Pasireotide Responsiveness in Acromegaly Is Mainly Driven by Somatostatin Receptor Subtype 2 Expression

Predictors of biochemical response to somatostatin receptor ligands in acromegaly

Although predictors of response to first-generation somatostatin receptor ligands (fg-SRLs), and to a lesser extent to pasireotide, have been studied in acromegaly for many years, their use is still not recommended in clinical guidelines. Is there insufficient evidence to use them? Numerous biomarkers including various clinical, functional, radiological and molecular markers have been identified. The first ones are applicable pre-surgery, while the molecular predictors are utilized for patients not cured after surgery. In this regard, factors predicting a good response to fg-SRLs are specifically: low basal GH, a low GH nadir in the acute octreotide test, T2 MRI hypointensity, a densely granulated pattern, high immunohistochemistry staining for somatostatin receptor 2 (SSTR2), and E-cadherin. However, there is still a lack of consensus regarding which of these biomarkers is more useful or how to integrate them into clinical practice. With classical statistical methods, it is complex to define reliable and generalizable cut-off values for a single biomarker. The potential solution to the limitations of traditional methods involves combining systems biology with artificial intelligence, which is currently providing answers to such long-standing questions that may eventually be finally included into the clinical guidelines and make personalized medicine a reality. The aim of this review is to describe the current knowledge of the main fg-SRLs and pasireotide response predictors, discuss their current usefulness, and point to future directions in the research of this field.

Biomarkers of response to treatment in acromegaly

INTRODUCTION

Medical treatment of acromegaly is based in a `trial and error` approach. First-generation somatostatin receptor ligands (fg-SRL) are prescribed as first-line medical therapy to the vast majority of patients, despite lack of disease control in approximately 60% of patients. However, other drugs used in acromegaly treatment are available (cabergoline, pasireotide and pegvisomant).

AREAS COVERED

In this article, we review and discuss the biomarkers of response to medical treatment in acromegaly.

EXPERT OPINION

Biomarkers for fg-SRL that can already be applied in clinical practice are: gender, age, pretreatment GH and IGF-I levels, cytokeratin granulation pattern, and the expression of somatostatin receptor type 2. Using biomarkers of response could guide treatment towards precision medicine with greater efficacy and lower costs.

Prolactin and Growth Hormone Signaling and Interlink Focused on the Mammosomatotroph Paradigm: A Comprehensive Review of the Literature

Prolactin (PRL) and growth hormone (GH) are peptide hormones that bind to the class 1 cytokine receptor superfamily, a highly conserved cell surface class of receptors. Both hormones control their own secretion via a negative autocrine loop in their own mammosomatotroph, lactotroph or somatotroph. In this regard, GH and PRL are regulated by similar signaling pathways involving cell growth and hormone secretion. Thus, GH and PRL dysregulation and pituitary neuroendocrine tumor (PitNET) development may have common pathogenic pathways. Based on cell linage, lactotroph and somatotroph PitNETs come from pituitary-specific POU-class homeodomain transcription factor (Pit-1). Mammosomatotroph and plurihormonal PitNETs are a unique subtype of PitNETs that arise from a single-cell population of Pit-1 lineage. In contrast, mixed somatotroph-lactotroph PitNETs are composed of two distinct cell populations: somatotrophs and lactotrophs. Morphologic features that distinguish indolent PitNETs from locally aggressive ones are still unidentified, and no single prognostic parameter can predict tumor aggressiveness or treatment response. In this review, we aim to explore the latest research on lactotroph and somatotroph PitNETs, the molecular mechanisms involved in PRL and GH axis regulation and the signaling pathways involved in their aggressiveness, particularly focused on mammosomatotroph and mixed subtypes. Finally, we summarize epidemiological, clinical, and radiological features of these exceptional tumors. We aim to shed light, from basic to clinical settings, on new perspectives and scientific gaps in this field.

Prospect of acromegaly therapy: molecular mechanism of clinical drugs octreotide and paltusotine

Somatostatin receptor 2 (SSTR2) is highly expressed in neuroendocrine tumors and represents as a therapeutic target. Several peptide analogs mimicking the endogenous ligand somatostatin are available for clinical use, but poor therapeutic effects occur in a subset of patients, which may be correlated with subtype selectivity or cell surface expression. Here, we clarify the signal bias profiles of the first-generation peptide drug octreotide and a new-generation small molecule paltusotine by evaluating their pharmacological characteristics. We then perform cryo-electron microscopy analysis of SSTR2-Gi complexes to determine how the drugs activate SSTR2 in a selective manner. In this work, we decipher the mechanism of ligand recognition, subtype selectivity and signal bias property of SSTR2 sensing octreotide and paltusotine, which may aid in designing therapeutic drugs with specific pharmacological profiles against neuroendocrine tumors.

De-escalation treatment with pasireotide for acromegaly: a long-term experience

INTRODUCTION

Pasireotide long-acting release (LAR) is approved for second-line treatment of acromegaly. Starting pasireotide LAR 40 mg every 4 weeks is recommended and then up-titrate to 60 mg monthly in case of IGF-I uncontrolled levels. We present three patients treated with a de-escalation approach with pasireotide LAR. CASE 1: A 61-year-old female diagnosed with resistant acromegaly was treated with pasireotide LAR 60 mg every 28 days. When IGF-I reached the lower age range, therapy was decreased to pasireotide LAR 40 mg and then to 20 mg. In 2021 and 2022, IGF-I value remained within the normal range. CASE 2: A 40-year-old female diagnosed with resistant acromegaly underwent three neurosurgeries. In 2011, she was enrolled in the PAOLA study and assigned to pasireotide LAR 60 mg. Due to IGF-I overcontrol and radiological stability, therapy was downscaled to 40 mg in 2016 and to 20 mg in 2019. The patient developed hyperglycemia, which was treated with metformin. CASE 3: A 37-year-old male diagnosed with resistant acromegaly was treated with pasireotide LAR 60 mg in 2011. In 2018, therapy was decreased to 40 mg due to IGF-I overcontrol and in 2022 to 20 mg. He developed hyperglycemia, but HbA1c values remained under 48 nmol/L for 7 years.

CONCLUSION

De-escalation treatment with pasireotide LAR may allow a greater proportion of patients to achieve control of acromegaly, particularly in selected cases of clinically aggressive acromegaly potentially responsive to pasireotide (high IGF-I values, invasion of the cavernous sinuses, partial resistance to first-line somatostatin analogues and positive expression of somatostatin receptor 5). Another benefit may be IGF-I oversuppression overtime. The major risk seems to be hyperglycemia.

Second line treatment of acromegaly: Pasireotide or Pegvisomant?

Acromegaly is a chronic disease with an increased mortality in case of persistently active disease. The treatment of acromegaly is mainly based on the surgical resection of the GH secreting pituitary tumor and, in cases with persistent disease, on the medical therapy with first generation somatostatin analogues (first gen-SSAs). Data from national registries, meta-analysis and epidemiology studies showed that 24%-65% of acromegaly patients treated with first gen-SSA did not reach the control of disease, requiring second line therapies, as the second gen-SSAs and the GH receptor antagonist. According to the high efficacy of these treatments and their molecular mechanisms of action, the choice of second line therapies should be personalized. In this review, we summarize the evidence on clinical, molecular and morphological aspects that may predict the response to second line therapies, in order to integrate and translate in the clinical practice for a patient-tailored therapeutic approach.

Innovative therapeutics in acromegaly

Acromegaly is a systemic disease associated with increased morbidity and mortality that can be prevented with adequate disease control. Three modalities of treatment (surgery, medical treatment, and radiotherapy) are available; however, a significant proportion of patients still maintain disease activity despite treatment. Therefore, there is a need for innovations in the treatment of acromegaly that include changes in the current trial and error approach and the development of new drugs. In this review, we summarize the recent innovations in the treatment of acromegaly and address the future perspectives in this field.

Predictive Factors of Somatostatin Receptor Ligand Response in Acromegaly-A Prospective Study

CONTEXT

Somatostatin receptor ligands (SRLs) are the cornerstone medical treatments for acromegaly; however, many patients remain unresponsive to SRLs. Well-established predictive markers of response are needed.

OBJECTIVE

We aimed to explore the relationship between responsiveness to SRLs relative to somatostatin (SST)2A and 5 receptor expression, adenoma granularity, and T2-weighted magnetic resonance imaging (MRI) signal intensity (T2WSI).

METHODS

We conducted a multicentric, prospective, observational cohort study, in France. Forty-nine naïve patients (ie, patients without preoperative SRL treatment) with active acromegaly following surgery were treated with octreotide (group 1; n = 47), or pasireotide if uncontrolled under first-generation SRLs (group 2; n = 9). Data were collected at baseline and months 3 and 6. Biochemical measurements, immunohistochemistry studies, and MRI readings were centralized.

RESULTS

In group 1, IGF-I decrease from baseline to month 6 positively correlated with SST2A immunoreactive score (IRS), P = 0.01. Densely granulated/intermediate adenomas had a greater IGF-I and GH decrease under octreotide compared with sparsely granulated adenomas (P = 0.02 and P = 0.006, respectively), and expressed greater levels of SST2A (P < 0.001), coupled with lower levels of SST5 (P = 0.004). T2WSI changed between preoperative MRI and month 6 MRI in one-half of the patients. Finally, SST5 IRS was higher in preoperative hyperintense compared with preoperative hypointense adenomas (P = 0.04), and most sparsely granulated and most hyperintense adenomas expressed high SST5 levels.

CONCLUSION

We prospectively confirm that SST2A and adenoma granularity are good predictors of response to octreotide. We propose the IRS for scoring system harmonization. MRI sequences must be optimized to be able to use the T2WSI as a predictor of treatment response.

Partial response to first generation SSA guides the choice and predict the outcome of second line therapy in acromegaly

INTRODUCTION

Treatment of acromegaly resistant to first generation somatostatin analogues (first gen-SSA) is often difficult. We aimed to investigate the role of partial response and resistance to first gen-SSA in the choice of second line treatments and their outcomes.

PATIENTS AND METHODS

A retrospective and multicenter study was conducted on 100 SSA-resistant acromegaly patients and treated with Pasireotide Lar (Pasi-Lar), Peg-V in monotherapy (m-Peg-V) or in combination with first gen-SSA (c-Peg-V).

RESULTS

Thirty-three patients (33%) were treated with m-Peg-V, 36 (36%) with c-Peg-V and 31 with Pasi-Lar (31%). According to logistic regression, m-Peg-V was chosen in older patients (p = 0.01) and with not-invasive adenomas (p = 0.009), c-Peg-V therapy in younger patients (p = 0.001), with invasive adenomas (p = 0.02), Pasi-Lar was in invasive adenomas (p = 0.01) and in patients partially responsive to first-gen SSA (p = 0.01). At the last follow-up, 68 patients (68%) reached the acromegaly control: 22 with m-Peg-V (32.4%), 23 with c-Peg-V (33.8%) and 23 with Pasi-Lar (33.8%). Patients non-responsive to c-Peg-V had higher IGF-I levels (median 3.2 x ULN, IQR: 1.6, p &lt; 0.001) and required higher Peg-V dosage (median 30 mg/daily IQR: 10, p = 0.002) as compared to responsive patients (median IGF-I x ULN: 2.1 IQR: 1.4; median Peg-V dosage 20 mg/daily IQR: 10). All patients responsive to Pasi-Lar were partially responsive to first gen-SSAs (p = 0.02).

CONCLUSION

Our data showed that c-Peg-V and Pasi-Lar are chosen for the treatment of invasive tumors. The partial response to first gen-SSA seems to be the main determinant for the choice of Pasi-Lar and positively predicts the treatment outcome.

Digital quantification of somatostatin receptor subtype 2a immunostaining: a validation study

OBJECTIVE

The aim of this study was to develop an open-source and reproducible digital quantitative analysis (DIA) of somatostatin receptor subtype 2a (SST2) staining in formalin-fixed paraffin-embedded tissues of pancreatic neuroendocrine tumors (panNETs) and growth hormone (GH)-secreting pituitary adenomas (GHomas).

DESIGN

SST2 immunostaining of 18 panNETs and 39 GHomas was assessed using a novel DIA protocol and compared with a widely used semi-quantitative immunoreactivity score (IRS).

METHODS

The DIA software calculates the staining intensity/area and the percentage of positive cells (%PC). Four representative images were selected for each sample by two independent selectors (S1 and S2), with the analysis performed by two independent analyzers (A1 and A2). Agreement between observers was calculated using the concordance correlation coefficient (CCC).

RESULTS

In panNETs, the CCC ranged 0.935-0.977 for intensity/area and 0.942-0.983 for %PC. In GHomas, the CCC ranged 0.963-0.997 for intensity/area and 0.979-0.990 for %PC. In both panNETs and GHomas, the DIA staining intensity was strongly correlated with the IRS (Spearman rho: 0.916-0.969, P < 0.001), as well as the DIA %PC with the IRS %PC (Spearman rh: 0.826-0.881, P < 0.001). In GHomas, the biochemical response to somatostatin receptor ligands correlated with SST2 expression, evaluated both as DIA intensity/area (Spearman rho: -0.448 to -0.527, P = 0.007-0.004) and DIA %PC (Spearman rho: -0.558 to -0.644, P ≤ 0.001).

CONCLUSIONS

The DIA has an excellent inter-observer agreement and showed a strong correlation with the widely used semi-quantitative IRS. The DIA protocol is an open-source, highly reproducible tool and provides a reliable quantitative evaluation of SST2 immunohistochemistry.

Efficacy of lanreotide 120 mg primary therapy on tumour shrinkage and ophthalmologic symptoms in acromegaly after 1 month

INTRODUCTION

Few studies have attempted to evaluate the early efficacy of first-generation somatostatin analogues in somatotroph macroadenomas.

OBJECTIVE

To investigate the short-term efficacy of primary therapy with lanreotide 120 mg at 1 and 3 months on tumour shrinkage and ophthalmologic symptoms in newly diagnosed patients with acromegaly.

DESIGN AND PATIENTS

This single-centre retrospective study included 21 patients with de novo acromegaly resulting from pituitary macroadenoma, with optic chiasm compression (Grade ≤ 2) and/or cavernous sinus invasion, treated with a monthly injection of lanreotide 120 mg. Clinical, hormonal, ophthalmologic and magnetic resonance imaging scan evaluations were conducted after the first and the third months of treatment.

RESULTS

Tumour volume reduction was more pronounced at 1 month; mean volume change: -31.4 ± 19.5%, p < .0001 than between the first and third month of treatment; mean volume reduction: -20.6 ± 13.4%, p = .0009. The mean volume change between baseline and the third month was - 46.4 ± 21.6, (p < .0001). A significant volume reduction (≥25%) was observed in 61.9% of individuals (13/21) at the first month. Among 14 individuals with optic chiasm compression and visual field defects, visual field normalization or improvement were observed in seven cases (50%), stabilization in four cases (28.5%), and mild worsening in three cases (21.4%) at 1 month. The decrease in growth hormone and IGF-1 serum values was significant at 1 month.

CONCLUSIONS

Primary treatment with lanreotide 120 mg in patients with somatotroph macroadenomas provides early significant tumour shrinkage with rapid improvement of visual symptoms at the end of the first month in 50% of patients.

Pasireotide-resistant Refractory Cushing's Disease without Somatostatin Receptor 5 Expression

Pasireotide, which has a high affinity for somatostatin receptor (SSTR) 5, has attracted attention as a new treatment for refractory Cushing's disease. The patient was a 28-year-old man. He had refractory Cushing's disease and underwent multiple surgeries, radiotherapy, and medication therapy. An examination of the adenoma by immunohistochemistry revealed a low SSTR5 expression. An USP8 mutation was not detected by reverse transcription polymerase chain reaction. Although we administered pasireotide, it was ineffective. While a further investigation is necessary, the analysis of SSTR5 expression may support the prediction of the efficiency of pasireotide for Cushing's disease. We report this case as a useful reference when considering whether or not to use pasireotide for refractory corticotroph adenomas.

Diagnosis and Treatment of Acromegaly: An Update

Acromegaly is typically caused by a growth hormone-secreting pituitary adenoma, driving excess secretion of insulin-like growth factor 1. Acromegaly may result in a variety of cardiovascular, respiratory, endocrine, metabolic, musculoskeletal, and neoplastic comorbidities. Early diagnosis and adequate treatment are essential to mitigate excess mortality associated with acromegaly. PubMed searches were conducted using the keywords growth hormone, acromegaly, pituitary adenoma, diagnosis, treatment, pituitary surgery, medical therapy, and radiation therapy (between 1981 and 2021). The diagnosis of acromegaly is confirmed on biochemical grounds, including elevated serum insulin-like growth factor 1 and lack of growth hormone suppression after glucose administration. Pituitary magnetic resonance imaging is advised in patients with acromegaly to identify an underlying pituitary adenoma. Transsphenoidal pituitary surgery is generally first-line therapy for patients with acromegaly. However, patients with larger and invasive tumors (macroadenomas) are often not in remission postoperatively. Medical therapies, including somatostatin receptor ligands, cabergoline, and pegvisomant, can be recommended to patients with persistent disease after surgery. Select patients may also be candidates for preoperative medical therapy. In addition, primary medical therapy has a role for patients without mass effect on the optic chiasm who are unlikely to be cured by surgery. Clinical, endocrine, imaging, histologic, and molecular markers may help predict the response to medical therapy; however, confirmation in prospective studies is needed. Radiation therapy is usually a third-line option and is increasingly administered by a variety of stereotactic techniques. An improved understanding of the pathogenesis of acromegaly may ultimately lead to the design of novel, efficacious therapies for this serious condition.

Personalized Medical Treatment in Patients with Acromegaly: A Review

Acromegaly is associated with significant morbidity and mortality if not appropriately treated. In addition to insulin-like growth factor 1 (IGF-1) and growth hormone (GH) normalization, and tumor shrinkage, treatment goals include symptom relief, managing complications and improving quality of life. Surgical resection is a first-line treatment in most patients, with few being pretreated pre-operatively with medications. Somatostatin receptor ligands (SRLs), injectable and more recently oral capsules, have been the cornerstone of first-line medical therapy for persistent disease. However, several factors, including sparsely granulated adenomas, absent/low somatostatin receptor (SSTR2) status, imaging T2-hyperintensity, young age and aryl hydrocarbon receptor interacting protein mutations could predict first-generation SRL resistance. Patients with these characteristics may be better candidates for the GH receptor antagonist, pegvisomant, or in cases of large tumors the second-generation SRL, pasireotide. Combination therapy should be further pursued in patients who remain biochemically uncontrolled or have high remnant tumor after monotherapy. An efficacious and cost-effective pegvisomant dose-sparing effect of SRLs when used in combination has been demonstrated. With such a wide array of medical treatment options, it is increasingly important to tailor treatment to patients' unique characteristics as well as preferences, with a goal of personalizing management to achieve high quality outcomes.

Clinical, hormonal and pathomorphological markers of somatotroph pituitary neuroendocrine tumors predicting the treatment outcome in acromegaly

BACKGROUND

Transsphenoidal adenomectomy (TSS) of somatotroph pituitary neuroendocrine tumor (PitNET) is the first-line treatment of acromegaly. Pharmacological treatment is recommended if surgery is contraindicated or did not lead to disease remission. The choice of treatment best fitting each patient should be based on thorough investigation of patients' characteristics. The current analysis attempts to create a tool for personalized treatment planning.

AIM

This study aimed to assess whether clinical, biochemical, imaging and pathological characteristics can predict surgical remission and response to first-generation somatostatin receptor ligands (SRLs) and pasireotide-LAR in acromegaly.

PATIENTS AND METHODS

A retrospective study of 153 acromegaly patients, treated in the Department of Endocrinology in Bielanski Hospital in Warsaw, Poland was performed. Data on demographics, hormonal and imaging results, pathological evaluation, and treatment outcome was extracted from the Polish Acromegaly Registry collecting information from 11 endocrinology centers in Poland and analyzed.

RESULTS

Patients with surgical remission had lower GH and IGF-1 concentrations at diagnosis (median GH 5.5 µg/L [IQR: 3.1-16.0] vs. 19.9 µg/L [IQR: 9.8-42.4], p=<0.001 and mean IGF-1 3.1xULN ± SD=1.2 vs. 3.7xULN ± SD=1.2, p=0.007, respectively) and smaller tumors (median 12.5mm [IQR: 9-19] vs. 23mm [IQR: 18-30], p<0.001). These tumors were more often densely granulated (DG) (73.2% vs. 40.0%, p=0.001) with positive staining for alpha-subunit (α-SU) (58.3% vs. 35.5%, p=0.021) and lower Ki-67 index (p=0.002). Patients responding well to SRLs were more often male (55.6% vs 44.4%, p=0.026), presented lower GH concentration (median GH 17.2 µg/L [IQR: 6.2-29.0] vs. 23.8 µg/L [IQR: 11.2-49.5], p=0.048) and had more often DG tumors (63.0% vs. 14.3%, p<0.001). No significant differences between good and poor-response to pasireotide-LAR groups were found. In multivariate logistic regression analysis fasting GH concentration <8.63 µg/L, maximal tumor diameter <15.5mm, normoprolactinemia and DG tumor turned out to be independent predictors of surgical remission (OR=0.92, p=0.026; OR=0.87, p=0.069, OR=3.86, p=0.096 and OR=3.05, p=0.181, respectively). Fasting GH concentration <36.6 µg/L and DG tumor turned out to be independent predictors of good response to first-generation SRLs (OR=0.96, p=0.06 and OR=10.68, p=0.002, respectively).

CONCLUSIONS

Younger age at diagnosis, male sex, lower GH, IGF-1 and PRL concentrations, smaller tumor size at diagnosis as well as positive α-SU staining, lower Ki-67 index and DG tumors predicted better treatment outcome in acromegaly patients.

Complicated Clinical Course in Incipient Gigantism Due to Treatment-resistant Aryl Hydrocarbon Receptor–Interacting Protein–mutated Pediatric Somatotropinoma

Background

Our objective was to describe the clinical course and treatment challenges in a very young patient with a pituitary adenoma due to a novel aryl hydrocarbon receptor–interacting protein (AIP) gene mutation, highlighting the limitations of somatostatin receptor immunohistochemistry to predict clinical responses to somatostatin analogs in acromegaly.

Case Report

We report the case of a 7-year-old boy presenting with headache, visual field defects, and accelerated growth following failure to thrive. The laboratory results showed high insulin-like growth factor I (IGF-I) (standardised deviation scores ( +3.49) and prolactin levels (0.5 nmol/L), and magnetic resonance imaging identified a pituitary macroadenoma. Tumoral/hormonal control could not be achieved despite 3 neurosurgical procedures, each time with apparent total resection or with lanreotide or pasireotide. IGF-I levels decreased with the GH receptor antagonist pegvisomant. The loss of somatostatin receptor 5 was observed between the second and third tumor resection. In vitro, no effect on tumoral GH release by pasireotide (with/without cabergoline) was observed. Genetic analysis revealed a novel germline AIP mutation: p.Tyr202∗ (pathogenic; class 4).

Discussion

In vitro response of tumor tissue to somatostatin may better predict tumoral in vivo responses of somatostatin analogs than somatostatin receptor immunohistochemistry.

Conclusion

We identified a novel pathologic AIP mutation that was associated with incipient acrogigantism in an extremely young patient who had a complicated course of disease. Growth acceleration can be masked due to failure to thrive. Tumoral growth hormone release in vivo may be predicted with in vitro exposure to somatostatin receptor analogs, as it cannot be assumed that all AIP-mutated somatotropinomas respond well to pasireotide.

Drug resistance in pituitary tumours: from cell membrane to intracellular signalling

The pharmacological treatment of pituitary tumours is based on the use of stable analogues of somatostatin and dopamine. The analogues bind to somatostatin receptor types 2 and 5 (SST2 and SST5) and dopamine receptor type 2 (DRD2), respectively, and generate signal transduction cascades in cancerous pituitary cells that culminate in the inhibition of hormone secretion, cell growth and invasion. Drug resistance occurs in a subset of patients and can involve different steps at different stages, such as following receptor activation by the agonist or during the final biological responses. Although the expression of somatostatin and dopamine receptors in cancer cells is a prerequisite for these drugs to reach a biological effect, their presence does not guarantee the success of the therapy. Successful therapy also requires the proper functioning of the machinery of signal transduction and the finely tuned regulation of receptor desensitization, internalization and intracellular trafficking. The present Review provides an updated overview of the molecular factors underlying the pharmacological resistance of pituitary tumours. The Review discusses the experimental evidence that supports a role for receptors and intracellular proteins in the function of SSTs and DRD2 and their clinical importance.

Somatostatin Receptor Subtype Expression in Patients with Acromegaly and Complicated Clinical Course

Somatostatin analogues are considered to be the first line of treatment in acromegaly. Somatostatin analogues of the first generation mainly target the somatostatin receptor (SSTR) subtype 2 and have been proven efficient in the majority of patients with acromegaly. Pasireotide was the first somatostatin analogue also substantially targeting the SSTR subtype 5. An efficient drug for Cushing’s disease tailored to suboptimal-responding patients with acromegaly then became available. We immunohistochemically investigated SSTR subtypes expression in pituitary adenomas from operated acromegaly patients with clinical relapse and a complicated clinical course. Patients received pasireotide in the course of their disease. The predictive value of SSTR subtypes immunhistochemical analysis for the therapeutic response is discussed.

Octreotide and Pasireotide Combination Treatment in Somatotroph Tumor Cells: Predominant Role of SST2 in Mediating Ligand Effects

Simple Summary

First-generation somatostatin receptor ligands, such as octreotide, are the first-line medical therapy in acromegaly. Octreotide shows preferential binding for somatostatin receptor subtype 2 (SST₂), while the second-generation ligand, pasireotide, has high affinity for multiple SSTs. We aimed to elucidate whether pasireotide acts via other receptors than SST₂ in somatotroph tumors, and to investigate the potential role of the combination therapy octreotide plus pasireotide. We found that octreotide and pasireotide are superimposable in reducing GH secretion in cultured somatotroph tumor cells, as well as in inhibiting cell proliferation and intracellular pathway activity in rat GH4C1 cells (a model of somatotroph tumors). We did not find any additive/synergistic effect for the combination treatment. Furthermore, we observed that co-incubation with a SST₂-selective antagonist reversed the inhibitory effect of both compounds. Therefore, the two drugs act mainly via SST₂ in somatotroph tumor cells, and their combination is not superior to single agent treatment.

Abstract

First-generation somatostatin receptor ligands (fg-SRLs), such as octreotide (OCT), represent the first-line medical therapy in acromegaly. Fg-SRLs show a preferential binding affinity for somatostatin receptor subtype-2 (SST₂), while the second-generation ligand, pasireotide (PAS), has high affinity for multiple SSTs (SST₅ > SST₂ > SST₃ > SST₁). Whether PAS acts via SST₂ in somatotroph tumors, or through other SSTs (e.g., SST₅), is a matter of debate. In this light, the combined treatment OCT+PAS could result in additive/synergistic effects. We evaluated the efficacy of OCT and PAS (alone and in combination) on growth hormone (GH) secretion in primary cultures from human somatotroph tumors, as well as on cell proliferation, intracellular signaling and receptor trafficking in the rat GH4C1 cell line. The results confirmed the superimposable efficacy of OCT and PAS in reducing GH secretion (primary cultures), cell proliferation, cAMP accumulation and intracellular [Ca²⁺] increase (GH4C1 cells), without any additive effect observed for OCT+PAS. In GH4C1 cells, co-incubation with a SST₂-selective antagonist reversed the inhibitory effect of OCT and PAS on cell proliferation and cAMP accumulation, while both compounds resulted in a robust internalization of SST₂ (but not SST₅). In conclusion, OCT and PAS seem to act mainly through SST₂ in somatotroph tumor cells in vitro, without inducing any additive/synergistic effect when tested in combination.

New and emerging pharmacological treatment options for acromegaly

Introduction: Transsphenoidal surgery is the first-line treatment for acromegaly, but even in referral centers, approximately 50% of patients are not cured, and adjuvant pharmacological treatment is necessary. Widely used therapies encompass different drug classes, such as injectable somatostatin receptor ligands (SRLs), oral dopamine agonists and injectable growth hormone receptor antagonists, but approximately 40% of patients still have disease activity in real-life practice. Therefore, there is a need for new medical therapies to allow disease control in a larger proportion of patients, increase quality of life, reduce morbidity and mortality and improve treatment adherence in acromegaly.Areas covered: In this review, the authors cover new and emerging drugs under development or drugs recently approved for the treatment of acromegaly.Expert opinion: Disease control is essential to reduce morbidity and mortality in acromegaly but is still not achieved in a significant proportion of patients or takes a long time to be achieved with currently available options and treatment algorithms. Therefore, the development of new drugs as well as the establishment of biomarkers of disease control to allow precision medicine will improve treatment and outcomes in acromegaly.

A Pituitary Society update to acromegaly management guidelines

Guidelines and consensus statements ensure that physicians managing acromegaly patients have access to current information on evidence-based treatments to optimize outcomes. Given significant novel recent advances in understanding acromegaly natural history and individualized therapies, the Pituitary Society invited acromegaly experts to critically review the current literature in the context of Endocrine Society guidelines and Acromegaly Consensus Group statements. This update focuses on how recent key advances affect treatment decision-making and outcomes, and also highlights the likely role of recently FDA-approved therapies as well as novel combination therapies within the treatment armamentarium.

Novel therapies for acromegaly

Acromegaly is a systemic disease associated with increased morbidity and mortality. Most of these comorbidities can be prevented or delayed with adequate disease treatment. Although three modalities of treatment (surgery, medical treatment, and radiotherapy) are available and new drugs were approved in the last decades, there are still some patients that maintain disease activity despite treatment. Therefore, there is a need for novel therapies for acromegaly and for that purpose new formulations of currently used drugs and also new drugs are currently under study. In this review, we summarize the novel therapies for acromegaly.

Somatostatin receptor expression and patients' response to targeted medical treatment in pituitary tumors: evidences and controversies

BACKGROUND

Somatostatin receptors (SSTs) are widely co-expressed in pituitary tumors. SST₂ and SST₅ are the most represented SST subtypes. First-generation somatostatin receptor ligands (SRLs) mainly target SST₂, while pasireotide, a multi-receptor ligand, shows high binding affinity for both SST₅ and SST₂. Therefore, SRLs are routinely used as medical treatment for GH-, TSH-, and ACTH-secreting pituitary tumors.

METHODS

Critical revision of literature data correlating SST expression with patients' response to SRLs.

RESULTS

SST₂ expression in somatroph tumors directly correlates with GH and IGF-1 decrease after first-generation SRL treatment. SST₂ immunohistochemistry represents a valuable tool to predict biochemical response to first-generation SRLs in acromegalic patients. Pasireotide seems to exert its biological effects via SST₂ in unselected patients. However, in those subjects resistant to first-generation SRLs, harbouring tumors with negligible SST₂ expression, pasireotide can act throughout SST₅. More than somatotroph tumors, TSH-omas represent the paradigm of tumors showing a satisfactory response to SRLs. This is probably due to the high SST₂ expression observed in nearly 100% of cases, as well as to the balanced amount of SST₅. In corticotroph tumors, pasireotide mainly act via SST₅, although there is a need for translational studies correlating its efficacy with SST expression in this peculiar tumor histotype.

CONCLUSIONS

The assumption "more target receptor, more drug efficacy" is not straightforward for SRLs. The complex pathophysiology of SSTs, and the technical challenges faced to translate research findings into clinical practice, still need our full commitment to make receptor evaluation a worthwhile procedure for individualizing treatment decisions.

Expression of S100 proteins is associated with HBV intrauterine transmission

PURPOSE

The mechanisms underlying HBV intrauterine transmission remain unknown. In this study, we explored the mechanism of HBV intrauterine transmission by iTRAQ proteomics analysis.

METHODS

iTRAQ technology was applied to perform comparative proteomics studies on six HBV^+/+ neonates and six HBV^+/- neonates whose mothers and fathers were HBsAg positive and paternal HBsAg negative, respectively. The data obtained from the mass spectrometer were analyzed using MASCOT ( https://matrixscience.com ) to qualitatively and quantitatively compare the differentially expressed proteins in the two groups. Gene Ontology and KEGG pathway analyses were performed to analyze the differentially expressed proteins. The expressions of HBV intrauterine transmission-related proteins in serum samples and corresponding placental tissues were further verified by immunohistochemistry and Western Blot. Then, the human trophoblast cell line (Swan71) infected with HBV was used to analyze the potential mechanisms of HBV intrauterine transmission under the mediation of differential proteins.

RESULTS

A total of 35 differentially expressed proteins, including 17 up-regulated proteins and 18 down-regulated proteins, were identified by comparing serum protein expression levels in HBV^+/+ and HBV^+/- neonates. The differentially expressed proteins were mainly related to RAGE receptor binding, NF-kappa B transcription factor activity, innate immune response, defense response to bacterium, and the signaling pathway in pathogenic microorganism infection. The expressions of S100A8/9/12 in HBV^+/+ maternal placenta tissue were significantly increased. The expressions of S100A8/9/12 proteins in Swan71 cells were significantly increased after HBV infection.

CONCLUSION

High expression of S100 proteins may be associated with the intrauterine-transplacental transmission of HBV.

Potential markers of disease behavior in acromegaly and gigantism

Introduction: Acromegaly and gigantism entail increased morbidity and mortality if left untreated, due to the systemic effects of chronic GH and IGF-1 excess. Guidelines for the diagnosis and treatment of patients with GH excess are well established; however, the presentation, clinical behavior and response to treatment greatly vary among patients. Numerous markers of disease behavior are routinely used in medical practice, but additional biomarkers have been recently identified as a result of basic and clinical research studies.Areas covered: This review focuses on genetic, molecular and genomic features of patients with GH excess that have recently been linked to disease progression and response to treatment. A PubMed search was conducted to identify markers of disease behavior in acromegaly and gigantism. Markers already considered as part of routine studies in clinical care guidelines were excluded. Literature search was expanded for each marker identified. Novel markers not included or only partially covered in previously published reviews on the subject were prioritized.Expert opinion: Recognizing the most relevant markers of disease behavior may help the medical team tailoring the strategies for approaching each case of acromegaly and gigantism. This customized plan should make the evaluation, treatment and follow up process more efficient, greatly improving the patients' outcomes.

SST5 expression and USP8 mutation in functioning and silent corticotroph pituitary tumors

OBJECTIVE

Somatostatin receptor type 5 (SST5) is inconsistently expressed by corticotroph tumors, with higher expression found in corticotropinomas having ubiquitin-specific protease 8 (USP8) mutations. Aims were to study the correlation between characteristics of corticotropinomas and SST5 expression/USP8 mutation status and to describe the response to pasireotide in 5 patients.

DESIGN

Retrospective cohort study.

METHODS

Clinico-biochemical, radiological and pathological data of 62 patients, operated for a functioning or silent corticotropinoma between 2013 and 2017, were collected. SST5 expression was measured by immunohistochemistry (clone UMB-4, Abcam, IRS>1 being considered positive) and Sanger sequencing was performed on 50 tumors to screen for USP8 mutations.

RESULTS

SST5 expression was positive in 26/62 pituitary tumors. A moderate or strong IRS was found in 15/58 corticotropinomas and in 13/35 functioning corticotropinomas. Among functioning tumors, those expressing SST5 were more frequent in women (22/24 vs 9/15, P=0.04) and had a lower grade (P=0.04) compared to others. USP8 mutations were identified in 13/50 pituitary tumors and were more frequent in functioning compared to silent tumors (11/30 vs 2/20, P=0.05). SST5 expression was more frequent in USP8mut vs USP8wt tumors (10/11 vs 7/19, P=0.007). Among treated patients, normal urinary free cortisol levels were obtained in 3 patients (IRS 0, 2, 6) while a 4-fold decrease was observed in one patient (IRS 4).

CONCLUSION

SST5 expression appears to be associated with functioning, USP8mut and lower grade corticotropinomas. A correlation between SST5 expression or USP8mut and response to pasireotide remains to be confirmed.

Acromegaly in the elderly patient

Acromegaly is an insidious disease, usually resulting from growth hormone hypersecretion by a pituitary adenoma. It is most often diagnosed during the 3rd to 4th decade of life. However, recent studies have shown an increase in the incidence and prevalence of acromegaly in the elderly, probably due to increasing life expectancy. As in the younger population with acromegaly, there is a delay in diagnosis, aggravated by the similarities of the aging process with some of the characteristics of the disease. As can be expected elderly patients with acromegaly have a higher prevalence of comorbidities than younger ones. The diagnostic criteria are the same as for younger patients. Surgical treatment of the pituitary adenoma is the primary therapy of choice unless contraindicated. Somatostatin receptor ligands are generally effective as both primary and postoperative treatment. The prognosis correlates inversely with the patient's age, disease duration and last GH level. Arch Endocrinol Metab. 2019;63(6):638-45.

The position of combined medical treatment in acromegaly

Advances in combination medical treatment have offer new perspectives for acromegaly patients with persistent disease activity despite receiving the available medical monotherapies. The outcomes of combination medical treatment may reflect both additive and synergistic effects. This review focuses on combination medical treatment and its current position in acromegaly, based on clinical studies evaluating the efficacy and safety of combined medical treatment(s) and our own experiences with combination therapy. Arch Endocrinol Metab. 2019;63(6):646-52.

Pasireotide-LAR in acromegaly patients treated with a combination therapy: a real-life study

PURPOSE

Little data are available regarding the safety and efficacy of switching to Pasireotide-LAR monotherapy in acromegaly patients with partial resistance to first-generation somatostatin agonists (1gSRL) who require combination treatment with cabergoline or pegvisomant.

METHOD

In this monocentric prospective study within a tertiary university hospital, 15 consecutive acromegalic adults partially resistant to 1gSRL treated with octreotide LAR or lanreotide SR, and cabergoline (n = 4, 3.5 mg/week) or pegvisomant (n = 11, median dose 100 mg/week), were switched to Pasireotide-LAR (8 with 40 mg/month; 7 with 60 mg/month). Immunohistochemical expression level of SSTR5 and the granulation pattern of nine somatotroph adenomas were retrospectively determined to test for a correlation with the therapeutic efficacy of Pasireotide-LAR.

RESULTS

Median IGF-1 concentration at the first evaluation (median 3 months) was similar to baseline (1.0 vs 1.1 ULN). 11/15 patients had IGF-1 levels ≤1.3 ULN before and after the switch but individual changes were variable. Hyperglycemia was frequent and greater in diabetic patients. 7/15 patients stopped Pasireotide-LAR due to lack of control of IGF-1 or intolerance. 8/15 patients received Pasireotide-LAR for a median of 29 months with IGF-1 levels ≤1.3 ULN and acceptable glucose tolerance (median HbA1c 6.1%). Two patients required initiation of oral antidiabetic treatment. The intensity of SSTR5 expression and the granulation pattern of adenomas were of limited value for the prediction of Pasireotide-LAR effectiveness.

CONCLUSION

Pasireotide-LAR may represent a suitable therapeutic alternative in a subset of acromegalic patients requiring combination therapy involving a 1gSRL.

Invited Review: Pathology of pituitary neuroendocrine tumours: present status, modern diagnostic approach, controversies and future perspectives from a neuropathological and clinical standpoint

Neuroendocrine tumours of the adenohypophysis have traditionally been designated as pituitary adenomas to underline their usually indolent growth and lack of metastatic potential. However, they may demonstrate a huge spectrum of growth patterns and endocrine disturbances, some of them significantly affecting health and quality of life. To predict tumour growth, risk of postoperative recurrence and response to medical therapy in patients with pituitary neuroendocrine tumours is challenging. A thorough histopathological and immunohistochemical diagnostic work-up is an obligatory part of a multidisciplinary effort to precisely define the tumour type and assess prognostic and predictive factors on an individual basis. In this review, we have summarized the current status in the pathology in pituitary neuroendocrine tumours based on the selection of references from the PubMed database. We have presented possible diagnostic approaches according to the current pituitary cell lineage-based classification. The importance of recognizing histological subtypes with potentially aggressive behaviour and identification of prognostic and predictive tissue biomarkers have been highlighted. Controversies related to particular subtypes of pituitary tumours and a still limited prognostic impact of the current classification indicate the need for further refinement. Multidisciplinary approach including clinical, pathological and molecular genetic characterization will be essential for improved personalized therapy and the search for novel therapeutic targets in patients with pituitary neuroendocrine tumours.

The Treatment of Refractory Pituitary Adenomas

Refractory pituitary adenomas (PAs) are defined as aggressive-invasive PAs characterized by a high Ki-67 index, rapid growth, frequent recurrence, and resistance to conventional treatments. It is notoriously difficult to manage refractory PAs because the efficacy of current therapeutic options is limited. The purpose of this review is to address currently employed and promising therapeutic strategies for the treatment of refractory PAs. Except for prolactinomas, neurosurgery is the first-line option, but most refractory PAs often recur or re-grow after initial surgery and require further treatments. Medical therapy, radiotherapy and re-operation are explored when surgery has failed to completely resect tumors; however, refractory PAs are usually resistant to these treatments. As a salvage treatment, temozolomide (TMZ) has shown promising results and is currently used for all types of refractory PAs. However, not all refractory PAs are responsive to TMZ treatment, and some of these PAs are resistant to TMZ. Although targeted therapies such as vascular endothelial growth factor, epidermal growth factor and mTOR inhibitors have also been used to treat refractory PAs, the effectiveness of these targeted therapies is still not known due to a lack of data from randomized prospective trials. As a novel therapeutic method, cancer immunotherapy is a promising strategy for the treatment of refractory PAs, but further preclinical research and clinical trials are needed to assess the efficacy of this new approach. In summary, early identification and a multidisciplinary approach are required to treat refractory PAs.

Precision medicine in the treatment of acromegaly

Acromegaly is a chronic disorder usually diagnosed late in the disease evolution, leading to substantial morbidity and mortality related to this long period of undiagnosed state as well as the difficulty in achieving normalization of GH hypersecretion and controlling tumor mass. First generation somatostatin analogues (SSA) are accepted as the first-line medical therapy or as second-line therapy in patients undergoing unsuccessful surgery. However, because a high percentage of patients experience SSA treatment failure, the inclusion of biomarkers associated with a successful or non-successful response to these drug (as well as to all classes of medical therapy) is necessary to better guide the choice of treatment, potentially allowing for a quicker achievement of disease control. The current treatment algorithms for acromegaly are based upon a "trial and error" approach with additional treatment options provided when disease is not controlled. In many other diseases, their therapeutic algorithms have been evolving towards personalizing treatment with medication that best matches individual disease characteristics, using biomarkers that identify therapeutic response, thus allowing the personalization of the therapy. It is time to introduce this approach to acromegaly treatment algorithms. This paper reviews the potential tools for doing so.