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Introduction: Clonal hematopoiesis (CH) is a common age-related premalignant condition defined by the presence of an acquired somatic mutation in a gene frequently mutated in myeloid malignancies characterized by a variant allele frequency (VAF) of ≥2%, without fulfillment of other diagnostic criteria for myeloid neoplasm. Incidence of CH increases with age and found in 10%-30% of people > 70 years of age. CH-related mutations confer an increased risk of myeloid neoplasms, cardiovascular diseases, and are linked to inferior survival in solid tumor patients treated with chemo/radiation therapy. Such mutations can act as a driver/amplifier of inflammation, especially through myeloid cells. To distinguish true disease drivers from background genetic events related to aging or environmental factors, we need a deeper understanding of the impact of CH in different tissue microenvironments and under therapeutic pressure for better risk stratification of CH carrier patients. Recent reports suggested high prevalence of CH-related mutations in lymphoma. Current analyses aimed to investigate: i) the prevalence of CH-related mutations in two real-world lymphoma cohorts from Molecular Epidemiology Resource (MER) MER-FL and MER-DLBCL, ii) CH-related mutational landscape in DLBCL and FL, iii) the impact of CH-related mutations on clinical outcomes. Methods: Whole exome sequencing (WES) derived from blood/PBMC from lymphoma patients with paired tumor samples was analyzed to identify CH-related myeloid drivers in 42 previously reported genes. We used Sention-Tnhaplotype2 somatic pipeline with a custom panel of normals from whole blood samples. To avoid tumor contamination, we filtered variants for which VAF in the tumor was higher than that in the germline sample. Other filtering criteria included HIGH/MODERATE impact; read count > 1 in both forward and reverse reads; gnomAD_AF < 0.01. We used the R “survival” package Cox regression implementation for outcome and other statistical analysis. Results: Genomic and clinical data of 507 patients from MER-FL and 383 patients from MER-DLBCL cohorts, with median age of 60 and 64 respectively, were available for analysis. CH-related mutations were present in 17.16% (87/507) in FL and 18.28% (70/383) in DLBCL cohorts with a VAF cut off >2%. The most common CH-related mutations were DNMT3A (5%), CREBBP (2%), TET2 (1%), ASXL1 (1%) and PPM1D (1%) in MER-FL while DNMT3A (5%), TET2 (3%), TP53 (3%), ASXL1 (2%) and PPM1D (1%) in MER-DLBCL cohort. Both the prevalence of CH-related mutations and their average VAF increased with age, consistent with literature. Finally, cox regression analysis suggested that CH-related mutations were associated with significantly inferior overall survival (OS) in both FL and DLBCL cohorts (HR 1.6 p=0.028 and HR 2.3 p=<0.001 respectively); however only in DLBCL this association was significant after age correction (HR 1.8 p=0.008). When separated by individual gene mutations, genes of interest with inferior OS included TP53 (n=4, HR 3.1, p=0.057) in FL and PPM1D (n=3 HR 2.6 p=0.1), TP53 (n=8 HR 2.1 p=0.1) and DNMT3A (n=14, HR=2.0, p=0.048) in DLBCL; however, these estimates did not quite reach statistical significance. Conclusions: Taken together, our exploratory analysis indicates that CH-related mutations associate with worse OS in lymphoma patients, supporting the rationale for evaluation of CH for the risk assessment in lymphoma. Furthermore, DLBCL displays of larger size effect, which may be related to different treatment regimes. Additional studies will be needed to elucidate the interaction between high dose chemotherapy regimes and CH-associated adverse events.

Background: Mosunetuzumab (Mosun), a CD20xCD3 bispecific antibody, received accelerated approval for the intravenous treatment of patients (pts) with relapsed/refractory (R/R) follicular lymphoma (FL) who have received ≥2 prior lines of systemic therapy. Mosun can be administered in the outpatient setting with a fixed treatment duration. In an ongoing Phase I/II study, Mosun administered subcutaneously (SC) induced durable responses with a manageable safety profile in pts with previously untreated low-tumor burden FL (LTB; Flinn et al. ASH 2023). Efficacy, safety and pharmacodynamic profiles of Mosun SC are being evaluated in an open-label, multicenter, Phase II study (MorningSun; NCT05207670) in pts with B-cell non-Hodgkin lymphomas, including previously untreated FL. Here we present >8-month follow-up efficacy, safety and biomarker data for Mosun SC in first-line, LTB FL. Methods: Pts had untreated Grade (Gr) 1 or 2 FL, LTB by Groupe d'Etude des Lymphomes Folliculaires criteria, Ann Arbor stage III/IV disease, and Eastern Cooperative Oncology Group performance status (ECOG PS) of 0-2. Mosun SC injection was administered with step-up dosing in Cycle (C) 1 (Day [D] 1, 5mg; D8, 45mg; D15, 45mg), then 45mg on D1 of each 21-day cycle. Hospitalization was not mandatory. Pts with a complete metabolic response (CMR) after C8 could complete therapy. Pts with a partial metabolic response (PMR) or stable disease continued treatment for up to 17 cycles. Dexamethasone premedication was mandatory in C1 and C2 and optional thereafter. The primary endpoint was progression-free survival at 24 months. Exploratory analyses assessed cytokine levels in pts with versus without cytokine release syndrome (CRS) and pharmacodynamic changes in T and B cells in a subgroup of pts. Results: As of February 7, 2024, 65 pts were enrolled in US community (n=41) and academic (n=24) centers. At baseline, median age was 63 years (range: 34-82). Most pts had an ECOG PS of 0 (83.1%) or 1 (15.4%); 29 pts (44.6%) had extranodal involvement and 3 pts (4.6%) had B symptoms. Median duration of follow-up was 8.6 months (95% confidence interval [CI]: 5.7-10.9). Median number of cycles was 8 (range: 1-17). Among 60 pts with ≥1 post-baseline tumor assessment, the objective response rate was 95.0% (95% CI: 86.1-99.0; n=57) and CMR was 83.3% (95% CI: 71.5-91.7; n=50). Median time to response was 2.8 months (range: 2.3-8.3). At data cut-off, responses were ongoing in 48 pts with a CMR and in 5 pts with a PMR. In 64 safety-evaluable pts, the most common adverse event (AE) was injection-site reaction (70.3%; Gr 1, 65.6%; Gr 2, 4.7%). CRS by ASTCT occurred in 30 pts (46.9%; Gr 1, 39.1%; Gr 2, 7.8%); CRS events presented early in C1 (53.1%; Gr1, 45.3%; Gr2, 7.8%) and C2 (Gr1, 1.6%). Nineteen pts received CRS treatment (tocilizumab, 7.8%; steroids, 7.8%; tocilizumab + steroids, 4.7%; fluids, 3.1%; low-flow oxygen, 1.6%); 8 pts had a serious AE and were hospitalized. All CRS events resolved. Other common AEs included headache (45.3%; Gr 1, 29.7%; Gr 2, 15.6%), fatigue (45.3%; Gr 1, 35.9%; Gr 2, 9.4%), maculo-papular rash (31.3%; Gr 1, 14.1%; Gr 2, 15.6%; Gr 3, 1.6%), and increased alanine aminotransferase (28.1%; Gr 1, 21.9%; Gr 2, 4.7%; Gr 3, 1.6%). Gr 3/4 AEs in ≥5% of pts were neutropenia without fever (12.5%; Gr 3, 4.7%; Gr 4, 7.8%) and lymphopenia (7.8%; Gr 3, 1.6%; Gr 4, 6.3%). Suspected immune effector cell-associated neurotoxicity syndrome occurred in 2 pts (confusional state, Gr 1, n=1; Gr 2, n=1); all events resolved. Infections occurred in 30 pts (46.9%; Gr 1, 7.8%; Gr 2, 31.3%; Gr 3, 7.8%) with the most common (≥10%) being COVID-19 (17.2%; Gr 1, 7.8%; Gr 2, 7.8%; Gr 3, 1.6%) and upper respiratory tract infections (12.5%; Gr 1, 3.1%; Gr 2, 9.4%). One pt had a Gr 5 (fatal) AE 13.7 months after treatment was completed (reported as unrelated to Mosun; cause unknown). After the first Mosun dose, cytokine levels significantly increased on C1D2 (interleukin-6, n=44, p≤0.001; interferon-γ and tumor necrosis factor-α, n=41, p≤0.001). This spike in cytokine levels did not differ in pts with (n=19) versus without (n=25) CRS events in C1. Conclusions: Mosun SC monotherapy shows encouraging high efficacy as a fixed-duration treatment in first-line LTB FL. A manageable safety profile was reported, supporting ease of access for patients with drug administration in outpatient settings. Longer follow-up is needed to confirm long-term durability of response and safety.

Introduction: Somatic mutations in RAS pathway genes are present in ~30% of patients with chronic myelomonocytic leukemia (CMML) and are usually associated with myeloproliferative features. Whether mutations in distinct RAS pathway genes share similar genomic context and have similar implications remains unknown. Such an understanding might inform future studies evaluating genotype-specific therapies (RAS-codon specific and pan-RAS inhibitors) or cooperative leukemogenic mechanisms. This multicenter study examines the landscape of RAS pathway mutations (RASMT) in CMML. Methods: Newly diagnosed CMML patients evaluated at MD Anderson Cancer Center (n=449, 54%) and Mayo Clinic (n=383, n=46%) were included after IRB approval. Clonal relationships were tested using Pearson goodness-of-fit. Clones with the highest variant allele frequency (VAF), or with VAF close to 40% were defined as dominant, and those present at VAF <20% in the presence of another dominant clone were defined as subclonal. RASMT genes included NRAS, KRAS, BRAF, CBL, CBLC, PTPN11 and NF1. Standard statistical measures were applied. Results: Among 832 CMML patients (median age 71 years, 68% male) 387 (47%) had myeloproliferative (MP) and 445 (53%) had myelodysplastic (MD) CMML. A total of 350 (42%) patients had RASMT with higher prevalence among MP-CMML compared to MD-CMML (55% vs 31%, p<0.001). Among patients with RASMT, 262 (32%), 59 (7%), 20 (2%), 6 (<1%) and 3 (<1%) had 1, 2, 3, 4 or 5 distinct RASMT, respectively. Importantly, 17 patients harbored a RASmt as the only detectable somatic mutation, with KRASMT being the most frequent (n=10, 59%), including 3 (18%) patients with >1 RASMT. Among RASMT patients, a trend for higher hemoglobin (12.7 vs 10.8 g/dL, p=0.054) was observed in NF1MT CMML and lower WBC (14.4 vs 27.9 x109/L, p=0.067) values in CBLMT CMML. In total, 479 somatic mutations in RAS pathway genes were identified the most frequent involving NRAS (n=169, 35%) followed by CBL (n=120, 25%), KRAS (n=102, 21%), PTPN11 (n=38, 8%), NF1 (n=34, 7%), BRAF (n=11, 2%) and CBLC (n=5, 1%). Most frequently involved codons for each RAS pathway gene were as follows: G594 (n=3) for BRAF, R420 (n=22) and C404 (n=15) for CBL, G12 (n=41; G12D: 13, G12C: 3) and A146 (n=16) for KRAS, G12 (n=116; G12D: 74, G12C: 5) for NRAS and A72 (n=8) for PTPN11. CBLMT CMML had higher ASXL1 (58% vs 44%, p=0.011), BRAF (8% vs 4%, p=0.017), IDH2 (10% vs 4%, p=0.024), KIT (5% vs 1%, p=0.038), SRSF2 (54% vs 40%, p=0.004), TET2 (59% vs 47%, p=0.019) and ZRSR2 (10% vs 4%, p=0.014) co-mutation frequency. Of note, DNMT3A mutations were mutually exclusive of CBLMT CMML (0% vs 7%, p=0.007), and multihit TET2 was more common among TET2MT/CBLMT vs TET2MT/CBLWT CMML (82% vs 67%, p =0.039). CMML with NF1 mutations had higher BCORL1 (8% vs 0%, p=0.005), PTPN11 (15% vs 3%, p=0.014) and SETBP1 (23% vs 8%, p=0.022) mutational cooccurrences. NRASMT CMML was enriched for ASXL1 (53% vs 43%, p=0.042), ETNK1 (5% vs 1%, p=0.004), GATA2 (4% vs 1%, p=0.034) and STAG2 (4% vs 1 %, p=0.023) mutations but had lower JAK2 (1% vs 6%, p=0.036) and TP53 (1% vs 5%, p=0.022) mutational frequency. PTPN11 mutations were associated with higher NF1 (29% vs 7%, p=0.014), SETBP1 (27% vs 9%, p=0.01) and WT1 (6% vs <1%, p=0.014) mutational cooccurrences and lower SRSF2 (23% vs 42%, p=0.05) frequency. We evaluated RAS mutant clonal dominance in 253 (72%) RASMT patients. NRAS (63% vs 38%), KRAS (63% vs 38%) and CBL (65% vs 35%) mutations were more frequently observed as dominant clones while PTPN11 (44% vs 56%), BRAF (25% vs 75%) and NF1 (35% vs 65%) mutations were more frequently subclonal events, particularly of TET2, ASXL1 or SRSF2 mutant clones. Presence of a RAS pathway mutation was associated with shorter LFS (36 vs 53 months, HR 1.5, 95% CI 1.1-2.2, p=0.020), with presence of multiple RAS mutations shortening LFS further (53, 43, 27 months for 0, 1 and >1, p=0.017). PTPN11 mutations predicted for shorter OS (18 vs 39 months, HR 1.7, 95% CI 1.0-2.8, p=0.035) and LFS (14 vs 36 months, HR 1.9, 95% CI 1.2-2.9, p=0.008). Presence of >1 RAS pathway mutation was associated with shorter OS in ASXL1MT/TET2MT CMML compared to those with no RAS mutations (24 vs 53 months, HR 4.2, 95% CI 1.6-10.8, p=0.004). Conclusions: RAS mutations exhibit distinct genomic features and clonal hierarchy in CMML and cooperate with other somatic mutations to drive clinical outcomes. This study forms the foundation for assessment of novel RAS pathway inhibitors in CMML.

Background: Systemic light chain (AL) amyloidosis is a clonal plasma cell disorder characterized by the deposition of misfolded immunoglobulin light chain products in vital organs, leading to significant organ dysfunction. The molecular mechanisms underlying its pathogenesis remain incompletely elucidated. Identifying the molecular mechanisms and novel therapeutic targets is critical for improving treatment strategies and patient outcomes. Our previous research work identified that the PI3K/AKT signaling pathway is overexpressed in AL amyloidosis (Zvida et al., Blood, 2022, Fishov et al., Cancer Med., 2023). This pathway plays a critical role in regulating cellular metabolism. Specifically activated AKT can phosphorylate and regulate various target proteins involved in metabolic processes. One of the significant targets is fatty acid synthase (FASN), an enzyme responsible for the synthesis of fatty acids. AKT can enhance FASN expression and activity, thereby promoting lipid biosynthesis. Additionally, elevated FASN levels can drive inflammation through increased fatty acid synthesis, which activates inflammatory signaling pathways and enhances cytokine production (Acosta-Martinez et al.,IJMC, 2022). Elevated levels of FASN have been associated with hematological malignancies and cell survival (Vanauberg, et al., Oncogenesis, 2023). However, its role in AL amyloidosis is yet to be elucidated. Aim: To determine the role of FASN in the pathology and inflammatory response in AL amyloidosis, and to evaluate the potential of targeting FASN and the PI3K/AKT pathway for therapeutic intervention. Methods: We profiled FASN expression in CD138+ bone marrow (BM) samples from patients with AL amyloidosis (n=20), Multiple Myeloma (MM) (n=20), Monoclonal Gammopathy of Undetermined (MGUS) (n=8) and Healthy Controls (HC) (n=6), using qRT-PCR. To further explore the relationship between the PI3K/AKT pathway and FASN, we treated ALMC-1 cells with Capivasertib (an AKT inhibitor) and assessed FASN protein levels, cell proliferation by WST-1 assay, cell cycle distribution by flow cytometry, light chain secretion by ELISA, and expression of AKT and its downstream targets via western blot analysis. Furthermore, TVB-2640 (FASN inhibitor) was used to evaluate the cell response to FASN inhibition. Results: Our analysis revealed a significant upregulation of FASN in AL amyloidosis BM samples compared to MM, MGUS, and HCs. Capivasertib treatment resulted in a dose-dependent reduction in FASN protein levels. Additionally, Capivasertib treatment inhibited cell proliferation, induced G1 phase cell cycle arrest, reduced light chain secretion, and decreased AKT protein expression and its downstream targets p4EBP pS6 and pERK. Elevated levels of proinflammatory cytokines, including TNF and IP-10 (CXCL-10), were observed in AL amyloidosis serum samples, suggesting the involvement of immune mechanisms and the PI3K/AKT pathway, potentially induced by FASN. Finally, treatment with TVB-2640 reduced cell viability and decreased the protein expression of LIPIN-1, which is one of the key target genes regulated by FASN. Conclusions: Our findings highlight the significant upregulation of FASN in AL amyloidosis and its regulation by the PI3K/AKT pathway. The observed effects of Capivasertib on FASN expression and cell proliferation, along with the upregulation of inflammatory cytokines, underscore the potential for targeting the PI3K/AKT signaling pathway and FASN in developing more specific therapeutic strategies for AL amyloidosis.

Multiple myeloma (MM), an incurable hematologic malignancy, presents significant challenges in managing its recurrence. The bone marrow tumor microenvironment (BM-TME) is critical to MM progression. However, classical immune checkpoint blockade (ICB) therapies, like anti-PD1, have shown limited efficacy in MM. Therefore, elucidating the compositional features and regulatory mechanisms of the TIME in MM is crucial for developing novel immunotherapeutic targets. Tissue-resident memory CD8+ T cells (CD8+ TRMs) reside indefinitely at multiple anatomical locations like the skin, intestine, and bone marrow, functioning as frontline responders against reencountered pathogens and tumors. Whether CD8+ TRMs within BM-TME are involved in the MM cell immune escape and pathogenesis has not been systematically elucidated. Firstly, we leverage single-cell RNA sequencing (scRNA-seq) to dissect the BM CD8+ T cells across patients at different stages of MM, and identify that CD69+CD8+ T subsets were BM residents, and the proportion of BM CD8+ TRMs between health donors and MM patients was comparable. Moreover, our findings indicated that BM CD8+ TRMs exhibit exhausted features and enrichment of NK genes with MM progresses. Importantly, we observed a considerable elevation of the NK gene KLRB1 and its encoded protein CD161 in BM CD8+ TRMs in MM patients. Immunofluorescence labeling of BM biopsy samples from MM patients confirmed the infiltration of the BM-TME with CD3+CD8+CD69+CD161+ cells. Then, we found that KLRB1 expression in BM CD8+ TRMs was higher than that of other classical inhibitory receptor genes (e.g., PDCD1, CTLA4, LAG3), and CLEC2D (encodes the ligand of CD161) was also markedly expressed in patients' MM cells, exhibiting considerably higher than classical immunosuppressive receptor ligand genes (e.g., PDL1, CD80, CD86). Moreover, patients with higher CLEC2D expression had unfavorable overall survival. We further found that the CD161 expression was higher in CD69+CD8+ TRMs compared to circulating CD69-CD8+ T cells, and the percentage of BM CD161+CD8+ TRMs in MM patients was significantly higher than in healthy donors, while there was no difference for PD-1, LAG3, and TIM3 expression. Notably, only a small fraction of BM CD8+ TRMs have mucosal-associated invariant T cell phenotypes (identified by CD161+TCR-Vα7.2+). Additionally, the CLEC2D expression of BM cells was analyzed, and the highest level of CLEC2D expression was observed in B cells from MM patients, followed by plasma cells. Importantly, CLEC2D expression in MM patients was significantly higher than in plasma cells from healthy donors. Next, to investigate whether the blockade of CD161 could restore the function of CD8+ TRMs, the primary BM cells from MM patients were isolated and stimulated ex vivo. Compared to the anti-PD-1 and isotype group, CD161 blocking presents enhanced CD8+ TRMs proliferation and cytokine secretion levels (TNF-α, IFN-γ, IL2), increasing MM cells apoptosis. Chimeric antigen receptor T (CAR-T) cell therapy has achieved impressive success in treating relapsed/refractory MM. How to prevent CAR-T cell exhaustion and enhance function remains a significant challenge. Therefore, we next set out to investigate the impact of CD161 on CAR-T cells. Our results demonstrated that CD161 was highly expressed in early peripheral blood (PB) CAR-T cells after infusion in MM patients but decreased with time. Moreover, the CD161 expression of CAR-T cells was considerably higher than endogenous T cells. Notably, BM-derived CAR-T cells have higher CD161 expression than PB counterparts for the same patient, suggesting CD161 may have BM-specific expression enrichment. After co-culturing MM and CAR-T cells in vitro for 24 hours, we found that blocking CD161 led to an augmented proportion of CAR-T cells, increased IFN-γ secretion, and a notable elevation in tumor cell apoptosis compared to the anti-PD-1 and isotype groups. Taken together, we demonstrated that CD8+ TRMs constitute a vital anti-tumor cell subset in the MM BM-TME, which exhibits a high expression of the inhibitory CD161 receptor, binding to the CLEC2D expressed by MM cells, thereby mediating the dysfunction of CD8+ TRMs. Blocking the CD161-CLEC2D pathway is expected to become a novel target for MM immunotherapy. The combination of CD161 inhibitors and CAR-T cell therapy can potentially enhance the anti-myeloma function of CAR-T cells.

Background: Cemsidomide (formerly CFT7455) is a novel, rationally designed, highly potent Ikaros Family Zinc Finger Protein 1/3 (IKZF1/3) MonoDACTM cereblon-based degrader. Cemsidomide has demonstrated best-in-class activity in multiple myeloma (MM) preclinical models and has also been shown to stimulate immune activation, providing combination rationale for various novel and standard of care therapies in MM. Methods: CFT7455-1101(NCT04756726) is an open-label, phase 1/2, multi-center, first-in-human study evaluating safety, efficacy, pharmacokinetics (PK), and pharmacodynamics (PD) of cemsidomide in patients (pts) with MM and non-Hodgkin's lymphoma who have relapsed from and/or are refractory to standard of care options. Eligible MM pts must have received lenalidomide, pomalidomide, a proteasome inhibitor, and an anti-CD38 antibody. The primary objective of the MM phase 1 portion of the study is to characterize the safety and tolerability of cemsidomide alone and in combination with dexamethasone (DEX) and to determine the maximum tolerated dose (MTD) and/or recommended doses for phase 2. Secondary objectives include assessments of antitumor activity according to the International Myeloma Working Group (IMWG) response criteria, PK, and PD. Dose escalation is guided by a Bayesian logistic regression model with an initial cohort size of 3-6 pts and a provision for additional pts to be enrolled in expansion cohorts at doses deemed safe. We report initial results from our ongoing cemsidomide plus DEX dose escalation arm. Results: As of July 3rd, 2024, 32 pts have been treated with cemsidomide at various doses plus DEX (20 or 40 mg weekly) in the ongoing dose escalation portion of the study. The median age was 64 (range 40-82) and pts had received a median of 6 prior lines of therapy (range 3-17). 21/32 (66%) of pts received prior treatment with a CAR-T or a bispecific antibody. 9/32 (28%) of pts had high-risk disease at screening and 6/32 (19%) of pts had extramedullary disease. Cemsidomide doses explored in dose-escalation and expansion cohorts included 50 µg MWF (n=6), 37.5 µg QD (n=12), 62.5 µg QD (n=10), and 75 µg QD (n=4), all on a 14 day on/14 day off dosing schedule. Systemic exposure of cemsidomide increased dose proportionally. At all dose levels, cemsidomide produced expected degradation of IKZF1 and IKZF3. To date only one dose-limiting toxicity has been observed (one pt in the 62.5 µg QD cohort experienced Grade 4 neutropenia lasting >7 days). 59% of pts experienced a grade ≥3 TEAE. Grade 3-4 TEAEs occurring in ≥10% of patients included neutropenia (34%), anemia (28%), infections (19%), lymphopenia (16%), and thrombocytopenia (13%). No pts experienced grade 3/4 fatigue, nausea, or vomiting. 5 pts have had treatment-related SAEs and 3 pts had an AE resulting in treatment discontinuation. As of the July 25th, 2024 efficacy cutoff, IMWG responses have been observed at all dose levels. The overall response rate among the 32 pts treated in dose escalation and expansion cohorts is 22% (1 sCR, 1 VGPR, and 5 PRs) with an additional 5 pts achieving minimal response (MR) for a clinical benefit rate of 38% (MR or better). To date, 2/4 (50%) pts in the 75 µg cohort have had a PR with expansion at 75 µg ongoing. Conclusions: Initial results from this ongoing phase 1 trial of cemsidomide in combination with DEX demonstrate encouraging efficacy and tolerability as an all-oral therapy in a heavily pre-treated MM population, with the majority of pts having received a CAR-T or bispecific antibody. As anticipated in MM, grade 3-4 toxicities consist largely of myelosuppression, which has been manageable. Given a favorable emerging safety profile and promising anti-myeloma activity, cemsidomide is potentially well suited to combine with other modalities, including proteosome inhibitors, monoclonal antibodies, antibody drug-conjugates and bispecific antibodies. Dose escalation will continue until an MTD and/or the recommended phase 2 doses are identified. Updated data will be presented at the conference.

Introduction: Talquetamab (Talq) is a GPRC5D targeting bispecific antibody recently approved for the treatment of relapsed refractory multiple myeloma (MM) based on the MonumenTAL-1 study. Real World Evidence (RWE) is needed to understand the safety and efficacy of Talq in patients treated outside of a clinical trial as they may have different outcomes and toxicities. Here we report outcomes of 118 patients treated with Talq. Methods: Patients treated with standard-of-care Talq were included. Data was collected through a retrospective chart review from 01/2023 until 7/2024 from 7 International Myeloma Foundation (IMF) associated MM academic centers. Results: 118 patients were included in the analysis. The median age was 64, 37% had HR disease, 22% had EMD at presentation. The median LOT was 6, median number of immunotherapies before TAL was 2 (range 1,4) and 71% received prior BCMA therapy. 72% were triple refractory and 44% were penta refractory. 25% (n=60) would not have been eligible for TAL clinical trial due to exclusion criteria and15% had an ECOG of 2 or greater. 18% (n=97) received TAL as an outpatient and the median number of hospital days was 9 (0,37) for inpatients. CRS during Step up Dose (SUD) 1 was present in 30% Gr 1 (57%), Gr2 (11%), Gr 3 (6%), CRS during SUD 2 was present in 31%, Gr 1 (65%), Gr 2 (11%), CRS during SUD 3 when administered was present in 14% , Gr 1 (82%), Gr 2 (6%) and with first full dose was 12% , Gr 1 (71%), unknown (29%). ICANS occurred in 6% (7/97), Gr 1 (14%), Gr 2 (29%), Gr 3 (14%) and unknown in 43% there was no evidence of HLH. Skin toxicity was present in 62% of patients (n=105/118) with 4% needing dose interruptions and presented as rash (20%), dryness (42%) and itching (20%). Nail toxicity was present in 20% (n=65/118), with 9% needing dose interruptions. Dysgeusia was present in 51% (n=97/118), with 10% needing dose interruptions. Oral toxicity manifest as stomatitis (10%), glossitis (1%), ulcerations (2%), dry mouth (27%), was present in 34% (n=61/118), with 12.5% needing dose interruptions. Infections were present in 34% (n=82/118) and CMV reactivation in 23% while only 1 patient needed treatment for CMV. The Overall Response Rate (ORR) was 64.9% with a VGPR rate or higher of 43.3% in this population. Updated efficacy data including PFS will be reported at the time of presentation Conclusions: This is the first largest RWE of the safety and efficacy of Talq in a heavily pretreated population with a high prior BCMA exposure. The ORR is consistent with a prior study by Jakubowiak et al which showed an ORR OF 65.7% after prior T cell engagers. The safety profile - CRS, ICANS, skin and oral toxicities was similar to the MonumenTAL study, CMV reactivation was higher and this may be related to treatment with prior immunotherapies and should be monitored in the future. This report shows that Talq has a similar safety and efficacy profile in the real world when sequenced after prior BCMA therapies.

Background: Despite recent major advances, multiple myeloma (MM) remains incurable using therapies that are currently available to patients. There are no available/approved targeted therapies for MM that allow for individualized therapeutic approaches to the disease. Fifteen to 20% of newly diagnosed MM patients have a translocation of chromosomes 4 and 14 [t(4;14)]. This translocation puts transcription of the gene encoding Multiple Myeloma SET domain-containing protein (MMSET or NSD2), a histone 3 lysine 36 methyltransferase, under the control of the IgH super enhancer. The super enhancer drives the overexpression of MMSET resulting in an abnormal histone code that promotes myelomagenesis. Presence of t(4;14) is associated with poor clinical prognosis (Caro Am Soc Clin Oncol Educ Book 2021). KTX-1001 is a first-in-class, selective and potent small molecule inhibitor of MMSET, and is the first investigational drug that targets the t(4;14) MM patient population. Methods: This Phase 1, first-in-human open-label study (NCT05651932) is designed to assess the safety, tolerability, and initial clinical activity of KTX-1001 in relapsed/refractory MM (RRMM) and has two parts: dose escalation (Part A) and dose expansion (Part B). In Part B, only t(4;14)+ MM patients will be evaluated in single agent and combination expansion cohorts. Patients with RRMM who have received ≥3 prior lines of therapy, including a proteasome inhibitor (PI), immunomodulatory drug (IMiD), and anti-CD38 antibody are eligible for the dose escalation part. The primary objective of the study is to determine a recommended phase 2 dose (RP2D) and schedule of KTX-1001. Secondary and exploratory objectives include pharmacokinetic (PK) and pharmacodynamic (PD) evaluation of KTX-1001, and assessment of preliminary efficacy. KTX-1001 is administered orally until disease progression, unacceptable toxicity, or patient withdrawal from the study. A Safety Review Committee (SRC) reviews all data prior to each dose escalation decision and on a regular basis. Results: As of June 14, 2024, 17 patients (pts) have been treated with KTX-1001 in Part A across 6 dose levels (SRC reviewed). Dose Level 7 has been reached with no dose limiting toxicities (DLTs). Ten of these patients are t(4;14) positive. Patients have received a median of 5 prior lines of therapy (range: 3-17), including 7 pts with prior BCMA CAR-T, 6 pts with prior BCMA bispecific and/or ADC, 5 pts with prior non-BCMA bispecific, and 12 pts with prior transplant. Patient demographics include a median age of 68 years (range: 50-83), 10 male/ 7 female, 13 white, 2 black or African American, 2 as other identified race, and 3 Hispanic or Latino pts. Six pts remain on treatment. KTX-1001 shows excellent tolerability to date, with treatment emergent AEs (TEAEs) (CTCAEv5.0) predominantly of grade 1 and 2 severity. Most frequently observed TEAEs suspected to be related to KTX-1001 include fatigue (35%), diarrhea (24%), and constipation (24%), for which no grade 3 or 4 events have been observed. Frequency and/or severity of TEAEs have not increased with escalating doses nor treatment duration, and no patients have discontinued due to an AE. Two heavily pre-treated patients [one known to be t(4;14)+] have demonstrated long-lasting stable disease and clinical benefit at 10 and 7 months respectively. Both patients have been intra-patient dose escalated. For PK and PD data collected to date, drug exposure and steady-state concentration of KTX-1001 (at C1D15, when steady state concentration has been reached) appear to be dose-proportional. PD data indicate a dose-dependent decrease in the H3K36me2 mark on treatment versus baseline across dose levels 1 through 6, suggesting that the RP2D may be reached by year end. Updated results will be presented at the congress. Conclusions: Dose escalation of KTX-1001 is ongoing with an excellent tolerability profile to date and demonstration of on-target pharmacodynamics that will inform the determination of the RP2D(s). These PD data support the targeted mechanism of action of KTX-1001 to selectively inhibit MMSET and break the t(4;14) histone code. Given KTX-1001's promising safety profile, single-agent and combination expansion cohorts with standard-of-care MM agents/classes will begin in 2025 to further optimize doses and provide proof of concept in Part B of the Phase 1 study.

Background: Multiple myeloma (MM) involves the proliferation of monoclonal plasma cells (PCs) in the bone marrow. The plasma cell labeling index (PCLI), indicating the percentage of PCs in the S-phase, is a key prognostic factor in newly diagnosed multiple myeloma (NDMM) patients. Methods: A retrospective study at Mayo Clinic analyzed bone marrow Affymetrix microarray datasets from 136 NDMM patients (2001-2012). Data normalization and quality assessment were followed by differential gene expression analysis using limma-voom, adjusted for age, BMPC percentage, and disease stage (RISS). Selected genes were dichotomized by median and subjected to logistic regression for high/low PCLI. Data from 594 patients with a Proliferation Index at baseline was pooled from the MMRF (CoMMpass) dataset for validation after normalization across assays. Results: The baseline characteristics of the patients are as follows: 62 (46%) were female and 74 (54%) were male, with a mean age at diagnosis of 61.6 ± 11.5 years. RISS staging included 36 patients (26.5%) at stage 1, 32 (23.5%) at stage 2, 29 (21.32%) at stage 3, and 39 patients (28.67%) with unknown stage. PCLI distribution showed 113 patients (83.7%) with <2%, and 23 (16.3%) ≥2%. Differential Analysis: The differential analyses reveal several critical insights. In the primary continuous differential analysis, 21,367 genes were analyzed, identifying 654 as differentially expressed with an FDR-adjusted p-value ≤0.05. Of these, 481 genes were upregulated (top 5: SPC25, TRAT1, PBK, E2F8, ASPM) and 173 were downregulated (top 5: SPARC, CD24, MYOF, CXCL12, VCAM1). Univariate and multivariate stratified analyses showed significant findings: 668 genes in age stratification, 395 genes in BMPC% stratification, and 536 genes in RISS stratification. In multivariate analysis, 408 genes were significant with an FDR-adjusted p-value <0.05 for PCLI and ≥0.05 for BMPC%, age, and RISS. 3-Fold Internal Validation: 240 significant genes were identified in fold 1, 25 in fold 2, and 167 in fold 3, with 21 genes common across all folds (e.g., MCM10, GTSE1, UBE2S, NCAPG, FOXM1, STMN1, NEK2, CENPF, MND1, HJURP, E2F8, TOP2A, SKA1, CCNB2, CCNF, CHAF1A, PBK, EXO1, AURKB, CDCA2, DHFR). 19 genes were common in the sensitivity analysis by excluding RISS 3. 20 genes were common in categorical analysis (Categories <1%, 1-2%, 2-3%, 3-4%, >4%). 3 Gene-Based Proliferation Score (3GPS): On univariate logistic regression analysis of 21 genes for high/low PCLI, 17 significant genes were identified. In the step-wise multivariate analysis, CDCA2 (OR=11.56), DHFR (OR=9.6), and CENPF (OR=6.11) were significant. Log-odds were used as weights. For the high expression(median and above) of gene as 1 and low expression as 0: 3GPS=2.4*CDCA2+ 2.3*DHFR +1.8*CENPF A cut-off of 2.4 was chosen as CDCA2 had the highest positive concordance rate (90.91%) versus DHFR (86.36%) and CENPF (77.27%). External Validation: In the CoMMpass dataset, the sensitivity and specificity for the presence of high expression of any of the 3 genes with ≥2 Proliferation Index (PI) were 92.4% and 73.8%, respectively (AUC=83.1%). The median 3GPS was 0 for <2 PI (n=238) and 6.5 for ≥2 PI (n=356). The sensitivity and specificity for the 3GPS in predicting ≥2 PI were 82.6% and 93.6%, respectively (AUC=88.1%). Pathway Analysis: Significant pathways using Reactome include polo-like kinase mediated events in G2/M transition, condensation of prometaphase chromosomes in metaphase, resolution of sister chromatid cohesion in anaphase, and APC-Cdc20 mediated degradation of Nek2A for regulation of the cell cycle. p53 signaling, cancer pathways, and microtubule regulation were also mapped. Survival Analysis: In our cohort, for CDCA2 quartiles (Q)3 and Q4, for CENPF Q3 and Q4, and for DHFR Q4 were associated with inferior overall survival. 3GPS ≥2.4 was associated with inferior survival of 60.28 months versus 111.5 months for <2.4 (p<0.01). In the validation dataset, median survival was not reached at 100 months (vs. high 79.7, p<0.01). The multivariate Cox model found 3GPS score ≥2.4 as an independent predictor (HR=1.64, 95% CI: 1.23 - 2.19), along with ECOG status, ISS stage, gender, age, and whether the patient underwent Stem Cell Transplant. Conclusion: CDCA2, DHFR, and CENPF are associated with ≥ 2% PCLI. The 3GPS score can serve as a measure of gene-based proliferation index. Prospective validation is needed for clinical practice.

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.