A phase I open-label, dose-escalation study of NUC-3373, a targeted thymidylate synthase inhibitor, in patients with advanced cancer (NuTide:301).

PURPOSE: 5-fluorouracil (5-FU) is inefficiently converted to the active anti-cancer metabolite, fluorodeoxyuridine-monophosphate (FUDR-MP), is associated with dose-limiting toxicities and challenging administration schedules. NUC-3373 is a phosphoramidate nucleotide analog of fluorodeoxyuridine (FUDR) designed to overcome these limitations and replace fluoropyrimidines such as 5-FU. PATIENTS AND METHODS: NUC-3373 was administered as monotherapy to patients with advanced solid tumors refractory to standard therapy via intravenous infusion either on Days 1, 8, 15 and 22 (Part 1) or on Days 1 and 15 (Part 2) of 28-day cycles until disease progression or unacceptable toxicity. Primary objectives were maximum tolerated dose (MTD) and recommended Phase II dose (RP2D) and schedule of NUC-3373. Secondary objectives included pharmacokinetics (PK), and anti-tumor activity. RESULTS: Fifty-nine patients received weekly NUC-3373 in 9 cohorts in Part 1 (n = 43) and 3 alternate-weekly dosing cohorts in Part 2 (n = 16). They had received a median of 3 prior lines of treatment (range: 0-11) and 74% were exposed to prior fluoropyrimidines. Four experienced dose-limiting toxicities: two Grade (G) 3 transaminitis; one G2 headache; and one G3 transient hypotension. Commonest treatment-related G3 adverse event of raised transaminases occurred in < 10% of patients. NUC-3373 showed a favorable PK profile, with dose-proportionality and a prolonged half-life compared to 5-FU. A best overall response of stable disease was observed, with prolonged progression-free survival. CONCLUSION: NUC-3373 was well-tolerated in a heavily pre-treated solid tumor patient population, including those who had relapsed on prior 5-FU. The MTD and RP2D was defined as 2500 mg/m2 NUC-3373 weekly. NUC-3373 is currently in combination treatment studies. TRIAL REGISTRATION: Clinicaltrials.gov registry number NCT02723240. Trial registered on 8th December 2015. https://clinicaltrials.gov/study/NCT02723240 .

Cinobufagin restrains the growth and triggers DNA damage of human hepatocellular carcinoma cells via proteasome-dependent degradation of thymidylate synthase.

Anti-tumor candidate drugs from natural products have gained increasing attention. Cinobufagin is a natural product isolated from the traditional chinese medicine Chansu. Herein, we find that cinobufagin inhibits the proliferation and colony-forming ability of human hepatoma HepG2 and SK-HEP-1 cells. Furthermore, cinobufagin induces G2-phase cell cycle arrest and DNA damage in cancer cells. Thymidylate synthase (TYMS), the major target of chemotherapeutic drugs 5-FU or other fluoropyrimidines, which catalyzes the conversion of dUMP to dTMP and provides the sole de novo source of thymidylate for DNA synthesis. We demonstrate that cinobufagin suppresses TYMS expression via proteasome-dependent degradation in human hepatoma cells, moreover, depletion of TYMS restrains the proliferation and colony formation of tumor cells, and the results of western blotting and immunofluorescence assay indicate DNA damage is induced in tumor cells transfected with TYMS-targeting siRNA (siTYMS), additionally, knockdown of TYMS enhances the inhibitory effect of cinobufagin on the proliferative potential of HepG2 and SK-HEP-1 cells. It is worth noting that cinobufagin in combination with 5-FU exhibits antagonism or synergism combined effects on the proliferation of human hepatoma cells, indicating that Chansu-related preparations such as cinobufacini injection and Huachansu capsules applied to clinical practice should be used with caution in combination with 5-FU for the treatment of liver cancer. Collectively, cinobufagin exerts good anti-hepatoma activity through inhibition of growth and induction of DNA damage by promoting the degradation of TYMS. Our results provide evidence that cinobufagin might be a potential agent for the treatment of cancers such as hepatocellular carcinoma. It can also promote the scientific development of Chansu, and has great significance for enriching the application of TCM in the development of new anti-tumor drugs.

Phase II Study of Pemetrexed as a Salvage Chemotherapy for Thymidylate Synthase-Low Squamous Cell Lung Cancer.

PURPOSE: Squamous cell carcinomas (SqCC) of the lung often express high levels of thymidylate synthase (TS), which is associated with primary resistance to pemetrexed. We explored the efficacy of pemetrexed in a selected population of patients with lung SqCC with low TS expression. MATERIALS AND METHODS: In this single-arm phase II trial, we enrolled 32 previously-treated patients with advanced lung SqCC exhibiting low immunohistochemical staining for TS (i.e., in 10% or less of tumor cells). The primary endpoint was 12-week progression-free survival (PFS) rate. RESULTS: Of 32 patients, eight patients (25%) had an Eastern Cooperative Oncology Group performance status of 2, and seven patients (22%) had previously received three or more lines of chemotherapy. The disease control rate from pemetrexed treatment was 30%, and no objective response was observed. The 12-week PFS rate was 24.5% (95% confidence interval [CI], 13.0 to 46.1). Median PFS was 1.3 months (95% CI, 1.3 to 2.7), and median overall survival was 11.8 months (95% CI, 8.1 to not applicable). Most of adverse events were grade 1 or 2. CONCLUSION: Pemetrexed demonstrated modest activity as a salvage chemotherapy in patients with advanced lung SqCC with low TS expression, although its toxicity was generally manageable.

Thymidylate synthase expression and prognosis in colorectal cancer: a meta-analysis of colorectal cancer survival data.

BACKGROUND: Although many studies have investigated the prognostic effect of thymidylate synthase (TS) in colorectal cancer, no consensus has been reached. The aim of this meta-analysis was to obtain a more precise estimate of the prognostic significance of TS expression in localized cancers treated by curative resection and adjuvant chemotherapy. MATERIALS AND METHOD: Seventeen eligible studies reporting survival in 2,893 patients stratified by TS expression were pooled using a fixed- or random-effects model. The main outcome measure was hazard ratio (HR). RESULTS: The overall HR for overall survival was 1.01 (95% CI 0.74-1.39, p=0.947), with an I2 of 64.4%. The total HR for disease-free survival was 1.36 (95% CI 0.97-1.89, p=0.072), with an I2 of 75.8%. In the TS protein-tested subgroup, the total HR for disease-free survival was 1.72 (95% CI 1.02-2.89, p=0.042), with an I2 of 81.3%. CONCLUSION: Our meta-analysis showed that, in the adjuvant setting, TS expression does not predict a poorer disease-free survival or a worse overall survival. Therefore, we believe that it is inappropriate to regard TS expression as a prognostic factor for patients with stage II and stage III colorectal cancer treated by surgery and adjuvant chemotherapy.

Pharmacogenetics of folate-related drug targets in cancer treatment.

Folate metabolism is the target of two major drug groups: folate antagonists (for example, methotrexate) and thymidylate synthase inhibitors (for example, 5-fluorouracil). These agents are used in the treatment of cancer, as well as for other conditions, such as rheumatoid arthritis. High-dose cancer treatment protocols can induce a state of acute folate depletion which may lead to significant treatment-related toxicity. Polymorphisms in folate-metabolizing enzymes may modify the therapeutic effectiveness and toxicity of these drugs. This review briefly summarizes the drugs targeting the folate pathway and describes common polymorphisms in folate-metabolizing enzymes and transport proteins. Pharmacogenetic studies investigating folate-related drug targets in the treatment of colorectal cancers and hematologic malignancies will subsequently be discussed. Findings to date illustrate a potential for targeting therapy based on patients' genotypes, in order to improve outcomes and reduce toxicity. However, larger, well-designed studies are needed to confirm these early findings.

Pharmacogenomics of thymidylate synthase in cancer treatment.

Cancer drugs such as 5-fluorouracil (5-FU) that target the enzyme thymidylate synthase (TS) have been and are still being widely used in cancer treatment, but as with other anti-cancer drugs, the majority of tumors do not respond to the treatment, whereas the patients still suffer drug-related toxicity. The most recent attempts at improving cancer treatment have taken the pharmacogenetic approach of identifying biochemical response determinants for response, so that patients with suboptimal determinants who unlikely to respond can be identified prior to treatment. Studies to date indicate that high intratumoral levels of TS gene expression or TS protein generally predict for non-response, whereas low levels are associated with a high response rate. Measuring these determinants requires tumor tissue and, in the case of gene expression, a technically demanding quantitative PCR procedure. Thus, considerable interest was generated by data suggesting that the variable number of a 28 base-pair (bp) segment in the promoter region of the TS gene was associated with TS gene expression and/or protein expression, as well as with tumor response to 5-FU therapy, toxicity and patient survival. However, not all studies have obtained the same results, so that the role of this TS polymorphism as a predictor of treatment outcome is still not clear and is currently under evaluation. This review will summarize pharmacogenomic studies of TS that were aimed at elucidating the function of this genetic polymorphism.