CD47抗体在实体瘤的适应症及临床试验入组人群

在肿瘤发生发展过程中，肿瘤细胞逃逸了免疫系统的监视；免疫逃逸机制对于研发新的抗肿瘤治疗方案具有重要的意义。免疫治疗旨在激活患者自身的免疫系统，是肿瘤治疗相关研究的前沿，具有广阔的应用前景。CD47是一种广泛表达的细胞表面分子，肿瘤细胞可能借此“别吃我”信号，逃避了肿瘤免疫；肿瘤干细胞中CD47的表达水平甚至比肿瘤细胞更高。通过使用抗CD47抗体阻断CD47-SIRPα通路，从而介导细胞吞噬作用，能够靶向性杀伤肿瘤细胞。现在多项关于CD47靶向治疗的临床试验正在进行中，包括两种单克隆抗体和一种融合蛋白。然而由于使用动物模型不一，可能高估了这些药物的临床疗效预测。现将CD47抗肿瘤治疗相关研究的背景及潜在问题加以综述，并对该治疗的未来应用前景予以展望。

肿瘤细胞通过表达免疫检查点逃避机体免疫系统攻击，免疫检查点抑制剂则通过靶向这些免疫检查点阻断肿瘤细胞对免疫系统的抑制，促进机体抗肿瘤免疫反应，从而产生强大的抗肿瘤效果。CD47作为固有免疫系统的免疫检查点，在多种不同类型的恶性肿瘤细胞表面过表达，它通过与巨噬细胞表面的信号调节蛋白α（SIRPα）结合转导抑制信号，抑制巨噬细胞对肿瘤细胞的吞噬，进而使肿瘤细胞逃避机体固有免疫系统的监视和攻击。阻断CD47/SIRPα信号轴可以激活巨噬细胞对肿瘤细胞的吞噬作用，启动机体抗肿瘤免疫反应，但是由于复杂的肿瘤微环境，阻断免疫细胞上的单一信号通路只能产生有限或轻微的影响。此外，单独使用靶向CD47/SIRPα信号轴的药物治疗肿瘤响应率较低，并且可能存在较严重的不良反应。为了克服上述问题，提高抗肿瘤效果，将靶向CD47/SIRPα信号轴的药物与其他抗肿瘤疗法联合应用成为最有效的策略之一。本文综述了近年来关于CD47/SIRPα信号轴的研究进展和基于靶向CD47/SIRPα信号轴药物的联合治疗策略。

巨噬细胞是肿瘤微环境的重要组成部分，肿瘤细胞通过表达分化群47（CD47）与巨噬细胞受体信号调节蛋白α（SIRPα）相互作用而避免被吞噬。目前通过阻断CD47-SIRPα的相互作用进而恢复巨噬细胞吞噬功能的研究已经受到了广泛关注，包括抗CD47抗体在内的多种药物已经开展了临床试验研究。然而常见的血液毒性限制了这类药物的临床应用，除了筛选肿瘤特异性结合的药物外，通过药物递送系统包载CD47抑制剂用于肿瘤的治疗是一种有效策略。通过以CD47-SIRPα的结构和信号通路为基础，详细综述了靶向CD47-SIRPα的递送系统，包括白蛋白、脂质等不同载体材料构建的纳米递送系统，凝胶递送系统和抗体偶联药物等，以期为临床药物开发提供借鉴。

肿瘤细胞可以通过多种途径逃避机体免疫系统的识别和清除，如诱导免疫抑制的肿瘤微环境，降低肿瘤细胞的免疫原性等；其中，肿瘤细胞逃避天然免疫系统如巨噬细胞等吞噬细胞清除的机制之一是上调细胞表面“别吃我”（don't eat me）信号的表达。整合素相关蛋白（IAP，即CD47）便是一种重要的自我信号，它通过与巨噬细胞上的配体信号调节蛋白α（SIRPα）结合，进而抑制巨噬细胞对肿瘤细胞的吞噬；此外，在天然免疫细胞如树突状细胞等向适应性免疫T细胞提呈抗原的过程中，CD47也发挥着抑制作用。因此，CD47在肿瘤免疫中发挥着重要的调节作用，靶向CD47是一个潜在的抗肿瘤方向。本文对CD47的抗肿瘤作用进行了详述，包括分子结构、信号转导、调节吞噬与促凋亡作用及成药性考虑等。

… Administration of anti-CD47 antibodies inhibited tumor growth in … that CD47 is expressed on a wide range of human solid tumors, … of CD47 on these cancers, as a “don't eat me” signal. …

Much progress has been made in targeting CD47 for cancer immunotherapy in solid tumors (ST) and hematological malignancies. We summarized the CD47-related clinical research and analyzed the research trend both in the USA and in China. As of August 28, 2021, there are a total 23 related therapeutic agents with 46 clinical trials in the NCT registry platform. Among these trials, 29 are in ST, 14 in hematological malignancies and 3 in both solid tumor and hematological malignancy. The ST include gastric cancer, head and neck squamous cell carcinoma and leiomyosarcoma, while the hematological malignancies include non-Hodgkin's lymphoma, acute myeloid leukemia, myelodysplastic syndrome, multiple myeloma and chronic myeloid leukemia. Majority of the CD47-related clinical trials are at the early phases, such as 31 at phase I, 14 at phase II and 1 at phase III in the USA and 9, 6, 1, in China, respectively. The targets and spectrums of mechanism of action include 26 with mono-specific and 20 with bi-specific targets in the USA and 13 with mono-specific and 3 with bi-specific targets in China. The new generation CD47 antibodies have demonstrated promising results, and it is highly hopeful that some candidate agents will emerge and make into clinical application to meet the urgent needs of patients.

CD47 is a widely expressed cell surface protein that functions as a regulator of phagocytosis mediated by cells of the innate immune system, such as macrophages and dendritic cells. CD47 serves as the ligand for a receptor on these innate immune cells, SIRP-alpha, which in turn delivers an inhibitory signal for phagocytosis. We previously found increased expression of CD47 on primary human acute myeloid leukemia (AML) stem cells, and demonstrated that blocking monoclonal antibodies directed against CD47 enabled the phagocytosis and elimination of AML, non-Hodgkin’s lymphoma (NHL), and many solid tumors in xenograft models. Here, we report the development of a humanized anti-CD47 antibody with potent efficacy and favorable toxicokinetic properties as a candidate therapeutic. A novel monoclonal anti-human CD47 antibody, 5F9, was generated, and antibody humanization was carried out by grafting its complementarity determining regions (CDRs) onto a human IgG4 format. The resulting humanized 5F9 antibody (Hu5F9-G4) bound monomeric human CD47 with an 8 nM affinity. Hu5F9-G4 induced potent macrophage-mediated phagocytosis of primary human AML cells in vitro and completely eradicated human AML in vivo, leading to long-term disease-free survival of patient-derived xenografts. Moreover, Hu5F9-G4 synergized with rituximab to eliminate NHL engraftment and cure xenografted mice. Finally, toxicokinetic studies in non-human primates showed that Hu5F9-G4 could be safely administered intravenously at doses able to achieve potentially therapeutic serum levels. Thus, Hu5F9-G4 is actively being developed for and has been entered into clinical trials in patients with AML and solid tumors (ClinicalTrials.gov identifier: NCT02216409).

Background The antiphagocytic molecule CD47 is overexpressed in a wide variety of cancer cells, and antibodies targeting CD47 for cancer therapies are currently under intensive investigation. However, owing to the ubiquitous expression of CD47 on healthy cells, anti-CD47 therapies often achieve only weak therapeutic benefits and can induce severe side effects. Here, we report the generation of a pH-dependent anti-CD47 antibody (BC31M4) which selectively binds to tumors under the acidic solid tumor microenvironment. Methods BC31M4 was generated using antibody phage display and a pH-dependent selection strategy. The pH-dependent binding and blocking activities of BC31M4 were verified using in vitro assays, and the structural basis of the pH-dependent binding property was characterized. BC31M4’s antitumor effect was confirmed by both phagocytosis assays and studies in xenograft models. The tumor selectivity, mechanism of action, PK properties, side effects, and therapeutic efficacy were further evaluated in humanized (hCD47 and its receptor hSIRPα) immunocompetent syngeneic mouse models. Results The crystal structure reveals that two histidines locate within the CDRs of the light chain directly contribute to the pH-dependent binding of BC31M4. BC31M4 promotes macrophage phagocytosis of tumor cells more potently at acidic-pH than at physiological-pH. Our hCD47/hSIRPα humanized syngeneic mouse model results demonstrated that BC31M4 selectively accumulates in tumors but not in normal tissues. BC31M4 causes minimal side effects and exhibits superior PK properties as compared to the other examined anti-CD47 antibodies. When combined with adoptive T cell transfer, BC31M4 efficiently promotes adaptive immune responses against tumors and also induces immune memory. Moreover, we show that BC31M4’s antitumor effects rely on an Fc that mediates strong effector functions. Conclusions Our study illustrates that the development of a tumor-selective, pH-dependent anti-CD47 antibody safely confers strong therapeutic effects against solid tumors, thus providing a promising therapeutic strategy to overcome the challenges of anti-CD47 therapy.

Overexpression of CD47 is frequently observed in various types of human malignancies, inhibiting myeloid-mediated elimination of tumor cells and affecting the prognosis of cancer patients. By mapping biomarker expression, immuno-positron emission tomography has been increasingly used for patient screening and response monitoring. By immunization alpacas with recombinant human CD47, we prepared a CD47-targeting nanobody C2 and developed [68Ga]Ga-NOTA-C2, followed by an exploration of the diagnostic value in CD47-expressing tumor models including gastric-cancer patient-derived xenograft models. By fusing C2 to an albumin binding domain (ABD), we synthesized ABDC2, which had increased in vivo half-life and improved targeting properties. We further labeled ABDC2 with 68Ga/89Zr/177Lu to develop radionuclide theranostic pairs and evaluated the pharmacokinetics and theranostic efficacies of the agents in cell- and patient-derived models. Both C2 and ABDC2 specifically reacted with human CD47 with a high KD value of 23.50 and 84.57 pM, respectively. [68Ga]Ga-NOTA-C2 was developed with high radiochemical purity (99 >%, n = 4) and visualized CD47 expression in the tumors. In comparison to the rapid renal clearance and short half-life of [68Ga]Ga-NOTA-C2, both [68Ga]Ga-NOTA-ABDC2 and [89Zr]Zr-DFO-ABDC2 showed prolonged circulation and increased tumor uptake, with the highest uptake of [89Zr]Zr-DFO-ABDC2 occurring at 72 h post-injection. Moreover, [177Lu]Lu-DOTA-ABDC2 radioimmunotherapy suppressed the tumor growth but was associated with toxicity, warranting further optimization of the treatment schedules. Taken together, we reported a series of nanobody-derived CD47-targeted agents, of which [68Ga]Ga-NOTA-C2 and [89Zr]Zr-DFO-ABDC2 are readily translatable. Optimization and translation of CD47-targeted theranostic pair may provide new prospects for CD47-targeted management of solid tumors.

The immune checkpoint CD47 is highly upregulated in several cancers as an innate immune escape mechanism. CD47 delivers a “don’t eat me” signal to its co-receptor signal regulatory protein α (SIRPα), thereby inhibiting phagocytosis. Blocking the CD47–SIRPα axis is a promising immunotherapeutic strategy against cancer. However, early trial data has demonstrated on-target off-leukemia toxicity. In addition, the ubiquitous expression pattern of CD47 might contribute to an antigen sink. In this study, we combined low-affinity CD47 checkpoint blockade and specific tumor targeting in a multivalent and multifunctional antibody construct to prevent CD47-related toxicities. First, we established a local inhibitory checkpoint monoclonal antibody (LicMAb) by fusing two N-terminal extracellular domains of SIRPα to a full-length anti-human mesothelin (MSLN)-IgG1 antibody, a well-described tumor-associated antigen in epithelial ovarian cancer (EOC) and pancreatic ductal adenocarcinoma (PDAC). Next, we evaluated the SIRPα-αMSLN LicMAb for mediating a tumor-restricted immune response as observed by antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP). Our data validates CD47 and MSLN as highly upregulated targets expressed on various solid cancer entities, particularly EOC. We show tumor-specific binding and CD47 blocking by the SIRPα-αMSLN LicMAb even in the presence of healthy CD47-expressing cells. Furthermore, the LicMAb induces NK-cell-mediated cytotoxicity and improves phagocytosis of EOC and PDAC tumor cells. Moreover, cell death in EOC-derived organoids was specifically LicMAb-driven. Hence, the SIRPα-αMSLN LicMAb combines a tumor-restricted blockade of the CD47–SIRPα axis with a specific antitumor response while preventing on-target off-tumor toxicities. Our data supports the multifunctional SIRPα-αMSLN LicMAb as a promising approach to treating solid tumors. The local inhibitory checkpoint monoclonal antibody (LicMAb) binds mesothelin (MSLN) with high affinity and simultaneously blocks CD47 on MSLN-expressing tumor cells to inhibit the “don’t eat me” signal. CD47 is blocked by the fused extracellular SIRPα domain that intrinsically has a low affinity. Furthermore, the SIRPα-αMSLN LicMAb is based on a human IgG1 backbone to provide an Fc receptor (FcR)-activating stimulus to enable direct NK-cell-mediated killing by granzyme B (GrzB) and perforin secretion, and an additional pro-phagocytic signal to phagocytic cells, such as macrophages (MØ). This leads to tumor-restricted antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) of cancer cells. This scheme was created with BioRender (BioRender.com/g77u465).

CD47 is a “don’t eat me” signal to phagocytes that is overexpressed on many tumor cells as a potential mechanism for immune surveillance evasion. CD47 and its interaction with signal-regulating protein alpha (SIRPα) on phagocytes is therefore a promising cancer target. Therapeutic antibodies and fusion proteins that block CD47 or SIRPα have been developed and have shown activity in preclinical models of hematologic and solid tumors. Anemia is a common adverse event associated with anti-CD47 treatment, but mitigation strategies—including use of a low ‘priming’ dose—have substantially reduced this risk in clinical studies. While efficacy in single-agent clinical studies is lacking, findings from studies of CD47–SIRPα blockade in combination with agents that increase ‘eat me’ signals or with antitumor antibodies are promising. Magrolimab, an anti-CD47 antibody, is the furthest along in clinical development among agents in this class. Magrolimab combination therapy in phase Ib/II studies has been well tolerated with encouraging response rates in hematologic and solid malignancies. Similar combination therapy studies with other anti-CD47–SIRPα agents are beginning to report. Based on these early clinical successes, many trials have been initiated in hematologic and solid tumors testing combinations of CD47–SIRPα blockade with standard therapies. The results of these studies will help determine the role of this novel approach in clinical practice and are eagerly awaited.

Chemotherapy plus epidermal growth factor receptor (EGFR) inhibitors, such as cetuximab, is standard therapy for KRAS wild-type (KRASwt) colorectal cancer (CRC); however, responses are infrequent. Magrolimab is a monoclonal antibody targeting CD47, an antiphagocytic signal overexpressed in solid tumors (STs). This open-label, multicenter phase 1b/2 study (NCT02953782) aimed to determine the recommended phase 2 dose (RP2D) and evaluate the safety, tolerability, and efficacy of magrolimab + cetuximab in patients with advanced CRC or other STs. A total of 78 patients were enrolled at eight study sites in the USA. In phase 1b, patients with advanced STs received weekly maintenance doses of magrolimab at 10–45 mg/kg and cetuximab at 200–250 mg/m2 following 3 + 3 dose-escalation. In phase 2, patients with anti–EGFR-refractory CRC received magrolimab + cetuximab at RP2Ds. Primary endpoints were dose-limiting toxicities, adverse events, and objective response rate (ORR; phase 2). The maximum tolerated dose was not reached in phase 1b. Two RP2Ds were explored in phase 2: magrolimab at 30 or 45 mg/kg plus cetuximab at 250 mg/m2. Most common treatment-related adverse events (TRAEs) were dermatitis acneiform (35.9%), infusion-related reactions (33.3%), dry skin (32.1%), fatigue (32.1%), and headache (29.5%). Most common grade ≥ 3 TRAEs were anemia (11.5%), increased blood bilirubin (9.0%), and decreased lymphocyte count (9.0%). Discontinuation of any study treatment owing to TRAEs occurred in 3.8% of patients. No deaths occurred due to TRAEs. In phase 2, ORR was 6.3% and 0% in the KRASwt and KRASmt CRC cohorts, respectively; disease control rate was 50.0% and 38.1%, and median overall survival was 9.5 and 7.6 months, respectively. These results indicate tolerability and potential antitumor activity when combining anti-CD47 therapy and cetuximab in heavily pretreated patients with CRC.

Accumulating evidence indicates that a small subset of cancer cells, termed the tumor-initiating cells or cancer stem cells (CSCs), construct a reservoir of self-sustaining cancer cells with the characteristic ability to self-renew and maintain the tumor mass. The CSCs play an important role in the tumor initiation, development, relapse, metastasis, and the ineffectiveness of conventional cancer therapies. CD47 is a ligand for signal-regulatory protein-α expressed on phagocytic cells and functions to inhibit phagocytosis. This study was to explore if the expression of CD47 is the mechanism used by lung cancer cells, especially CSCs, to escape phagocytosis in vitro and in vivo. Here, we selected CD133 as the marker for lung CSCs according to previous reports. We analyzed lung cancer and matched adjacent normal (non-tumor) tissue and revealed that CD47 is overexpressed on lung cancer cells, especially on lung CSCs. The mRNA expression levels of CD47 and CD133 correlated with a decreased probability of survival for multiple types of lung cancer. Blocking CD47 function with anti-CD47 antibodies enabled macrophage phagocytosis of lung cancer cells and lung CSCs. Anti-CD47 antibodies inhibited tumor growth in immunodeficient mouse xenotransplantation models established with lung cancer cells or lung CSCs and improved survival in tumor-bearing animals. These data indicate that CD47 is a valid target for cancer therapies, especially for anti-CSC therapies.

In the tumor microenvironment (TME), tumor-associated macrophages (TAMs) are the most abundant immune cells, which act as a key regulator in tumorigenesis and progression. Increasing evidence have demonstrated that the TME alters the nature of macrophages to maintain dynamic tissue homeostasis, allowing TAMs to acquire the ability to stimulate angiogenesis, promote tumor metastasis and recurrence, and suppress anti-tumor immune responses. Furthermore, tumors with high TAM infiltration have poor prognoses and are resistant to treatment. In the field of solid tumor, the exploration of tumor-promoting mechanisms of TAMs has attracted much attention and targeting TAMs has emerged as a promising immunotherapeutic strategy. Currently, the most common therapeutic options for targeting TAMs are as follows: the deletion of TAMs, the inhibition of TAMs recruitment, the release of phagocytosis by TAMs, and the reprogramming of macrophages to remodel their anti-tumor capacity. Promisingly, the study of chimeric antigen receptor macrophages (CAR-Ms) may provide even greater benefit for patients with solid tumors. In this review, we discuss how TAMs promote the progression of solid tumors as well as summarize emerging immunotherapeutic strategies that targeting macrophages.

… CD47, an immune checkpoint receptor frequently unregulated in various blood and solid tumors… and synergize with CD47 antibody in reducing tumor growth in macrophage-dependent …

2630Background: AK117 is a novel humanized IgG4 monoclonal antibody (mAb) targeting CD47, a macrophage immune checkpoint that allows tumor cells to evade immune destruction by phagocytic cells. CD4...

Selective CD47 blockade on CTLA-4high tumor-infiltrating Treg cells reduces systemic toxicity and enhances antitumor immunity. Targeting Treg cells Depletion of regulatory T (Treg) cells is an attractive strategy to promote antitumor immunity. One strategy that could deplete Treg cells is blockade of the “do not eat me” signal, CD47, which prevents Treg cells from being targets of phagocytosis. However, CD47 is broadly expressed, making Treg cell–specific targeting difficult. To selectively deplete Treg cells, Zhang et al. designed a heterodimer that combines an anti–cytotoxic T lymphocyte antigen 4 (CTLA-4) antibody, which targets intratumoral Treg cells, and the CD47 ligand, signal regulatory protein α (SIRPα). Treatment with this heterodimer increased phagocytosis of Treg cells, leading to their depletion, and promoted antitumor immunity in mouse models. Thus, dual targeting of CD47 and CTLA-4 selectively depletes Treg cells and can promote immune responses against solid tumors. Blockade of CD47, the “do not eat me” signal, has limited effects in solid tumors despite its potent antitumor effects in hematopoietic malignancies. Taking advantage of the high expression of cytotoxic T lymphocyte–associated protein 4 (CTLA-4) on Treg cells and abundant Fc receptor–expressing active phagocytes inside the tumor microenvironment (TME), we designed and tested a heterodimer combining an anti–CTLA-4 antibody, which targets Treg cells, with the CD47 ligand, signal regulatory protein α (SIRPα), to selectively block CD47 on intratumoral Treg cells. We hypothesized that heterodimer treatment would increase antibody-dependent cellular phagocytosis of the targeted Treg cells. We found that anti–CTLA-4×SIRPα preferentially depleted ICOShigh immunosuppressive Treg cells in the TME and enhanced immunity against solid tumors, including MC38 and CT26 murine colon cancers. Mechanistically, we found that CD47 expression on Treg cells limited anti–CTLA-4–mediated depletion and Fc on the heterodimer-enhanced depletion. Furthermore, anti-human CTLA-4×SIRPα depleted tumor Treg cells and exhibits less toxicity than anti-human CTLA-4 in a humanized mouse model. Collectively, these results demonstrate that simultaneously modulating both “eat me” and do not eat me signals induces Treg cell depletion inside the TME and may be an effective strategy for treating solid tumors.

ABSTRACT Background Immunotherapy is an emerging strategy in cancer therapeutics aimed at modulating the immune system to inhibit pro-tumor pathways and increase a tumor’s sensitivity to chemotherapy. Several clinically approved immunotherapy treatments, such as monoclonal antibody treatments, have been successful in solid tumors such as breast, colorectal, and pancreatic. However, an outstanding challenge of these strategies is tumor cell resistance. One target of interest for immune cell modulation is targeting macrophages that enter the tumor microenvironment. More specifically, an immune checkpoint of interest is CD47. CD47 is a transmembrane protein that inhibits phagocytic activity by acting as a “don’t eat me” signal. In both mice and humans, healthy cells can express CD47, while solid malignancies like colorectal and breast cancer express it most strongly. Methods Analysis of literature data on the physiological and functional roles of tissue-resident macrophages, along with the structure and mechanisms of action of the CD47 pathway was explored. We also explored how CD47 can influence different aspects of the tumor microenvironment (i.e. cellular metabolism and hypoxia) in addition to current clinical strategies and challenges associated with targeting CD47. Results Overall, it was discovered that CD47 is overexpressed in a variety of cancer types in addition to normal tissue, making it a promising treatment regimen to enhance the capability of macrophages to phagocytose tumor cells. However, treatment efficacy is varied in pre-clinical and clinical models due to various challenges such as off-target effects. Conclusion This review emphasizes the diverse functionality of macrophages in normal and cancerous tissue, while also emphasizing the importance of macrophage targeting and their clinical significance.

… When solid tumours were examined, a moderate increase in CD47 surface expression was … in both solid tumours and haematologic malignancies. A fully human anti-CD47 antibody, …

Purpose IMC-002 is a fully human cluster of differentiation 47-targeted immunoglobulin G4 monoclonal antibody, designed to minimize off-target effects. This study (NCT05276310) assessed its safety/tolerability and preliminary anti-tumor activity in patients with advanced solid tumors who were not eligible for or had progressed on standard treatment. Materials and Methods Here we report results from the initial 3 + 3 design dose-escalation part of a two-part Phase 1, open-label, dose-escalation/expansion study. IMC-002 was administered intravenously every 2 weeks at four doses (5, 10, 20, and 30 mg/kg). The primary objective was to assess safety/tolerability, including maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D). Secondary objectives included pharmacokinetics and clinical activity, including best overall response (BOR), disease control rate (DCR), and clinical benefit rate (CBR). Results Twelve patients were included in total, with three per dose level. Most patients (11/12) had stage IV disease; 7/12 had received three prior systemic therapies. No dose-limiting toxicities were observed and MTD was not reached. The most common treatment-related adverse events (TRAEs) were rash (9/12), vitreous floaters (8/12), and (hemolytic) anemia (5/12). There was no treatment-related thrombocytopenia, neutropenia, or infection. IMC-002 had dose-proportional pharmacokinetics, achieving steady state levels from Cycle 2. BOR was stable disease in six patients (DCR 50.0%). CBR was 33% (four patients maintaining disease control for ≥6 months). Conclusion IMC-002 demonstrated favorable safety/tolerability at doses of 5-30 mg/kg every 2 weeks. RP2D was defined as 20 mg/kg every 3 weeks. Preliminary anti-tumor activity was observed, with a CBR of 33%.

Simple Summary The interaction between cluster of differentiation 47 (CD47) on cancer cells and signal regulatory protein alpha (SIRPα) on immune cells, such as macrophages and dendritic cells, generates a “don’t eat me” signal. This is a common mechanism that provides cancer cells an escape from the innate immune system. Several therapeutics directed to CD47 or SIRPα have entered early clinical trials in recent years. In this article, we review the role of CD47/SIRPα axis in cancer, and summarize the literature on the efficacy and safety of therapeutics targeting CD47 or SIRPα. We also discuss the future implementation of these therapeutics in the treatments of various cancer types. Abstract In the past decade, the field of cancer immunotherapy has rapidly advanced, establishing a crucial role for immune checkpoint blockers in the treatment of a variety of cancer types. In parallel with these remarkable clinical developments, further efforts have focused on ways of unleashing adaptive immune responses against cancer. CD47, a cell surface molecule overexpressed by several cancer types that facilitates immune escape from macrophages, dendritic cells and natural killer cells, and its ligand SIRPα, have emerged as potential therapeutic targets. A number of agents directed to CD47/SIRPα have been developed and demonstrated preclinical activity. Early phase clinical trials are investigating CD47/SIRPα directed agents with available data, suggesting safety and preliminary activity. Herein, we provide an overview of the mechanistic rationale of targeting CD47/SIRPα axis and associated clinical evidence.

Purpose The treatment options for metastatic soft tissue sarcomas (STSs) are limited. In most cases, immunotherapy with immune checkpoint inhibitors has not been successful so far. Macrophages dominate the immune landscape of STSs; thus, combinatorial strategies aiming at both tumor-infiltrating lymphocytes and macrophages may represent a particularly relevant treatment approach for metastatic or recurrent STSs. Methods In this cohort study, 66 patients who underwent surgery for STSs were enrolled. Tumor cells and tumor-infiltrating immune cells were analyzed using flow cytometry and immunohistochemistry. In cell suspensions obtained from surgical resections, human T cells were activated by superparamagnetic polymer beads and cultured at a concentration of 0.3 × 10^6/µl in the absence or presence of therapeutic monoclonal antibodies (anti-PD-1, anti-CD47, and anti-PD-1 + anti-CD47). Supernatants from cell suspensions were analyzed using multiplex Luminex cytokine bead-based immunoassays. Results The most profound response to anti-CD47 therapy was observed in an undifferentiated pleiomorphic sarcoma which also displayed high expression of CD47 in the tumor microenvironment. Both anti-PD-1 and anti-CD47 therapies drastically increased the production of pro-inflammatory cytokines in the tumor microenvironment of STSs, but co-administration of both agents did not further increase cytokine secretion. Furthermore, all patient samples treated with a combination of both anti-PD-1 and anti-CD47 antibodies showed a dramatic reduction in cytokine secretion. Conclusion Our findings suggest that anti-PD-1 and anti-CD47 therapies do not enhance each other, and the combined application of anti-PD-1 and anti-CD47 agents in vitro limits rather than potentiates their efficacy.

Targeting CD47 is in the spotlight of cancer immunotherapy. Blocking CD47 triggers the recognition and elimination of cancer cells by the innate immunity. There are three CD47 antagonists in phase I clinical trials, but their potential efficacies are highly controversial. We raise our concern that NOD-based xenograft hosts tend to overestimate, while syngeneic mouse models could substantially underestimate the efficacy of anti-CD47 therapy. Such discrepancy may be resulted from specific reagent that alters CD47 clustering, and the highly variable avidities of interspecies and intraspecies CD47-SIRPα interaction. This problem can be addressed by alternative animal models for better recapitulation of human CD47-SIRPα interaction. Both fragment crystallizable (Fc) fragment-dependent effects, like antibody-dependent cell-mediated cytotoxicity (ADCC), and Fc-independent CD47 intrinsic functions are involved in anti-CD47 therapy. The latter may be SIRPα-dependent or SIRPα-independent, such as the case of calreticulin. It has not reached a consensus which of the factors predominate the process, but the answer to this question will determine the optimal pharmaceutical and clinical design of CD47 targeting strategies.

CD47-SIRPα interaction acts as a “don’t eat me” signal and is exploited by cancer to downregulate innate and adaptive immune surveillance. There has been intense interest to develop a mechanism of blockade, and we aimed to analyze the emerging data from early clinical trials. We performed a systematic review and meta-analysis of relevant databases and conference abstracts including clinical trials using CD47 and/or SIRPα inhibitors in cancer treatment. Nonlinear mixed models were applied for comparison of response and toxicity. We retrieved 317 articles, 24 of which were eligible. These included 771 response-evaluable patients with hematologic (47.1%) and solid tumors (52.9%). Of these, 6.4% experienced complete response, 10.4% partial response, and 26.1% stable disease for a 16.7% objective response rate (ORR), 42.8% disease control rate, and 4.8-month median duration of response. ORR was significantly higher for hematologic cancers (25.3%) than solid cancers (9.1%, p=0.042). Comparing by mechanism, seven CD47 monoclonal antibodies (mAbs) and six selective SIRPα blockers were given alone or combined with checkpoint inhibitors, targeted therapy, and/or chemotherapy. In solid cancers, selective SIRPα blockade showed a higher ORR (16.2%) than anti-CD47 mAbs (2.8%, p=0.079), which was significant for combination therapies (ORR 28.3% vs 3.0%, respectively, p=0.010). Responses were seen in head and neck, colorectal, endometrial, ovarian, hepatocellular, non-small cell lung, and HER2+gastroesophageal cancers. Dose-limiting toxicity (DLT) was seen in 3.3% of patients (5.4% anti-CD47 mAbs, 1.4% selective SIRPα blockers; p=0.01). The frequency of treatment-related adverse events (TRAEs) ≥grade 3 was 18.0%, similar between the two groups (p=0.082), and mostly laboratory abnormalities. For anti-CD47 mAbs, the most common toxicities included grade 1-2 fatigue (27.2%), headache (21.0%), and anemia (20.5%). For selective SIRPα blockers, these included grade 1-2 infusion reaction (23.1%) and fatigue (15.8%). Anti-CD47 mAbs were significantly more likely than selective SIRPα blockers to cause grade 1-2 fever, chills, nausea/vomiting, headache, and anemia. In conclusion, combination therapies using selective SIRPα blockade had higher response rates in solid tumors than anti-CD47 mAb combinations. Hematologic changes were the main TRAEs, and selective SIRPα blockers seemed to have a better grade 1-2 toxicity profile. Treatment was well-tolerated with minimal DLTs.

PURPOSE To evaluate the safety, pharmacokinetics, and pharmacodynamics of Hu5F9-G4 (5F9), a humanized IgG4 antibody that targets CD47 to enable phagocytosis. PATIENTS AND METHODS Adult patients with solid tumors were treated in four cohorts: part A, to determine a priming dose; part B, to determine a weekly maintenance dose; part C, to study a loading dose in week 2; and a tumor biopsy cohort. RESULTS Sixty-two patients were treated: 11 in part A, 14 in B, 22 in C, and 15 in the biopsy cohort. Part A used doses that ranged from 0.1 to 3 mg/kg. On the basis of tolerability and receptor occupancy studies that showed 100% CD47 saturation on RBCs, 1 mg/kg was selected as the priming dose. In subsequent groups, patients were treated with maintenance doses that ranged from 3 to 45 mg/kg, and most toxicities were mild to moderate. These included transient anemia (57% of patients), hemagglutination on peripheral blood smear (36%), fatigue (64%), headaches (50%), fever (45%), chills (45%), hyperbilirubinemia (34%), lymphopenia (34%), infusion-related reactions (34%), and arthralgias (18%). No maximum tolerated dose was reached with maintenance doses up to 45 mg/kg. At doses of 10 mg/kg or more, the CD47 antigen sink was saturated by 5F9, and a 5F9 half-life of approximately 13 days was observed. Strong antibody staining of tumor tissue was observed in a patient at 30 mg/kg. Two patients with ovarian/fallopian tube cancers had partial remissions for 5.2 and 9.2 months. CONCLUSION 5F9 is well tolerated using a priming dose at 1 mg/kg on day 1 followed by maintenance doses of up to 45 mg/kg weekly.

Abstract The macrophage checkpoint is an anti-phagocytic interaction between signal regulatory protein alpha (SIRPα) on a macrophage and CD47 on all types of cells – ranging from blood cells to cancer cells. This interaction has emerged over the last decade as a potential co-target in cancer when combined with other anti-cancer agents, with antibodies against CD47 and SIRPα currently in preclinical and clinical development for a variety of hematological and solid malignancies. Monotherapy with CD47 blockade is ineffective in human clinical trials against many tumor types tested to date, except for rare cutaneous and peripheral lymphomas. In contrast, pre-clinical results show efficacy in multiple syngeneic mouse models of cancer, suggesting that many of these tumor models are more immunogenic and likely artificial compared to human tumors. However, combination therapies in humans of anti-CD47 with agents such as the anti-tumor antibody rituximab do show efficacy against liquid tumors (lymphoma) and are promising. Here, we review such trials as well as key interaction and structural features of CD47-SIRPα.

Simple Summary Lung cancer is the leading cause of cancer-related death worldwide. Despite treatment advances, high rates of tumor recurrence emphasize the need for new therapeutic strategies. Tumors often acquire mechanisms to avoid detection by the immune system, allowing them to develop and metastasize. Immunotherapy is a type of treatment designed to overcome these mechanisms by reactivating the immune system to eliminate tumors. CD47 is a cell surface protein and marker of “self” expressed on cells throughout the body and prevents them from being “eaten” by cells of the immune system. Lung cancers exploit this “don’t eat me” signal by upregulating CD47 to evade the immune system, making it a promising therapeutic target. This review summarizes the roles of CD47 in tumor biology, its therapeutic potential in non-small cell lung cancer, and challenges that must be overcome to facilitate the clinical translation of CD47-targeted immunotherapy to improve lung cancer survival rates. Abstract The success of PD-1/PD-L1-targeted therapy in lung cancer has resulted in great enthusiasm for additional immunotherapies in development to elicit similar survival benefits, particularly in patients who do not respond to or are ineligible for PD-1 blockade. CD47 is an immunosuppressive molecule that binds SIRPα on antigen-presenting cells to regulate an innate immune checkpoint that blocks phagocytosis and subsequent activation of adaptive tumor immunity. In lung cancer, CD47 expression is associated with poor survival and tumors with EGFR mutations, which do not typically respond to PD-1 blockade. Given its prognostic relevance, its role in facilitating immune escape, and the number of agents currently in clinical development, CD47 blockade represents a promising next-generation immunotherapy for lung cancer. In this review, we briefly summarize how tumors disrupt the cancer immunity cycle to facilitate immune evasion and their exploitation of immune checkpoints like the CD47–SIRPα axis. We also discuss approved immune checkpoint inhibitors and strategies for targeting CD47 that are currently being investigated. Finally, we review the literature supporting CD47 as a promising immunotherapeutic target in lung cancer and offer our perspective on key obstacles that must be overcome to establish CD47 blockade as the next standard of care for lung cancer therapy.

Background CD47 blockade using SIRPα-Fc or anti-CD47 antibodies results in inhibition of the ‘do not eat’ signal and activation of phagocytosis and has emerged as a promising cancer treatment strategy. However, targeting CD47 leads to various hematological toxicities, particularly anemia and thrombocytopenia. Lemzoparlimab (also known as TJ011133 or TJC4) is a fully human, anti-CD47 IgG4 antibody that is endowed with a red blood cell (RBC) sparing property and unique binding epitope, potentially differentiating itself from other CD47 axis targeting therapies. Methods This phase 1 study (NCT03934814) is comprised of 2 parts. Part 1 consists of lemzoparlimab monotherapy dose escalation and 2 separate dose escalations of combination therapy with pembrolizumab or rituximab. The study is a standard 3+3 design. Part 2 is a dose expansion study. During monotherapy dose escalation, patients with relapsed/refractory solid tumors were administered an intravenous weekly dose (1 to 30 mg/kg) of lemzoparlimab to determine tolerability, safety, pharmacokinetics (PK), pharmacodynamics (PD) and anti-tumor activity based on Response Evaluation Criteria in Solid Tumors (RECIST v1.1) and iRECIST. Preliminary data from fully enrolled monotherapy cohorts in Part 1 are reported as of 17 July 2020. Results Twenty patients with relapsed/refractory solid tumors were enrolled to monotherapy dose escalation cohorts (1, 3, 10, 20 and 30 mg/kg). Lemzoparlimab toxicity was manageable up to 30 mg/kg without a dose-limiting toxicity (DLT) observed. The most common treatment-related adverse events (TRAEs) were anemia (30.0%, n=6), fatigue (25.0%, n=5), infusion-related reactions (20.0%, n=4), and diarrhea (15.0%, n=3). All TRAEs were Grade 1 or 2. A transient, non-dose-dependent average reduction of 1.5 mg/dL (range: 0.4–2.6 mg/dL) in hemoglobin during the first cycle was observed across all cohorts consistent with the results of pre-clinical good laboratory practice toxicity studies. Laboratory or clinical evidence of hemolysis was not observed in any cohort. Preliminary results indicate the PK of lemzoparlimab appears to be linear at mid- to high dose levels following a single dose. CD47 receptor occupancy shows complete saturation on peripheral T cells at peak concentrations of 20 mg/kg and above. Conclusions Lemzoparlimab appears safe up to 30 mg/kg with favorable PK and PD characteristics in patients with relapsed/refractory solid tumors to date. No TRAEs greater than Grade 2 have been observed. Results will be updated at presentation including available tumor response data. Trial Registration NCT03934814 Ethics Approval The study was approved by IRB, approval number 20190733.

The mammalian immune system consists of two distinct arms, nonspecific innate and more specific adaptive, with the innate immune response as the first line of defense and protection, which primes and amplifies subsequent adaptive responses. On the basis of this binary immune interplay, stimulation of T cells through checkpoint inhibitors (CIs), which bypasses innate involvement, seems likely to engender suboptimal or incomplete anticancer immunity, given that the successful induction of effect or responses depends on two-way innate/adaptive coordination. Indeed, the majority of patients-70%-80%, do not respond to CIs, which is potentially problematic if access to more optimal standard therapies is withheld or delayed in favor of ineffective or only marginally effective anti-PD-1/PD-L1 treatment. Therefore, stimulation of the innate immune response in combination with CIs (or other inducers of T cell cytotoxicity) has the potential to make the immune system "whole" and thereby to enhance and broaden the anti-tumor activity of PD-1/PD-L1 inhibitors for example, in relatively nonimmunogenic or "cold" tumor types. A critical innate macrophage immune checkpoint and druggable target is the antiphagocytic and "marker of self" CD47-SIRPα pathway, which is co-opted by cancer cells to mediate escape from immune-mediated clearance and checkpoint inhibition. This review summarizes the status of key CD47 antagonists in clinical trials, including the biologics, Hu5F9-G4 (5F9), TTI-621, and ALX148, as well as the small molecule, RRx-001, now in a Phase 3 clinical trial, which has not been previously included in CD47-SIRPα reviews focused on biologics. Hu5F9-G4 (5F9), TTI-621, ALX148, and RRx-001 are chosen as compounds with potentially promising data that have advanced the farthest in clinical development.

Recently, many immunosuppressive checkpoints such as PD-L1, CTLA-4 and CD47, were identified in succession and serve as potential immunotherapy targets in human cancers. Among them, CD47, a 'marker-of-self' protein that is overexpressed broadly across tumor types, is emerging as a novel potent macrophage immune checkpoint for cancer immunotherapy. In this review, we highlight the prominent role of CD47 as a 'don't-eat-me' signal that inhibits macrophage phagocytosis for immune evasion of a tumor and presents the opportunities and challenges for CD47 inhibitors both as monotherapy and in combination treatments for hematological cancers and solid tumors; some of these agents are currently in clinical trials.

Immunotherapy using PD-1 and CTLA4 inhibitors to stimulate T cell immunity has achieved significant clinical success. However, only a portion of patients benefit from T cell-based immunotherapy. Macrophages, the most abundant type of innate immune cells in the body, play an important role in eliminating tumor cells and infectious microbes. The phagocytic check point protein CD47 inhibits the phagocytic activity of macrophages through binding to SIRPα expressed on macrophages. Blockade of the interaction between CD47 and SIRPα could restore phagocytic activity and eliminate tumor cells in vitro and in vivo. In this manuscript, we review the mechanism of action and development status of agents (antibodies targeting CD47 and SIRPα, SIRPα-Fc fusion proteins, and bi-specific antibodies) that block CD47/SIRPα interaction in preclinical studies and in the clinical setting. In addition, small molecules, mRNA, and CAR-T/M that target the CD47/SIRPα axis are also reviewed in this article.

High expression levels of cluster of differentiation 47 (CD47) have been recognized as poor survival in several different cancers. Nevertheless, the significance of CD47 in patients with solid tumors remains controversial.

Background Novel treatments are needed to improve the poor prognosis of metastatic cancers. The ELEVATE Lung&UC study evaluated magrolimab plus docetaxel in patients with metastatic non-small cell lung cancer (mNSCLC), metastatic small cell lung cancer (mSCLC), and metastatic urothelial carcinoma (mUC). Methods This phase II, open-label, multi-arm study enrolled patients who had received 1–2 (mNSCLC, mSCLC) or 2–3 prior lines of therapy (mUC) in the locally advanced/metastatic setting. A safety run-in (SRI) cohort (mNSCLC/mSCLC/mUC) followed by a phase II cohort (three groups: mNSCLC, mSCLC, mUC) were planned. Primary endpoints were incidence of treatment-emergent adverse events (TEAEs; SRI and phase II) and objective response rate (ORR; phase II). Results The SRI cohort (n = 9) had no dose-limiting toxicities. In phase II (mNSCLC, 29 patients; mSCLC, 42 patients; mUC, 26 patients), ORRs were 17.2% (mNSCLC), 4.8% (mSCLC), and 3.8% (mUC). Grade ≥3 magrolimab-related TEAE rates were 48.3% (mNSCLC), 47.6% (mSCLC), and 57.7% (mUC). A fatal TEAE suspected as magrolimab related (intracranial hemorrhage) occurred in one patient with mSCLC and brain metastasis (phase II). The study was closed early, which limited the interpretation of results due to short follow-up and limited endpoint maturity. Discussion Adding magrolimab to docetaxel had manageable toxicity but no meaningful improvement in efficacy. These results provide insight into the safety and efficacy of anti-CD47–containing therapies and reinforce the need for treatments that address the unmet needs of patients with previously treated metastatic solid tumors.

Cluster of differentiation 47 (CD47) is a transmembrane protein that is widely and moderately expressed on the surface of various cells and can have an essential role in mediating cell proliferation, migration, phagocytosis, apoptosis, immune homeostasis and other related responses by binding to its ligands, integrins, thrombospondin-1 and signal regulatory protein α. The poor prognosis of cancer patients is closely associated with high expression of CD47 in glioblastoma, ovarian cancer, breast cancer, bladder cancer, colon cancer and hepatocellular carcinoma. Upregulation of CD47 expression facilitates the growth of numerous types of tumor cells, while downregulation of its expression promotes phagocytosis of tumor cells by macrophages, thereby limiting tumor growth. In addition, blocking CD47 activates the cyclic GMP-AMP (cGAMP) synthase/cGAMP/interferon gene stimulating factor signaling pathway and initiates an adaptive immune response that kills tumor cells. The present review describes the structure, function and interactions of CD47 with its ligands, as well as its regulation of phagocytosis and tumor cell fate. It summarizes the therapeutics, mechanisms of action, research advances and challenges of targeting CD47. In addition, this paper provides an overview of the latest therapeutic options for targeting CD47, such as chimeric antigen receptor (CAR) T-cells, CAR macrophages and nanotechnology-based delivery systems, which are essential for future clinical research on targeting CD47.

A transmembrane protein that is extensively expressed, CD47 has an important role in the senescence of cancer cells. Therapy-induced senescence (TIS) by chemotherapy and radiotherapy restrains tumor proliferation yet drives immune evasion and treatment resistance, where CD47 acts as a core regulatory molecule linking cellular senescence and tumor immune escape. In this mini-review, we summarize the mechanisms governing CD47 upregulation during TIS, ranging from DNA damage response signaling, metabolic reprogramming and epigenetic modulation to post-transcriptional RNA modification. After addressing how CD47 is upregulated in TIS, we summarized the function of CD47 in both the maintaining the senescent statue and preventing senescent escape. Three major pathways are addressed. TSP-1/CD47 axis functions as both senescence maintenance and preventing escape, while, p16/c-MYC/CD47 axis and CD47/QPCT axis are responsible for senescence maintenance. Moreover, we summarize the therapeutic strategies toward CD47 blockade as s senolytic way, pointing out a novel strategy for oncotherapy. Overall, CD47 is a pivotal molecular bridge between TIS and immune tolerance. Future research on the role CD47 of cancer senescence, especially after chemotherapy or radiotherapy, could provide novel insight for oncotherapy.

CD47 is a cell surface protein in the immunoglobulin superfamily which is normally expressed at low levels in every healthy cell. It´s main physiologic function is to act as an inhibitor of phagocytosis; this occurs throughout interaction with SIRPa expressed on macrophages. Interaction between CD47 and SIRPa leads to activation of tyrosine phosphatases that inhibit myosin accumulation at the submembrane assembly site of the phagocytic synapse, resulting in phagocytosis blockade. In this way CD47 acts as a “don´t eat me signal” for healthy self‐cells; accordingly, loss of CD47 leads to phagocytosis of aged or damaged cells. Taking advantage of this anti‐phagocytic signal provided by CD47, many types of tumors overexpress this protein, thereby avoiding phagocytosis by macrophages and aiding in the survival of cancer cells. The aim of this review is to describe the physiologic the pathophysiologic role of CD47; summarize the available high‐quality information about this molecule as a potential biomarker and/or therapeutic target in cancer; finally, we present an in‐depth analysis of the available information about CD47 in association with nonsmall cell lung cancer, EGFR mutations, and tumor microenvironment.

Background SL-172154 is a hexameric fusion protein adjoining the extracellular domain of SIRPα to the extracellular domain of CD40L via an inert IgG4-derived Fc domain. In preclinical studies, a murine equivalent SIRPα-Fc-CD40L fusion protein provided superior antitumor immunity in comparison to CD47- and CD40-targeted antibodies. A first-in-human phase I trial of SL-172154 was conducted in patients with platinum-resistant ovarian cancer. Methods SL-172154 was administered intravenously at 0.1, 0.3, 1.0, 3.0, and 10.0 mg/kg. Dose escalation followed a modified toxicity probability interval-2 design. Objectives included evaluation of safety, dose-limiting toxicity, recommended phase II dose, pharmacokinetic (PK) and pharmacodynamic (PD) parameters, and antitumor activity. Results 27 patients (median age 66 years (range, 33–85); median of 4 prior systemic therapies (range, 2–9)) with ovarian (70%), fallopian tube (15%), or primary peritoneal (15%) cancer received SL-172154. Treatment-emergent adverse events (TEAEs) were reported for 27 patients (100%), with 24 (88.9%) having a drug-related TEAE and infusion-related reactions being the most common. 12 patients (44.4%) had grade 3/4 TEAEs, and half of these patients (22.2%) had a drug-related grade 3/4 TEAE. There were no fatal adverse events, and no TEAEs led to drug discontinuation. SL-172154 Cmax and area under the curve increased with dose with greater than proportional exposure noted at 3.0 and 10.0 mg/kg. CD47 and CD40 target engagement on CD4+ T cells and B cells, respectively, approached 100% by 3.0 mg/kg. Dose-dependent responses in multiple cytokines (eg, interleukin 12 (IL-12), IP-10) approached a plateau at ≥3.0 mg/kg. Paired tumor biopsies demonstrated a shift in macrophages from an M2- to an M1-dominant phenotype and increased infiltration of CD8 T cells. PK/PD modeling showed near maximal margination of B cells and a dose-dependent production of IL-12 nearing a plateau at >3.0 mg/kg. The best response was stable disease in 6/27 (22%) patients. Conclusions SL-172154 was tolerable as monotherapy and induced, dose-dependent, and cyclical immune cell activation, increases in multiple serum cytokines, and trafficking of CD40-positive B cells and monocytes following each infusion. The safety, PK, and PD activity support 3.0 mg/kg as a safe and pharmacologically active dose. Trial registration number NCT04406623.