Anti-Hemojuvelin Monoclonal Antibody Alleviated Anemia Induced By Ruxolitinib Treatment in Mice

Myelofibrosis (MF) is a hematologic malignancy characterized by excessive proliferation of myeloid cells and release of pro-inflammatory cytokines, leading to bone marrow dysfunction. Janus kinase (JAK) inhibitors, such as ruxolitinib, represent the first-line treatment in MF therapy. While ruxolitinib is effective at alleviating symptoms, the anemia associated with ruxolitinib is a limitation for the treatment. Since anemia is already common in patients with newly diagnosed MF, there is an urgent need to minimize treatment-related anemia in patients with MF. DISC-0974 is a humanized anti-hemojuvelin (HJV) monoclonal antibody. It was designed to disrupt the interaction between HJV and the bone morphogenetic protein (BMP) receptor complex, leading to decreased hepcidin expression and increased iron availability for enhanced erythropoiesis. DISC-0974 is currently in clinical studies to treat anemia in patients with MF (NCT05320198) and chronic kidney disease (NCT05745883). The aim of this study was to evaluate whether DBIO-100, a murine analog of DISC-0974, could alleviate ruxolitinib-induced anemia in vivo. Wild-type C57BL/6J male mice were randomized to receive vehicle, ruxolitinib (90 mg/kg), DBIO-100 (20 mg/kg), or ruxolitinib in combination with DBIO-100 for 28 days. At the end of the study, all mice were euthanized for further analysis. The results showed that ruxolitinib alone reduced hemoglobin by 1.2 g/dL in wild-type C57BL/6J mice. Adding DBIO-100 to ruxolitinib treatment had a positive impact on improving hemoglobin (ie, observed an increase around 0.8 g/dL). Furthermore, the ruxolitinib/DBIO-100 combination groups also exhibited increasing trends for red blood cell count and hematocrit vs ruxolitinib alone. Moreover, mean corpuscular volume and mean corpuscular hemoglobin counts increased significantly in the ruxolitinib/DBIO-100 combination groups vs ruxolitinib alone. DBIO-100 suppressed serum hepcidin levels, confirming target engagement. With respect to iron availability, ruxolitinib administered twice daily led to modest increases in serum iron and transferrin saturation, whereas DBIO-100 alone or in combination with ruxolitinib caused further increases in both measurements. This study demonstrated that ruxolitinib treatment causes anemia in wild-type C57BL/6J mice. Adding DBIO-100, a mouse anti-HJV monoclonal antibody, can alleviate ruxolitinib-induced anemia and further enhance serum iron availability in vivo. In the ongoing Phase 1b clinical study of DISC-0974 in patients with anemia of MF (NCT05320198), 10 participants were treated with JAK inhibitors; durable response (mean hemoglobin ≥1.5 g/dL above baseline for ≥12 weeks) was achieved in 4 of 8 non-transfusion-dependent participants, and 1 of 2 transfusion-dependent participants achieved transfusion independence (≥12 consecutive weeks without transfusion). Taken together, these findings illustrate that targeting HJV to increase iron mobilization can counter the negative erythroid effects of ruxolitinib as well as the previously reported effects on anemia of inflammation. These data highlight the therapeutic potential of anti-HJV monoclonal antibodies in the treatment of anemia in diseases such as MF, in which ruxolitinib is a commonly used therapy that may be a significant additional factor in the development of anemia. The combination therapy may enhance the benefits of JAK inhibitors, particularly in the patient population with MF and anemia.