Autologous hematopoietic stem cell transplantation for multiple myeloma in the age of CAR T cell therapy.

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the management of relapsed and refractory myeloma, with excellent outcomes and a tolerable safety profile. High dose chemotherapy with autologous hematopoietic stem cell transplantation (AHCT) is established as a mainstream of newly diagnosed multiple myeloma (NDMM) management in patients who are young and fit enough to tolerate such intensity. This standard was developed based on randomized trials comparing AHCT to chemotherapy in the era prior to novel agents. More recently, larger studies have primarily shown a progression free survival (PFS) benefit of upfront AHCT, rather than overall survival (OS) benefit. There is debate about the significance of this lack of OS, acknowledging the potential confounders of the chronic nature of the disease, study design and competing harms and benefits of exposure to AHCT. Indeed upfront AHCT may not be as uniquely beneficial as we once thought, and is not without risk. New quadruple-agent regimens are highly active and effective in achieving a deep response as quantified by measurable residual disease (MRD). The high dose chemotherapy administered with AHCT imposes a burden of short and long-term adverse effects, which may alter the disease course and patient's ability to tolerate future therapies. Some high-risk subgroups may have a more valuable benefit from AHCT, though still ultimately suffer poor outcomes. When compared to the outcomes of CAR T cell therapy, the question of whether AHCT can or indeed should be deferred has become an important topic in the field. Deferring AHCT may be a personalized decision in patients who achieve MRD negativity, which is now well established as a key prognostic factor for PFS and OS. Reserving or re-administering AHCT at relapse is feasible in many cases and holds the promise of resetting the T cell compartment and opening up options for immune reengagement. It is likely that personalized MRD-guided decision making will shape how we sequence in the future, though more studies are required to delineate when this is safe and appropriate.

Efficacy of Selinexor in Relapsed/Refractory Multiple Myeloma (RRMM) Patients with del17p and Other High-Risk Abnormalities (A Retrospective Single-Center Study).

Selinexor (Seli) is a first-in-class, oral selective inhibitor of the nuclear export protein, exportin-1 (XPO1). Seli exhibits its antitumor effect through the blockage of XPO1, which increases nuclear retention of tumor suppressor proteins (TSPs), including p53, thereby limiting the translation of oncogenes, triggering cell cycle arrest and the death of malignant cells. Multiple Myeloma (MM) patients with del17p are deficient in TP53 and have a particularly poor prognosis. Given its unique mechanism of action, we investigated whether Seli has increased efficacy in RRMM patients with del17p compared to other high-risk cytogenetics (OHRC). This is an IRB-approved observational study of RRMM patients with high-risk cytogenetics (del17p, t (4;14), t (14;16) or gain 1q) or standard-risk cytogenetics treated at the Levine Cancer Institute (LCI) with a Seli-based regimen between January 2019 and December 2022. Time-to-event endpoints (PFS, OS) were evaluated using Kaplan-Meier (KM) methods. Log-rank tests compared time-to-event endpoints between cohorts [del17p vs. OHRC vs. standard risk]. We identified 40 RRMM patients with high-risk cytogenetics, including 16 patients with del17p and 24 patients with OHRC, as well as 20 with standard-risk cytogenetics. The median age was 62.5 vs. 69 vs. 65.5 years (del17p group vs. OHRC vs. standard risk). The median prior line of therapies was five (range: 3-16) with similar rates of prior autologous stem cell transplant in all arms (68.8% vs. 62.5% vs. 70.0%). The most frequently used regimens were Seli-Pomalidomide-dexamethasone(dex) or Seli-Carfilzomib-dex (Seli-Kd) in the del17p group and Seli-Kd in the OHRC and standard-risk groups. The median time to start the Seli-based regimen after initial MM diagnosis was 5.6 years for the del17p group, 4.1 years in OHRC, and 4.8 years in the standard-risk group. The median follow-up time after the start of the Seli-based regimen was 10.5 months (mos) in the del17p group, 8.4 mos in OHRC, and 10.3 mos in the standard-risk group. In the del17p group, 50% had an objective response, 41.7% in the OHRC, and 35% in the standard-risk group (p = 0.71). Depth of response was also similar across the arms (12.5% vs. 12.5% vs. 10.0% VGPR p = 0.99). The median OS was 10.9 mos in the del17p group, 10.3 mos in the OHRC, and 10.3 mos in the standard-risk group (p = 0.92). The median OS was 15.5 mos for patients who received Seli as a bridging therapy versus 9 mos for Seli use for other reasons rather than as a bridge. Overall, Seli-based regimens showed promising responses even in this heavily pretreated population. Our analysis suggests that Seli-based regimens lead to similar outcomes among RRMM patients with del17p, OHRC, and standard-risk cytogenetics. This contrasts with previously reported outcomes using combinations of novel therapies in this population, where the del17p patients often have a poorer prognosis. Interestingly, our data suggest that Seli is a particularly effective bridging modality for patients preparing for CAR-T cell therapies in our population. Further investigation into this population is warranted, including in earlier lines of therapy, in hopes of seeing a more durable response.

Standardizing Clinical Workflow for Assessing Minimal Residual Disease by Flow Cytometry in Multiple Myeloma.

INTRODUCTION: Minimal residual disease (MRD) status is an established prognostic biomarker for patients with multiple myeloma. Commonly used MRD testing techniques such as next generation sequencing or next generation flow cytometry can detect as little as one or two multiple myeloma plasma cells in 106 normal bone marrow cells. Early pull of bone marrow aspirates (BMA), necessary to achieve such level of sensitivity, can be difficult to secure in routine clinical practice due to the competing need for early pull samples for clinical response assessment, therefore introducing the risk of analytical interference during MRD testing. METHODS: To overcome this challenge, we standardized our workflow for collecting specimens by using a technical first pull after needle repositioning for MRD testing. To capture a comprehensive picture of MRD assay performance and specimen adequacy, we tested for MRD on 556 technical first pull bone marrow aspirates by next generation flow cytometry. Among the specimens, several key multiple myeloma treatment milestones were represented: end of induction therapy, two to three months post-autologous stem cell transplant, early and late stages of maintenance therapy. RESULTS: By using the technical first pull bone marrow aspirate, we achieved an analytical assay input of 10 million nucleated cells for 97.5% of specimens. Our analytical sensitivity reached 10-6; (i.e., 10 multiple myeloma plasma cells in 10 × 106 bone marrow cells). Twenty-four percent of specimens were significantly hemodiluted. Low assay input or hemodilution quantifiably lowered the assay sensitivity. CONCLUSION: Specimen adequacy is, therefore, an important metric to incorporate into MRD status reporting.

Transition from Intravenous to Subcutaneous Daratumumab Formulation in Clinical Practice.

INTRODUCTION: Daratumumab is an anti-CD38 monoclonal antibody widely used for treating patients with newly diagnosed or relapsed/refractory multiple myeloma. The subcutaneous formulation of daratumumab was developed with the purpose of minimizing the treatment burden (to patients and health care system) associated with intravenous daratumumab. Given its recent approval, there is a knowledge gap regarding the best practices that should be instituted for safe administration of subcutaneous daratumumab. METHODS: A retrospective chart review was performed from August 2020 until November 2020 to identify patients either switched to or treated upfront (daratumumab naive) with any subcutaneous daratumumab-based treatment regimen. All patients received appropriate premedications per institutional standards of care. The study end points were to report real-world data regarding administration-related reaction rates (at or following discharge from infusion center), as well as compare their incidence rates to those noted in the COLUMBA study (historical cohort). RESULTS: The study included 58 patients, of whom 38% (n = 22) were daratumumab naive. The majority (84%, n = 49) received subcutaneous daratumumab in combination with various antimyeloma regimens. There were no cases of administration-related reactions at infusion center or after discharge irrespective of previous exposure to intravenous daratumumab. None of the patients included herein required rescue home medications or visited the emergency department within 24 to 48 hours after subcutaneous daratumumab administration. These translated into a significant difference in incidence of administration-related reactions compared with historical cohort (0% vs. 13%, P = .003). CONCLUSION: Subcutaneous daratumumab was extremely well tolerated and could be safely administered without need for monitoring or rescue home medications.

Ex vivo efficacy of BCMA-bispecific antibody TNB-383B in relapsed/refractory multiple myeloma.

TNB-383B is a fully human BCMA-targeting T-cell engaging bispecific monoclonal antibody (T-BsAb). We assessed ex vivo efficacy of this drug to mediate killing of bone marrow mononuclear cells (BMMCs) freshly isolated from 10 patients with relapsed multiple myeloma (MM). BMMC were treated ex vivo with TNB-383B at doses ranging from 0.001-1 µg. Plasma cell (PC) lysis, viability, BCMA expression, CTL distribution, and degranulation were assessed by flow cytometry. Cytokine response to TNB-383B was quantified by multiplex protein assay. Dose-dependent PC lysis was triggered in all cases by TNB-383B at doses as low as 0.001 µg (P = .0102). Primary MM cells varied in BCMA expression. High BCMA+ PC count correlated with increased PC lysis (P = .005) and significant CTL degranulation specific to TNB-383B treatment (P = .0153 at 1 µg). High E:T ratio in bone marrow specimens led to lower viable and higher apoptotic PC compared with low E:T ratio (P < .001). Three cytokines were significantly modulated by TNB-383B: IL-2/TNFα increased by ∼4 ± 3.5-fold average (P < .005 at 1 µg) and IP10 increased by ∼50 ± 15-fold (P < .001 at 1 µg). We conclude that TNB-383B triggers primary PC lysis and CTL degranulation in a dose-dependent fashion ex vivo with no T cell expansion and mild increase of CRS-associated cytokines.

Elevated levels of polyamines alter chromatin in murine skin and tumors without global changes in nucleosome acetylation.

Polyamines affect nucleosome oligomerization and DNA conformation in vitro, yet little information exists regarding the influence of naturally synthesized polyamines on mammalian chromatin. Capitalizing on the relative inefficiency of a moderate ionic strength extraction buffer to dissociate histones, we obtained evidence of altered chromatin in transgenic mice that overexpress ornithine decarboxylase (ODC), which catalyzes polyamine synthesis. Dissociation of histones from chromatin in ODC transgenic mouse skin, as well as in tumors that develop spontaneously in ODC/Ras bigenic mice, is dramatically reduced relative to normal littermate skin. This could reflect tighter tethering of nucleosomes to DNA or a more compacted chromatin structure due to elevated intracellular concentrations of polyamines since this effect is reversible upon treatment with alpha-difluoromethylornithine (DFMO), a specific inhibitor of ODC enzymatic activity. Impeded release of nonhistone chromatin proteins HP-1beta and nucleophosmin, but not Lamin B, HDAC-1, HMGB, HMGN2, or HMGA1, suggests that polyamines exert selective effects on specific chromatin protein complexes. Moreover, overall acetylation, as well as specific methylation, of nucleosomes in ODC mice is unaffected, implying that access by histone modifying enzymes is not generally restricted. The abnormal chromatin environment fostered by elevated levels of polyamines may be a necessary prerequisite for epithelial tumor growth and maintenance.

Deregulation of polyamine biosynthesis alters intrinsic histone acetyltransferase and deacetylase activities in murine skin and tumors.

The essential requirement for polyamines for normal cell growth and differentiation may be partly attributed to their influence on gene expression, a process regulated by the acetylation state of nucleosomal histones. We used transgenic mice to examine the effects of constitutive expression of ornithine decarboxylase (ODC), a key rate-limiting enzyme in polyamine biosynthesis, on histone acetylation in epithelial cells in skin. As compared with the skin of normal littermate mice, both intrinsic histone acetyltransferase (HAT) and deacetylase activities are elevated in ODC transgenic skin. Skin tumors that form spontaneously in ODC/Ras double transgenic mice exhibit exceptionally high HAT activity having a distinct specificity for Lys-12 in the tail domain of histone H4, which may have implications for gene transcription. However, acetylation of histones by HAT enzymes was impeded in cultured ODC transgenic keratinocytes, and there were only modest changes in levels of acetylated histones in the skin of ODC transgenic mice. Treatment with the ODC enzyme inhibitor alpha-difluoromethylornithine, which results in regression of ODC/Ras tumors, reverses the effects on HAT and deacetylase enzyme function, implicating polyamine biosynthesis in the regulation of histone acetylation. Polyamines do not directly stimulate the enzymatic activity of either p300 or p300/CREB-binding protein (CBP)-associated factor, members of two distinct classes of HAT enzymes, implying that the elevated CBP/p300-associated HAT activity detected in ODC transgenic skin is attributable to indirect influence of polyamines. These results suggest that multiple mechanisms exist by which endogenous polyamines influence chromatin in mammals. Furthermore, they suggest that the elevated polyamine levels inherent in many solid tumors alter chromatin structure, likely affecting gene expression and promoting the neoplastic process.