HPV E7-specific Soluble T-cell Receptor Radiopharmaceutical Therapy

Committee/Faculty

Presenting Author(s)

AJ

Angela Y. Jia, n/a

MD PhD
Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University
Baltimore, Maryland, United States

Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.

Co-Author(s)

IM

Il Minn

PhD
Department of Radiology and Radiological Sciences, Division of Nuclear Medicine and Molecular Imaging, Johns Hopkins University
Baltimore, Maryland, United States

Disclosure: Disclosure information not submitted.
CH

Christian Hinrichs

MD
Department of Cancer Immunotherapy, Rutgers Cancer Institute of New Jersey
New Brunswick, New Jersey, United States

Disclosure: Disclosure information not submitted.
TS

Tanguy Seiwert

MD
Department of Oncology, Johns Hopkins University
Baltimore, Maryland, United States

Disclosure: Disclosure information not submitted.
CF

Carole Fakhry

MD
Department of Otolaryngology Head and Neck Surgery, Johns Hopkins University
Baltimore, Maryland, United States

Disclosure: Disclosure information not submitted.
RM

Ron Mease

PhD
Department of Radiology and Radiological Sciences, Division of Nuclear Medicine and Molecular Imaging, Johns Hopkins University
Baltimore, Maryland, United States

Disclosure: Disclosure information not submitted.
CF

Catherine Foss

PhD
Department of Radiology and Radiological Sciences, Division of Nuclear Medicine and Molecular Imaging, Johns Hopkins University
Baltimore, Maryland, United States

Disclosure: Disclosure information not submitted.
MP

Martin Pomper

MD PhD
Department of Radiology and Radiological Sciences, Division of Nuclear Medicine and Molecular Imaging, Johns Hopkins University
Baltimore, Maryland, United States

Disclosure: Disclosure information not submitted.
AK

Ana P. Kiess

MD PhD
Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University
Baltimore, Maryland, United States

Disclosure: Disclosure information not submitted.

Purpose: The E7 protein encoded by the high-risk human papilloma virus (HPV) can cause malignant transformation of cells by inactivating the retinoblastoma tumor suppressor protein. E7 is an attractive therapeutic target due to its constitutive expression in HPV-related cancers but not in normal tissues. While its intracellular location has made targeting challenging, there has been recent development of an E7-specific, human HLA-A*02:01-restricted T-cell receptor with high affinity and minimal cross-reactivity to other human epitopes (Jin et al, 2018). Here we report the design and synthesis of a radiolabeled soluble version of the E7-specific, human HLA-A*02:01-restricted soluble TCR (E7-sTCR).

Methodology: The full length α and β chains of E7-TCR were truncated prior to the constant region, cloned, and expressed using HEK293 cells. The α chain was engineered to contain a His tag. The soluble protein was purified using a Cu-NTA column. HLA-A*02:01-E6 served as negative control. Functional assay was assessed using surface plasmon resonance (SPR), where single cycle-kinetics were calculated with increasing concentrations of E7-sTCR. Tyrosine radioiodination was performed to radiolabel E7-sTCR with 124-I for in vitro characterization. A competitive binding assay was performed with 0.05 nM 124-I-E7-sTCR and dilutions of cold E7-sTCR.

Results: Western blot using anti-His Ab and anti-TRBC (T-receptor beta constant) confirmed production of the α/β heterodimer. Mass spectrometry data confirmed 1:1 ratio of α:β chains. Since purification was performed using the His-tag attached to the α-chain, a 1:1 ratio suggested that the protein remains as a dimer in solution. Authentic binding using SPR demonstrated a dissociation constant (Kd) of 430 pM between HLA-E7 (monomer) and E7-sTCR, with a half-life (T1/2) of 396 s; this is comparable to the native E7-TCR (Kd of ~500 pM, T1/2 of 254 s). There was no binding of E7-sTCR to HLA-E6. The competitive binding assay showed E7-specific binding of 124-I-E7-sTCR in 4050 cells (cervical cancer, HLA*02:01+, E7+) with IC50 of 1 nM and Ki of 0.90 nM. There was only non-specific binding of 124-I-E7-sTCR in control 293-A2 cells (HLA*02:01+, E7-).

Conclusions: We report the first soluble E7-specific TCR generated that retains the ability to target HLA-E7. This provides rationale for clinical development of E7-sTCR for systemic radiopharmaceutical therapy (RPT) for HPV-related cancers, and may provide a new platform for using sTCR-RPTs to target many other intracellular cancer specific antigens.

References: Jin BY, Campbell TE, Draper LM, et al. Engineered T cells targeting E7 mediate regression of human papillomavirus cancers in a murine model. JCI Insight 2018;3.