Markus Y. Mapara

RGI-2001, a glycolipid that binds CD1d receptor of antigen-presenting cells, can activate invariant natural killer T (NKT) cells and stimulate cytokine-dependent proliferation of regulatory T cells (Tregs). This open-label, multicenter phase 2b trial evaluated the safety and efficacy of RGI-2001 in combination with standard graft-versus-host disease (GVHD) prophylaxis in participants receiving myeloablative allogeneic hematopoietic cell transplantation (HCT). RGI-2001 was infused at a dose of 100 μg/kg for 6 weekly doses. The primary end point was grade 2 to 4 acute GVHD by day 100. A total of 49 participants received RGI-2001 in combination with tacrolimus and methotrexate. RGI-2001 was well tolerated, with no serious infusion reactions. Sixteen participants experienced grade ≥3 treatment-related adverse events, including decreased appetite, leukopenia, thrombocytopenia, and stomatitis. The cumulative incidence of grade 2 to 4 and 3 to 4 acute GVHD were 24.9% and 4.1%, respectively. Compared with the controls from the Center for International Blood and Marrow Research Transplant registry, participants receiving RGI-2001 experienced superior clinical outcomes, including day-180 grade 2 to 4 acute GVHD-free survival (70.8% vs 50.7%; adjusted hazard ratio, 0.45; 95% confidence interval, 0.30-0.68). Increasing NKT and Treg populations were observed after HCT, consistent with the proposed action of RGI-2001. In conclusion, RGI-2001 was well tolerated and was associated with low rates of acute GVHD and encouraging survival after myeloablative HCT. These results support strategies that target NKT and Treg cell populations to augment immunologic changes in allogeneic HCT recipients. This trial was registered at www.clinicaltrials.gov as #NCT04014790.

Supplementary Figures 1. Analysis of eIF4E protein levels by western blotting of whole cell extracts from primary stromal cells, CD138- cells, primary myeloma cells (CD138+) and normal plasma cells. Supplementary Figures 2. CT shRNA, eIF4E shRNA, PCDH-GFP or PCDH-eIF4E U266 cells were analyzed by Annexin V binding/ PI staining for apoptotic cells.

The absence of IFN-γ receptor (IFN-γR) or STAT1 signaling in donor cells has been shown to result in reduced induction of acute graft-versus-host disease (GVHD). In this study, we unexpectedly observed increased activation and expansion of donor lymphocytes in both lymphohematopoietic organs and GVHD target tissues of IFN-γR/STAT1–deficient recipient mice, leading to rapid mortality following the induction of GVHD. LPS-matured, BM-derived Ifngr1^–/– Stat1^–/– DCs (BMDCs) were more potent allogeneic stimulators and expressed increased levels of MHC II and costimulatory molecules. Similar effects were observed in human antigen-presenting cells (APCs) with knockdown of Stat1 by CRISPR/Cas9 and treatment with a JAK1/2 inhibitor. Furthermore, we demonstrated that the absence of IFN-γR/STAT1 signaling in hematopoietic APCs impaired the presentation of exogenous antigens, while promoting the presentation of endogenous antigens. Thus, the indirect presentation of host antigens to donor lymphocytes was defective in IFN-γR/STAT1–deficient, donor-derived APCs in fully donor chimeric mice. The differential effects of IFN-γR/STAT1 signaling on endogenous and exogenous antigen presentation could provide further insight into the roles of the IFN-γ/STAT1 signaling pathway in the pathogenesis of GVHD, organ rejection, and autoimmune diseases.

Recently, mitogen-activated protein kinase kinase kinase kinase 2 (MAP4K2) has emerged as an important key regulator of the stress-activated MAPK core signaling pathways. MAP4K2, also called Germinal Center Kinase (GCK), is predominantly and highly expressed in the germinal center of B cells. Recently we have shown that MAP4K2 knockdown in K- or N-RAS mutated MM cells induces MM cell growth inhibition, associated with the downregulation of critical transcriptional factors including IKZF1/3, BCL-6, and c-MYC proteins (Li et al. Blood 2021). Importantly, MAP4K2 silencing induces IKZF1 protein degradation without affecting IKZF1 mRNA level. Furthermore, IMiDs-resistant K-RAS ^Mut MM cells are sensitive to MAP4K2 inhibition induced IKZF1 degradation and cell growth suppression, suggesting that MAP4K2 inhibition overcomes IMiDs resistances in MM. To further validate MAP4K2 inhibition as a novel strategy to overcome IMiDs-resistance, we generated lenalidomide-resistant human myeloma cell lines. In this model, MM1S-LEN ^RES cells showed significantly decreased expression of CRBN protein compared to the parent cells. Accordingly, upon lenalidomide treatment, CRBN-mediated down-regulation of IKZF1, c-MYC, IKZF3 and IRF4 were abrogated in the MM1S-LEN ^RES cells. As expected, MM1S-LEN ^RES cells were resistant to lenalidomide induced growth inhibition in cell proliferation assay. In contrast, MAP4K2 inhibition using TL4-12 potently induced IKZF1, c-MYC, and IRF4 downregulation as well as cell proliferation inhibition, demonstrating that MAP4K2 regulates IKZF1 and cell growth independently of CRBN. These results indicate that MAP4K2 is a novel therapeutic target to overcome IMiDs-resistance MM. Iberdomide (CC-220) is an orally available IMiD® compound under development for the treatment of relapsed/refractory multiple myeloma. Previous biochemical and structural studies demonstrated that Iberdomide binds to cereblon with a higher affinity than lenalidomide or pomalidomide. Here, we evaluated the combination effects of Iberdomide with MAP4K2 silencing in MM. Tet-on sh-MAP4K2 lentivirus were introduced into RAS ^Mut MM cells to establish the inducible MAP4K2 knockdown cells upon doxycycline treatment. To address the combination effects, Tet-on sh-MAP4K2 RAS ^Mut MM cells were treated with doxycycline and different dosages of iberdomide. We found that MAP4K2 silencing strongly increased iberdomide-induced apoptosis (iberdomide alone vs. with MAP4K2 KD: 32% vs 92). Similar, in western blot assays, MAP4K2 silencing combined with Iberdomide significantly enhanced downregulation of IKZF1, c-MYC, and IRF4 compared to the iberdomide treatment alone. These data suggest that combination of iberdomide and MAP4K2 inhibition have synergetic anti-MM effects. Taken together, our findings demonstrate that MAP4K2 is a novel therapeutic target to bypass IMiDs resistance in RAS mutated MM. Combination of MAP4K2 inhibition with Iberdomide results in synergetic anti-cancer effects in MM, therefore could be a potent novel therapeutic regimen for patients with relapsed/refractory multiple myeloma.

Cellular therapies such as allogeneic hematopoietic stem cell transplantation (HSCT) and immune-effector cell therapy (IECT) continue to have a critical role in the treatment of patients with high risk malignancies and hematologic conditions. These therapies are also associated with inflammatory conditions such as graft-versus-host disease (GVHD) and cytokine release syndrome (CRS) which contribute significantly to the morbidity and mortality associated with these therapies. Recent advances in our understanding of the immunological mechanisms that underly GVHD and CRS highlight an important role for Janus kinases (JAK). JAK pathways are important for the signaling of several cytokines and are involved in the activation and proliferation of several immune cell subsets. In this review, we provide an overview of the preclinical and clinical evidence supporting the use of JAK inhibitors for acute and chronic GVHD and CRS.