Ide-cel vs standard regimens in triple-class-exposed relapsed and refractory multiple myeloma: updated KarMMa-3 analyses.

Outcomes are poor in triple-class-exposed (TCE) relapsed/refractory multiple myeloma (RRMM). In the phase 3 KarMMa-3 (clinicaltrials.gov; NCT03651128) trial, patients with TCE RRMM and 2-4 prior regimens were randomized 2:1 to idecabtagene vicleucel (ide-cel) or standard regimens (SRs). An interim analysis (IA) demonstrated significantly longer median progression-free survival (PFS; primary endpoint; 13.3 vs 4.4 months; P<.0001) and higher overall response rate (ORR) with ide-cel vs SRs. At final PFS analysis (median follow-up, 30.9 months), ide-cel further improved median PFS vs SRs (13.8 vs 4.4 months; hazard ratio (HR), 0.49; 95% confidence interval (CI), 0.38-0.63). PFS benefit with ide-cel vs SRs was observed regardless of number of prior lines of therapy, with greatest benefit after 2 prior lines (16.2 vs 4.8 months, respectively). ORR benefit was maintained with ide-cel vs SRs (71% vs 42%; complete response, 44% vs 5%). Patient-centric design allowed crossover from SRs (56%) to ide-cel upon progressive disease, confounding overall survival (OS) interpretation. At IA of OS, median (95% CI) was 41.4 (30.9-not reached [NR]) vs 37.9 (23.4-NR) months with ide-cel and SRs, respectively (HR, 1.01; 95% CI 0.73-1.40); median OS in both arms was longer than historical data (9-22 months). Two prespecified analyses adjusting for crossover showed OS favoring ide-cel. This trial highlighted the importance of individualized bridging therapy to ensure adequate disease control during ide-cel manufacturing. Ide-cel improved patient-reported outcomes vs SRs. No new safety signals were reported. These results demonstrate the continued favorable benefit-risk profile of ide-cel in early-line and TCE RRMM. NCT03651128.

Daratumumab-based quadruplet therapy for transplant-eligible newly diagnosed multiple myeloma with high cytogenetic risk.

In the MASTER study (NCT03224507), daratumumab+carfilzomib/lenalidomide/dexamethasone (D-KRd) demonstrated promising efficacy in transplant-eligible newly diagnosed multiple myeloma (NDMM). In GRIFFIN (NCT02874742), daratumumab+lenalidomide/bortezomib/dexamethasone (D-RVd) improved outcomes for transplant-eligible NDMM. Here, we present a post hoc analysis of patients with high-risk cytogenetic abnormalities (HRCAs; del[17p], t[4;14], t[14;16], t[14;20], or gain/amp[1q21]). Among 123 D-KRd patients, 43.1%, 37.4%, and 19.5% had 0, 1, or ≥2 HRCAs. Among 120 D-RVd patients, 55.8%, 28.3%, and 10.8% had 0, 1, or ≥2 HRCAs. Rates of complete response or better (best on study) for 0, 1, or ≥2 HRCAs were 90.6%, 89.1%, and 70.8% for D-KRd, and 90.9%, 78.8%, and 61.5% for D-RVd. At median follow-up (MASTER, 31.1 months; GRIFFIN, 49.6 months for randomized patients/59.5 months for safety run-in patients), MRD-negativity rates as assessed by next-generation sequencing (10-5) were 80.0%, 86.4%, and 83.3% for 0, 1, or ≥2 HRCAs for D-KRd, and 76.1%, 55.9%, and 61.5% for D-RVd. PFS was similar between studies and superior for 0 or 1 versus ≥2 HRCAs: 36-month PFS rates for D-KRd were 89.9%, 86.2%, and 52.4%, and 96.7%, 90.5%, and 53.5% for D-RVd. These data support the use of daratumumab-containing regimens for transplant-eligible NDMM with HCRAs; however, additional strategies are needed for ultra-high-risk disease (≥2 HRCAs). Video Abstract.

SOHO State of the Art Updates and Next Questions: Diagnosis and Management of Monoclonal Gammopathy of Undetermined Significance and Smoldering Multiple Myeloma.

Monoclonal proteins are common, with a prevalence in the United States around 5% and the incidence increases with age. Although most patients are asymptomatic, the vast majority of cases are caused by a clonal plasma cell disorder. Monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) are asymptomatic precursor conditions with variable risk of progression to multiple myeloma (MM). In recent years, significant progress has been made to better understand the factors that lead to the development of symptoms and progression to myeloma. In this review, we summarize the current diagnosis treatment guidelines for MGUS and SMM and highlight recent advances that underscore a shifting paradigm in the evaluation and management of plasma cell precursor conditions.

Safety and efficacy of belantamab mafodotin with pembrolizumab in patients with relapsed or refractory multiple myeloma.

BACKGROUND: Belantamab mafodotin (belamaf) has shown promising antimyeloma activity in relapsed or refractory multiple myeloma (RRMM) as a single agent. It was hypothesized that its multimodal activity may be enhanced by programmed cell death protein 1 pathway inhibition and activation of T cell-mediated antitumor responses. This study investigated the efficacy and safety of belamaf with pembrolizumab in patients with RRMM. METHODS: DREAMM-4 (NCT03848845) was an open-label, single-arm, phase 1/2 study divided into dose-escalation (part 1) and dose-expansion (part 2) phases. Patients were ≥18 years old with ≥3 prior lines of therapy including a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38 agent. Patients received belamaf (2.5 or 3.4 mg/kg, part 1; 2.5 mg/kg, part 2) and 200 mg pembrolizumab for ≤35 cycles. RESULTS: Of 41 enrolled patients, 34 (n = 6 part 1, n = 28 part 2) who received 2.5 mg/kg belamaf plus pembrolizumab were included in this final analysis. Sixteen patients (47%) achieved an overall response. Minimal residual disease negativity was achieved in three of 10 patients who had very good partial response or better. Five of eight patients who had prior anti-B-cell maturation antigen therapy achieved partial response or better, including two who had B-cell maturation antigen-refractory disease. Common grade ≥3 adverse events were keratopathy (38%) and thrombocytopenia (29%). Despite belamaf-related ocular events, quality-of-life measures remained stable over time. No new safety signals were observed. CONCLUSIONS: The results of DREAMM-4 demonstrated clinical activity and a favorable safety profile of belamaf plus pembrolizumab in patients with RRMM. This trial is registered at www. CLINICALTRIALS: gov as NCT03848845.

Waldenström Macroglobulinemia/Lymphoplasmacytic Lymphoma, Version 2.2024, NCCN Clinical Practice Guidelines in Oncology.

The treatment of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL) has evolved to include several new options. The NCCN Guidelines for WM/LPL provide a framework on which to base decisions regarding diagnosis, treatment, assessment of response to treatment, and follow-up of both newly diagnosed and previously treated WM/LPL.

Impact of Visceral Obesity on Clinical Outcome and Quality of Life for Patients with Multiple Myeloma: A Secondary Data Analysis of STaMINA (BMT CTN 0702) Trial.

Obesity is a common health problem in patients with multiple myeloma (MM) that has been linked to poor clinical outcomes and quality of life (QoL). We conducted a secondary analysis of the BMT CTN 0702, a randomized, controlled trial comparing outcomes of 3 treatment interventions after a single hematopoietic cell transplantation (HCT) (n = 758), to investigate the impact of visceral obesity, as measured by waist-to-hip ratio (WHR), on clinical outcomes and QoL in MM patients. A total of 549 MM patients, median age 55.5 years, were enrolled in the study. The majority of patients received triple-drug antimyeloma initial therapy before enrollment, and 29% had high-risk disease according to cytogenetic assessment. The median duration of follow-up was 6 years. There was no significant association between WHR and progression-free survival (PFS) or overall survival (OS) in MM patients undergoing HCT. Similarly, body mass index (BMI) did not significantly predict PFS or OS. Furthermore, there was no significant correlation between WHR and QoL measures. This study suggests that visceral obesity, as measured by WHR, might not have a significant impact on clinical outcomes in MM patients undergoing HCT. These findings add to the existing literature on the topic and provide valuable information for healthcare professionals and MM patients. Further studies are needed to confirm these results and to investigate other potential factors that may affect clinical outcomes and QoL in this patient population using modern imaging technologies to assess visceral obesity.

PD1+TIGIT+2B4+KLRG1+ Cells Might Underlie T Cell Dysfunction in Patients Treated with BCMA-Directed Chimeric Antigen Receptor T Cell Therapy.

Chimeric antigen receptor T cell (CAR-T) therapy has shown rapid, frequent, and deep responses in patients with relapsed/refractory multiple myeloma (RRMM). However, relapse frequently occurs following CAR-T therapy, and the cause of this resistance is not well defined. Among the potential mechanisms of resistance, T cell intrinsic factors may be an important source of failure. Here we used spectral flow cytometry to identify the changes in T cell phenotypes in bone marrow aspirates at different stages of multiple myeloma progression, including cases that relapsed after anti-BCMA CAR-T therapy. We identified completely different T cell phenotypes in RRMM and post CAR-T relapse cases compared to healthy donors and earlier stages of multiple myeloma, novel double-negative CD3+ T cells in RRMM and CAR-T relapsed cases, and differences in CD8 T cell phenotype at the baseline between peripheral blood and bone marrow from healthy donors. We found that the majority of T cells in RRMM patients and significant T cell subsets in post-CAR-T relapsed patients expressed multiple coinhibitory markers, including PD1, TIGIT, 2B4, and KLRG1.

Update on the current and future use of CAR-T to treat multiple myeloma.

Chimeric antigen receptor T-cell (CAR-T) therapy has become an important intervention in the management of relapsed and relapsed/refractory multiple myeloma (MM). Currently, B-cell maturation antigen (BCMA) is the most targeted surface protein due to its ubiquitous expression on plasma cells, with increasing expression of this essential transmembrane protein on malignant plasma cells as patients develop more advanced disease. This review will explore the earliest CAR-T trials in myeloma, discuss important issues involved in CAR-T manufacturing and processing, as well as review current clinical trials that led to the approval of the two commercially available CAR-T products, Idecabtagene vicleucel and ciltacabtagene autoleucel. The most recent data from trials investigating the use of CAR-T as an earlier line of therapy will be presented. Finally, the problem of relapses after CAR-T will be presented, including several theories as to why CAR-T therapies fail and possible clinical caveats. The next generation of MM-specific CAR-T will likely include new targets such as G-protein-coupled receptor class C, Group 5, member D (GPRC5D) and signaling lymphocyte activation molecular Family 7 (SLAMF7). The role of CAR-T in the treatment of MM will undoubtedly increase exponentially in the next decade.

Multiple Myeloma, Version 2.2024, NCCN Clinical Practice Guidelines in Oncology.

The treatment of relapsed/refractory multiple myeloma (MM) has evolved to include several new options. These include new combinations with second generation proteasome inhibitors (PI); second generation immunomodulators, monoclonal antibodies, CAR T cells, bispecific antibodies, selinexor, venetoclax, and many others. Most patients with MM undergo several cycles of remissions and relapse, and therefore need multiple lines of combination therapies. Selecting treatment options for relapsed/refractory MM requires consideration of resistance status to specific classes, and patient-specific factors such as age and other comorbidities should be considered. The NCCN Guidelines for MM provide a framework on which to base decisions regarding workup, treatment, and follow-up of newly diagnosed and previously treated MM. This manuscript outlines the recommendations from NCCN Guidelines for MM specific to relapsed/refractory disease.

Minimal residual disease response-adapted therapy in newly diagnosed multiple myeloma (MASTER): final report of the multicentre, single-arm, phase 2 trial.

BACKGROUND: For patients with newly diagnosed multiple myeloma, reaching minimal residual disease (MRD) negativity after treatment is associated with improved outcomes; however, the use of MRD to modulate therapy remains elusive. We present the final analysis of the MASTER trial of daratumumab, carfilzomib, lenalidomide, and dexamethasone (Dara-KRd) therapy in patients with newly diagnosed multiple myeloma, in which MRD status is used to modulate treatment duration and cessation. METHODS: MASTER was a multicentre, single-arm, phase 2 trial conducted in five academic medical centres in the USA. Eligible participants were 18 years or older with newly diagnosed multiple myeloma (measurable by serum or urine protein electrophoresis or serum free light chains), a life expectancy of at least 12 months, and an Eastern Cooperative Oncology Group performance status of 0-2, and had received no previous treatment for multiple myeloma except up to one cycle of therapy containing bortezomib, cyclophosphamide, and dexamethasone. The study was enriched for participants with high-risk chromosome abnormalities (HRCAs). During the induction phase, participants received four 28-day cycles of Dara-KRd, each comprising daratumumab (16 mg/kg intravenously on days 1, 8, 15, and 22), carfilzomib (56 mg/m2 intravenously on days 1, 8, and 15), lenalidomide (25 mg orally on days 1-21), and dexamethasone (40 mg orally or intravenously on days 1, 8, 15, and 22); induction was followed by autologous haematopoietic stem-cell transplantation and up to two phases of consolidation with Dara-KRd. We assessed MRD by next-generation sequencing after or during each phase. The primary endpoint was reaching MRD negativity (<10-5). Participants who reached MRD negativity after or during two consecutive phases stopped treatment and began observation with MRD surveillance (MRD-SURE); participants who did not reach two consecutive MRD-negative results received maintenance lenalidomide. Secondary endpoints included progression-free survival and cumulative incidence of progression. All analyses were conducted in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, NCT03224507, and is complete. FINDINGS: Between Mar 21, 2018, and Oct 23, 2020, 123 participants were recruited to the study, of whom 70 (57%) were men, 53 (43%) were women, 94 (76%) were non-Hispanic White, 25 (20%) were non-Hispanic Black, and four (3%) were of another race or ethnicity. The median age of participants was 61 years (IQR 55-68), and 24 (20%) were aged 70 years or older. The median duration of follow up was 42·2 months (IQR 34·5-46·0). Of the 123 participants, 53 (43%) had no HRCAs, 46 (37%) had one HRCA, and 24 (20%) had two or more HRCAs. For 118 (96%) of 123 participants, MRD was evaluable by next-generation sequencing; the remaining five had an absence of sufficiently unique clonogenic sequences to enable tracking by the assay. Of these 118 participants, 96 (81%, 95% CI 73-88) reached MRD of less than 10-5 (comprising 39 [78%, 64-88] of 50 participants with no HRCAs, 38 [86%, 73-95] of 44 participants with one HRCA, and 19 [79%, 58-93] of 24 participants with two or more HRCAs) and 84 (71%, 62-79) reached MRD-SURE and treatment cessation. 36-month progression-free survival among all 123 participants was 88% (95% CI 78-95) for participants with no HRCAs, 79% (67-88) for those with one HRCA, and 50% (30-70) for those with two or more HRCAs. For the 84 participants reaching MRD-SURE, the 24-month cumulative incidence of progression from cessation of therapy was 9% (95% CI 1-19) for participants with no HRCAs, 9% (1-18) for those with one HRCA, and 47% (23-72) for those with two or more HRCAs. 61 participants (comprising 52% of 118 MRD-evaluable participants and 73% of 84 participants who reached MRD-SURE) remain free of therapy and MRD-negative as of Feb 7, 2023. The most common grade 3-4 adverse events were neutropenia (43 patients, 35%), lymphopenia (28 patients, 23%), and hypertension (13 patients, 11%). Three treatment-emergent deaths were recorded: two sudden deaths and one due to viral infection, none of which were judged to be treatment-related. INTERPRETATION: This approach provided positive outcomes and a pathway for treatment cessation in most patients with newly diagnosed multiple myeloma. Outcomes for patients with ultra-high-risk multiple myeloma, defined as those with two or more HRCAs, remain unsatisfactory, and these patients should be prioritised for trials with early introduction of therapies with novel mechanisms of action. FUNDING: Amgen and Janssen Pharmaceuticals.

Humoral immune reconstitution following therapy with daratumumab, carfilzomib, lenalidomide, and dexamethasone (Dara-KRd), autologous hematopoietic cell transplantation, and measurable residual disease-response-adapted treatment cessation.

Quadruplet induction, autologous hematopoietic cell transplant (AHCT), and measurable residual disease (MRD) response-adapted consolidation yield an unprecedented depth of response in newly diagnosed multiple myeloma. Patients treated on MASTER (NCT03224507) ceased therapy and entered active surveillance (MRD-SURE) after achieving MRD negativity. This study characterizes quantitative changes in the immunoglobulin (Ig) gene repertoire by next-generation sequencing and serum gamma globulin levels. Quadruplet therapy leads to profound hypogammaglobulinemia and reduction in the Ig gene repertoire. Immune reconstitution (IR) is delayed in patients who received post-AHCT consolidation compared to those who do not. Eighteen months after treatment cessation, there was no statistically significant difference between the groups.

HAPLN1 matrikine: a bone marrow homing factor linked to poor outcomes in patients with MM.

The bone marrow (BM) microenvironment is critical for dissemination, growth, and survival of multiple myeloma (MM) cells. Homing of myeloma cells to the BM niche is a crucial step in MM dissemination, but the mechanisms involved are incompletely understood. In particular, any role of matrikines, neofunctional peptides derived from extracellular matrix proteins, remains unknown. Here, we report that a matrikine derived from hyaluronan and proteoglycan link protein 1 (HAPLN1) induces MM cell adhesion to the BM stromal components, such as fibronectin, endothelial cells, and stromal cells and, furthermore, induces their chemotactic and chemokinetic migration. In a mouse xenograft model, we show that MM cells preferentially home to HAPLN1 matrikine-conditioned BM. The transcription factor STAT1 is activated by HAPLN1 matrikine and is necessary to induce MM cell adhesion, migration, migration-related genes, and BM homing. STAT1 activation is mediated by interferon beta (IFN-ß), which is induced by NF-κB after stimulation by HAPLN1 matrikine. Finally, we also provide evidence that higher levels of HAPLN1 in BM samples correlate with poorer progression-free survival of patients with newly diagnosed MM. These data reveal that a matrikine present in the BM microenvironment acts as a chemoattractant, plays an important role in BM homing of MM cells via NF-κB-IFN-ß-STAT1 signaling, and may help identify patients with poor outcomes. This study also provides a mechanistic rationale for targeting HAPLN1 matrikine in MM therapy.

Molecular characterization stratifies VQ myeloma cells into two clusters with distinct risk signatures and drug responses.

Multiple myeloma (MM) is a cancer of malignant plasma cells in the bone marrow and extramedullary sites. We previously characterized a VQ model for human high-risk MM. The various VQ lines display different disease phenotypes and survival rates, suggesting significant intra-model variation. Here, we use whole-exome sequencing and copy number variation (CNV) analysis coupled with RNA-Seq to stratify the VQ lines into corresponding clusters: Group A cells had monosomy chromosome (chr) 5 and overexpressed genes and pathways associated with sensitivity to bortezomib (Btz) treatment in human MM patients. By contrast, Group B VQ cells carried recurrent amplification (Amp) of chr3 and displayed high-risk MM features, including downregulation of Fam46c, upregulation of cancer growth pathways associated with functional high-risk MM, and expression of Amp1q and high-risk UAMS-70 and EMC-92 gene signatures. Consistently, in sharp contrast to Group A VQ cells that showed short-term response to Btz, Group B VQ cells were de novo resistant to Btz in vivo. Our study highlights Group B VQ lines as highly representative of the human MM subset with ultrahigh risk.

The Management of Relapsed and Refractory Multiple Myeloma.

The treatment of patients with relapsed and refractory multiple myeloma has become increasingly complex due to the rising number of available therapies. Patients are also increasingly exposed to, and refractory to, multiple classes of therapy at the time of progression. Patients who are at an early point in their myeloma disease course are likely to have several effective options, but choices and prognosis are limited for relapsing patients who are more heavily pretreated, particularly if they are at least triple-class refractory. When selecting the next line of therapy, it remains essential to consider patient comorbidities and frailty as well as treatment history and disease risk. Fortunately, the myeloma treatment landscape continues to evolve with the development of therapies directed toward new biologic targets, such as B-cell maturation antigen. These new agents, including bispecific T-cell engagers and chimeric antigen receptor T-cell therapy, have shown unprecedented efficacy in late-line myeloma and will be increasingly used at earlier time points. Novel combinations of currently approved treatments, including quadruplets and salvage transplantation, also remain important options for consideration.

Inflammatory CD4/CD8 double-positive human T cells arise from reactive CD8 T cells and are sufficient to mediate GVHD pathology.

An important paradigm in allogeneic hematopoietic cell transplantations (allo-HCTs) is the prevention of graft-versus-host disease (GVHD) while preserving the graft-versus-leukemia (GVL) activity of donor T cells. From an observational clinical study of adult allo-HCT recipients, we identified a CD4+/CD8+ double-positive T cell (DPT) population, not present in starting grafts, whose presence was predictive of ≥ grade 2 GVHD. Using an established xenogeneic transplant model, we reveal that the DPT population develops from antigen-stimulated CD8 T cells, which become transcriptionally, metabolically, and phenotypically distinct from single-positive CD4 and CD8 T cells. Isolated DPTs were sufficient to mediate xeno-GVHD pathology when retransplanted into naïve mice but provided no survival benefit when mice were challenged with a human B-ALL cell line. Overall, this study reveals human DPTs as a T cell population directly involved with GVHD pathology.

Systemic Light Chain Amyloidosis, Version 2.2023, NCCN Clinical Practice Guidelines in Oncology.

Primary systemic light chain amyloidosis (SLCA) is characterized by production of light chains that get converted to amyloid fibrils with an affinity for visceral organs and causing organ dysfunction. The therapy for SLCA is directed to recovering the function of the affected organs by targeting the abnormal plasma cell clone and slowing deposition of amyloid fibrils. The NCCN Guidelines for SLCA provide recommendations for workup, diagnosis, and treatment of primary as well as previously treated SLCA.

HAPLN1 confers multiple myeloma cell resistance to several classes of therapeutic drugs.

Multiple myeloma (MM), a malignant plasma cell infiltration of the bone marrow, is generally considered incurable: resistance to multiple therapeutic drugs inevitably arises from tumor cell-intrinsic and tumor microenvironment (TME)-mediated mechanisms. Here we report that the proteoglycan tandem repeat 1 (PTR1) domain of the TME matrix protein, hyaluronan and proteoglycan link protein 1 (HAPLN1), induces a host of cell survival genes in MM cells and variable resistance to different classes of clinical drugs, including certain proteasome inhibitors, steroids, immunomodulatory drugs, and DNA damaging agents, in several MM cell lines tested. Collectively, our study identifies HAPLN1 as an extracellular matrix factor that can simultaneously confer MM cell resistance to multiple therapeutic drugs.

Selinexor-based regimens in patients with multiple myeloma after prior anti-B-cell maturation antigen treatment.

There is a lack of consensus on therapy sequencing in previously treated multiple myeloma, particularly after anti-B-cell maturation antigen (BCMA) therapy. Earlier reports on selinexor (X) regimens demonstrated considerable efficacy in early treatment, and after anti-BCMA-targeted chimeric antigen receptor-T cell therapy. Here, we present data from 11 heavily pretreated patients who predominantly received BCMA-antibody-drug conjugate therapy. We observe that X-containing regimens are potent and achieve durable responses with numerically higher overall response and clinical benefit rates, as well as median progression free survival compared to patients' prior anti-BCMA therapies, despite being used later in the treatment course. In an area of evolving unmet need, these data reaffirm the efficacy of X-based regimens following broader anti-BCMA therapy.

Outcomes with mismatched unrelated donor allogeneic hematopoietic stem cell transplantation in adults: A systematic review and meta-analysis.

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for various hematologic disorders. Alternative donor strategies such as mismatched unrelated donors (MMUD) offer the option of HSCT to patients lacking a human leukocyte antigen (HLA)-matched donor. We conducted a systematic review and meta-analysis to evaluate outcomes after MMUD-HSCT. Methods: A literature search was performed on PubMed, Cochrane Library, and ClinicalTrials.gov from the inception date through April 6, 2022. After screening 2477 manuscripts, 19 studies were included. Data was extracted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Pooled analysis was done using the meta-package by Schwarzer et al. Proportions with 95% confidence intervals (CI) were computed. Results: A total of 3336 patients from 19 studies were included. The median age was 52.1 years, and 53% of recipients were males. The graft source was bone marrow in 19% and peripheral blood stem cells in 81% of recipients. The median time to transplant from hematologic diagnosis was 10 (1-247) months. Hematologic diagnoses included myeloid (82.9%), lymphoid (41.1%), and other disorders (3%). The reduced intensity and myeloablative conditioning were used in 65.6% and 32% of recipients, respectively. In-vivo T-cell depletion was performed in 56.7% of the patients. Most patients had one (87.9%) or two (11.4%) antigen HLA-mismatch. The pooled 1-year overall survival (OS) was 63.9% (95% CI 0.57-0.71, n=1426/2706), and the pooled 3-year OS was 42.1% (95% CI 0.34.2-0.50, n=907/2355). The pooled progression-free survival was 46.6% (95% CI 0.39-0.55, n=1295/3253) after a median follow-up of 1.8 (range 1-6) years. The pooled relapse rate was 26.8% (95% CI 0.22-0.32, n=972/3253) after a median follow-up of 2.25 (1-3) years. The pooled incidence of acute (grade II-IV) graft-versus-host disease (GVHD) and chronic GVHD was 36.4% (95% CI 0.31-0.42, n=1131/3030) and 41.2% (95% CI 0.35-0.48, n=1337/3228), respectively. The pooled non-relapse mortality was 22.6% (95% CI 0.17-0.29, n=888/3196) after a median follow-up of 2.6 (1-5) years. Conclusion: MMUD-HSCT has demonstrated favorable outcomes with an acceptable toxicity profile. It represents a promising option in patients lacking an HLA-matched or haploidentical donor and may expand HSCT access to underrepresented racial and ethnic populations.

Impact of natural killer cells on outcomes after allogeneic hematopoietic stem cell transplantation: A systematic review and meta-analysis.

Background: Natural killer (NK) cells play a vital role in early immune reconstitution following allogeneic hematopoietic stem cell transplantation (HSCT). Methods: A literature search was performed on PubMed, Cochrane, and Clinical trials.gov through April 20, 2022. We included 21 studies reporting data on the impact of NK cells on outcomes after HSCT. Data was extracted following the PRISMA guidelines. Pooled analysis was done using the meta-package (Schwarzer et al.). Proportions with 95% confidence intervals (CI) were computed. Results: We included 1785 patients from 21 studies investigating the impact of NK cell reconstitution post-HSCT (8 studies/1455 patients), stem cell graft NK cell content (4 studies/185 patients), therapeutic NK cell infusions post-HSCT (5 studies/74 patients), and pre-emptive/prophylactic NK cell infusions post-HSCT (4 studies/77 patients). Higher NK cell reconstitution was associated with a better 2-year overall survival (OS) (high: 77%, 95%CI 0.73-0.82 vs low: 55%, 95%CI 0.37-0.72; n=899), however, pooled analysis for relapse rate (RR) or graft versus host disease (GVHD) could not be performed due to insufficient data. Higher graft NK cell content demonstrated a trend towards a better pooled OS (high: 65.2%, 95%CI 0.47-0.81 vs low: 46.5%, 95%CI 0.24-0.70; n=157), lower RR (high: 16.9%, 95%CI 0.10-0.25 vs low: 33%, 95%CI 0.04-0.72; n=157), and lower acute GVHD incidence (high: 27.6%, 95%CI 0.20-0.36 vs low: 49.7%, 95%CI 0.26-0.74; n=157). Therapeutic NK or cytokine-induced killer (CIK) cell infusions for hematologic relapse post-HSCT reported an overall response rate (ORR) and complete response (CR) of 48.9% and 11% with CIK cell infusions and 82.8% and 44.8% with NK cell infusions, respectively. RR, acute GVHD, and chronic GVHD were observed in 55.6% and 51.7%, 34.5% and 20%, and 20.7% and 11.1% of patients with CIK and NK cell infusions, respectively. Pre-emptive donor-derived NK cell infusions to prevent relapse post-HSCT had promising outcomes with 1-year OS of 69%, CR rate of 42%, ORR of 77%, RR of 28%, and acute and chronic GVHD rates of 24.9% and 3.7%, respectively. Conclusion: NK cells have a favorable impact on outcomes after HSCT. The optimal use of NK cell infusions post-HSCT may be in a pre-emptive fashion to prevent disease relapse.