Luspatercept for Treatment of Lower Risk Myelodysplastic Syndromes: Real World Data Replicates Medalist Study Results and Confirms Activity Among Hypomethylating Agents and Lenalidomide Treated Patients

Introduction: Luspatercept, TGF-B fusion trap protein, is a first in class erythroid maturating agent approved by FDA for treatment of red blood cell transfusion dependent (RBC-TD) lower risk myelodysplastic syndromes (LR-MDS) with ring sideroblasts (RS) based on the MEDALIST clinical trial. Red blood cell transfusion independence (RBC-TI) was observed in 38% of 153 patients (pts) treated with luspatercept compared to 13% of 76 pts in the placebo group.

We present to our knowledge first real-world data (RWD) in a large cohort of pts treated at our center with luspatercept for LR-MDS. More importantly, we address impact of prior therapies on response namely hypomethylating agents (HMA) as the original clinical trials excluded HMA treated pts.

Methods We identified all pts treated at Moffitt Cancer Center with luspatercept since the FDA approval. Baseline RBC transfusion burden (TB) was defined as: non- transfusion dependent (NTD) (0 units in 8 weeks prior luspatercept), low TB (LTB) (1-5 units /8weeks) and high TB (HTB) (≥ 6 units /8 weeks). A hematological response (HI) was defined as an (i) objective Hgb increase of > 1.5 g/dl in NTD, and (ii) RBC-TI with Hgb increase of 1.5 g/dl, or RBC-TI without Hgb 1.5 g/dl increase, or >50% reduction in RBC transfusion burden among RBC-TD.

Results Between February 2020 and December 2021, 114 pts were treated with luspatercept. Table-1 summarizes baseline characteristics in comparison to Medalist trial, the median age was 70 years. Seventy-three pts (67%) had MDS-RS subtype, 91% were intermediate or lower risk MDS by R-IPSS. SF3B1 mutation (MT) was detected in 71% (80/112). The mean Hgb level was 7.90 g/dl and 47% were RBC HTB transfusion dependent. The median serum erythropoietin (epo) level at time of referral was 122 U/L (19% > 500 U/L) (n=77). Majority had prior erythroid stimulating agents (ESA) (89%) with 29% hematological response to prior ESA, 59 pts (53%) had prior HMA therapy, and 42 patients (47%) had prior lenalidomide (len).

The overall HI rate to luspatercept was 39.5% (45/114). Table-2 summarizes detailed responses. HI correlated with baseline RBC-TB where 69% (9/13) NTD, 47% (21/47) LTB and 25% HTB (13/53) achieved HI respectively, p=.004. Almost 55% of pts needed dose escalation, 62 pts received 1.33 mg/kg and 63 pts received 1.75 mg among whom 40% (25 pts) demonstrated response to higher doses. Based on RBC-TB, 75% (6/8) NTD patients achieved HI with highest dose escalation, 40% (10/25) LTB pts achieved HI with dose escalation and 30% (9/30) HTB pts achieved response with dose escalation.

Among responders, the median duration of response was 15.6 months (2.6-27.3). As off last follow up, 56 pts (49%) discontinued treatment. Reason of discontinuation was lack of response in 47 pts, loss of response in 4 patients and adverse events in 5 pts (58 pts are still on therapy). The most common captured adverse events were fatigue (n=8), GI (n=4), shortness of breath and arthralgia (1 each).

The response rates were higher among SF3B1 MT pts compared to wild type, 48% (34/80) compared to 16% (5/32), p=.002. The response rate among pts with RS subtypes versus non-RS were 49% versus 28% respectively, p=.05. Among 14 pts with MDS/MPN-RS-T the HI rate was 79%.

HI for pts with serum epo < 500 U/L, was 48% (30/62) compared to 13% 2/15) for those with serum epo > 500, p=.01. Majority of pts with high serum epo level were RBC HTB at baseline 67% (10/15).

The HI rate was 30% (18/60) after HMA failure compared to 50% (27/54) in HMA naïve pts, (p=.03). More pts post HMA failure were RBC-HTB 62% compared to 30% in HMA naïve. The luspatercept HI among RBC-LTB HMA failure pts was 39% compared to 54% in HMA naïve LTB, however, it was 24% among HTB HMA failure compared to 25% among HMA naïve HTB. The HI rate was 33% (15/46) for len failure pts compared to 43% (29/67) naïve patients, (p=.3).

In multivariable analysis both SF3B1 mutation status and baseline RBC TB independently correlated with luspatercept response but not HMA failure.

Conclusions Our RWD confirms luspatercept clinical benefit and safety profile observed in the MEDALIST trial. Responses are dose dependent with 1/3 of patients who were dose escalated responding. Low baseline RBC-TB dependency and SF3B1 MT correlated with higher response rates. Luspatercept retained activity after HMA or lenalidomide failure however a trend of lower responses observed correlated with RBC-HTB among those patients.

Komrokji:CTI BioPharma, Innovent: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Consultancy, Honoraria, Speakers Bureau; Taiho Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; PharmaEssentia, Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Geron: Consultancy; Acceleron Pharma: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Honoraria, Speakers Bureau; Bristol Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Kuykendall:Pharmaessentia: Consultancy, Honoraria, Speakers Bureau; Imago Biosciences: Consultancy, Honoraria, Speakers Bureau; Incyte: Consultancy, Honoraria, Speakers Bureau; Blueprint: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Abbvie: Consultancy, Honoraria, Speakers Bureau; GSK - Sierra Oncology: Consultancy, Honoraria, Other: Research Support, Speakers Bureau; Prelude Pharmaceuticals: Other: Research Support; BMS: Consultancy, Honoraria, Other: Research Support, Speakers Bureau; Morphosys: Other: Research Support; Protagonist: Other: Research Support; CTI Biopharma: Consultancy, Honoraria, Speakers Bureau. Sweet:Syntrix Pharmaceuticals: Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; berGenBio: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Curis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AROG: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Mablytics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead Sciences, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding. Lancet:Servier: Consultancy; Agios/Servio: Consultancy; Astellas: Consultancy; Syntrix Pharmaceuticals: Research Funding; Novartis: Consultancy; Dava Oncology: Consultancy; Boxer Capital: Consultancy; Dedham Group: Consultancy; Jasper Therapeutics: Consultancy; Jazz: Consultancy; BerGenBio: Consultancy; Millenium Pharma/Takeda: Consultancy; ElevateBio Management: Consultancy; Daiichi Sankyo: Consultancy; Celgene/BMS: Research Funding; AbbVie: Consultancy. Padron:Incyte: Research Funding; Blueprint: Honoraria; BMS: Research Funding; Syntrix Pharmaceuticals: Research Funding; Kura: Research Funding; Stemline: Honoraria; Taiho: Honoraria. Sallman:Syndax: Membership on an entity's Board of Directors or advisory committees; Nemucore: Membership on an entity's Board of Directors or advisory committees; Syntrix Pharmaceuticals: Research Funding; Kite: Membership on an entity's Board of Directors or advisory committees; Lixte: Patents & Royalties: LB-100; Intellia: Membership on an entity's Board of Directors or advisory committees; Incyte: Speakers Bureau; Magenta: Consultancy; Aprea: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees.