A Systematic Review and Meta-Analysis of Luspatercept for Anemia Treatment in Low Risk Myelodysplastic Syndrome with Ring Sideroblast Subtype in Phase II and Phase III Clinical Trials
Authors: Akbar Arshia , Khan Waqas , Shah Zunairah , Anwar Muhammad Yasir , Aziz Muhammad Ali , Ahmed Zahoor , Farooqi Muhammad Saad , Baloch Ali Shahbaz , Hashmi Mydah Sajid , Khurshid Qasim , Dar Abdul Jabbar , Bahram Saman , Anwer Faiz 
Published: November 2020

Background: Low-risk Myelodysplastic Syndromes (MDS) patients commonly present with anemia and may become blood transfusions dependent upon progression. Luspatercept, a targeted drug for an activin receptor ligand has emerged as new anemia treatment in MDS for patients with ring sideroblasts and the patients with SF3B1 mutation. This systemic review highlights the efficacy of luspatercept in MDS patients whom erythropoietin stimulating agents (ESA) are not effective.
Methods: We conducted a comprehensive literature search using PubMed, Clinical trial.gov, Embase, Cochrane, and Web of science. Our search strategy included MeSH (Medical Subject Headings) terms and keywords for MDS and luspatercept including trade names and generic names from inception to 29 April 2020. Studies were selected according to PRISMA guidelines. The initial screening revealed 240 articles. After excluding review articles, duplicates, and non-relevant articles, finally we included two clinical trials, which reported transfusion independence (TI), an erythroid response (HI-E) in MDS patients with luspatercept. Proportions along with 95% Confidence Interval (CI) were extracted to compute pooled analysis using the 'meta' package by Schwarzer et al. in the R programming language (version 4.0.2) to report the efficacy of luspatercept. We pooled the results of the experimental arms of the two trials using the inverse variance method and logit transformation. Between studies, variance was calculated using DerSimonian-Laird Estimator.
Results: A total of 287 patients were enrolled and evaluated in two phases II/III trials. Platzbecker et al and Fenaux et al reported Erythropoietin stimulating agents (ESA) with one median prior line of therapy (n= 148, n=46). Fenaux et al. also reported iron chelation therapy (n=71) as a prior line of therapy. Patients having ring sideroblast positive &lt;15% (n=172) and SF3B mutation were present in 169 evaluable patients. Low-risk MDS (LR-MDS) patients are classified according to IPSS-R criteria, defined as being of very low (n=19), low (n=135), or intermediate-risk (n=44). Platzbecker et al. (2017) studied luspatercept in MDS patients (n=58) in the PACE phase II trial. Fenaux et al. (2020) studied the efficacy of luspatercept in MDS pts (n=219) in the MEDALIST phase III trial. The baseline Erythropoietin (EPO) levels were: levels &lt;200: n=191, level 200-500: n= 81, level &gt;500: n=57 for both studies. The baseline means hemoglobin (Hb) levels were eight before therapy.
TI for more than eight weeks was observed in 38% of patients in both the MEDALIST trial and PACE trial. The erythroid response was 53% and 63% in both trials respectively. In a Phase II study, for LR-MDS patients, the overall erythroid response was higher among patients (n= 69%) having ringed sideroblast status (&gt;15% ring sideroblast) and SF3B mutation (n=77%). The mean increase of Hb was observed in 29 out of 46 and 32 out of 41 pts in MEDALIST and PACE trial, respectively. Luspatercept proved to be efficacious in the pooled analysis i.e transfusion independence (TI): 38%, 95% CI 0.31-0.45; p =0.98, I2 = 0%), and erythroid response (HI-E): 54%, 95% CI 0.48-0.62; p=0.22, I2 = 32%) with an increase in mean Hb of 70% 95%: CI 0.59-0.78; I2 = 56%) (Figure 1).
CONCLUSION: In patients with low risk MDS positive ringed sideroblast or SF3B1 mutation status shows good responses with luspatercept treatment, with reduced transfusion dependence, and higher erythroid response.

Disclosures
Anwer: Incyte Pharmaceuticals: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Speakers Bureau; Millennium Pharmaceuticals: Research Funding; Celgene: Research Funding; Astellas Pharma: Research Funding; Acetylon Pharmaceuticals: Research Funding; Seattle Genetics: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Speakers Bureau; AbbVie Pharmaceuticals: Research Funding.