Abstract CT171: Combinatorial allogeneic NK cell therapy with Pembrolizumab for cholangiocarcinoma; interim report of open label Phase1/2a study

Combinatorial allogeneic NK cell therapy with Pembrolizumab for cholangiocarcinoma; interim report of open label Phase1/2a study Background: There are several things needed to be resolved for successful efficacy when NK cell therapy is applied for solid tumor; improvement of NK cell invasion into tumor, activation and production of a large number of NK cells, etc. Basically, in human, NK cell number is relatively small compared to other immune cells such as T cell and the number becomes severely low when NK cell is obtained from cancer patients. For these reasons, allogeneic NK cell has been used for clinical studies against various cancer types. Recently, we also have finished a phase1 study of allogeneic NK cell therapy for cholangiocarcinoma, enrolling 9 patients at inoperable and no chemotherapy favorable stage due to side effects. Four of nine patients (44%) showed SD (stable disease) after six NK cell injections and no severe AE (adverse event) was found. In this following phase 2a study, to bring out immuno-synergetic effect of NK cell therapy against the inoperably advanced bile duct cancer, we have designed a combinatorial protocol with using Pembrolizumab. Methods: Enrollment of 40 bile duct cancer patients has been finished for a combinatorial study of allogeneic NK cell therapy with Pembrolizumab at two different sites in Korea (ClinicalTrials gov, NCT03937895). Patients were eligible for the enrollment when they were inoperable and no chemotherapy favorable stage due to side effects, and also when they had PD-L1-positive score. For treatment, the most favorable method for highly activated allogeneic NK cell production has been determined from our previous study, resulting that 3x106 NK cells per kg are injected for each dose along with Pembrolizumab injection. Pembrolizumab (200mg) was given every 3 weeks for up to 9 times and NK cell injection was given for up to 18 times during the maximum injection period of Pembrolizumab. Results: Six patients (pts) were first enrolled for the pilot combinatorial study, dosing 6 times of NK cells and 3 times of Pembrolizumab. The result showed no severe AE from the injections. Among the five pts finished the injections, 2 pts showed SD (Stable Disease) and continued the treatment, being enrolled into the Phase 2a in which 34 more pts were enrolled. Among the 20 pts finished 6 NK cell and 3 Pembrolizumab injections (1st RECIST), 65% of pts showed SD. When 12 NK cell and 6 Pembrolizumab injections finished (2nd RECIST), pts had 40% and 20% of SD and PR (Partial remission). Of the 3 pts at 3rd RECIST (18 NK cell and 9 Pembrolizumab), 1 and 2 pts showed SD and PR, respectively. Finding pts experienced AE, a total of 6 AEs has been reported: no treatment-related AE, one grade 3 (Encephalopathy), and five grade 1-2 with common AE. In a recent safety and efficacy study of pembrolizumab alone (10mg/kg, every 2 weeks for up to 2 years) with 28 pts of advanced bile duct cancer showing PD-L1 expression, 17% pts showed PR, 17% pts and 52% had SD and PD (progressive disease), respectively. Although our study is still ongoing, continuing the combinatorial treatment gives rise to PR, suggesting that NK cell therapy with Pembrolizumab shows an immuno-synergetic effect for the cancer. Biomarker experiments with the injected NK cells supports our finding and we will discuss this at presentation. Citation Format: Yong Yoon Chung, Seung Woo Park, Jung-Min Im, Da-Kyung Yoo, Hyo-Cheon Cheon, Jae-Eun Kim, Kyeong-Pill Lim, Eun-Hee Yang, Hye-Jin choi, Hyo-Sun Chung, Seo-Yeon Kim, Ju-Yong Lee, In-Hye Jung, Seung Min Bang, Moon Jae Chung, Sung Ill Jang, Jae Hee Cho, Hee Seung Lee, Jung Youp Park, Jung Hyun Jo. Combinatorial allogeneic NK cell therapy with Pembrolizumab for cholangiocarcinoma; interim report of open label Phase1/2a study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT171.