It’s not yet time to abandon ruxolitinib in anemic myelofibrosis: Predictive factors of erythroid response to standard anemia-directed therapies combined with ruxolitinib

Ruxolitinib (RUX), the first JAK1/2 inhibitor approved for the treatment of myelofibrosis (MF), has significantly improved spleen and symptom control, demonstrating a survival benefit in responding patients (pts). However, on-target RUX-associated anemia represents a major therapeutic limitation, negatively affecting quality of life, prognosis, and treatment duration. Novel JAK1/2 inhibitors, such as momelotinib and pacritinib, also target ACVR1 and may ameliorate anemia both in RUX-naïve and -exposed pts. However, there is a number of standard anemia-directed therapies (ADT), including erythropoietin (EPO), danazol, steroids and immunomodulatory agents (e.g. thalidomide), that have been used for a long time to manage anemia in MF.

Information about the concurrent use of standard ADT with RUX is still scarce. Aims. To evaluate the impact of anemia on RUX drug survival, to assess the efficacy of various standard ADT in combination with RUX, to explore predictive factors of erythroid response and, finally, to analyze whether optimal anemia management with RUX-combined therapies can extend RUX drug survival. Retrospective registry study of pts with primary or secondary MF treated with RUX at 3 reference Hematology centers in Triveneto (Northern East region of Italy). Detailed clinical and laboratory data were collected at diagnosis and every 3 to 6 months during treatment for all pts. The definition of transfusion-dependent anemia (TDA) and response criteria for anemia were according to IWG-ELN 2024.

Anemia response was evaluated after 3, 6, 9 and 12 months of RUX and ADT combination: pts already exposed to ADT before or at RUX start were not included in this analysis. Statistical analyses were performed using “R” software. The overall study population included 238 pts (57.1% males) who started RUX from 2011 to 2024. Primary and secondary MF were 39.5% and 60.5%, respectively. Driver mutations were JAK2/CALR/MPL/triple negative in 191 (80.2%)/26 (10.9%)/12 (5%)/4 (1.7%) pts, respectively (information not available in 5). Median RUX survival for the overall study population was 48.9 months (95% CI: 37.8- 63.0).

At or after RUX start 164/238 pts (68.9%) developed moderate to severe anemia (Hb <10 g/dL), with a median time of 3 months (range 0-96) from RUX start. The presence of moderate to severe anemia at any time during RUX was associated to a significantly shorter RUX drug survival (median 42 vs 92 months, p=0.001). Anemia was treated with ADT in 77/164 pts (46.9%), while 68 pts received RBC transfusions only (41.5%) and the remaining cases did not receive specific treatments. EPO was the most frequently used ADT (46 pts, 59.7%), followed by steroids (25 pts, 32.5%), danazol (13 pts, 16.8%) and thalidomide (4 pts, 5.2%). Twelve pts received two or more different ADT, either concurrently or sequentially. Median time from RUX to EPO start was 6.8 months (range 1-138); median time from RUX to other ADT start ranged from 15.5 to 20 months. Rates of anemia major response to the combination of EPO and RUX ranged from 27.8% to 33.3% at 3-12 months, and 42.5% of pts received EPO for more than 12 months. Rates of anemia major response to the other ADT were considerably lower at all the timepoints (9-10% for steroids, 16-25% for danazol, 0% for thalidomide).The combination of EPO and RUX was associated with significantly superior RUX survival compared to other ADT (76.8 vs 33.3 months, p=0.0368). Pts non- TDA pre-EPO showed better RUX survival (78.4 vs 21.9 months, p=0.0016). Cumulative incidence of accelerated/blast phase (A/BP) at 60 months was 6.7% in pts treated with EPO alone vs 29.5% with other ADT +/- EPO (p=0.0108), suggesting a favorable safety profile for the use of EPO as unique supportive treatment for RUX-associated anemia.

A “Response to Ruxolitinib after 6 Month” (RR6) low/intermediate score was predictive of major response to EPO (64.5% vs 0% for pts with high score, p=0.0123). Notably, the achievement of major response was associated with a trend toward lesser progression to A/BP both in pts treated with EPO alone (p=0.0607) or other ADT (p=0.059). Proactive anemia management with EPO, initiated early before the establishment of TDA, is associated with better RUX survival and favorable safety profile. These results support a personalized approach integrating early prognostic assessment with optimized anemia management strategies, in order to maximize treatment benefits.

Durable efficacy and long-term safety with pelabresib plus ruxolitinib in JAK Inhibitor–Naive myelofibrosis: 96-week Results from the Phase III MANIFEST-2 study

Janus kinase inhibitor (JAKi) monotherapy, the standard of care for myelofibrosis (MF), improves splenomegaly and symptom burden but provides limited depth and durability of response. There is a significant unmet need for new combination strategies that adequately address the underlying disease biology and further improve clinical outcomes in MF.  Pelabresib (PELA) is an oral, small molecule inhibitor of bromodomain and extraterminal domain (BET) proteins and can act in a complementary manner with the JAK1/2 inhibitor ruxolitinib (RUX) by targeting inflammatory pathways that are regulated by BETmediated gene expression. PELA+RUX is being investigated in MANIFEST-2 (NCT04603495) in patients (pts) with JAKi-naive MF.

The study met its primary endpoint (Rampal RK. Nat Med. 2025). Here, updated 96-wk results from MANIFEST-2 are reported.  MANIFEST-2 is a double-blind, randomized, Phase III study in pts with JAKi-naive MF. Pts were randomized 1:1 to PELA or placebo (PBO) once daily with RUX twice daily.  Efficacy and safety endpoints were assessed at Wk 96, including ≥35% reduction in spleen volume (SVR35) response, total symptom score (TSS), hemoglobin (Hgb) response, safety, and survival outcomes.

As of March 2, 2025, pts had been followed for at least 96 wks, with 56.5% (121/214) of pts in the PELA+RUX arm and 59.3% (128/216) in the PBO+RUX arm completing 96 wks of assigned treatment. With a median follow-up of 115.9 wks at the cutoff date, approximately half of pts were still on assigned treatment (48.6% in the PELA+RUX arm vs 48.1% in the PBO+RUX arm).  Most common reasons for discontinuation were adverse events (AE; 21.0% vs 13.4%), physician decision (7.5% vs 14.8%), withdrawal of consent (10.3% vs 6.0%), and protocol-defined disease progression (5.1% vs 6.9%, respectively). At Wk 96, among evaluable pts on treatment, SVR35 response was observed in 91.5% (97/106) in the PELA+RUX arm vs 57.5% (65/113) in the PBO+RUX arm (difference, 34.0%), representing 45.3% (97/214) vs 30.1% (65/216) of the intent-to-treat population in each arm (difference, 15.2%), respectively, and showing sustained benefit in pts remaining on treatment. At Wk 96, absolute change in TSS from baseline was −15.07 in the PELA+RUX arm vs −12.48 in the PBO+RUX arm (difference, −2.59; 95% CI, −5.23 to 0.05); ≥50% reduction in TSS from baseline (TSS50) was achieved by 36.9% (79/214) and 28.2% (61/216) of pts, respectively, demonstrating durable responses in symptom improvement.

At Wk 96, dual SVR35 and TSS50 responses were reported in 31.8% (68/214) vs 15.7% (34/216) of pts, respectively. Hgb response was achieved by 17.8% (38/214) vs 11.6% (25/216) of pts in the PELA+RUX vs PBO+RUX arms. By 96 wks from the start of treatment, red blood cell transfusions were required in 33.1% (44/133) vs 39.9% (57/143) of evaluable pts, respectively.  Ongoing Wk 96 analyses of exploratory biomarker data, including the dynamics of variant allele frequencies of MF driver genes, will be presented. Treatment-emergent AEs were mainly low grade and remained similar between arms over time (PELA+RUX [n=212] vs PBO+RUX [n=214]: any grade, 99.5% vs 98.1%; Grade ≥3, 67.5% vs 70.1%). Externally and independently adjudicated leukemic transformations were reported in 5.1% (11/216) of pts on PELA+RUX and in 3.7% (8/214) of pts on PBO+RUX by the 96-wk data cutoff.

A total of 28 deaths and 22 progression-free survival (PFS) events were reported in the PELA+RUX arm vs 32 deaths and 34 PFS events in the PBO+RUX arm (overall survival [OS] HR, 0.986; 95% CI, 0.590–1.647; PFS HR, 0.746; 95% CI, 0.432–1.291; not powered for OS/PFS). These results represent the longest follow-up to date of a randomized combination trial in MF. After at least 96 wks of follow-up, PELA+RUX continued to show deep and durable improvements in splenic response, TSS, SVR35/TSS50 dual response, and anemia vs PBO+RUX, with stable or improving response rates among pts remaining on long-term treatment. PELA+RUX had a similar safety profile to PBO+RUX. The early imbalance in leukemic transformation cases decreased over time, and the observed frequency was in line with what is historically seen in MF. Longer-term follow-up showed numerically fewer deaths and fewer progression events in the PELA+RUX arm vs the PBO+RUX arm.

Overall findings suggest that PELA+RUX provides clinically meaningful benefits vs RUX monotherapy, with potential for disease modification and improving survival in pts with MF.

Real-world treatment duration of ruxolitinib and use of transfusion among 2268 patients with myelofibrosis: An analysis of the Medicare fee-for-service claims database

Ruxolitinib (RUX) is approved by the US Food and Drug Administration for the treatment of adults with intermediate- or high-risk myelofibrosis (MF). Median RUX treatment duration in the COMFORT-I/II trials was approximately 3 years and extended up to 5 years for some patients.

This study examined real-world duration of RUX treatment for MF, including subgroups with anemia and those requiring transfusions, based on a retrospective long-term follow-up in a large cohort of pts. This retrospective analysis used Medicare Fee-For-Service Parts A/B claims data and Part D Prescription Drug Event data to identify adults with ≥2 claims for MF from January 2016 to December 2023 and ≥1 claim for RUX from January 2017 to December 2021 (index date was the first RUX claim on or after the first MF claim).

Two anemia subgroups were evaluated based on either ≥1 anemia diagnosis (Dx) claim or ≥1 transfusion claim within 3 mo before index. Eligible patients were required to have continuous enrollment in Medicare Parts A/B/D for ≥12 mo before (baseline period) and ≥24 mo after index (follow up period). Pts with acute myeloid leukemia or myelodysplastic syndrome before index and those with hematopoietic cell transplant during the study period were excluded. Duration of RUX treatment was analyzed using the Kaplan-Meier method; clinical characteristics, MF-related treatments before and after RUX, and RUX doses were assessed descriptively.

Among 2268 eligible pts, median (IQR) age was 75 (70–80) years, 1210 (53%) were female, and 2019 (89%) were White. Nearly all pts (96%; n=2175) were aged ≥65 years and therefore intermediate to high risk. The most common comorbidities were renal disease (n=667 [29%]), peripheral vascular disease (n=557 [25%]), chronic pulmonary disease (n=552 [24%]), diabetes without complication (n=523 [23%]), and congestive heart disease (n=448 [20%]).  Pts in the subgroups (anemia Dx, n=1129; transfusion, n=387) had intermediate-2 or high-risk MF and other baseline characteristics similar to the overall population. Median (IQR) follow-up duration was 46 (33–63) mo.

Median (IQR) time from MF Dx to RUX initiation was 4.5 (1–12) mo, with 1577 (70%) pts starting RUX within 12 mo of Dx. Most pts were treatment naive (n=1564 [69%]); 659 ( hydroxyurea (HU) prior to RUX. During the baseline period, supportive medication for anemia was received by 277 (12%) pts overall (anemia Dx, n=197 [17%]; transfusion, n=102 [26%]), most commonly erythropoiesis-stimulating agents (n=251 [11%]) or danazol (n=43 [2%]). In the 90 days prior to RUX initiation, 384 (17%) had ≥1 blood transfusion.  The mean (SD) daily RUX dose was 23 (11) mg at initiation and 21 (11) mg at the last recorded dose. Overall, 2061 (91%) pts had a dose change during follow-up (mean [SD] daily dose change, −4.2 [14.7] mg), with a median (IQR) time to first dose change of 4 (2–14) mo; 1121 (49%) pts had a dose reduction and 940 (41%) had a dose increase. Among the 384 pts who required transfusion prior to index, 70% (n=267) received transfusions during months 0–3 and 52% (n=201) during months 10–12 post-index. Overall, 807 (36%) pts remained on RUX at the end of follow-up. Median (95% CI) RUX treatment duration was 37 (36–38) mo (subgroups: anemia Dx, 34 [32–36] mo; transfusion, 30 [28–33] mo).

After RUX discontinuation, 25% received another MF treatment; the most common treatments were HU (n=256 [11%]), fedratinib (n=186 [8%]), and pacritinib (n=115 [5%]).  In this real-world study with long-term follow-up of approximately 4 years, median duration of RUX treatment was 3.1 years. On average, pts started RUX early after MF diagnosis (median, 4.5 mo), and approximately one-third remained on RUX treatment at end of study period, regardless of age or baseline anemia status.

Most pts did not require transfusions at baseline. Among those who did require transfusions prior to RUX initiation, transfusion rates declined following RUX treatment, with nearly half becoming transfusion-free by the end of 1-year follow-up. These findings are consistent with data from the COMFORT trials and suggest that pts with MF can be treated long-term with RUX, including those with anemia and/or transfusion requirement, when managed with appropriate dose-optimizing strategies.

Changes in neutrophil-to-lymphocyte ratio (NLR) in patients with polycythemia vera treated with ruxolitinib reflect changes of JAK2 variant allele frequency (VAF)

The neutrophil-to-lymphocyte ratio (NLR) has received considerable interest as a simple and reliable marker of disease associated-inflammation in different settings, including cardiovascular diseases and cancer. In polycythemia vera (PV), NLR was associated with venous thrombosis (Carobbio A, BCJ 2022), overall mortality (Barbui T, BCJ 2024), and achievement of primary endpoints in LOW-PV trial (Barbui T, BJH 2024). Other observations indicated that NLR changes in PV patients (pts) receiving ropeginterferon alpha-2b (ropeg) were associated with JAK2V617F variant allele frequency (VAF) decrease (Barbui T; EHA2024, A1908).

The aim of the study was to evaluate levels and changes of NLR, total leukocytes (WBC), absolute neutrophil (ANC) and lymphocyte (ALC) counts, and correlate them with disease characteristics and JAK2 VAF modifications, in PV pts long-term treated with ruxolitinib (ruxo). Forty pts with PV who received ruxo, 10 mg BID for a median of 8.7y (4.7-9.8) as second line therapy because of intolerance (44.2%) or resistance (55.8%) to hydroxyurea, were included. Overall FU was 9.2y (1.3-14.5).

10 pts (25%) had history of major thrombosis. A complete clinical-hematologic response (CHR) and a molecular response (IWG-MRT criteria; Tefferi A, Blood 2013) was obtained in 32 (78%) and 41.5%, respectively. The median NLR value at baseline was 5.2 (1.6-25.0); we accordingly divided pts into a high (H-, above the median) and low (L-, below the median) NLR category, and compared them. At baseline, pts in the H-NLR had (median count x10⁹ /L; range) significantly higher WBC (12.6 vs 8.0; p=0.003), due to increased ANC (12.1; 5.1-26.3 vs 5.9; 4.0-15.8) compared to L-NLR (p<0.001); conversely, ALC was lower (1.4 (0.1-2.8) vs 2.2 (1.0-6.5) (p=0.001). Also, Hb level (15g/dL vs 14g/dL p=0.01) and PLT count (544 vs 323/L; p=0.004) were higher in H-NLR compared to L-NLR category. There was no baseline difference in disease duration, splenomegaly, ad history of cardiovascular events, between pts in the H- versus L-NLR category. In the entire cohort, NLR value at baseline was linearly correlated with JAK2 VAF (r=0.5, p=0.001).

Accordingly, JAK2 VAF (%±SD) was significantly higher in H-NLR compared to L-NLR category: 81.8±13.1% vs 54.8±23.8% (P<0.001). After starting ruxo (10 mg BID), the changes in NLR observed in the 2 categories differed. In the H-NLR, the median baseline NLR value of 9.6 (5.3-25.0) decreased to 5.4 (2.7-11.0; p=0.002), 5.2 (1.9-8.7; p=0.001) and 4.2 (1.3-11.5; p=0.001) at 1y, 2y and 3y, remaining steadily stable afterwards. Conversely, in the L-NLR group, no significant changes of NLR were observed: 3.1 (1.6-5.0) at baseline, then 2.6 (1.1-8.2; p=0.5), 3.0 (1.0-5.0;p=0.16) and 3.2 (1.0-7.7; p=0.29) at 1y, 2y and 3y, respectively.

Changes in H-NLR group were due to a decrease of WBC (-25% % (p=0.049), -32% (p=0.02) and -42% (p=0.002), at 1y, 2y and 3y), mostly accounted by decrease in ANC (-55% (p=0.001), -53% (p=0.002), -41%(p=0.001)); on the other hand, ALC remained unchanged (from a baseline 1.4 (0.1-2.8) to 1.35 (1.0-3.0; p=0.5), 1.24 (1.0-3.0,p=0.6) and 1.14 (1.0-5.0;p=0.4). During ruxo treatment, changes inJAK2 VAF proved different in the 2 NLR categories. In the H-NLR, the baseline VAF of 81.8±13.1% decreased to 72.0±17.6% (p=0.07), 62.1±26.0% (p=0.007) and 62.5±24.3% (p=0.006) at 1y, 2y and 3y, respectively.

Conversely in L-NLR group, the baseline VAF of 54.8±23.8% decreased to 37.7±24.7% (p=0.11), 43.4±30.8% (p=0.16) and 41.9±34.8% (p=0.21) at 1y, 2y and 3y, respectively. No differences were observed in terms of CHR (n=p=0.7), thrombosis (n=2), progression to MF (n= 16; p=0.37), evolution to AML (p=1.0), or death (p=0.55). Among HU-resistant/intolerant PV pts, higher (above the median) NLR reflected signs of myeloproliferation, including higher JAK2 VAF. Upon ruxo treatment, however, H-NLR pts showed the most impressive reduction of NLR due to preferential ANC decrease, that was also associated with JAK2 VAF decline, when compared to L-NLR pts.

The authors conclude that in H-NRL PV pts treated with ruxo, NLR proved to be a suitable biomarker mirroring changes in JAK2 VAF, clinically more friendly that PCR-based determination of VAF. Findings are reminiscent of observations in PV pts treated with ropeg-interferon in the LOW-PV and PROU-PV/CONTINUATION-PV study (Barbui T, EHA 2024). These findings deserve confirmation in other cohorts of ruxo-treated PV pts.

Ruxolitinib duration of treatment and effect on phlebotomy use among 2369 patients with polycythemia vera: A real-world analysis of the Medicare fee-for-service claims database

Ruxolitinib (RUX) is approved for the treatment of adults with polycythemia vera (PV) have inadequate response to or are intolerant of hydroxyurea (HU). The median duration of RUX treatment in the RESPONSE trial was approximately 5 years. This study examined RUX treatment duration in patients with PV based on long-term follow-up in a real-world setting. This retrospective analysis used Medicare Fee-For-Service Parts A/B claims data and Part D Prescription Drug Event data to identify adults with PV, defined as ≥2 claims for PV by International Classification of Diseases 10th Revision (ICD-10) Code D45, from January 2016 to December 2023; RUX treatment was defined by ≥1 claim from January 2017 to December 2021 (index date was the first RUX claim on or after the first PV claim).

Eligible patients were required to have continuous enrollment in medical and pharmacy benefits for ≥12 months before (baseline period) and ≥24 months after index (follow-up period). Patients with claims of primary or secondary myelofibrosis, essential thrombocythemia, acute myeloid leukemia, or myelodysplastic syndrome before index were excluded. Duration of RUX treatment was analyzed using the Kaplan-Meier method; clinical characteristics, PV related treatments before and after RUX, and RUX doses were assessed descriptively.

Among 2369 included patients, median (IQR) age was 75 (70–81) years, 60% (n=1411) were female, and 89% (n=2104) were White. Nearly all patients (98%; n=2311) were high-risk, with 97% (n=2300) aged ≥60 years, 16% (n=372) having a history of thrombotic events, and 15% (n=361) having both risk factors. Additionally, 27% of patients (n=633) had splenomegaly. The most common comorbidities were peripheral vascular disease (27%; n=646), chronic pulmonary disease (23%; n=552), diabetes without complication (23%; n=548), renal disease (21%; n=506), and cerebrovascular disease (20%; n=471). The median (IQR) follow-up duration was 51 (36–71) months. Median (IQR) time from PV diagnosis to RUX initiation was 15 (11–33) months, with 75% of patients (n=1773) starting RUX ≥12 months after diagnosis. The most common treatments during the baseline period prior to RUX initiation were HU (59%; n=1387) and anagrelide (7%; n=170); 29% of patients (n=691) received phlebotomy during the 6 months before index, with a median (IQR) of 2 (1–7) phlebotomy claims.

The mean (SD) RUX dose was 20.3 (9.3) mg daily or 10 mg twice daily (bid) at initiation and 19.4 (10.6) mg daily (10 mg bid) at the last recorded dose. Initial dose adjustments occurred at a median of 5 (2–15) months, with 41% of patients (n=970) undergoing a dose reduction and 40% (n=944) a dose escalation. Median (95% CI) RUX treatment duration was 42 (40–44) months, and 38% of patients (n=909) remained on RUX at the end of follow-up. Among the 691 patients who received phlebotomy at baseline, 60% (n=415) did not receive any phlebotomy during the first 6 months post-index, and 73% (n=506) did not receive any phlebotomy during months 7–12 post-index. After RUX discontinuation, the most common treatments among all 2369 patients were HU (17%; n=410) and phlebotomy (14%; n=323), followed by fedratinib (3%, n=66), anagrelide (3%; n=64), pacritinib (2%; n=41), and interferon (n<11).

In this large retrospective real-world study with over 4 years of follow-up, older patients with PV continued RUX treatment for a median of 3.6 years, and more than one-third of patients remained on RUX treatment at the end of the study period. Mean RUX dose used was 10 mg bid. Most patients who required phlebotomy at baseline became phlebotomy-free within 6 months after starting RUX. Nearly 4 years of continuous RUX use observed here is indicative of sustained clinical benefit and tolerability over a longer time frame, supporting its role as an effective long-term treatment option for patients with PV.