Targeting Cereblon with the High Affinity Immunomodulatory Compound CC-220: A Novel Therapeutic Agent for B Cell Dyscrasias

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1055-1055 ◽  
Author(s):  
Peter H Schafer ◽  
Emily Rychak ◽  
Derek Mendy ◽  
Anastasia Parton ◽  
Lori Capone ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Proliferation ◽  
T Cells ◽  
B Cell ◽  
Binding Studies ◽  
Employment Equity ◽  
Amino Terminal ◽  
High Affinity ◽  
Equity Ownership ◽  
Affinity Beads

Abstract Abstract 1055 Background: Cereblon (CRBN) is a component of the E3 ubiquitin ligase complex including CUL4A, DDB1, and ROC-1, and was found to be the molecular binding target of thalidomide (Thalomid®), lenalidomide (Revlimid®), and pomalidomide. CC-220 is a novel immunomodulatory compound developed with increased potency and is currently in development for the treatment of immune conditions. The effect of CC-220 on CRBN binding, ubiquitination, and cell proliferation was profiled. Methods: Binding studies to CRBN were conducted using thalidomide analog-conjugated beads in a competitive assay. Endogenous CRBN from human U266 multiple myeloma (MM) cells was measured by incubating cell extracts with varying concentrations of either CC-220 or pomalidomide as a positive control. Affinity beads coupled to a thalidomide acid analog were incubated with the U266 extracts and, after extensive washing of the beads, the bound proteins were eluted. CRBN binding to the thalidomide-coupled affinity beads was determined by quantitative CRBN immunoblot determination. CRBN ubiquitination was measured in HEK293T cells, which were transfected with an amino-terminal His-biotin-tagged CRBN construct, then preincubated with compounds for one hour followed by treatment with the MG132 proteasome inhibitor (to arrest degradation of ubiquitinated proteins). Cells were lysed and processed to measure CRBN ubiquitination by SDS-PAGE and immunoblot analysis using an anti-ubiquitin antibody. Cell proliferation studies were conducted in lenalidomide-sensitive and -refractory multiple myeloma cells. Lenalidomide-resistant or -sensitive H929 MM cell lines were treated with CC-220 for 5 days, and then cell proliferation and viability were assessed by 7-aminoactinomycin D (7-AAD) staining. T-cell costimulation was measured in purified primary human T cells stimulated using immobilized anti-CD3 antibody in cell culture for 2 days, and cytokine secretion was measured by ELISA. Immunoglobulin M and G (IgG and IgM) production was measured from normal donor peripheral blood mononuclear cells by culturing in the presence of the B cell differentiation factors recombinant human IL-2 (20 U/mL), IL-10 (50 ng/mL), IL-15 (10 ng/mL), His-tagged CD40 Ligand (50 ng/mL), polyHistidine mouse IgG1 antibody (5 μg/mL), and ODN 2006-Human TLR9 ligand (10 μg/mL) for 4 days, followed by IL-2, IL-10, IL-15, and IL-6 (50 ng/mL) for an additional 3 days. IgM and IgG were measured by ELISA. Results: In the competitive CRBN binding studies, preincubation with pomalidomide at a concentration of 3 μM resulted in approximately 50% less CRBN bound to the affinity beads, while CC-220 at a concentration of 0.1 μM resulted in similar CRBN binding. CRBN ubiquitination studies in the transfected HEK293T cells resulted in the following potencies: CC-220 IC50 = 0.19 μM; lenalidomide IC50 = 12.9 μM; and pomalidomide IC50 = 21.6 μM. The IC50 value for inhibition of proliferation by CC-220 shifted from 0.01 μM in the parental H929 cell line and 0.04 μM in the DMSO-treated subclone to 0.51–1.58 μM in the lenalidomide-resistant subclones. A 50% decrease in cell cycle (S-phase) was evident after 24 hours of treatment of H929 cells with CC-220. At 48 hours, CC-220 decreased expression of survivin and retinoblastoma protein (pRB) and increased expression of the cyclin-dependent kinase inhibitor p27. CC-220 costimulated IL-2 production by T cells with an EC50 of approximately 0.29 nM, compared with 10 nM for pomalidomide. CC-220 inhibited IgM and IgG production with an IC50 of 0.35 and 2.1 nM, respectively, compared to 17 nM and 63 nM for pomalidomide. Conclusions: The results indicate that CC-220 binds to CRBN with approximately 30-fold higher affinity than pomalidomide, and inhibits CRBN ubiquitination with approximately 110-fold greater potency than pomalidomide in this system. CC-220 is approximately 34-fold more potent than pomalidomide for costimulating IL-2 production by T cells, and is 30- to 48-fold more potent than pomalidomide for inhibiting immunoglobulin production. In summary, CC-220 is a novel high affinity CRBN ligand with cellular potencies 1 or 2 orders of magnitude greater than that of pomalidomide, and is currently in development for the treatment of immune conditions, including those involving B cell dyscrasias. Disclosures: Schafer: Celgene: Employment, Equity Ownership. Rychak:Celgene: Employment, Equity Ownership. Mendy:Celgene Corp.: Employment, Equity Ownership. Parton:Celgene Corp: Employment, Equity Ownership. Capone:Celgene Corp: Employment, Equity Ownership. Lopez-Girona:Celgene Corp: Employment, Equity Ownership. Daniel:Celgene Corporation: Employment. Chopra:Celgene Corp: Employment, Equity Ownership.

CC-122 Degrades the Lymphoid Transcription Factor Aiolos (IKZF3) By Modulating Cereblon and Shows Clinical Activity in a Phase Ib Study of Subjects with Relapsed or Refractory Non-Hodgkin’s Lymphoma and Multiple Myeloma

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3500-3500 ◽  
Author(s):  
Vincent Ribrag ◽  
Silvia Damien ◽  
Mecide Gharibo ◽  
Mercede Gironella ◽  
Armando Santoro ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
T Cells ◽  
Single Dose ◽  
B Cells ◽  
B Cell ◽  
Peripheral Blood ◽  
Memory T Cells ◽  
Cell Lymphoma ◽  
Employment Equity ◽  
Equity Ownership

Abstract Background: CC-122 is a novel non-phthalimide analog of the IMiDs® immunomodulatory drugs (lenalidomide and pomalidomide) and a first in class PPMTM (Pleiotropic Pathway Modifier) compound with multiple biological activities including potent anti-proliferative activity against B-lineage cells (10-fold greater than lenalidomide), anti-angiogenic activity (100-fold greater than lenalidomide) and immunomodulatory effects (10-fold greater than lenalidomide). The molecular target of CC-122 is cereblon (CRBN), a substrate receptor of the Cullin ring E3 ubiquitin ligase complex (CRL4CRBN). CC-122 promotes ubiquitination of lymphoid transcription factors Ikaros (IKZF1) and Aiolos (IKZF3) in a CRBN-dependent manner, leading to their subsequent degradation. Following establishment of 3mg once daily (QD) as the maximum tolerated dose (Blood 122:2905 2013), patients with advanced aggressive non-Hodgkin lymphoma (NHL), multiple myeloma (MM), and select solid tumors were enrolled in parallel expansion cohorts of up to 20 evaluable patients. CC-122 was dosed at 3 mg QD in 28-day cycles until disease progression. Results: As of May 1, 2014, 93 total patients were enrolled in the expansion phase of the study. The NHL cohort included 21 patients with diffuse large B-cell lymphoma (DLBCL) and 1 patient with mantle cell lymphoma, and twenty-four patients were enrolled in the MM cohort. Results in solid tumor cohorts will be reported separately. All patients were ECOG performance status 0-2, the median number of prior systemic therapies was 4 (NHL) and 6 (MM). The most common (> 20%) adverse events (AEs) (grades 1-4) included neutropenia (69.6%), anemia (52%), asthenia (50%), pyrexia (35%), diarrhea (30%), cough (30%), thrombocytopenia (28%), and constipation (22%). Grade 3/4 AEs occurring in more than one patient were neutropenia (52%), anemia (26%), febrile neutropenia (13%), and thrombocytopenia (7%). CC-122 dose reduction was required in 36.4% of patients with NHL and 63% of patients with MM, the majority of which was due to neutropenia and occurred during cycle 1 or 2. CC-122 systemic exposure in NHL and MM patients was generally comparable after administration of single and multiple doses. Peak concentrations were observed between 30 minutes and 2 hours (median Tmax concentration = 1.5 h). Four treated patients with DLBCL had objective responses; one patient with complete response (CR) and 3 with partial responses (PR). Responses were observed in patients with germinal center B cell (GCB), non-GCB and Myc/Bcl2 over-expressing DLBCL. Four treated patients with MM had PR, and two of these responders were progression free beyond 10 cycles. A single dose of CC-122 3mg resulted in decreased Aiolos protein expression at 1.5 and 5 hours compared with baseline in peripheral B cells (median 38% and 53%) and T cells (median 31% and 54%) in the combined NHL (n = 16) and MM (n = 19) cohorts. Decrease in expression of Aiolos protein from baseline was also observed in lymph node biopsies of patients with DLBCL. Furthermore, CC-122 treatment decreased CD19+ B cells (median = 57% of baseline), expanded CD4-/CD8+/CD45RA-/CD45RO+ cytotoxic memory T cells (median = 320% of baseline), and expanded CD4+/CD8-/CD45RA-/CD45RO+ helper memory T cells (median = 154% of baseline) in peripheral blood samples from patients with MM (n = 9) and NHL (n = 3-12) subjects. Additionally, ex vivo activation of T cells after a single dose of CC-122 compared with baseline, as measured by IL-2 production, increased by a median of 776% (NHL n = 3 and MM n = 7). Conclusions: CC-122 shows promising initial clinical and pharmacodynamic activity in heavily pretreated relapse/refractory NHL and MM patients. Biomarker analysis indicates that the 3 mg QD dose of CC-122 results in rapid CRBN target engagement and Aiolos degradation in the peripheral blood lymphocytes of patients with NHL and MM patients and in NHL tumor tissue. Exploration of an intermittent dosing to mitigate neutropenia-related dose reductions and interruptions is ongoing and clinical studies exploring drug combinations with CC-122 are underway. Disclosures Ribrag: Celgene Corp: Consultancy. Rasco:Celgene Corp: Membership on an entity's Board of Directors or advisory committees. Wei:Celgene Corp: Employment, Equity Ownership. James:Celgene Corp: Employment. Hagner:Celgene Corp: Employment, Equity Ownership. Gandhi:Celgene Corp: Employment, Equity Ownership. Chopra:Celgene Corp: Employment, Equity Ownership. DiMartino:Celgene Corp: Employment, Equity Ownership. Pourdehnad:Celgene Corp: Employment, Equity Ownership. Stoppa:Celgene Jansen: Honoraria.

scholarly journals TNB383B.0001: A Multicenter, Phase 1, Open-Label, Dose-Escalation Andexpansion Study of TNB-383B, a Bispecific Antibodytargeting BCMA in Subjects with Relapsed or Refractorymultiple Myeloma

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1874-1874 ◽  
Author(s):  
Ben Buelow ◽  
Anita D'Souza ◽  
Cesar Rodriguez ◽  
Ravi Vij ◽  
Rajneesh Nath ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Clinical Trials ◽  
T Cells ◽  
Dose Escalation ◽  
Research Funding ◽  
Phase 1 ◽  
Open Label ◽  
Employment Equity ◽  
High Affinity ◽  
Equity Ownership

Introduction Multiple myeloma (MM) is an incurable plasma cell malignancy with an estimated incidence in 2019 of ~32,000 in the United States. Although median survival is greater than 8 years, treatment options are limited for patients who relapse on or are refractory to standard treatment regimens containing proteasome inhibitors, immune-modulating drugs and anti-CD38 antibodies (triple refractory). Novel therapies are critical to the treatment of these patients. Chimeric antigen receptor T cells (CAR-Ts) and T-cell redirecting Bispecific Antibodies (T-BsAbs) targeting B-cell maturation antigen (BCMA) -a protein found exclusively on the surface of plasma cells- have shown efficacy against relapsed/refractory MM in early phase clinical trials. However, toxicity from over-activation of T-cells still hinders these approaches. Utilizing Teneobio's proprietary next generation sequencing (NGS)-based discovery tool incorporating in silico analysis of heavy chain only/fixed light chain antibody sequences (HCA/Flic, respectively) to enrich for antigen specific antibodies, we made a high affinity αBCMA HCA and a library of αCD3 Flic antibodies that showed a >2 log range of EC50s for T cell activation in vitro. TNB-383B combines a high affinity αBCMA HCA with a low-activating αCD3 Flic; in preclinical studies TNB-383B showed equivalent anti-tumor efficacy but significantly reduced cytokine secretion compared to BCMA-targeted T-BsAbs incorporating a strongly-activating αCD3 (similar in strength to the αCD3s used in other T-BsAbs currently in clinical trials). A Phase 1 study investigating the safety, pharmacokinetics, and preliminary activity of TNB-383B in patients with relapsed/refractory multiple myeloma (RRMM) is ongoing and described. This trial represents, to the best of our knowledge, the first reported clinical trial of a HCA/Flic hybrid antibody in humans. Study Design TNB383B.0001 (NCT03933735) is an open-label, multi-center study of TNB-383B in patients with RRMM. The study is divided into escalation (Arm A, N=24) and expansion (Arm B, N=48) arms. Subjects who have received 3 or more prior lines of therapy with exposure to a PI, an IMiD, and an anti-CD38 antibody are eligible for this study. Documentation of BCMA expression by tumor cells is not required for entry, although prior treatment with a BCMA-targeted agent is an exclusion criterion. Other key inclusion/exclusion criteria include EGFR of >30ml/min, ANC ≥1000/mm3 and platelets ≥50,000/mm3 and minimal bone marrow biopsy requirements on-study. Subjects must be admitted for 48 hours following the 1st dose in Cycle 1 (21-day cycle length), but TNB-383B may be administered on an outpatient basis thereafter. Dose Escalation TNB-383B is administered as an intravenous infusion. Dose escalation is proceeding via a 3+3 design with fixed (as opposed to weight based) doses per protocol. Arm B will be initiated once the maximum tolerated dose (MTD, or recommended phase 2 dose, RP2D) has been selected. Patients will be treated until progression, unacceptable toxicity, or other discontinuation criteria are met. One patient has been enrolled thus far. Statistical Methods and Study Endpoints In Arm A occurrence of dose limiting toxicities (DLTs) will drive identification of the MTD (or RP2D in line with standard practices. In Arm B accrual will be suspended if more than 33% of subjects experience a DLT event. Adverse events, laboratory profiles, physical exams, and vital signs will be assessed throughout the study. Adverse events will be graded according to the NCI CTCAE, version 5.0. Concentrations of TNB-383B and Anti-Drug Antibodies (ADA) will be determined at designated time points throughout the study. Values for standard pharmacokinetic parameters of TNB-383B including the maximum observed serum concentration (Cmax), the time to Cmax, area under the concentration-time curve, clearance, and terminal half-life will be determined using non-compartmental methods. The activity endpoints (determined using the IMWG uniform response criteria) include overall response rate, progression-free survival and overall survival. The relationship between biomarkers, including soluble BCMA and A Proliferation Inducing Ligand (APRIL; the endogenous ligand for BCMA), and activity will be assessed. Disclosures Buelow: Teneobio, Inc.: Employment, Equity Ownership. Rodriguez:Takeda, Amgen: Consultancy, Speakers Bureau. Vij:Janssen: Honoraria; Celgene: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Genentech: Honoraria; Takeda: Honoraria, Research Funding; Karyopharm: Honoraria; Sanofi: Honoraria. Nath:Teneobio, Inc.: Consultancy. Snyder:Teneobio, Inc.: Consultancy. Pham:Teneobio, Inc.: Employment, Equity Ownership. Patel:Teneobio, Inc.: Employment, Equity Ownership. Iyer:Teneobio, Inc.: Employment, Equity Ownership.

Tuning T Cell Affinity Improves Efficacy and Safety of Anti-CD38 × Anti-CD3 Bispecific Antibodies in Monkeys - a Potential Therapy for Multiple Myeloma

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1798-1798 ◽  
Author(s):  
Gregory L. Moore ◽  
Sung-Hyung Lee ◽  
Suzanne Schubbert ◽  
Yvonne Miranda ◽  
Rumana Rashid ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cell Activation ◽  
Bispecific Antibodies ◽  
Employment Equity ◽  
High Affinity ◽  
Cell Immunotherapy ◽  
Equity Ownership

Abstract CD38 is highly expressed on plasma cells and is an attractive target for multiple myeloma (MM) therapies. Several anti-CD38 antibodies including daratumumab and SAR650984 show promising results in clinical development, though such antibodies are not able to stimulate T cell-mediated killing of myeloma cells. To exploit a T cell immunotherapy mechanism while retaining the favorable drug properties of therapeutic antibodies, we designed bispecific antibodies that recruit T cells to CD38+ MM cells. Such bispecifics act via redirected T cell-cytotoxicity (RTCC) to stimulate T cell-mediated target cell killing regardless of T cell receptor antigen specificity. These anti-CD38 × anti-CD3 antibodies possess a full Fc domain and spontaneously form stable heterodimers that are readily manufactured. Their Fc domain lacks binding to Fcγ receptors to minimize nonselective T cell activation, yet retains binding to FcRn to maintain long serum half-life. We have previously reported that XmAb13551, a humanized and affinity-optimized anti-CD38 × anti-CD3 antibody, stimulates killing of the CD38+ MM cell line RPMI8226 by human T cells and suppresses human Ig levels in SCID mice engrafted with human PBMCs, showing much greater efficacy than daratumumab in these models (Blood 2014 124:4727). We also investigated efficacy of XmAb13551 in monkeys given a single dose of 2, 5, and 20 μg/kg. Within 1 hr after dosing, CD25 and CD69 activation markers were upregulated on T cells and within 8 hr, circulating CD38+ cells were depleted by > 95% at the 20 μg/kg dose. However, depletion of peripheral CD38+ cells was not sustained, suggesting that a large antigen sink was limiting drug exposure. Although higher dosing might overcome an antigen sink, higher doses of XmAb13551 (0.2 mg/kg or higher) resulted in a T cell-mediated cytokine release syndrome (CRS) in monkeys. We reasoned that an anti-CD38 × anti-CD3 antibody with reduced CD3 affinity would stimulate sufficient RTCC to deplete MM cells, yet would attenuate the acute T cell activation (and associated CRS) induced by high-affinity coengagement of T cells with CD38+ target cells. Using XmAb13551 as a starting point, we engineered a series of bispecifics retaining the same high-affinity (0.2 nM) binding to CD38, but with reduced affinity to CD3. We selected two antibodies - XmAb15426 and XmAb14702 - that have significantly reduced CD3 affinity. As expected, these molecules showed reduced potency in RTCC assays using T cells to kill RPMI8226 cells, with potency correlating with CD3 affinity (XmAb13551 > XmAb15426 >> XmAb14702). We next tested XmAb15426 and XmAb14702 at single doses of 0.5 mg/kg and 3 mg/kg, respectively, in cynomolgus monkeys. Both antibodies were well-tolerated at these higher doses, consistent with the moderate levels of IL6 observed in serum from the treated monkeys. Moreover, XmAb15426, with intermediate CD3 affinity, more effectively depletes CD38+ cells at 0.5 mg/kg compared to the original high-affinity XmAb13551 dosed at 2, 5 or 20 µg/kg. Depletion by XmAb15426 was more sustained compared to the highest dose of XmAb13551 in the previous study (7 vs. 2 days, respectively). Notably, although target cell depletion was greater for XmAb15426, T cell activation (CD69, CD25 and PD1 induction) was much lower in monkeys treated with XmAb15426 even dosed 25-fold higher than the 20 µg/kg XmAb13551 group. XmAb14702, with very low CD3 affinity, had little effect on CD38+ cells and T cell activation. Our results demonstrate that modulating T cell activation by attenuating CD3 affinity is a promising method to improve the therapeutic window of T cell-engaging bispecific antibodies. This strategy has potential to expand the set of antigens amenable to targeted T cell immunotherapy by improving tolerability and enabling higher dosing to overcome antigen sink clearance with targets such as CD38. We have shown that by reducing affinity for CD3, XmAb15426 effectively depletes CD38+ cells while minimizing the CRS effects seen with comparable doses of its high-affinity counterpart XmAb13551. Our preclinical data for XmAb15426 provide a rationale for clinical testing of this bispecific antibody in patients with multiple myeloma and other CD38+ malignancies. Disclosures Moore: Xencor, Inc.: Employment, Equity Ownership. Lee:Xencor, Inc.: Employment, Equity Ownership. Schubbert:Xencor, Inc.: Employment, Equity Ownership. Miranda:Xencor, Inc.: Employment, Equity Ownership. Rashid:Xencor, Inc.: Employment, Equity Ownership. Pong:Xencor, Inc.: Employment, Equity Ownership. Phung:Xencor, Inc.: Employment, Equity Ownership. Chan:Xencor, Inc.: Employment, Equity Ownership. Chen:Xencor, Inc.: Employment, Equity Ownership. Endo:Xencor, Inc.: Employment, Equity Ownership. Ardila:Xencor, Inc.: Employment, Equity Ownership. Bernett:Xencor, Inc.: Employment, Equity Ownership. Chu:Xencor, Inc.: Employment, Equity Ownership. Leung:Xencor, Inc.: Employment, Equity Ownership. Muchhal:Xencor, Inc.: Employment, Equity Ownership. Bonzon:Xencor, Inc.: Employment, Equity Ownership. Szymkowski:Xencor, Inc.: Employment, Equity Ownership. Desjarlais:Xencor, Inc.: Employment, Equity Ownership.

Population Pharmacokinetic and Pharmacodynamic Modeling of an Anti–Interleukin-6 Chimeric Monoclonal Antibody, Siltuximab (CNTO 328), in Patients with B-Cell Non-Hodgkin's Lymphoma, Multiple Myeloma, or Castleman's Disease

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1365-1365 ◽  
Author(s):  
Lanyi Xie ◽  
Lilian Y Li ◽  
Razelle Kurzrock ◽  
Frits van Rhee ◽  
Xiang Qin ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Monoclonal Antibody ◽  
B Cell ◽  
Treatment Period ◽  
Research Funding ◽  
Castleman’S Disease ◽  
Hodgkin's Lymphoma ◽  
Employment Equity ◽  
Dosing Regimens ◽  
Equity Ownership

Abstract Abstract 1365 Introduction Siltuximab (CNTO 328) is a chimeric, murine-human, monoclonal antibody that specifically binds human interleukin (IL)-6 with high affinity. C-reactive protein (CRP) can be a pharmacodynamic (PD) marker of IL-6 bioactivity, i.e., reductions in CRP suggest inhibition of systemic IL-6. A population mechanistic pharmacokinetic (PK)/PD model was developed to describe the relationship between siltuximab serum concentrations and CRP suppression in patients with B-cell non-Hodgkin's lymphoma (NHL), multiple myeloma (MM), or Castleman's disease (CD). Simulation was used to support the dose selection in the CD registration study and future clinical studies. Methods PK/PD data were obtained from a phase 1 clinical study examining multiple dosing regimens of siltuximab administered intravenously in patients with NHL, MM, or CD. Dosing regimens included siltuximab 2.8, 5.5, or 11 mg/kg every 2 weeks; 11 mg/kg every 3 weeks; or 5.5 mg/kg every week. Serial samples to determine serum concentration of siltuximab and serial CRP samples were collected following the first dose. NONMEM 7 was used to simultaneously fit a two-compartment PK model and an inhibitory indirect-response PD model to the observed data. Simulation of 1000 replications was then used to identify siltuximab dosage regimens that would maintain CRP suppression below the lower limit of quantification (LLOQ) of 1 mg/L. Results The mechanistic PK/PD model was able to describe the serum siltuximab and CRP concentration-time profiles. Volume of distribution and systemic clearance rate constant of siltuximab were estimated at 68.42 mL/kg and 0.0584/day, respectively. The PD parameter estimates (Kin and Kout of CRP) were 5.03 mg/L/day and 0.457/day, respectively, and were similar between the three disease types in this study. IC50was estimated at 9.73 μg/mL and was also similar between disease types. For all disease types, simulations showed that siltuximab 11 mg/kg every 3 weeks or 15 mg/kg every 4 weeks after the second dose would reduce serum CRP to below the LLOQ throughout the entire treatment period. However, lower dose intensive schedules, including a dose of 5.5 mg/kg every 2 weeks, would not reduce CRP to below the LLOQ at any time point during the treatment period. Conclusion The population PK/PD modeling and simulation support using a siltuximab dose of 11 mg/kg every 3 weeks or 15 mg/kg every 4 weeks in future clinical development studies. This dosing recommendation is supported by the observed efficacy dose-response relationship in patients with CD (J Clin Oncol 2010;28:3701–8). Disclosures: Xie: Johnson & Johnson: Employment, Equity Ownership. Li:Johnson & Johnson: Employment, Equity Ownership. Kurzrock:Johnson & Johnson: Honoraria, Research Funding. van Rhee:Johnson & Johnson: Research Funding. Qin:Johnson & Johnson: Employment, Equity Ownership. Reddy:Johnson & Johnson: Employment, Equity Ownership. Qi:Johnson & Johnson: Employment, Equity Ownership. Davis:Johnson & Johnson: Employment, Equity Ownership. Zhou:Johnson & Johnson: Employment, Equity Ownership. Puchalski:Johnson & Johnson: Employment, Equity Ownership.

Deep Sequencing Reveals Oligoclonality At The Immunoglobulin Locus In Multiple Myeloma Patients

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 401-401 ◽  
Author(s):  
Joaquin Martinez-Lopez ◽  
Mariateresa Fulciniti ◽  
Santiago Barrio ◽  
Victoria Carlton ◽  
Martin Moorhead ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
B Cell ◽  
High Frequency ◽  
Genomic Dna ◽  
Gene Rearrangement ◽  
Common Ancestor ◽  
B Cell Development ◽  
Employment Equity ◽  
A Cell ◽  
Equity Ownership

Abstract Introduction Immunoglobulin (Ig) gene rearrangement is a hallmark of early B-cell development. Multiple myeloma (MM) is a malignancy of the plasma cells, which are at the terminal stage of B cell development. MM is a clonal disease originating from the transformation process of a single plasma cell and, thus, myeloma cells are traditionally thought to have one clonal Ig gene sequence that remains stable throughout the course of the disease. Based on preliminary evidence of oligoclonality, we utilized the LymphoSIGHT™ platform, a high-throughput sequencing method, to detect evidence of oligoclonality at the Ig heavy and kappa chain (IGH and IGK) loci. The sequencing approach can be used to examine two general models for oligoclonality. In the first model, two unrelated clonal Ig sequences are observed indicating the presence of two independent myelomas. Alternatively, in the second model, two related myeloma clonal Ig sequences are observed indicating that both myeloma clones are derived from a common ancestor that arose after the pro B cell stage when VDJ recombination is completed. The common ancestor can be a cell with premalignant lesion or after the MM has developed. Using the sequencing platform, we looked for evidence of these two models of oligoclonality in 193 MM patients. Methods Two cohorts of newly diagnosed MM patients were included in this analysis (N=125, N=68). Using universal primer sets, we amplified IGH and IGK variable, diversity, and joining gene segments from genomic DNA or RNA from bone marrow collected at initial diagnosis. Amplified products were sequenced and analyzed using standardized algorithms for clonotype determination (Faham et al, Blood 2012). In the first cohort (N=125), we assessed gene rearrangement at the IGH-VDJ and IGK loci in 120 patients using RNA only and in 5 patients, we used both DNA and RNA to assess the IGH-VDJ, IGH-DJ and IGK loci. In the second cohort (N=68), we analyzed gene rearrangement at the IGH-VDJ, IGH-DJ and IGK loci using genomic DNA. Myeloma-specific clonotypes were identified for each patient based on their high frequency (5%) within the B-cell repertoire in the diagnostic sample. To identify clonotypes that are present in more than one cell we looked for patterns that are not consistent with having a maximum of one functional and one non-functional clonotype in a cell. Results We observed oligoclonality in 23 of 193 (12%) MM patients. Unrelated Ig sequences, which are consistent with the first model of oligoclonality, were present in 8 of the 193 (4%) patients. Fifteen of 193 (8%) patients exhibited related Ig clones, which is consistent with the second model of oligoclonality. In 4 of the 15 patients clones were related to each other via a somatic hypermutation process and differed by only a few bases (Figure 1), while in other 11 patients, the same VDJ sequence was associated with two distinct isotypes (IgA and IgG). Interestingly, in cases with both RNA and DNA sequencing and oligoclonality, we observed differential expression levels compared to clonal content at the DNA level, suggesting that a low frequency clone could be contributing as a predominant secretory clone. Conclusions This study demonstrates frequent oligoclonality in MM patients and suggests that this phenomenon does occur due to two distinct processes, either as unrelated sequences consistent with independent clones or as related sequences consistent with evolution after the MM malignant lesions occur. These findings shed light on the biology and pathogenesis of MM and may provide prognostic information. Currently, this analysis was limited to high frequency clones, using a threshold of 5% for identification of the myeloma-specific clones. Additional analysis is being performed to assess the presence of lower frequency clones, and data will be presented. Disclosures: Carlton: Sequenta, Inc. : Employment, Equity Ownership. Moorhead:Sequenta, Inc.: Employment, Equity Ownership. Faham:Sequenta, Inc. : Employment, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees.

A Novel and Highly Potent CAR T Cell Drug Product for Treatment of BCMA-Expressing Hematological Malignances

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3094-3094 ◽  
Author(s):  
Alena A. Chekmasova ◽  
Holly M. Horton ◽  
Tracy E. Garrett ◽  
John W. Evans ◽  
Johanna Griecci ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cell ◽  
Cell Lines ◽  
Drug Product ◽  
Single Chain ◽  
Employment Equity ◽  
Car T Cells ◽  
Car T ◽  
Equity Ownership

Abstract Recently, B cell maturation antigen (BCMA) expression has been proposed as a marker for identification of malignant plasma cells in patients with multiple myeloma (MM). Nearly all MM and some lymphoma tumor cells express BCMA, while normal tissue expression is restricted to plasma cells and a subset of mature B cells. Targeting BCMA maybe a therapeutic option for treatment of patients with MM and some lymphomas. We are developing a chimeric antigen receptor (CAR)-based therapy for the treatment of BCMA-expressing MM. Our anti-BCMA CAR consists of an extracellular single chain variable fragment (scFv) antigen recognition domain derived from an antibody specific to BCMA, fused to CD137 (4-1BB) co-stimulatory and CD3zeta chain signaling domains. Selection of our development candidate was based on the screening of four distinct anti-BCMA CARs (BCMA01-04) each comprised of unique single chain variable fragments. One candidate, BCMA02 (drug product name bb2121) was selected for further studies based on the robust frequency of CAR-positive cells, increased surface expression of the CAR molecule, and superior in vitro cytokine release and cytolytic activity against the MM cell lines. In addition to displaying specific activity against MM (U226-B1, RPMI-8226 and H929) and plasmacytoma (H929) cell lines, bb2121 was demonstrated to react to lymphoma cell lines, including Burkitt's (Raji, Daudi, Ramos), chronic lymphocytic leukemia (Mec-1), diffuse large B cell (Toledo), and a Mantle cell lymphoma (JeKo-1). Based on receptor density quantification, bb2121 can recognize tumor cells expressing less than 1000 BCMA molecules per cell. The in vivo pharmacology of bb2121 was studied in NSG mouse models of human MM and Burkitt's lymphoma. NSG mice were injected subcutaneously (SC) with 107 RPMI-8226 MM cells. After 18 days, mice received a single intravenous (IV) administration of vehicle or anti-CD19Δ (negative control, anti-CD19 CAR lacking signaling domain) or anti-BCMA CAR T cells, or repeated IV administration of bortezomib (Velcade®; 1 mg/kg twice weekly for 4 weeks). Bortezomib, which is a standard of care for MM, induced only transient reductions in tumor size and was associated with toxicity, as indicated by substantial weight loss during dosing. The vehicle and anti-CD19Δ CAR T cells failed to inhibit tumor growth. In contrast, treatment with bb2121 resulted in rapid and sustained elimination of the tumors, increased body weights, and 100% survival. Flow cytometry and immunohistochemical analysis of bb2121 T cells demonstrated trafficking of CAR+ T cells to the tumors (by Day 5) followed by significant expansion of anti-BCMA CAR+ T cells within the tumor and peripheral blood (Days 8-10), accompanied by tumor clearance and subsequent reductions in circulating CAR+ T cell numbers (Days 22-29). To further test the potency of bb2121, we used the CD19+ Daudi cell line, which has a low level of BCMA expression detectable by flow cytometry and receptor quantification analysis, but is negative by immunohistochemistry. NSG mice were injected IV with Daudi cells and allowed to accumulate a large systemic tumor burden before being treated with CAR+ T cells. Treatment with vehicle or anti-CD19Δ CAR T cells failed to prevent tumor growth. In contrast, anti-CD19 CAR T cells and anti-BCMA bb2121 demonstrated tumor clearance. Adoptive T cell immunotherapy approaches designed to modify a patient's own lymphocytes to target the BCMA antigen have clear indications as a possible therapy for MM and could be an alternative method for treatment of other chemotherapy-refractory B-cell malignancies. Based on these results, we will be initiating a phase I clinical trial of bb2121 for the treatment of patients with MM. Disclosures Chekmasova: bluebird bio, Inc: Employment, Equity Ownership. Horton:bluebird bio: Employment, Equity Ownership. Garrett:bluebird bio: Employment, Equity Ownership. Evans:bluebird bio, Inc: Employment, Equity Ownership. Griecci:bluebird bio, Inc: Employment, Equity Ownership. Hamel:bluebird bio: Employment, Equity Ownership. Latimer:bluebird bio: Employment, Equity Ownership. Seidel:bluebird bio, Inc: Employment, Equity Ownership. Ryu:bluebird bio, Inc: Employment, Equity Ownership. Kuczewski:bluebird bio: Employment, Equity Ownership. Horvath:bluebird bio: Employment, Equity Ownership. Friedman:bluebird bio: Employment, Equity Ownership. Morgan:bluebird bio: Employment, Equity Ownership.

scholarly journals Preclinical Development of CTX120, an Allogeneic CAR-T Cell Targeting Bcma

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1921-1921 ◽  
Author(s):  
Henia Dar ◽  
Daniel Henderson ◽  
Zinkal Padalia ◽  
Ashley Porras ◽  
Dakai Mu ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
T Cells ◽  
T Cell ◽  
Cell Targeting ◽  
Employment Equity ◽  
Term Survival ◽  
Car T Cells ◽  
Car T Cell ◽  
Car T ◽  
Equity Ownership

Abstract Autologous CAR-T cells targeting BCMA have induced robust and durable responses in patients with relapsed/refractory multiple myeloma. However, autologous cell therapies face several challenges which will likely limit the number of patients that will have access to these therapies. These limitations include manufacturing failure rates, wait time and supply constraints in addition to other factors such as reimbursement. Allogeneic CAR-T cells can potentially overcome these access challenges, and may have several other advantages over autologous therapies. Allogeneic CAR-T cells are derived from robust healthy donor T cells through a batch manufacturing process, which may result in a highly consistent product with greater potency and enable better safety management. Here we show further development and preclinical data for CTX120, an allogeneic "off the shelf" CAR-T cell targeting BCMA. CTX120 is produced using the CRISPR/Cas9 system to eliminate TCR and MHC class I, coupled with specific insertion of the CAR at the TRAC locus. CTX120 shows consistent and high percent CAR expression from this controlled insertion and exhibits target-specific cytotoxicity and cytokine secretion in response to BCMA positive cell lines. CTX120 CAR-T cells retain their cytotoxic capacity over multiple in vitro re-challenges, demonstrating durable potency and lack of exhaustion. In mouse models of multiple myeloma, CTX120 showed typical CAR-T persistence and eliminated tumors completely, resulting in long-term survival as compared to untreated animals. These data support the ongoing development of CTX120 for treatment of patients with multiple myeloma and further demonstrate the potential for our CRISPR/Cas9 engineered allogeneic CAR-T platform to generate potent CAR-T cells targeting different tumor antigens. Disclosures Dar: CRISPR Therapeutics: Employment, Equity Ownership. Henderson:CRISPR Therapeutics: Employment, Equity Ownership. Padalia:CRISPR Therapeutics: Employment, Equity Ownership. Porras:CRISPR Therapeutics: Employment, Equity Ownership. Mu:CRISPR Therapeutics: Employment, Equity Ownership. Kyungah:CRISPR Therapeutics: Employment, Equity Ownership. Police:CRISPR Therapeutics: Employment, Equity Ownership. Kalaitzidis:CRISPR Therapeutics: Employment, Equity Ownership. Terrett:CRISPR Therapeutics: Employment, Equity Ownership. Sagert:CRISPR Therapeutics: Employment, Equity Ownership.

scholarly journals Durable Clinical Responses in Heavily Pretreated Patients with Relapsed/Refractory Multiple Myeloma: Updated Results from a Multicenter Study of bb2121 Anti-Bcma CAR T Cell Therapy

Blood ◽  
2017 ◽  
Vol 130 (Suppl_1) ◽  
pp. 740-740 ◽  
Author(s):  
Jesus G. Berdeja ◽  
Yi Lin ◽  
Noopur Raje ◽  
Nikhil Munshi ◽  
David Siegel ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
T Cells ◽  
T Cell ◽  
Research Funding ◽  
Employment Equity ◽  
Car T Cells ◽  
Car T ◽  
Clinical Responses ◽  
Equity Ownership ◽  
Dose Levels

Abstract Introduction: Chimeric antigen receptor (CAR) T cell therapies have demonstrated robust and sustained clinical responses in several hematologic malignancies. Data suggest that achieving acceptable benefit:risk profiles depends on several factors, including the specificity of the antigen target and characteristics of the CAR itself, including on-target, off-tumor activity.To test the safety and efficacy of CAR T cells in relapsed and/or refractory multiple myeloma (RRMM), we have designed a second-generation CAR construct targeting B cell maturation antigen (BCMA) to redirect T cells to MM cells. BCMA is a member of the tumor necrosis factor superfamily that is expressed primarily by malignant myeloma cells, plasma cells, and some mature B cells. bb2121 consists of autologous T cells transduced with a lentiviral vector encoding a novel CAR incorporating an anti-BCMA scFv, a 4-1BB costimulatory motif and a CD3-zeta T cell activation domain. Methods: CRB-401 (NCT02658929) is a multi-center phase 1 dose escalation trial of bb2121 in patients with RRMM who have received ≥ 3 prior regimens, including a proteasome inhibitor and an immunomodulatory agent, or are double-refractory, and have ≥ 50% BCMA expression on malignant cells. Peripheral blood mononuclear cells are collected via leukapheresis and shipped to a central facility for transduction, expansion, and release testing prior to being returned to the site for infusion. Patients undergo lymphodepletion with fludarabine (30 mg/m2) and cyclophosphamide (300 mg/m2) daily for 3 days then receive 1 infusion of bb2121. The study follows a standard 3+3 design with planned dose levels of 50, 150, 450, 800, and 1,200 x 106 CAR+ T cells. The primary outcome measure is incidence of adverse events (AEs), including dose-limiting toxicities (DLTs). Additional outcome measures were quality and duration of clinical response assessed according to the IMWG Uniform Response Criteria for Multiple Myeloma, evaluation of minimal residual disease (MRD), overall and progression-free survival, quantification of bb2121 in blood, and quantification of circulating soluble BCMA over time. Results: Asof May 4, 2017, 21 patients (median 58 [37 to 74] years old) with a median of 5 (1 to 16) years since MM diagnosis, had been infused with bb2121, and 18 patients were evaluable for initial (1-month) clinical response. Patients had a median of 7 prior lines of therapy (range 3 to 14), all with prior autologous stem cell transplant; 67% had high-risk cytogenetics. Fifteen of 21 (71%) had prior exposure to, and 6 of 21 (29%) were refractory to 5 prior therapies (Bort/Len/Car/Pom/Dara). Median follow-up after bb2121 infusion was 15.4 weeks (range 1.4 to 54.4 weeks). As of data cut-off, no DLTs and no treatment-emergent Grade 3 or higher neurotoxicities similar to those reported in other CAR T clinical studies had been observed. Cytokine release syndrome (CRS), primarily Grade 1 or 2, was reported in 15 of 21 (71%) patients: 2 patients had Grade 3 CRS that resolved in 24 hours and 4 patients received tocilizumab, 1 with steroids, to manage CRS. CRS was more common in the higher dose groups but did not appear related to tumor burden. One death on study, due to cardiopulmonary arrest more than 4 months after bb2121 infusion in a patient with an extensive cardiac history, was observed while the patient was in sCR and was assessed as unrelated to bb2121. The overall response rate (ORR) was 89% and increased to 100% for patients treated with doses of 150 x 106 CAR+ T cells or higher. No patients treated with doses of 150 x 106 CAR+ T cells or higher had disease progression, with time since bb2121 between 8 and 54 weeks (Table 1). MRD negative results were obtained in all 4 patients evaluable for analysis. CAR+ T cell expansion has been demonstrated consistently and 3 of 5 patients evaluable for CAR+ cells at 6 months had detectable vector copies. A further 5 months of follow up on reported results and initial data from additional patients will be presented. Conclusions: bb2121 shows promising efficacy at dose levels above 50 x 106 CAR+ T cells, with manageable CRS and no DLTs to date. ORR was 100% at these dose levels with 8 ongoing clinical responses at 6 months and 1 patient demonstrating a sustained response beyond one year. These initial data support the potential of CAR T therapy with bb2121 as a new treatment paradigm in RRMM. CT.gov study NCT02658929, sponsored by bluebird bio and Celgene Disclosures Berdeja: Teva: Research Funding; Janssen: Research Funding; Novartis: Research Funding; Abbvie: Research Funding; Celgene: Research Funding; BMS: Research Funding; Takeda: Research Funding; Vivolux: Research Funding; Amgen: Research Funding; Constellation: Research Funding; Bluebird: Research Funding; Curis: Research Funding. Siegel: Celgene, Takeda, Amgen Inc, Novartis and BMS: Consultancy, Speakers Bureau; Merck: Consultancy. Jagannath: MMRF: Speakers Bureau; Bristol-Meyers Squibb: Consultancy; Merck: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Medicom: Speakers Bureau. Turka: bluebird bio: Employment, Equity Ownership. Lam: bluebird bio: Employment, Equity Ownership. Hege: Celgene Corporation: Employment, Equity Ownership. Morgan: bluebird bio: Employment, Equity Ownership, Patents & Royalties. Quigley: bluebird bio: Employment, Equity Ownership, Patents & Royalties. Kochenderfer: Bluebird bio: Research Funding; N/A: Patents & Royalties: I have multiple patents in the CAR field.; Kite Pharma: Research Funding.

scholarly journals A Novel CD20xCD3 Bispecific Fully Human Antibody Induces Potent Anti-Tumor Effects Against B Cell Lymphoma in Mice

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4501-4501 ◽  
Author(s):  
Bindu Varghese ◽  
Jayanthi Menon ◽  
Luis Rodriguez ◽  
Lauric Haber ◽  
Kara Olson ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
Tumor Cells ◽  
Bispecific Antibody ◽  
Tumor Regression ◽  
Employment Equity ◽  
Cynomolgus Monkeys ◽  
Nsg Mice ◽  
Equity Ownership

Abstract Bispecific antibodies that redirect effector T cells to kill tumor cells have shown considerable promise in both pre-clinical and clinical studies. However, these bispecific formats can have short half-lives necessitating constant infusion of the molecules into patients. We report here on a novel full-length human IgG CD20xCD3 bispecific antibody (REGN1979) that targets CD20 expressed on normal and malignant B cells and CD3 expressed on T cells in humans and cynomolgus monkeys. Our results demonstrate CD20-target cell-dependent activation and cytokine release by T cells, and efficient redirected T cell lysis of target tumor cells. Raji B cell lymphomas grown as tumors in NOD SCID IL2R gamma deficient (NSG) mice and co-implanted with human peripheral blood mononuclear (PBMC) cells were completely inhibited when treated at the time of implantation with a low dose (0.004 mg/kg; 2x/week) of REGN1979. As expected, T cells were required for this tumor inhibition, since treatment in the absence of human T cells was not effective. REGN1979 bispecific antibody also demonstrated potent activity against other tumor cells expressing CD20, as it significantly delayed CD20-transduced B16F10.9 tumor growth in immune-competent mice. Most importantly, REGN1979 induced dramatic tumor regression in large advanced (500-900 mm3) Raji tumors, associated with long-lasting tumor control. The tumor-infiltrating lymphocytes (TILs) in B cell lymphomas in these untreated NSG mice were found to express the inhibitory receptors Tim-3 and PD-1 and were the predominant fraction of T cells in the tumors and in the circulation. T cells in mice treated with REGN1979 showed decreased Tim-3 and PD-1 expression in the circulation accompanied by complete tumor regression. In further studies, REGN1979 (dosed at 0.4 mg/kg; 2x/week) was superior to rituximab therapy (dosed at 8 mg/kg; 5x/week) and comparable to the CD19xCD3 BiTE (dosed at 0.5 mg/kg; 5x/week) in suppressing established Raji tumors (200-400mm3). Pre-clinical studies in cynomolgus monkeys to assess activity of the bispecific antibody for depleting B cells in circulation and various lymphoid organs showed that a single injection of REGN1979 (0.1 mg/kg) was more potent at depleting CD20+ B cells in the mesenteric lymph nodes than a high dose of rituximab (30 mg/kg). In separate studies, REGN1979 was also found to have a long half-life (>14 days) in the circulation of monkeys following depletion of B cells. These studies show potent activity of a new class of fully human bispecific antibodies for treating tumors, and support clinical testing of REGN1979 in patients with CD20+ cancers. Figure 1 Figure 1. Disclosures Varghese: Regeneron Pharmaceuticals: Employment, Equity Ownership. Menon:Regeneron Pharmaceuticals: Employment, Equity Ownership. Rodriguez:Regeneron Pharmaceuticals: Employment, Equity Ownership. Haber:Regeneron Pharmaceuticals: Employment, Equity Ownership. Olson:Regeneron Pharmaceuticals: Employment, Equity Ownership. Duramad:Regeneron Pharmaceuticals: Employment, Equity Ownership. Oyejide:Regeneron Pharmaceuticals: Employment, Equity Ownership. Smith:Regeneron Pharmaceuticals: Employment, Equity Ownership. Thurston:Regeneron Pharmaceuticals: Employment, Equity Ownership. Kirshner:Regeneron Pharmaceuticals: Employment, Equity Ownership.

scholarly journals Immunotherapy with Long-Lived Anti-CD38 × Anti-CD3 Bispecific Antibodies Stimulates Potent T Cell-Mediated Killing of Human Myeloma Cell Lines and CD38+ Cells in Monkeys: A Potential Therapy for Multiple Myeloma

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4727-4727 ◽  
Author(s):  
Seung Y. Chu ◽  
Yvonne Miranda ◽  
Sheryl Phung ◽  
Hsing Chen ◽  
Rumana Rashid ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
T Cells ◽  
T Cell ◽  
Plasma Cells ◽  
Bispecific Antibodies ◽  
Cytotoxic T Cell ◽  
Antigen Specificity ◽  
Employment Equity ◽  
Activation Markers ◽  
Equity Ownership

Abstract CD38, being highly expressed on malignant plasma cells, is an attractive target of new therapies for multiple myeloma (MM). Several anti-CD38 antibodies including daratumumab are in clinical development; however, a limitation of such monospecific antibodies is their inability to stimulate cytotoxic T cell killing of myeloma cells. To exploit the potent mechanism of T cell immunotherapy yet preserve the favorable drug and dosing properties of therapeutic antibodies, we designed bispecific antibodies that recruit T cells to CD38+ MM cells. Such bispecifics act via a "redirected T cell-cytotoxicity" (RTCC) mechanism because they stimulate targeted T cell-mediated killing regardless of T cell receptor antigen specificity. Unlike other bispecific formats, these antibodies possess a full Fc domain and spontaneously form stable heterodimers that are readily manufactured. Their Fc domain was also engineered to abolish binding to Fcγ receptors (to reduce the potential for nonselective T cell activation), yet preserve binding to human FcRn (to maintain long serum half-life). We first generated a library of humanized and affinity-optimized anti-CD38 × anti-CD3 antibodies and measured their potency using RTCC assays in which antibodies stimulated killing of the human MM cell line RPMI8226 by human T cells. From this screen, we selected two candidates for further assessment. XmAb13243 and XmAb13551 have 21 and 0.2 nM affinities, respectively, for human CD38, and have identical T cell-engaging domains with 8 nM affinity for human CD3. XmAb13243 stimulated RTCC with an EC50 of 2.5 ng/ml (20 pM) after 24 hr, while XmAb13551 had an EC50 of ~100 pg/ml (~1 pM). In contrast to bispecific formats lacking an Fc domain, XmAb13243 and XmAb13551 had long half-lives in mice of ~7.6 and 8.3 days, respectively. Because these bispecifics were optimized for human CD38 and CD3 binding and do not crossreact with mouse antigens, we next evaluated efficacy in immunodeficient SCID mice engrafted with human PBMCs. In this model, engrafted human B cells differentiate into CD38+ plasma cells, which produce high levels of human Ig. Bispecific antibodies dosed at 0.2, 1, and 5 mg/kg, 7 and 15 days after engraftment, suppressed human IgG2, IgM, and IgE to below detectable levels by Day 14 (> 50-fold for IgG2, > 1,000-fold for IgM, and > 80-fold for IgE). Daratumumab at 5 mg/kg was markedly less potent than bispecifics, reducing IgG2 by 2-fold, IgM by 6-fold, and IgE by 3-fold. The control bispecific anti-RSV × anti-CD3 (which binds to T cells but not to CD38+ cells) had no effect on IgG2, IgM, or IgE levels. To investigate activity against an immune response requiring production of new human plasma cells, mice were vaccinated with tetanus toxoid 8 days after engraftment. Anti-CD38 × anti-CD3 bispecifics suppressed human anti-tetanus antibody titers to baseline (> 100-fold), while daratumumab suppressed titers by only 2-fold. We next assessed efficacy in cynomolgus monkeys. Unlike daratumumab, which does not crossreact with monkey CD38, XmAb13243 and XmAb13551 bind to both CD38 and CD3 in monkeys (23 and 0.3 nM, respectively, to CD38, and 6 nM to CD3 for both). We treated monkeys with a single dose of XmAb13243 or XmAb13551 at 2, 5, and 20 μg/kg. T cells were activated within 1 hr, as measured by dramatic increases in CD25 and CD69 activation markers. Within 8 hr, T cells depleted circulating CD38+ cells by > 95% at the 20 μg/kg dose. Our results demonstrate that XmAb13243 and XmAb13551 effectively recruit T cells to kill CD38+ cells in vivo. Our preclinical data in monkeys and humanized mice provide a rationale for clinical testing of anti-CD38 × anti-CD3 bispecific antibodies in patients with multiple myeloma and other CD38+ malignancies. Disclosures Chu: Xencor: Employment, Equity Ownership. Miranda:Xencor, Inc.: Employment, Equity Ownership. Phung:Xencor, Inc.: Employment, Equity Ownership. Chen:Xencor, Inc.: Employment, Equity Ownership. Rashid:Xencor, Inc.: Employment, Equity Ownership. Endo:Xencor, Inc.: Employment, Equity Ownership. Chan:Xencor, Inc.: Employment, Equity Ownership. Pong:Xencor, Inc.: Employment, Equity Ownership. Bonzon:Xencor, Inc.: Employment, Equity Ownership. Muchhal:Xencor, Inc.: Employment, Equity Ownership. Leung:Xencor, Inc.: Employment, Equity Ownership. Bernett:Xencor, Inc.: Employment, Equity Ownership. Moore:Xencor, Inc.: Employment, Equity Ownership. Szymkowski:Xencor, Inc.: Employment, Equity Ownership. Desjarlais:Xencor, Inc.: Employment, Equity Ownership.

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