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Evaluation of the novel TMPRSS6 antisense inhibitor sapablursen for treatment of polycythemia vera: Results of the imprssion clinical trial
Palmer, Jeanne , Vachhani, Pankit , Sillar, Jonathan R. , Fleischman, Angela, O’Neill, Caitlin , Jung, Shiangtung W., Ruckle, Jon, Bhanot, Sanjay , Barrett, Terry, How, Jonathan P. , Bose, Prithviraj , Mead, Adam J. , Gerds, Aaron T. , Baker, Ross , Hoffman, Ronald , Yousefi, Keyvan , Mesa, Ruben A.

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 82-82

10.1182/blood-2025-82 Get It

Abstract Background: Polycythemia vera (PV) is characterized by excessive erythrocytosis and elevated hematocrit (Hct), which is associated with increased risk of thrombotic events. Controlling Hct levels (<45%) is a key therapeutic goal to reduce thrombotic events. Sapablursen (ISIS 702843) is a liver-directed, ligand-conjugated antisense oligonucleotide that suppresses transmembrane serine protease 6 (TMPRSS6) to enhance hepcidin production thereby restricting iron availability and reduced erythrocytosis. We are reporting the topline results of the IMPRSSION study (NCT05143957), an ongoing global, open-label phase 2 trial evaluating the safety and efficacy of sapablursen for Hct control and reducing phlebotomy rate in patients with PV. Methods: Eligible patients met 2016 WHO diagnostic criteria for PV, were required to have >3 phlebotomies within six months prior to screening, including >1 phlebotomy in the last 12 weeks. There were no exclusions for HCT prior to randomization. Patients received monthly subcutaneous doses of sapablursen in Cohort A (high dose) or Cohort B (low dose), during a 37-week treatment period. The primary efficacy endpoint was the reduction in the frequency of phlebotomy during the last 20 weeks of the treatment period (Week 17-37) compared to baseline (defined as the mean weekly phlebotomy rate during the six months prior to screening through the first dose of sapablursen). Phlebotomy was performed when Hct levels were ≥45% or at the investigator's discretion, confirmation of Hct was not required for phlebotomy. Serial assessments of serum hepcidin, TSAT and ferritin were conducted. The 10-item Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score (MPN-SAF-TSS) assessed the change in symptoms from baseline to Week 37. Results: Forty-nine (49) patients received at least one dose of sapablursen (full analysis set) in either Cohort A (n=32) or Cohort B (n=17). The median age was 61 years, 40 (82%) were male, and 29 (59%) classified as high risk. The primary endpoint was met at both dose levels. The weekly phlebotomy rate (mean±SD) decreased from baseline of 0.15±0.07 (~7.8/yr) to 0.05±0.09 (~2.6/yr) during the primary endpoint window (Week 17-37) in Cohort A (n=32, p<0.0001; 95%CI, -0.13, -0.07), and from 0.17±0.07 (~8.9/yr) to 0.07±0.07 (~3.6/yr) in Cohort B (n=17, p=0.0001; 95%CI, -0.14, -0.06). The mean MPN-SAF-TSS was reduced at Week 37 by 32% in Cohort A (change from baseline LSM -6.2, p=0.005) and 11% in Cohort B (change from baseline LSM -2.7, p=0.344). The proportion of patients with Hct control (<45%) without phlebotomy from week 17 to 37 in Cohort A and B was 53% (17/32) and 35% (6/17), respectively. Serum hepcidin was increased from baseline values of 0.25±0.6 to 5.05±4.7 nM at Week 13 in Cohort A (p<0.0001) and from 0.68±1.7 to 2.06±3.6 nM in Cohort B (p=0.0142). A sustained low TSAT was observed between Weeks 17-37 (6.0±2.1% and 5.5±2.0% in Cohort A and 8.9±5.0% and 7.0±3.4% in Cohort B). Serum ferritin increased over time from 18±22 ng/mL and 28±58 ng/mL at baseline in Cohort A and B, respectively, to 44±47 ng/mL and 41±85 ng/mL at Week 37, respectively. Sapablursen was generally safe and well-tolerated. The incidence of injection site reactions was 12.2% (6/49). Injection site reactions did not recur following multiple injections, were not progressive and resolved spontaneously. There was one death on study due to transformation to AML which was deemed as not related to the study drug. Conclusions: Treatment of PV patients with sapablursen increased serum hepcidin, controlled Hct, reduced phlebotomy need and improved quality of life in a dose-dependent manner. These findings highlight the potential of sapablursen as a therapeutic approach in PV and support further development.
Updated efficacy and safety results of the Bruton tyrosine kinase (BTK) degrader BGB-16673 in patients with relapsed/refractory chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) from the ongoing phase 1 CaDAnCe-101 study
Ahn, Inhye, Parrondo, Ricardo, Thompson, Meghan, Frustaci, Annamaria, Allan, John, Ghia, Paolo, Mocanu, Irina, Weil, Damien Roos, Tam, Constantine, Stilgenbauer, Stephan, Trotman, Judith, Scarfo, Lydia, Lamanna, Nicole, Zhang, Yanan, Xu, Linlin, By, Kunthel, Fabre, Shannon, Persky, Daniel, Agarwal, Amit, Seymour, John, Ahn, Inhye, Parrondo, Ricardo, Thompson, Meghan, Frustaci, Annamaria, Allan, John, Ghia, Paolo, Mocanu, Irina, Roos-Weil, Damien , Tam, Constantine, Stilgenbauer, Stephan, Trotman, Judith, Scarfo, Lydia, Lamanna, Nicole, Zhang, Yanan, Xu, Linlin, By, Kunthel, Fabre, Shannon, Persky, Daniel, Agarwal, Amit, Seymour, John

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 85-85

10.1182/blood-2025-85 Get It

Abstract Introduction: BTK inhibitors are effective treatments for CLL/SLL; however, treatment intolerance and resistance to BTK inhibitors are major clinical challenges for many patients. BGB-16673 is an orally available protein degrader that blocks BTK signaling by tagging BTK for degradation through the cell's proteasome pathway, leading to tumor regression. CaDAnCe-101 (BGB-16673-101; NCT05006716) is an ongoing open-label, phase 1/2 study evaluating BGB-16673 monotherapy in patients with B-cell malignancies. Here, updated phase 1 safety and efficacy data are reported for patients with relapsed/refractory (R/R) CLL/SLL. Methods: Eligible patients must have confirmed R/R CLL/SLL (≥2 prior therapies), an ECOG performance status of 0-2 (0-1 in the EU), and adequate organ function. In the US, EU, and Australia, patients must have previously received a covalent BTK inhibitor (cBTKi). Patients received BGB-16673 once daily orally. The primary phase 1 objectives were to assess safety/tolerability (NCI-CTCAE v5.0; iwCLL hematologic toxicity criteria) and to establish the maximum tolerated dose and recommended dose for expansion. A secondary objective was to assess overall response rate (ORR) per iwCLL 2018 criteria with partial response with lymphocytosis (PR-L) modification and per 2014 Lugano criteria for SLL, with the first response assessment after 12 weeks of treatment. Results: As of May 23, 2025, 67 patients with CLL/SLL were enrolled and treated (50 mg, n=1; 100 mg, n=22; 200 mg, n=17; 350 mg, n=15; 500 mg, n=12). Patients had a median age of 70 years (range, 47-91 years) and a median of 4 prior lines of therapy (range, 2-10), including cBTKis (n=63 [94.0%]), BCL2is (n=55 [82.1%]), and noncovalent BTK inhibitors (ncBTKis; n=14 [20.9%]). At study baseline, 65.7% (44/67) of patients had CLL/SLL with del(17p) and/or TP53 mutation, 77.6% (38/49) with unmutated IGHV, 38.1% (24/63) with BTK mutation, and 15.9% (10/63) with PLCG2 mutation. Median study follow-up was 18.0 months (range, 0.3-31.0 months); 39 patients (58.2%) remained on treatment at the data cutoff. Overall, 95.5% of patients had any-grade treatment-emergent adverse events (TEAEs); any-grade TEAEs in ≥25% of patients were fatigue (37.3%), contusion/bruising (31.3%), diarrhea (28.4%), and neutropenia (28.4%). Grade ≥3 TEAEs occurred in 62.7% of patients; grade ≥3 TEAEs in ≥5% of patients were neutropenia (23.9%), pneumonia (10.4%), and thrombocytopenia (6.0%). Eight patients (11.9%) had a TEAE leading to dose reduction. TEAEs led to treatment discontinuation in 12 patients (17.9%), three (4.5%) of whom had treatment-related TEAEs (subdural hemorrhage, maculopapular rash, and disseminated aspergillosis). Four patients (6.0%) had TEAEs that led to death (all due to infections, including 1 fungal infection); no deaths were deemed related to treatment. In 66 response-evaluable patients (1 patient on treatment did not reach the first assessment by the data cutoff), ORR (PR-L or better) was 86.4% (n=57), with a 4.5% (n=3) complete response (CR)/CR with incomplete marrow recovery rate. At 200 mg, ORR was 93.8% (15/16), including 1 CR. The median time to first response was 2.8 months (range, 2.0-19.4 months). Thirty-three patients (49.3%) remained on treatment for ≥12 months. Responses deepened over time: of 22 patients with initial PR-L, 15 transitioned to partial response (PR); of 16 patients with initial stable disease, 1 transitioned to PR-L and 10 to PR. Responses were seen in patients previously treated with a cBTKi (53/62 [85.5%]) or ncBTKi (10/14 [71.4%]), with double (cBTKi and BCL2i; 39/42 [92.9%]) and triple exposure (cBTKi, BCL2i, and ncBTKi; 9/12 [75.0%]), with (18/24 [75.0%]) and without (36/39 [92.3%]) BTK mutations, with del(17p) and/or TP53 mutation (35/43 [81.4%]), and with PLCG2 mutation (9/10 [90.0%]). The 12-month progression-free survival rate was 79.2%; 15 patients (22.4%) had progressive disease (2 associated with Richter transformation to diffuse large B-cell lymphoma), and 4 (6.0%) died. Further exploratory analyses will be presented at the meeting.Conclusions: Data from the ongoing CaDAnCe-101 study demonstrate that the novel BTK degrader BGB-16673 has a tolerable safety profile and shows robust and deepening responses in patients with heavily pretreated R/R CLL/SLL, including those with prior BTK inhibitor treatment and BTK mutations. The 200-mg dose of BGB-16673 is being evaluated in phase 2 and 3 studies in patients with R/R CLL/SLL.
DIPSS-R: A revised age-agnostic clinical risk model for chronic phase primary myelofibrosis
Tefferi, Ayalew, Vannucchi, Alessandro, Bashir, Yassin, Abdelrheem, Ahmed, Abdelmagid, Maymona, Loscocco, Giuseppe Gaetano, Signori, leonardo, Borgi, Giulia, Boldrini, Valentina, Begna, Kebede, Reichard, Kaaren, He, Rong, Mendoza, Cinthya, Barbui, Tiziano, Passamonti, Francesco, Pardanani, Animesh, Gangat, Naseema, Guglielmelli, Paola, Tefferi, Ayalew, Vannucchi, Alessandro, Bashir, Yassin, Abdelrheem, Ahmed, Abdelmagid, Maymona, Loscocco, Giuseppe Gaetano, Signori, leonardo, Borgi, Giulia, Boldrini, Valentina, Begna, Kebede, Reichard, Kaaren, He, Rong, Mendoza, Cinthya, Barbui, Tiziano, Passamonti, Francesco, Pardanani, Animesh, Gangat, Naseema, Guglielmelli, Paola

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 84-84

10.1182/blood-2025-84 Get It

Abstract Background: The International Prognostic Scoring System (IPSS; Cervantes et al. Blood 2009;113) and dynamic IPSS (DIPSS; Passamonti et al. Blood 2010;115:1703) were developed about 15 years ago, based on 5 clinical risk factors: age >65 years, hemoglobin <10 g/dl, white blood cell count (WBC) >25 x 109/L, peripheral blood (PB) blasts ³1%, and constitutional symptoms. DIPSS-independent genetic risk factors have since been incorporated into molecular risk models with higher predictive accuracy (Guglielmelli et al. JCO 2018;36:310; Tefferi et al JCO 2018;36:1769). Because of its accessibility, DIPSS is often preferred for use in patient selection for clinical trials. The objective of the current study was to revise DIPSS by incorporating new and refined clinical risk variables and excluding those that are subjective (e.g., symptoms) or could exaggerate the need for therapy for older adults (e.g., age). Methods: Diagnostic criteria were according to the International Consensus Classification (Arber et al. Blood 2022; 140:1200). Severity of anemia was adjudicated by the Revised International Working Group-European LeukemiaNet criteria (Blood 2024; 144:1813). Receiver operating characteristic curve analysis was utilized to determine the optimal cutoff points for age, WBC, PB blast percentage, absolute monocyte count (AMC), and platelet count. Data were collected retrospectively corresponding to the time of first referral, which, in the majority of cases, coincided within one year of initial diagnosis and before initiation of cytoreductive therapy. Survival analysis was censored for allogenic stem cell transplantation (ASCT). Time-specific AUC was computed at pre-defined landmark time points and used to compare model performance between DIPSS and the revised model (DIPSS-R). Results: The discovery cohort from the Mayo Clinic included 1,073 patients (median age 65 years; 61% males) and the validation cohort from Italy 635 patients (median age 63 years; 60% males). In the discovery cohort, median follow-up (% deaths, AML, ASCTs) was 45 months (49%, 10%, 17%) and in the validation cohort 60 months (42%, 11%, 5%). In univariate analysis, the following correlated with inferior survival, in both the discovery and validation cohorts, with significance confirmed by multivariable analysis (MVA) in the discovery cohort: severe anemia (transfusion-dependent or hemoglobin level <8 g/dL in women or <9 g/dL in men), moderate anemia (hemoglobin level 8 to <10 in women or 9 to <11 in men), marked leukocytosis (WBC ≥25 x 109/L), moderate leukocytosis (WBC 11 to <25 x 109/L), age >65 years, PB blast ≥2%, AMC ≥1 x 109/L, platelet count <150 x 109/L, constitutional symptoms, and male sex. After excluding age, sex, and constitutional symptoms, MVA-derived HRs (95% CI) were 3.5 (2.8-4.4) for severe anemia, 2.0 (1.5-2.5) moderate anemia, 2.4 (1.8-3.3) marked leukocytosis, 1.5 (1.2-1.9) moderate leukocytosis, 1.7 (1.4-2.1) PB blast ≥2%, 1.5 (1.2-2.0) AMC ≥1 x 109/L, and 1.5 (1.2-1.8) platelet count <150 x 109/L. An HR-weighted risk model was subsequently developed (Figure 1) and validated (Figure 2) using the discovery and validation cohorts, respectively: low risk (0 points; N=205; median survival 226 months), intermediate-1 risk (1 point; N=253; 131 months), intermediate-2 risk (2-3 points; N=457; 62 months), and high risk (4-7 points; N=153; 31 months); the corresponding median survival estimates in the validation cohort were “not reached”, 205 months, 96 months, and 44 months (inter-risk category p values <0.01 in all instances). Ten-year predictive accuracy was comparable between DIPSS-R (AUC 0.78) and DIPSS (AUC 0.78), despite the exclusion of age and constitutional symptoms, as risk variables, from the revised model. Furthermore, predictive performance was superior for DIPSS-R vs. DIPSS when analysis was stratified by age: >65 years (AUC 0.77 vs. 0.74) and ≤65 years (AUC 0.71 vs. 0.66). MVA that included high (ASXl1, SRSF2, U2AF1) and low (CALR type 1/like) risk mutations, karyotype, and DIPSS-R variables showed independent prognostic contribution from all except thrombocytopenia (p=0.2; Figure 3). Conclusion: DIPSS-R utilizes disease-related, as opposed to host-related, predictors of survival whose prognostic contribution was independent and complementary to genetic risk factors. The model preserves global applicability and allows for a more accurate assessment of disease severity for practice and research purposes.
Phase 1 study of ktx-1001, a first-in-class oral MMSET/NSD2 inhibitor, demonstrates clinical activity in relapsed/refractory multiple myeloma
Usmani, Saad, Bories, Pierre, Gasparetto, Cristina, Dingli, David, Lonial, Sagar, Siegel, David, Yee, Andrew, Varga, Cindy, Trudel, Suzanne, Dachs, Laura Rosiñol, Rodriguez-Otero, Paula, Manier, Salomon, Berdeja, Jesús, Afrough, Aimaz, Baker, Warren, Hasheminasab, Seyed Alireza, Thakurta, Anjan, Sridharan, Vinidhra, Flynt, Erin, Barnett, Miriam, Versmee, Laura, Mateos, María-Victoria, Touzeau, Cyrille, Chung, Alfred, Roy, Vivek, Stadtmauer, Edward, Usmani, Saad, Bories, Pierre, Gasparetto, Cristina, Dingli, David, Lonial, Sagar, Siegel, David, Yee, Andrew, Varga, Cindy, Trudel, Suzanne, Dachs, Laura Rosiñol, Rodríguez‐Otero, Paula , Manier, Salomon, Berdeja, Jesús, Afrough, Aimaz, Baker, Warren, Hasheminasab, Seyed Alireza, Thakurta, Anjan, Sridharan, Vinidhra, Flynt, Erin, Barnett, Miriam, Versmee, Laura, Mateos, María-Victoria, Touzeau, Cyrille, Chung, Alfred, Roy, Vivek, Stadtmauer, Edward

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 250-250

10.1182/blood-2025-250 Get It

Abstract Background Translocation of chromosomes 4 and 14 (t(4;14)) results in overexpression of MMSET and has been associated with poor clinical outcomes in patients (pts) with multiple myeloma (MM). KTX-1001 is a first-in-class, potent, and selective oral inhibitor of MMSET (also known as NSD2) developed as the first investigational therapy to directly target the high-risk t(4;14) translocation, a key molecular driver in MM. KTX-1001 binds to and inhibits the catalytic SET domain of MMSET, thereby suppressing the deposition of dimethylated histone H3 lysine 36 (H3K36me2), leading to downregulation of oncogenic histone modifications and epigenetic reprogramming of malignant plasma cells. Preclinically, KTX-1001 synergistically inhibited cell viability in MM cell lines when combined with a proteasome inhibitor (PI), immunomodulatory drug (IMiD), or cereblon E3 ligase modulator (CELMoD™). Preliminary findings were previously reported from the initial cohort of 18 pts enrolled in a first-in-human phase 1 trial evaluating KTX-1001 in relapsed/refractory multiple myeloma (RRMM; NCT05651932; Bories et al. Blood. 2024;144[Suppl 1]:3370). Here, we present updated results from this study. Methods RRMM pts who received ≥3 prior therapies, including PI, IMiD and anti-CD38 monoclonal antibody (anti-CD38 mAb), received oral KTX-1001 across 9 dose levels using a 3+3 dose-escalation design. Primary objective was to determine the recommended Phase 2 dose (RP2D) and the maximum tolerated dose (MTD). Secondary objectives included pharmacokinetics, pharmacodynamics (PD), and primary efficacy. The dose expansion phase has been initiated to evaluate KTX-1001 in combination with either carfilzomib or the investigational CELMoD™ mezigdomide in t(4;14) RRMM pts. Results As of 13 June 2025, 40 pts have been treated in the monotherapy dose-escalation phase. The maximum tolerated dose (MTD) was exceeded due to dose-limiting toxicities (DLTs) in 2 pts: two Grade (Gr) 4 thrombocytopenia and one Gr 3 epistaxis. Backfill at selected dose levels is ongoing to further characterize safety profile and refine dose optimization. The median time from initial MM diagnosis was 8 years (range:2-20) with a median of 6.5 prior lines of therapy (range: 3-25). This included stem cell transplant (70%), BCMA CAR-T (42.5%), and non-CAR-T BCMA targeted drugs such as antibody-drug conjugates and bispecific antibodies (57.5%). The median age was69 years (range:50-83); 21 were female and 19 were male. Extra-medullary disease was present in 13 (32.5%) pts. Nineteen (47.5%) pts had t(4;14) translocation, 5 (12.5%) had 1q21 gain and 4 (10%) had deletion 17p. A total of 16 (40%) pts have shown a treatment response according to IMWG criteria or have achieved stable disease: 1 VGPR (10+ months), 1 PR (4+ months), 2 MR (3+ and 12 months), 12 SD (2-20+ months). KTX-1001 has demonstrated a favorable tolerability profile. Grade 3 or higher treatment-emergent adverse events (TEAEs) were reported in 31 (77.5%) pts. The most frequent (≥20% pts) Gr 3/4 TEAEs were thrombocytopenia in 12 pts (30%; grade 4 in 8 [20%]), neutropenia in 12 pts (30%; febrile neutropenia in 2 [5%]), anemia in 10 (25%) pts. Gr 3 infections were observed in 5 (12.5%) pts and fatigue in 5 (10%) pts. The main reason for treatment discontinuation was progressive disease (57.5%), other pts discontinued due to physician decision (5%), consent withdrawal (5%), and one pt due to adverse event. Twelve (30%) pts remain on treatment. At Cycle 1 Day 15, drug exposure and steady-state concentrations of KTX-1001 increased with dose. A dose-dependent reduction in H3K36me2, the primary PD marker of KTX-1001 activity, was observed in peripheral blood at Cycle 2 Day 1 and beyond, which plateaued above dose-level 4. Paired bone marrow samples further confirmed on-target PD effects, with a marked reduction in H3K36me2 levels in MM cells at Cycle 2 Day 1 with observed anti-MM effect of reduced proliferation of MM cells with concomitant increased proliferation in immune cells in pts achieving clinical benefit. ConclusionsKTX-1001 is a novel agent showing tolerable safety profile in RRMM and demonstrating promising single agent activity in heavily pretreated, triple class refractory RRMM including those with high-risk features. KTX is currently evaluated in ongoing study in combination with carfilzomib and the investigational CELMoD™ mezigdomide in t(4;14) RRMM pts.
The use and safety of peripheral intravenous catheters (PIV) vs central venous catheters (CVC) for lymphoma patients receiving frontline anthracycline-based chemotherapy: A large multicenter real-world analysis (RWA)
Glennan, Patrick, Nedved, Adrienne, Lukowski, Joseph , Minhaj, Adeeb A., Sanjurjo, Alexander , Harbhajan, Melinda, Norrell, Jacqueline , Mubeen, Suhaym , St‐Pierre, Frédérique , Kindl, Gabriel, Patel, Keem, Adewale, Olutobi, Allen, Harris, Luyten, Sophia, Dasari, Srilatha, Martin, Peter W., Lunning, Matthew A. , Nowakowski, Grzegorz S. , Tiger, Yun Kyoung , Sanjurjo, Alexander Daniel , Mubeen, Salmaan, Kindl, Gabriel, Adewale, Olutobi, Allen, Harris, Omer, Zulfa , Martin, Peter, Tolu, Seda , Casulo, Carla , Evens, Andrew M.

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 518-518

10.1182/blood-2025-518 Get It

Abstract Background: Given a potential risk of extravasation with vesicants and irritants, central venous catheters (CVCs), such as port-a-cath or peripherally inserted central catheters (PICC), are commonly used for the administration of anthracycline-based chemotherapy. However, CVC placement can result in treatment delay, deep vein thrombosis (DVT), catheter malfunction, and added burdens (eg, financial, travel, etc), partly due to the need for regular flushing. Peripheral intravenous (PIV) access is often utilized in the academic setting with select frontline chemotherapy regimens. However, there is limited data reporting on the safety of PIV in this setting. This large, multicenter RWA evaluated the use and associated complications of PIV and CVC for administering CHOP- or ABVD-based chemotherapy in patients (pts) with lymphoma. Methods: We conducted a retrospective RWA across 8 U.S. centers among pts aged ≥18 years with non-Hodgkin lymphoma and Hodgkin lymphoma who were consecutively treated with ABVD or CHOP-based anthracycline chemotherapy via PIV or CVC access between 2010-2024. Choice of catheter placement was at the discretion of the pt's treating physician. Detailed baseline and safety data were collected. The primary outcome was extravasation; secondary outcomes included infiltration, DVT, cellulitis, erythema, and pain. Standard definitions of extravasation and other complications were used (Jackson-Rose J. CJON 2017). Rates of complications were compared via Fischer exact testing. Results: A total of 1,414 pts were included in the analysis: 790 in each arm (ie, PIV vs CVC). Of these, 624 were unique to each group, while 166 pts received chemotherapy via both modalities (PIV and CVC during the treatment course). Overall, 78.9% of pts completed all treatment as planned via PIV. Median age was 63 years (IQR 45–75) in the PIV group and 61 years (IQR 40–73) in the CVC group. Male sex comprised 57% vs 51%, ECOG 0–1 performance status was 83% vs 76%, and advanced-stage disease (stage III/IV) was present in 51% vs 62%, respectively. Lymphoma subtypes were comparable: DLBCL/high-grade/B-cell NOS (54.5% vs 56.1%), Hodgkin lymphoma (27.2% vs 27.5%), T-cell lymphoma (12.4% vs 6.6%), and indolent/mantle cell lymphoma (5.6% vs 6.7%). Among those receiving chemotherapy via CVC, 78.5% were treated through a port-a-cath and 21.5% via PICC. CHOP-based and ABVD-based regimens were administered to 68% and 32% of PIV pts, and 69.6% and 30.4% of CVC pts, respectively. A total of 4,084 (PIV) vs 3,859 (CVC) treatment cycles were delivered, corresponding to 4,347 (PIV) vs 4,884 (CVC) anthracycline infusion days. There was 1 documented case of extravasation in the CVC group and 2 suspected cases in the PIV group (p=0.9); for PIV, this translates to a per pt risk of 0.3% (or 0.05% of infusion days). The two PIV cases involved elderly women with DLBCL receiving CHOP. Both developed localized symptoms post-infusion and were treated conservatively (DMSO/warm compresses or dexrazoxane/ice), with full symptom resolution within 1 week and 1 day, respectively. No tissue or vascular injury occurred. Additionally, there were no significant differences between the PIV and CVC groups in the rates of induration/swelling (1.8% vs 2.0%, p=0.85), phlebitis/cellulitis (2.4% vs 2.4%, p=0.9), venous thromboembolism (VTE; 1.4% vs 2.0%, p=0.32), or erythema (3.8% vs 5.1%, p=0.27). Pain or tenderness at the infusion site (8.5% vs 2.9%, p=0.001) and infiltration (1.4 vs 0.13%, p=0.006) were more frequent in the PIV group. Chronic vascular complications related to prior VTE was slightly lower in the PIV group (0.13% vs 0.9%, p=0.06), but not significant. Additional details from a propensity score-matched analysis will be presented at the meeting. Conclusions: This is the largest known analysis to date evaluating the safety of PIV access for anthracycline-based chemotherapy in >1,500 lymphoma pts over a recent 15-year period, representing >9,000 total treatments with CHOP or ABVD. PIV access was found to be safe and associated with a low rate of serious complications. Moreover, extravasation was rare and there was not a significant difference observed between PIV and CVC use. While PIV use was associated with higher rates of local pain/tenderness and infiltration, the events were uncommon and self-limited. Despite the widespread default to CVC placement in many centers, these findings support the selective use of PIV in appropriate pts as elucidated here.
External validation of TTP-14: A novel machine learning model that improves rapid diagnosis of immune TTP
Abou-Ismail, Mouhamed Yazan, Sridharan, Meera, Zhang, Chong, Kouides, Peter, Lim, Ming, Abou-Ismail, Mouhamed Yazan, Sridharan, Meera, Zhang, Chong, Kouides, Peter, Lim, Ming

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 850-850

10.1182/blood-2025-850 Get It

Abstract Background Due to the high mortality of immune thrombotic thrombocytopenic purpura (iTTP), rapid clinical evaluation and early intervention are crucial. The PLASMIC score remains a valuable and widely used tool for predicting severe ADAMTS13 deficiency. However, recent studies have shown variable performance across different populations. In addition, its variables may often be missing during initial presentation. Refining the accuracy of early iTTP evaluation could improve timely recognition and treatment, while reducing unnecessary interventions in those eventually ruled out for iTTP. Machine learning advancements offer several advantages for enhancing clinical prediction models: the ability to assess continuous variables, capture complex interactions between them, and handle missing data. We previously utilized XGBoost (extreme gradient boosting) to develop a novel machine learning tool, TTP-14, which improved upon the PLASMIC score's predictive performance in repeat 10-fold cross-validation achieving an AUC of 0.91 (Blood. 2024;144[Suppl 1]:2617). TTP-14 generates a predicted probability for iTTP, expressed as a continuous percentage estimate of iTTP diagnostic likelihood, and is also able to do so with missing variables. However, it has not previously been externally validated. Objectives To externally validate the ability of TTP-14 to predict iTTP diagnosis and improve upon the PLASMIC score. Methods We performed an external validation of TTP-14 using an independent cohort of patients with suspected iTTP at the Mayo Clinic. These patients were not part of the original multi-center development cohort of 106 iTTP patients from the University of Utah, Case Western Reserve University, Rochester Regional Health, and University of Illinois. For the validation cohort, we identified patients who underwent ADAMTS13 activity testing between 2010 and 2025 for evaluation of thrombotic microangiopathy at the Mayo Clinic. iTTP was defined as ADAMTS13 activity <10%, and controls as ADAMTS13 activity >20%. TTP-14 variables were collected at initial presentation: platelet count, lactate dehydrogenase, creatinine, international normalized ratio, reticulocyte percentage, active cancer, indirect bilirubin, mean corpuscular volume, total bilirubin, haptoglobin, neurologic deficit, hemoglobin, age, and history of transplant. Receiver operating characteristic curve (AUC) was reported with 95% confidence intervals (CI). While the model provides a continuous estimate and is not categorical, we evaluated clinically meaningful probability thresholds to illustrate performance in decision-relevant zones. Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were reported at these select thresholds and analyzed for patients with and without missing variables. Result We included 50 iTTP patients and 56 controls in the external validation cohort. 13 patients had missing PLASMIC variables. TTP-14 achieved an AUC of 0.96 (95% CI: 0.93–0.99), outperforming the PLASMIC score's AUC of 0.90 (95% CI: 0.83–0.96) in the same dataset, and improving upon TTP-14's previously reported cross-validated AUC of 0.91 (95% CI: 0.90–0.92) in the development cohort. Among patients with complete data (n = 93), applying select thresholds for clinical relevance demonstrated: Low risk cut-off (<5% predicted iTTP risk): Sensitivity = 98% Specificity = 71% PPV = 76% NPV = 97% Accuracy = 84% High risk cut-off (≥50% predicted iTTP risk): Sensitivity = 71% Specificity = 98% PPV = 97% NPV = 78% Accuracy = 85% In the full cohort (n = 106) that included those with missing PLASMIC variables, TTP-14 maintained excellent predictive performance with AUC = 0.95 (95% CI: 0.92–0.99). Performance metrics analyzed using the above thresholds also yielded similar results. Conclusion External validation of TTP-14 demonstrated high predictive accuracy for iTTP diagnosis (AUC = 0.96). TTP-14 outperformed the PLASMIC score in the validation cohort (AUC = 0.96 vs 0.90, respectively). TTP-14 offers more flexibility than the PLASMIC score by generating predictions even with incomplete data, and maintained excellent performance in the cohort that included those with missing variables (AUC = 0.95) Its refined accuracy and ability to predict iTTP despite missing data provide a key advantage, offering an alternative tool to improve rapid iTTP diagnosis. TTP-14 may help enhance early recognition and treatment of iTTP while reducing unnecessary interventions in non-TTP patients.
Aplastic anemia in pregnancy: A case series review of hematologic parameters, treatment, and maternal-fetal outcomes
Jabbouri, Selma EL, Go, Ronald S.

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 1422-1422

10.1182/blood-2025-1422 Get It

Abstract Introduction: Aplastic anemia (AA) affects approximately 1 in a million people per year in the United States and can present as a new diagnosis, progression, or relapse during pregnancy. Due to the rarity of the disease, there are limited data on its clinical presentation, hematologic parameters, treatment strategies, and maternal-fetal outcomes to guide diagnosis and management. Methods: We conducted a comprehensive literature review using PubMed, Google Scholar, and ScienceDirect to identify peer-reviewed studies published between 2001 and 2024. Articles were selected based on relevance and availability of clinical outcome data. We included cases of AA that were active during pregnancy—newly diagnosed, relapsed, or persistent. Data collected included patient demographics (age, sex), AA status (blood counts, disease severity, timing of presentation, management, and complications), fetal outcomes (gestational age and mode of delivery), and birth complications. Results: A total of 53 cases of AA during pregnancy were identified. Of these, 12 were diagnosed during pregnancy and 11 prior to pregnancy. For the 12 cases that developed during pregnancy, diagnoses were made across all trimesters: first (n=6), second (n=4), and third (n=2). Notably, in one patient, AA was active during the third and fourth pregnancies but not during the first or second, suggesting that AA can present intermittently across pregnancies in the same individual. The timing of diagnosis was unspecified in the remaining 30 cases. The median maternal age at AA diagnosis was 26.5 years (range: 19–38), and the median gestational age at birth was 37 weeks (range: 31–40). Among cases where timing was reported, 21% were diagnosed before pregnancy and 23% during pregnancy. Severity was reported in all 53 cases: 72% were classified as non-severe, 26% as severe, and 2% as very severe. Cesarean section was the primary delivery method in 66% of cases. At the time AA was diagnosed or active during pregnancy, median laboratory values were: hemoglobin 7.3 g/dL (range: 3.0–11.8), platelet count 26 × 10⁹/L (range: 8.0–103), and absolute neutrophil count 1.0 × 10⁹/L (range: 0.4–4.0). Maternal and fetal outcomes were reported in 60% and 59% of cases, respectively. Maternal complications included gestational hypertension (6%), gestational diabetes mellitus (6%), infections (23%), and bleeding (26%). Fetal outcomes were generally favorable, with approximately 57% of infants reported as healthy at birth. However, adverse outcomes such as preterm delivery (19%), intrauterine growth restriction (6%), low birth weight (6%), and neonatal intensive care unit admission (9%) were also observed. Maternal and fetal mortality occurred in 4% and 2% of cases, respectively. Treatments administered during pregnancy included red blood cell transfusions (17%), platelet transfusions (17%), and cyclosporine (15%). In the postpartum period, some patients required additional therapies: antithymocyte globulin (4%), eltrombopag (6%), and hematopoietic stem cell transplantation (8%). Conclusion: Aplastic anemia during pregnancy remains rare and clinically complex, with variable timing, severity, and outcomes. Our review underscores the need for early recognition and multidisciplinary management to reduce risks to both mother and fetus. The observation that AA may occur in some pregnancies but not others within the same individual raises important questions about underlying disease mechanisms. Broader, systematic studies are needed to clarify these patterns and to inform safer, more effective treatment strategies during pregnancy.
Comparison of real-world survival outcomes and time toxicity of CAR T-cell versus bispecific antibody therapies in relapsed/refractory follicular lymphoma: A multicenter cohort from 15 US academic institutions
Abbott, Diana, Amorim, Ana , Houshyar, Samin , Adhikari, Arjab, Patel, Dilan A. , Wanjiku, Christopher, Bock, Allison M. , Any, Haya Al, Desai, Nidhi , Gupta, S. C. , Altomare, Nicole , Trotier, Daniel, Ricker, Edd , Hill, Brian T. , Gupta, Supriya , Major, Ajay , Abbott, Diana , Snyder, Jordan Andrew , Ahmed, Nausheen , Villasboas, José C. , Sharp, John, Voorhees, Timothy , Wallace, Danielle, Wagner, Charlotte B , Brooks, Taylor , Tsang, Mazie , Rajab, Mohamed , Iqbal, Madiha , Gupta, Supriya, Karmali, Reem , Pophali, Priyanka A. , Cherng, Hua‐Jay J. , Gupta, Arjun

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 1798-1798

10.1182/blood-2025-1798 Get It

Abstract Background Chimeric antigen receptor T-cell (CAR-T) and bispecific antibody (BsAb) therapies are both effective for patients with relapsed/refractory (R/R) follicular lymphoma (FL), but differ in treatment schedules and associated “time toxicity,” or contact days spent physically interacting with the healthcare system. While contact days can be estimated from clinical trials, real-world data provides a more nuanced depiction of treatment-related time burden, which may guide treatment decision-making. The comparative time toxicity of CAR-T vs BsAb in R/R FL is not defined. Methods We conducted a multicenter retrospective study of adults with R/R grade 1-3A FL who received standard-of-care CAR-T (axi-cel, tisa-cel, liso-cel) or BsAb (mosunetuzumab, epcoritamab) in the third-line or later setting before Jan 1, 2025. Time toxicity was defined as outpatient or inpatient days with physical health care system contact, counting multiple visits on the same day as only one day. All days after treatment initiation were counted, regardless of disease progression, therapy completion, or relation to FL therapy. Median contact days over 1-year time horizon were compared, stratified by CAR-T vs BsAb, prior lines of therapy (LOT, 2 vs 3+), and time intervals (0-1, 1-3, 3-6, 6-9, and 9-12 months). Progression-free survival (PFS) and overall survival (OS) were calculated from day of CAR-T infusion or day 1, cycle 1 for BsAb. Cox regression and propensity matching (by age, ECOG, refractory to prior LOT, POD24) were used to assess predictors and survival associations with contact days. Results Among 209 patients from 15 U.S. academic centers, median age was 64, 37% were female, 61% received CAR-T (80% axi-cel, 7% liso-cel, 13% tisa-cel) and 39% BsAb (93% mosun, 7% epcor). Most had Grade 1-2 FL (72%), advanced stage (84%), and extranodal disease (51%). Median prior LOT was 3 (range 2-15), 41% were refractory to prior LOT, and 52% had POD24. Median number of BsAb doses was 10 (range 1-36). Patients receiving BsAb were significantly older (p<.01) and had higher CIRS comorbidity scores (p<.02) in both 2 and 3+ prior LOT cohorts, and had higher ECOG scores (p=.01) and were less likely to be refractory to prior LOT (p=.029) in 3+ LOT cohort. There were no differences in POD24 rates between CAR-T and BsAb. Median PFS for the entire cohort was 3.6 yrs; median OS was not reached. In the 2 prior LOT cohort (N=75), 60% received CAR-T and 40% BsAb. With median follow-up of 1.5 years, median PFS was not reached for CAR-T and 1.6 yrs for BsAb (p<.0001). In the 3+ prior LOT cohort (N=134), 62% received CAR-T and 38% BsAb. With median follow-up of 2 yrs, median PFS was 3.6 yrs for CAR-T and 1.6 yrs for BsAb (p=.0044). In propensity matched analysis, PFS was shorter for BsAb in both 2 LOT (HR 9.0, 95% CI 1.14-71.04, p=.037) and 3+ LOT (HR 3.25, 95% CI 1.06-9.97, p=.039) cohorts as compared to CAR-T. There were no significant differences in OS between CAR-T and BsAb. Median contact days were significantly higher for CAR-T vs BsAb in the 0-1 month interval: 19 vs 8 days in 2 LOT (p<.0001) and 18 vs 7 days in 3+ LOT (p<.0001) cohorts. There were no differences in contact days between CAR-T vs BsAb in subsequent time intervals. Over 1 year, CAR-T had significantly more time toxicity than BsAb: median 51 vs 36 contact days in 2 LOT (p<.0001) and 64 vs 38 days in 3L+ LOT (p<.0001) cohorts; these remained significant in the matched analysis. B symptoms (p=.04) and Grade ≥3 cytopenias (p=.007) were associated with higher contact days in 3+ LOT cohort in univariable analysis. Higher contact days were associated with inferior PFS (HR 1.01, 95% CI 1.00-1.02, p=.032) and OS (HR 1.01, 95% CI 1.00-1.02, p=.038) in 3+ LOT cohort regardless of treatment type. Discussion In this large real-world cohort of patients with R/R FL, CAR-T therapy resulted in better PFS but more time toxicity over the first year as compared to BsAb therapy. Excess time toxicity from CAR-T was driven by more contact days in the first month of treatment. This study provides benchmark data for counseling patients about expected time burden of CAR-T (51-64 days) and BsAb (36-38 days) over the first year of these therapies. Further, with superior PFS of CAR-T in this study and minimal impact of time toxicity on survival outcomes, these data can be used to better support shared decision-making in R/R FL by addressing patient preferences regarding both contact days as well as duration of disease control.
Hairy cell leukemia treatment strategies: A real-world multicenter experience
Fradin, James J. , Rein, Lisa , Holden, Troy, Shah, Shiv , Im, Annie , Szabó, Anikó , Carlson, Karen , Badar, Talha , Patel, Anand , Atallah, Ehab

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 1802-1802

10.1182/blood-2025-1802 Get It

Abstract Background Hairy cell leukemia (HCL) is a rare, indolent B-cell malignancy accounting for ~1% of all lymphoid neoplasms. While purine analogs remain the standard first-line therapy, the increasing use of combination regimens and targeted agents has expanded the therapeutic landscape. Data on long-term outcomes in real-world practice remain limited. Methods This is a retrospective, multicenter cohort study. We included 104 patients aged ≥18 years with a diagnosis of HCL who had at least one oncology visit from January 1, 2010, to July 17, 2025. Patients diagnosed prior to 2010 were left-truncated to account for survivorship bias. Data were abstracted from electronic medical records. Key outcomes included treatment patterns, response rates, overall survival (OS), and progression-free survival (PFS). Results The median age at diagnosis was 56.9 years (range 32.1–83.8), and 80% were male. Most patients (77%) were diagnosed during or after 2010. The most frequent frontline therapies were cladribine (63%), cladribine with rituximab (12%), rituximab monotherapy (9.7%), vemurafenib-based regimens (7.7%), splenectomy with or without interferon (3.8%), interferon monotherapy (2.9%), and other (1.9%). The overall complete response (CR) rate to first-line therapy was 63%, with 15% achieving a partial response (PR) and 22% having stable or no response. For patients receiving cladribine with rituximab first-line (n = 12), 92% had a CR. For patients receiving cladribine monotherapy first-line (n = 65), 63% had a CR and 12% had a PR. For patients receiving rituximab monotherapy first-line (n = 10), 50% had a CR and 20% had a PR. For patients receiving vemurafenib-based regimens first-line (n = 8), 75% had a CR. Among the 39 patients who received second-line therapy, the most common regimens included cladribine (31%), rituximab (26%), cladribine plus rituximab (18%), and vemurafenib-based regimens (13%). The CR rate after second-line therapy was 72%. For patients receiving cladribine with rituximab second-line (n = 7), 86% had a CR and 14% had a PR. For patients receiving cladribine monotherapy second-line (n = 12), 67% had a CR. For patients receiving rituximab monotherapy second-line (n = 10), 80% had a CR and 10% had a PR. For patients receiving vemurafenib-based regimens second-line (n = 5), 40% had a CR and 20% had a PR. Among the 17 patients who received third-line therapy, the most common regimens included rituximab (41%), cladribine (18%), and vemurafenib-based regimens (18%). The CR rate after third-line therapy was 50%. For patients receiving rituximab monotherapy third-line (n = 7), 43% had a CR and 14% had a PR. For patients receiving cladribine monotherapy third-line (n = 3), 33% had a CR. For patients receiving vemurafenib-based regimens third-line (n = 3), 67% had a CR and 33% had a PR. Overall, treatment-related hospitalizations for first-line therapy occurred in 27% of patients. 50% of patients receiving first-line cladribine with rituximab had treatment-related hospitalizations. 25% of patients receiving first-line vemurafenib-based treatment had treatment-related hospitalizations. 23% of patients receiving first-line cladribine monotherapy had treatment-related hospitalizations. 20% of patients receiving first-line rituximab monotherapy had treatment-related hospitalizations. Overall, after a median follow-up of 6.6 years (range 0.1–46), estimated OS was 96.6% at 5 years, 85.7% at 10 years, and 80.3% at 15 years. The median OS was 24.5 years [95% CI: 18.3, not reached]. Estimated PFS was 95.1% at 1 year, 89.9% at 3 years, 74.8% at 5 years, and 50.8% at 10 years. Median PFS was 12.2 years [95% CI: 7.0, not reached]. Estimated OS for first-line cladribine monotherapy was 100% at 5 years and 86.5% at 10 years. Estimated OS for first-line vemurafenib-based treatment was 85.7% at 5 years and 85.7% at 10 years. Conclusions This large real-world cohort provides important insights into the long-term management of HCL. Cladribine-based regimens remain the predominant first-line approach, with high response rates and durable remissions. However, treatment-related toxicity is common. Outcomes in later lines remain favorable, particularly with re-treatment using purine analogs or combination regimens. These findings underscore the importance of individualized treatment planning and the continued need for real-world evidence to inform care in rare hematologic malignancies.
Fixed-duration subcutaneous mosunetuzumab demonstrates sustained clinically meaningful outcomes in patients with previously untreated, low-tumor burden follicular lymphoma
Liu, Steve, Sharman, Jeff P. , Biondo, Juliana M.L., Jani, Prachi, Wu, Mei , Mun, Yong, Chopra, Vivek S. , Farighi, Rona, Muñoz, Javier, Yunus, Furhan, Budde, Elizabeth, Villasboas, José C. , Burke, John M. , Tun, Aung M. , Flinn, Ian W. , Budde, Elizabeth

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 1807-1807

10.1182/blood-2025-1807 Get It

Abstract Background: There remains an opportunity for new therapies to improve long-term outcomes for patients with low-tumor burden follicular lymphoma (FL). Mosunetuzumab is an off-the-shelf CD20xCD3 bispecific antibody, approved as an intravenous therapy for patients with relapsed/refractory FL after ≥2 lines of systemic therapy. Mosunetuzumab can be administered in the outpatient setting as a fixed-duration regimen. In an open-label, multicenter, Phase II study conducted mainly across US community sites (MorningSun; NCT05207670), mosunetuzumab administered subcutaneously (SC) induced high response rates with a manageable safety profile in patients with previously untreated low-tumor burden FL (Burke et al. ASH 2024). Here we present updated efficacy and safety data for mosunetuzumab SC in patients with previously untreated, low-tumor burden FL. Methods: Patients had untreated Grade 1 or 2 low-tumor burden FL per 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. Mosunetuzumab SC was administered with step-up dosing in Cycle 1 (Day [D]1, 5mg; D8, 45mg; D15, 45mg), then 45mg on D1 of each 21-day cycle. Hospitalization was not mandatory. Patients with a complete metabolic response after 8 cycles could complete therapy and patients with a partial metabolic response or stable disease continued treatment for up to 17 cycles. The primary endpoint was progression-free survival (PFS) at 24 months. Key secondary endpoints included objective response rate (ORR), time to response (TTR), overall survival (OS), duration of response (DOR), duration of complete response (DOCR), and safety. Exploratory analyses assessed pharmacodynamic changes in B-cell subsets. Here, we report interim data. Results: As of February 10, 2025 (clinical cut-off date), 101 patients were enrolled from US community (n=56) and academic (n=45) centers; 52 patients had completed treatment, 21 had discontinued (mainly due to adverse events [AEs; n=6] and progressive disease [n=5]), and 28 were ongoing on treatment. Median age was 65 years (range: 34–82). Most patients had an ECOG PS of 0 (81.2%) or 1 (18.8%) and 43 patients (42.6%) had extranodal involvement. Median duration of follow-up was 13.8 months (95% confidence interval [CI]: 11.5–16.9) and median number of cycles received was 10 (range: 3–17). The ORR was 98.0% (95% CI: 93.0–99.8) and the complete response rate was 89.1% (95% CI: 81.3–94.4). Median TTR was 2.8 months (range: 1.4–8.3). Landmark DOR and DOCR rates at 12 months were 91.8% (95% CI: 81.5–96.5) and 95.7% (95% CI: 82.6–99.0), respectively. The 12-month PFS and OS rates were 92.0% (95% CI: 83.8‒96.1) and 99.0% (95% CI: 93.2‒99.9), respectively. The most common AE was injection-site reaction (ISR, 81.2%; Grade 1, 74.3%; Grade 2, 5.9%; Grade 3, 1.0%). Grade 3/4 AEs were reported in 51.5% of patients; the most common (≥10%) events were cytopenias (36.6%) and infections (11.9%). Cytokine release syndrome (CRS) was reported in 48.5% of patients (Grade 1, 40.6%; Grade 2, 7.9%). Overall,infections occurred in 63.4% of patients (Grade 1, 7.9%; Grade 2, 42.6%; Grade 3, 11.9%; Grade 5, 1.0%) with the most common (≥10%) being upper respiratory tract infection (21.8%), COVID-19 (17.8%), sinusitis (13.9%), and pneumonia (11.9%). At the time of data cut-off, ISR, CRS, and infection AEs were resolved at rates of 98.2%, 100%, and 89.0%, respectively. Two patients had a Grade 5 AE (sepsis, n=1; unknown cause, n=1).No immune effector cell-associated neurotoxicity syndrome events were reported. B-cell depletion was observed following the first dose of mosunetuzumab, with subsequent B-cell recovery observed within six months of treatment completion. Conclusions: Fixed-duration mosunetuzumab SC demonstrates high efficacy rates with deep and sustained responses in patients with previously untreated, low-tumor burden FL. The manageable safety profile supports ease of outpatient administration without mandatory hospitalization, including in community oncology practices. Additionally, exploratory analyses demonstrating B-cell recovery after treatment completion also substantiate the use of mosunetuzumab SC as a fixed-duration regimen. These data support further evaluation of mosunetuzumab SC in patients with previously untreated, low-tumor burden FL.