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Background:We have previously reported that ∼50% of CLL patients (pts) experience rapid flare of disease when they discontinue ibrutinib therapy due to progression of disease (CLL or Richter's transformation [RT]) (Hampel et al, JCO suppl, 2018). This lead to the clinical practice of overlapping venetoclax with ibrutinib for combination therapy in this setting to prevent ibrutinib withdrawal.Aims:To evaluate the role of continuing ibrutinib beyond the start of salvage venetoclax in pts who have progression of disease on ibrutinib monotherapy, both in preventing ibrutinib withdrawal associated with ibrutinib discontinuation and in disease response.Methods:We identified all CLL pts at Mayo Clinic (3/2017–11/2018) who had disease progression on ibrutinib therapy, where venetoclax was added as subsequent treatment while ibrutinib was continued. CLL‐specific characteristics, treatment timeline and toxicities, and disease course following combination therapy were ascertained. All pts started venetoclax according to the weekly ramp‐up per the package instructions.Results:Eighteen pts treated with the addition of venetoclax to ibrutinib therapy were identified; indications were CLL progression (n = 13) and RT (n = 5). BTK or PLCG2 mutations were present in 8/13 pts. Median duration of follow‐up was 9.6 months after the start of combination therapy.The target venetoclax dose was reached by 5 weeks in 13 pts; reasons for delaying or stopping dose escalation included diarrhea (n = 2), sepsis (n = 2), and neutropenia (n = 1). No patient experienced a disease flare during venetoclax ramp‐up.The median duration of combination ibrutinib and venetoclax therapy was 3 months (range, 0–14 months). Of 18 pts who started combination therapy with ibrutinib and venetoclax, ibrutinib was discontinued in 10 pts. Reasons included hematopoietic stem cell transplant (n = 2), planned stop after adequate disease control (n = 4), financial reasons (n = 1), toxicity (neutropenia n = 1, immune thrombocytopenia/bleeding risk n = 1), and death (n = 1). Only 1 patient experienced ibrutinib withdrawal, which occurred following planned discontinuation after clinical complete response (CR) with a 41 day overlap and toleration of venetoclax 400 mg daily; management with re‐initiation of ibrutinib was effective in regaining disease control. Of 9 pts who stopped ibrutinib, 4 pts had a slow taper over 2–8 weeks, and 2 pts also received corticosteroids at the time of ibrutinib discontinuation.Among the other 8 pts who did not discontinue ibrutinib, 6 pts remain on the combination with venetoclax (median duration 6.5 months, range 3–14 months), and 2 pts continued on ibrutinib following venetoclax discontinuation due to disease progression (both pts received further combination of ibrutinib with multi‐agent chemotherapy).The overall response rate (ORR) to combination therapy with ibrutinib and venetoclax was 81% (CR/clinical CR n = 9, partial response n = 4, stable disease n = 1, and primary refractory disease n = 2). The duration of combination therapy was <4 weeks in 2 pts, precluding response assessment. The estimated 12‐month event‐free survival was 54% (95% CI 33–87%), and the estimated 12‐month overall survival from start of combination therapy was 79% (95% CI 60–100%); see Figure 1.Summary/Conclusion:Among CLL pts who develop progression of disease on ibrutinib monotherapy, continued ibrutinib therapy with addition of venetoclax was feasible, ameliorated ibrutinib withdrawal, and was associated with high ORR.image

Background:The expression of the receptor tyrosine kinase (RTK) Axl on cancer cells has been associated with poor prognosis and implicated in disease progression. Inhibition of Axl‐RTK with TP‐0903, a high affinity Axl‐RTK inhibitor induces robust apoptosis of several tumors, including chronic lymphocytic leukemia (CLL). Axl‐RTK inhibition has also been found to induce nonspecific immunomodulatory effects in syngeneic tumor models.Aims:We aimed to investigate the impact and downstream effects of Axl‐RTK inhibition on naïve T cells and chimeric antigen receptor T cells (CART), using CD19 directed CART cells (CART19) as a model.Methods:We utilized either PMA/Ionomycin or the CD19+ mantle cell lymphoma cell line, JeKo as a stimulant for naïve T cells and CART19, respectively. Cells were analyzed for cytokine profile, T cell phenotype, and kinetics after the stimulation in the presence or the absence of the Axl‐RTK inhibitor TP‐0903. Regarding in vivo experiment, a relapse JeKo xenograft model was used. Mice were treated with vehicle alone, TP‐0903 alone, CART19 alone, or TP‐0903 + CART19. Three weeks after the treatment, mice were re‐challenged with JeKo as a CART19 relapse model.Results:Stimulation of naïve T cells in the presence of the Axl‐RTK inhibitor TP‐0903 resulted in a significant reduction of Th2 cytokines and downregulation of inhibitory receptors. The differential expansion of either effector T cells or Tregs in the presence of TP‐0903 resulted in a preferential reduction of Tregs (Fig 1A). Axl‐RTK inhibition of CART19 led to Th1 polarization upon stimulation with the JeKo, as evident by the selective reduction of Th2 cytokine. Additionally, this resulted in a reduction of myeloid attracting cytokines, such as CXCL1, IL‐8, IL‐6, and IL‐10, cytokines implicated in the development cytokine release syndrome and neurotoxicity after CART cell therapy and in adaptive resistance to immunotherapy (Fig 1B). TP‐0903 also significantly downregulated inhibitory receptors on activated CARTs (Fig 1C). In our relapsed in vivo model, mice treated with CART19 + TP‐0903 rejected the JeKo challenge while mice received CART19 alone redeveloped disease, suggesting that Axl‐RTK inhibition enhanced CART cell persistence. Peripheral blood analysis of mice after the rechallenge showed a higher number of circulating T cells and lower level of MCP‐1. Western blotting was performed to investigate the downstream effect of Axl‐RTK inhibition on CART19 and it revealed a relatively selective inhibition of LCK on stimulated CART19. Transcriptome analysis of activated CARTs treated with TP‐0903 revealed >100 genes that were differentially expressed compared to untreated cells. Among these, Th cell and Treg polarization genes were significantly altered in activated CARTs treated with TP‐0903.imageFinally, we validated our findings in phase I clinical trial of TP‐0903 (NCT02729298). T cells isolated from 3 cancer patients showed a significant reduction of Tregs and Th1 polarization. This will be further investigated in a planned phase I clinical trial of TP‐0903 in relapsed/refractory CLL (NCT03572634).Summary/Conclusion:We showed for the first time that Axl‐RTK inhibition polarizes T cells into a Th1 functional phenotype, downregulates inhibitory receptors, and reduces myeloid associated cytokine production by CART19. The combination therapy yielded synergistic cytotoxicity against JeKo in vitro and in a CART19 relapse model. These findings encourage further study of Axl‐RTK inhibition with TP‐0903 as an enhancer of T cell immunotherapies.

PURPOSE Time to event is an important aspect of clinical decision making. This is particularly true when diseases have highly heterogeneous presentations and prognoses, as in chronic lymphocytic lymphoma (CLL). Although machine learning methods can readily learn complex nonlinear relationships, many methods are criticized as inadequate because of limited interpretability. We propose using unsupervised clustering of the continuous output of machine learning models to provide discrete risk stratification for predicting time to first treatment in a cohort of patients with CLL. PATIENTS AND METHODS A total of 737 treatment-naïve patients with CLL diagnosed at Mayo Clinic were included in this study. We compared predictive abilities for two survival models (Cox proportional hazards and random survival forest) and four classification methods (logistic regression, support vector machines, random forest, and gradient boosting machine). Probability of treatment was then stratified. RESULTS Machine learning methods did not yield significantly more accurate predictions of time to first treatment. However, automated risk stratification provided by clustering was able to better differentiate patients who were at risk for treatment within 1 year than models developed using standard survival analysis techniques. CONCLUSION Clustering the posterior probabilities of machine learning models provides a way to better interpret machine learning models.

Key Points This article characterizes a cryptic IGH/CCND1 rearrangement in MCL by NGS. Mate-pair sequencing can help in accurately diagnosing MCL in cases of cyclin-D1–positive B-cell lymphoma with negative CCND1 FISH studies.

Despite the remarkable outcomes of CD19-directed chimeric antigen receptor T (CART19) cell therapy in B-cell malignancies, the durable responses in diffuse large B-cell lymphoma are less than 40%, and strategies to enhance this response are desperately needed. Inhibition of AXL RTK with TP0903, a high-affinity AXL inhibitor has been found to induce robust apoptosis of malignant B cells. Here, we aimed to examine the role of AXL RTK inhibition with TP0903 on T-cell function in B-cell malignancies. First, we investigated the influence of TP0903 on CART19 cell phenotype and functions. Here, we used 41BB costimulated, lentiviral-transduced CART cells. AXL inhibition led to polarization of CART cells into a Th1 phenotype when T cells were stimulated with the CD19+ mantle cell lymphoma (MCL) cell line Jeko or with leukemic B cells isolated from patients with chronic lymphocytic leukemia (CLL), in the presence of TP0903 (Fig 1A). Exposure of activated CART cells to TP0903 also resulted in significant downregulation of inhibitory receptors on activated CART cells (Fig 1B), a reduction of conical cytokines known to be associated with the development of cytokine release syndrome (CRS) (Fig 1C). To investigate the effect of AXL RTK inhibition of CART cells with TP0903 in vivo, we established MCL xenografts through the injection of 1.0x106 of Jeko into NSG mice. A week later, mice were treated with either vehicle alone, TP0903 (20 mg/kg/day) alone, 0.5x106 of CART19 alone, or TP0903 (20mg/kg/day)+0.5x106 of CART19. Three weeks after the treatment, mice were rechallenged with 1.0x106 of Jeko. Mice treated with CART19 and TP0903 rejected the tumor challenge while mice previously treated with CART19 alone redeveloped MCL, suggesting that AXL inhibition enhanced CART cell persistence (Fig 1D). Finally, we validated our preclinical findings in correlative analyses of phase 1 clinical trial of TP0903 in patients with solid tumors (NCT02729298). Similar to our findings, there was a significant reduction in Tregs, reduction of inhibitory receptors and polarization to a Th1 phenotype. These findings will be further investigated in a planned phase 1 clinical trial of TP0903 in relapsed/refractory CLL (NCT03572634) In summary, we demonstrated for the first time that AXL inhibition polarizes T cells into a Th1 phenotype, downregulates inhibitory receptors, and synergizes with CART cells in B-cell malignancies. These findings encourage further study of TP0903 as an enhancer of T-cell immunotherapies.

Background: Unprecedented clinical outcomes were reported after CD19 chimeric antigen receptor T-cell (CART19) therapy. However, the complete response rate in chronic lymphocytic leukemia (CLL) is much lower, at approximately 20%–30%. Several immune defects have been identified in CLL that result from the complex interaction between CLL cells and the microenvironment. This leukemic microenvironment is rich with extracellular vesicles (EVs) secreted by B-CLL cells. Here, we aimed to investigate the role of EVs play in the diminished CART response seen in some CLL patients. Methods: EVs were isolated from peripheral blood of 16 patients with untreated CLL at different Rai stages and risk profile by FISH. Cytometry was used to determine size, number of particles per μl, and CD19 expression. To investigate the impact of EVs on CAR T-cell functions, CART19 cells were stimulated with either CLL B cells or the CD19-positive cell line JEKO and different effector functions were analyzed. Results: Two patterns of EVs in CLL patients were identified; a single versus 2 distinct EV populations, characterized by size (small [EVssmall] and large [EVslarge], Fig 1A). In 25% of patients, EVs were CD19 positive (EVCD19+). CD19 positivity was detected only in patients with the EVslarge (Fig 1B). The EVs concentration, CD19 expression (EVsCD19+ vs EVsCD19-), or the size (EVssmall vs EVslarge) did not correlate with disease stage (early vs advanced Rai stage) or risk profile of CLL (low vs high risk). To investigate our hypothesis that EVs could modulate CART19 function, CART19 cell effector functions were examined in the presence of EVsCD19+, EVsCD19-, EVssmall, or EVslarge. EVs alone were insufficient to stimulate CART19 cells. However when CART19 cells were stimulated with the CD19-positive cell line JEKO, their effector functions were reduced only in the presence of EVsCD19+ but not EVsCD19-. This included a significant reduction in CART-specific killing (Fig 1C) and a reduction in cytokine production. The impairment of CART cell functions was independent of the size of EVs, ie, there was no impairment of CART functions with large or small size EVCD19- in co-culture. Conclusion: We identify CD19-positive large size EVs from patients with CLL and demonstrate that these EVs play a role in the leukemic microenvironment by reducing CAR T-cell activity. Studies are ongoing to define the mechanism(s).

The prevalence, clinicopathologic correlates, and outcomes of previously untreated chronic lymphocytic leukemia (CLL) patients with IGH‐BCL2 and IGH‐BCL3 translocations are not well known. Using the Mayo Clinic CLL database, we identified patients seen between March 1, 2002 and September 30, 2016 who had FISH testing performed within 3 years of CLL diagnosis. The prognostic profile, time to first therapy (TTT), and overall survival (OS) of patients with IGH‐BCL2 and IGH‐BCL3 translocation were compared to patients without these abnormalities (non‐IGH group). Of 1684 patients who met the inclusion criteria, 38 (2.2%) had IGH‐BCL2, and 16 (0.9%) had IGH‐BCL3 translocation at diagnosis. Patients with IGH‐BCL3 translocation were more likely to have high and very‐high CLL‐International Prognostic Index, compared to patients with IGH‐BCL2 translocation and the non‐IGH group. The 5‐year probability of requiring therapy was significantly higher for IGH‐BCL3 compared to IGH‐BCL2 and non‐IGH groups (84% vs 33% vs 29%, respectively, P < 0.0001). The 5‐year OS was significantly shorter for IGH‐BCL3 compared to IGH‐BCL2 and non‐IGH groups (45% vs 89% vs 86%, respectively, P < 0.0001). On multivariable analyses, IGH‐BCL3 translocation was associated with a shorter TTT (hazard ratio [HR] = 2.7; P = 0.005) and shorter OS (HR = 5.5; P < 0.0001); IGH‐BCL2 translocation did not impact TTT and OS. In conclusion, approximately 3% of all newly diagnosed CLL patients have either an IGH‐BCL2 or IGH‐BCL3 translocation. Patients with IGH‐BCL3 translocations have a distinct prognostic profile and outcome. These results support the inclusion of an IGH probe during the routine evaluation of FISH abnormalities in newly diagnosed CLL.