Tunlametinib (HL-085) plus vemurafenib in patients with advanced BRAF V600-mutant solid tumors: an open-label, single-arm, multicenter, phase I study.

BACKGROUND: Tunlametinib (HL-085) is a novel, highly selective MEK inhibitor with substantial clinical activities in patients with NRAS-mutant melanoma. This phase I study evaluated the safety and preliminary efficacy of tunlametinib plus vemurafenib in patients with advanced BRAF V600-mutant solid tumors. METHODS: Patients with confirmed advanced BRAF V600-mutant solid tumors who had progressed on or shown intolerance or no available standard therapies were enrolled and received tunlametinib plus vemurafenib. This study consisted of a dose-escalation phase and a dose-expansion phase. Primary end points of this study were safety, the recommended phase II dose (RP2D), and preliminary efficacy. RESULTS: From August 17, 2018 to April 19, 2022, 72 patients were enrolled. No dose-limiting toxicities occurred, and the maximum tolerated dose was not reached. The RP2D for BRAF V600-mutant non-small cell lung cancer (NSCLC) patients was tunlametinib 9 mg plus vemurafenib 720 mg, twice daily (BID, bis in die). Until the data cut-off date of December 15, 2023, of 33 NSCLC patients with evaluable disease, the objective response rate (ORR) was 60.6% (20/33; 95% confidence interval [CI], 42.1-77.1), the median progression free survival (PFS) was 10.5 months (95%CI, 5.6-14.5) and median duration of response (DoR) was 11.3 months (95%CI, 6.8-NE). At the RP2D, ORR was 60.0% (9/15; 95% CI, 32.3-83.7), the median PFS was 10.5 months (95%CI, 5.6 -NE) and median DoR was 11.3 months (95%CI, 3.9-NE). Of 24 colorectal cancer patients with evaluable disease, the ORR was 25.0% (6/24; 95% CI, 5.6-NE). All 72 patients had treatment-related adverse events (TRAEs), and the most common grade 3-4 TRAEs were anemia (n = 13, 18.1%) and blood creatine phosphokinase increased (n = 10, 13.9%). Tunlametinib was absorbed rapidly with Tmax of 0.5-1 h. Vemurafeinib did not influence the system exposure of tunlametinib and vice versa, indicating no drug-drug interaction for this combination. CONCLUSIONS: Tunlametinib (HL-085) plus vemurafenib had a favorable safety profile and showed promising antitumor activity in patients with BRAF V600-mutant solid tumors. The RP2D for NSCLC was tunlametinib 9 mg BID plus vemurafeinib 720 mg BID. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03781219.

Preclinical characterization of tunlametinib, a novel, potent, and selective MEK inhibitor.

Background: Aberrant activation of RAS-RAF-MEK-ERK signaling pathway has been implicated in more than one-third of all malignancies. MEK inhibitors are promising therapeutic approaches to target this signaling pathway. Though four MEK inhibitors have been approved by FDA, these compounds possess either limited efficacy or unfavorable PK profiles with toxicity issues, hindering their broadly application in clinic. Our efforts were focused on the design and development of a novel MEK inhibitor, which subsequently led to the discovery of tunlametinib. Methods: This study verified the superiority of tunlametinib over the current MEK inhibitors in preclinical studies. The protein kinase selectivity activity of tunlametinib was evaluated against 77 kinases. Anti-proliferation activity was analyzed using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) or (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) assay. ERK and phospho-ERK levels were evaluated by Western blot analysis. Flow cytometry analysis was employed to investigate cell cycle and arrest. Cell-derived xenograft (CDX) and Patient-derived xenograft (PDX) models were used to evaluate the tumor growth inhibition. The efficacy of tunlametinib as monotherapy treatment was evaluated in KRAS/BRAF mutant or wild type xenograft model. Furthermore, the combination studies of tunlametinib with BRAF/KRASG12C/SHP2 inhibitors or chemotherapeutic agent were conducted by using the cell proliferation assay in vitro and xenograft models in vivo. Results: In vitro, tunlametinib demonstrated high selectivity with approximately 19-fold greater potency against MEK kinase than MEK162, and nearly 10-100-fold greater potency against RAS/RAF mutant cell lines than AZD6244. In vivo, tunlametinib resulted in dramatic tumor suppression and profound inhibition of ERK phosphorylation in tumor tissue. Mechanistic study revealed that tunlametinib induced cell cycle arrest at G0/G1 phase and apoptosis of cells in a dose-proportional manner. In addition, tunlametinib demonstrated a favorable pharmacokinetic profile with dose-proportionality and good oral bioavailability, with minimal drug exposure accumulation. Furthermore, tunlametinib combined with BRAF/KRASG12C/SHP2 inhibitors or docetaxel showed synergistically enhanced response and marked tumor inhibition. Conclusion: Tunlametinib exhibited a promising approach for treating RAS/RAF mutant cancers alone or as combination therapies, supporting the evaluation in clinical trials. Currently, the first-in-human phase 1 study and pivotal clinical trial of tunlametinib as monotherapy have been completed and pivotal trials as combination therapy are ongoing.

Phase I pharmacokinetic study of an oral, small-molecule MEK inhibitor tunlametinib in patients with advanced NRAS mutant melanoma.

Background: Malignant melanoma is an aggressive disease. Tunlametinib (HL-085) is a potent, selective, and orally bioavailable MEK1/2 inhibitor. The objective of this study was to determine the pharmacokinetics (PK) of tunlametinib and its main metabolite M8 in patients with NRAS-mutant melanoma following a single dose and multiple doses in a phase I safety and PK study. Methods: A multiple-center phase I study was performed in patients with melanoma including dose-escalation phase and dose-expansion phase. PK following a single oral dose and multiple doses of 0.5-18 mg twice daily was assessed. Results: A total of 30 participants were included in the dose escalation phase and then 11 patients were included in the dose-expansion phase (12 mg twice daily). Tunlametinib plasma concentration rapidly increased after dosing, with a Tmax of 0.5-1 h. Mean elimination half-life (t1/2) was dose-independent and had a range from 21.84 to 34.41 h. Mean apparent clearance (CL/F) and distribution volume (V/F) were 28.44-51.93 L/h and 1199.36-2009.26 L, respectively. The average accumulation ratios of AUC and Cmax after the multiple administration of tunlametinib were 1.64-2.73 and 0.82-2.49, respectively. Tunlametinib was rapidly transformed into the main metabolite M8 and M8 reached the peak concentration about 1 h after administration. Mean t1/2 of M8 was 6.1-33.54 h. The body exposure of M8 in plasma was 36%-67% of that of tunlametinib. There were general dose-proportional increases in maximum concentration (Cmax) and area under the curve (AUC) of tunlametinib and M8 both in the single dose phase and in the multiple doses phase. Conclusion: Tunlametinib was absorbed rapidly and eliminated at a medium speed after drug withdrawal. Pharmacokinetic body exposure increased in general dose-proportional manner from 0.5 mg up to 18 mg. Slight accumulation was found after multiple oral doses. The pharmacokinetics of tunlametinib and its metabolite suggest that twice daily dosing is appropriate for tunlametinib.