Research Progress in Tumor Immunotherapy Of Star Target CD47

Contact: Audrey Hu audrey.hu@wecistanche.com

CD47, a transmembrane protein, is a cell surface glycoprotein molecule that belongs to the immunoglobulin superfamily and binds to a variety of proteins, including integrin, thrombospondin-1, and signal-regulated protein alpha (SIRPα).

In 2009, Professor Irving L. Weissman, a well-known cancer stem cell expert at Stanford University School of Medicine, published a paper in Cell, showing that tumor cells highly express CD47, which releases "don't eat me" by binding to signal regulatory protein alpha (SIRPα) on the surface of macrophages. signal, thereby preventing tumor cells from being phagocytosed by macrophages.

In recent years, accumulating data have shown that the CD47-SIRPα axis is a key immune checkpoint in different cancers including hematological malignancies, similar to PD-1/PD-L1 in solid tumors. CD47-SIRPα blockade has emerged as a next-generation immune checkpoint blockade strategy for various malignancies after PD-1/PD-L1.

However, before becoming the current new focus of the field, the prospects for CD47 were rather bleak a few years ago.

In 2017, the European Phase I clinical trial of CD47 mAb Ti-061 (2016-004372-22) was terminated. Then, in 2018, the CD47 monoclonal antibody CC-90002 failed a Phase I clinical trial (NCT0264102). Severe hemolysis by CD47 monoclonal antibody is a major problem in these clinical failures. Repeated setbacks make the prospects for developing CD47 for cancer therapy very pessimistic.

In 2019, when the CD47 monoclonal antibody magrolimab and azacitidine were combined in the treatment of acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS), it showed excellent and sustainable efficacy with manageable hematological toxicity. Since then, the development of CD47-targeted drugs has gained a new lease of life and entered a new era.

Structure and ligands of CD47

CD47 is a glycosylated transmembrane protein expressed in various cell types. CD47 belongs to the immunoglobulin superfamily and is a supramolecular complex composed of integrins, G proteins and cholesterol. The structure of CD47 includes an extracellular variable region that interacts with corresponding ligands, a transmembrane region formed by a highly hydrophobic transmembrane segment, and a hydrophilic carboxyl-terminal intracellular region. After activation of CD47, it can mediate cell proliferation, migration, phagocytosis and A series of processes including apoptosis, immune homeostasis and inhibition of NO signaling.

Ligands for CD47 include SIRPα, thrombospondin-1 (TSP-1), and integrins (αvβ3 and α2β1). SIRPα, also known as SHPS-1, is a transmembrane protein whose extracellular domain contains three immunoglobulin superfamily-like domains: an NH2-terminal V-type domain and two C1-like IgSF domains, NH2 The terminal domain is capable of binding to CD47. SIRPα is highly expressed on the membrane of myeloid cells, such as macrophages, granulocytes, monocytes and myeloid dendritic cells. It regulates cell migration and phagocytic activity, as well as immune homeostasis and neural network formation. TSP-1 is a homotrimeric multi-domain extracellular matrix glycoprotein belonging to the extracellular secretory protein family, consisting of a variety of domains known to bind extracellular matrix components and cell surface receptors. TSP-1 is secreted by platelets, monocytes, macrophages and various other non-hematopoietic cells. Binding of TSP-1 to CD47 results in changes in intracellular calcium ion concentrations and cyclic adenylate/cyclophosphine concentrations that regulate cell survival and migration, and TSP-1 also induces cellular responses to tissue damage.

The pathophysiological function of CD47

Cancer cells take advantage of the "don't eat me" function of CD47 and express higher levels of CD47 on the surface than non-malignant cells; numerous studies have shown that CD47 is overexpressed in different types of tumors, including myeloma, leiomyosarcoma, acute lymphoblastic leukemia , non-Hodgkin lymphoma, breast cancer, osteosarcoma, head and neck squamous cell carcinoma. High CD47 expression levels correlate with treatment response and prognosis of cancer progression.

The expression of CD47 is used by macrophages to distinguish 'self' or 'non-self'. CD47 is expressed on the surface of non-malignant cells and various cancer cells, and can bind to the SIRPα transmembrane protein on myeloid cells (especially macrophages) to form the CD47-SIRPα signaling complex. The extracellular IgV domain of SIRPα binds to CD47, resulting in tyrosine phosphorylation at the intracellular ITIM motif; SIRPα also binds to the SH2 domain containing tyrosine phosphatase, both of which signal inhibition of myosin IIA accumulates at phagocytic synapses and promotes the release of "don't eat me" signals that inhibit macrophage-mediated phagocytosis and protect normal cells from damage by the immune system.

Conversely, when surface expression of CD47 is reduced, the CD47-SIRPα signaling pathway is attenuated, and macrophages can move toward and engulf these cells. CD47 on normal erythrocytes binds to SIRPα on the surface of macrophages to generate inhibitory signals that prevent phagocytosis, but when erythrocytes become senescent, the expression level of CD47 decreases, and senescent erythrocytes deficient in CD47 are considered foreign and are removed by erythrocytes in the spleen. Macrophages are rapidly cleared. CD47 and its ligands not only regulate immune responses, but also mediate various pathophysiological processes, such as neutrophil chemotaxis and nervous system development, and play regulatory roles in immune tolerance and T cell activation.

Clinical progress of targeted CD47 therapy abroad

In recent years, clinical research on CD47 monoclonal antibody has been carried out rapidly in the United States. As of August 28, 2021, 46 clinical trials of CD47-targeted therapy were registered in clinical trials. Patients with different types of cancer were studied in these clinical trials, including 29 trials in solid tumors and 14 trials in haematological malignancies and 3 mixed trials.

CC-90002

CC-90002 is the first-generation humanized anti-CD47 antibody to enter clinical research. The first clinical trial of CC-90002 (NCT02641002) was terminated in late 2018 because its preliminary monotherapy data in R/R AML and high-risk MDS failed to provide sufficient evidence for further dose escalation/expansion. CC-90002 was restarted in a clinical trial (NCT02367196) after modifying the dosing strategy and other procedures.

CC-90002 does not promote HA while maintaining high affinity binding to CD47 and inhibits CD47-SIRPα interaction. Studies on a panel of hematological cancer cell lines show concentration-dependent CC-90002-mediated phagocytosis in lenalidomide-resistant MM cell lines and patient AML cells. In non-human primates, CC-90002 exhibited acceptable pharmacokinetic properties and a favorable toxicity profile. These data demonstrate the potential activity of CC-90002 in hematological malignancies and provide the basis for clinical studies CC-90002-ST-001 (NCT02367196) and CC-90002-AML-001 (NCT0264102).

Hu5F9-G4 (5F9)

Hu5F9-G4 (5F9, Magrolimab) is a humanized IgG4 antibody that targets CD47 with high affinity. 5F9 induces macrophage-mediated phagocytosis of primary human AML cells in vitro and completely eradicates human AML in vivo . 5F9 has entered clinical trials in patients with AML and solid tumors (NCT02216409).

Studies have shown that Hu5F9-G4 alone or in combination with other antibodies may cause unexpected death of normal hematopoietic cells. For safety reasons, 5F9 has been designed with an improved dosing regimen. When 5F9 was used as monotherapy, response rates were relatively low in patients with relapsed/refractory AML/MDS and solid tumors. This may be due to the reduced affinity of IgG4 for Fcγ receptors on macrophages, thereby limiting antibody-dependent cellular phagocytosis (ADCP). In addition, plasma samples from patients treated with Hu5F9-G4 showed strong responses to all red blood cells and platelets.

Another phase Ib/II clinical trial of 75 patients with R/R non-Hodgkin lymphoma showed that the objective response rate (ORR) of 5F9 combined with rituximab was 49%, and the complete response rate (CR) was 49%. 21%. In another phase Ib study, in combination with the DNA demethylating agent azacitidine, ORR was 100% and CR was 55% in 11 untreated MDS patients and 14 untreated AML patients The CR was 64%.

TTI-621 and TTI-622

TTI-621 is a CD47-targeting SIRPα fusion protein that blocks CD47 through a decoy receptor (SIRPα-Fc). Clinical trials of TTI-621 in relapsed and refractory hematological malignancies demonstrated that systemic administration of TTI-621 resulted in CD47 blockade and a dose-dependent increase in phagocytosis-related cytokines, which were associated with transient reversible thrombocytopenia disease-associated, indicating enhanced macrophage-mediated clearance of circulating platelets, followed by a robust bone marrow regenerative response.

A phase I study of TTI-621 combined with rituximab in 164 patients with B-cell non-Hodgkin's lymphoma (B-NHL) showed that TTI-621 combined with rituximab was effective in R/R B-NHL and T Cellular non-Hodgkin lymphoma (T-NHL) patients were well tolerated and showed good monotherapy activity in R/R B-NHL patients. The ORR was 13% for all patients, 29% (2/7) for diffuse large B-cell lymphoma (DLBCL), 25% (8/32) for TTI-621 monotherapy in T-NHL and 25% (8/32) for DLBCL The ORR of TTI-621 combined with rituximab was 21% (5/24).

Meanwhile, a phase I dose-escalation study of another CD47 receptor blocker, TTI-622, in patients with advanced R/R lymphoma showed that one patient with stage 4 non-germinal center B-cell DLBCL initially achieved PR at week 8, CR was achieved at week 36. The difference between these two drugs is the different Fc subtypes. TTI-621 and TTI-622 use IgG1 Fc and IgG4 Fc, respectively. Since the interaction between the IgG4 Fc region of TTI-622 and the Fc receptor is more limited than that of IgG1, it is speculated that TTI-622 will deliver a milder "phagocytic" signal to macrophages.

ALX-148

ALX148 is a decoy receptor fusion protein consisting of a mutated SIRPα domain that binds CD47 with high affinity and an inactive Fc domain that alleviates HA and anemia. Results to date suggest that ALX148 is generally well tolerated with moderate adverse events when administered in combination with other anticancer drugs, such as Herceptin and Keytruda, in patients with solid tumors. Although no complete or partial responses were observed with monotherapy, the partial response rate was 22% in patients with HER2-positive gastric cancer in combination with trastuzumab and 16% in HNSC patients in combination with pembrolizumab.

Recent clinical data show that combining ALX148 with a standard dosing regimen of trastuzumab, ramucirumab, and paclitaxel has initially demonstrated a promising objective response rate of 72% and an estimated 12-month OS of 76%. Maximum tolerated dose not reached.

AO-176

AO-176 is a humanized anti-CD47 monoclonal antibody. AO-176 not only binds preferentially to tumor cells over normal cells, and binds more efficiently to tumors in an acidic microenvironment (low pH), but also directly kills tumor cells in a cell-autonomous manner, rather than antibody-dependent cells Toxicity (ADCC). Compared with other CD47 blocking antibodies, AO-176 binds negligibly to erythrocytes and does not induce HA and transient anemia.

A first-in-human study in patients with advanced solid tumors demonstrated that AO-176 is a well-tolerated anti-CD47 therapy with durable antitumor activity observed. Currently, clinical trials of AO-176 combined with paclitaxel in the treatment of some solid tumors (NCT03834948) and multiple myeloma (NCT04445701) are ongoing.

SRF231

SRF231 is a fully human IgG4 anti-CD47 antibody previously granted orphan drug designation by the FDA for the treatment of patients with multiple myeloma. SRF231 has dual antitumor activity: SRF231 can bind to CD32a on macrophages to induce FcγR-mediated phagocytosis of cancer cells, and it acts as a scaffold to deliver CD47-mediated death signals to tumor cells. Preclinical studies have shown that SRF231 can bind to CD47 with high affinity, kill cancer cells in vitro, and has strong anti-tumor activity. Furthermore, a potential safety advantage of SRF231 is that it does not cause detectable hemagglutination or phagocytosis.

TG-1801

TG-1801 is a bispecific antibody against CD19 and CD47. By targeting CD47 and CD19 in combination, TG-1801 has the potential to overcome the limitations of existing CD47-targeted therapies and avoid the side effects of indiscriminate blocking of CD47 on healthy cells. Currently, TG-1801 is undergoing two Phase I clinical trials (NCT03804996 and NCT04806305).

BI 765063

BI 765063 (OSE-172) is a humanized IgG4 monoclonal antibody antagonist of SIRPα that blocks the SIRPα/CD47 axis. BI 765063 was a single-agent dose-escalation phase I study in 50 patients with advanced solid tumors, including ovarian, colorectal, lung, breast, melanoma and kidney tumors, and showed a well-tolerated safety profile, Pharmacokinetics and Efficacy. One patient with hepatocellular carcinoma (HCC) with liver and lung metastases and seven previous treatments showed partial remission lasting 27 weeks after treatment.

There are also some CD47 monoclonal or biclonal antibodies and fusion proteins in clinical trials, such as DSP107 (NCT04937166, NCT04440735), IMC-002 (NCT04306224) and STI-6643 (NCT04900519).

Clinical progress of targeted CD47 therapy in China

In recent years, China has also made great progress in anti-CD47 therapy. According to the NMPA, at least 17 CD47-targeting drugs have been approved for clinical research, accounting for more than half of the global CD47-targeting drugs.

TJC4

TJC4 (also known as TJ011133, lemzoparlimab) is a highly differentiated erythropoietic CD47 antibody with unique epitopes. It has strong antitumor activity and minimizes binding to normal red blood cells, thereby reducing HA that may be caused by certain CD47 mAbs.

Preliminary results from a Phase I/IIa study of mzoparlimab (NCT04202003) demonstrated a well-tolerated safety profile and moderate clinical efficacy in 5 patients with R/R AML and MDS who had received 2-4 prior treatments . Of particular note, one patient with primary refractory AML achieved morphological leukemia-free status (MLFS) after receiving 2 cycles of lemzoparlimab at a dose of 1 mg/kg.

Currently, there are two ongoing Phase I clinical trials, NCT04895410 in MM and NCT04912063 in AML/MDS.

IBI188 and IBI322

IBI188 is a recombinant human anti-CD47 monoclonal antibody that specifically blocks the CD47-SIRPα axis. Preclinical results show that IBI188 treatment upregulates macrophage cell motility and inflammation-related genes, and IBI188-enhanced antitumor effects were observed in AML xenograft models. Currently, there are five ongoing clinical trials of IBI188 targeting different malignancies (NCT04861948, NCT04485065, NCT04485052, NCT03717103, NCT03763149).

IBI322 is a novel BsAb that targets both CD47 and PD-L1. It was approved for clinical research in China in January 2020, and the indications are solid tumors and hematological tumors. Currently, four IBI322-related clinical trials have been registered, namely NCT04912466, NCT04338659, NCT04328831 and NCT04795128, for different malignancies.

HX009

HX009 is a dual antibody that blocks both CD47 and PD-1. In theory, Hx009 can simultaneously activate innate and acquired immune responses, inhibit tumor immune escape, and release immune checkpoint immune suppression, thereby achieving a synergistic anti-tumor effect.

A Phase I clinical trial (NCT04097769) evaluated the safety and efficacy of HX009 in 21 patients with advanced malignancies. Of the 18 patients who had at least one post-baseline tumor assessment, 3 patients achieved PR and 6 patients had stable disease. Currently, there are two ongoing clinical trials, namely NCT04097769 and NCT04886271.

IMM01, IMM0306, IMM2902

IMM01 is a new generation of SIRPαFc fusion protein targeting CD47. As a monotherapy, it has strong antitumor activity in vivo. Currently, there is 1 ongoing clinical trial (CTR20191531). Preliminary results show unprecedented responses in some patients, especially in patients with R/R classical Hodgkin lymphoma (cHL). Among the five cHL enrolled subjects, one patient with PD-1-resistant disease achieved PR and continued treatment at 57 weeks, and three patients achieved SD, for an overall disease control rate of 80%.

IMM01 does not bind to human erythrocytes, and the immunogenicity of IMM01 is reduced after deglycosylation modification. Therefore, IMM01 has good PK, better tissue permeability and bioavailability, and better safety profile, which is reflected in the absence of anti-drug antibodies (ADA) and drug-related Serious Adverse Events (SAEs).

IMM0306 is a bispecific antibody trap that targets both CD47 and CD20. IMM0306 is designed to bind CD20 with a higher affinity than CD47, thereby avoiding CD47 binding in normal tissues, thereby reducing toxicity associated with CD47 targets. Currently, two clinical trials are underway (NCT04746131 and CTR20192612).

IMM2902 is another bispecific antibody trap that targets both CD47 and Her2. The program has recently been approved by the NMPA and FDA for a Phase I clinical trial in Her2-positive solid tumors.

AK117

AK117 is an anti-CD47 monoclonal antibody with a unique structure. It not only retained the antitumor activity but also eliminated the agglutination of erythrocytes and significantly reduced the phagocytic activity of macrophages on erythrocytes. A preliminary study of 15 patients with advanced or metastatic solid tumors in a Phase 1 clinical trial (NCT04349969) showed that AK117 was safe and well tolerated, with no observed infusion-related reactions (IRRs) or serious treatment-related Adverse Events (TRAEs).

As of August 30, 2021, 4 clinical trials are ongoing (NDS04900350, NCT0498088, NCT0478334 and NCT0434999). At the same time, there are 3 ongoing clinical trials in China (CTR2011305, CTR2010825, CTR20202684).

SHR-1603

SHR-1603 is a humanized IgG4 monoclonal antibody against CD47. Currently, one clinical trial each in the NCT (NCT03722186) and CDT (CTR20181964) systems is on hold.

ZL-1201

ZL-1201 is an anti-human CD47 monoclonal antibody. In July 2020, ZL-1201 injection was approved in China for clinical studies in patients with advanced solid tumors or hematological malignancies. Previously, it had been approved by the U.S. Food and Drug Administration for clinical trials in the United States. There is currently a Phase I clinical trial in patients with advanced cancer in the NCT system (NCT04257617) and a clinical trial in patients with locally advanced solid tumors or hematological malignancies in the CDT system (CTR2010973).

JMT601

JMT601 (CPO107) is a bispecific SIRPα fusion protein with synergistic targeting binding to CD20 and CD47. It is based on an approved anti-CD20 antibody with the addition of the CD47 binding fragment SIRPα. Preclinical toxicology studies have shown that JMT601 has no significant binding to CD20-negative cells, nor does it have significant effects on CD47-positive cells such as red blood cells and platelets. Currently, a Phase I/II multicenter clinical trial (NCT04853329) has been approved.

Other

There are also several potential candidates in clinical research, such as LQ001, PT217, HLX-24, etc. In conclusion, the CD47-SIRPα signaling pathway has great therapeutic potential, and CD47 has become another highly competitive target after PD-1/PD-L1 in cancer immunotherapy.

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