Abstract: BACKGROUND: Ruxolitinib (RUX) is a potent JAK1/JAK2 inhibitor that has demonstrated improvements in splenomegaly, MF-related symptoms, and quality of life measures and prolonged survival in 2 phase 3 studies. JAK signaling can activate the PI3K/mTOR pathway, and constitutive PI3K activation has been implicated in numerous cancers. Preclinical and early clinical results indicate benefit with inhibition of PI3K in MF. Buparlisib is a pan-PI3K inhibitor with specific and potent activity against class I PI3Ks. The aims of HARMONY are to evaluate the safety of co-administration of RUX and buparlisib in patients (pts) with MF and determine a recommended phase 2 dose (RP2D). METHODS: This is a dose-finding, phase 1b study (NCT01730248) of RUX plus buparlisib in intermediate- or high-risk MF pts. Pts must have palpable splenomegaly ≥ 5 cm below the costal margin and MF symptoms. There are 2 treatment groups (JAK inhibitor–naive pts [arm A] and pts not benefiting from prior JAK inhibition [arm B] ) and 2 study phases (dose escalation and expansion). Dose escalation is guided by a Bayesian logistic regression model with overdose control and depends on dose-limiting toxicities in cycle 1 and other safety findings. Each dose level consists of ≥ 3 evaluable pts; the 5 dose levels are (RUX [mg bid]/buparlisib [mg qd] ) 10/60, 15/60, 15/80, 20/80, 20/100. 9 evaluable pts are required at the final dose level to determine an RP2D and proceed to the expansion phase; 10 additional pts per arm will be treated at the RP2D. PK of RUX was assessed by LC-MS/MS on day 1 after the first dose of RUX and on days 2 and 8 when administered in combination with buparlisib. RESULTS: To date, 33 pts (arm A, n = 20; arm B, n = 13) have been treated in the dose-escalation phase. Baseline characteristics were (arm A and arm B) median age, 64 y (range, 48-79 y; 45% ≥ 65 y) and 61 y (53-74 y; 31% ≥ 65 y); male, 50% and 62%. RP2D was selected based on tolerability in the investigated dose levels, with additional confirmation from dose-selection recommendations derived through a Bayesian model.Currently, RUX 15 mg bid/buparlisib 60 mg qd was determined as the RP2D in both arms; the study is proceeding into the expansion phase. At data cutoff (April 1, 2014), 15 (75%) and 8 (62%) pts were ongoing in arm A and arm B with a median exposure of 11.3 wk (range, 2.3-48.4 wk) and 19.0 wk (range, 0.6-50.9 wk), respectively. The primary reasons for discontinuation included lack of efficacy (10%) in arm A and AEs (15%) in arm B; all other reasons were in 1 pt each. There was 1 death (arm A) from duodenal ulcers/perforation, assessed as not related to study drugs by the investigator. Despite the short follow-up, a ≥ 50% reduction from baseline in palpable spleen length was achieved by 70% and 54% of pts in arms A and B; 7 pts had a resolution of splenomegaly (6 in arm A; 1 in arm B). All pts with prior JAK inhibitor treatment, including 5 who had no previous spleen length reductions, had reductions with the combination. Hematologic AEs included anemia (all grade [grade 3/4]: arm A, 30% [15%] ; arm B, 31% [23%]) and thrombocytopenia (40% [10%] ; 62% [39%]). Nonhematologic AEs were primarily grade 1/2 (Table). Overall, 20% and 23% of pts experienced serious AEs; these occurred in 1 pt each, with the exception of pyrexia (n = 2). PK parameters of RUX were comparable when administered alone or in combination with buparlisib, suggesting a lack of impact of buparlisib on RUX PK. CONCLUSIONS: The combination of RUX and buparlisib was well tolerated, with early signs indicating promising efficacy even in pts who have previously failed JAKi; preliminary RP2D was assessed as RUX 15 mg bid/buparlisib 60 mg qd for both arms. Updated efficacy and safety for the dose-escalation phase will be presented (July 1, 2014 data cutoff). Table Nonhematologic AEs in ≥ 2 Pts in Either Arm Pts, % Arm A n = 20 Arm B n = 13 All Grade Grade 3/4 All Grade Grade 3/4 Abdominal distension 15 0 8 0 Abdominal pain 10 0 15 0 Abdominal pain lower 0 0 15 0 Abdominal pain upper 5 0 15 0 Diarrhea 10 0 46 8 Dyspepsia 10 0 0 0 Nausea 10 0 31 0 Stomatitis 15 5 8 8 Vomiting 5 0 15 0 Asthenia 0 0 31 0 Fatigue 10 0 23 0 General health deterioration 0 0 15 0 Edema peripheral 10 0 0 0 Pyrexia 15 0 23 15 Nasopharyngitis 15 0 15 0 Decreased appetite 5 0 46 8 Hyperglycemia 15 5 0 0 Hyperkalemia 5 5 15 0 Arthralgia 20 5 8 0 Pain in extremity 10 0 8 0 Dizziness 5 0 23 0 Anxiety 20 5 15 0 Confusional state 10 0 8 0 Depressed mood 0 0 15 8 Depression 0 0 15 8 Insomnia 5 0 15 0 Epistaxis 5 0 15 0 Hyperhidrosis 0 0 31 0 Night sweats 0 0 23 0 Hypertension 10 5 0 0 Disclosures Durrant: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Off Label Use: Yes; Ruxolitinib is a kinase inhibitor indicated for treatment of patients with intermediate or high-risk myelofibrosis, including primary myelofibrosis, post-polycythemia vera myelofibrosis and post-essential thrombocythemia myelofibrosis. Buparlisib is an investigational agent. Koren-Michowitz:Novartis: Honoraria, Research Funding. Lavie:Novartis: Membership on an entity's Board of Directors or advisory committees. Martinez-Lopez:Novartis: Research Funding; BMS: Honoraria; Celgene: Honoraria. Vannucchi:Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Research Funding. Stalbovskaya:Novartis: Employment, Equity Ownership. Atienza:Novartis: Employment. Iommazzo:Novartis: Employment. Gopalakrishna:Novartis: Employment. Gisslinger:AOP ORPHA: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen Cilag: Honoraria, Speakers Bureau; Geron: Consultancy; Sanofi Aventis: Consultancy.