Pregnancy in an NTBC-treated patient with hereditary tyrosinemia type I

Nitisinone treatment during two pregnancies and breastfeeding in a woman with tyrosinemia type 1 - a case report

OBJECTIVES

Tyrosinaemia type 1, an inherited disorder of tyrosine metabolism, is usually treated with a tyrosine-defined diet and since 2000 with nitisinone. So far, data about effects of nitisone during pregnancy and breastfeeding are rare. This is the first report of two pregnancies in a patient with tyrosinaemia type 1 while under treatment with nitisinone.

CASE PRESENTATION

We here present a 20-year-old female patient with tyrisonemia type 1 receiving treatment with nitisinone and a tyrosine-defined diet since she was diagnosed with tyrosinaemia type 1 at the age of 18 months. During two pregnancies blood concentrations of tyrosine, succinylacetone and nitisinone were measured regularly. Neither infant has tyrosinaemia type 1 and both showed an initial increase in concentrations of tyrosine, succinylacetone and nitisinone. All three metabolites dropped within two weeks after birth. Both were exclusively breastfed for about two weeks. Both children show age-appropriate physical and mental development.

CONCLUSIONS

Nitisinone therapy during pregnancy and the short breastfeeding period did not result in adverse events in our patient or her children. Regular assessments of tyrosine, succinylacetone and nitisinone should be made during pregnancy and the breastfeeding period in both the mother and the infant. For better understanding, in principle, all cases of pregnancy and breastfeeding with tyrosinemia type 1 should be assessed and followed to further evaluate the implications of tyrosinaemia type 1 and its treatment during pregnancy. Additionally, even though experience with breastfeeding is limited, medication with nitisinone is safe and there is no reason to consider breastfeeding unsafe or to not recommend it.

Long-term safety and outcomes in hereditary tyrosinaemia type 1 with nitisinone treatment: a 15-year non-interventional, multicentre study

BACKGROUND

Since the EU approval of nitisinone in 2005, prognosis for patients with hereditary tyrosinaemia type 1 has changed dramatically, with patients living with the disease now reaching adulthood for the first time in history. This study aimed to assess the long-term safety and outcomes of nitisinone treatment in patients with hereditary tyrosinaemia type 1.

METHODS

We did a non-interventional, non-comparative, multicentre study in 77 sites across 17 countries in Europe and collected retrospective and prospective longitudinal data in patients with hereditary tyrosinaemia type 1 who were treated with oral nitisinone during the study period (Feb 21, 2005, to Sept 30, 2019). There were no specific exclusion criteria. Patients were followed-up with an investigator at least annually for as long as they were treated, or until the end of the study. The primary endpoints, occurrence of adverse events related to hepatic, renal, ophthalmic, haematological, or cognitive or developmental function, were assessed in the complete set (all patients already receiving treatment at the index date [Feb 21, 2005] or starting treatment thereafter) and the index set (the subset of patients who had their first dose on the index date or later only).

FINDINGS

315 patients were enrolled during the study period (complete set). Additionally, data from 24 patients who had liver transplantation or died during the post-marketing surveillance programme were retrieved (extended analysis set; 339 patients). Median treatment duration was 11·2 years (range 0·7-28·4); cumulative nitisinone exposure was 3172·7 patient-years. Patients who were diagnosed by neonatal screening started nitisinone treatment at median age 0·8 months versus 8·5 months in those who presented clinically. Incidences of hepatic, renal, ophthalmic, haematological, or cognitive or developmental adverse events were low. Occurrence of liver transplantation or death was more frequent the later that treatment was initiated (none of 70 patients who started treatment at age <28 days vs 35 [13%] of 268 patients who started treatment at age ≥28 days). 279 (89%) of 315 patients were assessed as having either very good or good nitisinone treatment compliance. Treatment and diet compliance declined as patients aged. Suboptimal plasma phenylalanine and tyrosine levels were observed. The majority of patients were reported to have good overall clinical condition throughout treatment; 176 (87%) of 203 during the entire study, 98% following 1 year of treatment.

INTERPRETATION

Long-term nitisinone treatment was well tolerated and no new safety signals were revealed. Life-limiting hepatic disease appears to have been prevented by early treatment start. Neonatal screening was the most effective way of ensuring early treatment. Standardised monitoring of blood tyrosine, phenylalanine, and nitisinone levels has potential to guide individualised therapy.

FUNDING

Swedish Orphan Biovitrum (Sobi).

Case report: Maternal tyrosinemia type 1a under NTBC treatment with tyrosine- and phenylalanine restricted diet in Chile

We report the case of a 17-year-old girl with Tyrosinemia type 1a who carried a planned pregnancy to term while being under 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC, nitisinone) treatment and a tyrosine- and phenylalanine-restricted diet. She was on treatment since 2 months of age with poor metabolic control prior to her pregnancy (tyrosine 838 ± 106 umol/L). NTBC and a low tyrosine and phenylalanine diet were continued during her pregnancy. She unfortunately suffered from urinary tract infection and anemia during her pregnancy, with median plasma tyrosine and phenylalanine levels of 613 ± 106 umol/L (200-400 umol/L) and 40.2 ± 8 umol/L (35-90 umol/L), respectively. After 40 weeks of gestation, the patient gave birth to a healthy boy, with no adverse effects related to the use of NTBC. The newborn presented with a transitory elevation of plasma tyrosine levels and normal phenylalanine, methionine, and succinylacetone levels. By 12 months of age, the child was determined to have normal psychomotor development. At 20 months old, he was diagnosed with a mild developmental delay; however, global cognitive evaluation with the Wechsler Intelligence Scale for Children (WISC) test at 5 years old showed normal performance. Here, we discuss one of the few reported cases of nitisinone treatment during pregnancy and demonstrate a lack of teratogenicity and long-term cognitive disabilities.

First Scandinavian case of successful pregnancy during nitisinone treatment for type 1 tyrosinemia

Background Type 1 tyrosinemia is a hereditary metabolic disease in which tyrosine metabolites damage the liver and kidneys. Nitisinone medication revolutionized the treatment, but the effects of the drug during human pregnancy are unknown. Case presentation A 17-year-old tyrosinemia patient became pregnant. Nitisinone was continued throughout pregnancy with a varying serum concentration and dose ranging from 0.8 to 1.4 mg/kg/day. Blood tyrosine remained stable until it increased in late pregnancy. α-fetoprotein increased to 284 μg/L without new changes in liver. Urine succinylacetone remained undetectable, but there were signs of possibly reoccurring kidney tubulopathy. Fetal ultrasound monitoring was normal throughout the pregnancy and the newborn healthy. After the delivery, α-fetoprotein normalized, but tyrosine continued to rise for up to 1 year. The child is developing normally. Conclusions Pregnancy during nitisinone was successful, but tailoring of the drug dose and possibly reappearing complications, as also increasing serum tyrosine concentration after delivery warranted intensified surveillance.

Nutrition and medical support during pregnancy and lactation in women with inborn errors of intermediary metabolism disorders (IEMDs)

The establishment of expanded newborn screening (NBS) not only results in the early diagnosis and treatment of neonates with inborn errors of intermediary metabolism disorders (IEMDs) but also helps the affected females to reach the reproductive age under medical and dietetic support, as well as to give birth to normal infants. In this review, we aimed to focus on laboratory investigation tests, dietetic management and medical support for most known IEMD pregnant and lactating women, such as those suffering from aminoacidopathies, carbohydrate metabolic diseases and fatty acid (FAO) oxidation disorders.

Long-Term Outcomes and Practical Considerations in the Pharmacological Management of Tyrosinemia Type 1

Tyrosinemia type 1 (TT1) is a rare metabolic disease caused by a defect in tyrosine catabolism. TT1 is clinically characterized by acute liver failure, development of hepatocellular carcinoma, renal and neurological problems, and consequently an extremely poor outcome. This review showed that the introduction of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC) in 1992 has revolutionized the outcome of TT1 patients, especially when started pre-clinically. If started early, NTBC can prevent liver failure, renal problems, and neurological attacks and decrease the risk for hepatocellular carcinoma. NTBC has been shown to be safe and well tolerated, although the long-term effectiveness of treatment with NTBC needs to be awaited. The high tyrosine concentrations caused by treatment with NTBC could result in ophthalmological and skin problems and requires life-long dietary restriction of tyrosine and its precursor phenylalanine, which could be strenuous to adhere to. In addition, neurocognitive problems have been reported since the introduction of NTBC, with hypothesized but as yet unproven pathophysiological mechanisms. Further research should be done to investigate the possible relationship between important clinical outcomes and blood concentrations of biochemical parameters such as phenylalanine, tyrosine, succinylacetone, and NTBC, and to develop clear guidelines for treatment and follow-up with reliable measurements. This all in order to ultimately improve the combined NTBC and dietary treatment and limit possible complications such as hepatocellular carcinoma development, neurocognitive problems, and impaired quality of life.

Diagnosis and treatment of tyrosinemia type I: a US and Canadian consensus group review and recommendations

Tyrosinemia type I (hepatorenal tyrosinemia, HT-1) is an autosomal recessive condition resulting in hepatic failure with comorbidities involving the renal and neurologic systems and long term risks for hepatocellular carcinoma. An effective medical treatment with 2-[2-nitro-4-trifluoromethylbenzoyl]-1,3-cyclohexanedione (NTBC) exists but requires early identification of affected children for optimal long-term results. Newborn screening (NBS) utilizing blood succinylacetone as the NBS marker is superior to observing tyrosine levels as a way of identifying neonates with HT-1. If identified early and treated appropriately, the majority of affected infants can remain asymptomatic. A clinical management scheme is needed for infants with HT-1 identified by NBS or clinical symptoms. To this end, a group of 11 clinical practitioners, including eight biochemical genetics physicians, two metabolic dietitian nutritionists, and a clinical psychologist, from the United States and Canada, with experience in providing care for patients with HT-1, initiated an evidence- and consensus-based process to establish uniform recommendations for identification and treatment of HT-1. Recommendations were developed from a literature review, practitioner management survey, and nominal group process involving two face-to-face meetings. There was strong consensus in favor of NBS for HT-1, using blood succinylacetone as a marker, followed by diagnostic confirmation and early treatment with NTBC and diet. Consensus recommendations for both immediate and long-term clinical follow-up of positive diagnoses via both newborn screening and clinical symptomatic presentation are provided.

Clinical utility of nitisinone for the treatment of hereditary tyrosinemia type-1 (HT-1)

Medical therapy for hereditary hepatorenal tyrosinemia (hereditary tyrosinemia type 1, HT-1) with nitisinone was discovered incidentally, and is a by-product of agrochemistry. It blocks the catabolic pathway of tyrosine, thereby leading to a reduction in the accumulation of toxic metabolites in HT-1. It has to be combined with a low-protein diet supplemented with amino acid mixtures devoid of tyrosine and phenylalanine. This treatment option has completely changed the clinical course of patients suffering from HT-1 who used to die in the first few months to years of life from liver failure, renal dysfunction, and/or hepatocellular carcinoma (HCC). It is essential to start nitisinone therapy early in life to avoid sequelae; beginning treatment in the newborn period is ideal. As initial clinical symptoms of HT-1 are often atypical and because there is a clinically latent phase during the first few months of life in many patients, newborn screening is required to secure early diagnosis. Succinylacetone in blood is a reliable screening parameter whereas tyrosine is neither specific nor sensitive. Especially HCC, but also liver and kidney dysfunction, rickets, and neurological crises can be prevented in most patients if nitisinone therapy is started in the newborn period. It is essential to adhere to a low-protein diet to avoid tyrosine toxicity. Reversible eye symptoms may occur as a side-effect of nitisinone, but other side effects are rare. Neurocognitive development is impaired in some patients, and the reason for this is unclear. Metabolic monitoring includes measurement of tyrosine, succinylacetone, and nitisinone concentrations in blood.

Remaining Challenges in the Treatment of Tyrosinemia from the Clinician's Viewpoint

This chapter provides a clinical perspective on the challenges that stand between current clinical practice and a cure for hepatorenal tyrosinemia (HT1). HT1 has been transformed in the last 50 years from an aggressive often undiagnosed childhood disease causing liver failure or liver cancer, with infant death in most patients, to a condition that is detectable at birth, and for which treatment with nitisinone (NTBC) and diet can prevent detectable liver or kidney abnormalities. What challenges remain? The properties of the affected metabolic pathway and the broad spectrum of severity seen in untreated patients are incompletely understood but potentially important for patients. Available treatments have potential complications, including liver transplantation (risks of surgery and of immunosuppression to prevent rejection), nitisinone and diet therapy (hypertyrosinemia, corneal opacities, nutritional imbalances and possibly developmental delay). The detection of liver cancer is imperfect and laborious. The effects of tyrosinemia during pregnancy are little-known. Although animal models of HT1 are becoming standard research tools in cell replacement and gene modification therapy, these techniques are not currently applicable to HT1 itself. Treatment adherence is variable, causing concern about long term outcome for some patients. Around the world, there are great disparities in the diagnosis and treatment of HT1. Most affected individuals are born in places where newborn screening for HT1 is not performed and where appropriate treatment is not available. We hope that this list will help to focus on some of these remaining obstacles to a cure for HT1.