**Background:** Hepatocellular carcinoma (HCC) is a leading cause of cancer death with limited survival once systemic therapy is needed. Sorafenib, a multikinase inhibitor, is a standard systemic therapy for HCC. Beyond its anti-angiogenic and anti-proliferative effects, sorafenib is also a potent inhibitor of soluble epoxide hydrolase (sEH), an enzyme that metabolizes cytochrome P450 (CYP)-derived epoxy fatty acids into less active dihydroxy metabolites. Epoxy metabolites from omega-6 arachidonic acid (AA), such as epoxyeicosatrienoic acids (EETs), can promote tumor growth and angiogenesis, while omega-3-derived epoxides from docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), such as 19,20-EDP, have anti-angiogenic and anti-tumor effects. This study aimed to investigate the effect of sorafenib on plasma levels of these lipid mediators in HCC patients.
**Methods:** This sub-analysis included 43 patients from the palliative treatment arm of the randomized, controlled, multicenter phase II SORAMIC trial. All patients received sorafenib (starting at 200 mg twice daily, escalated to 400 mg twice daily, with dose adjustments as needed). Blood samples were collected at baseline (before sorafenib) and at the first follow-up visit after approximately 7–9 weeks of treatment. Plasma fatty acid composition was analyzed by gas chromatography (GC). CYP-derived epoxy and dihydroxy metabolites (EETs, DHETs, EDPs, DiHDPAs, EEQs, DiHETEs) were quantified by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Statistical comparisons were performed using the Wilcoxon matched-pairs signed-rank test.
**Key Results:** During sorafenib treatment, significant increases were observed in the levels of AA-derived epoxymetabolites 5,6-EET and 8,9-EET (p < 0.01 and p < 0.001, respectively). DHA- and EPA-derived epoxides (EDPs and EEQs) also tended to increase but did not reach statistical significance. The corresponding dihydroxy metabolites (DHETs, DiHDPAs, DiHETEs) were also significantly increased during treatment. When combining epoxy and dihydroxy metabolites, significantly higher levels of total AA-, DHA-, and EPA-derived products were found (p < 0.0001 for AA and DHA, p < 0.01 for EPA). In contrast, the relative plasma content of AA and DHA decreased significantly during sorafenib treatment (p < 0.0001 for both), and the n-6/n-3 ratio increased. The ratio of dihydroxy to epoxy metabolites (a marker of sEH activity) was higher during sorafenib treatment, significantly for DHA- and EPA-derived metabolites (p < 0.001), indicating no net sEH inhibition. However, the ratio of CYP products (epoxy + dihydroxy) to their respective substrate PUFA increased significantly for AA, DHA, and EPA (p < 0.0001 for AA and DHA, p < 0.05 for EPA), suggesting increased CYP-mediated metabolism. Notably, DHA-derived 19,20-EDP and 19,20-DiHDPA were the predominant DHA metabolites formed.
**Clinical Implications:** The study demonstrates that sorafenib treatment in HCC patients leads to increased levels of CYP-derived epoxy and dihydroxy metabolites from both n-6 and n-3 PUFAs, despite lower precursor fatty acid levels. The increase in potentially pro-tumorigenic EETs (from AA) is counterbalanced by a more pronounced increase in the ratio of DHA-derived 19,20-EDP to DHA, which has shown anti-angiogenic and anti-tumor effects in experimental models. These findings suggest that dietary supplementation with DHA could enhance the formation of beneficial n-3 epoxy-PUFA metabolites during sorafenib therapy, potentially improving anti-tumor efficacy. The lack of evidence for sEH inhibition in this human study contrasts with prior animal data, indicating that sorafenib's effects on lipid metabolism may be more complex. The study highlights the potential of pharmacolipidomics to identify lipid mediators that could be used to stratify or modify treatment response in HCC.