Immunotherapy in Multiple Myeloma-Time for a Second Major Paradigm Shift

The TGFβ type I receptor kinase inhibitor vactosertib in combination with pomalidomide in relapsed/refractory multiple myeloma: a phase 1b trial

Functional blockade of the transforming growth factor-beta (TGFβ) signalling pathway improves the efficacy of cytotoxic and immunotherapies. Here, we conducted a phase 1b study (ClinicalTrials.gov., NCT03143985) to determine the primary endpoints of safety, tolerability, and maximal tolerated dose (200 mg twice daily) for the orally-available TGFβ type I receptor kinase inhibitor vactosertib in combination with pomalidomide in relapsed and/or refractory multiple myeloma (RRMM) patients who had received ≥2 lines of chemoimmunotherapy. Secondary endpoints demonstrated sustained clinical responses, favorable pharmacokinetic parameters and a 6-month progression-free survival of 82%. Vactosertib combined with pomalidomide was well-tolerated at all dose levels and displayed a manageable adverse event profile. Exploratory analysis indicated that vactosertib co-treatment with pomalidomide also reduced TGFβ levels in patient bone marrow as well as the level of CD8+ T-cells that expressed the immunoinhibitory marker PD-1. In vitro experiments indicated that vactosertib+pomalidomide co-treatment decreased the viability of MM cell lines and patient tumor cells, and increased CD8+ T-cell cytotoxic activity. Vactosertib is a safe therapeutic that demonstrates tumor-intrinsic activity and can overcome immunosuppressive challenges within the tumor microenvironment to reinvigorate T-cell fitness. Vactosertib offers promise to improve immunotherapeutic responses in heavily-pretreated MM patients refractory to conventional agents.

Treatment Pattern, Healthcare Resource Utilization and Symptom Burden Among Patients with Triple Class Exposed Multiple Myeloma: A Population-Based Cohort Study

PURPOSE

This study aims to describe the treatment patterns, outcomes, health care utilization and symptom burden of triple class exposed (TCE) relapsed/refractory patents with multiple myeloma (MM) receiving a subsequent line of treatment (LOT).

METHODS

This is a retrospective observational cohort study using administrative databases in Ontario, Canada. Outcomes were captured for TCE patients receiving a subsequent LOT and included: treatment regimen details, time to next treatment (TTNT), overall survival (OS), health care utilization, palliative care referral, and patient reported symptoms.

RESULTS

Of the 16,777 patients diagnosed with MM between 2007-2021 in Ontario, 1358 (8%) patients were classified as TCE. Among the TCE MM patients, 489 (36%) received a subsequent LOT. The two most commonly administered therapies post TCE were carfilzomib/dexamethasone (n = 111, 22%) and pomalidomide/dexamethasone(n = 95, 19%). Median TTNT was 1.7 months (95%CI 1.2-2.4 months) and median OS 12.8 months (95%CI 10.8-16.5). Healthcare utilization was high with 276 (56%) of patients evaluated in an emergency department (ED) or admitted to hospital. There was high symptom burden as reported by patients with moderate-severe impairment in well-being, fatigue, pain and drowsiness noted in greater than 25% of the cohort. Palliative care referrals rates were low with only 10% (n = 48) patients referred to palliative care. Among the patients that died during study follow up, the majority died in hospital (n = 147,44%).

CONCLUSION

Our study reports one of the largest series of real-world TCE patients published and demonstrates the poor outcomes of TCE patients receiving a subsequent LOT.

Treg-derived TGF-β1 dampens cGAS-STING signaling to downregulate the expression of class I MHC complex in multiple myeloma

Multiple myeloma (MM) progression involves diminished tumor antigen presentation and an immunosuppressive microenvironment, characterized by diminished expression of major histocompatibility complexes (MHC) class I molecule and elevated programmed death ligand 1 (PDL1) in MM cells, along with an enriched population of regulatory T cells (Tregs). To investigate Treg's influence on MM cells, we established a co-culture system using Tregs from MM patients and the MM cell lines (MM.1S and SK-MM-1) in vitro and assessed the effects of intervening in the relevant pathways connecting Tregs and MM cells in vivo. In vitro, Tregs induced transforming growth factor beta-1 (TGF-β1) production, downregulated MHC I members, and increased PDL1 expression in MM cells. Treg-derived TGF-β1 suppressed the cGAS-STING pathway, contributing to the loss of MHC I molecule expression and PDL1 upregulation. Correspondingly, neutralizing TGF-β1 or activating the cGAS-STING pathway restored MHC I and PDL1 expression, effectively countering the pro-tumorigenic effect of Tregs on MM cells in vivo. These data elucidated how Tregs influence tumor antigen presentation and immunosuppressive signal in MM cells, potentially providing therapeutic strategies, such as neutralizing TGF-β1 or activating the cGAS-STING pathway, to address the immune escape and immunosuppressive dynamics in MM.

Multiple Myeloma: The Role of Autologous Stem Cell Transplantation in the Era of Immunotherapy

Upfront high-dose therapy with melphalan (HDM) followed by autologous stem cell transplantation (ASCT) has established itself as a core treatment for newly diagnosed multiple myeloma (NDMM) patients in the past 30 years. Induction therapy, HDM-ASCT, and subsequent consolidation and maintenance therapy comprise the current fundamental framework for MM treatment. The introduction of anti-CD38 monoclonal antibodies such as daratumumab and isatuximab has changed the treatment paradigm for transplant-eligible NDMM patients in that quadruplets have become the new standard induction therapy. The treatment landscape of MM is undergoing a transformative shift with the introduction of potent new immunotherapies, such as chimeric antigen receptor (CAR)-T cells and bispecific antibodies (BsAbs), which are currently used in the relapsed/refractory setting (RRMM) and are already being tested in the NDMM. This review will focus on the incorporation of immunotherapy in the treatment scenario of NDMM patients eligible for ASCT.

Chimeric antigen receptor T-cell therapy in multiple myeloma: A comprehensive review of current data and implications for clinical practice

Multiple myeloma (MM) is a hematologic malignancy defined by the clonal proliferation of transformed plasma cells. Despite tremendous advances in the treatment paradigm of MM, a cure remains elusive for most patients. Although long-term disease control can be achieved in a very large number of patients, the acquisition of tumor resistance leads to disease relapse, especially in patients with triple-class refractory MM (defined as resistance to immunomodulatory agents, proteosome inhibitors, and monoclonal antibodies). There is an unmet need for effective treatment options in these patients. Chimeric antigen receptor (CAR) T-cell therapy is a novel approach that has demonstrated promising efficacy in the treatment of relapsed, refractory MM (RRMM). These genetically modified cellular therapies have demonstrated deep and durable remissions in other B-cell malignancies, and current efforts aim to achieve similar results in patients with RRMM. Early studies have demonstrated remarkable response rates with CAR T-cell therapy in RRMM; however, durable responses with CAR T-cell therapies in myeloma have yet to be realized. In this comprehensive review, the authors describe the development of CAR T-cell therapies in myeloma, the outcomes of notable clinical trials, the toxicities and limitations of CAR T-cell therapies, and the strategies to overcome therapeutic challenges of CAR T cells in the hope of achieving a cure for multiple myeloma.

Real-world treatment patterns and outcomes of triple-class treated patients with multiple myeloma in the United States

OBJECTIVES

Although multiple myeloma (MM) survival has improved following the introduction of proteosome inhibitors, immunomodulatory drugs, and anti-CD38 therapies, patients become refractory to these agents. Real-world outcomes of triple-class exposed patients are limited and were investigated in this study.

METHODS

The Integra Connect Database was used to assess the treatment patterns of triple-class exposed patients with relapsed/refractory MM (RRMM) (January 2016-December 2019).

RESULTS

During this period, patients (N = 501) reached triple exposure in a median of three lines of therapy (LOTs) over 995 days. A new LOT was started in a median of 18 (1-691) days after triple exposure; 71% of the patients started a new LOT within 30 days. Throughout the follow-up period, 8% of the patients had a therapy gap greater than 90 days. Following triple exposure, 103/501 patients (21%) received only triple-class agents in subsequent LOTs, while 24 (4.8%) patients received only non-triple-class agents. The median apparent survival from initiation of first therapy after triple exposure was 308 days.

CONCLUSION

These results indicate that recycling of triple-class agents after previous exposure is widespread and prognosis in the RRMM population remains poor, highlighting the continuing unmet need for new agents with novel mechanisms to improve patient outcomes.

CD229 interacts with RASAL3 to activate RAS/ERK pathway in multiple myeloma proliferation

Multiple myeloma (MM) is an incurable plasma cell malignancy, while CAR-T therapy offers a new direction for the treatment of MM. Recently, signaling lymphocytic activation molecule family 3 (CD229), a cell surface immune receptor belonging to the signaling lymphocyte activating molecule family (SLAMF), is emerging as a CAR-T therapeutic target in MM. However, a clear role of CD229 in MM remains elusive. In this study, MM patients with elevated CD229 expression achieved poor prognosis by analyzing MM clinical databases. In addition, CD229 promoted MM cell proliferation in vitro as well as in xenograft mouse model in vivo. Mechanism study revealed that CD229 promoted MM cell proliferation by regulating the RAS/ERK signaling pathway. Further exploration employed co-immunoprecipitation coupled with mass spectrometry to identify RASAL3 as an important downstream protein of CD229. Additionally, we developed a co-culture method combined with the immunofluorescence assay to confirm that intercellular tyrosine phosphorylation mediated self-activation of CD229 to activate RAS/ERK signaling pathway via interacting with RASAL3. Taken together, these findings not only demonstrate the oncogenic role of CD229 in MM cell proliferation, but also illustrate the potential of CD229 as a promising therapeutic target for MM treatment.

Road testing new CAR design strategies in multiple myeloma

A deeper understanding of basic immunology principles and advances in bioengineering have accelerated the mass production of genetically-reprogrammed T-cells as living drugs to treat human diseases. Autologous and allogeneic cytotoxic T-cells have been weaponized to brandish MHC-independent chimeric antigen receptors (CAR) that specifically engage antigenic regions on tumor cells. Two distinct CAR-based therapeutics designed to target BCMA are now FDA-approved based upon robust, sustained responses in heavily-pretreated multiple myeloma (MM) patients enrolled on the KarMMa and CARTITUDE-1 studies. While promising, CAR T-cells present unique challenges such as antigen escape and T-cell exhaustion. Here, we review novel strategies to design CARs that overcome current limitations. Co-stimulatory signaling regions were added to second-generation CARs to promote IL-2 synthesis, activate T-cells and preclude apoptosis. Third-generation CARs are composed of multiple co-stimulatory signaling units, e.g., CD28, OX40, 4-1BB, to reduce exhaustion. Typically, CAR T-cells incorporate a potent constitutive promoter that maximizes long-term CAR expression but extended CAR activation may also promote T-cell exhaustion. Hypoxia-inducible elements can be incorporated to conditionally drive CAR expression and selectively target MM cells within bone marrow. CAR T-cell survival and activity is further realized by blocking intrinsic regulators of T-cell inactivation. T-Cells Redirected for Universal Cytokine Killing (TRUCKs) bind a specific tumor antigen and produce cytokines to recruit endogenous immune cells. Suicide genes have been engineered into CAR T-cells given the potential for long-term on-target, off-tumor effects. Universal allo-CAR T-cells represent an off-the-shelf source, while logic-gated CAR T-cells are designed to recognize tumor-specific features coupled with Boolean-generated binary gates that then dictate cell-fate decisions. Future generations of CARs should further revitalize immune responses, enhance tumor specificity and reimagine strategies to treat myeloma and other cancers.

Mechanisms of Action of the New Antibodies in Use in Multiple Myeloma

Monoclonal antibodies (mAbs) directed against antigen-specific of multiple myeloma (MM) cells have Fc-dependent immune effector mechanisms, such as complement-dependent cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP), but the choice of the antigen is crucial for the development of effective immuno-therapy in MM. Recently new immunotherapeutic options in MM patients have been developed against different myeloma-related antigens as drug conjugate-antibody, bispecific T-cell engagers (BiTEs) and chimeric antigen receptor (CAR)-T cells. In this review, we will highlight the mechanism of action of immuno-therapy currently available in clinical practice to target CD38, SLAMF7, and BCMA, focusing on the biological role of the targets and on mechanisms of actions of the different immunotherapeutic approaches underlying their advantages and disadvantages with critical review of the literature data.