Relationship Between Patient-Reported Outcomes (PROs) and Health-Related Quality of Life (HRQoL) and Efficacy in Patients with Myelofibrosis in the Phase III Persist-1 Trial of Pacritinib Vs. Best Available Therapy (BAT)

Introduction: Myelofibrosis (MF) is a life-threatening hematologic malignancy characterized by splenomegaly and debilitating symptoms including fatigue, abdominal pain, night sweats, bone pain, pruritus, and unintentional weight loss. The myeloproliferative neoplasm symptom assessment form (MPN-SAF) is a PRO tool designed to measure MF-related symptom burden and was developed and validated at Mayo Clinic. It was modified (MPN-SAF total symptom score [TSS] and TSS 2.0) for use in the PERSIST-1 and PERSIST-2 phase 3 trials. For PERSIST-1, when examining the 6 common symptoms in both TSS versions (tiredness, night sweats, early satiety, itchiness, bone pain, and abdominal pain), pacritinib-treated patients (pts) had significant improvements in TSS overall and in individual symptoms vs BAT; Pt Global Impression of Change (PGIC) was also significantly improved for pts receiving pacritinib. Improvements in EORTC-QLQ-C30 scales were noted in the pacritinib arm (Mesa, EHA 2015). The proportion of pts achieving spleen volume reduction (SVR) ≥35% at Week 24 was significantly greater with pacritinib vs BAT (ITT: 19.1% vs 4.7%, p=0.0003; evaluable at baseline and Week 24: 25.0% vs 5.9%; p=0.0001). This analysis examines relationships between TSS improvement and changes in splenomegaly and HRQoL outcomes.

Methods: Pts who received no prior JAK inhibitor therapy were randomized 2:1 to oral pacritinib 400 mg once daily or BAT. Pts were stratified by DIPSS risk (Int-1/Int-2 vs High) and platelet count (<50,000/μL vs 50,000/μL to <100,000/μL vs ≥100,000/μL). Pts must have had a baseline total TSS ≥13 using MPN-SAF TSS 2.0. Each symptom is rated on a scale from 0 (absent) to 10 (worst imaginable) using MPN-SAF TSS and TSS 2.0. Results for the 6 symptoms common to both TSS versions are reported. Additional PROs used for assessment of HRQoL included EORTC QLQ-C30 and EQ-5D-5L. In multivariate logistic regressions, odds of TSS reduction ≥50% at Week 24 were modeled as a function of Week 24 SVR ≥35%, spleen length reduction (SLR) ≥ 50%, PGIC, improvement in each EORTC scale, and improvement in EQ-5D-5L Overall Health State (OHS) and in each dimension individually while adjusting for treatment (pacritinib vs BAT). Correlations were examined in all pts and by baseline platelet counts (<50,000/μL, <100,000/μL, and ≥100,000/μL).

Results: A total of 327 pts were enrolled (PAC: 220, BAT: 107). 62% of pts had primary MF, 32% had baseline platelets <100,000/μL, and 16% had baseline platelets <50,000/μL. TSS reduction ≥50% was found to be associated with SVR ≥35% and  improvement in splenomegaly (SLR ≥50%). In the total pt population, there was a significant association between TSS reduction and SVR (odds ratio [OR]=2.60, p=0.016). In all pts, there was a significant association between TSS reduction and improvements in OHS as measured by EQ-5D-5L (OR=2.30, p=0.013). TSS reductions were also marginally associated with improvements in the QLQ-C30 Global Health Scale (GHS)/QoL Scale (OR=1.92, p=0.050) and, though not statistically significant, there was a trend of improvement in perceived overall health as measured by PGIC (OR=2.16, p=0.118). TSS reductions were further examined in pts grouped by baseline platelet count. Improvement in EQ-5D-5L OHS was marginally associated with TSS reductions in pts with platelets <50,000/μL (OR=6.03, p=0.057). For pts with platelets <100,000/μL, reductions in TSS were significantly associated with reductions in splenomegaly (SLR ≥50%; OR=9.53, p=0.004), and improvements in the QLQ-C30 GHS/QoL domain (OR=4.03, p=0.022) as well as the EQ-5D-5L OHS (OR=5.49, p=0.008). A significant association between TSS reductions and SVR ≥35% was observed in pts with platelets ≥100,000/μL (OR=3.99, p=0.005). In all pts, improvements in Fatigue as measured by QLQ-C30 were significantly associated with TSS reductions (OR=2.20, p=0.019) as well as in pts with baseline platelets <50,000/μL (OR=17.88, p=0.008) and <100,000/μL (OR=10.18, p<0.001).

Conclusions: In the total pt population, TSS reduction was associated with improvements in spleen response and perceived overall health. This trend was also observed in pts with low baseline platelet counts. Additionally, TSS reduction was significantly associated with improvements in fatigue, a major contributor to poor HRQoL in pts with MF. This reinforces the clinical relevance of measuring TSS using a validated instrument as an endpoint in MF trials.