A phase I study to evaluate the safety of multiantigen stimulated tumor specific cell therapy (MASCT-I) in subjects with advanced gastric cancer.

200 Background: Gastric cancer was the fifth cancer world wide and the third leading cause of cancer-related death. PD-1 antibody has been approved for treatment in gastric cancer patients with positive expression of PD-L1 and microsatellite instability. MASCT-I (Multi-Antigen Stimulated Cell Therapy-I Injection) is an autologous non-engineered immune cell therapy for solid tumor, it is composed of multiple-antigen peptides(15 tumor associated antigens) loaded mature dendritic cells (DCs) and in vitro DC stimulated and proliferated effector T cells, the combination of MASCT-I and PD1 antibody could have a synergistic anti-tumor effect. Methods: This is a single center, phase I trial to explore the safety and tolerance of the combination of MASCT-I and PD-1 antibody in advanced gastric cancer (NCT03393416). 15 patients with PD-L1 expression or microsatellite instability were enrolled between April 2018, and June 2019. Camrelizumab was administered once every two weeks, DC and T cells were sequential administered once a month. Therapy continued until the disease progresses. Results: Only adverse reaction below grade 2 was observed related to MASCT-I,such as fever, fatigue etc. Abnormal liver function and reactive capillary hyperplasia may be related to Camrelizumab. Among the 15 patients, the longest treatment duration was 18.9 months, and the median progression-free survival (mPFS) was 3.93 months, among which, mPFS of patients with microsatellite instability is 10.23 months, mPFS of patients expressing PD-L1 is 2.35 months, which is slightly higher than the historical data of Camrelizumab alone in the treatment of advanced gastric cancer (8 weeks for mPFS). The patient 1002 always had high content of CD8+ cells and NK cells and the positive immune response in their bodies, which may plays a role in killing the tumor cells. Conclusions: The combination of MASCT-I and Camrelizumab in the treatment of advanced gastric cancer or gastroesophageal junction cancer is a safe treatment regimen, and its efficacy deserves further study. Clinical trial information: NCT03393416.