The polyamine inhibitor SAM486A increases the efficacy of adagrasib in non-small cell lung cancer cells harboring KRAS mutation.

[BACKGROUND] Non-small cell lung cancer (NSCLC) accounts for most lung cancer cases and poses major challenges due to late-stage diagnosis and limited options. A substantial subset of NSCLC harbors KRAS mutations, most commonly at codon 12. Although KRAS inhibitors show clinical activity, their efficacy is frequently limited by acquired resistance. Polyamines (putrescine, spermidine, and spermine) regulate key cellular processes and are dysregulated during tumorigenesis. S-adenosylmethionine decarboxylase 1 (AMD1) inhibitors such as SAM486A reduce tumor cell proliferation and migration. Thus, we evaluated the combination of the KRAS inhibitor adagrasib with SAM486A in KRAS-mutant NSCLC, in vitro and in vivo.

[METHODS] In vitro assays included viability (MTT), clonogenic, BrdU incorporation, and Western blot analyses across four NSCLC cell lines. Drug-drug interactions were quantified using Combenefit software. In vivo efficacy was tested in C57BL/6 mice using an orthotopic model with LLC46 (KRAS/NRAS) cells and a metastatic model with LL2 (KRAS/NRAS) cells. Tumor growth was monitored by µCT or caliper measurements, and immunohistochemistry (PCNA) was used to assess proliferation.

[RESULTS] In vitro, adagrasib reduced AMD1 levels, and SAM486A synergistically enhanced its antiproliferative effects, particularly in KRAS-mutant cell lines, with minimal effects on KRAS-wild-type cells. In an orthotopic mouse model using a KRAS/NRAS NSCLC line, the combination provided minimal additional benefit over adagrasib monotherapy. In a metastatic model, however, the combination reduced tumor size and PCNA staining more than either monotherapy.

[CONCLUSIONS] Our results suggest that targeting polyamine metabolism with SAM486A enhances the efficacy of KRAS inhibitors and may mitigate resistance. This combination represents a promising therapeutic approach for KRAS-mutant NSCLC and warrants further clinical investigation.