CodeBreak 100: Activity of AMG 510, a novel small molecule inhibitor of KRASG12C, in patients with advanced colorectal cancer.

4018 Background: Kirsten rat sarcoma viral oncogene homolog (KRAS) p.G12C mutation is associated with poor prognosis in colorectal cancer (CRC). AMG 510 is a first-in-class small molecule that specifically and irreversibly inhibits KRAS G12C by locking it in the inactive guanosine diphosphate-bound state. In a previous interim analysis of the phase 1, first-in-human trial of AMG 510, we observed a favorable safety profile and preliminary antitumor activity in patients (pts) with advanced solid tumors harboring KRAS p.G12C. Here, we present updated data in pts with CRC. Methods: Key inclusion criteria were KRAS p.G12C mutation identified through molecular testing, measurable disease, and progression on standard therapy. Primary endpoint was safety. Secondary endpoints were objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), as assessed per RECIST 1.1, and overall survival (OS). Oral daily doses of 180, 360, 720, and 960mg were tested in the dose escalation phase, and 960mg dose was selected for the expansion phase. Results: As of Jan 8, 2020, 42 pts with CRC (21 female [50%], median age: 57.5 years [range: 33–82]) were enrolled and dosed (25 on 960mg). All pts received prior systemic therapies; 19 pts (45.2%) received > 3 prior lines. Median follow-up was 7.9 months (mos) (range: 4.2–15.9). 13 pts (31.0%) died, and 8 pts (19.0%) remained on treatment (tx). 22 (52.4%) and 8 (19.0%) pts had remained on tx for more than 3 and 6 months, respectively. Progressive disease was the most common reason for tx discontinuation. 20 pts (47.6%) had tx-related adverse events (TRAEs): 18 (42.9%) had grade 2 or lower TRAEs; 2 (4.8%) had grade 3 TRAEs, which were diarrhea (2.4%) and anemia (2.4%). There were no dose-limiting toxicities, fatal TRAEs, or TRAEs leading to tx discontinuation. Overall, ORR and DCR were 7.1% (3/42) and 76.2% (32/42), respectively. At 960mg, ORR and DCR were 12.0% (3/25) and 80.0% (20/25). 3 pts with PR had duration of response of 1.5, 4.2, and 4.3 months, respectively, and their responses were still ongoing at data cutoff. In all pts treated with all doses, median duration of stable disease was 4.2 mos (range: 2.5[+]–11.0). PFS/OS will be reported. Conclusions: In pts with heavily pretreated KRAS p.G12C mutant CRC, AMG 510 monotherapy was well tolerated, with the majority of pts achieving disease control. Study is ongoing. Clinical trial information: NCT03600883 .