Disease Burden in Patients With Acute Hepatic Porphyria: Experience From the Phase 3 ENVISION Study

Introduction: Acute hepatic porphyria (AHP) is a family of rare genetic diseases caused by defects in hepatic heme biosynthesis. Intravenous (IV) hemin is the standard of care for acute attacks and is at times used off label prophylactically, but can have acute (e.g. phlebitis) and chronic (e.g. iron overload) complications. The phase 3 ENVISION study (NCT03338816) showed givosiran reduced annualized attack rate (AAR) by 73% versus placebo in the double-blind (DB) period. Open-label extension data showed 85% of patients continuing givosiran were attack free at >15–18 months. Here we summarize data from ENVISION to assess the spectrum of disease burden associated with AHP. Methods: Patients (N=94) enrolled in ENVISION had experienced ≥2 attacks requiring hospitalization, urgent care, or IV hemin at home in the 6 months before the study. This analysis assessed AAR, daily worst pain (eDiary), comorbidity, concomitant medication, and quality of life (12-Item Short Form Health Survey [SF-12]). Results: Patients had severe disease burden at study entry, consistent with AHP burden shown in natural history studies. Patients reported a median of 4 (range, 0–46) attacks during the previous 6 months, despite 40% being on prophylactic hemin. Of all patients, 34% did not have attacks requiring hospitalization. Chronic symptoms, including pain, were experienced by 52% of patients daily or on most days between attacks. Baseline median SF-12 bodily pain score was 40 (scale 0–100), suggesting interference with normal functioning. Overall, 29% of patients used opioids daily or on most days between attacks. Most patients had comorbidities at baseline (47% had psychiatric disorders) (Table 1) and were taking concomitant medications. The median (Q1–Q3) ferritin level was 209 (48–719) µg/L (normal: female, 13–150 µg/L; male, 30–400 µg/L). A moderate linear correlation between longer time since AHP diagnosis and higher AAR with placebo during the 6-month DB period (r=0.403) suggests patients may experience worsening disease and complications over time. Givosiran provided clinical benefit, including reduction of daily worst pain and analgesics use. Conclusion: AHP disease burden, including the number of attacks, comorbidities, and concomitant medication use, has negative impacts on daily functioning. Earlier initiation of treatments, such as givosiran, that prevent attacks and reduce chronic manifestations of AHP may lead to improved prognosis for patients.