Transfer of Cellular and Humoral Anti-Tumor Immunity with Immune T Cells After Stem Cell Transplant (SCT) for Metastatic Breast Cancer Following “Vaccination” with Anti-CD3 x Anti-Her2/Neu Bispecific Antibody (Her2Bi) Armed Activated T Cells
Authors: Thakur Archana , Al-Kadhimi Zaid , Pray Cassara , Tomaszewski Elyse N. , Rathore Ritesh , Steele Patricia A. , Abidi Muneer H. , Ayash Lois , Schalk Dana L , Myers Karen , Mitchell Alice , Deol Abhinav , Uberti Joseph P. , Ratanatharathorn Voravit , Lum Lawrence G 
Published: October 2019

Abstract
Abstract 1914
Novel therapeutic approaches are needed for women with metastatic breast cancer (BrCa). In our phase I clinical trial, infusions of anti-CD3 activated T cells (ATC) armed with anti-CD3 x anti-Her2/neu bispecific antibody (Her2Bi) induced specific cytotoxicity (SC) directed at SK-BR-3 breast cancer cells by fresh peripheral blood lymphocytes (PBL) and induced elevated serum levels of Th1 cytokines. In this study, we took advantage of armed ATC induced anti-tumor immune responses by infusing “immune” T cells collected by leukopheresis. We expanded “immune T cells” with anti-CD3 and IL-2, followed by a cryopreservation for multiple re-infusions of ATC after high dose chemotherapy (HDC) and autologous stem cell transplant (SCT). We asked whether this approach would transfer anti-tumor responses back into patients after HDC and SCT to accelerate the development of cellular and humoral anti-tumor responses. This strategy of “prime” with armed ATC and “boost” with ATC was performed in 5 evaluable patients. The “priming” portion involved 8 infusions of (2 infusions/week for 4 weeks) armed ATC given with daily low dose IL-2 (300,000 IU/m2/day) and twice weekly GM-CSF (250 μg/m2). Approximately 3 weeks after the armed ATC infusions, patients underwent a second leukopheresis for the collection and expansion of ATC. The expanded ATC from 6 patients at an effector:target ratio (E/T) of 25:1 exhibited specific cytotoxicity (SC) ranging from 3.7–25.8 (mean = 13.6%) directed at the SK-BR-3. Phenotyping of the ATC showed a mean of 50.2 % (25–74) CD4+ cells, 30.4 % (16.3-51.3) CD8+ cells, 11.6% (4.5-24.3) CD56+CD16+ cells, and 29.5% (10.4–41) CD4+CD25+ cells. A separate leukopheresis after G-CSF stimulation was performed to obtain CD34+ cells for the SCT. After HDC and PBSCT, 5 evaluable patients received multiple infusions with a mean total of 54×109 ATC (16–110 × 109) beginning day +1 after SCT. No G-CSF was given to accelerate engraftment. There were no dose-limiting side effects or delays in engraftment. One patient developed sepsis, multiple organ failure and recovered fully with supportive care and antibiotics. Phenotyping at 2 weeks after SCT showed the mean proportions of CD4+ and CD8+ cells to be 55.5 and 17.7%, respectively. Specific cytotoxicity (SC) directed at SK-BR-3 targets ranged from 4.7 to 70% at E/T of 25:1 up to 18 months post SCT but not against a negative control cell line-Daudi. Mean serum anti-SK-BR-3 antibody levels were 800 ng/ml preSCT and 1500, 1080 and 1360 ng/ml at 1, 2, and 3 months post SCT, respectively. In vitro anti-SK-BR-3 antibody synthesis was assessed using a new assay (Thakur et al, Cancer Immunol Immunother EPub, 2011) showed easily detectable levels of in vitro anti-SK-BR-3 antibody synthesis. The mean anti-SK-BR-3 antibody synthesis in the presence of CpG in pre-immunotherapy (Pre-IT), mid-IT, 1 months post-IT, pre-SCT and 1, 2, and 3 months post-SCT is summarized in the table. PBL produced anti-SK-BR-3 antibody pre-SCT and there was clear recovery of anti-SK-BR-3 antibody synthesis by PBL at 2 and 3 months after SCT. These data show infusions of immune ATC transferred cytotoxic T lymphocytes and humoral antibody activity directed at tumor antigens. These novel findings suggest that adaptive immunity was transferred into patients by ATC infusions and the stem cell product after myeloablation and SCT leading to rapid reconstitution of anti-tumor immunity.Time PointsCulture ConditionsMean±SD (n=3)Pre-ITCpG23±27Mid-ITCpG66±671M Post-ITCpG41±67Pre-SCTCpG92±101M Post-SCTCpG9±182M Post-SCTCpG45±273M Post-SCTCpG82±55

Disclosures:
Lum: Transtarget Inc: Equity Ownership, Founder of Transtarget.