MEK inhibitor-based therapy in metastatic pancreatic adenocarcinoma with <i>KRAS</i> G12D or <i>KRAS</i> G12V alteration.

726 Background: Up to 95% of pancreatic ductal adenocarcinomas (PDAC) are driven by oncogenic alterations in the KRAS gene, with KRAS G12D (40%) and KRAS G12V (30%) mutations being the most common. However, in most cases, KRAS alterations are accompanied by alterations in other tumor suppressors such as TP53 , CDKN2A/B , and SMAD4 . Therefore, targeting KRAS alone may not be sufficient for effective treatment of PDAC . As part of the MCW-Master-PREDICT (NCT05802069) observational study, we evaluated the effectiveness of MEK inhibitor (MEK-inh)-based therapy, tailored to the unique molecular alterations of each patient’s tumor, in treating metastatic PDAC (mPDAC) with KRAS G12D or KRAS G12V alterations. Methods: From April 2022 to December 2023, 19 patients ( KRAS G12D=10 (53%), KRAS G12V=9 (47%)) were treated with MEK-inh-based therapy. Comprehensive genomic profiling was performed using Tempus xT (648 genes) in 15 patients (79%), FoundationOne (324 genes) in 4 patients (21%), and STRATA (429 genes) in 1 patient. The genomic characteristics, matched therapies, and treatment outcomes are provided (Table). Results: Of the 19 patients, 11 (58%) were female. The median age at the initiation of MEK-inh-based therapy was 67 years. Six (32%) patients received MEK-inh-based therapy as first or second-line treatment, while 13 (68%) patients were treated in the third to fifth-line. Among the 19 patients, the median overall survival (mOS) and median progression-free survival (mPFS) from the initiation of MEK-inh-based therapy were 5 and 2 months, respectively. The mOS from the time of MEK-inh-based therapy was 5.1 months for KRAS G12D, and 4.7 months for KRAS G12V (P=0.87). The mPFS from the time of MEK-inh-based therapy was 2.3 months for KRAS G12D and 1.4 months for KRAS G12V (P=0.12). Among all 19 patients, 4 (21%) patients had mPFS above 4 months ( KRAS G12V=1, KRAS G12D=3; 4.1, 4.3, 4.7, 9.9 months). Conclusions: The efficacy of MEK-inh-based therapy was limited in the late-line treatment of mPDAC for patients with KRAS G12D and KRAS G12V mutations. The potential role of MEK inhibitors in earlier lines of therapy, and their combination with KRAS inhibitors, requires further prospective evaluation. Tumor alterations and matched therapies. Altered gene KRAS G12V(N=9) KRAS G12D(N=10) Patients matched(N=19) Type of matched therapy KRAS G12D/V 9 (100%) 10 (100%) 19 (100%) MEK inhibitor TP53 7 (78%) 8 (80%) 8 (42%) VEGF/VEGR inhibitor* CDKN2A/B 8 (89%) 5 (50%) 9 (47%) CDK4/6 inhibitor** SMAD4 3 (33%) 4 (40%) 4 (21%) MEK inhibitor + (EGFR or pan-HER inhibitor) *** *PMID: 27466356; **PMID: 33472910; ***PMID: 36127339, PMID: 24625091. N= number of patients.