Ruxopeg, a Multi-Center Bayesian Phase 1/2 Adaptive Randomized Trial of the Combination of Ruxolitinib and Pegylated Interferon Alpha 2a in Patients with Myeloproliferative Neoplasm (MPN)-Associated Myelofibrosis
Authors: Kiladjian Jean-Jacques , Soret-Dulphy Juliette , Resche-Rigon Matthieu , Boyer-Perrard Francoise , Barraco Fiorenza , Rolland-Neyret Valérie , Capron Claude , Chevret Sylvie , Giraudier Stephane , Cassinat Bruno 
Published: October 2019

Abstract
Background
MPN-associated myelofibrosis (MF) is a condition characterized by splenomegaly, anemia, bone marrow (BM) fibrosis and debilitating symptoms. About 80% of patients (pts) harbor a driver mutations in JAK2, CALR or MPL genes that can be used as biomarkers for minimal residual disease assessment. Ruxolitinib (Rux) is a JAK inhibitor approved in intermediate or high risk (HR) MF to improve symptoms and splenomegaly but with little impact on the malignant clone and fibrosis. Interferon alpha (IFNa) can reduce mutant allele burden and fibrosis but is often poorly tolerated in highly symptomatic pts. The RUXOPEG study was designed to assess the efficacy and safety of the combination of Rux + IFNa in MF (NCT02742324).
Methods
RUXOPEG is a multi-center Bayesian Phase 1/2 adaptive trial. Phase 1 includes up to 9 cohorts of 3 pts with increasing doses of both drugs. Tested doses of Rux and IFNa are 10, 15 and 20 mg BID, and 45, 90 and 135 mcg/week, respectively. Phase 2 will randomize between the 2 best dose combinations selected from phase 1. Primary objective: identify the most efficacious dose combination that also satisfies safety requirements. Primary tolerance criterion is the occurrence of dose limiting toxicities (DLT) within 45 days; primary efficacy criterion is >50% reduction in spleen length within 6 months. Secondary objectives include molecular response, reduction of BM fibrosis, quality of life and symptoms evolution, event-free and overall survival. The planned total enrollment is 42 pts. Key inclusion criteria are: diagnosis of MF (WHO criteria), intermediate or HR (IPSS), need of active therapy, presence of a driver mutation. Key exclusion criteria: prior treatment (or contra-indication) with Rux or IFNa, eligibility for stem cell transplantation, inadequate liver, cardiac or renal function, autoimmune disease, history of depression.
Enrolment in 5 cohorts was completed in June 2018, and the last cohort for phase 1 will be opened in August. This abstract reports the current available data for the 5 cohorts who have completed the primary endpoint, but the presentation will provide the detailed analysis of primary and secondary endpoints of phase 1, which will be available in October 2018.
Results
Among the 15 pts currently enrolled in phase 1, 6 were females, mean age was 60.9 years (range: 38-72), 8 had primary MF, 5 post ET and 2 post PV MF. Median spleen size was 6 cm (range 0 - 18) by palpation and 18 cm (range 10-25) by imaging. Mean (range) blood counts were: hemoglobin 12 g/dL (8.5 - 13.8), WBC 18.3 G/L (8 - 35.5), platelets 457 G/L (157 - 906) and 6 pts had circulating blasts. 12 pts had JAK2V617F and 2 had CALR mutations; karytotype was normal in 9 pts, abnormal in 5 (very HR in 3). In 10 pts analyzed by NGS so far, 8 had additional mutations (1 in 5 pts, 3 in 1, and 4 in 2) in TET2 (n= 5), ASXL1 (4), DNMT3A (2), TP53 (2), SF3B1 (1) and SRSF2 (1) genes.
Safety: No DLT was observed in the 5 cohorts (primary safety criterion), the highest tested dose combination being Rux 15 mg BID + IFNa 135 mcg/week. The last cohort will test Rux 20 mg BID + IFNa 135 mcg/week. 4 serious adverse events have been reported: 1 AML transformation (very HR cytogenetics, 3% circulating blasts at baseline), 1 thrombotic event, 1 squamous cell carcinoma and 1 aggravation of Raynaud's phenomenon.
Efficacy: preliminary data show a clear decrease in spleen size at 6 months (median 0 cm by palpation, range 0-9; 12.1 cm by imaging, range 10-21) and improvement in blood counts (mean, range): hemoglobin 10.5 g/dL (9.7 - 12.5), WBC 8.6 G/L (5.4 - 11.1), platelets 267 G/L (80 - 486). According to IWG criteria, all the 10 pts evaluable at time of abstract preparation responded (3 partial response, 7 hematological improvement). JAK2V617F allele burden decreased from a mean of 75% (range 43- 96) at baseline to 46% (range 24 - 84) at 6 months. Encouraging results were also found in a patient with 5 mutations (figure1) with a clear decrease in JAK2V617F, ASXL1, DNMT3A and EZH2 mutations after 12 months of treatment.
Conclusion
RUXOPEG is the first study to formally assess the safety and efficacy of Rux + IFNa combination in MF patients never exposed to either drugs before. The first 5 dose combinations tested showed no DLT, confirming that this combination was generally well tolerated. Preliminary efficacy results are encouraging, including in patients who received very low doses of both drugs. Full results of the 6 cohorts tested in phase 1 and doses selected for phase 2 will be presented.

Disclosures
Kiladjian: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; AOP Orphan: Membership on an entity's Board of Directors or advisory committees, Research Funding. Giraudier:Novartis: Research Funding. Cassinat:Novartis: Research Funding; AOP Orphan: Research Funding.