Phase 1/2a Clinical Trial for the Evaluation of Safety and Efficacy of Allogeneic NK Cell ("SMT-NK") in Combination With Pembrolizumab for Patients With Gemcitabine-refractory Biliary Tract Cancer

The term of biliary tract cancer (BTC) or cholangiocarcinoma refers to all tumors that arise from the biliary tract or the biliary drainage system, including the gallbladder. According to the data from National Cancer Information Center in 2016, annual incidence of the cancer in Korea is 6,685 (13.1 per 100,000 population) which corresponds to about 2.9% of all cancers.

BTC is one of the most prognostic cancer with less than 30% of 5-year survival rate and the case with long-term survival can be possibly done with early detection of the cancer. However, most of BTC is found in advanced stages due to the difficulty of early detection, resulting in that the 5-year survival rate of the advanced BTC becomes less than 3%. More than 50% of the patients depends on Gemcitabine based chemotherapy but response rate of the chemotherapy remains around 30%. Thus, improving the survival rate with the standard chemotherapy is very limited and furthermore selection of second-line therapy is not easy. For this reason, development of an alternative therapeutic agent is urgently required.

NK (natural killer) cells are important cytotoxic innate immune cells that are involved in the elimination of cancer cells. Two main NK cell subsets have been defined on the basis of CD56 and CD16 expression: CD56^brightCD16- NK subset produces abundant cytokines including interferon-γ (IFN-γ) and tumor necrosis factor-α, whereas CD56^dimCD16+ NK subpopulation has high cytolytic activity and releases the granules containing perforin and granzymes.

Various clinical studies have been conducted to treat cancers using NK cells worldwide including Korea and therapeutic clinical results are shown for various cancers. The clinical application of NK cells is carried out by culturing and activating the NK cells isolated from blood of either patient (autologous) or blood donor (allogeneic). Recently, NK cell therapy for cholangiocarcinoma has been successfully done (NCT03358849) with allogeneic NK cell, showing safety and potential efficacy.

Like T cells, a recent study with digestive cancer has shown that NK cells also express PD-1, especially with more number of PD-1 in cancer patients than in healthy individuals, suggesting that blocking PD-1 can be used as a potential strategy to increase the anticancer activity of NK cells. Therefore, combined therapy with the immune-check point such as pembrolizumab can be useful in elevating the anticancer activity of NK cells.