Long-Term Safety, Efficacy, and Survival Findings From Comfort-II, a Phase 3 Study Comparing Ruxolitinib with Best Available Therapy (BAT) for the Treatment of Myelofibrosis (MF)

Ruxolitinib is a potent JAK1 & 2 inhibitor that has demonstrated superiority over traditional therapies for the treatment of MF. In the two phase 3 COMFORT studies, ruxolitinib demonstrated rapid and durable reductions in splenomegaly and improved MF-related symptoms and quality of life. COMFORT-II is a randomized, open-label study evaluating ruxolitinib versus BAT in patients (pts) with MF. The primary and key secondary endpoints were both met: the proportion of pts achieving a response (defined as a ≥ 35% reduction in spleen volume) at wk 48 (ruxolitinib, 28.5%; BAT, 0%; P < .0001) and 24 (31.9% and 0%; P < .0001), respectively. The present analyses update the efficacy and safety findings of COMFORT-II (median follow-up, 112 wk).

In COMFORT-II, 219 pts with intermediate-2 or high-risk MF and splenomegaly were randomized (2:1) to receive ruxolitinib (15 or 20 mg bid, based on baseline platelet count [100-200 × 10⁹/L or > 200 × 10⁹/L, respectively]) or BAT. Efficacy results are based on an intention-to-treat analysis; a loss of spleen response was defined as a > 25% increase in spleen volume over on-study nadir that is no longer a ≥ 35% reduction from baseline. Overall survival was estimated using the Kaplan-Meier method.

The median follow-up was 112 wk (ruxolitinib, 113; BAT, 108), and the median duration of exposure 83.3 wk (ruxolitinib, 111.4 [randomized and extension phases]; BAT, 45.1 [randomized treatment only]). Because the core study has completed, all pts have either entered the extension phase or discontinued from the study. The primary reasons for discontinuation were adverse events (AEs; ruxolitinib, 11.6%; BAT, 6.8%), consent withdrawal (4.1% and 12.3%), and disease progression (2.7% and 5.5%). Overall, 72.6% of pts (106/146) in the ruxolitinib arm and 61.6% (45/73) in the BAT arm entered the extension phase to receive ruxolitinib, and 55.5% (81/146) of those originally randomized to ruxolitinib remained on treatment at the time of this analysis. The primary reasons for discontinuation from the extension phase were progressive disease (8.2%), AEs (2.1%), and other (4.1%).

Overall, 70 pts (48.3%) treated with ruxolitinib achieved a ≥ 35% reduction from baseline in spleen volume at any time during the study, and 97.1% of pts (132/136) with postbaseline assessments experienced a clinical benefit with some degree of reduction in spleen volume. Spleen reductions of ≥ 35% were sustained with continued ruxolitinib therapy (median duration not yet reached); the probabilities of maintaining the spleen response at wk 48 and 84 are 75% (95% CI, 61%-84%) and 58% (95% CI, 35%-76%), respectively (Figure). Since the last report (median 61.1 wk), an additional 9 and 12 deaths were reported in the ruxolitinib and BAT arms, respectively, resulting in a total of 20 (14%) and 16 (22%) deaths overall. Although there was no inferential statistical testing at this unplanned analysis, pts randomized to ruxolitinib showed longer survival than those randomized to BAT (HR = 0.52; 95% CI, 0.27–1.00).

As expected, given the mechanism of action of ruxolitinib as a JAK1 & 2 inhibitor, the most common new or worsened grade 3/4 hematologic abnormalities during randomized treatment were anemia (ruxolitinib, 40.4%; BAT, 23.3%), lymphopenia (22.6%; 31.5%), and thrombocytopenia (9.6%; 9.6%). In the ruxolitinib arm, mean hemoglobin levels decreased over the first 12 wk of treatment and then recovered to levels similar to BAT from wk 24 onward; there was no difference in the mean monthly red blood cell transfusion rate among the ruxolitinib and BAT groups (0.834 vs 0.956 units, respectively). Nonhematologic AEs were primarily grade 1/2. Including the extension phase, there were no new nonhematologic AEs in the ruxolitinib group that were not observed previously (in ≥ 10% of pts), and only 1 pt had a new grade 3/4 AE (epistaxis).

In COMFORT-II, ruxolitinib provided rapid and durable reductions in splenomegaly; this analysis demonstrates that these reductions are sustained over 2 years of treatment in the majority of pts. Ruxolitinib-treated pts showed longer survival than those receiving BAT, consistent with the survival advantage observed in previous (Verstovsek et al. NEJM. 2012) and current analyses of COMFORT-I, as well as with the comparison of pts of the phase 1/2 study with matched historical controls (Verstovsek et al. Blood. 2012).

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Cervantes:Sanofi-Aventis: Advisory Board, Advisory Board Other; Celgene: Advisory Board, Advisory Board Other; Pfizer: Advisory Board, Advisory Board Other; Teva Pharmaceuticals: Advisory Board, Advisory Board Other; Bristol-Myers Squibb: Speakers Bureau; Novartis: AdvisoryBoard Other, Speakers Bureau. Kiladjian:Shire: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding. Niederwieser:Novartis: Speakers Bureau. Sirulnik:Novartis: Employment, Equity Ownership. Stalbovskaya:Novartis: Employment, Equity Ownership. McQuity:Novartis: Employment, Equity Ownership. Hunter:Incyte: Employment. Levy:Incyte: Employment, stock options Other. Passamonti:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Barbui:Novartis: Honoraria. Gisslinger:AOP Orphan Pharma AG: Consultancy, Speakers Bureau; Celgene: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Research Funding, Speakers Bureau. Vannucchi:Novartis: Membership on an entity's Board of Directors or advisory committees. Knoops:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Harrison:Shire: Honoraria, Research Funding; Sanofi: Honoraria; YM Bioscience: Consultancy, Honoraria; Novartis: Honoraria, Research Funding, Speakers Bureau.