Myelodysplastic syndromes (MDS) are heterogeneous neoplastic disorders of hematopoietic stem cells (HSCs). The current standard of care for patients with MDS is hypomethylating agent (HMA)-based therapy; however, almost 50% of MDS patients fail HMA therapy and progress to acute myeloid leukemia, facing a dismal prognosis due to lack of approved second-line treatment options. As cancer stem cells are the seeds of disease progression, we investigated the biological properties of the MDS HSCs that drive disease evolution, seeking to uncover vulnerabilities that could be therapeutically exploited. Through integrative molecular profiling of HSCs and progenitor cells in large patient cohorts, we found that MDS HSCs in two distinct differentiation states are maintained throughout the clinical course of the disease, and expand at progression, depending on recurrent activation of the anti-apoptotic regulator BCL-2 or nuclear factor-kappa B-mediated survival pathways. Pharmacologically inhibiting these pathways depleted MDS HSCs and reduced tumor burden in experimental systems. Further, patients with MDS who progressed after failure to frontline HMA therapy and whose HSCs upregulated BCL-2 achieved improved clinical responses to venetoclax-based therapy in the clinical setting. Overall, our study uncovers that HSC architectures in MDS are potential predictive biomarkers to guide second-line treatments after HMA failure. These findings warrant further investigation of HSC-specific survival pathways to identify new therapeutic targets of clinical potential in MDS.

Hypomethylating agents (HMA) are the most commonly used therapeutic intervention in chronic myelomonocytic leukemia (CMML). Due to the lack of CMML-specific clinical trials, the impact of these agents in the natural history of CMML is not fully understood. We present the largest retrospective series of CMML (n=151) treated with HMA. Mean age at diagnosis was 69 years (range 50–88). According to the CMML-specific prognostic scoring system (CPSS): 17 (15%) were low-risk, 45 (39%) intermediate-1 risk, 42 (36%) intermediate-2, and 12 (10%) high-risk. 35 (23%) patients received single agent azacitidine, 73 (48%) single agent decitabine, and 43 (29%) combinations. With a median follow-up of 17 months, overall response rate (ORR) was 75%, with 41% achieving complete response (CR). Median overall survival (OS) was 24 months (95%CI: 20–28) and event-free survival 14 months (95%CI: 11–17). By multivariate analysis, age < 70 years, higher levels of hemoglobin, absence of blast in peripheral blood and lower CPSS cytogenetic risk predicted for better OS. CR was significantly higher in those patients treated with decitabine (58.3%) when compared with azacitidine (20.6%) (p<0.001). 13 patients (9%) received allo-SCT after a median of 4 cycles of HMA. 66 patients (50%) had HMA failure: 26 primary (34%) and 50 secondary (66%), including 35 (46%) that transformed to AML. Outcomes after HMA failure were poor with OS of 7 months (95%CI: 3–12). In conclusion, HMA are effective in CMML but new agents and combinations are needed. This data could be a benchmark for further drug development in CMML.

Most clinical trials exclude patients with poor performance or comorbidities. To study whether patients with these characteristics can be treated within a clinical trial, we conducted a study for patients with acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS) with poor performance, organ dysfunction or comorbidities. Primary endpoint was 60-day survival. Study included stopping rules for survival and response. Treatment consisted on a combination of azacitidine and vorinostat. Thirty patients (16 with MDS, 14 with AML) were enrolled. Median follow-up was 7.4 months (0.3-29). Sixty-day survival was 83%. No stopping rules were met. Main adverse events (AEs) were grades 1 and 2 gastrointestinal toxicities. In view of these results, we expanded the study and treated 79 additional patients: 27 with azacitidine (AZA) and 52 with azacitidine and vorinostat (AZA+V). Median follow-up was 22.7 months (12.6-47.5). Sixty-day survival rate was 79% (AZA=67%, AZA+V=85%, P=0.07). Median overall survival was 7.6 months (4.5-10.7). Median event-free survival was 4.5 months (3.5-5.6). Main AEs included grades 1 and 2 gastrointestinal toxicities. Our results suggest this subset of patients can be safely treated within clinical trials and derive clinical benefit. Relaxation of standard exclusion criteria may increase the pool of patients likely to benefit from therapy.

In patients with venous thromboembolism (VTE), assessment of the risk of fatal recurrent VTE and fatal bleeding during anticoagulation may help to guide intensity and duration of therapy. We aimed to provide estimates of the case-fatality rate (CFR) of recurrent VTE and major bleeding during anticoagulation in a 'real life' population, and to assess these outcomes according to the initial presentation of VTE and its etiology. The study included 41,826 patients with confirmed VTE from the RIETE registry who received different durations of anticoagulation (mean 7.8 ± 0.6 months). During 27,110 patient-years, the CFR was 12.1% (95% CI, 10.2-14.2) for recurrent VTE, and 19.7% (95% CI, 17.4-22.1) for major bleeding. During the first three months of anticoagulant therapy, the CFR of recurrent VTE was 16.1% (95% CI, 13.6-18.9), compared to 2.0% (95% CI, 0-4.2) beyond this period. The CFR of bleeding was 20.2% (95% CI, 17.5-23.1) during the first three months, compared to 18.2% (95% CI, 14.0-23.2) beyond this period. The CFR of recurrent VTE was higher in patients initially presenting with PE (18.5%; 95% CI, 15.3-22.1) than in those with DVT (6.3%; 95% CI, 4.5-8.6), and in patients with provoked VTE (16.3%; 95% CI, 13.6-19.4) than in those with unprovoked VTE (5.5%; 95% CI, 3.5-8.0). In conclusion, the CFR of recurrent VTE decreased over time during anticoagulation, while the CFR of major bleeding remained stable. The CFR of recurrent VTE was higher in patients initially presenting with PE and in those with provoked VTE.

Background Pracinostat is a potent histone deacetylase inhibitor with antitumor activity in both solid tumor and acute myeloid leukemia (AML) cell lines. Pracinostat has modest clinical activity in advanced solid tumors. Given the higher preclinical sensitivity of hematologic malignancies to pracinostat, we conducted a phase 1 study to assess the safety, maximum tolerated dose (MTD), recommended phase II dose (RP2D), efficacy, pharmacokinetics and pharmacodynamics of pracinostat in advanced hematological malignancies. Methods Pracinostat was administered orally thrice weekly for 3 weeks on a 28-day cycle. Patients were assigned to seven dose levels using a 3+3 dose escalation design. Results Forty-four patients were enrolled, 25 had AML and 14 had myelodysplastic syndrome (MDS). The MTD was 120 mg and the RP2D was 60 mg. Two AML patients achieved a response; 1 complete remission (CR) and 1 complete cytogenetic response. Despite dose-dependent increase in the plasma concentration of pracinostat, similar increase in histone acetylation was not observed. As an extension, 10 additional MDS patients were enrolled to assess the safety and efficacy of pracinostat in combination with azacitidine. Six patients achieved CR and 3 achieved CR without platelet recovery with no added toxicity. Conclusions Pracinostat is safe with modest single-agent activity in hematological malignancies.