ACE-536 Increases Hemoglobin and Reduces Transfusion Burden in Patients with Low or Intermediate-1 Risk Myelodysplastic Syndromes (MDS): Preliminary Results from a Phase 2 Study

Abstract

Introduction. ACE-536, a recombinant fusion protein containing modified activin receptor type IIB and IgG Fc, is being developed for the treatment of anemias due to ineffective erythropoiesis, such as myelodysplastic syndromes (MDS). Patients with MDS often have elevated levels of erythropoietin (EPO) and may be non-responsive or refractory to erythropoiesis-stimulating agents (ESAs). MDS patients have also been shown to have increased serum GDF11 levels (Suragani R et al., Nature Medicine 2014) and increased Smad 2/3 signaling in the bone marrow (Zhou L et al., Blood 2008). ACE-536 binds to ligands in the TGF-ß superfamily, including GDF11, inhibits Smad 2/3 signaling, and promotes late-stage erythroid differentiation via a mechanism distinct from ESAs. RAP-536 (murine version of ACE-536) reduced Smad 2 signaling, increased hemoglobin (Hb) levels and decreased bone marrow erythroid hyperplasia in a mouse model of MDS (Suragani R et al., Nature Medicine 2014). In a healthy volunteer study, ACE-536 was well-tolerated and increased Hb levels (Attie K et al., Am J Hematol 2014). Aims. This is an ongoing, phase 2, multicenter, open-label, dose-finding study to evaluate the effects of ACE-536 on anemia in patients with Low or Int-1 risk MDS who have either high transfusion burden (HTB, defined as ≥4 units RBCs/8 weeks prior to baseline) or low transfusion burden (LTB, defined as <4 units RBCs/8 weeks prior to baseline). Study outcomes include erythroid response (either Hb increase in LTB patients or reduced transfusion burden in HTB patients), safety, tolerability, PK, and PD biomarkers. Methods.Inclusion criteria included Low or Int-1 risk MDS, age ≥ 18 yr, anemia (defined as either being HTB patient or having baseline Hb < 10.0 g/dL in LTB patient), EPO >500 U/L or nonresponsive/refractory to ESAs, no prior azacitidine or decitabine, and no current treatment with ESA, G-CSF, GM-CSF, or lenalidomide. In the dose escalation phase, ACE-536 was administered by subcutaneous (SC) injection once every 3 weeks in 7 sequential cohorts (n=3-6) at dose levels of 0.125, 0.25, 0.5, 0.75, 1.0, 1.33 and 1.75 mg/kg for up to 5 doses with a 3-month follow-up. An expansion cohort (n=30) is planned, and all patients completing this study may enroll in a 12-month extension study. Results. Preliminary data were available for 26 patients (7 LTB/19 HTB) as of 18 Jul 2014. Median age was 71 yr (range: 27-88 yr), 50% were female, 54% had prior EPO therapy and 15% had prior lenalidomide. 69% were WHO subtype RCMD, and the remaining patients were del(5q), RARS, or RAEB-1. Mean (SD) baseline Hgb for the LTB patients (n=7) was 9.1 (0.4) g/dL. Mean (SD) units RBC transfused in the 8 weeks prior to treatment was 0.9 (1.1) units for the LTB patients and 6.3 (2.4) units for the HTB patients. Two of the 7 LTB patients had an increase in mean Hb ≥1.5 g/dL over 8 weeks compared to baseline. Mean maximum Hb increase in the LTB patients was 0.8, 1.0, 2.2, and 2.7 g/dL in the 0.125 (n=1), 0.25 (n=1), 0.75 (n=3), and 1.75 (n=2) mg/kg dose groups, respectively. Six of the 7 LTB patients achieved RBC transfusion independence (RBC-TI) for ≥8 weeks during the study. Six of the 19 HTB patients had a ≥4 unit or ≥50% reduction in RBC units transfused over an 8-week interval during the treatment period compared to the 8 weeks prior to treatment; five of these 6 patients achieved RBC-TI ≥ 8 weeks during the study (range 71-152 days). Increases in neutrophil count following study drug administration were observed in some patients. ACE-536 was generally well tolerated. No related serious adverse events have been reported to date. The most frequent adverse events regardless of causality were: diarrhea (n=4, grade 1/2), bone pain, fatigue, muscle spasms, myalgia, and nasopharyngitis (n=3 each, grade 1/2). Conclusions. Based on preliminary data in Low or Int-1 MDS patients, ACE-536 administered SC every 3 weeks for up to 5 doses increased Hb levels or decreased transfusion requirement, with a favorable safety profile. These data strongly support further evaluation of longer-term treatment with ACE-536 in patients with MDS. Disclosures Platzbecker: Celgene: Honoraria, Research Funding. Germing:Celgene: Honoraria, Research Funding. Goetze:Celgene Corp: Honoraria; Novartis Pharma: Honoraria. Radsak:Celgene: Research Funding. Hankin:Acceleron Pharma: Employment, Equity Ownership. Wilson:Acceleron Pharma: Employment, Equity Ownership. Sherman:Acceleron Pharma: Employment, Equity Ownership. Attie:Acceleron Pharma: Employment, Equity Ownership.

Lenalidomide with or without erythropoietin in transfusion-dependent erythropoiesis-stimulating agent-refractory lower-risk MDS without 5q deletion

“…TI up to 30 to 40%, but in highly selected patient populations (31), (32) . Among innovative agents, the glutathione-Stransferase P1-1 (GSTP1-1) inhibitor Ezatiostat and the MAP kinase inhibitor ARRY 614 both gave a 29% erythroid response rate in heavily pretreated lower risk MDS without del5q (33), (34) , while early results using drugs with TGF beta pathway ligand traps (ACE 011 and ACE 536) appear promising (15), (35) .…”

Recent advances in the understanding of myelodysplastic syndromes with ring sideroblasts

“…In fact, transforming growth factor‐β superfamily ligand inhibitors were recently found to correct ineffective erythropoiesis and promote late‐stage erythroid differentiation in mice (Dussiot et al , ; Suragani et al , ). Preliminary results from a phase II study investigating luspatercept (ACE‐536), a modified activin receptor IIB‐IgG Fc, in MDS patients with low or intermediate‐1 International Prognostic Scoring System (IPSS) risk not candidate or unresponsive/refractory to erythropoiesis stimulating agents, showed that 82% of patients achieved an erythroid haematological improvement according to International Working Group criteria (Cheson et al , ), with a significantly higher response rate in patients with ring sideroblasts and SF3B1 mutation (Platzbecker et al , ; Giagounidis et al , ). Based on this observation, a phase III multicentre randomized clinical trial is currently ongoing in IPSS‐R very low, low, or intermediate risk MDS with ring sideroblasts who require RBC transfusions (ClinicalTrials.gov Identifier: NCT02631070).…”

Myelodysplasia is in the niche: novel concepts and emerging therapies

“…Currently, two clinical trials are recruiting patients to evaluate the effect of activin receptor type II ligand trap on anemia in patients diagnosed with low- or intermediate-1 risk MDS (ACE-011/sotatercept—NCT01736683; ACE-536/luspatercept—NCT01749514) and preliminary data suggest clinical activity. 115 …”