Kettani, Mobachir El

Abstract TP53 and PPM1D are key regulators of DNA damage response and repair, and somatic mutations in these genes often co-occur in hematopoietic cells, expanding under genotoxic stress. Unlike TP53 mutations, where mechanisms of progression are defined, pathways underlying clonal fitness and transformation in PPM1D mutant cells remain unclear. In collaboration with 5 academic institutions, we analyzed the clinical and molecular landscape of 337 patients with clonal hematopoiesis (CH) and clonal cytopenia of undetermined significance (CCUS) across 4 genotypes: PPM1Dmt/TP53wt (n = 170 [50%]), PPM1Dmt/TP53mt (n = 25 [7%]), TP53mt/PPM1Dwt (n = 17 [5%]), and TP53wt/PPM1Dwt (n = 125 [38%]). All PPM1D variants were truncating, located in exon 6 of the gene, with a median variant allele frequency (VAF) of 6% (range, 0.3%-64%). The PPM1Dmt/TP53mt genotype was most frequently encountered in therapy-related CH/CCUS (t-CH/t-CCUS; 80%, 66.5%, 76.5%, and 19%; P ≤ .001) and had a shorter time interval to detection from last genotoxic exposure (6.2, 5.9, 11.25, and 24.5 months; P ≤ .001) compared with PPM1Dmt/TP53wt, TP53mt/PPM1Dwt, and TP53wt/PPM1Dwt genotypes, respectively. Acknowledging the short follow-up duration, rates of malignant transformation were lower in the PPM1Dmt/TP53wt (2%) and PPM1Dmt/TP53mt (4%) groups compared with PPM1Dwt/TP53wt (12%) and PPM1Dwt/TP53mt (17%) groups (P ≤ .001), respectively. In summary, PPM1D mutations are frequently observed in t-CH/t-CCUS, with low median VAFs, and are associated with low rates of progression, even when comutated with TP53.

6538 Background: TP53 mutated ( TP53 mt ) high-risk myeloid neoplasm (HR-MN) confers a dismal prognosis in the contemporary era with only a subset of eligible patients (pts) able to achieve long-term remission with allogeneic stem cell transplantation (allo-HCT). Owing to poor outcomes, many physicians believe it is futile to treat older pts with disease-directed therapy, since curative intent allo-HCT cannot be offered. We sought to describe the outcomes of older pts with TP53 mt HR-MN receiving disease directed treatment. Methods: We conducted a multicenter observational study in collaboration with 11 U.S. academic centers under the COMMAND consortium. We reviewed the data of 451 older (≥ 60 years [yrs]) TP53 mt HR-MN (n= 282 acute myeloid leukemia [AML], n= 91 MDS transformed AML, n= 50 myeloproliferative neoplasm blast phase (MPN-BP) and n= 28 high-risk myelodysplastic syndromes [HR-MDS]) pts to analyze their outcome with disease directed treatment. Results: The median age was 70 yrs (range [R],60-90) and 58% were male. Proportions of pts with age ≥ 70 yrs were 47.5%. Eastern Cooperative Oncology Group Performance Status (ECOG-PS) was available in 68% (n= 306) of pts; 10.5%, 49%, 32% and 8.5% had ECOG-PS 0-3, respectively. The median bone marrow (BM) blast % was 32 (R, 5-99) and TP53 variant allele frequency (VAF) was 45% (R, 2-97). The proportion of pts with multi-hit (MH) TP53 mt and complex cytogenetics (CG) was 83% and 82%, respectively. 43 %, 31%, 20% and 6% received hypomethylating agent (HMA) + venetoclax, intensive chemotherapy, HMA and other low-intensity therapy, respectively. The complete remission rate with or without count recovery (CR/CRi) amongst evaluable patients (n= 356) was 37%. The median duration of response was 6.7 months (mo) (R, 5.9-7.5). Amongst 56 (12%) pts who underwent allo-HCT, the median overall survival (mOS) from time of allo-HCT was 21.9 mo. The mOS among pts ≥ 70 yrs was 6.5 mo. The mOS in mo was better in HR-MDS (16.4), compared to de novo AML (6.5), MDS transformed AML (7.1) and MPN-BP (5.27), p= 0.003. We conducted multivariable analysis for OS using baseline variables that were significant/ showed trend towards significance, on univariate analysis ( p <0.1). HR-MDS (HR; 0.43, 95% CI: 0.23-0.82, p= 0.01), CR/CRi (HR; 0.55, 95% CI: 0.39-0.77, p= <0.001) and allo-HCT (HR; 0.28, 95% CI: 0.16-0.47, p= <0.001) positively impacted OS. Whereas age ≥ 70 yrs showed trends towards inferior OS (HR; 1.31, 95% CI: 0.95-1.80, p=0.09). Complex CG (HR; 1.63, 95% CI: 0.83-3.21, p =0.15) and MH TP53 mut (HR; 1.30, 95% CI: 0.67-2.52, p= 0.42) did not retain significance for OS. Conclusions: Our multi-center study suggests that disease directed treatment in older TP53 mt HR-MN leads to modest response rates with short durations of response in the absence of allo-HCT. 12% of pts were able to receive allo-HCT with improvement in OS close to 2 yrs. The decision to treat this poor risk gp of pts should be based on individual pt characteristics and desires.

Background While central nervous system (CNS) disease is found in minority of patients (pts) at diagnosis of Ph+ ALL, later relapses can occur in pts despite adequate CNS prophylaxis. CNS disease can be managed with varying combinations of systemic, radiation, and intrathecal (IT) therapy and can be associated with significant toxicity, especially in older pts. While there are more durable systemic responses with 2nd or 3rd generation tyrosine kinase inhibitors (TKIs) based combinations, CNS penetration can vary by TKI. In this large multi-center study, we analyze the incidence of CNS disease in Ph+ ALL in the context of induction therapies and survival post relapse. Methods We conducted a multicenter observational study in collaboration with 10 U.S. academic centers under the COMMAND consortium and reviewed the incidence of CNS relapse in 505 Ph+ ALL pts. We evaluated baseline characteristics, treatment given prior to CNS relapse, and outcome post relapse. Results Baseline characteristics, initial treatment and outcome prior to CNS relapse Eighteen (3.56%) pts were identified to have CNS disease at relapse. Median age of the pts in years (yrs) was 51 (range [R], 22-75), median white blood cell (WBC) was 33.3 x 10(9)/L (R, 2.1-200) and 6 (33%) pts had additional cytogenetic abnormalities at diagnosis. Sixty-one percent (n= 11) of pts received intensive chemotherapy (IC) during induction; 2 (11%), 14 (78%) and 2(11%) of pts received 1st, 2nd or 3rd generation TKI-based combination during induction, respectively. All of pts achieved complete remission (CR), 45.5% achieved complete molecular remission (CMR) at 3 months from the time of diagnosis. Five (28%) pts received allogeneic stem cell transplantation (allo-HCT) as a consolidation therapy. Treatment received at CNS relapse and response The median time to CNS relapse after induction was 10.8 months (mo) (R, 2-79). All pts except 1 had isolated CNS relapse after CR1, 4/18 (22%) pts had T315I mutation at relapse. Twelve (67%) and 6 (33%) pts received intrathecal chemotherapy (IT) with TKI and systemic chemotherapy + TKI in addition to IT, respectively. Eleven (61%) pts received dasatinib, 5 (28%) pts received ponatinib and one (6%) pts each received bosutinib and imatinib at relapse. Ninety-three percent of pts achieved CR (n=3, not evaluable). Six (33%) pts underwent allo-HCT after CNS relapse, one of these transplanted pts had second allo-HCT. Survival after CNS relapse The median relapse free survival (RFS) and overall survival (OS) after CNS relapse was 9.8 (95% CI: 3.80-15.76) and 13.87 (95% CI: 4.08-23.65) mo, respectively. In subset analysis, we compared survival outcome among pts who had relapse without CNS involvement (n= 160/505 [32%]). The median RFS (9.9 vs 9.8, p= 0.88) and OS (31.53 vs 28.80, p= 0.57) after relapse was not significantly different among pts who had relapse with or without CNS involvement, respectively. We also compared OS among pts without relapse to those with relapse. The median OS was not reached (NR; 73% alive at 5 years), 28.80 and 31.53 months (p= &lt;0.001) among pts with no relapse, relapse with CNS and without CNS involvement, respectively. Conclusion Our retrospective analysis from a large database showed that CNS relapses were uncommon (3.56%) in adult pts with Ph+ ALL. A majority of pts (89%) received a 2nd or a 3rd generation TKI during induction. Approximately one quarter of pts with CNS relapse had emergence of T315I mutation. While almost all pts achieved CR, the RFS was relatively short. We did not see significant differences in survival among pts who had relapse with or without CNS involvement.

Background: Therapy-related myeloid neoplasms (t-MN) occur after exposure to DNA-damaging agentsincluding cytotoxic chemo and radiation therapy and are associated with dismal outcomes. TP53 and PPM1D (protein phosphatase Mn2+/Mg2+-dependent 1D) mutations (MT) disrupt the DNA damage response and repair (DDR) pathway, are often co-mutated (25-35%), and although enriched in t-MN (20%), can also be seen in age-related clonal hematopoiesis (CH) (5-10%). While progressive genomic instability with biallelic inactivation has been described as a mechanism of MN progression with TP53 MT, similar mechanisms remain to be elucidated for PPM1D MT. We conducted this study to assess the clinical phenotype and outcomes of TP53 and PPM1D co-mutated (PPM1DTP53m) versus PPM1D MT and wild type TP53 (PPM1DTP53wt) CH and MN. Methods: After approval from the Mayo Clinic IRB, the CH and MN databases were queried and 119 pts with PPM1D MT (CH= 26, clonal cytopenia of unknown significance [CCUS]= 64, myelodysplastic syndrome [MDS]=16, myeloproliferative neoplasm [MPN]=8, acute myeloid leukemia [AML]= 5) were identified. We analyzed baseline characteristics, karyotypic changes, somatic mutations, and survival outcomes between the PPM1DTP53m (n= 22) and PPM1DTP53wt (n= 97) groups (gp). Results: Baseline characteristics The median age in years (yrs) was 68.5 (range [R], 43-89) and 71 (R,30-92) in the PPM1DTP53m and PPM1DTP53wt gp (p= 0.65). 22% vs 18% (p=0.78), 58% vs 32% (p=0.03), 9% vs 32% (p=0.01), 7% vs 4.5% (p=&gt;0.99) and 3% vs 14% (p=0.07) pts met criteria for CH, CCUS, MDS, MPN and AML in the PPM1DTP53wt and PPM1DTP53m gp, respectively. Similarly, 19% vs 18% (p=&gt;0.99), 47% vs 32% (p=0.23), 7% vs 36% (p=0.001), 2% vs 0% (p=&gt;0.99) and 2% vs 14% (p=0.04) of pts met criteria for t-CH, t-CCUS, t-MDS, t-MPN and t-AML in the PPM1DTP53wt and PPM1DTP53m gp, respectively. All PPM1D variants were truncating, located in exon 6 of the gene, with median variant allele frequency (VAF) (8% [R,1-64] vs 5.5% [R,2-24], p= 0.10) and number of PPM1D MT (1 [R,1-5] vs 1 [R, 1-3], p=&gt;0.99) being similar between the two gp. While proportion of pts with t-MN were similar between the two gps (77% vs 86%, p= 0.40), cytogenetic (CG) abnormalities (67% vs 31%, p= 0.006), including monosomies (28% vs 2%, p= &lt;0.001) and complex CG (53% vs 4%, p= &lt;0.001) were more frequent in PPM1DTP53m gp compared to PPM1DTP53wt gp, respectively. The median TP53 MT VAF was 14% (R, 1-14); 50% had multi-hit TP53 MT. Somatic mutations in PPM1D MT myeloid neoplasm with and without TP53 MT Somatic co-mutations excluding TP53 were seen in 71% of pts; 73.5% in PPM1DTP53wt and 59% in PPM1DTP53m gp (p= 0.20). Apart from CBL (0% vs 9%,p=0.03), MT involving DNMT3A (20% vs 14%, p= 0.56), TET2 (15% vs. 14%, p= &gt;0.99), IDH1 (6% vs 19%, p= 0.07), splicing factors (8% vs 14%, p=0.08), ASXL1 (11% vs 4.5%, p=0.46), and JAK2 (9% vs 0%,p=0.20) were comparable between PPM1DTP53wt and PPM1DTP53m gps, respectively. The proportion of pts with ≥ 2 somatic co-mutations excluding TP53 MT were numerically higher in PPM1DTP53wt gp (43%) compared to PPM1DTP53m gp (23%) (p= 0.09). In the PPM1DTP53wt gp, other somatic driver mutations included RUNX1 (n= 7 [7%]; CH [n=1], CCUS [n=2], MDS [n=3], MPN [n=1]), NRAS (n=1 [1%]; CCUS), BCOR (n=1 [1%]; CCUS), and PTPN11 (n=1 [1%]; CCUS). Leukemic transformation and survival With a median follow up of 6.43 months (mo) (R, 0.23-36.4), median overall survival (mOS) in mo among high-risk MDS/AML (16.4 vs 15.0, p= 0.66) and CHIP/CCUS pts (35.79 vs 26.28, p= 0.93) was similar between PPM1DTP53wt and PPM1DTP53m gps, respectively. CHIP/CCUS pts harboring multiple vs single PPM1D MT had an inferior mOS (23.9 vs 36.7 mo, p= 0.05). Three (2.5%) MDS pts underwent AML transformation; 1 (1%) and 2 (10%) in PPM1DTP53wt and PPM1DTP53m gp, respectively (p= 0.07). Conclusions In our study, 18% of pts had concurrent TP53 and PPM1D MT (82% t-MN), with the PPM1DTP53wt genotype being more frequent in CCUS, while the PPM1DTP53m genotype was more frequent in MN. The PPM1DTP53m genotype had a higher frequency of CG abnormalities, including complex CG. Survival outcome was inferior and comparable in PPM1D MT MN with or without TP53 MT. While 73.5 % of the PPM1DTP53wt gp had somatic driver MT and 31% had karyotypic abnormalities, 22% had no additional MT or CG changes (all CH/CCUS), underscoring the need to understand how PPM1D MT contribute to hematopoietic dysfunction and MN.

Introduction: MPAL is a rare and heterogenous subtype of acute leukemia characterized by a single blast population with phenotypic expression of both myeloid and lymphoid lineages (biphenotypic) or multiple co-existing lineages of blasts that satisfy criteria for both acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). MPAL presents both a diagnostic and therapeutic challenge given its rarity and resistance to traditional therapies. Data suggest ALL-directed or hybrid therapies are most effective at inducing durable remissions as a bridge to allogeneic stem cell transplantation (Allo-SCT; Lazzarotto 2023, Rasekh 2021); however, many are single-institution with limited sample sizes. Methods: A retrospective analysis at 7 US academic centers was performed. Adult patients (pts) with a confirmed diagnosis of MPAL between 2003-2023 were included. Comparisons of categorical and continuous variables utilized the Fisher exact test and Wilcoxon rank-sum or Kruskal-Wallis test as appropriate. Time-to-event outcomes were calculated using the Kaplan-Meier method and compared using log-rank test. Results: A total of 79 pts with MPAL were included in this study. Median age at diagnosis was 61 years (range, 18-89); 52% were ≥ 60 years. Majority of pts were male (60%), non-Hispanic white (64%), and had an ECOG ≤ 1 (83%). Of the 50 pts with baseline CSF analysis, 5 (10%) had CNS disease. Phenotypically, the predominant blast population was biphenotypic in 68%, myeloid in 17%, and lymphoid in 15% of cases. KMT2A-rearrangement and BCR::ABL1 translocation constituted 4% and 14% of cases, respectively, and 30% of pts had complex cytogenetics. Most common mutations at baseline included RUNX1 (33%), DNMT3A (30%), FLT3-ITD (26%), TET2 (19%), WT1 (19%), NRAS (18%), TP53 (17%), and ASXL1 (14%) mutations. Of the 79 pts, 61 (77%) received intensive chemotherapy (IC), 12 (15%) received HMA-based regimens, 4 (5%) received other non-intensive regimens, and 2 (3%) transitioned to hospice prior to therapy. Among those receiving IC, 37 (61%) received ALL-directed therapies, 16 (26%) AML-directed, and 8 (13%) received hybrid regimens which included FLAG-VIPR (6/8), 7+3+vincristine (1/8), and cladrabine/low-dose cytarabine/vincristine/dexamethasone (1/8). Therapies were phenotype-discordant in 4/61 pts receiving IC; 3 myeloblast-predominant MPAL pts received ALL-directed therapy and one lymphoid-predominant pt received AML-directed therapy. Among 54 pts with predominant biphenotypic blasts, 52% received ALL-directed regimens. Of the 11 pts with BCR::ABL1 translocation, 8 (73%) received dasatinib, 2 (18%) ponatinib, and 1 (9%) received both. Only 30% of pts with FLT3-ITD mutated MPAL (5/17) received a FLT3 inhibitor. Overall, 56% of pts achieved complete remission (CR) or CR with incomplete count recovery (CRi), with a median duration of response of 16.7 months (IQR: 8.1-46.1). The rates of CR/CRi were 39%, 56%, and 75% for myeloid, biphenotypic, and lymphoid MPAL, respectively. All pts with CNS disease (5/5) cleared after induction. Thirty-seven percent of pts proceeded with Allo-SCT in first remission (23% of myeloid pts, 58% lymphoid, 35% biphenotypic). Thirty-two percent of responders (CR/CRi; 14/44) relapsed with a median time to relapse of 9.4 months (range, 0.5-42). Median overall survival (OS) for the entire cohort was 51 months (95% CI: 15-89). The 2-year OS rate was higher in pts with lymphoid-predominant phenotype (83%) compared to biphenotypic (55%) or myeloid-predominant phenotype (38%; p=0.16). Median OS was significantly longer in transplant versus non-SCT recipients (121 vs 14 months) with a 1-year OS rate of 97% vs. 59% (p&lt;0.0001), respectively. Among pts who achieved CR/CRi, median OS significantly longer in transplant versus non-SCT recipients (121 vs 55 months, p=0.031), with a 2-year OS rate of 91% vs 75%. Conclusions In this large multi-center study, there were differences in survival based on predominant blast phenotype, with improved OS in lymphoid-predominant MPAL. Although most pts with biphenotypic-predominant MPAL received ALL-directed regimens, OS was worse in this subtype compared to lymphoid-predominant MPAL. There was significantly improved OS among Allo-SCT recipients underscoring the importance of Allo-SCT in this subtype of acute leukemia. Additional studies are needed to understand this rare and heterogenous disease.

Background TP53-mutant (mt) myelodysplastic syndromes (MDS) are high-risk (HR) neoplasms, with high rates of AML progression and suboptimal response to hypomethylating agents (HMA). Given the lack of effective therapies for HR-MDS, azacitidine (AZA) was combined with venetoclax (VEN) in a phase Ib MDS study demonstrating safety and early efficacy (Garcia et al. ASH abstract 2023). We retrospectively sought to explore clinical outcomes comparing VEN + HMA, to HMA alone in TP53mt HR-MDS. Methods Among 221 TP53mt MDS pts treated at the Mayo Clinic between January 2007 and April 2024, we reviewed outcomes of pts who received HMA alone (n=98) or HMA+VEN combination (n=34) as their first-line chemotherapy regimen. MDS diagnosis was based on the 5th edition of WHO classification of hematolymphoid tumors (Khoury et al. Leukemia 2022). Responses were assessed according to the International Working Group 2006, MDS response criteria (Cheson et al Blood 2006). Results Baseline characteristics and response The median age (years [yrs]) was 65 (R,37-80) and 70 (range [R], 19-87) yrs in the HMA + VEN and HMA alone groups (gps) (p= 0.42), respectively. The median bone marrow (BM) blast % (9.5 [R, 0-18] vs 5 [R, 0-16], p= 0.01) and TP53 variant allele frequency (VAF) (42 [R, 6-96] vs 37 [R, 2-94], p= 0.03) were significantly higher in HMA + VEN compared to HMA gps, respectively. However, proportion of pts with biallelic (BA)/multihitTP53mt (85% vs 79%, p= 0.61) and complex cytogenetics (CG) (85% vs 81%, p= 0.85) were not different between HMA + VEN and HMA alone gps. The distribution of pts with frequently occurring myeloid co-mutations (ASXL1, TET2, DNMT3A, RAS, BCOR and splicing factor) were not significantly (NS) different between the two gps. IPSS-M scores were assessed in 108 (83%) pts; HR/very HR-MDS as per IPSS-M were NS different between HMA + VEN and HMA gps (100% vs 91%, p= 0.12). While the overall response rate (ORR) (76% vs 49%, p= 0.01) and marrow complete remission (mCR) rates (21% vs 7%, p= 0.05) were higher with HMA+VEN compared to HMA, CR rates were similar (17% vs 12%, p= 0.47). Higher proportion of pts were bridged to allogeneic stem cell transplantation (allo-HCT) (41% vs 20%, p= 0.02), while AML progression rates (29% vs 31%, p= &gt;0.99) were comparable between HMA + VEN and HMA gps, respectively. The non-relapse mortality (NRM) at day 60 (3% vs 3%, p=0.96) and day 90 (3% vs 4%, p=0.75) were comparable between HMA + VEN and HMA gps, respectively. RFS and OS The median follow-up from the time of initiation of HMA or HMA + VEN was 9.7 months (mo) (R, 0.3-90.6). The median RFS (8.47 vs 9.90 mo, p= 0.83) and OS (16.33 vs 14.20 mo, p= 0.66) from the time of initiation of therapy were comparable between the two gps. Similarly, among transplanted pts, there was no OS difference between HMA (21.7 mo) and HMA + VEN (18.43 mo) gps, respectively (p= 0.72). Comparable results for OS and RFS were obtained in both gps after censoring pts at the time of allo-HCT. Multivariable analysis for RFS and OS We conducted multivariable analysis (MVA) for RFS and OS using baseline variables that were significant/ trended towards significance (p&lt;0.1), on univariate analysis (UVA) censored at the time of allo-HCT. Achieving ORR (HR; 0.30, 95% CI: 0.14-0.62, p= 0.001) retained significance for better RFS in MVA. Interestingly CR (HR; 1.74, 95% CI; 0.63-4.77, p= 0.28), BA TP53mt (HR; 1.27, 95% CI; 0.13-11.72, p= 0.83) and complex CG (HR; 1.52, 95% CI 0.16-14.03, p= 0.70) did not retain significance for RFS in MVA. In MVA for OS, achievement of ORR (HR; 0.56, 95% CI; 0.30-1.05, p=0.07) and CR (HR; 0.32, 95% CI; 0.09-1.11, p=0.071) trended towards favorable OS. BA TP53mt status (p= 0.42) and complex CG (p= 0.19) did not significantly impact OS in UVA. Conclusion We conclude that while HMA+VEN combination therapy in comparison to HMA monotherapy led to improved response rates, with higher percentage of pts being bridged to allo-HCT, this was not associated with reduced risk of AML transformation, or improved RFS/OS. We eagerly await results from the prospective randomized trial of VEN + AZA in treatment-naïve HR-MDS (VERONA).