Contributions
Abstract: EP614
Type: E-Poster Presentation
Session title: Chronic lymphocytic leukemia and related disorders - Biology & Translational Research
Background
The phosphatidylinositol 3-kinase inhibitors (PI3Ki) idelalisib and duvelisib are approved for relapsed chronic lymphocytic leukemia (CLL). However, treatment intolerance and resistance remain clinical challenges. Strategies to overcome these challenges include targeting bypass mechanisms by using a different PI3Ki and combining different classes of targeted therapies. Direct drug testing on patient-derived primary cells may provide insights into patient-tailored therapeutic options.
Aims
The aims of this study were to (i) characterize the efficacy, selectivity, and synergy of 10 clinically relevant PI3Ki alone and in combination with the B-cell lymphoma-2 (BCL-2) antagonist venetoclax in primary CLL cells, (ii) investigate whether signaling molecules can serve as early biomarkers for drug sensitivity, and (iii) identify clinically relevant treatment options for CLL patients who have failed on a PI3Ki monotherapy.
Methods
We performed high-throughput drug sensitivity screens with 72h drug treatment of primary cells from 18 CLL patients and 3 healthy blood donors. A phospho-flow cytometry assay was applied to study intracellular signaling changes in primary CLL cells after 30 min of drug treatment ex vivo.
Results
The pan-PI3Ki buparlisib, copanlisib and pictilisib were most active in 72h assays, with up to 97% reduction in cell viability at 10 000 nM. However, treatment with the p110d-selective PI3Ki umbralisib plus venetoclax showed more selective targeting of CLL cells compared to normal B cell and T cells than combinations involving a pan-PI3Ki. Interestingly, distinct changes in cell signaling induced by 30 min of drug treatment predicted cell viability in 72h assays. AKT (pS473) and S6-ribosomal protein (pS235/S236) correlated with drug sensitivity to p110d-selective PI3Ki plus venetoclax, while BTK (pY551) correlated with sensitivity to pan-PI3Ki. Samples from patients no longer responding to idelalisib in vivo (n=4) showed high sensitivity to pan-PI3Ki ex vivo. Drug sensitivity assessment of an ibrutinib (BTK inhibitor), idelalisib and venetoclax refractory CLL patient indicated combination of idelalisib and venetoclax as a promising therapeutic option. The patient was treated with the combination, and obtained a good clinical response. Unfortunately, the patient experienced unacceptable gastrointestinal adverse effects as she had with idelalisib monotherapy, and the treatment was stopped. Interestingly, the patient continued to show a strong ex vivo response to the pan-PI3K inhibitors buparlisib, copanlisib and pictilisib, suggesting that these therapies may be considered for CLL patients who relapse on currently available targeted therapies.
Conclusion
These data provide insights into efficacy, selectivity, and synergy of combinatorial strategies in CLL, and indicate a potential for signaling molecules as early biomarkers for patient stratification. Ex vivo drug sensitivity assessment of CLL cells from a patient who had failed on all available targeted therapies in Norway indicated combined PI3K/BCL-2 inhibition as an effective treatment option. This demonstrates that ex vivo drug sensitivity assessments can guide clinical decisions in CLL. We further showed that CLL cells from refractory patients remain sensitive to pan-PI3Ki ex vivo, suggesting pan-PI3Ki as potential treatment options to be explored for relapsing CLL patients.
Keyword(s): BCL2, Chronic lymphocytic leukemia, PI3K, Targeted therapy
Abstract: EP614
Type: E-Poster Presentation
Session title: Chronic lymphocytic leukemia and related disorders - Biology & Translational Research
Background
The phosphatidylinositol 3-kinase inhibitors (PI3Ki) idelalisib and duvelisib are approved for relapsed chronic lymphocytic leukemia (CLL). However, treatment intolerance and resistance remain clinical challenges. Strategies to overcome these challenges include targeting bypass mechanisms by using a different PI3Ki and combining different classes of targeted therapies. Direct drug testing on patient-derived primary cells may provide insights into patient-tailored therapeutic options.
Aims
The aims of this study were to (i) characterize the efficacy, selectivity, and synergy of 10 clinically relevant PI3Ki alone and in combination with the B-cell lymphoma-2 (BCL-2) antagonist venetoclax in primary CLL cells, (ii) investigate whether signaling molecules can serve as early biomarkers for drug sensitivity, and (iii) identify clinically relevant treatment options for CLL patients who have failed on a PI3Ki monotherapy.
Methods
We performed high-throughput drug sensitivity screens with 72h drug treatment of primary cells from 18 CLL patients and 3 healthy blood donors. A phospho-flow cytometry assay was applied to study intracellular signaling changes in primary CLL cells after 30 min of drug treatment ex vivo.
Results
The pan-PI3Ki buparlisib, copanlisib and pictilisib were most active in 72h assays, with up to 97% reduction in cell viability at 10 000 nM. However, treatment with the p110d-selective PI3Ki umbralisib plus venetoclax showed more selective targeting of CLL cells compared to normal B cell and T cells than combinations involving a pan-PI3Ki. Interestingly, distinct changes in cell signaling induced by 30 min of drug treatment predicted cell viability in 72h assays. AKT (pS473) and S6-ribosomal protein (pS235/S236) correlated with drug sensitivity to p110d-selective PI3Ki plus venetoclax, while BTK (pY551) correlated with sensitivity to pan-PI3Ki. Samples from patients no longer responding to idelalisib in vivo (n=4) showed high sensitivity to pan-PI3Ki ex vivo. Drug sensitivity assessment of an ibrutinib (BTK inhibitor), idelalisib and venetoclax refractory CLL patient indicated combination of idelalisib and venetoclax as a promising therapeutic option. The patient was treated with the combination, and obtained a good clinical response. Unfortunately, the patient experienced unacceptable gastrointestinal adverse effects as she had with idelalisib monotherapy, and the treatment was stopped. Interestingly, the patient continued to show a strong ex vivo response to the pan-PI3K inhibitors buparlisib, copanlisib and pictilisib, suggesting that these therapies may be considered for CLL patients who relapse on currently available targeted therapies.
Conclusion
These data provide insights into efficacy, selectivity, and synergy of combinatorial strategies in CLL, and indicate a potential for signaling molecules as early biomarkers for patient stratification. Ex vivo drug sensitivity assessment of CLL cells from a patient who had failed on all available targeted therapies in Norway indicated combined PI3K/BCL-2 inhibition as an effective treatment option. This demonstrates that ex vivo drug sensitivity assessments can guide clinical decisions in CLL. We further showed that CLL cells from refractory patients remain sensitive to pan-PI3Ki ex vivo, suggesting pan-PI3Ki as potential treatment options to be explored for relapsing CLL patients.
Keyword(s): BCL2, Chronic lymphocytic leukemia, PI3K, Targeted therapy