Octreotide long-acting release (LAR): a review of its use in the management of acromegaly

Advance in peptide-based drug development: delivery platforms, therapeutics and vaccines

The successful approval of peptide-based drugs can be attributed to a collaborative effort across multiple disciplines. The integration of novel drug design and synthesis techniques, display library technology, delivery systems, bioengineering advancements, and artificial intelligence have significantly expedited the development of groundbreaking peptide-based drugs, effectively addressing the obstacles associated with their character, such as the rapid clearance and degradation, necessitating subcutaneous injection leading to increasing patient discomfort, and ultimately advancing translational research efforts. Peptides are presently employed in the management and diagnosis of a diverse array of medical conditions, such as diabetes mellitus, weight loss, oncology, and rare diseases, and are additionally garnering interest in facilitating targeted drug delivery platforms and the advancement of peptide-based vaccines. This paper provides an overview of the present market and clinical trial progress of peptide-based therapeutics, delivery platforms, and vaccines. It examines the key areas of research in peptide-based drug development through a literature analysis and emphasizes the structural modification principles of peptide-based drugs, as well as the recent advancements in screening, design, and delivery technologies. The accelerated advancement in the development of novel peptide-based therapeutics, including peptide-drug complexes, new peptide-based vaccines, and innovative peptide-based diagnostic reagents, has the potential to promote the era of precise customization of disease therapeutic schedule.

Octreotide versus Terlipressin as Adjuvant to Endoscopic Variceal Band Ligation in Bleeding Oesophageal Varices: A Systematic Review and Meta-Analysis

Background: Acute variceal bleeding (AVB) is a critical complication of portal hypertension, contributing significantly to mortality worldwide. Pharmacological interventions, including terlipressin and octreotide, have evolved to manage AVB, yet consensus on their comparative effectiveness remains elusive. This study conducts a comprehensive systematic review and meta-analysis of randomized control trials (RCTs) comparing terlipressin and octreotide in the management of AVB, aiming to provide insights into their relative benefits. Methods: This study included RCTs with head-to-head comparisons of terlipressin and octreotide. The search strategy covered PubMed, Scopus, and Cinahl databases, and the included studies involved adult patients with confirmed AVB undergoing endoscopic variceal band ligation (EVBL). Results: Seven RCTs meeting inclusion criteria were included in the meta-analysis. The assessed outcomes were: achieving haemostasis within 24 h, rebleeding rate, and mortality rate. The pooled analysis revealed no statistically significant differences between terlipressin and octreotide in achieving haemostasis (OR: 1.30, p = 0.23), rebleeding rates at 5 days (OR: 0.7, p = 0.23), and mortality at 42 days (OR: 0.9, p > 0.5). Conclusion: This meta-analysis suggests that terlipressin and octreotide exhibit similar efficacy in reducing bleeding, rebleeding rates, and mortality when used as adjuvants to EVBL in AVB. Clinicians are encouraged to consider individual patient characteristics and the broader clinical context when choosing between these agents. Future research should focus on addressing existing evidence gaps and enhancing understanding of variables influencing EVBL outcomes.

From biology to clinical practice: antiproliferative effects of somatostatin analogs in neuroendocrine neoplasms

Somatostatin analogs (SSA), specifically octreotide and lanreotide, have demonstrated antiproliferative effects in patients with neuroendocrine tumors (NET), a group of rare malignancies of diverse origin and presentation. A prominent feature of NET cells is the expression of G protein-coupled receptors called somatostatin receptors (SSTR). Although these SSTR are not uniformly present in NET, they can be instrumental in the diagnosis and treatment of NET. Apart from their application in nuclear imaging and radionuclide therapy, SSA have proven invaluable in the treatment of hormonal syndromes associated with certain NET (antisecretory effects of SSA), but it took more than two decades to convincingly demonstrate the antiproliferative effects of SSA in metastatic NET with the two pivotal studies PROMID and CLARINET. The current review summarizes three decades of SSA treatment and provides an overview of the clinical trial landscape for SSA monotherapy and combination therapy, including clinical implications and quality of life aspects, as well as ongoing fields of research.

Gastrointestinal Permeation Enhancers for the Development of Oral Peptide Pharmaceuticals

Recently, two oral-administered peptide pharmaceuticals, semaglutide and octreotide, have been developed and are considered as a breakthrough in peptide and protein drug delivery system development. In 2019, the Food and Drug Administration (FDA) approved an oral dosage form of semaglutide developed by Novo Nordisk (Rybelsus^®) for the treatment of type 2 diabetes. Subsequently, the octreotide capsule (Mycapssa^®), developed through Chiasma's Transient Permeation Enhancer (TPE) technology, also received FDA approval in 2020 for the treatment of acromegaly. These two oral peptide products have been a significant success; however, a major obstacle to their oral delivery remains the poor permeability of peptides through the intestinal epithelium. Therefore, gastrointestinal permeation enhancers are of great relevance for the development of subsequent oral peptide products. Sodium salcaprozate (SNAC) and sodium caprylate (C8) have been used as gastrointestinal permeation enhancers for semaglutide and octreotide, respectively. Herein, we briefly review two approved products, Rybelsus^® and Mycapssa^®, and discuss the permeation properties of SNAC and medium chain fatty acids, sodium caprate (C10) and C8, focusing on Eligen technology using SNAC, TPE technology using C8, and gastrointestinal permeation enhancement technology (GIPET) using C10.

Reprofiling of approved drugs against SARS-CoV-2 main protease: an in-silico study

Given the COVID-19 pandemic, currently, there are many drugs in clinical trials against this virus. Among the excellent drug targets of SARS-CoV-2 are its proteases (Nsp3 and Nsp5) that plays vital role in polyprotein processing giving rise to functional nonstructural proteins, essential for viral replication and survival. Nsp5 (also known as Mpro) hydrolyzes replicase polyprotein (1ab) at eleven different sites. For targeting Mpro, we have employed drug repurposing approach to identify potential inhibitors of SARS-CoV-2 in a shorter time span. Screening of approved drugs through docking reveals Hyaluronic acid and Acarbose among the top hits which are showing strong interactions with catalytic site residues of Mpro. We have also performed docking of drugs Lopinavir, Ribavirin, and Azithromycin on SARS-CoV-2 Mpro. Further, binding of these compounds (Hyaluronic acid, Acarbose, and Lopinavir) is validated by extensive molecular dynamics simulation of 500 ns where these drugs show stable binding with Mpro. We believe that the high-affinity binding of these compounds will help in designing novel strategies for structure-based drug discovery against SARS-CoV-2.Communicated by Ramaswamy H. Sarma.

Maintenance of response to oral octreotide compared with injectable somatostatin receptor ligands in patients with acromegaly: a phase 3, multicentre, randomised controlled trial

BACKGROUND

Despite biochemically responding to injectable somatostatin receptor ligands (iSRLs), many patients with acromegaly experience treatment burdens. We aimed to assess maintenance of biochemical response and symptomatic control with oral octreotide capsules versus iSRLs in patients with acromegaly who previously tolerated and responded to both.

METHODS

This global, open-label, randomised controlled phase 3 trial was done in 29 clinical sites in Austria, France, Germany, Hungary, Italy, Lithuania, Russia, Serbia, Spain, and the USA. Eligible patients were adults aged 18-75 years with acromegaly who were receiving iSRLs (long-acting octreotide or lanreotide autogel) for at least 6 months before baseline with a stable dose for at least 4 months, and were deemed to be biochemically responding (insulin-like growth factor I [IGF-I] <1·3 × upper limit of normal [ULN] and mean integrated growth hormone <2·5 ng/mL). In the 26-week run-in phase, all patients received oral octreotide (40 mg a day, optional titration to 60 or 80 mg a day). Eligibility for the randomised treatment phase was completion of the run-in phase as a biochemical responder (IGF-I <1·3 × ULN and mean integrated growth hormone <2·5 ng/mL at week 24) and investigator assessment of acromegaly being adequately controlled. Patients were randomly assigned (3:2) to oral octreotide capsules or iSRL at the same dose and interval as before enrolment. Randomisation and drug dispensing were conducted through a qualified randomisation service provider (eg, interactive web or voice response system). The primary endpoint was a non-inferiority assessment (margin -20 percentage points) of proportion of participants maintaining biochemical response throughout the randomised treatment phase (IGF-I <1·3 × ULN using time-weighted average; assessed by comparing the lower bound of the 2-sided 95% CI for the difference in biochemical response between groups). IGF-I was assessed once a month during the run-in and randomised treatment phases (single sample). Efficacy and safety assessments were performed on the randomised population. This trial is registered with ClinicalTrials.gov, NCT02685709.

FINDINGS

Between Feb 11, 2016, and Aug 20, 2020, 218 patients were assessed for eligibility. 72 patients were excluded, and 146 participants were enrolled into the run-in phase. 116 patients completed the run-in phase and 30 participants discontinued treatment. 92 participants were randomly assigned to oral octreotide (n=55) or iSRL (n=37). 50 (91%) of 55 participants who received oral octreotide (95% CI 44-53) and 37 (100%) of 37 participants who received iSRLs (34-37) maintained biochemical response. The lower bound of the 2-sided 95% CI for the adjusted difference in proportions between the two treatment groups achieved the prespecified non-inferiority criterion of -20% (95% CI -19·9 to 0·5). 19 (35%) of 55 participants in the oral octreotide group and 15 (41%) of 37 participants in the iSRL group had treatment-related adverse events; the most common of which in both groups were gastrointestinal.

INTERPRETATION

Oral octreotide was non-inferior to iSRL treatment, and might be a favourable alternative to iSRLs for many patients with acromegaly.

FUNDING

Chiasma.

TRANSLATION

For the Russian translation of the abstract see Supplementary Materials section.

Octreotide-Resistant Acromegaly: Challenges and Solutions

Acromegaly is a rare and severe disease caused by an increased and autonomous secretion of growth hormone (GH), thus resulting in high circulating levels of insulin-like growth factor 1 (IGF-1). Comorbidities and mortality rate are closely related to the disease duration. However, in most cases achieving biochemical control means reducing or even normalizing mortality and restoring normal life expectancy. Current treatment for acromegaly includes neurosurgery, radiotherapy and medical therapy. Transsphenoidal surgery often represents the recommended first-line treatment. First-generation somatostatin receptor ligands (SRLs) are the drug of choice in patients with persistent disease after surgery and are suggested as first-line treatment for those ineligible for surgery. However, only about half of patients treated with octreotide (or lanreotide) achieve biochemical control. Other available drugs approved for clinical use are the second-generation SRL pasireotide, the dopamine agonist cabergoline, and the GH-receptor antagonist pegvisomant. In the present paper, we revised the current literature about the management of acromegaly, aiming to highlight the most relevant and recent therapeutic strategies proposed for patients resistant to first-line medical therapy. Furthermore, we discussed the potential molecular mechanisms involved in the variable response to first-generation SRLs. Due to the availability of different medical therapies, the choice for the most appropriate drug can be currently based also on the peculiar clinical characteristics of each patient.

Octreotide-LAR in later-stage autosomal dominant polycystic kidney disease (ALADIN 2): A randomized, double-blind, placebo-controlled, multicenter trial

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent genetically determined renal disease. In affected patients, renal function may progressively decline up to end-stage renal disease (ESRD), and approximately 10% of those with ESRD are affected by ADPKD. The somatostatin analog octreotide long-acting release (octreotide-LAR) slows renal function deterioration in patients in early stages of the disease. We evaluated the renoprotective effect of octreotide-LAR in ADPKD patients at high risk of ESRD because of later-stage ADPKD.

METHODS AND FINDINGS

We did an internally funded, parallel-group, double-blind, placebo-controlled phase III trial to assess octreotide-LAR in adults with ADPKD with glomerular filtration rate (GFR) 15-40 ml/min/1.73 m2. Participants were randomized to receive 2 intramuscular injections of 20 mg octreotide-LAR (n = 51) or 0.9% sodium chloride solution (placebo; n = 49) every 28 days for 3 years. Central randomization was 1:1 using a computerized list stratified by center and presence or absence of diabetes or proteinuria. Co-primary short- and long-term outcomes were 1-year total kidney volume (TKV) (computed tomography scan) growth and 3-year GFR (iohexol plasma clearance) decline. Analyses were by modified intention-to-treat. Patients were recruited from 4 Italian nephrology units between October 11, 2011, and March 20, 2014, and followed up to April 14, 2017. Baseline characteristics were similar between groups. Compared to placebo, octreotide-LAR reduced median (95% CI) TKV growth from baseline by 96.8 (10.8 to 182.7) ml at 1 year (p = 0.027) and 422.6 (150.3 to 695.0) ml at 3 years (p = 0.002). Reduction in the median (95% CI) rate of GFR decline (0.56 [-0.63 to 1.75] ml/min/1.73 m2 per year) was not significant (p = 0.295). TKV analyses were adjusted for age, sex, and baseline TKV. Over a median (IQR) 36 (24 to 37) months of follow-up, 9 patients on octreotide-LAR and 21 patients on placebo progressed to a doubling of serum creatinine or ESRD (composite endpoint) (hazard ratio [HR] [95% CI] adjusted for age, sex, baseline serum creatinine, and baseline TKV: 0.307 [0.127 to 0.742], p = 0.009). One composite endpoint was prevented for every 4 treated patients. Among 63 patients with chronic kidney disease (CKD) stage 4, 3 on octreotide-LAR and 8 on placebo progressed to ESRD (adjusted HR [95% CI]: 0.121 [0.017 to 0.866], p = 0.036). Three patients on placebo had a serious renal cyst rupture/infection and 1 patient had a serious urinary tract infection/obstruction, versus 1 patient on octreotide-LAR with a serious renal cyst infection. The main study limitation was the small sample size.

CONCLUSIONS

In this study we observed that in later-stage ADPKD, octreotide-LAR slowed kidney growth and delayed progression to ESRD, in particular in CKD stage 4.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01377246; EudraCT: 2011-000138-12.

Medical Treatment with Somatostatin Analogues in Acromegaly: Position Statement

The Korean Endocrine Society (KES) published clinical practice guidelines for the treatment of acromegaly in 2011. Since then, the number of acromegaly cases, publications on studies addressing medical treatment of acromegaly, and demands for improvements in insurance coverage have been dramatically increasing. In 2017, the KES Committee of Health Insurance decided to publish a position statement regarding the use of somatostatin analogues in acromegaly. Accordingly, consensus opinions for the position statement were collected after intensive review of the relevant literature and discussions among experts affiliated with the KES, and the Korean Neuroendocrine Study Group. This position statement includes the characteristics, indications, dose, interval (including extended dose interval in case of lanreotide autogel), switching and preoperative use of somatostatin analogues in medical treatment of acromegaly. The recommended approach is based on the expert opinions in case of insufficient clinical evidence, and where discrepancies among the expert opinions were found, the experts voted to determine the recommended approach.

Cyclic Peptides that Govern Signal Transduction Pathways: From Prokaryotes to Multi-Cellular Organisms

Cyclic peptide scaffolds are key components of signal transduction pathways in both prokaryotic and eukaryotic organisms since they act as chemical messengers that activate or inhibit specific cognate receptors. In prokaryotic organisms these peptides are utilized in non-essential pathways, such as quorum sensing, that are responsible for virulence and pathogenicity. In the more evolved eukaryotic systems, cyclic peptide hormones play a key role in the regulation of the overall function of multicellular organisms, mainly through the endocrine system. This review will highlight several prokaryote and eukaryote systems that use cyclic peptides as their primary signals and the potential associated with utilizing these scaffolds for the discovery of novel therapeutics for a wide range of diseases and illnesses.

Octreotide-periplocymarin conjugate prodrug for improving targetability and anti-tumor efficiency: synthesis, in vitro and in vivo evaluation

Cardiac glycosides could increase intracellular Ca²⁺ ion by inhibiting the Na⁺/K⁺ATPase to induce apoptosis in many tumor cells. However, narrow therapeutic index, poor tumor selectivity and severe cardiovascular toxicity hinder their applications in cancer treatment. To improve the safety profile and tumor targetablility of cardiac glycosides, we designed octreotide conjugated periplocymarin, a cardiac glycoside isolated from Cortex periplocae. The conjugate showed higher cytotoxicity on MCF-7 cells and HepG2 tumor cells (SSTRs overexpression) but much less toxicity in L-02 normal cells. Tissue distribution studies of the conjugate using H₂₂ tumor model in mice showed higher accumulation in tumor and lower distribution in heart and liver than periplocymarin. Furthermore, in vivo anticancer effects of the conjugate on mice bearing H₂₂ cancer xenografts confirmed enhanced anti-tumor efficacy and decreased systemic toxicity. Altogether, octreotide-conjugated periplocymarin demonstrated tumor selectivity and may be useful as a targeting agent to improve the safety profile of cardiac glycosides for cancer therapy.

Progress in the formulation and delivery of somatostatin analogs for acromegaly

A 14 amino acid cystin bridge containing neuropeptide was discovered in 1973 and designated as growth hormone-inhibiting hormone, in other words, somatostatin. Its discovery led to the synthesis of three analogs which were licensed for the treatment of acromegaly: octreotide, lanreotide and pasireotide. Somatostatin analogs are currently approved only as either subcutaneous or intramuscular long-acting injections. We examine the challenges that must be overcome to create oral formulations of somatostatin analogs and examine selected clinical trial data. While octreotide has low intestinal permeability, similar to almost all other peptides, it has an advantage of being more stable against intestinal peptidases. The development of new oral formulation strategies may eventually allow for the successful oral administration of potent somatostatin analogs with high therapeutic indices.

Somatostatin analogues in acromegaly and gastroenteropancreatic neuroendocrine tumours: past, present and future

Acromegaly is a hormonal disorder that arises when the pituitary gland secretes excess growth hormone (GH), which in turn stimulates a concomitant increase in serum insulin-like growth factor 1 (IGF-1) levels. Gastroenteropancreatic neuroendocrine tumours (GEP-NET) constitute a heterogeneous group of tumours that can secrete serotonin and a variety of peptide hormones that may cause characteristic symptoms known as carcinoid syndrome or other symptoms and hormonal hypersecretion syndromes depending on the tumour's site of origin. Current medical therapy for the treatment of acromegaly and GEP-NET involves the administration of somatostatin analogues that effectively suppress excess hormone secretion. After its discovery in 1979, octreotide became the first synthetic biologically stable somatostatin analogue with a short-acting formulation of octreotide introduced into clinical practice in the late 1980s. Lanreotide, another somatostatin analogue, became available in the mid-1990s initially as a prolonged-release formulation administered every 10 or 14 days. Long-acting release formulations of both octreotide (Sandostatin LAR and Novartis) and lanreotide (Somatuline Autogel, Ipsen), based on microparticle and nanoparticle drug-delivery technologies, respectively, were later developed, which allowed for once-monthly administration and improved convenience. First-generation somatostatin analogues remain one of the cornerstones of medical therapy in the management of pituitary and GEP-NET hormone hypersecretion, with octreotide having the longest established efficacy and safety profile of the somatostatin analogue class. More recently, pasireotide (Signifor), a next-generation multireceptor-targeted somatostatin analogue, has emerged as an alternative therapeutic option for the treatment of acromegaly. This review summarizes the development and clinical success of somatostatin analogues.

The effect of somatostatin analogs on vitamin D and calcium concentrations in patients with acromegaly

PURPOSE

The goals of this study were to determine: (1) 25OH vitamin D (25OHD) and calcium levels in patients with acromegaly and their association with insulin-like growth factor (IGF-1) and (2) whether somatostatin analog (SSA) therapy effects calcium and 25OHD levels.

METHODS

125 patients with acromegaly were studied. Serum calcium and 25OHD levels were compared prior to and after vitamin D supplementation between patients receiving versus not receiving SSA in whom medical therapy included pegvisomant and/or dopamine agonists. Calcium and 25OHD levels were also evaluated longitudinally prior to and during short-term (mean 3 months, range 1-5) and long-term (mean 49 months, range 7-180) SSA administration. Vitamin D2 50,000 units weekly were given to 3 patients in the cross sectional and 1 in the longitudinal group; 400-4,000 units/day of D3 were given to 11 and 5 in respective groups.

RESULTS

In patients with a comparable mean IGF-1 index and season of testing, mean serum levels of 25OHD prior to vitamin D supplementation did not differ in patients receiving versus not receiving SSA (30 ± 3 vs. 30 ± 1 ng/ml, p = 0.99) and the prevalence of vitamin D sufficiency was similar between SSA and non SSA groups (42 vs. 57%, p = 0.20), prior to vitamin D supplementation. In patients with a comparable mean IGF-1 index and season of testing, mean serum 25OHD levels in patients increased after vitamin D supplementation in both those who were (37 ± 2 ng/ml, N = 23, p = 0.007) and were not receiving SSA (35 ± 1 ng/ml, N = 69, p = 0.005) compared to pre-D supplementation levels but were not different between these groups, p = 0.95) after D supplementation. Calcium and albumin were normal throughout longitudinal follow up. Calcium correlated with IGF-1 index (ρ = 0.29, p = 0.001, N = 125). In the longitudinal subset, serum calcium decreased transiently, in patients receiving short-term SSA (pretreatment 9.9 ± 0.1 mg/dl vs. short-term SSA 9.5 ± 0.1, p = 0.004). After long-term SSA therapy, calcium increased compared to levels on short-term therapy (9.8 ± 0.1 mg/dl vs. 9.5 ± 0.1, p = 0.017) and were unchanged compared to baseline. Mean vitamin D levels were sufficient at baseline prior to SSA therapy (33 ± 5.0 ng/ml), and did not change during short term (29 ± 6 ng/ml, p = 0.85) and long term SSA therapy (35 ± 5 ng/ml, p = 0.43).

CONCLUSIONS

Prior to and after vitamin D supplementation, patients with acromegaly receiving long-term SSA had vitamin D levels similar to those receiving other therapies, suggesting that long-term SSA therapy does not affect serum vitamin D. However, given the limitations of this retrospective study, further prospective studies evaluating the impact of SSA on vitamin D levels are necessary to confirm these findings definitively. Calcium levels are positively associated with IGF-1 index in patients with acromegaly. There is a transient decrease in calcium levels with short-term SSA use. The acute effect of SSA on calcium does not appear to be mediated by albumin, 25OHD or PTH and resolves with long-term SSA treatment. The transient decrease in calcium with short-term SSA use resolved with long-term SSA therapy.

Implications of Somatostatin Analogues in the Treatment of Acromegaly

Octreotide has an important role in the medical management of acromegaly. Its place in the management of acromegaly as an adjuvant therapy after neurosurgery is well established with a well-demonstrated efficacy. It can also be used in certain clinical conditions as a neoadjuvant treatment. Clinicians and patients should be aware of the possible side effects of octreotide treatment.

Oxalate nephropathy induced by octreotide treatment for acromegaly: a case report

Introduction

Oxalate nephropathy has various etiologies and remains a rare cause of renal failure. To the best of our knowledge, we report the first case of oxalate nephropathy following octreotide therapy.

Case presentation

We report the case of a 78-year-old Caucasian man taking chronic octreotide treatment for acromegaly who presented with acute oxalate nephropathy after antibiotic therapy. The diagnosis was confirmed by urinary analysis and a kidney biopsy. The recovery of renal function was favorable after hydration and withdrawal of octreotide therapy.

Conclusions

Oxalate nephropathy should be suspected in patients at risk who present with acute kidney injury after prolonged antibiotic treatment. This diagnosis should be distinguished from immuno-allergic interstitial nephritis and requires specific care. The evolution of this condition may be favorable if the pathology is identified correctly. Octreotide therapy should be considered a risk factor for enteric oxaluria.

Medical therapy in acromegaly

Acromegaly is a rare disease characterized by excess secretion of growth hormone (GH) and increased circulating insulin-like growth factor 1 (IGF-1) concentrations. The disease is associated with increased morbidity and premature mortality, but these effects can be reduced if GH levels are decreased to <2.5 μg/l and IGF-1 levels are normalized. Therapy for acromegaly is targeted at decreasing GH and IGF-1 levels, ameliorating patients' symptoms and decreasing any local compressive effects of the pituitary adenoma. The therapeutic options for acromegaly include surgery, radiotherapy and medical therapies, such as dopamine agonists, somatostatin receptor ligands and the GH receptor antagonist pegvisomant. Medical therapy is currently most widely used as secondary treatment for persistent or recurrent acromegaly following noncurative surgery, although it is increasingly used as primary therapy. This Review provides an overview of current and future pharmacological therapies for patients with acromegaly.

Place of cabergoline in acromegaly: a meta-analysis

CONTEXT

Cabergoline is widely considered to be poorly effective in acromegaly.

OBJECTIVE

The aim of this study was to obtain a more accurate picture of the efficacy of cabergoline in acromegaly, both alone and in combination with somatostatin analogs.

DESIGN

We systematically reviewed all trials of cabergoline therapy for acromegaly published up to 2009 in four databases (PubMed, Pascal, Embase, and Google Scholar). We identified 15 studies (11 prospective) with a total of 237 patients; none were randomized or placebo-controlled. A meta-analysis was conducted on individual data (n = 227).

RESULTS

Cabergoline was used alone in nine studies. Fifty-one (34%) of the 149 patients achieved normal IGF-I levels. In multivariate analysis, the decline in IGF-I was related to the baseline IGF-I concentration (β = 1.16; P <0.001), treatment duration (β = 0.28; P < 0.001), and baseline prolactin concentration (β = -0.18; P = 0.01), and with a trend toward a relation with the cabergoline dose (β = 0.38; P =0.07). In five studies, cabergoline was added to ongoing somatostatin analog treatment that had failed to normalize IGF-I. Forty patients (52%) achieved normal IGF-I levels. The change in IGF-I was significantly related to the baseline IGF-I level (β = 0.74; P < 0.001) but not to the dose of cabergoline, the duration of treatment, or the baseline prolactin concentration.

CONCLUSION

This meta-analysis suggests that cabergoline single-agent therapy normalizes IGF-I levels in one third of patients with acromegaly. When a somatostatin analog fails to control acromegaly, cabergoline adjunction normalizes IGF-I in about 50% of cases. This effect may occur even in patients with normoprolactinemia.

Resistance to somatostatin analogs in acromegaly

Somatostatin analogs (SA) are widely used in acromegaly, either as first-line or adjuvant treatment after surgery. First-line treatment with these drugs is generally used in the patients with macroadenomas or in those with clinical conditions so severe as to prevent unsafe reactions during anesthesia. Generally, the response to SA takes into account both control of GH and IGF-I excess, with consequent improvement of clinical symptoms directly related to GH and IGF-I excess, and tumor shrinkage. This latter effect is more prominent in the patients treated first-line and bearing large macroadenomas, but it is also observed in patients with microadenomas, even with little clinical implication. Predictors of response are patients' gender, age, initial GH and IGF-I levels, and tumor mass, as well as adequate expression of somatostatin receptor types 2 and 5, those with the highest affinity for octreotide and lanreotide. Only sporadic cases of somatostatin receptor gene mutation or impaired signaling pathways have been described in GH-secreting tumors so far. The response to SA also depends on treatment duration and dosage of the drug used, so that a definition of resistance based on short-term treatments using low doses of long-acting SA is limited. Current data suggest that response to these drugs is better analyzed taking together biochemical and tumoral effects because only the absence of both responses might be considered as a poor response or resistance. This latter evidence seems to occur in 25% of treated patients after 12 months of currently available long-acting SA.

Octreotide long-acting release (LAR): a review of its use in the management of acromegaly

Octreotide long-acting release (LAR) [Sandostatin LAR] is a somatostatin analogue with a well established clinical profile in patients with acromegaly. It binds to somatostatin receptor subtypes 2 and 5 with high potency to reduce the production and secretion of growth hormone (GH) and insulin-like growth factor (IGF)-I. Octreotide LAR is administered intramuscularly once every 28 days, in contrast to the subcutaneous formulation which requires administration two to three times daily. In several noncomparative trials, octreotide LAR was effective as primary therapy in normalizing GH and IGF-I levels and reducing tumour volume in patients with acromegaly. In addition, no significant difference was seen between octreotide LAR and surgery or lanreotide long-acting (LA) or lanreotide Autogel(R) (ATG) in small, randomized or observational, primary therapy trials. In another small, randomized trial, preoperative octreotide LAR followed by surgery was no more effective than surgery alone in terms of normalizing IGF-I levels, except in patients with macroadenoma. Octreotide LAR has also demonstrated good efficacy as postoperative adjuvant therapy, alone or in combination with pegvisomant, in randomized or noncomparative trials. In patients with different treatment histories (mixed populations), the efficacy of octreotide LAR appears to be generally similar to that of lanreotide ATG and greater than that of lanreotide LA, according to data from switching or crossover studies. Also in mixed populations, the efficacy of octreotide LAR was not significantly different to that of pegvisomant in terms of normalizing IGF-I levels in a randomized trial, and octreotide LAR demonstrated good efficacy in combination with cabergoline in a small, sequential-treatment trial. Octreotide LAR was generally well tolerated in clinical trials, with the most commonly occurring adverse events being gastrointestinal or hepatobiliary in nature. Thus, octreotide LAR continues to be a valuable option in the treatment of acromegaly.

Magnetic resonance imaging as a predictor of response to somatostatin analogs in acromegaly after surgical failure

CONTEXT

Transsphenoidal surgery is considered first-line therapy for acromegaly; however, there is often a need for adjunctive therapy. Somatostatin analogs (SSA) have greatly improved the effectiveness of medical treatment, but one third of patients are resistant.

OBJECTIVE

The aim was to evaluate whether magnetic resonance imaging (MRI) signal could predict long-term response to SSA in patients with active acromegaly after neurosurgery.

PATIENTS AND METHODS

Sixty-two patients who were active acromegalic after surgery were included in this retrospective study. Remaining pituitary tumor was classified as hyper-, iso-, or hypointense by evaluating T2-weighted MRI signal. Treatment with SSA at maximal effective doses was prescribed and evaluated at 6 and 12 months by monitoring IGF-I, GH, and T2 MRI.

RESULTS

Complete response to SSA treatment (defined as normal IGF-I) at 6 months was observed in 30%, partial response (defined as IGF-I between 2 and 3 sd score) in 15%, and no response in 55% of patients. At 12 months, 28, 20, and 52% were observed, respectively. MRI signal was hypointense in 40%, hyperintense in 48%, and isointense in 12%. At 6 months, complete response to SSA was observed in 71% of cases having hypointense MRI signal and in 20% of hyperintense (P = 0.04). At 12 months, 62% of hypointense remained well controlled, whereas in the hyperintense group, good, partial, or no response results did not change from that observed at 6 months (P = 0.04).

CONCLUSION

In active acromegalic patients after surgery, a hypointense T2-weighted MRI signal is associated with a better response to SSA treatment at 6 and 12 months.

NANETS treatment guidelines: well-differentiated neuroendocrine tumors of the stomach and pancreas

Well-differentiated neuroendocrine tumors (NETs) of the stomach and pancreas represent 2 major subtypes of gastrointestinal NETs. Historically, there has been little consensus on the classification and management of patients with these tumor subtypes. We provide an overview of well-differentiated NETs of the stomach and pancreas and describe consensus guidelines for the treatment of patients with these malignancies.

Somatostatin and somatostatin receptors: implications for neoplastic growth and cancer biology

Somatostatin agonists (SM-As) are capable of achieving durable symptomatic relief and significant clinical responses in certain tumours. Herein, we review the diverse direct and indirect mechanisms of antineoplastic activity elicited by SM-As as well as the hurdles that complicate their use as monotherapies in a broader range of malignancies. Emphasis is placed on recent clinical attempts to neutralise the IGF-mediated survival factor effects in the bone metastasis microenvironment in advanced prostate cancer. The first clinical trials of this 'anti-survival factor manipulation' strategy utilised the ability of SM-As to suppress the growth hormone-dependent liver-derived IGF-I bioavailability in combination with other drugs, such as dexamethasone, zolendronate and oestrogens, acting systemically and at the bone metastasis microenvironment. These regimens restored androgen ablation responsiveness in stage D3 prostate cancer patients and successfully produced objective clinical responses while only mild toxicities were observed. Furthermore, we focus on the preclinical experimental data of a targeted SM-A coupled to the super-potent doxorubicin derivative AN-201. The resulting conjugate (AN-238) has shown increased antitumour potency with a favourable toxicity profile. The potential use of novel SM-As as anticancer drugs is discussed in relation to data suggesting other direct and indirect treatment approaches pertaining to the somatostatin system.

Medical therapy of acromegaly: efficacy and safety of somatostatin analogues

Acromegaly is a chronic disease with signs and symptoms due to growth hormone (GH) excess. The most frequent cause of acromegaly is a GH-producing pituitary adenoma. Chronic GH excess is accompanied by long-term complications of the locomotor (arthrosis) and cardiovascular (atherosclerosis, cardiomyopathy) systems and is, when untreated, associated with an increased mortality. The aim of treatment of acromegaly is to improve symptoms, to achieve local tumour mass control, and to decrease morbidity and mortality. Treatment options include surgery, medical therapy and radiotherapy. Transsphenoidal surgery is the first choice of treatment when a definitive cure can be achieved, particularly in the case of microadenomas and when decompression of surrounding structures (optic chiasm, ophthalmic motor nerves) is indicated. Primary medical therapy has been increasingly applied in recent years, especially when a priori chances of surgical cure are low (because of adenoma size and localization) and in patients with advanced age and/or serious co-morbidity. In addition, preoperative primary medical therapy may result in tumour shrinkage, facilitating tumour resection, and may reduce perioperative complications due to GH excess. Within the spectrum of medical therapy, long-acting somatostatin analogues (somatostatins) are considered as first-line treatment. Treatment with somatostatin analogues results in GH control in approximately 60% of patients. In addition, somatostatin analogues induce tumour shrinkage in 30-50% of patients, particularly when applied as primary therapy. Prolonged treatment with somatostatin analogues appears to be safe and is usually well tolerated. The currently available somatostatin analogues, octreotide and lanreotide, seem to be equally effective; however, this should still be evaluated in prospective, randomized trials evaluating efficacy with respect to GH control and tumour shrinkage. In patients with an insufficient clinical and biochemical response to somatostatin analogues, combination therapy with dopamine receptor agonists or the GH receptor antagonist pegvisomant usually leads to disease control. New developments in the medical therapy of acromegaly include the universal somatostatin receptor agonist pasireotide, which has a broader affinity for all somatostatin receptor (sst) subtypes compared with the currently available somatostatin analogues with preferential affinity for the sst2 receptor, and chimeric compounds that interact with both somatostatin and dopamine receptors with synergizing effects on GH secretion.

From somatostatin to octreotide LAR: evolution of a somatostatin analogue

BACKGROUND

Acromegaly is characterized by overproduction of growth hormone (GH) by the pituitary gland. GH stimulates the synthesis of insulin-like growth factor-I (IGF-I), and the somatic growth and metabolic dysfunction that characterize acromegaly are a consequence of elevated GH and IGF-I levels. Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare, slow-growing neoplasms that have usually metastasized by the time of diagnosis. The majority of GEP-NETs are carcinoid tumors whose syndrome is caused by the hypersecretion of biogenic amines, peptides and polypeptides responsible for the principal symptoms of diarrhea and flushing.

METHODS

The MEDLINE and EMBASE databases were searched for preclinical and clinical studies of octreotide (Sandostatin* ), a potent synthetic somatostatin analogue, in patients with acromegaly or GEP-NETs.

OBJECTIVE

This article reviews the 20 years of clinical experience with octreotide and the impact it has made in patients with acromegaly or GEP-NETs.

RESULTS

Octreotide has proven to be an essential component in the management strategy of acromegaly and GEP-NETs over the past 20 years. The multiple beneficial effects of octreotide throughout the body, combined with its established safety profile (the most common adverse effects are injection-site pain and gastrointestinal events), have made it an appealing option for clinicians. The advent of the long-acting release (LAR) formulation of octreotide provided additional benefits to patients through monthly administration, while maintaining the efficacy and tolerability profile of the daily subcutaneous formulation.

CONCLUSIONS

Octreotide is a potent synthetic somatostatin analogue that has become the mainstay of medical therapy for tumor control in neuroendocrine disorders such as acromegaly and GEP-NETs. The development of octreotide LAR offered a further advancement; less frequent dosing provided valuable benefits in quality of life to patients, with equivalent efficacy and tolerability. Moreover, recent results from the PROMID study have confirmed the antiproliferative effect of octreotide LAR in patients with well-differentiated metastatic GEP-NETs of the midgut. New therapeutic uses of octreotide are currently under investigation in a variety of clinical settings.

Inhibition of peptide acylation in PLGA microspheres with water-soluble divalent cationic salts

PURPOSE

To test the potential of water-soluble divalent cationic salts to inhibit acylation of octreotide encapsulated in poly(D,L-lactic-co-glycolic acid)-star (PLGA) microspheres.

METHODS

The divalent cationic salts, calcium chloride and manganese chloride, previously shown to disrupt peptide sorption, were introduced in PLGA microspheres prepared by the double emulsion-solvent evaporation method. Peptide stability was monitored by reversed-phase high performance liquid chromatography (RP-HPLC) and identified by liquid chromatography coupled with mass spectrometry (LC-MS) during microsphere degradation under physiological conditions for 4 weeks. Microsphere morphology and salt content were examined by scanning electron microscopy (SEM) and inductively coupled plasma-optical emission spectroscopy (ICP-OES), respectively.

RESULTS

Addition of divalent cationic salts solely to the organic phase did not provide acylation inhibition. However, addition of the salt inhibitors to both the primary emulsion and the outer water phase resulted in improved drug and salt encapsulation efficiency as well as significantly decreased salt leaching and octreotide acylation. After 28 days, the extent of acylation inhibition afforded by divalent cations was > 58% relative to 13% for the NaCl control group.

CONCLUSIONS

Water-soluble divalent cationic salts represent a suitable class of stabilizer of peptide acylation in PLGA microspheres and this study provides an important formulation approach to maximize stabilizer potency.

Medical therapy of pituitary adenomas: effects on tumor shrinkage

The efficacy of dopamine-agonists (DA) in patients with prolactinomas and that of somatostatin analogues (SSA) in those with GH- and TSH-secreting adenomas is well established. More recently, data are accumulating suggesting a potential therapeutic role of DA also in patients with ACTH-secreting and clinically non-functioning (NFA) pituitary adenomas. This review aims at summarizing published results of DA and SSA on tumor shrinkage in patients with different histotypes of pituitary adenomas. Results of tumor shrinkage are of clinical relevance as tumor size is the one of the most important determinant of surgical outcome. While reduction of tumor size more than 50% of baseline size in macroprolactinomas treated with DA is a frequent finding in patients with GH-secreting adenomas treated with SSA tumor shrinkage only recently is becoming frequent thanks to the availability of depot formulations. Data on tumor shrinkage in patients with TSH-secreting adenomas treated with SSA are limited because of the rarity of these tumors. Very recently, DA have been reported of some efficacy also in patients with ACTH-secreting adenomas but data are still very limited. NFA respond very scantly to both DA and SSA even if receptors targeting these drugs are present. Whether this is due to limited receptor number or alterations of post-receptor pathway is still unknown.

[Evaluation of glucose metabolism in acromegalic patients before and after treatment with octreotide LAR]

AIM OF THE STUDY

To evaluate the glucose metabolism in acromegalic patients before and after treatment with octreotide LAR.

PATIENTS AND METHODS

This was a prospective and longitudinal study involving 30 patients from the acromegaly research outpatient clinic of the Endocrinology unit of the HUCFF/UFRJ. They underwent clinical and laboratorial evaluations, with measurements of growth hormone (GH), insulin-like growth factor type I (IGF-I), insulin, proinsulin, C peptide, glycosylated hemoglobin (HbA1c), IGF binding protein type 1 (IGFBP-1) and glucose, during oral glucose tolerance test (OGTT), before and after six months of treatment with octreotide LAR. The Wilcoxon signed-rank test was used and values of 5% were considered statistically significant.

RESULTS

We found 16 (54%) patients with normal glucose tolerance, 7 (23%) with impaired glucose tolerance and 7 (23%) diabetics. Twelve patients completed the six-month treatment, out of which three showed worsening of glucose tolerance and two (diabetics) had worse blood glucose control. Whereas there was an increase in waist circumference (p=0.03), there was a decrease in GH (p=0.04), with %IGF-I above the upper limit of reference values (% ULRV) [p=0.001], insulin (p=0.019), C peptide levels (p=0.002) and homeostatic model assessment (HOMA-IR) [p=0.039].

CONCLUSIONS

In this series, treatment with octreotide LAR led to a worsening of glucose tolerance in three non-diabetic patients and worsened glycemic control in two diabetics, in spite of reducing insulin resistance.

Gastrointestinal neuroendocrine tumors: pancreatic endocrine tumors

Pancreatic endocrine tumors (PETs) have long fascinated clinicians and investigators despite their relative rarity. Their clinical presentation varies depending on whether the tumor is functional or not, and also according to the specific hormonal syndrome produced. Tumors may be sporadic or inherited, but little is known about their molecular pathology, especially the sporadic forms. Chromogranin A appears to be the most useful serum marker for diagnosis, staging, and monitoring. Initially, therapy should be directed at the hormonal syndrome because this has the major initial impact on the patient's health. Most PETs are relatively indolent but ultimately malignant, except for insulinomas, which predominantly are benign. Surgery is the only modality that offers the possibility of cure, although it generally is noncurative in patients with Zollinger-Ellison syndrome or nonfunctional PETs with multiple endocrine neoplasia-type 1. Preoperative staging of disease extent is necessary to determine the likelihood of complete resection although debulking surgery often is believed to be useful in patients with unresectable tumors. Once metastatic, biotherapy is usually the first modality used because it generally is well tolerated. Systemic or regional therapies generally are reserved until symptoms occur or tumor growth is rapid. Recently, a number of newer agents, as well as receptor-directed radiotherapy, are being evaluated for patients with advanced disease. This review addresses a number of recent advances regarding the molecular pathology, diagnosis, localization, and management of PETs including discussion of peptide-receptor radionuclide therapy and other novel antitumor approaches. We conclude with a discussion of future directions and unsettled problems in the field.

Octreotide LAR for the treatment of acromegaly

BACKGROUND

Somatostatin analogs previously considered as adjuvant therapy in acromegaly are increasingly used as a first-line therapy in selected cases.

OBJECTIVE

To review the octreotide LAR pharmacological and clinical data, and discuss the impact of this agent on current treatment regimens.

METHODS

We reviewed PubMed publications since the first use of octreotide LAR in acromegaly, and historical articles related to the discovery and development of this molecule. We chose, for efficacy and safety data, reviews, clinical and randomized controlled trials that included >or=10 patients.

RESULTS/CONCLUSION

Octreotide LAR controls acromegaly in approximately 50-60% of patients by inhibiting GH and IGF-I secretion, and by reducing tumor size. This drug is well tolerated in most patients.

Somatostatin agonists for treatment of acromegaly

The discovery of somatotropin-release inhibitory factor (SRIF) in hypothalamic extract in 1970 led to the synthesis of the first somatostatin analog octreotide, discovery of five somatostatin receptor subtypes, and development of additional somatostatin receptor ligands (SRL) as pharmacotherapy for acromegaly and other neuroendocrine tumors. Long-acting formulations of SRL (octreotide LAR Depot, lanreotide SR and lanreotide autogel) assure improved patient compliance with weekly up to monthly injections, and are commonly used as primary or adjuvant treatment of acromegaly. We review SRL currently available, emphasizing long-acting compounds and their efficacy in controlling acromegaly. Disease control is evaluated by biochemical markers, tumor shrinkage, and disease-symptom improvement balanced against drug-related side effects.

Long-acting octreotide as rescue therapy in chronic bleeding from gastrointestinal angiodysplasia

BACKGROUND

Octreotide has shown to be effective against rebleeding from gastrointestinal angiodysplasias, but a long-term daily parenteral administration is recommended. Long-acting octreotide (LAR-OCT) could overcome such a limitation, but it has not been studied extensively.

AIM

To investigate the usefulness of long-acting octreotide in the control of chronic bleeding from gastrointestinal angiodysplasias.

METHODS

Thirteen patients with chronic gastrointestinal bleeding because of angiodysplasias were enrolled. Diagnosis was made by endoscopy and wireless video capsule. Long-acting octreotide was administered intramuscularly at a dosage of 10 mg/monthly for 1 year. Patients were followed up for a minimum period of 1 year, and haemoglobin levels, blood transfusions, iron supplementation and hospitalizations were recorded 1 year before and after starting long-acting octreotide therapy.

RESULTS

Follow-up ranged from 12 to 60 months. Nine of 13 patients (69%) did not need blood transfusions and iron supplementation any longer; a partial improvement was observed in one patient; no effect was found in the others. No side effect was recorded in any patient.

CONCLUSIONS

Long-acting octreotide for 1 year may be beneficial as a rescue therapy for controlling chronic bleeding from gastrointestinal angiodysplasias in patients not eligible for surgery. Its monthly administration represents an advantage, which makes such a formulation the choice when a long-term treatment is mandatory.

Stereotactic radiosurgery for pituitary adenomas: an intermediate review of its safety, efficacy, and role in the neurosurgical treatment armamentarium

OBJECT

Pituitary adenomas are very common neoplasms, constituting between 10 and 20% of all primary brain tumors. Historically, the treatment armamentarium for pituitary adenomas has included medical management, microsurgery, and fractionated radiotherapy. More recently, radiosurgery has emerged as a viable treatment option. The goal of this research was to define more fully the efficacy, safety, and role of radiosurgery in the treatment of pituitary adenomas.

METHODS

Medical literature databases were searched for articles pertaining to pituitary adenomas and stereotactic radiosurgery. Each study was examined to determine the number of patients, radiosurgical parameters (for example, maximal dose and tumor margin dose), duration of follow-up review, tumor growth control rate, complications, and rate of hormone normalization in the case of functioning adenomas. A total of 35 peer-reviewed studies involving 1621 patients were examined. Radiosurgery resulted in the control of tumor size in approximately 90% of treated patients. The reported rates of hormone normalization for functioning adenomas varied substantially. This was due in part to widespread differences in endocrinological criteria used for the postradiosurgical assessment. The risks of hypopituitarism, radiation-induced neoplasia, and cerebral vasculopathy associated with radiosurgery appeared lower than those for fractionated radiation therapy. Nevertheless, further observation will be required to understand the true probabilities. The incidence of other serious complications following radiosurgery was quite low.

CONCLUSIONS

Although microsurgery remains the primary treatment modality in most cases, stereotactic radiosurgery offers both safe and effective treatment for recurrent or residual pituitary adenomas. In rare instances, radiosurgery may be the best initial treatment for patients with pituitary adenomas. Further refinements in the radiosurgical technique will likely lead to improved outcomes.

Pituitary tumor disappearance in a patient with newly diagnosed acromegaly primarily treated with octreotide LAR

We describe the case of an acromegalic patient primarily treated with octreotide LAR in whom the pituitary tumor disappeared after 18 months of treatment. A 68-yr-old woman, with clinical suspicion of acromegaly, was admitted to our Unit with the ultrasonographical evidence of cardiac hypertrophy, arrhythmias, right branch block and interatrial septum aneurism. She referred hands and feet enlargement since the age of 30 and facial disfigurements since the age of 50. At the age of 45 she underwent surgery for carpal tunnel syndrome and at the age of 61 an euthyroid nodular goiter was diagnosed. Hormonal evaluation showed elevated circulating GH levels (25+/-3.2 ng/ml), not suppressible after oral glucose load, and elevated IGF-I levels (646 ng/ml), whereas the remaining pituitary function was normal. Visual perimetry was normal, whereas magnetic resonance imaging (MRI) showed an intrasellar pituitary adenoma with maximal diameter of 9 mm. In order to improve cardiovascular function before surgery, the patient started octreotide LAR 20 mg every 4 weeks for 3 months. Then based on IGF-I values, the dose was adjusted to 30 mg. After 6 months a second MRI showed significant tumor reduction (>50% of baseline maximal diameter), GH and IGF-I were within the normal range and the patient continued the treatment. After one-year therapy, an improvement of cardiac alterations was recorded and the patient was referred to the neurosurgeon. However, she refused the operation. At 18-month follow-up, MRI showed the complete disappearance of direct and indirect signs of pituitary adenoma. To our knowledge, this is the first case of complete radiological remission of pituitary tumor during octreotide LAR treatment in acromegaly.