Gerds, Aaron T.

Abstract Purpose: Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by systemic symptoms, cytopenias, organomegaly, and bone marrow fibrosis. JAK2 inhibitors afford symptom and spleen burden reduction but do not alter the disease course and frequently lead to thrombocytopenia. TGFβ, a pleiotropic cytokine elaborated by the MF clone, negatively regulates normal hematopoiesis, downregulates antitumor immunity, and promotes bone marrow fibrosis. Our group previously showed that AVID200, a potent and selective TGFβ 1/3 trap, reduced TGFβ1-induced proliferation of human mesenchymal stromal cells, phosphorylation of SMAD2, and collagen expression. Moreover, treatment of MF mononuclear cells with AVID200 led to increased numbers of progenitor cells (PC) with wild-type JAK2 rather than JAK2V617F. Patients and Methods: We conducted an investigator-initiated, multicenter, phase Ib trial of AVID200 monotherapy in 21 patients with advanced MF. Results: No dose-limiting toxicity was identified at the three dose levels tested, and grade 3/4 anemia and thrombocytopenia occurred in 28.6% and 19.0% of treated patients, respectively. After six cycles of therapy, two patients attained a clinical benefit by IWG-MRT criteria. Spleen and symptom benefits were observed across treatment cycles. Unlike other MF-directed therapies, increases in platelet counts were noted in 81% of treated patients with three patients achieving normalization. Treatment with AVID200 resulted in potent suppression of plasma TGFβ1 levels and pSMAD2 in MF cells. Conclusions: AVID200 is a well-tolerated, rational, therapeutic agent for the treatment of patients with MF and should be evaluated further in patients with thrombocytopenic MF in combination with agents that target aberrant MF intracellular signaling pathways.

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 .

7016 Background: Many patients (pts) with myelofibrosis (MF) experience anemia resulting from disease or JAK inhibitor therapy. The open-label, phase 2 ACE-536-MF-001 study (NCT03194542) evaluated the safety and efficacy of luspatercept (LUSPA) for the treatment of MF-related anemia. Methods: Eligible pts comprised 4 cohorts based on transfusion dependence (TD, defined as receiving 4–12 red blood cell [RBC] units/84 days [d] immediately up to cycle 1 d 1) and stable ruxolitinib (RUX) treatment; cohort 1: no TD, no RUX; cohort 2: TD, no RUX; cohort 3A: no TD, RUX; cohort 3B: TD, RUX. Pts received subcutaneous LUSPA 1.0 mg/kg (1.33 mg/kg for pts in cohort 3B expansion) with titration up to 1.75 mg/kg in 21-d cycles. Disease response was assessed at d 169 and treatment extended for pts showing clinical benefit; pts were followed for ≥ 3 years (y) post last dose. The primary endpoint was anemia response (defined as 84 consecutive d: ≥ 1.5 g/dL hemoglobin [Hgb] from baseline without transfusion [cohorts 1 and 3A] or RBC transfusion-free [cohorts 2 and 3B]); secondary endpoints included duration of response (DOR), transfusion frequency, change in Hgb level, and symptom response. Results: Of 95 pts in the ITT group, the most common reason for treatment discontinuation was lack of clinical benefit at d 169 (n = 28). Median (range) age was 71.0 (50–89) y. Most (54.7%) pts had primary MF, intermediate-risk 2 disease (75.8%), and > 2 y since initial diagnosis (74.7%). Median prior RUX therapy was 18.1 months (cohorts 3A/3B) and 84.7% of pts had baseline transfusion burden 6–12 units/84 d (cohorts 2/3B). Mean treatment duration was 42.8 weeks. Cohort 3B had the highest anemia response rate with 26.3% (95% CI, 13.4–43.1) of pts transfusion independent during the primary treatment period and 31.6% (95% CI, 17.5–48.7) transfusion independent during the entire treatment period; median (range) DOR was 448 d (85–1582). In cohort 3B: 19 (50.0%) pts had reduced transfusion burden by ≥ 50% during the primary treatment period; 8 (21.1%) pts achieved mean Hgb increase ≥ 1.5 g/dL from baseline throughout the entire treatment period and 6 (15.8%) achieved a mean ≥ 50% reduction in symptom score from baseline. Overall, 47.4% of pts had ≥ 1 treatment-related adverse event (TRAE), most frequently hypertension (17.9%, 5.3% grade ≥ 3); 3.2% of pts had a serious TRAE. One TRAE led to LUSPA discontinuation. Two (2.1%) pts had transformation to acute myeloid leukemia. Nine pts died on treatment from: post-procedural hemorrhage, pneumonia, intracranial hemorrhage, septic shock, ischemic stroke, multiple organ dysfunction syndrome, renal failure, pneumonitis, and myelofibrosis (n = 1 each); no deaths were considered related to the study drug. Conclusions: In pts with MF, the safety profile of LUSPA was consistent with previous studies and efficacy results showed promising improvements in anemia and transfusion burden in all cohorts. Clinical trial information: NCT03194542 .

AbstractHaploidentical donors offer a potentially readily available donor, especially for non-White patients, for blood or marrow transplantation (BMT). In this collaboration across North America, we retrospectively analyzed outcomes of first BMT using haploidentical donor and posttransplantation cyclophosphamide (PTCy) in MDS/MPN-overlap neoplasms (MDS/MPN), an otherwise incurable hematological neoplasm. We included 120 patients, 38% of non-White/Caucasian ethnicity, across 15 centers with median age at BMT 62.5 years. The median follow-up is 2.4 years. Graft failure was reported in 6% patients. At 3-years, nonrelapse mortality (NRM) was 25%, relapse 27%, grade 3-4 acute graft versus host disease (GVHD) 12%, chronic GVHD requiring systemic immunosuppression 14%, progression-free survival (PFS) 48% and overall survival (OS) 56%. On multivariable analysis, statistically significant associations included older age at BMT (per decade increment) with NRM (sdHR 3.28, 95%CI 1.30-8.25), PFS (HR 1.98, 95% 1.13-3.45) and OS (HR 2.01, 95% CI 1.11-3.63), presence of mutation in EZH2/RUNX1/SETBP1 with relapse (sdHR 2.61, 95%CI 1.06-6.44), and splenomegaly at BMT/prior splenectomy with OS (HR 2.20, 95%CI 1.04-4.65). Haploidentical donors are a viable option for BMT in MDS/MPN, especially for those disproportionately represented in the unrelated donor registry. Disease-related factors including splenomegaly and high-risk mutations dominate outcomes following BMT.

Abstract Novel treatment strategies are needed for the treatment of Philadelphia chromosome–positive (Ph+) acute lymphoblastic leukemia (ALL) in older patients. This trial evaluated the feasibility and outcomes with the anti-CD19 bispecific T-cell–engaging antibody, blinatumomab, in combination with dasatinib and steroids. Patients 65 years of age or older with Ph+ or Ph-like ALL (with dasatinib-sensitive fusions/mutations) were eligible and could be newly diagnosed or relapsed/refractory. Induction therapy consisted of dasatinib/prednisone. Patients not achieving response by day 56 proceeded to blinatumomab reinduction therapy. Patients achieving response with induction or reinduction therapy proceeded to blinatumomab/dasatinib postremission therapy for 3 cycles followed by dasatinib/prednisone maintenance. All patients received central nervous system prophylaxis with intrathecal methotrexate for a total of 8 doses. Response was assessed at days 28, 56, and 84 and at additional time points based on response parameters. Measurable residual disease was assessed centrally by 8-color flow cytometry at day 28. A total of 24 eligible patients with newly diagnosed Ph+ ALL were enrolled with a median age of 73 years (range, 65-87 years). This combination was safe and feasible. With a median of 2.7 years of follow-up, 3-year overall survival and disease-free survival were 87% (95% confidence interval [CI], 64-96) and 77% (95% CI, 54-90), respectively. Although longer follow-up is needed, these results are encouraging, and future trials are building on this backbone regimen. This trial was registered at www.clinicaltrials.gov as #NCT02143414.