Yogindra Vedvyas

Self-assembled nanoplatform for targeted delivery of chemotherapy agents via affinity-regulated molecular interactions.

Site-specific delivery of drugs while minimizing unwanted distribution has been one of the pursued goals in cancer therapy. In this endeavor, we have developed targeted polymeric nanoparticles called amphiphilic urethane acrylate nonionomer (UAN) for encapsulation of diverse water-insoluble drugs and diagnostic agents, as well as for simple and reproducible surface conjugation of targeting ligands. Using monoclonal antibodies or lymphocyte function-associated antigen-1 (LFA-1) I domain engineered for varying affinities to intercellular adhesion molecule (ICAM)-1, we were able to deliver UAN nanoparticles to human cancer cells with the efficiency dependent on the strength of the molecular interactions and the degree of ICAM-1 expression on cell surface. Compared to non-specific uptake of free drugs, targeted delivery of UAN nanoparticles carrying equal amount of drugs produced more potent cytotoxicity. Notably, without the targeting ligands attached, UAN nanoparticles were largely precluded from non-specific uptake by the cells, resulting in much lower toxicity. The versatility of our UAN nanoparticles in both payload encapsulation and presentation of targeting ligands may facilitate developing a robust platform for evaluating various combinations of cancer drugs and molecular interactions toward developing effective cancer therapy formulations.

Longitudinal PET imaging demonstrates biphasic CAR T cell responses in survivors

Clinical monitoring of adoptive T cell transfer (ACT) utilizes serial blood analyses to discern T cell activity. While useful, these data are 1-dimensional and lack spatiotemporal information related to treatment efficacy or toxicity. We utilized a human genetic reporter, somatostatin receptor 2 (SSTR2), and PET, to quantitatively and longitudinally visualize whole-body T cell distribution and antitumor dynamics using a clinically approved radiotracer. Initial evaluations determined that SSTR2-expressing T cells were detectable at low densities with high sensitivity and specificity. SSTR2-based PET was applied to ACT of chimeric antigen receptor (CAR) T cells targeting intercellular adhesion molecule-1, which is overexpressed in anaplastic thyroid tumors. Timely CAR T cell infusions resulted in survival of tumor-bearing mice, while later infusions led to uniform death. Real-time PET imaging revealed biphasic T cell expansion and contraction at tumor sites among survivors, with peak tumor burden preceding peak T cell burden by several days. In contrast, nonsurvivors displayed unrelenting increases in tumor and T cell burden, indicating that tumor growth was outpacing T cell killing. Thus, longitudinal PET imaging of SSTR2-positive ACT dynamics enables prognostic, spatiotemporal monitoring with unprecedented clarity and detail to facilitate comprehensive therapy evaluation with potential for clinical translation.

18F-Positron Emitting/Trimethine Cyanine-Fluorescent Contrast for Image-Guided Prostate Cancer Management

[18/19F]-4, an anionic GCPII/PSMA inhibitor for image-guided intervention in prostate cancer, is described. [19F]-4 is radiolabeled with a radiochemical yield that is ≥27% and a molar activity of 190 ± 50 mCi/μmol in a <1 h, one-step, aqueous isotopic exchange reaction. [19F]-4 allows PSMA expression to be imaged by fluorescence (FL) and [18F]-PET. PC3-PIP (PSMA-positive, EC50 = 6.74 ± 1.33 nM) cancers are specifically delineated in mice that bear 3 million (18 mg) PC3-PIP and PC3 (control, PSMA-negative) cells. Colocalization of [18/19F]-4 PET, fluorescence, scintillated biodistribution, and PSMA expression are observed.

Novel Strategy for Selection of Monoclonal Antibodies Against Highly Conserved Antigens: Phage Library Panning Against Ephrin-B2 Displayed on Yeast

Ephrin-B2 is predominately expressed in endothelium of arterial origin, involved in developmental angiogenesis and neovasculature formation through its interaction with EphB4. Despite its importance in physiology and pathological conditions, it has been challenging to produce monoclonal antibodies against ephrin-B2 due to its high conservation in sequence throughout human and rodents. Using a novel approach for antibody selection by panning a phage library of human antibody against antigens displayed in yeast, we have isolated high affinity antibodies against ephrin-B2. The function of one high affinity binder (named as ‘EC8’) was manifested in its ability to inhibit ephrin-B2 interaction with EphB4, to cross-react with murine ephrin-B2, and to induce internalization into ephrin-B2 expressing cells. EC8 was also compatible with immunoprecipitation and detection of ephrin-B2 expression in the tissue after standard chemical fixation procedure. Consistent with previous reports on ephrin-B2 induction in some epithelial tumors and tumor-associated vasculatures, EC8 specifically detected ephrin-B2 in tumors as well as the vasculature within and outside of the tumors. We envision that monoclonal antibody developed in this study may be used as a reagent to probe ephrin-B2 distribution in normal as well as in pathological conditions and to antagonize ephrin-B2 interaction with EphB4 for basic science and therapeutic applications.

[ 18 F ]RPS-544: A PET tracer for imaging the chemokine receptor CXCR4

INTRODUCTION CXCR4 specific [18F]-labeled positron emission tomography (PET) imaging agents are needed which would enable general distribution of the radiotracer for clinical investigation. We sought to synthesize, radiolabel and evaluate [18F]RPS-544, a novel non-peptide CXCR4 antagonist as a CXCR4 specific probe. We compared [18F]RPS-544 with the previously published [18F]-3 ([18F]RPS-510 in this paper) in a bi-lateral tumor model of differential CXCR4 expression for its ability to selectively target CXCR4 expression. METHODS Radiolabeling of [18F]RPS-544 and [18F]RPS-510 was performed by aromatic substitution on a 6-nitropyridyl group using no-carrier-added [18F]fluoride under basic conditions. 18F incorporation was determined by radioHPLC. Semi-preparative HPLC was used to purify the final product prior to reformulation. Imaging and biodistribution was performed in nude mice with bilateral PC3 (CXCR4+ and WT) xenograft tumors at 1, 2 and 4 h post injection. RESULTS RPS-544 bound CXCR4 with an IC50 of 4.9 ± 0.3 nM. [18F]RPS-544 showed preferential uptake in CXCR4+ tumors, with a CXCR4/WT ratio of 3.3 ± 1.3 at 1 h p.i. and 2.3 ± 0.5 at 2 h p.i. Maximum uptake in the CXCR4+ tumors was 3.4 ± 1.2%ID/g at 1 h p.i., significantly greater (p = 0.003) than the uptake in the WT tumor. Tumor/blood ratios were 2.5 ± 0.4 and 3.6 ± 0.3 at 1 and 2 h p.i. Tumor/muscle ratios were >4 at all time-points. Tumor/lung ratios were >2 at 1 h and 2 h p.i. Substantial uptake was observed in the liver (15-25%ID/g), kidneys (25-35%ID/g), the small intestine (1-7%ID/g) and the large intestine (1-12%ID/g). Blood concentrations varied over time (0.5-2%ID/g). All other organs showed uptake of <1%ID/g at all time points studied with clearance profiles similar to blood clearance. CONCLUSIONS Here we present, to the best of our knowledge, the first high affinity [18F]-labeled tracer, suitable for in vivo PET imaging of CXCR4. [18F]RPS-544 displayed high affinity for CXCR4 and good tumor uptake with a maximum uptake at 1 h p.i.. CXCR4 dependent uptake was demonstrated using bilateral tumors with differential CXCR4 expression as well as pharmacological blockade using the known CXCR4 antagonist, AMD-3100. Tissue contrast as judged by tumor to normal tissue ratios was positive in several key tissues. The structural and pharmacological similarities between [18F]RPS-544 and the approved drug AMD-3465, combined with the ease of synthesis and high molar activity (>185 GBq/μmol) achieved during radiosynthesis could lead to accelerated translation into the clinic.

CAR T therapy targeting ICAM-1 eliminates advanced human thyroid tumors

Purpose: Poorly differentiated thyroid cancer and anaplastic thyroid cancer (ATC) are rare yet lethal malignancies with limited treatment options. Many malignant tumors, including papillary thyroid cancer (PTC) and ATC, are associated with increased expression of ICAM-1, providing a rationale for utilizing ICAM-1–targeting agents for the treatment of aggressive cancer. We developed a third-generation chimeric antigen receptor (CAR) targeting ICAM-1 to leverage adoptive T-cell therapy as a new treatment modality. Experimental Design: ICAM-1 CAR T cells were applied to multiple malignant and nonmalignant target cells to investigate specific target cell death and “off-tumor” toxicity in vitro. In vivo therapeutic efficacy of ICAM-1 CAR T cells was examined in ATC mouse models established from a cell line and patient-derived tumors that rapidly develop systemic metastases. Results: ICAM-1 CAR T cells demonstrated robust and specific killing of PTC and ATC cell lines in vitro. Interestingly, although certain ATC cell lines showed heterogeneous levels of ICAM-1 expression, addition of cytotoxic CAR T cells induced increased ICAM-1 expression such that all cell lines became targetable. In mice with systemic ATC, a single administration of ICAM-1 CAR T cells mediated profound tumor killing that resulted in long-term remission and significantly improved survival. Patient-derived ATC cells overexpressed ICAM-1 and were largely eliminated by autologous ICAM-1 CAR T cells in vitro and in animal models. Conclusions: Our findings are the first demonstration of CAR T therapy against both a metastatic, thyroid cancer cell line and advanced ATC patient-derived tumors that exhibit dramatic therapeutic efficacy and survival benefit in animal studies. Clin Cancer Res; 23(24); 7569–83. ©2017 AACR.

Abstract 3750: Micromolar affinity CAR T cells to ICAM-1 achieves rapid tumor elimination while avoiding systemic toxicity

Introduction: Adoptive immune therapy has achieved great success in eradicating blood-borne cancers, prominently, the CD19 CAR T cells in B cell leukemia and lymphomas. However, CAR T cell therapy in solid tumors has been limited due to the scarcity of tumor antigens that are deemed safe for targeting. One strategy to overcome scarcity of tumor antigen is by tuning the affinity of CAR to limit T cell reaction with cells overexpressing target antigen while sparing cells with basal level expression. To rigorously test the idea of “affinity tuning”, we built variants of CARs possessing one million-fold difference in affinity spanning low nanomolar to high micromolar affinity to a target antigen, and examined the influence of CAR affinity on the rate of tumor killing and systemic toxicity. Methods: Antigen-binding domain of CAR was built from the inserted or I domain belonging to integrin LFA-1. Affinity of CAR expressed in T cells was confirmed by ICAM-1 binding by flow cytometry. For in vivo study, mice with systemic growth of ICAM-1 positive thyroid tumor were used, where tumors grew in lungs, liver, and bones. Tumor growth and killing were monitored by whole body luminescence imaging. Sera were collected for cytokine analysis. Body weight, cytokine profile, and overall behavior were used to assess the severity of systemic toxicity. Results: CAR T cells with a step-wise, one million-fold variation in affinity to ICAM-1 resulted in a rate of target killing in proportion to the increase in affinity and in ICAM-1 density. Owing to cross-reaction of human LFA-1 with murine ICAM-1, the influence of CAR affinity on efficacy and on-target, off-tumor toxicity was tested in mice bearing ICAM-1 positive human tumors. In vivo tumor elimination by CAR T cells was in contrast to in vitro affinity-dependent rate of target killing, demonstrating that micromolar affinity CAR T cells was superior to nanomolar affinity T cells in both tumor killing and safety aspects. Highest affinity CAR T cells led to uniform death of the host, caused by on-target, off-tumor toxicity, and high level cytokine release. Conclusion: Our study is the first comprehensive report examining the effect of CAR affinity on the rate of tumor killing, efficacy, and toxicity. In contrast to in vitro tumor killing effect, the increase in affinity of CAR beyond certain threshold was deleterious to T cell persistence and associated with more frequent tumor relapse. Our study highlights that CAR T cells approximating natural T cell receptor affinity is more efficacious in eliminating tumors with overexpressed antigens, and is safer by avoiding potential reaction with normal cells with basal expression of the same antigen. Citation Format: Enda Shevlin, Spencer Park, Yogindra Vedvyas, Marjan Zaman, Susan Park, Irene M. Min, Moonsoo M. Jin. Micromolar affinity CAR T cells to ICAM-1 achieves rapid tumor elimination while avoiding systemic toxicity [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 3750. doi:10.1158/1538-7445.AM2017-3750