European real-world data further confirm the efficacy of ruxolitinib in patients with PV refractory/intolerant to hydroxyurea

The results from the phase III trial RESPONSE (NCT01243944) led to ruxolitinib's approval for patients with polycythemia vera (PV) that showed resistance or intolerance to hydroxyurea. Treatment with ruxolitinib for 8 weeks achieved a hematocrit control without phlebotomy and a ≥ 35% reduction in spleen size in 20.9% of patients, significantly improving the results reported with the alternative therapies. After a 5-year follow-up, 70% of patients who initially benefited from ruxolitinib, maintained their response. Moreover, patients experienced fewer thromboembolic events and lower rates of serious AEs when compared with the best available treatment.¹

To further confirm the positive results of ruxolitinib in this setting in the real-world clinical practice and unselected patient population, Peter AW te Boekhorst, Erasmus Medical Center, NL, gathered the experience from 88 hospitals across Europe. Here, we summarize the key findings of the 52-week interim analysis presented at the 25th European Hematology Association (EHA) Virtual Congress.²

Study design

• Phase IV observational, non-interventional study, to monitor patients with PV treated with ruxolitinib for 24 months. Patients were eligible if they had started ruxolitinib treatment for up to 6 months before trial inclusion
• Primary endpoint: Describe patient and disease characteristics of 352 individuals treated with ruxolitinib according to the approved label, after confirmed resistance or intolerance to hydroxyurea
• Secondary endpoint: Report the safety and efficacy of ruxolitinib in real-world clinical practice, and report the cardiovascular risk in this patient population

Results

• This publication reports the 52-week interim results of 60 patients, 98.3% of which were resistant or intolerant to hydroxyurea according to European LeukemiaNet criteria
• Patient characteristics can be found in Table 1

Table 1. Baseline patient characteristics²

HU, hydroxyurea *Data available from 55 patients †Data available from 22 patients
Characteristic	N = 60 patients
Age, > 60 years, %	65
HU resistant, %	65.5
HU intolerant, %	61.7
Active infection, %	18
Secondary neoplasms, %	10
Thromboembolic events, %	17
Hematocrit*, %
< 40%	10.9
≥ 40 – ≤ 45%	45.1
> 45%	43.6
Splenomegaly†, %
No enlargement (0 cm)	50
Mild (< 4 cm)	13.6
Moderate (4–8 cm)	18.2
Massive (> 8 cm)	18.2
Phlebotomy-independent patients, %	38

 Efficacy

• Rapid reduction and subsequent stabilization of hematocrit levels were observed during the first 12 weeks of treatment
• 88% of patients achieved phlebotomy-independence during the first year of treatment with ruxolitinib compared with 38% at baseline. Similarly, only 5% of patients required three or more phlebotomies after ruxolitinib treatment compared with 40% before treatment
• In three patients the grade of splenomegaly was maintained, while eight patients showed a mean of 60% spleen reduction
• In the 81 surveys completed so far, 79% of patients reported much improved Pruritus Symptoms Impact Scale (PSIS) scores during treatment with ruxolitinib

Safety

• During the study, 80% of patients maintained continuous ruxolitinib dosing, while 17% of patients interrupted ruxolitinib once, and 3% more than once, mainly because of transient anemia and infections
• An increase in platelets from baseline was observed initially (average, 439 × 10⁹/L), but levels were back to baseline at week 52 (388.9 × 10⁹/L)
• Concomitant medication was frequent and needed to be monitored: 65% of patients were treated for cardiovascular disease, 70% for gastrointestinal or metabolic diseases and 73.3% received an anticoagulant treatment with acetylsalicylic acid at some point of the study
• Additional safety outcomes are reported in Table 2

Table 2. Severe adverse events reported during the study²

Grade 3–4 adverse events	Incidence, % (N = 60 patients)
Infections	5
Hypertension	5
Thromboembolic events	3
Secondary neoplasms	2

 Conclusion

The preliminary results of this observational study support the reported study results of ruxolitinib in patients with PV. Patients achieved hematocrit control, reduced the dependence on phlebotomies, and maintained or even reduced the spleen size during the first year of continuous treatment. This study is ongoing and will further describe ruxolitinib's role in PV management once the data from all 352 patients will be available.