Phase 3 Trial of RNAi Therapeutic Givosiran for Acute Intermittent Porphyria.

BACKGROUND: Up-regulation of hepatic delta-aminolevulinic acid synthase 1 (ALAS1), with resultant accumulation of delta-aminolevulinic acid (ALA) and porphobilinogen, is central to the pathogenesis of acute attacks and chronic symptoms in acute hepatic porphyria. Givosiran, an RNA interference therapy, inhibits ALAS1 expression. METHODS: In this double-blind, placebo-controlled, phase 3 trial, we randomly assigned symptomatic patients with acute hepatic porphyria to receive either subcutaneous givosiran (2.5 mg per kilogram of body weight) or placebo monthly for 6 months. The primary end point was the annualized rate of composite porphyria attacks among patients with acute intermittent porphyria, the most common subtype of acute hepatic porphyria. (Composite porphyria attacks resulted in hospitalization, an urgent health care visit, or intravenous administration of hemin at home.) Key secondary end points were levels of ALA and porphobilinogen and the annualized attack rate among patients with acute hepatic porphyria, along with hemin use and daily worst pain scores in patients with acute intermittent porphyria. RESULTS: A total of 94 patients underwent randomization (48 in the givosiran group and 46 in the placebo group). Among the 89 patients with acute intermittent porphyria, the mean annualized attack rate was 3.2 in the givosiran group and 12.5 in the placebo group, representing a 74% lower rate in the givosiran group (P<0.001); the results were similar among the 94 patients with acute hepatic porphyria. Among the patients with acute intermittent porphyria, givosiran led to lower levels of urinary ALA and porphobilinogen, fewer days of hemin use, and better daily scores for pain than placebo. Key adverse events that were observed more frequently in the givosiran group were elevations in serum aminotransferase levels, changes in serum creatinine levels and the estimated glomerular filtration rate, and injection-site reactions. CONCLUSIONS: Among patients with acute intermittent porphyria, those who received givosiran had a significantly lower rate of porphyria attacks and better results for multiple other disease manifestations than those who received placebo. The increased efficacy was accompanied by a higher frequency of hepatic and renal adverse events. (Funded by Alnylam Pharmaceuticals; ENVISION ClinicalTrials.gov number, NCT03338816.).

Computational disease model of phenobarbital-induced acute attacks in an acute intermittent porphyria mouse model.

INTRODUCTION: Acute intermittent porphyria (AIP) is characterized by hepatic over-production of the heme precursors when aminolevulinic acid (ALA)-synthase 1 is induced by endogenous or environmental factors. The aim of this study was to develop a semi-mechanistic computational model to characterize urine accumulation of heme precursors during acute attacks based on experimental pharmacodynamics data and support the development of new therapeutic strategies. METHODS: Male AIP mice received recurrent phenobarbital challenge starting on days 1, 9, 16 and 30. 24-h urine excretion of ALA, porphobilinogen (PBG) and porphyrins from challenges D1, D9 and D30 constituted the training data set to build the mechanistic model using the population approach. In a second study, porphyrin and porphyrin precursor excretion from challenge D16 were used as a validation data set. RESULTS: The computational model presented the following features: (i) urinary excretion of ALA, PBG and porphyrins was governed by unmeasured circulating heme precursor amounts, (ii) the circulating amounts of ALA and PBG were the precursors of circulating amounts of PBG and porphyrins, respectively, and (iii) the phenobarbital effect linearly increased the synthesis of circulating ALA and PBG levels. The model displayed good parameter precision (coefficient of variation below 32% in all parameters), and adequately described the experimental data. Finally, a theoretical hemin effect was implemented to illustrate the applicability of the model to dosage optimization in drug therapies. CONCLUSIONS: A semi-mechanistic disease model was successfully developed to describe the temporal evolution of urinary heme precursor excretion during recurrent biochemical-induced acute attacks in AIP mice. This model represents the first computational approach to explore and optimize current and new therapies.

Homozygous hydroxymethylbilane synthase knock-in mice provide pathogenic insights into the severe neurological impairments present in human homozygous dominant acute intermittent porphyria.

Acute intermittent porphyria (AIP) is an inborn error of heme biosynthesis due to the deficiency of hydroxymethylbilane synthase (HMBS) activity. Human AIP heterozygotes have episodic acute neurovisceral attacks that typically start after puberty, whereas patients with homozygous dominant AIP (HD-AIP) have early-onset chronic neurological impairment, including ataxia and psychomotor retardation. To investigate the dramatically different manifestations, knock-in mice with human HD-AIP missense mutations c.500G>A (p.Arg167Glu) or c.518_519GC>AG (p.Arg173Glu), designated R167Q or R173Q mice, respectively, were generated and compared with the previously established T1/T2 mice with ~30% residual HMBS activity and the heterozygous AIP phenotype. Homozygous R173Q mice were embryonic lethal, while R167Q homozygous mice (R167Q+/+) had ~5% of normal HMBS activity, constitutively elevated plasma and urinary 5-aminolevulinic acid (ALA) and porphobilinogen (PBG), profound early-onset ataxia, delayed motor development and markedly impaired rotarod performance. Central nervous system (CNS) histology was grossly intact, but CNS myelination was delayed and overall myelin volume was decreased. Heme concentrations in liver and brain were similar to those of T1/T2 mice. Notably, ALA and PBG concentrations in the cerebral spinal fluid and CNS regions were markedly elevated in R167Q+/+ mice compared with T1/T2 mice. When the T1/T2 mice were administered phenobarbital, ALA and PBG markedly accumulated in their liver and plasma, but not in the CNS, indicating that ALA and PBG do not readily cross the blood-brain barrier. Taken together, these studies suggest that the severe HD-AIP neurological phenotype results from decreased myelination and the accumulation of locally produced neurotoxic porphyrin precursors within the CNS.

Porfiria aguda intermitente con debut en el puerperio / Acute intermittent porphyria with debut in the puerperium

RESUMEN Objetivo: Las porfirias son trastornos que resultan de un defecto enzimático específico en la vía bioquímica de las porfirias. Los síntomas clínicos incluyen dolor abdominal, alteraciones gastrointestinales y manifestaciones psiquiátricas. Material y métodos: Mujer de 41 años, con diabetes gestacional y parto por cesárea hace 7 días, que acude a urgencias con convulsiones tónicoclónicas. En tratamiento antibiótico por infección de la herida quirúrgica. Los exámenes de laboratorio demostraron hiponatremia, hipokalemia y anemia. El diagnóstico de porfiria aguda intermitente (PAI) fue confirmado por el hallazgo de porfirinas elevadas en orina. La paciente fue dada de alta después de dos semanas. Resultados: se solicita un test rápido de PBG cuantitativo en orina, que resulta positivo (>10 mg PBG / g creatinina), por lo que se solicita un estudio completo de la enfermedad y se envían muestras a un hospital de referencia para análisis bioquímico y genético de PBGD/HMBS (Hidroximetilbilano sintetasa /PBG-desaminasa). Presenta la mutación c.815_818 del AGGA, que se trasmite de forma autosómica dominante, aunque con baja penetrancia. Conclusión: El diagnóstico de PAI es complejo debido al amplio espectro de síntomas, además el embarazo y el puerperio puede exacerbar la enfermedad.

SUMMARY Objective: Porphyrias are a heterogeneous group of either inherited or acquired disorders of the enzymatic biosynthesis of porphyrins. In these diseases, specific abnormalities of enzymes cause diverse clinical manifestations including abdominal pain, gastrointestinal alterations and psychiatric manifestations. Materials and methods: A 41-year-old woman with gestational diabetes and cesarean delivery 7 days ago with intradural anesthesia. She was admitted with tonic clonic seizures and diffuse abdominal pain. She is under antibiotic treatment for infection of the surgical wound. Laboratory exams showed hyponatremia, hypokalemia and anemia. A diagnosis of acute intermittent porphyria was confirmed with elevated porphyrinis in urine. Results: a rapid test of quantitative PBG in urine is permormed, which is positive (>10 mg PBG / g creatinin), so a complete study of the disease is requested and samples are sent to a reference hospital for biochemical and genetic analysis of PBGD / HMBS (Hydroxymethylbilane synthetase / PBG-deaminase). It presents the c.815_818 mutation of the AGGA, which is transmitted in an autosomal dominant manner, although with low penetrance. Conclusion: The diagnosis of acute intermittent porphyria is complex because of the wide spectrum of symptoms. Pregnancy or the puerperium might exacerbate the disease

Comprehensive analysis of the tryptophan metabolome in urine of patients with acute intermittent porphyria.

BACKGROUND: Acute intermittent porphyria (AIP) is a rare metabolic disorder due to a deficiency of porphobilinogen deaminase, the third enzyme of the heme biosynthetic pathway. This low enzymatic activity may predispose to the appearance of acute neurological attacks. Seminal studies suggested that AIP was associated with changes in tryptophan homeostasis with inconclusive results. Therefore, the aim of this study was to analyze the urinary metabolome of AIP patients focusing on tryptophan metabolism using state-of-the-art technology. METHODS: This was a case-control study including a group of 25 AIP patients with active biochemical disease and increased excretion of heme-precursors and 25 healthy controls. Tryptophan and related compounds and metabolites including: large neutral amino acids (LNAAs), serotonin, kynurenine, kynurenic acid and anthranilic acid were quantified in urine by liquid chromatography tandem-mass spectrometry (LC-MS/MS). Twenty-nine biological markers (including metabolic ratios and absolute concentrations) were compared between patients and controls. RESULTS: Significant differences were found in the tryptophan-kynurenine metabolic pathway. Compared to controls, AIP patients showed: (a) increased urinary excretion of kynurenine and anthranilic acid (P<0.005); (b): elevation of the kynurenine/tryptophan ratio (P<0.001) and (c): decrease of the kynurenic acid/kynurenine ratio (P=0.001). In contrast, no differences were found in the serotonin metabolic pathway independently of the markers and ratios used. CONCLUSIONS: The results of the study demonstrate that there is an imbalance in the kynurenine metabolic pathway in AIP patients, with an increase of the kynurenine/tryptophan ratio in urine and a reduction of the kynurenic acid/kynurenine ratio. The modified ratios suggest induction of indoleamine 2,3-deoxygenase and decreased activity of kynurenine aminotransferase in the liver. The results confirm that LC-MS/MS is useful for the characterization of the urinary metabolome of hepatic porphyrias.

Challenges in the successful management of a case of acute intermittent porphyria in India.

Acute intermittent porphyria (AIP) is a rare metabolic disease involving a defect in haem biosynthesis resulting in the accumulation and excessive secretion of porphyrins and its precursors. Acute attacks present with episodes of severe abdominal pain, nausea, confusion and severe life-threatening seizures. A high index of suspicion is required for the initial diagnosis of AIP.

Mass spectrometric characterisation of a condensation product between porphobilinogen and indolyl-3-acryloylglycine in urine of patients with acute intermittent porphyria.

We document the presence of a previously unknown species in the urine of patients with acute intermittent porphyria (AIP). The compound was fully characterised by liquid chromatography tandem mass spectrometry. Interpretation of both full spectrum acquisition and product ion spectra acquired in positive and negative ionisation modes by quadrupole time of flight MS allowed for the identification of a condensation product arising from porphobilinogen (PBG, increased in the urine of AIP patients) and indolyl-3-acryloylglycine (IAG, derived from indolylacrylic acid and present in human urine). The structure was unequivocally confirmed through comparison between the selected reaction monitoring chromatograms obtained from the urinary species and the condensation product qualitatively synthesised in the laboratory. Owing to the large amounts of both PBG and IAG in urine of AIP patients, the possible ex vivo formation of PBG-IAG in urine samples was evaluated. The product was spontaneously formed at room temperature, at 4 °C and even during storage at -20 °C when spiking a control sample with PBG. A positive correlation was found between PBG and PBG-IAG in samples collected from AIP patients. However, no correlation was found between PBG-IAG and IAG. Purified PBG-IAG did not form the characteristic chromogen after application of p-dimethylaminobenzaldehyde in HCl, thus suggesting that the current techniques used to measure PBG in urine of AIP patients based on Ehlrich's reaction do not detect this newly characterised PBG-IAG fraction.

A YOUNG GIRL WITH FITS.

A young girl presented with fits vomiting and epigastric pain. Investigations including CT-Scan brain, MRI brain, MRV brain and cerebrospinal fluid (CSF) examination were normal. Her urine was screened for porphobilinogen which was positive. She responded to intravenous dextrose and hypercaloric diet

Posterior reversible encephalopathy syndrome in acute intermittent porphyria.

BACKGROUND: Acute intermittent porphyria is an inherited disease that is rarely diagnosed in prepubertal children. It can affect the autonomic, peripheral, and central nervous system. Posterior reversible encephalopathy syndrome is a clinicoradiological entity characterized by headache, seizures, altered consciousness, and visual disorder associated with potentially reversible neuroradiological abnormalities predominantly in the parieto-occipital lobes. We report a child with acute intermittent porphyria who presented with radiological manifestations suggestive of posterior reversible encephalopathy syndrome. PATIENT: A 9-year-old girl underwent an appendectomy after developing abdominal pain. She subsequently developed bilateral visual disturbance, confusion, seizures, hypertension, tachycardia, nausea, vomiting, constipation, dark tea-colored urine, and recurrent abdominal pain. RESULTS: Initial brain magnetic resonance imaging revealed hyperintense gyriform lesions on T2-weighted images and hypointense to isointense lesions on T1-weighted images in both parieto-occipital lobes with mild enhancement. The diagnosis of acute intermittent porphyria was confirmed by increased urinary excretion of porphyrin precursors. Her clinical signs gradually improved after intravenous high-dose glucose treatment and symptomatic therapies. A repeat magnetic resonance imaging confirmed complete resolution of the parieto-occipital lesions, suggesting with posterior reversible encephalopathy syndrome. CONCLUSIONS: The association of abdominal pain, mental status changes, and autonomic dysfunction should arouse the suspicion of acute intermittent porphyria. Acute intermittent porphyria can be associated with posterior reversible encephalopathy syndrome.

Adrenal hormonal imbalance in acute intermittent porphyria patients: results of a case control study.

BACKGROUND: Acute Intermittent Porphyria (AIP) is a rare disease that results from a deficiency of hydroxymethylbilane synthase, the third enzyme of the heme biosynthetic pathway. AIP carriers are at risk of presenting acute life-threatening neurovisceral attacks. The disease induces overproduction of heme precursors in the liver and long-lasting deregulation of metabolic networks. The clinical history of AIP suggests a strong endocrine influence, being neurovisceral attacks more common in women than in men and very rare before puberty. To asses the hypothesis that steroidogenesis may be modified in AIP patients with biochemically active disease, we undertook a comprehensive analysis of the urinary steroid metabolome. METHODS: A case-control study was performed by collecting spot morning urine from 24 AIP patients and 24 healthy controls. Steroids in urine were quantified by liquid chromatography-tandem mass spectrometry. Parent steroids (17-hydroxyprogesterone; deoxycorticosterone; corticoesterone; 11-dehydrocorticosterone; cortisol and cortisone) and a large number of metabolites (N = 55) were investigated. Correlations between the different steroids analyzed and biomarkers of porphyria biochemical status (urinary heme precursors) were also evaluated. The Mann-Whitney U test and Spearman's correlation with a two tailed test were used for statistical analyses. RESULTS: Forty-one steroids were found to be decreased in the urine of AIP patients (P < 0.05), the decrease being more significant for steroids with a high degree of hydroxylation. Remarkably, 13 cortisol metabolites presented lower concentrations among AIP patients (P < 0.01) whereas no significant differences were found in the main metabolites of cortisol precursors. Nine cortisol metabolites showed a significant negative correlation with heme precursors (p < 0.05). Ratios between the main metabolites of 17-hydroxyprogesterone and cortisol showed positive correlations with heme-precursors (correlation coefficient > 0.51, P < 0.01). CONCLUSIONS: Comprehensive study of the urinary steroid metabolome showed that AIP patients present an imbalance in adrenal steroidogenesis, affecting the biosynthesis of cortisol and resulting in decreased out-put of cortisol and metabolites. This may result from alterations of central origin and/or may originate in specific decreased enzymatic activity in the adrenal gland. An imbalance in steroidogenesis may be related to the maintenance of an active disease state among AIP patients.

Urinary metabolic fingerprint of acute intermittent porphyria analyzed by (1)H NMR spectroscopy.

(1)H NMR is a nonbiased technique for the quantification of small molecules that could result in the identification and characterization of potential biomarkers with prognostic value and contribute to better understand pathophysiology of diseases. In this study, we used (1)H NMR spectroscopy to analyze the urinary metabolome of patients with acute intermittent porphyria (AIP), an inherited metabolic disorder of heme biosynthesis in which an accumulation of the heme precursors 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG) promotes sudden neurovisceral attacks, which can be life-threatening. Our objectives were (1) to demonstrate the usefulness of (1)H NMR to identify and quantify ALA and PBG in urines from AIP patients and (2) to identify metabolites that would predict the response to AIP crisis treatment and reflect differential metabolic reprogramming. Our results indicate that (1)H NMR can help to diagnose AIP attacks based on the identification of ALA and PBG. We also show that glycin concentration increases in urines from patients with frequent recurrences at the end of the treatment, after an initial decrease, whereas PBG concentration remains low. Although the reasons for this altered are elusive, these findings indicate that a glycin metabolic reprogramming occurs in AIPr patients and is associated with recurrence. Our results validate the proof of concept of the usefulness of (1)H NMR spectroscopy in clinical chemistry for the diagnosis of acute attack of AIP and identify urinary glycin as a potential marker of recurrence of AIP acute attacks.

Urinary excretion of porphyrins, porphobilinogen and δ-aminolaevulinic acid following an attack of acute intermittent porphyria.

BACKGROUND AND OBJECTIVES: The porphyrias are a group of rare, mainly inherited, diseases caused by a deficiency of one of the enzymes of the haem biosynthesis pathway. The biochemical hallmark of an acute attack is an increase in urine porphobilinogen (PBG), together with an increase in urinary excretion of δ-aminolaevulinic acid (ALA) and total urine porphyrins (TUP). In patients with acute intermittent porphyria (AIP) the concentrations of the porphyrin precursors are thought to remain elevated for many years following an acute attack, although this has not been well documented. METHODS: We measured urine ALA, PBG and TUP excretion in 20 patients with AIP following an attack of acute porphyria over a time period of 3 months to 23 years after their last documented acute attack. RESULTS: We showed that urinary concentrations of all metabolites remain elevated for many years. The urinary half life of TUP was 5.3 years, ALA 7.7 years and PBG 10.6 years. Even after 20 years, PBG concentrations remained elevated above the normal range. CONCLUSIONS: Our study highlights the difficulties of using urinary analysis for diagnosing recurrent attacks, and also raises important questions about the pathophysiology of the condition.

Gas chromatography-mass spectrometry profiling of steroids in urine of patients with acute intermittent porphyria.

OBJECTIVE: Acute intermittent porphyria (AIP) is an autosomal dominant disease that results from a deficiency of hydroxymethylbilane synthase, the third enzyme of the heme biosynthetic pathway. AIP carriers may present acute neurovisceral attacks with hepatic overproduction of heme-precursors. In some patients, remission of the acute symptoms leads to long-term hepatic metabolic abnormalities. In this study, gas chromatography-mass spectrometry (GC/MS) was used to investigate urinary steroid metabolome of AIP patients. DESIGN AND METHODS: Steroid profiling in urine was performed in a group of AIP patients with biochemically active disease (n=22) and healthy controls (n = 20). Five asymptomatic AIP family carriers were also studied. Commonly used ratios for the evaluation of disturbances in the steroid metabolism were calculated. RESULTS: We found that etiocholanolone/androsterone and tetrahydrocortisol/5α-tetrahydrocortisol (THF/5α-THF) metabolic ratios were significantly increased in the urine of AIP patients compared to controls (2.3 ± 0.3 vs 0.8 ± 0.1; p < 0.001 and 2.9 ± 0.7 vs 0.9 ± 0.1; p < 0.01). The (THF+5α-THF)/tetrahydrocortisone ratio was reduced among the AIP patients (p < 0.01). Quantification of the steroid absolute concentrations showed that these variations were due to a decrease of the 5α metabolites. Other ratios, like cortisol/cortisone and 6ß-hydroxycortisol/cortisol in the free steroid fraction did not show differences between patients and controls. All ratios were normal among the family carriers. CONCLUSION: A significant number of AIP patients present a basal decrease of steroid 5α-reductase activity in the liver. The deficiency may be related to malnutrition and hepatic energy misbalance associated with active AIP. Urinary steroid profiling by GC/MS may be a valuable tool to assess hepatic metabolome in AIP.

An odd case of heteroallelic acute intermittent porphyria in the Argentinean population.

AIP is an acute liver disorder caused by a deficiency of porphobilinogen deaminase (PBGD) characterized by neuroabdominal symptoms. It is an autosomal dominant disease. However, homozygous dominant AIP (HD-AIP) have been described. In some cases erythrodontia was observed. CEP is an autosomal recessive disease produced by mutations in the uroporphyrinogen III synthase gene (UROS), characterized by severe cutaneous lesions and erythrodontia. The aim of the work was to establish the differential diagnosis of porphyria in a patient with abdominal pain, neurological attacks, skin symptoms and erythrodontia. The PBGD activity was reduced 50% and the genetic analysis indicated the presence of two genetic variants in the PBGD gene, p.G111R and p.E258G, a new genetic variant, revealing a case of heteroallelic HD-AIP. The patient, first diagnosed as a carrier of a dual porphyria: AIP / CEP based on the excretion profile of porphyrins, precursors and her clinical symptoms, would be an atypical case of human HD-AIP. These results would also suggest the presence of a phenocopy of the CEP, induced by an endogenous or exogenous factor. Our findings highlight the importance of genetic studies for a proper diagnosis of porphyria, prevention of its manifestation and its treatment.