Vaccine-Induced Memory CD8(+) T Cells Provide Clinical Benefit in HER2 Expressing Breast Cancer: A Mouse to Human Translational Study.

Immune-based therapy for metastatic breast cancer has had limited success, particularly in molecular subtypes with low somatic mutations rates. Strategies to augment T-cell infiltration of tumors include vaccines targeting established oncogenic drivers such as the genomic amplification of HER2. We constructed a vaccine based on a novel alphaviral vector encoding a portion of HER2 (VRP-HER2). In preclinical studies, mice were immunized with VRP-HER2 before or after implantation of hHER2+ tumor cells and HER2-specific immune responses and antitumor function were evaluated. We tested VRP-HER2 in a phase I clinical trial where subjects with advanced HER2-overexpressing malignancies in cohort 1 received VRP-HER2 every 2 weeks for a total of 3 doses. In cohort 2, subjects received the same schedule concurrently with a HER2-targeted therapy. Vaccination in preclinical models with VRP-HER2 induced HER2-specific T cells and antibodies while inhibiting tumor growth. VRP-HER2 was well tolerated in patients and vaccination induced HER2-specific T cells and antibodies. Although a phase I study, there was 1 partial response and 2 patients with continued stable disease. Median OS was 50.2 months in cohort 1 (n = 4) and 32.7 months in cohort 2 (n = 18). Perforin expression by memory CD8 T cells post-vaccination significantly correlated with improved PFS. VRP-HER2 increased HER2-specific memory CD8 T cells and had antitumor effects in preclinical and clinical studies. The expansion of HER2-specific memory CD8 T cells in vaccinated patients was significantly correlated with increased PFS. Subsequent studies will seek to enhance T-cell activity by combining with anti-PD-1.

Crosby EJ ，Gwin W ，Blackwell K ，Marcom PK ，Chang S ，Maecker HT ，Broadwater G ，Hyslop T ，Kim S ，Rogatko A ，Lubkov V ，Snyder JC ，Osada T ，Hobeika AC ，Morse MA ，Lyerly HK ，Hartman ZC ... -  《-》

Heterologous human/rat HER2-specific exosome-targeted T cell vaccine stimulates potent humoral and CTL responses leading to enhanced circumvention of HER2 tolerance in double transgenic HLA-A2/HER2 mice.

DNA vaccines composed of heterologous human HER2 and rat neu sequences induce stronger antibody response and protective antitumor immunity than either HER2 or neu DNA vaccines in transgenic mice. We previously developed HER2-specific exosome-targeted T-cell vaccine HER2-TEXO capable of stimulating HER2-specific CD8+ T-cell responses, but only leading to partial protective immunity in double-transgenic HLA-A2/HER2 mice with self-immune tolerance to HER2. Here, we constructed an adenoviral vector AdVHuRt expressing HuRt fusion protein composed of NH2-HER21-407 (Hu) and COOH-neu408-690 (Rt) fragments, and developed a heterologous human/rat HER2-specific exosome-targeted T-cell vaccine HuRt-TEXO using polyclonal CD4+ T-cells uptaking exosomes released by AdVHuRt-transfected dendritic cells. We found that the HuRt-TEXO vaccine stimulates enhanced CD4+ T-cell responses leading to increased induction of HER2-specific antibody (∼70 µg/ml) compared to that (∼40 µg/ml) triggered by the homologous HER2-TEXO vaccine. By using PE-H-2Kd/HER223-71 tetramer, we determined that HuRt-TEXO stimulates stronger HER2-specific CD8+ T-cell responses eradicating 90% of HER2-specific target cells, while HER2-TEXO-induced CD8+ T-cell responses only eliminating 53% targets. Furthermore, HuRt-TEXO, but not HER2-TEXO vaccination, is capable of suppressing early stage-established HER2-expressing 4T1HER2 breast cancer in its lung metastasis or subcutaneous form in BALB/c mice, and of completely protecting transgenic HLA-A2/HER2 mice from growth of HLA-A2/HER2-expressing BL6-10A2/HER2 melanoma. HuRt-TEXO-stimulated HER2-specific CD8+ T-cells not only are cytolytic to trastuzumab-resistant HLA-A2/HER2-expressing BT474/A2 breast tumor cells in vitro but also eradicates pre-established BT474/A2 tumors in athymic nude mice. Therefore, our novel heterologous human/rat HER2-specific T-cell vaccine HuRt-TEXO, circumventing HER2 tolerance, may provide a new therapeutic alternative for patients with trastuzumab-resistant HER2+ breast tumor.

Xie Y ，Wu J ，Xu A ，Ahmeqd S ，Sami A ，Chibbar R ，Freywald A ，Zheng C ，Xiang J ... -  《-》

Sequential Anti-PD1 Therapy Following Dendritic Cell Vaccination Improves Survival in a HER2 Mammary Carcinoma Model and Identifies a Critical Role for CD4 T Cells in Mediating the Response.

Kodumudi KN ，Ramamoorthi G ，Snyder C ，Basu A ，Jia Y ，Awshah S ，Beyer AP ，Wiener D ，Lam L ，Zhang H ，Greene MI ，Costa RLB ，Czerniecki BJ ... -  《Frontiers in Immunology》

Targeting of the non-mutated tumor antigen HER2/neu to mature dendritic cells induces an integrated immune response that protects against breast cancer in mice.

Wang B ，Zaidi N ，He LZ ，Zhang L ，Kuroiwa JM ，Keler T ，Steinman RM ... -  《-》

Stimulation of Oncogene-Specific Tumor-Infiltrating T Cells through Combined Vaccine and αPD-1 Enable Sustained Antitumor Responses against Established HER2 Breast Cancer.

Despite promising advances in breast cancer immunotherapy, augmenting T-cell infiltration has remained a significant challenge. Although neither individual vaccines nor immune checkpoint blockade (ICB) have had broad success as monotherapies, we hypothesized that targeted vaccination against an oncogenic driver in combination with ICB could direct and enable antitumor immunity in advanced cancers. Our models of HER2+ breast cancer exhibit molecular signatures that are reflective of advanced human HER2+ breast cancer, with a small numbers of neoepitopes and elevated immunosuppressive markers. Using these, we vaccinated against the oncogenic HER2Δ16 isoform, a nondriver tumor-associated gene (GFP), and specific neoepitopes. We further tested the effect of vaccination or anti-PD-1, alone and in combination. We found that only vaccination targeting HER2Δ16, a driver of oncogenicity and HER2-therapeutic resistance, could elicit significant antitumor responses, while vaccines targeting a nondriver tumor-specific antigen or tumor neoepitopes did not. Vaccine-induced HER2-specific CD8+ T cells were essential for responses, which were more effective early in tumor development. Long-term tumor control of advanced cancers occurred only when HER2Δ16 vaccination was combined with αPD-1. Single-cell RNA sequencing of tumor-infiltrating T cells revealed that while vaccination expanded CD8 T cells, only the combination of vaccine with αPD-1 induced functional gene expression signatures in those CD8 T cells. Furthermore, we show that expanded clones are HER2-reactive, conclusively demonstrating the efficacy of this vaccination strategy in targeting HER2. Combining oncogenic driver targeted vaccines with selective ICB offers a rational paradigm for precision immunotherapy, which we are clinically evaluating in a phase II trial (NCT03632941).

Crosby EJ ，Acharya CR ，Haddad AF ，Rabiola CA ，Lei G ，Wei JP ，Yang XY ，Wang T ，Liu CX ，Wagner KU ，Muller WJ ，Chodosh LA ，Broadwater G ，Hyslop T ，Shepherd JH ，Hollern DP ，He X ，Perou CM ，Chai S ，Ashby BK ，Vincent BG ，Snyder JC ，Force J ，Morse MA ，Lyerly HK ，Hartman ZC ... -  《-》