Autosomal dominant acute porphyrias are rare inherited disorders of haem biosynthesis characterised by accumulation of potentially neurotoxic porphyrin precursors and attacks of severe abdominal pain with autonomic and neuropsychiatric features. Disease severity ranges from asymptomatic individuals to those with recurrent, life-threatening attacks. The International Porphyria Network invited 34 acute porphyria specialists from 17 countries to form an expert panel. The invited group included clinicians from diverse specialities (ie, internal medicine, haematology, endocrinology, gastroenterology, hepatology, neurology, and biochemistry), together with laboratory scientists and patient representatives. The panel met online (in 2023-25) to develop 15 evidence-based recommendations with the use of the Grading of Recommendations, Assessment, Development, and Evaluations framework addressing attack prevention, management of sporadic and recurrent attacks, long-term follow-up, surveillance for primary liver cancer, and family screening. The guidelines support safe, consistent clinical care and improved outcomes, recognising global variation in resources and access to high-cost drugs, and highlighting priorities for future research.

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.

Acute intermittent porphyria (AIP) is a rare metabolic disorder that is challenging to diagnose and treat. Symptoms are nonspecific and severe acute attacks may be life-threatening. This is a case of a previously healthy 21-year-old woman diagnosed with an acute attack of AIP following recurrent hospitalizations with undiagnosed abdominal pain over a 12-month period with gradual onset of motor neuropathy which resulted in complete paralysis and respiratory failure. Through our case, we will highlight the challenges in AIP diagnosis and management, its potential severity, and how an early diagnosis could have prevented severe disability.

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.

The cover image is based on the Original Article Efficacy and safety of givosiran for acute hepatic porphyria: 24-month interim analysis of the randomized phase 3 ENVISION study by Paolo Ventura et al., https://doi.org/10.1111/liv.15090.

The autosomal dominant acute hepatic porphyrias (AHPs), acute intermittent porphyria, hereditary coproporphyria (HCP) and variegate porphyria (VP), are low penetrance adult onset disorders caused by partial deficiency of enzymes of haem biosynthesis. All are associated with acute neurovisceral attacks, which are a consequence of the increased hepatic demand for haem triggered by hormones, stress, drugs or systemic infections which leads to upregulation of the pathway and overproduction of haem precursors 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG). Acute episodes are characterised by severe abdominal pain, nausea, vomiting, hyponatraemia, hypertension and tachycardia, behavioural disturbance and can progress to include seizures, peripheral motor neuropathy and posterior reversible encephalopathy syndrome if undiagnosed and untreated. VP and HCP may also present with photocutaneous skin lesions either alone or during acute symptoms. Diagnosis involves demonstrating increased excretion of PBG in urine. Treatment focuses on removing or managing triggers, supportive treatment and suppressing the hepatic haem pathway by administering human haemin. Chronic complications include hypertension, chronic kidney disease and hepatocellular carcinoma. A small proportion of symptomatic patients with AHP progress to repeated acute attacks which require preventative therapy. A new RNA interference therapy has recently been licensed and is likely to become the treatment of choice in this situation.

Introduction: Acute hepatic porphyria (AHP) is caused by defects in hepatic heme biosynthesis leading to accumulation of the neurotoxic heme intermediates 5-aminolevulinic acid (ALA) and porphobilinogen (PBG). Intravenous (IV) hemin, the recommended treatment for an acute attack, can have side effects. Givosiran reduced ALA and PBG levels, annualized attack rate (AAR; by 73%), hemin usage, and daily pain versus placebo in the 6-month, double-blind (DB) period of the ENVISION study (NCT03338816). Continued givosiran in the open-label extension (OLE) led to sustained clinical benefit, with 85% of patients attack free at months >15–18. Here we report data from the 24-month interim analysis of ENVISION. Methods: Patients with AHP (≥12 years old) with ≥2 attacks requiring hospitalization, urgent care, or IV hemin at home in the previous 6 months were randomized (1:1) to monthly subcutaneous givosiran 2.5 mg/kg (N = 48) or placebo (N = 46) for 6 months; 93 patients subsequently received givosiran 2.5 or 1.25 mg/kg in the OLE. Analysis included urinary ALA and PBG levels and annualized days of hemin use. QOL was assessed by 12-item Short Form Health Survey (SF-12), EuroQOL visual analog scale (EQ-VAS), and Porphyria Patient Experience Questionnaire (PPEQ). Results: During the OLE, givosiran led to a sustained lowering of median urinary ALA and PBG to near-normal levels in the continuous givosiran group and a >75% sustained reduction in the placebo crossover group. Continued givosiran treatment also led to a sustained reduction in attacks and hemin use in both groups (Table 1). Proportion of patients with zero attacks per 3-month interval improved over the OLE, with 83% of the continuous givosiran group attack free at months >21–24. Overall, 68% of patients did not require hemin during the OLE. Patients experienced further improvements in QOL and activities of daily living during the OLE versus the DB period, as assessed by SF-12 Physical Component Summary (Table 1), EQ-VAS, and PPEQ. Adverse events (AEs) included injection-site reactions and elevations of serum aminotransferases. Three patients (3.2%) discontinued treatment due to AEs. Conclusion: The ENVISION 24-month interim analysis further confirms that long-term givosiran provides sustained and continuous benefit to patients with AHP, maintaining reduced frequency of attacks and hemin use, and further improving QOL. The safety profile of givosiran remained acceptable and consistent with that previously observed.Table 1.: Efficacy of Long-term Givosiran in the Continuous Givosiran Group and Placebo Crossover Group in the DB and OLE Periods of the ENVISION. trial. AAR, annualized attack rate; DB, double-blind; OLE, open-label extension, SF-12, 12-item Short Form Health Survey.

BACKGROUND & AIMS:Upregulation of hepatic delta-aminolevulinic acid synthase 1 with accumulation of potentially toxic heme precursors delta-aminolevulinic acid and porphobilinogen is fundamental to the pathogenesis of acute hepatic porphyria.AIMS:evaluate long-term efficacy and safety of givosiran in acute hepatic porphyria.METHODS:Interim analysis of ongoing ENVISION study (NCT03338816), after all active patients completed their Month 24 visit. Patients with acute hepatic porphyria (≥12 years) with recurrent attacks received givosiran (2.5 mg/kg monthly) (n = 48) or placebo (n = 46) for 6 months (double-blind period); 93 received givosiran (2.5 mg or 1.25 mg/kg monthly) in the open-label extension (continuous givosiran, n = 47/48; placebo crossover, n = 46/46). Endpoints included annualized attack rate, urinary delta-aminolevulinic acid and porphobilinogen levels, hemin use, daily worst pain, quality of life, and adverse events.RESULTS:Patients receiving continuous givosiran had sustained annualized attack rate reduction (median 1.0 in double-blind period, 0.0 in open-label extension); in placebo crossover patients, median annualized attack rate decreased from 10.7 to 1.4. Median annualized days of hemin use were 0.0 (double-blind period) and 0.0 (open-label extension) for continuous givosiran patients and reduced from 14.98 to 0.71 for placebo crossover patients. Long-term givosiran led to sustained lowering of delta-aminolevulinic acid and porphobilinogen and improvements in daily worst pain and quality of life. Safety findings were consistent with the double-blind period.CONCLUSIONS:Long-term givosiran has an acceptable safety profile and significantly benefits acute hepatic porphyria patients with recurrent attacks by reducing attack frequency, hemin use, and severity of daily worst pain while improving quality of life.

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,.) In a randomized phase 3 trial involving patients with acute intermittent porphyria, the use of givosiran, an oligonucleotide drug designed to target messenger RNA encoding aminolevulinic acid synthase, led to a 74% lower annualized porphyria attack rate than the use of placebo at 6 months.

INTRODUCTION: Acute Hepatic Porphyria (AHP) is a family of rare genetic diseases due to enzyme defects in heme synthesis in the liver. Accumulation of toxic heme intermediates ALA and PBG may result in neurovisceral attacks and chronic manifestations. Intravenous (IV) hemin is approved to treat acute attacks and is sometimes used off-label prophylactically. In the ENVISION study in AHP patients, givosiran, an RNAi therapeutic, reduced the composite porphyria annualized porphyria attack rate (AAR) vs. placebo (pbo). A post-hoc analysis was conducted to evaluate outcomes in AHP patients with or without prior hemin prophylaxis prior to screening. METHODS: ENVISION (NCT03338816) is an ongoing Phase 3 global, randomized, pbo-controlled study, evaluating givosiran efficacy and safety in symptomatic AHP patients in a 6-month double blind (DB) period and an open label extension (OLE) period (30 months). Patients were required to discontinue prophylactic hemin treatment at study entry, but could receive hemin for acute attacks. Outcome measures included the composite porphyria AAR (defined as attacks requiring hospitalization, urgent care, or IV hemin at home). Analyses were descriptive. RESULTS: For AHP patients on prior hemin prophylaxis (median historical AAR: 9.0), a 77% reduction in mean AAR was observed with givosiran treatment vs. pbo in the DB period (Table 1). A similar reduction (63%) in mean AAR was observed in those without prior hemin prophylaxis (median historical AAR: 7.0). In both groups, further reduction in AAR was observed in patients who continued on givosiran in the OLE period (Table 1). A similar reduction in AAR was also observed in both groups of pbo patients who received givosiran in the OLE (Table 1). The percentage of patients with 0 composite attacks increased in each group following 6-months of givosiran treatment in the OLE with 55% and 67% in the patients who had continued givosiran treatment (Table 1). Additional analyses of outcome measures between the two groups will be presented. CONCLUSION: Clinically meaningful reduction in the AAR was observed in AHP patients treated with givosiran regardless of whether they received hemin prophylaxis prior to study entry, with further AAR reduction observed in those who continued to receive givosiran during the OLE. In addition, a similar benefit was observed in pbo patients who received givosiran for 6-months during the OLE period regardless of prior hemin prophylaxis use.Table 1

Background and Aims Acute hepatic porphyria comprises a group of rare genetic diseases caused by mutations in genes involved in heme biosynthesis. Patients can experience acute neurovisceral attacks, debilitating chronic symptoms, and long‐term complications. There is a lack of multinational, prospective data characterizing the disease and current treatment practices in severely affected patients. Approach and Results EXPLORE is a prospective, multinational, natural history study characterizing disease activity and clinical management in patients with acute hepatic porphyria who experience recurrent attacks. Eligible patients had a confirmed acute hepatic porphyria diagnosis and had experienced ≥3 attacks in the prior 12 months or were receiving prophylactic treatment. A total of 112 patients were enrolled and followed for at least 6 months. In the 12 months before the study, patients reported a median (range) of 6 (0‐52) acute attacks, with 52 (46%) patients receiving hemin prophylaxis. Chronic symptoms were reported by 73 (65%) patients, with 52 (46%) patients experiencing these daily. During the study, 98 (88%) patients experienced a total of 483 attacks, 77% of which required treatment at a health care facility and/or hemin administration (median [range] annualized attack rate 2.0 [0.0‐37.0]). Elevated levels of hepatic δ‐aminolevulinic acid synthase 1 messenger ribonucleic acid levels, δ‐aminolevulinic acid, and porphobilinogen compared with the upper limit of normal in healthy individuals were observed at baseline and increased further during attacks. Patients had impaired quality of life and increased health care utilization. Conclusions Patients experienced attacks often requiring treatment in a health care facility and/or with hemin, as well as chronic symptoms that adversely influenced day‐to‐day functioning. In this patient group, the high disease burden and diminished quality of life highlight the need for novel therapies.

BACKGROUND Induction of delta aminolevulinic acid synthase 1 (ALAS1) gene expression and accumulation of neurotoxic intermediates result in neurovisceral attacks and disease manifestations in patients with acute intermittent porphyria, a rare inherited disease of heme biosynthesis. Givosiran is an investigational RNA interference therapeutic agent that inhibits hepatic ALAS1 synthesis. METHODS We conducted a phase 1 trial of givosiran in patients with acute intermittent porphyria. In part A of the trial, patients without recent porphyria attacks (i.e., no attacks in the 6 months before baseline) were randomly assigned to receive a single subcutaneous injection of one of five ascending doses of givosiran (0.035, 0.10, 0.35, 1.0, or 2.5 mg per kilogram of body weight) or placebo. In part B, patients without recent attacks were randomly assigned to receive once‐monthly injections of one of two doses of givosiran (0.35 or 1.0 mg per kilogram) or placebo (total of two injections 28 days apart). In part C, patients who had recurrent attacks were randomly assigned to receive injections of one of two doses of givosiran (2.5 or 5.0 mg per kilogram) or placebo once monthly (total of four injections) or once quarterly (total of two injections) during a 12‐week period, starting on day 0. Safety, pharmacokinetic, pharmacodynamic, and exploratory efficacy outcomes were evaluated. RESULTS A total of 23 patients in parts A and B and 17 patients in part C underwent randomization. Common adverse events included nasopharyngitis, abdominal pain, and diarrhea. Serious adverse events occurred in 6 patients who received givosiran in parts A through C combined. In part C, all 6 patients who were assigned to receive once‐monthly injections of givosiran had sustained reductions in ALAS1 messenger RNA (mRNA), delta aminolevulinic acid, and porphobilinogen levels to near normal. These reductions were associated with a 79% lower mean annualized attack rate than that observed with placebo (exploratory efficacy end point). CONCLUSIONS Once‐monthly injections of givosiran in patients who had recurrent porphyria attacks resulted in mainly low‐grade adverse events, reductions in induced ALAS1 mRNA levels, nearly normalized levels of the neurotoxic intermediates delta aminolevulinic acid and porphobilinogen, and a lower attack rate than that observed with placebo. (Funded by Alnylam Pharmaceuticals; ClinicalTrials.gov number, NCT02452372.)

INTRODUCTION: Acute Hepatic Porphyria (AHP) is a family of rare genetic diseases due to enzyme deficiencies in heme biosynthesis in the liver that can lead to neurovisceral attacks and chronic symptoms. (1, 2) AHP is also associated with multiple long-term complications, including neuropathy (3,4), hypertension (5,6), chronic kidney disease (7), and hepatocellular carcinoma (8,9). METHODS: ENVISION (NCT03338816) was a Phase 3 global, multicenter, randomized, double-blind, placebo-controlled trial with an open label extension to evaluate the efficacy and safety of subcutaneous givosiran in AHP. Eligible patients had an AHP diagnosis and ≥2 attacks within the prior 6 months. At baseline detailed medical history and laboratory assessments were obtained. RESULTS: Ninety-four AHP patients enrolled, median (range) age 37.5 (19-65) years, 89% female, and median (range) of 6.5 (0.1–43) years since diagnosis. Patients had a median of 4 composite attacks in the preceding 6 months and 40% were on hemin prophylaxis prior to study. Half the patients experienced daily chronic symptoms and 29% used opioids daily/most days between attacks. Comorbidities reported on medical history included neuropathy (38%), central venous access complications (71%), iron overload (33%), liver disease (28%), and chronic kidney disease (18%). At baseline 17% of patients had liver transaminases > ULN and 34% had an eGFR < 60 mL/min/1.73m2. CONCLUSION: The baseline disease characteristics of the Phase 3 study population are consistent with findings reported in the AHP literature, underscoring the high rate of liver disease and central venous access complications in these patients, and highlighting the multi-systemic nature of AHP and the medical challenge it presents for diagnosis and treatment.