ctDNA as a biomarker in phase II study of tepotinib in advanced solid cancers with MET exon 14 skipping mutation or amplification (KCSG AL19-17).

Background: Tepotinib consistently demonstrated antitumor activity in patients with MET exon 14 skipping mutation (METex14) and promising activity in various cancers with MET amplification, according to previous reports. We assessed plasma ctDNA as a potential biomarker in MET-dysregulated advanced cancer patients with tepotinib treatment. Methods: KM-08 (KCSG AL19-17, NCT04647838) was a phase 2, multicenter study with tepotinib treatment for patients with advanced or metastatic solid cancers harboring either METex14 or MET amplification detected in tissue-based next-generation sequencing (NGS). For exploratory analyses, we analyzed the genetic profile using liquid-based NGS testing with AlphaLiquid-100 panel (IMBdx Inc. Seoul, KR) at baseline (T0), after six weeks during treatment (T1), and at the time of disease progression (T2). Results: Baseline ctDNA NGS data was available in 28 (80%) out of 35 patients enrolled in the trial. Among them, METex14 or MET amplification was detected in 18 patients, with a sensitivity of 64.3%. The most commonly co-mutated gene was TP53, followed by PIK3CA, ATM, MYCN, and KRAS. The objective response rate (ORR) in plasma MET positive (PM+) patients was higher (81.2%) than the ORR in plasma MET negative (PM−) patients’ group (30.0%). In contrast, PM− group had a longer progression-free survival (PFS) and overall survival (OS) than PM+ group. PFS was 11.0 months (95% CI 8.1, 13.9) vs 6.0 months (95% CI 3.6, 8.3) and OS was NR vs 14.0 months (95% CI 4.7, 23.3), respectively. The molecular responder (MR, MET alteration variant allele frequency [VAF] T1/T0 <50%) was 80.0% (12/15 patients), and the molecular non-responder (MNR, METVAF T1/T0≥50%) was 20.0% (3/15 patients). ORR was higher in the MR group (91.7%) than in the MNR group (33.3%). PFS and OS were longer in the MR group than in the MNR group, 6.0 months (95% CI 0.0, 14.5) vs 3.0 months (95% CI 1.4, 4.6) with P= 0.114 and NR vs 4.0 months (95% CI 2.4, 5.6) with P= 0.067, respectively. Out of the 20 patients with samples available at T2, one had an on-target mutation on MET (D1228N, and Y1230H) while two had off-target emerging oncogenic alterations in KRAS, BRAF, and ERBB2 genes. Conclusions: In the liquid biomarker analysis in the MET-dysregulated cancer patients who were treated with tepotinib, the presence of ctDNA METalteration at baseline was associated with a higher response rate but shorter PFS and OS. The molecular response was well correlated with the radiological response and associated with better outcomes. (Funded by Merck KGaA, Darmstadt, Germany, ClinicalTrials.gov number, NCT04647838.) Clinical trial information: NCT04647838.