Shah, Meera

e19014 Background: Stromal Antigen 2 ( STAG2), located on Xq25, is the most mutated (m) cohesin-complex gene in myeloid neoplasm (MN) patients (pts). mSTAG2 is present in around 5% of MN and has been linked to secondary AML and potential poor impact on outcome. Methods: We retrospectively screened MN pts who had next-generation sequencing (NGS) (OncoHeme) performed at Mayo Clinic between 2018-2021. m STAG2 pts were included at the date of NGS. Charts were reviewed for clinical information after obtaining IRB approval. BlueSky Software V7.40 was used for statistical analysis. Results: Characteristics: 70 pts with mSTAG2 MN were identified, their median age was 72 years (range 25-91); with 55 pts (79%) being males. Complete blood counts showed median white blood cell count of 2.8 x109/L, hemoglobin of 8.9 gm/dL and platelets of 89 x109/L. The diagnosis was MDS in 38 pts (54%), AML in 20 (29%), MDS/MPN in 9 (13%), MPN in 2 (3%), and CCUS in 1 (1%). 11 cases (16%) were defined as therapy-related MN (tMN). Cytogenetics were normal in 45 pts (64%) and abnormal in 22 (31%). 10/50 non-AML pts progressed to AML (after median time of 9.8 months). Hematopoietic cell transplantation (HCT) was done in 20 pts (29%). mSTAG2: median VAF (mVAF) was 50% (range, 5%-100%). Males had higher mVAF compared to females (64% vs. 27%, p= .001), and tMN pts had higher mVAF compared to de novo (dn) MN pts (66% vs. 43%, p= .03). mVAF had no correlation with disease classification (50% in AML, 52% in MDS, 41% in MDS/MPN, 36% in MPN and 5% in CCUS, p= .5). STAG2 mutations were nonsense, frameshift, and splice site in 50%, 37%, and 13%, respectively. Co-mutations : median number of co-mutations was 3 (range, 0-6). Most common co-mutations were ASXL1 (66%), SRSF2 (37%), TET2 (36%), RUNX1 (29%), IDH2 (21%), BCOR (20%) and U2AF1 (16%) while least common were TP53, SETBP and ZRSR2 (1% each). Neither number (p= .08) nor type of co-mutation correlated with MN classification. There was no difference in the co-mutational pattern between tMN and dnMN pts. Survival : median overall survival (mOS) was 16.3 months with a median follow up time of 24.5 months. Pts who received HCT had better OS compared to non-HCT pts (mOS not reached vs. 14.9 months, p= .003). Pts with an isolated m STAG2 had better OS than co-mutated pts (p= .04), while the type of STAG2 mutation did not affect OS (p= .3). Pts with tMN had worse OS than dnMN pts (9.9 vs. 20.4 months, p= .02). VAF ≥75% had a negative impact on OS (20.5 vs 8.1 months, p= .008). mOS did not differ based on MN diagnosis. On multivariate analysis, only HCT (HR 0.3, p= .01) and VAF ≥75% (HR 2.3, p= .02) had impact on OS. Conclusions: mSTAG2 was more common in elderly males and MDS diagnosis. mSTAG2 was uncommon as an isolated mutation, indicating a possible role in disease progression with preferred certain co-mutations ( ASXL1/SRSF2/RUNX1/IDH2). mOS was poor regardless of MN diagnosis indicating a molecularly driven significance of an aggressive disease. The study needs to be validated by larger studies.

e19010 Background: Mutated DEAD-box helicase 41 (m DDX41), and mutated GATA2 are germline mutations associated with familial predisposition syndromes. In this study, we compare the clinical characteristics and survival outcomes (OS) of m DDX41 and m GATA2 MN patients (pts). Methods: We retrospectively screened pts who had next-generation sequencing (NGS) (OncoHeme panel) performed at Mayo Clinic. 4,524 consecutive pts (2018-2021) were screened for DDX41 mutations and 3,872 for GATA2 mutations (2015-2020) and included 36 MN pts with m DDX41 genetic alterations, and 55 m GATA2 MN pts. m GATA2 cases were included at NGS date while m DDX41 were included at diagnosis date. Germline workup was not done in all cases. JMP 16.2.0 Software was used for statistical analysis. Results: Patient characteristics: The most common diagnosis was MDS (N = 22, 61% in m DDX41 N = 17, 31% in m GATA2 group; p = .0044). MDS/MPN overlap was seen in m GATA2 group only; (29% vs. 0%; p = .0004). Majority of pts were males with median age of 68 and 67 years for m DDX41 and m GATA2 pts; respectively (p = .7). m DDX41 pts had higher hemoglobin, platelets, and MCV (< .0001, 0.005, < .0001; respectively) and significantly lower white blood cells (WBC) count compared to m GATA2 pts (< .0001). All m DDX41-AML pts were (ELN) intermediate-risk, and 64% of m DDX41 MDS were intermediate risk (IPSS-R). In contrast, of m GATA2 pts 62% of AML were adverse risk and 44% of MDS very high risk. Majority of m DDX41 pts had normal karyotype (N = 32; 91% vs. N = 19, 37%; p < .0001), had isolated mutations (N = 23; 64%) and the most common co-mutations were DNMT3A (38%), ASXL1 (30%), JAK2 (23%). The majority of m GATA2 pts were co-mutated (96%) with a different co-mutation pattern ASXL1 (60%), SRSF2 (34%), RUNX1 (19%). Germline data: One m GATA2 pts had proven germline mutation, and 10/11 (91%) m DDX41 pts were confirmed Survival and progression in MDS/AML: After median follow-up of 30 months in MDS/AML, 7 (21%) m DDX41 and 23 (77%) m GATA2 pts died with superior OS in m DDX41 compared to m GATA2 pts with median OS of (136.7 vs. 6.8 months, p < .0001). Seven (31%) of 22 m DDX41 and 6 (35%) m GATA2 MDS pts progressed into AML with a median time to progression of (11.2 vs. 5.2 months, p = .045). The leukemia free survival (LFS) for m DDX41 MDS pts was significantly longer than LFS of m GATA2 MDS pts (24.4 vs. 6 months, p < .0001). Conclusions: We compare the outcomes of two unique mutations associated with germline predisposition. We found m DDX41 pts had fewer cytogenetic aberrations, no MDS/MPN overlap, and lower WBC count. Majority of m DDX41 MDS/AML pts were intermediate risk category, compared to predominance of adverse risk disease in m GATA2 pts, translating into better OS and LFS. This study is limited by the small size, lack of germline workup in all cases, and retrospective nature. However, it supports the favorable prognosis and indolent course of m DDX41 pts recently described.

TPS7080 Background: Myelodysplastic syndrome/myeloproliferative neoplasms (MDS/MPN) are classified as a distinct category under the World Health Organization (WHO) classification of myeloid neoplasms. MDS/MPN with RS and thrombocytosis (MDS/MPN-RS-T) and MDS/MPN, unclassifiable with > 15% bone marrow ring sideroblasts (MDS/MPN-U-RS) have similar clinical and pathological characteristics with symptomatic or transfusion-dependent anemia as the predominant morbidity. Luspatercept has been approved in myelodysplastic syndromes with ring sideroblasts (MDS-RS) and MDS/MPN overlap syndromes, based on the phase 3 MEDALIST clinical trial which primarily included MDS-RS patients with an objective erythroid response rate of approximately 40 per cent. In this trial, some MDS-RS patients also experienced an increase in neutrophil and platelet counts. This raises a safety concern for MDS/MPN patients with elevated platelet or WBC counts such as MDS/MPN-RS-T and MDS/MPN-U-RS. Previous studies have shown clinical and biological differences between MDS-RS and MDS/MPN-RS-T, with the latter group at a significantly elevated risk for thrombotic events. Additionally, several MDS/MPN-RS-T patients are on hydroxyurea which may blunt the erythroid response of luspatercept. Therefore, it is imperative to establish the safety and efficacy of luspatercept in this patient group. Methods: This is an investigator-initiated, prospective, phase II study of luspatercept in MDS/MPN overlap neoplasms with ring sideroblasts and thrombocytosis or unclassifiable with ring sideroblasts with 2 arms; hydroxyurea-independent (cohort A) and hydroxyurea-dependent (cohort B). Hydroxyurea and/or aspirin use is allowed as per investigator discretion. The primary goal is to study the efficacy and safety of luspatercept in MDS/MPN-RS-T or MDS/MPN-U-RS with symptomatic anemia. The primary endpoint is to assess erythroid response rate as per the 2015 International Working Group MDS/MPN response criteria. Secondary endpoints include response duration, time to acute myeloid leukemia (AML) transformation, thrombosis rate, AML-free and overall survival. Inclusion criteria include newly diagnosed or relapsed/refractory adult patients with WHO-defined diagnosis of MDS/MPN-RS-T or MDS/MPN-U-RS with symptomatic or transfusion-dependent anemia and unlikely to respond (EPO level > 200 IU/L) or intolerant to erythropoiesis stimulating agent (ESA) therapy. Prior therapy with lenalidomide, hypomethylating agents or immunosuppressive therapy is allowed. The overall plan is to enroll 54 patients across the three Mayo Clinic sites, Minnesota, Arizona and Florida. Enrollment to the trial began in January 2022 with 1 patient enrolled at the time of abstract submission. Clinical trial information: NCT05005182.

AbstractTherapy‐related myeloid neoplasms (t‐MN) are aggressive malignancies in need of effective therapies. The BCL‐2 inhibitor venetoclax represents a paradigm shift in the treatment of acute myeloid leukemia. However, the effectiveness of venetoclax has not been studied in a large cohort of t‐MN. We retrospectively analyzed 378 t‐MN patients, of which 96 (25.4%, 47 therapy‐related acute myeloid leukemia, 1 therapy‐related chronic myelomonocytic leukemia, 48 therapy‐related myelodysplastic syndrome) received venetoclax. Median interval from t‐MN to venetoclax initiation was 2.9 (Interquartile range [IQR] 0.7–12) months, and patients received a median of 3 (IQR 1–4) cycles. The composite complete remission (CRc) rate, median progression‐free survival (PFS), and overall survival (OS) were 39.1%, 4.9 months, and 7 months, respectively. The upfront use of venetoclax and achieving CRc were associated with improved survival, whereas the presence of Chromosome 7 abnormalities was associated with an inferior survival. Neither the TP53‐status nor the percent bone marrow blast predicted the likelihood of CRc or survival. Paired genetic analysis performed at venetoclax initiation and failure did not show the evidence of the selection of the TP53‐mutated clone. In a propensity‐matched analysis, the use of venetoclax‐based regimen as the first‐line therapy was associated with a superior survival compared to hypomethylating agent (HMA)‐based first‐line therapy (9.4 vs. 6.1 months, p = .01). We conclude that the upfront use of venetoclax with HMA improved survival, though PFS and OS remain poor. As the phenotype at diagnosis or the percent blasts did not predict outcomes, venetoclax should be studied in all t‐MN phenotypes.

Abstract The reduced-intensity conditioning regimen, fludarabine and melphalan, is frequently used in allogeneic hematopoietic stem cell transplantation (HSCT). Melphalan and the active metabolite of fludarabine, F-ara-A, are excreted via the kidneys. Existing methods to assess clearance in this setting are based on serum creatinine, which has known limitations for glomerular filtration rate (GFR) estimation in patients with malignancy. Measured GFR (mGFR) may better predict drug dosing to mitigate toxicity and increase the chances of successful engraftment. The primary objective of this study was to assess the association between mGFR and risk for nonrelapse mortality (NRM) in patients who have undergone allogeneic HSCT receiving conditioning with fludarabine and melphalan. In the 109 included patients, mGFR &lt;65 mL/min/1.73 m2 predicted a significantly higher rate of overall NRM (hazard ratio [HR], 2.13; 95% confidence interval [CI], 1.03-4.35; P = 04) and 1-year incidence of infection (HR, 2.63; 95% CI, 1.54-4.55; P &lt; .001) in addition to a significantly lower 2-year survival (P = .019). Kidney function estimated via estimated GFR (eGFR) and estimated creatinine clearance did not correlate with posttransplant outcomes. These results suggest that mGFR is a promising approach for assessing clearance in patients who have undergone allogeneic HSCT and may be preferred to standard creatinine-based eGFR strategies.