Pacritinib vs Best Available Therapy, Including Ruxolitinib, in Patients With Myelofibrosis: A Randomized Clinical Trial

Importance

Myelofibrosis is a hematologic malignancy characterized by splenomegaly and debilitating symptoms. Thrombocytopenia is a poor prognostic feature and limits use of Janus kinase 1 (JAK1)/Janus kinase 2 (JAK2) inhibitor ruxolitinib.

Objective

To compare the efficacy and safety of JAK2 inhibitor pacritinib with that of best available therapy (BAT), including ruxolitinib, in patients with myelofibrosis and thrombocytopenia.

Design, Setting, and Participants

For this phase 3 randomized international multicenter study-the PERSIST-2 study-of pacritinib vs BAT, 311 patients with myelofibrosis and platelet count 100 × 109/L or less were recruited for analysis. Crossover from BAT was allowed after week 24 or for progression of splenomegaly.

Interventions

Patients were randomized 1:1:1 to pacritinib 400 mg once daily, pacritinib 200 mg twice daily, or BAT.

Main Outcomes and Measures

Coprimary end points were rates of patients achieving 35% or more spleen volume reduction (SVR) and 50% or more reduction in total symptom score (TSS) at week 24. Efficacy analyses were performed on the intention-to-treat efficacy population, comprising all patients with a randomization date allowing for week 24 data.

Results

Overall, 311 patients (mean [SD] age, 63.70 [9.08] years; 171 men [55%] and 140 women [45%]) were included in the study; 149 patients (48%) had prior ruxolitinib. The most common BAT was ruxolitinib (44 patients [45%]); 19 patients (19%) received watchful-waiting only. The intention-to-treat efficacy population included 75 patients randomized to pacritinib once daily; 74, pacritinib twice daily, and 72, BAT. Pacritinib (arms combined) was more effective than BAT for 35% or more SVR (27 patients [18%] vs 2 patients [3%]; P = .001) and had a nonsignificantly greater rate of 50% or more reduction in TSS (37 patients [25%] vs 10 patients [14%]; P = .08). Pacritinib twice daily led to significant improvements in both end points over BAT (≥35% SVR: 16 patients [22%] vs 2 patients [3%]; P = .001; ≥50% reduction in TSS: 24 patients [32%] vs 10 patients [14%]; P = .01). Clinical improvement in hemoglobin and reduction in transfusion burden were greatest with pacritinib twice daily. For pacritinib once daily, pacritinib twice daily, and BAT, the most common (>10%) grade 3 or 4 adverse events were thrombocytopenia (32 patients [31%], 34 patients [32%], 18 patients [18%]), and anemia (28 patients [27%], 23 patients [22%], 14 patients [14%]). In the pacritinib once daily, twice daily, and BAT arms, discontinuation owing to adverse events occurred in 15 patients (14%), 10 patients (9%), and 4 patients (4%).

Conclusions and Relevance

In patients with myelofibrosis and thrombocytopenia, including those with prior anti-JAK therapy, pacritinib twice daily was more effective than BAT, including ruxolitinib, for reducing splenomegaly and symptoms.

Trial Registration

clinicaltrials.gov Identifier: NCT02055781.

Updated results from the phase 3 HELIOS study of ibrutinib, bendamustine, and rituximab in relapsed chronic lymphocytic leukemia/small lymphocytic lymphoma

We report follow-up results from the randomized, placebo-controlled, phase 3 HELIOS trial of ibrutinib+bendamustine and rituximab (BR) for previously treated chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) without deletion 17p. Overall, 578 patients were randomized 1:1 to either ibrutinib (420 mg daily) or placebo, in combination with 6 cycles of BR, followed by ibrutinib or placebo alone. Median follow-up was 34.8 months (range: 0.1-45.8). Investigator-assessed median progression-free survival (PFS) was not reached for ibrutinib+BR, versus 14.3 months for placebo+BR (hazard ratio [HR] [95% CI], 0.206 [0.159-0.265]; P < 0.0001); 36-month PFS rates were 68.0% versus 13.9%, respectively. The results are consistent with the primary analysis findings (HR = 0.203, as assessed by independent review committee, with 17-month median follow-up). Median overall survival was not reached in either arm; HR (95% CI) for ibrutinib+BR versus placebo: 0.652 (0.454-0.935; P = 0.019). Minimal residual disease (MRD)-negative response rates were 26.3% for ibrutinib+BR and 6.2% for placebo+BR (P < 0.0001). Incidence of treatment-emergent adverse events (including grades 3-4) were generally consistent with the initial HELIOS report. These long-term data support improved survival outcomes and deepening responses with ibrutinib+BR compared with BR in relapsed CLL/SLL.

Ibrutinib combined with bendamustine and rituximab (BR) in previously treated chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL): First results from a randomized, double-blind, placebo-controlled, phase III study

LBA7005

Background: The phase III HELIOS study evaluated the first-in-class, oral covalent BTK inhibitor ibrutinib in combination with BR (BR+ibr) vs BR plus placebo (BR+plb) in patients (pts) with previously treated CLL/SLL. The preplanned interim analysis reported here showed that the primary end point was met, upon which the IDMC recommended unblinding the study. Methods: Pts received BR ( ≤ 6 cycles) and were randomized 1:1 to ibr (420 mg daily) or plb. Purine analog refractoriness was a stratification factor. Pts with del17p ( > 20% of cells) were excluded. Primary end point was independent review committee (IRC)-assessed progression-free survival (PFS). Secondary end points included overall survival (OS) and overall response rate (ORR) per IRC. Results: 578 pts were randomized (289 per arm); median age 64 yrs; 38% Rai Stage III/IV; median 2 prior therapies. 6 cycles of BR were completed in 83% and 78% of pts in the ibr and plb arms, respectively. At a median follow-up of 17.2 months, IRC-assessed PFS was significantly longer with BR+ibr vs BR+plb (median not reached vs 13.3 months; HR: 0.203, 95% CI: 0.150-0.276, P< 0.0001); PFS results were consistent across high-risk subgroups. ORR and CR/CRi rates were 82.7% vs 67.8% (P< 0.0001) and 10.4% vs 2.8%. Median OS was not reached. 90 pts (31%) in the BR+plb arm with confirmed PD crossed over to receive ibr, as permitted per the protocol. Incidence of most AEs was similar between arms. The most common all-grade AEs with BR+ibr and BR+plb were neutropenia (58.2% vs 54.7%) and nausea (36.9% vs 35.2%); most common grade 3/4 AEs were neutropenia (53.7% vs 50.5%) and thrombocytopenia (15.0% each arm). Rates of grade 3/4 atrial fibrillation were 2.8% and 0.7%, and major hemorrhage were 2.1% and 1.7%. Fatigue (FACIT-Fatigue) was improved with BR+ibr vs BR+plb. Conclusions: The addition of ibr to BR reduced the risk of progression or death by 80% compared with BR+plb. ORR was also significantly improved. Safety of BR+ibr was consistent with the known profiles for BR and ibr. The data further support ibr as an important treatment option for pts with previously treated CLL/SLL. Clinical trial information: EudraCT No. 2012-000600-15; UTN No. U1111-1135-3745.