Association between ferritin, hemoglobin, and anemia response in jaktinib-treated patients with myelofibrosis: A post-hoc analysis of the ZGJAK006 study.
Authors: Zhang Yi , Zhou Hu , Xiao Zhi-Jian , Duan Minghui , Gao Sujun , He Guangsheng , Jing Hongmei , Li Junmin , Ma Liangming , Zhu Huanling , Chang Chunkang , Du Xin , Hong Mei , Li Xin , Liu Qingchi , Wang Wei , Xu Na , Yang Haiping , Zhao Qingwei , Jin Jie 
Published: June 2024

e18527 Background: Iron metabolism is disrupted in MF through the increased production of hepcidin, contributing to increased ferritin levels and iron-binding capacity, decreased serum iron levels and hemoglobin levels. Hepcidin production is upregulated by JAK/STAT pathway and BMP6/ACVR1/SMAD pathway. Jaktinib showed inhibition effects on JAK family and ACVR1 in preclinical studies. Anemia benefits with jaktinib treatment were observed in several clinical studies in MF pts. To explore the underlying mechanisms, we conducted a post-hoc analysis to investigate the change of ferritin levels during jaktinib treatment in MF pts with and without anemia response from a phase 2 study in pts who were intolerant to ruxolitinib (the ZGJAK006 study). Methods: Pts from the ZGJAK006 study were included if they were RBC transfusion dependent or with hemoglobin level ≤100 g/L at baseline. Transfusion dependence was assigned to pts with an average RBC transfusion of ≥2 U/month within 3 months prior to study drug administration. Pts without baseline ferritin results were excluded. Eligible pts were divided into 2 groups: anemia responders by week 24 and non-responders by week 24. Anemia response was defined as becoming RBC transfusion independent (defined by no transfusion in ≥12 consecutive weeks and hemoglobin ≥85 g/L) for transfusion-dependent pts or a ≥20 g/L increase in hemoglobin for non-transfusion-dependent pts with baseline hemoglobin ≤100 g/L. Results: A total of 39 pts were included in this post-hoc analysis, with 14 anemia responders and 25 non-responders. The baseline hemoglobin was similar in responders (median: 78.5 g/L) and non-responders (median: 78.0 g/L). The baseline levels of ferritin were higher than upper limit of normal in most pts (69.2%) with a median of 784.6 ng/mL in the overall population (697.5 ng/mL in responders and 785.0 ng/mL in non-responders). Ferritin decreased to 583.9 and 531.7 ng/mL at weeks 12 and 24, respectively. Notably, anemia responders had a fast reduction in ferritin and increase in hemoglobin compared to non-responders. In addition, the hemoglobin levels of those non-responders maintained were stable and eight non-responders had a ≥50% decrease in RBC infusion frequency or unit. Six (42.9%) of 14 responders and 10 (40.0%) of 25 non-responders achieved spleen volume reduction of ≥ 35% from baseline at week 24. Conclusions: In this post-hoc analysis of pts with anemic MF, jaktinib treatment led to improvement in iron metabolism and anemia. The results were in consistence with the known activities of jaktinib against JAK family and ACVR1. Moreover, similar spleen responses were observed for anemia responders and non-responders. Nevertheless, ferritin was the only marker of iron metabolism measured in this study, a translational biology study evaluating hepcidin may be needed to further support the clinical findings. Clinical trial information: NCT04217993 .