Lead Optimization Generates CYP11B1 Inhibitors of Pyridylmethyl Isoxazole Type with Improved Pharmacological Profile for the Treatment of Cushing's Disease.

Cushing's disease, characterized by elevated plasma cortisol levels, can be controlled by inhibition of 11ß-hydroxylase (CYP11B1). The previously identified selective and potent CYP11B1 inhibitor 5-((5-methylpyridin-3-yl)methyl)-2-phenylpyridine Ref 7 (IC50= 2 nM) exhibited promutagenic potential as well as very low oral bioavailability in rats (F = 2%) and was therefore modified to overcome these drawbacks. Successful lead optimization resulted in similarly potent and selective 5-((5-methoxypyridin-3-yl)methyl)-3-phenylisoxazole 25 (IC50 = 2 nM, 14-fold selectivity over CYP11B2), exhibiting a superior pharmacological profile with no mutagenic potential. Furthermore, compound 25 inhibited rat CYP11B1 (IC50 = 2 µM) and showed a high oral bioavailability (F = 50%) and sufficient plasma concentrations in rats, providing an excellent starting point for a proof-of-principle study.

ALD1613, a Novel Long-Acting Monoclonal Antibody to Control ACTH-Driven Pharmacology.

Adrenocorticotropic hormone (ACTH) is the primary regulator of adrenal glucocorticoid production. Elevated levels of ACTH play a critical role in disease progression in several indications, including congenital adrenal hyperplasia and Cushing disease. We have generated a specific, high-affinity, neutralizing monoclonal antibody (ALD1613) to ACTH. In vitro, ALD1613 neutralizes ACTH-induced signaling via all 5 melanocortin receptors and inhibited ACTH-induced cyclic adenosine monophosphate accumulation in a mouse adrenal cell line (Y1). ALD1613 administration to wild-type rats significantly reduced plasma corticosterone levels in a dose-dependent manner. In rodent models with either chronic infusion of ACTH or acute restraint stress-induced ACTH, corticosterone levels were significantly reduced by ALD1613. Administration of ALD1613 to nonhuman primates on days 1 and 7 stably reduced plasma cortisol levels >50% for 57 days. ALD1613 demonstrates the potential of a monoclonal antibody to be an effective therapeutic for conditions with elevated ACTH levels.

Clinical management of critically ill patients with Cushing's disease due to ACTH-secreting pituitary macroadenomas: effectiveness of presurgical treatment with pasireotide.

The management of critically ill Cushing's disease (CD) patients is extremely challenging. Pasireotide is indicated for the treatment of CD patients when pituitary surgery is unfeasible or has not been curative, but no data are available about the use of this drug as pre-operative treatment in critically ill patients. We report the effects of presurgical pasireotide therapy in CD patients in whom hypercortisolism caused life-threatening hypokalemia, alkalosis, and cardio-respiratory complications precluding surgical approach. Clinical, biochemical, and radiological data of two critically ill patients with ACTH-secreting pituitary macroadenoma, before and during first-line presurgical pasireotide treatment (600 µg s.c. bid). During the first 21 days of treatment, pasireotide therapy induced a rapid, partial decrease of plasma ACTH, serum cortisol, and urinary free cortisol levels, with the consequent normalization of serum potassium concentration and arterial blood gases parameters, in both the patients. They did not experience unmanageable side effects and underwent endoscopic transsphenoidal surgery after 4 weeks of effective treatment. Pre-operative MRI evaluation did not show pituitary tumor shrinkage. Surgical cure of CD was obtained in the first patient, while debulking allowed the pharmacological control of hypercortisolism in the second case. We suggest that pasireotide can induce a rapid improvement of clinical and metabolic conditions in critically ill CD patients in whom surgical approach is considered hazardous and need to be delayed.

Molecular basis of pharmacological therapy in Cushing's disease.

Cushing's disease (CD) is a severe endocrine condition caused by an adrenocorticotropin (ACTH)-producing pituitary adenoma that chronically stimulates adrenocortical cortisol production and with potentially serious complications if not or inadequately treated. Active CD may produce a fourfold increase in mortality and is associated with significant morbidities. Moreover, excess mortality risk may persist even after CD treatment. Although predictors of risk in treated CD are not fully understood, the importance of early recognition and adequate treatment is well established. Surgery with resection of a pituitary adenoma is still the first line therapy, being successful in about 60-70 % of patients; however, recurrence within 2-4 years may often occur. When surgery fails, medical treatment can reduce cortisol production and ameliorate clinical manifestations while more definitive therapy becomes effective. Compounds that target hypothalamic-pituitary axis, glucocorticoid synthesis or adrenocortical function are currently used to control the deleterious effects of chronic glucocorticoid excess. In this review we describe and analyze the molecular basis of the drugs targeting the disease at central level, suppressing ACTH secretion, as well as at peripheral level, acting as adrenal inhibitors, or glucocorticoid receptor antagonists. Understanding of the underlying molecular mechanisms in CD and of glucocorticoid biology should promote the development of new targeted and more successful therapies in the future. Indeed, most of the drugs discussed have been tested in limited clinical trials, but there is potential therapeutic benefit in compounds with better specificity for the class of receptors expressed by ACTH-secreting tumors. However, long-term follow-up with management of persistent comorbidities is needed even after successful treatment of CD.

High response rates and prolonged survival in patients with corticotroph pituitary tumors and refractory Cushing disease from capecitabine and temozolomide (CAPTEM): a case series.

BACKGROUND AND IMPORTANCE: Rarely, corticotrophic pituitary tumors take on an aggressive form characterized by rapid growth, invasion into local structures, compression of cranial nerves, and possible spread to distant sites. When conventional surgery, radiation therapy, and hormones fail to control progression and symptoms, alternative therapies are needed. A novel chemotherapeutic regimen of capecitabine and temozolomide (CAPTEM), originally designed in our laboratory, demonstrated dramatic antineoplastic effects against corticotrophic pituitary tumors. CLINICAL PRESENTATION: We present a case series of 4 patients with aggressive, adrenocorticotrophic hormone--producing pituitary tumors who had previously depleted all surgical, radiation, and hormonal therapies and were then treated with CAPTEM. Dramatic clinical improvements in neurological deficits and Cushing symptoms were evident in all patients after treatment was initiated. Confirmed by radiographic imaging, 2 of 4 patients demonstrated complete regression of disease, 1 patient had a 75% regression, and the fourth patient has ongoing stable disease for > 4.5 years at the time of this writing. Immunohistochemical analysis of patients' tumor samples showed low O-methyguanyl methyltransferase expression and adequate levels of mismatch repair enzymes (MLH-1, MSH-2, MSH-6, and PMS-2), which are important for the in vivo efficacy of CAPTEM. CONCLUSION: This is the first report of prolonged antitumor response to and radiographic complete remissions as a result of CAPTEM in patients with aggressive pituitary tumors who had exhausted all other therapies.

New prospects for drug treatment in Cushing disease.

Hypercortisolism induced by Cushing disease causes high morbidity and mortality. The treatment of choice is pituitary surgery, but it often fails to achieve cure, and other treatment modalities (radiotherapy, bilateral adrenalectomy) may therefore be required. If these treatments are not effective or while waiting for their results, hypercortisolism should be controlled with drugs. The classical drug treatments are those that act by inhibiting cortisol secretion by the adrenal gland (ketoconazole, metyrapone, mitotane, etomidate). The preliminary results of a new drug (LCI699) which is a potent enzyme inhibitor of cortisol secretion have been reported. A clinical trial of the safety and efficacy of mifepristone, a glucocorticoid receptor antagonist, has just been published. The drugs deserving more attention today are those with a direct action on the tumor by inhibiting ACTH secretion: somatostatin analogues (pasireotide), dopamine agonists (cabergoline), PPAR-γ, and retinoic acid. A special review is made of the available clinical trials with pasireotide and cabergoline.

Growth suppression of mouse pituitary corticotroph tumor AtT20 cells by curcumin: a model for treating Cushing's disease.

BACKGROUND: Pituitary corticotroph tumors secrete excess adrenocorticotrophic hormone (ACTH) resulting in Cushing's disease (CD). Standard treatment includes surgery and, if not successful, radiotherapy, both of which have undesirable side effects and frequent recurrence of the tumor. Pharmacotherapy using PPARgamma agonists, dopamine receptor agonists, retinoic acid or somatostatin analogs is still experimental. Curcumin, a commonly used food additive in South Asian cooking, has potent growth inhibitory effects on cell proliferation. Our laboratory recently demonstrated that curcumin inhibited growth and induced apoptosis in prolactin- and growth hormone-producing tumor cells. Subsequently, Schaaf et.al. confirmed our findings and also showed the in vivo effectiveness of curcumin to suppress pituitary tumorigenesis. However the molecular mechanism that mediate this effect of curcumin are still unknown. PRINCIPAL FINDINGS: Using the mouse corticotroph tumor cells, AtT20 cells, we report that curcumin had a robust, irreversible inhibitory effect on cell proliferation and clonogenic property. The curcumin-induced growth inhibition was accompanied by decreased NFkappaB activity. Further, curcumin down-regulated the pro-survival protein Bcl-xL, depolarized the mitochondrial membrane, increased PARP cleavage, which led to apoptotic cell death. Finally, curcumin had a concentration-dependent suppressive effect on ACTH secretion from AtT20 cells. CONCLUSION: The ability of curcumin to inhibit NFkappaB and induce apoptosis in pituitary corticotroph tumor cells leads us to propose developing it as a novel therapeutic agent for the treatment of CD.

A case of human intramuscular adrenal gland transplantation as a cure for chronic adrenal insufficiency.

Intramuscular endocrine gland transplantation has been well described as it pertains to parathyroid autotransplantation; however, transplantation of the adrenal gland is less well characterized. While adrenal autotransplantation in the setting of Cushing's disease has been described, intramuscular adrenal allotransplantation as a cure for adrenal insufficiency to our knowledge has not been previously carried out. Current treatment for adrenal insufficiency leaves patients without diurnal variation in cortisol release and susceptible to the detrimental effects of chronic hypercortisolism. We describe here the case of a 5-year-old girl with renal failure who had adrenal insufficiency following fulminant meningococcemia that led to requirements for both stress-dose steroid and mineralocorticoid replacement. Ten months after the onset of her disease, she received a simultaneous renal and adrenal gland transplant from her mother. The adrenal gland allograft was morselized into 1 mm(3) segments and implanted into three 2 cm pockets created in her rectus abdominis muscle. Three years after surgery, her allograft remains fully functional, responding well to adrenocorticotropin hormone stimulation and the patient does not require any steroid or mineral-corticoid supplementation. We believe this case represents the first description of successful functional intramuscular adrenal allograft transplantation with long-term follow up as a cure for adrenal insufficiency.

Pasireotide--a somatostatin analog for the potential treatment of acromegaly, neuroendocrine tumors and Cushing's disease.

Pasireotide (SOM-230) is a small somatostatin (SST) analog that is being developed by Novartis Pharma AG for the potential treatment of acromegaly, Cushing's disease and neuroendocrine tumors; the compound is currently in phase III clinical trials for Cushing's disease. Pasireotide exhibits high binding affinity to four of the five human (h)SST receptor subtypes, with IC50 values for hSST5 > hSST2 > hSST3 > hSST1; the compound displays no affinity for hSST4. The affinity profile of pasireotide resembles the profile of endogenous SSTs--a feature that is favorable given that different tumors exhibit differing SST receptor expression profiles. Pasireotide also exhibits a longer half-life than the clinically available SST analogs octreotide or lanreotide. Thus, this compound may be a better therapeutic agent than other analogs. In phase II clinical trials, pasireotide inhibited growth hormone (GH) secretion from GH-secreting pituitary tumors, controlled symptoms associated with metastatic carcinoid tumors, and inhibited adrenocorticotropic hormone secretion in Cushing's disease. However, a major advantage for pasireotide compared with octreotide was not demonstrated. Commonly encountered side effects for the compound included mild to moderate gastrointestinal events (diarrhea, abdominal discomfort, nausea and vomiting). The efficacy of pasireotide and any potential advantage over current therapies will need to be tested or validated in larger phase III clinical trials.