Thymidylate Synthase

当单独使用甲氨蝶呤 (MTX) 时，异常细胞 (Abs) 和微核双核细胞 (MNBN) 的百分比呈浓度依赖性增加。核分裂指数 (NDI) 随着 MTX 浓度的升高而下降。同样，在所有实验中，添加 50 μg/mL 亚叶酸显着降低了 MNBN (40-68%) 和 Abs (36-77%) 的百分比。此外，在 5 μg/mL 亚叶酸下，观察到抑制作用（MNBN 为 12% 至 54%，Abs 为 20% 至 61%）[1]。

在甲氨蝶呤 (MTX) 之后给予甲酰四氢叶酸（7.0 mg/kg；腹膜内注射；每隔一天；持续 3 周；Balb/c 幼年溶液）药物，似乎可以逆转 MTX 的生长抑制（长期关注 MTX 喂养的兔子）给予右旋普利 (5–20 mg/kg) 时，动脉粥样硬化进展缓慢 [2]。地拉普利（1-2 mg/kg，口服，每天一次，持续 5 周）在动物模型中研究高血压时：喂食兔子胆固醇 [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

219.84

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

注意： (1). 本产品在运输和储存过程中需避光。  (2). 请将本产品存放在密封且受保护的环境中（例如氮气保护），避免吸湿/受潮。

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)

配方 1 中的溶解度: ≥ 2.08 mg/mL (4.39 mM) (饱和度未知) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (这些助溶剂从左到右依次添加，逐一添加), 澄清溶液。
例如，若需制备1 mL的工作液，可将100 μL 20.8 mg/mL澄清DMSO储备液加入400 μL PEG300中，混匀；然后向上述溶液中加入50 μL Tween-80，混匀；加入450 μL生理盐水定容至1 mL。
*生理盐水的制备：将 0.9 g 氯化钠溶解在 100 mL ddH₂O中，得到澄清溶液。

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配方 2 中的溶解度: ≥ 2.08 mg/mL (4.39 mM) (饱和度未知) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (这些助溶剂从左到右依次添加，逐一添加), 澄清溶液。
例如，若需制备1 mL的工作液，可将 100 μL 20.8 mg/mL澄清DMSO储备液加入900 μL 20% SBE-β-CD生理盐水溶液中，混匀。
*20% SBE-β-CD 生理盐水溶液的制备（4°C，1 周）：将 2 g SBE-β-CD 溶解于 10 mL 生理盐水中，得到澄清溶液。

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配方 3 中的溶解度: ≥ 2.08 mg/mL (4.39 mM) (饱和度未知) in 10% DMSO + 90% Corn Oil (这些助溶剂从左到右依次添加，逐一添加), 澄清溶液。
例如，若需制备1 mL的工作液，可将 100 μL 20.8 mg/mL 澄清 DMSO 储备液加入到 900 μL 玉米油中并混合均匀。

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请根据您的实验动物和给药方式选择适当的溶解配方/方案：
1、请先配制澄清的储备液(如：用DMSO配置50 或 100 mg/mL母液(储备液));
2、取适量母液，按从左到右的顺序依次添加助溶剂，澄清后再加入下一助溶剂。以 下列配方为例说明 (注意此配方只用于说明，并不一定代表此产品 的实际溶解配方):
10% DMSO → 40% PEG300 → 5% Tween-80 → 45% ddH2O (或 saline);
假设最终工作液的体积为 1 mL, 浓度为5 mg/mL: 取 100 μL 50 mg/mL 的澄清 DMSO 储备液加到 400 μL PEG300 中，混合均匀/澄清；向上述体系中加入50 μL Tween-80，混合均匀/澄清；然后继续加入450 μL ddH2O (或 saline)定容至 1 mL；
3、溶剂前显示的百分比是指该溶剂在最终溶液/工作液中的体积所占比例;
4、 如产品在配制过程中出现沉淀/析出，可通过加热(≤50℃)或超声的方式助溶;
5、为保证最佳实验结果，工作液请现配现用！
6、如不确定怎么将母液配置成体内动物实验的工作液，请查看说明书或联系我们;
7、 以上所有助溶剂都可在 Invivochem.cn网站购买。