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 is rapidly absorbed. The apparent bioavailability of leucovorin was 97% for 25 mg, 75% for 50 mg, and 37% for 100 mg.
Duration of action: All routes: 3 to 6 hours.
Onset of action: Oral: 20 to 30 minutes. Intramuscular: 10 to 20 minutes. Intravenous: Less than 5 minutes.
Crosses blood-brain barrier in moderate amounts; largely concentrated in liver.
Elimination: Renal: 80-90%. Fecal: 5-8%.
For more Absorption, Distribution and Excretion (Complete) data for LEUCOVORIN (10 total), please visit the HSDB record page.

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Metabolism / Metabolites
Hepatic and intestinal mucosal, the main metabolite being the active 5-methyltetrahydrofolate. Leucovorin is readily converted to another reduced folate, 5,10-methylenetetrahydrofolate, which acts to stabilize the binding of fluorodeoxyridylic acid to thymidylate synthase and thereby enhances the inhibition of this enzyme.
In vivo, leucovorin calcium is rapidly and extensively converted to other tetrahydrofolic acid derivatives including 5-methyl tetrahydrofolate, which is the major transport and storage form of folate in the body. /Leucovorin calcium/
Hepatic and intestinal mucosal, mainly to 5-methyltetrahydrofolate (active). After oral administration, leucovorin is substantially (greater than 90%) and rapidly (within 30 minutes) metabolized. Metabolism is less extensive (about 66% after intravenous and 72% after intramuscular administration) and slower with parenteral administration.

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Biological Half-Life
6.2 hours
Terminal half-life for total reduced folates: 6.2 hours.

Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
Leucovorin (folinic acid; 5-formyltetrahydrofolic acid) and its levo- isomer, levoleucovorin, are folic acid derivatives that are normal components of breastmilk. Because leucovorin and levoleucovorin are used as therapeutic agents with potentially toxic drugs such as fluorouracil or methotrexate, the LactMed record of the drug it is used with should be consulted.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

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Protein Binding
~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-formyltetrahydrofolic acid is a formyltetrahydrofolic acid in which the formyl group is located at position 5. It has a role as an Escherichia coli metabolite and a mouse metabolite. It is a conjugate acid of a 5-formyltetrahydrofolate(2-).
Folinic Acid (also known as 5-formyl tetrahydrofolic acid or leucovorin) is the 5-formyl derivative of tetrahydrofolic acid, a necessary co-factor in the body. Commercially available leucovorin is composed of a 1:1 racemic mixture of the dextrorotary and levorotary isomers, while levoleucovorin contains only the pharmacologically active levo-isomer. In vitro, the levo-isomer has been shown to be rapidly converted to the biologically available methyl-tetrahydrofolate form while the dextro form is slowly excreted by the kidneys. Despite this difference in activity, the two commercially available forms have been shown to be pharmacokinetically identical and may be used interchangeably with limited differences in efficacy or side effects (Kovoor et al, 2009). As folate analogs, leucovorin and levoleucovorin are both used to counteract the toxic effects of folic acid antagonists, such as methotrexate, which act by inhibiting the enzyme dihydrofolate reductase (DHFR). They are indicated for use as rescue therapy following use of high-dose methotrexate in the treatment of osteosarcoma or for diminishing the toxicity associated with inadvertent overdosage of folic acid antagonists. Injectable forms are also indicated for use in the treatment of megaloblastic anemias due to folic acid deficiency when oral therapy is not feasible and for use in combination with 5-fluorouracil to prolong survival in the palliative treatment of patients with advanced colorectal cancer. Folic acid is an essential B vitamin required by the body for the synthesis of purines, pyrimidines, and methionine before incorporation into DNA or protein. However, in order to function in this role, it must first be reduced by the enzyme dihydrofolate reductase (DHFR) into the cofactors dihydrofolate (DHF) and tetrahydrofolate (THF). This important pathway, which is required for de novo synthesis of nucleic acids and amino acids, is disrupted when high-dose methotrexate is used for cancer therapy. As methotrexate functions as a DHFR inhibitor to prevent DNA synthesis in rapidly dividing cells, it also prevents the formation of DHF and THF. This results in a deficiency of coenzymes and a resultant buildup of toxic substances that are responsible for numerous adverse side effects associated with methotrexate therapy. As levoleucovorin and leucovorin are analogs of tetrahydrofolate (THF), they are able to bypass DHFR reduction and act as a cellular replacement for the co-factor THF, thereby preventing these toxic side effects.
Leucovorin is a Folate Analog.
Leucovorin has been reported in Capsicum annuum var. annuum with data available.
Leucovorin is a derivative of folic acid with chemoprotectant, antidote and synergistic activity. Leucovorin does not require metabolism by dihydrofolate reductase, the molecular target of folate antagonist-type chemotherapeutic drugs, and is converted to a tetrahydrofolate, which is the necessary folate for purine and pyrimidine synthesis. As this agent allows for some purine/pyrimidine synthesis to occur, the toxic effects of folic acid antagonist-type chemotherapeutic drugs are counteracted while still permitting the antitumor activity of the folic acid antagonist through dihydrofolate reductase inhibition. This agent also potentiates the effects of 5-fluorouracil and its derivatives by stabilizing the binding of 5-fluorouracil's converted form fluorodeoxyuridylic acid to its target enzyme thymidylate synthase, thus prolonging drug activity.
The active metabolite of FOLIC ACID. Leucovorin is used principally as an antidote to FOLIC ACID ANTAGONISTS.
See also: Leucovorin Calcium (has salt form) ... View More ...

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Drug Indication
For the treatment of osteosarcoma (after high dose methotrexate therapy). Used to diminish the toxicity and counteract the effects of impaired methotrexate elimination and of inadvertent overdosages of folic acid antagonists, and to treat megaloblastic anemias due to folic acid deficiency. Also used in combination with 5-fluorouracil to prolong survival in the palliative treatment of patients with advanced colorectal cancer.
FDA Label

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Mechanism of Action
As leucovorin is a derivative of folic acid, it can be used to increase levels of folic acid under conditions favoring folic acid inhibition (following treatment of folic acid antagonists such as methotrexate). Leucovorin enhances the activity of fluorouracil by stabilizing the bond of the active metabolite (5-FdUMP) to the enzyme thymidylate synthetase.
Leucovorin is a derivative of tetrahydrofolic acid, the reduced form of folic acid, which is involved as a cofactor for 1-carbon transfer reactions in the biosynthesis of purines and pyrimidines of nucleic acids. Impairment of thymidylate synthesis in patients with folic acid deficiency is thought to account for the defective DNA synthesis that leads to megaloblast formation and megaloblastic and macrocytic anemias. Because of its ready conversion to other tetrahydrofolic acid derivatives, leucovorin is a potent antidote for both the hematopoietic and reticuloendothelial toxic effects of folic acid antagonists (eg, methotrexate, pyrimethamine, trimethoprim). It is postulated that in some cancers leucovorin enters and rescues normal cells from the toxic effects of folic acid antagonists, in preference to tumor cells, because of a difference in membrane transport mechanisms; this principle is the basis of high dose methotrexate therapy with leucovorin rescue.

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.)