PO-423 Investigation of combined immune checkpoint blockade in human malignant pleural mesothelioma

Abstract

IntroductionTill today, human malignant pleural mesothelioma (MPM) remains an aggressive cancer with a poor prognosis due to the limited impact on overall survival of the current treatments. Data from us and others about the presence of the immune checkpoint-related molecules PD-1, PD-L1, TIM-3 and LAG-3 in MPM lay the basis to evaluate their suitability as immunotherapeutic targets. Two clinical trials that investigated PD-1 and PD-L1 inhibition in mesothelioma (KEYNOTE-28, JAVELIN trial) have shown promising results with room for improvement. It is of great interest to investigate the effect of combined treatments and compare them to stand-alone treatment to select the best therapeutic strategy for MPM.Material and methodsHuman cell lines representative for the epithelioid (NCI-H2818 and NCI-H2795) and sarcomatoid (NCI-H2731) subtypes of MPM were placed in allogeneic co-cultures with healthy donor peripheral blood mononuclear cells. The co-cultures were treated with the following immune checkpoint blocking antibodies: anti PD-1 (Nivolumab, BMS) or anti PD-L1 (Durvalumab, AstraZeneca) in combination with anti TIM-3 or anti LAG-3. Supernatant was collected and enzyme-linked immunosorbent assays and multiplex electrochemo-luminescence were used to look at the secretion of 7 cytokines, being IFNg, IL-2/5/6/10, IL-1b and TNF-a, as well as the enzyme granzyme B. Statistical analysis was done to investigate the differences between the treatment conditions.Results and discussionsTreatment with immune checkpoint blockers as monotherapy or in combination resulted in a significant increase in the secretion of granzyme B and the cytokines IFNg, IL-2, IL-5 and IL-10. Although the increased secretion was not always statistically significant for all 3 MPM cell lines of the two subtypes, the same trends were observed among them. Interestingly, highest concentrations of granzyme B and these 4 cytokines were noticed for monotherapy treatment with anti PD-1, anti PD-L1 or either of these antibodies with anti TIM-3. In vivo investigation of PD-1 or PD-L1 blockade in combination with TIM-3 or LAG-3 blockade is currently ongoing to validate our in vitro results.ConclusionOur data show that treatment with anti PD-1, anti PD-L1 or their respective combination with anti TIM-3 resulted in the highest secretion of cytokines and granzyme B, suggesting that these treatments stimulate the antitumor response the most. In vivo experiments are currently ongoing for validation.