Assessing Efficacy of Jaktinib Among Ruxolitinib-Intolerant Patients With Myelofibrosis

Findings from a Phase 2 Single-Arm Multicenter Study

Jie Jin, MD, PhD, Zhejiang University School of Medicine, Hangzhou, People's Republic of China, shares results from a phase 2 study assessing the efficacy of Janus kinase (JAK) inhibitor jaktinib among ruxolitinib-intolerant patients with myelofibrosis (MF).

Transcript: 

My name is Jie Jin. I'm a professor and the clinical hematologist at the first affiliated hospital, Zhejiang University School of Medicine, Hangzhou, China. Today, I'd like to share with you our findings from a study of jaktinib in patients with ruxolitinib-intolerant myelofibrosis. 

Ruxolitinib is the first JAK inhibitor approved for myelofibrosis. However, hematological toxicity, including anemia, obviously affects its use for [the] long-term in some patients. The reported incidence of grade 3 or high[er] anemia with ruxolitinib in Chinese patients is 48%, and available options after ruxolitinib discontinuation are limited with unsatisfying outcomes indicating an urgent need for new treatments. 

Jaktinib, a novel JAK and [activin A receptor type 1] (ACVR1) inhibitor showed promising activities on splenomegaly, anemia, and myelofibrosis symptoms in myelofibrosis patients. We conduct[ed] an open-label, single-arm, multicenter clinical trial to evaluate the efficacy and the safety objective in patients with myelofibrosis who were intolerant to ruxolitinib. The primary end point was the proportion of patients with at least a 35% reduction in spleen volume at week 24. The secondary end point included the change in myelofibrosis-related symptoms, anemic response, and the safety profile.

A total [of] 44 patients with myelofibrosis were enrolled [in] this study and received jaktinib 100 milligram BID. All were anemic at baseline, 19 had a history of blood transfusion within 3 months before enrollment, and 9 were transfusion-dependent. It was noted that 95% of them had experienced grade 3 or higher anemia to ruxolitinib previously. 

At week 24, 43% achieved [spleen volume reduction] (SVR) [of] 35[%] (SVR35). 62% achieved a 50% or more decrease in total symptom score, and 66% showed clinical improvement in those patients [who] achieved SVR35. 94% maintained their response for 48 weeks. Among the transfusion-independent patients, whose baseline hemoglobin at 100 grams per liter or less, 43% had a 20 gram per liter or more increase [in] hemoglobin by week 24. 11% of baseline transfusion-dependent patients converted to transfusion-independent. Besides, 58% and 47% [of] patients had [a] 50% or more decrease in [red blood cell] (RBC) infusion frequency and units respectively with [grade] 3 or high[er] anemia reported in 31% of the patients. Thank you.

Source: 

Zhang Y, Zhou H, Duan M, et al. Safety and efficacy of jaktinib (a novel JAK inhibitor) in patients with myelofibrosis who are intolerant to ruxolitinib: A single-arm, open-label, phase 2, multicenter study. Am J Hematol. Published online: October 2023. doi: 10.1002/ajh.27033