Background PD1 immune checkpoint inhibitors (ICIs) have resulted in significant improvements in the care of patients with advanced malignancies. PD1 based combinations including with CTLA4 and LAG3 represent the future of ICI immunotherapy and there is a need to better understand the rationale for investigating combinations involving other immune modulator therapeutic candidates across cancer types.

Methods We utilized real-world clinical and transcriptomic data collected under the Total Cancer Care Protocol (NCT03977402) and Avatar® project within the Oncology Research Information Exchange Network (ORIEN) of 18 cancer centers to which all included subjects provided an IRB-approved written informed consent at their participating institutions. Using RSEM we analyzed mRNA co-expression levels of PD-1 with 12 immune checkpoints including the co-inhibitory receptors LAG3, CTLA4, TIGIT, TIM3 (HAVCR2), VISTA (VSIR), BTLA and the positive co-signaling molecules CD28, OX40 (TNFRSF4), GITR (TNFRSF18), CD137 (TNFRSF9), CD27, HVEM (TNFRSF14) as well as PD-L1 (CD274). Pearson’s R coefficients and associated P values were calculated using SciPy 1.7.0. We defined Pearson’s coefficient > 0.5 and p < 10E-10 as significant correlation.

Results Co-expression of PD1 along with the 12 immune checkpoints and PD-L1 across select malignancies included in our analysis is shown in (table 1), including Pearson’s correlation and the associated P values, sorted by the level of correlation. In cutaneous melanoma, in terms of co-inhibitory receptors that suppress T cell activation, the expression of PD1 was significantly correlated with four molecules: LAG3, TIM3, TIGIT and VISTA; and only significantly correlated with one costimulatory molecule CD137. For urothelial carcinoma, there were 4 co-inhibitory (TIGIT, CTLA4, LAG3 and VISTA) and 4 co-stimulatory (OX40, CD27, CD137 and HVEM) molecules statistically correlated with PD1 expression. For pancreatic adenocarcinoma, only CD28 was deemed to be correlated with PD1 expression. No immune checkpoints were deemed significantly correlated with PD1 expression in the ovarian cancer cohort. Overall, in melanoma and to a certain extent in urothelial carcinoma, the co-expression of co-inhibitory molecules with PD1 was more dominant reflecting late exhausted T cells, as compared to co-stimulatory molecules likely more dominant in ovarian and pancreatic carcinomas reflecting less differentiated T cells.

Conclusions With PD1 blockade as a backbone for immune checkpoint targeting combinations, our interrogations of pan-cancer transcriptomic data provide support for multiple potential combination strategies in the tested malignancies that warrant further investigation. Melanoma and urothelial carcinoma as more immunogenic tumors reflected a PD1+immunoinhibitory dominant phenotype, while less immunogenic ovarian and pancreatic carcinomas reflected a trend toward a PD1+immunostimulatory phenotype.

Acknowledgements We are grateful to the participating patients and their family members as well as all research staff supporting the conduct of the Total Cancer Care protocol.

Trial Registration NCT03977402

Ethics Approval We utilized real-world clinical and transcriptomic data collected under the Total Cancer Care Protocol (NCT03977402) and Avatar® project within the Oncology Research Information Exchange Network (ORIEN) of 18 cancer centers to which all included subjects provided an IRB-approved written informed consent at their participating institutions.