Abstract OT1-16-01: A multicenter phase II study of vaccines to prevent recurrence in patients with HER-2 positive breast cancer

Background: HER2-positive breast cancer patients are commonly treated with neoadjuvant therapy including HER2-targeted therapy. Patients who have residual invasive disease have less favorable outcomes with an increased risk of recurrent disease than patients with complete pathologic response (pCR). It has also been observed that these non-pCR patients have low or absent anti-HER-2 CD4 Th1 responses. We hypothesized that correcting the anti-HER-2 CD4 Th1 response using vaccines will increase interferon gamma production which we have shown is a potent inducer of apoptosis and senescence in HER2-positive breast cancer. This study will be evaluating safety and immunogenicity of two vaccines (multivalent anti-oncodriver DNA vaccine (WOKVAC) or HER-2-pulsed dendritic cell vaccine (DC1)). Methods: This is a multi-center, phase 2, randomized study to determine the safety and tolerability of HER2 vaccines (DC1 and WOKVAC), assess immunogenicity, and evaluate recurrence free survival. Patients with HER2-positive early breast cancer (stage I-III) are eligible if they have residual invasive disease in the breast or axilla at surgery after receiving neoadjuvant chemotherapy plus HER2 -targeted therapy. Patients are randomly assigned in a 1:1 ratio to receive 1 of 2 adjuvant HER2 vaccines, either DC1 or WOKVAC for 1 year. A permuted-block randomization scheme was used with stratification according to residual cancer burden (RCB) (1+2 vs 3). The primary end points are safety and immunogenicity (immune response rate measured by ELISPOT). Each treatment arm will be assessed separately. Any statistical comparison between arms is purely exploratory, as this study is neither designed nor powered for comparative hypotheses. Secondary endpoints include recurrence-free survival. Exploratory analyses include the assessment of prognostic and predictive biomarkers including circulating tumor cells, serum HER2 levels, and other immune markers. The enrollment began in 2018 and we plan to accrue the total of 110 patients. ClinicalTrials.gov Identifier: NCT03384914

Citation Format: Hyo S Han, Mary Disis, Robert Wesolowski, Carla Fisher, Shipra Gandhi, Nancy Chan, William Gwin, Keerthi Gogineni, Rosemarie Mick, Christina Sierra Rodriguez, Deanna Hogue, Hien Liu, Ricardo Costa, Brian Czerniecki. A multicenter phase II study of vaccines to prevent recurrence in patients with HER-2 positive breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT1-16-01.

Combination of ultrasound-based mechanical disruption of tumor with immune checkpoint blockade modifies tumor microenvironment and augments systemic antitumor immunity

Background

Despite multimodal adjuvant management with radiotherapy, chemotherapy and hormonal therapies, most surgically resected primary breast cancers relapse or metastasize. A potential solution to late and distant recurrence is to augment systemic antitumor immunity, in part by appropriately presenting tumor antigens, but also by modulating the immunosuppressive tumor microenvironment (TME). We previously validated this concept in models of murine carcinoma treated with a novel predominately microcavitating version of high-intensity focused ultrasound (HIFU), mechanical high-intensity focused ultrasound (M-HIFU). Here we elucidated the mechanisms of enhanced antitumor immunity by M-HIFU over conventional thermal high-intensity focused ultrasound (T-HIFU) and investigated the potential of the combinatorial strategy with an immune checkpoint inhibitor, anti-PD-L1 antibody.

Methods

The antitumor efficacy of treatments was investigated in syngeneic murine breast cancer models using triple-negative (E0771) or human ErbB-2 (HER2) expressing (MM3MG-HER2) tumors in C57BL/6 or BALB/c mice, respectively. Induction of systemic antitumor immunity by the treatments was tested using bilateral tumor implantation models. Flow cytometry, immunohistochemistry, and single-cell RNA sequencing were performed to elucidate detailed effects of HIFU treatments or combination treatment on TME, including the activation status of CD8 T cells and polarization of tumor-associated macrophages (TAMs).

Results

More potent systemic antitumor immunity and tumor growth suppression were induced by M-HIFU compared with T-HIFU. Molecular characterization of the TME after M-HIFU by single-cell RNA sequencing demonstrated repolarization of TAM to the immunostimulatory M1 subtype compared with TME post-T-HIFU. Concurrent anti-PD-L1 antibody administration or depletion of CD4⁺ T cells containing a population of regulatory T cells markedly increased T cell-mediated antitumor immunity and tumor growth suppression at distant, untreated tumor sites in M-HIFU treated mice compared with M-HIFU monotherapy. CD8 T and natural killer cells played major roles as effector cells in the combination treatment.

Conclusions

Physical disruption of the TME by M-HIFU repolarizes TAM, enhances T-cell infiltration, and, when combined with anti-PD-L1 antibody, mediates superior systemic antitumor immune responses and distant tumor growth suppression. These findings suggest M-HIFU combined with anti-PD-L1 may be useful in reducing late recurrence or metastasis when applied to primary tumors.

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

PURPOSE

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).

PATIENTS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.