Purpose: Apixaban is recommended for patients with atrial fibrillation. Although routine monitoring of plasma concentrations is not typically advised, factors such as ethnicity, sex, and comorbidities can influence these levels. Our study analyzed the plasma apixaban concentrations (PAC) in patients to explore whether these levels, along with underlying conditions, offer enhanced insights for risk stratification. Methods: This study analyzed 49 patients with atrial fibrillation who had been taking apixaban for over a month, examined factor Xa levels within 6 h post-administration, and correlated PAC with clinical characteristics such as age, body weight, estimated glomerular filtration rate (eGFR), presence of heart failure, and bleeding events. Results: The mean plasma concentration of apixaban in all patients was 160.3 ± 77.5 ng/mL. Those taking apixaban 5 mg twice daily had higher plasma concentrations than those taking 2.5 mg twice daily (191.2 ± 75.3 ng/mL vs.137.2 ± 72.0 ng/mL, p = 0.014). Among the patients receiving a reduced dose, renal function and heart failure were significantly associated with plasma concentrations. No factors were associated with the plasma concentrations in patients receiving the standard dose. Notably, reduced-dose patients with heart failure had plasma concentrations comparable to those of individuals receiving the standard dose and exhibited a higher incidence of bleeding than the other groups. Conclusions PAC measurement revealed that apixaban dosages, classified based on age, body weight, and eGFR, were generally effective. Nonetheless, heart failure may increase plasma levels and correlate with an increased bleeding risk in Korean patients on reduced doses. Therefore, tailoring apixaban prescriptions to account for heart failure and other comorbidities may enhance treatment efficacy.

Purpose: The soluble form programmed death-ligand 1 (sPDL1) has immunosuppressive properties and is being studied as a candidate biomarker for immuno-oncology drug development. We measured the serum sPDL1 at pre-and post-chemotherapy and evaluated its prognostic implication and dynamics during chemotherapy in advanced gastric cancer (GC). Materials and Methods: We prospectively enrolled 68 GC patients who were candidates for palliative standard first-line chemotherapy, and serially collected blood at baseline and after one cycle of chemotherapy, at the best response and after disease progression. sPDL1 was measured using an enzyme-linked immunosorbent assay. Response to chemotherapy, overall survival (OS), progressionfree survival (PFS) and other prognostic factors including neutrophil-lymphocyte ratio (NLR) were obtained. The cut-off value of sPDL1 levels for survival analysis was found using C-statistics. Results: The median baseline sPDL1 was 0.8 ng/mL (range, 0.06 to 6.06 ng/mL). The median OS and PFS were 14.9 months and 8.0 months, respectively. sPDL1 and NLR showed a weak positive correlation (Spearman’s rho=0.301, p=0.013). Patients with low levels of sPDL1 at diagnosis (< 1.92 ng/mL) showed a better OS and PFS than patients with a high sPDL1. The baseline sPDL1 before treatment was higher in the progressive disease group than in the stable disease and partial response groups. Patients whose sPDL1 increased after the first cycle of chemotherapy showed worse PFS and OS. Following disease progression, sPDL1 increased compared with the baseline. Conclusion sPDL1 at prechemotherapy confers a prognostic value for PFS and OS in GC patients under palliative first-line chemotherapy. Dynamics of sPDL1 during chemotherapy correlates with disease progression.