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Development of a Novel Nanoparticle-based GMP Platform for the Generation of Tumor-Specific CD8+ T cells

Juan Carlos Varela1,2, Sojung Kim2, Lauren Suarez2, Dan Bednárik2, Kristi Jones2, Scott Carmer2, Mathias Oelke2

1 Department of Hematology and Oncology, Hollings Cancer Center, Medical University of South Carolina, Charleston, SC; 2NexImmune, Gaithersburg, MD.

Abstract Artificial Antigen Presenting Cells (aAPCs)

Figure 2. Erichment and Expansion of Antigen-specific CD8+ T cells. Leukopheresisproduct is collected from human donor and is put into a CliniMacs-Prodigy® cell expansion system (Myltenyi Biotech). Magnetic separation is used to deplete CD4+ T cells and to enrich for antigen-specific CD8+ T cells using our aAPCs. The enriched cell suspension is placed in G-REX expansion flasks in combination with a proprietary cytokine mix. Cultures are expanded for two weeks. Using this process we have consistently generated clinically-relevant numbers of CD8+ antigen-specific T cells.

Conclusions• We have generated a fully humanized, GMP-grade aAPCs that can be used for the enrichment and expansion of antigen-specific CD8+ T cells

• We have developed a novel GMP, semi-automatic T cell expansion platform using our humanized aAPCS

• Using our expansion platform we have successfully generated clinically-relevant numbers of AML-specific CD8+ T cells. These AML-specific T cells are a combination of central memory and effector memory T cells and are able to effectively kill an AML cells in vitro.

• The data presented here will the foundation for the development and implementation of a phase I clinical trial using AML-specific CD8+ T cells for the Treatment of AML relapsed after HSCT.

Phase I Clinical Trial in AML

Efficient ex-vivo generation of non-genetically engineered tumor-specific T cells remains a significant hurdle for the broad application of adoptive cell transfer (ACT) protocols for the treatment of cancer. Here, we describe a novel nanoparticle-based platform for generating tumor-specific T cells using artificial antigen presenting cells (aAPCs).Our aAPCs consist of a paramagnetic nanoparticle decorated with humanized HLA-A2-Ig dimer-molecules and anti-CD28 antibodies. aAPCs are loaded with tumor derived HLA-A2 restricted peptides and are used for the enrichment and expansion of tumor-specific CD8+ T cells. Using our aAPCs we have developed a fully enclosed semi-automated, GMP T cell expansion platform that consistently generates clinically relevant numbers of tumor-specific CD8+ T cells in only 14 days, thus obviating the need for dendritic cell-based T cell expansion.Utilizing this platform we simultaneously generated CD8+ T cells targeting the acute myeloid leukemia (AML) antigens WT1, PRAME, Survivin and Cyclin A1. During the 14 day expansion to clinically-relevant numbers of AML-specific CD8+T cells we observed fold changes in the range of 500 to >5000-fold. Importantly, the generated T cells were >90% of the memory phenotype consisting of both central memory and effector memory CD8+ T cells. In addition, we demonstrated that the AML-specific CD8+ T cells were able to mediate specific in vitro killing of the AML cell line THP-1.The results reported here will be the foundation for the development of a multi-institution phase I clinical trial of adoptive T cell transfer for the treatment of relapsed AML after allogeneic hematopoietic stem cell transplant.

Figure 1. Humanized Artificial Antigen Presenting Cells (aAPCs). aAPCs consist of a superparamagnetic iron-oxide nanoparticle decorated with humanized HLA-IgG4-A2 hinge dimer (signal 1) and humanized anti-CD28 antibody (signal 2). aAPCs can be loaded with a HLA-A2 restricted peptide of choice and lead to the activation and proliferation of antigen-specific CD8+ T cells.

GMP, Semi-automatic T cell Expansion Platform

MART1 as Model Antigen

Conclusions

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WT1(37) WT1(126) PRAME(142) PRAME(425) Survivin(95) TotalAMLspecificity

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1 in104 129500 3.92x106 302x

1 in105 12950 3.92x106 3027x

1 in106 1295 3.92x106 30270x

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Non-specific target: Unloaded NA8-MelSpecific target: MART1-loaded NA8-MelEffector cells: MART126Assay Time: 4 hours

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10:120:140:1E:TRatio

Non-specific target: K562 CML lineSpecific target: THP-1 AML lineEffector cells: Cocktail 1: WT137,126, PRAME142, 425 and survivin95

Cocktail 2: WT1235, PRAME435, survivin104, cyclin A1227, 34Assay Time: 6-8 hours

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CD45RA

Figure 3. Generation of MART1-specific CD8+ T cells. We optimized our expansion platform by using the model tumor antigen MART1. A) Representative FACS plots showing MART1-specifity after a 14-day expansion. B) Total numbers of MART1-specific CD8+ T cells on day 0 and after a 14-day expansion. C) Representative FACS plot showing the memory phenotype of MART1-specific CD8+ T cells on day 14 as determined by CD62L and CD45RA expression. D) In vitro cytotoxicity assay (CFSE-based) showing antigen-specific killing of MART1+ tumor cells by CD8+ MART1-specific T cells generated via our expansion platform

A) B)

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AML-specific Antigens

CD62L

CD45RA

CD62L

Figure 4. Generation of AML-specific CD8+ T cellls. Using our 14-day GMP, semiautomatic T cell expansion platform, we successfully generated clinically-relevant numbers of AML-specific T cells targeting the tumor-associated antigens WT1, PRAME, Cyclin A1 and Survivin. A) Percentages of AML-specific of CD8+ T cells after 14 days of batched expansion. B) Total number of AML-specific T cells on day 0 and day 14 following expansion. Table depicts calculated fold change using different precursor frequencies C) Representative FACS plot and graph showing the memory phenotype of the expanded CD8+ T cells on day 14. D) In vitro cytotoxicity assay (CFSE-based) showing antigen-specific killing of the AML cell line THP1 by AML-specific CD8+ T cells generated via our expansion platform.

A)

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Figure 5. Schema for a planned Phase I Clinical Trial using AML-specific CD8+ T cells for the Treatment of AML relapsed after Allogeneic Hematopoietic Stem Cell Transplant (HSCT). We are planning a multi-institutional phase I clinical trial using AML-specific CD8+ T cells generated via our expansion platform. The patient population will be AML patients who have relapsed after an allogeneic HSCT. The AML-specific CD8+ T cells will be generated from the HSCT donor. Primary objectives will be safety and dose finding. Secondary objective will be ORR at 30 days after T cell infusion.

Relapsed AML after Allo-HSCT

Azacitidine 75mg/m2

Infusion of Donor-derived AML-specific CD8+ T cells

DAYS 1-7 DAY 29

Low Dose IL-2

DAY 30-43 DAY 58

30-day ORR Read out

Enrichement and Expansion of donor-derived CD8+ T cells targeting WT1, PRAME and cyclin A1

Three dosing cohorts (3-5 patients each)• 5x107 Total CD8+ T cells• 1x108 Total CD8+ T cells• 2x108 Total CD8+ T cells

D)