Pituitary-Directed Therapies for Cushing's Disease

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.

Benign and Malignant Tumors of the Pituitary Gland

Pituitary gland tumors represent approximately 10-15% of all brain tumors and the most common neoplasms of the sellar region. Among them, pituitary adenomas are the widespread accounting for more than 80%. Recently, the fourth edition of the World Health Organization (WHO) 2017 classified pituitary tumors focusing on histopathologic and molecular genetics features and introduced new entities like pituitary blastoma. Most of pituitary gland neoplasms occur sporadically, whereas 5% are related to familial syndromes. They present with several clinical manifestations including signs and symptoms related to excessive hormone secretion by the tumor, signs of hormone deficits by the normal pituitary gland and others commonly secondary to mass effects, and compression of nearby structures such as the optic chiasm; headache and visual disturbance are the most frequent mass effect symptoms. Some tumors, however, are detected as an incidental finding on magnetic resonance imaging (MRI) or computed tomography (CT) scans performed for some other reasons. A correct evaluation involves the assessment of hypothalamic-pituitary hormonal function and an ophthalmological examination once a pituitary lesion is encountered. Surgery, more specifically transsphenoidal approach, represents the primary treatment chosen for the majority of pituitary tumors (except for prolactinomas where medical treatment is indicated) allowing for pathologic analysis and complete or partial tumor removal. On the contrary, to date, craniotomy is rarely performed. Sometimes, due to the proximity of critical structures and to tumor's location and characteristics, a successful surgical procedure may often not be achievable due to the high risks related to the procedure itself. Therefore, the treatment of pituitary tumors commonly requires a multimodal approach, including surgery, radiosurgery, radiation therapy, and medical therapy. Aggressive pituitary tumors or carcinomas are associated with poor prognosis due to limited therapeutic options. Furthermore, they tend to recur quickly after initial surgical treatment or present metastasis, may be unresponsive to therapy, and are difficult to manage. In this chapter, we provide an overview of the most common pituitary gland tumors focusing on epidemiology, new pathological features, diagnosis, available treatment, and prognosis.

Integrative Clinical, Radiological, and Molecular Analysis for Predicting Remission and Recurrence of Cushing Disease

CONTEXT

Adrenocorticotropin (ACTH)-secreting pituitary tumors (ACTHomas) are associated with severe comorbidities and increased mortality. Current treatments mainly focus on remission and prevention of persistent disease and recurrence. However, there are still no useful biomarkers to accurately predict the clinical outcome after surgery, long-term remission, or disease relapse.

OBJECTIVES

This work aimed to identify clinical, biochemical, and molecular markers for predicting long-term clinical outcome and remission in ACTHomas.

METHODS

A retrospective multicenter study was performed with 60 ACTHomas patients diagnosed between 2004 and 2018 with at least 2 years' follow-up. Clinical/biochemical variables were evaluated yearly. Molecular expression profile of the somatostatin/ghrelin/dopamine regulatory systems components and of key pituitary factors and proliferation markers were evaluated in tumor samples after the first surgery.

RESULTS

Clinical variables including tumor size, time until diagnosis/first surgery, serum prolactin, and postsurgery cortisol levels were associated with tumor remission and relapsed disease. The molecular markers analyzed were distinctly expressed in ACTHomas, with some components (ie, SSTR1, CRHR1, and MKI67) showing instructive associations with recurrence and/or remission. Notably, an integrative model including selected clinical variables (tumor size/postsurgery serum cortisol), and molecular markers (SSTR1/CRHR1) can accurately predict the clinical evolution and remission of patients with ACTHomas, generating a receiver operating characteristic curve with an area under the curve of 1 (P < .001).

CONCLUSION

This study demonstrates that the combination of a set of clinical and molecular biomarkers in ACTHomas is able to accurately predict the clinical evolution and remission of patients. Consequently, the postsurgery molecular profile represents a valuable tool for clinical evaluation and follow-up of patients with ACTHomas.

What to Do with Incidentally Discovered Pituitary Abnormalities?

Pituitary incidentalomas are discovered in approximately 10% to 40% of brain images. A complete patient history, physical examination, and dedicated pituitary function testing are needed, and subsequent results should lead to appropriate patient management. However, most lesions are asymptomatic pituitary adenomas or Rathke cleft cysts with a benign course. Many lesions can be clinically significant, including prolactinomas or other pituitary adenomas that warrant specific pituitary disease treatment. In other cases, mass effect causing visual compromise or refractory headache indicates a need for surgery. Here, various facets of a complex evaluation and treatment algorithm for pituitary incidentalomas are reviewed.

Recent Understanding and Future Directions of Recurrent Corticotroph Tumors

Corticotroph tumors (CTs) are pituitary neoplasms arising from the Tpit lineage, which may or not express adrenocorticotrophic hormone (ACTH). Functioning CTs cause Cushing's disease (CD), which has high morbidity and mortality due to hypercortisolemia. "Non-functioning" or silent CTs (SCT) and the Crooke's cell subtypes do not cause CD and may be asymptomatic until manifested by compressive symptoms and are more frequently found as macroadenoma. Both tend toward more aggressive behavior, recurrence, and a higher rate of malignant transformation to pituitary carcinoma. Tumorigenesis involves genetic, epigenetic, and post-transcriptional disruption of cell-cycle regulators, which increase cell proliferation, POMC overexpression, ACTH transcription, and/or hypersecretion. Furthermore, functioning CTs develop resistance to glucocorticoid-mediated negative feedback on ACTH secretion, through increased expression of testicular orphan nuclear receptor 4 (TR4), heat-shock protein 90 (HSP90), and loss-of-function mutation of CDK5 and ABL enzyme substrate 1 (CABLES1) gene. Overt autonomous hypercortisolemia is difficult to control, and multiple diagnostic studies and therapeutic modalities are commonly required. Cell-cycle regulation depends mainly on p27, cyclin E, cyclin-dependent kinases (CDKs), and the retinoblastoma protein (Rb)/E2F1 transcription factor complex. Gain-of-function mutations of ubiquitin-specific protease (USP) 8, USP48, and BRAF genes may subsequently cause overexpression of epithelial growth factor receptor (EGFR), and enhance POMC transcription, cell proliferation, and tumor growth. Epigenetic changes through micro RNAs and decreased DNA deacetylation by histone deacetylase type 2 (HDAC2), may also affect tumor growth. All the former mechanisms may become interesting therapeutic targets for CTs, aside from temozolomide, currently used for aggressive tumors. Potential therapeutic agents are EGFR inhibitors such as gefitinib and lapatinib, the purine analog R-roscovitine by dissociation of CDK2/Cyclin E complex, the HSP90 inhibitor silibinin (novobiocin), to reduce resistance to glucocorticoid-mediated negative feedback, and BRAF inhibitors vemurafenib and dabrafenib in BRAF V600E positive tumors. This review summarizes the molecular mechanisms related to CTs tumorigenesis, their diagnostic approach, and provides an update of the potential novel therapies, from the lab bench to the clinical translation.

Recurrence after pituitary surgery in adult Cushing's disease: a systematic review on diagnosis and treatment

PURPOSE

Recurrence after pituitary surgery in Cushing's disease (CD) is a common problem ranging from 5% (minimum) to 50% (maximum) after initially successful surgery, respectively. In this review, we give an overview of the current literature regarding prevalence, diagnosis, and therapeutic options of recurrent CD.

METHODS

We systematically screened the literature regarding recurrent and persistent Cushing's disease using the MESH term Cushing's disease and recurrence. Of 717 results in PubMed, all manuscripts in English and German published between 1980 and April 2020 were screened. Case reports, comments, publications focusing on pediatric CD or CD in veterinary disciplines or studies with very small sample size (patient number < 10) were excluded. Also, papers on CD in pregnancy were not included in this review.

RESULTS AND CONCLUSIONS

Because of the high incidence of recurrence in CD, annual clinical and biochemical follow-up is paramount. 50% of recurrences occur during the first 50 months after first surgery. In case of recurrence, treatment options include second surgery, pituitary radiation, targeted medical therapy to control hypercortisolism, and bilateral adrenalectomy. Success rates of all these treatment options vary between 25 (some of the medical therapy) and 100% (bilateral adrenalectomy). All treatment options have specific advantages, limitations, and side effects. Therefore, treatment decisions have to be individualized according to the specific needs of the patient.

Management of patients with persistent or recurrent Cushing's disease after initial pituitary surgery

INTRODUCTION

Treatment options for persistent and recurrent Cushing's disease (CD) include an individualized approach for repeat surgery, medical treatment, radiation therapy (RT), and bilateral adrenalectomy (BLA).

AREAS COVERED

In this expert opinion perspective, the authors review the latest treatment(s) for persistent/recurrent CD. A PubMed search was undertaken (English articles through May 2020) and relevant articles discussed. Repeat pituitary surgery should be considered in most patients with proven hypercortisolism; there is potential for cure with low risk of major complications. Medical therapy is valuable either alone, while awaiting the effects of RT, or in preparation for BLA. Medical therapy includes steroidogenesis inhibitors, agents that act at the pituitary or glucocorticoid receptor level, and novel agents in development. Radiation therapy has been used successfully to treat CD, but hypopituitarism risk and delayed efficacy (improved with radiosurgery) are major drawbacks. Laparoscopic BLA is safe and effective in patients with severe, difficult-to-manage hypercortisolism, but long-term follow-up is required as corticotroph tumor progression can develop.

EXPERT OPINION

Treatment of persistent/recurrent CD is challenging. Most patients require >1 therapy to achieve long-lasting remission. There is currently no ideal single treatment option that provides high and rapid efficacy, low adverse effects, and preserves normal pituitary-adrenal axis function.

The Role of Dopamine Agonists in Pituitary Adenomas

Dopamine agonist therapy is the primary therapy for prolactin-secreting adenomas and usually results in normoprolactinemia, eugonadism, and tumor reduction. Cabergoline is superior to bromocriptine with regard to efficacy and tolerance. Withdrawal of cabergoline can be attempted in patients with normal prolactin levels on low doses of medication and evidence of radiographic tumor involution. Dopamine agonists have been used off label in patients with acromegaly, Cushing disease, and nonfunctioning adenomas. A trial of cabergoline monotherapy can be effective in patients with biochemically mild acromegaly. Cabergoline combination with somatostatin receptor ligands or pegvisomant improves insulin-like growth factor level 1 in majority of patients.

Medical Management of Cushing's Syndrome: Current and Emerging Treatments

Endogenous Cushing's syndrome is a chronic disease associated with increased morbidity and mortality if not appropriately treated. Recurrence and/or persistence of hypercortisolemia after surgical treatment, especially for Cushing's disease, are high, and long-term medical treatment is used to decrease cortisol levels and risk of metabolic comorbidities. Medical treatment is also often required while waiting for radiation effects to take place. In some cases, severe or life-threatening hypercortisolism must be urgently and medically treated, via intravenous medications or with combination therapy, before patients can undergo surgery. In the last decade, medical treatment has progressed from a few steroidogenesis inhibitors to three novel drug groups: new inhibitors for steroidogenic enzymes with possibly fewer side effects, pituitary-directed drugs that aim to inhibit the pathophysiological pathways of Cushing's disease, and glucocorticoid receptor antagonists that block cortisol's action. Understanding the pathophysiology of Cushing's syndrome has also led to the identification of potential targets that may decrease adrenocorticotrophic hormone and/or cortisol excess, and/or decrease tumor cell proliferation, and induce senescence or apoptosis. We provide here a review of current and near-future medical options to treat Cushing's syndrome, and discuss updates on clinical trials and the efficacy and safety of novel or in-development drugs, as well as future potential targets.

Cushing's Disease

In patients with Cushing's disease (CD), prompt diagnosis and treatment are essential for favorable long-term outcomes, although this remains a challenging task. The differential diagnosis of CD is still difficult in some patients, even with an organized stepwise diagnostic approach. Moreover, despite the use of high-resolution magnetic resonance imaging (MRI) combined with advanced fine sequences, some tumors remain invisible. Surgery, using various surgical approaches for safe maximum tumor removal, still remains the first-line treatment for most patients with CD. Persistent or recurrent CD after unsuccessful surgery requires further treatment, including repeat surgery, medical therapy, radiotherapy, or sometimes, bilateral adrenalectomy. These treatments have their own advantages and disadvantages. However, the most important thing is that this complex disease should be managed by a multidisciplinary team with collaborating experts. In addition, a personalized and individual-based approach is paramount to achieve high success rates while minimizing the occurrence of adverse events and improving the patients' quality of life. Finally, the recent new insights into the pathophysiology of CD at the molecular level are highly anticipated to lead to the introduction of more accurate diagnostic tests and efficacious therapies for this devastating disease in the near future.

THE MULTIFARIOUS CUSHING'S - LESSONS FROM A CASE SERIES

Endogenous Cushing's syndrome is rare, with an incidence of 0.7-2.4 per a million people a year. Clinical presentation of Cushing syndrome can be pleomorphic, and establishing diagnosis can be difficult. Early recognition and rapid control of hypercortisolaemia are necessary to decrease morbidity and mortality in these patients. We report a series of 6 endogenous Cushing's syndromes of different etiologies (4 Cushing's disease and 2 adrenal Cushing's syndrome) assessed in our endocrine department over a decade (2009-2019). In order to highlight the diversity of clinical forms, diagnostic tools and specific management of this condition we labelled each case suggestively: the typical Cushing's disease, the Pseudo Cushing's, the elusive Cushing's disease, the mild autonomous cortisol hypersecretion, Cushing's syndrome in pregnancy and Cushing's disease with thromboembolism. We discussed their particularities which were revelatory for the diagnosis, such as dermatologic, cardiovascular, musculoskeletal, neuropsychiatric, or reproductive signs, reviewing literature for each manifestation. We also discuss the commonalities and differences in laboratory and imagistic findings. Therapeutic approach can also differ with respect to the particular condition of each patient and the multiple choices of therapy will be reviewed.

The molecular determinants of R-roscovitine block of hERG channels

Human ether-à-go-go-related gene (Kv11.1, or hERG) is a potassium channel that conducts the delayed rectifier potassium current (I_Kr) during the repolarization phase of cardiac action potentials. hERG channels have a larger pore than other K⁺channels and can trap many unintended drugs, often resulting in acquired LQTS (aLQTS). R-roscovitine is a cyclin-dependent kinase (CDK) inhibitor that induces apoptosis in colorectal, breast, prostate, multiple myeloma, other cancer cell lines, and tumor xenografts, in micromolar concentrations. It is well tolerated in phase II clinical trials. R-roscovitine inhibits open hERG channels but does not become trapped in the pore. Two-electrode voltage clamp recordings from Xenopus oocytes expressing wild-type (WT) or hERG pore mutant channels (T623A, S624A, Y652A, F656A) demonstrated that compared to WT hERG, T623A, Y652A, and F656A inhibition by 200 μM R-roscovitine was ~ 48%, 29%, and 73% weaker, respectively. In contrast, S624A hERG was inhibited more potently than WT hERG, with a ~ 34% stronger inhibition. These findings were further supported by the IC₅₀ values, which were increased for T623A, Y652A and F656A (by ~5.5, 2.75, and 42 fold respectively) and reduced 1.3 fold for the S624A mutant. Our data suggest that while T623, Y652, and F656 are critical for R-roscovitine-mediated inhibition, S624 may not be. Docking studies further support our findings. Thus, R-roscovitine’s relatively unique features, coupled with its tolerance in clinical trials, could guide future drug screens.

Functioning Pituitary Adenomas - Current Treatment Options and Emerging Medical Therapies

Pituitary adenomas are benign tumours comprising approximately 16% of all primary cranial neoplasms. Functioning pituitary adenomas (prolactinomas, somatotroph, corticotroph, thyrotroph and rarely gonadotroph adenomas) cause complex clinical syndromes and require prompt treatment to reduce associated morbidity and mortality. Treatment approaches include transsphenoidal surgery, medical therapy and radiation. Medical therapy is the primary therapy for prolactinomas, and surgery by a skilled neurosurgeon is the first-line approach for other functioning pituitary adenomas. A multimodal treatment is frequently necessary to achieve biochemical and clinical control, especially, when surgery is not curative or when medical therapy fails. Several emerging, novel, medical treatments for acromegaly, Cushing's disease and prolactinomas are in phase II and III clinical trials and may become effective additions to the current drug armamentarium. The availability of various management options will allow an individualised treatment approach based on the unique tumour type, clinical situation and patient preference.

Beetles as Model Organisms in Physiological, Biomedical and Environmental Studies - A Review

Model organisms are often used in biological, medical and environmental research. Among insects, Drosophila melanogaster, Galleria mellonella, Apis mellifera, Bombyx mori, Periplaneta americana, and Locusta migratoria are often used. However, new model organisms still appear. In recent years, an increasing number of insect species has been suggested as model organisms in life sciences research due to their worldwide distribution and environmental significance, the possibility of extrapolating research studies to vertebrates and the relatively low cost of rearing. Beetles are the largest insect order, with their representative - Tribolium castaneum - being the first species with a completely sequenced genome, and seem to be emerging as new potential candidates for model organisms in various studies. Apart from T. castaneum, additional species representing various Coleoptera families, such as Nicrophorus vespilloides, Leptinotarsa decemlineata, Coccinella septempunctata, Poecilus cupreus, Tenebrio molitor and many others, have been used. They are increasingly often included in two major research aspects: biomedical and environmental studies. Biomedical studies focus mainly on unraveling mechanisms of basic life processes, such as feeding, neurotransmission or activity of the immune system, as well as on elucidating the mechanism of different diseases (neurodegenerative, cardiovascular, metabolic, or immunological) using beetles as models. Furthermore, pharmacological bioassays for testing novel biologically active substances in beetles have also been developed. It should be emphasized that beetles are a source of compounds with potential antimicrobial and anticancer activity. Environmental-based studies focus mainly on the development and testing of new potential pesticides of both chemical and natural origin. Additionally, beetles are used as food or for their valuable supplements. Different beetle families are also used as bioindicators. Another important research area using beetles as models is behavioral ecology studies, for instance, parental care. In this paper, we review the current knowledge regarding beetles as model organisms and their practical application in various fields of life science.

Tumor-Directed Therapeutic Targets in Cushing Disease

CONTEXT

The most frequent cause of endogenous hypercortisolism is Cushing disease (CD), a devastating condition associated with severe comorbidities and high mortality. Effective tumor-targeting therapeutics are limited.

DESIGN

Search in PubMed with key words "corticotroph" and "Cushing's disease" plus the name of the mentioned therapeutic agent and in associated references of the obtained papers. Additionally, potential therapeutics were obtained from ClinicalTrials.gov with a search for "Cushing disease."

RESULTS

At present, the tumor-targeted pharmacological therapy of CD is concentrated on dopamine agonists (cabergoline) and somatostatin analogs (pasireotide) with varying efficacy, escape from response, and considerable side effects. Preclinical studies on corticotroph pathophysiology have brought forward potential drugs such as retinoic acid, silibinin, and roscovitine, whose efficacy and safety remain to be determined.

CONCLUSIONS

For many patients with CD, effective tumor-targeted pharmacological therapy is still lacking. Coordinated efforts are pivotal in establishing efficacy and safety of novel therapeutics in this rare but devastating disease.

Safety and Efficacy of Subcutaneous Pasireotide in Patients With Cushing's Disease: Results From an Open-Label, Multicenter, Single-Arm, Multinational, Expanded-Access Study

Introduction: The efficacy and safety of subcutaneous (sc) pasireotide have been evaluated in a Phase III trial. Here, we report safety and efficacy results from a multinational, expanded-access study of pasireotide sc in patients with Cushing's disease (CD) in a real-world setting (clinicaltrials.gov, identifier: NCT01582061). Methods: Adults with active CD previously untreated with pasireotide were enrolled; pasireotide sc was initiated at 600 μg twice daily (bid; EU countries) or 900 μg bid (non-EU countries; 600 μg bid in patients with impaired glucose metabolism). Pasireotide dose could be adjusted in 300 μg increments/decrements to a maximum of 900 μg bid or minimum of 300 μg bid for sustained urinary free cortisol (UFC) normalization/tolerability issues. Primary objective: document the safety of pasireotide sc in patients with CD. Key secondary objectives: assess the proportion of patients with mean UFC (mUFC) not exceeding the upper limit of normal (ULN) and changes from baseline in clinical signs/symptoms and quality of life (QoL) to weeks 12, 24, and 48. Results: One hundred and four patients received pasireotide: female, n = 84 (80.8%); median duration of pasireotide exposure, 25.1 weeks; median (range) baseline mUFC, 321.2 nmol/24 h (142-10,920; 2.3 × ULN [1.0-79.2]). Forty (38.5%) patients completed the study. The most common reasons for premature discontinuation of pasireotide were unsatisfactory therapeutic effect (n = 26, 25.0%) and adverse events (AEs; n = 20, 19.2%). Drug-related grade 3/4 AEs or drug-related serious AEs (primary endpoint) were documented in 42 (40.4%) patients, most commonly diabetes mellitus (n = 12, 11.5%) and hyperglycemia (n = 8, 7.7%). All patients experienced ≥1 AE and most (n = 102; 98.1%) reported ≥1 drug-related AE; six (5.8%) patients discontinued treatment because of hyperglycemia-related AEs. At weeks 12, 24, and 48, respectively, 36/66 (54.5%), 22/46 (47.8%), and 9/21 (42.9%) evaluable patients had normalized mUFC levels. Clinical signs/symptoms and QoL were also improved. Conclusions: In an international, real-world, clinical-practice setting, pasireotide sc was generally well-tolerated (no new safety signals were identified), effectively reduced UFC (normalization in ~50% of evaluable patients) and improved clinical signs and QoL in patients with CD. While hyperglycemia-related AEs were common, consistent with previous studies, most were manageable, with <6% of patients discontinuing treatment because of these events.

Cell Cycle Regulators and Lineage-Specific Therapeutic Targets for Cushing Disease

Cell cycle proteins are critical to pituitary development, but their contribution to lineage-specific tumorigenesis has not been well-elucidated. Emerging evidence from in vitro human tumor analysis and transgenic mouse models indicates that G1/S-related cell cycle proteins, particularly cyclin E, p27, Rb, and E2F1, drive molecular mechanisms that underlie corticotroph-specific differentiation and development of Cushing disease. The aim of this review is to summarize the literature and discuss the complex role of cell cycle regulation in Cushing disease, with a focus on identifying potential targets for therapeutic intervention in patients with these tumors.