Transmission-blocking strategies that slow the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and protect against coronavirus disease 2019 (COVID-19) are needed. We have developed an orally delivered adenovirus type 5–vectored SARS-CoV-2 vaccine candidate that expresses the spike protein. Here, we demonstrated that hamsters vaccinated by the oral or intranasal route had robust and cross-reactive antibody responses. We then induced a postvaccination infection by inoculating vaccinated hamsters with SARS-CoV-2. Orally or intranasally vaccinated hamsters had decreased viral RNA and infectious virus in the nose and lungs and experienced less lung pathology compared to mock-vaccinated hamsters after SARS-CoV-2 challenge. Naïve hamsters exposed in a unidirectional air flow chamber to mucosally vaccinated, SARS-CoV-2–infected hamsters also had lower nasal swab viral RNA and exhibited fewer clinical symptoms than control animals, suggesting that the mucosal route reduced viral transmission. The same platform encoding the SARS-CoV-2 spike and nucleocapsid proteins elicited mucosal cross-reactive SARS-CoV-2–specific IgA responses in a phase 1 clinical trial (NCT04563702). Our data demonstrate that mucosal immunization is a viable strategy to decrease SARS-CoV-2 disease and airborne transmission.

As new SARS-CoV-2 variants continue to emerge and impact communities worldwide, next-generation vaccines that enhance protective mucosal immunity may have a significant impact on productive infection and transmission. We have developed recombinant non-replicating adenovirus serotype 5 (rAd5) vaccines delivered by mucosal administration that express both target antigen and a novel molecular adjuvant within the same cell. Here, we describe the immunogenicity of three unique SARS-CoV-2 rAd5 vaccine candidates and their efficacy following viral challenge in non-human primates (NHPs). Intranasal immunization with rAd5 vaccines expressing Wuhan, or Beta variant spike alone, or Wuhan spike and nucleocapsid elicited strong antigen-specific serum IgG and IgA with neutralizing activity against multiple variants of concern (VOC). Robust cross-reactive mucosal IgA was detected after a single administration of rAd5, which showed strong neutralizing activity against multiple VOC. Additionally, mucosal rAd5 vaccination increased spike-specific IFN-γ producing circulating T-cells. Upon Beta variant SARS-CoV-2 challenge, all the vaccinated NHPs exhibited significant reductions in viral load and infectious particle shedding in both the nasal passages and lower airways. These findings demonstrate that mucosal rAd5 immunization is highly immunogenic, confers protective cross-reactive antibody responses in the circulation and mucosa, and reduces viral load and shedding after SARS-CoV-2 challenge.

Background: Leptomeningeal disease (LMD) is a devastating complication of metastatic breast cancer that leads to severe neurologic symptoms and poor prognosis. Current treatment options, including radiation and intrathecal chemotherapy, offer limited efficacy and are associated with significant toxicity. Generally, systemic therapy in LMD poorly penetrates the blood-brain barrier (BBB). Leveraging the L-type amino acid transporter 1 (LAT1) represents a unique therapeutic strategy, as LAT1 facilitates transport of medications across the BBB, and is also highly expressed in metastatic cancer cells. QBS72S is a first-in-class BBB-penetrant bifunctional molecule targeting overexpression of LAT1 to selectively eliminate cancer cells. It has shown preclinical efficacy in a mouse model of breast cancer LMD. Methods: This Phase 2a, single-arm, open-label clinical trial (NCT05305365) investigated the safety, cerebrospinal fluid (CSF) concentration, pharmacokinetics, and preliminary efficacy of QBS72S in participants with breast cancer brain metastases. Secondary endpoints included progression-free survival, overall survival, and duration of response. Correlative analyses included LAT1 immunohistochemistry and CSF cell-free RNA sequencing. Results: In this analysis, we report results from breast cancer participants with LMD (n = 10) treated with QBS72S. QBS72S was reliably detected in CSF, adequately tolerated, and two participants exhibited long-term radiographic stability or improvement lasting 6-7 months. Conclusions: These early findings support further investigation of QBS72S as a targeted therapy for LMD, addressing an urgent unmet need in metastatic breast cancer.