Bradykinin B2 Receptor Antagonist Research Articles

Targeting CD13/aminopeptidase N as a novel therapeutic approach for scleroderma fibrosis.

Systemic sclerosis (SSc) is an autoimmune multisystem disease with poorly understood pathogenesis and ineffective treatment options. Soluble CD13 (sCD13), generated by cleavage of cell surface CD13 via matrix metalloproteinase 14 (MMP14), signals through the bradykinin receptor B1 (B1R) to elicit pro-inflammatory, pro-arthritic, and pro-angiogenic responses. In this study we explored the anti-fibrotic potential of targeting the sCD13-B1R axis in SSc. The expression of CD13, B1R and MMP14 was examined in SSc skin and explanted dermal fibroblasts. The efficacy of B1R antagonists in the inhibition on fibrosis was determined in vitro and in vivo. Expression of the genes for CD13, B1R and MMP14 was elevated in skin biopsies from patients with diffuse cutaneous (dc)SSc. Notably, single cell analysis of SSc skin biopsies revealed the highest BDKRB1 expression in COL8A1-positive myofibroblasts, a population exclusively seen in SSc. TGF-β induced the expression of BDKRB1 and production of sCD13 by dcSSc skin fibroblasts. Treatment of dcSSc fibroblasts with sCD13 promoted fibrotic gene expression, signaling, cell proliferation, migration, and gel contraction. The profibrotic sCD13 or TGFβ responses were prevented by a B1R antagonist. Mice lacking Cd13 or Bdkrb1 were resistant to bleomycin-induced skin fibrosis and inflammation. Pharmacological B1R inhibition had a comparable antifibrotic effect. These results are the first to demonstrate a key role for sCD13 in SSc skin fibrosis, and suggest that targeting the sCD13-B1R signaling axis is a promising novel therapeutic approach for SSc.

R-954, a bradykinin B1 receptor antagonist, as a potential therapy in a preclinical endometriosis model

Endometriosis is a gynecological condition characterized by the growth of endometrium-like tissues outside of the uterine cavity. Currently available drugs are efficacious in treating endometriosis-related pain, however it’s not a targeted treatment. The aim of this work is to evaluate the effects of R-954, a bradykinin B1 receptor antagonist, in a murine model of endometriosis. The model was induced in animals through autologous transplantation of part of the uterine horn. After 51 days, it was observed that implants developed into endometriotic lesions. The administration of R-954 or progesterone, for 15 consecutive days, prevented the progression of cyst development, reduced the size and weight of the cysts. Both treatments also reduced cellular infiltrate and production of inflammatory mediators (interleukin-1β, interleukin-6, tumor necrosis factor). However, only R-954 decreased angiogenic factors (VEGF and VEGF receptor). In addition, treatment with the antagonist did not interfere in the females’ estrous cycle, as well as prevented gestational losses (reduction in the number of intermediate resorptions in pregnant females with endometriosis). Data suggested that R-954 has anti-inflammatory and anti-angiogenic effects; does not influence the estrous cycle; and prevents the number of gestational losses suggesting it as a good candidate for endometriosis treatment.

Advent of oral medications for the treatment of hereditary angioedema.

Hereditary angioedema (HAE) is a rare genetic disorder characterized by unpredictable, debilitating episodes of submucosal and/or subcutaneous tissue swelling, which may be life-threatening depending on anatomic location. The two primary management strategies for HAE are ready access to effective on-demand treatment in all patients and the prevention of attacks (short-term prophylaxis [STP] and long-term prophylaxis [LTP]) in appropriate patients. All approved on-demand and most LTP medications require subcutaneous or intravenous administration. Injection-related challenges include trypanophobia (fear of needles), difficulty with self-administration, injection-site reactions (e.g., pain, erythema, bleeding, bruising), and anxiety-all contributing to poor compliance and administration delays. Oral HAE treatments may improve outcomes by reducing treatment barriers. To review oral therapies, approved or in development, for on-demand treatment and/or prevention of HAE attacks. To provide a comprehensive review, data was obtained from publicly available resources through a targeted PubMed literature review and supplemented by information provided on company websites (search cutoff of May 31, 2024). Berotralstat, an oral plasma kallikrein (PKa) inhibitor, is approved for LTP. Sebetralstat, another PKa inhibitor, is the investigational first oral on-demand HAE treatment to complete a phase 3 trial. Deucrictibant, an oral bradykinin B2 receptor antagonist, has completed phase 2 trials for on-demand therapy and LTP. Several other oral PKa inhibitors (ATN249, VE-4666, and VE-4062) are in early development for LTP. Substantial advances have been made in the development of oral treatments for HAE. These treatments have the potential to improve and optimize clinical outcomes, satisfaction, and quality of life among patients with HAE.

Assessment of Radiolabelled Derivatives of R954 for Detection of Bradykinin B1 Receptor in Cancer Cells: Studies on Glioblastoma Xenografts in Mice.

Bradykinin B1 receptor (B1R) has garnered attention as a cancer therapeutic and diagnostic target. Several reports on radiolabelled derivatives of B1R antagonists have shown favourable properties as imaging agents in cells highly expressing hB1R following transfection. In the present study, we assessed whether radiolabelled probes can detect B1R endogenously expressed in cancer cells. To this end, we evaluated 111In-labelled derivatives of a B1R antagonist ([111In]In-DOTA-Ahx-R954) using glioblastoma cell lines (U87MG and U251MG) with different B1R expression levels. Cellular uptake studies showed that the specific accumulation of [111In]In-DOTA-Ahx-R954 in U87MG was higher than that in U251MG, which correlated with B1R expression levels. Tissue distribution in U87MG-bearing mice revealed approximately 2-fold higher radioactivity in tumours than in the muscle in the contralateral leg. The specific accumulation of [111In]In-DOTA-Ahx-R954 in the tumour was demonstrated by the reduction in the tumour-to-plasma ratios in nonlabelled R954-treated mice. Moreover, ex vivo autoradiographic images revealed that the intratumoural distribution of [111In]In-DOTA-Ahx-R954 correlated with the localisation of B1R-expressing glioblastoma cells. In conclusion, we demonstrated that [111In]In-DOTA-Ahx-R954 radioactivity correlated with B1R expression in glioblastoma cells, indicating that radiolabelled derivatives of the B1R antagonist could serve as promising tools for elucidating the involvement of B1R in cancer.

Kinin B1 receptor and TLR4 interaction in inflammatory response.

We aimed to broaden our understanding of a potential interaction between B1R and TLR4, considering earlier studies suggesting that lipopolysaccharide (LPS) may trigger B1R stimulation. We assessed the impact of DBK and LPS on the membrane potential of thoracic aortas from C57BL/6, B1R, or TLR4 knockout mice. Additionally, we examined the staining patterns of these receptors in the thoracic aortas of C57BL/6 and in endothelial cells (HBMEC). DBK does not affect the resting membrane potential of aortic rings in C57BL/6 mice, but it hyperpolarizes preparations in B1KO and TLR4KO mice. The hyperpolarization mechanism in B1KO mice involves B2R, and the TLR4KO response is independent of cytoplasmic calcium influx but relies on potassium channels. Conversely, LPS hyperpolarizes thoracic aorta rings in both C57BL/6 and B1KO mice, with the response unaffected by a B1R antagonist. Interestingly, the absence of B1R alters the LPS response to potassium channels. These activities are independent of nitric oxide synthase (NOS). While exposure to DBK and LPS does not alter B1R and TLR4 mRNA expression, treatment with these agonists increases B1R staining in endothelial cells of thoracic aortic rings and modifies the staining pattern of B1R and TLR4 in endothelial cells. Proximity ligation assay suggests a interaction between the receptors. Our findings provide additional support for a putative connection between B1R and TLR4 signaling. Given the involvement of these receptors and their agonists in inflammation, it suggests that drugs and therapies targeting their effects could be promising therapeutic avenues worth exploring.

Bradykinin attenuates endothelial-mesenchymal transition following cardiac ischemia-reperfusion injury

AimsEndothelial-mesenchymal transition (EndMT) is a crucial pathological process contributing to cardiac fibrosis. Bradykinin has been found to protect the heart against fibrosis. Whether bradykinin regulates EndMT has not been determined. Materials and methodsRats were subjected to ligation of the left anterior descending coronary artery for 1 h and subsequent reperfusion to induce cardiac ischemia-reperfusion (IR) injury. Bradykinin (0.5 μg/h) was infused by an osmotic pump implanted subcutaneously at the onset of reperfusion. Fourteen days later, the functional, histological, and molecular analyses were performed to investigate the changes in cardiac fibrosis and EndMT. Human coronary artery endothelial cells were utilized to determine the molecular mechanisms in vitro. ResultsBradykinin treatment improved cardiac function and decreased fibrosis following cardiac IR injury, accompanied by ameliorated EndMT and increased nitric oxide (NO) production. In vitro experiments found that bradykinin mitigated transforming growth factor β1 (TGFβ1)-induced EndMT. Significantly, the bradykinin B2 receptor antagonist or endothelial nitric oxide synthase inhibitor abolished the effects of bradykinin on EndMT inhibition, indicating that the bradykinin B2 receptor and NO might mediate the effects of bradykinin on EndMT inhibition. ConclusionBradykinin plays an essential role in the process of cardiac fibrosis. Bradykinin preserves the cellular signature of endothelial cells, preventing them from EndMT following cardiac IR injury, possibly mediated by bradykinin B2 receptor activation and NO production.

Bradycardic effect of endothelial-specific bradykinin type-II receptors overexpression in mice: impact on blood pressure

Abstract Background/Introduction Polymorphisms of the gene encoding for the bradykinin type-II receptors (B2R) has been shown to decrease the expression of B2R and increased vascular resistance and blood pressure in humans. Purpose We aimed to study the role of endothelial B2R on systolic blood pressure (SBP) and heart rate (HR) using a novel mice model with endothelial-specific B2R overexpression (B2tg) as compared with transgene negative littermates (B2n) and on differential expression of proteins potentially relevant to vascular tension. Methods Human and murine B2R expression levels were quantified by rtPCR. Thoracic aortic tissues were used for vascular reactivity studies and proteomic analysis. SBP and HR were measured by the tail-cuff method at baseline, after administration of the COX inhibitor diclofenac (10 mg/kg/day), B2R antagonist icatibant (1 mg/kg) or NOS inhibitor L-NAME (100 mg/kg/day). Results In aortic tissues of B2tg human B2R were exclusively expressed (n=6, P=0.0005), while murine B2R expression levels remained unchanged. Similar results were found in skeletal muscle tissues used as an estimate for resistance vessels. Aortic ring studies revealed a concentration-dependent constriction to bradykinin in wild-type mice (maximal vasoconstriction 9.6±3.0%, n=5) whereas aortic rings of B2tg showed concentration-dependent relaxation (-27.4±4.1%, n=12). SBP was significantly lower in B2tg (125.0 ±1.6 mmHg) as compared to B2n (129.9±1.1 mmHg, n=9, P=0.03). Diclofenac treatment slightly but not significantly reduced SBP in B2n (to 125.5±2.4 mmHg, P=0.09) and in B2tg (to 119.8±2.8 mmHg, n=9, P=0.12), however the difference in SBP remained (P=0.03). In a pilot study, L-NAME administration did also not change the SBP difference between B2n and B2tg (9.9±10.3 mmHg, n=3-4). In contrast, icatibant administration abolished the difference between the groups (B2n 128.6±4.6 vs B2tg 128.3±2.0 mmHg, n=8, P=ns) suggesting the involvement of endothelial B2R in SBP reduction. Interestingly, in the same mice, HR was significantly lower in B2tg (571.4±20.8 bpm) as compared to B2n (626.7±13.7 bpm, P=0.02). While diclofenac didn’t affect HR, icatibant significantly increased HR to (630.8±21.8 bpm in B2tg and 685.5±16.4 bpm in B2n, n=8, P=0.01). Only in B2tg, there was a significant strong correlation between SBP and HR (r=0.76, P=0.016). Analysis of proteomic data revealed differential upregulation of proteins related to cell adhesion (CD44), extracellular matrix (hyaluronidase), and differential downregulation of proteins related to oxidative stress (superoxide dismutase) in B2tg. Conclusion Endothelial B2R overexpression reduces SBP and HR. SBP reduction is not dependent on two major vascular pathways stimulated by products of NOS and COX but appears to be related to endothelial B2R-dependent HR reduction. Hence, agonism at B2R could be a valuable target for development of new cardiovascular drugs.

Genetic Ablation and Pharmacological Blockade of Bradykinin B1 Receptor Unveiled a Detrimental Role for the Kinin System in Chagas Disease Cardiomyopathy.

Chagas disease, the parasitic infection caused by Trypanosoma cruzi, afflicts about 6 million people in Latin America. Here, we investigated the hypothesis that T. cruzi may fuel heart parasitism by activating B1R, a G protein-coupled (brady) kinin receptor whose expression is upregulated in inflamed tissues. Studies in WT and B1R-/- mice showed that T. cruzi DNA levels (15 days post infection-dpi) were sharply reduced in the transgenic heart. FACS analysis revealed that frequencies of proinflammatory neutrophils and monocytes were diminished in B1R-/- hearts whereas CK-MB activity (60 dpi) was exclusively detected in B1R+/+ sera. Since chronic myocarditis and heart fibrosis (90 dpi) were markedly attenuated in the transgenic mice, we sought to determine whether a pharmacological blockade of the des-Arg9-bradykinin (DABK)/B1R pathway might alleviate chagasic cardiomyopathy. Using C57BL/6 mice acutely infected by a myotropic T. cruzi strain (Colombian), we found that daily treatment (15-60 dpi) with R-954 (B1R antagonist) reduced heart parasitism and blunted cardiac injury. Extending R-954 treatment to the chronic phase (120-160 dpi), we verified that B1R targeting (i) decreased mortality indexes, (ii) mitigated chronic myocarditis, and (iii) ameliorated heart conduction disturbances. Collectively, our study suggests that a pharmacological blockade of the proinflammatory KKS/DABK/B1R pathway is cardioprotective in acute and chronic Chagas disease.

Kinin B2 and B1 Receptors Activation Sensitize the TRPA1 Channel Contributing to Anastrozole-Induced Pain Symptoms.

Aromatase inhibitors (AIs) cause symptoms of musculoskeletal pain, and some mechanisms have been proposed to explain them. However, signaling pathways downstream from kinin B2 (B2R) and B1 (B1R) receptor activation and their possible sensitizing of the Transient Receptor Potential Ankyrin 1 (TRPA1) remain unknown. The interaction between the kinin receptor and the TRPA1 channel in male C57BL/6 mice treated with anastrozole (an AI) was evaluated. PLC/PKC and PKA inhibitors were used to evaluate the signaling pathways downstream from B2R and B1R activation and their effect on TRPA1 sensitization. Anastrozole caused mechanical allodynia and muscle strength loss in mice. B2R (Bradykinin), B1R (DABk), or TRPA1 (AITC) agonists induced overt nociceptive behavior and enhanced and prolonged the painful parameters in anastrozole-treated mice. All painful symptoms were reduced by B2R (Icatibant), B1R (DALBk), or TRPA1 (A967079) antagonists. We observed the interaction between B2R, B1R, and the TRPA1 channel in anastrozole-induced musculoskeletal pain, which was dependent on the activation of the PLC/PKC and PKA signaling pathways. TRPA1 seems to be sensitized by mechanisms dependent on the activation of PLC/PKC, and PKA due to kinin receptors stimulation in anastrozole-treated animals. Thus, regulating this signaling pathway could contribute to alleviating AIs-related pain symptoms, patients' adherence to therapy, and disease control.

An Update of Carbazole Treatment Strategies for COVID-19 Infection

The Coronavirus disease 2019 (COVID-19) outbreak was declared by the World Health Organization (WHO) in March 2020 to be a pandemic and many drugs used at the beginning proved useless in fighting the infection. Lately, there has been approval of some new generation drugs for the clinical treatment of severe or critical COVID-19 infections. Nevertheless, more drugs are required to reduce the pandemic’s impact. Several treatment approaches for COVID-19 were employed since the beginning of the pandemic, such as immunomodulatory, antiviral, anti-inflammatory, antimicrobial agents, and again corticosteroids, angiotensin II receptor blockers, and bradykinin B2 receptor antagonists, but many of them were proven ineffective in targeting the virus. So, the identification of drugs to be used effectively for treatment of COVID-19 is strongly needed. It is aimed in this review to collect the information so far known about the COVID-19 studies and treatments. Moreover, the observations reported in this review about carbazoles as a treatment can signify a potentially useful clinical application; various drugs that can be introduced into the therapeutic equipment to fight COVID-19 or their molecules can be used as the basis for designing new antivirals.

Bradykinin B1 receptor antagonist protects against cold stress-induced erectile dysfunction in rats.

Erectile dysfunction (ED) demonstrates seasonal variation with higher rates in winter, and we hypothesize that endothelial damage in erectile tissue caused by bradykinin receptor B1 (B1R) might be detrimental to this change. To find out direct correlations between cold stress and ED, through which to further investigate the functional roles of B1R in erectile tissue and to elucidate the therapeutic roles of the B1R antagonist in a cold stress-induced ED rat model. Cold stress rat models are established through long-term intermittent exposure to low temperature. After their erectile function was assessed, ED rats were treated with the B1R antagonist through intraperitoneal injection. Penile tissues were obtained at the end of the experiment after measurement of intracavernosal pressure/mean arterial pressure (ICP/MAP); the location and distribution of cytokine expression were determined by immunohistochemistry; cytokine levels and NOS and CD31 expression were detected by Western blotting; and collagen fibers and smooth muscles were observed through Masson staining. Cold stress impairs erectile function, and the B1R antagonist protects against it. We observed decreased erection frequency, prolonged erection latency time, decreased ICP/MAP, overexpression of B1R, increased expression of cytokines on cavernous sinus endothelium, and increased levels of collagen fibers/smooth muscles on erectile tissue in response to cold stress. Also, NOS and CD31 expression was downregulated. B1R antagonist treatment shows enhanced erectile function through increased erection frequency, shortened erection latency time, and increased ICP/MAP. Also, it reduces collagen fibers/smooth muscles, TNF-α, TGF-β1, and IL-6 and upregulates the expression of nNOS and CD31. Our findings cast new light on the correlations between cold stress and erectile function and potential new applications of existing B1R antagonist drugs in the field of ED. Our data support that cold stress impairs erectile function. B1R-mediated, cytokine-induced corpus cavernosum fibrosis and endothelial damage might be the main reason behind it, and B1R inhibition protects against fibrosis and endothelial damage. Other ways of B1R antagonist blocking methods in different types of ED still need to be investigated. Long-term intermittent cold stress impairs erectile function, and B1R-mediated, cytokine-induced corpus cavernosum fibrosis and endothelial damage might be the main reason behind it. B1R inhibition also protects against fibrosis and endothelial damage. Our data support the hypothesis that cold stress impairs erectile function and that B1R blockade ameliorates the symptoms of ED, possibly by reversing fibrosis and endothelial damage in erectile tissue.

Inhibition of angiotensin converting enzyme increases PKCβI isoform expression via activation of substance P and bradykinin receptors in cultured astrocytes of mice.

Angiotensin-converting enzyme inhibitor (ACEi) inhibits the catalysis of angiotensin I to angiotensin II and the degradation of substance P (SP) and bradykinin (BK). While the possible relationship between ACEi and SP in nociceptive mice was recently suggested, the effect of ACEi on signal transduction in astrocytes remains unclear. This study examined whether ACE inhibition with captopril or enalapril modulates the levels of SP and BK in primary cultured astrocytes and whether this change modulates PKC isoforms (PKCα, PKCβI, and PKCε) expression in cultured astrocytes. Immunocytochemistry and Western blot analysis were performed to examine the changes in the levels of SP and BK and the expression of the PKC isoforms in primary cultured astrocytes, respectively. The treatment of captopril or enalapril increased the immunoreactivity of SP and BK significantly in glial fibrillary acidic protein-positive cultured astrocytes. These increases were suppressed by a pretreatment with an angiotensin-converting enzyme. In addition, treatment with captopril increased the expression of the PKCβI isoform in cultured astrocytes, while there were no changes in the expression of the PKCα and PKCε isoforms after the captopril treatment. The captopril-induced increased expression of the PKCβI isoform was inhibited by a pretreatment with the neurokinin-1 receptor antagonist, L-733,060, the BK B1 receptor antagonist, R 715, or the BK B2 receptor antagonist, HOE 140. These results suggest that ACE inhibition with captopril or enalapril increases the levels of SP and BK in cultured astrocytes and that the activation of SP and BK receptors mediates the captopril-induced increase in the expression of the PKCβI isoform.

Therapeutic Polypeptides and Peptidomimetics: Powerful Tools for COVID-19 Treatment.

The coronavirus disease 2019 (COVID-19) pandemic has swept the whole world and brought about a public health crisis of unprecedented proportions. To combat the rapid transmission and possible deaths due to the disease, researchers and companies around the world are developing all possible strategies. Due to the advantages of safety, specificity, and fewer adverse effects, polypeptide and peptidomimetic drugs are considered promising strategies. This review comprehensively summarizes and discusses the progress in development of peptide drugs for use in the treatment of COVID-19. Based on the latest results in this field, we divided them into clinically approved drugs, clinical trial drugs, and clinically ineffective drugs, and outlined the molecular targets and mechanisms of action one by one to reveal their feasibility as promising therapeutic agents for COVID-19. Notably, monoclonal antibodies have shown beneficial effects in the early stages of infection, while Paxlovid can significantly reduce hospitalization and mortality among non-vaccinated patients. Among clinical experimental drugs, both the interleukin-1 receptor antagonist anakinra and the bradykinin B2 receptor antagonist icatibant are well tolerated and effective in patients with COVID-19, but long-term trials are needed to confirm the durability of efficacy.

Spectroscopic characterization and in vitro studies of biological activity of bradykinin derivatives

Eleven multiple analogs of bradykinin—a peptide that is a natural ligand of B1 and B2 receptors but does not bind or activate the B1 receptor unless Arg9 is removed from the sequence by the action of carboxypeptidase N—were synthesized. Their biological activity was examined on T-REx cell lines expressing B1 or B2 receptors using the intracellular IP1 assay. The mRNA expression of B1R and B2R in the lysate of tumor cell lines, e.g., U87-MG (human astrocytoma), SHP-77 (human small cell lung cancer), and H4 (human brain glioma), was determined. For five B1R antagonists, adsorption at the liquid/solid interface (Au nanoparticles (AuNPs) served as the solid surface) was discussed in terms of the vibrations of molecular fragments (structural factors) responsible for the biological properties of these analogs.

DEVELOPMENT OF PHVS719: AN ORAL EXTENDED-RELEASE BRADYKININ B2 RECEPTOR ANTAGONIST TO PREVENT HEREDITARY ANGIOEDEMA ATTACKS

<h3>Introduction</h3> Hereditary angioedema (HAE) is managed by either of two treatment paradigms: on demand or prophylaxis. PHA121, an orally active bradykinin B2 receptor antagonist, is being developed as two drug products to optimize patient choice. PHVS416, the softgel capsule providing quick absorption for fast onset of symptom relief, is currently in clinical trials for treatment of acute attacks; PHVS719, an extended-release tablet, is being developed for use in prophylaxis. <h3>Methods</h3> To develop a daily oral pill for the prevention of attacks, we developed a PHA121 formulation (PHVS719) providing 24 h plasma exposure. Our strategy relied upon a combination of an optimally designed extended-release formulation and the ability of PHA121 to be absorbed throughout the full gastrointestinal tract. <h3>Results</h3> PHA121 is absorbed following intracolonic administration in rats. A human mass balance study showed only 3% PHA121 excreted in feces and oral bioavailability of 57%. An in vitro dissolution experiment conducted with PHVS719 in conditions mimicking fasted and fed gastrointestinal environments showed a linear dissolution of PHA121 over time. Using PHVS719, a PK study in healthy volunteers demonstrated that a single 40 mg dose provides 24 h plasma exposure above the anticipated therapeutic level. Together these data provide evidence that PHVS719 is optimally suited to serve as a once-daily oral pill. <h3>Conclusion</h3> The active ingredient PHA121 is under clinical investigation in the form of two therapeutic treatment modalities: PHVS416 softgel capsule providing quick absorption for fast symptom relief and PHVS719 once-daily extended-release tablet providing 24 hours coverage to prevent attacks from occurring.

Treatment of hereditary angioedema-single or multiple pathways to the rescue.

Hereditary angioedema (HAE) is a rare disease caused by mutations in the SERPING1 gene. This results in deficient or dysfunctional C1 esterase inhibitor (C1-INH) and affects multiple proteases involved in the complement, contact-system, coagulation, and fibrinolytic pathways. Current options for the treatment and prevention of HAE attacks include treating all affected pathways via direct C1-INH replacement therapy; or specifically targeting components of the contact activation system, in particular by blocking the bradykinin B2 receptor (B2R) or inhibiting plasma kallikrein, to prevent bradykinin generation. Intravenously administered plasma-derived C1-INH (pdC1-INH) and recombinant human C1-INH have demonstrated efficacy and safety for treatment of HAE attacks, although time to onset of symptom relief varied among trials, specific agents, and dosing regimens. Data from retrospective and observational analyses support that short-term prophylaxis with intravenous C1-INH products can help prevent HAE attacks in patients undergoing medical or dental procedures. Long-term prophylaxis with intravenous or subcutaneous pdC1-INH significantly decreased the HAE attack rate vs. placebo, although breakthrough attacks were observed. Pathway-specific therapies for the management of HAE include the B2R antagonist icatibant and plasma kallikrein inhibitors ecallantide, lanadelumab, and berotralstat. Icatibant, administered for treatment of angioedema attacks, reduced B2R-mediated vascular permeability and, compared with placebo, reduced the time to initial symptom improvement. Plasma kallikrein inhibitors, such as ecallantide, block the binding site of kallikrein to prevent cleavage of high molecular weight kininogen and subsequent bradykinin generation. Ecallantide was shown to be efficacious for HAE attacks and is licensed for this indication in the United States, but the labeling recommends that only health care providers administer treatment because of the risk of anaphylaxis. In addition to C1-INH replacement therapy, the plasma kallikrein inhibitors lanadelumab and berotralstat are recommended as first-line options for long-term prophylaxis and have demonstrated marked reductions in HAE attack rates. Investigational therapies, including the activated factor XII inhibitor garadacimab and an antisense oligonucleotide targeting plasma prekallikrein messenger RNA (donidalorsen), have shown promise as long-term prophylaxis. Given the requirement of lifelong management for HAE, further research is needed to determine how best to individualize optimal treatments for each patient.

Function and structure of bradykinin receptor 2 for drug discovery.

Type 2 bradykinin receptor (B2R) is an essential G protein-coupled receptor (GPCR) that regulates the cardiovascular system as a vasodepressor. Dysfunction of B2R is also closely related to cancers and hereditary angioedema (HAE). Although several B2R agonists and antagonists have been developed, icatibant is the only B2R antagonist clinically used for treating HAE. The recently determined structures of B2R have provided molecular insights into the functions and regulation of B2R, which shed light on structure-based drug design for the treatment of B2R-related diseases. In this review, we summarize the structure and function of B2R in relation to drug discovery and discuss future research directions to elucidate the remaining unknown functions of B2R dimerization.

Large Predominance of Off-Label Prescriptions of C1-Inhibitor Concentrates and Icatibant in a Real-Life Setting: A Retrospective Clinical Study.

C1-inhibitor (C1INH) concentrates and the selective bradykinin B2 receptor antagonist icatibant are approved only for treating hereditary angioedema with C1INH deficiency. Yet, they are regularly prescribed off label in other types of bradykinin-mediated angioedema including angiotensin-converting enzyme inhibitor (ACEi)-related and undetermined angioedema. We conducted a retrospective chart review of inpatient prescriptions of C1INH concentrates and icatibant between 2016 and 2020 in the University Hospital of Angers. The first outcome was the proportion of prescriptions with explicit indication. Then, we determined the compliance of prescriptions with European Medicines Agency approvals and the French bradykinin-mediated angioedema reference center guidelines. Finally, we estimated the economic impact of inappropriate prescribing. The therapeutic indication was explicit in 90.4% of prescriptions (n=66/73). Only 17.8% of prescriptions were for hereditary angioedema with C1INH deficiency, while 31.5% were for ACEi-related and 28.7% for undetermined angioedema. However, most off-label prescriptions were consistent with the French bradykinin-mediated angioedema reference center guidelines (73.3%). We estimated that 13% of drug expenditures were potentially excessive. The predominance of off-label prescriptions may be explained by the infrequency of hereditary angioedema and the absence of approved alternatives in other types of bradykinin-mediated angioedema. Most attacks were related to ACEis. Epinephrine was rarely prescribed as first-line therapy in attacks of unknown origin. Given the high prices of these drugs, we advocate the development of a readily available management algorithm of angioedema to reduce inappropriate prescriptions in our center. In addition, we think that the drug prescription circuit should be redesigned to ensure the traceability of prescribed vials in the dispensing areas.

The Icatibant Outcome Survey: 10 years of experience with icatibant for patients with hereditary angioedema.

In patients with hereditary angioedema (HAE), bradykinin causes swelling episodes by activating bradykinin B2 receptors. Icatibant, a selective bradykinin B2 receptor antagonist, is approved for on-demand treatment of HAE attacks. The Icatibant Outcome Survey (IOS; NCT01034969) is an ongoing observational registry initiated in 2009 to monitor the effectiveness/safety of icatibant in routine clinical practice. As of March 2019, 549 patients with HAE type 1 or 2 from the IOS registry had been treated of 5995 total attacks. This article reviews data published from IOS over time which have demonstrated that the effectiveness of icatibant in a real-world setting is comparable to efficacy in clinical trials; one dose is effective for the majority of attacks; early treatment (facilitated by self-administration) leads to faster resolution and shorter attack duration; effectiveness/safety of icatibant has been shown across a broad range of patient subgroups, including children/adolescents and patients with HAE with normal C1 inhibitor levels; and tolerability has been demonstrated in patients aged ≥65 years. Additionally, this review highlights how IOS data have provided valuable insights into patients' diagnostic journeys and treatment behaviours across individual countries. Such findings have helped to inform clinical strategies and guidelines to optimise HAE management and limit disease burden. This research was sponsored by Takeda Development Center Americas, Inc. Takeda Development Center Americas, Inc., provided funding to Excel Medical Affairs for support in writing and editing this manuscript.

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.