Pasireotide treatment does not modify hyperglycemic and corticosterone acute restraint stress responses in rats.

Pasireotide is a new-generation somatostatin analog that acts through binding to multiple somatostatin receptor subtypes. Studies have shown that pasireotide induces hyperglycemia, reduces glucocorticoid secretion, alters neurotransmission, and potentially affects stress responses typically manifested as hyperglycemia and increased corticosterone secretion. This study specifically aimed to evaluate whether pasireotide treatment modifies glucose and costicosterone secretion in response to acute restraint stress. Male Holtzman rats of 150-200 g were treated with pasireotide (10 µg/kg/day) twice-daily for two weeks or vehicle for the same period. Blood samples were collected at baseline and after 5, 10, 30, and 60 min of restraint stress. The three experimental groups comprised of vehicle + restraint (VEHR), pasireotide + restraint (PASR), and pasireotide + saline (PASNR). Following pasireotide treatment, no significant differences in baseline glucose and corticosterone levels were observed among the three groups. During restraint, hyperglycemia was observed at 10 min (p < .01 for both comparisons), peaked at 30 min (p < .01 for both comparisons) and showed higher 60 min areas under glucose curves in the VEHR and PASR stressed groups when compared to the non-stressed PASNR group (p < .05 for both comparisons). Restraint also increased corticosterone secretion in the VEHR and PASR stressed groups at 5 min (p < .01 for both comparisons), and peaked at 30 min (p < .01 for both comparisons) with corresponding higher 60 min areas under corticosterone curves when compared to the non-stressed PASNR group (p < .01 for both comparisons). In conclusion, pasireotide treatment does not modify hyperglycemic- and corticosterone-restraint stress responses, thus preserving acute stress regulation.

Radiotherapy and pasireotide treatment of a growth hormone producing pituitary tumor in a diabetic dog.

An 8-year-old castrated male border terrier dog was diagnosed with acromegaly resulting from a growth hormone secreting pituitary tumor. Sixteen daily fractions of radiation therapy were delivered followed, approximately 1 year later, by administration of pasireotide. The aforementioned treatment was considered effective and should be further evaluated in similar cases.

Radiothérapie et traitement au pasiréotide pour une tumeur pituitaire produisant une hormone de croissance chez un chien diabétique. Un chien Terrier-Border castré âgé de 8 ans a été diagnostiqué avec de l'acromégalie découlant d'une tumeur pituitaire secrétant une hormone de croissance. Seize fractions quotidiennes de radiothérapie ont été administrées et ont été suivies, environ un an plus tard, de l'administration du pasiréotide. Le traitement précédemment mentionné a été considéré efficace et devrait être étudié de plus près dans des cas similaires.(Traduit par Isabelle Vallières).

Somatostatin receptor activation is involved in the control of daily torpor in a seasonal mammal.

Siberian hamsters (Phodopus sungorus) show spontaneous daily torpor only after ∼2 mo in winter-like short photoperiods (SP). Although some SP-induced hormonal changes have been demonstrated to be necessary for the occurrence of seasonal torpor, the whole set of preconditions is still unknown. Recent findings provide evidence that the hypothalamic pituitary growth axis is involved in endocrine responses to SP exposure in the photoperiodic hamsters. To examine whether suppression of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) secretion affects the incidence of daily torpor, we used two somatostatin receptor agonists, pasireotide (SOM230) and octreotide, with different affinity profiles for receptor subtypes. Pasireotide strikingly increased the torpor frequency in male hamsters compared with sham-treated controls, and torpor duration was often increased, which in some cases exceeded 12 h. In contrast, administration of octreotide reduced the body weight of SP hamsters but had only a marginal effect on torpor frequency in males and no effect in females. Together with measured concentrations of circulating IGF-1, the present results strongly suggest that reduced activity of the GH/IGF-1 axis is not critical for stimulation of torpor expression but activation of specific somatostatin receptors is critical. This putative role for certain somatostatin receptor subtypes in torpor induction provides a promising new approach to unravel the endocrine mechanisms of torpor regulation.

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

The somatostatin analog pasireotide and the 11ß-hydroxylase inhibitor osilodrostat (LCI699) reduce cortisol levels by distinct mechanisms of action. There exists a scientific rationale to investigate the clinical efficacy of these two agents in combination. This manuscript reports the results of a toxicology study in rats, evaluating different doses of osilodrostat and pasireotide alone and in combination. Sixty male and 60 female rats were randomized into single-sex groups to receive daily doses of pasireotide (0.3mg/kg/day, subcutaneously), osilodrostat (20mg/kg/day, orally), osilodrostat/pasireotide in combination (low dose, 1.5/0.03mg/kg/day; mid-dose, 5/0.1mg/kg/day; or high dose, 20/0.3mg/kg/day), or vehicle for 13weeks. Mean body-weight gains from baseline to Week 13 were significantly lower in the pasireotide-alone and combined-treatment groups compared to controls, and were significantly higher in female rats receiving osilodrostat monotherapy. Osilodrostat and pasireotide monotherapies were associated with significant changes in the histology and mean weights of the pituitary and adrenal glands, liver, and ovary/oviduct. Osilodrostat alone was associated with adrenocortical hypertrophy and hepatocellular hypertrophy. In combination, osilodrostat/pasireotide did not exacerbate any target organ changes and ameliorated the liver and adrenal gland changes observed with monotherapy. Cmax and AUC0-24h of osilodrostat and pasireotide increased in an approximately dose-proportional manner. In conclusion, the pasireotide and osilodrostat combination did not exacerbate changes in target organ weight or toxicity compared with either monotherapy, and had an acceptable safety profile; addition of pasireotide to the osilodrostat regimen may attenuate potential adrenal gland hyperactivation and hepatocellular hypertrophy, which are potential side effects of osilodrostat monotherapy.

Lung volume quantified by MRI reflects extracellular-matrix deposition and altered pulmonary function in bleomycin models of fibrosis: effects of SOM230.

Idiopathic pulmonary fibrosis is a progressive and lethal disease, characterized by loss of lung elasticity and alveolar surface area, secondary to alveolar epithelial cell injury, reactive inflammation, proliferation of fibroblasts, and deposition of extracellular matrix. The effects of oropharyngeal aspiration of bleomycin in Sprague-Dawley rats and C57BL/6 mice, as well as of intratracheal administration of ovalbumin to actively sensitized Brown Norway rats on total lung volume as assessed noninvasively by magnetic resonance imaging (MRI) were investigated here. Lung injury and volume were quantified by using nongated or respiratory-gated MRI acquisitions [ultrashort echo time (UTE) or gradient-echo techniques]. Lung function of bleomycin-challenged rats was examined additionally using a flexiVent system. Postmortem analyses included histology of collagen and hydroxyproline assays. Bleomycin induced an increase of MRI-assessed total lung volume, lung dry and wet weights, and hydroxyproline content as well as collagen amount. In bleomycin-treated rats, gated MRI showed an increased volume of the lung in the inspiratory and expiratory phases of the respiratory cycle and a temporary decrease of tidal volume. Decreased dynamic lung compliance was found in bleomycin-challenged rats. Bleomycin-induced increase of MRI-detected lung volume was consistent with tissue deposition during fibrotic processes resulting in decreased lung elasticity, whereas influences by edema or emphysema could be excluded. In ovalbumin-challenged rats, total lung volume quantified by MRI remained unchanged. The somatostatin analog, SOM230, was shown to have therapeutic effects on established bleomycin-induced fibrosis in rats. This work suggests MRI-detected total lung volume as readout for tissue-deposition in small rodent bleomycin models of pulmonary fibrosis.

SOM230: a new therapeutic modality for Cushing's disease.

A rational drug design approach involving transposition of functional groups from SRIF into a reduced size cyclohexapeptide template has led to the discovery of SOM230, a novel, stable cyclohexapeptide somatostatin mimic which exhibits unique high affinity binding to human somatostatin receptors (sst1-5). This unique receptor subtype binding profile, in particular the exceptional high affinity binding to sst5, led to SOM230 being approved by EMEA and FDA in 2012 as the first effective pituitary directed therapeutic modality for Cushing's disease.

Ultra-rapid growth of biphasic nanowires in micro- and hypergravity.

Aluminium/aluminium oxide wires form under microgravity, earth conditions, and hypergravity in different forms. While under 0.04 G the biphasic wires are predominantly linear, they form bundles of wires of high curvature at 1 G and 1.8 G. The absence (0.04 G) and presence (1 G, 1.8 G) of gradients are reflected by the agglomeration and growth direction of the nanowires.

Monoclonal antibodies against the human somatostatin receptor subtypes 1-5: development and immunohistochemical application in neuroendocrine tumors.

BACKGROUND: Activation of somatostatin receptors (sstr1-5) by somatostatin and its analogues exerts an inhibitory effect on hormone secretion and provides the basis for the treatment of a range of endocrine diseases such as acromegaly, Cushing's disease and neuroendocrine tumors (NET). The lack of well-characterized commercially available sstr subtype-specific antibodies prevents routine identification of the sstr expression profile in patients. METHODS: We generated and characterized new mouse monoclonal antibodies (mAbs) targeting the five human sstr subtypes using ELISA and immunohistochemistry, and tested their suitability in formalin-fixed and paraffin-embedded (FFPE) human tissues and archival samples of normal pancreatic tissue and NET. RESULTS: All mAbs were highly specific with no cross-reactivity. The sstr1-5 immunoreactivity in gastrointestinal NET (n=67) was correlated with clinicopathologic data. With the exception of sstr3, NET were highly positive for all receptor subtypes (42, 63, 6, 32 and 65% of tumors were positive for sstr1, sstr2a, sstr3, sstr4 and sstr5, respectively). sstr1, sstr2a and sstr5 were present at the plasma membrane and in the cytoplasm of tumor cells, whereas sstr3 and sstr4 were almost exclusively cytoplasmic. Immunoreactivity of sstr1, sstr2a and sstr4 tended to decrease as tumor aggressiveness increased. sstr5 showed an opposite pattern, with higher staining in well-differentiated carcinomas compared with well-differentiated tumors. sstr5 immunoreactivity was correlated with the presence of metastases and angioinvasion, suggesting a possible association with more aggressive behavior. CONCLUSION: Determination of the sstr1-5 by immunohistochemistry using subtype-specific mAbs is feasible in FFPE tissue and may provide a tool for routine clinical practice.

Combination of pasireotide and octreotide: effects on GH and IGF-I secretion and glucose metabolism in healthy volunteers.

PURPOSE: To assess the pharmacokinetics, pharmacodynamics and tolerability of different doses of octreotide and pasireotide (subcutaneous [sc] and long-acting release [LAR]) when co-administered in healthy volunteers. METHODS: This was an exploratory, Phase I, single-centre study. Healthy adults were enrolled in a staggered approach into seven cohorts to receive octreotide and pasireotide (sc and LAR formulations), alone or in combination. Plasma drug concentrations, growth hormone (GH), insulin-like growth factor I (IGF-I), and plasma glucose were assessed at baseline, immediately after sc treatment, and 21 and 28 days after LAR treatment. RESULTS: Of 88 enrolled subjects, 52 and 82 participated in sc and LAR dosing phases, respectively. There were no relevant pharmacokinetic interactions between octreotide and pasireotide. In combination, pasireotide sc (150 µg) and octreotide sc (100/300 µg) resulted in numerically greater reductions in insulin levels and a higher incidence of AEs than either single agent; the rapid (within 1 h) increase in plasma glucose after pasireotide was delayed with combination treatment. Octreotide sc and pasireotide sc, alone or in combination, reduced IGF-I levels and led to undetectable GH levels in most subjects. During the LAR phase, addition of a low dose of pasireotide (5 mg) to a standard dose of octreotide (20 mg) resulted in an ~2-fold reduction in median IGF-I versus octreotide 20 mg 21 days post-dose; this effect was numerically greater than seen for pasireotide 20 mg alone. Peak plasma glucose was substantially lower after LAR than sc dosing. Interestingly, glucose levels were also numerically lower in the pasireotide 5 mg plus octreotide 20 mg group than for 20 mg of octreotide or pasireotide alone. AEs were less frequent after LAR than sc dosing. CONCLUSIONS: Combined low doses of pasireotide LAR (5 mg) and octreotide LAR (10-30 mg) provided greater suppression of IGF-I than either single agent and did not increase blood glucose or incidence of AEs versus either agent alone.

Somatostatin analogue pasireotide (SOM230) inhibits catecholamine secretion in human pheochromocytoma cells.

Increasingly common, neuroendocrine tumors (NETs) are regarded nowadays as neoplasms potentially causing debilitating symptoms and life-threatening medical conditions. Pheochromocytoma is a NET that develops from chromaffin cells of the adrenal medulla, and is responsible for an excessive secretion of catecholamines. Consequently, patients have an increased risk for clinical symptoms such as hypertension, elevated stroke risk and various cardiovascular complications. Somatostatin analogues are among the main anti-secretory medical drugs used in current clinical practice in patients with NETs. However, their impact on pheochromocytoma-associated catecholamine hypersecretion remains incompletely explored. This study investigated the potential efficacy of octreotide and pasireotide (SOM230) on human tumor cells directly cultured from freshly resected pheochromocytomas using an implemented catecholamine secretion measurement by carbon fiber amperometry. SOM230 treatment efficiently inhibited nicotine-induced catecholamine secretion both in bovine chromaffin cells and in human tumor cells whereas octreotide had no effect. Moreover, SOM230 specifically decreased the number of exocytic events by impairing the stimulation-evoked calcium influx as well as the nicotinic receptor-activated inward current in human pheochromocytoma cells. Altogether, our findings indicate that SOM230 acts as an inhibitor of catecholamine secretion through a mechanism involving the nicotinic receptor and might be considered as a potential anti-secretory treatment for patients with pheochromocytoma.

Effect of SOM230 (pasireotide) on corticotropic cells: action in dogs with Cushing's disease.

SOM230 (pasireotide) is a multiligand somatostatin (SRIF) analog able to bind to somatostatin receptor (SSTR) subtypes 1, 2, 3 and 5, and trigger antisecretory and antiproliferative signaling cascades. Canines have become in vivo models to test the pharmacological treatment of corticotropinomas because they frequently develop Cushing's disease in a spontaneous manner, due to adrenocorticotropic hormone (ACTH)-producing pituitary adenomas. Different levels of expression of SSTR2 and SSTR5 have been shown in both mouse AtT20 cells and canine tumoral corticotropinoma cells. The objective of this study was to evaluate whether SOM230 controls both tumor cell growth and hormone synthesis, therefore controlling the disease. SOM230 was tested in dogs suffering from Cushing's disease (10 animals were treated continuously during 6 months, and another 10 were treated with 3 cycles consisting of 2 months of treatment followed by a 2-month rest period). A significant decrease in ACTH, urinary cortisol creatinine ratio, adenoma size (magnetic nuclear resonance) and improvement of clinical signs were obtained, without side effects. AtT20 cells treated with SOM230 suppressed pro-opiomelanocortin (POMC) promoter activity through SSTR2, via the G(i) α-subunit, and reduced Nur77/Nurr1 transcriptional activity. We conclude that SOM230, in addition to its well-described antisecretory effects, inhibits, as shown in AtT20 cells, ACTH synthesis at the POMC transcriptional level, an effect mediated mainly through SSTR2, and limits tumor growth. The controlled Cushing's disease in the dogs that received the treatment indicates that SOM230 has a potential therapeutic use in humans suffering from Cushing's disease.

Somatostatin receptors in non-neuroendocrine malignancies: the potential role of somatostatin analogs in solid tumors.

Somatostatin receptors (sstrs) are G-protein-coupled receptors that mediate various physiological effects when activated by the neuropeptide somatostatin or its synthetic analogs. In addition to the well-documented antisecretory effects of sstr(2)-preferential somatostatin analogs octreotide and lanreotide, ligand binding to sstr initiates an inhibitory action on tumor growth. This effect may result from both indirect actions (suppression of growth factors and growth-promoting hormones [e.g., GH/IGF-1 axis] and inhibition of angiogenesis) and direct actions (activation of antigrowth activities [e.g., apoptosis]). As solid tumor cells express multiple sstrs, there is a rationale to evaluate the potential antitumor effects of pasireotide (SOM230), a multireceptor-targeted somatostatin analog with high binding affinity for sstr(1-3) and sstr(5). Pasireotide reduces systemic IGF-1 levels more potently than currently available somatostatin analogs and has been well tolerated in clinical trials.

Revalidation, synonymies, and notes in American Callichromatini (Coleoptera, Cerambycidae, Cerambycinae).

The unpublished formal synonymy of Callichroma chiriquina Bates, 1879, C. opiparum Bates, 1874, C. compressipes Casey, 1912, and C. regalis Casey, 1912 is commented. Schwarzerion carinatum Schmidt, 1924 is removed from the synonym of Callichroma holochlorum holochlorum Bates, 1872, and transferred to the synonymy of Callichroma euthalia Bates, 1879. The species group name euthalium is corrected. The type-localities of Schwarzerion carinatum are reported as Colombia and West Indies, and the institution where one of the syntypes is deposited is corrected. Callichroma collarti Fuchs, 1959 is revalidated, and Callichroma magnificum Napp Martins, 2009 is considered its junior synonym. The status of the specimens of the type series of Callichroma collarti is commented. Additionally, the holotype of Callichroma opiparum Bates, 1874, and the lectotype of Callichroma chiriquina Bates, 1879 are illustrated for the first time.

Gender-Specific Efficacy Revealed by Head-to-Head Comparison of Pasireotide and Octreotide in a Representative In Vivo Model of Nonfunctioning Pituitary Tumors.

Invasive nonfunctioning pituitary tumors (NFPTs) are non-resectable neoplasms associated with frequent relapse and significant comorbidities. Current treatments, including somatostatin receptor 2 (SSTR2)-directed somatostatin analogs (SSAs), often fail against NFPTs. Thus, identifying effective therapies is clinically relevant. As NFPTs express SSTR3 at high levels, pasireotide, a multireceptor-targeted SSA, might be beneficial. Here we evaluated pasireotide in the only representative model of spontaneous NFPTs (MENX rats) in vivo. Octreotide long-acting release (LAR), pasireotide LAR, or placebo, were administered to age-matched, tumor-bearing MENX rats of both sexes for 28 d or 56 d. Longitudinal high-resolution magnetic resonance imaging monitored tumor growth. While tumors in placebo-treated rats increased in volume over time, PTs in drug-treated rats displayed significant growth suppression, and occasional tumor shrinkage. Pasireotide elicited stronger growth inhibition. Radiological responses correlated with tumors' proliferation rates. Both SSAs, but especially pasireotide, were more effective in female vs. male rats. Basal Sstr3 expression was significantly higher in the former group. It is noteworthy that female human NFPTs patients also have a trend towards higher SSTR3 expression. Altogether, our studies provide the rationale for testing pasireotide in patients with residual/recurrent NFPTs. If confirmed, the sex-related SSTR3 expression might be used as criteria to stratify NFPTs patients for treatment with pasireotide.

Pharmacologic Normalization of Pancreatic Cancer-Associated Fibroblast Secretome Impairs Prometastatic Cross-Talk With Macrophages.

BACKGROUND & AIMS: Cancer-associated fibroblasts (CAFs) from pancreatic adenocarcinoma (PDA) present high protein synthesis rates. CAFs express the G-protein-coupled somatostatin receptor sst1. The sst1 agonist SOM230 blocks CAF protumoral features in vitro and in immunocompromised mice. We have explored here the therapeutic potential of SOM230, and underlying mechanisms, in immunocompetent models of murine PDA mimicking the heavy fibrotic and immunosuppressive stroma observed in patient tumors. METHODS: Large-scale mass spectrometry analyses were performed on media conditioned from 9 patient PDA-derived CAF primary cultures. Spontaneous transgenic and experimental (orthotopic co-graft of tumor cells plus CAFs) PDA-bearing mice were longitudinally ultrasound-monitored for tumor and metastatic progression. Histopathology and flow cytometry analyses were performed on primary tumors and metastases. Stromal signatures were functionally validated through bioinformatics using several published, and 1 original, PDA database. RESULTS: Proteomics on the CAF secretome showed that SOM230 controls stromal activities including inflammatory responses. Among the identified secreted proteins, we validated that colony-stimulating factor 1 (CSF-1) (a macrophage growth factor) was reduced by SOM230 in the tumor and plasma of PDA-harboring mice, alongside intratumor stromal normalization (reduced CAF and macrophage activities), and dramatic metastasis reduction. In transgenic mice, these SOM230 benefits alleviate the chemotherapy-induced (gemcitabine) immunosuppressive stroma reshaping. Mechanistically, SOM230 acts in vivo on CAFs through sst1 to disrupt prometastatic CAF production of CSF-1 and cross-talk with macrophages. We found that in patients, stromal CSF-1 was associated with aggressive PDA forms. CONCLUSIONS: We propose SOM230 as an antimetastatic therapy in PDA for its capacity to remodel the fibrotic and immunosuppressive myeloid stroma. This pharmacotherapy should benefit PDA patients treated with chemotherapies.

Differential effects of octreotide and pasireotide on somatostatin receptor internalization and trafficking in vitro.

OBJECTIVE: The clinically used somatostatin analogs, octreotide and lanreotide, act primarily by binding to somatostatin receptor 2 (sst2). In contrast, the novel multireceptor ligand pasireotide (SOM230) binds with high affinity to somatostatin receptor subtypes sst1, sst2, sst3, and sst5. SOM230 is currently under clinical evaluation for treatment of acromegaly, Cushing's disease, and octreotide-resistant carcinoid tumors. However, the effects of SOM230 on internalization and postendosomal sorting of individual human somatostatin receptor subtypes have not been determined so far. RESULTS: Here we show that SOM230 was less potent than octreotide in inducing internalization and signaling of sst2 receptors expressed in human embryonic kidney cells. In contrast, SOM230 was more potent than octreotide in inducing internalization and signaling of sst3 and sst5 receptors. Both SOM230 and octreotide stimulated a rapid down-regulation of sst3 but not of sst2 or sst5 receptors. SOM230 and octreotide profoundly differed in their patterns of sst2-stimulated beta-arrestin mobilization. Whereas octreotide-mediated receptor activation led to the formation of stable complexes facilitating the internalization of sst2 and beta-arrestin-2 into the same endocytic vesicles, SOM230-mediated receptor activation led to the formation of unstable complexes that dissociated at or near the plasma membrane. Consequently, sst2 receptors recycled rapidly to the plasma membrane after endocytosis in SOM230-treated cells, but not in octreotide-treated cells. CONCLUSION: We show that SOM230 modulates somatostatin receptor trafficking in a manner clearly distinct from octreotide and somatostatin. These findings may provide an explanation for the differential regulation of somatostatin receptor responsiveness during long-term administration of stable somatostatin analogs.

The somatostatin analog SOM230 (pasireotide) ameliorates injury of the intestinal mucosa and increases survival after total-body irradiation by inhibiting exocrine pancreatic secretion.

Somatostatin analogs ameliorate intestinal injury after localized irradiation. This study investigated whether SOM230, a novel, metabolically stable analog with broad receptor affinity, reduces intestinal injury and lethality in mice exposed to total-body irradiation (TBI). Male CD2F1 mice were exposed to 7-15 Gy TBI. Twice-daily administration of SOM230 (1, 4 or 10 mg/kg per day) or vehicle was started either 2 days before or 4 h after TBI and continued for either 14 or 21 days. Parameters of intestinal and hematopoietic radiation injury, bacterial translocation, and circulating cytokine levels were assessed. Animal survival was monitored for up to 30 days. SOM230 increased survival (P < 0.001) and prolonged survival time (P < 0.001) whether administration was initiated before or after TBI. There was no benefit from administration for 21 compared to 14 days. The survival benefit of SOM230 was completely reversed by co-administration of pancreatic enzymes (P = 0.009). Consistent with the presumed non-cytoprotective mechanism of action, SOM230 did not influence hematopoietic injury or intestinal crypt lethality. However, SOM230 preserved mucosal surface area (P < 0.001) and reduced bacterial translocation in a dose-dependent manner (P < 0.001). Circulating IL-12 levels were reduced in SOM230-treated mice (P = 0.007). No toxicity from SOM230 was observed. SOM230 enhances animal survival whether administration begins before or after TBI; i.e., it is effective both as a protector and as a mitigator. The mechanism likely involves reduction of intraluminal pancreatic enzymes. Because of its efficacy and favorable safety profile, SOM230 is a promising countermeasure against radiation and should undergo further development.

SOM230, a new somatostatin analogue, is highly effective in the therapy of growth hormone/prolactin-secreting pituitary adenomas.

PURPOSE: We have previously shown that transgenic mice ubiquitously overexpressing the HMGA2 gene develop growth hormone/prolactin-secreting pituitary adenomas. This animal model has been used to evaluate the therapeutic efficacy of SOM230, a somatostatin analogue with high affinity for the somatostatin receptor subtypes 1, 2, 3, and 5, on the growth of the pituitary adenomas. EXPERIMENTAL DESIGN: Four groups of 3- and 9-month-old HMGA2 transgenic mice were treated for 3 months with a continuous s.c. injection of two different dosages of SOM230 (5 or 50 microg/kg/h), one dose of octreotide, corresponding to that used in human therapy, and a placebo, respectively. The development of the tumor before and after therapy was monitored by magnetic resonance imaging of the pituitary region and evaluation of the serum prolactin levels. RESULTS: The highest dose of SOM230 induced a drastic regression of the tumor, whereas octreotide was not able to induce any significant tumor regression, although tumor progression was significantly slowed down. No significant differences were observed between the animals treated with the lowest dose of SOM230 and those receiving placebo. CONCLUSIONS: These results clearly support the efficacy of the SOM230 treatment in human pituitary adenomas secreting prolactin based on the dramatic tumor shrinkage and fall in prolactin levels. This beneficial effect could be of crucial clinical usefulness in patients bearing tumors resistant to dopaminergic drugs.

Phase I, open-label study of pasireotide in patients with BRAF-wild type and NRAS-wild type, unresectable and/or metastatic melanoma.

INTRODUCTION: Somatostatin analogues exert antitumour activity via direct and indirect mechanisms. The present study was designed to assess the safety and efficacy of pasireotide in patients with BRAF-wild type (WT) and NRAS-WT metastatic melanoma. PATIENTS AND METHODS: Patients with unresectable and/or metastatic melanoma or Merkel cell carcinoma were eligible. Pasireotide was administered at different doses for ≤8 weeks in dose-escalation phase, followed by long-acting pasireotide 80 mg or lower dose in case of toxicity in follow-up phase up to six additional months. Primary endpoint was safety in the first 8 weeks of dose-escalation phase. RESULTS: The study was terminated early due to slow recruitment. Of the 10 patients with metastatic melanoma enrolled, only four reached the high dose level: two patients reached 3600 µg in dose-escalation and follow-up phases and two patients reached 3600 µg in dose-escalation and long-acting pasireotide 80 mg in follow-up phases and were stable for >5 months. Most common adverse events (AEs) during dose-escalation phase in ≥2 patients (20%) were: diarrhoea (50%), nausea (50%), fatigue (20%), hyperglycaemia (20%), hypophosphatemia (20%), chills (20%) and tumour pain (20%). Grade 3 or 4 study drug-related AEs were diarrhoea and nausea, reported in one patient. Partial response was documented in one patient and stable disease in another. CONCLUSIONS: Pasireotide was well tolerated, and safety results were similar to those previously reported in other indications. Further studies are needed to evaluate its antitumour activity alone and in combination with other drugs in melanoma.

Pasireotide, a multiple somatostatin receptor subtypes ligand, reduces cell viability in non-functioning pituitary adenomas by inhibiting vascular endothelial growth factor secretion.

Somatostatin (SRIF) analogs have been employed in medical therapy of non-functioning pituitary adenomas (NFA), with contrasting results. Previous evidence showed that SRIF can exert its antiproliferative effects by reducing vascular endothelial growth factor (VEGF) secretion and action, and that VEGF expression may be related to pituitary tumor growth. The aim of our study was to clarify the possible effects of a multireceptor SRIF ligand on VEGF secretion and cell proliferation in human NFA primary cultures. We assessed the expression of SRIF receptors (SSTR1-5), the in vitro effects on VEGF secretion, and on cell viability of SRIF and of the stable SRIF analog pasireotide (SOM230), which activates SSTR1, 2, 3, and 5. Twenty-five NFA were examined by RT-PCR for expression of alpha-subunit, SSTR, VEGF, and VEGF receptors 1 (VEGF-R1) and 2 (VEGF-R2). Primary cultures were tested with SRIF and with pasireotide. All NFA samples expressed alpha-sub, VEGF and VEGFR-1 and 2, while SSTR expression pattern was highly variable. Two different groups were identified according to VEGF secretion inhibition by SRIF. VEGF secretion and cell viability were reduced by SRIF and pasireotide in the 'responder' group, but not in the 'non-responder' group, including NFA expressing SSTR5. SRIF and pasireotide completely blocked forskolin-induced VEGF secretion. In addition, SRIF and pasireotide completely abrogated the promoting effects of VEGF on NFA cell viability. Our data demonstrate that pasireotide can inhibit NFA cell viability by inhibiting VEGF secretion, and suggest that the multireceptor-SSTR agonist pasireotide might be useful in medical therapy of selected NFA.