Chan, Winny

Abstract Background: Parenteral DNA methyltransferase inhibitors (DNMTi) such as azacitidine and decitabine (DEC), including an attenuated 3-day regimen, are recommended in the NCCN Guidelines for patients (pts) with lower-risk myelodysplastic syndromes (LR-MDS) with clinically significant cytopenias. However, parenteral administration requires frequent clinic visits, which imposes a substantial burden on pts, particularly those requiring long-term therapy. Oral DMTIs offer more flexible dosing and maintenance of pts' autonomy. Oral DEC-cedazuridine (DEC-C) is a fixed-dose combination tablet containing DEC (35 mg) and cedazuridine (100 mg). ASTX727-03 (NCT03502668) is a randomized, open-label, multicenter, phase 1/2 clinical trial evaluating safety, efficacy, and pharmacokinetics (PK) of various DEC-C doses and regimens in pts with LR-MDS. Phase 1 identified a 5-day regimen of DEC 10 mg/cedazuridine 100 mg as the optimized low-dose (LD) regimen. Phase 2 compares this LD regimen with the attenuated standard-dose (SD) regimen. Here, we report phase 2 results on efficacy, safety, PK, and pharmacodynamic (PD) data. Methods: Adults (aged ≥18 years) with International Prognostic Scoring System (IPSS) low-risk or Intermediate-1 MDS, ECOG PS 0−2, and ≥1 cytopenia or red blood cell (RBC) transfusion dependence were randomized 1:1 to receive oral DEC-C LD (10 mg x 5 days) or SD (35 mg x 3 days). The primary endpoint was hematologic response. Secondary endpoints included PK, PD (by LINE-1 demethylation), time to bone marrow blasts >5%, leukemia-free survival (LFS), overall survival (OS), and safety. Results: As of October 31, 2024, 81 pts were treated (LD arm: n=40; SD arm: n=41) and completed a median of 8.8 months on treatment. At cutoff, 17 (42.5%) and 12 (28.6%) LD and SD pts, respectively, were still continuing the study; 9 (22.5%) and 6 (14.6%) pts respectively, had discontinued treatment due to hematopoietic stem cell transplant. Median age was 70 (LD) and 75 (SD) years; 75.0% (LD) and 68.3% (SD) had IPSS Int-1 risk MDS and 60.0% vs 41.5% had IPSS-Molecular Lower-Risk MDS (very low, low, or moderate-low). Low-risk prognostic scoring system risk distribution was similar: Category 1 (2.5% vs 4.9%), Category 2 (47.5% vs 46.3%), and Category 3 (50.0% vs 48.8%). After a median follow-up of 29.3 months, median OS was 23.9 months (95% confidence interval [CI]: 13.0, not estimable [NE]) in the LD arm vs 26.0 months (95% CI: 19.4, 28.5) in the SD arm. Median LFS was 23.8 months (95% CI: 13.0, NE) and 25.7 months (95% CI: 17.8, 26.5), respectively. Hematologic improvement per International Working Group 2006 criteria was achieved in 27.5% (LD) and 26.8% (SD) of pts. Among RBC transfusion–dependent pts, 52.4% (LD) and 37.5% (SD) achieved ≥56-day independence and 47.6% (LD) and 20.8% (SD) achieved ≥112-day independence. Pts received a median of 10 (LD) and 9 (SD) cycles. Delayed cycles occurred in 72.5% (LD) vs 82.9% (SD) of pts; dose reductions occurred in 40.0% (LD) and 46.3% (SD) of pts. Both treatment regimens caused a decrease in blood counts, reaching a nadir before recovering in each cycle. Neutropenia was more pronounced during early cycles and was more severe in the SD arm. Blood counts across all lineages remained stable or improved through ≥12 cycles with the LD arm, suggesting a more favorable safety and tolerability profile. Grade ≥3 adverse events (AEs) occurred in 85.0% and 90.2% of pts in the LD and SD arms, respectively; treatment discontinuation due to AEs occurred in 2.5% and 17.1% of pts, respectively. Most commonly reported treatment-emergent AEs were anemia (42.5% LD, 39.0% SD), fatigue (32.5% LD, 43.9% SD), and thrombocytopenia (37.5% LD, 39.0% SD). Three deaths occurred in the trial: 2 in the LD arm, which were both unrelated to study treatment, and 1 in the SD arm (Pseudomonal bacteremia in Cycle 1), which was treatment related. Total AUC0–24 was 199 ng*h/mL in the LD arm and 465 ng*h/mL in the SD arm; AUC for all cycles of the LD arm was approximately half of the SD arm. Maximal % LINE-1 demethylation rate was lower with LD than SD, but narrowed by Cycle 3. Conclusion: LD oral DEC-C demonstrated comparable clinical benefit to SD oral DEC-C, with improved safety and tolerability, including fewer dose modifications and less severe myelosuppression. These findings support LD DEC-C as a potential optimal regimen for pts with LR-MDS. Clinical trial registration: NCT03502668

Background: Oral decitabine/cedazuridine (ASTX727) is a fixed dose combination of decitabine (35 mg) and the cytidine deaminase inhibitor cedazuridine (100 mg) given once daily X 5 days on a 28-day cycle producing pharmacokinetic (PK) exposure equivalent to the standard intravenous (IV) decitabine regimen of 20 mg/m 2 daily X 5 days on a 28-day cycle. This was demonstrated in the pivotal ASCERTAIN study (Garcia-Manero, et al, ASH 2019) as it provided a PK bridge to existing decitabine data and demonstrated median OS was 31.7 mo. (Savona,et al. Intl. MDSF International Congress on MDS, 2021). Subjects were initially classified by the International Prognosis Scoring System (IPSS) for historical reasons, however IPSS-R and IPSS-M are enhancements to IPSS that provide dynamic risk assessment for predicting clinical outcomes in MDS. Here, the objective was to re-classify the MDS subjects enrolled on the ASCERTAIN study by IPSS-R and IPSS-M and measure the impact of informing patient outcomes based on re-calculated risk assessment. Methods: One hundred thirty-three subjects with MDS/CMML (chronic myelomonocytic leukemia) were enrolled in ASCERTAIN and were randomly assigned either IV decitabine for cycle 1 and oral decitabine/cedazuridine for cycle 2 or the opposite treatment sequence. All subjects continuing beyond cycle 2 received oral decitabine/cedazuridine for all subsequent cycles until treatment discontinuation for disease progression, toxicity, patient's decision, or HSCT. Whole blood collected prior to treatment was used for DNA isolation and molecular abnormalities identified using next-generation sequencing (NGS) hematologic malignancy panel of 179 genes including all genes commonly mutated in MDS. In the initial analysis of clinical outcomes, subjects were classified by IPSS with response assessment by IWG 2006 IPSS low and Int-1 risk levels were categorized as lower-risk MDS (LR-MDS), whereas IPSS Int-2 and high-risk categories were categorized as higher-risk MDS (HR-MDS). Subjects with sufficient data based on (e.g., available heme parameters, cytogenetics, NGS etc.) were reclassified by IPSS-R and IPSS-M. Subjects with IPSS-R score of ≤3.5 or IPSS-M of either very low, low, or moderate low were categorized as LR-MDS. Similarly subjects with IPSS-R score of >3.5 or an IPSS-M categorization of either moderate high, high, or very high were categorized as HR-MDS. Reclassified subjects were reassessed for CR (Complete Response), OS, and LFS and Harrell's concordance index (c-index) was used to describe the level of agreement between each scale and outcomes. Results: Based on the available data, the number of MDS subjects in the different risk classifications were the following: IPSS: 117, IPSS-R: 104, and IPSS-M: 105. Thirteen and 12 subjects on the IPSS could not be reclassified in the IPSS-R and IPSS-M, respectively, including 5 Int-1 and 2 low-risk MDS cases. CMML subjects were excluded from these analyses. Re-classification generally resulted in the upgrade of the subjects from LR-MDS to HR-MDS (Fig. 1). Thirty-one (26.5%) subjects from IPSS were reallocated in the IPSS-R to different risk categories; 3 (9.7%) were downgraded and 28 (90.3%) were upgraded. Similarly on reclassification with IPSS-M 34 (32.4%) of the patients reclassified; 5 (14.8%) were downgraded and 29 (85.3%) were upgraded. For IPSS LR-MDS, 23.2% of patients achieved CR, and 22.9% in the IPSS HR-MDS. Similarly, 21.6% patients achieved CR in the IPSS-R LR-MDS, and 23.9% in the IPSS-R HR-MDS; 26.3% patients achieved CR in the IPSS-M LR-MDS, and 20.9% in the IPSS-M HR-MDS. The c-index for the IPSS was .64 (OS) and .67 (LFS), IPSS-R was .70 (OS) and .71 (LFS), and .75 (OS) and .78 (LFS) for the IPSS-M (Table1). Conclusion: Reclassification from IPSS to IPSS-R or IPSS-M upgraded multiple subjects from a LR to a HR category, describing the ASCERTAIN patient population as a majority higher risk population with worse prognosis than previously assumed based on the IPSS. The efficacy as measured by the CR rates did not change when the LR and HR categories were defined by the different risk stratification systems. In contrast, the c-index improves with migration from IPSS to IPSS-R to IPSS-M, indicating an increased discriminatory ability of IPSS-M score in comparison to IPSS and IPSS-R, to predict patient outcomes.