Abstract 5252: Liquid biopsies to prospectively select patients with KRAS or NRAS mutant hepatocellular carcinoma (HCC) in two phase II studies with Refametinib

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Background: In a retrospective analysis performed in a phase II study evaluating efficacy and safety of the MEK-inhibitor refametinib plus sorafenib in Asian patients with HCC (Lim et al., Clin Cancer Res, in press), patients with mutant RAS appeared to exhibit a particularly robust clinical response to refametinib plus sorafenib compared to patients with wild-type RAS. To further investigate clinical activity of refametinib as monotherapy or in combination with sorafenib in HCC patients with mutant RAS, two Ph II studies for patients with unresectable HCC have been initiated; refametinib monotherapy ([NCT01915589][1]) and refametinib plus sorafenib combination therapy ([NCT01915602][2]). Since RAS mutations are very rare events in HCC and biopsies are not routinely taken in patients with underlying liver cirrhosis, only liquid biopsies seemed feasible for prospective patient selection. Therefore, Sysmex Inostics’ BEAMing (Beads, Emulsions, Amplification, and Magnetics) technology based on cell-free circulating DNA in plasma is used to select patients for KRAS/NRAS Mutation status prior to enrollment. Patients are eligible if they exhibit any one or multiple of 13 KRAS/NRAS mutations. Results: Between Sep 2013 and Nov 2014 more than 1000 plasma samples from patients with unresectable HCC enrolled in the refametinib monotherapy study or the refametinib plus sorafenib combination study, have been tested at a CLIA certified laboratory in Baltimore, MD. The turnaround time from shipping the plasma sample from the clinical trial site to the results reporting was 6-10 days. Out of 1004 samples from 116 trial sites in 18 countries, 47 (4.7%) have been reported to harbor a KRAS and / or a NRAS mut. The following mutations have been reported: KRAS\_G12A, KRAS\_G12C, KRAS\_G12D, KRAS\_G12R, KRAS_ G12S, KRAS\_G12V, KRAS\_G13D, NRAS\_Q61K, NRAS\_Q61L, NRAS\_Q61H, NRAS\_Q61R. The frequency of the mutant allele ranged from 0.02% to 9.75%. No obvious differences in the incidence of any of the mutations with regards to geography, demographic factors are other baseline characteristics have been observed. Conclusion: To our knowledge this is the largest dataset of KRAS and NRAS mutations in HCC. The observed prevalence of RAS mutations of approximately 5% across both trials is well in line with published data including the COSMIC database. Our data support that prospective selection of patients with HCC for KRAS or NRAS mutation is feasible with a turn-around time of 1-2 weeks depending on geographical region. These data further support the broad utility of such approaches for large randomized prospective studies in patients with specific tumor genetic profiles. The clinical outcome of the 2 clinical studies will help understand whether KRAS or NRAS can potentially be a predictive marker for response to refametinib in patients with HCC. Citation Format: Heiko Krissel, Andrea Hennig, Danny Zhang, Rodrigo Ito, Christine Gonschorek, Fabricio Souza, Martina Poethig, Kathleen Schostack, Joachim Reischl, Philipp Angenendt, Barrett H. Childs, Michael Teufel. Liquid biopsies to prospectively select patients with KRAS or NRAS mutant hepatocellular carcinoma (HCC) in two phase II studies with Refametinib. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5252. doi:10.1158/1538-7445.AM2015-5252 [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01915589&atom=%2Fcanres%2F75%2F15_Supplement%2F5252.atom [2]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01915602&atom=%2Fcanres%2F75%2F15_Supplement%2F5252.atom