scholarly journals AO-176, a Highly Differentiated Clinical Stage Anti-CD47 Antibody, Exerts Potent Anti-Tumor Activity in Preclinical Models of Multiple Myeloma As a Single Agent and in Combination with Approved Therapeutics

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 3-4
Author(s):  
William Casey Wilson ◽  
John Richards ◽  
Robyn J Puro ◽  
Gabriela Andrejeva ◽  
Ben J Capoccia ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Growth Inhibition ◽  
Clinical Stage ◽  
Single Agent ◽  
Standard Of Care ◽  
Tumor Growth Inhibition ◽  
Private Company ◽  
Xenograft Models ◽  
Rpmi 8226 ◽  
Anti Tumor Activity

Upregulation of tumor CD47, the "don't eat me" signal, to evade immune surveillance is a common escape mechanism that evolves during cancer development, progression, and relapse. Previous studies have shown multiple myeloma (MM) cells leverage this mechanism through broad upregulation of CD47 compared to non-malignant plasma cells, making CD47 an attractive therapeutic target for this disease. We recently reported that AO-176, a clinical stage humanized anti-CD47 IgG2 antibody, possesses differentiated characteristics such as preferential binding of tumor cells compared to normal cells, a lack of binding to red blood cells, non-ADCC direct tumor killing and elicits immunogenic cell death with DAMP induction, all in addition to single-agent phagocytosis. In this study, AO-176's anti-tumor activity in MM was evaluated. Immunohistochemical analyses of MM patient tumors with upregulated CD47 expression showed infiltration of innate immune cells such as macrophages and dendritic cells, both previously shown to be involved in anti-CD47 antibody mechanisms of action. AO-176 binding was confirmed on human cell lines frequently used in MM xenograft models. AO-176 exerted substantial single agent in vivo anti-tumor activity in multiple MM xenograft models when dosed at 25 mg/kg, including significant tumor growth inhibition of RPMI-8226 xenografted mice, and complete responses (CRs) in (10/10) NCI-H929 xenografted mice. These CRs were durable, with treated mice tumor-free up to 120 days post antibody dosing. Immunohistochemical analysis of AO-176 treated tumors from both models showed increased numbers of macrophages and dendritic cells compared to controls. An AO-176 dose response study resulted in CRs and increases in overall survival down to 10 mg/kg, with CRs observed as low as 3 mg/kg during dosing. In addition, we found that large NCI-H929 tumors (up to 1600mm3) showed pronounced regression after AO-176 treatment. The anti-tumor activity of AO-176 was also evaluated in combination with several standard of care MM therapies. When combined with the proteasome inhibitor bortezomib, AO-176 treatment at both 10 mg/kg and 25 mg/kg resulted in profound RPMI-8226 xenograft growth inhibition, near-total CRs (19/20 mice), and extended survival at both doses. Combining AO-176 and the anti-CD38 antibody daratumumab or immunomodulatory drugs (lenalidomide/pomalidomide) both produced significant enhancement of anti-tumor activity in xenograft models. The combined regimen of AO-176 with daratumumab led to significant MM.1S tumor growth inhibition compared to AO-176 or daratumumab alone. Both lenalidomide and pomalidomide combined with AO-176 resulted in significantly increased MM.1S tumor growth inhibition and extended survival compared to AO-176 alone, with an increased number of CRs observed in the combination groups compared to monotherapy groups. In summary, the pre-clinical potent single agent activity and enhanced activity when combined with standard of care anti-MM agents, warrants further development of AO-176 in MM treatment. AO-176 is being evaluated in phase 1 clinical trials for the treatment of patients with solid tumors (NCT03834948) and with MM (NCT04445701). Disclosures Wilson: Arch Oncology: Current Employment, Current equity holder in private company. Richards:Arch Oncology: Current Employment, Current equity holder in private company. Puro:Arch Oncology: Current Employment, Current equity holder in private company. Andrejeva:Arch Oncology: Current Employment, Current equity holder in private company. Capoccia:Arch Oncology: Current Employment, Current equity holder in private company. Donio:Arch Oncology: Current Employment, Current equity holder in private company. Hiebsch:Arch Oncology: Current Employment, Current equity holder in private company. Chakraborty:Arch Oncology: Current Employment, Current equity holder in private company. Sung:Arch Oncology: Current Employment, Current equity holder in private company. Pereira:Arch Oncology: Current Employment, Current equity holder in private company.

scholarly journals 769 A single dose of intratumoral TransCon™ TLR7/8 agonist monotherapy promoted sustained activation of antigen presenting cells resulting in CD4+ and CD8+ T cell activation and tumor growth inhibition

2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A804-A804
Author(s):  
Luis Zuniga ◽  
Karan Uppal ◽  
Kathy Bang ◽  
Enping Hong ◽  
Simran Sabharwal ◽  
...  
Keyword(s):  
T Cells ◽  
Tumor Growth ◽  
Growth Inhibition ◽  
Tumor Antigen ◽  
Tumor Growth Inhibition ◽  
Tlr Agonists ◽  
Syngeneic Mouse ◽  
Antigen Presenting ◽  
Anti Tumor Activity ◽  
Dose Dependent

BackgroundThe use of pattern recognition receptor agonists (PRRAs) such as Toll-like receptor (TLR) agonists is an attractive approach for cancer immunotherapy. TLR agonism elicits anti-tumor activity by activating antigen presenting cells (APCs) to promote a proinflammatory microenvironment and anti-tumor immunity. Local delivery of TLR agonists has shown encouraging preclinical and clinical anti-tumor benefit. However, intratumoral (IT) delivery of naked PRRAs may lead to rapid effusion from the tumor microenvironment, potentially impacting their effectiveness in inducing local inflammation and may promote systemic cytokine release, increasing the risk of adverse effects.MethodsTransConTM TLR7/8 Agonist was designed to address the current limitations of PRRA therapies and IT delivery through sustained and controlled release of resiquimod, a potent TLR7/8 agonist, following IT administration of a hydrogel depot.ResultsA single IT injection of TransCon TLR7/8 Agonist induced potent tumor growth inhibition in a dose-dependent manner in syngeneic mouse CT26 tumors. Following IT TransCon TLR7/8 Agonist treatment, acute and sustained upregulation of cell surface markers indicative of activation of APCs, such as CD54, CD69, and CD86, in the tumor was observed by fluorescence activated flow cytometry (FACs). Additionally, TransCon TLR7/8 Agonist treatment was associated with an increase in the frequency of APCs with an activated phenotype in tumor draining lymph nodes (LNs). Further, a concomitant potentiation in the frequency of activated CD4 and CD8 T cells in tumor draining LNs following IT TransCon TLR7/8 Agonist treatment was observed, as demonstrated by increased expression of Ki67, ICOS, or granzyme B.ConclusionsThese data support that a single IT dose of TransCon TLR7/8 Agonist can mediate robust anti-tumor activity as a monotherapy in the CT26 syngeneic mouse tumor model while promoting local activation of intratumoral APCs. Such activation may promote tumor antigen uptake and migration to tumor-associated lymphoid tissue, as evidenced by an increase in APCs with an activated phenotype in tumor draining LNs following TransCon TLR7/8 Agonist treatment. Activated tumor antigen-bearing APCs can promote the priming and activation of tumor-specific T cells in the tumor-draining LNs. Consistently, a dose-dependent increase in the frequency of T cells with an activated effector phenotype in tumor draining LNs following administration of TransCon TLR7/8 Agonist was observed. These preclinical data further support TransCon TLR7/8 Agonist as a novel and potentially efficacious PRRA therapy. A clinical trial to evaluate safety and efficacy of TransCon TLR7/8 Agonist as monotherapy, and in combination with pembrolizumab, in cancer patients has been initiated (transcendIT-101; NCT04799054).Ethics ApprovalThe animal studies performed described were performed in accordance with the “Guide for the Care and Use of Laboratory Animals: Eighth Edition” and approved by the institutional animal care and use committee (IACUC).

Anti-Tumor Activity of the Aurora a Inhibitor MLN8237 in Diffuse Large B-Cell Lymphoma Preclinical Models.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1592-1592 ◽  
Author(s):  
Jessica J Huck ◽  
Mengkun Zhang ◽  
Marc L Hyer ◽  
Mark G Manfredi
Keyword(s):  
Tumor Growth ◽  
Growth Inhibition ◽  
Tumor Model ◽  
B Cell Lymphoma ◽  
Tumor Growth Inhibition ◽  
Aurora A ◽  
Hct 116 ◽  
Xenograft Models

Abstract Aurora A kinase is a serine/threonine protein kinase that is essential for normal transit of cells through mitosis. In many tumor types the Aurora A gene is amplified and/or the protein is over-expressed. The Aurora A small-molecule inhibitor MLN8237 demonstrated robust tumor growth inhibition in xenograft models of solid tumors grown subcutaneously (S.C.) in immunocompromised mice. Here we explored the antitumor activity of MLN8237 in models of diffuse large B-cell lymphoma (DLBCL) both in vitro and in vivo. In vivo three established DLBCL xenograft models (OCI-Ly7, OCI-Ly19, and WSU-DLCL2; all cells expressing luciferase) and a primary DLBCL tumor model PHTX-22-06 were tested using MLN8237 at different doses. Rituximab, an anti-CD20 monoclonal antibody that is active against CD20+ malignant B cells and is a standard of care agent was used for comparison. Using these model systems, tumor cells were injected either I.V. (to evaluate disseminated disease), or S.C. in severe combined immunodeficient mice (SCID). Animals were dosed orally for 21 days with MLN8237 (QD or BID) at various doses, or Rituximab dosed at 10mg/kg IV (once/week) and tumor growth inhibition was monitored using either bioluminescent imaging for the disseminated models or vernier calipers for the S.C. models. Tumor growth inhibition by MLN8237 was dose dependent with 20 mg/kg bid being the most efficacious dose (TGI>100% in both disseminated OCI-Ly19 and WSU models). All animals in the OCI-Ly19 disseminated model 20 mg/kg BID treatment group demonstrated regressions and remained disease free until the end of the study, day 65. In this study the Rituximab treated animals were euthanized on day 31 due to a high level of tumor burden. In the primary tumor model, PHTX-22-06, MLN8237 dosed at 20 mg/kg BID was also the most efficacious with a TGI of 95%. Moreover, tumor growth inhibition was durable as determined by prolonged tumor growth delay (>50 days). Significant efficacy was achieved in all models tested, whether grown as disseminated or subcutaneous models. A noted increase in durability of response was observed with MLN8237 treatment when compared with previous data from solid tumor models. In vitro, MLN8237 treatment increased levels of apoptosis in the OCI-Ly19 cells in comparison to the solid tumor cell line HCT-116 (colon). Greater Annexin V positive cells and greater cleaved PARP and Caspase-3 signals were detected in the MLN8237 treated OCI-Ly19 cells when compared to HCT-116 cells. The demonstration of robust and durable anti-tumor activity in preclinical models treated with MLN8237 provides the basis for its clinical evaluation as a treatment option for DLBCL. MLN8237 is currently in multiple Phase I clinical trials.

scholarly journals 683 A novel mechanism of neuropilin-1 inhibition results in improved tumor growth inhibition in vivo

2020 ◽  
Vol 8 (Suppl 3) ◽  
pp. A722-A722
Author(s):  
Eric Zhu ◽  
Daniel Blom ◽  
Shalini Sethumadhavan ◽  
Chengfeng Merriman ◽  
Katherine Molloy ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Tumor Growth ◽  
Growth Inhibition ◽  
Tumor Growth Inhibition ◽  
Factor V ◽  
Multiple Cancer ◽  
Neuropilin 1 ◽  
Cancer Models ◽  
Anti Tumor Activity

BackgroundNeuropilin-1 (NRP1) is a co-receptor that complexes with diverse ligands and their cognate receptors. As such, it plays a role in multiple different biological processes, including axon guidance and angiogenesis. NRP1 contains two CUB domains (a1 and a2) involved in binding the ligand Semaphorin3A (SEMA3A), two Factor V/VIII domains (b1 and b2) involved in VEGF ligand binding and one MAM domain (c domain). While functional antibodies with anti-tumor activity have been generated against the SEMA3A and VEGF binding domains, little attention has been paid to the c domain of NRP1, which has been implicated in the dimerization of NRP1, a prerequisite for functionality. We therefore hypothesized that c domain-binding antibodies would offer an opportunity to generate functional inhibitors of both SEMA3A and VEGF signaling and therefore improved anti-tumor activity.MethodsRecombinant human NRP1 comprising all subdomains was used to identify fully human anti-NRP1 antibodies. Specific antibodies were tested for their ability to block NRP1 interactions with recombinant SEMA3A and VEGF protein in vitro. Blocking antibodies were subsequently assessed for their functional effects, such as inhibition of SEMA3A-mediated growth cone collapse. Antibodies with diverse binding characteristics were then tested for in vivo anti-tumor activity in multiple cancer models of interest.ResultsRecombinant NRP1 containing the a1, a2, b1, b2 and c subdomains was used to successfully identify a series of specific monoclonal antibodies that cross-reacted with Cynomolgus monkey and mouse NRP1, but not human NRP2. Except for the a2 domain, epitope mapping showed an even distribution of mAbs for binding to each of the NRP1 subdomains, including the c domain that has been proposed to play a role in dimerization. Using biolayer interferometry, we identified antibody classes with direct SEMA3A and/or VEGF blocking properties. Further optimization of these antibodies yielded mAbs with subnanomolar affinities that showed significant tumor growth inhibition in multiple mouse models, including anti-PD1 non-responsive models.ConclusionsHere we demonstrate the identification of fully human monoclonal antibodies that specifically bind to the c domain of human NRP1. A subset of these c domain binders do not block either SEMA3A or VEGF binding to NRP1 but do show in vivo efficacy, suggesting a role for the c domain of NRP1 in the formation of functional (dimeric) complexes. Thus, c domain binding antibodies show remarkable inhibition of tumor growth in mouse cancer models and offer a novel means of therapeutic intervention in patients who are refractory to immune checkpoint inhibition.

Synergistic Anti-Tumor Effect of KPT-8602, a Second Generation Selective Inhibitor of Nuclear Export (SINE) Compound, and Panobinostat, a Pan-Histone Deacetylase (HDAC) Inhibitor in Multiple Myeloma

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3298-3298 ◽  
Author(s):  
Christian Argueta ◽  
Hua Chang ◽  
Trinayan Kashyap ◽  
Sivan Elloul ◽  
Sharon Friedlander ◽  
...  
Keyword(s):  
Dna Damage ◽  
Tumor Growth ◽  
Growth Inhibition ◽  
Cell Viability ◽  
Nuclear Export ◽  
Tumor Regression ◽  
Single Agent ◽  
Tumor Growth Inhibition ◽  
Employment Equity ◽  
Equity Ownership

Abstract Background: XPO1 (Exportin-1/CRM1) is the non-redundant nuclear exporter of over 200 cargos including the major tumor suppressor proteins. Deregulated nuclear export by changes in XPO1 expression is a common characteristic for a broad range of cancers and may aid in the evasion of anti-neoplastic mechanisms. As a result, inhibition of XPO1 has emerged as a promising area of cancer treatment. The Selective Inhibitor of Nuclear Export (SINE) compounds, selinexor, as well as a second generation, KPT-8602, bind to the XPO1 cargo binding pocket and disrupt XPO1-mediated nuclear export, resulting in cancer specific cell death. Although selinexor has been evaluated in >1,500 patients and has manageable tolerability, KPT-8602 may have improved tolerability and efficacy based on decreased brain penetration in animal models allowing more frequent dosing. Currently, the safety, tolerability and efficacy of KPT-8602 is being evaluated in a phase 1 trial of patients with relapsed/refractory multiple myeloma (MM; NCT02649790). Since selinexor synergizes with a broad array of anti-MM agents in patients, KPT-8602 is an excellent candidate for combination therapies. In this study, we investigated the use and mechanism of combining KPT-8602 with the pan-histone deacetylase (HDAC) inhibitor, panobinostat, in MM cell lines and in a xenograft mouse model of MM. Methods : MM.1S cells were treated with single agent KPT-8602, panobinostat or a combination of both. The effects of KPT-8602 and/or panobinostat on cell viability were examined using standard viability assays after 72 hours of treatment. Total RNA or protein levels were examined after 24 hours using quantitative PCR or immunoblots, respectively. Immune compromised mice were injected subcutaneously with MM.1S cells. Tumors were allowed to grow to ~150 mm3before treatment. The mice were treated with vehicle, sub-therapeutic doses of KPT-8602 (5 mg/kg PO QDx5) or panobinostat (5 mg/kg IP QDx5) alone or in combination. Tumor growth and animal weights was monitored to determine tumor growth inhibition (TGI), tumor regression, and tolerability to treatment. The tumors were then harvested for immunohistochemical (IHC) analysis. Results : The combination of KPT-8602 and panobinostat was highly effective against MM.1S cell viability. A synergistic anti-cancer effect was observed against MM.1S cells grown in culture and in mice. In cells, the MTT IC50of KPT-8602 was shifted from 50 to 23 nM by the addition of sub cytotoxic concentrations of panobinostat. In mice, single agent treatment with KPT-8602 led to 96.5% tumor growth inhibition whereas panobinostat resulted in 69.4% tumor growth inhibition within 22 days. Remarkably, in the combination of KPT-8602 and panobinostat, 3 out of 8 tumors totally disappeared and the overall tumor regression was 95%, (Figure 1). Both drugs, as single agents and in combination were well tolerated and no significant changes in weight were observed. Gene and protein expression studies revealed that although both compounds target independent proteins (e.g. HDACs or XPO1), the combination significantly enhances markers of cell death (cleavage of PARP-1, caspase-3, etc.). Curiously, KPT-8602 enhances the inhibitory effect panobinostat has on deacetylation as evidenced by histone acetylation. Moreover, DNA damage, as indicated by ϒ-H2AX, significantly increases in the presence of both compounds. Conclusion : KPT-8602 and panobinostat are dissimilar drugs with unique mechanisms of action, and individually affect a broad range of cellular processes. Here we show that the combination of these drugs can dramatically increase the already potent anti-cancer properties of these compounds in MM cell lines. In addition, KPT-8602 enhances the inhibitory effect exerted by panobinostat on histone deacetylation, which coincides with an increase induction of DNA damage. It should be noted that both panobinostat and SINE compounds have been shown to downregulate checkpoint and DNA damage response (DDR) proteins (e.g. RAD51 and Chk1). We hypothesize that the combination of KPT-8602 and panobinostat promotes significant chromatin remodeling in the presence of a compromised DDR pathway, which destabilizes genomic integrity in MM cells and leads to a synergistic effect on cell viability. Together, these data provide rational support for the study of KPT-8602 and panobinostat in clinical trials. Figure 1 Figure 1. Disclosures Argueta: Karyopharm Therapeutics: Employment, Equity Ownership. Chang:Karyopharm Therapeutics: Employment, Equity Ownership. Kashyap:Karyopharm Therapeutics: Employment, Equity Ownership. Elloul:Rubius Therapeutics: Employment. Friedlander:Karyopharm Therapeutics: Employment. Lee:Karyopharm Therapeutics: Employment, Equity Ownership. Kauffman:Karyopharm Therapeutics Inc: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Shacham:Karyopharm Therapeutics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Senapedis:Karyopharm Therapeutics: Employment, Equity Ownership. Baloglu:Karyopharm Therapeutics: Employment, Equity Ownership.

scholarly journals The Anti-Tumor Effect of the Ubiquitin-Activating Enzyme (UAE) Inhibitor TAK-243 on Pre-Clinical Models of Multiple Myeloma

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3296-3296 ◽  
Author(s):  
Junling Zhuang ◽  
Hans Lee ◽  
Isere Kuiatse ◽  
Hua Wang ◽  
Fazal Shirazi ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Drug Resistance ◽  
Tumor Growth ◽  
Growth Inhibition ◽  
Er Stress ◽  
Cell Lines ◽  
Caspase 3 ◽  
Tumor Growth Inhibition ◽  
Xenograft Models

Abstract Background: The ubiquitin-proteasome system (UPS) has been validated as a target in multiple myeloma (MM) through the success of proteasome inhibitors such as bortezomib, but drug resistance is an emerging challenge. Targeting some of the upstream components of the UPS, such as the E1 ubiquitin activating enzyme (UAE), could therefore be a promising alternative. TAK-243 (MLN7243) specifically blocks the ubiquitin conjugation cascade through the formation of a TAK-243-ubiquitin adduct, thereby inhibiting the UAE. Our aim was to explore the effectiveness of TAK-243 against pre-clinical myeloma models, and to understand some its mechanisms of action. Methods: We performed pre-clinical studies in myeloma cell lines and mouse models using TAK-243. Downstream effects were evaluated using viability, apoptosis assays, western blotting, gene expression profiling (GEP), and Reverse Phase Protein Array (RPPA) techniques. Results: MM1.S and MOLP-8 TP53 wild-type cell lines were sensitive to TAK-243, with median inhibitory concentrations (IC50) of 25 nM at 24 hours based on viability assays. In otherwise isogenic cell lines in which TP53 was suppressed using genome editing techniques, the IC50 was ~40 nM, but higher TAK-243 concentrations of 100 nM overcame resistance due to TP53 inactivation. Similarly, TAK-243 was able to overcome resistance to both conventional (dexamethasone) and novel (bortezomib, lenalidomide) drugs in paired sensitive and resistant cell line models. After treatment with TAK-243, Annexin V and TO-PRO3 staining determined that viable MM1.S cells were induced into early or late apoptosis. This was accompanied by a significant increase in cleaved caspase-3, -8, and -9 as detected by flow cytometry, and in cleaved caspase-7 detected by RPPA and western blot. Exposure to TAK-243 reduced the cellular content of ubiquitin-protein conjugates, and did not enhance expression levels of a fusion protein degraded by the proteasome in a ubiquitin-independent manner, indicating the lack of direct proteasome inhibition. GEP analysis and RPPA detected enhanced expression of p53-pathway related proteins, including MDM2, TP53, and p21 in TAK-243 treated MM1.S cells. Several mRNAs and proteins in the ER stress pathway, including ATF6, ATF4, IRE1a and XBP1 were also elevated, as were many non-coding RNAs and DNA-damage related genes. Combination experiments in MM cell lines demonstrated synergy between TAK-243 and lenalidomide, pomalidomide, panobinostat, melphalan and doxorubicin. Finally, TAK-243 demonstrated in vivo antitumor activity against MM1.S and MOLP-8 xenograft models when dosed at 12.5 mg/kg IV twice-weekly for 2 weeks (tumor growth inhibition of 60% and 73%, respectively). Elevation of BiP, ATF4, XBP1s and cleaved-caspase 3 was detected within the first 24 hrs after dosing in the sensitive MM1.S xenografts. In contrast, RPMI 8226 cells, which showed a 2000 nM IC50 in cell culture, were also resistant to TAK-243 in vivo, with no tumor growth inhibition detected. Conclusions: TAK-243 is a UAE inhibitor that is active against myeloma cells in vitro and in xenograft models in vivo, overcomes conventional and novel drug resistance, and its action is associated with stimulation of the TP53 and ER stress pathways. Thus, it may deserve further evaluation as an anti-myeloma agent. Disclosures Berger: Takeda Pharmaceuticals: Employment. Hyer:Takeda Pharmaceuticals: Employment. Chattopadhyay:Takeda Pharmaceuticals: Employment. Syed:Takeda Pharmaceuticals: Employment. Shi:Takeda Pharmaceuticals: Employment. Yu:Takeda Pharmaceuticals International Co, Cambridge, MA: Employment. Shinde:Takeda Pharmaceuticals: Employment. Kreshock:Takeda Pharmaceuticals: Employment. Tirrell:Takeda Pharmaceuticals: Employment. Menon:Takeda Pharmaceuticals: Employment. Orlowski:Takeda Pharmaceuticals: Research Funding.

scholarly journals CD47 Monoclonal Antibody SRF231 Is a Potent Inducer of Macrophage-Mediated Tumor Cell Phagocytosis and Reduces Tumor Burden in Murine Models of Hematologic Malignancies

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1843-1843 ◽  
Author(s):  
Pamela M Holland ◽  
Emmanuel Normant ◽  
Ammar Adam ◽  
Caroline M Armet ◽  
Rachel W O'Connor ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
T Cell ◽  
Tumor Growth ◽  
Tumor Cell ◽  
Growth Inhibition ◽  
Single Agent ◽  
B Cell Lymphoma ◽  
Hematologic Malignancies ◽  
Tumor Growth Inhibition ◽  
Phagocytic Uptake

Abstract The transmembrane protein CD47 is an immunoglobulin superfamily member involved in multiple cellular processes, including cell migration, adhesion and T cell function. The interaction between CD47 and signal regulatory protein alpha (SIRPα), an inhibitory protein expressed on macrophages, prevents phagocytosis of CD47-expressing cells. CD47 was originally identified as a tumor antigen on human ovarian cancer and was subsequently shown to be expressed on multiple human tumor types, including both hematologic and solid tumors. In many hematologic cancers, high CD47 expression is associated with poor clinical outcomes. CD47 is also expressed at low levels on virtually all non-malignant cells, and loss of expression or changes in membrane distribution may serve as markers of aged or damaged cells, particularly on red blood cells (RBC). High expression of CD47 on tumors blocks phagocytic uptake, subsequent antigen cross-presentation and T cell activation, which collectively contribute to tumor immune evasion. Agents that block the CD47-SIRPα interaction can restore phagocytic uptake of CD47+ target cells and lower the threshold for macrophage activation, which can enhance the efficacy of therapeutic antibodies with ADCC-enabling activity. We developed and characterized a CD47 blocking antibody and evaluated its activity in multiple hematologic models. SRF231 is a fully human monoclonal antibody that binds with high affinity to human CD47 and blocks the CD47-SIRP▢ interaction. SRF231 promotes macrophage-mediated phagocytic clearance of several hematologic primary tumor samples and cell lines in vitro. For example, SRF231 increases phagocytosis of Raji tumor cell line targets with an EC50 of ~300 ng/ml. Enhanced phagocytosis is preferential for tumor cells over normal leukocytes and RBC. Tumor cell phagocytosis can be enhanced in the presence of opsonizing antibodies (e.g., anti-CD20 Ab) when co-administered with SRF231. In vivo efficacy of SRF231 was assessed in several preclinical murine xenograft models of hematologic malignancies. Notably, SRF231 administration led to profound tumor growth inhibition in models of multiple myeloma, diffuse large B cell lymphoma and Burkitt's lymphoma as a single agent and in combination with opsonizing antibodies. In the Raji xenograft model, single agent therapy leads to 112% tumor growth inhibition. This anti-tumor activity is at least partially dependent on macrophages, as depletion of macrophages via clodronate administration leads to reduced tumor growth inhibition. Tumor-associated macrophage (TAM) numbers and polarization status are also modulated by SRF231 treatment. In summary, the CD47 mAb SRF231 induces robust tumor cell phagocytosis and tumor clearance both alone and in combination with opsonizing antibodies in pre-clinical models of myeloma and lymphoma. These properties warrant further development of SRF231 in hematologic malignancies. SRF231 is currently in IND-enabling studies and is expected to enter clinical trials in 2017. Disclosures No relevant conflicts of interest to declare.

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