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Objectives: Telemedicine is a growing field, with limited data around its utility supporting pediatric emergency care telephone triage. We instituted telemedicine physician support for nurse telephone triage decisions. When the nursing protocols recommended urgent or emergent care, a telemedicine physician reviewed and modified care urgency if appropriate. Our primary study objectives were to evaluate the proportion of patients who were downgraded to less urgent care and assess for potential harm related to the downgrade in care urgency. Methods: We conducted a retrospective observational cohort study of pediatric telephone calls to the Mayo Clinic Health System nurse triage line that were directed to the emergency department telemedicine physician from January 1, 2019, to December 31, 2019. Electronic medical records of patients whose care urgency was downgraded and presented to medical care within 72 hours of the triage call were reviewed. Results: There were 8559 nurse line calls regarding pediatric patients, 882 of which were referred to the telemedicine physician. Among these, 396/882 (44.9%, 95% confidence interval 41.6–48.3) were downgraded. Of downgraded cases, 198 (50.0%) patients sought care within 72 hours of the original call, of which 193 (97.5%) patients were discharged home from that medical visit and 5 (2.5%) patients required admission. No patients were determined to have suffered harm due to the downgrade of visit urgency. Conclusions: Our data suggests that telemedicine physicians can safely downgrade nurse triage care recommendations for pediatric patients. Most downgraded patients sought outpatient care, avoiding unnecessary utilization of the emergency department without evidence of associated harm.

Introduction: Primary diffuse large B-cell lymphoma (DLBCL) of the central nervous system (CNS), traditionally referred to as primary CNS lymphoma (PCNSL), is a rare type of primary large B-cell lymphoma of immune-privileged sites with significantly poorer prognosis than systemic DLBCL. Genetic profiles of PCNSL were widely studied, whereas the tumor microenvironment has not been well characterized. Patients and Methods: A series of molecular analyses were performed using DLBCL FFPE tissues collected by the International Lymphoma Consortium. First, multiplex fluorescent immunohistochemistry (mfIHC) using antibodies for CD20, PAX5, CD3, CD4, CD8, FOXP3, CD45RO, CD68, CD56, PD-1, PD-L1, PD-L2, and CTLA-4 was performed on PCNSL tissues from 121 immunocompetent patients and de novo systemic DLBCL tissues from 405 patients. Digital quantification results for 405 patients with EBV-negative systemic DLBCL or primary testicular (PT) DLBCL have been reported previously. The preliminary mfIHC results of PCNSL will be presented. Second, mfIHC for multiple B cell biomarkers, CD3, CD4, CD8, CD68, CD163, CD11c, and CD31 were performed for 10 PCNSL validation cases, 24 PT-DLBCL and 451 systemic DLBCL tissues (unpublished). Third, RNA samples were extracted and sequenced for the targeted 1408 cancer-associated genes, successfully in 142 PCNSL cases, including 102 cases evaluated by either of these two mfIHC panels and additional 40 PCNSL cases, Results: First, in the first large mfIHC cohort, PCNSLs compared with de novo systemic nodal or extranodal DLBCL had significantly higher mean/median CD56+ cell densities whereas lower T cell densities (consistent with the immune privilege), as well as lower CD45RO+, PD-1+, and FOXP3+ percentages in T cells whereas higher CD4¯CD8¯ double-negative percentages in T cells. Prognostic analysis in the PCNSL cohort showed that high CD56+ cell densities and high CD45RO+CD8+ T cell densities were associated with significantly poorer and better patient survival, respectively, which are opposite to their prognostic effects in systemic DLBCL as previously reported. Twelve patients had very high PD-L1 expression in B cells and significantly poorer survival in the PCNSL cohort. Second, as validation, the 10 PCNSL cases in the second mfIHC study showed significantly less T cells than systemic DLBCL and PT-DLBCL cases, and low CD8 T cell densities and having low percentage of CD8 T cells adjacent to tumor cells were associated with significantly poorer survival. Immunofluorescence landscapeand spatial analysisrevealed significant differences in immune privilege between PCNSL and PT-DLBCL. Third, gene expression profiling analysis by targeted RNA-seq identified 282 significantly differentially expressed genes between PCNSL and systemic DLBCL, referred to as the PCNSL signature. Unsupervised clustering analysis divided the PCNSL cohort into two clusters, which had no significant difference in MYD88 mutation frequencies analyzed at the mRNA level. Importantly, the cluster with higher expression of many neural glial genes in the PCNSL signature had significantly poorer survival, which remained significant in multivariate analysis adjusting for clinical factors and/or treatments, two PCNSL subcohorts (as training and validation cohorts), and methotrexate-treated patients. NCAM1 (Neural Cell Adhesion Molecule 1, encoding CD56) was among the upregulated PCNSL signature genes, explaining the poorer prognosis associated with higher CD56+ cell densities in PCNSL by the mfIHC analysis. Summary: Our studies represent the largest immunophenotypic and gene expression profiling studies currently in PCNSL, a rare type of primary DLBCL of immune-privileged sites. Multiplex immunofluorescence revealed the immune landscape in PCNSL in comparison with systemic and testicular DLBCL, and identified prognostic immune biomarkers. Targeted RNA-seq identified a PCNSL gene signature enriched with neuronal-glial genes and showing significant prognostic effect in PCNSL. These novel findings in the PCNSL microenvironment warrant further studies.

BACKGROUND ELRA is a humanized, BCMA/CD3 bispecific antibody. In the phase 2 registrational MagnetisMM-3 (MM-3) trial, SC ELRA given as 2 step-up priming doses (12 mg on day 1 and 32 mg on day 4 of cycle 1) followed by 76 mg QW in patients (pts) with RRMM naive to BCMA-directed therapy resulted in an ORR of 61.0%. With a median follow-up of 28.4 mos, the median DOR, PFS, and OS were not reached (NR; 2-year rate, 66.9%), 17.2, and 24.6 mos, respectively. Overall, 56.3% of pts had CRS (grade 2, 14.3%; no grade ≥3). Most events occurred after doses 1 (44.5%), 2 (20.2%), and 3 (5.9%); 0.8% (1 pt) had CRS with doses ≥4. Recurrent CRS occurred in 15.1% of pts. The phase 1/2 MagnetisMM-9 (MM-9; NCT05014412) study is examining an alternative priming regimen and longer dosing intervals of ELRA. Here, we present updated MM-9 results. METHODS In MM-9, pts with RRMM and disease refractory to ≥1 IMiD drug, ≥1 PI, and ≥1 anti-CD38 antibody were given SC ELRA as step-up priming doses of 4 and 20 mg on Day 1 and Day 4 of Cycle 1, respectively. After the priming doses, ELRA 76 mg was given QW for the next 6 cycles (Part 1) or for 1 cycle followed by 116 (dose level 1 [DL1]) or 152 (dose level 2 [DL2]) mg Q2W for the next 5 cycles (Part 2A). After 6 cycles, the dosing frequency was decreased from QW to Q2W (Part 1) or from Q2W to Q4W (Part 2) in pts who achieved ≥PR lasting ≥2 months. The recommended phase 2 dose from Part 2A (152 mg, DL2) was evaluated in Part 2B (dose expansion). The primary endpoint for both parts is grade ≥2 CRS rate per ASTCT criteria during Cycle 1. Secondary endpoints include evaluation of efficacy and adverse events. Data cutoff: February 13, 2024. RESULTS Overall, 85 pts (median age, 64.0 y) were treated with ELRA. The majority (72.9%) of pts had R-ISS stage I/II disease (23.5% with R-ISS stage III); 31.8% had high-risk cytogenetics. Median number of prior lines of therapy was 5.0 (range, 1-12). The median treatment duration was 8.6, 2.9, 1.4, and 3.3 mos, in Part 1, Part 2A DL1, Part 2A DL2, and Part 2B, respectively. Median follow-up for pts overall (n=85), in Part 1 (n=33), Part 2A DL1 (n=12), Part 2A DL2 (n=11), and Part 2B (n=29) was 10.4, 23.3, 16.5, 15.2, and 9.3 mos, respectively. Overall, the ORR was 58.8%. For pts in Part 1, Part 2A DL1, Part 2A DL2, or Part 2B, ORR was 66.7%, 58.3%, 36.4%, and 58.6%, respectively; median DOR was NR (9-mo rate: 86.4%), 10.8 mos (9-mo rate: 80.0%), NR (9-mo rate: 100.0%), and NR (9-mo rate: 84.8%); median PFS was 17.1 (9-mo rate: 62.8%), 11.6 (9-mo rate: 50.9%), 1.6 mos (9-mo rate: 40.0%), and NR (9-mo rate: 57.1%); median OS was NR (9-mo rate: 75.8%), 17.4 mos (9-mo rate: 66.7%), NR (9-mo rate: 60.0%), and NR (9-mo rate: 72.4%), respectively. For pts in Part 1, Part 2A DL1, Part 2A DL2, and Part 2B, grade ≥2 CRS rates during Cycle 1 were 15.2%, 16.7%, 27.3%, and 6.9%, respectively. For pts in Part 1, Part 2A DL1, Part 2A DL2, and Part 2B, CRS rates were 30.3%, 33.3%, 36.4%, and 24.1% after dose 1, 27.3%, 25.0%, 36.4%, and 24.1% after dose 2, 15.2%, 33.3%, 27.3%, and 20.7% after dose 3, 6.1%, 8.3%, 0%, and 3.4% after dose 4, and 6.1%, 16.7%, 9.1%, and 0% after doses ≥5. Recurrent CRS occurred in 18.2%, 33.3%, 18.2%, and 17.2% of pts in Part 1, Part 2A DL1, Part 2A DL2, and Part 2B. The most common (>60%) TEAEs (any grade/grade ≥3) were hematologic TEAEs (Part 1, 75.8%/75.8%; Part 2A DL1, 83.3%/83.3%; Part 2A DL2, 81.8%/81.8%; Part 2B, 79.3%/69.0%), infections (Part 1, 78.8%/48.5%; Part 2A DL1, 83.3%/66.7%; Part 2A DL2, 72.7%/63.6%; Part 2B, 62.1%/37.9%), and CRS (Part 1, 60.6%/0%; Part 2A DL1, 83.3%/0%; Part 2A DL2, 90.9%/9.1%; Part 2B, 48.3%/0%). Grade 5 TEAEs not including PD were infection (n=4), fall (n=1), subdural hematoma (n=1), and food poisoning (n=1). CONCLUSIONS The 4/20 mg step-up priming regimen and alternative dosing schedules in MM-9 resulted in similar efficacy vs the step-up regimen used in the registrational MM-3 study (12/32 mg). Responses were durable with encouraging PFS and OS with the alternative step up and longer dosing schedule. While the overall safety signals with the alternative step up regimen are similar to those seen with MM-3, the CRS profile differed with more CRS events after each subsequent dose and a higher prevalence of recurrent CRS. Thus, the optimal ELRA step-up regimen remains 12/32 mg from the original regimen in the MM-3 study. In addition, these early results suggest that reducing the dose frequency of ELRA may not compromise efficacy.

Introduction The International Prognostic Scoring System (IPSS) and its revised version (IPSS-R) were developed using datasets from patients (pts) with untreated MDS. The cytogenetic risk groups used in IPSS-R were expanded to 5 groups from the 3 used in IPSS. Among the new groups introduced in IPSS-R is the “very complex” karyotype (VCK) where ≥4 karyotypic abnormalities are seen compared to “complex karyotype (CK)” with only 3 abnormalities. However, the prognostic impact of VCK vs CK, as well as individual cytogenetic abnormalities and TP53 mutation (TP53mut) status within the CK and VCK subgroups in pts with MDS treated with hypomethylating agents (HMAs) has not been well studied. Hence, we analyzed these questions in a large cohort of HMA-treated MDS pts in the icMDS VALIDATE database. Methods The icMDS VALIDATE database contains MDS pts treated with frontline HMA monotherapy or HMA-based combinations from 22 specialized international centers. Pts with unknown HMA type, date of HMA initiation, missing age, missing sex, missing cytogenetic data, bone marrow or peripheral blood blasts ≥20%, or missing survival status were excluded. We performed time-to-event analyses using the Kaplan-Meier method and compared groups by the log-rank test. We measured overall survival (OS) from time of HMA initiation. VALIDATE protocol was exempted, acknowledged, or approved by all centers' IRBs. VALIDATE is supported by an independent grant from Abbvie. Results A total of 1940 pts were included. Median age was 70 (range: 18-99) years and 66% were men. According to IPSS-R cytogenetic risk groups, 1.9% (37) were very good, 43.4% (841) good, 15.5% (301) intermediate, 11.6% (226) poor, and 27.6% (535) very poor. By HMA type, 71% of pts were treated with azacitidine, 14% with decitabine, 6% with HMA and venetoclax, and 9% with another HMA combination. Approximately 28% of pts underwent allogeneic hematopoietic stem cell transplant (alloHSCT). The IPSS-R cytogenetic risk groups had different OS (p<0.001)with median OS (mOS; months [mo], 95% CI) as follows: very good (43.4, 34.7-72.5), good (41.7, 36.4-46.8), intermediate (24.5, 23.1-32.4), poor (24.2, 19.2-28.5), and very poor (13.6, 12.5-14.5). The difference remained significant (p=0.001) after censoring at time of alloHSCT with mOS as follows: very good (40.4, 23.2-64.3), good (24.3, 22.2-26.3), intermediate (19.3, 15.1-22.2), poor (12.2, 10.3-14.8), and very poor (9.1, 8.2-19.7). Interestingly, the difference between mOS for intermediate and poor risk cytogenetics became more apparent after censoring at time of alloHSCT. Next, we compared the outcomes of pts with CK and VCK to non-complex karyotype (NCK) MDS. The mOS for pts with VCK MDS (13.6 mo, 12.5-14.5) was worse compared to pts with CK (19.9 mo, 19.9-16.8; p=0.004) and NCK (36.1 mo, 32.7-37.8; p<0.001) MDS. Among the 1458 pts with available molecular data, more pts with VCK (75%, 330) MDS had a concurrent TP53mut compared to pts with CK (40%, 21; p<0.001) and NCK (7%, 64 p<0.001) MDS. Considering only patients with TP53mut MDS, mOS for pts with VCK (12.2, 11.1-13.9) was worse compared with NCK (24.2, 16-1-53.1; p<0.001) but not with CK (19.9, 9.5-NR; p=0.9); the difference between CK and NCK was not significant (p=0.16). Among pts with TP53 wildtype (TP53WT) MDS, VCK (15.0, 13.2-18.2) had a similar mOS to TP53WT CK (18.8, 12.6-41.1; p=0.19) while both groups had worse mOS compared to TP53WT NCK (33.4, 30.1-37.0) (p=0.01). In a survival analysis of 616 pts with MDS with ≥3 cytogenetic abnormalities, -17/del(17p) (12.8 mo; p=0.009), inv(3)/t(3q)/del(3q) (10.9 mo; p=0.006), and del(7q) (12.1mo; p=0.024), though not -7 (12.6mo; p=0.23), were associated with lower mOS compared to the pts with MDS without these abnormalities (14.3mo). Conclusions Using one of the largest databases of HMA-treated MDS pts, we show that IPSS-R cytogenetic risk categories associate with significantly different survivals among HMA-treated MDS pts, even after censoring at time of alloHSCT. Importantly, VCK MDS was associated with worse mOS compared to CK and NCK MDS but not in pts with a concurrent TP53mut. Among pts with MDS with ≥3 chromosomal abnormalities, having -17/del(17p), inv(3)/t(3q)/del(3q), or del(7q) was associated with worse survival.

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.

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.

Introduction: Progression-free survival (PFS), a common endpoint used in multiple myeloma (MM) trials, is defined as the time to the earliest occurrence of disease progression or death. Disease progression in MM is determined by the International Myeloma Working Group (IMWG) Uniform Response Criteria based on imaging and biomarkers from blood, urine, and bone marrow biopsy testing. In clinical trials, IMWG-recommended assessments are protocol-based. However, in routine care, they are often performed and recorded differently based on a multitude of factors. Algorithms to ascertain progression events using routinely collected biomarker data are important to classify disease progression and align with trial-defined endpoints. The aim of this study was to construct and evaluate an optimized real-world Progression (rwP) algorithm using real-world data (RWD) and demonstrate how biomarker data are captured and used to derive endpoints in routine practice. Method: A cohort of 270 transplant ineligible newly diagnosed MM (NDMM) patients starting on lenalidomide and dexamethasone (Rd) and meeting select MAIA (NCT02252172) trial eligibility criteria were included from the nationwide Flatiron Health electronic health record-derived deidentified database from 2015 to 2023. A rwP algorithm was developed using key IMWG-recommended biomarkers, including serum protein electrophoresis (SPEP), urine protein electrophoresis (UPEP), and serum free light chains (FLCs). The initial baseline value for each biomarker was identified, if available, during either the pre-treatment period (45 days prior through 7 days after first line treatment (1L) start) or the on-treatment period (8 days after 1L start through 1L end). Available biomarkers were followed for disease assessment. If any subsequent lab value during 1L treatment was less than the initial baseline value, the subsequent “on-treatment baseline” value was adopted as the new lowest value; otherwise, the initial value was used as the “on-treatment baseline” value for assessing progression events. Three hierarchies, which describe the order of utilizing key IMWG-recommended biomarkers to define rwP events, were explored, including: i) strict hierarchy (SH) [SPEP > UPEP > FLCs], ii) partial hierarchy (PH) [SPEP = UPEP > FLCs], and iii) no hierarchy (NH) [SPEP = UPEP = FLCs]. The PH option closely resembles the IMWG criteria, with FLCs only used for rwP assessments when no measurable SPEP/UPEP are identified. The NH approach considers all available biomarkers equally and resembles how they are utilized in real-world clinical practice. The feasibility of requiring confirmatory events following the first suggestion of progression was also explored. Assays following the progression event up to the end of 1L were considered as confirmatory progression events if they met IMWG criteria. Results: We applied the rwP algorithm with each hierarchy to all eligible NDMM patients (N = 270). The SH, PH, and NH approaches respectively identified 106 (39.3%), 106 (39.3%), and 123 (45.6%) patients with progression events. Results from the SH and PH approach are consistent likely due to the rarity of UPEP usage in clinical practice. The NH approach captured more progression events because FLCs are used in the presence of measurable SPEP or UPEP, resulting in 73 progression events captured by FLCs in comparison to 32 from other approaches, potentially increasing false-positive capture due to the volatility of FLC results. Among the 106 PH-identified patients who progressed, 84 (79.2%) had IMWG-recommended tests following their progression event, and 74 (69.8%) had their progression confirmed before the end of 1L, with 35 (33.0%) receiving their confirmatory reading within 2 months after progression. These results suggest that requiring confirmatory testing as part of the rwP is feasible, though it may introduce false negatives for patients receiving clinical progression confirmation instead of getting confirmatory labs in routine clinical practice. Conclusion: We present a comprehensive assessment of important design choices for an rwP algorithm for NDMM, including a hierarchy of key assays and the inclusion of confirmatory testing. Further validation of the algorithm with health care provider assessments and the inclusion of bone marrow biopsy and imaging data is important for evaluating the performance of the algorithm in RWD.

Introduction ABBV-383 is a differentiated BCMA x CD3 bispecific antibody (fully humanized IgG4) T-cell engager composed of a bivalent BCMA binding domain with high avidity, a low-affinity CD3-binding domain, and a present but silenced-Fc tail retaining the FcRn binding allowing for an extended half-life and thereby, enabling dosing convenience. ABBV-383 monotherapy has shown promising activity and improved CRS safety profile with modified dexamethasone (Dex) premedication in patients (pts) with RRMM (NCT03933735; Rodriguez et al., JCO 2024;42[suppl 16]:7531). Here, ER and CRS PK/PD analyses supporting the selection of optimal SUD for ABBV-383 are reported. Methods ER-efficacy (N=286) and -safety (N=290) analyses were conducted using logistic regression methodology (R version 4.3.2) combining data from escalation (0.025-120 mg Q3W) and expansion (20, 40, 60 mg Q3W and 60 mg Q4W) cohorts of phase 1 study NCT03933735 and Arm A of phase 1b study NCT05650632 evaluating step-up dose (2 or 4 mg on Day 1) with a full dose (60 mg on Day 4) in pts with RRMM. Pts received modified Dex with full dose in expansion cohorts of 60 mg Q4W and 2/60 mg Q4W. In all other cohorts with or without SUD, pts received low Dex. Based on prior knowledge (JCO 2024;42[suppl 16]:7541), the safety endpoints (CRS: any-grade and ≥ G2) were modeled with Cycle 1 total (unbound + bound to soluble BCMA) Cmax, while objective response rate (ORR) was modeled with free (unbound + partially bound to soluble BCMA) Cavg. CRS ER models included a priori selected Dex (low vs. modified) and SUD (yes vs. no) as predictors. Relevant pt-specific covariates were tested in all models. CRS PK/PD analyses included total PK, IL-6, and CRS data (N=199) from the first 3 cycles of the above phase 1/1b studies. A semi-mechanistic indirect response PK/IL-6 model was developed to correlate total PK and IL-6 (NONMEM 7.5). Maximal IL-6 concentrations were derived using post hoc estimates from the PK/IL-6 model and correlated with CRS events (logistic regression; R version 4.3.2). The models included effects of time-dependent Dex (low vs. modified) and SUD (yes vs. no). The overall modeling approach was assessed by comparing observed and predicted CRS rates. Simulations were conducted for various dosing regimens, including one or two SUD and Dex premedication scenarios to support the selection of the optimal SUD. Results Consistent with clinical observations (separate abstract submission), any-grade CRS model predicted probabilities suggested two key outcomes: 1) premedication with modified Dex improves the CRS safety profile compared to the low Dex (42% vs 69% for 60 mg Q4W); 2) modified Dex with SUD further improves the CRS safety profile of ABBV-383 compared to low Dex with SUD (29% vs 43% for 2/60 mg Q4W). Consistent with prior work, no ER relationship was observed for ≥ G2 CRS (p > 0.05). The ORR model resulted in a predicted probability of 68% ORR (closely matching with overall observed 64% ORR) with no impact of SUD and modified Dex. Only soluble BCMA was selected as a covariate in the ORR ER model. The final semi-mechanistic PK/IL-6 model well captured the observed IL-6 data, and the CRS rates (predicted by the logistic regression models) closely matched with the observed data. The CRS PK/PD analyses findings were consistent with the clinical observations and ER analyses key outcomes 1 and 2. The CRS PK/PD analyses predictions comparing the 1-SUD vs 2-SUD (untested) regimens with modified Dex suggested that 1) among the 2-SUD regimens with modified Dex, the 2/3/60 mg regimen would have the maximum reduction of 4% points in any-grade CRS compared to the 2/60 mg 1-SUD regimen, however, with substantial overlap of confidence intervals and with no decrease in ≥ G2 CRS (< 0.5% point); 2) 4 mg as an intermediate SUD in a 2-SUD regimen would lead to higher any-grade and ≥ G2 CRS rates (~9% and 3% points higher, respectively), compared to the 2/60 mg Q4W regimen. Conclusions ER and CRS PK/PD analyses suggested that modified Dex and SUD improve the CRS safety profile of ABBV-383 with no impact on efficacy (ORR) in pts with RRMM. The CRS PK/PD predictions indicated that implementation of 2-SUDs provide minimal additional or no improvement in CRS safety profile compared to 1-SUD. Overall, the 1-SUD dosing regimen of 2 mg with modified premedication prior to the full dose of 60 mg Q4W showed promising results and can be considered for future evaluation and studies.

Introduction Monoclonal antibodies (MoAbs) directed against CD38 are a mainstay in multiple myeloma (MM). Downregulation of CD38 expression is a resistance mechanism of antigenic escape, however, cell surface expression may return. While this tumor cell plasticity is likely driven by epigenetic mechanisms, it is unknown if MM cells can develop permanent resistance to anti-CD38 MoAb by acquiring genomic events leading to biallelic disruption of CD38 thus precluding re-treatment. Here, we report biallelic loss of CD38 as a recurrent mechanism of resistance, often via convergent evolution where distinct subclones are advantaged towards the same selective pressure. Methods We interrogated two sets of patients (Mayo Clinic; n = 31, Calgary University; n =19) with relapse following anti-CD38 MoAbs. Two additional cases of interest were selected from Heidelberg University. Whole genome sequencing (WGS, 60-100x) or whole exome sequencing (WXS), flow cytometry (flow), and bulk RNAseq were used to validate the effect of genomic events on CD38. Missense mutations predicted to affect CD38 MoAb binding were validated with site-directed mutagenesis of a CD38 plasmid, transduction into K562 MM cells, and CD38 MoAb binding assays. Results The prevalence of biallelic inactivation of CD38 at anti-CD38 MoAb relapse was 6% (3/50). An additional selected biallelic event was noted in the Heidelberg set. Each case is described in detail: MM-19 (Calgary) received daratumumab (Dara), lenalidomide, and dexamethasone (Dex), and then had a second exposure to Dara, following relapse. At this second relapse, WGS was performed on two independent extramedullary disease localizations in the liver. Both samples had unique, large deletions (>3 Mb) on chromosome 4 coupled with additional unique focal deletions involving CD38. Flow confirmed the presence of CD138+/CD38- plasma cell populations in both sites. A second case of convergent evolution was seen in a patient (Mayo) after seventh-line Dara/Len/Dex. WGS revealed a common deletion encompassing CD38. On the remaining allele, one subclone had a structural variation-mediated loss of CD38(cancer cell fraction; CCF 40%) while another harbored an L153H missense mutation (CCF 60%). Flow confirmed presence of two CD138+ clones; one with diminished CD38 expression. L153H was functionally validated to abrogate Dara binding, while maintaining CD38 expression. The third sample was collected after fifth-line Dara and sixth-line Dara/Bortezomib/Dex (Heidelberg) and represents another case of convergent evolution with a common loss of chromosome 4 and two subclones detected by WGS (P98Lfs*12, CCF 39% resulting in biallelic inactivation; R140G, CCF 61%). Bulk RNAseq revealed, in comparison to NDMM from CoMMpass, CD38 expression below the first decile. Notably, the R140G variant reduced binding affinity to Dara but not to Isatuximab (Isa). A fourth case (Mayo) relapsing after 6 months of Dara-based therapy similarly had a focal deletion of CD38 with an L18Sfs*16 frameshift deletion on the remaining allele associated with a 4.35-fold reduction in CD38 expression by RNAseq compared to pre-treatment. Interestingly, in 3/4 cases the CD38-negative clone emerged after a second exposure to anti-CD38 MoAb, suggesting emergence with the first exposure and then selection during the second. One other monoallelic event (C275Y; Heidelberg) was detected post-Isa. Copy number of the alternate allele is not known given targeted sequencing methodology, but the variant was seen to reduce binding affinity to both Dara and Isa. The prevalence of monoallelic loss of CD38 in newly diagnosed MM from MMRF CoMMpass was 7% (50/701) and two patients had mutations in CD38, but there were no cases of biallelic loss suggesting these events are driven by treatment pressure. Conclusion Distinction of the mode of CD38 loss is valuable for predicting outcome of re-challenge to anti-CD38 MoAbs. We see here an estimated 5-10% of anti-CD38 MoAb relapses are characterized by genomic antigen escape. Results here are in line with antigen escape to BCMA- and GPRC5D-directed immunotherapies (Lee et al, Nat Med 2023), suggesting that acquired antigen escape resulting from prolonged exposure to the selective pressures of immunotherapy is a recurrent mechanism of resistance in MM. Moreover, in select cases, non-overlapping resistance mutations provide rationale for switching agents at second exposure.

Introduction: ELA026 is a first-in-class human monoclonal antibody directed against signal regulatory protein (SIRP)α/β1/γ and is under clinical investigation in secondary hemophagocytic lymphohistiocytosis (sHLH). sHLH is a life-threatening hyperinflammatory condition caused by failure to terminate the activation and proliferation of natural killer (NK), T cells and macrophages after an initial immune response. There are no approved therapies for sHLH. With a mortality rate of approximately 50% at 2 months (Lionel et al. 2023), malignancy-associated HLH (mHLH) is the deadliest subtype of sHLH. Cytotoxic, multi-agent chemotherapy (including etoposide) does not address the poor prognosis associated with mHLH (Xie et al. 2013). Directly targeting the pathogenic SIRP(+) myeloid cells and T lymphocytes represents a novel approach to resolving this severe hyperinflammatory condition. Methods: This is an open-label, single-arm, Phase 1b global multicenter study (NCT05416307) evaluating the safety, efficacy, pharmacokinetics, and pharmacodynamics of ELA026 in adult and pediatric patients with newly diagnosed and previously treated sHLH. The study is expanding enrollment to evaluate a fixed-dose regimen consisting of a priming phase of 0.1 mg/kg Day 1 and 0.3 mg/kg Days 2-4, followed by a maintenance phase of 0.5 mg/kg twice weekly beginning on Day 8. ELA026 is administered intravenously, with the option to transition to subcutaneous administration upon hospital discharge. The treatment period is 12 weeks with the option to extend in patients deriving ongoing clinical benefits. Enrollment in this cohort is restricted to frontline settings based on the experience that relapsed/refractory sHLH patients exhibited poor survival even with HLH disease control and died from complications related to severe baseline comorbidities. Response is evaluated using a modified HLH-2004 criteria (Locatelli et al. 2020) and survival is calculated from the time of HLH diagnosis. All patients receive dexamethasone as background therapy and premedication initially. Patients with mHLH may also receive cancer-directed therapies concurrently. Primary pharmacodynamic (PD) effects (monocyte and lymphocyte reduction) and secondary PD effects (C-reactive protein [CRP], ferritin, and sCD25 reduction) were best evaluated and attributed to ELA026 during windows of treatment without concurrent chemotherapy effects. Results: As of July 15, 2024, 12 treatment-naïve mHLH patients have enrolled in all cohorts of the study, with a median age of 47 years (range 21-78). The following malignancies were represented: 7 T-cell lymphoma, 2 DLBCL, 1 AML, 1 Hodgkin lymphoma, and 1 T-cell ALL. In this group, response rate was 100% with 2 mCR and 9 PR by Week 4 and survival was 88% at 2 months (7/8; 4 patients are alive and have not reached 2 months on study). Median survival has not been reached; median follow-up is 2.3 months (range 0.1-15.9 months). In terms of PD effects, monocyte and lymphocyte reduction generally occurred following the first priming dose and ferritin and CRP were reduced by an average of 40% and 50% by Day 6, respectively, for patients with windows of ELA026 treatment without concurrent chemotherapy effects. Study-wide (all patients dosed), treatment-related infusion reactions (~20%) and cytopenias (~30%) were generally manageable with supportive care and dosing modifications. One serious adverse event, a grade 4 infusion reaction, was assessed as related in a relapsed/refractory mHLH patient with acute liver failure and poor hemodynamic reserve. Infection risks are expected for this patient population, which were mitigated with growth factor support and antimicrobial prophylaxis. No deaths were related to study drug. Updated study results will be provided at the 2024 ASH meeting in San Diego. Conclusion: Data suggest ELA026 is well-tolerated to date in sHLH patients and results in a 100% response rate and improved 2-month survival in treatment-naïve mHLH patients. The study is enrolling in an expanded cohort to further assess efficacy in this patient population.