Abstract CT007: Phase 1/2 trial of copanlisib in combination with nivolumab for microsatellite stable (MSS) colorectal cancer (CRC)

Abstract Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Alpha (PIK3CA) is frequently mutated in CRC, leading to constitutive activation and enhanced cellular growth. PI3K also regulates immunity; inhibition of this pathway suppresses Tregs and myeloid derived suppressor cells resulting in enhanced anti-tumor immune responses. Murine experiments combining PD-1 and PI3K inhibition showed an increased CD8+ T cell:Treg ratio and improved survival compared to either alone. We launched a multicenter phase I/II investigation of copanlisib (PI3K inhibitor) and nivolumab (anti-PD-1) in 2 cohorts of patients with metastatic MSS CRC, Cohort 1: PIK3CA mutant (PI3KCAm) and Cohort 2: PIK3CA wild type (PIK3CAwt). From 2/2019 to 4/2022, 39 patients were enrolled: 6 in the phase 1 portion and 33 in phase 2 (22 PIK3CAm/17 PIK3CAwt). All patients had received at least 2 lines of prior therapy. Patient demographics and best treatment responses are in Table 1. There were no dose-limiting toxicities; toxicities were as expected and tolerable, most commonly hypertension in 16 (41%) patients and maculopapular rash in 4 (10%) patients. 3 patients in cohort 1 (14%) had partial responses (PR) and 3 had stable disease (SD): (range 1.7-4.7 mo.). One patient in Cohort 2 (6%) had a PR and 4 had SD: (range 3.8-7.4 mo.). Notably, all 4 responses have lasted more than 2 years. The trial incorporated robust translational correlates for mechanism interrogation with serial biopsies and blood draws. We will report circulating cytokine profiling, mass cytometry on PBMCs, and highly multiplexed immunofluorescence imaging (CyCIF) on paired pre- and on-treatment tissue specimens to i) dissect immune and PI3K pathway changes with treatment ii) correlate these to clinical responses and iii) determine baseline biomarkers of response and mechanism of effect. Overall copanlisib/nivolumab was well tolerated. The PIK3CAm CRC cohort met the primary endpoint for objective response rate but later than 6 months as responses were evolving. Table 1: Demographics and Best Treatment Responses of Patients Treated on NCT03711058: Study of Copanlisib and Nivolumab in MSS Colorectal Cancer Age Sex Race RAS-RAF status Best Response TMB Total (n=39) 58 (40-83) F: 53%(21), M: 47%(18) AA: 15%(6), AS: 8%(3), W: 77%(30) Altered: 67%(26), Wild type: 33%(13) PR: 10%(4), SD: 18%(7), PD: 72%(28) 5 (1-10) PIK3CA mutant (n=22) 57.5 (42-83) F: 73%(16), M: 27%(6) AA:23%(5), AS: 9%(2), W: 68%(15) Altered: 73%(16), Wild type: 27%(6) PR: 14%(3), SD: 14%(3), PD: 73%(16) 5 (1-10) Exon 9 mutation (n=13) 58 (45-83) F: 77%(10), M: 23%(3) AA: 15%(2), AS: 8%(1), W: 77%(10) Altered 85%(11), Wild type: 15%(2) PR: 8%(1), SD: 8%(1), PD: 85%(11) 7.9 (1-18) Exon 20 mutation (n=5) 62 (43-76) F: 80%(4), M: 20%(1) AA: 20%(1), W: 80%(4) Altered: 80%(4), Wild type: 20%(1) PR: 20%(1), SD: 20%(1), PD: 60%(3) 4 (3-8) Other (n=4) 46 (42-54) F: 50%(2), M: 50%(2) AS: 25%(1), AA: 50%(2), W: 25%(1) Altered: 75%(3), Wild type: 25%(1) PR: 25%(1), PD: 75%(3) 5.3 (3-7.6) PIK3CA wild type (n=17) 59 (40-81) F: 29%(5), M: 71%(12) AA: 6%(1), AS: 6%(1), W: 82%(15) Altered: 59%(10), Wild type: 41%(7) PR: 6%(1), SD: 24%(4), PD: 71%(12) 5.5 (1-9) AA: African American, AS: Asian, C: Caucasian, F: Female, M: Male, PD: Progressive disease, PR: Partial Response, SD: Stable disease Citation Format: Eric S. Christenson, Jeremiah A. Wala, Rose Parkinson, Natalie B. Collins, Christopher Jakubowski, Jea-Ren Lin, Hao Wang, Won Jin Ho, Sabrina Chan, Rachel Klein, Yvette Cetasaan, Emma Johnson, Maureen Berg, Jeffrey Meyerhardt, Benjamin Schlechter, Harshabad Singh, Peter K. Sorger, Marios Giannakis, Nilofer Azad. Phase 1/2 trial of copanlisib in combination with nivolumab for microsatellite stable (MSS) colorectal cancer (CRC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT007.