Abstract 4861: Copanlisib enhances the effectiveness of anti-PD1 therapies for colorectal cancer
Authors: Schmitz Alexa E. , Maduscha Kennedy J. , Makkar Sarbjeet , Pasch Cheri A. , DeStefanis Rebecca A. , Emmerich Philip B. , Deming Dustin A. 
Published: April 2023

Introduction: Immunotherapies are increasingly being used for patients diagnosed with cancer, however, for metastatic colorectal cancer (CRC), more than 95% of patients have shown little to no clinical benefit to immunotherapy. Previous work from our lab has shown that copanlisib, a PI3K inhibitor, was found to enhance MHC class I expression in Kras mutant CT26 murine colon cancer cells. Here we examine the potential for anti-cancer activity with the combination of copanlisib and anti-PD1 treatments using this model.

Methods: The impact of copanlisib on CT26 cells was performed using the WST assay and the expression of MHC class I was assessed using flow cytometry. CT26 flank allografts were generated in Balb/C mice and subsequently treated for 15 days with copanlisib (10 mg/kg), anti-PD1 (0.2 mg, BioXCell) or the combination. An IgG2a antibody (BioXCell) was used as a control. Tumors were measured twice a week using a caliper. Tumors were excised, and prepared for immunohistochemistry for CD8, CD4, perforin, granzyme B, and F480 was performed. Staining was quantified as the number of positive staining cells per 20X field of view (FOV).

Results: CT26 viability in response to 200 nM copanlisib was relatively unchanged as compared with untreated controls. Via flow cytometry, a 75% increase in mean fluorescent intensity (MFI) for MHC class I was observed comparing control to copanlisib (p=0.003). In vivo, after 15 days there was no difference in the growth rate of those cancers treated with control versus copanlisib or anti-PD1. A significant reduction in growth rate was observed with the combination of anti-PD1 with copanlisib compared to the other arms (median fold change=3.62; control: 7.49, p=0.002, copanlisib: 8.88, p=0.003; anti-PD1: 8.93, p=0.002). There were no differences in CD8 T cell and perforin expression between the treatment groups. Granzyme B expression was higher in the combination compared (median/FOV= 44) to the control (27, p= 0.01). Additionally, a significant reduction in F480 expression was seen in the combination compared to the other treatment groups (median/FOV=43; control: 139, p&lt;0.001, copanlisib: 110, p&lt;0.001; anti-PD1:149, p&lt;0.001).

Conclusions: In conclusion, copanlisib in combination with anti-PD1 demonstrated enhanced anti-tumor activity in Balb/c mice that were injected with CT26 CRC cells. This response was correlated with increased granzyme B expression and a reduction in macrophages with the combination treatment. Further studies will expand on the mechanism of this combination therapy.

Citation Format: Alexa E. Schmitz, Kennedy J. Maduscha, Sarbjeet Makkar, Cheri A. Pasch, Rebecca A. DeStefanis, Philip B. Emmerich, Dustin A. Deming. Copanlisib enhances the effectiveness of anti-PD1 therapies for colorectal cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4861.