Mln2480, An Investigational Oral Pan-Raf Kinase Inhibitor, In Patients (Pts) With Relapsed Or Refractory Solid Tumors: Phase I Study

2547 Background: MLN2480 is an investigational pan-RAF kinase inhibitor. In vivo, MLN2480 showed antitumor activity in melanoma, colon, lung, and pancreatic cancer xenograft models. This first-in-human study aimed to evaluate the safety of MLN2480, determine the MTD/recommended phase 2 dose (RP2D), and evaluate pharmacokinetics (PK) and preliminary efficacy. Methods: Pts aged ≥18 yrs with advanced solid tumors who had failed/were not candidates for standard therapy received oral MLN2480 every other day (Q2D) in 22-d cycles, with dose escalation (3+3 design) based on DLTs in cycle 1. AEs were graded per NCI-CTCAE v4.03. Blood samples for plasma PK assessment were taken pre-dose and at multiple times post-dose, d 1 and 21, cycle 1. Results: 24 pts (10 male, median age 64.5 yrs [range 37–83]) have been treated at 20, 40, 80, 135, 200, and 280 mg (n=4, 3, 3, 3, 4, and 7), respectively. The most common tumors included colorectal cancer in 11 pts and non-small-cell lung cancer in 2 pts. Pts received a median of 2 (range 1–6) cycles. 2 pts treated at 280 mg had DLTs: grade 3 macular rash and grade 3 periorbital edema. 20 pts had drug-related AEs, including fatigue 46%, arthralgia 25%, maculopapular rash 21%, and myalgia 17%. 4 pts had drug-related grade ≥3 AEs, which included the 2 DLTs listed above, anemia, dyspnea, and fatigue. No keratocanthomas/ squamous cutaneous carcinomas have been seen to date. 4 pts discontinued due to AEs. There were 3 on-study deaths (1 treatment-related per investigator; dyspnea and respiratory failure). At 20–200 mg MLN2480 PK data (13 pts) exhibited rapid absorption (median T max 2 hr), low fluctuation at steady state (mean peak to trough ratio 2.1), and mean accumulation half-life of 67 hr. Overall mean accumulation was 2.6-fold following repeated Q2D dosing for 21 d. Steady-state (d 21) exposures increased in an approximately dose-proportional manner over 20–200 mg range. No pts had an objective response to date; no pts with BRAF mutation enrolled to date. Conclusions: In this first-in-human study (n=24), the safety profile of MLN2480 up to 200 mg Q2D was acceptable. Accrual continues at 200 mg to confirm the MTD. Melanoma expansion cohorts are planned at the RP2D using a Q2D 28-d cycle. Clinical trial information: NCT01425008.