Neurovisceral Attacks Research Articles

Systemic messenger RNA replacement therapy is effective in a novel clinically relevant model of acute intermittent porphyria developed in non-human primates

ObjectiveAcute intermittent porphyria (AIP) is a rare metabolic disorder caused by haploinsufficiency of hepatic porphobilinogen deaminase (PBGD), the third enzyme of the heme biosynthesis. Individuals with AIP experience neurovisceral attacks...

Porphyria in pregnancy with exacerbation after delivery due to COVID-19

We present a case of acute intermittent porphyria (AIP) diagnosed in a pregnant woman with subsequent exacerbation after delivery due to COVID-19 infection. The patient’s symptoms manifested with acute neurovisceral attacks - abdominal pain followed by flaccid quadriparesis, sensory disturbances, hypertension and disturbance in electrolyte levels. The blood plasma test and a 24-hour urine collection revealed increased levels of urine porphobilinogen, 5-aminolevulinic acid and uroporphyrins, which led to the diagnosis of AIP. The patient received i.v. human hemin with positive outcome. After delivery she was again admitted to the hospital due to abdominal pain and trunk hyperesthesia that occurred after a mild course of COVID-19 infection. The second administration of human hemin led to the improvement of the patient's condition. The aim of this case report is to indicate that even with severe risk factors of AIP such as infection and pregnancy, proper diagnostics can increase the chance of quick recovery.

An overview of porphyrias

Porphyrias are predominantly genetic metabolic disorders caused by dysregulation of specific enzymes in porphyrin-heme biosynthesis. The enzymatic dysfunction leads to formation and excretion of intermediate metabolic products in the form of porphyrins and/or their precursors δ‑aminolevulinic acid and porphobilinogen, which have cyto- and tissue-toxic properties. Clinically, porphyrias are extremely diverse, with symptoms ranging from skin changes on light-exposed areas of the body to potentially life-threatening neurovisceral attacks. Biochemical tests in urine, blood and stool are used for diagnosis, which can be supplemented by molecular genetic analyses. Treatment of the various forms of porphyria is complex and often requires close interdisciplinary cooperation between different medical specialties.

Understanding Hepatic Porphyrias: Symptoms, Treatments, and Unmet Needs.

Hepatic porphyrias are a group of metabolic disorders that are characterized by overproduction and accumulation of porphyrin precursors in the liver. These porphyrins cause neurologic symptoms as well as cutaneous photosensitivity, and in some cases patients can experience life-threatening acute neurovisceral attacks. This review describes the acute hepatic porphyrias in detail, including acute intermittent porphyria, hereditary coproporphyria, and variegate porphyria, as well as the hepatic porphyrias with cutaneous manifestations such as porphyria cutanea tarda and hepatoerythropoietic porphyria. Each section will cover disease prevalence, clinical manifestations, and current therapies, including strategies to manage symptoms. Finally, we review new and emerging treatment modalities, including gene therapy through use of adeno-associated vectors and chaperone therapies such as lipid nanoparticle and small interfering RNA-based therapeutics.

Case-based discussion of the acute hepatic porphyrias: Updates on pathogenesis, diagnosis and management.

The acute hepatic porphyrias (AHPs) include three autosomal dominant disorders, acute intermittent porphyria, variegate porphyria and hereditary coproporphyria, and the ultra-rare autosomal recessive 5-aminolevulinic acid dehydratase-deficient porphyria. All four are characterized by episodic acute neurovisceral attacks that can be life-threatening if left untreated. The attacks are precipitated by factors that induce hepatic 5-aminolevulinic acid synthase 1 (ALAS1), resulting in accumulation of the porphyrin precursors, 5-aminolevulinic acid and porphobilinogen, which are believed to cause neurotoxicity. Diagnosis of these rare disorders is often delayed because the symptoms are non-specific with many common aetiologies. However, once clinical suspicion of an AHP is raised, diagnosis can be made by specialized biochemical testing, particularly during attacks. Moderate or severe attacks are treated with intravenous hemin infusions, together with supportive care to relieve pain and other symptoms. Prophylactic treatments are recommended in patients with confirmed recurrent attacks (≥4 attacks in a maximum period of 12 months), the most effective being givosiran, an RNAi therapeutic targeting hepatocyte ALAS1 mRNA. AHP patients with clinically and/or biochemically active disease are at elevated risk for developing long-term complications, including chronic kidney disease, chronic hypertension and hepatocellular carcinoma, thus, surveillance is recommended. Here, using a case-based format, we provide an update on the pathogenesis, diagnosis and treatment of the AHPs based on literature review and clinical experiences.

Cimetidine Does Not Inhibit 5-Aminolevulinic Acid Synthase or Heme Oxygenase Activity: Implications for Treatment of Acute Intermittent Porphyria and Erythropoietic Protoporphyria.

Acute intermittent porphyria (AIP) is characterized by acute neurovisceral attacks that are precipitated by the induction of hepatic 5-aminolevulinic acid synthase 1 (ALAS1). In erythropoietic protoporphyria (EPP), sun exposure leads to skin photosensitivity due to the overproduction of photoreactive porphyrins in bone marrow erythroid cells, where heme synthesis is primarily driven by the ALAS2 isozyme. Cimetidine has been suggested to be effective for the treatment of both AIP and EPP based on limited case reports. It has been proposed that cimetidine acts by inhibiting ALAS activity in liver and bone marrow for AIP and EPP, respectively, while it may also inhibit the hepatic activity of the heme catabolism enzyme, heme oxygenase (HO). Here, we show that cimetidine did not significantly modulate the activity or expression of endogenous ALAS or HO in wildtype mouse livers or bone marrow. Further, cimetidine did not effectively decrease hepatic ALAS activity or expression or plasma concentrations of the putative neurotoxic porphyrin precursors 5-aminolevulinic acid (ALA) and porphobilinogen (PBG), which were all markedly elevated during an induced acute attack in an AIP mouse model. These results show that cimetidine is not an efficacious treatment for acute attacks and suggest that its potential clinical benefit for EPP is not via ALAS inhibition.

A randomized, placebo-controlled study of givosiran in patients with acute hepatic porphyrias (ENVISION): Final (36-month) analysis of the Taiwan Cohort

Background/purposeAcute hepatic porphyrias (AHP) are rare genetic disorders associated with acute neurovisceral attacks and chronic symptoms. This analysis was conducted to examine the long-term efficacy and safety of givosiran in Taiwanese participants in the ENVISION study (NCT03338816). MethodsPatients (age ≥12 years) with AHP and recurrent attacks were randomized to receive givosiran 2.5 mg/kg or placebo for 6 months during the double-blind period. Patients then switched from placebo to givosiran (placebo crossover group) or continued taking givosiran (continuous givosiran group) during a 30-month open-label extension period. The total study duration was 36 months. An analysis was conducted that included patients enrolled in Taiwan (N = 7). ResultsDuring the double-blind period and open-label extension period, the median annualized attack rates were 0.0 and 0.0, respectively, in the continuous givosiran group (n = 5) and 15.1 and 4.6, respectively, in the placebo crossover group (n = 2; 70 % decrease). Median annualized days of hemin use in the double-blind period and open-label extension period were 0.0 and 0.0, respectively, in the continuous givosiran group, and 23.8 and 5.0, respectively, in the placebo crossover group (79 % decrease). EQ-5D VAS scores remained relatively stable in both groups, and PPEQ responses indicated improved functioning and satisfaction in both groups. Delta-aminolevulinic acid and porphobilinogen levels remained low with long-term givosiran treatment. Serious adverse events were reported by 3 patients (43 %). ConclusionLong-term efficacy and safety results in the Taiwan cohort are consistent with those in the global cohort.

First Report of a Low-Frequency Mosaic Mutation in the Hydroxymethylbilane Synthase Gene Causing Acute Intermittent Porphyria.

Acute porphyrias are a group of monogenetic inborn errors of heme biosynthesis, characterized by acute and potentially life-threatening neurovisceral attacks upon exposure to certain triggering factors. Biochemical analyses can determine the type of acute porphyria, and subsequent genetic analysis allows for the identification of pathogenic variants in the specific gene, which provides information for family counselling. In 2017, a male Swiss patient was diagnosed with an acute porphyria while suffering from an acute attack. The pattern of porphyrin metabolite excretion in urine, faeces, and plasma was typical for an acute intermittent porphyria (AIP), which is caused by inherited autosomal dominant mutations in the gene for hydroxymethylbilane synthase (HMBS), the third enzyme in the heme biosynthetic pathway. However, the measurement of HMBS enzymatic activity in the erythrocytes was within the normal range and Sanger sequencing of the HMBS gene failed to detect any pathogenic variants. To explore the molecular basis of the apparent AIP in this patient, we performed third-generation long-read single-molecule sequencing (nanopore sequencing) on a PCR product spanning the entire HMBS gene, including the intronic sequences. We identified a known pathogenic variant, c.77G>A, p.(Arg26His), in exon 3 at an allelic frequency of ~22% in the patient's blood. The absence of the pathogenic variant in the DNA of the parents and the results of additional confirmatory studies supported the presence of a de novo mosaic mutation. To our knowledge, such a mutation has not been previously described in any acute porphyria. Therefore, de novo mosaic mutations should be considered as potential causes of acute porphyrias when no pathogenic genetic variant can be identified through routine molecular diagnostics.

Efficacy and safety of givosiran for acute hepatic porphyria: Final results of the randomized phase III ENVISION trial

Acute hepatic porphyria (AHP) is caused by defects in hepatic heme biosynthesis, leading to disabling acute neurovisceral attacks and chronic symptoms. In ENVISION (NCT03338816), givosiran treatment for 6 months reduced attacks and other disease manifestations, compared with placebo. Here we report data from the 36-month final analysis of ENVISION. Ninety-four patients with AHP (age ≥12 years) and recurrent attacks were randomized 1:1 to monthly double-blind subcutaneous givosiran 2.5mg/kg (N=48) or placebo (N=46) for 6 months. In the open-label extension (OLE) period, 93 patients received givosiran 2.5 or 1.25mg/kg for 6 months or more before transitioning to 2.5mg/kg. Endpoints were exploratory unless otherwise noted. During givosiran treatment, median annualized attack rate (AAR) was 0.4. Through Month 36, annualized days of hemin use remained low in the continuous givosiran group (median, 0.0 to 0.4) and decreased in the placebo crossover group (16.2 to 0.4). At end of OLE, in the continuous givosiran and placebo crossover groups, 86% and 92%, respectively, had 0 attacks. AAR was lower than historical AAR in 98% and 100%, respectively (post hoc analysis), and there were 0 days of hemin use in 88% and 90%, respectively. The 12-item Short Form Health Survey physical and mental component scores increased by 8.6 and 8.1, respectively (continuous givosiran) and 9.4 and 3.2, respectively (placebo crossover). EQ-5D health-related questionnaire scores increased by 18.9 (continuous givosiran) and 9.9 (placebo crossover). Lowering of urinary delta-aminolevulinic acid and porphobilinogen levels was sustained. Safety findings demonstrated a continued positive risk/benefit profile for givosiran. Long-term monthly givosiran treatment provides sustained and continued improvement in clinical manifestations of AHP. Acute hepatic porphyria (AHP) is a group of rare, chronic, multisystem disorders associated with overproduction and accumulation of neurotoxic heme intermediates (delta-aminolevulinic acid [ALA] and porphobilinogen [PBG]), sometimes resulting in recurrent acute attacks and long-term complications. Givosiran, a small interfering RNA that prevents accumulation of ALA and PBG, is approved for the treatment of AHP. These final 36-month results of ENVISION, a phase 3 study of givosiran in patients with AHP and recurrent attacks, show that long-term monthly treatment with givosiran leads to continuous and sustained reductions in annualized attack rate and use of hemin over time, as well as improved quality of life, with an acceptable safety profile. These results are important to physicians, patients, families, and caregivers who are grappling with this debilitating and potentially life-threatening disease with few effective and tolerable treatment options. NCT03338816.

Key terms and definitions in acute porphyrias: Results of an international Delphi consensus led by the European porphyria network.

Acute porphyrias are a group of rare inherited disorders causing acute neurovisceral attacks. Many terms used frequently in the literature and clinical practice are ambiguous, which can lead to confusion in the way patients are managed, studied, and reported in clinical studies. Agreed definitions are a necessary first step in developing management guidelines and will facilitate communication of results of future clinical research. The Delphi method was used to generate consensus on key terms and definitions in acute porphyria. The process started with a brainstorming phase offered to all members of the European Porphyria Network followed by two Delphi rounds among international experts in the field of porphyria (the Acute Porphyria Expert Panel). A consensus of 75% or more was defined as the agreement threshold. A total of 63 respondents from 26 countries participated in the brainstorming phase, leading to the choice of nine terms and definitions. A total of 34 experts were invited to take part in the Delphi rounds. Seven of the initial nine terms and definitions which entered the first Delphi round achieved the threshold for agreement. Following a second Delphi round, all nine definitions achieved agreement.Agreement on the definitions for nine important terms describing acute porphyrias represents a significant step forward for the porphyria community. It will facilitate more accurate comparison of outcomes among porphyria centres and in clinical trials and provide a strong framework for developing evidence-based clinical guidelines.

Understanding Carbohydrate Metabolism and Insulin Resistance in Acute Intermittent Porphyria.

Porphobilinogen deaminase (PBGD) haploinsufficiency (acute intermittent porphyria, AIP) is characterized by neurovisceral attacks associated with high production, accumulation and urinary excretion of heme precursors, δ-aminolevulinic acid (ALA) and porphobilinogen (PBG). The estimated clinical penetrance for AIP is extremely low (<1%), therefore it is likely that other factors may play an important role in the predisposition to developing attacks. Fasting is a known triggering factor. Given the increased prevalence of insulin resistance in patients and the large urinary loss of succinyl-CoA to produce ALA and PBG, we explore the impact of reduced availability of energy metabolites in the severity of AIP pathophysiology. Classic studies found clinical improvement in patients affected by AIP associated with the administration of glucose and concomitant insulin secretion, or after hyperinsulinemia associated with diabetes. Molecular studies have confirmed that glucose and insulin administration induces a repressive effect on hepatic ALA Synthase, the first and regulatory step of the heme pathway. More recently, the insulin-mimicking α-lipoic acid has been shown to improve glucose metabolism and mitochondrial dysfunction in a hepatocyte cell line transfected with interfering RNA targeting PBGD. In AIP mice, preventive treatment with an experimental fusion protein of insulin and apolipoprotein A-I improved the disease by promoting fat mobilization in adipose tissue, increasing the metabolite bioavailability for the TCA cycle and inducing mitochondrial biogenesis in the liver. In this review, we analyze the possible mechanisms underlying abnormal hepatocellular carbohydrate homeostasis in AIP.

Quantifying the impact of symptomatic acute hepatic porphyria on well-being via patient-reported outcomes: Results from the Porphyria Worldwide Patient Experience Research (POWER) study.

Acute hepatic porphyria (AHP) is a group of rare genetic diseases of heme biosynthesis resulting in severe neurovisceral attacks and chronic complications that negatively impact patients' well-being. This study evaluated the impacts of AHP on patients' physical and emotional health from a global perspective. Adult patients from the United States, Italy, Spain, Australia, Mexico, and Brazil with AHP with >1 porphyria attack within the past 2 years or receiving intravenous hemin and/or glucose for attack prevention completed an online survey assessing demographics, health characteristics, and patient-reported outcomes. Results were analyzed collectively and by patient subgroups. Ninety-two patients with AHP across the six countries completed the survey. More than 70% of patients reported that their physical, emotional, and financial health was fair or poor. Among patients who reported pain, fatigue, and muscle weakness, 94.3%, 95.6%, and 91.4%, respectively, reported that these symptoms limited daily activities. Moderate to severe depression was present in 58.7% of patients, and moderate to severe anxiety in 48.9% of patients. Of the 47% of patients who were employed, 36.8% reported loss in productivity while at work. Among patients, 85.9% reported that they had to change or modify goals that were important to them because of AHP. Aside from differences in healthcare utilization and pain severity, scores did not significantly vary with attack rate or use of hemin or glucose prophylactic treatments. AHP substantially impacts patients' physical and emotional well-being, regardless of hemin or glucose prophylactic treatment or frequency of attacks. This multinational study demonstrates that there is substantial disease burden for patients with AHP, even among those experiencing sporadic attacks or using prophylactic treatment.

Clinical features of Japanese patients with acute hepatic porphyria.

Acute hepatic porphyria (AHP) is a family of rare genetic diseases of heme biosynthesis characterized by severe neurovisceral attacks. The clinical characteristics of patients with AHP as well as the prevalence of AHP in Japan are not well understood. The objectives of this study were to describe clinical characteristics of AHP at time of diagnosis in Japanese patients and to estimate the prevalence of AHP. Patients with porphyria were selected from Japan's Medical Data Vision health care claims database between April 2008 and June 2020. Patient characteristics before and at time of AHP diagnosis were evaluated. Prevalence per 100 000 was estimated during the study period. A total of 391 cases of AHP were included. At time of AHP diagnosis, mean age was 44 years, and the most common type was acute intermittent porphyria. Median time to diagnosis was 3months, but some patients remained undiagnosed for several years. The most common complications included metabolic disorders (54%) and diabetes mellitus (39%). In addition, the well-known complications of AHP, including hypertension (22%) and malignant neoplasms of digestive organs (22%), were observed. About 10% of patients received medications that may have aggravated porphyria attacks. The estimated prevalence of AHP in Japan during the study period was 1.18 cases per 100 000 population. At time of diagnosis, many patients with AHP in Japan are already experiencing a high burden of disease-related complications. Raising AHP awareness may aid physicians in providing an earlier diagnosis and reducing lifetime disease burden.

S1372 Changes in Acute Hepatic Porphyria Health Impacts Since Initial Diagnosis: Results From the Porphyria Worldwide Patient Experience Research (POWER) Study

Introduction: Acute hepatic porphyria (AHP) is caused by genetic mutations in heme biosynthetic enzymes, affecting the liver. Patients can experience acute neurovisceral attacks, chronic symptoms, long-term complications, and negative impact on many quality-of-life domains. This study evaluated patient perceptions of changes in their disease characteristics and impacts on quality-of-life domains since AHP diagnosis among the overall study population and in subgroups based on time since first symptoms/diagnosis. Methods: Adults with > 1 AHP attack within the past 2 years or receiving intravenous hemin and/or glucose for attack prevention were administered in an online survey from January 19 to April 26, 2021. Patients taking givosiran were excluded. Subgroup analyses evaluated differences in patients experiencing active disease for 0–5 years versus ≥ 6 years. Patient-reported outcomes for anxiety and depression were assessed using the Generalized Anxiety Disorder-7 (GAD-7) scale (0–21) and the Patient Health Questionnaire (PHQ-8) scale (0–24), respectively. Results: Of 92 patients with AHP, mean age was 41.1 years, and 90% of patients were women. Mean time to diagnosis was 6.4 years, and mean duration of disease was 16.9 years. Most patients experienced negative (very or somewhat negative) impacts on emotional health (90%), physical health (87%), financial health (75%), social health (70%), and cognitive health (66%) since diagnosis. Disease characteristics described as worsening (much worse or somewhat worse) since diagnosis, included chronic pain (66%), kidney disease (55%), and acute pain (48%) (Figure). Patients with active disease for 0–5 years (N=20, 22%) had mean age 33.9 years and experienced median 2.5 attacks in the past 2 years versus 43.4 years and 5 attacks in patients with active disease for ≥ 6 years (N=67, 73%). GAD-7 scores ≥ 10 and ≥ 15 (severe anxiety) were reported in 35% and 20%, respectively, of patients experiencing AHP for 0–5 years and in 51% and 28%, respectively, of patients experiencing AHP for ≥ 6 years. A PHQ-8 score ≥ 10, indicating moderate-to-severe depression, was reported in 30% of patients experiencing AHP for 0–5 years compared with 66% for those experiencing AHP for ≥ 6 years. Conclusion: Patients with AHP experience negative impacts across multiple health domains and worsening in some disease characteristics since initial diagnosis. Patients with longer duration of disease activity (≥ 6 years) may have poorer perceived health status than those with 0–5 years.Figure 1.: Patient Perceptions of Changes in Disease Characteristics Since Disease Onset.

Development and validation of diagnostic algorithms for the laboratory diagnosis of porphyrias.

Porphyrias are rare metabolic disorders of the haem synthesis. They can present with acute neurovisceral attacks, cutaneous symptoms, or a combination of both. As they present with a wide variety of clinical symptoms, diagnosis is often delayed and correct interpretation of porphyria-related tests remains a challenge for many physicians. We developed and validated two algorithms for the laboratory diagnosis of porphyrias based on presenting symptoms. Based on a literature search and clinical/laboratory expertise, we developed algorithms for acute and cutaneous porphyrias. We validated these algorithms using all porphyria related laboratory test requests between January 1st 2000 and September 30th 2020 in UZ Leuven. In addition, we also evaluated our algorithm using samples from the European porphyria network (EPNET) external quality assessment scheme (2010-2021). Sensitivity of the algorithm for acute porphyria was 100.0% [74.9%-100.0%] (13 acute intermittent porphyria (AIP) and 1 variegate porphyria [VP]) with a specificity of 98.5% [91.0%-100.0%] (65 patients). Sensitivity of the algorithm for cutaneous porphyria was 100% [95.1%-100.0%] (7 VP, 59 porphyria cutanea tarda (PCT), 23 erythropoietic protoporphyria (EPP), 2 X-linked erythropoietic protoporphyria [XLEPP]) with a specificity of 93.9% [82.9%-98.5%]. There were no diagnostic samples of other types of porphyria. The algorithms correctly identified 18 of the 19 EPNET porphyria cases. One of the two hereditary coproporphyria cases was missed. The algorithms for acute and cutaneous porphyria showed high sensitivity and specificity and can be used to aid the clinician in correctly interpreting the laboratory findings of porphyria-related tests.

Disease burden in patients with acute hepatic porphyria: experience from the phase 3 ENVISION study

BackgroundAcute hepatic porphyria (AHP) is a family of four rare genetic diseases, each involving deficiency in a hepatic heme biosynthetic enzyme. Resultant overproduction of the neurotoxic intermediates δ-aminolevulinic acid (ALA) and porphobilinogen (PBG) leads to disabling acute neurovisceral attacks and progressive neuropathy. We evaluated the AHP disease burden in patients aged ≥ 12 years in a post hoc analysis of the Phase 3, randomized, double-blind, placebo-controlled ENVISION trial of givosiran (NCT03338816), an RNA interference (RNAi) therapeutic that targets the enzyme ALAS1 to decrease ALA and PBG production. We analyzed baseline AHP severity via chronic symptoms between attacks, comorbidities, concomitant medications, hemin-associated complications, and quality of life (QOL) and evaluated givosiran (2.5 mg/kg monthly) in patients with and without prior hemin prophylaxis on number and severity of attacks and pain scores during and between attacks.ResultsParticipants (placebo, n = 46; givosiran, n = 48) included patients with low and high annualized attack rates (AARs; range 0–46). At baseline, patients reported chronic symptoms (52%), including nausea, fatigue, and pain; comorbidities, including neuropathy (38%) and psychiatric disorders (47%); concomitant medications, including chronic opioids (29%); hemin-associated complications (eg, iron overload); and poor QOL (low SF-12 and EuroQol visual analog scale scores). A linear relationship between time since diagnosis and AAR with placebo suggested worsening of disease over time without effective treatment. Givosiran reduced the number and severity of attacks, days with worst pain scores above baseline, and opioid use versus placebo.ConclusionsPatients with AHP, regardless of annualized attack rates, have considerable disease burden that may partly be alleviated with givosiran.

Neurological Manifestations of Acute Porphyrias.

Porphyrias constitute a group of rare metabolic disorders that result in a deficiency of the heme biosynthetic pathway and lead to the accumulation of metabolic intermediaries. Patients with porphyria can experience recurrent neurovisceral attacks which are characterized by neuropathic abdominal pain and acute gastrointestinal symptoms, including nausea, vomiting, and constipation. Depending on the type of porphyria, patients can present with cutaneous manifestations, such as severe skin photosensitivity, chronic hemolysis, or evidence of neurologic dysfunction, including alterations in consciousness, neurovascular involvement, seizures, transient sensor-motor symptoms, polyneuropathy, and behavioral abnormalities. More recently, cases of posterior reversible encephalopathy syndrome, cerebral vasoconstriction, and acute flaccid paralysis have also been described. While the exact pathogenic mechanisms linking the accumulation of abnormal heme biosynthetic intermediaries to neurologic manifestations have not been completely elucidated, it has been proposed that these manifestations are more common than previously thought and can result in permanent neurologic injury. This article reviews the basic principles of heme synthesis as well as the pathogenic mechanism of disease, presentation, and treatment of acute hepatic porphyrias with emphasis on those with neurologic manifestations.

Endothelial Dysfunction in Acute Hepatic Porphyrias

Background Acute hepatic porphyrias (AHPs) are a group of rare diseases caused by dysfunctions in the pathway of heme biosynthesis. Although acute neurovisceral attacks are the most dramatic manifestations, patients are at risk of developing long-term complications, several of which are of a vascular nature. The accumulation of non-porphyrin heme precursors is deemed to cause most clinical symptoms. Aim We measured the serum levels of endothelin-1 (ET-1) and nitric oxide (NO) to assess the presence of endothelial dysfunction (ED) in patients with AHPs. Forty-six patients were classified, according to their clinical phenotype, as symptomatic (AP-SP), asymptomatic with biochemical alterations (AP-BA), and asymptomatic without biochemical alterations (AP-AC). Results Even excluding those under hemin treatment, AP-SP patients had the lowest NO and highest ET-1 levels, whereas no significant differences were found between AP-BA and AP-AC patients. AP-SP patients had significantly more often abnormal levels of ED markers. Patients with the highest heme precursor urinary levels had the greatest alterations in ED markers, although no significant correlation was detected. Conclusions ED is more closely related to the clinical phenotype of AHPs than to their classical biochemical alterations. Some still undefined disease modifiers may possibly determine the clinical picture of AHPs through an effect on endothelial functions.

Beta‐catenin inhibition as a novel therapeutic strategy for porphyria

Background– The porphyrias are metabolic disorders caused by enzymatic defects in heme biosynthesis, leading to excessive accumulation of porphyrins and their precursors in the liver or bone marrow, the most active tissues in heme biosynthesis. The specific patterns of accumulation of the heme precursors aminolevulinic acid (ALA) and other intermediate compounds define clinical features of these diseases such as acute neurovisceral attacks, skin lesions, and mental changes. These debilitating diseases remain incurable, and there is an unmet need to develop effective therapies to treat them. Because the liver is either a source or sink for porphyrins, we investigated the role of Wnt/beta‐catenin pathway in this disease. Wnt/beta‐catenin signaling is an evolutionarily conserved pathway that plays an important role in liver health and pathophysiology by regulating genes important in metabolism and proliferation.Methods– 3,5‐Diethoxycarbonyl‐1,4‐dihydrocollidine (DDC) induces hepatic porphyria in mice and is utilized to identify signaling pathways involved in injury progression. The metabolism of DDC creates a potent inhibitor of ferrochelatase (FC), the terminal enzyme in the heme pathway, which causes the buildup of porphyrin precursors. These precursors can cause cellular abnormalities such as oxidative stress, mitochondrial dysfunction, protein aggregation and inhibition of crucial functions such as autophagy. We studied pharmacological inhibition of Wnt/beta‐catenin signaling by utilizing a beta‐catenin DsiRNA formulated into a lipid nanoparticle in mice fed DDC diet.Results– Our data demonstrates that mice with pharmacologically inhibited beta‐catenin have decreased liver injury due to significantly fewer porphyrin deposits. This is due to suppression of ALA‐S and ALA‐D enzymes which catalyze the first and second steps of heme biosynthesis respectively. Significantly, we identified a strong TCF4 binding site in the intron region of the Alad gene, implicating ALA‐D as a direct Wnt/beta‐catenin target. Our data, therefore, establishes a novel role of the Wnt/beta‐catenin pathway in regulating heme biosynthesis by inhibiting early steps in heme biosynthesis pathway and reducing toxic porphyrin accumulation. Furthermore, our data reveal that mice lacking beta‐catenin have increased induction of autophagy over baseline that contributes to the protection from injury by clearing accumulated toxic porphyrins.Conclusions– These observations collectively offer a novel opportunity to remedy porphyria by targeting the Wnt/beta‐catenin signaling pathway. Our next studies will further validate ALA‐D as the mechanistic target of beta‐catenin in the heme biosynthesis pathway. Because prior research has established crosstalk between autophagy and the Wnt signaling pathway, we will also investigate the role of beta‐catenin in regulating autophagy during porphyria.

Givosiran for the treatment of acute hepatic porphyria

Introduction Acute hepatic porphyrias (AHPs) are a family of rare inherited disorders characterized by enzyme dysfunctions in the hepatic pathway of heme biosynthesis. In AHPs, accumulation of the neurotoxic porphyrin precursors delta-aminolevulinic acid and porphobilinogen, caused by enhanced activity of hepatic aminolevulinate synthase 1 (ALAS1), is associated with acute, potentially life-threatening neurovisceral attacks. Symptoms during and between attacks dramatically reduce patients’ quality of life (QoL). Givosiran is the first mRNA-targeted treatment for AHPs, silencing ALAS1 expression. Areas covered For givosiran, this review summarizes its chemistry, mechanism of action, pharmacokinetics, pharmacodynamics, safety, preclinical and clinical data in AHP, postmarketing surveillance, and regulatory status. A literature search of public and internal databases was performed, bibliographies of retrieved articles were manually searched to identify additional studies of relevance, and information was also provided by Alnylam Pharmaceuticals. Expert opinion Givosiran is a small interfering RNA (siRNA) therapeutic that reduces hepatic activity of ALAS1 and decreases accumulation of neurotoxic porphyrin precursors in patients with AHPs, ultimately reducing the number of acute attacks and improving symptoms and QoL between attacks. As AHPs are lifelong diseases, long-term safety data are needed for givosiran as an siRNA-based therapy.