In vitro pharmacological profile of PHA-022121, a small molecule bradykinin B2 receptor antagonist in clinical development

Current and Emerging Therapeutics in Hereditary Angioedema

Angioedema is characterized by transient movement of fluid from the vasculature into the interstitial space leading to subcutaneous or submucosal non-pitting edema. Current evidence suggests that most angioedema conditions can be grouped into 2 categories: mast cell-mediated (previously termed histaminergic) or bradykinin-mediated angioedema. Although effective therapies for mast cell-mediated angioedema have existed for decades, specific therapies for bradykinin-mediated angioedema have more recently been developed. In recent years, rigorous studies of these therapies in treating hereditary angioedema (HAE) have led to regulatory approvals of medication for HAE management thereby greatly expanding HAE treatment options.

Clinical Progress in Hepatic Targeting for Novel Prophylactic Therapies in Hereditary Angioedema

Hereditary angioedema (HAE) is typically caused by a deficiency of the protease inhibitor C1 inhibitor (C1INH). The absence of C1INH activity on plasma kallikrein and factor XIIa leads to overproduction of the vasoactive peptide bradykinin, with resulting angioedema. As the primary site of C1INH and prekallikrein production, the liver is recognized as an important therapeutic target in HAE, leading to the development of hepatic-focused treatment strategies such as GalNAc-conjugated antisense technology and gene modification. This report reviews currently available data on hepatic-focused interventions for HAE that have advanced into human trials. Donidalorsen is an investigational GalNAc3-conjugated antisense oligonucleotide that binds to prekallikrein mRNA in the liver and reduces the expression of prekallikrein. Phase 2 data with subcutaneous donidalorsen demonstrated a significant reduction in HAE attack rate compared with placebo. Phase 3 trials are underway. ADX-324 is a GalNAc3-conjugated short-interfering RNA being investigated in HAE. BMN 331 is an investigational AAV5-based gene therapy vector that expresses wild-type human C1INH and is targeted to hepatocytes. A single intravenous dose of BMN 331 is intended to replace the defective SERPING1 gene and enable patients to produce functional C1INH. A first-in-human phase 1/2 study is ongoing with BMN 331. NTLA-2002 is an investigational in vivo clustered regularly interspaced short palindromic repeats/Cas9-based therapy designed to knock out the prekallikrein-coding KLKB1 gene in hepatocytes; a phase 1/2 study is ongoing. Findings from these and other ongoing studies are highly anticipated with the expectation of expanding the array of treatment options in HAE.

Highly effective and selective FeBr3-promoted deuterium bromination/cyclization of 1,n-enynes

A highly effective and selective FeBr3-promoted deuterium bromination/cyclization of 1,n-enynes is reported. On the one hand, the Lewis acid FeBr3 as a catalyst promotes cyclization of 1,n-enynes to afford deuterium heterocyclic frameworks with high efficiency. On the other hand, FeBr3 serves as the bromine source (with D2O as the deuterium source) to promote the formation of the desired deuterated pyrrole derivatives containing alkenyl bromide groups. This protocol provides an effective pathway to afford deuterated alkenyl brominative compounds as (Z)-isomers with high yields and selectivity, offering a new method for introducing 2H into organic compounds.

Deuterium in drug discovery: progress, opportunities and challenges

Substitution of a hydrogen atom with its heavy isotope deuterium entails the addition of one neutron to a molecule. Despite being a subtle change, this structural modification, known as deuteration, may improve the pharmacokinetic and/or toxicity profile of drugs, potentially translating into improvements in efficacy and safety compared with the non-deuterated counterparts. Initially, efforts to exploit this potential primarily led to the development of deuterated analogues of marketed drugs through a 'deuterium switch' approach, such as deutetrabenazine, which became the first deuterated drug to receive FDA approval in 2017. In the past few years, the focus has shifted to applying deuteration in novel drug discovery, and the FDA approved the pioneering de novo deuterated drug deucravacitinib in 2022. In this Review, we highlight key milestones in the field of deuteration in drug discovery and development, emphasizing recent and instructive medicinal chemistry programmes and discussing the opportunities and hurdles for drug developers, as well as the questions that remain to be addressed.

Development of a multigram synthesis of the bradykinin receptor 2 agonist FR-190997 and analogs thereof

Using Fujisawa's B2R agonist FR-190997, we recently demonstrated for the first time that agonism at the bradykinin receptor type 2 (B2R) produces substantial antiproliferative effects. FR-190997 elicited an EC₅₀ of 80 nM in the triple-negative breast cancer cell line MDA-MB-231, a much superior performance to that exhibited by most approved breast cancer drugs. Consequently, we initiated a program aiming primarily at synthesizing adequate quantities of FR-190997 to support further in vitro and in vivo studies toward its repurposing for various cancers and, in parallel, enable the generation of novel FR-190997 analogs for an SAR study. Prerequisite for this endeavor was to address the synthetic challenges associated with the FR-190997 scaffold, which the Fujisawa chemists had constructed in 20 steps, 13 of which required chromatographic purification. We succeeded in developing a 17-step synthesis amenable to late-stage diversification that eliminated all chromatography and enabled access to multigram quantities of FR-190997 and novel derivatives thereof, supporting further anticancer research based on B2R agonists.

Are noscapine and raloxifene ligands of the bradykinin B2 receptor? An assessment based on the human umbilical vein contractility assay

The centrally acting antitussive opiate derivative, noscapine, has been claimed to be a non-competitive bradykinin B₂ receptor antagonist. Raloxifene, a selective estrogen receptor modulator, was predicted to bind the bradykinin B₂ receptor and to exert a partial agonist activity. These intriguing claims suggest that new molecular scaffolds ("chemotypes") may be identified for small molecule ligands of kinin receptors and that some off-target effects of noscapine or raloxifene may be mediated by bradykinin B₂ receptors. An established contractile bioassay for ligands of the bradykinin B₂ receptor, the isolated human umbilical vein, was exploited to characterize the inhibitory effect of noscapine and raloxifene on the B₂ receptor-mediated contractile response to bradykinin. Observed effects were compared with those of the peptide antagonist icatibant, a potent, selective and competitive B₂ receptor antagonist. Our results indicate that neither noscapine (2.5 µM) nor raloxifene (20 µM) behave as B₂ receptor antagonists in concentrations that vastly exceeded an effective concentration of the control antagonist, icatibant; further, none of these drugs had direct contractile effects. It is suggested that the previously reported B₂ receptor inhibitory effect of noscapine, a putative sigma-receptor agonist, might result from an indirect physiological antagonism, while raloxifene did not appear to have any significant affinity for the B₂ receptors.

A comprehensive review on current understanding of bradykinin in COVID-19 and inflammatory diseases

Bradykinin, a member of the kallikrein–kinin system (KKS), is a potent, short-lived vasoactive peptide that acts as a vasodilator and an inflammatory mediator in a number of signaling mechanisms. Bradykinin induced signaling is mediated through kinin B1 (BDKRB1) and B2 (BDKRB2) transmembrane receptors coupled with different subunits of G proteins (G_αi/G_α0, G_αq and G_β1γ2). The bradykinin-mediated signaling mechanism activates excessive pro-inflammatory cytokines, including IL-6, IL-1β, IL-8 and IL-2. Upregulation of these cytokines has implications in a wide range of clinical conditions such as inflammation leading to fibrosis, cardiovascular diseases, and most recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In SARS-CoV-2 infection, bradykinin is found to be at raised levels and is reported to trigger a diverse array of symptoms. All of this brings bradykinin to the core point as a molecule of immense therapeutic value. Our understanding of its involvement in various pathways has expanded with time. Therefore, there is a need to look at the overall picture that emerges from the developments made by deciphering the bradykinin mediated signaling mechanisms involved in the pathological conditions. It will help devise strategies for developing better treatment modalities in the implicated diseases. This review summarizes the current state of knowledge on bradykinin mediated signaling in the diverse conditions described above, with a marked emphasis on the therapeutic potential of targeting the bradykinin receptor.