Over a daily distribution, nitisinone (5, 10 mg/kg; venous access; 5 weekly for 6 weeks) inhibits HPPD in a way that is both dose- and time-suppressive [2]. In OCA-1A and OCA-1B animals, nitisinone (4 mg/kg; venous access; once daily; 1 month apart) inhibits tyrosine [3]. In the OCA-1B model, nitisinone (4 mg/kg; once daily; one month apart) increases melanin concentration in ocular tissue melanosomes and pigmentation of the hair and iris [3]. Note: Type 1 Ocular-Clusive Albinism (OCA1). OCA-1A and OCA-1B are the two variants of OCA1. While some melanin is formed at night, the top lacks functional tyrosinase and so lacks melanin [3].

Cell viability assay[1]
Cell Types: human primary fibroblasts (HFb)
Tested Concentrations: 0.01-10 μM
Incubation Duration: 72 h Nitisinone (0.01-10 μM; 72 h) promotes tyrosine accumulation in a dose-dependent manner[ 1].
Experimental Results: In human cell cultures, tyrosine accumulated in large amounts within the cells.

Animal/Disease Models: Male Wistar rat (120-150 g) [2].
Doses: 5, 10 mg/kg.
Doses: po (oral gavage); 5 days a week for 6 weeks.
Experimental Results: HPPD was inhibited in rat liver in a dose- and time-dependent manner. (Rat liver animal model, incubated with 0-200 nM nitisinone for 3 minutes).

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Animal/Disease Models: C57BL/6J mice (WT mice), Tyrc-2J/c-2J mice (OCA-1A model), and Tyrc-h/ch mice (OCA-1B model) (all 3 to 4 months old age) age) [3].
Doses: 4 mg/kg
Route of Administration: po (oral gavage); one time/day; once every other day for 1 month.
Experimental Results: After 1 month in the OCA-1A and OCA-1B models, plasma tyrosine levels increased 4- to 6-fold compared to placebo-treated controls. In the OCA-1B model, there is increased iris pigmentation and increased pigmentation in areas of physical new hair growth. The number of pigmented melanosomes was Dramatically increased in the OCA-1B model. The irises of Tyrc-h/ch pups born to nitisinone-treated mothers demonstrated extensive pigmentation.

Absorption, Distribution and Excretion
Capsules and liquid formulations are bioequivalent in terms of plasma concentration-time curves and maximum plasma concentration (Cmax). Biological Half-Life Approximately 54 hours.

Hepatotoxicity
Type 1 tyrosinemia is a rare condition, and clinical experience with nitisidone is limited. Mild elevations in serum transaminase levels may occur during treatment, but are usually mild (below 3 times the upper limit of normal [ULN]) and often resolve spontaneously without dose adjustment. Elevated transaminase levels are usually asymptomatic and do not cause increases in serum alkaline phosphatase or bilirubin levels, thus rarely requiring dose adjustment. There are currently no reports of clinically significant liver injury in experimental studies of nitisidone treatment for tyrosinemia or for other tyrosine metabolism disorders (such as alkaptonuria). Probability Score: E (Unlikely to be the cause of clinically significant liver injury). Use during Pregnancy and Lactation ◉ Overview of Use During Lactation Blood concentrations of nitisidone in two exclusively breastfed infants of one mother were well below the therapeutic range and decreased from the first postpartum measurement to levels observed in the second week of breastfeeding. The infants experienced no adverse reactions and showed normal growth and development. If the mother needs to use nitisidone, breastfeeding does not need to be discontinued. Until more data are available, it is recommended to monitor the concentrations of nitisidone, tyrosine, and succinylacetone in the blood of breastfed infants.
◉ Effects on breastfed infants
A patient with type 1 tyrosinemia was taking nitisidone at a dose of 40 mg daily or 0.44 mg/kg daily, in addition to a low-tyrosine and phenylalanine diet. She continued taking the medication during her first pregnancy and postpartum. During her second pregnancy, the dose of nitisidone was increased to 60 mg daily at week 11 of gestation and to 80 mg daily at week 28, and continued at this dose postpartum. Both infants were exclusively breastfed for 2 weeks postpartum. They experienced no adverse reactions and showed normal growth and development.
◉ Effects on lactation and breast milk
As of the revision date, no relevant published information was found.

[1]. Inhibition of para-Hydroxyphenylpyruvate Dioxygenase by Analogues of the Herbicide Nitisinone As a Strategy to Decrease Homogentisic Acid Levels, the Causative Agent of Alkaptonuria. ChemMedChem. 2016 Apr 5;11(7):674-8.

[2]. Inhibition of 4-hydroxyphenylpyruvate dioxygenase by 2-(2-nitro-4-trifluoromethylbenzoyl)-cyclohexane-1,3-dione and 2-(2-chloro-4-methanesulfonylbenzoyl)-cyclohexane-1,3-dione. Toxicol Appl Pharmacol. 1995 Jul;133(1):12-9.

[3]. Nitisinone improves eye and skin pigmentation defects in a mouse model of oculocutaneous albinism. J Clin Invest. 2011 Oct;121(10):3914-23.

[4]. Nitisinone: a review. Orphan Drugs: Research and Reviews, 2017, 7.

Nitisinone is a cyclohexanone compound with a structure of cyclohexane-1,3-dione substituted at the 2-position with a 2-nitro-4-(trifluoromethyl)benzoyl group. It is used to treat type 1 hereditary tyrosinemia. Nitisinone is an EC 1.13.11.27 (4-hydroxyphenylpyruvate dioxygenase) inhibitor. It belongs to the cyclohexanone, C-nitro, (trifluoromethyl)benzene, and mesotrione classes. Nitisinone is a synthetic, reversible 4-hydroxyphenylpyruvate dioxygenase inhibitor. It is used to treat type 1 hereditary tyrosinemia. Its trade name is Orfadin. Nitisinone is a 4-hydroxyphenylpyruvate dioxygenase inhibitor. The mechanism of action of nitisidone is as an inhibitor of phenylpyruvate dioxygenase, cytochrome P450 2C9, cytochrome P450 2E1, organic anion transporter 1, and organic anion transporter 3. Nitisidone is a tyrosine catabolism inhibitor used to treat hereditary tyrosinemia type 1, in which the accumulation of tyrosine metabolic intermediates leads to severe, progressive liver and kidney damage. Nitisidone is associated with mild, transient elevations in serum transaminases, but has not been found to be associated with clinically significant acute liver injury or jaundice. Drug Indications: For adjunctive treatment of hereditary tyrosinemia type 1, in conjunction with dietary restrictions on tyrosine and phenylalanine. FDA Label: For the treatment of adults and children (any age) diagnosed with hereditary tyrosinemia type 1 (HT1), in conjunction with dietary restrictions on tyrosine and phenylalanine.
For the treatment of adult and pediatric patients diagnosed with hereditary tyrosinemia type 1 (HT1), dietary restriction of tyrosine and phenylalanine is required.
Orfadin is indicated for the treatment of adult and pediatric patients (any age) with hereditary tyrosinemia type 1 (HT1). Diagnosis of hereditary tyrosinemia type 1 (HT1) combined with dietary restriction of tyrosine and phenylalanine. Alkaloid Urinary Ulcers (AKU) Orfadin is indicated for the treatment of adult patients with AKU.
Treatment of Type 1 Tyrosinemia

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Mechanism of Action
Nitrazone is a competitive inhibitor of 4-hydroxyphenylpyruvate dioxygenase, an upstream enzyme of fumaroacetoacetate hydrolase (FAH) in the tyrosine catabolism pathway. Nitrazone prevents the accumulation of catabolism intermediates maleate and fumaroacetoacetate by inhibiting normal tyrosine catabolism in patients with hereditary tyrosinemia type 1 (HT-1).

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Pharmacodynamics
Hereditary tyrosinemia type 1 is caused by a deficiency of fumaroacetylacetase (FAH), the last enzyme in the tyrosine catabolism pathway. Nitisidone inhibits tyrosine catabolism by preventing the formation of catabolism intermediates. In HT-1 patients, these catabolism intermediates are converted into the toxic metabolites succinylacetone and succinylacetate, leading to the observed hepatotoxicity and nephrotoxicity. Succinylacetone can also inhibit the porphyrin synthesis pathway, leading to the accumulation of 5-aminolevulinic acid, a neurotoxin and the culprit behind the porphyria crisis specific to HT-1.

C14H10F3NO5

329.23

329.051

104206-65-7

115355

Light yellow to yellow solid powder

1.5±0.1 g/cm3

486.2±45.0 °C at 760 mmHg

129-131°C

247.9±28.7 °C

0.0±1.2 mmHg at 25°C

1.535

1.37

0

8

2

23

524

0

MVOGOEKATQJYHW-CIAYNJNFSA-M

InChI=1S/C38H50N6O9S.K/c1-6-22-19-38(22,35(47)43-54(49,50)25-13-14-25)42-32(45)29-18-24-20-44(29)34(46)31(37(2,3)4)41-36(48)53-30-16-21(30)10-8-7-9-11-27-33(52-24)40-28-17-23(51-5)12-15-26(28)39-27;/h6,12,15,17,21-22,24-25,29-31H,1,7-11,13-14,16,18-20H2,2-5H3,(H3,41,42,43,45,47,48);/q;+1/p-1/t21-,22-,24-,29+,30-,31-,38-;/m1./s1

potassium ((1R,2S)-1-((33R,35S,91R,92R,5S)-5-(tert-butyl)-17-methoxy-4,7-dioxo-2,8-dioxa-6-aza-1(2,3)-quinoxalina-3(3,1)-pyrrolidina-9(1,2)-cyclopropanacyclotetradecaphane-35-carboxamido)-2-vinylcyclopropane-1-carbonyl)(cyclopropylsulfonyl)amide

MK5172 K; MK 5172 potassium; MK-5172 potassium, Trade name: Zepatier‎.

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)

DMSO : ~41.67 mg/mL (~126.57 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (7.59 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 (7.59 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.)