Background: Immunotherapy has revolutionized the therapeutical regimen for nasopharyngeal carcinoma (NPC), yet its response rate remains insufficient. Programmed death-ligand 1 (PD-L1) on small extracellular vesicles (sEVs) mediates local and peripheral immunosuppression in tumors, and the mechanism of PD-L1 loading into these vesicles is garnering increasing attention. Latent membrane protein 1 (LMP1), a key viral oncoprotein expressed in Epstein-Barr virus (EBV)-positive NPC, contributes to remodeling the tumor microenvironment. However, the precise mechanisms by which LMP1 modulates tumor immunity in NPC remain unclear. Here, we aimed to investigate the roles and regulatory mechanisms of LMP1 and sEV PD-L1 in NPC immune evasion.

Methods: We analyzed the impact of LMP1 on tumor-infiltrating lymphocyte abundance in NPC tissues and humanized tumor-bearing mouse models using multiplex immunofluorescence (mIF) and flow cytometry, respectively. Transmission electron microscopy and nanoparticle tracking analysis were employed to characterize sEVs. Immunoprecipitation-mass spectrometry was utilized to identify proteins interacting with LMP1. The regulatory effects of sEVs on tumor microenvironment were assessed by monitoring CD8⁺ T cell proliferation and interferon-γ (IFN-γ) expression via flow cytometry. Furthermore, the expression patterns of LMP1 and downstream regulators in NPC were analyzed using mIF and survival analysis.

Results: High LMP1 expression in NPC patient specimens and mouse models was associated with restricted infiltration of CD8⁺ T cells. Additionally, LMP1 promoted sEV PD-L1 secretion, leading to inhibition of CD8⁺ T cell viability and IFN-γ expression in vitro. Mechanistically, LMP1 recruited apoptosis-linked gene 2-interacting protein X (ALIX) through its intracellular domain and bound PD-L1 through its transmembrane domain, thereby facilitating the loading of PD-L1 into ALIX-dependent sEVs. Disruption of ALIX diminished LMP1-induced sEV PD-L1 secretion and enhanced the anti-tumor immunity of CD8⁺ T cells both in vitro and in vivo. Moreover, increased expression levels of LMP1 and ALIX were positively correlated with enhanced immunosuppressive features and worse prognostic outcomes in NPC patients.

Conclusion: Our findings uncovered the mechanism by which LMP1 interacts with ALIX and PD-L1 to form a trimolecular complex, facilitating PD-L1 loading into ALIX-dependent sEV secretion pathway, ultimately inhibiting the anti-tumor immune response in NPC. This highlights a novel target and prognostic marker for NPC immunotherapy.

Background: The combination of anti-PD-1 antibody serplulimab and chemotherapy is considered standard first-line therapy for advanced esophageal squamous cell carcinoma (ESCC), but few later-line treatments are available. Here we evaluated the therapeutic efficacy of the recombinant, humanized anti-EGFR antibody HLX07 when used alone or together with serplulimab and chemotherapy against advanced ESCC.

Methods: This open-label, non-randomized, two-cohort, phase 2 trial involved patients 18-75 years old with histologically or cytologically confirmed locally advanced, unresectable, or metastatic ESCC, and an Eastern Cooperative Oncology Group performance status of 0-1. Patients who had failed first-line immuno-chemotherapy or at least two lines of other systemic therapy received HLX07 monotherapy intravenously at a dose of 1,000 mg once every 2 weeks (Q2W). Patients with no prior systemic therapy received HLX07 (1,000 mg, day 1) and serplulimab (200 mg, day 1) intravenously Q2W for up to 2 years, concurrently with cisplatin (50 mg/m², day 1) for up to 8 cycles and 5-fluorouracil (1,200 mg/m², days 1-2) for up to 12 cycles intravenously Q2W. The primary endpoints were progression-free survival (PFS) and objective response rate (ORR).

Results: Overall, 50 patients were enrolled. In the HLX07 monotherapy group, ORR was 15.0% (3/20), and the median PFS was 1.5 months (95% confidence interval [CI], 1.3 to 3.7). The median duration of response was not reached, and the rate of patients showing an objective response lasting at least 6 months was 66.7% (95% CI, 5.4 to 94.5). Two (10.0%, 2/20) patients experienced grade 3-4 treatment-related adverse events (TRAEs), including hypomagnesemia, hypocalcemia, and fatigue. No patient experienced grade 5 TRAEs. In the HLX07 combination group, the ORR was 60.0% (18/30), and the median PFS was 7.8 months (95% CI, 3.3 to 9.1). Fourteen (46.7%, 14/30) patients experienced grade 3-4 TRAEs, and one (3.3%, 1/30) patient died due to serplulimab-related pneumonitis.

Conclusions: HLX07 monotherapy and its combination with serplulimab and chemotherapy showed manageable toxicity and promising antitumor activity in patients with recurrent or metastatic ESCC. Randomized controlled trials are warranted to further establish the safety and efficacy of HLX07 against ESCC.

Trial registration: This trial was registered at Clinicaltrials.gov (NCT05221658).