Refractory CLL Research Articles

Varnimcabtagene Autoleucel (ARI-0001) for Relapsed or Refractory Chronic Lymphocytic Leukemia (CLL) and Richter Transformation (RT)

Background: The prognosis of CLL patients that do not respond to targeted therapy is unfavourable, especially in the case of adverse genomic aberrations (e.g. TP53 alterations or complex karyotype) or after transformation to aggressive B lymphoma (Richter transformation, RT). In patients with refractory CLL, anti-CD19 CAR-T (CART19) therapy has achieved complete response (CR) rates of 19-45%, with RT usually excluded from pivotal trials. However, long-term remission in CLL patients still remains a challenge with CART19 therapy. Methods: We present the outcomes of all patients with relapsed or refractory (R/R) CLL with or without RT treated with the academic CART19 varnimcabtagene autoleucel (var-cel) from November/2017 to May/2023, including patients from the CART19-BE-01 trial and subsequent compassionate use programme. Patients received lymphodepletion with fludarabine (90 mg/m2) and cyclophosphamide (900 mg/m2) followed by 0.1-1 (CLL) and 0.5-5 (RT) x10e6 CART19 cells/kg in single or fractionated administration (10%, 30% and 60%) in a single institution. Results: A total of 20 patients underwent leukapheresis and var-cel production. At screening patients had a median age of 58 years (44-74), 47% were females, with a median of 4 prior lines of therapy (2-9) including ibrutinib (89%), venetoclax (53%), R-CHOP (58%) and allo-HCT (21%). All patients had high-risk features, including unmutated IGHV (90%), TP53 lesions (89%), complex karyotype (43%) and RT (63%), as well as elevated LDH (74%), extramedullary disease (84%), and CSF infiltration (16%). Median bone marrow infiltration at screening was 18% (3-85), and median tumour metabolic volume (TMV) was 55 ml (0-1217). Var-cel manufacturing was performed in a median of 8 days (7-9). One patient required 2 apheresis and 1 RT patient died due to progressive disease without receiving var-cel. All patients received bridging therapy (BT), based on BTKi (53%), venetoclax (26%), chemotherapy (10%), steroids (10%) and radiotherapy (5%). Despite BT, all patients received var-cel either with stable disease (44%) or progressive disease (56%), in a median of 29 days (18-81) from apheresis to infusion. Fifty-eight percent of patients received 100% of the planned dose. The remainder received 10-30% due to early cytokine release syndrome (CRS), with a final median infused dose of 1 (0.4-5) x10e6 CART19 cells/kg. CRS was observed in 89% of patients, being severe in 11%. Only mild ICANS was developed in 11%. Tocilizumab and corticosteroids were administered in 44% and 17% of patients, respectively. Median duration of CRS and ICANS was 4.5 days (1-17) and 3 days (2-4), respectively. Absolute B-cell aplasia (0 B-cells/mL) was achieved in 94% of patients in a median of 14 days (7-34), with median duration not reached for CLL and RT. Tmax peak CART19 concentration was observed at day +24 (median, 7-148). With a median follow-up of 8,4 months (0.3-66.7), the overall response rate was 83%, with 83% achieving an MRD-negative CR (flow) in bone marrow (BM) and peripheral blood, and 67% achieving CR on extramedullary lesions (PET/CT). Median PFS and DOR was not achieved for either CLL or RT (figure 1). Disease progression was observed in 7 (39%) patients in a median of 63 days (7-237), 43% of which occurred due to CD19-negative antigen escape despite active CART19 persistence. No relapses have been observed after CR was achieved. By univariate analysis there was no significant differences for PFS regarding presence of RT, SD vs PD at infusion, high vs low LDH, BM infiltration (> or < 20%), or TMV (> or < 25 ml). However, PFS was shorter among patients with both, high BM infiltration plus high TMV, in comparison to patients with either low burden at BM and/or TMV (median PFS 2 months vs not reached, p = 0.0293) (figure 2). Conclusions: Administration of the CART19 var-cel (ARI-0001) was feasible in 95% of CLL/RT patients, with robust and durable var-cel engraftment in 89% of treated patients, and durable complete responses observed in 61% of patients. These initial outcomes or var-cel in this population contrasts with the overall findings of CART19 therapy in CLL/RT and encourages to further develop var-cel on this high-risk population.

A Phase 2 Study of Acalabrutinib, Umbralisib, and Ublituximab (AU2) in Treatment-Naïve and Relapsed or Refractory Chronic Lymphocytic Leukemia (CLL)

Background Targeting the B-cell receptor (BCR) signaling pathway is highly effective for the treatment of CLL. However, attainment of undetectable minimal residual disease (uMRD) is infrequent with current BCR targeting strategies. Here, we report results of a phase 2 study testing time-limited dual BCR inhibitor therapy with a BTK inhibitor acalabrutinib and a PI3Kδ inhibitor umbralisib. With the goal of enhancing depth of remission, a glycoengineered anti-CD20 antibody ublituximab was initiated during Cycle (C) 7. Methods In this investigator-sponsored trial, eligible patients with treatment-naïve (TN) or relapsed or refractory (RR) CLL received up to 24 cycles of AU2 (NCT04624633). Each cycle was 28 days. Daily oral doses of acalabrutinib (100mg BID) and umbralisib (800mg QD) began on C1 Day (D) 1. Ublituximab IV began on C7 for 6 cycles (D1, 2, 8, and 15 of C7, D1 of C8-12). Treatment was stopped after C12 if patients achieved complete response (CR) by IWCLL criteria, while all others continued acalabrutinib and umbralisib until C24. In March 2023, umbralisib was withdrawn from drug development, and those who were receiving study therapy at the time continued acalabrutinib alone until C24. The primary endpoint was the CR rate after C24. MRD was assessed in peripheral blood (PB) and bone marrow (BM) using multi-color flow cytometry at 10 -4. Results The study enrolled 29 patients from December 2020 to January 2022. The median age at enrollment was 63 years (range 40-77). Most patients were male (62%), had TN CLL (72%), and had unmutated IGHV (79%). RR CLL patients had a median of 1 prior line of therapy, most frequently (88%) with chemoimmunotherapy. Genetic alterations were commonly observed at study enrollment, including deletion 17p or TP53 mutation (21%), deletion 11q or ATM mutation (38%), trisomy 12 (24%), and mutations of NOTCH1(45%), SF3B1 (24%), and RAS/RAF pathway (21%). 7% had complex karyotype defined as ≥3 abnormalities. At a median follow-up of 23 months (range 2-29), with 7 patients still receiving therapy prior to reaching C24, there were no deaths, Richter's transformations, or CLL progression events on the study. The rates of CR, BM uMRD, and PB uMRD at best response were 30%, 44%, and 67%, respectively (Table 1). There were no statistically significant differences in CR and uMRD rates between TN and RR groups at best response. CR and BM uMRD rates improved during the second year of therapy (CR rate: 11% after C12, 28% after C24; BM uMRD rate: 22% after C12, 39% after C24). PB uMRD occurred earlier than BM uMRD, and the rate (44%) remained unchanged between C12 and C24. After completion of study therapy, PB MRD was monitored every 3 months. Five patients had MRD conversion at the end of therapy or shortly after treatment cessation. Median time from the last uMRD to detectable MRD (dMRD) in PB was 3 months (range 3-6). Most (80%, n=4/5) patients with MRD conversion had partial response or dMRD in BM at best response. Two patients stopped treatment early (due to the diagnosis of second cancer and G4 transaminitis, in 1 patient each). In addition, 7 (24%) patients stopped umbralisib between C15-19 due to discontinuation of drug supply; these patients remained on acalabrutinib monotherapy until C24. All others completed up to 24 cycles of treatment including 3 (10%) patients who stopped therapy per protocol after C12 once CR was achieved. Dose reduction of umbralisib (38%) was more common than acalabrutinib (7%) and was most frequently due to diarrhea (21%) and transaminitis (14%). Only 2 (7%) patients required temporary dose reduction of acalabrutinib to avoid drug-drug interaction. Notable adverse events included diarrhea or colitis (76%, 10% Grade 3 or higher [G≥3]), bruising (69%, 0% G≥3), transaminitis (62%, 17% G≥3), COVID-19 infection (55%, 7% G≥3), hypertension (52%, 10% G≥3), rash (24%, 0% G≥3), and pneumonitis (7%, 3% G≥3). One (3%) patient had Pneumocystis jirovecii pneumonia while being off of mandatory prophylaxis due to non-compliance. None had atrial fibrillation. Conclusions Dual inhibition of the BCR signaling pathway with up to 2 years of AU2 provided a time-limited treatment option for TN and RR CLL patients. Immune-related adverse events were frequently observed and required dose reduction of umbralisib in 38% of the patients but most were then able to stay on therapy. Longer follow-up is required to determine durability of remission off therapy.

A bispecific T cell engager recruits both type 1 NKT and Vγ9Vδ2-T cells for the treatment of CD1d-expressing hematological malignancies

Bispecific Tcell engagers (bsTCEs) hold great promise for cancer treatment but face challenges due to the induction of cytokine release syndrome (CRS), on-target off-tumor toxicity, and the engagement of immunosuppressive regulatory Tcells that limit efficacy. The development of Vγ9Vδ2-T cell engagers may overcome these challenges by combining high therapeutic efficacy with limited toxicity. By linking a CD1d-specific single-domain antibody (VHH) to a Vδ2-TCR-specific VHH, we create a bsTCE with trispecific properties, which engages not only Vγ9Vδ2-T cells but also type 1 NKT cells to CD1d+ tumors and triggers robust proinflammatory cytokine production, effector cell expansion, and target cell lysis invitro. We show that CD1d is expressed by the majority of patient MM, (myelo)monocytic AML, and CLL cells and that the bsTCE triggers type 1 NKT and Vγ9Vδ2-T cell-mediated antitumor activity against these patient tumor cells and improves survival in invivo AML, MM, and T-ALL mouse models. Evaluation of a surrogate CD1d-γδ bsTCE in NHPs shows Vγ9Vδ2-T cell engagement and excellent tolerability. Based on these results, CD1d-Vδ2 bsTCE (LAVA-051) is now evaluated in a phase 1/2a study in patients with therapy refractory CLL, MM, or AML.

Rituximab and High-Dose Methylprednisolone Debulking Prior to Venetoclax for Patients with Relapsed or Refractory CLL

Rituximab and High-Dose Methylprednisolone Debulking Prior to Venetoclax for Patients with Relapsed or Refractory CLL

Rapid Tumor Debulking of Relapsed/Refractory CLL Patients By PI3Kδ Inhibition and Anti-CD20 Monoclonal Antibody Treatment

Introduction Effective multi-targeted drug combinations could rapidly achieve deep remissions in CLL allowing for defined duration treatment. The combination of a novel highly-specific phosphoinositide 3-kinase delta (PI3Kδ) inhibitor and casein kinase 1 epsilon (CSK1ε) inhibitor, umbralisib (UMB), and a glycoengineered chimeric monoclonal antibody (mAb) targeting a unique epitope on CD20, ublituximab (UBL), with the BCL2 inhibitor venetoclax (VEN) may decrease drug resistance, reduce risk of tumor lysis syndrome (TLS) and achieve higher levels of undetectable minimal residual disease (MRD). This triple agent therapy is being evaluated in relapsed or refractory CLL patients (U2-VEN, ClinicalTrials.gov NCT03379051). Patients received oral 800 mg UMB once-daily. For Cycle 1, UBL was given via IV on Day 1 (150 mg), Day 2 (750 mg), Day 8 (900 mg), Day 15 (900 mg), and then on Day 1 in Cycles 2 and 3 (900 mg); for 3 cycles of 28 days, followed by consolidation with UMB and VEN for cycles 4 to 24. Patient (n = 25) blood samples were collected Pre- and Post-treatment on days of UBL administration during cycles 1-3. Our studies focused on UMB and UBL treatment effects on: 1) The decrease in the circulating CLL tumor burden and thus the subsequent risk of TLS from the addition of VEN to the regimen; and 2) CD20 antigen loss on CLL cells, a major mechanism of anti-CD20 mAb resistance. Methods Blood was analyzed by clinical laboratory automated cell counter and then stained with antibodies against CD3, CD5, CD19, and CD20 for flow cytometry analysis. CLL cell counts were calculated from flow cytometry and clinical laboratory results. To quantitate CD20 surface molecules, peripheral blood mononuclear cells were isolated and stained for flow cytometry analysis with the addition of a Molecules of Equivalent Soluble Fluorochrome standard curve. All human specimen collection and usage was conducted with written informed consent after approval of our Institutional Research Subjects Review Board according to the ethical guidelines of the Declaration of Helsinki. Results Average CLL cell counts (47 x 109/L) decreased rapidly after administration of the first dose of UMB and UBL (C1D1 Post, 26 x 109/L), which rebounded the next day (C1D2 Pre, 43 x 109/L) and then decreased after the second treatment (C1D2 Post, 24 x 109/L). By Day 15, the average CLL cell count had dropped to 9 x 109/L, which decreased further to 5 x 109/L by the start of cycle 3 (Fig. 1). Notably, the variation in CLL cell counts (error bars) decreases over treatment time, suggesting that most CLL patients' tumor burdens are decreasing to a similar low level independent of starting CLL cell count. The change in average CLL cell count between Pre and Post measurements is initially very high (45% decrease C1D1) with decreasing effectiveness over treatment time (8% decrease C3D1). This change could be due to the loss of CLL cell membrane CD20 levels leading to mAb resistance. Pre-treatment (C1D1 Pre) average CLL cell membrane CD20 levels (n=18) were 29,000 CD20 molecules/cell. This decreased to 9,000 molecules/cell after the first treatment (C1D1 Post), stabilized at 9,100 molecules/cell on the next day (C1D2 Pre) and then decreased further after the second treatment (C1D2 Post) to 1600 molecules/cell. After day 8 treatment, CD20 levels remained at 1,000 molecules/cell or less until the end of this study (C3D1). Discussion UMB and UBL rapidly decrease circulating CLL counts over three cycles of treatment, reducing most CLL patient tumor burden to similar low levels. This clinical response could facilitate addition of VEN in the 4thcycle of therapy by decreasing the risk of TLS. The rapid loss of surface CD20 from CLL cells to 1,000 CD20 molecules/cell or less by C1D8 Post has the potential to cause acquired resistance to anti-CD20 mAb therapy. This rapid and sustained loss of CD20 levels is consistent with that reported at standard doses for other anti-CD20 mAbs. However, an effect of concomitant UMB on CD20 levels cannot be ruled out. Previous work suggests that lower anti-CD20 mAb doses can prevent these large decreases in CD20 levels and increase UBL efficacy. In conclusion, our initial data show that treatment with a selective PI3Kδ and CSK1ε inhibitor (UMB) combined with an anti-CD20 mAb (UBL) is effective in decreasing CLL cell counts in all patients assessed in the U2-VEN clinical trial. However, treatment efficacy could be limited by large decreases in the CLL surface CD20 levels. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Lipase-triggered drug release from BCL2 inhibitor ABT-199-loaded nanoparticles to elevate anti-leukemic activity through enhanced drug targeting on the mitochondrial membrane

Selective BCL2 inhibitor ABT-199 has been approved to treat hematological malignancies including acute myeloid leukemia (AML). However, acquired drug resistance and severe side effects occur after extended treatment limiting the clinical usage of ABT-199. Here, we successfully encapsulated pure ABT-199 in amphiphilic mPEG-b-PTMC169 block copolymer, forming mPEG-b-PTMC169@ABT-199 nanoparticles (abbreviated as PEG-ABT-199), which presented better aqueous dispersion and higher efficiency of loading and encapsulation than pure ABT-199. We then compared the anti-leukemic ability of pure ABT-199 and PEG-ABT-199 in vitro and in vivo. PEG-ABT-199 had a lower IC50 value compared with pure ABT-199 in MV4-11 and MOLM-13 cell lines. In addition, PEG-ABT-199 significantly induced apoptosis and decreased colony number than pure ABT-199. Most importantly, PEG-ABT-199 markedly reduced leukemic burden, inhibited the infiltration of leukemic blasts in the spleen, and extended the overall survival (OS) in MLL-AF9-transduced murine AML compared with free ABT-199. Meanwhile, the blank PEG169 NP was non-toxic to normal hematopoiesis in vitro and in vivo, suggesting that PEG169 NP is a safe carrier. Mechanistically, PEG-ABT-199 enhanced mitochondria-targeted delivery of ABT-199 to trigger the collapse of mitochondrial membrane potential (MMP), the release of cytochrome c (cyt-c), and mitochondria-based apoptosis. In conclusion, our results suggest that PEG-ABT-199 has more vital anti-leukemic ability than pure ABT-199. PEG-ABT-199 has potential application in clinical trials to alleviate side effects and improve anti-leukemia ability. Statement of significanceATB-199, an orally selective inhibitor for BCL2 protein, presents marked activity in relapsed or refractory AML, T-ALL, and CLL patients. However, ABT-199 resistance severely limits the further clinical usage because of off-target effects, non-specific toxicities, and low delivery of drugs. To reduce the side-effects and improve the solubility and bioavailability, ABT-199 was encapsulated into the amphiphilic mPEG-b-PTMC block copolymer by co-assembly method to obtain mPEG-b-PTMC@ABT-199 nanoparticles (PEG-ABT-199). PEG-ABT-199 has several advantages compared with pure ABT-199. 1.PEG-ABT-199 presents better aqueous dispersion and higher efficiencies of loading and encapsulation than pure ABT-199. 2. PEG-ABT-199 substantially enhances the anti-leukemic ability in vitro and in vivo compared with pure ABT-199. 3. PEG-ABT-199 has little effects on normal cells. 4. PEG-ABT-199 can reduce treatment cost.

Glycerophosphoinositol Promotes Apoptosis of Chronic Lymphocytic Leukemia Cells by Enhancing Bax Expression and Activation.

An imbalance in the expression of pro- and anti-apoptotic members of the Bcl-2 family of apoptosis-regulating proteins is one of the main biological features of CLL, highlighting these proteins as therapeutic targets for treatment of this malignancy. Indeed, the Bcl-2 inhibitor Venetoclax is currently used for both first-line treatment and treatment of relapsed or refractory CLL. An alternative avenue is the transcriptional modulation of Bcl-2 family members to tilt their balance towards apoptosis. Glycerophosphoinositol (GroPIns) is a biomolecule generated from membrane phosphoinositides by the enzymes phospholipase A2 and lysolipase that pleiotropically affects key cellular functions. Mass-spectrometry analysis of GroPIns interactors recently highlighted the ability of GroPIns to bind to the non-receptor tyrosine phosphatase SHP-1, a known promoter of Bax expression, suggesting that GroPIns might correct the Bax expression defect in CLL cells, thereby promoting their apoptotic demise. To test this hypothesis, we cultured CLL cells in the presence of GroPIns, alone or in combination with drugs commonly used for treatment of CLL. We found that GroPIns alone increases Bax expression and apoptosis in CLL cells and enhances the pro-apoptotic activity of drugs used for CLL treatment in a SHP-1 dependent manner. Interestingly, among GroPIns interactors we found Bax itself. Short-term treatments of CLL cells with GroPIns induce Bax activation and translocation to the mitochondria. Moreover, GroPIns enhances the pro-apoptotic activity of Venetoclax and Fludarabine in CLL cells. These data provide evidence that GroPIns exploits two different pathways converging on Bax to promote apoptosis of leukemic cells and pave the way to new studies aimed at testing GroPIns in combination therapies for the treatment of CLL.

Zanubrutinib, Obinutuzumab, and Venetoclax in Chronic Lymphocytic Leukemia: Early MRD Kinetics Define a High-Risk Patient Cohort with Delayed Bone Marrow Undetectable MRD and Earlier Post-Treatment MRD Recurrence

Zanubrutinib, Obinutuzumab, and Venetoclax in Chronic Lymphocytic Leukemia: Early MRD Kinetics Define a High-Risk Patient Cohort with Delayed Bone Marrow Undetectable MRD and Earlier Post-Treatment MRD Recurrence

Obinutuzumab for CLL Relapsed and Refractory Patients When New Oral Drugs an Not Available

Introduction:The management of relapsed or refractory chronic lymphocytic leukemia (r/r CLL) has undergone profound changes due to a better understanding of the disease's biology and the new drugs. The choice of the best treatment at any time after the first line therapy, for a single patient, during the course of the disease depends on age, performance status, comorbidities, renal function, and effectiveness of the previous treatment received. In many countries, although approved by regulatory agencies, new therapeutic options are not available for the patients or can be offered just for a restricted group. In Brasil, for relapsed or refractory CLL patients, ibrutinib is not funded by the public nor private health insurance. This real world scenario imposes a limitation on standard international guidelines CLL treatment recommendations.Objective:To describe the acute toxicity and responses to treatment with Obinutuzumab, outside of a clinical trial, for CLL relapsed and refractory patients.Methods:Descriptive, real word, case series report of unfit refractory or relapsed CLL patients treated with obinutuzumab with or without chlorambucil as the second line and beyond. Data were obtained from a questionnaire collected through patient-record forms completed by attending physicians.Results:A total of 14 patient-completed questionnaires were analyzed. Median age was 72 (51-84) years, 10 pts (71%) had ECOG status ≥ 0-2. Four pts (28%) had ≥ 3 comorbidities and 11 pts (78%) an impaired renal function at baseline with a creatinine clearance of 30-70ml/min. No data on cytogenetic or IGHV status was collected. Previous treatments were FC or FCR in 7 pts (50%) and all patients were treated with rituximab in the previous line therapy. Prior obinutuzumab infusion, 3 pts (23%) presented thrombocytopenia grade 3 CTC, and median ALC was 49.938 (1.890- 194.000). Seven (50%) patients experienced infuse reaction in cycle one (6 pts CTC 2, pt 1 CTC 2). Some of the cycles were delayed in 7 pts (50%) and interrupted in 2 (15%) due to hematologic toxicity. Chlorambucil was associated in 12 (85%) and 2 pts (15%) were treated with obinutuzumab in monotherapy. Neutropenia 3/4 CTC was observed in 9 pts (64%) and thrombocytopenia 3 CTC in one patient. Median obinutuzumab cycles were 5 (1-6), and the overall response was achieved by 13 pts (9 CR + 3 PR, Hallek 2008). As of July 2017, one death was described in a patient with a severe and prolong hematologic toxicity after the first cycle of Clb+obinutuzumab in which bone marrow biopsy demonstrated persistent CLL infiltration. This patient started ibrutinib treatment but died of H1N1 infection. So far, 13 pts were alive, without further serious adverse event.Conclusion:New drugs for r/r CLL treatment are not available in some countries. Obinutuzumab demonstrated a superior efficacy over Rituximab in CLL patients. Although the administration of Obinutuzumab to CLL relapsed or refractory patients was not tested in large clinical trials, it can be an alternative for unfit patients. The results of this descriptive, real world data demonstrated that obinutuzumab was effective, with no unexpected AE/SAE. The r/r CLL unfit population, previously exposed to fludarabine, needs a special attention considering the safety aspects. Acknowledgments for Matheus Golçalves and Celso Rodrigues on behalf of Brazilian CLL Group. DisclosuresFogliatto:Roche: Honoraria, Other: Travel Support; accomodations; Novartis: Honoraria, Other: Travel support; AbbVie: Other: Travel Support.

Phase 1 Study of Lenalidomide and Ibrutinib in Combination with Rituximab in Relapsed and Refractory CLL and SLL

BackgroundAlthough effective, ibrutinib has a CR rate of 10% in relapsed/refractory CLL. Attempts to improve upon its activity include the addition of other agents. The combination of lenalidomide and rituximab has demonstrated an ORR 66%, CR 12% in this setting. Based on these data, we proposed a phase I study of rituximab, lenalidomide, and ibrutinib in relapsed/refractory CLL.MethodsPatients with previously treated CLL or SLL requiring treatment with adequate organ function, ECOG <2, and measurable disease were eligible. Patients received rituximab 375 mg/m2 Cycle 1-6 Day 1, lenalidomide as per cohort dose Cycle 1-12 Day 1-21, and ibrutinib 420 mg daily starting from Day 1 and continuing until progression or intolerance. Dose escalation used a standard 3+3 design from a starting level of lenalidomide 5 mg (DL1) and increasing to 15 mg (DL3) through 3 dose levels. Patients received allopurinol for tumor lysis prophylaxis. Aspirin was recommended for those at high risk for thrombosis. The primary endpoint was the recommended phase II doses (RP2D) of lenalidomide and ibrutinib for combination with rituximab in previously treated CLL/SLL. The secondary endpoints were safety and efficacy. Once the MTD was determined, there was to be a 10-patient expansion cohort.ResultsTwelve CLL patients were enrolled between May 2014 - January 2017: DL1 (n=3), DL2 (n=6), DL3 (n=3). Median age was 64 years (range 50-75); 83% were male, 67% had an ECOG score of 1, and 50% had Rai Stage III/IV disease. Prognostic features included: 42% del 13q, 42% trisomy 12, 25% del 11q, 8% del 17p, 67% umutated IGVH, 17% ZAP-70 expression 20%, and 50% CD38 expression > 30%. Patients had received a median of 1 prior therapy (1-7), primarily rituximab with fludarabine or bendamustine. Three pts had received lenalidomide > 2 years prior to enrollment; none had progressed on the agent. No patients had ibrutinib previously.There were 2 dose-limiting toxicities of grade 4 neutropenia at DL3, thus DL2 (L 10 mg, I 420 mg) was found to be the RP2D. Six patients withdrew from study: 1 due to progressive disease, 5 due to persistent grade 4 neutropenia despite G-CSF support. Prolonged grade 4 neutropenia occurred at all dose levels; 1 patient in DL2 was able to continue with dose reduction.Most common adverse events (all grades) were fatigue (67%), neutropenia (58%), infection (58%), thrombocytopenia (42%), edema (42%), pain (42%), rash (42%). Most common grade 3/4 adverse events were neutropenia (58%), thrombocytopenia (16%), and infection (16%). Serious adverse events included neutropenia, thrombocytopenia, hemolytic anemia, aspergillus pneumonia, rash, tumor lysis syndrome, urinary tract infection.The ORR for all patients was 66.7%; 1 patient achieved a CR. In DL1, 2 patients had stable disease and 1 patient had progressive disease. One patient in DL3 was not evaluable for response assessment as they withdrew for toxicity. The ORR at the RP2D was 100% (1 CR). Most patients achieved their best response at the first assessment of 10 weeks. At median follow-up time of 6.8 months, the median time on treatment was 6.4 mo (0.66-25+). The 12-month PFS was 91.9% (50.8-98.7%). There was no progression at the RP2D.ConclusionThe combination of rituximab, lenalidomide, and ibrutinib in relapsed/refractory CLL was associated with sustained grade 4 neutropenia, which prompted study withdrawal in several patients. It appeared to occur more frequently than previous reports with rituximab-lenalidomide (50%) or single-agent ibrutinib (30%). Preliminary ORR data of the regimen were comparable to prior reports of the rituximab-lenalidomide doublet and ibrutinib in this population. Furthermore, there was no significant improvement in CR rate. Given these findings, the study was terminated. DisclosuresUjjani:Gilead: Consultancy; Abbvie: Research Funding, Speakers Bureau; Genentech: Consultancy; Pharmacyclics: Consultancy, Research Funding. Skarbnik:Genentech: Speakers Bureau; Gilead: Speakers Bureau; Abbvie: Other: Ad board, Speakers Bureau; Novartis: Speakers Bureau; Seattle Genetics: Speakers Bureau. Cheson:Celgene: Consultancy; Roche-genentech: Consultancy, Research Funding; Pharmacyclics: Research Funding.

Polatuzumab Vedotin Alone or in Combination with Obinutuzumab Synergistically Enhances In-Vitro Cytotoxicity and Cytokine Release Against CD20+/ CD79b+ Burkitt Lymphoma (BL) /Primary Mediastinal Large B Cell Lymphoma (PMBL)

Background: Pediatric Burkitt Lymphoma (PBL) represents the most common malignancy in childhood and adolescent non-Hodgkin Lymphoma (NHL) but occurs in less than 5% of adult NHL cases (Hochberg/Cairo et al, BJH 2009; Miles/Cairo, BJH. 2012). Mature B-cell NHL, including Burkitt lymphoma (BL) and primary mediastinal large B cell lymphoma (PMBL) express CD20+/CD79b+ and have an excellent prognosis with rituximab based immunochemotherapy (Cairo et al Blood. 2007,Goldman/Cairo et al. Leukemia, 2013, Gerrard/Cairo et al. Blood. 2013). The prognosis of PBL has significantly improved over the last 40 years through the use of short and intense multi-agent immunochemotherapy, however, a subset of patients with relapsed/refractory disease has immunochemotherapy resistant disease and a dismal prognosis (≤ 20% 5 yr. EFS),(Cairo et al.Blood. 2007; Cairo et al. JCO.2012). It is therefore critical to investigate and to develop targeted translational strategies in BL/PMBL in order to reduce acute morbidities, decrease late effects, and provide new options for those with recurrent disease.The hu-anti-CD79b-vc-MMAE (Polatuzumab Vedotin, PV) an antibody drug conjugate (ADC) has demonstrated significant preclinical activity against indolent CD79b+NHL (Polson et. al.Can. Res.2009). More recently PV has well tolerated in adults with CD79b refractory CLL (Palanca-Wessels et al. Lancet Oncol, 2014). Obinutuzumab, a glycoengineered type II CD20 antibody, has been shown to enhance cell death and antibody dependent cytotoxicity assay (ADCC) vs. rituximab (RTX) (Herter et al, Clinc Can Res, 2013). We previously observed that PV or obinutuzumab alone (Awasthi/Cairo et al., AACR 2017, Awasthi/Cairo et al., BJH 2015) significantly enhanced tumor cell death and increased overall survival against BL and PMBL xenografted mice. However, additive/synergistic effects of PV with obinutuzumab against mature PMBL/BL are unknown.Objective: To determine the efficacy of the PV, obinutuzumab or RTX alone or in combination with PV+ obinutuzumab vs. PV+RTX against PMBL and RTX sensitive/resistant BL tumor cell lines.Methods: Raji/Raji4RH (provided by M. Barth, MD, Roswell Park Cancer Institute) and PMBL: Karpas1106P (ATCC, USA) tumor cells were cultured in RPMI with 10 or 20% FBS.Tumor cells were incubated with PV (generously supplied by Genentech Inc.) with obinutuzumab (generously provided by Roche) or rituximab (100ug/ml) for 4 hrs with NK cells.PBMCs were expanded with lethally irradiated K562-mbIL21-41BBL cells (Lee et al, PLoS One, 2012).CD56+/CD3- isolated and expanded NK cells were used for cytotoxicity assay. Cytotoxicity was determined by DELFIA cytotoxicity assay at 10:1 E: T ratio and cytokine secretion was measured by multiplex ELISA assay kit.Results: Obinutuzumab+NK, RTX+NK (100µg/ml) compared to PV+NK cells (20ug/ml, 10:1E:T ratio) significantly enhanced cell lysis in Raji, 65.9±2.4% vs. 38.9±5.4% vs. 44.24±8.1%, (p=0.001 and p=0.001), Raji4RH, 52.8±9.4% vs. 16.04±7.2% vs.47.0±8.2% (p=0.03 and p=NS), respectively and Karpas1106P, 66.10±5.3% vs.48.2±3.9% vs. 61.6±10.06% (p=0.004 and NS), respectively. PV+ obinutuzumab+NK, further significantly improved in-vitro cytotoxicity compared to PV+ rituximab+NK, Raji, 93.6±6.1% vs 79.9±5.3% (p=0.007, Figure 1A), Raji4RH, 78.07±2.05% vs 63.5±0.16% (p=0.004, Figure1B) and Karpas1106P, 88.3±6.3 %vs.73.03±3.03% (p=0.003, Figure1C), respectively. Furthermore, IFN-g level from supernatant of PV+obinutuzumab+NK was significantly increased compared to obinutuzumab+NK alone, Raji, 22.14±2.1 vs. 9.41±6.5 ug/ml (p=0.01), Raji4RH, 20.30±9.8vs.17.02±2.5 ug/ml (p=0.05) and Karpas1106P, 18.10±1.5vs.9.56±5.5 ug/ml (p=0.03), respectively.Conclusion: Our preliminary data indicates thatPV in combination with obinutuzumab significantly enhances cell death in RTX sensitive/resistant CD79b+/CD20+ BL and PMBL compared to obinutuzumab or PV alone. Furthermore, PV+ obinutuzumab significantly enhanced cytokine secretion in BL (RTX sensitive/resistant) and PMBL compared to obinutuzumab alone. [Display omitted] DisclosuresKlein:Roche: Employment, Equity Ownership, Other: patents. Lee:Miltenyi: Speakers Bureau; Cyto-Sen Therapeutics, Inc: Other: Founder, Vice President, Medical Director; Intellia Therapeutics, Inc: Consultancy; Courier Therapeutics, Inc: Membership on an entity's Board of Directors or advisory committees. Cairo:Jazz Pharmaceuticals: Speakers Bureau.

TG‐1701, A SELECTIVE BRUTON TYROSINE KINASE (BTK) INHIBITOR, AS MONOTHERAPY AND IN COMBINATION WITH UBLITUXIMAB AND UMBRALISIB (U2) IN PATIENTS WITH B‐CELL MALIGNANCIES

Introduction: TG-1701 is a selective, covalent BTK inhibitor administered once daily (QD). Both the “U2” combination (anti-CD20 mAb ublituximab + the PI3Kδ-CK1ϵ inhibitor umbralisib) and BTK inhibition are highly active in treatment-naive (TN) and relapsed/ refractory (R/R) CLL, each having previously demonstrated superiority over standard chemoimmunotherapy. Herein we report the results of the dose escalation of TG-1701 monotherapy and TG-1701+U2. Methods: Patients (pts) with R/R CLL, MCL and Waldenstrom's (WM) were enrolled in an ongoing Ph 1 study initially evaluating dose escalation (DE) of oral TG-1701 QD continuously administered in 28-day cycles (100, 200, 300, and 400 mg). After characterizing the safety profile of TG-1701 monotherapy, we implemented a parallel DE arm of TG-1701+U2. Select dose levels of TG-1701 monotherapy were expanded. All pts were treated until disease progression, unacceptable toxicity, or investigator/patient decision to withdraw. Results: As of 03 February 2021, 123 pts were treated with TG-1701 as follows: 25 in the monotherapy DE arm, 61 in the 200 mg disease-specific cohorts (20 CLL [5 TN], 21 MCL [4 TN], 20 WM [8 TN]), 20 in the 300 mg CLL cohort (4 TN), and 17 in the 1701+U2 DE arm. The median # of prior therapies was 1 (range, 1-10). All pts were BTKi-naive. All 123 pts were evaluable for safety. TG-1701 was well tolerated and the maximum tolerated dose (MTD) for monotherapy was not reached at 400 mg (demonstrating near 100% saturation of the BTK at all dose levels studied). Treatment emergent adverse events (TEAE) of clinical interest included atrial fibrillation (AF 4.0% of pts, G ≥3 in 1 case), G ≥3 hypertension (2.4%), and bleeding events (18.7%, all G1-2). No cases of ventricular tachyarrhythmia were reported. TEAEs leading to TG-1701 dose reduction occurred in 6.5% of pts. TEAEs leading to treatment discontinuation occurred in 1.6% of pts (AF, COVID-19). At the data cut-off, 119 pts were evaluable for response, including 40 in DE (Table). The median duration of response has not been reached among responders overall. The median follow-up (mFU range) was 15.9 mos (1.3-28.6+) in DE and 8.5 mos (1.4-15.6+) in disease-specific cohorts. Best change from baseline in tumor burden in pts in the 1701+U2 combination arm is presented in the figure below. Conclusions: TG-1701 exhibits an encouraging safety and efficacy profile. The combination of 1701+U2 has been well tolerated and dose escalation continues. The combination shows enhanced depth of response over TG-1701 monotherapy.

Acalabrutinib: a highly selective, potent Bruton tyrosine kinase inhibitor for the treatment of chronic lymphocytic leukemia

Inhibiting the activity of Bruton tyrosine kinase (BTK) prevents the activation of the B‐cell receptor (BCR) signaling pathway, which in turn prevents both B‐cell activation and BTK‐mediated activation of downstream survival pathways. Acalabrutinib is an orally available, highly selective, next-generation inhibitor of BTK. Based on the results of two key phase 3 trials (ELEVATE-TN in patients with previously untreated chronic lymphocytic leukemia [CLL] and ASCEND in patients with relapsed or refractory CLL), which demonstrated superior progression-free survival while maintaining favorable tolerability, acalabrutinib was granted US Food and Drug Administration (FDA) approval in 2019 for the treatment of patients with CLL. Acalabrutinib appears to offer similar efficacy but a significantly improved tolerability profile to first-generation agents. Acalabrutinib is a good candidate to combine with other anti-cancer therapies, including B-cell lymphoma 2 inhibitors and monoclonal antibodies, a factor that may help to further improve clinical outcomes in CLL.

A Phase 1/2 Study of Umbralisib, Ublituximab, and Venetoclax (U2-Ven) in Patients with Relapsed or Refractory Chronic Lymphocytic Leukemia (CLL)

A Phase 1/2 Study of Umbralisib, Ublituximab, and Venetoclax (U2-Ven) in Patients with Relapsed or Refractory Chronic Lymphocytic Leukemia (CLL)

Ibrutinib Induces Durable Remissions in Treatment-Naïve CLL Patients with 17p Deletion/TP53 Mutations: Five Year Follow-up from a Phase 2 Study

Ibrutinib Induces Durable Remissions in Treatment-Naïve CLL Patients with 17p Deletion/TP53 Mutations: Five Year Follow-up from a Phase 2 Study

Continued Long Term Responses to Ibrutinib + Venetoclax Treatment for Relapsed/Refractory CLL in the Blood Cancer UK TAP Clarity Trial

Continued Long Term Responses to Ibrutinib + Venetoclax Treatment for Relapsed/Refractory CLL in the Blood Cancer UK TAP Clarity Trial

Highlights from ASCO 2020: updates on the treatment of chronic lymphocytic leukemia.

Because of the global coronavirus pandemic, the 2020 annual scientific meeting of the American Society of Clinical Oncology took place virtually, 29-30 May. At the meeting, results from key studies about the treatment of chronic lymphocytic leukemia (cll) were disseminated. Studies examined the efficacy and safety of ibrutinib, acalabrutinib, zanubrutinib, and venetoclax as monotherapy or in combination with novel agents for patients with treatment-naïve and relapsed or refractory cll. Our meeting report describes the foregoing studies and presents interviews with investigators and commentaries by Canadian hematologists about potential effects on Canadian practice.

Clinical Outcomes of CLL Patients with Relapsed or Refractory Disease after CD19-Specific CAR-T Therapy

<h3>Background</h3> Chimeric antigen receptor T-cell (CAR-T) therapy has shown promising efficacy in high-risk CLL but progressive disease after CAR-T is not uncommon. We studied outcomes of pts with relapsed or refractory CLL after CAR-T to establish a benchmark for trials in this setting. <h3>Methods</h3> CLL pts treated with CD19-specific CAR-T on a clinical trial (NCT01865617) were reviewed. We identified pts with stable or progressive disease (SD/PD) on initial assessment or with relapse after a complete or partial response (CR/PR). Multivariable models included variables related to disease, treatment and CAR-T procedure. <h3>Results</h3> 28 pts had SD/PD (n=16; 57%) or relapsed (n=12; 43%) disease after CAR-T. Five pts (18%) had prior allo-SCT. Five pts (18%) received bridging therapy after leukapheresis. CAR-T adverse events included CRS in 22 pts (grade 3 in 2) and NT in 7 (grade 3 in 5). 5 of 11 pts who received Venetoclax (Ven) after CAR-T had progressed on it before but had a median duration of response (DOR) of 5 months (2-8) which was not different from pts who were Ven responsive before CAR-T [5 months (1-10); p = 0.95). This was not true for Ibrutinib (IB) with DOR of 2 months (0.5-7) in pre-CAR-T IB failed vs. 12.25 months (6-18.5) in pre-CAR-T IB responsive pts (p = 0.001). Fourteen pts (51%) had repeat CAR-T therapy (CR=3, PR=3) with DOR after second CAR-T of 5.5 months (1-33). Six pts (23%) received an allo-SCT median 6.5 months after CAR-T progression (CR=2, PR=1). History of progression on both IB and Ven before CAR-T was strongly associated with poor OS [hazard ratio (HR) 11.2 (95% CI: 2.5-50.5); p=0.002]. Receiving an allo-SCT after CAR-T progression was associated with an improved OS [HR 0.14 (95% CI: 0.02-0.97); p=0.04]. [Fig-1] <h3>Conclusion</h3> This data sets a benchmark for clinical trials that intend to improve outcome of CLL pts with progression after CAR-T. OS after CAR-T progression was significantly shorter in pts who received CAR-T after failing both IB and Ven compared to others. This finding supports referring high-risk CLL pts for CAR-T treatment after progression on IB and while still responsive to Ven. For eligible pts, allo-SCT seems to provide a higher chance of survival in pts who progress after CAR-T.

Relapsed or Refractory CLL after CD19-Specific CAR-T Therapy: Treatment Patterns and Clinical Outcomes

Relapsed or Refractory CLL after CD19-Specific CAR-T Therapy: Treatment Patterns and Clinical Outcomes

UK CLL Forum 5 Year Update on 315 Relapsed Refractory CLL Patients Treated with Ibrutinib in 66 UK and Ireland Centres

Introduction UK and Ireland clinicians gained non-trial access to ibrutinib for relapsed / refractory CLL through a named patient scheme (NPS) for 7 months in 2014, and the UK CLL Forum has been following a cohort of 315 NPS patients treated with ibrutinib at 66 UK and Ireland hospitals. We now update this dataset with up to 5 years follow-up. Results The primary end-points of the study were Discontinuation Free Survival (DFS) and Overall Survival (OS). Of the original 315 patients, 213 have stopped ibrutinib and 159 patients have died, with all living patients having a survival update in 2019. With 55.6 months median follow-up, median DFS was 33.5 months (95% CI: 28.4-29.3) and median OS was 55.9 months (95% CI: 42.5-N/A) (Figure 1A and 1B). Four years after starting ibrutinib, 37.0% of patients were still taking ibrutinib and 52.4% were still alive. Both DFS and OS were inferior for older (age &gt; median) and PS 2+ patients. Patients with 17p- have inferior DFS and OS compared to patients with other defined cytogenetic aberrations (13q-, 11q-, t(12)) and more patients with 17p- compared with non-17p- stopped ibrutinib for progressive CLL (PD) (26.4% vs 18.8%; p=0.01) and Richter's Syndrome (12.1% vs 8.3%; p=0.05). First relapse patients had more than a 3 fold lower rate of ibrutinib discontinuation due to CLL progression (7.1% versus 24.5%; two-tailed Fisher's exact test; p=0.001) compared with patients receiving ibrutinib at later lines of therapy, although DFS and OS for these groups were similar. With multivariable analysis of pre-treatment factors, older age, PS2+, 17p- and &gt;1 prior line of therapy retained significance for earlier ibrutinib discontinuation and age, PS2+ and 17p- associated with inferior OS. To analyze any potential impact of reduced ibrutinib dosing during the first year of therapy, we originally classified all patients alive at 12 months into 4 groups, depending on first-year ibrutinib treatment. Group A: No dose reductions or breaks &gt;14 days; Group B: Dose reductions, but no breaks &gt; 14 days; Group C: Breaks &gt; 14 days but back on ibrutinib by 1 year; Group D: stopped ibrutinib permanently but still alive at 1 year. With extended follow-up, patients dose reduced in year 1 are very likely to have on-going dose reductions beyond the first year (86% patients in group B are still dose reduced beyond 4 years, compared with 12% in group A). Groups A and B retain similar DFS and OS initially, although beyond 2 years the curves separate (Figure 1C and 1D) (DFS HR: 1.62 (1.05-2.50), OS HR: 1.52 (0.86-2.70)). Interestingly, the dose-reduced group do not have a higher incidence of disease progression, (PD A:24.8%, PD B:23.8%), but have a higher chance of discontinuation for all non-PD causes (A:23.6%, B:42.9%). With longer follow-up, patients from groups C and D had significantly impaired OS compared with group A, with 4 year OS 39.4% and 16.7% respectively compared with 76.4% for group A (p&lt;0.001). Considering all patients who discontinued ibrutinib, stopping for AEs decreased over time (year 1: 57%, 2: 53%, 3: 30%, 4: 21%). Stopping for infection was much more common in the first year (19.5%) compared with years 2 to 4 (8.4%). The risk of stopping ibrutinib due to PD-CLL increases with time (year 1: 11%, 2: 18.6%, 3: 42.5%, 4: 57.6%). Of the PD-CLL patients, treatment with venetoclax had the best OS (n=43; 1 year OS: 77.5%) compared with the 7 treated with rituximab / idelalisib (1 year OS: 42.9%) and 14 treated with other strategies (including palliative care) (1 year OS: 10%). Although this supports the use of venetoclax for disease progression post ibrutinib, there are two potentially significant biases; more palliative patients did not receive venetoclax and patients who relapsed within 1 year of starting ibrutinib, who were potentially more unstable biologically, did not receive venetoclax (unavailable in the UK pre-2016) Conclusions With approaching 5 years of follow-up, around one third of 'real-world' UK / Ireland patients treated with ibrutinib for relapsed / refractory CLL remain on ibrutinib. Our data suggest that younger, better performance status patients who have had fewer prior lines of therapy and no evidence of 17p deletion seem most likely to remain on ibrutinib long-term. Likewise, patients who remain free of adverse events that often associate with dose reductions and treatment breaks, have the best chances of remaining on ibrutinib. Treatment of PD-CLL with venetoclax post ibrutinib shows encouraging results. Disclosures CLL Forum: Roche: Other: Sponsorship of the UK CLL Forum; Abbvie: Other: Sponsorship of the UK CLL Forum; Janssen: Other: Sponsorship of the UK CLL Forum; Gilead: Other: Sponsorship of the UK CLL Forum. Follows:Janssen: Consultancy, Honoraria, Speakers Bureau; Abbvie: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Speakers Bureau; AZ: Consultancy, Honoraria, Speakers Bureau.