Selinexor-Based Triplet Regimens in Patients With Multiple Myeloma Previously Treated With Anti-CD38 Monoclonal Antibodies

BACKGROUND

The increasing use of anti-CD38 monoclonal antibodies (αCD38 mAbs) for newly diagnosed or early relapsed multiple myeloma (MM), especially in non-transplant eligible patients, may lead to more patients developing αCD38 mAb-refractory disease earlier in the treatment course with fewer treatment options.

PATIENTS AND METHODS

We analyzed the efficacy and safety of selinexor-based triplets (selinexor+dexamethasone [Sd] plus pomalidomide [SPd, n = 23], bortezomib [SVd, n = 16] or carfilzomib (SKd, n = 23]) in a subset of STOMP (NCT02343042) and BOSTON (NCT03110562) study patients treated previously with αCD38 mAbs.

RESULTS

Sixty-two patients (median 4 prior therapies, range 1 to 11, 90.3% refractory to αCD38 mAb) were included. Overall response rates (ORR) in the SPd, SVd and SKd cohorts were 52.2%, 56.3%, and 65.2%, respectively. Overall response rate was 47.4% among patients who had MM refractory to the third drug reintroduced in the Sd-based triplet. Median progression-free survival in the SPd, SVd, and SKd cohorts was 8.7, 6.7, and 15.0 months, respectively, and median overall survival was 9.6, 16.9, and 33.0 months, respectively. Median time to discontinuation in the SPd, SVd, and SKd cohorts was 4.4, 5.9, and 10.6 months, respectively. The most common hematological adverse events were thrombocytopenia, anemia, and neutropenia. Nausea, fatigue, and diarrhea were primarily grade 1/2. Adverse events were generally manageable with standard supportive care and dose modifications.

CONCLUSION

Selinexor-based regimens may offer effective and well-tolerated therapy to patients with relapsed and/or refractory MM who had disease previously exposed or refractory to αCD38 mAb therapy and could help address the unmet clinical need in these high-risk patients.

The roles of bone remodeling in normal hematopoiesis and age-related hematological malignancies

Prior research establishing that bone interacts in coordination with the bone marrow microenvironment (BMME) to regulate hematopoietic homeostasis was largely based on analyses of individual bone-associated cell populations. Recent advances in intravital imaging has suggested that the expansion of hematopoietic stem cells (HSCs) and acute myeloid leukemia cells is restricted to bone marrow microdomains during a distinct stage of bone remodeling. These findings indicate that dynamic bone remodeling likely imposes additional heterogeneity within the BMME to yield differential clonal responses. A holistic understanding of the role of bone remodeling in regulating the stem cell niche and how these interactions are altered in age-related hematological malignancies will be critical to the development of novel interventions. To advance this understanding, herein, we provide a synopsis of the cellular and molecular constituents that participate in bone turnover and their known connections to the hematopoietic compartment. Specifically, we elaborate on the coupling between bone remodeling and the BMME in homeostasis and age-related hematological malignancies and after treatment with bone-targeting approaches. We then discuss unresolved questions and ambiguities that remain in the field.

Siltuximab as a primary treatment for cytokine release syndrome in a patient receiving a bispecific antibody in a clinical trial setting

Introduction

Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) are common toxicities associated with immunotherapies, including T cell redirecting bispecific antibodies. Although cooperative group guidelines recommend the use of tocilizumab or other IL-6/IL-6R inhibitors for the management of CRS and ICANS, reports on the use of siltuximab, an IL-6 inhibitor, for the treatment of CRS are limited.

Case report

We present the case of a 77-year-old male who received T cell redirecting bispecific antibody therapy with talquetamab for relapsed/refractory multiple myeloma (RRMM) and developed CRS with concurrent ICANS after receiving a second dose of talquetamab.

Management and Outcome

The patient received an infusion of siltuximab. The patient recovered from CRS within 1 h of siltuximab administration and ICANS within 7 h of siltuximab administration. Patient tolerated the subsequent dose of talquetamab with no evidence of CRS and continued on study.

Discussion

This case describes the successful use of siltuximab for the management of CRS in a patient treated with a T cell redirecting bispecific antibody for RRMM.

Application of risk factors for venous thromboembolism in patients with multiple myeloma starting chemotherapy, a real-world evaluation

INTRODUCTION

Within the first year of diagnosis, up to 1 in 3 multiple myeloma (MM) patients will experience a venous thromboembolism (VTE). The International Myeloma Working Group (IMWG) has thromboprophylaxis guidelines that stratify patients into low or high risk for thrombosis and subsequently recommend thromboprophylaxis, but it is unknown if these recommendations are being followed or if they are effective. The purpose of this study was to assess efficacy of the IMWG guidelines and investigate other potential VTE risk factors.

METHODS

Study participants were treated at the University of Kansas Medical Center between 2007 and 2013, and charts were reviewed to extract data. Cases (MM and VTE) were matched to controls (MM and no VTE) at approximately 1:3 ratio based on gender, age (±5 years), and time of MM diagnosis (±5 years).

RESULTS

A total of 80 cases and 211 controls were matched. Most patients (82%) were considered high risk for experiencing a VTE at the time of their MM diagnosis and 18% were considered low risk. Neither risk category (P = 0.16) nor thromboprophylaxis at baseline (P = 0.37) predicted VTE, though cases were more likely than controls to have an increased risk of thrombosis at the time of clot compared to their baseline risk (P = 0.09).

CONCLUSION

Our results suggest that IMWG guidelines are not being consistently followed and therefore could not be validated. Additional risk factors were not identified, but risk for VTE may change over time suggesting patients may require ongoing assessment of VTE risk and thromboprophylaxis throughout the disease course.

Abstract 4026: Growth of monoclonal gammopathy of undetermined significance (MGUS) in a 3-dimensional co-culture in vitro model

Introduction: Multiple Myeloma (MM) is an incurable cancer with a pre-malignant clonal phase of disease called monoclonal gammopathy of undetermined significance (MGUS). Most patients with MGUS do not develop MM and the biology underlying this potential transformation is unclear. Investigations to prevent the development of MM from MGUS is limited by infrequent MGUS progression. MGUS cells have historically proven difficult to grow in vitro because of slow rates of proliferation and difficulty in sustaining cell cultures. An in vitro model of MGUS that circumvents these challenges by recreating a supportive bone marrow microenvironment will allow further investigation into the pathogenesis of disease progression. Herein, we examine a novel stroma-based in vitro model of MGUS and MM using bone marrow stromal cells to support and maintain a bi-directional relationship within the clonal plasma cell population.

Aim: To grow MGUS derived plasma cells by recreating a supportive bone marrow microenvironment using a 3-dimensional in vitro model.

Methods: We collected a CD38+ cell fraction and a bone marrow stromal fraction from patients with plasma cell dyscrasias using a Miltenyl Biotec column Separator. We seeded stromal cells from a female, kappa expressing MGUS patient or a healthy donor onto a polyglycolic acid/ poly L-lactic acid 90/10 (PLGA) copolymer scaffold. Then, a CD38+ cell fraction from a male patient with lambda secreting PCL or MM cell line U266 or MM1.s (both male, lambda expressing cell lines) were added to create 3D co-culture conditions. For comparison, a 2 dimensional co-culture condition was created by growing MM patient cells or cell lines over a bone marrow stromal cell layer without scaffold.. After one week, samples were formalin fixed and sectioned for immunohistochemistry (IHC) and stained with CD138, kappa, lambda, and ki-67. Fluorescent in situ hybridization (FISH) was used to label X and Y chromosomes.

Results: IHC demonstrated proliferation of CD138+ cells evident by Ki-67 expression in in 3-D co-culture systems. There was no growth of the patient derived CD38+ cells in 2-D co-culture and the proliferation of of cell lines was diminished in 2-D versus 3-D. When seeded on healthy donor stroma in 3-D, the CD38+ cells from all sources were lambda restricted. When seeded on the MGUS stroma, the MM1.s cells were lambda restricted while PCL cells showed both kappa and lambda expression with a dominance of kappa expression, and U266 cells showed kappa restriction. FISH demonstrated a female chromosomal pattern with X,Y in the plasma cells from the 3D co-cultures in the case of U266 or PCL cell 3-D co-culture with MGUS stroma.

Conclusion: This is the first demonstration of in vitro growth of plasma cells from a patient with MGUS. We speculate the aggressive plasma cells from the U266 cell line and the PCL sample induced the growth of a CD38- cell fraction and caused differentiation to plasma cells.

Citation Format: Brea C. Lipe, Omar Aljitawi, Tara Lin, Joseph Fontes. Growth of monoclonal gammopathy of undetermined significance (MGUS) in a 3-dimensional co-culture in vitro model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4026. doi:10.1158/1538-7445.AM2015-4026

IgG kappa monoclonal gammopathy of undetermined significance presenting as acquired type III Von Willebrand syndrome

Acquired von Willebrand syndrome (AVWS) is a rare bleeding disorder associated with hematoproliferative disorders, autoimmune conditions, neoplasia and cardiovascular disorders that often present a diagnostic challenge. Monoclonal gammopathy of undetermined significance (MGUS) is one of the most common causes of AVWS that typically presents later in life with mucocutaneous or postsurgical bleeding and multimers consistent with type I or II von Willebrand disease (VWD). Here, we present the case of a patient with a 32-year history of type III VWD that was ultimately found to be AVWS related to an IgG MGUS. In this case report, we highlight the diagnostic challenges of AVWS to ensure proper identification and potentially lifesaving treatment of this rare disorder.

Bone marrow transplant for multiple myeloma: impact of distance from the transplant center

PURPOSE

This study investigated the impact of prognostic variables, including the distance a patient lives from a transplant center, on the outcome of autologous hematopoietic stem cell transplantation (ASCT) for multiple myeloma.

METHODS

This retrospective analysis included 77 myeloma patients who received an ASCT at Dartmouth Hitchcock Medical Center between 1996 and 2009, 70 of whom were treated between 2002 and 2009. Using linear regression and univariate analysis, we examined the impact of distance from the transplant center on survival. Kaplan-Meier curves identified overall and event-free survival. An association between distance from the transplant center and survival was examined using Cox regression analysis, while adjusting for patient-, disease-, and treatment-related variables.

RESULTS

Increasing distance from the transplant center correlated with improved overall survival (P=.004), but had no impact on disease-free survival (P=.26).

CONCLUSIONS

These results suggest that the distance from a transplant center should not be a barrier to ASCT for eligible patients with multiple myeloma.

Abstract 1256: A role for lipoprotein lipase in fatty acid acquisition by breast, prostate and liposarcoma tumors

The importance of de novo fatty acid (FA) synthesis for tumor cell growth is well established, and we have now examined the hypothesis that the uptake of exogenous FA provides an alternative FA fuel source for tumors.

Background: Many tumor cells utilize FA as a major energy source, and they do not survive if the supply is interrupted. In order to obtain lipids, tumors can synthesize fatty acids from glucose-derived precursors using fatty acid synthase (FASN), or they could potentially hydrolyze diet-derived triglycerides from circulating lipoproteins using the enzyme lipoprotein lipase (LPL), and take up the free fatty acids using the cell surface channel CD36. It is also conceivable that they could obtain lipids by receptor-mediated endocytosis, using syndecan (Sdc1) and LPL. The latter two of these three mechanisms have not been examined.

Methods: We employed cDNA microarray and quantitative RT-PCR to study mRNA expression, measured secreted LPL enzyme activity, and produced a monoclonal antibody for LPL protein analysis and immunohistochemistry (IHC). We also assessed cellular uptake of fluorescently labeled very low density lipoproteins (VLDL). We studied cell lines and/or tumor tissues for expression of FASN, Spot 14 (a nuclear protein that drives FASN expression), LPL, CD36, and Sdc1.

Results:

1. By RT-PCR, FASN and Spot14, a driver of FASN gene expression, are expressed in all cell lines (45 breast cancer, 1 liposarcoma, 1 cervical carcinoma, 3 prostate cancer) and tumor tissues (160 breast cancer, 24 liposarcoma, 10 prostate cancer) examined.

2. By RT-PCR and enzyme activity assays, LPL is expressed only in liposarcoma and triple-negative breast cancer cell lines. Prostate cancer cells secrete negligible LPL.

3. Addition of exogenous LPL and triglyceride substrate to culture media enhanced the growth of breast cancer and liposarcoma cell lines, but not prostate cancer cell lines.

4. Provision of exogenous LPL, however, rescued prostate cancer cell lines from the cytotoxicity of FASN inhibition.

5. siRNA-mediated knockdown of LPL impaired the growth of HeLa cells,

6. In contradistinction to observations in cell lines, IHC demonstrated brisk expression of LPL in all liposarcomas, prostate tumors, and breast cancer tumors examined, irrespective of ER/PR or HER2/neu status.

7. CD36 is expressed in the majority of tumors examined by IHC, including 98% of breast cancers.

8. Sdc1 and CD36 are expressed in triple-negative DU4475 breast cancer cells, but they did not endocytose labeled VLDL particles.

Conclusions: These data demonstrate that, in addition to de novo FA synthesis, tumors can utilize diet-derived fat, and that this can fuel their growth. Our findings provide a mechanism, namely lipolysis by LPL and uptake by CD36, for the link between dietary fat intake and tumor progression. Inhibition of lipolysis, as well as lipogenesis, may be a necessary strategy to target the FA requirement of aggressive tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1256. doi:10.1158/1538-7445.AM2011-1256

Lipoprotein lipase links dietary fat to solid tumor cell proliferation

Many types of cancer cells require a supply of fatty acids (FA) for growth and survival, and interrupting de novo FA synthesis in model systems causes potent anticancer effects. We hypothesized that, in addition to synthesis, cancer cells may obtain preformed, diet-derived FA by uptake from the bloodstream. This would require hydrolytic release of FA from triglyceride in circulating lipoprotein particles by the secreted enzyme lipoprotein lipase (LPL), and the expression of CD36, the channel for cellular FA uptake. We find that selected breast cancer and sarcoma cells express and secrete active LPL, and all express CD36. We further show that LPL, in the presence of triglyceride-rich lipoproteins, accelerates the growth of these cells. Providing LPL to prostate cancer cells, which express low levels of the enzyme, did not augment growth, but did prevent the cytotoxic effect of FA synthesis inhibition. Moreover, LPL knockdown inhibited HeLa cell growth. In contrast to the cell lines, immunohistochemical analysis confirmed the presence of LPL and CD36 in the majority of breast, liposarcoma, and prostate tumor tissues examined (n = 181). These findings suggest that, in addition to de novo lipogenesis, cancer cells can use LPL and CD36 to acquire FA from the circulation by lipolysis, and this can fuel their growth. Interfering with dietary fat intake, lipolysis, and/or FA uptake will be necessary to target the requirement of cancer cells for FA.