Rosenblat, Todd

Abstract Introduction: The interleukin-3 receptor alpha chain (CD123) is a cell-surface target aberrantly expressed on various myeloid neoplasms including blastic plasmacytoid dendritic cell neoplasm (BPDCN), acute myeloid leukemia (AML), chronic myelomonocytic leukemia (CMML), and myelofibrosis (MF). Tagraxofusp (TAG, SL-401), a first-in-class CD123-targeted therapy, is the only treatment approved by the FDA and EMA for patients (pts) with BPDCN. It has also been investigated in phase 1/2 clinical trials for AML (including pts with minimal residual disease [MRD]), CMML, and MF. We report the aggregated safety data of TAG monotherapy from trials in BPDCN, AML, CMML, and MF. Methods: An integrated safety analysis was performed for pts who received TAG monotherapy in three phase 1/2, multicenter clinical studies: Study 0114 (NCT02113982; BPDCN/AML), Study 0214 (NCT02270463; AML with/without MRD), and Study 0314 (NCT02268253; CMML/MF; Table 1). Pts received the recommended phase 2 dose of 12 mcg/kg/day (d) IV on d1-3 (MF and CMML) or d1-5 (BPDCN and AML) and were analyzed for incidence and timing of treatment-related adverse events (TRAEs), AEs of interest, and discontinuations. Safety data for TAG monotherapy, reported as individual case study reports (ICSRs) postapproval (US) and from an early access program (EAP; EU) are also presented. Results: In total, 201 pts receiving TAG (12 mcg/kg/d) in a clinical trial setting were included: BPDCN, n=86; AML, n=36; AML with/without MRD, n=10; CMML, n=33; MF, n=36. As of Jul 2021, 11 (6%) pts discontinued TAG due to any-grade (Gr) TRAE. Most common TRAEs (any-Gr) are shown in Table 2 and included hypoalbuminemia (41%), increased alanine aminotransferase (ALT; 40%), increased aspartate aminotransferase (AST; 39%), and thrombocytopenia (26%). The most common Gr ≥3 TRAEs were thrombocytopenia (n=41; 20%), increased AST (n=40; 20%), and increased ALT (n=35; 17%). Tumor lysis syndrome occurred in 5% of pts and 1.5% had infusion-related reactions. Any-Gr and Gr ≥3 hematologic TRAEs are presented in Table 3. Most common was thrombocytopenia. All TRAEs were transient in nature; prolonged bone marrow suppression was not observed. Overall, 23% (47/201) of pts experienced ≥1 treatment-related serious AE. Onset of most TRAEs, irrespective of Gr, commonly occurred in cycle 1 and resolved by cycle 2. Although the number of pts in cycles ≥2 was lower than in cycle 1, the incidence rates of common TRAEs also substantially decreased in subsequent cycles. Capillary leak syndrome (CLS) occurred in 17% of the overall 201 pts. The majority of all CLS events were nonsevere, Gr ≤2 (n=22; 63%); also reported were Gr 3, n=10 (29%); Gr 4, n=3 (9%), and 2 pts experienced a Gr 5 event. Onset of CLS was usually within the first week of cycle 1 (median time to onset [range], d: 5.5 [1-51]) and resolved quickly (median time to resolution [range], d: 5.0 [2-69]); no pts experienced the first onset after cycle 2. Of the 15 pts who resumed treatment after an initial CLS event, only 1 pt experienced a recurrence. The most common AEs reported as ICSRs postapproval and from an EAP (December 2018 to June 2021) were CLS, blood albumin decreased, thrombocytopenia, pyrexia, and hepatic enzyme increased. No new safety signals that would alter the safety profile were observed. Conclusions: This integrated analysis represents the largest collection of safety data (N=201) following treatment with TAG monotherapy. TAG has an established and manageable safety profile, with the vast majority of AEs reported as transient and decreasing in frequency/severity with increasing cycles. CLS was reported in 17% of pts; onset was usually within cycle 1, resolved quickly (median time to resolution: 5.0 d) by early intervention measures including holding treatment, and no pts experienced first onset after cycle 2. Risk-minimization guidelines for CLS were developed and implemented during clinical trials and incorporated into prescribing information. No myelosuppression or cumulative toxicity was observed over multiple treatment cycles. The safety profile observed postapproval and in the EAP was consistent with the clinical trial data reported, reflecting successful adoption of risk-management strategies in real-world practice. These data confirm the favorable benefit-risk profile of TAG monotherapy has been maintained in the 3 years following US approval. Figure 1 Figure 1. Disclosures Pemmaraju: ASCO Leukemia Advisory Panel: Membership on an entity's Board of Directors or advisory committees; Sager Strong Foundation: Other; Blueprint Medicines: Consultancy; Incyte: Consultancy; Bristol-Myers Squibb Co.: Consultancy; Pacylex Pharmaceuticals: Consultancy; Cellectis S.A. ADR: Other, Research Funding; Aptitude Health: Consultancy; Celgene Corporation: Consultancy; CareDx, Inc.: Consultancy; Springer Science + Business Media: Other; Daiichi Sankyo, Inc.: Other, Research Funding; Samus: Other, Research Funding; Clearview Healthcare Partners: Consultancy; Dan's House of Hope: Membership on an entity's Board of Directors or advisory committees; MustangBio: Consultancy, Other; Abbvie Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; HemOnc Times/Oncology Times: Membership on an entity's Board of Directors or advisory committees; ASH Communications Committee: Membership on an entity's Board of Directors or advisory committees; LFB Biotechnologies: Consultancy; Novartis Pharmaceuticals: Consultancy, Other: Research Support, Research Funding; Protagonist Therapeutics, Inc.: Consultancy; Affymetrix: Consultancy, Research Funding; DAVA Oncology: Consultancy; Plexxicon: Other, Research Funding; Roche Diagnostics: Consultancy; Stemline Therapeutics, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; ImmunoGen, Inc: Consultancy. Kantarjian: NOVA Research: Honoraria; Aptitude Health: Honoraria; Immunogen: Research Funding; BMS: Research Funding; Precision Biosciences: Honoraria; Novartis: Honoraria, Research Funding; Ascentage: Research Funding; Pfizer: Honoraria, Research Funding; Astra Zeneca: Honoraria; Astellas Health: Honoraria; Jazz: Research Funding; Ipsen Pharmaceuticals: Honoraria; Amgen: Honoraria, Research Funding; Daiichi-Sankyo: Research Funding; KAHR Medical Ltd: Honoraria; AbbVie: Honoraria, Research Funding; Taiho Pharmaceutical Canada: Honoraria. Sweet: Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; AROG: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Bristol Meyers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees. Wang: Kite Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board; Jazz Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board; DAVA Oncology: Consultancy, Speakers Bureau; BMS/Celgene: Membership on an entity's Board of Directors or advisory committees; Stemline Therapeutics: Consultancy, Honoraria, Other: Advisory board, Speakers Bureau; Genentech: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy, Honoraria, Other: Advisory Board; Takeda: Consultancy, Honoraria, Other: Advisory board; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Other: Advisory Board, Speakers Bureau; Kura Oncology: Consultancy, Honoraria, Other: Advisory board, steering committee, Speakers Bureau; Novartis: Consultancy, Honoraria, Other: Advisory Board; Mana Therapeutics: Consultancy, Honoraria; Rafael Pharmaceuticals: Other: Data safety monitoring committee; Gilead: Consultancy, Honoraria, Other: Advisory board; Daiichi Sankyo: Consultancy, Honoraria, Other: Advisory board; PTC Therapeutics: Consultancy, Honoraria, Other: Advisory board; Genentech: Consultancy; MacroGenics: Consultancy. Lane: N-of-One: Consultancy, Honoraria; Stemline Therapeutics: Research Funding; Qiagen: Consultancy, Honoraria; AbbVie: Research Funding. Ali: Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Speakers Bureau; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees. Stein: Amgen: Consultancy, Speakers Bureau; Celgene: Speakers Bureau; Stemline: Speakers Bureau. Yacoub: Agios: Membership on an entity's Board of Directors or advisory committees; Acceleron Pharma: Membership on an entity's Board of Directors or advisory committees; CTI Biopharma: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Incyte: Speakers Bureau. Rizzieri: Celltron/Teva: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: presentation to FDA for biosimilar review ; AROG: Other; Amgen: Other: personal fee; Bayer: Consultancy, Honoraria; Kite: Other: personal fee; Mustang: Consultancy, Honoraria; Stemline Therapeutics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Incyte: Other: personal fee; Gilead: Other: personal fee; Jazz: Other: personal fee; Pharmacyclics: Other. Vasu: Seattle Genetics: Other: travel support; Boehringer Ingelheim: Other: Travel support; Kiadis, Inc.: Research Funding; Omeros, Inc.: Membership on an entity's Board of Directors or advisory committees. Gupta: AbbVie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy; Constellation Pharma: Consultancy, Honoraria; Pfizer: Consultancy; BMS-Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sierra Oncology: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Research Funding. Lee: BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pin Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Innate: Consultancy, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees. Schiller: Sangamo: Research Funding; Actinium Pharmaceuticals, Inc: Research Funding; FujiFilm: Research Funding; Pfizer: Current equity holder in publicly-traded company, Research Funding; Abbvie: Research Funding; Karyopharm: Research Funding; Onconova: Research Funding; Celator: Research Funding; Actuate: Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Trovagene: Research Funding; Deciphera: Research Funding; Gamida Cell Ltd.: Research Funding; Forma: Research Funding; Ono-UK: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Arog: Research Funding; Takeda: Research Funding; Geron: Research Funding; Jazz: Consultancy, Honoraria, Research Funding, Speakers Bureau; PrECOG: Research Funding; Kite/Gilead: Honoraria, Research Funding, Speakers Bureau; Mateon: Research Funding; Constellation Pharmaceuticals: Research Funding; Daiichi-Sankyo: Research Funding; Tolero: Research Funding; Stemline Therapeutics, Inc.: Honoraria, Research Funding, Speakers Bureau; Samus: Research Funding; Astellas: Honoraria, Research Funding, Speakers Bureau; Regimmune: Research Funding; BMS/Celgene: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; Agios: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Current equity holder in publicly-traded company, Honoraria, Research Funding, Speakers Bureau; Bio: Research Funding; Elevate: Research Funding; Delta-Fly: Research Funding; Genentech-Roche: Research Funding; Ariad: Research Funding; Sanofi: Honoraria, Research Funding, Speakers Bureau; Pharma: Consultancy; Johnson & Johnson: Current equity holder in publicly-traded company; Biomed Valley Discoveries: Research Funding; Eli Lilly: Research Funding; ASH foundation: Other: Chair-unpaid; Sellas: Research Funding; Ono: Consultancy; Incyte: Consultancy; AstraZeneca: Consultancy; Kaiser Permanente: Consultancy; Cyclacel: Research Funding; MedImmune: Research Funding; Ambit: Research Funding; Leukemia & Lymphoma Society: Research Funding; Bluebird Bio: Research Funding; Boehringer-Ingleheim: Research Funding; Cellerant: Research Funding; CTI Biopharma: Research Funding; Janssen: Research Funding; Kura Oncology: Research Funding; Pharmacyclics: Honoraria, Speakers Bureau; Millennium: Research Funding; National Marrow Donor Program: Research Funding; NIH: Research Funding; Onyx: Research Funding; Pharmamar: Research Funding; UC Davis: Research Funding; UCSD: Research Funding; Evidera: Consultancy; NCI: Consultancy; Novartis: Speakers Bureau. Foran: trillium: Research Funding; actinium: Research Funding; aptose: Research Funding; novartis: Honoraria; OncLive: Honoraria; servier: Honoraria; gamida: Honoraria; takeda: Research Funding; boehringer ingelheim: Research Funding; abbvie: Research Funding; certara: Honoraria; bms: Honoraria; pfizer: Honoraria; sanofi aventis: Honoraria; revolution medicine: Honoraria; taiho: Honoraria; syros: Honoraria; kura: Research Funding; h3bioscience: Research Funding; aprea: Research Funding; sellas: Research Funding; stemline: Research Funding. Walter: Macrogenics: Consultancy, Research Funding; Jazz: Research Funding; Pfizer: Consultancy, Research Funding; Selvita: Research Funding; Amphivena: Consultancy, Other: ownership interests; Agios: Consultancy; Astellas: Consultancy; BMS: Consultancy; Genentech: Consultancy; Janssen: Consultancy; Kite: Consultancy; Immunogen: Research Funding; Celgene: Consultancy, Research Funding; Aptevo: Consultancy, Research Funding; Amgen: Research Funding. Sieminski: Stemline Therapeutics: Current Employment, Current holder of stock options in a privately-held company. Patnaik: Kura Oncology: Research Funding; Stemline Therapeutics: Membership on an entity's Board of Directors or advisory committees; Stemline Therapeutics: Membership on an entity's Board of Directors or advisory committees. Mughal: Oxford University Press, Informa: Other: financial benefit and/or patents ; Stemline: Current Employment, Current holder of stock options in a privately-held company. Konopleva: Calithera: Other: grant support, Research Funding; Reata Pharmaceuticals: Current holder of stock options in a privately-held company, Patents & Royalties: intellectual property rights; Genentech: Consultancy, Honoraria, Other: grant support, Research Funding; Agios: Other: grant support, Research Funding; Ascentage: Other: grant support, Research Funding; AstraZeneca: Other: grant support, Research Funding; Rafael Pharmaceuticals: Other: grant support, Research Funding; Forty Seven: Other: grant support, Research Funding; Ablynx: Other: grant support, Research Funding; Eli Lilly: Patents & Royalties: intellectual property rights, Research Funding; Novartis: Other: research funding pending, Patents & Royalties: intellectual property rights; Stemline Therapeutics: Research Funding; KisoJi: Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria, Other: grant support; Cellectis: Other: grant support; Sanofi: Other: grant support, Research Funding; AbbVie: Consultancy, Honoraria, Other: Grant Support, Research Funding.

Background: Guadecitabine is a next generation subcutaneous (SC) hypomethylating agent (HMA) resistant to degradation by cytidine deaminase which results in prolonged in vivo exposure to the active metabolite decitabine. We conducted a phase 2 study of guadecitabine in 102 Myelodysplastic Syndromes (MDS), and Chronic Myelomonocytic leukemia (CMML) patients. International guidelines recommend a minimum of 4 to 6 cycles of HMA treatment to gain maximum benefit, but some suggest that treatment may not be beneficial if no response was observed after 4 cycles. No prospective studies have confirmed the correlation between an HMA number of cycles with response and survival using landmark methodology. We present here the results of landmark response and survival analyses based on number of cycles and whether patients had an objective response or not. M ethods: Landmark response based on 2006 IWG criteria, and overall survival (OS) analyses for patients alive at or beyond month 3 and month 5 (time of planned start of cycle 4 and cycle 6 respectively) were conducted. Objective response (OR) was defined as patients who had Complete Response (CR), Partial Response (PR), marrow (m)CR, or Hematological Improvement (HI). Landmark OS was compared between patients who received at least 4 or 6 cycles and those who did not. The landmark methodology avoids the bias of early deaths before cycles 4 and 6 attributing a survival benefit in those who did not die early and were able to get more cycles. We also compared the result in responding and non-responding patients to see if survival benefit was restricted to responding patients only. Results: The study completed enrolment with 102 patients: 53 patients after HMA failure (relapsed/refractory or r/r), and 49 HMA-naive patients (Treatment Naïve or TN) with a median follow up for the entire study of 3.2 years (IQR 2.9-3.5 years). Median age was 71 and 72 years for TN MDS/CMML and r/r MDS/CMML patients respectively. Median OS was 23.4 months (m) for TN MDS/CMML patients and 11.7 m for r/r MDS/CMML patients. Of the 102 patients treated, 37 patients (36.3%) and 58 (56.9%) received less than 4 and 6 cycles respectively. The landmark analysis population was 91 patients for the 4-cycle analysis and 87 patients for the 6-cycle analysis. In those patients, the primary reasons for treatment discontinuation before cycle 4 or 6 respectively were patient decision (9.8% and 11.8%), and investigator decision (5.9% and 9.8%) while early progression accounted for 3.9% and 10.8% of those patients. There were no major baseline characteristics difference between patients who received at least 4 and 6 cycles and those who did not in the patients included in the landmark analyses. In the landmark analysis, patients who received at least 4 cycles (65 patients) had an OR rate of 68% compared to 15% in 26 patients who received <4 cycles (p <0.0001) and median OS of 20.4 m compared to 15.2 m respectively (HR 0.78, 95% CI 0.45-1.3, p 0.36). Those who received at least 6 cycles (44 patients) had an OR rate of 82% compared to 26% in 43 patients who received < 6 cycles (p<0.0001), and median OS of 23.8 m vs 13.6 m respectively (HR 0.51, 95% CI 0.3-0.85, p 0.009). Results were consistent when r/r MDS/CMML and HMA-naïve MDS/CMML were analyzed separately. Landmark OS analysis also favored those who received guadecitabine for at least 4 or 6 cycles compared to those who received <4 and < 6 cycles even in the absence of objective response (OS HR of 0.82 and 0.42 respectively) but the sample size was small to show statistical significance (p 0.58 and 0.10 respectively) Summary/Conclusions: In a prospective phase 2 study of 102 MDS/CMML patients treated with the HMA guadecitabine, patients who were alive at the planned start of cycle 4 and cycle 6 did not continue treatment primarily because of patient or investigator decision in addition to early progression. Those who were alive and continued treatment for at least 4 or 6 cycles achieved highly significant objective response benefit compared to those who did not. Survival benefit was highly significant for those who received at least 6 cycles and was not restricted to patients who had an objective response. It is important to weigh reasons for treatment discontinuation carefully before discontinuing guadecitabine HMA treatment in MDS/CMML patients before 6 cycles to maximize response and survival benefit. Disclosures Savona: Selvita: Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm Therapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Patents & Royalties; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Sunesis: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding. Kantarjian:Takeda: Honoraria; Astex: Research Funding; Immunogen: Research Funding; Cyclacel: Research Funding; Ariad: Research Funding; Pfizer: Honoraria, Research Funding; BMS: Research Funding; Agios: Honoraria, Research Funding; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Daiichi-Sankyo: Research Funding; AbbVie: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Jazz Pharma: Research Funding. Roboz:Trovagene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sandoz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Otsuka: Consultancy, Membership on an entity's Board of Directors or advisory committees; Orsenix: Consultancy, Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Eisai: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celltrion: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astex: Consultancy, Membership on an entity's Board of Directors or advisory committees; Argenx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amphivena: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Actinium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees. O'Connell:Genentech: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Astex: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Shionogi: Membership on an entity's Board of Directors or advisory committees. Yee:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astex: Research Funding; Hoffman La Roche: Research Funding; MedImmune: Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding; Millennium: Research Funding; Astellas: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Stock:Research to Practice: Honoraria; UpToDate: Honoraria; Kite, a Gilead Company: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Daiichi: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees. Griffiths:Appelis Pharmaceuticals: Other: PI on a clinical trial; Abbvie, Inc.: Consultancy, PI on a clinical trial; Celgene, Inc: Consultancy, Research Funding; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Appelis Pharmaceuticals: Other: PI on a clinical trial; Onconova Therapeutics: Other: PI on a clinical trial; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Abbvie, Inc.: Consultancy; New Link Genetics: Consultancy; Persimmune: Consultancy; Boston Scientific: Consultancy; Genentech, Inc.: Research Funding; Genentech, Inc.: Research Funding; Boston Scientific: Consultancy; Persimmune: Consultancy; Onconova Therapeutics: Other: PI on a clinical trial; Novartis Inc.: Consultancy; Celgene, Inc: Consultancy, Research Funding; New Link Genetics: Consultancy; Partner Therapeutics: Consultancy; Novartis Inc.: Consultancy; Partner Therapeutics: Consultancy. Jabbour:Takeda: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Adaptive: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Cyclacel LTD: Research Funding. Podoltsev:Boehringer Ingelheim: Research Funding; Genentech: Research Funding; Blueprint Medicines: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Research Funding; Sunesis Pharmaceuticals: Research Funding; Alexion: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Kartos Therapeutics: Research Funding; Astellas Pharma: Research Funding; Samus Therapeutics: Research Funding; Jazz Pharmaceuticals: Research Funding; Astex Pharmaceuticals: Research Funding; Celgene: Other: Grant funding, Research Funding; Arog Pharmaceuticals: Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AI Therapeutics: Research Funding; Pfizer: Research Funding; CTI Biopharma: Research Funding. Su:Astex Pharmaceuticals, Inc.: Employment. Azab:Astex Pharmaceuticals, Inc.: Employment. Garcia-Manero:AbbVie: Research Funding; Celgene: Consultancy, Research Funding; Helsinn: Research Funding; Novartis: Research Funding; Amphivena: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Onconova: Research Funding; H3 Biomedicine: Research Funding; Merck: Research Funding.

Background: Guadecitabine is a next generation subcutaneous (SC) hypomethylating agent (HMA) resistant to degradation by cytidine deaminase which results in prolonged in vivo exposure to the active metabolite decitabine. We conducted a phase 2 study of guadecitabine in 206 AML patients. International guidelines recommend a minimum of 4 to 6 cycles of HMA treatment to gain maximum benefit, but some suggest that treatment may not be beneficial if no response was observed after 4 cycles. No prospective studies have confirmed the correlation between an HMA number of cycles with response and survival using landmark methodology. We present here the results of landmark response and survival analyses based on number of cycles and whether patients had an objective response or not. M ethods: Landmark response (CR, CRi, or CRp based on 2003 IWG criteria, grouped together as composite CR or CRc), and overall survival (OS) analyses for patients alive at or beyond month 3 and month 5 (time of planned start of cycle 4 and cycle 6 respectively) were conducted. Landmark OS was compared between patients who received at least 4 or 6 cycles and those who did not. The landmark methodology avoids the bias of early deaths before cycles 4 and 6 attributing a survival benefit in those who did not die early and were able to get more cycles. We also compared the result in responding and non-responding patients to see if survival benefit was restricted to responding patients only. Results: The study completed enrolment with 206 AML patients: 103 patients (50%) for each of Treatment Naïve (TN) unfit for intensive chemotherapy, and relapsed/refractory (r/r) AML. Median age was 68.5y (range 22-92y), ECOG PS ≥2 in 26%, poor risk cytogenetics in 41%, secondary AML in 26%, and median baseline BM blasts % was 40% in the total AML population. 108 patients (52.4%), and 155 patients (75%) received <4 and <6 cycles respectively. The primary reasons for treatment discontinuation before 4 and 6 cycles respectively (% from the total population of 206 patients) were early progression (20.4, and 30.6%), and early death (12.6%, and 17%). However, 9.7% and 14% discontinued treatment before 4 or 6 cycles respectively as a result other less objective reasons such as patient decision, investigator decision, or adverse events which might have been manageable without treatment discontinuation. The landmark analysis population included 161 patients for 4-cycle analysis, and 133 for the 6-cycle analysis. In those patients, there were no major differences in baseline characteristics between those who received at least 4 or 6 cycles and those who did not. In the landmark analysis comparing those who received at least 4 cycles (97 patients) and those who did not (64 patients), CRc rate was 62% vs 25% (p < 0.0001) and median OS was 13.7 m vs 6.1 respectively (HR 0.53, 95% CI 0.37-0.75, p 0.0003). In the landmark analysis comparing those who received at least 6 cycles (51 patients) and those who did not (82 patients) the CRc rate was 82.4% vs 35.4% (p < 0.0001), and median OS of 19.9 m vs 8.8 m respectively (HR 0.42, 95% CI 0.27-0.64, p <0.0001). The results were consistent when TN and r/r AML patients were analyzed separately. More interestingly the landmark OS benefit in patients who received at least 4 or 6 cycles was also evident in patients who did not have an objective CRc. Patients with no CRc who received at least 4 cycles had a median OS of 8 m vs 5.4 m in those who did not (HR 0.63, 95% CI 0.40-0.98,p 0.04). Patients with no CRc who received at least 6 cycles had a median OS of 12.9 vs 8 m in those who did not (HR 0.40, 95% CI 0.17-0.94, p 0.03). Summary/Conclusions: In a prospective phase 2 study of 206 TN and r/r AML patients treated with the HMA guadecitabine, patients who were alive at or beyond 3 and 5 months who continued treatment for at least 4 or 6 cycles respectively achieved a highly significant response and survival benefit compared to those who discontinued treatment before cycle 4 or 6. The survival benefit was evident even in patients who did not have an objective response. Reasons for treatment discontinuation should be weighed carefully before stopping HMA treatment with guadecitabine before 4 or 6 cycles in AML patients to maximize response and survival benefit. Failure to achieve an objective response after 4 cycles should not be a reason for treatment discontinuation as long as patient can still benefit. Disclosures Yee: MedImmune: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astex: Research Funding; Hoffman La Roche: Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding; Millennium: Research Funding; Astellas: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees. Roboz:AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Actinium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amphivena: Consultancy, Membership on an entity's Board of Directors or advisory committees; Argenx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astex: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celltrion: Consultancy, Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees; Eisai: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Orsenix: Consultancy, Membership on an entity's Board of Directors or advisory committees; Otsuka: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sandoz: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Trovagene: Consultancy, Membership on an entity's Board of Directors or advisory committees. O'Connell:BMS: Membership on an entity's Board of Directors or advisory committees; Shionogi: Membership on an entity's Board of Directors or advisory committees; Astex: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees. Griffiths:Boston Scientific: Consultancy; Boston Scientific: Consultancy; Abbvie, Inc.: Consultancy; Persimmune: Consultancy; Genentech, Inc.: Research Funding; Novartis Inc.: Consultancy; Novartis Inc.: Consultancy; New Link Genetics: Consultancy; Appelis Pharmaceuticals: Other: PI on a clinical trial; Partner Therapeutics: Consultancy; Appelis Pharmaceuticals: Other: PI on a clinical trial; Onconova Therapeutics: Other: PI on a clinical trial; New Link Genetics: Consultancy; Abbvie, Inc.: Consultancy, PI on a clinical trial; Celgene, Inc: Consultancy, Research Funding; Onconova Therapeutics: Other: PI on a clinical trial; Partner Therapeutics: Consultancy; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Persimmune: Consultancy; Celgene, Inc: Consultancy, Research Funding; Astex Phramaceuticals/Otsuka Pharmaceuticals: Consultancy, Research Funding; Genentech, Inc.: Research Funding. Stock:Daiichi: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Research to Practice: Honoraria; Kite, a Gilead Company: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; UpToDate: Honoraria. Garcia-Manero:Amphivena: Consultancy, Research Funding; Helsinn: Research Funding; Novartis: Research Funding; AbbVie: Research Funding; Celgene: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Onconova: Research Funding; H3 Biomedicine: Research Funding; Merck: Research Funding. Savona:AbbVie: Membership on an entity's Board of Directors or advisory committees; Selvita: Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sunesis: Research Funding; Karyopharm Therapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Patents & Royalties; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding. Ravandi:Macrogenix: Consultancy, Research Funding; Selvita: Research Funding; Cyclacel LTD: Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Menarini Ricerche: Research Funding; Xencor: Consultancy, Research Funding. Daver:Astellas: Consultancy; Daiichi Sankyo: Consultancy, Research Funding; Forty-Seven: Consultancy; Incyte: Consultancy, Research Funding; Servier: Research Funding; Incyte: Consultancy, Research Funding; NOHLA: Research Funding; Jazz: Consultancy; Glycomimetics: Research Funding; NOHLA: Research Funding; Abbvie: Consultancy, Research Funding; Agios: Consultancy; Celgene: Consultancy; Sunesis: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Karyopharm: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Astellas: Consultancy; Hanmi Pharm Co., Ltd.: Research Funding; Forty-Seven: Consultancy; Agios: Consultancy; Otsuka: Consultancy; Jazz: Consultancy; Immunogen: Consultancy, Research Funding; Glycomimetics: Research Funding; Sunesis: Consultancy, Research Funding; Hanmi Pharm Co., Ltd.: Research Funding; Karyopharm: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Otsuka: Consultancy; Celgene: Consultancy; Daiichi Sankyo: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Servier: Research Funding; BMS: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Immunogen: Consultancy, Research Funding. Jabbour:AbbVie: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Cyclacel LTD: Research Funding; Adaptive: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; BMS: Consultancy, Research Funding. Su:Astex Pharmaceuticals, Inc.: Employment. Azab:Astex Pharmaceuticals, Inc.: Employment. Kantarjian:Pfizer: Honoraria, Research Funding; Astex: Research Funding; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Cyclacel: Research Funding; Takeda: Honoraria; Immunogen: Research Funding; Jazz Pharma: Research Funding; Amgen: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; Agios: Honoraria, Research Funding; BMS: Research Funding; Ariad: Research Funding; Daiichi-Sankyo: Research Funding; Novartis: Research Funding.

Abstract Background: Guadecitabine SC (SGI-110) is a dinucleotide next generation HMA resistant to degradation by cytidine deaminase resulting in extended in vivo exposure to its active metabolite decitabine. A Phase 1 established 60 mg/m2 QDx5 as the biologically effective dose (BED), and 90 mg/m2 QDx5 as the Maximum tolerated dose (MTD) in MDS patients given in 28-day cycles (Issa et al, 2015, Lancet Oncology). Phase 2 is conducted to evaluate dose response between the BED and MTD in both untreated MDS patients, and patients previously treated with other HMAs. M ethods: Int, or HR MDS, and CMML patients who were either treatment-naïve (TN) or relapsed/refractory to other HMAs (r/r) were randomized to either 60 mg/m2 or 90 mg/m2 QDx5 every 28 days. Efficacy was evaluated by the clinical responses of CR, PR, marrow CR (mCR), and Hematological Improvement (HI) based on the International Working Group Criteria 2006, as well as transfusion-independence, and overall survival (OS). Adverse events (AEs) were graded by the CTCAE v4 criteria. Results: The study completed target enrolment with 102 patients: 53 r/r MDS, and 49 TN MDS. Fifty three patients were randomized to 60 mg/m2 and 49 patients to 90 mg/m2 QDx5 with a median follow up of 3.2 years (IQR 2.8-3.5 years). Median age was 72 and 71 years for r/r and TN MDS respectively. Most baseline patient characteristics were well balanced between the 2 treatment dose groups except that more CMML patients were randomized to the 60 mg/m2 group (28%) vs. 14% in the 90 mg/m2 group, and more patients with baseline BM blasts >5% were in the 90 mg/m2 group (67%) vs. 38% in the 60 mg/m2 group. Most patients were RBC transfusion-dependent at baseline (57%). In the r/r MDS cohort, most patients (58%) received their last HMA treatment <3 month before enrolment, and most of them received ≥6 months of prior HMA treatment (77%). Median number of treatment cycles was 5 for both r/r and TN MDS (range 1-37 in r/r MDS and 1-49 in TN MDS). In the TN MDS cohort CR was achieved in 11 (22%) of patients with no major difference between the 2 dose groups (19% in the 60 mg/m2 group vs 27% in the 90 mg/m2 group). Overall CR+mCR was achieved in 18 patients (37%) in TN MDS patients and median OS was 23.4 months. In the r/r MDS cohort, CR was achieved in 4% of patients in each of the 2 dose groups. Overall CR+mCR in the r/r MDS cohort was achieved in 17 patients (32%), with a median duration of response of 7.9 months, and median OS of 11.7 months. No significant difference in response or OS between the 2 dose groups was observed. In patients who were RBC transfusion-dependent at baseline, transfusion independence for at least 8 weeks was achieved in 42% of TN MDS, and 15% in r/r MDS patients. In the overall population of 102 TN and r/r MDS patients there were no major differences in OS based on DNMT3A or TET2 mutation status while patients with TP53 mutations had worse median OS (7.4 months) compared to those without TP53 mutations (22.6 months). Other baseline prognostic factors for worse OS were BM blasts >5%; RBC transfusion-dependence; IPSS High Risk; and ECOG Performance Status of >1. Overall incidence of Grade ≥3 AEs regardless of relationship to treatment was reported in 83 vs. 96% for 60 and 90 mg/m2 dose groups respectively. There was a slightly higher but non-significant difference in Grade ≥3 thrombocytopenia (57 vs 41.5%); neutropenia (51 vs 39.6%); febrile neutropenia (43% vs 32%); and pneumonia (32.7 vs. 26.4%) for the 90 mg/m2 compared to 60 mg/m2 dose group. Early 30, 60, and 90-day all-cause mortality was observed in 0, 3.7%, and 5.7% in the 60 mg/m2 dose group respectively; and in 2%, 4%, and 12% in the 90 mg/m2 dose group respectively. Conclusions: Guadecitabine at both dose groups is a well-tolerated novel HMA with clinical activity in the treatment of both TN and r/r Int and HR MDS, and CMML patients. In TN MDS patient CR rate of 22% and median OS of 23.4 months compare well with first generation HMA efficacy (Fenaux et al, 2009, Lancet Oncology). Activity in r/r MDS who previously failed prior HMAs is particularly promising (CR+mCR in 32% of patients with median duration of response and overall survival of almost 8 and 12 months respectively). A phase 3 trial (ASTRAL-3) of guadecitabine vs Physician Treatment Choice in r/r MDS and CMML patients previously treated with azacitidine or decitabine is actively enrolling (ClinicalTrials.gov ID: NCT02907359). Disclosures Ritchie: NS Pharma: Research Funding; Bristol-Myers Squibb: Research Funding; Novartis: Consultancy, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Celgene: Consultancy, Other: Travel, Accommodations, Expenses, Speakers Bureau; Pfizer: Consultancy, Research Funding; ARIAD Pharmaceuticals: Speakers Bureau; Astellas Pharma: Research Funding. Savona:Boehringer Ingelheim: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding. Kropf:Celegene: Consultancy; Takeda: Consultancy. Daver:Pfizer: Consultancy; Sunesis: Consultancy; Pfizer: Research Funding; ImmunoGen: Consultancy; ARIAD: Research Funding; Novartis: Research Funding; Incyte: Research Funding; Otsuka: Consultancy; Novartis: Consultancy; Karyopharm: Consultancy; Alexion: Consultancy; Incyte: Consultancy; Karyopharm: Research Funding; BMS: Research Funding; Kiromic: Research Funding; Daiichi-Sankyo: Research Funding; Sunesis: Research Funding. Jabbour:Pfizer: Consultancy, Research Funding; Novartis: Research Funding; Abbvie: Research Funding; Takeda: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding. Yee:Celgene, Novartis, Otsuka: Membership on an entity's Board of Directors or advisory committees; Agensys, Astex, GSK, Onconova, Genentech/Roche: Research Funding. Stock:Jazz Pharmaceuticals: Consultancy. Griffiths:Alexion Inc.: Honoraria, Research Funding; Astex/Otsuka Pharmaceuticals: Honoraria, Research Funding; Celgene, Inc: Honoraria, Research Funding; Novartis, Inc.: Research Funding; Pfizer, Inc.: Research Funding. Podoltsev:Astex Pharmaceuticals: Research Funding; LAM Therapeutics: Research Funding; Sunesis Pharmaceuticals: Research Funding; Genentech: Research Funding; Boehringer Ingelheim: Research Funding; Daiichi Snakyo: Research Funding; Astellas Pharma: Research Funding; Pfizer: Research Funding; Celator: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding. Berdeja:Genentech: Research Funding; Bluebird: Research Funding; Amgen: Research Funding; Novartis: Research Funding; Glenmark: Research Funding; Takeda: Research Funding; Bristol-Myers Squibb: Research Funding; Teva: Research Funding; Sanofi: Research Funding; Poseida Therapeutics, Inc.: Research Funding; Celgene: Research Funding; Janssen: Research Funding. Naim:Astex Pharmaceuticals, Inc.: Employment. Hao:Astex Pharmaceuticals, Inc.: Employment. Azab:Astex Pharmaceuticals, Inc.: Employment. Roboz:Orsenix: Consultancy; Roche/Genentech: Consultancy; Roche/Genentech: Consultancy; Otsuka: Consultancy; Bayer: Consultancy; Pfizer: Consultancy; Jazz Pharmaceuticals: Consultancy; Argenx: Consultancy; Sandoz: Consultancy; Celltrion: Consultancy; Bayer: Consultancy; Orsenix: Consultancy; Pfizer: Consultancy; Astex Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy; Sandoz: Consultancy; Daiichi Sankyo: Consultancy; Novartis: Consultancy; Janssen Pharmaceuticals: Consultancy; Cellectis: Research Funding; Eisai: Consultancy; Celgene Corporation: Consultancy; Jazz Pharmaceuticals: Consultancy; Celgene Corporation: Consultancy; Janssen Pharmaceuticals: Consultancy; Eisai: Consultancy; Novartis: Consultancy; Otsuka: Consultancy; Argenx: Consultancy; Celltrion: Consultancy; Astex Pharmaceuticals: Consultancy; Aphivena Therapeutics: Consultancy; AbbVie: Consultancy; Aphivena Therapeutics: Consultancy; AbbVie: Consultancy; Cellectis: Research Funding.

Abstract Introduction: Guadecitabine (SGI-110) is a novel next-generation HMA administered as a small volume subcutaneous (SC) injection which results in extended decitabine exposure. Phase 2 studies have been conducted in TN-AML patients who were not candidates for intensive chemotherapy using two different doses and schedules of guadecitabine. We report here a comparative efficacy and safety analysis of the 5-day and 10-day regimens. Methods: TN-AML patients who were not candidates for intensive chemotherapy based on age (≥ 65 y), poor performance status (PS 2), comorbidities, or poor risk cytogenetics were enrolled in 2 separate treatment cohorts in the Phase 2 study. In the first cohort, patients were randomized (1:1) to either 60 mg/m2/d or 90 mg/m2/d on Days 1-5 (5-day regimen). In the second cohort, patients were treated with 60 mg/m2/d on Days 1-5 and Days 8-12 (10-day regimen) for up to 4 cycles, followed by 60 mg/m2/d Days 1-5 in subsequent cycles. Cycles were scheduled every 28 days for both regimes with dose reductions/delays allowed based on response and tolerability. Patients remained on treatment as long as they continued to benefit with no unacceptable toxicity. The primary endpoint was the composite Complete Response (CRc): Complete Response (CR) + CR with incomplete platelet recovery (CRp) + CR with incomplete neutrophil recovery (CRi) using modified International Working Group (IWG) criteria (Cheson et al, 2003). Secondary endpoints included overall survival (OS), and safety. Results: There was no difference in efficacy or safety between 60 and 90 mg/m2/d on the 5-day regimen (Yee et al, European Hematology Association meeting 2014, S647), so data are reported here for the two doses combined on the 5-day cohort. There were 51 patients treated in the 5-day regimen cohort and 52 treated with the 10-day regimen. There was no statistically significant difference in patient characteristics between the 2 regimens; median age 77.9 vs. 77.3 years ; male 59% vs. 65%; PS 2 or higher 35% vs. 40%; median BM blasts 40.0% vs. 49.5%; poor risk cytogenetics 46% vs. 43% for the 5-day and 10-day cohorts, respectively. Follow up of the 10-day cohort patients was shorter as it started after completion of enrolment of the 5-day cohort. The median follow up was 25.7 and 12.4 months and median number of cycles was 5 (range 1-26) and 3 (range 1-13) for the 5-day and 10-day cohorts, respectively. There was no significant difference in the primary efficacy endpoint, CRc, between the 2 regimens (p=0.43). CRc was achieved in 29/51 patients (57%) on the 5-day regimen (19 CR, 3 CRp, and 7 CRi) and in 25/52 patients (48%) on the 10-day regimen (16 CR, 5 CRp, and 4 CRi). Median OS was 10.5 and 8.7 months for the 5-day and 10-day cohorts, respectively (p=0.89). The 30, 60, and 90-day all-cause mortality rates were not statistically significant between the two cohorts: 5.9%, 15.7%, and 21.6% on the 5-day regimen and 1.9%, 17.3%, and 28.8% on the 10-day regimen. The most common Grade ≥3 AEs regardless of relationship to guadecitabine were: febrile neutropenia 59% vs. 60%, thrombocytopenia 47% vs. 38%, neutropenia 39% vs. 33%, anemia 27% vs. 19%, pneumonia 24% vs. 27%; and sepsis 12% vs. 19%, for the 5-day and 10-day cohorts respectively, none of which was statistically significant. Fifteen patients remain on treatment (5 from the 5-day cohort and 10 from the 10-day cohort). Conclusions: Guadecitabine is clinically active with a good safety profile in TN-AML patients not candidates for intensive chemotherapy. Unlike in relapsed/refractory AML, where the 10-day regimen of guadecitabine showed a trend toward improved efficacy (Roboz et al, Annals of Oncology 25 Supplement 4, 2014), there was no significant difference in either efficacy or safety between the 5-day and 10-day regimens in newly diagnosed AML patients. Guadecitabine 60 mg/m2/d SC Days 1-5 is currently being investigated in an 800-patient multicenter randomized phase 3 study in TN-AML patients unfit to receive intensive chemotherapy (ASTRAL-1 Phase 3 clinical trial: ClinicalTrials.gov reference NCT02348489). Disclosures Kropf: Teva Pharmaceuticals: Consultancy. O'Connell:Celgene: Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees. Griffiths:Astex: Research Funding; Alexion Pharmaceuticals: Honoraria; Celgene: Honoraria. Rizzieri:Teva: Other: ad board, Speakers Bureau; Celgene: Other: ad board, Speakers Bureau. Stock:Gilead: Membership on an entity's Board of Directors or advisory committees. Savona:Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees. Rosenblat:Astex Pharmaceuticals, Inc.: Research Funding. Berdeja:Celgene: Research Funding; Onyx: Research Funding; BMS: Research Funding; Abbvie: Research Funding; Array: Research Funding; Curis: Research Funding; Acetylon: Research Funding; MEI: Research Funding; Janssen: Research Funding; Novartis: Research Funding; Takeda: Research Funding. Wilson:Astex Pharmaceuticals, Inc.: Employment. Lowder:Astex Pharmaceuticals, Inc.: Employment. Taverna:Astex Pharmaceuticals, Inc.: Employment. Hao:Astex Pharmaceuticals, Inc.: Employment. Azab:Astex Pharmaceuticals, Inc.: Employment. Issa:Janssen: Consultancy; Astex Pharmaceuticals, Inc.: Consultancy.

Abstract Background: SGI-110 is a second generation HMA formulated as a dinucleotide of decitabine (DAC) and deoxyguanosine delivered as a small volume SC injection that yields longer half-life and more extended DAC exposure than DAC IV infusion. A phase 1 clinical trial of SGI-110 demonstrated a differentiated pharmacokinetic profile from DAC IV, potent hypomethylation, and clinical responses in previously treated patients with MDS and AML (Kantarjian et al. 2012). Phase 1 established 60 mg/m2 QDx5 as the biologically effective dose (BED), and 90 mg/m2QDx5 as the Maximum tolerated dose (MTD) in MDS patients given in 28-day cycles. Phase 2 is conducted to evaluate dose response between the BED and MTD in MDS patients. Methods: Int, or HR MDS, and CMML patients who were either treatment-naïve or previously treated were randomized to either 60 mg/m2 or 90 mg/m2QDx5 every 28 days. Efficacy was evaluated by the clinical responses of CR, PR, marrow CR (mCR), and Hematological Improvement (HI) based on the International Working Group Criteria 2006 as well as transfusion-independence. Adverse events (AEs) as graded by the CTCAE v4 criteria and pharmacodynamic biological activity as measured by Long Interspersed Nucleotide Element LINE-1 (an index of global DNA methylation) were also assessed. Patients are being followed for overall survival. Results: The study completed target enrolment with 102 patients: 53 who were refractory or have relapsed on prior treatment, and 49 previously untreated. Fifty three patients were randomized to 60 mg/m2 and 49 patients to 90 mg/m2 QDx5 with a median follow up of 8.2 months (range 1-21). Most baseline patient characteristics were well balanced between the 2 treatment arms with no significant differences in median age (71.7 vs. 72.5 y); male gender (70 vs. 61%); ECOG PS 2 (15 vs. 12%); HR MDS (28 vs. 37%); transfusion-dependence (57 vs. 55%), median baseline Hb (9.25 vs. 9.3 g/dL); platelets count (42.5 vs. 45 x109/L), and neutrophils count (1.19 vs. 1.16 x109/L) for the 60 and 90 mg/m2 QDx5 respectively. However, there were 15 CMML patients (28%) randomized to 60 mg/m2 vs. only 7 CMML patients (14%) randomized to 90 mg/m2(p=0.097). All but 2 patients in the previously treated group received one or more HMA. At the time of the data cutoff, 38 of 102 patients (37%) were still on treatment. Median number of treatment cycles was 4 for previously treated patients, and 5 for the treatment naïve group (range 1-22 cycles). CR+mCR were observed in 10/53 (19%), and 11/49 (22%) in the 60 and 90 mg/m2 arms respectively (p=0.8). CR was observed in 7/49 treatment naïve patients (14%) while CR+mCR were observed in 11/53 previously treated patients (21%) with no significant differences between 60 and 90 mg/m2 arms. Transfusion independence for at least 8 weeks was reported in 32% and 24% for platelets and RBCs respectively with no difference between the 2 treatment arms. Treatment naïve patients benefited from higher rate of transfusion-independence (58% and 46% for platelets and RBCs respectively). Potent demethylation was achieved in both treatment arms with a mean LINE-1 DNA demethylation of 27.3 and 30.5% for 60 and 90 mg/m2 respectively (p=0.12). Overall incidence of Grade ≥3 AEs regardless of relationship to treatment was reported in 81 vs. 88% for 60 and 90 mg/m2 treatment arms respectively (p=0.42).There was a slightly higher but non-significant difference in Grade ≥3 thrombocytopenia (51 vs 38%) and pneumonia (20 vs. 13%) for the 90 mg/m2 arm compared to 60 mg/m2. Early 8-week any-cause mortality occurred in 3/102 patients treated (3%), 2 at 60 and 1 at 90 mg/m2. Follow up for survival is still ongoing. Conclusions: SC SGI-110 is a well-tolerated novel HMA with biological and clinical activity in the treatment of Int and HR MDS, and CMML patients with particularly promising activity in patients previously treated with azacitidine or decitabine. Clinical responses, transfusion independence, DNA demethylation as assessed by LINE-1, and Safety did not significantly differ between the 2 treatment doses. Disclosures Tibes: Astex Pharmaceuticals, Inc.: Research Funding. Rosenblat:Astex Pharmaceuticals, Inc.: Research Funding. Yee:Astex Pharmaceuticals, Inc.: Research Funding. Griffiths:Astex Pharmaceuticals, Inc.: Research Funding. Issa:Astex Pharmaceuticals, Inc.: Consultancy, Research Funding. Naim:Astex Pharmaceuticals, Inc.: Employment. Taverna:Astex Pharmaceuticals, Inc.: Employment. Hao:Astex Pharmaceuticals, Inc.: Employment. Azab:Astex Pharmaceuticals, Inc.: Employment. Roboz:Astex Pharmaceuticals, Inc.: Consultancy.

Abstract Background: SGI-110 (guadecitabine) is a novel HMA that prolongs in vivo exposure of the active moiety decitabine following subcutaneous (SC) administration. We previously reported guadecitabine clinical activity in previously untreated elderly AML with Overall Complete Response (CR+CRi+CRp) of 55% using a standard 5-day regimen (Yee et al, 2014). Here we report the first results of a more intensive 10-day regimen in the same patient population. Methods: Elderly AML patients (≥ 65y) with at least one of the following characteristics were enrolled: age ≥ 75y; poor Performance Status (PS) ≥ 2; significant comorbidities particularly cardiopulmonary dysfunction; poor risk cytogenetics; or secondary AML. Guadecitabine 60 mg/m2/d SC was administered for 10 days (Days 1-5; and 8-12) for the first 1-2 cycles followed by the 5-day regimen (Days 1-5) for subsequent cycles. Cycles were scheduled every 28 days. Primary endpoint was Overall Complete Response (Overall CR). Secondary endpoints included Overall Survival, Safety including all-cause 30-day and 60-day early mortality, and global maximum DNA demethylation from baseline by LINE-1 assay. Results: Fifty two patients were treated with median age 77 (range 66-92) including 40 (77%) ≥75y; 34 (65%) male; 21 (40%) PS ≥ 2; 19 (36%) poor risk cytogenetics; and 13 (25%) secondary AML. The median bone marrow blasts percentage was 49% (range 16-98%). All patients had a minimum follow up of 3 months; 26 (50%) patients remain on treatment at the time of the analysis. Overall CR was observed in 24 patients (46%):14 CR (27%), 8 CRi (15%), and 2 CRp (4%). There was no significant difference between median DNA demethylation in responders (- 27%) and non-responders (-28%). Early all-cause 30-day and 60-day mortality occurred in 2 (4%) and 10 (19%) patients respectively. The most common Grade ≥3 Adverse Events considered by investigators to be drug-related were febrile neutropenia (33%), thrombocytopenia (27%), neutropenia (21%), anemia (15%), bacteremia (10%), and pneumonia (6%). Conclusions: Administration of guadecitabine as a more intense 10-day regimen for the first 1-2 cycles was active with acceptable toxicity. However, and although it was not a randomized comparison, the 10-day regimen did not result in higher rate of Overall CR in previously untreated AML than what was previously reported for the 5-day regimen. A Phase III randomized clinical trial in previously untreated AML patients not considered candidates for intensive chemotherapy has been initiated with the 5-day regimen of guadecitabine. Reference: Yee K, Daver N, Kropf P, et al: European Hematology Association Meeting, June 12-15, 2104; Milan, Italy. Abstract S647. Citation Format: Gail Roboz, Hagop Kantarjian, Patricia Kropf, Ellen Richie, Nitin Jain, Elizabeth Griffiths, Nikola A. Podoltsev, Katherine Walsh, Casey O'Connell, Wendy Stock, David Rizzieri, Raoul Tibes, Todd Rosenblat, Woonbok Chung, Pietro Taverna, Xiang Yao Su, Sue Naim, Mohammad Azab, Jean-Pierre Issa. First results of a 10-day regimen of SGI-110 (guadecitabine), a second generation hypomethylating agent (HMA) in previously untreated elderly AML who are not candidates for intensive chemotherapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT321. doi:10.1158/1538-7445.AM2015-CT321