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bioRxiv · 10.64898/2026.01.21.700721

Prevalence and Actionability of MTAP Loss in Oncogene-Driven Lung Cancer

Abstract

BackgroundMethylthioadenosine phosphorylase (MTAP) loss co-occurs with actionable genomic alterations in non-small cell lung cancer (NSCLC) and creates vulnerability to protein arginine methyltransferase 5 (PRMT5) inhibition. Estimates of prevalence of MTAP loss rely on next-generation sequencing which can underestimate copy losses. Moreover, the activity of PRMT5 inhibitors in oncogene-driven NSCLC is not well established. MethodsWe assessed MTAP expression by immunohistochemistry (IHC) in 243 NSCLCs (n=132 early stage, n=111 metastatic), including 33 specimens with paired lymph nodes. Antiproliferative activity of PRMT5 inhibitor monotherapy and in combination with tyrosine kinase inhibitors (TKIs) was evaluated in MTAP-deleted NSCLC cell lines harboring EGFR or KRAS mutations or ALK rearrangements. ResultsAmong 243 NSCLC specimens from 240 patients (72% with driver alterations, 90% adenocarcinoma), MTAP loss was identified in 43 (18%) specimens from 40 (17%) patients, including 18 (14%) early-stage and 22 (20%) metastatic tumors. MTAP loss occurred in 24% of stage 4 driver-positive NSCLCs versus 14% of driver-negative tumors (p=0.314). Twenty (61%) lung-nodal pairs demonstrated concordance; eight cases only exhibited decreased MTAP expression in nodes. Variable sensitivity to PRMT5 inhibitors was observed in 22 MTAP-deleted NSCLC cell lines (9 EGFR-mutant, 7 KRAS-mutant, 6 ALK-rearranged), with responses seen in TKI-sensitive and TKI-resistant lines. SDMA (symmetric dimethylarginine) expression did not predict PRMT5 inhibitor sensitivity. TKI + PRMT5 inhibitor combos had greater activity than monotherapy. ConclusionsMTAP loss occurs in 1-in-5 oncogene-driven metastatic NSCLCs. PRMT5 inhibitor activity is independent of TKI exposure, driver alteration, and SDMA expression and enhanced by addition of TKI. These findings support clinical evaluation of PRMT5 inhibitor + TKI combinations for advanced NSCLC.

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BibTeXRIS

Sakai, T., Piotrowska, Z., Wang, C., Yeap, B. Y., Heist, R. S., Lin, J. J., Highfield, L. E., Peterson, J. L., Banwait, M., Liang, J., Madhavan, M., Hata, A. N., Mino-Kenudson, M., Dagogo-Jack, I.. 2026-01-23. Prevalence and Actionability of MTAP Loss in Oncogene-Driven Lung Cancer. https://doi.org/10.64898/2026.01.21.700721

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