Welcome to the MDS 2023 Congress Calendar

Abstract Body

The most frequently encountered cytopenia in IPSS-R lower risk MDS is anemia, which is responsible for the poor quality of life and clinical complications of these patients. While therapy with erythropoietic stimulating agents ( ESAs) is active in the vast majority of cases if rightly selected, some patients do not respond, or become irresponsive to ESAs. Novel agents with very different mode of action show promising clinical results in anemic LR-MDS refractory/relapsed after ESAs. Luspatercept, a TGFbeta family ligand-trap induces nearly 50% of RBC transfusion independence in MDS with ring sideroblasts ( RS), but it has been shown to be active also in transfusion dependent non-RS LR MDS both in first line and after failure of ESA treatment. The telomerase inhibitor imetelstat has shown efficacy and disease modifying activity in LR MDS ESA refractory or relapsed, who did not receive lenalidomide or hypomethylating agents. More recently, a randomized study vs placebo confirmed the activity of imetelstat in this setting, both in inducing RBC transfusion independence and in targeting the dysplastic clone. Another approach has been represented by the oral hypoxia–inducible factor (HIF) prolyl hydroxylase inhibitor roxadustat, tested in anemic LR- MDS pts (IPSS-R ≤4.5), non del(5q), low transfusion burden and endogenous EPO ≤400 U/L. This agent was also active in determining hematological improvement, mostrly in MDS-RS negative. Modulation of dose and schedule of hypomethylating agents, both injectable and in oral formulation is currently explored and preliminary results are positive.

Abstract Body

Half of the patients with myelodysplastic syndromes (MDS) carry heterozygous mutations in splicing factor genes. The most common mutation targeting SF3B1 gene induces an archetypal phenotype of acquired ineffective erythropoiesis characterized by an erythroid-rich and dysplastic bone marrow with accumulation of immature erythroblasts and ring sideroblasts (RS) responsible for a severe anemia. SF3B1 mutation confers a favorable outcome excluding association with high-risk mutation (RUNX1, mTP53) or chr 3, 5 or 7 abnormality.

SF3B1 mutation comes up in the hematopoietic stem cell frequently as the first initiating genetic event. In Sf3b1^K700E/+ mice models, anemia progressively develops, but mutant hematopoietic stem and progenitor cells (HSPCs) have a competitive disadvantage in transplantation assays. Combining epigenetic factor deletion and Sf3b1^K700E/+ mutation in mice, improves double mutant HSPC expansion and rescues their competitive activity. Co-editing of high-risk mutations with SF3B1 mutation in human primary CD34⁺ cells or in induced pluripotent stem cells allows immature HSPCs expansion and impairs myeloid and erythroid differentiation.Thus, co-mutations and/or a fitted microenvironment may support clonal selection and disease evolution in humans.

SF3B1 is a component of the U2 spliceosome involved in the recognition and binding of a branchpoint in introns to initiate pre-mRNA splicing. Mutations affect the HEAT domains that form a platform interacting with the pre-mRNAs. Most mis-splicing events are specific to SF3B1 mutation including the use of alternative 3’ splice site and the reduction of intron retention, which are not observed when other splicing factor genes SRSF2 or U2AF1 are mutated, suggesting a gain-of-function. RNA-sequencing and functional analyses performed on CD34⁺ cells or erythroblasts have identified mis-splicing events related to impaired erythroid development affecting upstream or downstream regulators of heme and iron metabolism TMEM14C, PPOX, EIF2AK1, ABCB7 and ERFE. Thereby, the downregulation of ABCB7 (for ATP binding cassette subfamily B member 7) is strongly linked to the accumulation of RS while the increased expression of the hepcidin transcriptional repressor ERFE (for erythroferrone), secondary to the translation of a splicing variant exhibiting a neo-junction, contributes to systemic iron overload. The degradation or, alternatively, the translation of variant transcripts orchestrate major changes in the transcriptome and proteome.

MDS with mutation in splicing factors may share common deregulated pathways such as innate immune signaling, inflammatory response, DNA repair or cell cycle control. U2AF1- or SF3B1 gene mutations activate chronic innate immune signaling and NF-kB pathway through the activation of IRAK4/TRAF6. Activation of DNA repair pathway associates with distinct features of DNA replication stress depending on the type of mutation. SRSF2 or U2AF1 mutation produces the formation of unscheduled DNA:RNA hybrids or R-loops across the genome that represent obstacles on the way of replication forks leading to fork stalling and double strand breaks. By contrast, SF3B1 mutation is associated with a loss of R-loops. SF3B1-mutated cells exhibit augmented DNA synthesis, accelerated replication forks, and single-stranded DNA exposure meaning that these cells are less prone to genomic instability. Chronic DNA replication stress associated with the loss of R-loops are hallmarks of SF3B1-mutated ineffective erythropoiesis.

Understanding the divergences between MDS with SF3B1 gene mutation and MDS with mutations in SRSF2 or U2AF1 genes would help with the decision for personalized treatment.

Background And Aims

Current therapies for MDS and AML, including hypomethylating agents (HMAs) & Venetoclax (Ven) have failed to eliminate therapy-resistant leukemic stem cells(LSC's). Elevated levels of the transcription factor STAT3 are observed in MDS LSC's. An increased level of STAT3 in MDS/AML patients is predictive of a poor prognosis. We sought to query if STAT3 is a therapeutic target in therapy resistant MDS/AML.

Methods

STAT3 is overexpressed in a Ven resistant MOLM13 AML line, and in an HMA resistant cell THP1 AML cell line. Pyrimethamine (PYR), an FDA approved anti-parasitic drug, inhibited STAT3 transcriptional activity at concentrations readily achieved in patients. PYR induced apoptosis in multiple leukemic cells within its therapeutic index (p<0.005). PYR significantly decreased proliferation when combined with azacytidine (AZA) (P= 0.0109) or venetoclax (P= 0.0271) treatments in HMA/Ven resistant cell lines. PYR and Ven drug combination showed strong synergy in an HMA resistant cell line (Z score = 14.523) and Ven resistant cell line (Z score = 11.065). (Fig1) An in vivo study demonstrated that PYR treatment lead to a significant decrease of blasts counts in an HMA resistant cell-line derived xenograft (CDX) leukemic mouse model compared to a PBS control. In addition, primary MDS patient samples treated with PYR show increased myeloid differentiation compared to healthy controls.

Results

Our results show that HMA and Ven resistant MDS/AML is sensitive to PYR treatment within the therapeutic index of STAT3 inhibition (5-10 uM). PYR with Ven drug combination demonstrates synergy.

Conclusions

Our current findings support STAT3 inhibition as a therapeutic strategy after the failure of HMA/Ven in MDS/AML.

Background And Aims

Azacitidine is a mainstay of therapy for MDS-related diseases. The purpose of our study is to elucidate the effect of gene mutations on hematological response and overall survival (OS), particularly focusing on their post-treatment clone size.

Methods

We enrolled a total of 449 patients with MDS or related myeloid neoplasms. They were analyzed for gene mutations in pre- (n=449) and post- (n=289) treatment bone marrow samples using targeted-capture sequencing to assess the impact of gene mutations and their post-treatment clone size on treatment outcomes.

Results

In Cox proportional hazard modeling, multi-hit TP53 mutation (HR, 2.03; 95% CI, 1.42-2.91; P<.001), EZH2 mutation (HR, 1.71; 95% CI, 1.14-2.54; P=.009), and DDX41 mutations (HR, 0.33; 95% CI, 0.17-0.62; P<.001), together with age, high-risk karyotypes, low platelet, and high blast counts, independently predicted OS. Post-treatment clone size accounting for all drivers significantly correlated with International Working Group (IWG)-response (P<.001, trend test), except for that of DDX41-mutated clones, which did not predict IWG-response. Combined, IWG-response and post-treatment clone size further improved the prediction of the original model and even that of a recently proposed molecular prediction model, IPSS-M (c-index, 0.653 vs 0.688; P<.001, likelihood ratio test).

Conclusions

In conclusion, evaluation of post-treatment clone size, together with pre-treatment mutational profile as well as IWG-response have a role in better prognostication of azacitidine-treated myelodysplasia patients.