Phase II study results of a replacement therapy for hereditary angioedema with subcutaneous C1-inhibitor concentrate

BACKGROUND

Hereditary angioedema (HAE) due to C1 inhibitor deficiency manifests as recurrent swelling attacks that can be disabling and sometimes fatal. Long-term prophylaxis with twice-weekly intravenous injections of plasma-derived C1-inhibitor (pdC1-INH) has been established as an effective treatment. Subcutaneous (SC) administration of pdC1-INH has not been studied in patients with HAE.

METHODS

This open-label, dose-ranging, crossover study (COMPACT Phase II) was conducted in 18 patients with type I or II HAE who received two of twice-weekly 1500, 3000, or 6000 IU SC doses of highly concentrated volume-reduced CSL830 for 4 weeks each. The mean trough plasma levels of C1-INH functional activity, C1-INH and C4 antigen levels during Week 4, and overall safety and tolerability were evaluated. The primary outcome was model-derived steady-state trough C1-INH functional activity.

RESULTS

After SC CSL830 administration, a dose-dependent increase in trough functional C1-INH activity was observed. C1-INH and C4 levels both increased. The two highest dose groups (3000 and 6000 IU) achieved constant C1-INH activity levels above 40% values, a threshold that was assumed to provide clinical protection against angioedema attacks. Compared with intravenous injection, pdC1-INH SC injection with CSL830 showed a lower peak-to-trough ratio and more consistent exposures. All doses were well tolerated. Mild-to-moderate local site reactions were noted with pain and swelling being the most common adverse event.

CONCLUSIONS

Subcutaneous volume-reduced CSL830 was well tolerated and led to a dose-dependent increase in physiologically relevant functional C1-INH plasma levels. A clinical outcome study of SC CSL830 in patients with HAE warrants further investigation.

Current drugs in early development for hereditary angioedema: potential for effective treatment

Hereditary angioedema (HAE) through C1 inhibitor deficiency is a rare but important disease. It is characterized by recurrent episodes of angioedema, which commonly affects the skin (in the form of swelling in the extremities, face and genitals) as well as the gastrointestinal tract (abdominal pain attacks). In approximately 1% of cases of angiodema-related swelling, there is obstruction of the upper airway, which is potentially life-threatening. Therefore, HAE due to C1 inhibitor deficiency may be associated with significant morbidity and mortality. Recent research has added to our ever-increasing understanding of the pathogenesis of HAE, which has, in addition, new clinical trials with new therapeutic agents and strategies. The following editorial covers drugs currently under investigation that have the potential to be promising new therapeutic options. While some compounds show promise for the future, there are currently no oral treatments available for the treatment of acute attacks. Furthermore, some of the intravenous therapies currently available require numerous injections and do not always prevent acute attacks. Attenuated androgens also may have problematic side effects, highlighting the need for new treatment options.