Development of [18F]AldoView as the First Highly Selective Aldosterone Synthase PET Tracer for Imaging of Primary Hyperaldosteronism

Emerging trends in small molecule inhibitors targeting aldosterone synthase: A new paradigm in cardiovascular disease treatment

Aldosterone synthase (CYP11B2) is the rate-limiting enzyme in aldosterone production. In recent years, CYP11B2 has become an appealing target for treating conditions associated with excess aldosterone, such as hypertension, heart failure, and cardiometabolic diseases. Several small-molecule inhibitors of CYP11B2 have demonstrated efficacy in both preclinical studies and clinical trials. Among them, the tetrahydroisoquinoline derivative Baxdrostat has entered clinical trial phases and demonstrated efficacy in treating patients with hypertension. However, the high homology (>93 %) between CYP11B2 and steroid-11β-hydroxylase (CYP11B1), which catalyzes cortisol production, implies that insufficient drug specificity can lead to severe side effects. Developing selective inhibitors for CYP11B2 remains a considerable challenge that requires ongoing attention. This review summarizes recent research progress on small-molecule inhibitors targeting CYP11B2, focusing on structure-activity relationships (SAR) and structural optimization. It discusses strategies for enhancing the specificity and inhibitory activity of inhibitors, while also exploring potential applications and future prospects for CYP11B2 inhibitors, providing a theoretical foundation for developing the new generation of CYP11B2-targeted medications.

Multifocal, Asymmetric Bilateral Primary Aldosteronism Cannot be Excluded by Strong Adrenal Vein Sampling Lateralization: An International Retrospective Cohort Study

BACKGROUND

Primary aldosteronism (PA) has been broadly dichotomized into unilateral and bilateral forms. Adrenal vein sampling (AVS) lateralization indices (LI) ≥2 to 4 are the standard-of-care to recommend unilateral adrenalectomy for presumed unilateral PA. We aimed to assess the rates and characteristics of residual PA after AVS-guided adrenalectomy.

METHODS

We conducted an international, retrospective, cohort study of patients with PA from 7 referral centers who underwent unilateral adrenalectomy based on LI≥4 on baseline and/or cosyntropin-stimulated AVS. Aldosterone synthase (CYP11B2) immunohistochemistry and next generation sequencing were performed on available formalin-fixed paraffin-embedded adrenal tissue.

RESULTS

The cohort included 283 patients who underwent AVS-guided adrenalectomy, followed for a median of 326 days postoperatively. Lack of PA cure was observed in 16% of consecutive patients, and in 22 patients with lateralized PA on both baseline and cosyntropin-stimulated AVS. Among patients with residual PA postoperatively, 73% had multiple CYP11B2 positive areas within the resected adrenal tissue (versus 23% in those cured), wherein CACNA1D mutations were most prevalent (63% versus 33% in those cured). In adjusted regression models, independent predictors of postoperative residual PA included Black versus White race (odds ratio, 5.10 [95% CI, 1.45-17.86]), AVS lateralization only at baseline (odds ratio, 8.93 [95% CI 3.00-26.32] versus both at baseline and after cosyntropin stimulation), and CT-AVS disagreement (odds ratio, 2.75 [95% CI, 1.20-6.31]).

CONCLUSIONS

Multifocal, asymmetrical bilateral PA is relatively common, and it cannot be excluded by robust AVS lateralization. Long-term postoperative monitoring should be routinely pursued, to identify residual PA and afford timely initiation of targeted medical therapy.

Room-Temperature CuI-Catalyzed N-Arylation of Cyclopropylamine

A general and efficient CuI/N-carbazolyl-1H-pyrrole-2-carbohydrazide catalyst system was developed for the N-arylation of cyclopropylamine using aryl bromides at room temperature. Herein, 5 mol % CuI and 5 mol % of the ligand were used to synthesize N-aryl cyclopropylamines in moderate to excellent yields. This protocol was scaled up to produce the desired product at gram levels and has been generalized for C-N coupling between aryl bromides and amines at room temperature.

Treating Primary Aldosteronism-Induced Hypertension: Novel Approaches and Future Outlooks

Primary aldosteronism (PA) is the most common cause of secondary hypertension and is associated with increased morbidity and mortality when compared with blood pressure-matched cases of primary hypertension. Current limitations in patient care stem from delayed recognition of the condition, limited access to key diagnostic procedures, and lack of a definitive therapy option for nonsurgical candidates. However, several recent advances have the potential to address these barriers to optimal care. From a diagnostic perspective, machine-learning algorithms have shown promise in the prediction of PA subtypes, while the development of noninvasive alternatives to adrenal vein sampling (including molecular positron emission tomography imaging) has made accurate localization of functioning adrenal nodules possible. In parallel, more selective approaches to targeting the causative aldosterone-producing adrenal adenoma/nodule (APA/APN) have emerged with the advent of partial adrenalectomy or precision ablation. Additionally, the development of novel pharmacological agents may help to mitigate off-target effects of aldosterone and improve clinical efficacy and outcomes. Here, we consider how each of these innovations might change our approach to the patient with PA, to allow more tailored investigation and treatment plans, with corresponding improvement in clinical outcomes and resource utilization, for this highly prevalent disorder.

Primary aldosteronism: molecular medicine meets public health

Primary aldosteronism is the most common single cause of hypertension and is potentially curable when only one adrenal gland is the culprit. The importance of primary aldosteronism to public health derives from its high prevalence but huge under-diagnosis (estimated to be <1% of all affected individuals), despite the consequences of poor blood pressure control by conventional therapy and enhanced cardiovascular risk. This state of affairs is attributable to the fact that the tools used for diagnosis or treatment are still those that originated in the 1970-1990s. Conversely, molecular discoveries have transformed our understanding of adrenal physiology and pathology. Many molecules and processes associated with constant adrenocortical renewal and interzonal metamorphosis also feature in aldosterone-producing adenomas and aldosterone-producing micronodules. The adrenal gland has one of the most significant rates of non-silent somatic mutations, with frequent selection of those driving autonomous aldosterone production, and distinct clinical presentations and outcomes for most genotypes. The disappearance of aldosterone synthesis and cells from most of the adult human zona glomerulosa is the likely driver of the mutational success that causes aldosterone-producing adenomas, but insights into the pathways that lead to constitutive aldosterone production and cell survival may open up opportunities for novel therapies.

Fluorinated aldosterone synthase (CYP11B2)-inhibitors for differential diagnosis between bilateral and unilateral conditions of primary aldosteronism

The enzyme aldosterone synthase (CYP11B2) is specifically expressed in aldosterone-producing tissue of the adrenal cortex and is overexpressed in aldosterone-producing adenomas (APA). It therefore represents an ideal target for molecular imaging, particularly for the differential diagnosis between bilateral hyperplasia and unilateral APA in primary aldosteronism. However, the presence of the cortisol-producing enzyme 11β-hydroxylase (CYP11B1) in the adrenal cortex remains very challenging owing to its high homology to CYP11B2. Within this study, we efficiently synthesized a variety of disubstituted fluorinated pyridines and pyrazines by Suzuki coupling reactions. These compounds were evaluated for their ability to inhibit CYP11B1 and CYP11B2 in transfected Y1 cells and in NCI-h295 cells. Several compounds were found to exhibit excellent affinity (IC50 < 10 nM) to CYP11B2 as well as strong selectivity (up to 125-fold) over CYP11B1. These findings support the further development of an analogous 18F-labelled PET tracer.

Advances in the molecular imaging of primary aldosteronism

Primary aldosteronism (PA) is the most common cause of secondary hypertension. It predisposes to adverse outcomes such as nephrotoxicity and cardiovascular damage, which are mediated by direct harm from hypertension to the target organs. Accurate subtype diagnosis and localization are crucial elements in choosing the type of treatment for PA in clinical practice since the dominant side of aldosterone secretion in PA affects subsequent treatment options. The gold standard for diagnosing PA subtypes, adrenal venous sampling (AVS), requires specialized expertise, the invasive nature of the procedure and high costs, all of which delay the effective treatment of PA. Nuclide molecular imaging is non-invasive and has wider applications in the diagnosis and treatment of PA. This review aims to provide a summary of the application of radionuclide imaging in the diagnosis, treatment management and prognostic assessment of PA.

Development of carbazole-based fluorescent probe for highly sensitive application in fluoride ion detection

Fluorine is a necessary element for human, which is closely related to life activities, such as metabolism of teeth and bone tissue. A small amount of fluoride ions can promote the strengthen of our body. However, a large amount of fluoride ions will damage the human immune system to produce organ diseases. Sensitive and rapid detection of fluoride ions has attracted great interests for researchers. In this work, a reactive fluorescent probe SCP for detection of fluoride ions with high quantum yield was designed and synthesized based on the carbazole ring. Subsequently, the photophysical properties of the probe SCP were carefully studied. At last, SCP performed 62.8% quantum yield in physiological condition, excellent ability of quantitative analysis, well selectivity, and distinguishing features for HepG2 cell imaging.

First-in-human evaluation of [18F]CETO: a novel tracer for adrenocortical tumours

PURPOSE

[11C]Metomidate positron emission tomography (PET) is currently used for staging of adrenocortical carcinoma and for lateralization in primary aldosteronism (PA). Due to the short half-life of carbon-11 and a high non-specific liver uptake of [11C]metomidate there is a need for improved adrenal imaging methods. In a previous pre-clinical study para-chloro-2-[18F]fluoroethyletomidate has been proven to be a specific adrenal tracer. The objective is to perform a first evaluation of para-chloro-2-[18F]fluoroethyletomidate positron emission computed tomography ([18F]CETO-PET/CT) in patients with adrenal tumours and healthy volunteers.

METHODS

Fifteen patients underwent [18F]CETO-PET/CT. Five healthy volunteers were recruited for test-retest analysis and three out of the five underwent additional [15O]water PET/CT to measure adrenal blood flow. Arterial blood sampling and tracer metabolite analysis was performed. The kinetics of [18F]CETO were assessed and simplified quantitative methods were validated by comparison to outcome measures of tracer kinetic analysis.

RESULTS

Uptake of [18F]CETO was low in the liver and high in adrenals. Initial metabolization was rapid, followed by a plateau. The kinetics of [18F]CETO in healthy adrenals and all adrenal pathologies, except for adrenocortical carcinoma, were best described by an irreversible single-tissue compartment model. Standardized uptake values (SUV) correlated well with the uptake rate constant K1. Both K1 and SUV were highly correlated to adrenal blood flow in healthy controls. Repeatability coefficients of K1, SUV65-70, and SUV120 were 25, 22, and 17%.

CONCLUSIONS

High adrenal uptake combined with a low unspecific liver uptake suggests that 18F]CETO is a suitable tracer for adrenal imaging. Adrenal SUV, based on a whole-body scan at 1 h p.i., correlated well with the net uptake rate Ki.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT05361083 Retrospectively registered 29 April 2022. at,  https://clinicaltrials.gov/ct2/show/NCT05361083.

Oxidation-Cyclisation of Biphenyl Thioethers to Dibenzothiophenium Salts for Ultrarapid 18F-Labelling of PET Tracers

¹⁸F-labelled radiotracers are in high demand and play an important role for diagnostic imaging with positron emission tomography (PET). Challenges associated with the synthesis of the labelling precursors and the incorporation of [¹⁸F]fluoride with practical activity yields at batch scale are the main limitations for the development of new ¹⁸F-PET tracers. Herein, we report a high-yielding and robust synthetic method to access naked dibenzothiophenium salt precursors of complex PET tracers and their labelling with [¹⁸F]fluoride. C-S cross-coupling of biphenyl-2-thioacetate with aryl halides followed by sequential oxidation-cyclisation of the corresponding thioethers gives dibenzothiophenium salts in good to excellent yields. Labelling of neutral and electron-deficient substrates with [¹⁸F]fluoride is ultrarapid and occurs under mild conditions (1 min at 90 °C) with high activity yields. The method enables facile synthesis of complex and sensitive radiotracers, as exemplified by radiofluorination of three clinically relevant PET tracers [¹⁸F]UCB-J, [¹⁸F]AldoView and [¹⁸F]FNDP, and can accelerate the development and clinical translation of new ¹⁸F-radiopharmaceuticals.

Impact of dedicated multidisciplinary service on patient selection and outcomes for surgical treatment of primary aldosteronism

BACKGROUND

Primary aldosteronism is the most common surgically curable cause of endocrine hypertension. Management of the unilateral subtype of primary aldosteronism with adrenalectomy requires multidisciplinary input. It is unclear if a dedicated endocrine hypertension service confers better outcomes compared to standard care offered by individual clinicians.

METHODS

In this retrospective study, patients from the Monash University Endocrine Surgery Database were divided into either the endocrine hypertension service group, where patients were managed by a dedicated multidisciplinary team, or the standard group, where patients were managed by individual clinicians. The comparisons included patient selection for surgery, perioperative blood pressure control, and surgical cure rate.

RESULTS

Despite similar perioperative blood pressure, patients in the endocrine hypertension service group (n = 41) were on fewer antihypertensive medications (1 vs 2, P = .011) compared to the standard group (n = 55). A larger proportion of patients in the endocrine hypertension service group had either bilateral adrenal nodules or no adrenal lesions on computed tomography (41% vs 18%, P = .013). Patients in the standard group had larger adrenal lesions on computed tomography (median 15 mm vs 10 mm, P = .032). Postoperatively, the biochemical cure rate was higher in the endocrine hypertension service group at 6 to 12 months (97% vs 76%, P = .021).

CONCLUSION

Patients managed by endocrine hypertension service were more likely to be diagnosed with surgically curable primary aldosteronism without a unilateral adrenal adenoma on imaging, required fewer medications for perioperative blood pressure control, and experienced superior postoperative outcomes. Referral to a dedicated endocrine hypertension service is recommended for patients with primary aldosteronism who wish to pursue a surgical cure.

Primary aldosteronism - a multidimensional syndrome

Primary aldosteronism is a common cause of hypertension and is a risk factor for cardiovascular and renal morbidity and mortality, via mechanisms mediated by both hypertension and direct insults to target organs. Despite its high prevalence and associated complications, primary aldosteronism remains largely under-recognized, with less than 2% of people in at-risk populations ever tested. Fundamental progress made over the past decade has transformed our understanding of the pathogenesis of primary aldosteronism and of its clinical phenotypes. The dichotomous paradigm of primary aldosteronism diagnosis and subtyping is being redefined into a multidimensional spectrum of disease, which spans subclinical stages to florid primary aldosteronism, and from single-focal or multifocal to diffuse aldosterone-producing areas, which can affect one or both adrenal glands. This Review discusses how redefining the primary aldosteronism syndrome as a multidimensional spectrum will affect the approach to the diagnosis and subtyping of primary aldosteronism.

Personalized Treatment of Patients With Primary Aldosteronism

Primary aldosteronism (PA) is a highly prevalent yet underdiagnosed secondary cause of hypertension. PA is associated with increased cardiovascular and renal morbidity compared with patients with primary hypertension. Thus, prompt identification and targeted therapy of PA are essential to reduce cardiovascular and renal morbidity and mortality in a large population with hypertension. Unilateral adrenalectomy is preferred for lateralized PA as the only potentially curative therapy. Surgery also mitigates the risk of cardiovascular and renal complications associated with PA. Targeted medical therapy, commonly including a mineralocorticoid receptor antagonist, is offered to patients with bilateral PA and those who are not surgical candidates. Novel therapies, including nonsteroidal mineralocorticoid receptor antagonists and aldosterone synthase inhibitors, are being developed as alternative options for PA treatment. In this review article, we discuss how to best individualize therapy for patients with PA.

Visible-light-catalyzed C-H arylation of (hetero)arenes via arylselenonium salts

A novel photo-induced C-H arylation of (hetero)arenes has been developed. Aryl selenonium salts as an aryl source led to the arylation of aromatic (hetero)cyclic compounds via C-Se bond activation under blue LED irradiation. The method simply utilizes the safe and clean energy source and yields a range of site-selective biphenyl or bi-heterocyclic products in medium to good yields. Furthermore, the borylation and Sonogashira coupling of aryl selenonium salts proceed in good yields as well. From the results, it is shown that selenonium salts are more reactive than sulfonium salts.

High Prevalence of Autonomous Aldosterone Production in Hypertension: How to Identify and Treat It

PURPOSE OF REVIEW

Primary aldosteronism (PA) affects millions of individuals worldwide. When unrecognized, PA leads to cardiovascular and renal complications via mechanisms independent from those mediated by hypertension. In this review, we emphasize the importance of PA screening in at-risk populations, and we provide options for customized PA therapy, with consideration for a variety of clinical care settings.

RECENT FINDINGS

Compelling evidence puts PA at the forefront of secondary hypertension etiologies. Cardiovascular and renal damage likely begins in early stages of renin-independent aldosterone excess. PA must be considered not only in patients with resistant hypertension or hypokalemia, but also when hypertension is associated with obstructive sleep apnea or atrial fibrillation, or in those with early-onset hypertension. Screening with plasma aldosterone and renin is widely accessible, and targeted PA therapy can successfully circumvent the excess cardiorenal risk relative to equivalent primary hypertension. Identifying and treating PA in early stages provide opportunities for personalized hypertension therapy in a large number of patients. Additionally, early targeted therapy of PA is essential for pivoting the care of such patients from reactive to preventive of cardiovascular and renal morbidity and mortality.

Adrenal Venous Sampling for Subtype Diagnosis of Primary Hyperaldosteronism

Adrenal venous sampling (AVS) is the key procedure for lateralization of primary hyperaldosteronism (PA) before surgery. Identification of the adrenal veins using computed tomography (CT) and intraoperative cortisol assay facilitates the success of catheterization. Although administration of adrenocorticotropic hormone (ACTH) has benefits such as improving the success rate, some unilateral cases could be falsely diagnosed as bilateral. Selectivity index of 5 with ACTH stimulation to assess the selectivity of catheterization and lateralization index (LI) >4 with ACTH stimulation for unilateral diagnosis is used in many centers. Co-secretion of cortisol from the tumor potentially affects the lateralization by the LI. Patients aged <35 years with hypokalemia, marked aldosterone excess, and unilateral adrenal nodule on CT have a higher probability of unilateral disease. Patients with normokalemia, mild aldosterone excess, and no adrenal tumor on CT have a higher probability of bilateral disease. Although no methods have 100% specificity for subtype diagnosis that would allow bypassing AVS, prediction of the subtype should be considered when recommending AVS to patients. Methodological standardization and strict indication improve diagnostic quality of AVS. Development of non-invasive imaging and biochemical markers will drive a paradigm shift in the clinical practice of PA.