Shenmai injection (SMI) is a well-defined herbal preparation that is widely and clinically used as an adjuvant therapy for cancer. Previously, we found that SMI synergistically enhanced the activity of chemotherapy on colorectal cancer by promoting the distribution of drugs in xenograft tumors. However, the underlying mechanisms and bioactive constituents remained unknown. In the present work, the regulatory effects of SMI on tumor vasculature were determined, and the potential anti-angiogenic components targeting tumor endothelial cells (TECs) were identified. Multidimensional pharmacokinetic profiles of ginsenosides in plasma, subcutaneous tumors, and TECs were investigated. The results showed that the concentrations of protopanaxadiol-type (PPD) ginsenosides (Rb1, Rb2/Rb3, Rc, and Rd) in both plasma and tumors, were higher than those of protopanaxatriol-type (Rg1 and Re) and oleanane-type (Ro) ginsenosides. Among PPD-type ginsenosides, Rd exhibited the greatest concentrations in tumors and TECs after repeated injection. In vivo bioactivity results showed that Rd suppressed neovascularization in tumors, normalized the structure of tumor vessels, and improved the anti-tumor effect of 5-fluorouracil (5FU) in xenograft mice. Furthermore, Rd inhibited the migration and tube formation capacity of endothelial cells in vitro . In conclusion, Rd may be an important active form to exert the anti-angiogenic effect on tumor after SMI treatment.

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2581 Background: Even though immune checkpoint inhibitor (ICI) such as anti-PD-1 mAb has emerged as effective treatment for tumor regression, the response rate of ICI monotherapy in solid tumor is low. Many studies have demonstrated that the efficacy of combination therapy of ICI and anti-angiogenesis was superior to monotherapy. Penpulimab (AK105), a humanized IgG1 mAb that blocks PD-1 binding to PD-L1, engineered to eliminate FcγR binding and ADCC/ADCP completely. Here, we explore a new combined therapy of penpulimab and anlotinib, an oral multi-targeted tyrosine kinase receptor inhibitor. Methods: MC38-hPD-L1 tumor-bearing B-hPD-1 humanized mouse model were conducted to investigate the effects of anlotinib (1 mg/kg, every day, p.o) or penpulimab (5 mg/kg, twice a week, i.p) alone or in combination. Immunofluorescence was applied to elucidate tumor vessel normalization. In vivo imaging was conducted to detect the distribution of AF647-labelled penpulimab after anlotinib treatment. Flow cytometry and other techniques were performed to investigate intratumoral immune cells. Results: After 3-week treatment, immunotherapeutic administration of anlotinib or penpulimab showed moderate inhibition of tumor growth (tumor volume: 66.5% and 58.4% of control group, respectively), while combined treatment of anlotinib with penpulimab significantly decreased tumor volume to 36.5% of control group. Tissue pathological and blood biochemical results showed no significant toxic and side effects. Immunohistochemistry revealed that anlotinib induced tumor vascular normalization, indicated by decreased CD31+ area, increased α-SMA around tumor vessels and reduced GLUT1+ area. Furthermore, anlotinib markedly enhanced the delivery of AF647-penpulimab into tumors. Combining anlotinib with penpulimab also promoted infiltration and activity of anti-tumoral immune cells by reducing the level of immune checkpoint TIM3 and increasing the IFNγ secretion from T cells. Conclusions: Our work provides a strong scientific rationale for the combination therapy of anlotinib and penpulimab to improve tumor microenvironment and immunotherapy, which highlights the clinical potential for this new combined therapy.

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