Osilodrostat (LCI699), a potent 11β-hydroxylase inhibitor, administered in combination with the multireceptor-targeted somatostatin analog pasireotide: A 13-week study in rats

Quantification of osilodrostat in horse urine using LC/ESI-HRMS to establish an elimination profile for doping control

Aim: The use of osilodrostat, developed as a medication for Cushing's disease but categorized as an anabolic agent, is banned in horses by both the International Federation of Horseracing Authorities and the Fédération Equestre Internationale. For doping control purposes, elimination profiles of hydrolyzed osilodrostat in horse urine were established and the detectability of free forms of osilodrostat and its major metabolite, mono-hydroxylated osilodrostat (M1c), was investigated.Materials & methods: Post-administration urine samples obtained from a gelding and three mares were analyzed to establish the elimination profiles of osilodrostat using a validated method involving efficient enzymatic hydrolysis followed by LC/ESI-HRMS analysis.Results: Applying the validated quantification method with an LLOQ of 0.05 ng/ml, hydrolyzed osilodrostat could be quantified in post-administration urine samples from 48 to 72 h post-administration; by contrast, both hydrolyzed osilodrostat and M1c were detected up to 2 weeks. In addition, confirmatory analysis identified the presence of hydrolyzed osilodrostat for up to 72 h post-administration.Conclusion: For doping control purposes, we recommend monitoring both hydrolyzed M1c and osilodrostat because of the greater detectability of M1c and the availability of a reference material of osilodrostat, which is essential for confirmatory analysis.

Pharmacokinetic study of osilodrostat and identification of mono-hydroxylated metabolite in equine plasma for the purpose of doping control

RATIONALE

Osilodrostat is an inhibitor of 11-beta-hydroxylase (CYP11B) and is used for the treatment of Cushing's disease but also categorized as an anabolic agent. The use of osilodrostat is prohibited in horseracing and equestrian sports. To the best of our knowledge, this is the first metabolic study of osilodrostat in equine plasma.

METHODS

Potential metabolites of osilodrostat were identified by differential analysis using data acquired from pre- and post-administration plasma samples after protein precipitation with liquid chromatography electrospray ionization high-resolution mass spectrometry (LC/ESI-HRMS). [Correction added on 27 January 2023, after first online publication: In the preceding sentence, "C-HRMS" was changed to "LC/ESI-HRMS" in this version.] For quantification of osilodrostat, a strong cation exchange solid-phase extraction was employed, and the extracts were analyzed using LC/ESI-triple quadrupole tandem mass spectrometry (LC/ESI-QqQ-MS/MS) to establish its elimination profile. Such extracts were further analyzed using LC/ESI-HRMS to investigate the detectability of osilodrostat and its identified mono-hydroxylated metabolite over a 2-week sampling period.

RESULTS

Mono-hydroxylated osilodrostat was identified based on the differential analysis and mass spectrometric interpretations, and it was found to be the most abundant metabolite in plasma. Elimination profile of osilodrostat in plasma was successfully established over the 24-h post-administration period. Both osilodrostat and its mono-hydroxylated metabolite were detected up to the last sampling point at 2 weeks using HRMS, and osilodrostat could be confirmed up to 8-day post-administration with its reference material using HRMS as well.

CONCLUSIONS

For doping control, screening of both the parent drug osilodrostat and its mono-hydroxylated metabolite in equine plasma would be recommended due to their extended detection windows of up to 2 weeks. Given the availability of reference material for potential confirmation in forensic samples, osilodrostat is considered the most appropriate monitoring target.

Clinical Utility of Osilodrostat in Cushing's Disease: Review of Currently Available Literature

Cushing's disease (CD) is caused by endogenous hypercortisolism as a result of adrenocorticotropin (ACTH) secretion from a pituitary tumor. The condition is associated with multiple comorbidities and increased mortality. First-line therapy for CD is pituitary surgery, performed by an experienced pituitary neurosurgeon. Hypercortisolism may often persist or recur after initial surgery. Patients with persistent or recurrent CD will generally benefit from medical therapy, often administered to patients who underwent radiation therapy to the sella and are awaiting its salutary effects. There are three groups of medications directed against CD, including pituitary-targeted medications that inhibit ACTH secretion from tumorous corticotroph cells, adrenally-directed medications that inhibit adrenal steroidogenesis and a glucocorticoid receptor (GR) antagonist. The focus of this review is osilodrostat, a steroidogenesis inhibitor. Osilodrostat (LCI699) was initially developed to lower serum aldosterone levels and control hypertension. However, it was soon realized that osilodrostat also inhibits 11-beta hydroxylase (CYP11B1), leading to a reduction in serum cortisol levels. The focus of drug development then shifted from treatment of hypertension to treatment of hypercortisolism in CD. In a series of studies (LINC 1 through 4), osilodrostat was shown to be effective in normalizing 24-h urinary free cortisol (UFC) in the majority of treated patients and was approved for patients with CD who have failed surgery or are not surgical candidates. Further study is needed to examine the role of combination therapy as well as long-term outcomes of treated patients. Osilodrostat was shown to have an overall good safety profile. Most common adverse effects include nausea, headache, fatigue, arthralgias, dizziness, prolonged QTc interval, hypokalemia. In females, the drug can cause hirsutism and acne. Osilodrostat is administered twice daily, making it a good choice for patients with difficulty adhering to more complex regimens. Osilodrostat has an important, albeit adjunctive, role in the management of patients with CD.

Osilodrostat oral tablets for adults with Cushing's disease

INTRODUCTION

Endogenous Cushing's syndrome (CS) is a rare, multi-systemic condition resulting from chronic glucocorticoid excess sustained by a pituitary adenoma (Cushing's disease, CD), an adrenal adenoma or, less frequently, a neuroendocrine tumor. The optimal first-line option is surgery, but when it is contraindicated/refused, or in case of severe, life-threatening disease, medical treatment is a first-line choice. Osilodrostat (LCI699, Isturisa®) is a new, orally active adrenal steroidogenesis inhibitor currently approved by the FDA and EMA for the treatment of endogenous CS.

AREAS COVERED

We illustrate the pharmacologic profile of osilodrostat and summarize the efficacy and safety of osilodrostat from the first phase I studies to the most recent evidence.

EXPERT OPINION

Osilodrostat acts as a potent, reversible inhibitor of 11β-hydroxylase (CYP11B1) and 18-hydroxylase (or aldosterone synthase, CYP11B2), counteracting both gluco- and mineralocorticoid production. According to the results of the LINC1, LINC2, and LINC3 studies and the preliminary findings of LINC4, osilodrostat offers an excellent efficacy in controlling hypercortisolism with a good tolerability. The non-negligible risk of adrenal insufficiency/steroid withdrawal symptoms, hypokalemia, and hyperandrogenism disorders, and the possibility, albeit rare, of pituitary tumor enlargement, require further confirmation and careful monitoring.

Individualized medical treatment options in Cushing disease

Cushing disease (CD) is caused by a pituitary tumor which oversecretes adrenocorticotropic hormone (ACTH). It is a serious endocrine disease associated with increased mortality and impaired quality of life. The management of CD remains challenging. Although transsphenoidal surgery is the treatment of choice in most cases, in approximately half of CD patients, second or third-line treatment options are needed. Currently, new medical therapies are available which target adrenal steroidogenesis, pituitary somatostatin and dopamine receptors, and glucocorticoid receptors. Selection of which medication to use should be individualized and is determined by many factors including severity of the disease, possible side effects, patients preferences and local availability. The aim of this article is to describe currently available medical therapy to help clinicians individualize the treatment options in the context of recently updated Pituitary Society recommendations.

Advances in the medical treatment of Cushing's syndrome

Cushing's syndrome is associated with multisystem morbidity and, when suboptimally treated, increased mortality. Medical therapy is an option for patients if surgery is not successful and can be classified into pituitary-directed drugs, steroid synthesis inhibitors, and glucocorticoid receptor antagonists. In the last decade there have been new developments in each drug category. Targeting dopamine and somatostatin receptors on corticotroph adenomas with cabergoline or pasireotide, or both, controls cortisol production in up to 40% of patients. Potential new targets in corticotroph adenomas include the epidermal growth factor receptor, cyclin-dependent kinases, and heat shock protein 90. Osilodrostat and levoketoconazole are new inhibitors of steroidogenesis and are currently being evaluated in multicentre trials. CORT125134 is a new selective glucocorticoid receptor antagonist under investigation. We summarise the drug therapies for various forms of Cushing's syndrome and focus on emerging drugs and drug targets that have the potential for new and effective tailor-made pharmacotherapy for patients with Cushing's syndrome.

Sensitive quantification of the somatostatin analog AP102 in plasma by ultra-high pressure liquid chromatography-tandem mass spectrometry and application to a pharmacokinetic study in rats

AP102 is a di-iodinated octapeptide somatostatin agonist (SSA) designed to treat acromegaly and neuroendocrine tumors. A sensitive and selective method was validated for the quantification of AP102 in plasma following the European Medicines Agency (EMA) and Food and Drug Administration (FDA) guidelines. Sample preparation was performed using solid-phase extraction microplates. Chromatographic separation was achieved on an ultra-high pressure liquid chromatography (UHPLC) C18 column in 6.0 minutes. The compounds were quantified using multiple reaction monitoring on a tandem quadrupole mass spectrometer with ¹³ C,¹⁵ N-labeled AP102 as internal standard. Calibration ranged from 50 to 10000 pg/mL. The lower limit of quantification (LLOQ) was measured at 20 pg/mL, and robust analytical performances were obtained with trueness at 99.2%-100.0%, intra-assay imprecision at 2.5%-4.4%, and inter-assay imprecision at 8.9%-9.7%. The accuracy profiles (total error) built on the 3 concentrations levels showed accuracy within the 70%-130% range. AP102 is remarkably stable since no proteolytic fragments were detected on plasma samples analyzed by Orbitrap-MS. Pharmacokinetic studies were conducted in rats, after single dose (1, 3, and 10 μg/kg, sc) and continuous subcutaneous administration (osmotic minipumps for 28 days, 3.0 or 10.0 μg/kg/h). AP102 showed a rapid absorption by the subcutaneous route (T_max : 15-30 minutes) and a fast elimination (t_1/2 : 33-86 minutes). The PK profile of AP102 exhibited a mean clearance of 1.67 L/h and a mean distribution volume at steady state of 7.16 L/kg, about 10-fold higher than those observed with other SSA or non- and mono-iodinated AP102. LogD_7.4 determination confirmed the lipophilic properties of AP102 that might influence its distribution in tissues.

Pituitary-Directed Therapies for Cushing's Disease

Cushing's disease (CD) is caused by a pituitary corticotroph neuroendocrine tumor inducing uncontrolled hypercortisolism. Transsphenoidal surgery is the first-line treatment in most cases. Nonetheless, some patients will not achieve cure even in expert hands, others may not be surgical candidates and a significant percentage will experience recurrence. Many patients will thus require medical therapy to achieve disease control. Pharmacologic options to treat CD have increased in recent years, with an explosion in knowledge related to pathophysiology at the molecular level. In this review, we focus on medications targeting specifically pituitary adrenocorticotropic hormone-secreting tumors. The only medication in this group approved for the treatment of CD is pasireotide, a somatostatin receptor ligand. Cabergoline and temozolomide may also be used in select cases. Previously studied and abandoned medical options are briefly discussed, and emphasis is made on upcoming medications. Mechanism of action and available data on efficacy and safety of cell cycle inhibitor roscovitine, epidermal growth factor receptor inhibitor gefitinib, retinoic acid, and silibinin, a heat shock protein 90 inhibitor are also presented.

Usefulness of Simultaneous Measurement of Plasma Steroids, Including Precursors, for the Evaluation of Drug Effects on Adrenal Steroidogenesis in Rats

The aim of this study was to evaluate the usefulness of simultaneous measurement of plasma steroids, including precursors, for the evaluation of drug effects on adrenal steroidogenesis in vivo. Plasma concentrations of corticosterone and its precursors were examined in rats dosed with compounds that affect adrenal steroidogenesis via different modes of action as well as the relationships of the changes with blood chemistry and adrenal histopathology. Male rats were dosed with tricresyl phosphate, aminoglutethimide, trilostane (TRL), metyrapone (MET), ketoconazole (KET), or mifepristone for 7 days. In the TRL, MET, and KET groups, precursor levels were markedly increased, while there were no significant changes in the corticosterone level, suggesting that the precursors are more sensitive biomarkers to detect the effect on adrenal steroidogenesis. Also, the precursors with increased levels were those that are normally metabolized by the inhibited enzymes, reflecting the modes of action of the compounds. In addition, different patterns of changes were observed in blood chemistry and histopathology, supporting the mechanism suggested by the steroid changes. These results show that simultaneous measurement of plasma steroids, including precursors, can be a valuable method to sensitively evaluate drug effects on adrenal steroidogenesis and to investigate the underlying mechanisms.

Updates on the role of adrenal steroidogenesis inhibitors in Cushing's syndrome: a focus on novel therapies

PURPOSE

Endogenous Cushing's syndrome (CS) is a rare disease that results from exposure to high levels of cortisol; Cushing's disease (CD) is the most frequent form of CS. Patients with CS suffer from a variety of comorbidities that increase the risk of mortality. Surgical resection of the disease-causing lesion is generally the first-line treatment of CS. However, some patients may not be eligible for surgery due to comorbidities, and approximately 25 % of patients, especially those with CD, have recurrent disease. For these patients, adrenal steroidogenesis inhibitors may control cortisol elevation and subsequent symptomatology. CS is rare overall, and clinical studies of adrenal steroidogenesis inhibitors are often small and, in many cases, data are limited regarding the efficacy and safety of these treatments. Our aim was to better characterize the profiles of efficacy and safety of currently available adrenal steroidogenesis inhibitors, including drugs currently in development.

METHODS

We performed a systematic review of the literature regarding adrenal steroidogenesis inhibitors, focusing on novel drugs.

RESULTS

Currently available adrenal steroidogenesis inhibitors, including ketoconazole, metyrapone, etomidate, and mitotane, have variable efficacy and significant side effects, and none are approved by the US Food and Drug Administration for CS. Therefore, there is a clear need for novel, prospectively studied agents that have greater efficacy and a low rate of adverse side effects. Efficacy and safety data of current and emerging adrenal steroidogenesis inhibitors, including osilodrostat (LCI699) and levoketoconazole (COR-003), show promising results that will have to be confirmed in larger-scale phase 3 studies (currently ongoing).

CONCLUSIONS

The management of CS, and particularly CD, remains challenging. Adrenal steroidogenesis inhibitors can be of major interest to control the hypercortisolism at any time point, either before or after surgery, as discussed in this review.

Update on medical treatment for Cushing's disease

Cushing's disease (CD) is the most common cause of endogenous Cushing's syndrome (CS). The goal of treatment is to rapidly control cortisol excess and achieve long-term remission, to reverse the clinical features and reduce long-term complications associated with increased mortality. While pituitary surgery remains first line therapy, pituitary radiotherapy and bilateral adrenalectomy have traditionally been seen as second-line therapies for persistent hypercortisolism. Medical therapy is now recognized to play a key role in the control of cortisol excess. In this review, all currently available medical therapies are summarized, and novel medical therapies in phase 3 clinical trials, such as osilodrostat and levoketoconazole are discussed, with an emphasis on indications, efficacy and safety. Emerging data suggests increased efficacy and better tolerability with these novel therapies and combination treatment strategies, and potentially increases the therapeutic options for treatment of CD. New insights into the pathophysiology of CD are highlighted, along with potential therapeutic applications. Future treatments on the horizon such as R-roscovitine, retinoic acid, epidermal growth factor receptor inhibitors and somatostatin-dopamine chimeric compounds are also described, with a focus on potential clinical utility.

Current strategies for the treatment of severe Cushing's syndrome

Severe Cushing's syndrome may present an acute emergency in patients diagnosed with Cushing's syndrome with recent onset of at least one of the following: sepsis, opportunistic infection; intractable hypokalaemia, uncontrolled hypertension; heart failure; gastrointestinal hemorrhage; acute psychosis; progressive debilitating myopathy; thromboembolism; uncontrolled hyperglycemia and ketoacidosis. The biochemical definition includes serum cortisol ≥41μg/dl (1100 nmol/l) and/or severe hypokalemia (<3.0 mmol/l) or urine free cortisol fivefold the upper limit of normal. Treatment focuses on the management of severe metabolic disturbances followed by rapid resolution of the hypercortisolemia and subsequent confirmation of the cause. We emphasize the control of the hypokalemia, hypertension, diabetes and any psychotic state, anti-coagulation, monitoring and vigorous therapy of opportunistic infections. The ideal first-line therapies include metyrapone and ketoconazole, followed by parenteral etomidate; if all else fails life-saving bilateral adrenalectomy should be considered.