Landau, Heather

Background: Plasma cell dyscrasia (PCD) is a rare but important cause of end stage kidney disease (ESKD). Kidney transplant is the treatment of choice in patients with ESKD. However, the complexity of PCD care and risk of disease recurrence poses challenges to kidney transplant candidacy and outcomes. We examined the current clinical practice patterns of clinicians who care for patients with PCD and identified barriers to kidney transplantation for patients with PCD. Methods: A web-based survey was developed and distributed from January to July 2024 to kidney transplant clinicians (American Society of Transplant (AST) members), hematologists (PCD experts), and onco-nephrologists. Results: Seventy clinicians (50 transplant nephrologists, 18 hematologists, and two surgeons) from 42 transplant centers in the US participated in the survey. Clinical practice patterns pre and post kidney transplant for patients with PCD are highly variable among institutions, and only 36% reported having a protocol for pre- and post-transplant management for patients with PCD. Particularly, the requirement for pre-transplant hematologic remission criteria, induction and maintenance immunosuppression regimens and protocols for prophylaxis and screening for opportunistic infection are areas of future study. Clinicians listed lack of data and practice guidance as well as communication challenges among multiple specialties especially hematology and kidney transplant clinicians as notable barriers. Conclusions: Our study identified the highly variable current practice patterns when evaluating and managing patients with PCD for kidney transplant. Our findings emphasize the need for collecting and sharing clinical data to support standardized practices and serve as a basis for the upcoming multi-societal management recommendation for kidney transplant for patients with PCD.

Abstract Background B-cell maturation antigen (BCMA)-targeting immunotherapies represent a promising class of treatment for the management of immunoglobulin light chain (AL) amyloidosis, a disease that is related to clonal plasma cells. Etentamig is a 2nd generation, off-the-shelf, fully human BMCA X CD3 bispecific antibody with bivalent BCMA domain and low CD3 affinity that targets both BCMA-expressing plasma cells and CD3-expressing T cells. Etentamig monotherapy is being studied in multiple myeloma (MM) in an ongoing phase 3 study (NCT06158841). Here, we report the first safety and efficacy results from M24-209, an open-label phase 1/2 study evaluating etentamig monotherapy in patients (pts) with relapsed/refractory (RR) AL amyloidosis from dose level 1 (DL1). Methods The phase 1 dose escalation (ESC) portion of the study (NCT06158854) with etentamig enrolled pts with RR AL amyloidosis with ≥1 prior lines of therapy (LOT), including a proteasome inhibitor and an anti-CD38 monoclonal antibody with no prior BCMA exposure. Eligible pts were required to have a difference in involved and uninvolved serum free light chain (dFLC) of ≥50 mg/L, and pts with Mayo Clinic 2004 cardiac risk stage IIIb with NT-proBNP ≥8500 pg/ml were excluded. Three dose groups were explored in dose ESC (etentamig dose levels [DL] 1, 2, and 3). In all cohorts, pts will receive up to 24 cycles of treatment and will be followed until disease progression. In dose ESC, the primary objectives are to determine safety/tolerability, pharmacokinetic/pharmacodynamic, and recommended phase 2 dose. The secondary objectives include evaluation of efficacy as measured by hematologic response and organ response. Responses are investigator assessed per consensus guidelines (Comenzo, et al. Leukemia. 2012. 26[11]:2317-25; Palladini G, et al. Amyloid. 2021 [Epub];28[1]:1-2). Results As of 17 July 2025, all DLs in dose ESC have been fully enrolled, and 12 pts have been treated with etentamig at DL1. Due to short follow-up, this initial report only includes data from DL1, with further follow-up data from ESC to be included at the time of presentation. Median duration of follow up in DL1 was 9.4 months (8.3–13.8) with 83% of pts continuing treatment. Median age for pts was 72 years (range, 56–85 years). Median number of prior LOT was 2 (range, 1–6), and median time from initial diagnosis was 3.6 years. Thirty-three percent have received a prior stem cell transplant and 50% previously received the regimen of daratumumab with cyclophosphamide, bortezomib, and dexamethasone in combination. Median dFLC at study baseline was 110. 5 mg/L (range, 56.6–617.5). At baseline, 83% of pts had cardiac involvement, 25% had renal involvement, and 8% had hepatic involvement. Eighty-three percent of pts had lambda AL amyloidosis. Treatment-emergent adverse events were reported in 100% (42% Grade ≥3) of pts at DL1. Cytokine release syndrome (CRS) occurred in 2 pts (17%, all Grade 1), with no instances of any grade immune effector cell-associated neurotoxicity syndrome (ICANS). CRS occurring after the first dose had median time to onset of 6.8 hours (range, 6.7–6.9). Grade ≥3 infections occurred in 1 pt (8%, all Grade 3). Grade ≥3 neutropenia also occurred in 1 pt (8%, all Grade 3), and no Grade ≥3 events of thrombocytopenia or anemia occurred. No Grade 5 events have occurred. Within the dose ESC DL1 cohort, the overall hematologic response rate was 100%, with all pts achieving ≥VGPR and 83% of pts achieving complete response (CR). The median time to CR was 0.9 months (0.3–9.3). The median duration of response has not yet been reached and 100% of pts remain in their best overall response by investigator assessment. To date, no pts have experienced hematologic progression on study. Cardiac response was observed in 30% of evaluable pts. Renal response was seen in 67% of evaluable pts. Conclusions In the DL1 cohort, etentamig showed a manageable safety profile in AL amyloidosis with low incidence and severity of CRS, no ICANS, and limited Grade ≥3 cytopenia events. Deep and rapid hematologic responses were observed with 100% ≥VGPR rate and 83% hematologic CR rate. Additional dose-level data will be presented at the time of the meeting. All pts remain in ongoing follow-up and evaluation, and the study will begin the dose expansion (EXP) portion after dose selection.

Abstract Consumption of a Western diet and high body mass index (BMI) are risk factors for progression from premalignant phenotypes to multiple myeloma, a hematologic cancer. In the NUTRIVENTION trial (NCT04920084), we administered a high-fiber, plant-based diet (HFPBD; meals for 12 weeks, coaching for 24 weeks) to 23 participants with myeloma precursor states and elevated BMI. The intervention was feasible and improved quality of life and modifiable risk factors: metabolic (BMI, insulin resistance), microbiome (diversity, composition), and immune (inflammation, monocyte subsets). Disease progression trajectory improved (n = 2) or was stable. Findings were translated to Vk*MYC mice modeling the myeloma precursor state, in which a high-fiber diet (HFD) delayed disease progression through improved metabolism and microbiome composition, leading to increased short-chain fatty acid production that reinvigorated antitumor immunity and inhibited tumor growth. These effects from fiber consumption were independent of calorie restriction and weight loss. A HFD is a low-risk intervention that may delay progression to myeloma. Significance: A HFPBD in participants with precursor plasma cell disorders and an elevated BMI improved metabolic, microbiome, and immune biomarkers of disease. In a subset, it may delay progression to myeloma. In mouse models, a HFD delayed progression to myeloma independent of calorie restriction. See related commentary by Fairfield and Reagan, p. 623

Abstract Isatuximab is an immunoglobulin G1κ monoclonal antibody that binds with high affinity to CD38 expressed on plasma cells. Anti-CD38 antibodies have shown efficacy as monotherapy and in combination in a variety of settings for patients with multiple myeloma and light chain (AL) amyloidosis. This multicenter, cooperative group phase 2 trial was designed to evaluate hematologic response, organ response, and safety of isatuximab monotherapy for the treatment of relapsed AL amyloidosis. Isatuximab at 20 mg/kg was administered IV weekly during the first 28-day cycle, and then every other week during cycles 2 to 24. Forty-three patients were registered, with 35 patients being evaluable for response. The overall hematologic response rate was 77.1%, with 57% of patients achieving a very good partial response (VGPR) or better. The median time to partial response (PR) or better was 1.1 months. Renal response occurred in 50% (7/14) of patients with renal involvement, and cardiac response occurred in 57% (8/14) of patients who were evaluable utilizing N-terminal pro b-type natriuretic peptide (NT-proBNP) with cardiac involvement. The most common treatment-related grade ≥3 adverse events included lymphopenia (n = 3, 8.5%) and infection (n = 2, 6%). Isatuximab demonstrated substantial efficacy in previously treated patients with AL amyloidosis, and was associated with a good safety profile. This trial was registered at www.clinicaltrials.gov as #NCT03499808.

ABSTRACTThe optimal conditioning schedule and CD34+ cell dose for autologous stem cell transplantation (ASCT) for AL amyloidosis is unknown. Patients (n = 1704) who underwent ASCT for AL amyloidosis between 2003 and 2020 in 9 centers were included. Data on melphalan conditioning dose, number of conditioning days, whether a rest day between conditioning and stem cell infusion was given or not, and infused CD34+ cell dose were collected. Full‐dose melphalan (≥ 180 mg/m2) was administered in 63.7% of the patients, and 80.4% had melphalan split into 2‐day conditioning. A rest day (day −1) between the conditioning regimen and stem cell infusion was provided in 52.5% of patients. The median infused CD34+ cell count was 4.7 × 106/kg. An infused CD34+ cell count ≥ 4.5 × 106/kg was associated with a shorter time to neutrophil and platelet engraftment. In a nominal regression analysis, full‐dose melphalan, 1‐day melphalan conditioning, and omitting a rest day between conditioning and stem cell infusion were independent predictors of post‐ASCT higher deep hematological response. The median follow‐up was 8.6 years, and 38% of patients died. Independent predictors of superior overall survival in multivariate Cox regression analysis included full‐dose melphalan, having no rest day, and infused CD34+ cells ≥ 4.5 × 106/kg. Independent predictors of higher day‐100 transplant‐related mortality (TRM) in nominal logistic regression analysis included poorer performance status, NT‐proBNP/BNP ≥ 1800/400 pg/mL, serum albumin < 2.5 g/dL, CD34+ cells < 4.5 × 106/kg, and not having a rest day. In conclusion, 1 day of melphalan conditioning and administration of CD34+ cells ≥ 4.5 × 106/kg are recommended for ASCT in AL amyloidosis.

Autologous stem cell transplantation (ASCT) in AL amyloidosis effectively produces a high overall hematological response rate, complete response rate, and durable remissions. However, it is a high-dose chemotherapy-based therapy with high morbidity which can be offered only to a subset of AL amyloidosis patients who are considered fit for this therapy. Transplant-related mortality (TRM) in AL amyloidosis has decreased over the past three decades due to improvement in patient selection. New therapeutic options question the utilization of ASCT. A model to predict TRM can improve the decision-making process, patient selection and further reduce TRM. AL amyloidosis patients (n=1718) from 9 centers globally, transplanted in the years 2003-2020 were included. Pre-ASCT variables of interest were assessed for association with Day-100 all-cause mortality, including age at ASCT (≥ 60 years), sex, light chain isotype, ECOG performance status (ECOG PS; 0, 1 and 2/3), the difference between involved and uninvolved light chains (dFLC; ≥180 mg/L), N-terminal prohormone of B natriuretic peptide (NT-proBNP; ≥1800 pg/mL) or B-type natriuretic peptide (BNP; ≥400 pg/mL), left ventricle ejection fraction (LVEF, &lt;50%), interventricular septum (&gt;16 mm), corrected diffusing capacity for carbon monoxide (cDLCO; ≤65% of predicted), forced expiratory volume in one second (FEV1; ≤65% of predicted), serum albumin (&lt;2.5 g/dL), estimated glomerular filtration rate (eGFR; &lt;30 mL/min/m2), alkaline phosphatase (&gt;X2 upper limit of normal), and systolic blood pressure (&lt;100 mmHg). Troponins could not be included in our modeling given the multitude of assays used across institutions and periods that could not be reconciled. A random forest (RF) classifier with 10-fold cross-validation was used to assist in variable selection. The final model variables were selected based on statistical performance and clinical relevance. The model was fitted using logistic regression. The median age at ASCT was 58, and 40% of patients were women. The most frequently involved organs were the kidneys (69%) and the heart (52%). Mayo 2004 stages I and II were collectively present in 83% of patients. Day-100 TRM occurred in 75 patients (4.4%) with the 3 main causes being shock (n=27), cardiac arrhythmia (n=26), and organ failure (n=22). Age at ASCT, sex, and light chain isotype were not predictors of Day-100 TRM. Across the other pre-ASCT variables, adverse features were present from 6.9% (LVEF &lt;50%) to 25.8% (dFLC ≥180 mg/L) of patients. Ten factors were associated with Day-100 TRM on univariate analysis. The odds ratio of these variables ranged from 1.6 to 10.2. RF classifier using all these variables identified a model with an area under the curve (AUC) of 0.72±0.12. Using the importance hierarchy function to refine the model selection, a 4-variable model [NT-proBNP/BNP ≥1800/400 pg/mL, serum albumin &lt;2.5 g/dL, ECOG PS 1 or 2/3, and systolic blood pressure &lt;100 mmHg] was built with an AUC of 0.70±0.12. Based on logistic regression coefficients, ECOG PS 2/3 was assigned two points, while other adverse predictors were assigned 1-point each (model score range 0-5). We then applied the model scoring to our study population. Score distribution was as follows: 0 (n=431, 25.1% of patients), 1 (n=688,40.1%), 2 (n=413, 24.0%), and 3 and above (n=186, 10.8%). Day-100 TRM rates were 0.46%, 3.2%, 5.8%, and 14.5% for 0, 1, 2, and ≥3 points, respectively. The respective rates for the years 2003-2011 were 1.1%, 3.3%, 6.4%, and 19.2%, while for the years 2012-2020 0%, 3.1%, 5.2%, and 8.4%. We developed a simple clinical tool to predict the Day-100 TRM risk in AL patients undergoing ASCT. This tool will allow more informed decision making weighing the individual benefits and risks of ASCT compared to other therapies.

Introduction: Light-chain amyloidosis (ALA) is a rare plasma cell disorder characterized by multiorgan involvement. Patients often present with non-specific symptoms, which can lead to a delay in diagnosis. This is associated with progressive organ involvement and shorter survival. Reducing the time from symptom onset to diagnosis is a critical step in improving outcomes. This study was designed to evaluate the clinical prodrome and challenges associated with the diagnosis of ALA from the patient perspective. Methods: This retrospective study surveyed patients with ALA through the online HealthTree® Cure Hub platform, which helps patients navigate their disease in a holistic way. The survey consisted of 32 questions, including 23 multiple-choice, 7 date-entry, and two free-response questions. Data on diagnosis and demographics were extracted from the electronic health record and self-reported data linked to HealthTree® Cure Hub. Results were reported as numbers and percentages, and comparisons were made by age (≥70 vs. &lt;70 years) and sex. The following statistical methods were used: Fisher's exact test for categorical data, two-sample t-test and F-test for normally distributed continuous data, Wilcoxon rank-sum test for skewed data and Spearman correlation coefficient. Results: We surveyed 248 patients. Of those, a total of 87 patients with a self-reported diagnosis of ALA completed the questionnaire between March 12, 2023, and May 8, 2024. The median age was 66 years; 55% were female, and 91% were white. The most common initial symptoms prompting patients to seek medical evaluation were fatigue/weakness (47%), swelling (38%), shortness of breath (28%), chest pain (23%), and foamy urine (22%). Pain in hands/feet, carpal tunnel syndrome, loss of appetite, hoarseness, macroglossia, diarrhea, periorbital puffiness, nail changes, and erectile dysfunction each accounted for &lt;10% of cases. Signs and symptoms were first detected by patients themselves in 58% of cases, by a physician in 33% and by a family member or friend for the rest. The median number of symptoms per individual was 2; 31% reported only one symptom, 37% 2-3, 18% 4-6, and 14% &gt;6; with chest pain being the most common (39%), followed by swelling (22%), shortness of breath (13%), and foamy urine (13%); one patient reported erectile dysfunction and another reported arrhythmias as their only symptom. There was a correlation between hoarseness and nail changes (ρ=0.71), and carpal tunnel syndrome and orthostatic hypotension (ρ=0.63). Only 16% were aware of ALA as a condition prior to symptom onset. Thirty six percent presented to a general practitioner for initial evaluation; about 50% sought a specialist, including a myeloma/amyloid specialist (21%), and 14% were first evaluated in the emergency department. While most patients (45%) were diagnosed by a hematologist/oncologist, patients reported seeing a median of 3 physicians (range: 1-10) before the diagnosis was established. Among responders, 61% reported having myeloma at the time of testing. After diagnosis, about 50% were referred to a center specialized in ALA, and 72% met with a stem cell transplant specialist. Most patients reported receiving multidisciplinary care, with a median of 3 additional specialists participating in ALA care (range: 0-16). More than half of patients (59%) felt the diagnosis was delayed; among those, 42%, 24%, 24%, and 11% reported a delay of 1-6, 7-12, 13-24, and &gt;24 months, respectively. The proportion of patients reporting &gt;12-month delay was higher among older patients (54% vs. 27%, P=0.02). A quarter of responders felt their treatment was delayed. Half of patients felt the diagnostic delay contributed to a decrease in treatment efficacy and 48% did not feel that all medical professionals were knowledgeable about ALA. Only 38% felt the diagnostic process was simple and easy within their healthcare system. Conclusion: Most patients with AL amyloidosis initially present with non-specific symptoms, with fatigue/weakness being the most common. Over a third were evaluated first by a general practitioner, and about a third reported a diagnostic delay of &gt;12 months. The diagnostic process is associated with high healthcare utilization, even among patients with concurrent multiple myeloma. Increasing disease awareness among patients and medical providers may shorten the time to diagnosis and contribute to improved outcomes.

Background: Isatuximab is an IgG1κ monoclonal antibody that binds with high affinity to CD38 expressed on plasma cells in light chain (AL) amyloidosis. Anti-CD38 antibodies have shown efficacy alone and in combination in a variety of settings for patients with multiple myeloma and light chain (AL) amyloidosis. Here we report the final analysis of a multi-center, cooperative group prospective phase II study of isatuximab in previously treated patients with AL amyloidosis (NCT03499808). Methods: Eligibility included: age ≥18 years, relapsed or refractory systemic AL amyloidosis, ≥1 prior line of therapy, measurable disease, ≥1 organ involved, not refractory to daratumumab, Eastern Cooperative Oncology Group performance status ≤2, creatinine clearance ≥25 mL/min, and NT-proBNP ≤8500 pg/mL. Patients received isatuximab intravenously 20 mg/kg weekly during the first 28-day cycle and every other week during cycles 2 through 24 for a maximum of 24 cycles. The primary objective was hematologic response with secondary objectives of organ response, safety, progression free survival, and overall survival. Results: Forty-three patients were registered, with 35 patients being eligible for response. The median age of the evaluable patients was 70 years (range, 40.1-79.5) with the majority (66%, n=23) having a lambda clonal plasma cell dyscrasia. The most common cytogenetic abnormality using fluorescence in situ hybridization was translocation t(11;14) observed in ten patients (29%). The most common prior treatment was a proteasome inhibitor (94%, n=33) while 46% (n=16) had undergone autologous stem cell transplant. Eighteen patients (51%) had single organ involvement while 17 (49%) had multiple organs involved. The distribution of organ involvement was typical for AL amyloidosis with cardiac involvement in 25 patients (71%) and renal involvement in 14 (40%). As of December 30, 2022, no new safety concerns were identified. The most common treatment related grade ≥3 adverse events included lymphopenia (n=3, 8.5%) and infection (n=2, 6%). The overall hematologic response rate was 77.1% with a rapid median time to partial response or better of 1.1 months. Two patients (6%) achieved a hematological complete response (CR), 18 (51%) had a very good partial response (VGPR), and 7 (20%) had a partial response (PR). At 24 months from hematologic response, the rate of patients still in response was estimated at 81% (95% confidence interval (CI): 67, 96). The 24-month estimated overall survival was 85% (95% CI: 73%, 97%). Renal response occurred in 50% (7/14) of patients with renal involvement with a median time to response of 18.5 months. Cardiac response occurred in 56% (14/25) of patients with cardiac involvement with a median time to response of 16.6 months. Conclusions: Isatuximab monotherapy resulted in high rates of hematologic response in relapsed AL amyloidosis which translated into organ responses. Treatment appears safe and was well tolerated. Support: NIH/NCI/NCTN grant awards U10CA180888, U10CA180819, CA180820, and CA180821; and in part by Sanofi-Aventis (Sanofi US)

Introduction: Systemic amyloid light chain (AL) amyloidosis is a rare disease with severe sequelae, including cardiac and renal dysfunction and failure. Various biomarker-based staging systems have been established to inform prognosis and treatment. However, a single International Classification of Diseases, Tenth Revision (ICD-10) diagnosis code collectively applies to all stages of the disease, and while several studies have reported disease costs using healthcare claims data, stage-specific costs are not well understood. The current study aimed to estimate the healthcare utilization and costs of prevalent patients with AL amyloidosis by Mayo 2012 stage (I, II, III, IV). Methods: A multi-center medical chart review of patients with AL amyloidosis was conducted across six hematology clinics in the United States. Enrolled patients were ≥18 years old with a diagnosis of AL amyloidosis, documentation of Mayo 2012 stage at diagnosis, ≥1 office visit during the 6 months prior to the site's IRB approval date, and ≥1 year of available medical records. We collected 1 year of healthcare utilization data for each patient, in addition to clinical characteristics at diagnosis, which was prior to the 1-year observation period for most patients. Observation periods ranged from 11/2020 to 6/2023. Demographics, AL amyloidosis clinical history (e.g., organ involvement, lines of therapy, treatment response), laboratory values, and AL amyloidosis-related healthcare utilization (e.g., office visits, laboratory tests, procedures, medications, emergency department visits, inpatient stays) were collected. Patients were stratified by Mayo 2012 stage at diagnosis. Patients' 1-year healthcare costs were calculated by combining abstracted utilization data with the Centers for Medicare and Medicaid Services 2023 Physician Fee Schedule for procedures, Medi-Span® Price Rx® Pro for pharmacy and drug administration costs, and published literature for costs unavailable in these sources. Costs were adjusted to 2023 USD using the Consumer Price Index inflation calculator from the US Bureau of Labor Statistics. Results: The study included 61 patients: 15 stage I, 16 stage II, 17 stage III, and 13 stage IV. Overall, patients had a mean age at diagnosis of 62.4 years (standard deviation ([SD] 10.1), 39.3% were female (n=24), and 67.2% (n=41) of patients were non-Hispanic White, 14.8 % (n=9) Non-Hispanic Black, 6.6% (n=4) Asian, 1.6% (n=1) Hispanic, and 9.8% (n=6) other race/ethnicity. Most patients had Medicare (45.9%, n=28) or private health insurance (34.4%, n=21). The average duration of disease (i.e., time from diagnosis to date of last office visit prior to their site's IRB approval date) was 4.5 years (SD 3.5). All patients had involvement of ≥1 organ system and 45.9% (n=28) had involvement of ≥2 organ systems at diagnosis. More than half of patients had renal (55.7%, n=34) or cardiac (52.5%, n=32) involvement. Nearly all patients completed first-line therapy at any point prior to their last office visit (93.4%, n=57); a minority of patients (9.8%, n=6) initiated first-line therapy, and 3 patients (4.9%) had a hematopoietic stem cell transplantation, one each in stages I, II, and III, during the study period. The median estimated AL amyloidosis-related healthcare costs (USD) during the 1-year study period were $95,253 (interquartile range [IQR] $2,869-497,504) for stage I, $190,796 ($5,249-499,470) for stage II, $414,677 ($28,365-533,081) for stage III, and $523,504 ($191,830-526,596) for stage IV. Discussion: This is the first study of AL amyloidosis that reports costs of care stratified by Mayo 2012 stage. In a prevalent population with AL amyloidosis, we found that overall, patients with AL amyloidosis have significant ongoing costs of care after completion of initial therapy at each Mayo 2012 stage, with stage IV patients having the highest AL amyloidosis-related costs. The percent of patients with cardiac or renal organ involvement is possibly higher than represented in this study; given the rapid progression and high early mortality rate seen with stage III and IV disease, some of these patients may not have fulfilled the 1-year observation period requirement and thus were excluded from the study. These data describe the significant and continued burden faced by patients with AL amyloidosis and the health care system for the years beyond initial diagnosis and completion of front-line treatment.

Introduction Poor diet quality, elevated body mass index (BMI), insulin resistance, microbiome dysbiosis, inflammation as well as immune dysfunction have all been implicated in progression from monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) to multiple myeloma (MM). Plant-based diets have been associated with reduced risk of MGUS and MM in epidemiological studies. Whether a dietary intervention can impact these modifiable risk factors and delay disease progression has not been investigated. Methods We conducted a pilot, single-arm trial providing controlled high fiber plant based dietary (HFPBD) intervention for 12 weeks and health coaching for 24 weeks in 20 patients with MGUS/SMM with BMI≥25 (NCT04920084). The primary endpoint was feasibility (adherence and BMI reduction). Secondary and exploratory endpoints included quality of life, metabolic markers (insulin, adiponectin, leptin, LDL cholesterol), microbiome (diversity and composition by 16S and shotgun sequencing) and immune profiling in peripheral blood (flow cytometry and Olink inflammation panel) and bone marrow (scRNAseq and ATACseq). We also conducted an in vivo study in transgenic Vk*MYC mice fed a high fiber or control diet at the phase of mouse(m)SMM. The mice were monitored for the progression to active mMM. Differences in microbiome and immune response profiles between high fiber- and control-treated mice were assessed via microbiome 16S sequencing and flow cytometry. Results The HFPBD intervention was safe, feasible, improved quality of life and addressed modifiable risk factors - metabolic profile (improved BMI, insulin resistance, adiponectin leptin ratio), microbiome profile (increased alpha-diversity and butyrate producers) and immune (decreased inflammation and increased anti-inflammatory classical monocyte) subsets. A reduction in long-term progression trajectory was observed in 2 patients. Consistently, the high fiber diet delayed progression from mSMM to mMM in Vk*MYC mice increasing median progression-free survival from 12 weeks in the control arm to 30 weeks in the high fiber diet intervention arm. Additionally, in the intervention arm 40% of mice did not progress to mMM during the study period whereas all mice in the control arm progressed. Both human and mouse data showed that HFPBD modulated gut microbiota composition favoring the expansion of butyrate-producing bacteria. Additionally, short-chain fatty acids were increased in the feces of mice fed a high fiber diet. Integrated analysis from human bone marrow and peripheral blood analysis indicated that the dietary intervention reduced inflammatory biomarkers and skewed the immune response towards T helper and CD14+ monocytes. Consistently, the bone marrow of Vk*MYC mice fed high fiber diet was more infiltrated by IFNg-producing T lymphocytes while displaying less exhausted T cells and immunosuppressive myeloid cells. Conclusion This is the first interventional clinical trial and in vivo study to show that a HFPBD intervention may delay progression from MGUS/SMM to MM. To our knowledge there has been no similar dietary interventional study in hematological cancers or solid tumors. Together our in vivo and clinical data support the beneficial anti-inflammatory role of a HFPBD providing a link between diet, microbiota, and immune modulation to delay disease progression in MGUS/SMM.