8630 Background: Development of therapies targeting KRAS have transformed KRAS from undruggable to druggable. However, patients with KRASG12C-mutant non-small cell lung cancer (NSCLC) with brain metastasis (BM) have a poor prognosis. JMKX001899, a new potent oral small-molecule KRASG12C inhibitor, irreversibly and selectively binds KRASG12C, locking it in its inactive state. Its antitumor activity in the intracranial is unclear. Methods: In order to verify the activity of new KRASG12C inhibitor JMKX001899 in KRASG12C-mutant NSCLC with BM, murine models were employed for investigating the efficacy. 5-6 weeks old female Balb/c nude mice were implanted intracranially with H358-Luc and H23-Luc cells. Baseline bioluminescent imaging (BLI) was used to monitor the tumor burden and total flux was calculated by Living Image. Ten days after implantation, oral once-daily dosing of vehicle, sotorasib (AMG510) at 100 mg/kg, 30 mg/kg and JMKX001899 at 100 mg/kg, 30 mg/kg, 10 mg/kg was started and continued for 21 days. The tumor burden was monitored by BLI weekly. The mice were weighed per 3 days. Results: At the 30mg/kg and 100mg/kg dose level, the mean cerebrospinal fluid (CSF)-to-unbound plasma ratios (Kp,uu) was 0.18-0.50, which determined JMKX001899 CSF exposure was sufficient to mediate regression tumors in experimental BM models. In mice bearing intracranial xenografts of H358-Luc and H23-Luc, oral JMKX001899 100mg/kg once daily treatment for 21 days resulted in significant inhibition of brain tumor growth revealed by BLI, compared with vehicle and AMG510. H358-Luc xenografts responded particularly well to the JMKX001899 treatment, showed by the ratio of 14 days and 0 days total bioluminescence flux (vehicle vs. AMG510 100mg/kg vs. JMKX001899 100mg/kg, 0.85 vs. 0.89 vs. 0.01, p < 0.05). In addition, JMKX001899 at 100mg/kg once daily demonstrated an increase in over survival. JMKX001899 100 mg/kg once daily treatment was well tolerated with minimal sign of overt toxicity or animal weight loss. Conclusions: The preclinical models in vivo suggest the new KRASG12C inhibitor JMKX001899 penetrates the central nervous system and show great inhibition of KRASG12C-mutant NSCLC with BM, which demonstrates therapeutic activity of JMKX001899 in BM. These data support further development of JMKX001899 in patients with KRASG12C-mutant NSCLC with BM.
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