Phase Ib study of sabatolimab (MBG453), a novel immunotherapy targeting TIM-3 antibody, in combination with decitabine or azacitidine in high- or very high-risk myelodysplastic syndromes

Novel Peptide-Based 68Ga-Labeled Radiotracer for Preclinical Studies of TIM3 Expression

T-cell immunoglobulin and mucin domain-3 (TIM3) is an immune checkpoint that plays a negative regulatory role in the immune response. TIM3-targeted drugs inhibit this negative regulation, thereby modulating the level of immune response activation. In the previous investigation, several peptides targeting TIM3 were identified through screening from a phage peptide library. In this research, three peptides were selected to construct the radioactive molecular probes according to the characteristic that targeting TIM3 drugs would lead to the increase of interferon-γ (IFN-γ) secretion. Molecular docking was performed to assess the binding properties of the selected peptides with the TIM3 protein. To further enhance the targeting properties, one of the peptides with a higher-affinity peptide was structurally modified. Then, 68Ga was used to construct the peptide probe 68Ga-DOTA-peptide by labeling the six peptides with 68Ga riboprobes, and the binding affinity and specificity were assessed using TIM3 overexpressing cell line A549TIM3 and the parental A549 cells. In addition, in Micro-PET/CT imaging, transfected model mice were dynamically imaged for 30 min after injection of 3.7-7.4 MBq 68Ga-DOTA-peptides via the tail vein. Meanwhile, the same dose of molecular probes was injected in the MC38 model (colorectal cancer in mice) and the CCRCC (clear cell renal cell carcinoma) xenografted model, followed by static scans at 15, 30, and 60 min postinjection. Finally, immunohistochemical (IHC) staining was performed to assess TIM3 expression in the dissected tumor tissues. The molecular docking results showed that the binding energy of P26 to TIM3 protein was -6.5 kcal/mol, which was lower than that of P24 to TIM3 protein, -3.6 kcal/mol, indicating that the affinity of P26 peptide to TIM3 protein was higher than that of P24 and P20 peptide. After structural modification of the P26 peptide, P26NH2, r-NH2, and P26X2 were obtained, and the above peptides were successfully constructed into six targeting TIM3 peptide probes by 68Ga labeling. Cellular uptake experiments demonstrated that 68Ga-DOTA-P26, 68Ga-DOTA-P26NH2, and 68Ga-DOTA-r-NH2 showed significantly higher uptake in A549TIM3 cells than in A549 cells and could be blocked by the unlabeled peptide. Micro-PET imaging experiments showed that the uptake of each probe in the A549TIM3 model tumor tissue was significantly higher than that in the A549 model tumor tissue, and a comparison of the tumor-to-cardiac uptake ratios of each group showed that the 68Ga-DOTA-P26 had a better tumor-to-cardiac uptake ratio in the A549TIM3 model than several other molecular probes, and in the MC38 model, similar results were obtained, with the difference that the 68Ga-DOTA-P26NH2 had the highest tumor-to-cardiac uptake ratio in the CCRCC model. Finally, validation by IHC showed that A549TIM3, MC38, and CCRCC tumor tissues had varying degrees of TIM3 expression. Upon comparison of ex vivo and in vivo studies, one of them, the 68Ga-DOTA-P26 probe, demonstrated significant target specificity for TIM3. These results suggest that studying peptide probes targeting TIM3 will promote the process of TIM3-targeted drug research and is expected to guide the application of TIM3 immune checkpoint drugs in immunotherapy.

The role of Tim-3 blockade in the tumor immune microenvironment beyond T cells

Numerous preclinical studies have demonstrated the inhibitory function of T cell immunoglobulin mucin domain-containing protein 3 (Tim-3) on T cells as an inhibitory receptor, leading to the clinical development of anti-Tim-3 blocking antibodies. However, recent studies have shown that Tim-3 is expressed not only on T cells but also on multiple cell types in the tumor microenvironment (TME), including dendritic cells (DCs), natural killer (NK) cells, macrophages, and tumor cells. Therefore, Tim-3 blockade in the immune microenvironment not only affect the function of T cells but also influence the functions of other cells. For example, Tim-3 blockade can enhance the ability of DCs to regulate innate and adaptive immunity. The role of Tim-3 blockade in NK cells function is controversial, as it can enhance the antitumor function of NK cells under certain conditions while having the opposite effect in other situations. Additionally, Tim-3 blockade can promote the reversal of macrophage polarization from the M2 phenotype to the M1 phenotype. Furthermore, Tim-3 blockade can inhibit tumor development by suppressing the proliferation and metastasis of tumor cells. In summary, increasing evidence has shown that Tim-3 in other cell types also plays a critical role in the efficacy of anti-Tim-3 therapy. Understanding the function of anti-Tim-3 therapy in non-T cells can help elucidate the diverse responses observed in clinical patients, leading to better development of relevant therapeutic strategies. This review aims to discuss the role of Tim-3 in the TME and emphasize the impact of Tim-3 blockade in the tumor immune microenvironment beyond T cells.

Targeted therapies for myelodysplastic syndromes/neoplasms (MDS): current landscape and future directions

INTRODUCTION

Myelodysplastic syndromes/neoplasms (MDS) are a heterogeneous group of hematologic malignancies that are stratified into high-risk (HR-MDS) and low-risk (LR-MDS) categories. Until recently, LR-MDS has been typically managed by supportive measures and erythropoiesis-stimulating agents (ESAs); whereas management of HR-MDS typically included hypomethylating agents and allogeneic hematopoietic stem cell transplant. However, the limited rates and durations of response observed with these interventions prompted the search for targeted therapies to improve the outcomes among patients with MDS.

AREAS COVERED

Here, we review the current landscape of targeted therapies in MDS. These include pyruvate kinase and hypoxia-inducible factor (HIF) activators; TGF-beta, telomerase, BCL2 and isocitrate dehydrogenase (IDH) inhibitors; as well as novel approaches targeting inflammation, pyroptosis, immune evasion, and RNA splicing machinery.

EXPERT OPINION

This review highlights the progress and challenges in MDS treatment. Despite some promising results, many therapies remain in early development or have faced setbacks, emphasizing the need for a more comprehensive understanding of the disease's pathobiology. Continued research into targeted therapies, homogenous clinical trial designs, as well as increased incorporation of molecular prognostic tools and artificial intelligence into trial design are essential for developing effective treatments for MDS and improving patient outcomes.

Immune-dysregulation harnessing in myeloid neoplasms

Myeloid malignancies arise in bone marrow microenvironments and shape these microenvironments in favor of malignant development. Immune suppression is one of the most important stages in myeloid leukemia progression. Leukemic clone expansion and immune dysregulation occur simultaneously in bone marrow microenvironments. Complex interactions emerge between normal immune system elements and leukemic clones in the bone marrow. In recent years, researchers have identified several of these pathological interactions. For instance, recent works shows that the secretion of inflammatory cytokines such as tumor necrosis factor-α (TNF-α), from bone marrow stromal cells contributes to immune dysregulation and the selective proliferation of JAK2V617F+ clones in myeloproliferative neoplasms. Moreover, inflammasome activation and sterile inflammation result in inflamed microenvironments and the development of myelodysplastic syndromes. Additional immune dysregulations, such as exhaustion of T and NK cells, an increase in regulatory T cells, and impairments in antigen presentation are common findings in myeloid malignancies. In this review, we discuss the role of altered bone marrow microenvironments in the induction of immune dysregulations that accompany myeloid malignancies. We also consider both current and novel therapeutic strategies to restore normal immune system function in the context of myeloid malignancies.

Impact of p53-associated acute myeloid leukemia hallmarks on metabolism and the immune environment

Acute myeloid leukemia (AML), an aggressive malignancy of hematopoietic stem cells, is characterized by the blockade of cell differentiation, uncontrolled proliferation, and cell expansion that impairs healthy hematopoiesis and results in pancytopenia and susceptibility to infections. Several genetic and chromosomal aberrations play a role in AML and influence patient outcomes. TP53 is a key tumor suppressor gene involved in a variety of cell features, such as cell-cycle regulation, genome stability, proliferation, differentiation, stem-cell homeostasis, apoptosis, metabolism, senescence, and the repair of DNA damage in response to cellular stress. In AML, TP53 alterations occur in 5%-12% of de novo AML cases. These mutations form an important molecular subgroup, and patients with these mutations have the worst prognosis and shortest overall survival among patients with AML, even when treated with aggressive chemotherapy and allogeneic stem cell transplant. The frequency of TP53-mutations increases in relapsed and recurrent AML and is associated with chemoresistance. Progress in AML genetics and biology has brought the novel therapies, however, the clinical benefit of these agents for patients whose disease is driven by TP53 mutations remains largely unexplored. This review focuses on the molecular characteristics of TP53-mutated disease; the impact of TP53 on selected hallmarks of leukemia, particularly metabolic rewiring and immune evasion, the clinical importance of TP53 mutations; and the current progress in the development of preclinical and clinical therapeutic strategies to treat TP53-mutated disease.

Infections and antimicrobial prophylaxis in patients with myelodysplastic syndromes

Infectious complications are an important cause of morbidity and mortality in patients with myelodysplastic syndromes (MDS). Preventing infections could significantly improve both survival and quality of life. Unfortunately, both infections and antimicrobial prophylaxis in patients with MDS are incompletely assessed due to the heterogeneity of disorders included in each publication, changing definitions over time, and lack of standardized prophylaxis practices. Despite these limitations, some basic statements can be made. Infections in MDS are associated with neutropenia. Patients with lower-risk (LR) MDS tend to have fewer infections compared to patients with higher-risk (HR) MDS, which may be related to the different prevalence of neutropenia in the 2 groups. Pneumonia is the most common infection, and bacteria are the most common pathogens. Invasive fungal infections (IFI) are uncommon. Reactivation of latent viruses are rare. With the limited data available, we agree that antibacterial prophylaxis can be considered in patients with HR-MDS during severe neutropenia and early cycles of therapy when infections are most likely to occur. Given the low prevalence of IFI and viral reactivation, antimicrobial prophylaxis for these pathogens is less likely to be advantageous for most patients, although antifungal prophylaxis with activity against mold is commonly used in patients with persistent, profound neutropenia. Ultimately, improved data collection regarding infections and antimicrobial prophylaxis is needed to improve care for patients with MDS.

Sabatolimab plus hypomethylating agents in previously untreated patients with higher-risk myelodysplastic syndromes (STIMULUS-MDS1): a randomised, double-blind, placebo-controlled, phase 2 trial

BACKGROUND

Sabatolimab is an immunotherapy targeting T-cell immunoglobulin domain and mucin domain-3 (TIM-3), an immuno-myeloid regulator expressed on immune cells and leukaemic stem cells. In this trial, we compared the efficacy and safety of sabatolimab plus hypomethylating agent with placebo plus hypomethylating agents in previously untreated patients with higher-risk myelodysplastic syndromes.

METHODS

STIMULUS-MDS1 was a multicentre, randomised, double-blind, placebo-controlled, phase 2 study done at 54 investigational sites in 17 countries. Adult patients (aged ≥18 years) with intermediate-risk, high-risk, and very high-risk myelodysplastic syndromes (according to Revised International Prognostic Scoring System criteria) who had not received previous treatment were included. Patients were randomly assigned (1:1) to intravenous sabatolimab (400 mg on day 8 and 22) or placebo plus a hypomethylating agent (intravenous decitabine 20 mg/m2 on day 1-5 or intravenous or subcutaneous azacitidine 75 mg/m2 on day 1-7 or day 1-5 and day 8 and 9) every 28 days until treatment discontinuation. The two primary endpoints were complete response rate and progression-free survival, assessed in the full analysis set, which included all randomly assigned patients. Complete response was analysed, as prespecified, 7 months after the last patient was randomly assigned. All other analyses presented, including progression-free survival, were done at the final data cutoff prespecified via a protocol amendment on Sept 2, 2021. Safety was assessed in in all patients who received at least one dose of study treatment. This study is registered with ClinicalTrials.gov, NCT03946670, and is ongoing.

FINDINGS

Between July 29, 2019, and Aug 10, 2020, 127 patients were randomly assigned to sabatolimab plus a hypomethylating agent group (sabatolimab group; n=65) or placebo plus a hypomethylating agent (placebo group; n=62). The median age of participants was 73 years (IQR 69-77), of whom 86 (68%) of 127 patients were male and 77 (61%) were White. The primary endpoints were not met. Complete response (cutoff date of March 10, 2021) was achieved in 14 (22%; 95% CI 12·3-33·5) of 65 patients in the sabatolimab group vs 11 (18%; 9·2-29·5) of 62 patients in the placebo group (p=0·77). At the cutoff date of the final analysis (March 1, 2022), median follow-up for progression-free survival was 17·8 months (IQR 16·6-19·4) in the sabatolimab group and 19·2 months (17·7-22·3) in the placebo group, and the median progression-free survival was 11·1 months (95% CI 7·6-17·6) in the sabatolimab group vs 8·5 months (6·9-11·3) in the placebo group (hazard ratio 0·75 [95% CI 0·48-1·17]; p=0·1022). The most common adverse events of any grade were neutropenia (35 [56%] of 62 patients in the sabatolimab group vs 43 [68%] of 63 patients in the placebo group), thrombocytopenia (30 [48%] vs 32 [51%]), constipation (29 [47%] vs 24 [38%]), diarrhoea (27 [44%] vs 14 [22%]), anaemia (22 [35%] vs 34 [54%]), febrile neutropenia (22 [35%] vs 15 [24%]), and leukopenia (15 [24%] vs 20 [32%]). One patient developed a serious potential treatment-related immune-mediated adverse event in the sabatolimab group. There was one treatment-related death in the sabatolimab group due to pneumonitis.

INTERPRETATION

The addition of sabatolimab to hypomethylating agents in this study did not result in a significant improvement in complete response rates or progression-free survival. Sabatolimab had a manageable safety in most patients with higher-risk myelodysplastic syndromes. A randomised phase 3 trial is ongoing to assess the potential benefit of sabatolimab plus azacitidine on overall survival in this setting.

FUNDING

Novartis Pharmaceuticals.