Abstract 5186: Spatial single-cell deconvolution of the bone marrow microenvironment to define predictive biomarker for response to immunotherapy in patients treated with a check point inhibitor in smoldering multiple myeloma, phase II trial of nivolumab in combination with lenalidomide and low dose dexamethasone

Abstract Background:The immune system is critical for response and resistance in all cancer types and therapies. Patients with Smoldering Multiple Myeloma (SMM) have altered immune cell composition in the bone marrow (BM). However, little is known about the role of BM spatial immune profiling in patients treated with checkpoint inhibitors in MM. Methods: We performed spatial profiling with imaging mass cytometry of trephine biopsies of the BM (n=15; pre-treatment n=7 and post-treatment n=8) from patients with high-risk SMM enrolled in a phase II trial of nivolumab in combination with lenalidomide and low dose dexamethasone (NCT02903381). Patients received 6 cycles of induction therapy of nivolumab (240mg) at days 1 and 15, in combination with lenalidomide (25mg) at days 1-21 and dexamethasone at days 1, 8, and 15. The induction phase was followed by nivolumab (240mg) and lenalidomide (25mg) maintenance for another 6 cycles. A treatment cycle was defined as 28 consecutive days for a total of 12 months period. Event monitoring was performed up to 3 years. The primary efficacy outcome was progression-free survival 2 years after treatment. Results: Eight patients were enrolled on this study from January 2017 to June 2017. The study was put on hold due to the toxicity of checkpoint inhibitors observed in other trials of MM. The median age for all patients at enrolment was 60 years (range 49 to 81), with 5 males (62%) and 3 females (38%). All patients met criteria for high risk SMM disease. Median follow-up for all 8 patients was 38.7 months. Median overall survival was not reached; median progression-free survival was 33.8 months. Seven total patients had a response of Minimal Response (MR) or better, and 4 patients who initially responded eventually progressed. The total number of patients who were followed for at least two years and remained progression-free was 4 of 8 evaluable patients (50%; 90% CI: 19 - 81%).Spatial profiling with a panel of 37 markers on the pre-treatment samples allowed us to assess the states and abundances of multiple immune subpopulations, including rare regulatory NK cells. To assess the accuracy of our cell type annotation, we correlated the proportion of malignant plasma cells identified per patient with the value determined by pathologists for clinical diagnosis. These measures were significantly positively correlated (R=0.92, p<0.01). Spatial neighborhood analysis revealed statistically significant interactions enriched in the responders, even with our small sample size (t-test; p < 0.05). Conclusions and future directions: This pilot study suggests that BM spatial immune profiling before receiving immune check point inhibitors can be a biomarker for response in patients with SMM. Citation Format: Yoshinobu Konishi, Giuseppe Tarantino, Yiwen He, Romanos Sklavenitis-Pistofidis, Sujal I. Shah, Katherine Towle, Christian J. Cea-Curry, Oksana Zavidij, Ruben D. Carrasco, Scott J. Rodig, Jon C. Aster, David Liu, Gad Getz, Irene M. Ghobrial. Spatial single-cell deconvolution of the bone marrow microenvironment to define predictive biomarker for response to immunotherapy in patients treated with a check point inhibitor in smoldering multiple myeloma, phase II trial of nivolumab in combination with lenalidomide and low dose dexamethasone [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5186.