HSV-2; HSV-1; Nucleoside Antimetabolite/Analog; Thymidylate Synthase

Trifluridine has a notably lower number of HSV-1-positive swabs infected rabbits' eyes compared to the untreated eyes.[4] Compared to mice that are continuously infused with trifluridine, humans have higher antitumor activity and greater DNA incorporation. When compared to treatment with 5-FU derivatives, trifluridine significantly slows tumor growth and prolongs survival in mice by gradually accumulating in tumor cell DNA in a TPI-independent manner.[5] In the New Zealand rabbit ocular model, trifluridine causes a significant reduction in viral titers, fewer HSV-1-positive eyes/total during the treatment period, lower keratitis scores, fewer eyes with keratitis/total, and a shorter time to resolution of keratitis.[6]

Absorption, Distribution and Excretion
After oral administration of LONSURF with [14C]-trifluridine, at least 57% of the administered trifluridine was absorbed. Following a single dose of LONSURF (35 mg/m2) in patients with advanced solid tumors, the mean times to peak plasma concentrations (Tmax) of trifluridine was around 2 hours. Trifluridine area under the concentration-time curve from time 0 to the last measurable concentration (AUC0-last) was approximately 3-fold higher and maximum concentration (Cmax) was approximately 2-fold higher after multiple dose administration (twice daily for 5 days a week with 2 days rest for 2 weeks followed by a 14-day rest, repeated every 4 weeks) than after single-dose administration. Following a single oral administration of LONSURF at 35 mg/m2 in patients with cancer, the mean time to peak plasma concentration (Tmax) of trifluridine was around 2 hours. For the ophthalmic formulation, systemic absorption appears to be negligible. A standardized high-fat, high-calorie meal decreased trifluridine Cmax by approximately 40% but did not change trifluridine AUC compared to those in a fasting state in patients with cancer following administration of a single dose of LONSURF 35 mg/m2. In a dose finding study (15 to 35 mg/m2 twice daily), the AUC from time 0 to 10 hours (AUC0-10) of trifluridine tended to increase more than expected based on the increase in dose.
After single oral administration of LONSURF (60 mg) with [14C]-trifluridine, the total cumulative excretion of radioactivity was 60% of the administered dose. The majority of recovered radioactivity was eliminated into urine (55% of the dose) as FTY and trifluridine glucuronide isomers within 24 hours and the excretion into feces and expired air was <3% for both. The unchanged trifluridine was <3% of administered dose recovered in the urine and feces.
Following a single dose of LONSURF (35 mg/m²) in patients with advanced solid tumours, the apparent volume of distribution (Vd/F) for trifluridine was 21 L.
Following a single dose of LONSURF (35 mg/m²) in patients with advanced solid tumours, the oral clearance (CL/F) for trifluridine was 10.5 L/hr.
Following topical application of trifluridine to the eye, the drug penetrates the cornea and can be detected in the aqueous humor.
Systemic absorption following ocular application of trifluridine appears to be negligible. In one study in healthy individuals, topical application of trifluridine 1% ophthalmic solution to the eyes 7 times daily for 14 consecutive days did not result in detectable serum concentrations of trifluridine or 5-carboxy-2'-deoxyuridine.
During in vitro studies using excised rabbit corneas, the major metabolite of trifluridine, 5-carboxy-2'-deoxyuridine, was found on the endothelial side of the cornea in addition to the parent compound; however, detectable levels of the metabolite have not been found in the aqueous humor in humans.
It is unlikely that trifluridine is excreted in human milk after ophthalmic instillation of trifluridine because of the relatively small dosage (Metabolism / Metabolites
Trifluridine is not metabolized by cytochrome P450 (CYP) enzymes. Trifluridine is mainly eliminated by metabolism via thymidine phosphorylase to form an inactive metabolite, 5-(trifluoromethyl) uracil (FTY). No other major metabolites were detected in plasma or urine. Other minor metabolites, such as 5-carboxy-2'-deoxyuridine found on the endothelial side of the cornea or 5-carboxyuraci, were also detected, but only at low or trace level in plasma and urine.
The major metabolite of trifluridine (5-carboxy-2'-deoxyuridine appears) to have some antiviral activity but substantially less than that of the parent drug.
19F NMR spectroscopy has been used to study further the metabolism of 5-trifluoromethyl-2'-deoxyuridine (trifluridine; F3TdR). The synthesis and characterization of alpha-trifluoromethyl-beta-alanyl glycine (F3MBAG), a putative new metabolite of F3TdR, are now reported. This study describes ex vivo and in vivo detection of F3MBAG and other previously reported metabolites of trifluridine, using 19F NMR spectroscopy, in male BALB/C mice bearing EMT-6 tumors. A parallel 19F NMR spectroscopic study was also performed on rats dosed with F3TdR, to observe the qualitative pattern of F3TdR metabolism in another species. Unexpectedly, 5-trifluoromethyl-5,6-dihydroxyuracil (DOHF3T), alpha-trifluoromethyl-beta-ureidopropionic acid (F3MUPA) and fluoride, which result from the metabolic degradation of F3TdR and which were detected in various biological samples from mice dosed with F3TdR, could not be identified in rat urine or in homogenized tissue extracts. The presence of these metabolites in intact tissues is uncertain since in this study 19F NMR spectroscopy of these samples always displayed a broad resonance "hump" across the range of chemical shifts that would encompass these metabolites. No clear explanation for the loss of spectroscopic resolution in this region has been rationalized. N-Carboxy-alpha-trifluoromethyl-beta-alanine (F3MBA-CO2), alpha-trifluoromethyl-beta-alanyl alanine (F3MBAA) and N-acetyl-alpha-trifluoromethyl-beta-alanine (Ac-F3MBA) were synthesized and characterized, but were not detected as metabolites in any of the biological specimens examined.

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Biological Half-Life
After administration of LONSURF 35 mg/m², the mean elimination and steady-state half-life (t_1/2) of trifluridine was 1.4 hours and 2.1 hours respectively. For the ophthalmic formulation, the half-life is significantly shorter, approximately only 12 minutes.

Hepatotoxicity
Pooled analyses of preregistration clinical trials reported that serum enzyme elevations occurred in up to 24% of patients on trifluridine/tipiracil therapy, but were also elevated in 27% of controls. Similarly, ALT values above 5 times ULN occurred in 2% of trifluridine/tipiracil treated compared to 4% of placebo treated subjects. In these and subsequent studies, clinically apparent liver adverse reactions attributed to trifluridine/tipiracil were not reported.
Likelihood score: E (unlikely cause of clinically apparent liver injury).

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Protein Binding
_In vitro_ findings suggest that the protein binding of trifluridine in human plasma is greater than 96%, where it is mainly bound to human serum albumin. Protein binding of trifluridine is independent of drug concentration and presence of tipiracil.

[1]. Cancer Chemother Pharmacol . 2015 Aug;76(2):325-33.

[2]. Int J Oncol . 2015;46(6):2327-34.

[3]. Mol Cell Endocrinol . 2014 Jan 25;382(1):1-7.

[4]. Invest Ophthalmol Vis Sci . 1989 Apr;30(4):678-83.

[5]. Oncol Rep . 2014 Dec;32(6):2319-26.

[6]. Invest Ophthalmol Vis Sci . 1999 Feb;40(2):378-84.

Trifluridine is a pyrimidine 2'-deoxyribonucleoside compound having 5-trifluoromethyluracil as the nucleobase. An antiviral drug used mainly in the treatment of primary keratoconjunctivitis and recurrent epithelial keratitis. It has a role as an antiviral drug, an antimetabolite, an EC 2.1.1.45 (thymidylate synthase) inhibitor and an antineoplastic agent. It is a nucleoside analogue, an organofluorine compound and a pyrimidine 2'-deoxyribonucleoside.
Trifluridine is a fluorinated pyrimidine nucleoside that is structurally related to [idoxuridine]. It is an active antiviral agent in ophthalmic solutions used mainly in the treatment of primary keratoconjunctivitis and recurrent epithelial keratitis due to herpes simplex virus. It displays effective antiviral activity against Herpes simplex virus type 1 and 2. The combination product of trifluridine with tipiracil marketed as Lonsurf has been approved in Japan, the United States, and the European Union for the treatment of adult patients with metastatic colorectal cancer who have been previously treated with fluoropyrimidine-, oxaliplatin- and irinotecan-based chemotherapy, an anti-VEGF biological therapy, and if RAS wild-type, an anti-EGFR therapy. In the anticancer therapy, trifluridine acts as a thymidine-based nucleoside metabolic inhibitor that gets incorporated into DNA of cancer cells following cell uptake to aberrate DNA function during cell replication.
Trifluridine is a Nucleoside Analog Antiviral and Nucleoside Metabolic Inhibitor. The mechanism of action of trifluridine is as a Nucleic Acid Synthesis Inhibitor.
Trifluridine/tipiracil is the combination of an antineoplastic pyrimidine analogue (trifluridine) with an inhibitor of its metabolism (tipiracil) that is used in the therapy of refractory, metastatic colorectal cancer. Trifluridine/tipiracil is associated with a low rate of transient serum enzyme elevations during therapy, but has not been implicated in cases of clinically apparent acute liver injury with jaundice.
Trifluridine is a fluorinated thymidine analog with potential antineoplastic activity. Trifluridine is incorporated into DNA and inhibits thymidylate synthase, resulting in inhibition of DNA synthesis, inhibition of protein synthesis, and apoptosis. This agent also exhibits antiviral activity. (NCI04)
An antiviral derivative of THYMIDINE used mainly in the treatment of primary keratoconjunctivitis and recurrent epithelial keratitis due to HERPES SIMPLEX virus. (From Martindale, The Extra Pharmacopoeia, 30th ed, p557)
See also: Tipiracil hydrochloride; trifluridine (component of); Trifluridine; tipiracil (component of).

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Drug Indication
As a standalone product, trifluridine is used for the ophthalmic treatment of primay keratoconjunctivitis and recurrent epithelial keratitis due to herpes simplex virus, types 1 and 2. Trifluridine is also available as a combination product with [tipiracil], which is indicated either alone or in combination with [bevacizumab] for the treatment of adult patients with metastatic colorectal cancer who have been previously treated with fluoropyrimidine-, oxaliplatin- and irinotecan-based chemotherapy, an anti-VEGF biological therapy, and if RAS wild-type, an anti-EGFR therapy. This combination product is also used for adult patients with metastatic gastric or gastroesophageal junction adenocarcinoma and were previously treated with at least two prior lines of chemotherapy that included a fluoropyrimidine, a platinum, either a taxane or irinotecan, and if appropriate, HER2/neu-targeted therapy.
FDA Label

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Mechanism of Action
The mechanism of action of trifluridine as an antiviral agent has not been fully elucidated, but appears to involve the inhibition of viral replication. Trifluridine gets incorporated into viral DNA during replication, which leads to the formation of defective proteins and an increased mutation rate. Trifluridine also mediates antineoplastic activities via this mechanism; following uptake into cancer cells, trifluridine is rapidly phosphorylated by thymidine kinase to its active monophosphate form. Subsequent phosphorylation produces trifluridine triphosphate, which is readily incorporated into the DNA of tumour cells in place of thymidine bases to perturb DNA function, DNA synthesis, and tumour cell proliferation. As trifluridine is subject to rapid degradation by TPase and readily metabolised by a first-pass effect following oral administration, tipiracil is added in the antineoplastic combination product as an inhibitor of TPase to increase the bioavailability of trifluridine. Trifluridine monophosphate also reversibly inhibits thymidylate synthetase (TS), an enzyme that is necessary for DNA synthesis and which levels are shown to be elevated different cancer cell lines. Up-regulation of the expression of the TS enzyme may also lead to the resistance to antineoplastic therapies, such as 5-fluorouracil (5-FU). [A35289 However, this inhibitory effect is not considered to be sufficient enough to fully contribute to the cytotoxicity in cancer cells.
Trifluridine is a fluorinated pyrimidine nucleoside with in vitro and in vivo activity against herpes simplex virus, types 1 and 2 and vacciniavirus. Some strains of adenovirus are also inhibited in vitro. ...Trifluridine interferes with DNA synthesis in cultured mammalian cells. However, its antiviral mechanism of action is not completely known
The exact mechanism of antiviral activity of trifluridine has not been fully elucidated, but appears to involve inhibition of viral replication. Trifluridine, instead of thymidine, is incorporated into viral DNA during replication which results in the formation of defective proteins and an increased mutation rate. Trifluridine also reversibly inhibits thymidylate synthetase, an enzyme required for DNA synthesis.
Trifluridine has shown antiviral activity in vitro and in vivo against herpes simplex virus types 1 and 2 (HSV-1 and HSV-2). The drug is active in vitro against vaccinia virus and has shown in vivo activity in the treatment of vaccinia keratitis in rabbits. Trifluridine also has shown antiviral activity in cell culture against some strains of adenovirus. Trifluridine is inactive against bacteria, fungi, and Chlamydia.

C10H11F3N2O5

296.2

296.062

C, 40.55; H, 3.74; F, 19.24; N, 9.46; O, 27.01

70-00-8

6256

White to off-white solid powder

1.6±0.1 g/cm3

190-193 °C(lit.)

1.534

0.07

3

8

2

20

464

3

FC(C1C(N([H])C(N(C=1[H])[C@@]1([H])C([H])([H])[C@@]([H])([C@@]([H])(C([H])([H])O[H])O1)O[H])=O)=O)(F)F

VSQQQLOSPVPRAZ-RRKCRQDMSA-N

InChI=1S/C10H11F3N2O5/c11-10(12,13)4-2-15(9(19)14-8(4)18)7-1-5(17)6(3-16)20-7/h2,5-7,16-17H,1,3H2,(H,14,18,19)/t5-,6+,7+/m0/s1

1-[(2R,4S,5R)-4-hydroxy-5-(hydroxymethyl)oxolan-2-yl]-5-(trifluoromethyl)pyrimidine-2,4-dione

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (8.44 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (8.44 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (8.44 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)