ALBERT

Description: B-cell maturation antigen (BCMA) is a protein expressed by normal and malignant plasma cells. We are conducting a phase I clinical trial of an anti-BCMA chimeric antigen receptor (CAR-BCMA) that incorporates an anti-BCMA single-chain variable fragment, a CD28 domain, and a CD3-zeta T-cell activation domain (Carpenter et al. Clinical Cancer Research 2013). Autologous T cells are genetically modified to express the CAR with a gamma-retroviral vector. Patients receive a single infusion of CAR-BCMA T cells. Before the CAR T-cell infusions, patients receive a chemotherapy regimen of 300 mg/m2 of cyclophosphamide and 30 mg/m2 of fludarabine with each chemotherapy agent given daily for 3 days. The purpose of the chemotherapy is to enhance activity of the CAR T cells by depleting endogenous leukocytes. Twelve patients have been enrolled, and 11 patients have been treated on one of 4 dose levels, 0.3x106, 1x106, 3x106, and 9x106CAR+ T cells/kg of bodyweight. Patients had advanced multiple myeloma (MM) with a median of 7 prior lines of therapy. Of the 6 patients treated on the lowest 2 dose levels, one patient had a transient partial remission (PR) of 2 weeks duration; the other 5 patients had responses of stable disease (SD). On the 3rddose level, 2 patients obtained responses of stable disease, and one patient obtained a response of very good PR (VGPR) with complete elimination of MM bone disease on positron emission tomography (PET) scan, normalization of serum free light chains, and clearance of bone marrow plasma cells. Toxicity among patients on the first 3 dose levels was mild and included cytopenias attributable to chemotherapy, fever in 3 patients, and signs of cytokine release syndrome including tachycardia and hypotension in Patient 8 who had a VGPR. Two patients have been treated on the highest dose level of 9x106CAR+ T cells/kg. The first patient on this dose level, Patient 10, had MM making up 90% of total bone marrow cells before treatment. Starting 4 hours after infusion of CAR T cells, Patient 10 exhibited signs of cytokine release syndrome including fever, tachycardia, dyspnea, acute kidney injury, coagulopathy, hypotension requiring vasopressor support, and muscle damage manifesting as an elevated creatine kinase level and weakness. His neutrophil count was less than 500/µL before the CAR-BCMA T-cell infusion and remained below 500/µL for 40 days after the CAR T-cell infusion before recovering. He also experienced prolonged thrombocytopenia. Patient 10’s myeloma was rapidly eliminated after CAR-BCMA T-cell infusion. By immunohistochemistry staining for CD138, bone marrow plasma cells decreased from 90% before treatment to 0% one month after the CAR T-cell infusion. The serum M-protein decreased from 1.6 g/dL before treatment to undetectable 2 months after treatment. The serum and urine immunofixation electrophoresis tests were negative 2 months after the CAR T-cell infusion. Patient 10’s current myeloma response is stringent complete remission. The second patient treated on the 9x106CAR+ T cells/kg dose level, Patient 11, had IgG lambda MM with 80% bone marrow plasma cells before treatment. Patient 11 experienced signs of cytokine release syndrome with toxicities including fever, tachycardia, hypotension, delirium, hypoxia, and coagulopathy. Patient 11’s M-protein decreased from 3.6 g/dL before treatment to 0.8 g/dL 4 weeks after treatment. His serum lambda free light chain decreased from 95.9 mg/dL before treatment to 0.15 mg/dL 4 weeks after treatment. Four weeks after CAR T-cell infusion, bone marrow plasma cells were undetectable. T cells containing the CAR-BCMA gene were detected in the blood of all 10 patients evaluated with peak levels of 0.04 to 18.2% of blood mononuclear cells. Patient 10 had the highest peak absolute number of blood CAR T cells with 51 CAR+ T cells/µL. Blood levels of IL-6 and other inflammatory cytokines were highest in patients with clinical signs of cytokine release syndrome, and the 3 patients with the highest serum IL-6 levels also had the most impressive anti-myeloma responses. Before treatment, the mean serum BCMA level of treated patients was 243 ng/mL. In responding patients, serum BCMA levels decreased after treatment. Toxicities in patients receiving CAR-BCMA T cells were similar to toxicities in leukemia patients treated with anti-CD19 CAR T cells. Our findings demonstrate strong anti-myeloma activity in the first clinical trial of a CAR targeting BCMA. Disclosures: Wang: Celgene: Research Funding. Kochenderfer:bluebird bio Inc.: Research Funding. Off Label Use: Use of cyclophosphamide and fludarabine as a conditioning regimen for adoptively-transferred T cells will be part of the presentation.

Description: Background: Preclinical and clinical results suggest improved anti-lymphoma activity of combining anti-CD20 and anti-CD22 MAbs. Our aim was to develop a recombinant bispecific MAb against CD20 and CD22 antigens, and to evaluate its anti-tumor potency compared to the parental MAbs. Methods: Tetravalent anti-CD20/CD22 bsMAb in the form of anti-CD20 IgG linked to two anti-CD22 scFv’s was prepared recombinantly. The ability of the bsMAb to inhibit cell growth and mediate CDC and ADCC was evaluated by cell-based assays. Phosphorylation and distribution of CD22 in B-lymphoma cells treated with the bsMAb were studied by immunoblotting. The extension of survival of disseminated Daudi lymphoma cells in SCID mice also was evalauted. Results: In contrast to the parental anti-CD22 MAb, epratuzumab, the bsMAb did not internalize in Ramos cells. In CDC tests, the bsMAb showed no cytotoxic effects, similar to epratuzumab, although it did bind C1q complement protein, unlike epratuzumab. In ADCC, the bsMAb was as potent as the parental humanized anti-CD20 Mab, hA20, in inducing target-cell lysis. The anti-CD20/CD22 bsMAb has distinct effects on NHL B-cell lines compared to each parental monospecific MAb or in combination:

Description: Introduction Progressive malignancy is the leading cause of death after allogeneic hematopoietic stem cell transplantation (alloHSCT). After alloHSCT, B-cell malignancies are often treated with infusions of unmanipulated donor lymphocytes (DLIs) from the transplant donor. DLIs are frequently not effective at eradicating malignancy, and DLIs often cause graft-versus-host disease (GVHD), which is a potentially lethal allogeneic immune response against normal recipient tissues. Methods We conducted a clinical trial of allogeneic T cells that were genetically engineered to express a chimeric antigen receptor (CAR) targeting the B-cell antigen CD19. The CAR was encoded by a gamma-retroviral vector and included a CD28 costimulatory domain. Patients with B-cell malignancies after alloHSCT received a single infusion of CAR T cells. No chemotherapy or other therapies were administered. The T cells were obtained from each recipient's alloHSCT donor. Findings Eight of 20 treated patients obtained remissions, including 6 complete remissions (CR) and 2 partial remissions. The response rate was highest for acute lymphoblastic leukemia with 4/5 patients obtaining minimal-residual-disease-negative CRs, but responses also occurred in chronic lymphocytic leukemia (CLL) and lymphoma. The longest ongoing CR is 30+ months in a patient with CLL. No patient developed new-onset acute GVHD after CAR T-cells were infused. Toxicities included fever, tachycardia, and hypotension. Median peak blood CAR T-cell levels were higher in patients who obtained remissions (39 CAR+ cells/mL) than in patients who did not obtain remissions (2 CAR+ cells/mL, P=0.001). Presence of endogenous normal or malignant blood B lymphocytes before CAR T-cell infusion was associated with higher post-infusion median blood CAR T-cell levels (P=0.04). Compared to patients who did not obtain a remission of their malignancies, patients obtaining remissions had a higher CD8:CD4 ratio of blood CAR+ T cells at the time of peak CAR T-cell levels (P=0.007). The mean percentage of CAR+CD8+ T cells expressing the programmed cell death-1 (PD-1) protein increased from 12% at the time of infusion to 82% at the time of peak blood CAR T-cell levels (P

Description: Background: Chimeric antigen receptors (CARs) are fusion proteins that combine antigen-recognition domains and T-cell signaling domains. T cells genetically modified to express CARs directed against the B-cell antigen CD19 can cause remissions of B-cell malignancies. Most CARs in clinical use contain components derived from murine antibodies. Immune responses have been reported to eliminate CAR T cells in clinical trials, especially after second infusions of CAR T cells (C. Turtle et al., Journal of Clinical Investigation, 2016). These immune responses could be directed at the murine components of CARs. Such immune responses might limit the persistence of the CAR T cells, and anti-CAR immune responses might be an especially important problem if multiple infusions of CAR T cells are administered. Development of fully-human CARs could reduce recipient immune responses against CAR T cells. Methods: We designed the first fully-human anti-CD19 CAR (HuCAR-19). The CAR is encoded by a lentiviral vector. This CAR has a fully-human single-chain variable fragment, hinge and transmembrane regions from CD8-alpha, a CD28 costimulatory domain, and a CD3-zeta T-cell activation domain. We conducted a phase I dose-escalation trial with a primary objective of investigating the safety of HuCAR-19 T cells and a secondary objective of assessing anti-lymphoma efficacy. Low-dose chemotherapy was administered before HuCAR-19 T-cell infusions to enhance CAR T-cell activity. The low-dose chemotherapy consisted of cyclophosphamide 300 mg/m2 daily for 3 days and fludarabine 30 mg/m2 daily for 3 days on the same days as cyclophosphamide. HuCAR-19 T cells were infused 2 days after the end of the chemotherapy regimen. Patients with residual lymphoma after a first treatment were potentially eligible for repeat treatments if dose-limiting toxicities did not occur with the first treatment. Repeat infusions were given at the same dose level as the first infusion or 1 dose level higher than the first infusion. Findings: A total of 11 HuCAR-19 T-cell infusions have been administered to 9 patients; 2 patients received 2 infusions each. So far, there is an 86% overall response rate (Table). Grade 3 adverse events (AEs) included expected cytokine-release syndrome toxicities such as fever, tachycardia, and hypotension. Corticosteroids were used to treat toxicity in Patient 3. The interleukin-(IL)-6 receptor antagonist tocilizumab was used to treat toxicity in Patient 4, and both tocilizumab and corticosteroids were used to treat toxicity in Patient 8. Only 1 of 8 evaluable patients, Patient 3, has experienced significant neurological toxicity to date. This patient experienced encephalopathy that was associated with a cerebrospinal fluid (CSF) white blood cell count of 165/mm3. Almost all of the CSF white cells were CAR T cells, and the CSF IL-6 level was elevated. All toxicities have resolved fully in all patients. In Patient 1, tumor biopsies revealed a complete loss of CD19 expression by lymphoma cells after 2 HuCAR-19 T-cell infusions, which to our knowledge is the first documented complete loss of CD19 expression by lymphoma after anti-CD19 CAR T-cell therapy. This loss of CD19 expression was associated with lymphoma progression. After first CAR-19 T-cell infusions, HuCAR-19 cells were detectable in the blood of every patient. The median peak number of blood CAR+ cells was 26/microliter (range 3 to 1005 cells/microliter). Blood HuCAR-19 cells were detected after second infusions in the blood of both patients who received second infusions. Patient 1 obtained a partial response after a second infusion after only obtaining stable disease after a first infusion. We detected elevations of inflammatory cytokines including IL-6, interferon gamma, and IL-8 in the serum of patients experiencing clinical toxicities consistent with cytokine-release syndrome. Interpretation: T cells expressing HuCAR-19 have substantial activity against advanced lymphoma, and infusions of HuCAR-19 T cells caused reversible toxicities attributable to cytokine-release syndrome. Disclosures Kochenderfer: Kite Pharma: Patents & Royalties, Research Funding; bluebird bio: Patents & Royalties, Research Funding.

Description: Key Points Anti-BCMA T cells have impressive activity against MM.

Description: Combination immunotherapy with anti-CD20 and anti-CD22 mAbs shows promising activity in non-Hodgkin lymphoma. Therefore, bispecific mAbs (bsAbs) were recombinantly constructed from veltuzumab (humanized anti-CD20) and epratuzumab (humanized anti-CD22) and evaluated in vitro and in vivo. While none of the parental mAbs alone or mixed had notable antiproliferative activity against Burkitt lymphoma cells when not cross-linked, the bsAbs [eg, anti-CD20 IgG-anti–CD22 (scFv)2] were inhibitory without cross-linking and synergistic with B-cell antigen (BCR)-mediated inhibition. The bsAbs demonstrated higher antibody-dependent cellulary cytoxicity (ADCC) activity than the parental mAbs, but not complement-dependent cytoxicity (CDC) of the parental CD20 mAb. Cross-linking both CD20 and CD22 with the bsAbs resulted in the prominent redistribution of not only CD20 but also CD22 and BCR into lipid rafts. Surprisingly, appreciable translocation of CD22 into lipid rafts was also observed after treatment with epratuzumab. Finally, the bsAbs inhibited Daudi lymphoma transplant growth, but showed a significant advantage over the parental anti-CD20 mAb only at the highest dose tested. These results suggest that recombinantly fused, complementary, bispecific, anti-CD20/22 antibodies exhibit functional features distinct from their parental antibodies, perhaps representing new candidate therapeutic molecules.