Prolonged adrenocortical blockade following discontinuation of Osilodrostat

Medical Therapy of Endogenous Cushing's Syndrome with Steroidogenesis Inhibitors: Treatment Rationale, Available Drugs, and Therapeutic Effects

Endogenous Cushing's syndrome (CS) is a rare disease characterized by a glucocorticoid excess. If inadequately treated, hypercortisolism can lead to increased morbidity and mortality. Surgical removal of the underlying tumor is the first-line treatment but is sometimes not feasible or even contraindicated. Additionally, in cases with severe CS, rapid control of hypercortisolism may be required. In these scenarios, steroidogenesis inhibitors represent a therapeutic alternative to surgery. Over the last years, the knowledge of the broad therapeutic effects of steroidogenesis inhibitors per se and the number of available drugs have increased. However, large comparative studies are still lacking. Accordingly, the decision on which drug to be used in a certain patient or clinical setting may be difficult. This review aims to summarize the main characteristics of steroidogenesis inhibitors.

Prolonged Adrenal Insufficiency After Osilodrostat Exposure With Eventual Recovery of Adrenal Function

Osilodrostat is an 11β-hydroxylase inhibitor used in the treatment of adult patients with Cushing disease. Prolonged adrenal insufficiency (AI) after osilodrostat use is a rare but significant adverse effect. We present the case of a 41-year-old woman treated with osilodrostat for persistent hypercortisolism following pituitary surgery and Gamma Knife radiosurgery. After 11 months of osilodrostat therapy, she reported AI symptoms, and biochemical testing revealed low serum cortisol following cosyntropin stimulation as well as high plasma adrenocorticotropic hormone (ACTH). The patient was started on physiologic replacement dose of hydrocortisone, which was discontinued 23 months after last osilodrostat exposure when laboratory testing revealed recovery of endogenous cortisol production. The mechanism responsible for the prolonged AI noted with osilodrostat use is unclear and unexpected, given the short half-life of the drug. Although prolonged AI after osilodrostat use is not well understood, providers should be aware of this potential adverse effect and have a low threshold to test for AI in patients reporting AI-related symptoms.

Prolonged adrenal insufficiency following discontinuation of osilodrostat treatment for intense hypercortisolism

The cases of 3 patients with Cushing's disease who developed long-term adrenal insufficiency after discontinuation of prolonged osilodrostat therapy were recently described for the first time. We report 2 additional cases of persistent prolonged adrenal insufficiency after discontinuation of osilodrostat treatment for intense hypercortisolism due to Cushing's disease and ectopic ACTH syndrome. In addition, we show for that adrenal insufficiency in these patients was associated with low/normal 11-deoxycortisol concentrations despite high plasma ACTH concentrations. These results suggest that CYP11B1 is not the only target of osilodrostat and that, in vivo, osilodrostat has other prolonged and strong inhibitory effect on adrenal steroidogenesis upstream of CYP11B1. Knowledge of this remnant effect is important for the care of patients with Cushing's syndrome treated with osilodrostat. Further studies are needed to clarify the frequency and the mechanisms of this remnant effect.

Current and Emerging Pharmacological Therapies for Cushing's Disease

Cushing's Disease (CD), hypercortisolism due to pituitary ACTH secreting neuroendocrine neoplasm, is associated with increased morbidity and, if untreated, mortality in about half of the affected individuals. Consequently, the timely initiation of effective treatment is mandatory. Neurosurgery is the first line and the only potentially curative treatment; however, 30% of patients will have persistent disease post-surgery. Furthermore, a small percentage of those initially controlled will develop hypercortisolism during long-term follow- up. Therefore, patients with persistent or recurrent disease, as well as those considered non-eligible for surgery, will need a second-line therapeutic approach, i.e., pharmacotherapy. Radiation therapy is reserved as a third-line therapeutic option due to its slower onset of action and its unfavorable profile regarding complications. During the past few years, the understanding of molecular mechanisms implicated in the physiology of the hypothalamus-pituitary-adrenal axis has evolved, and new therapeutic targets for CD have emerged. In the present review, currently available treatments, compounds currently tested in ongoing clinical trials, and interesting, potentially new targets emerging from unraveling molecular mechanisms involved in the pathophysiology of Cushing's disease are discussed.

Pharmacological Treatment of Cushing's Syndrome

The 1st line treatment of Cushing's syndrome is surgery, whatever the aetiology. The role of pharmacological treatment is clear in cases where surgery fails or is impossible, in cases of metastases, or while awaiting the delayed effects of radiotherapy. However, certain situations remain controversial, in particular the possible role of pharmacological treatment as a preparation for surgery. This situation must be divided into 2 parts, severe hypercortisolism with immediate vital risk and non-severe hypercortisolism with diagnostic delay. The initiation and adjustment of treatment doses is also controversial, with the possibility of titration by gradual dose increase based on biological markers, or a more radical "block and replace" approach in which the ultimate goal is to achieve hypocortisolism, which can then be supplemented. Each of these approaches has its advantages and drawbacks and should probably be reserved for different patient profiles depending on the severity of hypercortisolism. In this review, we will focus specifically on these 2 points, namely the potential role of preoperative pharmacological treatment and, more generally, the optimal way to initiate and monitor drug treatment to ensure that eucortisolism or hypocortisolism is achieved. We will define for each part which profiles of patients should be the most adapted to try to give advice on the optimal management of patients with hypercortisolism.