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
The capsule and liquid formulations are bioequivalent in both the plasma concentration-time curve and maximum plasma concentration (Cmax).

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Biological Half-Life
~54 hours

Hepatotoxicity
Type 1 tyrosinemia is a rare disease and clinical experience with use of nitisinone is limited. Therapy can be accompanied by mild elevations in serum aminotransferase levels, but these are generally mild (less than 3 times the upper limit of normal [ULN]) and often resolve even without dose modification. The aminotransferase elevations are not accompanied by symptoms or increases in serum alkaline phosphatase or bilirubin levels and rarely require dose modification. There have been no reports of clinically apparent liver injury attributed to nitisinone in the treatment of tyrosinemia or in experimental studies of its use in other disorders of tyrosine metabolism such as alkaptonuria.
Likelihood score: E (unlikely cause of clinically apparent liver injury).

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Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
Blood levels in two exclusively breastfed infants of one mother were far below the therapeutic range and dropped from the initial postpartum measurement to levels taken during the second week of breastfeeding. The infants had no adverse reactions and grew normally. If nitisinone is required by the mother, it is not a reason to discontinue breastfeeding. Until more data are available, monitoring the breastfed infant’s blood nitisinone, tyrosine and succinylacetone concentrations might be advisable.
◉ Effects in Breastfed Infants
A patient with type-1 tyrosinemia was taking nitisinone 40 mg daily or 0.44 mg/kg daily in addition to a low tyrosine and phenylalanine diet. She continued on this regimen during her first pregnancy and postpartum. In her second pregnancy, the nitisinone dosage was increased to 60 mg daily in the week 11 of pregnancy, to 80 mg daily in the week 28 and continued at that dosage postpartum. Both infants were exclusively breastfed for 2 weeks postpartum. They showed no adverse reactions and grew normally.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

[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 that is cyclohexane-1,3-dione substituted at position 2 by a 2-nitro-4-(trifluoromethyl)benzoyl group. It is used in the treatment of hereditary tyrosinemia type 1. It has a role as an EC 1.13.11.27 (4-hydroxyphenylpyruvate dioxygenase) inhibitor. It is a member of cyclohexanones, a C-nitro compound, a member of (trifluoromethyl)benzenes and a mesotrione.
Nitisinone is a synthetic reversible inhibitor of 4-hydroxyphenylpyruvate dioxygenase. It is used in the treatment of hereditary tyrosinemia type 1. It is sold under the brand name Orfadin.
Nitisinone is a 4-Hydroxyphenyl-Pyruvate Dioxygenase Inhibitor. The mechanism of action of nitisinone is as a Hydroxyphenylpyruvate Dioxygenase Inhibitor, and Cytochrome P450 2C9 Inhibitor, and Cytochrome P450 2E1 Inducer, and Organic Anion Transporter 1 Inhibitor, and Organic Anion Transporter 3 Inhibitor.
Nitisinone is an inhibitor of the tyrosine catabolism that is used to treat hereditary tyrosinemia, type 1, in which accumulation of intermediates of tyrosine metabolism causes severe and progressive hepatic and renal injury. Nitisinone has been associated with mild, transient serum aminotransferase elevations, but has not been linked to instances of clinically apparent acute liver injury or jaundice.

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Drug Indication
Used as an adjunct to dietary restriction of tyrosine and phenylalanine in the treatment of hereditary tyrosinemia type 1.
FDA Label
Treatment of adult and paediatric (in any age range) patients with confirmed diagnosis of hereditary tyrosinemia type 1 (HT 1) in combination with dietary restriction of tyrosine and phenylalanine.
Treatment of adult and paediatric patients with confirmed diagnosis of hereditary tyrosinemia type 1 (HT-1) in combination with dietary restriction of tyrosine and phenylalanine.
Hereditary tyrosinemia type 1 (HT 1)Orfadin is indicated for the treatment of adult and paediatric (in any age range) patients with confirmed diagnosis of hereditary tyrosinemia type 1 (HT 1) in combination with dietary restriction of tyrosine and phenylalanine. Alkaptonuria (AKU)Orfadin is indicated for the treatment of adult patients with alkaptonuria (AKU).
Treatment of tyrosinemia type 1

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Mechanism of Action
Nitisinone is a competitive inhibitor of 4-hydroxyphenyl-pyruvate dioxygenase, an enzyme upstream of fumarylacetoacetate hydrolyase (FAH) in the tyrosine catabolic pathway. By inhibiting the normal catabolism of tyrosine in patients with hereditary tyrosinemia type 1 (HT-1), nitisinone prevents the accumulation of the catabolic intermediates maleylacetoacetate and fumarylacetoacetate.

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Pharmacodynamics
Hereditary tyrosinemia type 1 occurs due to a deficiency in fumarylacetoacetase (FAH), the final enzyme in the tyrosine catabolic pathway. Nitisinone inhibits catabolism of tyrosine by preventing the catabolic intermediates. In patients with HT-1, these catabolic intermediates are converted to the toxic metabolites succinylacetone and succinylacetoacetate, which are responsible for the observed liver and kidney toxicity. Succinylacetone can also inhibit the porphyrin synthesis pathway leading to the accumulation of 5-aminolevulinate, a neurotoxin responsible for the porphyric crises characteristic of 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.)