Integrin-αvß6 targeted peptide-toxin therapy in a novel αvß6-expressing immunocompetent model of pancreatic cancer.

Previously we reported that a novel αvß6-specific peptide-drug conjugate (SG3299) could eliminate established human pancreatic ductal adenocarcinoma (PDAC) xenografts. However the development of effective therapies for PDAC, which is an essential need, must show efficacy in relevant immunocompetent animals. Previously we reported that the KPC mouse transgenic PDAC model that closely recapitulates most stages of development of human PDAC, unlike in humans, failed to express αvß6 on their tumours or metastases. In this study we have taken the KPC-derived PDAC line TB32043 and engineered a variant line (TB32043mb6S2) that expresses mouse integrin αvß6. We report that orthotopic implantation of the αvß6 over-expressing TB32043mb6S2 cells promotes shorter overall survival and increase in metastases. Moreover, systemic treatment of mice with established TB32043mb6S2 tumours in the pancreas with SG2399 lived significantly longer (p < 0.001; mean OS 48d) compared with PBS or control SG3511 (mean OS 25.5d and 26d, respectively). Thus SG3299 is confirmed as a promising candidate therapeutic for the therapy of PDAC.

Therapeutic Targeting of Glioblastoma and the Interactions with Its Microenvironment.

Glioblastoma (GBM) is the most common primary malignant brain tumour, and it confers a dismal prognosis despite intensive multimodal treatments. Whilst historically, research has focussed on the evolution of GBM tumour cells themselves, there is growing recognition of the importance of studying the tumour microenvironment (TME). Improved characterisation of the interaction between GBM cells and the TME has led to a better understanding of therapeutic resistance and the identification of potential targets to block these escape mechanisms. This review describes the network of cells within the TME and proposes treatment strategies for simultaneously targeting GBM cells, the surrounding immune cells, and the crosstalk between them.

Discovery of a Novel Potent and Selective HSD17B13 Inhibitor, BI-3231, a Well-Characterized Chemical Probe Available for Open Science.

Genome-wide association studies in patients revealed HSD17B13 as a potential new target for the treatment of nonalcoholic steatohepatitis (NASH) and other liver diseases. However, the physiological function and the disease-relevant substrate of HSD17B13 remain unknown. In addition, no suitable chemical probe for HSD17B13 has been published yet. Herein, we report the identification of the novel potent and selective HSD17B13 inhibitor BI-3231. Through high-throughput screening (HTS), using estradiol as substrate, compound 1 was identified and selected for subsequent optimization resulting in compound 45 (BI-3231). In addition to the characterization of compound 45 for its functional, physicochemical, and drug metabolism and pharmacokinetic (DMPK) properties, NAD+ dependency was investigated. To support Open Science, the chemical HSD17B13 probe BI-3231 will be available to the scientific community for free via the opnMe platform, and thus can help to elucidate the pharmacology of HSD17B13.

Survival Outcomes and Prognostic Factors in Glioblastoma.

Background: IDH-wildtype glioblastoma is the most common malignant primary brain tumour in adults. As there is limited information on prognostic factors outside of clinical trials; thus, we conducted a retrospective study to characterise the glioblastoma population at our centre. Methods: Demographic, tumour molecular profiles, treatment, and survival data were collated for patients diagnosed with glioblastoma at our centre between July 2011 and December 2015. We used multivariate proportional hazard model associations with survival. Results: 490 patients were included; 60% had debulking surgery and 40% biopsy only. Subsequently, 56% had standard chemoradiotherapy, 25% had non-standard chemo/radio-therapy, and 19% had no further treatment. Overall survival was 9.2 months. In the multivariate analysis, longer survival was associated with debulking surgery vs. biopsy alone (14.9 vs. 8 months) (HR 0.54 [95% CI 0.41−0.70]), subsequent treatment after diagnosis (HR 0.12 [0.08−0.16]) (standard chemoradiotherapy [16.9 months] vs. non-standard regimens [9.2 months] vs. none [2.0 months]), tumour MGMT promotor methylation (HR 0.71 [0.58−0.87]), and younger age (hazard ratio vs. age < 50: 1.70 [1.26−2.30] for ages 50−59; 3.53 [2.65−4.70] for ages 60−69; 4.82 [3.54−6.56] for ages 70+). Conclusions: The median survival for patients with glioblastoma is less than a year. Younger age, debulking surgery, treatment with chemoradiotherapy, and MGMT promotor methylation are independently associated with longer survival.

Impact of Dietary Sodium Reduction on the Development of Obesity and Type 2 Diabetes in db/db Mice.

The impact of dietary sodium reduction on mouse models of type 2 diabetes is not well understood. Therefore, we analyzed the effect of a low-salt diet on obesity and parameters of type 2 diabetes in db/db mice. Five-week-old male db/db and lean db/m mice were fed a normal salt (0.19% Na+, NS) or a low-salt diet (<0.03% Na+, LS) for 5 weeks. Body and organ weight and parameters of glucose and insulin tolerance were analyzed. Plasma levels of steroids were determined by liquid chromatography tandem mass spectrometry. Body weight, glucose, and insulin tolerance were not affected by LS. The amount of gonadal adipose tissue showed a trend to be increased by LS whereas liver, pancreas, kidney, heart, and adrenal weight remained unaffected. LS reduced urinary sodium-to-creatinine ratio but did not affect plasma Na+ levels in both genotypes. Plasma and urinary potassium-to-creatinine ratio did not differ in all groups of mice. Aldosterone as a major determinant of changes in dietary sodium remained unaffected by LS in db/db mice as well as further investigated steroid hormones. The present study showed reduced sodium-to-creatinine ratio, but no additional effects of dietary sodium reduction on major metabolic parameters and steroid levels in obese and hyper-glycemic db/db mice.

CEACAM7 Is an Effective Target for CAR T-cell Therapy of Pancreatic Ductal Adenocarcinoma.

PURPOSE: To investigate whether CEACAM7 represents a novel therapeutic target for treating pancreatic ductal adenocarcinoma (PDAC) and to generate CEACAM7-targeting CAR T cells to test this hypothesis. EXPERIMENTAL DESIGN: We identified CEACAM7 (CGM2), a member of the CEA family of proteins with expression restricted to the colon and pancreas, as a potential CAR T-cell target for PDAC. We probed a panel of PDAC tumor sections as well as patient-derived PDAC cell cultures for CEACAM7 expression. We generated CAR-targeting CEACAM7, and assessed antitumor efficacy of CEACAM7 CAR T cells using in vitro and in vivo models. RESULTS: We show here that CEACAM7 is expressed in a large subset of PDAC tumors, with low to undetectable expression in all normal tissues tested. CEACAM7 is also expressed in primary PDAC cultures isolated from patient-derived tumors, with high expression within the cancer stem cell-enriched subset. CAR T cells targeting CEACAM7 are capable of targeting antigen-expressing tumor cells, and mediate remission in patient-derived xenograft tumors. CONCLUSIONS: We identify CEACAM7 as a potential therapeutic target in PDAC and describe the development of CEACAM7-targeted CAR T cells with efficacy against PDAC.

Phase 1/2a trial of intravenous BAL101553, a novel controller of the spindle assembly checkpoint, in advanced solid tumours.

BACKGROUND: BAL101553 (lisavanbulin), the lysine prodrug of BAL27862 (avanbulin), exhibits broad anti-proliferative activity in human cancer models refractory to clinically relevant microtubule-targeting agents. METHODS: This two-part, open-label, phase 1/2a study aimed to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of 2-h infusion of BAL101553 in adults with advanced or recurrent solid tumours. The MTD was determined using a modified accelerated titration design in phase I. Patients received BAL101553 at the MTD and at lower doses in the phase 2a expansion to characterise safety and efficacy and to determine the recommended phase 2 dose (RP2D). RESULTS: Seventy-three patients received BAL101553 at doses of 15-80 mg/m2 (phase 1, n = 24; phase 2a, n = 49). The MTD was 60 mg/m2; DLTs observed at doses ≥60 mg/m2 were reversible Grade 2-3 gait disturbance with Grade 2 peripheral sensory neuropathy. In phase 2a, asymptomatic myocardial injury was observed at doses ≥45 mg/m2. The RP2D for 2-h intravenous infusion was 30 mg/m2. The overall disease control rate was 26.3% in the efficacy population. CONCLUSIONS: The RP2D for 2-h infusion of BAL101553 was well tolerated. Dose-limiting neurological and myocardial side effects were consistent with the agent's vascular-disrupting properties. CLINICAL TRIAL REGISTRATION: EudraCT: 2010-024237-23.

Integrin αvß6-specific therapy for pancreatic cancer developed from foot-and-mouth-disease virus.

Goals of investigation: The 5-year survival rate for pancreatic ductal adenocarcinoma (PDAC) has remained at <5% for decades because no effective therapies have been identified. Integrin αvß6 is overexpressed in most PDAC and represents a promising therapeutic target. Thus, we attempted to develop an αvß6-specific peptide-drug conjugate (PDC) for therapy of PDAC. Methodology: We conjugated the DNA-binding pyrrolobenzodiazepine (PBD)-based payload SG3249 (tesirine) to an αvß6-specific 20mer peptide from the VP1 coat protein of foot-and-mouth-disease virus (FMDV) (forming conjugate SG3299) or to a non-targeting peptide (forming conjugate SG3511). PDCs were tested for specificity and toxicity on αvß6-negative versus-positive PDAC cells, patient-derived cell lines from tumor xenografts, and on two different in vivo models of PDAC. Immunohistochemical analyses were performed to establish therapeutic mechanism. Results: The αvß6-targeted PDC SG3299 was significantly more toxic (up to 78-fold) for αvß6-expressing versus αvß6-negative PDAC cell lines in vitro, and achieved significantly higher toxicity at equal dose than the non-targeted PDC SG3511 (up to 15-fold better). Moreover, SG3299 eliminated established (100mm3) Capan-1 PDAC human xenografts, extending the lifespan of mice significantly (P=0.005). Immunohistochemistry revealed SG3299 induced DNA damage and apoptosis (increased γH2AX and cleaved caspase 3, respectively) associated with significant reductions in proliferation (Ki67), ß6 expression and PDAC tumour growth. Conclusions: The FMDV-peptide drug conjugate SG3299 showed αvß6-selectivity in vitro and in vivo and can specifically eliminate αvß6-positive cancers, providing a promising new molecular- specific therapy for pancreatic cancer.

A phase II open label, randomised study of ipilimumab with temozolomide versus temozolomide alone after surgery and chemoradiotherapy in patients with recently diagnosed glioblastoma: the Ipi-Glio trial protocol.

BACKGROUND: Median survival for patients with glioblastoma is less than a year. Standard treatment consists of surgical debulking if feasible followed by temozolomide chemo-radiotherapy. The immune checkpoint inhibitor ipilimumab targets cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and has shown clinical efficacy in preclinical models of glioblastoma. The aim of this study is to explore the addition of ipilimumab to standard therapy in patients with glioblastoma. METHODS/DESIGN: Ipi-Glio is a phase II, open label, randomised study of ipilimumab with temozolomide (Arm A) versus temozolomide alone (Arm B) after surgery and chemoradiotherapy in patients with recently diagnosed glioblastoma. Planned accrual is 120 patients (Arm A: 80, Arm B: 40). Endpoints include overall survival, 18-month survival, 5-year survival, and adverse events. The trial is currently recruiting in seven centres in the United Kingdom. TRIAL REGISTRATION: ISRCTN84434175. Registered 12 November 2018.

Integrin-Mediated TGFß Activation Modulates the Tumour Microenvironment.

TGFß (transforming growth factor-beta) is a pleotropic cytokine with contrasting effects in cancer. In normal tissue and early tumours, TGFß acts as a tumour suppressor, limiting proliferation and inducing apoptosis. However, these effects are eventually abrogated by the loss or inactivation of downstream signalling within the TGFß pathway, and in established tumours, TGFß then acts as a tumour promotor through multiple mechanisms including inducing epithelial-to-mesenchymal transition (EMT), promoting formation of cancer-associated fibroblasts (CAFs) and increasing angiogenesis. TGFß is secrereted as a large latent complex and is embedded in the extracellular matrix or held on the surface of cells and must be activated before mediating its multiple functions. Thus, whilst TGFß is abundant in the tumour microenvironment (TME), its functionality is regulated by local activation. The αv-integrins are major activators of latent-TGFß. The potential benefits of manipulating the immune TME have been highlighted by the clinical success of immune-checkpoint inhibitors in a number of solid tumour types. TGFß is a potent suppressor of T-cell-mediated immune surveillance and a key cause of resistance to checkpoint inhibitors. Therefore, as certain integrins locally activate TGFß, they are likely to have a role in the immunosuppressive TME, although this remains to be confirmed. In this review, we discussed the role of TGFß in cancer, the role of integrins in activating TGFß in the TME, and the potential benefits of targeting integrins to augment immunotherapies.

Inhibitors of Aldosterone Synthase.

The mineralocorticoid aldosterone is an important regulator of blood pressure and electrolyte balance. However, excess aldosterone can be deleterious as a driver of inflammation, vascular remodeling and tissue fibrosis associated with cardiometabolic diseases. Mineralocorticoid receptor antagonists (MRA) and renin-angiotensin-aldosterone system (RAAS) antagonists are current clinical therapies used to antagonize deleterious effects of aldosterone in patients. MRAs compete with aldosterone for binding at its cognate receptor thereby limiting its effect while RAS antagonists reduce aldosterone levels indirectly by blocking the stimulatory effect of angiotensin. Both MRAs and RAS antagonists can result in incomplete inhibition of the harmful effects of excess aldosterone. Aldosterone synthase (AS) inhibitors (ASI) attenuate the production of aldosterone directly and have been proposed as an alternative to MRAs and RAS blockers. Cortisol synthase (CS) is an enzyme closely related to AS and responsible for generating the important glucocorticoid cortisol, required for maintaining critical metabolic and immune responses. The importance of selectivity against CS is shown by early examples of ASIs that were only modestly selective and as such, attenuated cortisol responses when evaluated in patients. Recently, next-generation, highly selective ASIs have been described and are presently being evaluated in the clinic as an alternative to angiotensin and MR antagonists for cardiometabolic disease. Herein we provide a brief review of the challenges associated with discovery of selective ASIs and the transition from the early compounds that paved the way toward the next-generation of highly selective ASIs currently under development.

Patritumab with Cetuximab plus Platinum-Containing Therapy in Recurrent or Metastatic Squamous Cell Carcinoma of the Head and Neck: An Open-Label, Phase Ib Study.

PURPOSE: Patritumab plus cetuximab with platinum as first-line therapy for patients with recurrent and/or metastatic (R/M) squamous cell carcinoma of the head and neck (SCCHN) was evaluated for safety and to determine the recommended phase II combination dose. PATIENTS AND METHODS: Patients aged ≥18 years with confirmed R/M SCCHN received intravenous patritumab (18 mg/kg loading dose; 9 mg/kg maintenance dose every 3 weeks) + cetuximab (400 mg/m2 loading dose; 250 mg/m2 maintenance dose weekly) + cisplatin (100 mg/m2 every 3 weeks) or carboplatin (AUC of 5) for six cycles or until toxicity, disease progression, or withdrawal. Primary endpoints were dose-limiting toxicities [DLT; grade ≥3 (21-day observation period)] and treatment-emergent adverse events (TEAE). Pharmacokinetics, human antihuman antibodies (HAHA), tumor response, progression-free survival (PFS), and overall survival (OS) were assessed. RESULTS: Fifteen patients completed a median (range) of 8.7 (2.0-20.7) patritumab cycles. No DLTs were reported. Serious adverse events were reported in 9 patients (patritumab-related n = 4). TEAEs (N = 15 patients) led to patritumab interruption in 7 patients. Patritumab-related dose reductions were reported in 1 patient. Patritumab (18 mg/kg) pharmacokinetics (N = 15) showed mean (SD) AUC0-21d of 2,619 (560) µg/day/mL and maximum concentration of 499.9 (90.4) µg/mL. All patients were HAHA-negative at study end (single, transient low titer in 1 patient). Tumor response rate (complete plus partial response; N = 15) was 47%. Median (95% confidence interval) PFS and OS (N = 15) were 7.9 (3.7-9.7) and 13.5 (6.6-17.5) months, respectively. CONCLUSIONS: Patritumab (18 mg/kg loading dose, 9 mg/kg maintenance dose) plus cetuximab/platinum was tolerable, active in SCCHN, and selected as the phase II dose regimen.

Harnessing the immune system in glioblastoma.

Glioblastoma is the most common primary malignant brain tumour. Survival is poor and improved treatment options are urgently needed. Although immunotherapies have emerged as effective treatments for a number of cancers, translation of these through to brain tumours is a distinct challenge, particularly due to the blood-brain barrier and the unique immune tumour microenvironment afforded by CNS-specific cells. This review discusses the immune system within the CNS, mechanisms of immune escape employed by glioblastoma, and the immunological effects of conventional glioblastoma treatments. Novel therapies for glioblastoma that harness the immune system and their current clinical progress are outlined, including cancer vaccines, T-cell therapies and immune checkpoint modulators.

A study of the focal adhesion kinase inhibitor GSK2256098 in patients with recurrent glioblastoma with evaluation of tumor penetration of [11C]GSK2256098.

Background: GSK2256098 is a novel oral focal adhesion kinase (FAK) inhibitor. Preclinical studies demonstrate growth inhibition in glioblastoma cell lines. However, rodent studies indicate limited blood-brain barrier (BBB) penetration. In this expansion cohort within a phase I study, the safety, tolerability, pharmacokinetics (PK), and clinical activity of GSK2256098 were evaluated in patients with recurrent glioblastoma. Biodistribution and kinetics of [11C]GSK2256098 were assessed in a substudy using positron-emission tomography (PET). Methods: Patients were treated with GSK2256098 until disease progression or withdrawal due to adverse events (AEs). Serial PK samples were collected on day 1. On a single day between days 9 and 20, patients received a microdose of intravenous [11C]GSK2256098 and were scanned with PET over 90 minutes with parallel PK sample collection. Response was assessed by MRI every 6 weeks. Results: Thirteen patients were treated in 3 dose cohorts (1000 mg, 750 mg, 500 mg; all dosed twice daily). The maximum tolerated dose was 1000 mg twice daily. Dose-limiting toxicities were related to cerebral edema. Treatment-related AEs (>25%) were diarrhea, fatigue, and nausea. Eight patients participated in the PET substudy, with [11C]GSK2256098 VT (volume of distribution) estimates of 0.9 in tumor tissue, 0.5 in surrounding T2 enhancing areas, and 0.4 in normal brain. Best response of stable disease was observed in 3 patients, including 1 patient on treatment for 11.3 months. Conclusions: GSK2256098 was tolerable in patients with relapsed glioblastoma. GSK2256098 crossed the BBB at low levels into normal brain, but at markedly higher levels into tumor, consistent with tumor-associated BBB disruption. Additional clinical trials of GSK2256098 are ongoing.

Dihydrobenzisoxazole-4-one compounds are novel selective inhibitors of aldosterone synthase (CYP11B2) with in vivo activity.

6,7-Dihydro-5H-2,1-benzisoxazol-4-one analogs are potent inhibitors of aldosterone synthase (CYP11B2) with selectivity over the highly homologous enzyme cortisol synthase (CYP11B1). These compounds are unique among inhibitors of CYP11B2 in their lack of a strong-heme binding group such as a pyridine or imidazole. Poor metabolic stability in hepatocyte incubations was found to proceed via a reduction of the isoxazole ring. While the enzyme responsible for the reductive metabolism remains unknown, the rate of metabolism could be attenuated by the addition of polar functionality. The in vitro CYP11B2 potency and selectivity were confirmed in vivo in a cynomolgus monkey model by the inhibition of ACTH stimulated aldosterone production without impacting plasma cortisol concentrations.

Dabrafenib and trametinib in BRAFV600E mutated glioma.

BRAFV600E mutations have been identified in a number of glioma subtypes, most frequently in pleomorphic xanthoastrocytoma, ganglioglioma, pilocytic astrocytoma, and epithelioid glioblastoma. Although the development of BRAF inhibitors has dramatically improved the clinical outcome for patients with BRAFV600E mutant tumors, resistance develops in a majority of patients due to reactivation of the MAPK pathway. Addition of MEK inhibition to BRAF inhibition improves survival. Here we report successful treatment of two patients with BRAFV600E mutant pleomorphic xanthoastrocytoma using the BRAF inhibitor dabrafenib in combination with the MEK inhibitor trametinib.

Impact of Aldosterone Synthase Inhibitor FAD286 on Steroid Hormone Profile in Human Adrenocortical Cells.

Inhibition of aldosterone synthase (CYP11B2) is an alternative treatment option to mineralocorticoid receptor antagonism to prevent harmful aldosterone effects. FAD286 is the best characterized aldosterone synthase inhibitor. However, to date, no study has used sensitive liquid chromatography-tandem mass spectrometry to characterize in detail the effect of FAD286 on the secreted steroid hormone profile of adrenocortical cells. Basal aldosterone production in NCI-H295R cells was detectable and 9-fold elevated after stimulation with angiotensin II. FAD286 inhibited this increase, showing a maximal effect at 10 nmol/l. Higher concentrations of FAD286 did not further reduce aldosterone concentrations, but showed a parallel reduction in corticosterone, cortisol and cortisone levels, reflecting additional inhibition of steroid-11ß-hydroxylase (CYP11B1). Pregnenolone, progesterone and 17-OH-progesterone levels remained unaffected. In conclusion, the aldosterone synthase inhibitor FAD286 lowers angiotensin II-induced aldosterone concentrations in adrenocortical cells but the relative lack of selectivity over CYP11B1 is evident at higher FAD286 concentrations.

The Aldosterone Synthase Inhibitor FAD286 is Suitable for Lowering Aldosterone Levels in ZDF Rats but not in db/db Mice.

Inhibition of aldosterone synthase is an alternative treatment option to mineralocorticoid receptor antagonism to prevent harmful aldosterone actions. FAD286 is one of the best characterized aldosterone synthase inhibitors to date. FAD286 improves glucose tolerance and increases glucose-stimulated insulin secretion in obese and diabetic ZDF rats. However, there is limited knowledge about the dose-dependent effects of FAD286 on plasma aldosterone, corticosterone, and 11-deoxycorticosterone in ZDF rats and in db/db mice, a second important rodent model of obesity and type 2 diabetes. In addition, effects of FAD286 on plasma steroids in mice and rats are controversial. Therefore, obese Zucker diabetic fatty (ZDF) rats and db/db mice were treated with FAD286 for up to 15 weeks and plasma steroids were evaluated using highly sensitive liquid chromatography-tandem mass spectrometry. In ZDF rats, FAD286 (10 mg/kg/d) treatment resulted in nearly complete disappearance of plasma aldosterone while corticosterone levels remained unaffected and those of 11-deoxycorticosterone were increased ~4-fold compared to vehicle control. A lower dose of FAD286 (3 mg/kg/d) showed no effect on plasma aldosterone or corticosterone, but 11-deoxycorticosterone was again increased ~4-fold compared to control. In contrast to ZDF rats, a high dose of FAD286 (40 mg/kg/d) did not affect plasma aldosterone levels in db/db mice although 11-deoxycorticosterone increased ~2.5-fold. A low dose of FAD286 (10 mg/kg/d) increased plasma aldosterone without affecting corticosterone or 11-deoxycorticosterone. In conclusion, the aldosterone synthase inhibitor, FAD286, lowers plasma aldosterone in obese ZDF rats, but not in obese db/db mice.

Dabrafenib in BRAFV600-mutated anaplastic pleomorphic xanthoastrocytoma.

Pleomorphic xanthoastrocytoma (PXA) is a rare brain tumor. Anaplastic features are found in 20-30% of cases of PXA and are associated with poor outcomes. Typical treatment is with gross total resection, followed by radiation therapy and cytotoxic chemotherapy at relapse. BRAFV600 mutations have been identified in 38-60% of patients with PXA. Several case reports and small case series have identified clinical benefit with BRAF inhibition in patients with BRAFV600-mutated PXA. We report the second published case of successful treatment with the BRAF inhibitor dabrafenib in a female patient with relapsed anaplastic PXA with a BRAFV600 mutation, and the first published case of dabrafinib treatment following intolerance to vemurafenib.

Selectivity of BI 689648, a Novel, Highly Selective Aldosterone Synthase Inhibitor: Comparison with FAD286 and LCI699 in Nonhuman Primates.

The mineralocorticoid aldosterone is an important regulator of blood pressure, volume, and electrolyte balance. However, excess aldosterone can be deleterious as a driver of vascular remodeling and tissue fibrosis associated with cardiometabolic diseases. Aldosterone synthase (AS) inhibitors (ASI) attenuate the production of aldosterone directly and have been proposed as an alternative to mineralocorticoid receptor antagonists for blocking the pathologic effects of excess aldosterone. Discovery of selective ASIs has been challenging because of the high sequence identity (93%) AS shares with cortisol synthase (CS), and the low identity of rodent AS compared with human (63%). Using cynomolgus (cyno) monkey-based models, we identified BI 689648 [6-(5-methoxymethyl-pyridin-3-yl)-3,4-dihydro-2H-[1,8]naphthyridine-1-carboxylic acid amide], a novel, highly selective ASI that exhibits an in vitro IC50 of 2 nM against AS and 300 nm against CS (150-fold selectivity) compared with the recently described ASIs FAD286 [4-(5,6,7,8-tetrahydroimidazo[1,5-a]pyridin-5-yl)benzonitrile] (3 nM AS; 90 nM CS; 40-fold) and LCI699 (4-[(5R)-6,7-dihydro-5H-pyrrolo[1,2-c]imidazol-5-yl]-3-fluorobenzonitrile) (10 nM AS; 80 nM CS; 8-fold). After oral administration in cyno monkeys, BI 689648 (5 mg/kg) exhibits a peak plasma concentration of ∼500 nM. For in vivo profiling we used an adrenocorticotropin-challenge model in which BI 689648 was >20-fold more selective compared with FAD286 and LCI699. Because both FAD286 and LCI699 failed to provide adequate selectivity for CS when tested in patients, the desire for more selective molecules to test the ASI hypothesis remains high. Therefore, highly selective aldosterone synthase inhibitors such as BI 689648 represent an important step forward toward developing ASIs with greater potential for clinical success in cardiometabolic diseases.