Hematologic Response To Oral Azacitidine (CC-486) In Subjects With WHO-Defined RAEB-1 Or RAEB-2 Myelodysplastic Syndromes (MDS)

Subcutaneous (SC) azacitidine prolongs overall survival in subjects with higher-risk MDS (Fenaux, JCO, 2009). Previous Phase I and II studies have shown extended oral azacitidine dosing schedules to be safe and effective in subjects with IPSS-defined lower-risk MDS (Garcia-Manero et al, ASH 2010 and ASH 2012).

To assess the efficacy and safety of extended oral azacitidine dosing schedules in subjects with WHO-defined RAEB-1 or RAEB-2 MDS.

The subset of subjects with WHO-defined RAEB-1 or RAEB-2 MDS from two ongoing Phase I/II studies was included in this ad hoc analysis. Subjects received oral azacitidine 300mg QD or 200mg BID for 14 or 21 days of repeated 28-day cycles. For purposes of this analysis, subject data were analyzed collectively. Hematologic responses were defined by International Working Group (IWG) 2006 criteria. Overall Response was calculated as any response of complete or partial remission (CR or PR), RBC or platelet transfusion independence (TI), and/or any hematologic improvement (HI). Marrow complete remission (mCR) was not included in Overall Response. Serious treatment-emergent adverse events (STEAEs) that occurred in 2 or more subjects are reported.

Of 23 subjects in all, 20 received 300mg QD oral azacitidine x 14 or 21 days/28-day cycle and 3 received oral azacitidine 200mg BID x 14 days/28-day cycle. Subjects had median age of 71 (range: 36 - 90) years and were predominantly male (61%). Fourteen subjects (61%) had a diagnosis of RAEB-1 and 9 (39%) had RAEB-2, median time from diagnosis was 2.1 (0.1 - 33.2) months, and ECOG performance status scores were 0 (n=4, 17%), 1 (n=15, 65%), or 2 (n=4, 17%). Five subjects had received prior MDS treatments (azacitidine injection; erythropoiesis stimulating agent [ESA]; thalidomide; azacitidine injection and decitabine; G-CSF, anti-thymocyte globulin, methylprednisolone, cyclosporine, and ESA). Median number of oral azacitidine treatment cycles was 3 (1 - 29). Overall Response was achieved by 11/22 subjects (50%) (Table ). Four subjects achieved mCR only and are not included in the Overall Response category. RBC TI was achieved by 5/12 subjects (42%) and platelet TI was achieved by 2/5 subjects (40%). Two subjects were able to consolidate remission and proceed to allogeneic stem cell transplant and 1 subject progressed to AML on-study. Oral azacitidine was generally well tolerated. Three subjects discontinued treatment due to an AE. STEAEs were consistent with the known safety profile of SC azacitidine. Of 8 subjects who had an STEAE of febrile neutropenia, pneumonia, and/or septic shock, 3 were severely neutropenic (ANC <0.5 x 10⁹/L) at baseline. Other STEAEs were diarrhea, nausea, and vomiting (n=2 subjects each).

This analysis in subjects with RAEB-1 and RAEB-2 is the first to assess extended oral azacitidine dosing schedules in higher-risk MDS. One-half of treated subjects achieved a hematologic response to oral azacitidine, which is easy to administer and was generally well-tolerated. Two Phase III studies of extended oral azacitidine dosing (in lower-risk MDS and as maintenance therapy in older patients with AML) are ongoing. Results of these large studies will better elucidate the use of extended oral azacitidine dosing schedules in treating hematologic malignancies.

Gore:Celgene Corporation: Consultancy. Cogle:Celgene Corporation: Honoraria, Research Funding. Conkling:US Oncology: Research Funding. Beach:Celgene Corporation: Employment. Hetzer:Celgene Corporation: Employment. Dong:Celgene Corporation: Employment. Skikne:Celgene Corporation: Employment.