The Fully human anti-CD47 antibody SRF231 exerts dual-mechanism antitumor activity via engagement of the activating receptor CD32a

Preclinical Development of SGN-CD47M: Protease-Activated Antibody Technology Enables Selective Tumor Targeting of the Innate Immune Checkpoint Receptor CD47

CD47 is a cell-surface glycoprotein that is expressed on normal human tissues and plays a key role as a marker of self. Tumor cells have co-opted CD47 overexpression to evade immune surveillance, and thus blockade of CD47 is a highly active area of clinical exploration in oncology. However, clinical development of CD47-targeted agents has been complicated by its robust expression in normal tissues and the toxicities that arise from blocking this inhibitory signal. Furthermore, pro-phagocytic signals are not uniformly expressed in tumors, and antibody blockade alone is often not sufficient to drive antitumor activity. The inclusion of an IgG1 antibody backbone into therapeutic design has been shown to not only serve as an additional pro-phagocytic signal but also exacerbate toxicities in normal tissues. Therefore, a need persists for more selective therapeutic modalities targeting CD47. To address these challenges, we developed SGN-CD47M, a humanized anti-CD47 IgG1 mAb linked to novel masking peptides through linkers designed to be cleaved by active proteases enriched in the tumor microenvironment (TME). Masking technology has the potential to increase the amount of drug that reaches the TME while concomitantly reducing systemic toxicities. We demonstrate that SGN-CD47M is well tolerated in cynomolgus monkeys and displays a 20-fold improvement in tolerability to hematologic toxicities when compared with the unmasked antibody. SGN-CD47M also displays preferential activation in the TME that leads to robust single-agent antitumor activity. For these reasons, SGN-CD47M may have enhanced antitumor activity and improved tolerability relative to existing therapies that target the CD47-signal regulatory protein α interaction.

The Physiological and Therapeutic Role of CD47 in Macrophage Function and Cancer

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.

The Immune Response of Cancer Cells in Breast and Gynecologic Neoplasms

Cancer diseases constitute a major health problem which leads to the death of millions of people annually. They are unique among other diseases because cancer cells can perfectly adapt to the environment that they create themselves. This environment is usually highly hostile and for normal cells it would be hugely difficult to survive, however neoplastic cells not only can survive but also manage to proliferate. One of the reasons is that they can alter immunological pathways which allow them to be flexible and change their phenotype to the one needed in specific conditions. The aim of this paper is to describe some of these immunological pathways that play significant roles in gynecologic neoplasms as well as review recent research in this field. It is of high importance to possess extensive knowledge about these processes, as greater understanding leads to creating more specialized therapies which may prove highly effective in the future.

Development of pharmacological immunoregulatory anti-cancer therapeutics: current mechanistic studies and clinical opportunities

Immunotherapy represented by anti-PD-(L)1 and anti-CTLA-4 inhibitors has revolutionized cancer treatment, but challenges related to resistance and toxicity still remain. Due to the advancement of immuno-oncology, an increasing number of novel immunoregulatory targets and mechanisms are being revealed, with relevant therapies promising to improve clinical immunotherapy in the foreseeable future. Therefore, comprehending the larger picture is important. In this review, we analyze and summarize the current landscape of preclinical and translational mechanistic research, drug development, and clinical trials that brought about next-generation pharmacological immunoregulatory anti-cancer agents and drug candidates beyond classical immune checkpoint inhibitors. Along with further clarification of cancer immunobiology and advances in antibody engineering, agents targeting additional inhibitory immune checkpoints, including LAG-3, TIM-3, TIGIT, CD47, and B7 family members are becoming an important part of cancer immunotherapy research and discovery, as are structurally and functionally optimized novel anti-PD-(L)1 and anti-CTLA-4 agents and agonists of co-stimulatory molecules of T cells. Exemplified by bispecific T cell engagers, newly emerging bi-specific and multi-specific antibodies targeting immunoregulatory molecules can provide considerable clinical benefits. Next-generation agents also include immune epigenetic drugs and cytokine-based therapeutics. Cell therapies, cancer vaccines, and oncolytic viruses are not covered in this review. This comprehensive review might aid in further development and the fastest possible clinical adoption of effective immuno-oncology modalities for the benefit of patients.

TP53-mutated acute myeloid leukemia and myelodysplastic syndrome: biology, treatment challenges, and upcoming approaches

Improved understanding of TP53 biology and the clinicopathological features of TP53-mutated myeloid neoplasms has led to the recognition of TP53-mutated acute myeloid leukemia/myelodysplastic syndrome (TP53m AML/MDS) as a unique entity, characterized by dismal outcomes following conventional therapies. Several clinical trials have investigated combinations of emerging therapies for these patients with the poorest molecular prognosis among myeloid neoplasms. Although some emerging therapies have shown improvement in overall response rates, this has not translated into better overall survival, hence the notion that p53 remains an elusive target. New therapeutic strategies, including novel targeted therapies, immune checkpoint inhibitors, and monoclonal antibodies, represent a shift away from cytotoxic and hypomethylating-based therapies, towards approaches combining non-immune and novel immune therapeutic strategies. The triple combination of azacitidine and venetoclax with either magrolimab or eprenetapopt have demonstrated safety in early trials, with phase III trials currently underway, and promising interim clinical results. This review compiles background on TP53 biology, available and emerging therapies along with their mechanisms of action for the TP53m disease entity, current treatment challenges, and recently published data and status of ongoing clinical trials for TP53m AML/MDS.

Gentulizumab, a novel anti-CD47 antibody with potent antitumor activity and demonstrates a favorable safety profile

BACKGROUND

Targeting CD47/SIRPα axis has emerged as a promising strategy in cancer immunotherapy. Despite the encouraging clinical efficacy observed in hematologic malignancies through CD47-SIRPα blockade, there are safety concerns related to the binding of anti-CD47 antibodies to CD47 on the membrane of peripheral blood cells.

METHODS

In order to enhance the selectivity and therapeutic efficacy of the antibody, we developed a humanized anti-CD47 monoclonal antibody called Gentulizumab (GenSci059). The binding capacity of GenSci059 to CD47 was evaluated using flow cytometry and surface plasmon resonance (SPR) methods, the inhibitory effect of GenSci059 on the CD47-SIRPα interaction was evaluated through competitive ELISA assays. The anti-tumor activity of GenSci059 was assessed using in vitro macrophage models and in vivo patient-derived xenograft (PDX) models. To evaluate the safety profile of GenSci059, binding assays were conducted using blood cells. Additionally, we investigated the underlying mechanisms contributing to the weaker binding of GenSci059 to erythrocytes. Finally, toxicity studies were performed in non-human primates to assess the potential risks associated with GenSci059.

RESULTS

GenSci059 displayed strong binding to CD47 in both human and monkey, and effectively inhibited the CD47-SIRPα interaction. With doses ranging from 5 to 20 mg/kg, GenSci059 demonstrated potent inhibition of the growth of subcutaneous tumor with the inhibition rates ranged from 30.3% to complete regression. Combination of GenSci059 with 2.5 mg/kg Rituximab at a dose of 2.5 mg/kg showed enhanced tumor inhibition compared to monotherapy, exhibiting synergistic effects. GenSci059 exhibited minimal binding to hRBCs compared to Hu5F9-G4. The binding of GenSci059 to CD47 depended on the cyclization of N-terminal pyroglutamic acid and the spatial conformation of CD47, but was not affected by its glycosylation modifications. A maximum tolerated dose (MTD) of 450 mg/kg was observed for GenSci059, and no significant adverse effects were observed in repeated dosages up to 10 + 300 mg/kg, indicating a favorable safety profile.

CONCLUSION

GenSci059 selectively binds to CD47, effectively blocks the CD47/SIRPα axis signaling pathway and enhances the phagocytosis effects of macrophages toward tumor cells. This monoclonal antibody demonstrates potent antitumor activity and exhibits a favorable safety profile, positioning it as a promising and effective therapeutic option for cancer.

Targeting CD47-SIRPα axis for Hodgkin and non-Hodgkin lymphoma immunotherapy

The interaction between cluster of differentiation 47 (CD47) and signal regulatory protein α (SIRPα) protects healthy cells from macrophage attack, which is crucial for maintaining immune homeostasis. Overexpression of CD47 occurs widely across various tumor cell types and transmits the "don't eat me" signal to macrophages to avoid phagocytosis through binding to SIRPα. Blockade of the CD47-SIRPα axis is therefore a promising approach for cancer treatment. Lymphoma is the most common hematological malignancy and is an area of unmet clinical need. This review mainly described the current strategies targeting the CD47-SIRPα axis, including antibodies, SIRPα Fc fusion proteins, small molecule inhibitors, and peptides both in preclinical studies and clinical trials with Hodgkin lymphoma and non-Hodgkin lymphoma.

CC-96673 (BMS-986358), an affinity-tuned anti-CD47 and CD20 bispecific antibody with fully functional fc, selectively targets and depletes non-Hodgkin's lymphoma

Cluster of differentiation 47 (CD47) is a transmembrane protein highly expressed in tumor cells that interacts with signal regulatory protein alpha (SIRPα) and triggers a "don't eat me" signal to the macrophage, inhibiting phagocytosis and enabling tumor escape from immunosurveillance. The CD47-SIRPα axis has become an important target for cancer immunotherapy. To date, the advancement of CD47-targeted modalities is hindered by the ubiquitous expression of the target, often leading to rapid drug elimination and hematologic toxicity including anemia. To overcome those challenges a bispecific approach was taken. CC-96673, a humanized IgG1 bispecific antibody co-targeting CD47 and CD20, is designed to bind CD20 with high affinity and CD47 with optimally lowered affinity. As a result of the detuned CD47 affinity, CC-96673 selectively binds to CD20-expressing cells, blocking the interaction of CD47 with SIRPα. This increased selectivity of CC-96673 over monospecific anti-CD47 approaches allows for the use of wild-type IgG1 Fc, which engages activating crystallizable fragment gamma receptors (FcγRs) to fully potentiate macrophages to engulf and destroy CD20+ cells, while sparing CD47+CD20- normal cells. The combined targeting of anti-CD20 and anti-CD47 results in enhanced anti- tumor activity compared to anti-CD20 targeting antibodies alone. Furthermore, preclinical studies have demonstrated that CC-96673 exhibits acceptable pharmacokinetic properties with a favorable toxicity profile in non-human primates. Collectively, these findings define CC-96673 as a promising CD47 × CD20 bispecific antibody that selectively destroys CD20+ cancer cells via enhanced phagocytosis and other effector functions.

Discovery of Anti-CD47 Peptides as Innate Immune Checkpoint Inhibitors

Cancer immunotherapy targeting adaptive immune cells has been attracting considerable interest due to its great success in treating multiple cancers. Recently, there is also increasing interest in agents that can stimulate innate immune cell activities. Immune checkpoint inhibitors targeting innate immune cells can block inhibitory interactions ('don't eat me' signals) between tumor cells and phagocytes. CD47 is a transmembrane protein overexpressed in various cancers and acts as a potent 'do not eat me' signal that contributes to the immune evasion of cancer cells. Anti-CD47 peptides that can bind to CD47 and block CD47/SIRPα interaction were discovered using a novel phage display biopanning strategy. Anti-CD47 peptides enhanced the macrophage-mediated phagocytosis of NCI-H82 tumor cells in vitro. Unlike anti-CD47 antibodies, these peptides do not induce the agglutination of RBCs. Moreover, anti-CD47 peptides exhibit high specificity for MC-38 cancer cells expressing CD47. CMP-22 peptide showed the ability to increase the antitumor activity of doxorubicin and extends the survival of CT26 tumor-bearing mice. The discovered anti-CD47 peptides can be considered potential candidates for cancer immunotherapy by blocking the CD47/SIRPα interaction, especially in combination with chemotherapy, to elicit synergistic effects.

Signaling pathways in macrophages: molecular mechanisms and therapeutic targets

Macrophages play diverse roles in development, homeostasis, and immunity. Accordingly, the dysfunction of macrophages is involved in the occurrence and progression of various diseases, such as coronavirus disease 2019 and atherosclerosis. The protective or pathogenic effect that macrophages exert in different conditions largely depends on their functional plasticity, which is regulated via signal transduction such as Janus kinase-signal transducer and activator of transcription, Wnt and Notch pathways, stimulated by environmental cues. Over the past few decades, the molecular mechanisms of signaling pathways in macrophages have been gradually elucidated, providing more alternative therapeutic targets for diseases treatment. Here, we provide an overview of the basic physiology of macrophages and expound the regulatory pathways within them. We also address the crucial role macrophages play in the pathogenesis of diseases, including autoimmune, neurodegenerative, metabolic, infectious diseases, and cancer, with a focus on advances in macrophage-targeted strategies exploring modulation of components and regulators of signaling pathways. Last, we discuss the challenges and possible solutions of macrophage-targeted therapy in clinical applications. We hope that this comprehensive review will provide directions for further research on therapeutic strategies targeting macrophage signaling pathways, which are promising to improve the efficacy of disease treatment.

Perspectives of targeting LILRB1 in innate and adaptive immune checkpoint therapy of cancer

Immune checkpoint blockade is a compelling approach in tumor immunotherapy. Blocking inhibitory pathways in T cells has demonstrated clinical efficacy in different types of cancer and may hold potential to also stimulate innate immune responses. A novel emerging potential target for immune checkpoint therapy is leukocyte immunoglobulin-like receptor subfamily B member 1 (LILRB1). LILRB1 belongs to the superfamily of leukocyte immunoglobulin-like receptors and exerts inhibitory functions. The receptor is expressed by a variety of immune cells including macrophages as well as certain cytotoxic lymphocytes and contributes to the regulation of different immune responses by interaction with classical as well as non-classical human leukocyte antigen (HLA) class I molecules. LILRB1 has gained increasing attention as it has been demonstrated to function as a phagocytosis checkpoint on macrophages by recognizing HLA class I, which represents a 'Don't Eat Me!' signal that impairs phagocytic uptake of cancer cells, similar to CD47. The specific blockade of the HLA class I:LILRB1 axis may provide an option to promote phagocytosis by macrophages and also to enhance cytotoxic functions of T cells and natural killer (NK) cells. Currently, LILRB1 specific antibodies are in different stages of pre-clinical and clinical development. In this review, we introduce LILRB1 and highlight the features that make this immune checkpoint a promising target for cancer immunotherapy.

Anti-Tumor Strategies by Harnessing the Phagocytosis of Macrophages

Macrophages are essential for the human body in both physiological and pathological conditions, engulfing undesirable substances and participating in several processes, such as organism growth, immune regulation, and maintenance of homeostasis. Macrophages play an important role in anti-bacterial and anti-tumoral responses. Aberrance in the phagocytosis of macrophages may lead to the development of several diseases, including tumors. Tumor cells can evade the phagocytosis of macrophages, and "educate" macrophages to become pro-tumoral, resulting in the reduced phagocytosis of macrophages. Hence, harnessing the phagocytosis of macrophages is an important approach to bolster the efficacy of anti-tumor treatment. In this review, we elucidated the underlying phagocytosis mechanisms, such as the equilibrium among phagocytic signals, receptors and their respective signaling pathways, macrophage activation, as well as mitochondrial fission. We also reviewed the recent progress in the area of application strategies on the basis of the phagocytosis mechanism, including strategies targeting the phagocytic signals, antibody-dependent cellular phagocytosis (ADCP), and macrophage activators. We also covered recent studies of Chimeric Antigen Receptor Macrophage (CAR-M)-based anti-tumor therapy. Furthermore, we summarized the shortcomings and future applications of each strategy and look into their prospects with the hope of providing future research directions for developing the application of macrophage phagocytosis-promoting therapy.

[Latest Findings on the Role of CD47 in Tumor Immune Evasion and Related Targeted Therapies]

CD47 is an immunoglobulin that is overexpressed on the surface of a variety of cancer cells. CD47 forms a signaling complex with signal regulatory protein alpha (SIRPα), prompting the escape of cancer cells from macrophage-mediated phagocytosis. In recent years, CD47 has been shown to be highly expressed in many types of solid tumors and is associated with poor prognosis in patients. More and more studies have shown that inhibition of the CD47-SIRPα signaling pathway can promote adaptive immune responses and enhance the phagocytosis of tumor cells by macrophages. Humanized anti-CD47 IgG4 monoclonal antibody has been studied in clinical trials for the treatment of a variety of advanced solid tumors and lymphomas, demonstrating a sound safety profile and achieving partial remission in some patients. In this review we discuss the structure and function of CD47 and the mechanism of CD47 regulation in tumors, summarize the research progress in therapeutic antibody drugs targeting CD47 and a bottleneck in research that targeted drugs are more prone to result in serious adverse effects, and evaluated the potential of the applying CD47-SIRPα signaling pathway in anti-cancer therapy.

Blocking CD47-SIRPα Signal Axis as Promising Immunotherapy in Ovarian Cancer

Among the three primary gynecological malignancies, ovarian cancer has the lowest incidence but the worst prognosis. Because of the poor prognosis of ovarian cancer patients treated with existing treatments, immunotherapy is emerging as a potentially ideal alternative to surgery, chemotherapy, and targeted therapy. Among immunotherapies, immune checkpoint inhibitors have been the most thoroughly studied, and many drugs have been successfully used in the clinic. CD47, a novel immune checkpoint, provides insights into ovarian cancer immunotherapy. This review highlights the mechanisms of tumor immune evasion via CD47-mediated inhibition of phagocytosis and provides a comprehensive insight into the progress of the relevant targeted agents in ovarian cancer.

Promising drugs and treatment options for pediatric and adolescent patients with Hodgkin lymphoma

Currently-available therapies for newly-diagnosed pediatric and adolescent patients with Hodgkin lymphoma result in >95% survival at 5 years. Long-term survivors may suffer from long-term treatment-related side effects, however, so the past 20 years have seen clinical trials for children and adolescents with HL gradually abandon the regimens used in adults in an effort to improve this situation. Narrower-field radiotherapy can reduce long-term toxicity while maintaining good tumor control. Various risk-adapted chemo-radiotherapy strategies have been used. Early assessment of tumor response with interim positron emission tomography and/or measuring metabolic tumor volume has been used both to limit RT in patients with favorable characteristics and to adopt more aggressive therapies in patients with a poor response. Most classical Hodgkin's lymphoma relapses occur within 3 years of initial treatment, while relapses occurring 5 years or more after diagnosis are rare. As the outcome for patients with relapsed/refractory classical Hodgkin lymphoma remains unsatisfactory, new drugs have been proposed for its prevention or treatment. This review summarizes the important advances made in recent years in the management of pediatric and adolescent with classical Hodgkin lymphoma, and the novel targeted treatments for relapsed and refractory classical Hodgkin lymphoma.

Ligufalimab, a novel anti-CD47 antibody with no hemagglutination demonstrates both monotherapy and combo antitumor activity

BACKGROUND

CD47 is a widely expressed transmembrane glycoprotein that delivers an antiphagocytic signal on macrophages through its interaction with SIRPα. CD47 is highly expressed in cancer cells and its overexpression is correlated with poor prognosis. CD47 blocking antibodies are actively being developed worldwide for cancer therapy, and the most challenging concern is associated with hematotoxicity. Ligufalimab (AK117) is a novel humanized IgG4 anti-CD47 antibody without hemagglutination effect. Blockade of CD47-SIRPα pathway by AK117 leads to a promising therapeutic strategy for cancer treatment with unique safety features.

METHODS

AK117 was discovered through a screening hierarchy excluding hemagglutination. AK117 was characterized by detecting CD47-SIRPα blocking potential. Its effect on human red blood cells was examined and the mechanism of its binding with erythrocytes was studied. The abilities of AK117 and its combination with various opsonizing antibodies to promote macrophage-dependent phagocytosis of multiple human tumor cells were determined using fluorescence microscopy and flow cytometry. In vivo, the antitumor efficacy of AK117 monotherapy and combination with AK112 (an anti-PD-1/VEGF-A bispecific antibody) was assessed in a variety of xenograft models. Toxicologic studies were evaluated in non-human primates.

RESULTS

AK117 bound to CD47 with high affinity and blocked the CD47-SIRPα interaction. AK117 did not induce hemagglutination and showed significantly lower degree of erythrophagocytosis compared with Hu5F9-G4, and this mechanism of hemagglutination resistance might be related to the binding conformation. AK117 enhanced macrophage-mediated phagocytosis in both hematologic cancer and solid tumor cell lines as a single agent or in combination with cetuximab and rituximab in vitro, respectively. The antitumor effects of AK117 as a single agent or in combination with AK112 were also encouraging in various xenograft models. In non-human primates, AK117 showed less hematotoxicity compared with Hu5F9-G4.

CONCLUSIONS

AK117 eliminated hemagglutination and also enabled to maintain full effectiveness of CD47 blockade on tumor cells, which resulted in excellent antitumor efficacy and favorable safety profile of AK117. A series of clinical trials of AK117 as a therapeutic agent in combination with various agents such as AK112 are in progress for the treatment of multiple hematologic malignancies and solid tumors.

Targeting CXCR4 and CD47 Receptors: An Overview of New and Old Molecules for a Biological Personalized Anticancer Therapy

Biological therapy, with its multifaceted applications, has revolutionized the treatment of tumors, mainly due to its ability to exclusively target cancer cells and reduce the adverse effects on normal tissues. This review focuses on the therapies targeting the CXCR4 and CD47 receptors. We surveyed the results of early clinical trials testing compounds classified as nonpeptides, small peptides, CXCR4 antagonists or specific antibodies whose activity reduces or completely blocks the intracellular signaling pathways and cell proliferation. We then examined antibodies and fusion proteins against CD47, the receptor that acts as a “do not eat me” signal to phagocytes escaping immune surveillance. Despite these molecules being tested in early clinical trials, some drawbacks are emerging that impair their use in practice. Finally, we examined the ImmunoGenic Surrender mechanism that involves crosstalk and co-internalization of CXCR4 and CD47 upon engagement of CXCR4 by ligands or other molecules. The favorable effect of such compounds is dual as CD47 surface reduction impact on the immune response adds to the block of CXCR4 proliferative potential. These results suggest that a combination of different therapeutic approaches has more beneficial effects on patients’ survival and may pave the way for new accomplishments in personalized anticancer therapy.

Bortezomib-resistant multiple myeloma patient-derived xenograft is sensitive to anti-CD47 therapy

Multiple myeloma (MM) remains an incurable hematologic malignancy due to its frequent drug resistance and relapse. Cluster of Differentiation 47 (CD47) is reported to be highly expressed on MM cells, suggesting that the blockade of CD47 signaling pathway could be a potential therapeutic candidate for MM. In this study, we developed a bortezomib-resistant myeloma patient-derived xenograft (PDX) from an extramedullary pleural effusion myeloma patient sample. Notably, anti-CD47 antibody treatments significantly inhibited tumor growth not only in MM cell line-derived models, including MM.1S and NCI-H929, but also in the bortezomib-resistant MM PDX model. Flow cytometric data showed that anti-CD47 therapy promoted the polarization of tumor-associated macrophages from an M2- to an M1-like phenotype. In addition, anti-CD47 therapy decreased the expression of pro-angiogenic factors, increased the expression of anti-angiogenic factors, and improved tumor vascular function, suggesting that anti-CD47 therapy induces tumor vascular normalization. Taken together, these data show that anti-CD47 antibody therapy reconditions the tumor immune microenvironment and inhibits the tumor growth of bortezomib-resistant myeloma PDX. Our findings suggest that CD47 is a potential new target to treat bortezomib-resistant MM.

CD47: Beyond an immune checkpoint in cancer treatment

The transmembrane protein, CD47, is recognized as an important innate immune checkpoint, and CD47-targeted drugs have been in development with the aim of inhibiting the interaction between CD47 and the regulatory glycoprotein SIRPα, for antitumor immunotherapy. Further, CD47 mediates other essential functions such as cell proliferation, caspase-independent cell death (CICD), angiogenesis and other integrin-activation-dependent cell phenotypic responses when bound to thrombospondin-1 (TSP-1) or other ligands. Mounting strategies that target CD47 have been developed in pre-clinical and clinical trials, including antibodies, small molecules, siRNAs, and peptides, and some of them have shown great promise in cancer treatment. Herein, the authors endeavor to provide a retrospective of ligand-mediated CD47 regulatory mechanisms, their roles in controlling antitumor intercellular and intracellular signal transduction, and an overview of CD47-targetd drug design.

Immunotherapy for Pediatric Acute Lymphoblastic Leukemia: Recent Advances and Future Perspectives

Pediatric acute lymphoblastic leukemia (ALL) is the most common subtype of childhood leukemia, which is characterized by the abnormal proliferation and accumulation of immature lymphoid cell in the bone marrow. Although the long-term survival rate for pediatric ALL has made significant progress over years with the development of contemporary therapeutic regimens, patients are still suffered from relapse, leading to an unsatisfactory outcome. Since the immune system played an important role in the progression and relapse of ALL, immunotherapy including bispecific T-cell engagers and chimeric antigen receptor T cells has been demonstrated to be capable of enhancing the immune response in pediatric patients with refractory or relapsed B-cell ALL, and improving the cure rate of the disease and patients’ quality of life, thus receiving the authorization for market. Nevertheless, the resistance and toxicities associated with the current immunotherapy remains a huge challenge. Novel therapeutic options to overcome the above disadvantages should be further explored. In this review, we will thoroughly discuss the emerging immunotherapeutics for the treatment of pediatric ALL, as well as side-effects and new development.

Are We Moving the Needle for Patients with TP53-Mutated Acute Myeloid Leukemia?

The currently available therapeutic options for patients with TP53-mutated acute myeloid leukemia (AML) are insufficient, as they translate to a median overall of only 6-9 months, and less than 10% of patients undergoing the most aggressive treatments, such as intensive induction therapy and allogeneic hematopoietic stem cell transplantation, will be cured. The lack of clear differences in outcomes with different treatments precludes the designation of a standard of care. Recently, there has been growing attention on this critical area of need by way of better understanding the biology of TP53 alterations and the disparities in outcomes among patients in this molecular subgroup, reflected in the development and testing of agents with novel mechanisms of action. Promising preclinical and efficacy data exist for therapies that are directed at the p53 protein rendered dysfunctional via mutation or that inhibit the CD47/SIRPα axis or other immune checkpoints such as TIM-3. In this review, we discuss recently attractive and emerging therapeutic agents, their preclinical rationale and the available clinical data as a monotherapy or in combination with the currently accepted backbones in frontline and relapsed/refractory settings for patients with TP53-mutated AML.

CD47xCD19 bispecific antibody triggers recruitment and activation of innate immune effector cells in a B-cell lymphoma xenograft model

Background

CD47/SIRPα axis is recognized as an innate immune checkpoint and emerging clinical data validate the interest of interrupting this pathway in cancer, particularly in hematological malignancies. In preclinical models, CD47/SIRPα blocking agents have been shown to mobilize phagocytic cells and trigger adaptive immune responses to eliminate tumors. Here, we describe the mechanisms afforded by a CD47xCD19 bispecific antibody (NI-1701) at controlling tumor growth in a mouse xenograft B-cell lymphoma model.

Methods

The contribution of immune effector cell subsets behind the antitumor activity of NI-1701 was investigated using flow cytometry, transcriptomic analysis, and in vivo immune-cell depletion experiments.

Results

We showed that NI-1701 treatment transformed the tumor microenvironment (TME) into a more anti-tumorigenic state with increased NK cells, monocytes, dendritic cells (DC) and MHCII^hi tumor-associated macrophages (TAMs) and decreased granulocytic myeloid-derived suppressor cells. Notably, molecular analysis of isolated tumor-infiltrating leukocytes following NI-1701 administration revealed an upregulation of genes linked to immune activation, including IFNγ and IL-12b. Moreover, TAM-mediated phagocytosis of lymphoma tumor cells was enhanced in the TME in the presence of NI-1701, highlighting the role of macrophages in tumor control. In vivo cell depletion experiments demonstrated that both macrophages and NK cells contribute to the antitumor activity. In addition, NI-1701 enhanced dendritic cell-mediated phagocytosis of tumor cells in vitro, resulting in an increased cross-priming of tumor-specific CD8 T cells.

Conclusions

The study described the mechanisms afforded by the CD47xCD19 bispecific antibody, NI-1701, at controlling tumor growth in lymphoma mouse model. NI-1701 is currently being evaluated in a Phase I clinical trial for the treatment of refractory or relapsed B-cell lymphoma (NCT04806035).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40164-022-00279-w.

CD47-SIRPα-targeted therapeutics: status and prospects

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.

Targeting macrophage-mediated tumor cell phagocytosis: An overview of phagocytosis checkpoints blockade, nanomedicine intervention, and engineered CAR-macrophage therapy

Immunotherapy has been developing at an unprecedented speed with promising therapeutic outcomes in the wide spectrum of cancers. Up until now, most immunotherapies have focused on adaptive immunity; however, investigating the potential of macrophage phagocytosis and consequent adaptive immune cross-priming has led to a growing interest in exploiting macrophages in cancer therapy. In light of the positive evidence from preclinical studies and early clinical data, targeting macrophage phagocytosis has become a promising therapeutic strategy. Here, we review therapies based on harnessing and amplifying macrophage phagocytosis, such as blocking phagocytosis checkpoints and exploiting nanoparticles as efficient approaches in elevating macrophages-mediated phagocytosis. The present study introduces CAR-macrophage as the state-of-the-art modality serving as the bridge between the innate and adaptive immune system to mount a superior anti-tumor response in the treatment of cancer. We also take a look at the recent reports of therapies based on CAR-engineered macrophages with the hope of providing a future research direction for expanding the application of CAR-macrophage therapy.

CD47-targeted cancer immunogene therapy: Secreted SIRPα-Fc fusion protein eradicates tumors by macrophage and NK cell activation

CD47 protects healthy cells from macrophage attack by binding to signal regulatory protein α (SIRPα), while its upregulation in cancer prevents immune clearance. Systemic treatment with CD47 antibodies requires a weakened Fc-mediated effector function or lower CD47-binding affinity to prevent side effects. Our approach combines “the best of both worlds,” i.e., maximized CD47 binding and full Fc-mediated immune activity, by exploiting gene therapy for paracrine release. We developed a plasmid vector encoding for the secreted fusion protein sCV1-hIgG1, comprising highly efficient CD47-blocking moiety CV1 and Fc domain of human immunoglobulin G1 (IgG1) with maximized immune activation. sCV1-hIgG1 exhibited a potent bystander effect, blocking CD47 on all cells via fusion protein secreted from only a fraction of cells or when transferring transfection supernatant to untransfected cells. The CpG-free plasmid ensured sustained secretion of sCV1-hIgG1. In orthotopic human triple-negative breast cancer in CB17-severe combined immunodeficiency (SCID) mice, ex vivo transfection significantly delayed tumor growth and eradicated one-third of tumors. In intratumoral transfection experiments, CD47 blockage and increased migration of macrophages into the tumor were observed within 17 h of a single injection. Natural killer (NK) cell-mediated lysis of sCV1-hIgG1-expressing cells was demonstrated in vitro. Taken together, this approach also opens the opportunity to block, in principle, any immune checkpoints.

Targeting CD47 for cancer immunotherapy

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/SIRPα pathway mediates cancer immune escape and immunotherapy

The adaptive immune checkpoints such as PD-1(programmed death-1)/PD-L1 (programmed death-ligand 1) play an important role in cancer immunotherapy, whereas increasing evidence suggests that cancer cell evades immune surveillance by innate immune checkpoints such as SIRPα (signal-regulatory protein α)/CD47 (cluster of differentiation 47). In multiple types of cancer cells and solid tumor tissues, highly expressed CD47 protein level has been observed, which is triggered by some transcription factors including NFκB, Myc, and HIF. As a transmembrane protein, the binding of CD47 to SIRPα ligand on phagocytes results in phagocytosis resistance and cancer cell immune escape. In contrast, CD47-SIRPα interaction blockade enhances cancer cell clearance by phagocytes such as macrophages and dendritic cells (DCs) to activate an innate immune response, whereas this process could promote antigen cross-presentation by antigen present cells (APCs) leading to T cell priming, consequently, activates an adaptive antitumor immune response. In this review, we discussed the current SIRPα-CD47 axis-mediated cancer cell immune escape and immunotherapy, which could provide an effective antitumor strategy by the innate and adaptive immune response.

CD47-targeting antibodies as a novel therapeutic strategy in hematologic malignancies

CD47 is a surface glycoprotein expressed by host cells to impede phagocytosis upon binding to macrophage SIRPα, thereby represents an immune checkpoint known as the "don't-eat-me" signal. However, accumulating evidence shows that solid and hematologic tumor cells overexpress CD47 to escape immune surveillance. Thus, targeting the CD47-SIRPa axis by limiting the activity of this checkpoint has emerged as a key area of research. In this review, we will provide an update on the landscape of CD47-targeting antibodies for hematological malignancies, including monoclonal and bi-specific antibodies, with a special emphasis on agents in clinical trials and novel approaches to overcome toxicity.

Modulation of CD47-SIRPα innate immune checkpoint axis with Fc-function detuned anti-CD47 therapeutic antibody

Cluster of differentiation 47 (CD47) is a transmembrane protein ubiquitously expressed on human cells but overexpressed on many different tumor cells. The interaction of CD47 with signal-regulatory protein alpha (SIRPα) triggers a "don't eat me" signal to the macrophage, inhibiting phagocytosis. Thus, overexpression of CD47 enables tumor cells to escape from immune surveillance via the blockade of phagocytic mechanisms. We report here the development and characterization of CC-90002, a humanized anti-CD47 antibody. CC-90002 is unique among previously reported anti-CD47 bivalent antibodies that it does not promote hemagglutination while maintaining high-affinity binding to CD47 and inhibition of the CD47-SIRPα interaction. Studies in a panel of hematological cancer cell lines showed concentration-dependent CC-90002-mediated phagocytosis in acute lymphoblastic leukemia, acute myeloid leukemia (AML), lenalidomide-resistant multiple myeloma (MM) cell lines and AML cells from patients. In vivo studies with MM cell line-derived xenograft models established in immunodeficient mice demonstrated significant dose-dependent antitumor activity of CC-90002. Treatment with CC-90002 significantly prolonged survival in an HL-60-disseminated AML model. Mechanistic studies confirmed the binding of CC-90002 to tumor cells and concomitant recruitment of F4-80 positive macrophages into the tumor and an increase in expression of select chemokines and cytokines of murine origin. Furthermore, the role of macrophages in the CC-90002-mediated antitumor activity was demonstrated by transient depletion of macrophages with liposome-clodronate treatment. In non-human primates, CC-90002 displayed acceptable pharmacokinetic properties and a favorable toxicity profile. These data demonstrate the potential activity of CC-90002 across hematological malignancies and provided basis for clinical studies CC-90002-ST-001 (NCT02367196) and CC-90002-AML-001 (NCT02641002).

Innate Immune Checkpoint Inhibitors: The Next Breakthrough in Medical Oncology?

While immunotherapy has revolutionized the treatment of many types of advanced cancer, most patients still do not derive benefit. The currently available immune checkpoint inhibitors target the adaptive immune system, generating a T-cell antitumor response. However, an antitumor immune response depends on a complex interplay of both innate and adaptive immune cells. The innate immune system is a promising new target, and innate immune checkpoint inhibitors can disrupt inhibitory interactions ("don't eat me" signals) between tumor and both phagocytes and natural killer cells. The checkpoint inhibitor may also provide a stimulatory interaction ("eat me" signal), or this can be achieved through use of combination therapy. This generates antitumor effector functions including phagocytosis, natural cytotoxicity, antibody-dependent effects, and synergistic activation of the adaptive immune system via antigen presentation. This is a rapidly expanding area of drug development, either alone or in combination (with anticancer antibodies or adaptive immune checkpoint inhibitors). Here, we comprehensively review the mechanism of action and up-to-date solid tumor clinical trial data of the drugs targeting phagocytosis checkpoints (SIRPα/CD47, LILRB1/MHC-I, and LILRB2/MHC-I) and natural killer-cell checkpoints (TIGIT/CD112 + CD155, PVRIG/CD112, KIRs/MHC-I, and NKG2A-CD94/HLA-E). Innate immune checkpoint inhibitors could once again revolutionize immune-based cancer therapies.

Harnessing and Enhancing Macrophage Phagocytosis for Cancer Therapy

Cancer immunotherapy has revolutionized the paradigm for the clinical management of cancer. While FDA-approved cancer immunotherapies thus far mainly exploit the adaptive immunity for therapeutic efficacy, there is a growing appreciation for the importance of innate immunity in tumor cell surveillance and eradication. The past decade has witnessed macrophages being thrust into the spotlight as critical effectors of an innate anti-tumor response. Promising evidence from preclinical and clinical studies have established targeting macrophage phagocytosis as an effective therapeutic strategy, either alone or in combination with other therapeutic moieties. Here, we review the recent translational advances in harnessing macrophage phagocytosis as a pivotal therapeutic effort in cancer treatment. In addition, this review emphasizes phagocytosis checkpoint blockade and the use of nanoparticles as effective strategies to potentiate macrophages for phagocytosis. We also highlight chimeric antigen receptor macrophages as a next-generation therapeutic modality linking the closely intertwined innate and adaptive immunity to induce efficacious anti-tumor immune responses.

CD47 (Cluster of differentiation 47): an anti-phagocytic receptor with a multitude of signaling functions

CD47 is a tumor-associated antigen best known for its ability to bind counter-receptors on the surface of professional phagocytes as an immune-evasion strategy. ⁣Recently, CD47 has been shown to play a role as a signaling receptor, involving a number of cell physiological processes.⁣⁣ This review provides a comprehensive survey of the signaling pathways triggered by CD47 ligand-mediated cell death in tumor cells. Such an understanding should lead to improvement of CD47-targeted anti-tumor therapeutics able to both neutralize the anti-phagocytic role and trigger autonomous tumor cell death.

CD47 as a Potential Target to Therapy for Infectious Diseases

The integrin associated protein (CD47) is a widely and moderately expressed glycoprotein in all healthy cells. Cancer cells are known to induce increased CD47 expression. Similar to cancer cells, all immune cells can upregulate their CD47 surface expression during infection. The CD47-SIRPa interaction induces an inhibitory effect on macrophages and dendritic cells (dendritic cells) while CD47-thrombospondin-signaling inhibits T cells. Therefore, the disruption of the CD47 interaction can mediate several biologic functions. Upon the blockade and knockout of CD47 reveals an immunosuppressive effect of CD47 during LCMV, influenza virus, HIV-1, mycobacterium tuberculosis, plasmodium and other bacterial pneumonia infections. In our recent study we shows that the blockade of CD47 using the anti-CD47 antibody increases the activation and effector function of macrophages, dendritic cells and T cells during viral infection. By enhancing both innate and adaptive immunity, CD47 blocking antibody promotes antiviral effect. Due to its broad mode of action, the immune-stimulatory effect derived from this antibody could be applicable in nonresolving and (re)emerging infections. The anti-CD47 antibody is currently under clinical trial for the treatment of cancer and could also have amenable therapeutic potential against infectious diseases. This review highlights the immunotherapeutic targeted role of CD47 in the infectious disease realm.

Preclinical and Clinical Development of Therapeutic Antibodies Targeting Functions of CD47 in the Tumor Microenvironment

CD47 is a ubiquitously expressed cell surface glycoprotein that functions as a signaling receptor for thrombospondin-1 and as the counter-receptor for signal regulatory protein-α (SIRPα). Engaging SIRPα on macrophages inhibits phagocytosis, and CD47 thereby serves as a physiological marker of self. However, elevated CD47 expression on some cancer cells also protects tumors from innate immune surveillance and limits adaptive antitumor immunity via inhibitory SIRPα signaling in antigen presenting cells. CD47 also mediates inhibitory thrombospondin-1 signaling in vascular cells, T cells, and NK cells, and blocking inhibitory CD47 signaling on cytotoxic T cells directly increases tumor cell killing. Therefore, CD47 functions as an innate and adaptive immune checkpoint. These findings have led to the development of antibodies and other therapeutic approaches to block CD47 functions in the tumor microenvironment. Preclinical studies in mice demonstrated that blocking CD47 can limit the growth of hematologic malignancies and solid tumors and enhance the efficacy of conventional chemotherapy, radiation therapy, and some targeted cancer therapies. Humanized CD47 antibodies are showing promise in early clinical trials, but side effects related to enhanced phagocytic clearance of circulating blood cells remain a concern. Approaches to circumvent these include antibody preloading strategies, development of antibodies that recognize tumor-specific epitopes of CD47, SIRPα antibodies, and bivalent antibodies that restrict CD47 blockade to specific tumor cells. Preclinical and clinical development of antibodies and related biologics that inhibit CD47/SIRPα signaling are reviewed, including strategies to combine these agents with various conventional and targeted therapeutics to improve patient outcome for various cancers.