Efficacy and safety of givosiran for acute hepatic porphyria: 24‐month interim analysis of the randomized phase 3 ENVISION study

Abstract 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.


| INTRODUC TI ON
Acute hepatic porphyria (AHP) is a family of four rare genetic diseases characterized by potentially life-threatening acute attacks and, for some patients, chronic manifestations impacting daily functioning and quality of life (QOL). [1][2][3][4] The AHP types are acute intermittent porphyria (AIP; most common), variegate porphyria (VP), hereditary coproporphyria (HCP), and delta-aminolevulinic acid (ALA) dehydratase-deficiency porphyria. 2,5 Clinical manifestations are due to pathogenic mutations leading to deficiency in an enzyme of hepatic heme biosynthesis. 6 These defects predispose for triggering factors inducing delta-aminolevulinic acid synthase 1 (ALAS1), the initial and normally rate-controlling enzyme of the heme biosynthesis pathway 7,8 ; trigger factors may lead to further induction of ALAS1. 9 In AHP, this can lead to accumulation of the potentially toxic porphyrin precursors ALA and porphobilinogen (PBG), thought to be causal for disease manifestations, as well as porphyrins. [9][10][11] The most severe symptoms of AHP occur during acute neurovisceral attacks, which manifest most commonly as severe abdominal pain, nausea, vomiting, tachycardia, hypertension, hyponatraemia, mental status changes, muscle weakness, and change in urine colour to red/brown. 1,3,4,12 Attacks often require hospitalization and, without prompt treatment, can result in paralysis, respiratory failure, and, rarely, permanent neurologic deficits or death. 4,13,14 Approximately 3% to 8% of symptomatic patients with AIP experience recurrent attacks (≥4 attacks/year). 13,15,16 Some patients also experience debilitating chronic symptoms between attacks, such as pain, fatigue, and nausea. 4,17 Long-term complications and comorbidities related to AHP can include chronic kidney disease (CKD), fixed systemic arterial hypertension, chronic neuropathy, and liver disease (including aminotransferase elevations, fibrosis, cirrhosis, and hepatocellular carcinoma). [3][4][5]16,[18][19][20][21] Prior to the approval of givosiran, treatment options were limited, and disease management focused on avoidance of attack triggers and use of intravenous (IV) glucose or hemin for attacks. 12 For patients experiencing recurrent attacks, the impact of the disease can be severe 4,17 ; Pharmaceuticals.
Handling Editor: Luca Valenti (≥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. 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.

K E Y W O R D S
Acute hepatic porphyria, ALA synthase-1, givosiran, health-related quality of life, RNAi therapeutics

Lay Summary
Acute hepatic porphyria is a rare genetic disease that involves potentially life-threatening acute attacks and, for some patients, persistent symptoms impacting their ability to perform daily activities. In this evaluation of information compiled from the ongoing ENVISION study, long-term givosiran treatment benefited acute hepatic porphyria patients with repeated attacks by reducing the number of attacks, hemin use, and daily pain while improving quality of life. Long-term givosiran use is safe and effective for patients with acute hepatic porphyria who experience repeated attacks. management may include prophylactic hemin, and, rarely, liver transplantation has been used as the treatment of last resort. 6,22 Hemin treatment carries the risk of adverse events (AEs), both acute (eg, headache, phlebitis) and chronic (eg, iron overload, venous thrombosis, venous obliteration, and central venous catheter complications). 5,10,12,23 Givosiran is a subcutaneously administered RNA interference therapeutic approved for the treatment of AHP in adults (USA, Brazil, Canada), [24][25][26] and in adults and adolescents aged 12 years and older (European Economic Area, United Kingdom, Switzerland, Japan). 27 Targeting messenger RNA (mRNA) encoding ALAS1, givosiran lowers induced ALAS1, thereby preventing accumulation of ALA and PBG. [28][29][30][31] Clinical studies have demonstrated that givosiran treatment leads to sustained lowering of urinary ALAS1 mRNA, ALA and PBG levels, and, in patients experiencing recurrent attacks, reduces the annualized attack rate (AAR) compared with placebo. 30,32 Givosiran treatment for 6 months during the double-blind period of the randomized, placebo-controlled, phase 3 study in 94 patients with AHP and recurrent attacks (ENVISION) led to reductions in porphyria attack rate, hemin usage, ALA and PBG levels, and daily worst pain compared with placebo. 28 Patients treated with givosiran also showed improvement in QOL and patient-reported outcomes. After the double-blind period, all on-study patients received givosiran during the open-label extension (OLE) period, which aims to assess the long-term efficacy and safety of givosiran in patients with AHP.
Here we report interim data from the patients in ENVISION who completed at least 24 months on study.

| Study design and patients
ENVISION (NCT03338816) is a 36-month study evaluating the efficacy and safety of givosiran in patients with AHP: a 6-month, double-blind, randomized, placebo-controlled period, 28 and a 30month OLE period. The present analysis reflects cumulative efficacy and safety data as of the data cutoff date of June 24, 2020, at which time all active patients had at least completed the Month 24 visit.
Eligible patients were aged ≥12 years with a documented diagnosis of AHP and a confirmed AHP genetic mutation or biochemical and clinical criteria consistent with AHP, had ≥2 porphyria attacks (requiring hospitalization, urgent healthcare visit, or treatment with IV hemin at home) within the 6 months prior to baseline, and agreed to discontinue prophylactic hemin (hemin only permitted for acute attacks). During the double-blind period, patients were randomized (1:1) to monthly givosiran (2.5 mg/kg) or placebo for 6 months.
The lower dose was introduced in a protocol amendment to assess efficacy and safety. Those enrolled before the amendment received 2.5 mg/kg; therefore, dose allocation in the OLE was not balanced.

| Outcome measures and safety assessments
Efficacy assessments including AAR of composite porphyria attacks (defined as attacks requiring hospitalization, urgent healthcare visit, or IV hemin administration at home and hereinafter referred to as "composite attacks" or "attacks"), annualized days of hemin use, and urinary levels of ALA and PBG were collected throughout the study. Patientreported outcomes included daily worst pain, fatigue, and nausea  • Long-term givosiran treatment was well tolerated.

| Statistical analysis
analysed according to whether patients received givosiran in the doubleblind period before receiving givosiran in the OLE (continuous givosiran group) or received placebo in the double-blind period and crossed over to givosiran in the OLE (placebo crossover group). Analyses of efficacy outcomes were descriptive. Safety assessments were analysed in all patients who received at least one dose of givosiran; cumulative safety data from first dose of givosiran through June 24, 2020 were reported.

| ENVISION population
Of 94 patients enrolled in the double-blind period, 89 had AIP, two had VP, one had HCP, and two had AHP without identified mutations. Of the 48 patients randomized to receive givosiran in the double-blind period, 47 entered the OLE (continuous givosiran group). One patient with VP did not enter the OLE due to abnormal liver function tests and treatment discontinuation (discussed in  Figure S1). Continuous givosiran and placebo crossover groups were generally well balanced with respect to baseline demographic and clinical characteristics (Table 1).
At data cutoff, 10 patients had discontinued treatment and 7 patients had withdrawn from the study ( Figure S1); overall, 87 givosiran-treated patients remained in the study. Primary reasons for treatment discontinuation were AEs (n = 4, 1 in the double-blind period and 3 in the OLE), pregnancy (n = 1), noncompliance with study drug (n = 1), and participant decision (n = 4).

| Annualized attack rate and hemin use
Long-term treatment with givosiran led to sustained AAR reduction ( Figure 1A). Patients in the continuous givosiran group had a sustained AAR reduction (median AAR 1.00 and 0.00 during the double-blind and OLE periods, respectively). In the placebo crossover group, median AAR decreased from 10.65 in the double-blind period to 1.35 in the OLE. During givosiran treatment, median AAR was 0.46 and 1.35 in the continuous givosiran and placebo crossover groups, respectively, and 0.63 in all givosiran patients. The proportion of patients with zero composite attacks per 3-month interval increased during the OLE compared with the double-blind period from 67% at Month >3 to 6 to 83% at Month >21 to 24 (continuous givosiran group) and from 24% to 76% (placebo crossover group) ( Figure 1B).
Long-term givosiran treatment was associated with a sustained reduction in hemin use ( Figure 1C). In the continuous givosiran group, median annualized days of hemin use were 0.00 during the doubleblind period (0-6 months) and 0.00 during the OLE (>6 months).

| Pharmacodynamics
Long-term givosiran treatment led to a sustained lowering of median urinary ALA and PBG to near-normal levels in the continuous givosiran group, and a >75% reduction in the placebo crossover group during the OLE (Figures 2A and B)  The two patients with acute hepatic porphyria without an identified mutation were considered by the trial investigator to have acute intermittent porphyria on the basis of biochemical analysis. c Composite porphyria attacks are attacks requiring hospitalization, an urgent healthcare visit, or IV hemin treatment at home. d One patient in the placebo group did not meet inclusion criterion of ≥2 composite porphyria attacks within 6 months prior to screening (patient had 2 attacks that were treated at home without IV hemin). This was identified as a protocol deviation. e Symptoms were chronic if patients experienced symptoms of porphyria daily or on most days when not having an attack and were reported by Investigators. f Opioid use was defined as chronic if patients reported taking them for porphyria daily or most days when not having an attack.

| 167
VENTURA ET Al F I G U R E 1 Attack frequency and hemin use with long-term givosiran treatment. A, Median AAR. † Descriptive analysis. ‡ Placebo crossover patients receiving givosiran 2.5 mg/kg (n = 29) or 1.25 mg/kg (n = 17). B, Proportion of patients with zero attacks by 3-month intervals. Baseline represents 6 months prior to randomization. § One patient did not meet an inclusion criterion and was enrolled in the study (did not have the requisite number of attacks in the 6 months prior to randomization  the givosiran group and increased by 12% in the placebo group (data not shown).

| Safety
AEs were reported in 90 (96%) patients; the majority of events were mild or moderate in severity. Severe AEs were reported in 27 (29%) patients. The most frequently reported AEs (in ≥10% of patients) were injection-site reaction (ISR), nausea, fatigue, nasopharyngitis, and headache ( TA B L E 2 Safety overview in patients with AHP during givosiran treatment described below). Two patients at one site had SAEs of blood homocysteine increased, based on laboratory assessments performed by the investigator that were not prespecified in the protocol. The elevations of homocysteine were considered medically significant events and considered possibly related to givosiran by the investigator. One of these patients had a concurrent SAE of hypersensitivity, and the other had a concurrent SAE of pancreatitis. 36 Both withdrew from the study due to the SAEs of blood homocysteine increased.
There were no deaths related to givosiran during the study.
Hepatic AEs were reported in 17 (18%) patients; all were mild or moderate in severity, the majority being serum aminotransferase elevations. A total of 10 patients (11%) had alanine aminotransferase (ALT) levels more than 3 times the upper limit of normal (ULN), of whom 3 patients (3%) had ALT levels more than 5 times ULN.
One patient with ALT greater than 8 times the ULN, reported as an SAE of liver function test abnormal, discontinued treatment (due to a protocol-defined stopping rule) and withdrew from the study at the end of the double-blind period. The ALT elevations generally occurred approximately 3 to 6 months after givosiran was started, and then resolved subsequently ( Figure S10). No patients discontinued givosiran due to hepatic events during the OLE period.
Twenty-one patients (22%) reported renal AEs, which were mostly increased creatinine and/or decreased estimated glomerular filtration rate (eGFR); most events were mild or moderate in severity and none led to treatment discontinuation. Small decreases in eGFR observed early in therapy stabilized over Months 12 to 24 ( Figure S11). Some patients with pre-existing kidney disease showed a small, continued decrease in their eGFR. No patients discontinued givosiran due to renal events during the OLE period.
ISRs occurred in 37% of patients and 6% of the 2152 doses of givosiran given; all ISRs were mild or moderate in severity, and none led to discontinuation. The most common symptoms of ISRs included erythema, pruritus, rash, pain, and swelling at the injection site.
On laboratory evaluation, there have been no notable changes in haematology parameters related to givosiran. Mean values for lipase and amylase have remained generally stable during the study; however, intermittent elevations of lipase and amylase have been observed in some patients. The proportion of patients with shifts in lipase and amylase were comparable between the placebo and givosiran groups during the double-blind period, without any imbalances.

| D ISCUSS I ON
Disease burden is substantial and treatment options are limited for patients with AHP who experience recurrent attacks and chronic symptoms between attacks. 4,12,17,37 Natural history data suggest that up to 65% experience chronic, debilitating symptoms such as pain, fatigue, and nausea that negatively impact daily functioning and QOL. 4,28,[38][39][40] Hemin is recommended for treatment of acute attacks that do not respond to treatment with glucose and in patients who display neurologic symptoms or require hospitalization 7,41,42 ; it is also used for prophylaxis. 4,43 However, repeated prophylactic use of hemin may be associated with reduced efficacy, and it is associated with AEs such as venous damage and thrombophlebitis, coagulation abnormalities, and secondary iron overload. 5,28,44,45 Compared to placebo, givosiran treatment has been shown to have significant clinical efficacy and an acceptable safety profile in patients with AHP. 28 Consistent with the results from the double-blind period, this 24-month interim analysis of the ENVISION study confirms that long-term givosiran dosing leads to continuous and sustained reductions in AAR and hemin use, with 83% and 76% of patients being attack-free (continuous givosiran and placebo crossover groups, respectively), and 68% and 49% of patients, respectively, not requiring supplemental hemin. Lower opioid use occurred against a background of patient-reported reduced daily worst pain (12-month data). Long-term givosiran dosing resulted in improvements in several patient-reported outcomes, including physical functioning, activities of daily living, and overall health status assessment scores.
The SF-12 PCS score increased by 8.9 points in the continuous givosiran group and 10.0 points in placebo crossover patients in the OLE.
In other chronic diseases, a ≥2-to 5-point increase is considered a clinically meaningful improvement. 38,39 Sustained and continuous improvements in the attack rate, the proportion of patients who remained attack-free, and patient-reported outcomes were associated with sustained lowering of ALA and PBG levels, the toxic heme intermediates considered causal for disease manifestations. 2,11 During the OLE period, the protocol was amended to assess the efficacy and safety of a lower dose of givosiran ( Elevations of blood homocysteine have been reported in patients with AHP, with a correlation of higher levels in those with greater disease activity. 36,47-49 As 2 SAEs of blood homocysteine increases were observed in the present ENVISION study, 36 analyses of blood homocysteine levels were performed on exploratory samples, which included levels collected before, during, and after givosiran treatment. During these analyses, blood homocysteine levels were also noted to be increased compared with available baseline levels. 50,51 Blood homocysteine levels increased in all patients in one analysis (9/9 patients) and in most patients in the second analysis (14/15 patients). 50,51 The degree of homocysteine elevation varied among patients. 50,51 The long-term consequences of homocysteine elevations in patients with AHP are unknown. Additional work on the possible implications is needed.
The study is limited by the relatively small number of patients in the study population. However, the ongoing ENVISION study is the largest intervention study to date for this rare disease.
The 24-month data from this phase 3 study show that long-term dosing with givosiran is well tolerated and provides sustained and continuous benefit to patients with AHP, as reflected by a durable reduction in frequency of attacks, hemin use to treat attacks, levels of toxic heme intermediates ALA and PBG, daily pain, and opioid use. Givosiran treatment was also associated with improvement in assessments of physical functioning and QOL.

E TH I C S A PPROVA L S TATE M E NT
The study was approved by central and local institutional review boards or ethics committees and was conducted in accordance with Good Clinical Practice guidelines and the provisions of the Declaration of Helsinki.

ACK N OWLED G EM ENTS
The sponsor was involved in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

AUTH O R S CO NTR I B UTI O N S
All authors had full access to all of the data in the study and take re-

TR I A L R EG I S TR ATI O N N U M B E R
ClinicalTrials.gov, NCT03338816.

PATI E NT CO N S E NT S TATE M E NT
All patients provided written informed consent.

DATA AVA I L A B I L I T Y S TAT E M E N T
De-identified individual participant data that support these results will be made available in a secure-access environment 12 months after study completion and when the product and indication have been approved for no less than 12 months in the US and the EU.
Access will be provided contingent upon the approval of a research proposal and the execution of a data sharing agreement.