Kallikrein inhibitors for angioedema: the progress of preclinical and early phase studies

INTRODUCTION

Hereditary angioedema (HAE) is a rare genetic disorder characterized by recurrent edema and predominantly caused by the dysregulation of the kinin-kallikrein system.

AREAS COVERED

This manuscript presents the results of preclinical and early clinical trials of newer drugs targeting the dysregulated kinin-kallikrein system. ATN-249 is an oral drug that has shown promising results in preclinical and Phase I studies, and good tolerability in the prophylactic treatment of attacks. KVD900 is also an oral agent developed for the on-demand treatment of HAE attacks. It has shown positive results in Phase I/II studies, with rapid absorption. The third drug, IONIS-PKKRx, is an antisense oligonucleotide targeting plasma prekallikrein mRNA. It has shown a dose-dependent reduction of plasma prekallikrein levels and proenzyme activation in Phase I/II studies, and has shown promising results. STAR-0215 is a long acting anti-activated kallikrein monoclonal antibody. A Phase 1a single ascending dose trial evaluated its safety, pharmacokinetics, and pharmacodynamics. Lastly, NTLA-2002 is an investigational gene-editing therapy.

EXPERT OPINION

The targeted treatment of the dysregulated kinin-kallikrein system with specific inhibitors is promising for the prevention of angioedema attacks. Ongoing phase III studies will provide further insight into the efficacy and long-term safety of these novel therapies, potentially expanding treatment options for HAE treatment.

Evaluation of patient-reported outcome measures for on-demand treatment of hereditary angioedema attacks and design of KONFIDENT, a phase 3 trial of sebetralstat

BACKGROUND

Hereditary angioedema (HAE) with C1-inhibitor deficiency (HAE-C1-INH) is characterized by recurrent, debilitating episodes of swelling. Sebetralstat, an investigational oral plasma kallikrein inhibitor, demonstrated promising efficacy for on-demand treatment of HAE-C1-INH in a phase 2 trial. We describe the multipronged approach informing the design of KONFIDENT, a phase 3 randomized, placebo-controlled, three-way crossover trial evaluating the efficacy and safety of sebetralstat in patients aged ≥12 years with HAE-C1-INH.

METHODS

To determine an optimal endpoint to measure the beginning of symptom relief in KONFIDENT, we engaged patients with HAE on clinical outcome measures and subsequently conducted analyses of phase 2 outcomes. Sample size was determined via a simulation-based approach using phase 2 data.

RESULTS

Patient interviews revealed a strong preference (71%) for the Patient Global Impression of Change (PGI-C) over other measures and indicated a rating of "A Little Better" as a clinically meaningful milestone. In phase 2, a rating of "A Little Better" demonstrated agreement with attack severity improvement and resolution on the Patient Global Impression of Severity and had better sensitivity than "Better." Simulations indicated that 84 patients completing treatment would ensure at least 90% power for assessing the primary endpoint of time to beginning of symptom relief defined as a PGI-C rating of at least "A Little Better" for two time points in a row.

CONCLUSIONS

Patient feedback and phase 2 data support PGI-C as the primary outcome measure in the phase 3 KONFIDENT trial evaluating sebetralstat, which has the potential to be the first oral on-demand treatment for HAE-C1-INH attacks.

Absorption, metabolism, and excretion of [14C]-sebetralstat (KVD900) following a single oral dose in healthy male participants

Sebetralstat is an investigational oral plasma kallikrein inhibitor for the on-demand treatment of hereditary angioedema. Six healthy male participants received one dose of 600 mg (540 µCi) [¹⁴C]-sebetralstat. Plasma concentrations of sebetralstat and levels of total radioactivity in plasma, urine, and faeces were determined. Metabolite profiles of radioactivity were generated, and major metabolites structurally characterised.Radioactivity was rapidly absorbed and was excreted with a mean of 95.8% (63.4% faeces; 32.4% urine) recovered by 216 h. Sebetralstat was the major drug-related component in urine and faeces, although metabolism predominated overall (main metabolites: M19 (des-[methoxy-fluoro-methylpyridine]-sebetralstat), M10 (N-des-pyridone-sebetralstat-carboxylic acid), M3 (pyridine O-desmethyl-sebetralstat), and M34 (pyridine dioxy-dihydro-sebetralstat)). Sebetralstat was the main radiolabelled component in plasma (mean of 64.1% of the total radioactivity AUC_0-24), followed by relatively low proportions of metabolites: M19 (7.10%), M3 (4.01%), and M10 (4.00%). Although M19 was >10% of the plasma radioactivity AUC_0-24, in one participant it comprised a mean of <10% of AUC_0-24. Plasma levels of M19 were measured at the NOAEL dose in a rat toxicology study, where higher exposure was observed vs. that in humans.Given these findings and the lack of pharmacological activity of M19, it was concluded that there was no unique or disproportionate circulating metabolite in humans.