BACKGROUNDHereditary angioedema (HAE) is a serious and potentially life-threatening condition that causes acute attacks of swelling, pain and reduced quality of life. People with Type I HAE (approximately 80% of all HAE cases) have insufficient amounts of C1 esterase inhibitor (C1-INH) protein; people with Type II HAE (approximately 20% of all cases) may have normal C1-INH concentrations, but, due to genetic mutations, these do not function properly. A few people, predominantly females, experience HAE despite having normal C1-INH levels and C1-INH function (rare Type III HAE). Several new drugs have been developed to treat acute attacks and prevent recurrence of attacks. There is currently no systematic review and meta-analysis that included all preventive medications for HAE.OBJECTIVESTo assess the benefits and harms of interventions for the long-term prevention of HAE attacks in people with Type I, Type II or Type III HAE.SEARCH METHODSWe used standard, extensive Cochrane search methods. The latest search date was 3 August 2021.SELECTION CRITERIAWe included randomised controlled trials in children or adults with HAE that used medications to prevent HAE attacks. The comparators could be placebo or active comparator, or both; approved and experimental drug trials were eligible for inclusion. There were no restrictions on dose, frequency or intensity of treatment. The minimum length of four weeks of treatment was required for inclusion; this criterion excluded the acute treatment of HAE attacks.DATA COLLECTION AND ANALYSISWe used standard Cochrane methods. Our primary outcomes were 1. HAE attacks (number of attacks per person, per population) and change in number of HAE attacks; 2. mortality and 3. serious adverse events (e.g. hepatic dysfunction, hepatic toxicity and deleterious changes in blood tests). Our secondary outcomes were 4. quality of life; 5. severity of breakthrough attacks; 6. disability and 7. adverse events (e.g. weight gain, mild psychological changes and body hair). We used GRADE to assess certainty of evidence for each outcome.MAIN RESULTSWe identified 15 studies (912 participants) that met the inclusion criteria. The studies included people with Type I and II HAE. The studies investigated avoralstat, berotralstat, subcutaneous C1-INH, plasma-derived C1-INH, nanofiltered C1-INH, recombinant human C1-INH, danazol, and lanadelumab for the prevention of HAE attacks. We did not find any studies on the use of tranexamic acid for prevention of HAE attacks. All drugs except avoralstat reduced the number of HAE attacks compared with placebo. For breakthrough attacks that occurred despite prophylactic treatment, intravenous and subcutaneous forms of C1-INH and lanadelumab reduced attack severity. It is not known whether other drugs have a similar effect, as the severity of breakthrough attacks in people taking drugs other than C1-INH and lanadelumab was not reported. For quality of life, avoralstat, berotralstat, C1-INH (all forms) and lanadelumab increased quality of life compared with placebo; there were no data for danazol. Four studies reported on changes in disability during treatment with C1-INH, berotralstat and lanadelumab; all three drugs decreased disability compared with placebo. Adverse events, including serious adverse events, did not occur at a rate higher than placebo. However, serious adverse event data and other adverse event data were not available for danazol, which prevented us from drawing conclusions about the absolute or relative safety of this drug. No deaths were reported in the included studies. The analysis was limited by the small number of studies, the small number of participants in each study and the lack of data on older drugs, therefore the certainty of the evidence is low. Given the rarity of HAE, it is not surprising that drugs were rarely directly compared, which does not allow conclusions on the comparative efficacy of the various drugs for people with HAE. Finally, we did not identify any studies that included people with Type III HAE. Therefore, we cannot draw any conclusions about the efficacy or safety of any drug in people with this form of HAE.AUTHORS' CONCLUSIONSThe available data suggest that berotralstat, C1-INH (subcutaneous, plasma-derived, nanofiltered and recombinant), danazol and lanadelumab are effective in lowering the risk or incidence (or both) of HAE attacks. In addition, C1-INH and lanadelumab decrease the severity of breakthrough attacks (data for other drugs were not available). Avoralstat, berotralstat, C1-INH (all forms) and lanadelumab increase quality of life and do not increase the risk of adverse events, including serious adverse events. It is possible that danazol, subcutaneous C1-INH and recombinant human C1-INH are more effective than berotralstat and lanadelumab in reducing the risk of breakthrough attacks, but the small number of studies and the small size of the studies means that the certainty of the evidence is low. This and the lack of head-to-head trials prevented us from drawing firm conclusions on the relative efficacy of the drugs.
