Abstract: Ruxolitinib (RUX) is a Janus kinase 1/2 inhibitor (JAKi) approved in the EU for treating disease‑related splenomegaly or symptoms in adults patients with myelofibrosis (MF). This is an interim analysis of JAKoMo, a prospective, non‑interventional, phase IV study in MF. Between 2012–2019 (cutoff March 2021), 928 patients (JAKi-naïve and -pretreated) enrolled from 122 German centers. This analysis focuses on JAKi-naïve patients. RUX was administered according to the Summary of Product Characteristics. Compared to the COMFORT-I, -II, and JUMP trials, patients in JAKoMo were older (median 73 years), had poorer Eastern Cooperative Oncology Group (ECOG) performance statuses (16.5% had ECOG ≥ 2), and were more transfusion dependent (48.5%). JAKoMo represents the more challenging patients with MF encountered outside of interventional studies. However, patients with low-risk International Prognostic Scoring System (IPSS) scores or without palpable splenomegaly were also included. Following RUX treatment, 82.5% of patients experienced rapid (≤ 1 month), significant decreases in palpable spleen size, which remained durable for 24 months (60% patients). Symptom assessment scores improved significantly in Month 1 (median –5.2) up to Month 12 (–6.2). Common adverse events (AEs) were anemia (31.2%) and thrombocytopenia (28.6%). At cutoff, 54.3% of patients had terminated the study due to, death, AEs, or deterioration of health. No new safety signals were observed. Interim analysis of the JAKoMo study confirms RUX safety and efficacy in a representative cohort of real-world, elderly, JAKi-naïve patients with MF. Risk scores were used in less than half of the patients to initiate RUX treatment. Trial registration: NCT05044026; September 14, 2021.

Abstract: Introduction: The licenced starting dose of bosutinib is 400 mg QD for first line therapy and 500 mg QD in later lines in CML. Gastrointestinal (GI) adverse events (AE) are observed in up to 90% in similar patient cohorts (BYOND, Hochhaus et al; Leukemia 2020). The goal of this study was to evaluate whether a bosutinib step-in dosing regimen decreases GI toxicity while maintaining optimal efficacy in patients (pts) with CML after failure or intolerance to 2G-TKIs. Methods: This is the first and final analysis of the BODO "Bosutinib Dose Optimization Study" trial (NCT02577926), which is a multicenter, open-label single arm phase II study testing tolerability and efficacy of 2 nd & 3 rd line bosutinib step-in dosing in chronic phase CML pts intolerant and/or refractory to previous imatinib, and/or nilotinib, and/or dasatinib therapy. Bosutinib was commenced with 300 mg QD and was (in the absence of & gt;G1 toxicities) dose-increased by increments of 100 mg daily dosing every 14 days if applicable up to a maximum dose of 500 mg QD. The primary endpoint (PE) was the incidence of grade 2 to 4 GI toxicity AEs within 6 months after registration. 127 pts were planned to be recruited. However, due to slow recruitment, the trial had to be stopped prematurely after inclusion of 57 pts. The 95% confidence interval (CI) around the estimated rate of the PE was calculated in accordance with Clopper and Pearson. Results: Pts´ characteristics are presented in Table 1. 23 (40.4%) pts were intolerant, 20 resistant (35.1%), and 14 (24.6%) both intolerant and resistant to previous TKI treatment. 20 (35.1%) pts entered the study in molecular response (at least MMR at screening). The probability of MMR after 24 months of treatment was 79% (95% CI: 65.8% to 87.5%); probabilities of MMR, MR4, MR4.5 are shown in Figure 1. Six out of 7 intolerant pts without MMR at baseline reached MMR or better molecular response with bosutinib. Thirty pts were refractory to previous therapy (19 being resistant; 11 being resistant and intolerant) lacking baseline MMR, of which 19 pts achieved MMR or better (2 pts with MR4.5, 2 with MR4 and 15 with MMR). Eight out of 30 pts did not achieve MMR and 3 experienced complications (2 pts with SAEs that led to discontinuation and 1 death). No patient progressed to accelerated/blast phase on treatment. Two pts died (1 CML progression (no MMR with bosutinib, death 6 months after allogenic stem cell transplant); 1 cerebral cavernoma unrelated to bosutinib). In the overall patient population (N = 57), all pts had ≥1 any grade TEAE and 71.9% of patients had ≥1 grade 3/4 TEAE. SAEs occurred in 28.1% of pts. A total of 949 AEs were reported during the study. The most frequently reported AEs (SOC terms) were GI disorders (n=346, 36.5%) and investigations (n=206, 21.7%). Among the GI events (n=346) diarrhea (55.5%), nausea (16.2%) and abdominal pain (9.8%) were most common; among investigations (n=206) liver enzyme increases were most frequent (ALT increase (26.7%), AST increase 17%). The PE was evaluated for 50 out of 57 pts (4 pts with treatment & lt; 14 days + 3 pts with observation & lt; 6 months were excluded from the analysis). Twenty pts did not develop any clinically relevant GI-toxicity during the first 6 months. Thus, the rate of GI-toxicity (grade 2 to 4) within the first 6 months of treatment was 60.0% (95% confidence interval: 45.2% to 73.6%), accordingly, the alternative hypothesis of the trial (GI-toxicity was assumed to be less than 40%) could not be accepted. However, only in 1 patient GI-toxicity led to discontinuation. Twenty-five pts discontinued bosutinib prematurely (17 due to AEs; 5 with insufficient response; 3 with other reasons). Conclusion: This is 1 of the largest cohorts published on the efficacy and safety of bosutinib after intolerance/failure to first-line 2G-TKIs. Given the limitations of a single-arm study with incomplete recruitment, we could not demonstrate an advantage of the step-in dosing concept chosen here to reduce the frequency of grade 2-4 GI toxicity overall. However, using this regimen, bosutinib was able to induce optimal responses in almost two thirds of pts previously resistant to 2G-TKIs while GI toxicity rarely led to treatment discontinuation. We conclude that treatment with bosutinib is safe (rates of AEs being similar to other trials (e.g. BYOND)) and efficacious as 2 nd and 3 rd line therapy after failure of previous 2G-TKI therapy whereas an advantage of run-in dosing regimens remains to be proven. Figure 1 Figure 1. Disclosures Isfort: Mundipharma: Other: Travel reimbursement; Amgen: Other: Travel reimbursement; Roche: Other: Travel reimbursement; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Hexal: Other: Travel reimbursement; Alexion: Other: Travel reimbursement; BMS: Honoraria; Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel reimbursement; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel reimbursement. Wolf: Roche: Honoraria, Research Funding; MSD: Honoraria, Research Funding; BMS-Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Takeda: Honoraria; Gilead: Honoraria; Incyte: Honoraria; GEMOAB: Honoraria. Teichmann: Pfizer: Membership on an entity's Board of Directors or advisory committees. Crysandt: Incyte: Honoraria; Pfizer: Membership on an entity's Board of Directors or advisory committees. Burchert: Novartis: Honoraria, Research Funding; AOP Orphan: Honoraria, Research Funding; Pfizer: Honoraria; Incyte: Honoraria; Gilead: Honoraria; BMS: Honoraria. Hochhaus: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Research Funding; Pfizer: Research Funding; Incyte: Research Funding. Saussele: Pfizer: Honoraria; Incyte: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Roche: Honoraria. Kiani: Novartis Pharma GmbH: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Göthert: Bristol-Myers Squibb: Consultancy, Honoraria, Other: Travel reimbursement; Incyte: Consultancy, Honoraria, Other: Travel reimbursement; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: Travel reimbursement; Proteros Biostructures: Consultancy; AOP Orphan Pharmaceuticals: Honoraria, Other: Travel reimbursement; zr pharma & : Honoraria. Schafhausen: Swedish Orphan Biovitrum AB: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Honoraria, Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Blueprint Medicines: Membership on an entity's Board of Directors or advisory committees. Brümmendorf: Novartis: Honoraria, Patents & Royalties, Research Funding; Janssen: Honoraria; Bristol Myers: Research Funding; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Repeat Diagnostics: Research Funding; Takepart Media: Honoraria.

Abstract: The approved dose of bosutinib in chronic phase CML is 400 mg QD in first-line and 500 mg QD in later-line treatment. However, given that gastrointestinal (GI) toxicity typically occurs early after treatment initiation, physicians often tend to start therapy with lower doses although this has never been tested systematically in prospective trials in the Western world. The Bo sutinib Do se Optimization (BODO) Study, a multicenter phase II study, investigated the tolerability and efficacy of a step-in dosing concept of bosutinib (starting at 300 mg QD) in chronic phase CML patients in 2 nd or 3 rd line who were intolerant and/or refractory to previous TKI treatment. Of 57 patients included until premature closure of the study due to slow recruitment, 34 (60%) reached the targeted dose level of 500 mg QD following the 2-weekly step-in dosing regimen. While the dosing-in concept failed to reduce GI toxicity (grade II–IV, primary study endpoint) to  〈  40% (overall rate of 60%; 95% CI: 45–74%), bosutinib treatment (mean dosage: 403 mg/day) showed remarkable efficacy with a cumulative major molecular remission (MMR) rate of 79% (95% CI: 66 to 88%) at month 24. Of thirty patients refractory to previous therapy and not in MMR at baseline, 19 (64%) achieved an MMR during treatment. GI toxicity did not significantly impact on patient-reported outcomes (PRO) and led to treatment discontinuation in only one patient. Overall, the results of our trial support the efficacy and safety of bosutinib after failure of second-generation TKI pre-treatment. Trial registration: NCT02577926.

Abstract: TL in LSCs is significantly shortened at diagnosis of CML and correlates with LSC burden. TL in nonleukemic myeloid cells in deep molecular remission is unaffected by long-term TKI treatment.

Abstract: Patients (pts) with polycythemia vera (PV) suffer from pruritus, night sweats, and other symptoms, as well as from thromboembolic complications and progression to post-PV myelofibrosis. Ruxolitinib (RUX) is approved for second-line therapy in high-risk PV pts with hydroxyurea intolerance or resistance. The RuxoBEAT trial (NCT02577926, registered on October 1, 2015, at clinicaltrials.gov) is a multicenter, open-label, two-arm phase-IIb trial with a target population of 380 pts with PV or ET, randomized to receive RUX or best available therapy. This pre-specified futility analysis assesses the early clinical benefit and tolerability of RUX in previously untreated PV pts (6-week cytoreduction was allowed). Twenty-eight patients were randomly assigned to receive RUX. Compared to baseline, after 6 months of treatment, there was a significant reduction of median hematocrit (46 to 41%), the median number of phlebotomies per year (4.0 to 0), and median patient-reported pruritus scores (2 to 1), and a trend for reduced night sweat scores (1.5 to 0). JAK2V617F allele burden, as part of the scientific research program, also significantly decreased. One hundred nine adverse events (AEs) occurred in 24/28 patients (all grade 1 to 3), and no pt permanently discontinued treatment because of AEs. Thus, treatment with ruxolitinib in untreated PV pts is feasible, well-tolerated, and efficient regarding the above-mentioned endpoints.

Abstract: Background. Thrombembolic (TE) and bleeding (B) events pose a severe risk for patients (pts) with myeloproliferative neoplasms (MPN). Multiple disease-related factors have been identified that contribute to these events, such as the interaction between platelets, leucocytes, and endothelial cells. However, not all pts develop thrombosis or severe bleeding, suggesting that further contributing factors may play a role, including specific comorbidities and cardiovascular risk factors. Aims. The aim of our analysis was to evaluate the association between thromboembolic events, specific comorbidities, and cardiovascular risk factors in MPN pts. Methods. We analyzed clinical data frompts treated at the MPN Center at RWTH Aachen University hospital. All pts were aged ≥18 years and carried a diagnosis of classical BCR-ABL negative MPN (polycythemia vera [PV], essential thrombocythemia [ET] , primary and secondary myelofibrosis [MF]), as defined by WHO criteria (2008). In addition, data about MPN disease complications, age, cardiovascular risk factors (smoking habits, arterial hypertension, diabetes mellitus, obesity, and hyperlipoproteinemia) and MPN subtype were included. Comorbidities were scored using three different comorbidity scales (CIRS, Charlson comorbidity index, and ACE-27). Results. 75 MPN pts were included in this analysis, 25 with PV, 19 ET pts and 31 pts with MF (19 pts with PMF, 9 Post-PV-MF pts and 3 pts with Post-ET-MF). Characterization of pts regarding age, sex, thrombembolic/bleeding events as well as median scores in comorbidity scales are shown in Table 1. In addition, pts were divided into a group with (Group TE+B) or without (Group no TE+B) thromboembolic or severe bleeding events. 40 patients (53.3%) had previously experienced a thrombembolic or bleeding event. These pts showed significantly higher median comorbidity scores (CIRS of 6.5 vs. 2.0, p 〈 0,001, Charlson score of 1 vs. 0, p 〈 0,001, and median ACE-27 of 2 vs. 0, p 〈 0,001). Presence of classic cardiovascular risk factors among groups TE+B vs. no TE+B was heterogeneous (10 vs. 11 (ex-)smokers; 18 vs. 9 pts with arterial hypertension; 9 vs. 14 pts with a BMI 〉 25; 4 vs. 1 pts with diabetes mellitus; 4 vs. 0 pts with hyperlipoproteinemia). TE+B pts had high scores in certain CIRS categories (each category includes a scale of 0-4) especially in categories regarding cardiac diseases, hypertension, vascular disease & endocrinological disease (see Table 2). Furthermore, more than one third of the TE+B pts had also neurological (16/40 pts. (40%) vs. 3/35 (8.6%) in the no TE+B group) and upper-GI-disease (13/40 pts (32.5%) vs. 8/35 (22.9%) in the no TE+B group). Summary and Conclusions. Given the obvious limitations of this analysis due to small sample numbers, this analysis provides an indication that classic cardiovascular risk factors (especially diabetes mellitus, arterial hypertension, and hyperlipoproteinemia) and additional comorbidities contribute to the risk of thromboembolic and bleeding events in pts with classical MPN. Clinical trials should address whether the improvement of such risk factors in addition to anti-MPN treatment can minimize the risk of such events. Table 1. Characterization of pts Subtype of MPN Number of patients Median age at diagnosis (range) Number of patients that developed thromboembolic events (TE) or bleeding (B)* Number of patients without thromboembolic/bleeding events Median CIRS score(Range 0-56) Median Charlson comorbidity index(Range 0-37) Median ACE-27 score(Range 0-3) Polycythemia vera 25(11m/14f) 58 (31-77) 15 (15 TE, 2 B) 10 6 1 1 Essential Thrombo-cythemia 19(10m/9f) 54 (23-64) 6 (5 TE, 1 B) 13 4 0 1 All Myelofibrosis 31(22m/9f) 63 (29-77) 19 (16 TE, 7 B) 12 5 0 1 Myelofibrosis PMF 19(16m/3f) 61 (29-77) 11 (9 TE, 4 B) 8 4 0 1 Post-PV-MF 9(3m/6f) 63 (42-73) 7 (6 TE, 3 B) 2 8 1 1 Post-ET-MF 3(3m/no f) 68 (68-73) 1 (1 TE) 2 13 2 2 · Few Pts had suffered from both thromboembolic and bleeding events Table 2. Number of pts in the TE+B group in comparison to the no TE+B group in certain CIRS categories subdivided according to score CIRS category (TE+B pts vs. no TE+B pts) Score of 0 per category Score of 1 per category Score of 2 per category Score of 3 per category Score of 4 per category Cardiac disease 20 vs. 30 6 vs. 2 5 vs. 3 9 vs. 0 0 vs. 0 Hypertension 22 vs. 26 2 vs. 0 4 vs. 6 12 vs. 3 0 vs. 0 Vascular disease 21 vs. 32 3 vs. 1 12 vs. 0 3 vs. 1 1 vs. 1 Endocrinological disease 21 vs. 26 0 vs.1 19 vs.7 0 vs.1 0 vs.0 Disclosures Isfort: Pfizer: Honoraria; BMS: Honoraria; Mundipharma: Other: Travel & Accomodation; Roche: Other: Travel & Accomodation; Novartis: Other: Travel & Accomodation; Amgen: Other: Travel & Accomodation; Hexal: Other: Travel & Accomodation. Bruemmendorf:Ariad: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Patent on the use of imatinib and hypusination inhibitors: Patents & Royalties. Koschmieder:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel reimbursement for scientific conferences, Research Funding; Novartis Foundation: Research Funding; Baxalta/CTI: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel reimbursement for scientific conferences; Janssen Cilag: Other: Travel reimbursement for scientific conferences.

Abstract: Introduction: Ph-negative myeloproliferative neoplasms (MPN) represent a heterogeneous group of hematological malignancies which differ in various aspects such as clinical manifestation, underlying genetic aberrations, cytomorphological features and life expectancy. However, across all subtypes, patients (pts) with MPN often suffer from severe symptoms, resulting in an impairment of the quality of life (QoL). Methods: The German Study Group for MPN (GSG-MPN) Bioregistry is a non-interventional prospective study including pts of at least 18 years with diagnosis of Ph-negative MPN according to WHO criteria (2008) having provided written informed consent. The Bioregistry study also includes assessment of QoL at baseline and on an annual basis, with all pts completing the standardized MPN-SAF-TSS questionnaire (German version) and an additional item indicating pts' subjective overall QoL on an 11-point Likert scale. Total scores range from 0 to 90 and were calculated if at least 6 items were answered (Emanuel RM et al., J Clin Oncol. 2012; 30 (33): 4098-103.)). Clinical variables, as documented in the registry, included comorbidities, reported symptoms as assessed by the physician, bleeding, and thromboembolic events (TEE). For statistical analysis, standard descriptive methods, Spearman correlation coefficient, Wilcoxon test/Kruskal-Wallis test for significance testing, and Kendall´s tau-b statistics were used. Results: 1,403 pts who had completed at least six items of the QoL assessment at baseline were included in this analysis. Median age at diagnosis was 58 years (interquartile range [IQR] 22), 98% were Caucasian, 50% were female. 494 pts were diagnosed with essential thrombocythemia (ET, 35%), 444 pts with polycythemia vera (PV, 32%), 302 pts with primary myelofibrosis (PMF, 22%), 83 pts with MPN-unclassifiable (MPNu, 6%), 43 pts with post-ET-myelofibrosis (pET-MF, 3%) and 37 pts with post-PV-myelofibrosis (pPV-MF, 3%). The most common complaint reported via the MPN-SAF-TSS was fatigue, occurring in more than 80% of the pts in all entities except MPNu (77%). More than 50 % of pts in each entity reported to suffer from early satiety, night sweats, concentration problems, or overall impairment of QoL. Table 1 summarizes all 9 symptoms and overall QoL from the questionnaire categorized by entity. Interestingly, the pts suffering from PET-MF reported the highest symptom burden, while PPV-MF pts showed the lowest overall symptom burden (median total QoL score of 23 vs. 16; p=0.01). The strongest correlations among the different symptoms were seen for fatigue and overall QoL (Spearman´s rho 0.57, p 〈 0.001) as well as concentration problems and overall QoL (Spearman´s rho 0.33, p 〈 0.001). Furthermore, the impact of variables such as age, comorbidities and TEE on QoL was assessed. Abdominal discomfort increased with age (rho = -0.14, p 〈 0.001). A history of TEE before baseline assessment correlated significantly with fatigue scores (Spearman rho= 0.07, p 〈 0.01) and with concentration problems (rho=0.07, p 〈 0.01). With an increasing number of TEE, scores for both of these items worsened over time (p 〈 0.01, respectively). Moreover, MPN-total score (MPN-TSS) was higher in pts with more comorbidities (Median: 18 (IQR:23), and 25 (27) for pts with 〈 3 versus ≥3 comorbidities, respectively, p= 0.017). Next, we compared data on 5 of the pts symptoms (reported in the questionnaire) to their assessment by the treating physician (only 5 items were available both in the questionnaire and in our registry database) in order to understand whether the "physician´s opinion" is congruent with the patient´s reported outcome in the questionnaire. While there were clear associations between the two data sources, there were also significant discrepancies, e.g., the physician did not indicate fatigue in about 20% of pts with self-assessed fatigue score of 〉 =6 points. The most concordant symptom was night sweats (further details in table 2). Conclusions: Most MPN pts suffer from a significant symptom burden which impairs their QoL. TEE influence fatigue and concentration problems. The perception of symptoms (particularly with respect to fatigue) differs between pts and treating physician which suggests that questionnaires should be used on a routine basis in order to faithfully reflect patient´s degree of suffering from MPN and/or treatment. Disclosures Isfort: Amgen: Other: i.e. travel support; Mundipharma: Other: i.e. travel support; Roche: Other: i.e. travel support; Incyte/Ariad: Consultancy; Pfizer: Consultancy, Honoraria, Other: i.e. travel support; BMS: Honoraria; Novartis: Consultancy, Honoraria, Other: i.e. travel support; Alexion: Other: i.e. travel support; Hexal: Other: i.e. travel support. Stegelmann:Novartis: Consultancy, Honoraria. Al-Ali:Gilead: Consultancy, Research Funding; Otsuka: Consultancy, Honoraria; Alexion: Honoraria; Novartis: Consultancy, Honoraria, Other: Travel support, Research Funding; Celgene: Honoraria, Other: Travel support, Research Funding. Goethert:BMS: Consultancy, Honoraria, Other: i.e. travel support; Incyte: Consultancy, Honoraria, Other: i.e. travel support; Pfizer: Consultancy, Honoraria; Novartis: Honoraria; Proteros Biostructures: Honoraria; AOP Orphan: Other: i.e. travel support. Haenel:Novartis: Honoraria; Takeda: Honoraria; Roche: Honoraria; Amgen: Honoraria. Platzbecker:Celgene: Research Funding. Griesshammer:Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Brümmendorf:Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Janssen: Consultancy; Merck: Consultancy; Takeda: Consultancy.