Post-essential Thrombocythemia Myelofibrosis Research Articles

Development and validation of a model for the early prediction of progression from essential thrombocythemia to post-essential thrombocythemia myelofibrosis: a multicentre retrospective study

Essential thrombocythemia (ET), a myeloproliferative neoplasm (MPN), has a substantial risk of evolving into post-essential thrombocythemia myelofibrosis (post-ET MF). This study aims to establish a prediction nomogram for early prediction of post-ET MF in ET patients. The training cohort comprised 558 patients from 8 haematology centres between January 1, 2010, and May 1, 2023, while the external validation cohort consisted of 165 patients from 6 additional haematology centres between January 1, 2010, and May 1, 2023. Univariable and multivariable Cox regression analysis was performed to identified independent risk factors and establish a nomogram to predict the post-ET MF free survival. Both bias-corrected area under the curve (AUC), calibration curves and concordance index (C-index) were employed to assess the predictive accuracy of the nomogram. Multivariate Cox regression demonstrated that elevated red blood cell distribution width (RDW), elevated levels of lactate dehydrogenase (LDH) and the level of haemoglobin (Hb), a history of smoking and the presence of splenomegaly were independent risk factors for post-ET MF. The C-index displayed of the training and validation cohorts were 0.877 and 0.853. The 5 years, 10 years AUC values in training and external validation cohorts were 0.948, 0.769 and 0.978, 0.804 respectively. Bias-corrected curve is close to the ideal curve and revealed a strong consistency between actual observation and prediction. We developed a nomogram capable of predicting the post-ET MF free survival probability at 5 years and 10 years in ET patients. This tool helps doctors identify patients who need close monitoring and appropriate counselling. This research was funded by the Key R&D Program of Zhejiang (No. 2022C03137); the Public Technology Application Research Program of Zhejiang, China (No. LGF21H080003); and the Zhejiang Medical Association Clinical Medical Research special fund project (No. 2022ZYC-D09).

Evolving landscape of JAK inhibition in myelofibrosis: monotherapy and combinations.

Myeloproliferative neoplasms (MPNs) are characterized by clonal myeloproliferation in 1 or more of the hematopoietic stem cell lineages. Primary myelofibrosis (MF), post-polycythemia vera MF, and post-essential thrombocythemia MF have the worst prognosis and are characterized by the presence of cytokine-mediated symptom complex, splenomegaly, progressive marrow failure, and clonal instability, leading to leukemic transformation. The key therapeutic aims encompass the management of symptoms, splenomegaly, and anemia and the improvement of survivals. These therapeutic aims have evolved with the availability of Jak inhibitors and novel agents, making disease modification potentially achievable. Novel agents may potentially target MPN stem cells, epigenetic alterations, signaling pathways, and apoptotic pathways. In this case-based review, we outline our approach to the management of MF and discuss the therapeutic landscape of MF, highlighting the utility of Jak inhibitors and novel Jak inhibitor-based combinations.

Real-world clinical characteristics of post-essential thrombocythemia and post-polycythemia vera myelofibrosis.

There are few prospective studies on patients with post-essential thrombocythemia myelofibrosis (PET-MF) and post-polycythemia vera myelofibrosis (PPV-MF). Therefore, we conducted a nationwide longitudinal prospective survey to clarify the clinical characteristics of these diseases. A total of 197 PET-MF and 117 PPV-MF patients diagnosed between 2012 and 2021 were analyzed. The median age at diagnosis was 70.0years for both diseases. The time from diagnosis of ET or PV to that of MF was 9.6 and 10.4years, respectively, with no significant difference. Patients with PPV-MF had higher hemoglobin levels and white blood cell counts than those with PET-MF, whereas those with PET-MF had higher platelet counts than those with PPV-MF. Although splenomegaly was more frequent in patients with PPV-MF at diagnosis, there was no difference in the frequency of constitutional symptoms. Ruxolitinib was the most common treatment administered to 74.6% and 83.8% of patients with PET-MF and PPV-MF, respectively. Patients with PET-MF and PPV-MF had similar prognoses, with 3-year overall survival (OS) of 0.742 in PET-MF and 0.768 in PPV-MF patients. In both diseases, leukemic transformation was the leading cause of death, followed by infection. The 3-year OS for patients with PET/PPV-MF and primary MF diagnosed during the same period was 0.754 and 0.626, respectively, with no significant difference. This survey provides real-world clinical features and prognostic data on secondary myelofibrosis in the ruxolitinib era.

Role of Splenic Irradiation Prior to Transplant for Myelofibrosis: A Global Collaboration

JAK inhibitors and novel agents have shown promising reduction of spleen size in newly diagnosed myelofibrosis. However, not all patients will respond or they eventually progress at some point. Despite hematopoietic cell transplantation (HCT) being the only curative treatment option to date, splenomegaly prior to HCT remains a particular challenge. On the other hand, numbers of patients eligible for HCT continue to increase worldwide, and thus management of splenomegaly becomes more and more relevant. One approach to reduce spleen size prior to HCT could be splenic irradiation. However, evidence on its role remains scarce. We took advantage of a global collaboration between European, US, and Latin American centers to investigate the role of splenic irradiation as part of the HCT platform for patients with myelofibrosis. Radiation therapy had to be given within 3 months prior to or be part of conditioning therapy for HSCT. Detailed information on irradiation as well as post-HCT safety profiles was collected in addition to usual patient-, disease-, and transplant-related variables. This global collaborative study included 52 patients, of whom 71% had primary myelofibrosis, 17% post polycythemia vera and 12% post essential thrombocythemia myelofibrosis. Median age at HCT was 60 years (range, 32-76). Risk category according to DIPSS prior to irradiation was intermediate-1 in 20%, intermediate-2 in 52%, and high in 28%. Driver mutation status was JAK2 in 44%, CALR in 40%, MPL in 4%, and triple negative in 12%. Four patients had portal vein thrombosis before irradiation. Ruxolitinib before irradiation was received by 76% and 4% received fedratinib. Reduced intensity conditioning HCT was received by 73% and 85% were matched related or matched unrelated donor transplants. Median time from irradiation to HCT was 2 weeks (range, 0.9-12 weeks) and median spleen size prior to irradiation was 23 cm (range, 14-35). Spleen size was measured by ultrasound in 70%, CT scan in 20%, and physical examination in 10%. Median total irradiation dose was 7 Gy (range, 3-12), fractionated in a median of 5 administrations (range, 2-12). Splenic irradiation resulted in a significant spleen reduction prior to HCT but was also associated with significant reduction in platelet and leukocyte counts ( Table). Spleen size did not correlate with blood counts prior or after irradiation. Higher platelet count prior to irradiation correlated with higher counts after irradiation (r=0.83; P<0.001). There was no correlation between irradiation dose and post-irradiation hematological toxicities. Only 1 patient had non-hematological adverse events (tumor lysis syndrome). Neutrophil engraftment was achieved by 90% within a median of 18 days after HCT and platelet engraftment was achieved by 81% within a median of 38 days. Median follow-up of the total cohort was 2.7 years and 3-year overall survival was 66% (95% CI, 52-80%; Figure). Non-relapse mortality was 27% (95% CI, 15-39%) and cumulative incidence of relapse was 11% (95% CI, 2-20%; Figure). Incidence of acute GVHD grade II-IV and chronic GVHD was 25% and 38%, respectively. Increased spleen size (as continuous variable) prior to irradiation was associated with worse outcome (P=0.05), showing 3-year survival of 73% for spleen ≤25cm vs 42% for >25cm, and non-relapse mortality of 58% vs 14%, respectively (P=0.02). No effect of spleen size after irradiation on outcomes was observed. All 4 patients with portal vein thrombosis died (2-year survival 25%). A multivariable model showed that larger spleen size before irradiation, lower hemoglobin levels, CALR/MPL-unmuated driver mutation genotype, and presence of portal vein thrombosis were significantly associated with worse survival ( Table). This first international and largest study to date on splenic irradiation as part of the HCT algorithm for patients with myelofibrosis and splenomegaly showed a significant impact of spleen size on overall survival and non-relapse mortality, while relapse rates were low. In addition, lower hemoglobin levels and presence of portal vein thrombosis at time of irradiation predicted worse outcomes.

Transform-1: A Randomized, Double-Blind, Placebo-Controlled, Multicenter, International Phase 3 Study of Navitoclax in Combination with Ruxolitinib Versus Ruxolitinib Plus Placebo in Patients with Untreated Myelofibrosis

Background: Janus kinase inhibitors (JAKis) provide symptom improvement and spleen volume reduction in patients with primary, post-polycythemia vera, and post-essential thrombocythemia myelofibrosis (MF). There remains a substantial unmet need for therapies that alter disease trajectory, improve outcomes, and enhance survival. The COMFORT-1 and -2 studies established JAKi monotherapy as standard-of-care with spleen volume reduction of ≥35% at Week 24 (SVR 35W24) of 42% and SVR 35W48 of 29%, respectively. In combination with the JAKi ruxolitinib, navitoclax, an orally available inhibitor of antiapoptotic B-cell lymphoma 2 proteins (BCL-X L, BCL-2, BCL-W), was shown to have pronounced antitumor activity in patients with MF in the phase 2 REFINE trial (NCT03222609). TRANSFORM-1 is an ongoing, phase 3, double-blind, placebo-controlled, multicenter, international study evaluating the safety and efficacy of navitoclax plus ruxolitinib (NAV + RUX) compared with placebo plus ruxolitinib (PBO + RUX) in JAK2i-naïve adults with MF. Methods: TRANSFORM-1 (NCT04472598) enrolled adult patients with intermediate-2 or high-risk MF with measurable splenomegaly, evidence of MF-related symptoms, no prior JAK2i treatment, and ECOG Performance Score ≤2. Patients were randomized 1:1 to receive NAV (starting dose of 200 mg [platelet {PLT} >150 × 10 9/L] or 100 mg escalated to 200 mg once daily if tolerated after ≥7 days [PLT ≤150 × 10 9/L]) or PBO, plus RUX at label dose, based on stratification factors of intermediate-2 vs high-risk MF and PLT ≤200 × 10 9/L vs >200 × 10 9/L. The primary endpoint was SVR 35W24. Secondary endpoints included change in total symptom score at Week 24 (TSS W24) assessed using 7-item MFSAF v4.0 (scale 0-70), SVR 35 at any time, duration of SVR 35, anemia response (per International Working Group criteria), reduction in marrow fibrosis, overall survival, leukemia-free survival, reduction in PROMIS Fatigue scale, and improvement in EORTC QLQ-C30 physical functioning scale. Exploratory endpoints include progression-free survival. Results: At data cutoff, April 13, 2023, 252 patients were enrolled with a median (range) follow-up of 14.9 (0.0-29.5) months; 125 patients were randomized to receive NAV + RUX and 127 to receive PBO + RUX. Most patients were male (57%), median (range) age was 69 (37-87) years, and patient demographics were similar between treatment arms ( Table 1). TRANSFORM-1 met its primary endpoint, with 79 patients (63.2%) in the NAV + RUX arm achieving SVR 35W24 compared with 40 patients (31.5%) in the PBO + RUX arm ( P<0.0001). Notably, SVR 35 at any time was achieved by 96 patients (77%) with NAV + RUX compared with 53 patients (42%) with PBO + RUX. Median (range) time to SVR 35 response was 12.3 (10.1-48.3) weeks with NAV + RUX versus 12.4 (11.3-72.3) weeks with PBO + RUX. Median duration of SVR 35 was not reached (NR) in the NAV + RUX arm compared with 19.4 months (95% CI 16.8, NR) in the PBO + RUX arm. At Week 24, the mean change in TSS from baseline was -9.7 (95% CI: -11.8, -7.6) with NAV + RUX compared with -11.1 (95% CI: -13.2, -9.1) with PBO + RUX arm ( P=0.2852). Grade ≥3 adverse events (AEs) were experienced by 85% of patients with NAV + RUX and 70% with PBO + RUX. The most common AEs (>30% of patients receiving NAV; Table 2) were thrombocytopenia, anemia, diarrhea, and neutropenia. Serious AEs were experienced by 26% of patients with NAV + RUX and 32% with PBO + RUX, including anemia (NAV + RUX: n=2; PBO + RUX: n=1), thrombocytopenia (NAV + RUX: n=2), and neutropenia (NAV + RUX: n=1). With NAV + RUX, AEs led to NAV dose reduction in 101 (81%) patients and NAV interruption in 87 (70%) patients of which 83 (67%) and 65 (52%) were due to thrombocytopenia, respectively. Of all enrolled patients, 83 (33%) discontinued study treatment; most common (>5% total patients) reason for NAV/PBO discontinuation were AEs (n=32; 39% of discontinuations) and physician decision (n=14; 17% of discontinuations). In each arm, 13 (10%) patients died; 6 with NAV + RUX and 5 with PBO + RUX died ≤30 days post-final dose. Conclusions: This first randomized trial in JAKi-naïve MF with NAV + RUX combination led to an SVR 35W24 rate that was twice as high as PBO + RUX ( P<0.0001). The responses were durable; AEs of thrombocytopenia and anemia were common but manageable with dose modification without any clinically significant sequalae. Additional evaluation is ongoing.

Chaperon Protein GRP78 Released from MPN Cells Increase Expression of Lysyl Oxidase in Human Stroma Cell Line

Impaired function of the endoplasmic stress (ER) response causes numerous pathological conditions, including tissue fibrosis. In the present study, we aimed to determine the pathological role of ER stress response systems in myeloproliferative neoplasms (MPNs). We found an increased expression of the chaperone protein glucose-regulated protein (GRP)78, which is a central regulator of ER stress in megakaryocytes from primary myelofibrosis (PMF) (n=7) or post-essential thrombocythemia myelofibrosis(POST-ET-MF) patients (n=2) regardless of the type of driver mutation. In accord with these notions, we found that GRP78 was overexpressed in JAK2V617F-harboring cell lines (HEL and SET-2) and in UT-7/TPO cells overexpressing either type1 or type2 mutant form of calreticulin. To address the mechanism responsible for the induction of GRP78, we treated the HEL and SET-2 cells with 4-phenyl butyric acid and tauroursodeoxycholic acid both of which are well known inhibitors of ER stress, however, these inhibitors did not affect the expression levels of GRP78. These results indicated that overexpression of GRP78 shown in these cells were not a result of activation of ER stress. In contrast, ruxolitinib, an inhibitor of JAK2V617F, blocked GRP78 expression in these cells. We also found ruxolitinib blocked nuclear accumulation of the transcription factor 4 (ATF4), one of the main transcription factors which regulate GRP78. Furthermore, knockdown of ATF4 using siRNA also resulted in suppression of GRP78 levels in HEL and SET-2 cells. These results suggested that JAK2V617F induce GRP78 through activation of ATF4. We also confirmed that megakaryocytes from MF patients had statistically higher nuclear to cytoplasmic intensity of ATF4 compared to megakaryocytes found in control subjects. For the next step, we tried to find out the pathological action of GRP78 in MPN cells. Although the GRP78 usually works as chaperon protein in cytosol, some cancer cells secret GRP78 into tumor microenvironment and activates signal transduction molecules in surrounding cells. Therefore, we hypothesized that overexpressed GRP78 proteins in MPN cells may secret and modulate phenotype of bone marrow stroma cells. Initially, we confirmed the presence of GRP78 proteins in culture media from HEL and SET-2 cells. Next, we investigated whether GRP78 secreted by HEL and SET-2 cells affect phenotype of bone marrow stromal cells. For this purpose, we used human bone marrow stroma cell line, HS-5. HS-5 cells were co-cultured with HEL or SET-2 cells with trans-well system, and changes of several key molecules involved in development of fibrosis were analyzed. We found that co-culture with HEL or SET-2 cells clearly indued expression of lysyl oxidase (LOX) , which mediate cross-linking of collagen fiber and induce tissue fibrosis , in HS-5 cells. Anti-GRP78 neutralizing antibody abrogated LOX elevation, in contrast, recombinant form of GRP78 proteins induced LOX proteins in HS-5. According to the above results, we examined LOX expression in bone marrow specimens from MF patients. The areas of LOX expression cells were statistically higher in MF patients compared to control group. In addition, high power field observations detected not only in round cells but also in spindle like cells expressed LOX in MF patients, suggesting that bone marrow stromal cells in MF patients express LOX. In conclusion, we demonstrated that GRP78 was overexpressed both in MPN derived cell lines and also in primary megakaryocytes from MF patients. Our observations proposed that overexpressed GRP78 in MPN cells contribute development of myelofibrosis through secreted in microenvironment and induced expression of extracellular matrix modulating enzyme LOX in bone marrow stromal cells.

Efficacy and Safety of Fedratinib in Patients with Myelofibrosis Previously Treated with Ruxolitinib: Results from the Phase 3 Randomized FREEDOM2 Study

Introduction Patients (pts) with myelofibrosis (MF) treated with the Janus kinase inhibitor (JAKi) ruxolitinib (RUX) show spleen volume reduction (SVR) and symptom reduction. However, most develop RUX intolerance or relapsed/refractory (R/R) disease and survival rates after RUX discontinuation are poor. Fedratinib (FEDR) delivered SVR and symptom reduction in the JAKARTA2 and FREEDOM studies (C Harrison et al. Am J Hematol 2020; V Gupta et al. Blood 2022). FREEDOM2 (NCT03952039) was a phase 3, open-label, randomized study to evaluate the safety and efficacy of FEDR compared with best available therapy (BAT) in pts with MF previously treated with RUX. Methods Pts aged ≥ 18 years with primary, post-polycythemia vera, or post-essential thrombocythemia MF with Dynamic International Prognostic Scoring System (DIPSS) score ≥ intermediate-2, splenomegaly (≥ 450 cm 3), platelets ≥ 50 x 10 9/L, peripheral blood myeloblasts < 5%, and normal baseline thiamine, R/R or intolerant to RUX, were randomized 2:1 to FEDR 400 mg/day or BAT in 28-day cycles, with stratification by spleen size, platelet count, and RUX R/R vs intolerant. Crossover to FEDR was permitted for progressive disease or after cycle 6 (EOC6) response assessment. Pts were treated until intolerance or lack of efficacy and followed-up every 3 months until death, withdrawal of consent, or study closure. The primary endpoint was SVR ≥ 35% (SVR35) at EOC6; secondary endpoints included symptom response (≥ 50% reduction in total symptom score measured by Myelofibrosis Symptom Assessment Form), SVR ≥ 25% (SVR25), durability of SVR and symptom response, and safety. Results Overall, 201 pts were initially randomized and treated, 134 and 67 pts in the FEDR and BAT arms, respectively; subsequently, 46 (68.7%) pts from the BAT arm crossed over to FEDR. Median (interquartile range) age was 70 (64-74) years, 52.2% were male, and most had primary MF (54.7%) and intermediate-2 DIPSS risk (76.1%). Assessed by aggregated group, most pts in the BAT arm received RUX (70.1%), hydroxyurea (10.4%), or RUX plus hydroxyurea (7.5%). At the data cutoff of December 27, 2022 (median follow-up, 15 months), pts receiving FEDR had significantly higher rates of SVR35 at EOC6 compared with BAT (35.8% vs 6.0%; P < 0.0001), as well as superior SVR25 at EOC6 and SVR35 during the full treatment course ( Table, Figure). SVR35 benefit with FEDR was observed across subgroups. The FEDR arm also showed higher rates of symptom response at EOC6 compared with BAT (34.1% vs 16.9%; P = 0.0033; Table). Median treatment duration was 43 weeks of FEDR and 24.7 weeks of BAT. During the first 6 cycles in the safety population: 70 (52.2%) pts on FEDR and 20 (29.9%) pts on BAT had dose interruption/reduction; median time to first reduction/interruption was 44.0 days for FEDR and 56.5 days for BAT. Treatment-emergent adverse events (TEAEs) leading to permanent treatment discontinuation occurred in 13 (9.7%) and 4 (6.0%) pts in the FEDR and BAT arms, respectively, during the first 6 cycles. During the first 6 cycles, 132 (98.5%) pts on FEDR and 65 (97.0%) pts on BAT had ≥ 1 TEAE; treatment-related AEs (TRAEs) occurred in 109 (81.3%) and 23 (34.3%) pts in the FEDR and BAT arms, respectively. The most frequently occurring TRAEs with FEDR were diarrhea (38.1% FEDR vs 0.0% BAT) and nausea (32.1% FEDR vs 1.5% BAT); most cases were grade 1/2. Grade 3/4 TRAEs occurred in 52 (38.8%) pts in FEDR and 8 (11.9%) pts in BAT arms, most frequently thrombocytopenia (11.9% FEDR vs 3.0% BAT) and anemia (9.0% FEDR vs 9.0% BAT). In the FEDR arm, 22 (16.4%) pts had thiamine levels below normal range, compared with 2 (3.0%) pts receiving BAT; most cases occurred prior to the study amendment of prophylactic thiamine supplementation. There was a single grade 1 case of suspected Wernicke's encephalopathy in the FEDR arm during cycle 3, which resolved fully 24 hours after thiamine supplementation (0 cases in BAT arm). Two pts each in FEDR and BAT arms had TRAEs of infection. Conclusions In this phase 3 randomized study in pts with MF and prior RUX treatment, FEDR demonstrated superior SVR and symptom response rates compared with BAT. Most pts on BAT received RUX, highlighting a clinical need for an alternative JAKi. Differences in AE and discontinuation rates in the first 6 cycles are consistent with other studies comparing JAKi with BAT. AE mitigation strategies were effective and no new safety concerns for FEDR were identified. Study support Bristol Myers Squibb

Modulation of TGF-β Superfamily Signaling By Ker-050 Demonstrated Potential to Treat Myelofibrosis and Mitigate Ruxolitinib-Associated Cytopenia

Background: Myelofibrosis (MF) is a disorder characterized by unrestrained proliferation of myeloid precursors and dysfunctional Janus kinase (JAK) signaling. Fibroblast proliferation, bone remodeling, and marrow fibrosis within the osteohematopoietic niche (OHN) result in ineffective and extramedullary hematopoiesis. Clinical manifestations include anemia, splenomegaly, and often disabling symptoms. JAK inhibitors, such as ruxolitinib, have been shown to improve spleen size and symptoms but are associated with dose-limiting cytopenia, reducing their utility for many patients. KER-050 is an investigational, modified activin receptor type IIA ligand trap designed to inhibit select TGF-β superfamily ligands (activins A, B, GDFs 8, 11) to address ineffective hematopoiesis by promoting differentiation of erythroid and megakaryocytic precursors. Here, we present new data from an ongoing Phase 2 study (NCT05037760) evaluating KER-050 as a monotherapy and in combination with ruxolitinib in participants with MF. Methods: This ongoing Phase 2 study is evaluating the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and efficacy of KER-050 administered with or without ruxolitinib in participants with anemia and primary MF, post-essential thrombocythemia MF, or post-polycythemia vera MF. Part 1 involves parallel dose escalation arms (1A: monotherapy, 1B: combination with ruxolitinib) to identify the dose(s) of KER-050 to be evaluated in Part 2. Data are presented as of the data cutoff date of April 3, 2023. Results: A total of 24 participants were enrolled (n=12 in Arm 1A and n=12 in 1B). One participant recently enrolled in Arm 1B at dose level III (3.0 mg/kg) had limited exposure at the time of data cutoff and is not included in the PD findings reported below. All participants met the criteria for higher-risk disease by DIPSS and 41.7% met IWG 2013 transfusion-dependent (TD) criteria (Table 1). The median duration of KER-050 treatment was 116 days (range 26 to 474), with 62.5% of participants ongoing as of the cutoff date. Most participants (91.7%) had at least 1 treatment-emergent adverse event (TEAE). No dose-limiting toxicities and no treatment-related severe or serious TEAEs have been observed. Most frequently observed TEAEs in ≥15% of participants were fatigue (including asthenia) (37.5%), and diarrhea (20.8%). Mean increases in hemoglobin (Hgb), reticulocytes, and soluble transferrin receptor (sTfR) were observed over the first 12 weeks of treatment in non-TD (NTD) participants for whom changes in markers of erythropoiesis were less confounded by ongoing transfusions (Figure 1). Overall, 7 of 13 (53.8%) NTD participants achieved a mean Hgb increase of ≥1.0 g/dL over the first 12 weeks and 2 of 13 (15.4%) achieved an increase of ≥1.5 g/dL. Increases in Hgb were also observed among TD participants, with 3/10 (30%) having a Hgb increase ≥1 g/dL over the first 12 weeks and one participant achieving a transfusion reduction ≥50% over at least 12 weeks (data not shown). For this participant (dose level I, Arm 1B), transfusion burden decreased from 9 red blood cell (RBC) units/12 weeks at baseline to 2 RBC units/12 weeks. Another participant (dose level I, Arm 1B), who received 4 RBC units/12 weeks at baseline, achieved a 20-week transfusion-free period with concomitant increases in Hgb, sTfR and platelets. Across treatment arms, platelet values were generally maintained if not increased. Additionally, for one participant receiving KER-050 monotherapy (dose level I), spleen size decreased by 38% from 2569 cm 3 at baseline to 1592 cm 3 at 24 weeks, coinciding with a 55% reduction in MF-SAF-TSS score from 56 to 25. Summary: Preliminary data from this ongoing Phase 2 study suggest that KER-050 is generally well tolerated and support the potential of KER-050 to improve key aspects of MF, including cytopenia, spleen size, and symptoms. Despite data being limited thus far to the 2 lowest dose levels, encouraging increases in markers of hematopoiesis have been observed as well as an initial case of reduced spleen size in a participant receiving KER-050 monotherapy. Updated analyses available at the time of presentation will provide further insight into the potential of KER-050 to treat MF and mitigate ruxolitinib-associated cytopenia.

Pelabresib in Combination with Ruxolitinib for Janus Kinase Inhibitor Treatment-Naïve Patients with Myelofibrosis: Results of the MANIFEST-2 Randomized, Double-Blind, Phase 3 Study

Background Myelofibrosis (MF) is characterized by bone marrow fibrosis, anemia, splenomegaly and MF-associated symptoms. These hallmarks result from dysregulation of the JAK/STAT pathway and BET-mediated MF target gene modulation. Pelabresib (CPI-0610; pela) is an investigational oral small-molecule drug designed to inhibit BET-mediated gene transcription involved in MF pathogenesis. Preclinical data support the potential of combining pela with therapiesthat target overlapping pathways, such as JAK/STAT, to improve response by inhibiting the molecular drivers of MF. The Phase 3 MANIFEST-2 trial was initiated based on compelling data from Arm 3 of the ongoing Phase 2 MANIFEST study (NCT02158858), which is evaluating the combination of pela and ruxolitinib (rux) in JAK inhibitor (JAKi) treatment-naïve patients (pts) with MF. In Arm 3 of MANIFEST, primary endpoint analyses at 24 Weeks (Wks) for the 84 pts enrolled reported SVR35 (≥35% reduction in spleen volume from baseline) in 68% of pts and TSS50 (≥50% reduction in Total Symptom Score [TSS] from baseline) in 56% of pts (Mascarenhas, et al. 2023). Aims MANIFEST-2 (NCT04603495) is a global, Phase 3, randomized, double-blind, active-control study of pela + rux versus placebo + rux in JAKi treatment-naïve pts with primary MF, post-polycythemia vera MF or post-essential thrombocythemia MF. The aim of this study is to evaluate the efficacy and safety of pela + rux. Here we present the study design and baseline patient stratification for MANIFEST-2. Results from the primary analysis of MANIFEST-2 will be presented at the ASH Annual Meeting 2023. Methods The MANIFEST-2 study schema is shown in Figure 1. Key eligibility criteria include a DIPSS score of Intermediate-1 (Int-1) or higher, platelet count ≥100 × 10 9/L, spleen volume ≥450 cm 3 by CT or MRI, ≥2 symptoms with an average score ≥3 or a TSS of ≥10 using the MFSAF v4.0, peripheral blast count <5% and an ECOG performance status ≤2. Patient randomization was stratified by DIPSS risk category (Int-1 vs Int-2 vs High), platelet count (>200 × 10 9/L vs 100-200 × 10 9/L) and spleen volume (≥1800 cm 3 vs <1800 cm 3). Double-blind treatment of pela (125-175 mg) or placebo was administered once daily for 14 consecutive days, followed by a 7-day break, which is considered one cycle of treatment. Rux (5-25 mg) was administered twice daily based on platelet counts and spleen response for all 21 days of the cycle. The primary endpoint is SVR35 response at Wk 24. Secondary endpoints include TSS50, percentage change in TSS, safety, pharmacokinetics, changes in bone marrow fibrosis, progression-free survival, overall survival, conversion from transfusion dependence to independence and rate of red blood cell transfusion for the first 24 wks. Results A total of 591 pts were screened at 138 sites. Following the screening process, 431 pts from North America, Europe, Asia and Australia were randomized. The number of pts assigned to each randomization stratum are presented in Table 1; the majority of pts presented with DIPSS Int-1 or -2, had a platelet count above 200 × 10 9/L and spleen volume below 1800 cm 3. The study opened for enrolment in November 2020; the first patient received their initial treatment on April 22, 2021, and the last patient received their first treatment on March 2, 2023. The last patient is expected to reach the 24-wk primary endpoint on August 31, 2023, following which a primary analysis will occur. As of June 27, 2023 there were 383 pts ongoing in the study. Conclusion The Phase 3 MANIFEST-2 study was initiated based on compelling data from the ongoing Phase 2 MANIFEST study, in which the combination of pela and rux in Arm 3 demonstrated significant clinical activity and disease-modifying potential without clinically relevant treatment-limiting toxicity. MANIFEST-2 has completed recruitment and will provide definitive efficacy results of combination therapy in JAKi treatment-naïve pts with MF. As DIPSS Int-1 pts have been excluded or underrepresented in prior randomized trials in MF, MANIFEST-2 will also provide important insights in assessing the benefits of starting treatment at an earlier stage of the disease. Primary results from the pivotal Phase 3 MANIFEST-2 trial of pela and rux versus placebo and rux in JAKi treatment-naïve pts may have the potential to influence the MF treatment paradigm and will be presented at the ASH Annual Meeting 2023.

PXS5505-MF-101: A Phase 1/2a Study to Evaluate Safety, Pharmacokinetics and Pharmacodynamics of Pxs-5505 in Patients with Primary, Post-Polycythemia Vera or Post-Essential Thrombocythemia Myelofibrosis

Background: Myelofibrosis (MF) is characterized by a progressive increase in extracellular matrix in the bone marrow (BM) associated with decreased production of hematopoietic cells. Though Janus kinase (JAK) inhibitors provide clinical benefit in patients (pts) with MF, they have no direct effect on BM fibrosis (BMF) and thereby limited disease modifying effects. MF is associated with elevated expression of most lysyl oxidase (LOX) isoforms which cross link collagen and elastin. PXS-5505 is a pan-LOX inhibitor that prevents the cross-linking of collagen and elastin and exhibits anti-fibrotic effects in murine models of MF. PXS5505-MF-101 is an ongoing multi-center phase 1/2a study of PXS-5505 in pts with primary, post-polycythemia vera (PV) or post-essential thrombocythemia (ET) MF. (NCT04676529) The study started with two phases: Dose Escalation (DEP) and Cohort Expansion (CEP). The DEP has been completed, establishing a dose of 200mg BID to carry forward into the CEP. During the CEP, up to 24 pts are to be treated for 6 months. Preliminary data from the CEP is presented here. Methods: Study objectives are to determine PXS-5505 safety/tolerability, pharmacokinetics (PK) and pharmacodynamics (PD), BMF changes, spleen volume and MF symptoms (MFSAF). Eligible pts must have primary or post-ET/PV MF of Int-2/high risk; relapsed/refractory or intolerant/ineligible to available JAK inhibitors and have symptomatic disease. Results: At data cutoff (30/Jun/2023), 21 pts have enrolled in the CEP (7 F and 14 M); age 60-86 yrs (median 72 yrs); of these, 10 have completed 24 weeks of Rx and 20 pts have completed ≥1-month Rx. 8 pts had post-ET MF, 5 post-PV MF and 8 PMF; 9 pts have withdrawn from the CEP. Total drug exposure in the CEP is 372 weeks, median 162 days (min 25, max 191). Preliminary CEP PK data are consistent with the DEP with steady state reached by Day 28 with no accumulation observed past this point. The PD data from the DEP demonstrated excellent inhibition of LOX as measured by LOX and LOXL2 target engagement (data previously presented) and this level of inhibition continues to be observed in CEP. [Figure 1] All 9 pts completing 24 weeks PXS-5505 with baseline (BL) biopsies available showed stable reticulin fibrosis at each visit; collagen fibrosis was reduced in 5/9 pts. [Figure 2] Hematological parameters were stable; 7/10 pts had stable/improved hemoglobin and 8/10 had stable/improved platelets over 24 weeks including 3 pts with Grade 4 thrombocytopenia at BL. 4/10 pts had improvements in MF-SAF TSS of ≥20% with 2/10 pts of ≥40% at 24 weeks. No SVR35 responses were seen. There has been 1 fatal AE (febrile neutropenia) on Rx, and 2 post-Rx discontinuation/completion (sepsis, acute myocardial infarction), all unrelated. There have been 6 Rx related adverse events (TRAEs); 2 Grade 1 (vomiting, urticaria), 2 Grade 2 (purpura, hypomagnesaemia), 1 Grade 3 (platelet count decreased), 1 Grade 4 (anemia, noted as leading to drug withdrawal). There have been no serious TRAEs reported. Enrolment into the CEP continues and an additional cohort is planned using PXS-5505 as an add-on to Ruxolitinib Rx. Conclusion: PXS-5505 has been well tolerated with no dose limiting toxicity or serious TRAEs. PD results indicate excellent LOX inhibition at the 200mg BID level. Further, there are preliminary indications of disease modification characterized by stable/improved blood counts and an improvement in collagen fibrosis. These results are encouraging given the poor prognosis seen after Ruxolitinib discontinuation in pts with MF and warrant continued investigation in an earlier Rx setting.

The chaperone protein GRP78 released from MPN cells increases the expression of lysyl oxidase in a human stromal cell line

Impaired function of the endoplasmic stress (ER) response causes numerous pathological conditions, including tissue fibrosis. In the present study, we aimed to determine the pathological role of ER stress response systems in myeloproliferative neoplasms (MPNs). We found increased expression of the chaperone protein glucose-regulated protein (GRP) 78, a central regulator of ER stress, in megakaryocytes from primary myelofibrosis or postessential thrombocythemia myelofibrosis patients. GRP78 was overexpressed in JAK2V617F-harboring cell lines; however, inhibitors of ER stress did not affect the expression levels of GRP78. In contrast, ruxolitinib, a well-known inhibitor of JAK2V617F, clearly blocked GRP78 expression in these cells through downregulation of transcription factor 4 (ATF4). Interestingly, GRP78 was secreted from HEL and SET-2 cells into culture media. Coculture of these cells with HS-5 cells, a human bone marrow stroma-derived cell line, induced enhanced expression of lysyl oxidase (LOX), which mediates cross-linking of collagen fibers and induces tissue fibrosis, in HS-5 cells. An anti-GRP78 neutralizing antibody abrogated LOX elevation; in contrast, recombinant GRP78 protein induced LOX protein expression in HS-5 cells. Our observations suggest that the oncogenic protein JAK2V617F induces overexpression and release of GRP78, which may induce a fibrotic phenotype in surrounding bone marrow stromal cells.

Role of Next Generation Immune Checkpoint Inhibitor (ICI) Therapy in Philadelphia Negative Classic Myeloproliferative Neoplasm (MPN): Review of the Literature.

The Philadelphia chromosome-negative (Ph-) myeloproliferative neoplasms (MPNs), which include essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF), are enduring and well-known conditions. These disorders are characterized by the abnormal growth of one or more hematopoietic cell lineages in the body's stem cells, leading to the enlargement of organs and the manifestation of constitutional symptoms. Numerous studies have provided evidence indicating that the pathogenesis of these diseases involves the dysregulation of the immune system and the presence of chronic inflammation, both of which are significant factors. Lately, the treatment of cancer including hematological malignancy has progressed on the agents aiming for the immune system, cytokine environment, immunotherapy agents, and targeted immune therapy. Immune checkpoints are the molecules that regulate T cell function in the tumor microenvironment (TME). The first line of primary immune checkpoints are programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte antigen-4 (CTLA-4). Immune checkpoint inhibitor therapy (ICIT) exerts its anti-tumor actions by blocking the inhibitory pathways in T cells and has reformed cancer treatment. Despite the impressive clinical success of ICIT, tumor internal resistance poses a challenge for oncologists leading to a low response rate in solid tumors and hematological malignancies. A Phase II trial on nivolumab for patients with post-essential thrombocythemia myelofibrosis, primary myelofibrosis, or post-polycythemia myelofibrosis was performed (Identifier: NCT02421354). This trial tested the efficacy of a PD-1 blockade agent, namely nivolumab, but was terminated prematurely due to adverse events and lack of efficacy. A multicenter, Phase II, single-arm open-label study was conducted including pembrolizumab in patients with primary thrombocythemia, post-essential thrombocythemia or post-polycythemia vera myelofibrosis that were ineligible for or were previously treated with ruxolitinib. This study showed that pembrolizumab treatment did not have many adverse events, but there were no pertinent clinical responses hence it was terminated after the first stage was completed. To avail the benefits from immunotherapy, the paradigm has shifted to new immune checkpoints in the TME such as lymphocyte activation gene-3 (LAG-3), T cell immunoglobulin and mucin domain 3 (TIM-3), T cell immunoglobulin and ITIM domain (TIGIT), V-domain immunoglobulin-containing suppressor of T cell activation (VISTA), and human endogenous retrovirus-H long terminal repeat-associating protein 2 (HHLA2) forming the basis of next-generation ICIT. The primary aim of this article is to underscore and elucidate the significance of next-generation ICIT in the context of MPN. Specifically, we aim to explore the potential of monoclonal antibodies as targeted immunotherapy and the development of vaccines targeting specific MPN epitopes, with the intent of augmenting tumor-related immune responses. It is anticipated that these therapeutic modalities rooted in immunotherapy will not only expand but also enhance the existing treatment regimens for patients afflicted with MPN. Preliminary studies from our laboratory showed over-expressed MDSC and over-expressed VISTA in MDSC, and in progenitor and immune cells directing the need for more clinical trials using next-generation ICI in the treatment of MPN.

Clinical Characteristics and Outcomes of Patients with Primary and Secondary Myelofibrosis According to the Genomic Classification Using Targeted Next-Generation Sequencing.

Myelofibrosis (MF) is a heterogeneous disease regarding its mutational landscape, clinical presentation, and outcomes. The aim of our work is to evaluate the genomic classification of MF considering whether it is primary or secondary. One-hundred seventy-five patients, 81 with primary MF (PMF) and 94 with secondary MF (SMF) were hierarchically allocated into eight molecular groups. We found that TP53 disruption/aneuploidy (n = 16, 9%) was more frequent (12% versus 6%) and showed higher allele burden (57% versus 15%, p = 0.01) in SMF than in PMF, and was associated with shorter survival (median 3.5 years). Mutations in chromatin/spliceosome genes (n = 72, 41%) represented the most frequent genomic group in PMF. Homozygous JAK2 mutation (n = 40, 23%) was enriched with old patients with SMF after long-standing polycythemia vera, whereas MF with heterozygous JAK2 mutation (n = 22, 13%) was similarly distributed among PMF and SMF. MF with CALR mutation (n = 19, 11%) predominated in post-essential thrombocythemia MF. The remaining genomic groups were infrequent. TP53 disruption, chromatin/spliceosome mutation, and homozygous JAK2 mutation were associated with significantly shorter survival and higher risk of progression. In conclusion, genomic classification reveals different pathogenic pathways between PMF and SMF and provides relevant information regarding disease phenotype and outcomes.

Momelotinib versus danazol in symptomatic patients with anaemia and myelofibrosis previously treated with a JAK inhibitor (MOMENTUM): an updated analysis of an international, double-blind, randomised phase 3 study

The MOMENTUM study met all key endpoints at week 24, demonstrating symptom, spleen, and anaemia benefits with momelotinib versus danazol in patients with myelofibrosis. In this updated analysis, we report duration of week 24 responses and new responses with momelotinib through week 48. MOMENTUM is an international, double-blind, randomised, phase 3 study done at 107 sites across 21 countries. Patients were 18 years or older with primary, post-polycythaemia vera, or post-essential thrombocythaemia myelofibrosis, previously treated with an approved Janus kinase (JAK) inhibitor for 90 days or more (≥28 days with haematological complications), and had an Eastern Cooperative Oncology Group performance status of 2 or less. Patients were randomly assigned (2:1) to either the momelotinib group (200 mg orally once per day) or danazol group (300 mg orally twice per day) through week 24 via non-deterministic biased coin minimisation and an interactive response system. Stratification factors were Total Symptom Score (TSS; <22 vs ≥22), spleen size (<12 cm vs ≥12 cm), transfusion burden (0 units vs 1-4 units vs ≥5 units), and study site. After week 24, all patients initially randomly assigned to either group who remained on the study received open-label momelotinib. The primary endpoint, which has already been reported, was Myelofibrosis Symptom Assessment Form TSS response rate at week 24. Predefined secondary endpoints were duration of week 24 TSS and transfusion independence responses, safety, and survival, which are summarised post hoc at the week 48 data cutoff (May 17, 2022). TSS, transfusion independence, and splenic responses at week 48 were defined post hoc and assessed in all evaluable patients who entered the open-label period and provided sufficient data. The timing of this updated analysis was defined post hoc after all patients had the opportunity to complete their week 48 assessments, as most patients entered an extended access study (NCT03441113) after week 48. This study is registered with ClinicalTrials.gov, number NCT04173494, and is now complete. Between April 24, 2020, and Dec 3, 2021, a total of 195 patients were randomised (130 [67%] in the momelotinib group and 65 [33%] in the danazol group). 93 (72%) of 130 patients in the momelotinib group and 41 (63%) of 65 in the danazol group entered the momelotinib open-label extension period. Median follow-up was 48·4 weeks (IQR 40·6-55·7). Among TSS-evaluable patients at week 48, 30 (45%) of 67 patients in the momelotinib group who continued treatment and 15 (50%) of 30 in the danazol group who crossed over were responders. TSS responders at any time during the open-label period by week 48 were 46 (61%) of 75 evaluable patients in the momelotinib group who continued and 19 (59%) of 32 in the danazol group who crossed over, including most week 24 responders plus new responders after week 24. No new safety signals emerged with long-term follow-up. The most common non-haematological treatment-emergent adverse events in momelotinib-treated patients over the entire study period as of the data cutoff were diarrhoea (45 [26%] of 171) and asthenia (28 [16%]); the most common grades 3-4 treatment-emergent adverse events were thrombocytopenia (33 [19%]) and anaemia (19 [11%]). Serious treatment-emergent adverse events were reported in 79 (46%) of 171 patients, and fatal treatment-emergent adverse events were reported in 30 (18%); two fatal treatment-emergent adverse events were considered possibly related to momelotinib (rotaviral enteritis and Staphylococcus pneumonia). Momelotinib was associated with durable symptom, spleen, and anaemia benefits, late responses after week 24, and favourable safety through week 48. These results highlight the potential benefits of treatment with momelotinib in patients with myelofibrosis, particularly those with anaemia. Sierra Oncology, a GSK company.

Novel therapeutics for myelofibrosis.

Myelofibrosis (MF) includes primary MF, post-essential thrombocythemia MF, and post-polycythemia vera MF. MF is a progressive myeloid neoplasm characterized by ineffective clonal hematopoiesis, extramedullary hematopoiesis, a reactive bone marrow environment resulting in reticulin deposition and fibrosis, and a propensity for leukemia transformation. The identification of driver mutations in JAK2, CALR, and MPL has contributed to a better understanding of disease pathogenesis and has led to the development of MF-specific therapies, such as JAK2 inhibitors. Despite the fact that ruxolitinib and fedratinib have been clinically developed and approved, their use is limited due to adverse effects such as anemia and thrombocytopenia. Recently, pacritinib has been approved for a group of thrombocytopenic patients with significant unmet clinical needs. In symptomatic and anemic patients with prior JAK inhibitor exposure, momelotinib was superior to danazol in preventing exacerbation of anemia and in controlling MF-associated signs and symptoms, such as spleen size. Although the development of JAK inhibitors is remarkable, modifying the natural course of the disease remains a priority. Therefore, many novel treatments are currently under clinical development. Agents targeting bromodomain and extra-terminal protein, anti-apoptotic protein Bcl-xL, and phosphatidylinositol-3-kinase delta have been studied in combination with JAK inhibitors. These combinations have been employed in both the frontline and "add-on" approaches. In addition, several agents are being studied as monotherapies for ruxolitinib-resistant or -ineligible patients. We reviewed several new MF treatments in the advanced stages of clinical development and treatment options for cytopenic patients.

Momelotinib versus danazol in symptomatic patients with anaemia and myelofibrosis (MOMENTUM): results from an international, double-blind, randomised, controlled, phase 3 study

Janus kinase (JAK) inhibitors approved for myelofibrosis provide spleen and symptom improvements but do not meaningfully improve anaemia. Momelotinib, a first-in-class inhibitor of activin A receptor type 1 as well as JAK1 and JAK2, has shown symptom, spleen, and anaemia benefits in myelofibrosis. We aimed to confirm the differentiated clinical benefits of momelotinib versus the active comparator danazol in JAK-inhibitor-exposed, symptomatic patients with anaemia and intermediate-risk or high-risk myelofibrosis. MOMENTUM is an international, double-blind, randomised, controlled, phase 3 study that enrolled patients at 107 sites across 21 countries worldwide. Eligible patients were 18 years or older with a confirmed diagnosis of primary myelofibrosis or post-polycythaemia vera or post-essential thrombocythaemia myelofibrosis. Patients were randomly assigned (2:1) to receive momelotinib (200 mg orally once per day) plus danazol placebo (ie, the momelotinib group) or danazol (300 mg orally twice per day) plus momelotinib placebo (ie, the danazol group), stratified by total symptom score (TSS; <22 vs ≥22), spleen size (<12 cm vs ≥12 cm), red blood cell or whole blood units transfused in the 8 weeks before randomisation (0 units vs 1-4 units vs ≥5 units), and study site. The primary endpoint was the Myelofibrosis Symptom Assessment Form (MFSAF) TSS response rate at week 24 (defined as ≥50% reduction in mean MFSAF TSS over the 28 days immediately before the end of week 24 compared with baseline). MOMENTUM is registered with ClinicalTrials.gov, number NCT04173494, and is active but not recruiting. 195 patients were randomly assigned to either the momelotinib group (130 [67%]) or danazol group (65 [33%]) and received study treatment in the 24-week randomised treatment period between April 24, 2020, and Dec 3, 2021. A significantly greater proportion of patients in the momelotinib group reported a 50% or more reduction in TSS than in the danazol group (32 [25%] of 130 vs six [9%] of 65; proportion difference 16% [95% CI 6-26], p=0·0095). The most frequent grade 3 or higher treatment-emergent adverse events with momelotinib and danazol were haematological abnormalities by laboratory values: anaemia (79 [61%] of 130 vs 49 [75%] of 65) and thrombocytopenia (36 [28%] vs 17 [26%]). The most frequent non-haematological grade 3 or higher treatment-emergent adverse events with momelotinib and danazol were acute kidney injury (four [3%] of 130 vs six [9%] of 65) and pneumonia (three [2%] vs six [9%]). Treatment with momelotinib, compared with danazol, resulted in clinically significant improvements in myelofibrosis-associated symptoms, anaemia measures, and spleen response, with favourable safety. These findings support the future use of momelotinib as an effective treatment in patients with myelofibrosis, especially in those with anaemia. Sierra Oncology.

Phase 1/2a Study to Evaluate Safety, Pharmacokinetic and Pharmacodynamic Dose Escalation and Expansion Study of Pxs-5505 in Patients with Primary, Post-Polycythemia Vera or Post-Essential Thrombocythemia Myelofibrosis

Background: Janus kinase (JAK) inhibitors for myelofibrosis (MF) treatment have provided major clinical benefits, but do not improve cytopenias and demonstrate only modest effects on bone marrow fibrosis (BMF). High discontinuation rates are observed due to loss of therapeutic effect or drug induced toxicity. Reducing BMF may normalize the hematopoietic environment and improve symptoms of MF, particularly blood cell counts. Limited therapeutic options highlight the need for novel, effective therapies for primary MF (PMF). Lysyl oxidases (LOX) are a family of enzymes responsible for the critical post-translational modification essential for the biogenesis of cross-linked collagen and elastin, which form the basis of reticulin in bone marrow (BM). Importantly, several members of the lysyl oxidase family are upregulated in MF providing a rationale to therapeutically inhibit all lysyl oxidases. PXS-5505 is a pan-lysyl oxidase inhibitor that prevents the cross-linking of collagen and elastin and consequently exhibits anti-fibrotic effects in murine models of MF. PXS5505-MF-101 is an ongoing, multi-center, open-label phase 1/2a study evaluating the safety and tolerability of PXS-5505 in patients with primary, post-polycythemia vera (PV) or post-essential thrombocythemia (ET) myelofibrosis (NCT04676529). Herein, we present the study design and preliminary data from the dose escalation phase of this study. Methods: The primary objective is to determine the safety and tolerability of PXS-5505In patients with MF. Secondary objectives include determination of appropriate dose, pharmacokinetics (PK) and pharmacodynamics (PD), changes in BMF using European Consensus, spleen volume and MF symptoms (MFSAF). Efficacy endpoints are exploratory. Eligible patients must have PMF or post-ET/PV MF of intermediate/high risk, relapsed/refractory, intolerant or not eligible to available JAK inhibitors (ruxolitinib, febratinib), including those with severe thrombocytopenia, and requiring therapy for symptomatic disease. Patients participating in the DEP required BM biopsy within 6 months of the re-initiation of treatment with PXS-5505. For patients entering the CEP a BM biopsy must have been performed within 3 months prior to Day 1 treatment. The study consists of two phases: Dose Escalation Phase (DEP) and Cohort Expansion Phase (CEP). The DEP followed a 3+3 design with a starting dose of 100 mg PXS-5505 twice daily (BID) for 4 weeks (Level 1), escalating to 150 mg BID (Level 2) and to 200 mg BID (Level 3). The DEP was to determine the maximum tolerated dose (MTD) or if all doses were well tolerated, the dose which provided the highest target engagement PK and PD measures during dose escalation (Day 0, week 1 and week 4) included, maximum plasma concentration (C1hr=Cmax), minimum plasma concentration (Cmin) and LOX and LOXL2 inhibition in plasma which would subsequently be the dose selected for the CEP. Intra patient dose escalation was allowed and patients participating in the DEP phase were able to continue on the CEP up to 6 months of therapy. During the CEP, 24 patients will be treated at the dose determined from the DEP phase. At data cutoff (21 July 2022) the DEP was completed and enrollment for the CEP continues. Results: Five patients were enrolled in the DEP. This included three patients with post ET MF, one patient with post PV MF and one patient with post ET MF. The median age was 71 years (range, 60-77) and all were female. There were no suspected unexpected serious adverse reactions (SUSAR) or dose limiting toxicities during the dose escalation phase. One patient terminated early following transformation to AML (24 days post treatment initiation). Interim PK data from the DEP phase demonstrated that PK properties in patients were similar to PK in healthy volunteers as previously reported at all dose levels (ACTRN12619000332123). At the 200mg BID level the mean (trough) LOX inhibition was 94% and 91% (days 7 and 28), respectively (Figure 1). Similarly, the mean (trough) LOXL2 inhibition was 94% and 93% (days 7 and 28), respectively. Enrolment in the CEP continues and preliminary data will be presented. Conclusion: These findings indicate that excellent targeted LOX and LOXL2 inhibition is being achieved at the 200mg BID level which has been selected as the recommended dose for the currently ongoing expansion phase with no dose limiting toxicity seen. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Safety and Effectiveness of Ruxolitinib in Real-World Patients with Myelofibrosis: A 2-Year Observational Study from Taiwan

Introduction Ruxolitinib (RUX) is an approved JAK1/JAK2 inhibitor for the treatment of intermediate or high-risk myelofibrosis, including primary myelofibrosis (PMF), post-polycythemia vera myelofibrosis (PPV-MF), and post-essential thrombocythemia myelofibrosis (PET-MF), but real-world safety and efficacy of RUX in Taiwan are not well understood. This study was conducted to evaluate the safety and efficacy of treatment with RUX with intermediate-2 or high risk PMF, PPV-MF or PET-MF in routine clinical practice. Method This 2-year, single-arm, multicenter, post-marketing surveillance registry collected data on the safety, tolerability, efficacy, and other clinical information of adult patients (pts) aged ≥20 years with a confirmed diagnosis of intermediate-2 or high-risk PMF, PPV-MF, or PET-MF who either received RUX or starting RUX in accordance with the general clinical practice in Taiwan. Primary endpoint included collection of adverse events (AEs), AE of special interest (AESIs; anemia, thrombocytopenia, leukocytosis, hepatitis B virus (HBV) infection or reactivation, tuberculosis (TB) infection, and other infections), and serious adverse events (SAEs) throughout the study. Key secondary endpoints included treatment duration, discontinuation rates, dosage of prescribed RUX, Myeloproliferative Neoplasm symptom assessment form (MPN-10) score after study entry and change in spleen size, specifically in naïve patients who were eligible for spleen response evaluation. Results A total of 99 (51% PMF, 22.4% PPV-MF, and 26.5% PET-MF) pts were recruited, of which 38 (38.4%) pts discontinued due to consent withdrawal (n=11), death (n=10), discontinued prescription of RUX for 3 months (n=4), AEs (n = 2), unsatisfactory therapeutic effect (n=2), administrative problems (n=1), disease progression (n=1), required immediate stem cell transplantation (n=1), and others (n=6). Median age was 68.1 (range: 38.3-87.2) years and gender ratio was balanced, with 97 Taiwanese pts (98.0%). Median disease duration was 13.9 months (range: 0-967.6 months) and 70.7% and 28.3% of pts were identified with the risk of intermediate-2 or high using IPSS/DIPSS risk assessment, respectively. Majority of the recruited pts were RUX pre-treated (n=75; 75.8%) and 24.2% (n=24) pts were RUX-naïve at baseline. During the study, 88 pts (89.8%) had 673 AEs, and 44 (44.9%) experienced 159 SAEs. Half of the pts (55.1%) had moderate or severe SAEs and 39 pts recovered. Over 80% of SAEs (n=131) were not related to RUX. Major AESIs were anemia (29.6%) and thrombocytopenia (20.4%). There were no HBV infection or reactivation reported; 2% of pts had TB while 3% of pts had herpes zoster infections. The major reported infection was pneumonia (20.4%). Key safety data are summarized in Table 1. Most pts had their AEs resolved (77.6%), while 10 deaths occurred due to AEs (10.2%). Majority of the pts (41.8%) received a daily dose of RUX 20 mg at the enrolment, with an average mean daily dose of 22.7±9.2 mg (Figure 1). For naïve pts, mean initial dose was 18.8 ± 8.50 mg and gradually titrated up to 22.3 ± 8.69 mg at 3 months and to 24.0 ± 9.17 mg at 6 months. Among 98 pts, 13.3% pts whose platelet counts between 100-200×103/μL and 21.4% pts whose platelet counts were >200×103/μL were treated with RUX 5-10 mg twice daily. Among 27 RUX pre-treated patients (mean RUX duration before study entry: 17.0 ± 20.98 months), spleen size by palpation was relatively stable throughout the study period. For the 7 RUX naïve pts, the mean spleen size change from baseline was -15.9 %± 28.72 at 12 weeks, -30.8% ± 31.28 at 24 weeks, -54.2% ± 41.93 at 48 weeks and -52.0% ± 36.41 at 96 weeks. However, it should be interpreted with caution due to the small pt pool. A total of 65 pts (65.7%) had >50% improvement in the symptom response by MPN-10 during 2-year study period. . Conclusion This is the first real-world study in Taiwan to evaluate safety and efficacy with RUX in patients with MF. It was observed that physicians employed a conservative strategy for a lower starting dose with gradual titration resulting in comparable safety profile, but lower incidences of thrombocytopenia compared to published clinical trials. The majority of pts reported continuous symptomatic improvement and a small number of RUX naïve pts had pronounced spleen size reduction. Further investigations are required to evaluate whether optimal dose of RUX or titration speed would improve spleen response. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Efficacy and Safety of Ropeginterferon Alfa-2b for Pre-Fibrotic Primary Myelofibrosis and DIPSS Low/Intermediate-1 Risk Myelofibrosis

Most patients with early/pre-fibrotic primary myelofibrosis (pre-PMF) and dynamic international prognostic scoring system (DIPSS) low or intermediate-1 risk myelofibrosis (MF) progress to overt PMF or higher risk MF. There is currently no consensus on the optimal treatment strategies in these patients. Ropeginterferon alfa 2b (P1101) is a next generation monopegylated interferon alfa-2b developed specifically to treat myeloproliferative neoplasms (MPN). The P1101MF study is a multicenter phase 2 study of P1101 for patients with pre-PMF and DIPSS low/intermediate-1 risk MF (NCT04988815). Key eligibility included the need for cytoreduction, morphologically confirmed pre-PMF, overt PMF, post-polycythemia vera MF (PPV-MF) or post-essential thrombocythemia MF (PET-MF), and DIPSS low/intermediate-1 risk category. The primary outcome was the clinicohematologic complete response (CHCR) rate at 24 and 48 weeks. Secondary outcomes included adverse events (AEs), changes in allele burden of driver genes and other non-driver mutations, changes in quality-of-life (QOL), changes in cytokine profiles and changes in bone marrow morphology. Patients received P1101 at a starting dose of 250mcg followed by 350mcg at week 2 and 500mcg every 2 weeks from week 4 onwards. At the data cut-off of 28 July 2022, 56 patients (33 men, 23 women) with a median age of 58 (range: 30-87) were enrolled. Thirty eight patients (68%) had pre-PMF, 5 (9%) had overt PMF, 3 (5%) had PPV-MF and 10 (18%) had PET-MF. Next-generation sequencing (NGS) in 53 patients showed JAK2V617F in 39 patients (74%), CALR mutations in 13 patients (25%) and MPL mutation in 1 patient (2%). On day 1, the mean white blood cell (WBC) count, hemoglobin concentration, platelet count, and lactate dehydrogenase (LDH) level were 9.4 x 109/L (range: 3.3-33.95), 12.5 g/dL (range: 7.1-15.9), 520 x 109/L (range: 113-1038) and 359 IU/L (range: 136-1146) respectively. The median duration of follow-up was 24 (2-28) weeks. Forty-six and 30 patients completed 12 and 24 weeks of treatment respectively. At 12 and 24 weeks the CHCR rate was 74% and 67%, respectively. At 24 weeks, 36 (92%) of 39 JAK2V617F mutated patients had stable or improved JAK2V617F allele burden by droplet digital polymerase reaction (ddPCR). Three patients (8%) had >50% reduction in the JAK2V617F allele burden with one patient achieving undetectable JAK2V617F from week 16 onwards. Disease progression or blastic transformation were not observed during the study. The most common AEs were malaise (N=22, 39%; Grade 1-2, N=21; Grade 3-4, N=1), anemia (N=12, 21%; Grade 1-2, N=8; Grade 3-4, N=4), muscle pain (N=11, 20%; Grade 1-2, N=11; Grade 3-4, N=0) and hair loss (N=10, 18%; Grade 1-2, N=10; Grade 3-4; N=0) . There were no treatment discontinuations, safety signals or deaths related to treatment. In summary, P1101 was well-tolerated, effective in cytoreduction and induced molecular responses. The recruitment of patients is ongoing.

Modulation of TGF-β Superfamily Signaling to Treat Myelofibrosis and Mitigate JAK Inhibitor Toxicity: A Report on the Phase 2 Study of Ker-050 in Participants with Myelofibrosis

Background: Myelofibrosis (MF) is a disorder characterized by unrestrained proliferation of myeloid precursors and dysfunctional Janus kinase (JAK) signaling. Hyperplastic and dysplastic megakaryocyte expansion in MF releases inflammatory cytokines. These cytokines promote fibroblast proliferation, bone remodeling, and marrow fibrosis, disrupting the osteohematopoietic niche and leading to ineffective and extramedullary hematopoiesis (Vainchenker et al. 2017). Clinical manifestations include splenomegaly, anemia, and often disabling constitutional symptoms. JAK inhibitors, such as ruxolitinib, have been shown to improve spleen size and symptoms, but are associated with dose-limiting anemia and thrombocytopenia, reducing their utility for many patients (Verstovsek et al. 2012). KER-050 is an investigational product designed to alter signaling of TGF-β superfamily ligands, restoring balance to the osteohematopoietic niche and promoting differentiation of erythroid and megakaryocytic precursors. It is a modified activin receptor type IIA ligand trap that inhibits TGF-β superfamily ligands, including activins A and B and growth and differentiation factors (GDFs) 8 and 11. Preclinical studies have demonstrated that KER-050 induces erythropoiesis, increases platelet counts, improves bone mass, and prevents fibrosis. A preclinical study previously presented demonstrated that RKER-050 can reverse ruxolitinib-associated reductions in hemoglobin, hematocrit, and red blood cell count, indicating potential for KER-050 to mitigate ruxolitinib toxicity. In two clinical studies, including an ongoing study in participants with myelodysplastic syndromes (MDS), KER-050 has been well-tolerated. Accumulated clinical data demonstrate that KER-050 can stimulate erythropoiesis and thrombopoiesis in both healthy post-menopausal women and MDS participants with ineffective hematopoiesis. Here we present data from the first clinical study of KER-050 in participants with MF (NCT05037760). The objective of this study is to evaluate the potential of KER-050 as monotherapy and in combination with ruxolitinib to treat the underlying pathology of MF and mitigate JAK inhibitor-associated cytopenias. Methods: This ongoing Phase 2 open-label study is evaluating the safety, tolerability, pharmacokinetics PK), pharmacodynamics (PD), and efficacy of KER-050 administered with or without ruxolitinib in participants with primary myelofibrosis (PMF), post-essential thrombocythemia myelofibrosis (post-ET MF), and post-polycythemia vera myelofibrosis (post-PV MF) who have anemia (hemoglobin ≤ 10 g/dL or receiving transfusions). Part 1 involves parallel dose escalation arms (1A: monotherapy, 1B: combination with ruxolitinib) to evaluate the safety and tolerability of KER-050 and identify the dose(s) of KER-050 to be evaluated in Part 2 (Figure 1). Changes in hemoglobin, transfusion burden, spleen size, the Myelofibrosis Symptom Assessment Form Total Symptom Score (MF-SAF-TSS), PK and incidence of accelerated MF and acute myeloid leukemia are assessed as secondary endpoints. This study is also evaluating markers of multilineage hematopoiesis, bone remodeling, iron metabolism, inflammation, and marrow fibrosis. Frequency of ruxolitinib dose modification and quality of life will be explored. Results: Preliminary results from Part 1 will be presented. At the time of this writing, 5 patients have received KER-050 on study, 3 in Arm 1A and 2 in Arm 1B. Three participants have completed the dose-limiting toxicity (DLT) assessment period and no DLTs have been experienced. Data evaluated to date indicate a PD effect consistent with previous preclinical and clinical studies of KER-050. Summary: KER-050 is designed to alter TGF-β superfamily signaling, restoring balance to the osteohematopoietic niche and promoting multilineage hematopoietic differentiation. Here we present data from the first study of KER-050 in participants with MF evaluating the potential for KER-050 to impact key aspects of the MF disease state (anemia, spleen size, symptoms, progression), as monotherapy and in combination with ruxolitinib. The potential for KER-050 to mitigate ruxolitinib toxicity and related dose-reductions is being investigated. Exploratory analyses of the KER-050 impact on inflammation, bone remodeling, iron metabolism, and marrow fibrosis, as available, will be shared. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal