Thymidylate Synthase

The percentage of aberrant cells (Abs) and micronucleated binucleated cells (MNBN) increased concentration-dependently when methotrexate (MTX) was used alone. The nuclear division index (NDI) falls as MTX concentration rises. Similarly, in all experiments, the addition of 50 μg/mL leucovorin dramatically decreased the percentages of MNBN (40-68%) and Abs (36-77%). Additionally, at 5 μg/mL leucovorin, inhibitory effects were noted (12% to 54% for MNBN and 20% to 61% for Abs) [1].

Leucovorin (7.0 mg/kg; i.p.; every other day; for 3 weeks; Balb/c Juvenile Solution) medication is administered after methotrexate (MTX) and seems to reverse the growth inhibition of MTX (Long-Term Give attention to MTX Fed rabbits atherosclerosis progresses slowly when given dextrapril (5–20 mg/kg) [2]. Delapril (1-2 mg/kg, po, once daily for 5 weeks) When studying hypertension in an animal model: Fed rabbits cholesterol [2]

Animal/Disease Models: 24 3weeks old Balb/c young growing male mice (11.88±0.25 g) [2]
Doses: 7.0 mg/kg
Route of Administration: intraperitoneal (ip) injection; every other day; for 3 weeks
Experimental Results: After MTX administration appears to reverse this growth inhibition.

Absorption, Distribution and Excretion
Following oral administration, leucovorin calcium is rapidly absorbed. The apparent bioavailability of leucovorin calcium at doses of 25 mg, 50 mg, and 100 mg is 97%, 75%, and 37%, respectively. Duration of Action: All routes of administration: 3 to 6 hours. Onset of Action: Oral: 20 to 30 minutes; Intramuscular: 10 to 20 minutes; Intravenous: Less than 5 minutes. Moderate amounts cross the blood-brain barrier; primarily concentrated in the liver. Excretion: Renal: 80–90%. Fecal: 5–8%. For more complete data on the absorption, distribution, and excretion of leucovorin calcium (10 types), please visit the HSDB record page. Metabolism/Metabolites Primarily metabolized in the liver and intestinal mucosa; the major metabolite is active 5-methyltetrahydrofolate. Calcium folinate is readily converted to another reduced form of folic acid—5,10-methylenetetrahydrofolate. The latter stabilizes the binding of fluorodeoxypyridinic acid to thymidine synthase, thereby enhancing its inhibitory effect on the enzyme. In vivo, calcium folinate is rapidly and extensively converted to other tetrahydrofolate derivatives, including 5-methyltetrahydrofolate, which is the main transport and storage form of folic acid in the body. Calcium folinate is primarily metabolized in the liver and intestinal mucosa, mainly to 5-methyltetrahydrofolate (the active ingredient). After oral administration, calcium folinate is rapidly metabolized (within 30 minutes), with a metabolic rate exceeding 90%. The metabolic rate is lower after intravenous injection (approximately 66%), and approximately 72% after intramuscular injection. Parenteral administration results in a slower metabolic rate.

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Biological Half-Life
6.2 hours
The terminal half-life of total reduced folic acid is 6.2 hours.

Effects During Pregnancy and Lactation
◉ Overview of Medication Use During Lactation
Leucovorin calcium (folate; 5-formyltetrahydrofolate) and its levorotatory isomer, levofolinate calcium, are folic acid derivatives and normal components of breast milk. Because levofolinate calcium and levofolinate calcium are often used in combination with potentially toxic drugs such as fluorouracil or methotrexate, relevant drug records in the LactMed database should be consulted.
◉ Effects on Breastfed Infants
No published information found as of the revision date.
◉ Effects on Lactation and Breast Milk
No published information found as of the revision date.

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Protein Binding Rate
~15%

[1]. Inhibition of methotrexate-induced chromosomal damage by folinic acid in V79 cells. Mutat Res, 1998. 397(2): p. 221-8.

[2]. Effect of methotrexate and folinic acid on skeletal growth in mice. Acta Paediatr. 2003 Dec;92(12):1438-44.

5-Formyltetrahydrofolate is a formyltetrahydrofolate with the formyl group at the 5-position. It is a metabolite of Escherichia coli and mice. It is the conjugate acid of 5-formyltetrahydrofolate (2-). Folliculate (also known as 5-formyltetrahydrofolate or calcium folinate) is a 5-formyl derivative of tetrahydrofolate and is an essential cofactor for humans. Commercially available calcium folinate consists of a 1:1 racemic mixture of dextrorotatory and levorotatory isomers, while levorotatory calcium folinate contains only the pharmacologically active levorotatory isomer. In vitro studies have shown that the levorotatory isomer is rapidly converted to the bioavailable form of methyltetrahydrofolate, while the dextrorotatory isomer is slowly excreted by the kidneys. Despite the difference in activity, the pharmacokinetic properties of the two commercially available formulations have been shown to be identical, with limited differences in efficacy and side effects, and they are interchangeable (Kovoor et al., 2009). As folic acid analogs, leucovorin calcium and levofolinate calcium are used to counteract the toxic effects of folic acid antagonists such as methotrexate, which work by inhibiting dihydrofolate reductase (DHFR). They are suitable as salvage therapy after high-dose methotrexate treatment in osteosarcoma, or to mitigate toxicity caused by accidental overdose of folic acid antagonists. Injectable formulations are also suitable for treating megaloblastic anemia caused by folic acid deficiency when oral therapy is not feasible, and for palliative care in advanced colorectal cancer in combination with 5-fluorouracil to prolong patient survival. Folic acid is an essential B vitamin required for the synthesis of purines, pyrimidines, and methionines before they are integrated into DNA or proteins. However, folic acid must first be reduced by dihydrofolate reductase (DHFR) to the cofactors dihydrofolate (DHF) and tetrahydrofolate (THF) to exert its function. This important synthetic pathway (essential for the de novo synthesis of nucleic acids and amino acids) is disrupted when high-dose methotrexate is used in cancer treatment. Because methotrexate, as a DHFR inhibitor, inhibits DNA synthesis in rapidly dividing cells, it also inhibits the production of DHF and THF. This leads to coenzyme deficiency and ultimately the accumulation of toxic substances, which are the culprits behind many adverse side effects of methotrexate treatment. Since levofolinic acid and folinic acid are analogs of tetrahydrofolate (THF), they bypass the reducing action of dihydrofolate reductase (DHFR) and act as cellular substitutes for the cofactor THF, thus avoiding these toxic side effects. Levofolinic acid is a folic acid analog. It has been reported that folinic acid is present in capsicum (Capsicum annuum var. annuum), and relevant data exist. Levofolinic acid is a derivative of folic acid with chemoprotective, detoxifying, and synergistic effects. Levofolinic acid can be converted to tetrahydrofolate without being metabolized by dihydrofolate reductase (the molecular target of folic acid antagonist chemotherapy drugs), and tetrahydrofolate is folic acid essential for the synthesis of purines and pyrimidines. Because this drug allows for partial purine/pyrimidine synthesis, it can counteract the toxicity of folate antagonist chemotherapy drugs, while still maintaining the antitumor activity of folate antagonists by inhibiting dihydrofolate reductase. This drug can also enhance the activity of 5-fluorouracil and its derivatives by stabilizing the binding of its 5-fluorouracil metabolite, fluorodeoxyuridine, to its target enzyme, thymidylate synthase, thereby prolonging drug activity.
Active metabolite of folic acid. Calcium folinate is mainly used as an antidote for folate antagonists.
See also: Calcium folinate (salt form)...see more...

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Drug Indications
For the treatment of osteosarcoma (after high-dose methotrexate treatment). For reducing and counteracting the toxicity caused by methotrexate clearance disorders and accidental overdose of folate antagonists, and for the treatment of megaloblastic anemia due to folate deficiency. It can also be used in combination with 5-fluorouracil to prolong palliative survival in patients with advanced colorectal cancer.
FDA Label
Mechanism of Action
Because leucovorin is a derivative of folic acid, it can be used to increase folic acid levels in situations favorable for folic acid inhibition (e.g., after treatment with folic acid antagonists such as methotrexate). Leucovorin enhances the activity of fluorouracil by stabilizing the binding of its active metabolite (5-FdUMP) to thymidine synthase. Leucovorin is a derivative of tetrahydrofolate, the reduced form of folic acid, which participates as a cofactor in the single-carbon transfer reaction in the biosynthesis of purines and pyrimidines in nucleic acids. Impaired thymidine synthesis in patients with folic acid deficiency is considered a cause of DNA synthesis defects, leading to megaloblast formation and megaloblastic anemia and megaloblastic anemia. Because leucovorin is readily converted to other tetrahydrofolate derivatives, it is a potent antidote for the hematopoietic and reticuloendothelial system toxicity caused by folic acid antagonists (such as methotrexate, pyrimethamine, and trimethoprim). It is speculated that in some cancers, due to differences in membrane transport mechanisms, leucovorin enters and rescues normal cells from the toxic effects of folic acid antagonists, rather than tumor cells; this principle forms the basis of high-dose methotrexate combined with leucovorin rescue therapy.

C20H23N7O7

473.446

473.166

C, 50.74; H, 4.90; N, 20.71; O, 23.65

58-05-9

Folinic acid calcium;1492-18-8;Folinic acid calcium salt pentahydrate;6035-45-6;Folinic acid disodium;163254-40-8;Folinic acid calcium hydrate;1097832-14-8;Folinic acid-d4 calcium hydrate

135403648

Off-white to light yellow solid powder

1.68g/cm3

245ºC (decomp)

1.748

1.152

7

10

9

34

911

1

O=C(O)CC[C@@H](C(O)=O)NC(C1=CC=C(NCC2N(C=O)C3=C(N=C(N)NC3=O)NC2)C=C1)=O

VVIAGPKUTFNRDU-ABLWVSNPSA-N

InChI=1S/C20H23N7O7/c21-20-25-16-15(18(32)26-20)27(9-28)12(8-23-16)7-22-11-3-1-10(2-4-11)17(31)24-13(19(33)34)5-6-14(29)30/h1-4,9,12-13,22H,5-8H2,(H,24,31)(H,29,30)(H,33,34)(H4,21,23,25,26,32)/t12?,13-/m0/s1

(2S)-2-[[4-[(2-amino-5-formyl-4-oxo-3,6,7,8-tetrahydropteridin-6-yl)methylamino]benzoyl]amino]pentanedioic acid

Leucovorin; Folinic acid; HSDB-6544; HSDB6544; HSDB 6544

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: (1). This product requires protection from light (avoid light exposure) during transportation and storage.  (2). Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture.

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

DMSO: 95~250 mg/mL (200.7~528.1 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (4.39 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 20.8 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: ≥ 2.08 mg/mL (4.39 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 20.8 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: ≥ 2.08 mg/mL (4.39 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 20.8 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.)