Safety and Efficacy of Intratumoral Injections of Chimeric Antigen Receptor (CAR) T Cells in Metastatic Breast Cancer

Abstract

Chimeric antigen receptors (CARs) are synthetic molecules that provide new specificities to T cells. Although successful in treatment of hematologic malignancies, CAR T cells are ineffective for solid tumors to date. We found that the cell-surface molecule c-Met was expressed in ~50% of breast tumors, prompting the construction of a CAR T cell specific for c-Met, which halted tumor growth in immune-incompetent mice with tumor xenografts. We then evaluated the safety and feasibility of treating metastatic breast cancer with intratumoral administration of mRNA-transfected c-Met-CAR T cells in a phase 0 clinical trial (NCT01837602). Introducing the CAR construct via mRNA ensured safety by limiting the non-tumor cell effects (on-target/off-tumor) of targeting c-Met. Patients with metastatic breast cancer with accessible cutaneous or lymph node metastases received a single intratumoral injection of 3 × 107 or 3 × 108 cells. CAR T mRNA was detectable in peripheral blood and in the injected tumor tissues after intratumoral injection in two and four patients, respectively. mRNA c-Met-CAR T cells cell injections were well tolerated, as none of the patients had study drug–related adverse effects greater than grade 1. Tumors treated with intratumoral injected mRNA c-Met-CAR T cells were excised and analyzed by immunohistochemistry, revealing extensive tumor necrosis at the injection site, cellular debris, loss of c-Met immunoreactivity, all surrounded by macrophages at the leading edges and within necrotic zones. We conclude that intratumoral injections of mRNA c-Met-CAR T cells are well tolerated and evoke an inflammatory response within tumors.

Characterization of triple‐negative breast cancer preclinical models provides functional evidence of metastatic progression

“…Furthermore, high‐lipid content and low‐cellular density in the tumor stroma generated a softer tumor mass with a threefold higher EPR effect, thereby providing a model to assess EPR‐related passive tumor accumulation, especially important for the effectiveness of nanomedicinal approaches to cancer treatment . The flexibility and permeability of the MDA‐MB‐231‐Luc model stroma may also provide a means to assess intratumoral administration strategies …”

“…7,30,31 The flexibility and permeability of the MDA-MB-231-Luc model stroma may also provide a means to assess intratumoral administration strategies. 32 The metabolomic comparison of 4T1 and MDA-MB-231-Luc primary tumors suggests that specific metabolic alterations could explain the differences observed in growth rates, with guanosine and uracil (a pyrimidine derivative) the two most relevant soluble metabolites contributing to model discrimination. Interestingly, Tayyari et al 33 reported that TNBC tumors displayed increased pyrimidine synthesis and elevated levels of myoinositol and taurine, similar to findings in our 4T1 primary tumors.…”

mRNA as novel technology for passive immunotherapy

“…However, this could be a consequence of the murine origin of this domain. In another trial, mRNAtransfected CAR T cells were injected intratumorally in metastatic breast cancer patients [253]. Treatment was well tolerated and elicited an inflammatory response within tumors.…”

Chimeric Antigen Receptor T Cells: Extending Translation from Liquid to Solid Tumors

“…69 In addition to gammaretroviral and lentiviral vectors, novel SIN vectors based on alpharetroviral Rous sarcoma virus and foamy virus 70,71 have also been created, which tend to have a more neutral integration behavior with respect to localization close to promoter/enhancer elements and gene transcription units, 72 and are thus considered to be safer tools for genetic modification. 73,74 Other interesting modalities for delivery of CARs were successfully developed and applied in clinical trials, including mRNA delivery 75,76 and Sleeping Beauty transposons. 77 While lentiviral, gammare-troviral, and alpharetroviral vectors can be used to deliver transgene cassettes up to approximately 8-10 kb in size, 78-81 the non-viral Sleeping Beauty transposon/transposase system can efficiently transfer transgene cassettes >10 kb in length, although with lower efficiency than transfer of 7 kb transgenes.…”