Reduction In Allele Burden Research Articles

Clinical impact of mutated JAK2 allele burden reduction in polycythemia vera and essential thrombocythemia.

The variant allele frequency (VAF) of driver mutations (JAK2, CALR) in myeloproliferative neoplasms is associated with features of advanced disease and complications. Ruxolitinib and interferon were reported to variably reduce the mutant VAF, but the long-term impact of molecular responses (MR) remains debated. We prospectively measured changes in JAK2 and CALR VAF in 77 patients with polycythemia vera and essential thrombocythemia, treated with ruxolitinib for a median of 8 years, and assessed correlation with complete clinical and hematological response (CCHR) and outcomes. At last observation time, JAK2 VAF reduced overall from a median of 68% (range, 20%-99%) to 3.5% (0%-98%). A profound and durable MR (DMR; defined as a VAF stably ≤2%), including complete MR in 8%, was achieved in 20% of the patients, a partial MR (PMR; VAF reduction >50% of the baseline level) in 25%, and 56% had no molecular response (NMR). A CCHR was reached by 69% overall, independently of any degree of MR achieved; conversely, a DMR correlated with longer duration of CCHR and, most importantly, with reduced rate of progression to myelofibrosis and with longer myelofibrosis-free, event-free and progression-free survival. Achievement of PMR also had some favorable impact on outcomes, compared to NMR. A baseline JAK2 VAF <50%, and a VAF reduction of ≥35% after 2 years of treatment, predicted for the achievement of DMR and reduced progression to myelofibrosis. Overall, these findings support the clinical value of achieving profound, durable MR and its consideration as surrogate endpoint in future clinical trials.

Effective Management of Polycythemia Vera With Ropeginterferon Alfa-2b Treatment.

Polycythemia vera (PV) is a myeloproliferative neoplasm. Ropeginterferon alfa-2b is a new-generation polyethylene glycol-conjugated proline-interferon. It is approved for the treatment of PV at a starting dose of 100 µg (50 µg for patients receiving hydroxyurea (HU)) and dose titrations up to 500 µg by 50 µg increments. The study was aimed at assessing its efficacy and safety at a higher starting dose and simpler intra-patient dose escalation. Forty-nine patients with PV having HU intolerance from major hospitals in China were treated biweekly with an initial dose of 250 µg, followed by 350 µg and 500 µg thereafter if tolerated. Complete hematological response (CHR) was assessed every 12 weeks based on the European LeukemiaNet criteria. The primary endpoint was the CHR rate at week 24. The secondary endpoints included CHR rates at weeks 12, 36 and 52, changes of JAK2V617F allelic burden, time to first CHR, and safety assessments. The CHR rates were 61.2%, 69.4% and 71.4% at weeks 24, 36, and 52, respectively. Mean allele burden of the driver mutation JAK2V617F declined from 58.5% at baseline to 30.1% at 52 weeks. Both CHR and JAK2V617F allele burden reduction showed consistent increases over the 52 weeks of the treatment. Twenty-nine patients (63.0%) achieved partial molecular response (PMR) and two achieved complete molecular response (CMR). The time to CHR was rapid and median time was 5.6 months according to central lab results. The CHRs were durable and median CHR duration time was not reached at week 52. Mean spleen index reduced from 55.6 cm2 at baseline to 50.2 cm2 at week 52. Adverse events (AEs) were mostly mild or moderate. Most common AEs were reversible alanine aminotransferase and aspartate aminotransferase increases, which were not associated with significant elevations in bilirubin levels or jaundice. There were no grade 4 or 5 AEs. Grade 3 AEs were reversible and manageable. Only one AE led to discontinuation. No incidence of thromboembolic events was observed. The 250-350-500 µg dosing regimen was well tolerated and effectively induced CHR and MR and managed spleen size increase. Our findings demonstrate that ropeginterferon alfa-2b at this dosing regimen can provide an effective management of PV and support using this dosing regimen as a treatment option.

Exploratory Study on Impact of Comorbid Sleep Apnea Treatment in Patients with Polycythemia Vera and Essential Thrombocythemia

Background: Systemic inflammation has been implicated in the progression of myeloproliferative neoplasms (MPNs), polycythemia vera (PV) and essential thrombocythemia (ET). Obstructive sleep apnea (OSA) is a highly prevalent disorder that can lead to TNF-driven systemic inflammation. OSA leads to oxidative stress and NF-kB driven inflammatory gene expression through the mechanistic pathways of intermittent hypoxia and autonomic activation. We therefore sought to understand the prevalence of OSA in patients with MPNs and the feasibility of understanding the impact of treating comorbid sleep apnea in patients with PV and ET. Methods: Patients with PV and ET diagnosed using the 2008 or 2016 WHO criteria underwent STOP-BANG questionnaires to evaluate for the likelihood of OSA. Based on the finding of 3 or more positive responses on STOP-BANG questionnaire (PLoS One 2015;10:e0143697), patients underwent further evaluation with polysomnography or home sleep apnea test to diagnose OSA at an American Academy of Sleep Medicine-certified sleep laboratory (Figure 1). Patients with apnea-hypopnea index (AHI) of 5 or more events per hour and Eastern Cooperative Oncology Group scale score of 0-2 underwent continuous positive airway pressure therapy (CPAP). Effects of CPAP therapy on MPN-symptom assessment form total symptom scores (MPN-SAF TSS), JAK2V617F, MPL and CALR allelic burden, and exploratory endpoints of changes in inflammatory and thrombotic markers were ascertained (Figure 1). Comparisons with observational cohorts were planned to ascertain changes in the above endpoints at 0-, 3- and 6-months intervals (Figure 1). Based on a 40% reduction in allele burden (SD of 25%) and correlation of 0.5 between paired measurements, it was estimated that using a paired t-test with 27 evaluable patients will provide a 95% power to detect a 20% change in JAK2V617F burden from 40% to 20%. Similarly, assuming a 50% correlation (SD of 16) between pre- and post-therapy MPN-SAF TSS scores, 27 evaluable patients will provide a 80% power to detect a change of 10 at the two-sided 0.025 significance level. Results: Screening for OSA in patients with ET and PV revealed a high prevalence of OSA risk based on STOP-BANG scores. 26/29 males (mean age 63.6±11.8 years; BMI 29±3.3) and 16/26 females (mean age 61.5±12.8 years; BMI 28.2±6.5) had STOP-BANG scores of 3 or more. 8 patients with PV and ET have so far been enrolled into this study. 6/8 patients (age ranges from 41-74 years; 4 females and 2 males) with OSA (AHI 5-56 events/hr; 4% oxygen desaturation index 4.7-30/hr) underwent CPAP therapy. 1/6 patients in the CPAP arm did not tolerate CPAP and was excluded. 5/6 patients completed study procedures as did 2 additional patients without OSA in the observational study arm. Of 5/6 patients undertaking CPAP, 3/5 had the JAK2V617F mutations whereas 2/5 had the CALR mutation. JAK2V617F allele burdens at baseline in 2/5 patients were 80.7% and 4% at baseline and reduced to 73% and 1% at 6 months respectively whereas the third patient had undetectable JAK2V617F burdens throughout the study. All except one patient experienced improvement in MPN-SAF TSS scores after 6 months of CPAP therapy. While all 5 patients treated with CPAP showed improvements in C-reactive protein levels, analysis of NFkB1, TNF and IL-6 transcript levels showed mixed results. Similar mixed results were found with hypoxia-inducible factor (HIF) target gene expression ( SLC2A1, VEGF-A, EDN1) and markers of iron turnover (% transferrin saturation, transferrin, iron and ferritin levels) despite reduction in erythropoietin values in 4/5 patients with CPAP therapy at 6 months. Conclusions: Given the significant likelihood of OSA in patients with PV and ET (as based on STOP-BANG scores of 3 or more), there is need to evaluate and treat for OSA. Preliminary results show abnormalities in inflammatory markers with reductions in C-reactive protein and erythropoietin levels following CPAP therapy even though mixed results were noted in inflammatory and HIF-target gene transcripts, and markers of iron turnover. Larger studies and longer follow-up are required to understand the impact of OSA on not only the thrombotic and inflammatory milieu in patients with MPNs, but also the benefit of treating on prevention of disease progression and thrombotic manifestations common in MPNs. Funding: Huntsman Interventional Trial Grant CTO #HCI-17-HEM 28.

Ruxolitinib Treatment in Polycythemia Vera Results in Reduction in JAK2 Allele Burden in Addition to Improvement in Hematocrit Control and Symptom Burden

Introduction:In the pivotal RESPONSE and RESPONSE 2 trials, the Janus kinase (JAK)1/JAK2 inhibitor ruxolitinib was superior to best available therapy (BAT) at providing hematocrit control and complete hematologic response, as well as in improving disease-related symptoms, in patients with polycythemia vera (PV). Here we report the results of a post hoc pooled efficacy analysis using data from the RESPONSE studies. Methods:RESPONSE and RESPONSE 2 were randomized, open-label, multicenter phase 3 trials that assessed efficacy and safety of ruxolitinib in adults with PV who had resistance or intolerance to hydroxyurea. Splenomegaly was required for enrollment into RESPONSE but not for RESPONSE 2; patients in both studies were randomized 1:1 to ruxolitinib (starting dose, 10 mg twice daily) or BAT (most commonly hydroxyurea [59%, 49%] or interferon formulations [12%, 13%] in RESPONSE and RESPONSE 2, respectively). Patients in either trial who were randomized to BAT could cross over to ruxolitinib at the time of primary analysis (Week 32 in RESPONSE; Week 28 in RESPONSE 2) or later for efficacy or safety reasons. In this pooled analysis, hematocrit control was assessed in the pooled population at Weeks 28 and 80 and was defined as hematocrit &amp;lt;45% that was maintained since Week 16 with ≤1 phlebotomy occurring postrandomization and before Week 4. Symptom control (using the Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score [MPN-SAF TSS]) and changes over time in JAK2V617F allele burden were also assessed. Response rate 95% CIs were calculated using the Clopper-Pearson exact method, and the odds ratio (OR) and 95% CI for comparisons of the proportion of patients achieving ≥50% reduction from baseline in MPN-SAF TSS were calculated by the Mantel-Haenszel method. Results:Overall, 371 patients were randomized in RESPONSE and RESPONSE 2 (ruxolitinib, n=184; BAT, n=187). Patient baseline characteristics were similar across trials and treatment groups and have been previously published. Mean (SD) age in the overall pooled analysis population was 61.8 (11.0) years; most patients were male (62.5%) and White (88.1%). At Week 28, 62.0% (95% CI, 54.5%-69.0%) of ruxolitinib patients achieved hematocrit control compared with 18.2% (12.9%-24.5%) of BAT patients (Figure 1). Durable hematocrit control was maintained to Week 80 by 47.3% (95% CI, 39.9%-54.8%) of patients randomized to ruxolitinib (nearly all patients in the BAT arm crossed over to ruxolitinib). The percentage of patients achieving ≥50% reduction from baseline in MPN-SAF TSS at Week 16 (the only common timepoint in both studies) was higher for ruxolitinib vs BAT (48.7% [95% CI, 40.7%-56.8%] vs 18.0% [95% CI, 12.5%-24.6%]; OR, 4.3 [95% CI, 2.6-7.2]). Mean (SD) change from baseline to Week 16 in MPN-SAF TSS was −4.4 (10.0) for ruxolitinib patients and 0.6 (6.9) for BAT patients. JAK2V617F allele burden decreased consistently from baseline to Week 208 in patients randomized to ruxolitinib. Mean JAK2V617F allele burden decreased from 66.1% to 41.4% at 4 years. Best change from baseline in JAK2V617F allele burden is shown in Figure 2, with a decrease of ≥25% in 57.1% of patients randomized to ruxolitinib and ≥50% decrease in 38.9%. Similar reductions in JAK2V617F allele burden were observed following crossover from BAT to ruxolitinib (Figure 2), with a best decrease of ≥25% and ≥50% in 48.7% and 35.3% of patients, respectively. Analysis of the BAT group is limited by small patient numbers after Week 32, as most patients crossed over to ruxolitinib, with a best decrease of ≥25% and ≥50% in 7.2% and 2.6% of patients respectively. Conclusions:In this pooled analysis of RESPONSE and RESPONSE 2, patients with PV treated with ruxolitinib achieved durable hematocrit control through Week 80 and had better symptom control at Week 16 than those who received BAT. Reductions in JAK2V617F allele burden were consistently observed through Week 208 in patients treated with ruxolitinib, including those who crossed over from BAT. Taken together, these results provide further evidence of the patient benefit of ruxolitinib in patients with PV with or without splenomegaly.

Tamoxifen for the treatment of myeloproliferative neoplasms: A Phase II clinical trial and exploratory analysis

Current therapies for myeloproliferative neoplasms (MPNs) improve symptoms but have limited effect on tumor size. In preclinical studies, tamoxifen restored normal apoptosis in mutated hematopoietic stem/progenitor cells (HSPCs). TAMARIN Phase-II, multicenter, single-arm clinical trial assessed tamoxifen’s safety and activity in patients with stable MPNs, no prior thrombotic events and mutated JAK2V617F, CALRins5 or CALRdel52 peripheral blood allele burden ≥20% (EudraCT 2015-005497-38). 38 patients were recruited over 112w and 32 completed 24w-treatment. The study’s A’herns success criteria were met as the primary outcome ( ≥ 50% reduction in mutant allele burden at 24w) was observed in 3/38 patients. Secondary outcomes included ≥25% reduction at 24w (5/38), ≥50% reduction at 12w (0/38), thrombotic events (2/38), toxicities, hematological response, proportion of patients in each IWG-MRT response category and ELN response criteria. As exploratory outcomes, baseline analysis of HSPC transcriptome segregates responders and non-responders, suggesting a predictive signature. In responder HSPCs, longitudinal analysis shows high baseline expression of JAK-STAT signaling and oxidative phosphorylation genes, which are downregulated by tamoxifen. We further demonstrate in preclinical studies that in JAK2V617F+ cells, 4-hydroxytamoxifen inhibits mitochondrial complex-I, activates integrated stress response and decreases pathogenic JAK2-signaling. These results warrant further investigation of tamoxifen in MPN, with careful consideration of thrombotic risk.

A Single-Arm, Open-Label, Multicenter Study to Assess Molecular Response of P1101 Therapy in Patients with Polycythemia Vera and Elevated Hematocrit: Results from 12-Month Core Study

Background: The treatment goals of Polycythemia Vera (PV) have been focused on reducing the thrombotic and hemorrhagic risks and preventing disease transformation. A short-term way to confirm the effect of treatment is to check peripheral blood count remission. Recently, published researches have demonstrated that JAK2 driver mutation is associated with not only disease progression but hematologic response. Although it is still controversial whether a decrease in JAK2 mutation should be one of the treatment goals or not, the molecular response (MR) is frequently assessed in clinical trials. Moreover, the interest in treatment is moving toward disease modification. Ropeginterferon alfa-2b(P1101) showed it was more effective in achieving durable hematological and molecular remissions than hydroxyurea and well tolerated during long-term application. However, there are limited data on the clinical relevance of MR during P1101 and the efficacy and safety of P1101 in Eastern Asians. Aims: The aim of this study is to evaluate clinical and molecular response, and the association between efficacy and MR. In addition, the safety and tolerability of P1101 were also collected. Methods: This single-arm, open-label study has been performed in 16 hospitals in Korea. Patients were eligible if 19 years or older with PV diagnosed by WHO's 2016 criteria, requiring cytoreductive therapy and elevated hematocrit (Hct) (&amp;gt;45%). Patients were treated with P1101, S.C. q2w, at a starting dose of 250 µg, followed by 350 µg(week 2), 500 µg(week 4), and thereafter until week 48 (core study period). The JAK2 Val617Phe allele burden was assessed every 3 months. The chi-square test was used to determine any association between complete hematologic response (CHR) and MR using the Phi coefficient as a measure of strength association. Results: With a data cut-off date of 10 Jul 2023, a total of 99 patients were enrolled and 77 patients are under treatment including extension period in the study. Twenty patients dropped out including 2 patients due to adverse events and 2 patients completed core study. Total 95 patients were included in this analysis as FA (full analysis) set: 52 (54.7%) patients was HU-naïve and 43 (45.3%) patients was HU-resistant/intolerant(R/I). The median age was 58 years (range, 26-81) and 53.7% were male. The percentagesof patients with low and high risk were 56.8% and 43.2%, repectively. Until now, 94, 87, 79, and 60 patients were evaluable at 3, 6, 9, and 12 months, respectively. CHR was achieved in 25 (27%) of 94, 40 (46%) of 87 patients, 45 (57%) of 79 patients, and 38 (63%) of 60 patients at 3, 6, 9, and 12 months, respectively. Twenty-eight (32%) of 88, 29 (36%) of 80 patients, 32 (52%) of 62 patients, and 23 (61%) of 38 patients achieved the MR at 3, 6, 9, and 12 months, respectively. The Phi Coefficient for determining of association between CHR and MR was 0.56 (P&amp;lt;0.0001), 0.48 (P&amp;lt;0.0001), 0.4735 (P=0.0002), and 0.4938 (P=0.0041) at each time point (Table 1). Regarding the calculated absolute change from baseline of JAK2 allele burden at each time point, a faster and deeper decreasing pattern was shown in CHR responders compared to non-responders (Table 2). Regarding the Hct, platelets, and WBC, the mean value of all parameters significantly decreased to the normal range after 6 months and were consistent in normal until 12 months. Moreover, there is also no significance difference between HU naïve vs R/I and low vs High risk. In terms of safety, a total of 160 treatment-emergent adverse events (TEAEs) and 84 treatment-related adverse events (TRAE) were reported. The most common TEAEs (%, n/95) were alopecia (18%, 17/95) and adverse events related to liver function (16%, 15/95), respectively. Onset time of TRAEs distributed 8, 22, 27, 18, and 8 during week 0-4, 4-12, 12-24, 24-36, and 36-48, respectively. There were no unexpected TEAEs. Two serious adverse drug reactions (1 hepatotoxicity and 1 bipolar disorder) were reported. Conclusion: The updated data showed consistent results with the previous 2022 ASH meeting abstract that ropeginterferon alfa-2b therapy, with rapid dose optimization, induced hematological response, reduced JAK2 allele burden, and was well tolerated in Korean patients. Moreover, we clarified the association between efficacy and MR as assessed by reduction in JAK2 allele burden. More data will be updated during the meeting.

A Single-Arm, Open-Label, Multicenter Study to Assess Molecular Response of P1101 Therapy in Patients with Polycythemia Vera and Elevated Hematocrit

Background: Polycythemia Vera (PV) is the commonest myeloproliferative neoplasm, characterized by clonal stem cell proliferation of the erythroid, myeloid, and megakaryocytic lines, and risk for thrombotic events and transformation into post-PV myelofibrosis and acute myeloid leukemia. The excessive myeloproliferation in PV is driven by JAK2 somatic driver mutations. Although hydroxyurea (HU) remains the myelosuppressive agent of first choice, HU treatment can be associated with cytopenias and often unsatisfactory hematological control over time, aphthous and leg ulcers, and concern for the second primary malignancy. Recently, ropeginterferon alfa-2b, a monopegylated IFNa, which had an extended elimination half-life, enabling less frequent dosing and improved tolerability, developed and evaluated the efficacy and safety in comparison to hydroxyurea treatment. An open-label, randomised phase III study (PROUD-PV and CONTINUATION-PV) showed is more effective in achieving durable hematological and molecular remissions than hydroxyurea and is well tolerated during long-term application. However, there are limited data on the clinical relevance of molecular response during ropeginterferon alfa-2b and the efficacy and safety of ropeginterferon alfa-2b in Eastern Asian patients. Aims: The aim of this study is to evaluate clinical and molecular responses, and the association between efficacy and molecular response as assessed by reduction in JAK2 Val617Phe allele burden. In addition, the safety and tolerability of ropeginterferon alfa-2b were also collected. Methods: This single-arm, open-label, multicenter study has been performed in 13 hospitals in Korea. Patients were eligible if 19 years or older with PV diagnosed by WHO's 2016 criteria, requiring cytoreductive therapy and elevated hematocrit (hematocrit >45%). Patients were treated with ropeginterferon alfa-2b, subcutaneously every 2 weeks, at a starting dose of 250 µg, followed by 350 µg at week 2, 500 µg at week 4, and thereafter until week 48. The quantitative JAK2 Val617Phe allele burden was assessed every 3 months Results: With a data cut-off date of 19 Jul 2022, a total of 74 patients were enrolled including 42 (56.8%) patients in HU naïve and 32 (43.2%) patients in HU-resistance/intolerance. The median age was 58 years (range, 26-81) and 58.1% were male. The percentages of patients with low and high risk were 55.4% and 44.6%, respectively. Among the 74 patients, 70 patients continue in the study, and 4 dropped out. Until now, 45, 20, and 6 patients were evaluable at 3, 6, and 9 months, respectively. During the dose escalation period, 4.44% of evaluable patients needed the dose reduction. At baseline, mean hematocrit (%) was 50.53 ± 3.99, which significantly decreased to 47.00 ± 5.58, 42.60 ± 5.92, and 41.68 ± 4.60 at 3, 6, and 9 months, respectively. WBC and PLT also decreased steadily over time; at baseline, mean WBC (x 109/L) was 14.16 ± 6.01, which significantly decreased to 7.17 ± 3.40, 6.16 ± 3.50, and 4.45 ± 1.57 at 3, 6, and 9 months, respectively, and at baseline, mean PLT (x 109/L) was 560.03 ± 299.21, which significantly decreased to 336.53 ± 234.11, 274 ± 167.59, and 249.50 ± 256.18 at 3, 6, and 9 months, respectively. The JAK2 Val617Phe allele burden changes, which were analyzed with available samples so far, showed a trend for rapid decreasing pattern; at baseline, mean JAK2 Val617Phe allele burden (%) was 59.70 ± 27.91(n=39), which significantly decreased to 42.41 ± 23.83 (n=16) and 37.14 ± 13.41 (n=5) at 3 and 6 months, respectively. Updated data with molecular response per individual patient will be presented in the meeting. In addition, although grade 1/2 adverse events (n=20) and grade 3 adverse events (n=4) were reported, there were no drug-related serious adverse events. Conclusion: Our data demonstrated that ropeginterferon alfa-2b therapy with rapid dose optimization induced hematological response and reduction of JAK2 Val617Phe allele burden, and was well tolerated in Korean patients with polycythemia vera and elevated hematocrit. Updated data with longer follow-up will be presented in the meeting.

A Phase Ib Dose-finding Study of Panobinostat and Ruxolitinib in Myelofibrosis.

A Phase Ib Dose-finding Study of Panobinostat and Ruxolitinib in Myelofibrosis.

The MDM2 antagonist idasanutlin in patients with polycythemia vera: results from a single-arm phase 2 study

Idasanutlin, an MDM2 antagonist, showed clinical activity and a rapid reduction in JAK2 V617F allele burden in patients with polycythemia vera (PV) in a phase 1 study. This open-label phase 2 study evaluated idasanutlin in patients with hydroxyurea (HU)-resistant/-intolerant PV, per the European LeukemiaNet criteria, and phlebotomy dependence; prior ruxolitinib exposure was permitted. Idasanutlin was administered once daily on days 1 through 5 of each 28-day cycle. The primary end point was composite response (hematocrit control and spleen volume reduction > 35%) in patients with splenomegaly and hematocrit control in patients without splenomegaly at week 32. Key secondary end points included safety, complete hematologic response (CHR), patient-reported outcomes, and molecular responses. All patients (n = 27) received idasanutlin; 16 had response assessment (week 32). Among responders with baseline splenomegaly (n = 13), 9 (69%) attained any spleen volume reduction, and 1 achieved composite response. Nine patients (56%) achieved hematocrit control, and 8 patients (50%) achieved CHR. Overall, 43% of evaluable patients (6/14) showed a ≥50% reduction in the Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score (week 32). Nausea (93%), diarrhea (78%), and vomiting (41%) were the most common adverse events, with grade ≥ 3 nausea or vomiting experienced by 3 patients (11%) and 1 patient (4%), respectively. Reduced JAK2 V617F allele burden occurred early (after 3 cycles), with a median reduction of 76%, and was associated with achieving CHR and hematocrit control. Overall, the idasanutlin dosing regimen showed clinical activity and rapidly reduced JAK2 allele burden in patients with HU-resistant/- intolerant PV but was associated with low-grade gastrointestinal toxicity, leading to poor long-term tolerability. This trial was registered at www.clinincaltrials.gov as #NCT03287245.

MPN-180: A Novel Mechanism of Action of Midostaurin in Systemic Mastocytosis: Beyond KIT Inhibition

Context: Constitutively active KIT tyrosine kinase harboring the D816V mutation is the major driver of systemic mastocytosis (SM) pathogenesis. We have previously reported that the loss of function of SETD2 histone methyltransferase due to reduced protein stability is a common cooperating event in advanced SM (advSM). Objective: To dissect the mechanisms of action of midostaurin in advSM and to explore the potential of SETD2 as a marker of response to therapy. Materials: The mast cell (MC) leukemia cell line HMC-1 (negative for SETD2) and primary neoplastic MCs from 10 advSM patients, collected at regular time points during midostaurin treatment. Results: This study started from our preliminary observations indicating that aurora kinase A (AKA) is overexpressed and hyperactivated in advSM and is implicated in SETD2 proteasomal degradation. The new gold standard of therapy in advSM is midostaurin, which targets KIT andseveral other kinases, including AKA. We, thus, investigated whether midostaurin treatment may result in efficient AKA inhibition and subsequent SETD2 rescue. To this purpose, the HMC-1 cell line was treated with 5 µM midostaurin for 24 h, and phospho-AKA (T288), SETD2, and H3K36me3 (surrogate marker of SETD2 activity) were evaluated by WB. Midostaurin reduced AKA phosphorylation by 60%, partially restoring SETD2 expression and activity. We next wondered whether the same happens in patients treated with midostaurin. We, thus, collected and performed WB analysis on neoplastic mast cells from advSM patients before and during midostaurin treatment. We found that midostaurin may target AKA and rescue SETD2 expression and function in vivo and that SETD2/H3K36me3 rescue correlates with the clinical response to midostaurin and the reduction of KIT D816V allele burden, as assessed by digital PCR at 3, 6, and 12 months. In 8 patients who responded to midostaurin, SETD2/H3K36me3 rescue was detected by WB as early as 3 months after treatment onset, whereas 2 refractory patients did not show any increase in SETD2/H3K36me3 and maintained an unaltered KIT allele burden. Conclusions: Midostaurin treatment induces AKA partial dephosphorylation and consequent rescue of SETD2 expression and function in vitro and in vivo SETD2/H3K36me3 may serve as a biomarker of response to midostaurin. Supported by AIRC project 23001

Outcome of Myelodysplastic Syndrome Patients with TP53 Mutation Treated with Hypomethylating Agents

▪IntroductionMyelodysplastic syndrome (MDS) patients (pts) with TP53 gene mutation (MT) have poor outcome. Recent studies suggested higher response rates to hypomethylating agents (HMA) among TP53 MT MDS pts. Those studies were limited by small number of TP53 MT. We compared the outcomes in a large cohort of TP53 MT MDS patients to those with wild type TP53 (WT) treated with HMA.MethodsWe identified MDS patients who underwent next generation sequencing (NGS) for TP53 MT who received hypomethylating agents in our MDS database. NGS included a panel of up to 54 genes with VAF threshold of 5% and minimum depth of coverage was 500X. We compared baseline characteristics between pts with TP53 MT and WT; chi square was used for categorical variables and t-test for continuous variables. Patients with low or intermediate-1 risk International prognostic scoring system (IPSS) were categorized as lower risk MDS (LR-MDS) and those with intermediate-2 or high risk IPSS as higher risk MDS (HR-MDS). The best response rate to HMA treatment was reported utilizing international working group criteria (IWG 2006); overall response was reported as HI+ which included complete response (CR), marrow CR, partial response and hematological improvement. Kaplan Meier estimates were used for overall survival (OS) where median OS was calculated from time of diagnosis, log rank test was used for comparison and cox regression analysis for multivariable analysis.ResultsWe identified 508 pts who underwent testing for TP53 MT and were treated with azacitidine or decitabine, 102 pts had TP53 MT. Table-1 summarizes baseline characteristics between the two groups. Among TP53 MT pts, 97 (95%) received azacitidine and 5 (5%) pts had decitabine as the first line HMA compared to 374(92%) treated with azacitidine and 32 (8%) with decitabine in TP53 WT pts as the first HMA (p= .3).Best response to HMA (HI+) was 41% (CR 18%) and 32% (CR 9%) among pts with TP53 MT and WT, respectively (p =.06). Among pts with LR-MDS the best response rates were 32% vs 25% (p=0.4) and in pts with HR-MDS the best response rates were 44% and 41% respectively in TP53 MT and WT (p=0.7). Median OS was 14 mo for TP53 MT MDS pts compared to 41 mo for TP53 WT pts (p<.005). The median OS was 45 and 65 mo. respectively in LR-MDS TP 53 MT and WT pts (p= 0.3). Among HR-MDS pts the median OS was 12 and 21 mo, respectively (p< .005).The median OS was 15 mo and 41 mo among pts with TP53 MT and WT who achieved CR, respectively (p <.005).For pts who underwent allogeneic hematopoietic stem cell transplant (AHSCT) the median OS was 16 mo for TP53 MT and 74 mo for TP53 WT (p=.008).After adjusting for age, R-IPSS, complex karyotype TP53 MT was independently associated with worse overall survival in HMA treated patients, HR 1.4 (p = .048).ConclusionsWe observed a trend for higher response rates among MDS pts with TP53 MT treated with HMA compared to TP53 WT. The median OS was inferior among TP53 MT MDS patients. The benefit of AHSCT among TP53 MT pts is not clear. The value of TP53 allele burden reduction and clearance with treatment and prior to AHSCT should be further investigated. [Display omitted] DisclosuresKomrokji:Novartis: Honoraria, Speakers Bureau; Celgene: Honoraria. Sallman:Celgene: Research Funding. Padron:Incyte: Honoraria, Research Funding. Sweet:Ariad: Consultancy, Speakers Bureau; Otsuka: Consultancy; Novartis Pharmaceuticals: Consultancy, Speakers Bureau; Karyopharm: Consultancy, Research Funding; Pfizer: Consultancy; Incyte: Research Funding. Lancet:Boehringer Ingelheim: Consultancy; Jazz Pharmaceuticals: Consultancy; Janssen: Consultancy; Erytech: Consultancy; Celgene: Consultancy; BioSight: Consultancy; Pfizer: Other: Institutional research funding, Research Funding; Bio-Path Holdings: Consultancy; Novartis: Consultancy.

Current Management of Chronic Neutrophilic Leukemia.

Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative neoplasm (MPN) characterized by oncogenic driver mutations in colony-stimulating factor 3 receptor (CSF3R). Due in large part to the rarity of the disease and dearth of clinical trials, there is currently no standard of care for CNL. Available therapies range from conventional oral chemotherapy to targeted JAK inhibitors to hematopoietic stem cell transplant (HSCT), the latter representing the only potentially curative modality. For this reason, coupled with CNL's typically aggressive clinical course, allogeneic HSCT remains the primary recommended therapy for eligible patients. For ineligible patients, a number of nontransplant therapies have been evaluated in limited trials. These agents may additionally be considered "bridging" therapies pre-transplant in order to control myeloproliferation and alleviate symptoms. Historically, the most commonly utilized first-line agent has been hydroxyurea, though most patients ultimately require second (or subsequent)-line therapy; still hydroxyurea remains the conventional frontline option. Dasatinib has demonstrated efficacy in vitro in cases of CSF3R terminal membrane truncation mutations and may cautiously be considered upfront in such instances, though no substantive studies have validated its efficacy in vivo. Numerous other chemotherapy agents, practically re-appropriated from the pharmaceutical arsenal of MPN, have been utilized in CNL and are typically reserved for second/subsequent-line settings; these include interferon-alpha (IFN-a), hypomethylating agents, thalidomide, cladribine, and imatinib, among others. Most recently, ruxolitinib, a JAK1/2 inhibitor targeting JAK-STAT signaling downstream from CSF3R, has emerged as a potentially promising new candidate for the treatment of CNL. Increasingly robust data support the clinical efficacy, with associated variable reductions in allele burden, and tolerability of ruxolitinib in patients with CNL, particularly those carrying the CSF3RT618I mutation. Similar to conventional nontransplant strategies, however, no disease-modifying or survival benefits have been demonstrated. While responses to JAK-STAT inhibition in CNL have not been uniform, data are sufficient to recommend consideration of ruxolitinib in the therapeutic repertory of CNL. There remains a major unmet need for prospective trials with investigational therapies in CNL.

Effects of Tamoxifen on the Mutant Allele Burden and Disease Course in Patients with Myeloproliferative Neoplasms - Results of the Tamarin Study

Effects of Tamoxifen on the Mutant Allele Burden and Disease Course in Patients with Myeloproliferative Neoplasms - Results of the Tamarin Study

A pharmacokinetic evaluation of ropeginterferon alfa-2b in the treatment of polycythemia vera

ABSTRACT Introduction Polycythemia vera (PV) is a Philadelphia chromosome-negative chronic myeloproliferative neoplasm (MPN). A newly developed PV treatment option, ropeginterferon alfa-2b, contains recombinant human alfa monoisomer as an active ingredient, resulting in a novel pharmacologic profile and improved tolerability. Efficacy studies conclude remarkable long-term hematological response and sustained JAK2V617F allele burden reduction. Ropeginterferon alfa-2b compound has been approved for the treatment of polycythemia vera without symptomatic splenomegaly. Areas covered Current clinical trials are investigating the role of ropeginterferon alfa-2b in the first-line setting of treatment for PV. The safety and efficacy results of completed trials are summarized in this review. Metabolic, pharmacokinetic issues are also discussed of ropeginterferon alfa-2b. Expert opinion Ropeginterferon alfa-2b is a targeted therapeutic option in the treatment of PV, representing a significant improvement compared to conventional cytoreductive therapies. The single isomer entity of the recombinant human interferon alfa-2b and the mono-pegylation method imparts favorable properties to the compound. The use of ropeginterferon alfa-2b allows extended dosing interval, reduces side effects, and may increase the overall survival of PV patients by reducing the risk of progression to myelofibrosis or acute leukemia. Clinical data suggests that the compound may provide a disease-modifying option for PV patients with asymptomatic splenomegaly.

Novel Concepts of Treatment for Patients with Myelofibrosis and Related Neoplasms.

Simple SummaryMyelofibrosis (MF) is an advanced form of a group of rare, related bone marrow cancers termed myeloproliferative neoplasms (MPNs). Some patients develop myelofibrosis from the outset, while in others, it occurs as a complication of the more indolent MPNs, polycythemia vera (PV) or essential thrombocythemia (ET). Patients with PV or ET who require drug treatment are typically treated with the chemotherapy drug hydroxyurea, while in MF, the targeted therapies termed Janus kinase (JAK) inhibitors form the mainstay of treatment. However, these and other drugs (e.g., interferons) have important limitations. No drug has been shown to reliably prevent the progression of PV or ET to MF or transformation of MPNs to acute myeloid leukemia. In PV, it is not conclusively known if JAK inhibitors reduce the risk of blood clots, and in MF, these drugs do not improve low blood counts. New approaches to treating MF and related MPNs are, therefore, necessary.Janus kinase (JAK) inhibition forms the cornerstone of the treatment of myelofibrosis (MF), and the JAK inhibitor ruxolitinib is often used as a second-line agent in patients with polycythemia vera (PV) who fail hydroxyurea (HU). In addition, ruxolitinib continues to be studied in patients with essential thrombocythemia (ET). The benefits of JAK inhibition in terms of splenomegaly and symptoms in patients with MF are undeniable, and ruxolitinib prolongs the survival of persons with higher risk MF. Despite this, however, “disease-modifying” effects of JAK inhibitors in MF, i.e., bone marrow fibrosis and mutant allele burden reduction, are limited. Similarly, in HU-resistant/intolerant PV, while ruxolitinib provides excellent control of the hematocrit, symptoms and splenomegaly, reduction in the rate of thromboembolic events has not been convincingly demonstrated. Furthermore, JAK inhibitors do not prevent disease evolution to MF or acute myeloid leukemia (AML). Frontline cytoreductive therapy for PV generally comprises HU and interferons, which have their own limitations. Numerous novel agents, representing diverse mechanisms of action, are in development for the treatment of these three classic myeloproliferative neoplasms (MPNs). JAK inhibitor-based combinations, all of which are currently under study for MF, have been covered elsewhere in this issue. In this article, we focus on agents that have been studied as monotherapy in patients with MF, generally after JAK inhibitor resistance/intolerance, as well as several novel compounds in development for PV/ET.

Real-world experience with Ropeginterferon-alpha 2b (Besremi) in Philadelphia-negative myeloproliferative neoplasms

Ropeginterferon alpha-2b (Ropeg) is a novel pegylated interferon-alpha recently approved for the treatment of polycythemia vera (PV) in Europe. However, other than data from clinical trials, little is known about this agent in real world practice. A compassionate use program employing Ropeg for treating patients with unmet medical need was initiated in Taiwan in 2017. Herein, we collected clinical data and assessed the safety as well as efficacy of Ropeg in nine patients treated in this program. Collectively, among evaluable patients, both the molecular response and complete blood count remission rates were 62.5%. Most therapy-related side effects were mild, and there was no treatment discontinuation attributable to intolerable adverse events. The agent also showed efficacy in symptom amelioration and spleen size reduction. Although no specific patterns of cytokine level alteration could be identified, significantly attenuated plasma levels of inflammation markers were observed in one particular patient who happened to have normalized spleen size and most remarkable reduction in JAK2 mutant allele burden, indicating all-around improvement in every aspect of this case. Furthermore, plasma hepcidin levels increased in two-thirds of PV patients, illustrating the potential of Ropeg to restore normal regulation of erythropoiesis. Using RNA sequencing on pre- and post-treatment samples from one patient, we demonstrated altered expression of genes participating in IFN response, inflammation, apoptosis, and cellular differentiation. Conclusively, observed signs of efficacy and safety in our real-world experience prove Ropeg as a promising option for the treatment of MPN.

Efficacy of the Pan-Bcl-2 Inhibitor (Obatoclax) As a Single Agent to Treat Myeloproliferative Neoplasm in JAK2V617F Murine Transplantation Model

Background: The Jak2V617F mutation represents the most common molecular abnormality present in Philadelphia chromosome-negative Classical Myeloproliferative Neoplasms (Ph-neg MPNs). The differential expression of genes/proteins between the hematopoietic stem cells (HSC) and the more committed bone marrow progenitors may reveal, at least in part, the contribution of each cell type to the pathogenesis of the disease. Recently, it has been shown that the deregulation of molecules of the BCL2 family in MPN increases the survival of the transformed hematopoietic stem and progenitor cells (HSPCs), which may contribute the progression of the disease (Figueiredo-Pontes et al, Blood #122:2852 2013). In this context, it is possible that the inhibition of Bcl-2 proteins may increase the sensibility of transformed HSPC to apoptosis leading to the control of myeloid proliferation and potential reduction of the Jak2 mutation allele burden. To date, the treatment of Ph-neg MPNs remains non-curative despite the development of Jak2 inhibitors, which improve the clinical features but fail to eliminate leukemic initiating cells. Aim: Therefore, we aimed to study if the modulation of Bcl-2 proteins could have an impact in the control of MPN. Methods: Wild type CD45.1 C57BL/6 mice (age: 10-12 weeks) were transplanted with 5x106 total bone marrow from CD45.2 C57BL/6 mice (age: 10-12 weeks old) harboring the Jak2V617F mutation after lethal irradiation. All transplanted mice presented at least 80% of chimerism and developed MPN features (increased red blood cells (RBC), white blood cells (WBC) and platelets counts, elevated hematocrit and hemoglobin) 6 weeks post-transplantation. Treatment with vehicle (5% dimethylacetamide 0.5% methylcellulose, n=5) or Bcl-2 inhibitor (GX15-070 - the BH3 mimetic obatoclax 3 mg/Kg/day, n=6) once a day by oral gavage was started 7 weeks after transplant for a time period of 4 weeks. Spleen and bone marrow were collected from euthanized mice to evaluate both chimerism and frequency of HSC by using fluorescence-conjugated antibodies against CD45.1, CD45.2, Ter119, CD19, CD4, CD8 CD3, CD71, cKit, Sca-1, CD48, CD150, CD16/32 and CD34. Data are represented as means and standard error of mean (mean ± SEM). The statistical significance was defined as p≤0.05 and analyzed by the Mann Whitney test. Results: Mice treated with obatoclax exhibited a reduction of 32% in spleen weight compared to the vehicle group, but did not reach statistical significance (Control=0.19 ±0.01 g vs Obatoclax=0.13 ±0.03 g; p=0.3). No differences were observed in blood counts (RBC, WBC or platelets) between vehicle and obatoclax-treated mice. In addition, treatment with the pan-Bcl-2 inhibitor did not affect the number of Lineage negative, Sca-1+, c-Kit+ (LSK) cells (Control=5.8x104±2.8x104vs Obatoclax=4.7x104±1.2x104, p=0.9), MPP (Control=1.9x104±2.8x104vs Obatoclax=1.9x104±8.5x103, p=0.9), ST-HSC (Control=2.8x104±1.9x104vs Obatoclax=4.4x104±4x103, p=0.2) and LT-HSC (Control=9.8x103±4.7x103vs Obatocalx=1x104±2.4x103, p=0.9). Similarly, no differences were observed in the number of myeloid progenitors between the groups: (Control=6x105±1.7x105vs Obatoclax=1x106±1.9x105, p=0.1), MEP (Control=2.7x105±7.7x104vs Obatoclax=2.9x105±6.3x104,p=0.9), CMP (Control=9.8x104±2.1x104vs Obatoclax=2.3x105±4.4x104, p=0.06) and GMP (Control=1.5x105±6.5x104vs Obatoclax=3.6x105±8.8x104, p=0.08). The frequency of erythroid progenitors in the BM (Early progenitors, Control=18.0% ±3% vs Obatoclax=26.0%±1.4%, p=0.052, and late erythroid cells, Control=38.4%±9.5% vs Obatoclax=49.0%±2.7%, p=0.4) was also not altered by Bcl-2 inhibition. Conclusion: Our findings are in accordance with a phase II clinical trial demonstrating that obatoclax has no clinical activity in patients with Myelofibrosis. (Parikh et al, CLML 2010). Thus, we concluded that obatoclax did not reduce MPN burden in our model, when used as a single agent administrated orally. Yet, we cannot exclude the possibility that that the modulation of Bcl-2 overexpression at MPN initiating cells level could render these cells sensitive to the JAK2 inhibition. Hence, further studies will be necessary to assess whether the combination of obatoclax with other drugs such as JAK2 inhibitors could result in improved therapeutic response. Disclosures Mullally: Janssen: Research Funding. Kobayashi:Taiho Pharmaceutical: Research Funding; MiNA therapeutics: Research Funding; Pfizer: Consultancy; Ono Pharmaceutica: Consultancy; Chugai Pharmaceutical: Honoraria; Boehringer Ingelheim: Honoraria; Roche Diagnostic: Honoraria. Figueiredo-Pontes:Novartis: Honoraria.

Ruxolitinib for Patients (Pts) with Polycythemia Vera: Responders Vs Non-Responders As Defined in the Response Trial

Introduction: The RESPONSE trial (NCT01243944) compared ruxolitinib (Rux) and best available therapy (BAT) in pts with polycythemia vera (PV) who were intolerant of or resistant to hydroxyurea (HU) according to modified European LeukemiaNET criteria. In the primary analysis, at week (Wk) 32, 60% of (pts) randomized to Rux achieved HCT control (HCT &lt;45%). The present analysis evaluated the effect of baseline characteristics on HCT response at Wk 32, and aimed to determine the long-term clinical efficacy of Rux in pts who did and did not achieve the protocol-defined HCT control (i.e., HCT control responders and non-responders at Wk 32) in RESPONSE at Wk 256. Methods: Adult pts with phlebotomy-dependent PV with splenomegaly, and resistant to or intolerant of HU were enrolled. Pts were randomized to receive Rux (at a starting dose of 10 mg BID) or single-agent BAT (1:1). HCT control was defined as lack of phlebotomy eligibility between Wks 8−32 with no more than 1 phlebotomy eligibility between randomization and Wk 8. Phlebotomy eligibility was based on protocol-defined HCT values (HCT &gt; 45% and ≥ 3 percentage points higher than baseline or &gt; 48%, whichever was lower; regardless of receipt of phlebotomy), and pts with missing data or assessments outside of protocol-defined time windows were considered non-responders. In this analysis, a logistic regression model was fitted to identify the significant baseline factors to predict HCT control response at Wk 32. Time to phlebotomy eligibility in the HCT control responders and time from the first phlebotomy eligibility to the second phlebotomy eligibility in the HCT control non-responders were plotted, and the changes in hematological parameters (HCT, WBC and platelet count), spleen volume and allele burden over time, up to Wk 256, were studied in HCT control responders and non-responders who were randomized to Rux treatment arm in RESPONSE. Results: A total of 222 pts were randomized to receive either Rux (n = 110) or BAT (n = 112). Baseline WBC (P=0.0198) and baseline JAK2 V617F allele burden (P=0.0159), were found to be predictors of the HCT response within Rux treated pt group (n = 110). In the HCT responder subgroup of the Rux arm, 23% (15/66) pts needed their first phlebotomy by Wk 256. In the HCT non-responder subgroup of the Rux arm, out of 28 patients who experienced their first phlebotomy between Wk 8 and Wk 32, 64% (18/28) of pts required subsequent phlebotomy by Wk 256, with a median duration of 28.4 Wks (12.7, NA). Pts receiving Rux demonstrated controlled hematologic parameters (HCT, WBC, and platelets) over the course of study, regardless of whether they were HCT control responders and HCT control non-responders at Wk 32. From Wk 48 to Wk 80, 97% HCT control responder pts and 84% HCT control non-responder pts of the Rux treatment arm required no phlebotomies. From Wk 80 to Wk 256, 91% and 68% of the evaluable pts in the Rux treatment arm remained phlebotomy-free for HCT control responders and non-responders, respectively. By Wk 256, spleen volume on an average was reduced from baseline by approximately 35% and 50% for HCT control responders and non-responders, respectively. In pts with available assessments, allele burden on an average was reduced approximately from 80% at baseline to 55% at Wk 256 in the HCT control responders, and approximately from 70% at baseline to 40% at Wk 256 in the HCT control non-responders. Conclusions: The results from present analysis demonstrated that the benefits of the Rux treatment were not limited to pts who achieved HCT control at Wk 32. Patients treated with Rux were able to maintain hematological parameters, spleen volume reduction, and JAK2 V617F allele burden reduction for a longer duration (up to 5 years), regardless of whether they were HCT control responders or non-responders at Wk 32. Disclosures Verstovsek: Constellation: Consultancy; Pragmatist: Consultancy; Incyte: Research Funding; Roche: Research Funding; NS Pharma: Research Funding; Celgene: Consultancy, Research Funding; Gilead: Research Funding; Promedior: Research Funding; CTI BioPharma Corp: Research Funding; Genetech: Research Funding; Blueprint Medicines Corp: Research Funding; Novartis: Consultancy, Research Funding; Sierra Oncology: Research Funding; Pharma Essentia: Research Funding; Astrazeneca: Research Funding; Ital Pharma: Research Funding; Protaganist Therapeutics: Research Funding. Kiladjian:Novartis: Honoraria, Research Funding; Celgene: Consultancy; AOP Orphan: Honoraria, Research Funding. Wroclawska:Novartis Pharma AG: Employment. Dong:Novartis: Employment. Vannucchi:Celgene: Membership on an entity's Board of Directors or advisory committees; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees; Italfarmaco: Membership on an entity's Board of Directors or advisory committees.

Inhibitory effects of midostaurin and avapritinib on myeloid progenitors derived from patients with KIT D816V positive advanced systemic mastocytosis

Advanced systemic mastocytosis (advSM) is characterized by the presence of an acquired KIT D816V mutation in >90% of patients. In the majority of patients, KIT D816V is not only detected in mast cells but also in other hematopoietic lineages. We sought to investigate the effects of the KIT-inhibitors midostaurin and avapritinib on single-cell-derived myeloid progenitor cells using granulocyte-macrophage colony-forming-units of patients with KIT D816V positive advSM. Colonies obtained prior to treatment were incubated in vitro with midostaurin (n = 10) or avapritinib (n = 11) and showed a marked reduction (≥50%) of KIT D816V positive colonies in 3/10 (30%) and 7/11 (64%) patient samples, respectively. Three of those 7 (43%) avapritinib responders were resistant to midostaurin in both, in vitro and in vivo. Colonies from four patients with high-risk molecular profile and aggressive clinical course were resistant to both drugs. The in vitro activity of midostaurin strongly correlated with clinical and molecular responses, e.g., relative reduction of KIT D816V allele burden and the proportion of KIT D816V positive colonies obtained after six months midostaurin-treatment in vivo. We conclude that the colony inhibition assay provides useful information for prediction of responses on midostaurin and that avapritinib has a superior in vitro activity compared to midostaurin.

Ruxolitinib for the Treatment of Inadequately Controlled Polycythemia Vera without Splenomegaly: 156-Week Follow-up from the Phase 3 Response-2 Study

BACKGROUNDRuxolitinib (RUX), a potent Janus kinase (JAK)1/JAK2 inhibitor, is approved for hydroxyurea (HU)-resistant/-intolerant patients (pts) with polycythemia vera (PV) based on findings from the RESPONSE study (NCT01243944). RUX proved superior to best available therapy (BAT) in maintaining hematocrit (Hct) control without phlebotomy eligibility, normalizing blood cell count, reducing spleen volume, and improving symptoms in pts with PV with splenomegaly who are resistant to or intolerant of HU. RESPONSE-2 (NCT02038036) is a global, multicenter, open-label, phase 3 trial comparing RUX with BAT in HU-resistant or -intolerant pts with PV without splenomegaly. In the primary analysis at wk 28, RUX proved superior to BAT in controlling Hct without phlebotomy eligibility, normalizing blood cell count, and improving symptoms. Responses were durable at 80 wk of follow-up. Here we evaluate the long-term safety and efficacy of RUX after a follow-up of 156 wk.METHODSPatients were randomized 1:1 to RUX 10 mg twice daily or BAT; BAT patients could cross over to RUX starting at wk 28. The primary endpoint was Hct control at wk 28 (absence of phlebotomy eligibility [Hct >45% and ≥3% higher than baseline, or >48%] from wk 8 to 28, with ≤1 phlebotomy eligibility up to wk 8). The key secondary endpoint was complete hematologic remission (CHR; Hct control, white blood cell count <10×109/L, platelet count ≤400×109/L) at wk 28. Other endpoints included changes in patient-reported outcomes and in JAK2 V617F allele burden over time. Durability of Hct control (ie, primary response), CHR, and safety were evaluated at wk 156.RESULTSAt data cutoff (April 6, 2018), 65/74 RUX pts were still on treatment. Primary reasons for discontinuation were adverse events (AEs; 5.4%), consent withdrawal (2.7%), death, disease progression, and physician decision (1.4% each). All 75 BAT pts had discontinued; 58 pts had crossed over to RUX; 46 were ongoing. Reasons for early discontinuation in crossover pts were AEs (13.8%), consent withdrawal (3.4%), death (1.7%), and disease progression (1.7%). Median exposure was 168.5 wk for RUX, 28.4 wk for BAT, and, in crossover pts, 137.0 wk for RUX.At wk 156, durable Hct control was achieved in 41.9% of RUX pts (31/74). The Kaplan-Meier estimated median duration of Hct control had not been reached (Figure A). Durable CHR was achieved in 24.3% of RUX pts (18/74; estimated median duration, 35.9 weeks; Figure B). RUX also led to durable improvements in PV-associated symptoms, with approximately half of RUX pts (48%) continuing to achieve a ≥50% reduction in MPN-SAF TSS at wk 156. Pts in the RUX arm also continued to experience improvements in all 5 dimensions of the EQ-5D-5L assessment. Pts who crossed over to RUX derived benefits from RUX therapy as well, achieving Hct control following crossover, with Hct decreasing over time. As seen in RUX pts, crossover pts experienced a reduction in JAK2 V617F allele burden over time from the time of crossover.The safety profile of RUX was consistent with previous reports. The most common AEs were anemia (exposure-adjusted rate per 100 pt-years, 10.7), increased weight (8.5), arthralgia (6.8), and hypertension (6.0) in the RUX arm and anemia (12.8), nasopharyngitis (7.1), and increased weight (6.4) in pts after crossover. Of interest, exposure-adjusted rates of herpes zoster were 3.8 with RUX and 5.0 in crossover pts. Overall, exposure-adjusted rates of AEs with RUX were lower than those reported at 80 wk of follow-up. The exposure-adjusted rate of thromboembolic events was higher in the BAT arm (3.7; RUX, 2.6). As expected given prior HU exposure, nonmelanoma skin cancer was the most common second malignancy in RUX-treated pts (randomized, 3.4; crossover, 2.8). No RUX-treated pts developed AML; 1 pt (RUX arm; 0.4) developed myelofibrosis. Three pts died on study: 1 in the RUX arm (metastatic melanoma), 1 in the BAT arm (septic shock), and 1 after crossover (general health deterioration).CONCLUSIONSIn this 156-wk follow-up, RUX provided durable Hct control and CHR in pts with PV without splenomegaly. RUX was well tolerated, with 88% of randomized pts and 79% of crossover pts still receiving RUX at the time of this analysis. AEs were consistent with previous reports, and no new safety signals were observed. Overall, findings are consistent with those from RESPONSE and support RUX as the standard of care for second-line therapy in pts with inadequately controlled PV. [Display omitted] DisclosuresPassamonti:Novartis: Consultancy, Honoraria, Speakers Bureau. Palandri:Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Saydam:Gilead: Honoraria; Celgene: Honoraria; Novartis: Honoraria, Research Funding, Speakers Bureau; BMS: Honoraria. Devos:Novartis: Consultancy; Takeda: Consultancy; Celgene: Consultancy. Vannucchi:Celgene: Membership on an entity's Board of Directors or advisory committees; ITALFARMACO: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Bensasson:Novartis: Employment. Kandra:Novartis: Employment, Research Funding. Morando:Novartis: Employment, Equity Ownership. Griesshammer:Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.