Abstract P035: A phase 1 pharmacokinetic trial of single agent trametinib a MEK inhibitor in advanced cancer patients with hepatic dysfunction: An NCI Organ Dysfunction Working Group (ODWG) study (NCI 9591)
Authors: Voon Pei Jye , Chen Eric X. , Chen Helen X. , Lockhart Albert C. , Sahebjam Solmaz , Kelly Karen , Vaishampayan Ulka N. , Subbiah Vivek , Razak Albiruni R. , Renouf Daniel J. , Hotte Sebastien J. , Singh Arti , Bedard Philippe L. , Hansen Aaron R. , Percy Ivy S. , Wang Lisa , Stayner Lee-Anne , Siu Lillian L. , Spreafico Anna 
Published: December 2021

Background Trametinib (Mekinist ®) is an oral bioavailable MEK 1/2 inhibitor that is FDA approved in combination with BRAF inhibitor Dabrafenib for BRAFV600 mutant solid tumors. The single agent recommended phase 2 dose (RP2D) is 2 mg daily (QD). No clinical data is available on recommendation of trametinib dosing in various degrees of hepatic dysfunction (HD). This study was designed to evaluate RP2D, maximum tolerated dose (MTD), and pharmacokinetic (PK) profile of trametinib as primary endpoints in patients (pts) with genomically unselected advanced solid tumors with various degrees of HD. Methods Advanced cancer pts with ECOG ≤2, adequate renal and bone marrow functions, were stratified (NCI ODWG Criteria) into 4 HD groups: normal (NO), mild (ML), moderate (MD), severe (SV). NO group was enrolled as control subjects and was not evaluable for dose limiting toxicity (DLT). Trametinib was given QD on a 28-days cycle, with dose escalation based on a “3+3” design within each HD group (starting dose: NO, ML: 2mg; MD: 1.5 mg; SV: 1mg). Due to the long half-life of trametinib, PK samples were collected at days 15-16 in cycle 1. Differences in PK parameters among liver function groups were evaluated using analysis of variance (ANOVA). Results Out of 46 pts enrolled (2 pts ineligible), 44 (NO=17, ML=7, MD (1.5mg)=4, MD (2mg)=5, SV (1mg)=9, SV (1.5mg)=2) were evaluable for safety and 22 for PK analysis. The most common cancer type was GI-non CRC cancer (n=16, 36%). The most common all-grade treatment related adverse events (TRAEs) were acneiform rash (NO=53%, HD=48% of pts), nausea (NO=65%, HD=22%), diarrhea (NO=53%, HD=26%) and fatigue (NO=59%, HD=15%). Grade 3/4 TRAEs occurred in 27% (n=12) of pts (NO=8, 47%; HD=4, 15%). No treatment related deaths occurred. DLT was evaluable in 15 pts (ML=6, MD (1.5mg)=3, MD (2mg)=2, SV (1mg)=3 and SV (1.5mg)=1). One DLT (grade 3 acneiform rash) was observed in an SV pt (1.5mg). Dose interruptions or reductions due to TRAEs occurred in 15 pts (34%) [NO=9, 53%; ML=2, 29%; MD (1.5mg)=1, 33%; MD (2mg)=2, 33%; SV (1mg)=1, 11%; SV (1.5mg)=1; 50%]. Best response was stable disease in all HD groups (33 to 75%) and 54% in NO group. There were no significant differences for PK parameters of Cmax (p=0.18), Cmin (p=0.16), Cavg (p=0.62), or AUC0-24 (p=0.11) (NO vs ML, NO vs MD, NO vs SV, ML vs MD, ML vs SV, MD vs SV), when trametinib was normalized to 2 mg dose. However, only limited PK data were available for the MD (n=3) and SV (n=3) groups compared to NO (n=10) and ML (n=6) groups. Trametinib is heavily protein bound, with no correlation between serum albumin level and unbound trametinib fraction (p=0.26). Conclusion RP2D for trametinib in ML pts is 2 mg QD. There are insufficient number of evaluable pts to declare RP2D for MD and SV HD groups. No DLTs were noted in the highest dose cohorts that reached 3 evaluable pts: 1.5 mg QD in MD group, and 1 mg QD in SV group. It may be appropriate for pts with MD and SV HD to start trametinib at 1.5 mg QD and 1 mg QD respectively, and monitored closely for toxicity.

Citation Format: Pei Jye Voon, Eric X. Chen, Helen X. Chen, Albert C. Lockhart, Solmaz Sahebjam, Karen Kelly, Ulka N. Vaishampayan, Vivek Subbiah, Albiruni R. Razak, Daniel J. Renouf, Sebastien J. Hotte, Arti Singh, Philippe L. Bedard, Aaron R. Hansen, Ivy S. Percy, Lisa Wang, Lee-Anne Stayner, Lillian L. Siu, Anna Spreafico. A phase 1 pharmacokinetic trial of single agent trametinib a MEK inhibitor in advanced cancer patients with hepatic dysfunction: An NCI Organ Dysfunction Working Group (ODWG) study (NCI 9591) [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P035.