Long-term Extension Study of Zanubrutinib (BGB-3111) in Patients With B-cell Malignancies
Investigational Immunotherapeutics for B-Cell Malignancies
The use of rituximab-based chemoimmunotherapy regimens has remarkably improved the response rates, long-term outcomes, and quality of life of patients with B-cell malignancies. However, a substantial number of patients exhibit either primary or acquired resistance to rituximab, which suggests that novel immunotherapeutics with distinct mechanisms of action are necessary. A series of monoclonal antibodies with specificity against different surface antigens expressed on malignant B cells (eg, CD22, CD23, CD40, CD70) and novel immunotherapeutics (eg, bispecific monoclonal antibodies, small-modular immunopharmaceuticals, T-cell engagers) are currently in clinical or final preclinical stages of development. Although these agents offer reason for optimism, considerable challenges lie ahead in establishing their real clinical value, as well as in integrating them into current therapeutic algorithms for patients with B-cell malignancies. This review describes some of the most promising investigational immunotherapeutics for the treatment of B-cell malignancies.
Abstract Abstract 2834 Poster Board II-810 Background: Monoclonal gammopathy of undetermined significance (MGUS) results arises from a clonal proliferation of differentiated plasma cells and is a necessary precursor to development of multiple myeloma and some other B cell malignancies. Despite a high incidence in the general population (1-2% of adults in the 6th and 7th decades) and increased relative risk for later malignancy, there are few reports about the clinical course and prognosis of MGUS in long-term immunosuppressed patients. We aimed to evaluate the significance of MGUS in patients undergoing solid transplants in terms of clinical outcomes and rate of transformation to secondary B cell malignancy. Material and methods: We reviewed the medical records of 1493 patients on which kidney (living donor related, living donor-unrelated and deceased donor), liver and pancreatic transplants were performed at Mayo Clinic Arizona, between January 1, 1999 and July 31, 2009 to determine the incidence of MGUS and to further evaluate long-term follow up. At MCA patients are routinely screened using SPEP and for those where an M-spike is detected or suspected immunofixation is required for confirmation. MGUS was defined as previously reported. Patients who had anemia unrelated to their PCD were included. Statistical Methods: Patients were observed until death or, for those still alive, until July 2009. The major goal of the study was to assess the impact of MGUS on transplant outcomes and progression to active myeloma or related disorders. Patients who did not experience progression were censored at the time of last follow-up. Nominal variables were compared using Fisher's exact test. A two-tailed P value less than .05 was considered significant. Results In this series, SPEP was performed in 1199 out of 1593 cases (75%) before transplantation. The most common abnormalities detected by SPEP included a normal pattern (70%), polyclonal pattern (16.8%), hypoalbuminemia (8%), hypogammaglobulinemia (2.4%) and the presence of M spike (2.8%). Immunofixation revealed the presence of a monoclonal immunoglobulin in 34 patients: IgG 30 cases (88%), IgM in 2 (6%) and biclonal disease in 2 (6%). The median age at diagnosis of MGUS was 60 years (range, 46 to 84 years), and included 63.7% of males. Clinical characteristics of the MGUS cases are seen in Table 1. Two MGUS patients were diagnosed only after the transplant was performed (338 and 1082 days respectively). There was no association between post-transplant lymphoproliferative (PTLPD) and MGUS and even when some MGUS patients died (7/34, 20%) death was not associated with progression of the monoclonal clone or development of a PTLPD or other malignancy. MGUS does not impact transplant outcomes. PTLPD disorders developed in 6 cases and none was associated with a MGUS. After a median of 88 months no MGUS patient developed transformation to active myeloma or a related disorder. Overall survival after transplantation was not significantly different among MGUS and Non- MGUS cases (6.48 vs 8.36 years p>0.05). Discussion Despite the frequency of MGUS in the general population there are few studies which have assessed MGUS in solid organ transplant patients. An increased incidence of monoclonal gammopathy in patients with autoimmune disease and in older non-transplant populations suggests that impaired immunity might lead to development of MGUS and later monoclonal B-cell malignancies. Interestingly, we identified two cases where MGUS appeared after transplant. In this series, we report on the incidence and follow/up of MGUS in patients screened before transplantation. The primary outcome for transplant recipients is unaffected by the presence of MGUS and incidence is in accordance with the expected frequency (2.8%). Patients with MGUS do not appear to be at risk for progression due to chronic immunosuppression. Testing for MGUS before transplantation is not cost-efficient and therefore would not be recommended. To our knowledge this is the largest series of MGUS and transplant outcome yet reported. Disclosures: Stewart: Takeda-Millenium, Celgene, Novartis, Amgen: Consultancy; Takeda, Millenium: Research Funding; Genzyme, Celgene, Millenium, Proteolix: Honoraria.
Abstract Abstract SCI-27 Targeted therapy in hematologic malignancies has achieved significant therapeutic success when relatively selective inhibition is attainable to a target dispensable to the majority of normal cells. The best appreciated example of this is imatinib in chronic myeloid leukemia (CML), in which a single translocation forms a fusion protein involving the tyrosine kinase ABL that molecularly defines the disease. Kinase inhibition of ABL in this setting by imatinib (or other second- and third-generation kinase inhibitors) promotes durable, long-term remission in CML patients. The great majority of B-cell malignancies lack a characteristic translocation, activating mutation, or other aberration that facilitates such targeted therapy as employed in CML. Nonetheless, a common global signaling pathway involving the B-cell receptor (BCR) pathway has emerged as one that might be important to the control of these diseases. Furthermore, mouse models of select kinase targets (phosphoinositide-3 kinase p110 isoform-delta and Bruton's tyrosine kinase [BTK]) have shown that these are dispensable relative to long-term survival. Indeed, knockout or mutation of BTK and p110 delta each have a modest phenotype outside of diminished B-cell development and function. Based upon these preclinical observations, several molecules targeting BCR signaling have come forward to the clinic with exciting results across a wide range of B-cell malignancies. GS-1101 is a selective phosphoinositide-3 kinase p100 delta inhibitor with a very favorable toxicity profile that has shown promising clinical activity in low-grade lymphoma and chronic lymphocytic leukemia (CLL). The toxicity of this orally administered agent is quite modest in the majority of patients and allows sustained continuous dosing. Similarly, ibrutinib is an irreversible inhibitor of BTK and has shown promising clinical potential in an even broader range of B-cell malignancies, including diffuse large B-cell lymphoma, mantle cell lymphoma, low-grade lymphoma, and CLL. Toxicity with ibrutinib has also been modest, allowing long-term continuous dosing. Notably, each of these agents also produces an atypical mobilization of malignant lymphocytes into the blood soon after treatment. This treatment lymphocytosis is BCR-target-related due to diminished CXCR4/SDF-1 interface between tumor cells and stromal cells in the bone marrow, with egress of these cells to the blood. GS-1101 and ibrutinib are now entering phase III studies for regulatory approval and offer great potential to change the treatment paradigm of both CLL and B-cell non-Hodgkin lymphoma (NHL). Questions moving forward with these agents will include molecular predictors of response, feasibility and efficacy of combining with other effective therapies, and mechanisms of resistance. The scientific session presentation will provide an overview of the most promising BCR signaling agents in CLL and NHL clinical trials. Disclosures: No relevant conflicts of interest to declare.
Abstract Abstract 964 Introduction: Bruton's tyrosine kinase (Btk) is a downstream mediator of B-cell receptor signaling. PCI-32765 is a potent, selective, irreversible and orally bioavailable small molecule inhibitor of Btk. We have previously reported initial efficacy and safety data with this agent in various B-cell malignancies (ASCO 2010 abstract # 8012). We now report updated efficacy and safety of PCI-32765 in patients (pts) with long-term dosing. Pts and Methods: Pts on the Phase 1 study were treated with escalating doses over 6 cohorts. Cohort 1 was dosed at 1.25 mg/kg/day with subsequent dose escalation (2.5, 5.0, 8.3, 8.3 continuous dosing, and 12.5 mg/kg/day) based on safety evaluation. Pts were analyzed according to histology, pretreatment clinical and laboratory characteristics, PCI-32765 dose levels, overall response (OR), and response duration. Results: Responses and time on study (≥ 6 months) are summarized in Table 1. Of 47 pts enrolled in the Phase 1 study, 20 pts (43%) achieved an OR including 3 complete remissions (CR) and 17 partial remissions (PR). Fourteen of 47 pts have been on study ≥ 6 months; of these 8 pts demonstrated a PR or better and 6 pts maintained stable disease (SD). Responses were observed irrespective of pretreatment risk factors such as performance status, lactate dehydrogenase (LDH) levels, or disease burden. Durable responses were seen at all dose levels and across various histologic subtypes (Table 1) and currently 9 of 14 pts with treatment ≥ 6 months are still on study. Study-drug related Grade ≥ 3 toxicities were reported in 9/47 pts (19%). Five of 47 pts discontinued study drug due to adverse events: neutropenia (Grade 3) lasting > 7 days, hypersensitivity reaction (Grade 3), small bowel obstruction (Grade 3), anemia (Grade 2), and exacerbation of chronic obstructive pulmonary disease (Grade 3). No evidence of cumulative hematologic toxicity or long-term safety signals have been observed. No treatment-related deaths have been reported. Conclusion: PCI-32765 is a novel oral Btk inhibitor that induces durable objective responses in various relapsed or refractory B-cell malignancies. The favorable safety profile and lack of cumulative hematologic toxicities support further studies of both monotherapy and combination treatment with PCI-32765. Disclosures: Fowler: Pharmacyclics: Consultancy, Research Funding. Off Label Use: This phase I trial describes the results of a first in human Phase I trial. This drug is not FDA approved for the treatment of malignancy. Sharman:Pharmacyclics, Inc: Honoraria, PI grant. Smith:pharmacyclics: Research Funding. Boyd:pharmacyclics: Research Funding. Grant:pharmacyclics: Research Funding. Kolibaba:pharmacyclics: Research Funding. Furman:Pharmacyclics, Inc: Research Funding. Buggy:pharmacyclics: Employment. Loury:Pharmacyclics: Employment, Equity Ownership. Hamdy:pharmacyclics: Employment. Advani:Pharmacyclics, Inc: Honoraria, PI grant.
Abstract Abstract 4038 Background MLN0128 is an investigational, oral, potent, and selective, ATP site inhibitor of the mTOR complexes 1 and 2 (TORC1/2), and is structurally and mechanistically distinct from rapamycin and rapalogs, which primarily target TORC1. Constitutive activation of the mTOR pathway has been demonstrated in MM cell lines and primary pt samples; dual TORC1/2 inhibition has been shown to be more active than TORC1 inhibition alone. MLN0128 has been shown to inhibit proliferation and induce apoptosis in MM cell lines and pt samples (Maiso et al. Blood 2011); mTOR activation has also been seen in NHL and WM, providing the rationale for investigation of MLN0128 in these diseases. The primary objectives of this phase 1 study, the first report of TORC1/2 inhibition in MM and B cell malignancies, are to determine safety/tolerability and the maximum tolerated dose (MTD) of multiple dosing schedules of MLN0128 in relapsed/refractory MM, NHL or WM. Secondary objectives include evaluation of pharmacokinetics (PK), pharmacodynamics, and preliminary antitumor activity. Methods Eligible pts were aged ≥18 yrs with ECOG performance status 0–2, and included pts with relapsed/refractory MM/WM, and pts with NHL who had failed/were ineligible for standard-of-care therapy. Pts received oral MLN0128 daily (QD), or QD for 3 days on and 4 days off each week (QDx3d QW), in 28-day cycles, for ≤1 year. Dose was escalated using a modified Fibonacci schema (standard 3+3 design) based on dose-limiting toxicities (DLTs) in cycle 1. Adverse events (AE) were graded using NCI-CTCAE v4.0. Blood samples were collected at multiple timepoints for PK analysis. Response was assessed using the IMWG uniform response criteria (MM; plus EBMT criteria for minimal response [MR]), IWG revised response criteria (NHL), and updated Third International Workshop criteria (WM). Results At data cut-off (June 18, 2012) 37 pts (30 MM; 4 NHL – 2 DLBCL, 1 mantle cell, 1 lymphoplasmacytic lymphoma [LL]; 3 WM) had been enrolled to 6 dose levels (Table). Median age was 60 yrs (range 46–85), 20 were male, and median number of prior systemic therapies was 2 (range 1–10) including chemotherapy in 89%, autologous transplant in 46%, and steroids in 38%. DLTs are shown in the table. The QD MTD is 6 mg; the MTD for QDx3d QW has not yet been defined. Pts have been treated for a median of 3 cycles (range 1–8); 9 (24%) received ≥4 cycles, and 3 (8%) are ongoing. Pts discontinued due to progressive disease (n=14), pt/investigator decision (n=10), AE (n=4), or multiple/other reasons (n=6). Overall, 89% of pts had ≥1drug-related AE, the most common were nausea (43%), fatigue (41%), hyperglycemia (35%), thrombocytopenia (32%), mucosal inflammation, vomiting, and anemia (each 19%). Overall, 43% of pts had drug-related grade 3/4 AEs, including thrombocytopenia (16%), fatigue (8%), mucosal inflammation, and neutropenia (each 5%); 57% had dose reductions/modifications, and 27% discontinued due to AEs. Overall, 19% of pts had serious AEs, none were considered related to MLN0128. One pt with advanced MM and multiple plasmacytomas who had had several relapses on prior therapies received two doses of 2 mg QD MLN0128 and subsequently died from a subdural hemorrhage, considered unrelated to MLN0128. The pt had a history of pneumonia and was receiving anticoagulation therapy. MLN0128 exhibited a dose-dependent increase in exposure with a plasma half-life of ∼8 hours, and did not accumulate in plasma with repeat dosing. Among 27 pts evaluable for confirmed responses, 1 MM pt (7 mg QD) achieved a MR lasting ∼2 months, and 13 MM pts (2 at 2 mg QD, 4 each at 4 mg QD and 7 mg QD, 2 at 9 mg QDx3d QW, and 1 at 12 mg QDx3d QW) and 2 WM pts (at 6 mg QD and 9 mg QDx3d QW) had stable disease. Conclusions To date, in this first study of TORC1/2 inhibition in MM and B cell malignancies, oral MLN0128 has been observed as generally well tolerated, with a limited incidence of hyperglycemia, a toxicity associated with PI3k/Akt/mTOR pathway inhibition (Busaidy et al. J Clin Oncol 2012). The preliminary antitumor activity supports further research in this pt population. Disclosures: Ghobrial: Millennium pharmaceuticals Inc.: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Off Label Use: Use of the investigational agent MLN0128, an oral TORC1/2 inhibitor, in the treatment of relapsed and/or refractory MM, NHL, or WM. Siegel:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium pharmaceuticals Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Onyx: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Vij:Millennium Pharmaceuticals Inc.: Speakers Bureau. Wolf:Millennium Pharmaceuticals, Inc.: Honoraria, Speakers Bureau. Matous:Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium Pharmaceuticals, Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees. Lipman:Millennium Pharmaceuticals, Inc.: Employment, offered Takeda stock as part of company long term incentive plan Other. Patel:Millennium Pharmaceuticals, Inc.: Employment, offered Takeda stock as part of company long term incentive plan Other. Le:Intellikine, LLC.: Former employee and stockholder Other. Rommel:Intellikine, LLC.: Former employee and stockholder Other. Berk:Intellikine, LLC. : Former employee and stockholder, Former employee and stockholder Other; Millennium Pharmaceuticals, Inc.: Consultancy.
Abstract Inherited gain-of-function mutations in PIK3CD encoding PI3Kδ (phosphoinositide 3-kinase delta) lead to accumulation of senescent T cells, lymphadenopathy, splenomegaly and immune-deficiency (Activated PI3Kδ Syndrome, APDS). Clinical manifestations include multilineage cytopenias and susceptibility to B cell Non-Hodgkins Lymphoma. We recently reported use of leniolisib (CDZ173), a novel, potent and selective oral PI3Kd inhibitor in six APDS patients in a 12-week, open-label, multi-center, within-subject dose-escalation study (Rao et al, Blood 23 November 2017). Leniolisib was safe and well tolerated and led to a dose-dependent reduction in PI3K/AKT pathway activity and improved the immune dysregulation with normalization of circulating transitional and naïve B cells and reduction in PD-1+CD4+ and senescent CD57+CD8+ T cells. Elevated serum IgM and other biomarkers including IFNg, TNF, CXCL13 and CXCL10 normalized or decreased with leniolisib. Cytopenias and lymphoproliferation improved in all patients with index lymph node sizes and spleen volumes reduced by 39% and 40%, respectively. Here we report the long term follow up safety and efficacy data in all six patients (Table 1) who have continued treatment with leniolisib in an extension study at 70 mg b.i.d (ClinicalTrials.gov number NCT02859727). These patients have been treated for up to 949 days (as of July 20th 2018). Three of them were lymphoma survivors. Three patients were treated with rapamycin prior to starting leniolisib. No patient in the 12-week clinical trial or in the long term extension study has experienced any significant adverse events. Notably, side effects prevalent with mTOR or other PI3K inhibitors such as diarrhea/colitis, skin rashes, susceptibility to infections or liver enzyme elevation were absent. Three patients have stopped immunoglobulin supplementation as a reflection of the normalization of their B cell function. Cytopenias, including anemia, thrombocyopenia, neutropenia and lymphopenia have continued to improve. (Figure 1: Showing representative improvement of laboratory data including normalization of IgM for patient 002, following 18 months of treatment with leniolisib; Figure2: Showing improvement of lymphoproliferation in CT scans from 2016 and 2018 for Patient 003. This patient stopped leniolisib for 15 months from October 2016 until January 2018 leading to worsening lymphoproliferation that improved promptly on resumption of therapy). Available data on longterm safety, effects on lymphoproliferation and immune dysregulation in the ongoing leniolisib extension study will be shared during the meeting. The results support safe and efficacious long term inhibition of PI3Kδ protein as a new targeted therapeutic approach in APDS and other disorders of nonmalignant lymphopoliferation associated with hyperactive PI3Kinase pathway. Disclosures Rao: novartis: Research Funding. Dalm:Novartis: Research Funding. Sediva:Novartis: Research Funding. van Hagen:Novartis: Research Funding. Cabanski:Novartis: Employment. Valentin:Novartis: Employment. de Buck:Novartis: Employment. Kalis:Novartis: Employment. Hasselberg:Novartis: Employment. Burkhart:Novartis: Employment. Kucher:Novartis: Employment. Sloth:Novartis: Employment. Uzel:Novartis: Research Funding.
Abstract Introduction: CD19-directed chimeric antigen receptor T (CART19) cell therapies have shown impressive clinical outcomes in CD19+ B-cell malignancies. All the FDA-approved CART19, including tisagenlecleucel, axicabtagene ciloleucel, brexucabtagene autoleucel, and lisocabtagene maraucel use an anti-CD19 single-chain variable fragments (scFv) derived from the FMC63 antibody that binds to a CD19 epitope that is located in the membrane-distal portion of CD19. While this CART19 products are very effective in the clinic, the majority of patients still fails treatment or eventually relapses due to several mechanisms of resistance, including CAR T cell dysfunction in the immunosuppressive microenvironment. Novel strategies to enhance the activity of CART cells are critically needed. We and others recently demonstrated that modifications of the binding region of the CAR (scFv) (Singh N., Nat Med, 2021) can drastically change the interaction between the CAR T cell and the cancer cells, potentially improving the anti-tumor effect. In this study, we aimed to develop a novel anti-CD19 CAR that binds to a membrane-proximal domain of CD19 with the goal of improving CART functions. Moreover, we hypothesized that such a CART product would be active against B-cell acute lymphoblastic leukemia (B-ALL) blasts that present aberrant expression of the CAR19(FMC63) on the surface as we described in two pediatric B-ALL patients relapsed after CART19 (CTL019) at our Institution (Ruella M., Nat Med, 2018). Methods and Results: To these goals, we screened a chicken immune scFv library against the CD19 extracellular domain. We selected an scFv clone (1218) that was not competing with FMC63 for CD19 binding in competition enzyme immunoassays and real-time interaction analysis. The chicken 1218 scFv was humanized by CDR-grafting to human germline genes and backmutations (h1218 scFv) and was confirmed to be specific for CD19 in cell microarray assays and flow cytometry analyses. In order to define the epitope that was recognized by the 1218 scFv, we performed mutagenesis assays replacing several residues of human CD19 with monkey CD19 residues showed that, as compared to FMC63, the epitope of the h1218 scFv is localized in a membrane-proximal location shown by three-dimensional modeling (Teplyakov A., Proteins, 2018) (Fig. 1A). Key residues needed for the binding of the h1218 scFv were identified as T51, S53, E55, K59 and K63, while the membrane-distal amino acid H218 is recognized as a key residue for FMC63 binding. Therefore, we designed a novel CAR construct using the h1218 scFv, a 4-1BB costimulatory and CD3z signaling domains, using a lentiviral backbone. This CAR(h1218) construct was very active in vitro in human T cells demonstrating cytotoxicity, cytokine release, and proliferation upon encounter with CD19+ leukemic and lymphoma cells (NALM6, RAJI, and OCI-Ly18) (data not shown). Moreover, CART19(h1218) showed enhanced long-term (12 days) tumor control as compared to CART19(FMC63) against wild type NALM6 (data not shown). In vivo, CART19(h1218) cells (1.5x10 6 CAR+ cells/mouse) demonstrated tumor clearance against both Raji (CD19+ B-cell lymphoma) and Nalm6 (CD19+ B-cell leukemia) xenografts (Fig. 1B). Remarkably, in a more challenging stress- test model with lower CART doses (0.75x10 6 CAR+ cells/mouse) CART19(h1218) demonstrated stronger tumor control against Nalm6 cells as compared to CART19(FMC63) (Fig. 1C). Furthermore, our group recently described the occurrence of a B-ALL relapse characterized by the expression of the CAR19 itself on the cell surface due to accidental transduction of leukemic cells during manufacturing. The CART19(h1218) product but not CART19(FMC63) was able to recognize and kill CAR19(FMC63)-expressing leukemic cells in vitro at varying E:T ratios. Of note, in a long-term (12 days) in vitro killing assay using a low, challenging E:T ratio of 0.125:1 we observed potent and prolonged tumor control (Fig. 1D). Conclusions: These results indicate that the development of a CAR binder able to recognize an alternative and membrane-proximal epitope of CD19 might lead to improved anti-leukemia and lymphoma activity and can recognize CAR19(FMC63)+ blasts that are not recognized by CART19(FMC63). This novel CART19(h1218) product will be tested in phase I-II clinical trials for patients with B-cell malignancies. Figure 1 Figure 1. Disclosures Patel: AbClon Inc.: Research Funding. Kim: Abclon Inc.: Current Employment. Lee: AbClon Inc.: Research Funding. Guruprasad: AbClon Inc.: Research Funding. Kim: AbClon Inc.: Current Employment. Choi: AbClon Inc.: Current Employment. Kim: AbClon Inc.: Current Employment. Kim: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Park: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Cui: AbClon Inc.: Current Employment. Yoon: AbClon Inc.: Current Employment. Kim: AbClon Inc.: Research Funding. Kim: AbClon Inc.: Research Funding. Hwang: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Chung: AbClon Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding. Ruella: Novartis: Patents & Royalties; BMS, BAYER, GSK: Consultancy; AbClon: Consultancy, Research Funding; Tmunity: Patents & Royalties; viTToria biotherapeutics: Research Funding.
Abstract Abstract 3738 Poster Board III-674 Introduction HLA-DR is currently under investigation as a target for antibody (mAb) therapy of B-cell malignancies. IMMU-114, a humanized IgG4 form of the murine anti-HLA-DR mAb, L243, recognizes a conformational epitope in the a-chain of HLA-DR. We have previously reported that IMMU-114 lacks effector-cell functions while displaying potent antitumor activity against B-cell lymphomas in vitro and in vivo. Here, we further investigated the cytotoxic effects of IMMU-114 on leukemia, lymphoma, and multiple myeloma (MM) cell lines, as well as clinical specimens of CLL, and explored the signaling pathways involved. Methods Binding and cytotoxicity of IMMU-114 was examined on a panel of NHL, AML, MCL, ALL, and CLL cell lines. Induction of apoptosis (Annexin V binding), ROS generation (dihydoehidium staining), changes in mitochondrial membrane potential (ψM, TMRE staining) and effects on the ERK1/2 and JNK pathways (immunoblot analyses) were evaluated on selected cell lines. The effects of various inhibitors on IMMU-114-mediated apoptosis also were determined. Studies were performed in tumor-bearing SCID mice. Results High expression of HLA-DR was detected on the cell surface of all MCL, ALL, HC, CLL, and NHL cell lines tested, as well as 2/3 AML and 5/6 MM cell lines. IMMU-114 was cytotoxic to 2/2 MCL, 2/2 CLL, 2/4 ALL, 1/1 HC, 2/2 NHL and 2/2 MM cell lines without any added anti-Fc second crosslinking antibody. IMMU-114 was consistently more cytotoxic than anti-CD20 mAbs on these cell lines, as well as on rituximab-resistant variants of Raji and SU-DHL-4. Despite positive staining, AML cell lines, Kasumi-3 and GDM-1, were not killed by IMMU-114. Four of 6 CLL patient samples expressed HLA-DR at markedly higher levels than CD20, with the remaining 2 showing similar HLA-DR and CD20 expression. Approximately 60% cytotoxicity was obtained after incubation with IMMU-114 in CLL patient cells. Induction of apoptosis as well as changes in ψM and ROS correlated with sensitivity of cell lines to IMMU-114-mediated cytotoxicity. Time-course analyses demonstrated that IMMU-114 induced approximately 46% change of ψM and 24% enhancement of ROS in as little as 30 min in Raji cells. These changes were abrogated in the presence of ROS inhibitor, N-acetyl cysteine. Immunoblot analyses revealed that IMMU-114 induces phosphorylation of ERK and JNK mitogen-activated protein (MAP) kinases in all cells defined as IMMU-114-sensitive by the cytotoxicity assays, but not IMMU-114-resistant cell lines. The p38 pathway was found to be constitutively active in these cell lines. Inhibition of ERK, JNK, or ROS by their respective inhibitors decreased apoptosis, although the inhibition was not complete when any single inhibitor was used. This could be due to activation of multiple pathways, since inhibition of 2 or more pathways by specific inhibitors abolishes the apoptosis induced by IMMU-114. Activation (5-fold increases of phosphorylation) of ERK1/2 and JNK signaling pathways also was observed in CLL patient samples following IMMU-114 incubation. Further studies revealed caspase-independent apoptosis and activation of apoptosis-inducing factor (AIF) mediated by IMMU-114. The therapeutic activity of IMMU-114 was evaluated in vivo in 3 NHL models, WSU-FSCCL, Namalwa, and Raji. IMMU-114 was more effective than anti-B-cell mAbs such as rituximab, in all models. For example, in WSU-FSCCL, IMMU-114 treatment yielded 100% long-term survival. Although rituximab also induced significant responses compared to untreated mice (median survival time of 87.5 vs. 36 days for untreated controls, P<0.0001), no long-term survivors were seen. Conclusion IMMU-114 is cytotoxic to a variety of hematological malignancies, and its potent activity can be related to high antigen expression of target cells and hyperactivation of ERK and JNK pathways upon binding to HLA-DR. Clinical evaluation of IMMU-114 is planned. Disclosures: Gupta: Immunomedics Inc.: Employment. Stein:Garden State Cancer Center: Employment. Cardillo:Immunomedics Inc.: Employment. Chang:Immunomedics Inc.: Employment. Goldenberg:Immunomedics Inc.: Consultancy, Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.
7511 Background: Novel targeted agents are emerging for B-cell malignancies, but few studies have safely combined these agents. Ublituximab (UTX) is a novel glycoengineered mAb targeting a unique epitope on the CD20 antigen. TGR-1202 is a next generation, once daily PI3Kδ inhibitor, demonstrating a favorable safety profile compared to prior inhibitors, including in long-term follow up (Burris, 2016). This Ph 1 trial evaluates the safety/efficacy of the triplet combination of a novel anti-CD20 mAb + PI3Kδ + BTK inhibitor (ibrutinib) in pts with B-cell malignancies. Methods: Eligible pts had CLL or rel/ref NHL w/o limit to prior therapies, including those ref to prior PI3Kδ or BTK inhibitors. UTX dosed on D1, 8, 15 of C1; D1 of C2-6, and C9 & 12. TGR-1202 dose escalated (400/600/800mg QD), ibrutinib dosed at 420mg (CLL) or 560mg (NHL), both on C1D1. Results: 38 pts were enrolled: 20 CLL/SLL and 18 NHL, including 6 follicular (FL), 6 DLBCL, 4 mantle cell (MCL) and 2 marginal zone (MZL). Med age 65 yrs (range 32-85); 29 M/9 F; med prior tx = 3 (range 0-6). 2 pts were ref to prior PI3Kδ and 2 were prev treated with ibrutinib (1 ref/1 rel). MTD was not reached. Most common ( > 20%) all causality AE’s were fatigue (42%), diarrhea (39%), dizziness (34%), nausea (32%), neutropenia, pyrexia, rash, infusion reaction, insomnia (each at 29%), thrombocytopenia, cough (each at 26%), anemia (24%) and sinusitis (21%). GR 3/4 AE’s were minimal, the only event > 10% was neutropenia (16%). ORR amongst 36 evaluable pts is shown in the table below. 53% of evaluable CLL pts had high-risk cytogenetics and 4/6 DLBCL pts were non-GCB. One CLL pt (17p/11q del) ref to both PI3Kδ and ibrutinib achieved a CR. Med time on study is 10 mos (range 1 – 27+ mos). Med DOR not reached (range 3 – 24+ mos). Conclusions: This is the first known triple combination of an anti-CD20 mAb + PI3Kδ + BTK inhibitor. The combination of UTX, TGR-1202, and ibrutinib has been well tolerated with activity observed across heavily pre-treated and high-risk B-cell malignancies. Expansion cohorts at the highest dose (800mg TGR-1202 + full dose ibrutinib) are underway. Future trials for the triplet are warranted. Clinical trial information: NCT02006485. [Table: see text]
The last several years have seen an explosion of novel therapies for chronic lymphocytic leukemia (CLL). These include the antibody obintutuzumab (GA-101), as well as small-molecule inhibitors of key pathways involved in the pathogenesis of CLL, specifically the B-cell receptor (BCR) pathway (especially Bruton's tyrosine kinase [BTK] and P13K), and the antiapoptotic pathway (especially BCL-2). We will consider each in turn, focusing on the molecules most advanced in clinical development. There has also been extensive development in rewiring the patient's own immune system to treat CLL. This has been done through modifying autologous T cells to express a chimeric antigen receptor (CAR). Thus far all CAR-T preparations have targeted the CD19 antigen. This is a good rational for B-cell malignancies as CD19 expression is limited to B-cell malignancies and normal B cells. The in vivo amplification of the transduced T cells relies on signaling and co-signaling domains and provides significant killing of CLL cells. As exciting as these novel agents and approaches are, they obviously beg the question, will chemotherapy as a treatment for CLL soon be obsolete? Although chemotherapy is associated with known short-term toxicities, it has the advantage of being completed in a short period of time and being relatively inexpensive in comparison to novel therapies. In addition, long-term follow-up of results with chemoimmunotherapy have now identified a group of patients whose remissions are maintained for more than 10 years. An important question that will arise going forward is how to incorporate novel agents without eliminating the long term benefits possible with chemoimmunotherapy in a subset of patients with CLL.
