolgus monkeys at all dose levels tested, with 10 mg/kg, the highest dose administered, defined as the highest non-severely toxic dose (HNSTD).

Conclusion: MGC018, a preclinical candidate comprised of a humanized mAb targeting B7-H3, conjugated to the potent DNA alkylating payload DUBA via a cleavable peptide linker, exhibited a favorable preclinical profile. MGC018 demonstrated potent antitumor activity in vivo toward B7-H3-expressing tumor xenografts at clinically relevant dose levels. MGC018 was tolerated in cynomolgus monkeys, a relevant toxicology model, at exposure levels in excess of those required for antitumor activity. Our findings support the clinical development of MGC018 to evaluate its potential as an ADC therapeutic for B7-H3-expressing solid cancers.

Citation Format: Juniper A. Scribner, Jennifer G. Brown, Sharad Sharma, Hua Li, Michael Chiechi, Pam Li, Thomas Son, Anushka De Costa, Yan Chen, Francine Chen, Bhaswati Barat, Ling Huang, Christina Wolff, Jeff Hooley, Tim E. Hotaling, Timur Gaynutdinov, Valentina Ciccarone, James Tamura, Scott Koenig, Syd Johnson, Paul A. Moore, Ezio Bonvini, Deryk Loo. Preclinical development of MGC018, a duocarmycin-based antibody-drug conjugate targeting B7-H3 for solid cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 820.

Development of MGD007, a gpA33 x CD3-Bispecific DART Protein for T-Cell Immunotherapy of Metastatic Colorectal Cancer

We have developed MGD007 (anti-glycoprotein A33 x anti-CD3), a DART protein designed to redirect T cells to target gpA33 expressing colon cancer. The gpA33 target was selected on the basis of an antibody-based screen to identify cancer antigens universally expressed in both primary and metastatic colorectal cancer specimens, including putative cancer stem cell populations. MGD007 displays the anticipated-bispecific binding properties and mediates potent lysis of gpA33-positive cancer cell lines, including models of colorectal cancer stem cells, through recruitment of T cells. Xenograft studies showed tumor growth inhibition at doses as low as 4 μg/kg. Both CD8 and CD4 T cells mediated lysis of gpA33-expressing tumor cells, with activity accompanied by increases in granzyme and perforin. Notably, suppressive T-cell populations could also be leveraged to mediate lysis of gpA33-expressing tumor cells. Concomitant with CTL activity, both T-cell activation and expansion are observed in a gpA33-dependent manner. No cytokine activation was observed with human PBMC alone, consistent with the absence of gpA33 expression on peripheral blood cell populations. Following prolonged exposure to MGD007 and gpA33 positive tumor cells, T cells express PD-1 and LAG-3 and acquire a memory phenotype but retain ability to support potent cell killing. In cynomolgus monkeys, 4 weekly doses of 100 μg/kg were well tolerated, with prolonged PK consistent with that of an Fc-containing molecule. Taken together, MGD007 displays potent activity against colorectal cancer cells consistent with a mechanism of action endowed in its design and support further investigation of MGD007 as a potential novel therapeutic treatment for colorectal cancer. Mol Cancer Ther; 17(8); 1761-72. ©2018 AACR.

Mental health care needs and preferences for mothers of children with a disability

BACKGROUND

Mothers of children with a disability are at increased risk of poor mental health compared with mothers of typically developing children. The aim of the study was to describe the mental health care needs and preferences for support of mothers of children and young people aged 0-25 years with a disability.

METHODS

A cross-sectional study was used, using an online survey with 294 mothers of children with a disability. Questions were asked about mental health, perceived need for support, barriers to accessing mental health care, and preferences for support. Descriptive and chi-squared analyses were performed.

RESULTS

High rates of mental ill health were self-identified in the previous 12 months, with reported clinically significant depression (44%), anxiety (42%), and suicidality (22%). Nearly half (48%) of the mothers reported high to very high psychological distress. Although 75% of mothers perceived a need for professional support, only 58% attempted to access this. Key barriers to accessing support were caregiving duties making it difficult to schedule appointments (45%) and not perceiving the mental health problem as serious enough to require help (36%). Individual counselling was the preferred type of support (66%) followed by professionally guided relaxation (49%) and education about mental health (47%). Support was considered most critical at the time of diagnosis and during medical intervention for their child.

CONCLUSIONS

Although mental health problems were common and mothers perceived the need for professional help, several key barriers were preventing mothers from accessing help. Our study suggests that improving mothers' knowledge of when and where to seek help (mental health literacy) may encourage their access to support. There also needs to be more accessible treatment to mothers given the high care demands that are placed upon them.

Robust, tunable, and high purity triggered single photon source at room temperature using a nitrogen-vacancy defect in diamond in an open microcavity

We report progress in the development of tunable room temperature triggered single photon sources based on single nitrogen-vacancy (NV) centres in nanodiamond coupled to open access optical micro-cavities. The feeding of fluorescence from an NV centre into the cavity mode increases the spectral density of the emission and results in an output stream of triggered single photons with spectral line width of order 1 nm, tunable in the range 640 - 700 nm. We record single photon purities exceeding 96% and estimated device efficiencies up to 3%. We compare performance using plano-concave microcavities with radii of curvature from 25 μm to 4 μm and show that up to 17% of the total emission is fed into the TEM₀₀ mode. Pulsed Hanbury-Brown Twiss (HBT) interferometry shows that an improvement in single photon purity is facilitated due to the increased spectral density.

Isolated Lateral Meniscal Tear in the Dog

degenerative changes of the involved stifle joint associated with a “bucket handle” tear of the caudal body of the lateral meniscus. Surgical excision of the torn section of meniscus was beneficial in the first patient but this patient had persistant difficulty with the leg after exercise. Gross and microscopic pathology of the involved stifle in the second patient showed the meniscal lesion to be associated with severe cartilage fibrillation of the overlying lateral femoral condyle. As in human beings, the mechanism of injury may have been placement of the foot during vigorous external rotation of the femur with the stifle flexed. Extension of the limb from this position could have resulted in an isolated tear of the lateral meniscus.

Tailoring CD19xCD3-DART exposure enhances T-cells to eradication of B-cell neoplasms

Many patients with B-cell malignancies can be successfully treated, although tumor eradication is rarely achieved. T-cell-directed killing of tumor cells using engineered T-cells or bispecific antibodies is a promising approach for the treatment of hematologic malignancies. We investigated the efficacy of CD19xCD3 DART bispecific antibody in a broad panel of human primary B-cell malignancies. The CD19xCD3 DART identified 2 distinct subsets of patients, in which the neoplastic lymphocytes were eliminated with rapid or slow kinetics. Delayed responses were always overcome by a prolonged or repeated DART exposure. Both CD4 and CD8 effector cytotoxic cells were generated, and DART-mediated killing of CD4⁺ cells into cytotoxic effectors required the presence of CD8⁺ cells. Serial exposures to DART led to the exponential expansion of CD4 ⁺ and CD8 ⁺ cells and to the sequential ablation of neoplastic cells in absence of a PD-L1-mediated exhaustion. Lastly, patient-derived neoplastic B-cells (B-Acute Lymphoblast Leukemia and Diffuse Large B Cell Lymphoma) could be proficiently eradicated in a xenograft mouse model by DART-armed cytokine induced killer (CIK) cells. Collectively, patient tailored DART exposures can result in the effective elimination of CD19 positive leukemia and B-cell lymphoma and the association of bispecific antibodies with unmatched CIK cells represents an effective modality for the treatment of CD19 positive leukemia/lymphoma.

Bayesian Networks to Compare Pest Control Interventions on Commodities Along Agricultural Production Chains

The production of an agricultural commodity involves a sequence of processes: planting/growing, harvesting, sorting/grading, postharvest treatment, packing, and exporting. A Bayesian network has been developed to represent the level of potential infestation of an agricultural commodity by a specified pest along an agricultural production chain. It reflects the dependency of this infestation on the predicted level of pest challenge, the anticipated susceptibility of the commodity to the pest, the level of impact from pest control measures as designed, and any variation from that due to uncertainty in measure efficacy. The objective of this Bayesian network is to facilitate agreement between national governments of the exporters and importers on a set of phytosanitary measures to meet specific phytosanitary measure requirements to achieve target levels of protection against regulated pests. The model can be used to compare the performance of different combinations of measures under different scenarios of pest challenge, making use of available measure performance data. A case study is presented using a model developed for a fruit fly pest on dragon fruit in Vietnam; the model parameters and results are illustrative and do not imply a particular level of fruit fly infestation of these exports; rather, they provide the most likely, alternative, or worst-case scenarios of the impact of measures. As a means to facilitate agreement for trade, the model provides a framework to support communication between exporters and importers about any differences in perceptions of the risk reduction achieved by pest control measures deployed during the commodity production chain.

Women in academic psychiatry in the United Kingdom

Although there seems to be a shared impression that the proportion of women in academic psychiatry is substantially lower than in National Health Service (NHS) posts, we are not aware of any empirical data on this. In the USA, women physicians have been shown to be more likely to pursue an academic career than men (Nonnemaker, 2000), but the number who advance to Professor appears significantly lower than expected (Reiser et al, 1993; Nonnemaker, 2000). Women in academic psychiatry in Canada also appear less likely to advance to senior positions than their male colleagues (Penfold, 1987). A recent survey of 44 academic institutions in the UK, carried out by the National Centre for Social Research (Blake & La Valle, 2000), found that women occupied lower grade academic posts than their male counterparts and therefore were less eligible to apply for project research grants. Those that were eligible were as successful in gaining funding as their male colleagues.

Variation in 'fast-track' referrals for suspected cancer by patient characteristic and cancer diagnosis: evidence from 670 000 patients with cancers of 35 different sites

BACKGROUND

In England, 'fast-track' (also known as 'two-week wait') general practitioner referrals for suspected cancer in symptomatic patients are used to shorten diagnostic intervals and are supported by clinical guidelines. However, the use of the fast-track pathway may vary for different patient groups.

METHODS

We examined data from 669 220 patients with 35 cancers diagnosed in 2006-2010 following either fast-track or 'routine' primary-to-secondary care referrals using 'Routes to Diagnosis' data. We estimated the proportion of fast-track referrals by sociodemographic characteristic and cancer site and used logistic regression to estimate respective crude and adjusted odds ratios. We additionally explored whether sociodemographic associations varied by cancer.

RESULTS

There were large variations in the odds of fast-track referral by cancer (P<0.001). Patients with testicular and breast cancer were most likely to have been diagnosed after a fast-track referral (adjusted odds ratios 2.73 and 2.35, respectively, using rectal cancer as reference); whereas patients with brain cancer and leukaemias least likely (adjusted odds ratios 0.05 and 0.09, respectively, for brain cancer and acute myeloid leukaemia). There were sex, age and deprivation differences in the odds of fast-track referral (P<0.013) that varied in their size and direction for patients with different cancers (P<0.001). For example, fast-track referrals were least likely in younger women with endometrial cancer and in older men with testicular cancer.

CONCLUSIONS

Fast-track referrals are less likely for cancers characterised by nonspecific presenting symptoms and patients belonging to low cancer incidence demographic groups. Interventions beyond clinical guidelines for 'alarm' symptoms are needed to improve diagnostic timeliness.

A pilot randomized controlled trial comparing effectiveness of prism glasses, visual search training and standard care in hemianopia

OBJECTIVE

Pilot trial to compare prism therapy and visual search training, for homonymous hemianopia, to standard care (information only).

METHODS

Prospective, multicentre, parallel, single-blind, three-arm RCT across fifteen UK acute stroke units.

PARTICIPANTS

Stroke survivors with homonymous hemianopia.

INTERVENTIONS

Arm a (Fresnel prisms) for minimum 2 hours, 5 days per week over 6 weeks. Arm b (visual search training) for minimum 30 minutes, 5 days per week over 6 weeks. Arm c (standard care-information only).

INCLUSION CRITERIA

Adult stroke survivors (>18 years), stable hemianopia, visual acuity better than 0.5 logMAR, refractive error within ±5 dioptres, ability to read/understand English and provide consent.

OUTCOMES

Primary outcomes were change in visual field area from baseline to 26 weeks and calculation of sample size for a definitive trial. Secondary measures included Rivermead Mobility Index, Visual Function Questionnaire 25/10, Nottingham Extended Activities of Daily Living, Euro Qual, Short Form-12 questionnaires and Radner reading ability. Measures were post-randomization at baseline and 6, 12 and 26 weeks.

RANDOMIZATION

Randomization block lists stratified by site and partial/complete hemianopia.

BLINDING

Allocations disclosed to patients. Primary outcome assessor blind to treatment allocation.

RESULTS

Eighty-seven patients were recruited: 27-Fresnel prisms, 30-visual search training and 30-standard care; 69% male; mean age 69 years (SD 12). At 26 weeks, full results for 24, 24 and 22 patients, respectively, were compared to baseline. Sample size calculation for a definitive trial determined as 269 participants per arm for a 200 degree² visual field area change at 90% power. Non-significant relative change in area of visual field was 5%, 8% and 3.5%, respectively, for the three groups. Visual Function Questionnaire responses improved significantly from baseline to 26 weeks with visual search training (60 [SD 19] to 68.4 [SD 20]) compared to Fresnel prisms (68.5 [SD 16.4] to 68.2 [18.4]: 7% difference) and standard care (63.7 [SD 19.4] to 59.8 [SD 22.7]: 10% difference), P=.05. Related adverse events were common with Fresnel prisms (69.2%; typically headaches).

CONCLUSIONS

No significant change occurred for area of visual field area across arms over follow-up. Visual search training had significant improvement in vision-related quality of life. Prism therapy produced adverse events in 69%. Visual search training results warrant further investigation.

Abstract 4089: Quantitative prediction of human pharmacokinetics for duvortuxizumab from cynomolgus monkey data: a translational pharmacokinetic modeling approach

Duvortuxizumab (also known as JNJ-64052781 and MGD011) is a bispecific CD19 x CD3 DART® molecule designed to simultaneously target CD19-positive cells for recognition and elimination by CD3-expressing T-lymphocytes as effector cells. Duvortuxizumab is currently in clinical development for the potential treatment of B-cell malignancies. Here we report the results from a translational PK model that utilized duvortuxizumab pharmacokinetic (PK) data from cynomolgus monkeys to predict duvortuxizumab PK in humans.

The PK of duvortuxizumab administered by intravenous infusion was evaluated in cynomolgus monkeys in two separate studies. Study 1 evaluated intra-animal escalating doses from 0.5 to 100 µg/kg or repeated doses from 0.005 to 0.5 µg/kg administered over a period of up to 4 weeks. Serum concentrations of duvortuxizumab above the lower limit of quantification were obtained at dose levels &gt;0.5 µg/kg. Study 2 evaluated duvortuxizumab doses of 0.2, 2, 5, or 10 µg/kg administered once weekly for 4 weeks. Dose-proportional increases in maximum concentration (Cmax) were observed across the dose ranges evaluated, and no significant differences between male and female animals were observed.

PK modeling analysis, which integrated data from both study 1 and study 2 at 0.2 to 100 µg/kg dose levels, was performed to further understand the PK behavior of duvortuxizumab in cynomolgus monkeys. Duvortuxizumab PK was reasonably characterized using a two compartment model with linear clearance (CL) from the central compartment. Model estimated parameters were CL = 0.797 mL/h/kg; volume of distribution for the central compartment (V1) = 51.7 mL/kg; intercompartmental clearance (Q) = 2.29 mL/h/kg; and volume of distribution for the peripheral compartment (V2) = 88.8 mL/kg. Assuming a body weight of 3 kg and 70 kg for a cynomolgus monkey and a human, respectively, human PK parameters were estimated using an allometric scaling factor of 0.75 for CL and 1.0 for volume in the translational PK model.

Observed duvortuxizumab PK values obtained from an ongoing, first-in-human (FIH), phase 1 dose-escalation trial in patients with relapsed or refractory B-cell malignancies (NCT02454270) were used to validate the translational PK model. Comparison of the predicted and observed duvortuxizumab PK profiles suggested that the translational PK model using the allometric scaling method reasonably predicted duvortuxizumab PK profiles in humans at multiple dose levels (15 to 100 ng/kg).

In conclusion, the developed translational PK model successfully predicted duvortuxizumab PK in humans and has been used to aid dose escalation of duvortuxizumab in the ongoing FIH study. This work showcases the potential of translational PK modeling in supporting the selection of a FIH dose escalation strategy utilizing preclinical PK information.

Citation Format: Xiling Jiang, Hua Li, Jeff Nordstrom, Jennifer Brown, Liqin Liu, Syd Johnson, Ralph Alderson, Pamela L. Clemens, Jacintha Shenton, Imran Khan, Olivia Gardner, Yu-Nien Sun, Weirong Wang. Quantitative prediction of human pharmacokinetics for duvortuxizumab from cynomolgus monkey data: a translational pharmacokinetic modeling approach [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4089. doi:10.1158/1538-7445.AM2017-4089

Abstract 4608: A 5T4 x CD3 bispecific DART® molecule with extended half-life for T-cell immunotherapy of cancers

Introduction: 5T4 (trophoblast glycoprotein), an oncofetal antigen involved in embryo development, is expressed on the cell surface of multiple cancers. Several 5T4-directed interventions have been reported, including a cancer vaccine and an antibody-drug conjugate. A superantigen-driven redirected cell killing modality was also developed, but obstacles, such as immunogenicity, remain to a successful 5T4 therapeutic molecule. We have developed an Fc-bearing 5T4 x CD3 DART® bispecific protein designed to redirect T cells to target 5T4-expressing tumors.

Methods: 5T4 x CD3, a humanized Fc-bearing DART molecule, was stably expressed in CHO cells and purified to homogeneity via a standard antibody-purification platform. In vitro characterization and functional studies were performed with 5T4-positive tumor cell lines and human T cells. In vivo studies were performed in immune-deficient tumor-bearing mice co-implanted with activated human T cells or reconstituted with human peripheral blood mononuclear cells (PBMCs). Pharmacokinetic studies were performed in both human FcRn transgenic mice and cynomolgus monkeys.

Results: 5T4 x CD3 demonstrated bispecific binding properties to both human and cynomolgus monkey antigens. In redirected cytolysis studies, 5T4 x CD3 mediated lysis of 5T4-positive pancreatic, lung, renal, triple-negative breast, and ovarian cancer cell lines with EC50 values ranging between 0.03 and 0.08 ng/mL. 5T4 x CD3 displayed favorable pharmacokinetics with a prolonged circulating half-life in human FcRn transgenic mice and cynomolgus monkeys. Tumor clearance studies in NOD/SCID mice implanted subcutaneously with activated human T cells and tumor cells demonstrated robust inhibition of tumor growth upon intravenous administration of 5T4 x CD3 at doses as low as 0.8 μg/kg, but not with a CD3-binding control DART protein. In addition, human PBMC-reconstituted NOD/SCID/IL2 gamma-chain null mice were implanted intradermally with renal and pancreatic tumor cell lines or orthotopically with a triple-negative breast cancer line and, after tumor establishment, were treated with 5T4 x CD3. Anti-tumor activity was observed at doses as low as 4 μg/kg. Immunohistochemical analysis of tumor xenografts confirmed tumor clearance was associated with T-cell recruitment into the tumor mass.

Conclusions: In summary, 5T4 x CD3 displays robust antitumor activity against several cancer cell lines in vitro and in vivo together with a favorable pharmacokinetic profile and merits further consideration as a potential treatment for 5T4-positive cancers.

Citation Format: Ling Huang, Gurunadh Chichili, Ralph Alderson, Francine Chen, Jennifer Brown, Hua Li, Valentina Ciccarone, Jim Tamura, Daorong Liu, Liqin Liu, Syd Johnson, Ezio Bonvini, Paul Moore. A 5T4 x CD3 bispecific DART® molecule with extended half-life for T-cell immunotherapy of cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4608. doi:10.1158/1538-7445.AM2017-4608

Abstract 3642: Tumor-antigen expression-dependent activation of the CD137 costimulatory pathway by bispecific DART® proteins

Introduction: CD137 (4-1BB) is a co-stimulatory molecule expressed by activated T and NK cells that, upon interaction with its CD137 ligand, further supports cell activation, proliferation and survival. Activation via CD137 holds great promise for cancer immunotherapy; however, current CD137 agonistic interventions are associated with systemic safety concerns. To develop a therapeutic modality that reduces the potential for systemic CD137 effects, we applied the DART® bispecific platform to generate proteins that can induce tumor-antigen dependent T-cell activation.

Methods: DART molecules were constructed containing anti-CD137 variable regions together with either anti-HER2 or anti-EphA2 variable regions. DART binding properties were evaluated by ELISA or flow cytometry; signaling responses assessed using a NF-κB luciferase reporter cell line expressing CD137. Co-stimulatory activity was characterized with primary human T cells in the presence or absence of tumor target antigen-expressing cells.

Results: ELISA and flow cytometry analysis demonstrated that both HER2 x CD137 and EphA2 x CD137 DART molecules bind their respective target antigens. Co-culturing of a CD137/NF-κB reporter cell line with tumor lines expressing HER2 or EphA2 revealed tumor antigen-dependent CD137 pathway activation by HER2 x CD137 and EphA2 x CD137 DART molecules, respectively. To evaluate the effects of HER2 x CD137 and EphA2 x CD137 DART molecules on T-cell responses, co-stimulation T-cell assays were performed. In the presence of the relevant antigen-positive cell line, each respective DART molecule was able to promote T-cell proliferation and cytokine release in a HER2 or EphA2-dependent manner. No T-cell co-stimulation was observed by either DART molecule in the absence of antigen-expressing tumor cells. Furthermore, the level of tumor antigen-dependent co-stimulation supported by the DART molecules correlated with the level of tumor target expression. Consistent with the preferential induction of CD137 by the CD8 T cell subset, CD137-based DART proteins induced a substantial increase in the fraction of CD8+ central memory and effector memory T cells in the presence of the proper tumor antigen expressing cells.

Conclusions: HER2 x CD137 and EphA2 x CD137 DART proteins promote T-cell co-stimulation in a tumor antigen-dependent manner and may provide an opportunity to target the CD137 co-stimulatory pathway for cancer immunotherapy, while limiting systemic T-cell activation and related side effects.

Citation Format: Liqin Liu, Chia-Ying K. Lam, Vatana Long, Lusiana Widjaja, Yinhua Yang, Kalpana Shah, Doug Smith, Joanna Pan, Syd Johnson, Ezio Bonvini, Paul Moore. Tumor-antigen expression-dependent activation of the CD137 costimulatory pathway by bispecific DART® proteins [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3642. doi:10.1158/1538-7445.AM2017-3642

Abstract 42: Preclinical development of a duocarmycin-based antibody-drug conjugate targeting B7-H3 for solid cancer

Introduction: B7-H3, a member of the B7 family of immunomodulatory molecules, is overexpressed in a wide range of solid cancers. B7-H3 overexpression has been correlated with disease severity and poor outcome in several cancer types. Proof-of-concept studies targeting B7-H3 demonstrated that auristatin-based B7-H3 antibody-drug conjugates (ADCs) exhibited potent cytotoxicity in vitro and antitumor activity in vivo toward a range of B7-H3-expressing tumor cell lines. Based on these preliminary results, we undertook preclinical development of a B7-H3 ADC comprised of a humanized B7-H3 mAb conjugated to a potent DNA alkylating payload.

Methods: Chimeric B7-H3 mAbs were conjugated to vc-seco-DUocarmycin-hydroxyBenzamide Azaindole (DUBA) (ADC conjugated and provided by Synthon Biopharmecuticals B.V). In vitro and in vivo activity studies were conducted with tumor cell lines that overexpress B7-H3. Based on the potency analysis, together with the biophysical properties and immunohistochemistry (IHC) profiles of the candidates, a lead mAb was selected for preclinical development. The mAb was humanized via CDR grafting and conjugated to DUBA to yield the development candidate MGC018. In vitro and in vivo studies were then conducted with MGC018 to confirm and extend the results with the chimeric ADCs.

Results: Confirming our previous data and consistent with a growing body of literature, B7-H3 mAbs exhibited strong reactivity toward carcinoma cells and the vasculature of solid cancers. Chimeric B7-H3-DUBA ADCs demonstrated specific, dose-dependent cytotoxicity toward B7-H3-positive tumor cell lines in vitro and potent antitumor activity in vivo. The humanized ADC development candidate, MGC018, retained the favorable biophysical properties and the normal tissue-versus-tumor IHC profile of the parental mAb. MGC018 displayed cytotoxicity toward B7-H3-positive tumor cell lines in vitro, with IC50 values in the sub-nM range, and potent antitumor activity in vivo, resulting in tumor stasis and tumor regression in mice bearing B7-H3-positive human tumor xenografts, representing breast, lung and ovarian cancers.

Conclusion: MGC018, a preclinical candidate comprised of a humanized mAb targeting B7-H3 conjugated to the potent DNA alkylating payload DUBA via a cleavable peptide linker, exhibited a favorable preclinical profile, with strong reactivity toward tumor cells and tumor-associated vasculature, limited normal tissue reactivity, potent cytotoxicity in vitro and antitumor activity in vivo toward a range of B7-H3-expressing tumor cell lines representing several cancer types. Our findings support further preclinical development of MGC018 to evaluate its potential as an ADC therapeutic for B7-H3-expressing solid cancers.

Citation Format: Thomas Son, Juniper A. Scribner, Jeff Hooley, Michael Chiechi, Pam Li, Timothy E. Hotaling, Anushka De Costa, Yan Chen, Francine Chen, Bhaswati Barat, Valentina Ciccarone, Timur Gaynutdinov, James Tamura, Scott Koenig, Syd Johnson, Paul A. Moore, Ezio Bonvini, Deryk Loo. Preclinical development of a duocarmycin-based antibody-drug conjugate targeting B7-H3 for solid cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 42. doi:10.1158/1538-7445.AM2017-42

Abstract 3637: Co-targeting of PD-1 and CTLA-4 inhibitory pathways with bispecific DART® and TRIDENT™ molecules

Introduction: Immunotherapy with the combination of monoclonal antibodies (mAbs) that block PD-1 (nivolumab) and CTLA-4 (ipilimumab) has shown clinical benefit beyond that observed with either mAb alone. We have developed PD-1 x CTLA-4 bispecific proteins aimed at inducing antitumor immunity through simultaneous blockade of both checkpoint molecules. Two proteins, a tetravalent PD-1 x CTLA-4 bispecific DART® protein (bivalent for both PD-1 and CTLA-4) and a trivalent PD-1 x CTLA-4 TRIDENT™ protein (bivalent for PD-1 but monovalent for CTLA-4) were engineered; the TRIDENT protein was designed to promote CTLA-4 blockade through avidity when bound to PD-1 on cells co-expressing both receptors, thus favoring PD-1 over CTLA-4 blockade in cells that do not co-express both molecules.

Methods: Proteins were engineered from humanized PD-1 and CTLA-4 mAb sequences and demonstrated favorable biophysical properties. Binding assays were performed by ELISA or flow cytometry. Co-ligation of PD-1 and CTLA-4 was assessed in an enzyme-fragment complementation assay (DiscoverX). T-cell activation was tested in reporter cells, staphylococcus enterotoxin B-stimulated PBMCs or MLR assays.

Results: Both DART and TRIDENT proteins showed equivalent potency in binding immobilized recombinant PD-1 or PD-1-expressing cell lines, inhibition of PD-1 interaction with PD-L1 or PD-L2 as well as reversal of PD-1/PD-L1 mediated T-cell signal inhibition. In all assays, both formats showed activities that were comparable to those of the precursor PD-1 mAb. With respect to CTLA-4, the DART protein showed a minor potency loss in binding to CTLA-4 expressing cells, inhibition of CTLA-4/B7 interaction and reversal of T-cell signal inhibition compared to the precursor mAb. The TRIDENT protein, however, showed substantial lower potency than the DART protein in all CTLA-4 assays, consistent with the monovalent nature of the CTLA-4 arm. Importantly, in cells that co-express both receptors, DART and TRIDENT proteins show comparable co-engagement of PD-1 and CTLA-4, as shown by enzyme-fragment complementation, suggesting that anchoring through PD-1 compensates for the decreased CTLA-4 avidity of the TRIDENT molecule when both target receptors are expressed. Similarly, in T-cell co-activation assays, both DART and TRIDENT proteins showed a comparable increase in IFN-gamma response that recapitulated that observed with the combination of the individual parental mAbs.

Conclusion: Both PD-1 x CTLA-4 DART and TRIDENT bispecific molecules block PD-1 and CTLA-4 pathways, with the TRIDENT protein demonstrating a PD-1-biased binding preference, consistent with its design intended to reduce CTLA-4 blockade in the absence of PD-1 co-expression. Both molecules showed comparable T-cell activation activity. Further development of bispecific PD-1 x CTLA-4 molecules for cancer treatment is warranted.

Citation Format: Gurunadh R. Chichili, Kalpana Shah, Ross La Motte-Mohs, Alex Berezhnoy, Daorong Liu, Jessica Hill, Leilei He, Christine Shoemaker, Jennifer Brown, Kurt Stahl, Hua Li, Jonathan Li, Sergey Gorlatov, Jim Tamura, Valentina Ciccarone, Ralph Alderson, Ezio Bonvini, Paul A. Moore, Syd Johnson. Co-targeting of PD-1 and CTLA-4 inhibitory pathways with bispecific DART® and TRIDENT™ molecules [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3637. doi:10.1158/1538-7445.AM2017-3637

Abstract 38: Target validation, antibody discovery and preclinical data supporting ADAM9 as an antibody-drug conjugate therapeutic target for solid tumors

Introduction: A target-unbiased approach based on intact cell immunizations with fetal progenitor cells and cancer stem cells, followed by an immunohistochemistry (IHC) screen for cancer-specific candidates, led to the identification of anti-ADAM9 (a disintegrin and metalloproteinase) mAbs with highly differential tumor-versus-normal tissue binding. ADAM9 is a cell surface protein over-expressed in multiple tumors, with a possible role in promotion and progression of cancer through multiple mechanisms, including modulation of adhesion and migration as well as processing of tumorigenic and pro-angiogenic factors. In this preclinical study, we performed target/mAb validation and evaluated the therapeutic potential of anti-ADAM9 antibody-drug conjugates (ADCs) toward ADAM9-expressing solid cancers.

Methods: IHC was performed with anti-ADAM9 mAbs to confirm and extend available data of human normal and tumor tissue expression. Epitope mapping studies were conducted to define epitope-specificity. mAbs were also screened to identify those that efficiently internalized into tumor cells. In vitro cellular processing studies were performed to further evaluate the mAbs as ADC candidates. Selected mAbs were converted to ADCs via chemical conjugation to potent anti-microtubule (DM4) or DNA alkylating (DGN549) agents; in vitro cytotoxicity studies were conducted with tumor cell lines representing human cancer types that overexpress ADAM9. A lead mAb was then selected for humanization and affinity maturation to yield a development candidate.

Results: Anti-ADAM9 mAbs exhibited strong reactivity toward the tumor epithelium of solid cancers, including pancreatic, kidney, prostate, bladder, breast, colon, lung, and ovarian cancer, but limited reactivity toward normal tissues. Anti-ADAM9 mAbs were efficiently internalized and processed by tumor cell lines, including lines with only modest ADAM9 expression. Anti-ADAM9 ADCs exhibited specific, dose-dependent cytotoxicity toward ADAM9-positive cancer cell lines in vitro, with IC50 values in the sub-nanomolar range. Humanization and affinity maturation of the lead mAb yielded a development candidate that retains potent antitumor activity toward ADAM9-positive tumor cell lines and equivalent, high affinity binding to both human and cynomolgus monkey ADAM9.

Conclusion: ADAM9 is a cell surface antigen that is over-expressed on a wide range of solid cancers. Anti-ADAM9 mAbs that were strongly reactive with representative tumors exhibited high affinity for the antigen and were efficiently internalized and processed by ADAM9-bearing tumor cells. Anti-ADAM9 ADCs demonstrated dose-dependent cytotoxicity in vitro toward a panel of ADAM9-positive tumor cell lines. Our findings demonstrate that an ADC targeting ADAM9 may serve as a potential therapeutic for ADAM9-expressing solid tumors.

Citation Format: Juniper A. Scribner, Bhaswati Barat, Stuart W. Hicks, Nicholas C. Yoder, Thomas Son, Lusiana Widjaja, Gundo Diedrich, Sergey Gorlatov, Jeff Hooley, Ann Easton, Peter Lung, Anushka De Costa, Francine Chen, Michael Chiechi, Pam Li, Monica Licea, Timothy E. Hotaling, Michael Spliedt, Valentina Ciccarone, Nadia Gantt, James Tamura, Megan E. Fuller, Molly McShea, Scott Koenig, Syd Johnson, Paul A. Moore, Ezio Bonvini, Deryk Loo. Target validation, antibody discovery and preclinical data supporting ADAM9 as an antibody-drug conjugate therapeutic target for solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 38. doi:10.1158/1538-7445.AM2017-38

THE PREVALENCE OF TUBERCULOSIS IN CATTLE AND THEIR HANDLERS IN NORTH TONGU, VOLTA REGION, GHANA

BACKGROUND

The need to understand the contribution of bovine tuberculosis (BTB) to the general tuberculosis burden in a poor resource setting is paramount. The aim of this study is to determine the burden of BTB among herdsmen and cattle in the North Tongu district of Volta Region in Ghana.

MATERIALS AND METHODS

A cross- sectional study was conducted in the North Tongu District of the Volta Region between the period of October 2011- March 2012. A well-structured questionnaire was used to collect socio-demographic information and possible risk factor information on cattle from participants. Sputum samples from 68 herdsmen and blood samples from 200 cattle belonging to these herdsmen were also collected. Sputum samples were analyzed using Ziehl- Neelsen staining while Anigen Rapid BTB Test was used for Cattle blood samples.

RESULTS

Ninety percent (61/68) of respondents were also found to consume fresh milk while 84% (57/68) do not use protective clothing. Of a total of 1580 cattle owned by the herdsmen, 200 cattle consisting of 14 bulls and 186 cows were screened where the prevalence of bovine TB was 19% (38/200) and those affected were all females. All (100%) human sample tested negative for Acid-Fast Bacilli (AFB). However, the seropositivity of cattle and kraal density were statistically associated (p= 0.001).

CONCLUSION

Bovine TB is prevalent in cattle in North Tongu district. Although herdsmen indulge in risky lifestyles that expose them to BTB, a zero prevalence of BTB was observed, further study is envisaged using a larger sample size.

Combined Analysis of Neutrino and Antineutrino Oscillations at T2K

T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrino- and antineutrino-mode beams. The data include all runs from January 2010 to May 2016 and comprise 7.482×10^{20} protons on target in neutrino mode, which yielded in the far detector 32 e-like and 135  μ-like events, and 7.471×10^{20} protons on target in antineutrino mode, which yielded 4 e-like and 66  μ-like events. Reactor measurements of sin^{2}2θ_{13} have been used as an additional constraint. The one-dimensional confidence interval at 90% for the phase δ_{CP} spans the range (-3.13, -0.39) for normal mass ordering. The CP conservation hypothesis (δ_{CP}=0, π) is excluded at 90% C.L.

An experimental study of the putative mechanism of a synthetic autonomous rotary DNA nanomotor

DNA has been used to construct a wide variety of nanoscale molecular devices. Inspiration for such synthetic molecular machines is frequently drawn from protein motors, which are naturally occurring and ubiquitous. However, despite the fact that rotary motors such as ATP synthase and the bacterial flagellar motor play extremely important roles in nature, very few rotary devices have been constructed using DNA. This paper describes an experimental study of the putative mechanism of a rotary DNA nanomotor, which is based on strand displacement, the phenomenon that powers many synthetic linear DNA motors. Unlike other examples of rotary DNA machines, the device described here is designed to be capable of autonomous operation after it is triggered. The experimental results are consistent with operation of the motor as expected, and future work on an enhanced motor design may allow rotation to be observed at the single-molecule level. The rotary motor concept presented here has potential applications in molecular processing, DNA computing, biosensing and photonics.

Abstract P4-06-07: Fibroblast growth factor receptor activation and breast tumor progression in a mouse xenograft model of obesity

This abstract was withdrawn by the authors.

Measurement of Coherent π^{+} Production in Low Energy Neutrino-Carbon Scattering

We report the first measurement of the flux-averaged cross section for charged current coherent π^{+} production on carbon for neutrino energies less than 1.5 GeV, and with a restriction on the final state phase space volume in the T2K near detector, ND280. Comparisons are made with predictions from the Rein-Sehgal coherent production model and the model by Alvarez-Ruso et al., the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. We observe a clear event excess above background, disagreeing with the null results reported by K2K and SciBooNE in a similar neutrino energy region. The measured flux-averaged cross sections are below those predicted by both the Rein-Sehgal and Alvarez-Ruso et al.