Hidetsugu Fujigaki

BACKGROUND: Cisplatin-induced nephrotoxicity (CIN) is a major dose-limiting adverse event that can lead to both acute and chronic kidney injury. The formation of thiol-cisplatin conjugates within renal tubular cells has been implicated as a key mechanism underlying CIN. Flopropione is an inhibitor of cysteine conjugate β-lyase 1, an enzyme that catalyzes the formation of the thiol-cisplatin conjugate, which might prevent CIN. OBJECTIVE: We designed a clinical trial to evaluate the safety of flopropione in patients receiving cisplatin-based chemotherapy and explore its efficacy in preventing CIN. METHODS: This is a phase 1 and 2a, single-center, randomized, open-label trial conducted in patients undergoing cisplatin therapy. Participants are randomized in a 5:2 ratio per cohort to receive either flopropione or no treatment. On the day of cisplatin administration, the flopropione group receives oral flopropione twice daily (80 mg in cohort 1, 160 mg in cohort 2, and 240 mg in cohort 3). On the following day, all cohorts receive 3 doses of 80 mg of oral flopropione. A step-up dose escalation design is adopted, progressing from cohort 1 to 3 after confirming safety at each level. The primary end point is the safety of flopropione use in combination with cisplatin; the secondary end points include changes in the levels of urinary biomarkers of nephrotoxicity such as neutrophil gelatinase-associated lipocalin, liver-type fatty acid-binding protein, and kidney injury molecule-1. Blood and urine samples are collected within 48 hours before cisplatin administration and at 24 hours, 48 hours, and 1 week after its initiation for safety and efficacy assessments. RESULTS: The first participant was registered in July 2024. As of January 2026, participant registration is ongoing. The final participant will complete the study by March 2026. Publication of results is expected by March 2027. CONCLUSIONS: This study is expected to contribute to advances in preventive strategies for CIN by providing evidence that inhibition of cysteine conjugate β-lyase 1 by flopropione may attenuate CIN. TRIAL REGISTRATION: Japan Registry of Clinical Trials jRCTs041220021; https://jrct.mhlw.go.jp/en-latest-detail/jRCTs041220021. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/87907.

ObjectivesReports have shown that the kynurenine pathway, one of the pathways by which tryptophan is metabolized, is activated in patients with diffuse large B-cell lymphoma (DLBCL). Activation of the kynurenine pathway triggers the production of various metabolites, such as kynurenine (Kyn), 3-hydroxykynurenine (3-HK), 3-hydroxyanthranilic acid (3-HAA), kynurenic acid (KA), and anthranilic acid (AA), which contribute to immune tolerance. The current study aimed to investigate the changes in metabolites of kynurenine pathway in DLBCL patients and evaluate their performance predicting DLBCL.MethodsChanges in metabolites of kynurenine pathway were examined using high-performance liquid chromatography in 35 DLBCL patients (age 61.2 ± 13.5 years) and 44 healthy controls (age 58.5 ± 12.5 years).ResultsDLBCL patients had significantly higher levels of 3-HK, AA, and 3-HAA but lower levels of tryptophan (Trp) and KA compared to healthy controls. Given that the ratio of each metabolite represents the change in the Kyn pathway, the 3-HK/KA ratio was examined. Notably, DLBCL patients had a significantly higher 3-HK/KA ratio compared to healthy controls. In DLBCL, the area under the receiver operative characteristic (ROC) curve for 3-HK/KA (0.999) was higher than that for lactate dehydrogenase (0.885) and comparable to that for soluble interleukin-2 receptor (sIL-2R) (0.997). Based on ROC curve analysis, the 3-HK/KA ratio was found to be useful biomarker for the diagnosis of DLBCL.ConclusionOur results suggest that the 3-HK/KA ratio is a clinically useful biomarker of DLBCL. Moreover, its combination with existing markers, such as sIL-2R, can improve its effectiveness of diagnosing DLBCL.

BACKGROUND: The accumulation of quinolinic acid (QUIN) in cerebrospinal fluid and serum may be used as a biomarker for various neuropsychiatric and inflammatory diseases. In this study, we developed a highly sensitive method to measure QUIN. METHODS: A reverse-phase high-performance liquid chromatography (HPLC) with fluorescence detection was established based on the enzymatic conversion of QUIN to nicotinic acid mononucleotide by recombinant quinolinic acid phosphoribosyltransferase, followed by the formation of fluorescent (BODIPY)-labeled deamido-NAD by recombinant nicotinic acid mononucleotide adenyltransferase. RESULTS: BODIPY-deamido-NAD was isocratically eluted within 6 minutes using reverse-phase chromatography and its chromatographic peak was resolved. The calibration range, precision, and analytical recovery of the QUIN assay are suitable for the analysis of biological fluids. Compared with published quantitation limits for QUIN measurement by HPLC, this method is at least 30-fold more sensitive and has a lower limit of detection of 5.0 nmol/L. The sensitivity was comparable to that previously reported for gas chromatography/mass spectrometry (GC/MS) and the quantitation results of QUIN from samples of cerebrospinal fluid correlated well with that of the GC/MS method. CONCLUSIONS: We established a novel method to quantify QUIN in biological samples. Due to its high sensitivity and the fact that it does not rely on MS instrumentation, this method has the potential for widespread adoption in research laboratories.