Oncolytic virotherapy has shown great promise in mediating targeted tumor destruction through tumor-selective replication and induction of anti-tumor immunity; however, obstacles remain for virus candidates to reach the clinic. These include avoiding neutralizing antibodies, preventing stimulation of the adaptive immune response during intravenous administration, and inducing sufficient apoptosis and immune activation so that the body’s defense can work to eradicate systemic disease. We have developed a co-formulation of oncolytic viruses (OVs) with Imagent^® lipid-encapsulated, perfluorocarbon microbubbles (MBs) to protect the OVs from the innate and adaptive immune system. Once inside the MB, the viral particles become acoustically active such that external ultrasound can target the delivery of the virus locally within the tumor. Humanized NSG female mice (Hu-CD34⁺ NSG-SGM3) engrafted in their flanks with MDA-MB-231-Luc triple-negative breast cancer (TNBC) cells were transduced with MB/OVs, with or without adjuvant Pembrolizumab treatment, and tumor sizes and tumor necrosis were assessed. The presence of CD8⁺ (cytotoxic T-cells), CD4⁺ (helper T-cells), and CD25⁺ (Tregs) tumor-infiltrating lymphocytes (TILs) was quantified in the tumor samples by immunohistochemistry. In an in vivo model of humanized mice engrafted with a human immune system, we observed significantly greater tumor necrosis and smaller tumor mass in human TNBC xenografts systemically treated with MB/OV complexes in the presence or absence of pembrolizumab adjuvant treatment, compared to controls. Additionally, we observed a low ratio of CD4⁺/CD8⁺ TILs and a high ratio of CD8⁺/CD25⁺ TILs in the MDA-MB-231 xenografts treated with MB/OVs complexes with or without pembrolizumab adjuvant treatment, compared to controls. Our study demonstrated the feasibility of using MBs to target OVs to TNBC through diagnostic ultrasound, which decreased tumor mass by increasing tumor necrosis and stimulated a local and systemic antitumoral immune response by increasing intratumoral CD8⁺ T-cytotoxic lymphocyte infiltration and decreasing CD25⁺ Treg cells.

Background/Objectives: Immune checkpoint inhibitors targeting the PD-1/PD-L1 axis have transformed cancer treatment, yet therapeutic responses remain limited in many solid tumors due to poor and uneven drug distribution within the tumor microenvironment (TME). Here, we evaluated whether co-formulation of an anti-PD-1 antibody (RMP1-14, murine surrogate for pembrolizumab) with Imagent^® microbubble/liposome (MBLP) complexes and ultrasound activation could enhance tumor-specific delivery while reducing systemic exposure. Methods: Immunocompetent MC-38 colorectal tumor-bearing mice (B6(Cg)-Tyrc-2J/J, 7-week-old females) received isotype control, isotype/MBLP/US, RMP1-14 alone, RMP1-14/MBLP, or RMP1-14/MBLP/US. Survival was analyzed by Kaplan–Meier curves, tumor necrosis by H&E staining, antibody biodistribution by immunohistochemistry, and tumor perfusion by laser speckle imaging. Results: No significant differences in tumor size or body weight were observed between groups. Survival analysis showed significant improvements in the RMP1-14 (p = 0.013) and RMP1-14/MBLP/US (p = 0.047) groups versus isotype controls, with the RMP1-14/MBLP/US group achieving the longest mean survival (57.8 days vs. 26.5 days for RMP1-14 alone) and complete tumor regression in 2/8 mice. The RMP1-14/MBLP/US group demonstrated significantly greater tumor necrosis than all other groups. Immunohistochemical analysis confirmed a 6.1-fold increase in intratumoral antibody accumulation with MBLP/US versus RMP1-14 alone (p = 0.0003), alongside significantly reduced off-target exposure in spleen, liver, kidney, and heart. Laser speckle imaging revealed a transient ~30% increase in tumor perfusion during MBLP/US treatment, consistent with cavitation-mediated hemodynamic effects. Conclusions: These findings demonstrate that MBLP/US co-formulation enhances intratumoral delivery of checkpoint inhibitors, improves survival, and reduces systemic organ exposure, representing a promising platform to improve the efficacy and safety profile of antibody-based immunotherapy.

Head and neck squamous cell carcinoma (HNSCC) accounts for ~3% of U.S. cancer diagnoses, and many patients present with locally or regionally advanced disease. Despite multimodal standard-of-care (SOC) treatment, the median overall survival for recurrent or metastatic disease remains ~12 months. Acquired resistance to cisplatin (CDDP) and radiotherapy (RT) remains a central barrier to durable response, motivating neoadjuvant strategies to improve efficacy in resistant tumors. Benzyl isothiocyanate (BITC) is a dietary phytochemical with selective anticancer activity. Across four patient-matched HNSCC cell lines spanning a range of intrinsic sensitivities to CDDP or RT, pretreatment with BITC before RT and CDDP significantly increased HNSCC cell death as measured by caspase-3/7 activity, regardless of each cell line’s single-agent sensitivity. Within 24 h, BITC elevated cytoplasmic ROS across all lines: BITC-resistant cell lines countered this with a more robust increase in the GSH/GSSG ratio and retained viability, whereas the BITC-sensitive lines mounted a weaker glutathione (GSH) response and required rescue with exogenous GSH or N-acetylcysteine (NAC), indicating redox-sensitive cytotoxicity. Transcriptomic time-course analysis suggested that BITC induces a coordinated stress response, including proteotoxic HSF1 activation, and suppresses DNA replication and homologous recombination repair, thereby supporting a transcriptional basis for the observed sensitization to DNA-damaging therapy. By enhancing the efficacy of RT and CDDP in HPV-negative HNSCC, BITC may be a promising neoadjuvant strategy to improve the therapeutic index of chemotherapy and radiation in these patients, warranting further investigation.