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.

An investigational oral plasma kallikrein inhibitor for on-demand treatment of hereditary angioedema: a two-part, randomised, double-blind, placebo-controlled, crossover phase 2 trial.

BACKGROUND: Guidelines recommend effective on-demand therapy for all individuals with hereditary angioedema. We aimed to assess the novel oral plasma kallikrein inhibitor, sebetralstat, which is in development, for on-demand treatment of hereditary angioedema attacks. METHODS: In this two-part phase 2 trial, individuals with type 1 or 2 hereditary angioedema aged 18 years or older were recruited from 25 sites, consisting of specialty outpatient centres, across nine countries in Europe and the USA. Individuals were eligible if they had experienced at least three hereditary angioedema attacks in the past 93 days, were not on prophylactic therapy, and had access to and the ability to self-administer conventional attack treatment. In part 1 of the trial, participants were given a single 600 mg open-label oral dose of sebetralstat to assess safety, pharmacokinetics, and pharmacodynamics of the dose. Part 2 was a randomised, double-blind, placebo-controlled, two-sequence, two-period (2 × 2) crossover trial; participants were randomly assigned (1:1) to either sequence 1, in which they were given a single dose of 600 mg of sebetralstat to treat the first eligible attack and a second dose of placebo to treat the second eligible attack, or sequence 2, in which they were given placebo to treat the first eligible attack and then 600 mg of sebetralstat to treat the second eligible attack. Participants and investigators were masked to treatment assignment. The primary endpoint was time to use of conventional attack treatment within 12 h of study drug administration, which was assessed in all participants who were randomly assigned to treatment and who received study drug for two attacks during part 2 of the study. Safety was assessed in all participants who received at least one dose of study drug, starting in part 1. This study is registered with ClinicalTrials.gov, NCT04208412, and is completed. FINDINGS: Between July 2, 2019, and Dec 8, 2020, 84 individuals were screened and 68 were enrolled in part 1 and received sebetralstat (mean age 38·3 years [SD 13·2], 37 [54%] were female, 31 [46%] were male, 68 [100%] were White). 42 (62%) of 68 participants completed pharmacokinetic assessments. Sebetralstat was rapidly absorbed, with a geometric mean plasma concentration of 501 ng/mL at 15 min. In a subset of participants (n=6), plasma samples obtained from 15 min to 4 h after study drug administration had near-complete protection from ex vivo stimulated generation of plasma kallikrein and cleavage of high-molecular-weight kininogen. In part 2, all 68 participants were randomly assigned to sequence 1 (n=34) or sequence 2 (n=34). 53 (78%) of 68 participants treated two attacks (25 [74%] in the sequence 1 group and 28 [82%] in the sequence 2 group). Time to use of conventional treatment within 12 h of study drug administration was significantly longer with sebetralstat versus placebo (at quartile 1: >12 h [95% CI 9·6 to >12] vs 8·0 h [3·8 to >12]; p=0·0010). There were no serious adverse events or adverse event-related discontinuations. INTERPRETATION: Oral administration of sebetralstat was well tolerated and led to rapid suppression of plasma kallikrein activity, resulting in increased time to use of conventional attack treatment and faster symptom relief versus placebo. Based on these results, a phase 3 trial to evaluate the efficacy and safety of two dose levels of sebetralstat in adolescent and adult participants with hereditary angioedema has been initiated (NCT05259917). FUNDING: KalVista Pharmaceuticals.

Pharmacological suppression of the kallikrein kinin system with KVD900: An orally available plasma kallikrein inhibitor for the on-demand treatment of hereditary angioedema.

BACKGROUND: Hereditary angioedema (HAE) is a rare genetic disease that leads to recurrent episodes of swelling and pain caused by uncontrolled plasma kallikrein (PKa) activity. Current guidelines recommend ready availability of on-demand HAE treatments that can be administered early upon attack onset. This report describes the pharmacological and pharmacodynamic properties of the novel oral small-molecule PKa inhibitor KVD900 as a potential on-demand treatment for HAE. METHODS: Pharmacological properties of KVD900 on PKa and closely related serine proteases were characterized using kinetic fluorogenic substrate activity assays. Effects of KVD900 on PKa activity and kallikrein kinin system activation in whole plasma were measured in the presence of dextran sulphate (DXS)-stimulation using a fluorogenic substrate and capillary immunoassays to quantify high molecular weight kininogen (HK), plasma prekallikrein and Factor XII cleavage. Pharmacodynamic effects of orally administered KVD900 were characterized in plasma samples from six healthy controls in a first in human phase 1 clinical trial and from 12 participants with HAE in a phase 2 clinical trial. RESULTS: KVD900 is a selective, competitive and reversible inhibitor of human PKa enzyme with a Ki of 3.02 nM. The association constant (Kon ) of KVD900 for PKa is >10 × 106  M-1  s-1 . Oral administration of KVD900 in a first-in-human clinical trial achieved rapid and near complete inhibition of DXS-stimulated PKa enzyme activity and HK cleavage and reduced plasma prekallikrein and Factor XII activation in plasma. In individuals with HAE, orally administered KVD900 inhibited DXS-stimulated PKa activity in plasma by ≥95% from 45 min to at least 4 h post-dose and provided rapid protection of HK from cleavage. CONCLUSION: KVD900 is a fast-acting oral PKa inhibitor that rapidly inhibits PKa activity, kallikrein kinin system activation and HK cleavage in plasma. On-demand administration of KVD900 may provide an opportunity to halt the generation of bradykinin and reverse HAE attacks.

KVD900, an oral on-demand treatment for hereditary angioedema: Phase 1 study results.

BACKGROUND: Attacks of hereditary angioedema are attributed to excessive plasma kallikrein (PKa) activity, which cleaves high-molecular-weight kininogen to generate the proinflammatory hormone bradykinin. OBJECTIVE: We evaluated the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of KVD900, an orally administered inhibitor of PKa in healthy adults. METHODS: KVD900 was administered in 2 clinical studies. In the first study, healthy adult men received single ascending doses (5-600 mg) of KVD900 capsule or placebo, single 100 mg doses of KVD900 tablet and KVD900 capsule (crossover), and single 600 mg doses of KVD900 (6 × 100 mg tablets) under fed and fasting conditions (crossover). In a second study, 3 cohorts of healthy adults were provided 600 mg of KVD900 tablets at 8-, 4-, and 2-hour intervals. RESULTS: Overall, 98 healthy participants received KVD900. All adverse events (AEs) were mild, except for a single moderate AE (headache). Exposure to KVD900 was proportional to dose. The PK parameters for KVD900 600 mg in tablet form under fasted conditions were mean (coefficient of variation) maximum plasma concentration of 6460 (22.0) ng/mL, mean (coefficient of variation) area under the curve (AUC0-24) of 18,600 (22.5) h⋅ng/mL, and median (range) time to maximum plasma concentration of 0.5 (0.33-1.5) hours. Mean PKa inhibition was essentially complete (>98%) between 20 minutes and 3 hours, and >90% inhibition was maintained for at least 8 hours after dosing. High-molecular-weight kininogen cleavage protection at the 600 mg dose was attained within 20 minutes and maintained for 8 to 10 hours. CONCLUSION: These phase 1 studies evaluated the PK/PD profile of KVD900, showing that KVD900 rapidly achieves near-complete PKa inhibition and is generally safe and well tolerated. GOV IDENTIFIER: NCT04349800.

New benzylureas as a novel series of potent, nonpeptidic vasopressin V2 receptor agonists.

Vasopressin (AVP) is a hormone that stimulates an increase in water permeability through activation of V2 receptors in the kidney. The analogue of AVP, desmopressin, has proven an effective drug for diseases where a reduction of urine output is desired. However, its peptidic nature limits its bioavailability. We report herein the discovery of potent, nonpeptidic, benzylurea derived agonists of the vasopressin V2 receptor. We describe substitutions on the benzyl group to give improvements in potency and subsequent modifications to the urea end group to provide improvements in solubility and increased oral efficacy in a rat model of diuresis. The lead compound 20e (VA106483) is reported for the first time and has been selected for clinical development.

Non-peptide oxytocin agonists.

A library of compounds targeted to the vasopressin/oxytocin family of receptors was screened for activity at a cloned human oxytocin receptor using a reporter gene assay. Potency and selectivity were optimised to afford compound 39, EC50 = 33 nM. This series of compounds represents the first disclosed, non-peptide, low molecular weight agonists of the hormone oxytocin (OT).