Derkach, Andriy

Background: The COVID-19 pandemic had an outsized impact on individuals with immune compromise, such as multiple myeloma, leading to increased rates of severe COVID, hospitalization, and death in these groups. The pandemic also demonstrated the need for rapid and efficient evidence generation to address rapidly changing medical needs and accelerated the use of innovative trial designs to accomplish this goal. Methods: We designed and established a prospective, decentralized study within a site-based provider network, COVID-19 OutcomeS in Myeloma and the Impact of VaCcines (COSMIC), for patients with multiple myeloma at ASH Research Collaborative sites to monitor outcomes related to COVID-19 infection and vaccination. The direct-to-patient approach was accomplished using a study application accessed with a QR code provided to patients during usual clinical care. All study activities occurred within the patient portal at Baseline, Day 30, and Day 180, minimizing burden on site personnel and staff. Study activities included eligibility confirmation, consenting, electronic health record (EHR) data permissions, and patient-reported outcome (PRO) surveys. PRO data (EORTC QLQ-C30, EORTC QLQ MY-20) were made available to clinicians through the portal to visualize results from their patients. Patients shared if they received a COVID-19 vaccination or booster and if they had a COVID-19 infection. Patients with a history of COVID-19 infection included method of confirmation and if hospitalization was required. Patients were provided compensation for participation. Automated text and email messages were sent at three separate intervals: 24 hours, Day 8, and Day 15 for participants who initiated but did not complete study activities. A personal email reminder per participant was sent for those whose second study visit window was approaching. ASH Research Collaborative clinicians met regularly to share best practices related to enrollment and study conduct, thereby creating an innovative evidence generation learning community. We studied the feasibility of data collection in a decentralized format by focusing on the number of participants who interacted with the system, those who consented, and those who completed baseline PRO assessments. Results: The COSMIC study rapidly accrued and consented 200 patients from eight participating ASH Research Collaborative sites over four months (1/22/2024 through 5/17/2024): 69% self-reported as non-Hispanic White (NHW). Of enrolled participants, 57.5% opted to permission sharing of their EHR data, which included disease and treatment-related clinical data, laboratory results, pathology reports, and imaging reports. A total of 196 patients (98%) provided demographic and COVID-related disease and vaccine data at baseline; nearly all of these patients (n=195) provided baseline PRO data, and 150 patients provided further information at Day 30 at the time of this analysis. Those who did not provide Day 30 data were not significantly different from those who did in terms of age (median: 68 [no Day 30 data] vs. 67 [Day 30 data] years; p=0.44), sex (41% [no Day 30 data] vs. 47% [Day 30 data] Female; p=0.47), or race (65% [no Day 30 data] vs. 71% [Day 30 data] NHW; p=0.60). A higher proportion of Hispanic patients were retained at Day 30 (13/15=87%) vs. 78% of non-Hispanic patients or those who declined reporting ethnicity (2/7=29%; p=0.007). COVID-19 vaccination data were submitted by 196 patients, 186 of whom had ever received a COVID-19 vaccination. Data on number, type, brand, and dates for these vaccinations were provided. Conclusions: The COSMIC study conducted by the ASH Research Collaborative was able to rapidly accrue a diverse cohort of patients using a decentralized workflow within a site-based provider network, with high consent and compliance rates. This platform, and the innovative evidence generation learning community of ASH Research Collaborative investigators and patients, sets a precedent to address a variety of real-world questions related to disease management, infections, vaccinations, and PROs in this population of patients with multiple myeloma.

Background: Data from the ASH Research Collaborative COVID-19 Registry for Hematology demonstrated that patients with multiple myeloma and other immune compromise had elevated risk for severe complications from COVID-19 infection. To address current evidence gaps and to demonstrate proof of concept for a pandemic preparedness and response network, the ASH Research Collaborative Multiple Myeloma Program developed a prospective, decentralized study within a site-based provider network to investigate COVID-19 infections, vaccinations, and quality of life in patients with multiple myeloma. Methods: We designed and established the COVID-19 OutcomeS in Myeloma and the Impact of VacCines (COSMIC) to study COVID-19 in patients with multiple myeloma at ASH Research Collaborative network sites. A study application was accessed with a QR code and shared with patients during usual clinical care. Patients provided consent, optionally gave permission for electronic health record data collection, and completed patient-reported outcomes (EORTC QLQ-C30 and MY20) at baseline, Day 30, and Day 180 through the study portal. Clinicians at participating sites facilitated study enrollment and shared best practices monthly to accelerate study execution. Study objectives related to feasibility of data collection in a decentralized format are reported in a separate abstract. Here, we report interim results related to SARS-CoV-2 vaccination history, COVID-19 infection, and how these relate to patient reported outcomes and clinical outcomes in enrolled participants. Results: The COSMIC study rapidly accrued and consented 200 patients from eight participating ASH Research Collaborative sites over four months (1/22/2024 through 5/17/2024). Consented participants' ages ranged from 29 to 93 years, with median of 67 years; 46% were female, 69% were non-Hispanic White (NHW), 17% were non-Hispanic Black (NHB), and 8% were Hispanic/Latino. Of the 196 patients who reported COVID-19 data, 111 (57%) reported at baseline that they had a history of COVID-19 infection, with 12 having required hospitalization for this (12/111=11%). Overall, 95% (186/196) reported a history of COVID-19 vaccination, where the median number of vaccinations was 4 (range: 1 to 6); 44 patients (23%) expressed willingness to discuss getting a yearly booster vaccine with their provider. At 1-month follow-up, there were 3 additional patients who reported a COVID-19 infection and 18 patients who received an additional COVID-19 vaccination. The baseline EORTC QLQ-C30 median Global Health Status/QOL score was 66.7 (mean=64.4, range: 8.3 - 100, n=196). This overall global QOL score was not significantly different between those who did vs. did not have a history of COVID-19 infection (mean [SD]: 63.7 [19.3] vs. 65.8 [17.6]; p=0.57). In analyses adjusted for age, biological sex, and race/ethnicity group, history of COVID-19 infection was not associated with HRQOL (odds ratio=0.93, 95% CI: 0.78 - 1.10; p=0.38). Data collection is ongoing and final study results will be reported at a later date. Conclusion: COSMIC is a prospective, decentralized study within a site-based provider network conducted by the ASH Research Collaborative Multiple Myeloma Program that demonstrates the feasibility of using an innovative evidence generation strategy to drive rapid accrual of patients to address a rapidly evolving area of need. The COSMIC study also provides proof of concept that a real-world evidence generation network can play an important role in national pandemic preparedness and response. The COSMIC experience reinforces the ability to accrue diverse patient populations representing the demographic of myeloma patients in the US.

Background: Patients with acute lymphoblastic leukemia (ALL) receiving L-asparaginase (ASP) based induction therapy have a high risk of venous thromboembolism (VTE). Studies investigating universal thromboprophylaxis strategies have yielded sub-optimal results. Risk prediction models are needed to identify high-risk patients who would be candidates for intensification of thromboprophylaxis, and lower risk patients who are unlikely to benefit. Aims: Derive and externally validate a risk prediction model for VTE in patients with ALL receiving ASP therapy. Methods: We conducted a multicenter, international, cohort study of patients with newly-diagnosed ALL receiving ASP-based induction therapy (≥18yrs). The derivation and external validation cohorts included 306 and 97 patients without VTE prior to ASP therapy, respectively. Patients on therapeutic anticoagulation at index were excluded. Patients were followed from date of first ASP dose for 100 days post ALL diagnosis or until VTE, therapeutic anticoagulation or death. Candidate predictors were documented at ALL diagnosis and included demographics, disease and treatment characteristics, VTE history, comorbidities, thromboprophylaxis, complete blood count, fibrinogen and d-dimer. D-dimer was only analyzed within the 7 derivation cohort centers who routinely tested this at ALL diagnosis with <20% missing values. Primary outcome was VTE at any site (centrally confirmed). Secondary outcomes included major bleeding by ISTH criteria. Cause-specific Cox proportional hazard regression was performed to identify VTE risk factors in the derivation cohort while treating death as a competing event. Variables with p-value <0.1 on univariable analysis were included in a multivariable model and subsequently used in the risk model if p-value <0.05. Lastly, the derived VTE risk prediction model was tested in the external validation cohort for association with time to VTE using cause-specific Cox proportional hazard model. All analyses were stratified by center and use of low molecular weight heparin prophylaxis (at any dose on the date of first ASP dose). Results: The cumulative incidence of VTE in the derivation cohort was 17% at 30 days (95% confidence interval [CI] 13% - 21%) and 22% at 90 days (95% CI 17% - 27%). The multivariable model included hyperlipidemia (hazard ratio [HR] 1.35; 95% CI 0.56 - 3.27), body mass index ≥ 25 kg/m² (HR 1.49; 95% CI 0.75 - 2.95), platelet count ≥ 25 x 10⁹/L (HR 1.42; 95% CI 0.67 - 3.00), increasing hemoglobin per 1 g/dL (HR 1.17; 95% CI 1.03 - 1.32) and d-dimer ≥ 1 µg FEU/mL (HR 2.68; 95% CI 1.08 - 6.66). Hemoglobin as a continuous variable and d-dimer ≥ 1 µg FEU/mL were included in the final model and used to create a risk score which was weighted by estimated log-HR sum of these risk factors. The lowest risk quartile (risk score below 2.1) successfully differentiated between a lower 30-day cumulative VTE incidence (4%, 95% CI 0.72% - 12%) compared with the other quartiles (20%, 95% CI 14% - 27%; HR 4.40, 95% CI 1.54 - 12.5) which were defined as high risk (score ≥2.1). The risk score's negative predictive value (NPV) for VTE at 30 days was 96% and positive predictive value (PPV) was 20%. The validation cohort (n=97 from 3 external cohorts with routine d-dimer measurement) included 16 (16.5%) patients in the low-risk group and 81 (83.5%) in the high-risk group, with a 30-day VTE incidence of 6.3% (95% CI 0% - 17%) and 21% (95% CI 12% - 30%), respectively (HR 6.22; 95% CI 0.85 - 45.8; p = 0.073)). The NPV (93.7%) and PPV (21%) were comparable to the derivation cohort. The 30-day incidence of major bleeding was 0% (95% CI NR - NR) in low-risk patients (HR 1.36; 95% CI 0.27 - 6.77) and 2.0% (95% CI 0.55% - 5.4%) in the high-risk group. Conclusion: Patients with ALL receiving ASP induction therapy have a 17% VTE risk at 30 days. We derived and externally validated a VTE risk prediction model based upon d-dimer and hemoglobin. This model successfully identifies at least 16.5% of patients with ALL who have a low VTE risk after ASP treatment. Using this model, novel prevention strategies which may be associated with cost and risk could now be tailored to patients with higher risk. Prospective studies are needed to validate the model's performance and role in VTE risk management.

Introduction Poor diet quality, elevated body mass index (BMI), insulin resistance, microbiome dysbiosis, inflammation as well as immune dysfunction have all been implicated in progression from monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) to multiple myeloma (MM). Plant-based diets have been associated with reduced risk of MGUS and MM in epidemiological studies. Whether a dietary intervention can impact these modifiable risk factors and delay disease progression has not been investigated. Methods We conducted a pilot, single-arm trial providing controlled high fiber plant based dietary (HFPBD) intervention for 12 weeks and health coaching for 24 weeks in 20 patients with MGUS/SMM with BMI≥25 (NCT04920084). The primary endpoint was feasibility (adherence and BMI reduction). Secondary and exploratory endpoints included quality of life, metabolic markers (insulin, adiponectin, leptin, LDL cholesterol), microbiome (diversity and composition by 16S and shotgun sequencing) and immune profiling in peripheral blood (flow cytometry and Olink inflammation panel) and bone marrow (scRNAseq and ATACseq). We also conducted an in vivo study in transgenic Vk*MYC mice fed a high fiber or control diet at the phase of mouse(m)SMM. The mice were monitored for the progression to active mMM. Differences in microbiome and immune response profiles between high fiber- and control-treated mice were assessed via microbiome 16S sequencing and flow cytometry. Results The HFPBD intervention was safe, feasible, improved quality of life and addressed modifiable risk factors - metabolic profile (improved BMI, insulin resistance, adiponectin leptin ratio), microbiome profile (increased alpha-diversity and butyrate producers) and immune (decreased inflammation and increased anti-inflammatory classical monocyte) subsets. A reduction in long-term progression trajectory was observed in 2 patients. Consistently, the high fiber diet delayed progression from mSMM to mMM in Vk*MYC mice increasing median progression-free survival from 12 weeks in the control arm to 30 weeks in the high fiber diet intervention arm. Additionally, in the intervention arm 40% of mice did not progress to mMM during the study period whereas all mice in the control arm progressed. Both human and mouse data showed that HFPBD modulated gut microbiota composition favoring the expansion of butyrate-producing bacteria. Additionally, short-chain fatty acids were increased in the feces of mice fed a high fiber diet. Integrated analysis from human bone marrow and peripheral blood analysis indicated that the dietary intervention reduced inflammatory biomarkers and skewed the immune response towards T helper and CD14+ monocytes. Consistently, the bone marrow of Vk*MYC mice fed high fiber diet was more infiltrated by IFNg-producing T lymphocytes while displaying less exhausted T cells and immunosuppressive myeloid cells. Conclusion This is the first interventional clinical trial and in vivo study to show that a HFPBD intervention may delay progression from MGUS/SMM to MM. To our knowledge there has been no similar dietary interventional study in hematological cancers or solid tumors. Together our in vivo and clinical data support the beneficial anti-inflammatory role of a HFPBD providing a link between diet, microbiota, and immune modulation to delay disease progression in MGUS/SMM.

ABSTRACTSpleen volume reduction (SVR) is a key endpoint in inhibitors of Janus kinase (JAK) inhibitor studies. Retrospective analyses have demonstrated an association between SVR and improved overall survival (OS) among patients treated with ruxolitinib with a platelet count > 100 × 109/L. Whether this association occurs in patients with thrombocytopenia is unclear. Pacritinib, a JAK2/IRAK1/ACVR1 inhibitor, demonstrated improved SVR versus best available therapy (BAT [best available therapy]; including ruxolitinib) in patients with myelofibrosis and platelet counts ≤ 100 × 109/L in the PERSIST‐2 study. Patients on study at the start of the 12‐week SVR window on pacritinib 200 mg twice daily or BAT were included. OS was evaluated among SVR responders versus non‐responders using different SVR thresholds (≥ 35%, ≥ 20%, ≥ 10%, and > 0%). Among patients on pacritinib (n = 89), SVR ≥ 10% demonstrated the greatest separation in OS curves between responders and non‐responders (HR, 0.00; 95% CI, 0.00–0.14; p < 0.01), though SVR ≥ 0% and SVR ≥ 20% were also associated with improved OS. No SVR threshold conferred OS benefit on BAT (n = 84), including ruxolitinib (n = 39). In patients with myelofibrosis and platelets ≤ 100 × 109/L, achieving SVR on pacritinib, but not BAT (including ruxolitinib), was associated with significant OS benefit, suggesting that pacritinib may offer a unique survival advantage in patients with myelofibrosis and thrombocytopenia who achieve any SVR. Trial Registration: ClinicalTrials.gov number: NCT02055781

PURPOSE Outcomes for patients with newly diagnosed multiple myeloma (NDMM) are heterogenous, with overall survival (OS) ranging from months to over 10 years. METHODS To decipher and predict the molecular and clinical heterogeneity of NDMM, we assembled a series of 1,933 patients with available clinical, genomic, and therapeutic data. RESULTS Leveraging a comprehensive catalog of genomic drivers, we identified 12 groups, expanding on previous gene expression–based molecular classifications. To build a model predicting individualized risk in NDMM (IRMMa), we integrated clinical, genomic, and treatment variables. To correct for time-dependent variables, including high-dose melphalan followed by autologous stem-cell transplantation (HDM-ASCT), and maintenance therapy, a multi-state model was designed. The IRMMa model accuracy was significantly higher than all comparator prognostic models, with a c-index for OS of 0.726, compared with International Staging System (ISS; 0.61), revised-ISS (0.572), and R2-ISS (0.625). Integral to model accuracy was 20 genomic features, including 1q21 gain/amp, del 1p, TP53 loss, NSD2 translocations, APOBEC mutational signatures, and copy-number signatures (reflecting the complex structural variant chromothripsis). IRMMa accuracy and superiority compared with other prognostic models were validated on 256 patients enrolled in the GMMG-HD6 (ClinicalTrials.gov identifier: NCT02495922 ) clinical trial. Individualized patient risks were significantly affected across the 12 genomic groups by different treatment strategies (ie, treatment variance), which was used to identify patients for whom HDM-ASCT is particularly effective versus patients for whom the impact is limited. CONCLUSION Integrating clinical, demographic, genomic, and therapeutic data, to our knowledge, we have developed the first individualized risk-prediction model enabling personally tailored therapeutic decisions for patients with NDMM.

Background: Pacritinib is a JAK1-sparing inhibitor of JAK2/IRAK1/ACVR1 that demonstrated symptom benefit measured by TSS (v2.0, excluding tiredness) vs best available therapy (BAT) in PERSIST-2, which enrolled cytopenic myelofibrosis patients with platelets ≤100×10 9/L. Recent datashowed that in patients with cytopenic MF, a ≥10% reduction in spleen volume at 12 weeks is associated with improved survival in patients treated with pacritinib ( Ajufo H, et al., J Clin Oncol;2023:14(16):Suppl). Surprisingly, this association was not confirmed in patients treated with BAT (82% of whom were on ruxolitinib). The association between other important measures of clinical benefit such as symptom burden reduction and anemia improvement on survival in patients treated with pacritinib has not previously been described. Methods: Patients randomized to pacritinib 200 mg BID and to BAT on PERSIST-2 were included if they were alive and on study at the start of the week 12 efficacy assessment period. Survival was assessed by Total Symptom Score (TSS; v2.0 excluding tiredness) reduction at various thresholds (≥50%, ≥20%, ≥10%, &gt;0%) and transfusion independence (TI) response. TI was assessed among patients who required red blood cell (RBC) transfusion at baseline (within 90 days) and was defined, for the purposes of a landmark survival analysis, as the absence of RBC transfusions over any 12-week period from first dose through week 14 (allowing for a ±2-week window around week 12). Overall survival (OS) was estimated via the K-M method following the landmark approach; survival in responders vs non-responders was compared using the log-rank test. Results: Of the 59 patients treated with pacritinib who had a reduction of TSS≥10%, the median age was 67 years, 25% had a baseline high-risk DIPSS, median platelet count was 61 x10 9/L, median hemoglobin was 9.7 g/dL, and baseline TSS was 19.1. Reduction of TSS≥10% was associated with improved OS, with 1 death among 59 responders vs 4 deaths among 30 non-responders (hazard ratio [HR]=0.12, 95% confidence interval [CI]: 0.01, 0.79] P=0.021, Fig 1a). Similar to spleen volume reduction, the association between TSS response and OS weakened at more stringent TSS response thresholds (Fig 1c, e), with the BAT arm not showing an association between TSS response and OS at any threshold. (Fig 1b, d, f). In order to assess the relationship of specific TSS domains and survival , a landmark OS analysis was performed based on ≥20% reduction in physical function scores (sum of ‘tiredness’ and 'inactivity'), spleen-related symptom scores (sum of 'abdominal discomfort', ‘early satiety’, and 'left rib pain'), and cytokine-related symptom scores (sum of 'itching', ‘night sweats’, and ‘bone pain‘). For cytokine-related symptoms, the number of deaths in PAC responders was significantly different compared to non-responders, with 0 deaths among 35 responders vs 2 among 15 non-responders ( P=0.0325). Conversely the deaths among responders (2/22) vs non-responders (2/20) were not significantly different in the BAT arm. For the physical function and spleen-related symptom subscales, no significant differences between PAC responders and non-responders was observed (HR=0.60; 95% CI [0.05, 6.74] P=0.679) and (HR=0.26; 95% CI 0.02, 2.93, P=0.2435) respectively. Among 36 patients on PAC who received RBC transfusions at baseline, 7 achieved TI over at least a 12-week period up to the time of the landmark analysis. There were no deaths among TI responders compared to 2 (6.9%) among TI non-responders. There were too few TI responders on BAT (only 2 out of 38) to assess the impact on survival. Conclusion: In cytopenic myelofibrosis patients enrolled in PERSIST-2, having a reduction of TSS≥10% on full-dose PAC was associated with OS benefit - a finding that has not been noted with other JAK inhibitors to date. By contrast, this association was not found with BAT, (82% of these patients received ruxolitinib). Thus, reductions in TSS in patients treated with PAC were associated with an OS benefit. It is possible that pacritinib, with its distinctive mechanism of action, may offer a unique survival advantage for MF patients with moderate or severe thrombocytopenia, and further studies are required to understand the potential mechanisms of these distinct clinical observations. Study funded by CTI BioPharma Corp., a Sobi company.

Introduction: Myelofibrosis (MF) is a clonal hematologic malignancy characterized by constitutive JAK-STAT activation and aberrant cytokine signaling. Allogeneic hematopoietic stem cell transplantation (allo-HCT) remains the only potentially curative therapy in MF. The contribution of disease-, patient- and donor-related factors to allo-HCT outcomes remains to be fully elucidated, as well as the presence of somatic mutations in genes such as ASXL1, EZH2, SRSF2, U2AF1 and IDH1/2 which are associated with worse prognosis in MF patients (pts). In this large multi- center retrospective analysis, we aimed to study the impact of clinical and molecular mutations on transplant outcomes. Methods: This analysis including 498 pts from 11 centers in North America and Canada. Univariate proportional-hazard Cox regression analysis stratified by center was used to assess the association of patient, transplant, and disease characteristics on overall survival (OS). Baseline patient demographic data and disease characteristics were selected as covariates in the multivariate analysis. Results: Pts transplanted between 2002-2021 were included in this analysis. Baseline and transplant characteristics are summarized in table 1. The 1- and 2-year OS was 77% (95% CI; 73-81) and 70% (95% CI; 66-74) and non-relapse mortality (NRM) 19% (95% CI: 17-21) and 23% (95% CI: 19-27), respectively. The cumulative incidence (CMI) of relapse at 1- and 2-years was 12% (95% CI; 10-14) and 16% (95% CI; 12-20). The CMI of acute graft versus host disease (aGVHD) grade II-IV was 31% (95% CI; 27-35) at 3 months and 42% (95% CI; 38-46) at 1-year post-transplant and grade was III-IV 13% (95% CI; 11-15) and 18% (95% CI; 14-22), respectively. The CMI of neutrophil engraftment at 1 and 3 months was 90% (95% CI: 87-93) and 97% (95% CI: 95-95) and for platelets 55% (95% CI: 50-59) and 80% (95% CI: 76-83). Univariate analysis included pts (age and gender), transplant (donor type and conditioning regimen intensity) and disease characteristics (DIPSS, mutations, cytogenetics (CG), blood counts, and spleen size). Hemoglobin &gt; 10 g/dL (HR .5, 95% CI .34 -.73 p=3 x 10 -4) and platelets &gt;50× 10 9/L (HR .59, 95% CI .42-.81, p=.0013) prior to transplant were associated with improved OS. High risk DIPSS was associated with decreased OS (p=0.0002). Mutations in ASXL1, EZH2, IDH1/2, U2AF1 and SRSF2 were not associated with decreased OS in this analysis (Figure 1). However, mutations in ZRSR2 were associated with inferior OS (HR 2.07, 95% CI 1.08-3.95, p=.0252). Lastly, JAK2 which had the most frequent mutations was not associated with OS (HR .0.93, 95% CI .65-1.31). There was no association between the CG risk groups and OS. Splenomegaly, measured radiographically, had no impact on OS but was strongly associated with engraftment (better engraftment defined as HR&gt;1). For platelets, spleen size of 15.6-18.9 cm HR of 0.69 (95% CI .47-1, p=.0489) and size &gt;18.9-22.5 cm HR of 0.48 ( 95% CI .33-.7, p=1x10^-4). For neutrophils, spleen size &gt;19.9-22.5 cm had a HR of 0.68, (95% CI .48-.96, p=.0268) and size&gt;22.5 cm had a HR of 0.65 (95% CI .46-.91, p=.0114). Mismatched unrelated (MMURD) and haplo identical donors had no impact on survival but were associated with delayed platelet engraftment; MMURD (HR .67, 95% CI .47-.96, p=.0298) and haploidentical donors (HR .56, 95% CI .39-.8, p=.0017). In a multivariate analysis adjusted for age, gender, highest DIPSS, donor type and conditioning regimen, platelets &gt; 50× 10 9/L (HR .61, 95% CI .44-.87, p=.0053) hemoglobin &gt;10 g/dL (HR .6, 95% CI .4-.9, p=.0244) and lower DIPSS at the time of transplant were associated with improved OS. Conclusions: In this large multicenter analysis only clinical variables; hemoglobin and platelets, were found to be associated with OS after allo-HCT in MF patients. Somatic mutations associated with poor prognosis were not associated with OS suggesting that transplant can overcome their negative impact. Splenomegaly was associated with delayed engraftment but not OS. Interestingly, using alternative donors (MMURD and haplo identical) didn't have a negative effect on OS, possibly reflecting the use of post-transplant cyclophosphamide for GVHD prophylaxis in recent years. These results highlight the importance of biologic factors in the prognostication of outcomes in MF pts undergoing allo-HCT independent of somatic mutations. Supported by the American Society of Hematology (ASH) and MPN Research Foundation

7018 Background: MF is a life-limiting malignancy characterized by marrow fibrosis, splenomegaly, and progressive cytopenias. JAK2 inhibitors can reduce spleen volume, which is considered a surrogate for disease response. For example, ≥10% SVR on ruxolitinib (RUX) is associated with improved OS among patients with platelet (PLT) counts ≥100×109/L. RUX cannot be administered at full dose in patients with lower PLTs, and it is not known whether the association between SVR and OS persists in such patients. PAC is a JAK1-sparing inhibitor of JAK2/IRAK1/ACVR1 that demonstrated SVR benefit vs BAT (including RUX) in PERSIST-2, which enrolled MF patients with PLTs ≤100×109/L. Here we present a retrospective landmark OS analysis of the relationship between SVR and OS on PERSIST-2. Methods: This analysis includes PERSIST-2 patients who were alive and on study at the start of the 12-week SVR window (study week 10) on PAC 200 mg BID or BAT. Spleen volume was assessed radiographically (MRI or CT). OS was evaluated among SVR responders vs non-responders within each treatment arm using different SVR thresholds (≥35%, ≥20%, ≥10%, > 0%) and a landmark analysis methodology. OS was compared using the log-rank test. Results: Among patients on PAC (n = 89), any SVR ( > 0%) at 12 weeks was significantly associated with improved survival (HR = 0.08 [95% CI: 0.01, 0.51], P = 0.0007). Among all SVR response thresholds, SVR ≥10% demonstrated the greatest separation in OS curves between responders vs. non-responders on PAC, with no deaths on study among 65 responders compared to 5 deaths among 24 non-responders (HR = 0.0 [95% CI: 0.0, 0.14], P < 0.0001). By contrast, SVR did not predict OS benefit on BAT (n = 84), including RUX (n = 39). For example, 11% (3/28) of patients on BAT who achieved SVR ≥10% died compared to a similar number (14%, 8/56) of non-responders (HR = 0.63 [95% CI: 0.17, 2.37], P = 0.49). Of the 28 patients on BAT who achieved SVR ≥10%, 23 (82%) were treated with RUX. Among these 23 patients, most patients were receiving low-dose RUX at the time of the landmark: 78% were on ≤10 mg BID and 43% were on £5 mg BID. By contrast, the median relative dose intensity on PAC was 100% (200 mg BID) through week 12 among both SVR ≥10% responders and non-responders. Conclusions: In MF patients with PLTs ≤100×109/L, achieving SVR on full-dose PAC was associated with significant OS benefit. By contrast, this association was not found with BAT, even though most responders were on RUX, albeit at low doses. As PAC can be given at full dose regardless of PLT count, it is possible that PAC may offer a unique survival advantage for MF patients with moderate or severe thrombocytopenia who achieve spleen reduction. Clinical trial information: NCT02055781 .