CD28 Antagonist Research Articles

Antagonism of CD28 blocks allergic responses in the ovalbumin-induced asthmatic model mice.

Allergen-reactive T helper (Th) 2 cells play a pivotal role in initiating asthma pathogenesis. The absence or interruption of CD28 signaling causes significant consequences for T-cell activation, leading to reduced cell proliferation and interleukin (IL)-2 production. A novel compound, Cyn-1324, exhibits a higher binding affinity to CD28 than CD80. Thus, targeting the CD28-CD80 interaction emerges as a promising therapeutic approach for allergic asthma. However, the impact of CD28 antagonists on allergen-induced asthma remains unreported. In this study, we explored the effects of intranasally administered Cyn-1324 on airway inflammation in the ovalbumin (OVA)-induced murine allergic model. The results revealed a significant reduction in airway hyper-responsiveness (AHR), eosinophil recruitment, and cell infiltration in lung tissues, as well as decreased OVA-specific IgE in serum and Th2 cytokine levels in OVA-stimulated lymphocyte cultures. Additionally, we demonstrated the immunosuppressive effects of Cyn-1324 in vitro, including decreased T-cell proliferation and IL-2 secretion, together with increased p27kip1 expression via inhibiting the PI3K signaling pathway. Notably, Cyn-1324 not only inhibited the NF-κB pathway, but also appeared to suppress p38 activation, which is downstream of CD3 signaling, and reduced calcium-induced NFAT protein expression. These findings suggest that Cyn-1324 alleviates allergic responses by inhibiting the CD28-CD80 interaction and holds promise as an immunosuppressive agent for allergic patients.

New Developments and Therapeutic Drug Monitoring Options in Costimulatory Blockade in Solid Organ Transplantation: A Systematic Critical Review.

In this review, the authors summarized the latest developments in costimulatory blockade to prevent rejection after solid organ transplantation (SOT) and discussed possibilities for future research and the need for therapeutic drug monitoring (TDM) of these agents. Studies about costimulatory blockers in SOT in humans or animal transplant models in the past decade (2014-2024) were systematically reviewed in PubMed, European Union clinical trials (EudraCT), and ClinicalTrials.gov. Seventy-five registered clinical trials and 58 published articles were found on costimulation blockade of the CD28-CD80/86, CD40-CD40L, and OX40-OX40L pathways. Belatacept, an antagonist of the CD28-CD80/86 pathway, is the only approved costimulatory agent in SOT, hence accounting for most of the research. Other identified costimulatory blocking agents included abatacept and CD28 antagonists tegoprubart, dazodalibep, and TNX-1500. Although tegoprubart was unsuccessful in pancreas transplantation in nonhuman primates, trials in human kidney transplantation are underway. Dazodalibep trials faced recruitment challenges. TNX-1500 was unsuccessful in animal studies and is currently not pursued in humans. After discontinuation of iscalimab (CD40-CD154 pathway antagonist) in SOT, the alternatives, bleselumab and KPL404, showed promising results in kidney transplantation and cardiac xenotransplantation. Studies on secondary costimulatory pathway antagonists, such as OX40-OX40L, have only used animal models. Despite the low interindividual variability in pharmacokinetics (PK) in all studied agents, TDM could be useful for optimizing dosing in PK/pharmacodynamic (PD) studies. The routine use of costimulation blockade in SOT is hindered by problems in efficacy compared with the standard of care. Costimulatory inhibitors could be combined in a calcineurin inhibitor-free regimen. Future PK/pharmacodynamic studies in costimulatory agents and personalized medicine could warrant TDM of these agents.

Abstract 117: Improved PBMC humanized mouse models for immuno-oncology drugs evaluation

Abstract It has been demonstrated that anti-PD(L)1 therapy could significantly improve survival outcomes for patients with metastatic solid cancers, such as melanoma, non-small cell lung cancer and MSI-H colorectal cancer. However, more than half of these patients (NCT02563002, NCT02142738, NCT02563002) do not respond to immune checkpoint blockade (ICB) therapy, and 90% of colorectal cancer patients have MSS/pMMR characteristics and almost no response at all, which drives scientists to design novel drug candidates urgently and integrate tumor and tumor microenvironment (TME) signals systemically to rejuvenate exhausted immune system and overcome ICB resistance. LIDE has developed both traditional PBMC humanized mice model, and human immune cells and cancer co-inoculated model for IO drugs functional evaluation in the last 5-years by using unique PBMC donor selection and standard cancer biobank (PDX patient-derived xenografts, CDX cell derived xenograft) establishment. Cancer biopsies with MDM2 amplification or DNMT3A alternation have been shown resistant to PD1-Ab therapy but sensitive to chemical combo-therapy, and pMMR cancer PDX models seem responsible well to EGFR targeted, CD39-CD73-Adenosine targeted therapy. Human IL15 transgenic mice are used as one useful tool to investigate in vivo function of NK cells, NK engagers/modulators as well as drugs with ADCC (Antibody dependent cell-mediated cytotoxicity) effect. The activated immune cells and cancer co-transfer model, can significantly delay the graft-versus-host-reaction for another month compared with traditional PBMC humanized model, and archives maximal therapeutic effect of the testing drugs by pre-activating T cells with specific tumor antigens. Dendritic cells or macrophages could be successfully introduced into this co-inoculated system to work together with T cells, mimic human tumor tissue complexity, to help determine the overall effect induced by integrated signals. It seems CD40 agonist or CD47 antagonist could well synergies with anti-PD(L)1 to control melanoma and triple negative breast cancer development, respectively. This optimized PBMC humanized cancer-bearing mice models have been tested for various cancer targets, e.g. PD(L)1, Tim3, Lag3, Tigit, PVRIG, TGFβ1, CD73/CD39, CD47/Sirpa, DLL3/CD3, Claudin18.2/4-1BB, B7-H3, GITR, to better understand the interaction between cancer cells and immune cells. Citation Format: Bin Xie, Xin Hou, Pengfei Yang, Yanbing Zhou, Danyi Wen. Improved PBMC humanized mouse models for immuno-oncology drugs evaluation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 117.

Genetically Engineered Macrophages Co-Loaded with CD47 Inhibitors Synergistically Reconstruct Efferocytosis and Improve Cardiac Remodeling Post Myocardial Ischemia Reperfusion Injury.

Efferocytosis, mediated by the macrophage receptor MerTK (myeloid-epithelial-reproductive tyrosine kinase), is a significant contributor to cardiac repair after myocardial ischemia-reperfusion (MI/R) injury. However, the death of resident cardiac macrophages (main effector cells), inactivation of MerTK （main effector receptor), and overexpression of "do not eat me" signals (brake signals, such as CD47), collectively lead to the impediment of efferocytosis in the post-MI/R heart. To date, therapeutic strategies targeting individual above obstacles are relatively lacking, let alone their effectiveness being limited due to constraints from the other concurrent two. Herein, inspired by the application research of chimeric antigen receptor macrophages (CAR-Ms) in solid tumors, a genetically modified macrophage-based synergistic drug delivery strategy that effectively challenging the three major barriers in an integrated manner is developed. This strategy involves the overexpression of exogenous macrophages with CCR2 (C-C chemokine receptor type 2) and cleavage-resistant MerTK, as well as surface clicking with liposomal PEP-20 (a CD47 antagonist). In MI/R mice model, this synergistic strategy can effectively restore cardiac efferocytosis after intravenous injection, thereby alleviating the inflammatory response, ultimately preserving cardiac function. This therapy focuses on inhibiting the initiation and promoting active resolution of inflammation, providing new insights for immune-regulatory therapy.

An agonistic anti-signal regulatory protein α antibody for chronic inflammatory diseases

Signal regulatory protein (SIRPα) is an immune inhibitory receptor expressed by myeloid cells to inhibit immune cell phagocytosis, migration, and activation. Despite the progress of SIRPα and CD47 antagonist antibodies to promote anti-cancer immunity, it is not yet known whether SIRPα receptor agonism could restrain excessive autoimmune tissue inflammation. Here, we report that neutrophil- and monocyte-associated genes including SIRPA are increased in inflamed tissue biopsies from patients with rheumatoid arthritis and inflammatory bowel diseases, and elevated SIRPA is associated with treatment-refractory ulcerative colitis. We next identify an agonistic anti-SIRPα antibody that exhibits potent anti-inflammatory effects in reducing neutrophil and monocyte chemotaxis and tissue infiltration. In preclinical models of arthritis and colitis, anti-SIRPα agonistic antibody ameliorates autoimmune joint inflammation and inflammatory colitis by reducing neutrophils and monocytes in tissues. Our work provides a proof of concept for SIRPα receptor agonism for suppressing excessive innate immune activation and chronic inflammatory disease treatment.

Selective CD28 blockade impacts T cell differentiation during homeostatic reconstitution following lymphodepletion.

Costimulation blockade targeting the CD28 pathway provides improved long-term renal allograft survival compared to calcineurin inhibitors but may be limited as CTLA-4-Ig (abatacept, belatacept) blocks both CD28 costimulation and CTLA-4 coinhibition. Directly targeting CD28 while leaving CTLA-4 intact may provide a mechanistic advantage. Fc-silent non-crosslinking CD28 antagonizing domain antibodies (dAb) are currently in clinical trials for renal transplantation. Given the current standard of care in renal transplantation at most US centers, it is likely that lymphodepletion via thymoglobulin induction therapy could be used in patients treated with CD28 antagonists. Thus, we investigated the impact of T cell depletion (TCD) on T cell phenotype following homeostatic reconstitution in a murine model of skin transplantation treated with anti-CD28dAb. Skin from BALB/cJ donors was grafted onto C56BL/6 recipients which were treated with or without 0.2mg anti-CD4 and 10μg anti-CD8 one day prior to transplant and with or without 100μg anti-CD28dAb on days 0, 2, 4, 6, and weekly thereafter. Mice were euthanized six weeks post-transplant and lymphoid cells were analyzed by flow cytometry. Anti-CD28dAb reversed lymphopenia-induced differentiation of memory CD4+ T cells in the spleen and lymph node compared to TCD alone. Mice treated with TCD+anti-CD28dAb exhibited significantly improved skin graft survival compared to anti-CD28dAb alone, which was also improved compared to no treatment. In addition, the expression of CD69 was reduced on CD4+ and CD8+ T cells in the spleen and lymph node from mice that received TCD+anti-CD28dAb compared to TCD alone. While a reduced frequency of CD4+FoxP3+ T cells was observed in anti-CD28dAb treated mice relative to untreated controls, this was balanced by an increased frequency of CD8+Foxp3+ T cells that was observed in the blood and kidney of mice given TCD+anti-CD28dAb compared to TCD alone. These data demonstrate that CD28 signaling impacts the differentiation of both CD4+ and CD8+ T cells during homeostatic reconstitution following lymphodepletion, resulting in a shift towards fewer activated memory T cells and more CD8+FoxP3+ T cells, a profile that may underpin the observed prolongation in allograft survival.

GPC2 antibody–drug conjugate reprograms the neuroblastoma immune milieu to enhance macrophage-driven therapies

BackgroundAntibody–drug conjugates (ADCs) that deliver cytotoxic drugs to tumor cells have emerged as an effective and safe anticancer therapy. ADCs may induce immunogenic cell death (ICD) to promote additional endogenous...

Abstract 3500: AUR103 an oral small molecule CD47 antagonist in combination with azacytidine and bortezomib exhibits potent anti-tumor activity in myeloma and leukemia models in vitro and in vivo

Abstract The CD47/signal regulatory protein alpha axis is a critical regulator of myeloid cell activation and serves as an immune checkpoint for macrophage mediated phagocytosis. Targeting CD47-SIRPα axis is emerging as one of the promising new immunotherapy approaches that targets innate immune response. Number of clinical trials are in progress to evaluate CD47/SIRPα blocking therapies. Most of these molecules are either anti-CD47 antibodies or SIRPα-Fc recombinant proteins. We have developed a novel small molecule CD47 antagonist, AUR103 as a therapeutic agent for solid and hematological cancers. AUR103 is efficacious as a single agent in tumors with high expression of “eat-me” signals and synergizes well in combination with tumor-targeting antibodies. We hypothesized that agents capable of inducing “eat-me” signals such as calreticulin (CRT) a pro-phagocytic signal, will synergize with AUR103 to enhance phagocytosis and antitumor activity. Here, we report the anti-tumor efficacy of AUR103 in combination with azacytidine and bortezomib in acute myeloid leukemia and multiple myeloma model of cancer, respectively.In the phagocytosis assay, HL-60 human myeloid leukemia or NCI-H929 human multiple myeloma cells were treated with azacytidine or bortezomib for 48 hours. Cells were stained with CFSE and were further treated with AUR103. Cells were then added to human macrophages and allowed to undergo phagocytosis. Phagocytosis of target cells was measured by detecting cells that were double positive for APC and CFSE by FACS. HL-60 cells were orthotopically implanted in NOD SCID mice while NCI-H929 multiple myeloma cells were sub-cutaneously implanted in NOD SCID mice. Tumor bearing mice were treated with AUR103 (10 and 30 mg/kg, b.i.d, and po) as a single agent or in combination with azacytidine (5 mg/kg i.p., twice weekly) or bortezomib (0.4 mg/kg i.v., twice weekly). AUR103 in combination with azacytidine and bortezomib significantly enhanced phagocytosis of HL-60 and NCI-H929 tumor cells, respectively when compared to individual treatments. In the combination efficacy studies, AUR103 combination treatments with azacytidine and bortezomib were well tolerated without any signs of toxicity. In the HL-60 orthotopic model, AUR103 combination with azacytidine significantly reduced the engraftment of HL-60 tumor cells. AUR103 combination with bortezomib resulted in enhanced tumor growth inhibition in NCI-H929 tumor model when compared to individual treatments. These results demonstrate the therapeutic potential of AUR103 in combination with agents that are capable of inducing “eat-me” or pro-phagocytic signals. Citation Format: Girish C. Daginakatte, Sasikumar Pottayil, Sudarshan Naremaddepalli, Gundala Chennakrishnareddy, Prasad Bilugudi, Sai Krishna Tangella, Sandeep Patil, Nagesh Gowda, Kiran Aithal, Wesley Roy Balasubramanian, Amit Dhudashiya, Samiulla Dodheri, Kavitha Nellore, Susanta Samajdar, Murali Ramachandra. AUR103 an oral small molecule CD47 antagonist in combination with azacytidine and bortezomib exhibits potent anti-tumor activity in myeloma and leukemia models in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3500.

Targeting Ovarian Carcinoma with TSP-1:CD47 Antagonist TAX2 Activates Anti-Tumor Immunity.

Simple SummaryDue to the nonspecific nature of disease symptoms and late diagnosis, prognosis for ovarian cancer remains poor, while its incidence is increasing dramatically. Current treatment options lead to recurrence for over 80% of patients, and there is a real and urgent need to identify new therapeutic targets, especially in the field of immuno-oncology. Among possibilities, thrombospondin-1 (TSP-1) is a matricellular protein being overexpressed within ovarian tumors, for which interaction with CD47 receptor was reported as directly inhibiting adaptive immunity. We engineered the first-ever orthosteric antagonist that is selective for TSP-1:CD47 interaction, namely TAX2. TAX2 is a cyclic peptide targeting tumor-overexpressed thrombospondin-1 (TSP-1) to prevent CD47 receptor activation. TAX2 acts as a modulator of the tumor-tolerant microenvironment, reprogramming highly vascularized tumors into poorly angiogenic ones, while concomitantly activating the tumor-inhibiting immune system. A large body of in vivo efficacy data support the proof-of-concept for TAX2 use as an anti-cancer therapy.TAX2 peptide is a cyclic peptide that acts as an orthosteric antagonist for thrombospondin-1 (TSP-1) interaction with CD47. TAX2 was first described for its anti-angiogenic activities and showed anti-cancer efficacy in numerous preclinical models. Here, we aimed at providing an extensive molecular characterization of TAX2 mode of action, while evaluating its potential in ovarian cancer therapy. Multidisciplinary approaches were used to qualify a TAX2 drug candidate in terms of stability, solubility and potency. Then, efficacy studies, together with benchmark experiments, were performed in relevant mouse models of ovarian carcinoma. TAX2 peptide appears to be stable and soluble in clinically relevant solvents, while displaying a favorable safety profile. Moreover, clinical data mining allowed for the identification of TSP-1 as a relevant pharmacological target in ovarian cancer. In mice, TAX2 therapy inhibits ovarian tumor growth and metastatic dissemination, while activating anti-cancer adaptive immunity. Interestingly, TAX2 also synergizes when administered in combination with anti-PD-1 immune checkpoint inhibitiors. Altogether, our data expose TAX2 as an optimized candidate with advanced preclinical characterization. Using relevant syngeneic ovarian carcinoma models, we highlighted TAX2’s ability to convert poorly immunogenic tumors into ones displaying effective anti-tumor T-cell immunity.

Caspase-cleavable peptide-doxorubicin conjugate in combination with CD47-antagonizing nanocage therapeutics for immune-mediated elimination of colorectal cancer

Here we report a novel combination of a caspase-cleavable peptide-doxorubicin conjugate (MPD-1) with CD47-antagonizing nanocage therapeutics for the treatment of microsatellite-stable (MSS) colorectal cancer (CRC). MPD-1 (i) upregulated markers of immunogenic cell death (ICD) in tumor, and increased co-stimulatory markers on dendritic cells (DCs), (ii) enhanced CD8+ T cell infiltration and antigen presenting cell (APC) activation, and (iii) showed negligible off-target immune-related toxicity compared to free dox. Then, the CD47 antagonist FS nanocage, a SIRPα-expressing ferritin nanocage, was co-administered with MPD-1 that resulted in 95.2% (p < 0.001) tumor growth inhibition in an established CRC model. T cell-mediated elimination of tumors was also confirmed by the tumor-specific activation of T cells detected by IFNγ and tumor-free mice were observed (95%) that bared a memory response when re-challenged. The strategically developed MPD-1 is an ideal adjuvant to immunotherapy and the combination with FS nanocage triggers potent immunity against MSS CRC. In summary, we present an approach to initiate and stimulate immune-mediated eradication of cancer cells using synergistic immunogenic agents targeting the MSS CRC.

Abstract 901: Ferritin nanocages to deliver CD47 antagonist, SIRPγ, for cancer immunotherapy

Abstract Eliciting effective tumor antigen-specific immunity requires targeting the initial stages of the anticancer immunity cycle, including activation of antigen presenting cells (APCs) for tumor antigen uptake and presentation, and T cell priming. Here, the research aimed to explore the novel immunotherapeutic strategy using protein nanocage platform that enhances the phagocytic activity of phagocytes in combination with treatment of immunogenic cell death inducing agents, which could boost processing of antigens by APCs, thereby trigger efficient antitumor immunity. The recombinant ferritin protein nanocages expressing SIRPγ peptides, named FHSirpγ, was designed to interact with CD47 of cancer cells, which could effectively blocking ‘don't eat me signal', CD47. The binding affinity of FHSirpγ to cancer cells was reinforced by adapting several mutations on protein sequence, which showed up to 10 folds of improvement. Therefore, FHSirpγ was able to successfully stimulate phagocytosis of phagocytes toward various cancer cells, e.g. HT29, B16F10, CT26.CL25 and J558, up to approximately 2 folds in vitro. In the aspect of improvement in antigen release, Carfilzomib(CFZ), the FDA approved 2nd generation proteasome inhibitor on multiple myeloma, was treated to cancer cells, which showed tolerable level of cell cytotoxicities and enhanced release of danger associated molecular patterns(DAMPs), such as HSP70 and HMGB1, which were detected from cell culture medium after 24hrs of incubation on above mentioned cell lines. The antitumorigenic efficacy was preliminary verified in the case of B16F10 and J558 implanted murine tumor model, which showed approximately 75% of tumor growth regression when FHSirpγ and CFZ were treated intravenously. Overall, treatment of FHSirpγ showed antitumor efficacy via enhancement of phagocytosis in vivo and in vitro, especially when combined with immunogenic cell death inducer. Citation Format: Yoonjeong Choi, Insan Kim. Ferritin nanocages to deliver CD47 antagonist, SIRPγ, for cancer immunotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 901.

A single-valent long-acting human CD47 antagonist enhances antibody directed phagocytic activities.

Many cancer cells express CD47 as a 'don't eat me' signal to mask their presences from immune recognition and destruction. Such a signal is transmitted when CD47 binds to the signal regulatory protein-α (SIRPα) on macrophages to cut the phagocytic reaction. Most recent studies have focused on developing CD47 blocking agents with different affinities and avidities in order to optimize the therapeutic window between efficacy and toxicities involving normal cells expressing CD47. We described in this study a new design to fuse one CD47 binding domain of SIRPα with a pharmacokinetics modifying domain F8. The resulted single valent long-acting CD47 antagonist SIRPα-F8 was able to bind to CD47 and disrupt CD47-SIRPα axis. However, by itself it cannot trigger endocytosis and has no effect on tumor growth. Only when used in combination with the anti-CD20 mAbs, there were greatly improved phagocytic activities towards CD20 positive cancer cells. In vivo the combination also resulted in better tumor growth inhibition comparing to the vehicle control group. In addition, we showed that the F8 fusion bound to hFcRn only inside endosomes at pH 6.0, enabled hFcRn mediated recycling and thus greatly extended the circulation half-life in hFcRn knock-in mice. Taken together, the SIRPα-F8 design may suggest a new option to improve the therapeutic index of antibody treatment in clinical use towards tumors.

Selective Costimulation Blockade With Antagonist Anti-CD28 Therapeutics in Transplantation.

Nephrotoxicity of calcineurin inhibitors and uncontrolled effector function of alloreactive T lymphocytes are main drivers of transplant dysfunctions. T lymphocytes either directly damage tissues or indirectly promote inflammation and antibody responses. Beside inhibitors of calcium-dependent pathways and antimetabolites, modulators of T-cell costimulation are elected pharmacological tools to enable interference with immune-mediated transplant dysfunctions. CD28 and CTLA-4 are major costimulatory and coinhibitory cell surface signaling molecules interacting with CD80/86, known to be critically important for immune response of committed T cells and regulation. Initial bench to beside translation, 2 decades ago, resulted in the development of belatacept CTLA-4 fused with an immunoglobulin Fc domain, a biologic inhibiting interaction of both CD28 and CTLA-4 with CD80/86. Despite proven effectiveness in inhibiting alloimmune responses, clinical use of belatacept in kidney transplantation revealed a substantially high incidence of acute, cell-mediated rejection. The cause of belatacept-resistant graft rejection was allocated to elevated pretransplant frequencies of CD28 memory T cells. Owing to different requirements in CD28 costimulatory and CTLA-4 coinhibitory signals to control naive and memory T cells, selective antagonists of CD28-CD80/86 interactions have been developed on the rationale that preservation of CTLA-4-mediated regulatory mechanisms would result in a better control of alloreactivity and would represent a regulatory T-cell-compatible immunosuppression. After the successful testing of selective CD28 antagonists in First In Human studies, this review delineates how this shift in paradigm performed in preclinical transplantation models and evaluates its clinical potential.

Treg Modulation With CD28 and IL-6 Receptor Antagonists

Treg Modulation With CD28 and IL-6 Receptor Antagonists

Intralesional Administration of the CD47 Antagonist TTI-621 (SIRPαFc) Induces Responses in Both Injected and Non-Injected Lesions in Patients with Relapsed/Refractory Mycosis Fungoides and Sézary Syndrome: Interim Results of a Multicenter Phase I Trial

BackgroundCD47 is an immune checkpoint that binds signal regulatory protein alpha (SIRPα) and delivers a “do not eat” signal to suppress macrophage phagocytosis. Tumor cells, including T-cell lymphomas, frequently overexpress CD47 to escape immune surveillance. TTI-621 (SIRPαFc) is a fusion protein consisting of the CD47 binding domain of human SIRPα linked to the Fc region of human IgG1, designed to enhance phagocytosis and antitumor activity by blocking the CD47-SIRPα interaction between malignant cells and macrophages, and engaging activating Fcγ receptors. It is hypothesized that direct intralesional (IL) administration of TTI-621 may enhance both local and systemic antitumor activity.MethodsA multicenter, open-label Phase 1 study is ongoing to characterize the safety, tolerability, pharmacokinetics, pharmacodynamics and antitumor activity of IL injections of TTI-621 (NCT02890368) in adult patients with relapsed/refractory (R/R) percutaneously accessible solid tumors and mycosis fungoides (MF) who have progressed on standard anticancer therapy or for whom no other approved therapy exists. The current report analyzed a cohort of R/R MF/Sézary syndrome (SS) patients enrolled by the data cut-off date. Patients received induction therapy consisting of a single IL injection (1, 3 or 10 mg), three 10 mg injections over one week, or six 10 mg injections over two weeks distributed across one to three lesions. The protocol was recently amended to enable weekly post-induction IL maintenance dosing and to explore IL TTI-621 administration in combination with subcutaneous pegylated interferon-α2a. Responses were evaluated using the Composite Assessment of Index Lesion Severity (CAILS) score a week after induction therapy and at later time points in some patients. Serial biopsies were collected to assess the impact of TTI-621 on the tumor microenvironment.ResultsTwenty-two patients (16 M/6F, median age 65.5 years, range 32-85) were enrolled as of June 15, 2018. Primary diagnosis included MF (n=18), MF with transformation (n=3) and SS (n=1). Clinical stages included stage IA (n=2), IB (n=3), IIA (n=1), IIB (n=13), IVA (n=2) and IVB (n=1). Patients received a median of 3 prior systemic therapy regimens. Twenty-one patients were treated with TTI-621 monotherapy and one patient with TTI-621 in combination with pegylated interferon-α2a. Single and multiple IL injections of up to 10 mg TTI-621 have been well tolerated. The most frequently reported treatment-related adverse events (AEs) were chills (n=8), injection site pain (n=7) and fatigue (n=6). All treatment-related AEs were Grade 1 or 2 in severity. No treatment-related serious AEs or dose-limiting toxicity have been observed. CAILS scores for injected lesions obtained after the last injection were available for 17 patients: 15 (88%) had measurable improvement; 7 (41%) exhibited ≥50% decrease from baseline (Figure 1). Responses were rapid and in some patients occurred after a single injection of varying doses of TTI-621. CAILS scores continued to decrease in 5/5 (100%) monotherapy patients for which post-induction therapy assessments were conducted. Seven patients with reduced CAILS of varying degree (-14% to -67%) in the injected lesions had paired assessments available in adjacent, non-injected lesions. In 6/7 patients, a reduction in CAILS was observed in the non-injected lesions (-12% to -67%), indicating that TTI-621 could induce local-regional responses that were not confined to the site of injection. Additionally, one patient with transformed MF exhibited clear evidence of abscopal effects with rapid resolution of lesions on the abdomen, left flank/back and arms less than two weeks after receiving IL TTI-621 injections in lesions on the foot and leg. The only SS patient on study achieved a reduction in circulating Sézary cells after a single 3 mg local injection of TTI-621.ConclusionsPreliminary data from this ongoing study indicate that IL TTI-621 administration is well-tolerated and has single agent activity in heavily pre-treated MF/SS patients across various disease stages. The rapid responses observed occurred in both injected and non-injected lesions indicating a local-regional effect with initial evidence of distant abscopal or systemic effects. Enrollment in this study is continuing to evaluate the impact of weekly maintenance dosing and further characterize the systemic effect and durability of responses. [Display omitted] DisclosuresQuerfeld:Kyowa: Membership on an entity's Board of Directors or advisory committees; Acelion: Membership on an entity's Board of Directors or advisory committees; Bioniz: Membership on an entity's Board of Directors or advisory committees; Medivir: Membership on an entity's Board of Directors or advisory committees; Trillium Therapeutics: Membership on an entity's Board of Directors or advisory committees. Thompson:Trillium Therapeutics: Research Funding. Taylor:Trillium Therapeutics: Research Funding. Johnson:Trillium Therapeutics: Employment. Catalano:Trillium Therapeutics: Employment. Petrova:Trillium Therapeutics: Employment. Thompson:Trillium Therapeutics: Employment. Uger:Trillium Therapeutics: Employment. Shou:Trillium Therapeutics: Employment. Akilov:Kyowa Kirin: Consultancy; Pfizer: Research Funding; Seattle Genetics: Consultancy; Trillium Therapeutics: Research Funding; Actelion Pharmaceuticals: Consultancy.

Abstract 3852: Combination efficacy and safety profile of an orally bioavailable small molecule agent targeting CD47/SIRPα axis

Abstract Introduction: Most of the immunotherapies currently approved in the clinic target immune checkpoint proteins that suppress T-cell responses. There is growing evidence that the innate immune system also plays an important role in the initiation and propagation of enduring antitumor responses. Targeting CD47-SIRPα axis is emerging as one of the promising new immunotherapy approaches that targets innate immune response. A number of clinical trials are in progress to evaluate CD47/SIRPα blocking therapies. Most of these molecules are either anti-CD47 antibodies or SIRPα-Fc recombinant proteins. We are developing a novel small molecule CD47 antagonist, AUR-104, as therapeutic agent for solid and hematalogical cancers. AUR-104 is a CD47 antagonist that disrupts CD47- SIRPα interaction and enhances phagocytosis of tumor cells. AUR-104 exhibits good drug-like properties and demonstrates antitumor activity in several pre-clinical tumor models. Here, we report the anti-tumor efficacy of AUR-104 in combination with tumor specific antibodies in pre-clinical models of cancer and also present the safety profile of AUR-104 in rodents. Materials and Methods: Syngeneic murine tumor models: MC38 colon carcinoma cells were subcutaneously implanted in C57BL/6J mice while A20 B-cell lymphoma cells were implanted in BALB/c mice. Tumor bearing mice were treated with AUR-104 (30 mg/kg, b.i.d, and po) as a single agent or in combination with anti-PD1 antibody (100 µg/animal) or anti-PDL1 antibody (200 µg/animal). Tumor volumes were recorded with calliper's measurement over period of treatment. A single dose maximum tolerated dose (MTD) study in BALB/c mouse followed by a 14-day repeat dose toxicity study in BALB/c mouse: Adult male and female BALB/c, are dosed with AUR-104 at ascending doses up to the limit dose. End points monitored include clinical observations, toxicokinetic parameters, body weights, food consumption, hematology, clinical pathology investigations, organ weights and histopathology of selected tissues. Results: AUR-104 combination treatment with anti-PD1 antibody significantly enhanced anti-tumor efficacy in MC38 colon carcinoma model. Combination study with anti-PDL1 antibody in A20 tumor model is in progress. Preliminary observations from efficacy studies indicate that AUR-104 combination treatments with antibodies are well tolerated without any signs of toxicity. Advance in vitro safety evaluation and in vivo 14 day repeat day toxicity study in mice are being initiated. In summary, AUR-104 plus anti-PD1 antibody was a well-tolerated drug combination that exhibited a much greater in vivo antitumor response as compared to the single agent treatments. These results demonstrate the therapeutic potential of CD47 antagonist AUR-104 in combination with other tumor specific antibodies for the treatment of cancer. Citation Format: Girish Daginakatte, Sasikumar Pottayil, Gundala Chennakrishna, Wesley Roy Balasubramanian, Sudarshan Naremaddepalli, Archana Bhumireddy, Sandeep Patil, Kavitha Nellore, Priyabrata Chand, Kiran Aithal, Amit Dhudashiya, Samiulla DS, Rajesh Eswarappa, Murali Ramachandra. Combination efficacy and safety profile of an orally bioavailable small molecule agent targeting CD47/SIRPα axis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3852.

Interventions for necrotizing soft tissue infections in adults

Interventions for necrotizing soft tissue infections in adults

A selective CD28 antagonist and rapamycin synergise to protect against spontaneous autoimmune diabetes in NOD mice.

The CD28/B7 interaction is critical for both effector T cell activation and forkhead box P3 (FOXP3)+ regulatory T cell (Treg) generation and homeostasis, which complicates the therapeutic use of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4)-immunoglobulin fusion protein (CTLA-4Ig) in autoimmunity. Here, we evaluated the impact of a simultaneous and selective blockade of the CD28 and mammalian target of rapamycin (mTOR) pathways in the NOD mouse model of type 1 diabetes. NOD mice were treated with PEGylated anti-CD28 Fab' antibody fragments (PV1-polyethylene glycol [PEG], 10mg/kg i.p., twice weekly), rapamycin (1mg/kg i.p., twice weekly) or a combination of both drugs. Diabetes incidence, pancreatic islet infiltration and autoreactive T cell responses were analysed. We report that 4week administration of PV1-PEG combined with rapamycin effectively controlled the progression of autoimmune diabetes in NOD mice at 10weeks of age by reducing T cell activation and migration into the pancreas. Treatment with rapamycin alone was without effect, as was PV1-PEG monotherapy initiated at 4, 6 or 10weeks of age. Prolonged PV1-PEG administration (for 10weeks) accelerated diabetes development associated with impaired peripheral Treg homeostasis. This effect was not observed with the combined treatment. CD28 antagonist and rapamycin treatment act in a complementary manner to limit T cell activation and infiltration of pancreatic islets and diabetes development. These data provide new perspectives for the treatment of autoimmune diabetes and support the therapeutic potential of protocols combining antagonists of CD28 (presently in clinical development) and the mTOR pathway.

Abstract B007: Potent antitumor activity of a novel and orally available small-molecule antagonist targeting the CD47/SIRPα pathway

Abstract Antibodies targeting PD-1 and PD-L1 towards stimulation of T cells have revolutionized cancer therapy because of the highly durable response in multiple cancer indications. Although macrophages and other myeloid immune cells offer much promise as effectors of cancer immunotherapy, efforts to modulate them for therapeutic benefit have gained momentum only in the last few years. The CD47/signal regulatory protein alpha (SIRPα) axis is a critical regulator of myeloid cell activation and serves as an immune checkpoint for macrophage-mediated phagocytosis. Because of its frequent upregulation in several cancers, CD47 contributes to immune evasion and cancer progression. Disruption of CD47-SIRPα interaction is now being evaluated as a therapeutic strategy for cancer with the use of monoclonal antibodies targeting CD47 or SIRPα, and engineered receptor decoys. In view of the requirement for the intravenous dosing for all reported CD47 targeting agents, we sought to discover and develop an orally available small-molecule CD47 antagonist. An oral CD47 agent potentially offers the convenience, flexibility to adjust the dose and schedule to address any emergent adverse events, and ease of combination therapy. Through rational design based on the crystal structure of CD47/SIRPα interacting interface, we generated a series of peptides capable of disrupting CD47-SIRPα interactions. Relative binding affinities of the peptides were determined in a newly established cellular assay that utilizes a SIRPα-derived peptide as the probe. The high-affinity peptides were further truncated to identify the shortest peptide pharmacophore. The elements of this pharmacophore were incorporated into nonpeptidic small-molecule scaffolds, resulting in lead compounds disrupting CD47/SIRPα interaction. The lead CD47 antagonists induced phagocytototic activity of human macrophages to a similar extent as commercially available anti-CD47 antibodies. Further optimization of these leads resulted in compounds with desirable physicochemical properties and good oral bioavailability. An advanced lead CD47 antagonist inhibited primary tumor growth (~90%TGI) in a mouse syngeneic model of B-cell lymphoma upon twice-a-day oral dosing. Biomarker characterization and efficacy studies in additional tumor models are ongoing. These findings support further development of these orally bioavailable agents for use in the clinic. Citation Format: Pottayil G. Sasikumar, Chennakrishnareddy Gundala, Wesley R. Balasubramanian, Sudarshan S. Naremaddepalli, Archana Bhumireddy, Sandeep S. Patil, Amit A. Dhudashiya, Vijaysai Rayavarapu, Anirudha Lakshminarasimhan, Dodheri S. Samiulla, Kiran Aithal, Girish Daginakatte, Murali Ramachandra. Potent antitumor activity of a novel and orally available small-molecule antagonist targeting the CD47/SIRPα pathway [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B007.

Reltecimod. T-cell-specific surface glycoprotein CD28 (TP44) antagonist, CD28 homodimer interface mimetic peptide, Treatment of necrotizing soft-tissue infection

Reltecimod. T-cell-specific surface glycoprotein CD28 (TP44) antagonist, CD28 homodimer interface mimetic peptide, Treatment of necrotizing soft-tissue infection