Novel NPEPL1 Inhibitor C301-9181 Shows Promise Against Liver Cancer

Hepatocellular carcinoma, the most common form of primary liver cancer, remains one of the deadliest malignancies worldwide, with prognosis poor and therapeutic options limited. Now, a team of researchers in Shanghai and Fujian, China, has identified a previously underappreciated driver of the disease — an enzyme called aminopeptidase-like 1, or NPEPL1 — and developed a novel small-molecule inhibitor, C301-9181, that directly targets it. The study, published in the Journal of Experimental & Clinical Cancer Research, offers a potential new therapeutic strategy for a cancer that urgently needs one.

NPEPL1 belongs to the aminopeptidase family, a group of enzymes that cleave amino acids from the N-termini of peptides and proteins. While aminopeptidases have long been recognized as players in cellular metabolism, their roles in cancer have been less well characterized than those of other metabolic enzymes. The new research shows that NPEPL1 is markedly overexpressed in hepatocellular carcinoma, and that its upregulation correlates significantly with poor prognosis. Patients whose tumors expressed high levels of the enzyme fared worse overall, making NPEPL1 a potential prognostic biomarker as well as a therapeutic target.

To probe the enzyme’s function, the team performed knockdown and overexpression experiments in hepatocellular carcinoma cell lines. When NPEPL1 was knocked down, cell proliferation, migration, and invasion all declined, while apoptosis — programmed cell death — increased. Overexpressing the enzyme produced the opposite effects. These results support an oncogenic role for NPEPL1 in hepatocellular carcinoma, meaning the enzyme actively promotes tumor growth and spread rather than merely accompanying it.

The researchers also uncovered the mechanism by which NPEPL1 is switched on in cancer cells. Serum response factor, or SRF, a well-known transcription factor, directly binds to three sites in the NPEPL1 promoter and transcriptionally activates the gene. This finding links NPEPL1 to a broader transcriptional program that drives tumor progression, and suggests that the enzyme’s overexpression is not accidental but actively orchestrated by the cancer cell’s regulatory machinery.

Peptidomics profiling — a technique that maps the peptides present in a cell — revealed that NPEPL1 functions as a hydrophobic and aliphatic aminopeptidase, preferentially cleaving N-terminal hydrophobic residues. Through this activity, the enzyme remodels translation and mitochondrial metabolism in hepatocellular carcinoma cells, reshaping the metabolic landscape that fuels tumor growth. This metabolic reprogramming is increasingly recognized as a hallmark of cancer, and the new study adds NPEPL1 to the growing list of metabolic enzymes that tumors co-opt for their own benefit.

With the target validated, the team turned to virtual screening to find a molecule that could inhibit it. From a large library of candidate compounds, they identified C301-9181, a small molecule that directly binds NPEPL1 with micromolar affinity — a dissociation constant of 2.77 micromolar. The inhibitor suppresses both NPEPL1 expression and aminopeptidase activity, and exhibits anti-hepatocellular carcinoma efficacy in vitro and in vivo, with an acceptable biosafety profile.

In cell culture experiments, C301-9181 showed antiproliferative activity comparable to sorafenib, a first-line targeted therapy for hepatocellular carcinoma, and superior to lenvatinib, another approved drug. Notably, the compound demonstrated greater selectivity than sorafenib, suggesting it may spare normal cells more effectively. When combined with either sorafenib or lenvatinib, C301-9181 enhanced the anti-cancer effects of both existing drugs, pointing to potential combination strategies.

In xenograft models — mice implanted with human hepatocellular carcinoma tumors — C301-9181 inhibited tumor growth in vivo. The researchers also evaluated biosafety by measuring liver and kidney function markers, including aspartate aminotransferase, alanine aminotransferase, total bilirubin, blood urea nitrogen, and creatinine, finding no significant toxicity at therapeutic doses. These results warrant further preclinical evaluation of the compound.

The work, led by Yu Qin, Wenjuan Xiao, Yanan Song, and Wei Xia, was supported by funding from the Health Commission of Pudong New Area, the Shanghai Key Laboratory of Molecular Imaging, and other regional programs. The authors have filed two patent applications related to the findings, one covering the application of the human NPEPL1 gene in tumor therapy and another covering small-molecule compounds targeting NPEPL1 for tumor-targeted therapeutic drugs. All animal experiments were approved by the Institutional Animal Care and Use Committee of Shanghai Rat & Mouse Biotech, and clinical pathological sections were approved by the Ethics Committee of Gongli Hospital of Shanghai Pudong New Area.

As with any early-stage discovery, the road from laboratory to clinic is long. C301-9181 binds NPEPL1 with micromolar rather than nanomolar affinity, and the compound will need optimization before it can be considered for clinical trials. Nonetheless, the study provides a complete arc — from target identification through mechanism, inhibitor discovery, and in vivo validation — that is rare in a single paper. For patients with hepatocellular carcinoma, whose options remain limited despite recent advances in immunotherapy and targeted agents, the identification of NPEPL1 as a druggable metabolic dependency offers a genuinely new direction, and one that could eventually complement existing therapies rather than replace them.

Subject of Research: Targeting SRF-activated aminopeptidase NPEPL1 with a novel small-molecule inhibitor offers a potential therapeutic strategy for hepatocellular carcinoma

Article Title: Targeting SRF-activated aminopeptidase NPEPL1 with a novel small-molecule inhibitor offers a potential therapeutic strategy for hepatocellular carcinoma

Article References: Qin, Y., Xiao, W., Song, Y., & Xia, W. (2026). Targeting SRF-activated aminopeptidase NPEPL1 with a novel small-molecule inhibitor offers a potential therapeutic strategy for hepatocellular carcinoma. Journal of Experimental & Clinical Cancer Research. https://doi.org/10.1186/s13046-026-03852-x

Image Credits: AI Generated

DOI: 10.1186/s13046-026-03852-x

Keywords: Targeting, SRF-activated, aminopeptidase, NPEPL1, novel, small-molecule, inhibitor, offers, potential, therapeutic, strategy, hepatocellular