Phase I dose-finding study of oral ERK1/2 inhibitor LTT462 in patients (pts) with advanced solid tumors harboring MAPK pathway alterations.

Abstract

3640 Background: LTT462 is an investigational small molecule inhibitor of ERK1/2, which has demonstrated preclinical activity in multiple MAPK activated cancer cells and xenograft models. This first-in-human study was designed to evaluate the safety and tolerability of LTT462 in advanced solid tumors harboring MAPK pathway alterations (NCT02711345). Methods: The dose-escalation part of this Phase I, open-label study, enrolled adult and adolescent pts with advanced solid tumors harboring ≥1 documented MAPK pathway alteration with progressive disease (PD) despite standard therapy, or for whom there is no effective standard treatment. Oral LTT462 was given once daily (QD) at 45–600 mg or twice daily (BID) at 150 mg or 200 mg. Objectives were to determine the maximum tolerated dose (MTD) using a Bayesian hierarchical logistic regression model guided by escalation with overdose control, and characterize safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of LTT462. Results: Sixty-five pts (median age 60 years) including 1 pt aged 15 were enrolled in the dose-escalation; most pts (22%) had 3 prior therapies. Most common primary sites for cancer were in the colon (n = 21; 32%), ovary (n = 9; 14%), and pancreas (n = 7; 11%). All pts discontinued, the majority due to PD (n = 44; 68%). Eleven pts experienced DLTs; 6 pts experienced Grade 3 eye disorder DLTs (4 pts retinopathy, 2 pts chorioretinopathy). Treatment-related adverse events (TRAEs) were reported for 89% of pts, most commonly ( > 30%) diarrhea (n = 25; 38%) and nausea (n = 22; 34%). Grade 3/4 TRAEs were reported in 29% of pts; most common was retinopathy (n = 4; 6%). MTD of LTT462 was 400 mg QD and 150 mg BID. Overall, 8 pts (12%) had stable disease (SD) and 35 pts (54%) had PD. An unconfirmed partial response was reported in a pt with cholangiocarcinoma with BRAF mutation; best change in sum of target lesions per RECIST 1.1 was -33.9%. LTT462 increased plasma peak drug concentration and drug exposure at increasing doses between 45–450 mg QD. Exposure at LTT462 600 mg QD was lower than anticipated, indicating potential saturation of absorption at this dose. LTT462 inhibited ERK1/2 and reduced DUSP6 expression relative to baseline in most pts evaluated. Conclusions: LTT462 is well tolerated. Limited clinical activity was reported with single agent LTT462; best overall response was SD. An ongoing study is investigating LTT462 in combination with the RAF inhibitor, LXH254, in NSCLC and melanoma. Clinical trial information: NCT02711345 .