Towards effective immunotherapy of myeloma: enhanced elimination of myeloma cells by combination of lenalidomide with the human CD38 monoclonal antibody daratumumab

Immunomodulatory drugs: a promising clinical ally for cancer immunotherapy

While immunomodulatory imide drugs (IMiDs) have been authorised for treatment of haematological cancers for over two decades, the appreciation of their ability to stimulate antitumour T cell and natural killer (NK) cell responses is relatively recent. Clinical trial data increasingly show that targeted immunotherapies, such as antibodies, T cells, and vaccines, improve outcomes when delivered in combination with the IMiD derivatives lenalidomide or pomalidomide. Here, we review these clinical data to highlight the relevance of IMiDs in combinatorial immunotherapy for both haematological and solid tumours. Further research into the molecular mechanisms of IMiDs and an increased understanding of their immunomodulatory effects may refine the specific applications of IMiDs and improve the design of future clinical trials, moving IMiDs to the forefront of combinatorial cancer immunotherapy.

Daratumumab during Myeloma Induction Therapy Is Associated with Impaired Stem Cell Mobilization and Prolonged Post-Transplant Hematologic Recovery

Daratumumab is being increasingly integrated into first-line multiple myeloma (MM) induction regimens, leading to improved response depth and longer progression-free survival. Autologous stem cell transplantation (ASCT) is commonly performed as a consolidation strategy following first-line induction in fit MM patients. We investigated a cohort of 155 MM patients who received ASCT after first-line induction with or without daratumumab (RVd, n = 110; D-RVd, n = 45), analyzing differences in stem cell mobilization, apheresis, and engraftment. In the D-RVd group, fewer patients successfully completed mobilization at the planned apheresis date (44% vs. 71%, p = 0.0029), and more patients required the use of rescue plerixafor (38% vs. 28%, p = 0.3052). The median count of peripheral CD34+ cells at apheresis was lower (41.37 vs. 52.19 × 106/L, p = 0.0233), and the total number of collected CD34+ cells was inferior (8.27 vs. 10.22 × 106/kg BW, p = 0.0139). The time to recovery of neutrophils and platelets was prolonged (12 vs. 11 days, p = 0.0164; and 16 vs. 14 days, p = 0.0002, respectively), and a higher frequency of erythrocyte transfusions (74% vs. 51%, p = 0.0103) and a higher number of platelet concentrates/patients were required (4 vs. 2; p = 0.001). The use of daratumumab during MM induction might negatively impact stem cell mobilization and engraftment in the context of ASCT.

Efficacy of elotuzumab for multiple myeloma deteriorates after daratumumab: a multicenter retrospective study

Elotuzumab-based regimens are sometimes selected for multiple myeloma treatment after daratumumab-based regimens. However, there has been insufficient discussion on the efficacy of elotuzumab after daratumumab. We used Kansai Myeloma Forum registration data in a multicenter retrospective evaluation of the efficacy of elotuzumab after daratumumab. Overall survival (OS) rate and time to next treatment (TTNT) were significantly worse in the cohort given elotuzumab after daratumumab (Dara cohort, n = 47) than in the cohort with no history of daratumumab administration before elotuzumab (No-Dara cohort, n = 80, OS: P = 0.03; TTNT: P = 0.02; best response: P < 0.01). In the Dara cohort, OS and TTNT rates were worse with sequential elotuzumab use after daratumumab than with non-sequential (OS: P = 0.02; TTNT: P = 0.03). In patients given elotuzumab < 180 days after daratumumab, OS (P = 0.08) and best response (P = 0.21) tended to be worse, and TTNT was significantly worse (P = 0.01), than in those given elotuzumab after ≥ 180 days. These findings were confirmed by subgroup analyses and multivariate analyses. Monoclonal-antibody-free treatment might be preferable after daratumumab-based regimens. If possible, elotuzumab-based regimens should be considered only ≥ 180 days after daratumumab use.

Effect of prior lenalidomide or daratumumab exposure on hematopoietic stem cell collection and reconstitution in multiple myeloma

BACKGROUND

The roles of Lenalidomide (Len) and Daratumumab (Dara) in multiple myeloma treatment are well-established, yet their influences on hematopoietic stem cell harvesting and reconstitution remain disputed.

METHODS

We conducted a systematic database review to identify cohort studies or RCTs evaluating the effect of the use of Len or Dara on hematopoietic stem cell collection and peripheral blood count recovery in multiple myeloma patients. Effects on hematopoietic collection or reconstitution were estimated by comparing standardized mean differences (SMD) and mean differences (MD), or median differences.

RESULTS

Eighteen relevant studies were identified, summarizing mobilization results. For Len, data from 13 studies were summarized, including total CD34+ cell yield, collection failure rate, and time to neutrophil and platelet engraftment. Results indicated that Len exposure led to decreased stem cell collection [SMD=-0.23, 95% CI (-0.34, -0.12)]. However, collection failure (<2×106) could be mitigated by plerixafor [OR=2.14, 95% CI (0.96, 4.77)]. For Dara, two RCTs and three cohort studies were included, showing that Dara exposure resulted in a reduction in total stem cells even with optimized plerixafor mobilization [SMD=-0.75, 95% CI (-1.26, -0.23)], and delayed platelet engraftment recovery [MD=1.20, 95% CI (0.73, 1.66)].

CONCLUSIONS

Our meta-analysis offers a comprehensive view of Len and Dara's impacts on hematopoietic stem cell collection and reconstitution in multiple myeloma. Len usage could lead to reduced stem cell collection, counteracted by plerixafor mobilization. Dara usage could result in diminished stem cell collection and delayed platelet engraftment.

Additivity predicts the efficacy of most approved combination therapies for advanced cancer

Most advanced cancers are treated with drug combinations. Rational design aims to identify synergistic combinations, but existing synergy metrics apply to preclinical, not clinical data. Here we propose a model of drug additivity for progression-free survival (PFS) to assess whether clinical efficacies of approved drug combinations are additive or synergistic. This model includes patient-to-patient variability in best single-drug response plus the weaker drug per patient. Among US Food and Drug Administration approvals of drug combinations for advanced cancers (1995-2020), 95% exhibited additive or less than additive effects on PFS times. Among positive or negative phase 3 trials published between 2014-2018, every combination that improved PFS was expected to succeed by additivity (100% sensitivity) and most failures were expected to fail (78% specificity). This study shows synergy is neither a necessary nor common property of clinically effective drug combinations. The predictable efficacy of approved combinations suggests that additivity can be a design principle for combination therapies.

Ixazomib, daratumumab and low-dose dexamethasone in intermediate-fit patients with newly diagnosed multiple myeloma: an open-label phase 2 trial

Background

The outcome of non-transplant eligible newly diagnosed multiple myeloma (NDMM) patients is heterogeneous, partly depending on frailty level. The aim of this study was to prospectively investigate the efficacy and safety of Ixazomib-Daratumumab-low-dose dexamethasone (Ixa-Dara-dex) in NDMM intermediate-fit patients.

Methods

In this phase II multicenter HOVON-143 study, IMWG Frailty index based intermediate-fit patients, were treated with 9 induction cycles of Ixa-Dara-dex, followed by maintenance with ID for a maximum of 2 years. The primary endpoint was overall response rate on induction treatment. Patients were included from October 2017 until May 2019. Trial Registration Number: NTR6297.

Findings

Sixty-five patients were included. Induction therapy resulted in an overall response rate of 71%. Early mortality was 1.5%. At a median follow-up of 41.0 months, median progression-free survival (PFS) was 18.2 months and 3-year overall survival 83%. Discontinuation of therapy occurred in 77% of patients, 49% due to progression, 9% due to toxicity, 8% due to incompliance, 3% due to sudden death and 8% due to other reasons. Dose modifications of ixazomib were required frequently (37% and 53% of patients during induction and maintenance, respectively), mainly due to, often low grade, polyneuropathy. During maintenance 23% of patients received daratumumab alone. Global quality of life (QoL) improved significantly and was clinically relevant, which persisted during maintenance treatment.

Interpretation

Ixazomib-Daratumumab-low-dose dexamethasone as first line treatment in intermediate-fit NDMM patients is safe and improves global QoL. However, efficacy was limited, partly explained by ixazomib-induced toxicity, hampering long term tolerability of this 3-drug regimen. This highlights the need for more efficacious and tolerable regimens improving the outcome in vulnerable intermediate-fit patients.

Funding

Janssen Pharmaceuticals, Takeda Pharmaceutical Company Limited.

Evidence-based mechanisms of synergy with IMiD agent-based combinations in multiple myeloma

Treatment of multiple myeloma (MM) has seen great advances in recent years, and a key contributor to this change has been the effective use of combination therapies, which have improved both the depth and duration of patient responses. IMiD agents (lenalidomide and pomalidomide) have both tumoricidal and immunostimulatory functions, and due to their multiple mechanisms of action have become the backbone of numerous combination treatments in the newly diagnosed and relapsed/refractory settings. Although IMiD agent-based combination regimens provide improved clinical outcomes for patients with MM, the mechanisms underpinning these combinations are not well understood. In this review we describe the potential mechanisms of synergy leading to the enhanced activity observed when IMiD agents and other drug classes are used in combination through interrogation of the current knowledge surrounding their mechanism of actions.

Therapeutic strategies to enhance immune response induced by multiple myeloma cells

Multiple myeloma (MM)as a haematological malignancy is still incurable. In addition to the presence of somatic genetic mutations in myeloma patients, the presence of immunosuppressive microenvironment greatly affects the outcome of treatment. Although the discovery of immunotherapy makes it possible to break the risk of high toxicity and side effects of traditional chemotherapeutic drugs, there are still obstacles of ineffective treatment or disease recurrence. In this review, we discuss therapeutic strategies to further enhance the specific anti-tumor immune response by activating the immunogenicity of MM cells themselves. New ideas for future myeloma therapeutic approaches are provided.

Daratumumab with lenalidomide and dexamethasone in relapsed or refractory multiple myeloma patients - real world evidence analysis

We performed real world evidence (RWE) analysis of daratumumab, lenalidomide and dexamethasone (Dara-Rd) versus lenalidomide and dexamethasone (Rd) treatment in relapsed/refractory multiple myeloma patients (RRMM). In total, 240 RRMM patients were treated with Dara-Rd from 2016 to 2022 outside of clinical trials in all major Czech hematology centers. As a reference, 531 RRMM patients treated with Rd were evaluated. Patients' data were recorded in the Czech Registry of Monoclonal Gammopathies (RMG). Partial response (PR) or better response (ORR) was achieved in significantly more patients in Dara-Rd than in Rd group (91.2% vs. 69.9%; p < 0.001). The median progression free survival (PFS) was 26.9 months in the Dara-Rd and 12.8 months in the Rd group (p < 0.001). Median overall survival (OS) was not reached in the Dara-Rd compared to 27.2 months in the Rd group (p = 0.023). In patients with 1-3 previous treatment lines, there was significant PFS benefit of Dara-Rd compared to Rd (median PFS not reached vs. 13.2 months; p < 0.001). In patients with > 3 previous treatment lines, there was no significant PFS benefit of Dara-Rd treatment (7.8 months vs. 9.9 months; p = 0.874), similarly in patients refractory to PI + IMIDs (11.5 months vs. 9.2 months; p = 0.376). In RWE conditions, the median PFS in RRMM patients treated with Dara-Rd is shorter when compared to clinical trials. In heavily pretreated RRMM patients, efficacy of Dara-Rd treatment is limited; best possible outcomes of Dara-Rd are achieved in minimally pretreated patients.

Putting the best foot forward when treating newly diagnosed multiple myeloma

Multiple myeloma (MM) remains an incurable disease. In Australia, patients receive sequential lines of novel agent (NA)-based lines of therapy (LOTs), including proteasome inhibitors, immunomodulatory drugs and CD38-targeting monoclonal antibodies within the constraints of the pharmaceutical benefits scheme. We propose that induction with a quadruplet incorporating all three drug classes and dexamethasone at diagnosis is the best approach to gain disease control.

Tumor and microenvironmental mechanisms of resistance to immunomodulatory drugs in multiple myeloma

Resistance to immunomodulatory drugs (IMiDs®) is a major cause of treatment failure, disease relapse and ultimately poorer outcomes in multiple myeloma (MM). In order to optimally deploy IMiDs and their newer derivates CRBN E3 ligase modulators (CELMoDs®) into future myeloma therapeutic regimens, it is imperative to understand the mechanisms behind the inevitable emergence of IMiD resistance. IMiDs bind and modulate Cereblon (CRBN), the substrate receptor of the CUL4CRBN E3 ubiquitin ligase, to target novel substrate proteins for ubiquitination and degradation. Most important of these are IKZF1 and IKZF3, key MM survival transcription factors which sustain the expression of myeloma oncogenes IRF4 and MYC. IMiDs directly target MM cell proliferation, but also stimulate T/NK cell activation by their CRBN-mediated effects, and therefore enhance anti-MM immunity. Thus, their benefits in myeloma are directed against tumor and immune microenvironment - and in considering the mechanisms by which IMiD resistance emerges, both these effects must be appraised. CRBN-dependent mechanisms of IMiD resistance, including CRBN genetic aberrations, CRBN protein loss and CRBN-substrate binding defects, are beginning to be understood. However, only a proportion of IMiD-resistant cases are related to CRBN and therefore additional mechanisms, which are currently less well described, need to be sought. These include resistance within the immune microenvironment. Here we review the existing evidence on both tumor and immune microenvironment mechanisms of resistance to IMiDs, pose important questions for future study, and consider how knowledge regarding resistance mechanism may be utilized to guide treatment decision making in the clinic.

Ecto-calreticulin expression in multiple myeloma correlates with a failed anti-tumoral immune response and bad prognosis

Immunogenic cell death (ICD) has been proposed to be a crucial process for antitumor immunosurveillance. ICD is characterized by the exposure and emission of Damage Associated Molecular Patterns (DAMP), including calreticulin (CRT). A positive correlation between CRT exposure or total expression and improved anticancer immunosurveillance has been found in certain cancers, usually accompanied by favorable patient prognosis. In the present study, we sought to evaluate CRT levels in the plasma membrane of CD38⁺ bone marrow mononuclear cells (BMMCs) isolated from 71 patients with varying degrees of multiple myeloma (MM) disease and examine the possible relationship between basal CRT exposure and the bone marrow immune microenvironment, as well as its connection with different clinical markers. Data show that increased levels of cell surface-CRT were associated with more aggressive clinical features and with worse clinical prognosis in MM. High CRT expression in MM cells was associated with increased infiltration of NK cells, CD8⁺ T lymphocytes and dendritic cells (DC), indicative of an active anti-tumoral immune response, but also with a significantly higher presence of immunosuppressive Treg cells and increased expression of PD-L1 in myeloma cells.

Reshaping the tumor microenvironment: The versatility of immunomodulatory drugs in B-cell neoplasms

Immunomodulatory drugs (IMiDs) such as thalidomide, lenalidomide and pomalidomide are antitumor compounds that have direct tumoricidal activity and indirect effects mediated by multiple types of immune cells in the tumor microenvironment (TME). IMiDs have shown remarkable therapeutic efficacy in a set of B-cell neoplasms including multiple myeloma, B-cell lymphomas and chronic lymphocytic leukemia. More recently, the advent of immunotherapy has revolutionized the treatment of these B-cell neoplasms. However, the success of immunotherapy is restrained by immunosuppressive signals and dysfunctional immune cells in the TME. Due to the pleiotropic immunobiological properties, IMiDs have shown to generate synergetic effects in preclinical models when combined with monoclonal antibodies, immune checkpoint inhibitors or CAR-T cell therapy, some of which were successfully translated to the clinic and lead to improved responses for both first-line and relapsed/refractory settings. Mechanistically, despite cereblon (CRBN), an E3 ubiquitin ligase, is considered as considered as the major molecular target responsible for the antineoplastic activities of IMiDs, the exact mechanisms of action for IMiDs-based TME re-education remain largely unknown. This review presents an overview of IMiDs in regulation of immune cell function and their utilization in potentiating efficacy of immunotherapies across multiple types of B-cell neoplasms.

Molecular Determinants Underlying the Anti-Cancer Efficacy of CD38 Monoclonal Antibodies in Hematological Malignancies

CD38 was first discovered as a T-cell antigen and has since been found ubiquitously expressed in various hematopoietic cells, including plasma cells, NK cells, B cells, and granulocytes. More importantly, CD38 expression levels on malignant hematopoietic cells are significantly higher than counterpart healthy cells, thus presenting itself as a promising therapeutic target. In fact, for many aggressive hematological cancers, including CLL, DLBCL, T-ALL, and NKTL, CD38 expression is significantly associated with poorer prognosis and a hyperproliferative or metastatic phenotype. Studies have shown that, beyond being a biomarker, CD38 functionally mediates dysregulated survival, adhesion, and migration signaling pathways, as well as promotes an immunosuppressive microenvironment conducive for tumors to thrive. Thus, targeting CD38 is a rational approach to overcoming these malignancies. However, clinical trials have surprisingly shown that daratumumab monotherapy has not been very effective in these other blood malignancies. Furthermore, extensive use of daratumumab in MM is giving rise to a subset of patients now refractory to daratumumab treatment. Thus, it is important to consider factors modulating the determinants of response to CD38 targeting across different blood malignancies, encompassing both the transcriptional and post-transcriptional levels so that we can diversify the strategy to enhance daratumumab therapeutic efficacy, which can ultimately improve patient outcomes.

Multiple Myeloma Therapy: Emerging Trends and Challenges

Multiple myeloma (MM) is a complex hematologic malignancy characterized by the uncontrolled proliferation of clonal plasma cells in the bone marrow that secrete large amounts of immunoglobulins and other non-functional proteins. Despite decades of progress and several landmark therapeutic advancements, MM remains incurable in most cases. Standard of care frontline therapies have limited durable efficacy, with the majority of patients eventually relapsing, either early or later. Induced drug resistance via up-modulations of signaling cascades that circumvent the effect of drugs and the emergence of genetically heterogeneous sub-clones are the major causes of the relapsed-refractory state of MM. Cytopenias from cumulative treatment toxicity and disease refractoriness limit therapeutic options, hence creating an urgent need for innovative approaches effective against highly heterogeneous myeloma cell populations. Here, we present a comprehensive overview of the current and future treatment paradigm of MM, and highlight the gaps in therapeutic translations of recent advances in targeted therapy and immunotherapy. We also discuss the therapeutic potential of emerging preclinical research in multiple myeloma.

Redirecting T-cell Activity with Anti-BCMA/Anti-CD3 Bispecific Antibodies in Chronic Lymphocytic Leukemia and Other B-cell Lymphomas

T-cell redirecting bispecific antibodies hold high promise for treatment of B-cell malignancies. B-cell maturation antigen (BCMA) exhibits high expression on normal and malignant mature B cells including plasma cells, which can be enhanced by inhibition of γ-secretase. BCMA is considered a validated target in multiple myeloma but whether mature B-cell lymphomas can be targeted by the BCMAxCD3 T-cell redirector teclistamab is currently unknown. BCMA expression on B-cell non-Hodgkin lymphoma and primary chronic lymphocytic leukemia (CLL) cells was assessed by flow cytometry and/or IHC. To assess teclistamab efficacy, cells were treated with teclistamab in presence of effector cells with/without γ-secretase inhibition. BCMA could be detected on all tested mature B-cell malignancy cell lines, while expression levels varied per tumor type. γ-secretase inhibition universally increased BCMA surface expression. These data were corroborated in primary samples from patients with Waldenstrom's macroglobulinemia, CLL, and diffuse large B-cell lymphoma. Functional studies with the B-cell lymphoma cell lines revealed teclistamab-mediated T-cell activation, proliferation, and cytotoxicity. This was independent of the level of BCMA expression, but generally lower in mature B-cell malignancies compared with multiple myeloma. Despite low BCMA levels, healthy donor T cells and CLL-derived T cells induced lysis of (autologous) CLL cells upon addition of teclistamab. These data show that BCMA is expressed on various B-cell malignancies and that lymphoma cell lines and primary CLL can be targeted using teclistamab. Further studies to understand the determinants of response to teclistamab are required to identify which other diseases might be suitable for teclistamab targeting.

Significance

Besides reported BCMA expression on multiple myeloma, we demonstrate BCMA can be detected and enhanced using γ-secretase inhibition on cell lines and primary material of various B-cell malignancies. Furthermore, using CLL we demonstrate that low BCMA-expressing tumors can be targeted efficiently using the BCMAxCD3 DuoBody teclistamab.

SAR442085, a novel anti-CD38 antibody with enhanced antitumor activity against multiple myeloma

Anti-CD38 monoclonal antibodies (mAbs) represent a breakthrough in the treatment of multiple myeloma (MM), yet some patients fail to respond or progress quickly with this therapy, highlighting the need for novel approaches. In this study we compared the preclinical efficacy of SAR442085, a next-generation anti-CD38 mAb with enhanced affinity for activating Fcγ receptors (FcγR), with first-generation anti-CD38 mAb daratumumab and isatuximab. In surface plasmon resonance and cellular binding assays, we found that SAR442085 had higher binding affinity than daratumumab and isatuximab for FcγRIIa (CD32a) and FcγRIIIa (CD16a). SAR442085 also exhibited better in vitro antibody-dependent cellular cytotoxicity (ADCC) against a panel of MM cells expressing variable CD38 receptor densities including MM patients' primary plasma cells. The enhanced ADCC of SAR442085 was confirmed using NK-92 cells bearing low and high affinity FcγRIIIa (CD16a)-158F/V variants. Using MM patients' primary bone marrow cells, we confirmed that SAR442085 had an increased ability to engage FcγRIIIa, resulting in higher natural killer (NK) cell activation and degranulation against primary plasma cells than preexisting Fc wild-type anti-CD38 mAbs. Finally, using huFcgR transgenic mice that express human Fcγ receptors under the control of their human regulatory elements, we demonstrated that SAR442085 had higher NK cell-dependent in vivo antitumor efficacy and better survival than daratumumab and isatuximab against EL4 thymoma or VK*MYC myeloma cells overexpressing human CD38. These results highlight the preclinical efficacy of SAR442085 and support the current evaluation of this next-generation anti-CD38 antibody in phase I clinical development in patients with relapsed/refractory MM.

Regulation of CD38 on Multiple Myeloma and NK Cells by Monoclonal Antibodies

CD38 is highly expressed on multiple myeloma (MM) cells and plays a role in regulating tumor generation and development. CD38 monoclonal antibodies (mAbs) have been used as an effective therapy for MM treatment by various mechanisms, including complement-dependent cytotoxic effects, antibody-dependent cell-mediated cytotoxicity, antibody-dependent cellular phagocytosis, programmed cell death, enzymatic modulation, and immunomodulation. Although CD38 mAbs inhibit the proliferation and survival of MM cells, there are substantial side effects on antitumoral NK cells. The NK-mediated immune response needs to be further evaluated to minimize the adverse effects of NK cell loss. The killing effect of CD38 mAbs on CD38high NK cells should be minimized and the potential combination of CD38low/- NK cells and CD38 mAbs should be maximized to better benefit from their therapeutic efficacy against MM. CD38 mAb effects against MM can be maximized by combination therapies with immunomodulatory imide drugs (IMiDs), proteasome inhibitors (PIs), anti-programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) antibodies, or cellular therapies for the treatment of MM, especially in patients with relapsed or refractory MM (R/R MM) and drug-resistant MM.

Pyrroline-5-Carboxylate Reductase 1: a novel target for sensitizing multiple myeloma cells to bortezomib by inhibition of PRAS40-mediated protein synthesis

Background

Multiple myeloma (MM) remains an incurable cancer despite advances in therapy. Therefore, the search for new targets is still essential to uncover potential treatment strategies. Metabolic changes, induced by the hypoxic bone marrow, contribute to both MM cell survival and drug resistance. Pyrroline-5-carboxylate reductase 1 and 2 (PYCR1 and PYCR2) are two mitochondrial enzymes that facilitate the last step in the glutamine-to-proline conversion. Overexpression of PYCR1 is involved in progression of several cancers, however, its’ role in hematological cancers is unknown. In this study, we investigated whether PYCR affects MM viability, proliferation and response to bortezomib.

Methods

Correlation of PYCR1/2 with overall survival was investigated in the MMRF CoMMpass trial (653 patients). OPM-2 and RPMI-8226 MM cell lines were used to perform in vitro experiments. RPMI-8226 cells were supplemented with ¹³C-glutamine for 48 h in both normoxia and hypoxia (< 1% O₂, by chamber) to perform a tracer study. PYCR1 was inhibited by siRNA or the small molecule inhibitor pargyline. Apoptosis was measured using Annexin V and 7-AAD staining, viability by CellTiterGlo assay and proliferation by BrdU incorporation. Differential protein expression was evaluated using Western Blot. The SUnSET method was used to measure protein synthesis. All in vitro experiments were performed in hypoxic conditions.

Results

We found that PYCR1 and PYCR2 mRNA expression correlated with an inferior overall survival. MM cells from relapsed/refractory patients express significantly higher levels of PYCR1 mRNA. In line with the strong expression of PYCR1, we performed a tracer study in RPMI-8226 cells, which revealed an increased conversion of ¹³C-glutamine to proline in hypoxia. PYCR1 inhibition reduced MM viability and proliferation and increased apoptosis. Mechanistically, we found that PYCR1 silencing reduced protein levels of p-PRAS40, p-mTOR, p-p70, p-S6, p-4EBP1 and p-eIF4E levels, suggesting a decrease in protein synthesis, which we also confirmed in vitro. Pargyline and siPYCR1 increased bortezomib-mediated apoptosis. Finally, combination therapy of pargyline with bortezomib reduced viability in CD138⁺ MM cells and reduced tumor burden in the murine 5TGM1 model compared to single agents.

Conclusions

This study identifies PYCR1 as a novel target in bortezomib-based combination therapies for MM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02250-3.

Harnessing the Potential of NK Cell-Based Immunotherapies against Multiple Myeloma

Natural killer (NK) cell-based therapies have emerged as promising anticancer treatments due to their potency as cytolytic effectors and synergy with concurrent treatments. Multiple myeloma (MM) is an aggressive B-cell malignancy that, despite development of novel therapeutic agents, remains incurable with a high rate of relapse. In MM, the inhospitable tumor microenvironment prevents host NK cells from exerting their cytolytic function. The development of NK cell immunotherapy works to overcome this altered immune landscape and can be classified in two major groups based on the origin of the cell: autologous or allogeneic. In this review, we compare the treatments in each group, such as autologous chimeric antigen receptor (CAR) NKs and allogeneic off-the-shelf NK cell infusions, and their combinatorial effect with existing MM therapies including monoclonal antibodies and proteasome inhibitors. We also discuss their placement in clinical treatment regimens based on the immune profile of each patient. Through this examination, we would like to discover precisely when each NK cell-based treatment will produce the maximum benefit to the MM patient.

The Effect of Duration of Lenalidomide Maintenance and Outcomes of Different Salvage Regimens in Patients with Multiple Myeloma (MM)

The optimal duration of lenalidomide maintenance post-autologous stem cell transplant (ASCT) in Multiple Myeloma (MM), and choice of therapy at relapse post-maintenance, need further evaluation. This retrospective study assessed outcomes of patients with MM (n = 213) seen at Mayo Clinic, Rochester between 1/1/2005-12/31/2016 who received lenalidomide maintenance post-ASCT. The median PFS was 4 (95% CI: 3.4, 4.5) years from diagnosis of MM; median OS was not reached (5-year OS: 77%). Excluding patients who stopped lenalidomide maintenance within 3 years due to progression on maintenance, ≥3 years of maintenance had a superior 5-year OS of 100% vs. 85% in <3 years (p = 0.011). Median PFS was 7.2 (95% CI: 6, 8.5) years in ≥3 years vs. 4.4 (95% CI: 4.3, 4.5) years in <3 years (p < 0.0001). Lenalidomide refractoriness at first relapse was associated with inferior PFS2 [8.1 (95% CI: 6.4, 9.9) months vs. 19.9 (95% CI: 9.7, 30.2; p = 0.002) months in nonrefractory patients]. At first relapse post-maintenance, median PFS2 was superior with daratumumab-based regimens [18.4 (95% CI: 10.9, 25.9) months] versus regimens without daratumumab [8.9 (95% CI: 5.5, 12.3) months; p = 0.006]. Daratumumab + immunomodulatory drugs had superior median PFS2 compared to daratumumab + bortezomib [NR vs 1 yr (95% CI: 0.5, 1.5); p = 0.004].

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.

Cancer therapies based on targeted protein degradation - lessons learned with lenalidomide

For decades, anticancer targeted therapies have been designed to inhibit kinases or other enzyme classes and have profoundly benefited many patients. However, novel approaches are required to target transcription factors, scaffolding proteins and other proteins central to cancer biology that typically lack catalytic activity and have remained mostly recalcitrant to drug development. The selective degradation of target proteins is an attractive approach to expand the druggable proteome, and the selective oestrogen receptor degrader fulvestrant served as an early example of this concept. Following a long and tragic history in the clinic, the immunomodulatory imide drug (IMiD) thalidomide was discovered to exert its therapeutic activity via a novel and unexpected mechanism of action: targeting proteins to an E3 ubiquitin ligase for subsequent proteasomal degradation. This discovery has paralleled and directly catalysed myriad breakthroughs in drug development, leading to the rapid maturation of generalizable chemical platforms for the targeted degradation of previously undruggable proteins. Decades of clinical experience have established front-line roles for thalidomide analogues, including lenalidomide and pomalidomide, in the treatment of haematological malignancies. With a new generation of 'degrader' drugs currently in development, this experience provides crucial insights into class-wide features of degraders, including a unique pharmacology, mechanisms of resistance and emerging therapeutic opportunities. Herein, we review these past experiences and discuss their application in the clinical development of novel degrader therapies.

Three-Dimensional Reconstructed Bone Marrow Matrix Culture Improves the Viability of Primary Myeloma Cells In-Vitro via a STAT3-Dependent Mechanism

Primary myeloma (PM) cells are short-lived in conventional culture, which limited their usefulness as a study model. Here, we evaluated if three-dimensional (3D) culture can significantly prolong the longevity of PM cells in-vitro. We employed a previously established 3D model for culture of bone marrow mononuclear cells isolated from 15 patients. We assessed the proportion of PM cells, viability and proliferation using CD38 staining, trypan blue exclusion assays and carboxy fluorescein succinimidyl ester (CFSE) staining, respectively. We observed significantly more CD38+ viable cells in 3D than in conventional culture (65% vs. 25%, p = 0.006) on day 3. CFSE staining showed no significant difference in cell proliferation between the two culture systems. Moreover, we found that PM cells in 3D culture are more STAT3 active by measure of pSTAT3 staining (66% vs. 10%, p = 0.008). Treatment of IL6, a STAT3 activator significantly increased CD38+ cell viability (41% to 68%, p = 0.021). In comparison, inhibition of STAT3 with Stattic significantly decreased PM cell viability in 3D culture (38% to 17% p = 0.010). Neither IL6 nor Stattic affected the PM cell viability in conventional culture. This study suggests that 3D culture can significantly improve the longevity of PM cells in-vitro, and STAT3 activation can further improve their viability.

Measurement of ex vivo resistance to proteasome inhibitors, IMiDs, and daratumumab during multiple myeloma progression

The oncogenic drivers and progression factors in multiple myeloma (MM) are heterogeneous and difficult to target therapeutically. Many different MM drugs have emerged, however, that attack various phenotypic aspects of malignant plasma cells. These drugs are administered in numerous, seemingly interchangeable combinations. Although the availability of many treatment options is useful, no clinical test capable of optimizing and sequencing the treatment regimens for an individual patient is currently available. To overcome this problem, we developed a functional ex vivo approach to measure patients' inherent and acquired drug resistance. This method, which we termed myeloma drug sensitivity testing (My-DST), uses unselected bone marrow mononuclear cells with a panel of drugs in clinical use, followed by flow cytometry to measure myeloma-specific cytotoxicity. We found that using whole bone marrow cultures helped preserve primary MM cell viability. My-DST was used to profile 55 primary samples at diagnosis or at relapse. Sensitivity or resistance to each drug was determined from the change in MM viability relative to untreated control samples. My-DST identified progressive loss of sensitivity to immunomodulatory drugs, proteasome inhibitors, and daratumumab through the disease course, mirroring the clinical development of resistance. Prospectively, patients' ex vivo drug sensitivity to the drugs subsequently received was sensitive and specific for clinical response. In addition, treatment with <2 drugs identified as sensitive by My-DST led to inferior depth and duration of clinical response. In summary, ex vivo drug sensitivity is prognostically impactful and, with further validation, may facilitate more personalized and effective therapeutic regimens.

Bone Marrow Mesenchymal Stromal Cells Can Render Multiple Myeloma Cells Resistant to Cytotoxic Machinery of CAR T Cells through Inhibition of Apoptosis

PURPOSE

The microenvironment of multiple myeloma (MM) can critically impair therapy outcome, including immunotherapies. In this context, we have earlier demonstrated that bone marrow mesenchymal stromal cells (BMMSC) protect MM cells against the lytic machinery of MM-reactive cytotoxic T cells (CTL) and daratumumab-redirected natural killer (NK) cells through the upregulation of antiapoptotic proteins Survivin and Mcl-1 in MM cells. Here, we investigated the significance of this mode of immune escape on T cells engineered to express chimeric antigen receptors (CAR T cells).

EXPERIMENTAL DESIGN

We tested the cytolytic ability of a panel of 10 BCMA-, CD38-, and CD138-specific CAR T cells with different affinities against a model MM cell line and against patient-derived MM cells in the presence versus absence of BMMSCs.

RESULTS

Although BMMSCs hardly protected MM cells from lysis by high-affinity, strongly lytic BCMA- and CD38-CAR T cells, they significantly protected against lower affinity, moderately lytic BCMA-, CD38-, and CD138-specific CAR T cells in a cell-cell contact-dependent manner. Overall, there was a remarkable inverse correlation between the protective ability of BMMSCs and the lytic activity of all CAR T cells, which was dependent on CAR affinity and type of costimulation. Furthermore, BMMSC-mediated resistance against CAR T cells was effectively modulated by FL118, an inhibitor of antiapoptotic proteins Survivin, Mcl-1, and XIAP.

CONCLUSIONS

These results extend our findings on the negative impact of the microenvironment against immunotherapies and suggest that outcome of CAR T cell or conventional CTL therapies could benefit from inhibition of antiapoptotic proteins upregulated in MM cells through BMMSC interactions.

Bone Marrow Mesenchymal Stromal Cell-mediated Resistance in Multiple Myeloma Against NK Cells can be Overcome by Introduction of CD38-CAR or TRAIL-variant

We have recently shown the strong negative impact of multiple myeloma (MM)-bone marrow mesenchymal stromal cell (BMMSC) interactions to several immunotherapeutic strategies including conventional T cells, chimeric antigen receptor (CAR) T cells, and daratumumab-redirected NK cells. This BMMSC-mediated immune resistance via the upregulation of antiapoptotic proteins in MM cells was mainly observed for moderately cytotoxic modalities. Here, we set out to assess the hypothesis that this distinct mode of immune evasion can be overcome by improving the overall efficacy of immune effector cells. Using an in vitro model, we aimed to improve the cytotoxic potential of KHYG-1 NK cells toward MM cells by the introduction of a CD38-specific CAR and a DR5-specific, optimized TRAIL-variant. Similar to what have been observed for T cells and moderately lytic CAR T cells, the cytolytic efficacy of unmodified KHYG-1 cells as well as of conventional, DR5-agonistic antibodies were strongly reduced in the presence of BMMSCs. Consistent with our earlier findings, the BMMSCs protected MM cells against KHYG-1 and DR5-agonistic antibodies by inducing resistance mechanisms that were largely abrogated by the small molecule FL118, an inhibitor of multiple antiapoptotic proteins including Survivin, Mcl-1, and XIAP. Importantly, the BMMSC-mediated immune resistance was also significantly diminished by engineering KHYG-1 cells to express the CD38-CAR or the TRAIL-variant. These results emphasize the critical effects of microenvironment-mediated immune resistance on the efficacy of immunotherapy and underscores that this mode of immune escape can be tackled by inhibition of key antiapoptotic molecules or by increasing the overall efficacy of immune killer cells.

Case Report: Resetting the Humoral Immune Response by Targeting Plasma Cells With Daratumumab in Anti-Phospholipid Syndrome

Introduction

Monoclonal antibodies (mAb) targeting plasma cells are malignant gammopathy designed and approved therapies. In recent years, these antibodies have also been increasingly introduced for non-malignant conditions such as autoimmune-mediated diseases. The Anti-Phospholipid Syndrome (APS) is an immune-mediated disorder in which autoantibodies against phospholipid associated proteins could elicit the activation of the coagulation cascade in specific situations. Therefore, the mainstream treatment for APS patients is the use of anticoagulant therapy. However, there are refractory patients who would benefit from targeting the antibodies rather than their effects. Rituximab, a B-cell depleting mAb, and intravenous immunoglobulins (IVIG) have been used in APS patients without showing a clear beneficial effect or a significant drop in anti-phospholipid antibody (aPL) levels.

Clinical case

We present our first APS case treated with daratumumab, an anti-CD38 mAb, in a 21-year-old patient with APS who presented with recurrent venous thromboembolic events despite adequate anticoagulant therapy. She tested positive for lupus anticoagulant, anti-cardiolipin IgG, anti-beta-2-glycoprotein-I IgG and anti-phosphatidylserine/prothrombin IgG and IgM. She was administered one dose weekly of daratumumab for 4 weeks. The treatment showed an adequate safety profile and was well tolerated. The patient was discharged after undergoing a clinically significant improvement. After the therapy, her levels of positive aPL declined significantly and most continued to decrease during the next three months. The patient experienced a new thrombotic episode two years after the therapy associated with poor adherence to antithrombotic therapy.

Conclusions

The treatment with daratumumab showed an adequate safety profile, was well tolerated and led to a significant clinical improvement. Levels of aPL lowered on therapy and the next three months and then rose again during follow-up. Further investigation is needed to better elucidate the role and optimal timing and doses of daratumumab in treatment of refractory APS.

CD38 deletion of human primary NK cells eliminates daratumumab-induced fratricide and boosts their effector activity

Multiple myeloma (MM) is a plasma cell neoplasm that commonly expresses CD38. Daratumumab (DARA), a human monoclonal antibody targeting CD38, has significantly improved the outcome of patients with relapsed or refractory MM, but the response is transient in most cases. Putative mechanisms of suboptimal efficacy of DARA include downregulation of CD38 expression and overexpression of complement inhibitory proteins on MM target cells as well as DARA-induced depletion of CD38high natural killer (NK) cells resulting in crippled antibody-dependent cellular cytotoxicity (ADCC). Here, we tested whether maintaining NK cell function during DARA therapy could maximize DARA-mediated ADCC against MM cells and deepen the response. We used the CRISPR/Cas9 system to delete CD38 (CD38KO) in ex vivo expanded peripheral blood NK cells. These CD38KO NK cells were completely resistant to DARA-induced fratricide, showed superior persistence in immune-deficient mice pretreated with DARA, and enhanced ADCC activity against CD38-expressing MM cell lines and primary MM cells. In addition, transcriptomic and cellular metabolic analysis demonstrated that CD38KO NK cells have unique metabolic reprogramming with higher mitochondrial respiratory capacity. Finally, we evaluated the impact of exposure to all-trans retinoic acid (ATRA) on wild-type NK and CD38KO NK cell function and highlighted potential benefits and drawbacks of combining ATRA with DARA in patients with MM. Taken together, these findings provide proof of concept that adoptive immunotherapy using ex vivo expanded CD38KO NK cells has the potential to boost DARA activity in MM.

Role and Modulation of NK Cells in Multiple Myeloma

Myeloma tumor cells are particularly dependent on their microenvironment and sensitive to cellular antitumor immune response, including natural killer (NK) cells. These later are essential innate lymphocytes implicated in the control of viral infections and cancers. Their cytotoxic activity is regulated by a balance between activating and inhibitory signals resulting from the complex interaction of surface receptors and their respective ligands. Myeloma disease evolution is associated with a progressive alteration of NK cell number, phenotype and cytotoxic functions. We review here the different therapeutic approaches that could restore or enhance NK cell functions in multiple myeloma. First, conventional treatments (immunomodulatory drugs-IMids and proteasome inhibitors) can enhance NK killing of tumor cells by modulating the expression of NK receptors and their corresponding ligands on NK and myeloma cells, respectively. Because of their ability to kill by antibody-dependent cell cytotoxicity, NK cells are important effectors involved in the efficacy of anti-myeloma monoclonal antibodies targeting the tumor antigens CD38, CS1 or BCMA. These complementary mechanisms support the more recent therapeutic combination of IMids or proteasome inhibitors to monoclonal antibodies. We finally discuss the ongoing development of new NK cell-based immunotherapies, such as ex vivo expanded killer cell immunoglobulin-like receptors (KIR)-mismatched NK cells, chimeric antigen receptors (CAR)-NK cells, check point and KIR inhibitors.

Monoclonal Antibodies and Antibody Drug Conjugates in Multiple Myeloma

Multiple myeloma is the second most common hematologic malignancy. Current treatment strategies are mainly based on immunomodulatory drugs, proteasome inhibitors or combination of both. Novel agents added to these backbone treatments represent a promising strategy in treatment of newly diagnosed as well as relapsed and refractory multiple myeloma patients. In this respect, the incorporation of monoclonal antibodies into standard-of-care regimens markedly improved prognosis of myeloma patients during the last years. More specifically, monoclonal anti-CD38 antibodies, daratumumab and isatuximab, have been implemented into treatment strategies from first-line treatment to refractory disease. In addition, the monoclonal anti-SLAM-F7 antibody elotuzumab in combination with immunomodulatory drugs has improved the clinical outcomes of patients with relapsed/refractory disease. Belantamab mafodotin is the first approved antibody drug conjugate directed against B cell maturation antigen and is currently used as a monotherapy for patients with advanced disease. This review focuses on clinical efficacy and safety of monoclonal antibodies as well as antibody drug conjugates in multiple myeloma.

Isatuximab for the treatment of relapsed/refractory multiple myeloma

INTRODUCTION

Although new drug classes have significantly extended survival of patients with multiple myeloma, they continue to experience multiple relapses and/or become refractory to treatment. Therefore, novel therapies and treatment combinations with different mechanisms of action are needed to improve the outcomes of patients with relapsed/refractory multiple myeloma.

AREAS COVERED

Here, the authors review the published data regarding the development and clinical investigation of isatuximab, a CD38 monoclonal antibody, for treatment of patients with relapsed/refractory multiple myeloma. The mechanisms of action, clinical efficacy, and safety of isatuximab treatment are summarized.

EXPERT OPINION

Isatuximab is approved in combination with pomalidomide/dexamethasone for the treatment of adults with relapsed/refractory multiple myeloma who have received at least two prior therapies, including lenalidomide and a proteasome inhibitor. Isatuximab displays a manageable safety profile, with infusion reactions being the most common adverse events. Isatuximab is currently being further evaluated in combination with other backbone regimens in relapsed/refractory and newly diagnosed multiple myeloma.

Facts and Hopes in Multiple Myeloma Immunotherapy

Among the hallmarks of cancer is the ability of neoplastic cells to evade and suppress immune surveillance to allow their growth and evolution. Nowhere is this as apparent as in multiple myeloma, a cancer of antibody-producing plasma cells, where a complex interplay between neoplastic cells and the immune microenvironment is required for the development and progression of disease. Decades of research has led to the discovery of a number of therapeutic agents, from cytotoxic drugs to genetically engineered cells that mediate their antimyeloma effects at least partially through altering these immune interactions. In this review, we discuss the history of immunotherapy and current practices in multiple myeloma, as well as the advances that promise to one day offer a cure for this deadly disease.

Flow cytometric evaluation of CD38 expression levels in the newly diagnosed T-cell acute lymphoblastic leukemia and the effect of chemotherapy on its expression in measurable residual disease, refractory disease and relapsed disease: an implication for anti-CD38 immunotherapy

Background

Recently, anti-CD38 monoclonal antibody (Mab) therapy has become a focus of attention as an additional/alternative option for many hematological neoplasms including T-cell acute lymphoblastic leukemia (T-ALL). It has been shown that antitumor efficacy of anti-CD38-Mab depends on the level of CD38 expression on tumor cells. Reports on CD38 expression in T-ALL are scarce, and data on the effect of cytotoxic chemotherapy on CD38 expression are limited to very few samples. Moreover, it lacks entirely in refractory disease and in adult T-ALL. We report the flow cytometric evaluation of CD38 expression in T-ALL blasts at diagnosis and the effect of cytotoxic chemotherapy on its expression in measurable residual disease (MRD), refractory disease (MRD≥5%), and relapsed disease in a large cohort of T-ALL.

Methods

The study included 347 samples (188 diagnostic, 100 MRD, 24 refractory and 35 relapse samples) from 196 (children: 85; adolescents/adults: 111) patients with T-ALL. CD38-positive blasts percentages (CD38-PBPs) and expression-intensity (mean fluorescent intensity, CD38-MFI) were studied using multicolor flow cytometry (MFC). MFC-based MRD was performed at the end-of-induction (EOI-MRD, day 30–35) and end-of-consolidation (EOC-MRD, day 78–85) subsequent follow-up (SFU-MRD) points.

Results

Patients were classified into early thymic precursor subtype of T-ALL (ETPALL, 54/188, 28.7%), and non-ETPALL (134/188, 71.3%). Of 188, EOI-MRD assessment was available in 152, EOC-MRD was available in 96 and SFU-MRD was available in 14 patients. CD38 was found positive in 97.9% (184/188) of diagnostic, 88.7% (110/124) MRD (including 24-refractory) and 82.9% (29/35) relapsed samples. Median (95% CI) of CD38-PBPs/MFI in diagnostic, MRD, refractory, and relapsed T-ALL samples were, respectively, 85.9% (82.10%–89.91%)/4.2 (3.88–4.47), 74.0% (58.87%–83.88%)/4.6 (3.67–6.81), 79.6% (65.25%–96.11%)/4.6 (3.33–8.47) and 85.2% (74.48%–93.01%)/5.6 (4.14–8.99). No significant difference was noted in CD38 expression between pediatric versus adult and patients with ETPALL versus non-ETPALL. No change was observed in CD38-MFI between diagnostic versus MRD and diagnostic versus relapsed paired samples. However, we noticed a mild drop in the CD38-PBPs in MRD samples compared with the diagnostic samples (p=0.016).

Conclusion

We report an in-depth analysis of CD38 expression in a large cohort of T-ALL at diagnosis, during chemotherapy, and at relapse. Our data demonstrated that CD38 is robustly expressed in T-ALL blasts with a little effect of cytotoxic chemotherapy making it a potentially effective target for antiCD38-Mab therapy.

What Is New in the Treatment of Smoldering Multiple Myeloma?

Smoldering multiple myeloma (SMM), an asymptomatic plasma cell neoplasm, is currently diagnosed according to the updated IMWG criteria, which reflect an intermediate tumor mass between monoclonal gammopathy of undetermined significance (MGUS) and active MM. However, SMM is a heterogeneous entity and individual case may go from an "MGUS-like" behavior to "early MM" with rapid transformation into symptomatic disease. This wide range of clinical outcomes poses challenges for prognostication and management of individual patients. However, initial studies showed a benefit in terms of progression or even survival for early treatment of high-risk SMM patients. While outside of clinical trials the conventional approach to SMM generally remains that of close observation, these studies raised the question of whether early treatment should be offered in high-risk patients, prompting evaluation of several different therapeutic approaches with different goals. While delay of progression to MM with a non-toxic treatment is clearly achievable by early treatment, a convincing survival benefit still needs to be proven by independent studies. Furthermore, if SMM is to be considered less biologically complex than MM, early treatment may offer the chance of cure that is currently not within reach of any active MM treatment. In this paper, we present updated results of completed or ongoing clinical trials in SMM treatment, highlighting areas of uncertainty and critical issues that will need to be addressed in the near future before the "watch and wait" paradigm in SMM is abandoned in favor of early treatment.

Expanded NK cells from umbilical cord blood and adult peripheral blood combined with daratumumab are effective against tumor cells from multiple myeloma patients

In this study we evaluated the potential of expanded NK cells (eNKs) from two sources combined with the mAbs daratumumab and pembrolizumab to target primary multiple myeloma (MM) cells ex vivo. In order to ascertain the best source of NK cells, we expanded and activated NK cells from peripheral blood (PB) of healthy adult donors and from umbilical cord blood (UCB). The resulting expanded NK (eNK) cells express CD16, necessary for carrying out antibody-dependent cellular cytotoxicity (ADCC). Cytotoxicity assays were performed on bone marrow aspirates of 18 MM patients and 4 patients with monoclonal gammopathy of undetermined significance (MGUS). Expression levels of PD-1 on eNKs and PD-L1 on MM and MGUS cells were also quantified. Results indicate that most eNKs obtained using our expansion protocol express a low percentage of PD-1⁺ cells. UCB eNKs were highly cytotoxic against MM cells and addition of daratumumab or pembrolizumab did not further increase their cytotoxicity. PB eNKs, while effective against MM cells, were significantly more cytotoxic when combined with daratumumab. In a minority of cases, eNK cells showed a detectable population of PD1⁺ cells. This correlated with low cytotoxic activity, particularly in UCB eNKs. Addition of pembrolizumab did not restore their activity. Results indicate that UCB eNKs are to be preferentially used against MM in the absence of daratumumab while PB eNKs have significant cytotoxic advantage when combined with this mAb.

Why Immunotherapy Fails in Multiple Myeloma

Multiple myeloma remains an incurable disease despite great advances in its therapeutic landscape. Increasing evidence supports the belief that immune dysfunction plays an important role in the disease pathogenesis, progression, and drug resistance. Recent efforts have focused on harnessing the immune system to exert anti-myeloma effects with encouraging outcomes. First-in-class anti-CD38 monoclonal antibody, daratumumab, now forms part of standard treatment regimens in relapsed and refractory settings and is shifting to front-line treatments. However, a non-negligible number of patients will progress and be triple refractory from the first line of treatment. Antibody-drug conjugates, bispecific antibodies, and chimeric antigen receptors (CAR) are being developed in a heavily pretreated setting with outstanding results. Belantamab mafodotin-blmf has already received approval and other anti-B-cell maturation antigen (BCMA) therapies (CARs and bispecific antibodies are expected to be integrated in therapeutic options against myeloma soon. Nonetheless, immunotherapy faces different challenges in terms of efficacy and safety, and manufacturing and economic drawbacks associated with such a line of therapy pose additional obstacles to broadening its use. In this review, we described the most important clinical data on immunotherapeutic agents, delineated the limitations that lie in immunotherapy, and provided potential insights to overcome such issues.

Preclinical Rationale for Targeting the PD-1/PD-L1 Axis in Combination with a CD38 Antibody in Multiple Myeloma and Other CD38-Positive Malignancies

Simple Summary

The CD38-targeting antibody daratumumab mediates its anti-myeloma activities not only through direct effects on tumor cells, but also by its effects on T-cell immunity through depletion of CD38⁺ immune suppressor cells. We hypothesized that combining daratumumab with modulators of other potent immune inhibitory pathways, such as the PD-1/PD-L1 axis, may further improve its efficacy. We show that during MM progression there is increased expression of the PD-1/PD-L1 pathway components in the bone marrow microenvironment. Although nivolumab (a PD-1 checkpoint inhibitor) moderately increased T-cell frequencies in ex vivo experiments with bone marrow samples from MM patients, no single agent activity was observed, and addition of nivolumab did not enhance the activity of daratumumab in these short-term assays. However, with a longer treatment duration, in mouse experiments, we demonstrate that anti-CD38 and anti-PD-1 antibodies synergize to eradicate MM cells. In addition, our results suggest that this combined immunotherapeutic approach may also be beneficial in other CD38-positive malignancies.

Abstract

The CD38-targeting antibody daratumumab mediates its anti-myeloma activities not only through Fc-receptor-dependent effector mechanisms, but also by its effects on T-cell immunity through depletion of CD38⁺ regulatory T-cells, regulatory B-cells, and myeloid-derived suppressor cells. Therefore, combining daratumumab with modulators of other potent immune inhibitory pathways, such as the PD-1/PD-L1 axis, may further improve its efficacy. We show that multiple myeloma (MM) cells from relapsed/refractory patients have increased expression of PD-L1, compared to newly diagnosed patients. Furthermore, PD-1 is upregulated on T-cells from both newly diagnosed and relapsed/refractory MM patients, compared to healthy controls. In short-term experiments with bone marrow samples from MM patients, daratumumab-mediated lysis was mainly associated with the MM cells’ CD38 expression levels and the effector (NK-cells/monocytes/T-cells)-to-target ratio, but not with the PD-L1 expression levels or PD-1⁺ T-cell frequencies. Although PD-1 blockade with nivolumab did not affect MM cell viability or enhanced daratumumab-mediated lysis in short-term ex vivo experiments, nivolumab resulted in a mild but clear increase in T-cell numbers. Moreover, with a longer treatment duration, PD-1 blockade markedly improved anti-CD38 antibody-mediated cytotoxicity in vivo in murine CD38⁺ tumor models. In conclusion, dual targeting of CD38 and PD-1 may represent a promising strategy for treating MM and other CD38-positive malignancies.

Monoclonal Antibodies: Leading Actors in the Relapsed/Refractory Multiple Myeloma Treatment

Multiple myeloma is a complex hematologic malignancy, and despite a survival improvement related to the growing number of available therapeutic options since 2000s, it remains an incurable disease with most patients experiencing relapse. However, therapeutic options for this disease are constantly evolving and immunotherapy is becoming the mainstay of the therapeutic armamentarium of Multiple Myeloma (MM), starting with monoclonal antibodies (MoAbs) as elotuzumab, daratumumab and isatuximab. Elotuzumab, the first in class targeting SLAMF7, in combination with lenalidomide and dexamethasone and daratumumab, directed against CD38, in combination with Rd and with bortezomib and dexamethasone (Vd), have been approved for the treatment of relapsed/refractory MM (RRMM) after they demonstrated excellent efficacy. More recently, another anti-CD38 MoAb named isatuximab was approved by FDA in combination with pomalidomide-dexamethasone (Pd) in the same setting. Many phase II and III trials with regimens containing these MoAbs are ongoing, and when available, preliminary data are very encouraging. In this review we will describe the results of major clinical studies that have been conducted with elotuzumab, daratumumab and isatuximab in RRMM, focusing on phase III trials. Moreover, we will summarized the emerging MoAbs-based combinations in the RRMM landscape.

VIS832, a novel CD138-targeting monoclonal antibody, potently induces killing of human multiple myeloma and further synergizes with IMiDs or bortezomib in vitro and in vivo

Therapeutically targeting CD138, a define multiple myeloma (MM) antigen, is not yet approved for patients. We here developed and determined the preclinical efficacy of VIS832, a novel therapeutic monoclonal antibody (MoAb) with differentiated CD138 target binding to BB4 that is anti-CD138 MoAb scaffold for indatuximab ravtansine (BT062). VIS832 demonstrated enhanced CD138-binding avidity and significantly improved potency to kill MM cell lines and autologous patient MM cells regardless of resistance to current standard-of-care therapies, via robust antibody-dependent cellular cytotoxicity and phagocytosis mediated by NK and macrophage effector cells, respectively. Specifically, CD38-targeting daratumumab-resistant MM cells were highly susceptible to VIS832 which, unlike daratumumab, spares NK cells. Superior maximal cytolysis of VIS832 vs. daratumumab corresponded to higher CD138 vs. CD38 levels in MM cells. Furthermore, VIS832 acted synergistically with lenalidomide or bortezomib to deplete MM cells. Importantly, VIS832 at a sub-optimal dose inhibited disseminated MM1S tumors in vivo as monotherapy (P < 0.0001), and rapidly eradicated myeloma burden in all mice concomitantly receiving bortezomib, with 100% host survival. Taken together, these data strongly support clinical development of VIS832, alone and in combination, for the therapeutic treatment of MM in relapsed and refractory patients while pointing to its potential therapeutic use earlier in disease intervention.

Immunotherapeutic and Targeted Approaches in Multiple Myeloma

The multiple myeloma (MM) therapeutic landscape has evolved significantly with the approval of numerous novel agents, including next generation proteasome inhibitors (PIs), immunomodulatory agents (IMIDs), and monoclonal antibodies (MoABs) targeting CD38 and SLAMF7. While these discoveries have led to an unprecedented improval in patient outcomes, the disease still remains incurable. Immunotherapeutic approaches have shown substantial promise in recent studies of chimeric antigen receptor T-cell (CAR T-cell) therapy, bispecific antibodies, and antibody drug conjugates targeting B-cell maturation antigen (BCMA). This review will highlight these novel and targeted therapies in MM, with particular focus on PIs, IMIDs, MoAb and BCMA-directed immunotherapy.

CD38: targeted therapy in multiple myeloma and therapeutic potential for solid cancers

INTRODUCTION

CD38 is expressed by some cells of hematological malignancies and tumor-related immunosuppressive cells, including regulatory T cells, regulatory B cells, and myeloid-derived suppressor cells. CD38 is an effective target in some hematological malignancies such as multiple myeloma (MM). Daratumumab (Dara), a CD38-targeting antibody, can eliminate CD38^high immune suppressor cells and is regarded as a standard therapy for MM because of its outstanding clinical efficacy. Other CD38 monospecific antibodies, such as isatuximab, MOR202, and TAK079, showed promising effects in clinical trials.

AREA COVERED

This review examines the expression, function, and targeting of CD38 in MM and its potential to deplete immunosuppressive cells in solid cancers. We summarize the distribution and biological function of CD38 and discuss the application of anti-CD38 drugs in hematological malignancies. We also analyz the role of CD38⁺ immune cells in the tumor microenvironment to encourage additional investigations that target CD38 in solid cancers. PubMed and ClinicalTrials were searched to identify relevant literature from the database inception to 30 April 2020.

EXPERT OPINION

There is convincing evidence that CD38-targeted immunotherapeutics reduce CD38⁺ immune suppressor cells. This result suggests that CD38 can be exploited to treat solid tumors by regulating the immunosuppressive microenvironment.

Novel Approaches to Improve Myeloma Cell Killing by Monoclonal Antibodies

The monoclonal antibodies (mAbs) have significantly changed the treatment of multiple myeloma (MM) patients. However, despite their introduction, MM remains an incurable disease. The mAbs currently used for MM treatment were developed with different mechanisms of action able to target antigens, such as cluster of differentiation 38 (CD38) and SLAM family member 7 (SLAMF7) expressed by both, MM cells and the immune microenvironment cells. In this review, we focused on the mechanisms of action of the main mAbs approved for the therapy of MM, and on the possible novel approaches to improve MM cell killing by mAbs. Actually, the combination of anti-CD38 or anti-SLAMF7 mAbs with the immunomodulatory drugs significantly improved the clinical effect in MM patients. On the other hand, pre-clinical evidence indicates that different approaches may increase the efficacy of mAbs. The use of trans-retinoic acid, the cyclophosphamide or the combination of anti-CD47 and anti-CD137 mAbs have given the rationale to design these types of combinations therapies in MM patients in the future. In conclusion, a better understanding of the mechanism of action of the mAbs will allow us to develop novel therapeutic approaches to improve their response rate and to overcome their resistance in MM patients.

Immune-based therapies in the management of multiple myeloma

Multiple myeloma (MM) is a clonal plasma cell malignancy affecting a predominantly elderly population. The continued development of newer therapies with novel mechanisms of action has reshaped the treatment paradigm of this disorder in the last two decades, leading to a significantly improved prognosis. This has in turn resulted in an increasing number of patients in need of therapy for relapsed/refractory disease. Immune-based therapies, including monoclonal antibodies, immune checkpoint inhibitors, and most promisingly, adoptive cellular therapies represent important therapeutic strategies in these patients due to their non-cross resistant mechanisms of actions with the usual frontline therapies comprising of immunomodulatory drugs (IMiDs) and proteasome inhibitors (PIs). The anti-CD38 antibodies daratumumab and more recently isatuximab, with their excellent efficacy and safety profile along with its synergy in combination with IMiDs and PIs, are being increasingly incorporated in the frontline setting. Chimeric antigen receptor-T cell (CART) therapies and bi-specific T-cell engager (BiTE) represent exciting new options that have demonstrated efficacy in heavily pretreated and refractory MM. In this review, we discuss the rationale for use of immune-based therapies in MM and summarize the currently available literature for common antibodies and CAR-T therapies that are utilized in MM.

Daratumumab subcutaneous formulation for the treatment of multiple myeloma

INTRODUCTION

Intravenous daratumumab has shown unprecedented anti-myeloma activity when used as a single agent or in combination with other myeloma therapies. Recently, a subcutaneous formulation of daratumumab was approved for use in both the United States and European Union based on data which showed shorter infusion times and decreased rate of infusion reactions while maintaining non-inferior efficacy.

AREAS COVERED

We cover the physiology behind subcutaneous daratumumab and summarize the relevant clinical data with a particular focus on the pharmacokinetics, pharmacodynamics, safety, and clinical efficacy. Articles used to generate this review were obtained by searching pubmed (https://pubmed.ncbi.nlm.nih.gov/) with the search terms 'subcutaneous daratumumab' and 'daratumumab hyaluronidase'.

EXPERT OPINION

Subcutaneous daratumumab is associated with lower risk of infusion reactions and decreased administration time while maintaining non-inferior efficacy. We support the use of subcutaneous daratumumab for all approved indications and for investigational use moving forward.

An evaluation of subcutaneous daratumumab for the treatment of multiple myeloma

INTRODUCTION

A subcutaneous formulation of daratumumab, a human immunoglobulin G1 kappa monoclonal antibody targeting CD38, recently achieved FDA approval for both newly diagnosed and relapsed refractory multiple myeloma amid promises to decrease infusion times and rates of infusion reactions in myeloma patients.

AREAS COVERED

In this article the biology behind subcutaneous administration of oncologic antibody therapies is reviewed and the subcutaneous formulation of daratumumab is covered in depth. The most recent results from the PAVO, COLUMBA, and PLEIADES clinical trials evaluating subcutaneous daratumumab as a single agent, and in combination, in both newly diagnosed, and relapsed and refractory myeloma patients are summarized. The efficacy, safety, and PK data from these trials are reviewed, and the potential of the subcutaneous formulation to improve quality of life in myeloma patients and decrease healthcare resource use is discussed.

EXPERT OPINION

Subcutaneous daratumumab is non-inferior to conventional intravenous daratumumab with lower risk of infusion-related reactions and decreased administration time. Based on these data, and the recent FDA and European Commission approvalsthe widespread use of the subcutaneous formulation for both conventional and investigational practice is supported.

CD38 and Anti-CD38 Monoclonal Antibodies in AL Amyloidosis: Targeting Plasma Cells and beyond

Immunoglobulin light chain amyloidosis (AL amyloidosis) is a rare systemic disease characterized by monoclonal light chains (LCs) depositing in tissue as insoluble fibrils, causing irreversible tissue damage. The mechanisms involved in aggregation and deposition of LCs are not fully understood, but CD138/38 plasma cells (PCs) are undoubtedly involved in monoclonal LC production.CD38 is a pleiotropic molecule detectable on the surface of PCs and maintained during the neoplastic transformation in multiple myeloma (MM). CD38 is expressed on T, B and NK cell populations as well, though at a lower cell surface density. CD38 is an ideal target in the management of PC dyscrasia, including AL amyloidosis, and indeed anti-CD38 monoclonal antibodies (MoAbs) have promising therapeutic potential. Anti-CD38 MoAbs act both as PC-depleting agents and as modulators of the balance of the immune cells. These aspects, together with their interaction with Fc receptors (FcRs) and neonatal FcRs, are specifically addressed in this paper. Moreover, the initiallyavailable experiences with the anti-CD38 MoAb DARA in AL amyloidosis are reviewed.