Generation Somatostatin Analogs Research Articles

Diabetes mellitus in acromegaly: prevalence, pathophysiological particulars and treatment strategies

The prevalence of diabetes mellitus in acromegaly is significantly higher than that in the general population. Carbohydrate metabolism abnormalities often precede other phenotypic manifestations of acromegaly. The review presents data on the prevalence of carbohydrate metabolism disorders in acromegaly and describes their pathophysiological characteristics and approaches to treatment.
 Growth hormone (GH) excess is recognized as a key factor of glucose homeostasis abnormalities due to decreased insulin sensitivity (resulting from active lipolysis) and direct stimulation of insulin secretion. Insulin-like growth factor 1 (IGF1) improves insulin sensitivity; however, the GH diabetogenic effects prevail over the insulin-sensitizing impact of IGF1. Surgical and radiation treatment for somatotropinoma may indirectly improve carbohydrate metabolism, because they decrease the GH levels. Treatment with first generation somatostatin analogues can both improve glycemic control due to decreased GH levels and worsen it due to deterioration of postprandial insulin release, especially in patients with already manifest carbohydrate metabolism disorders. The GH receptor antagonist pegvisomant blocks the effects of excess GH on the target tissues without suppressing insulin secretion, which results in better glucose control; treatment with this agent can be preferred in patients with acromegaly and diabetes mellitus. Management of carbohydrate metabolism disorders in acromegaly is done in accordance with general treatment principles for type 2 diabetes mellitus.

CD68+ and CD8+ immune cells are associated with the growth pattern of somatotroph tumors and response to first generation somatostatin analogs.

Somatotropinomas are pituitary tumors with a heterogenous clinical behavior. The tumor microenvironment regulates the interaction between tumor cells and the host immune system, potentially modulating tumor behavior. Here, we aimed to investigate the tumor immune infiltration in a cohort of medically naïve acromegaly patients. A retrospective, monocenter study was designed to analyze the presence of CD3+, CD20+, CD138+, CD4+, CD8+, CD68+ immune cells in samples of somatotropinomas and their prognostic significance on tumor behavior and response to first generation somatostatin analogs (fg-SSA). Thirty-six patients (23 females) were included in the study. Macroadenomas were identified in 23 cases: 12 with cavernous sinus invasion. The number of CD8+ lymphocytes positively correlated with CD4+ lymphocytes (p = .05, r:0.245) and with CD68+ macrophages (p = .01, r = 0.291). The CD8+/CD4+ ratio inversely correlated with CD68+/CD8+ ratio (p < .001, r = -0.626). CD68+ macrophages positively correlated with tumor size (maximum diameter p = .003, r = 0.574; volume p = .009, r = 0.566) and were more numerous in somatotropinomas with Ki-67 > 3% (median 65/HPF, IQR:15), compared to cases with Ki67 < 3% (median 50/HPF, IQR:22, p < .001). CD8+ and CD138+ lymphocytes were more numerous in cases responsive to fg-SSA (respectively median 18/HPF IQR:18 and median 8/HPF IQR: 6.5) as compared to fg-SSA nonresponsive cases (median 14.5/HPF IQR:40 p = .03; median 3.5/HPF IQR: 14 p = .03). CD8+ lymphocytes act as single predictor of response to fg-SSA, independently from age, GH and IGF-I levels, tumor dimension and invasion. Our results support that lymphocytes and macrophages generate an immune network in somatotropinomas and the characteristic of the immune infiltrate may predict treatment outcome.

Targeted treatment with somatostatin analogues: widening horizons of clinical practice

Targeted treatment with somatostatin analogues (SA) in acromegaly and neuroendocrine neoplasms may have some benefits compared to curative treatments, because these agents decrease excessive hormone secretion and exert a tumor-suppressive effect. Monotherapy and combination therapy with SA is well tolerated and bears no risk of debilitating iatrogenic complications. In acromegaly caused by somatotropin producing pituitary tumor, first generation SA are treatment of choice after non-radical adenomectomy, as well as in the cases when patients reject surgery. Treatment efficacy depends on the pathomorphological types of somatotropic tumors, which are different in their receptor phenotype, clinical scenario and proliferative activity. The first generation SA are successfully used for medical treatment of other pituitary tumors (thyrotropic, corticotropic, gonadotropic, lactotropic with resistance to dopamine agonists), as well as for adjuvant therapy of neuroendocrine and non-endocrine neoplasms and elimination of various gastrointestinal disorders. The anti-secretory and anti-tumor effects of SA have been proven for gastroenteropancreatic tumors (carcinoid syndrome, vipomas, gastrinomas, insulinomas, glucagonomas, somatostatinomas). Targeted selection of patients for treatment with first generation SA based on the receptor phenotypes of malignant cells would facilitate more rapid achievement of biochemical remission, improvement of quality of life and survival.

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

IntroductionTreatment 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 methodsA 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).ResultsThirty-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 < 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).ConclusionOur 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.

Real-World Experience With Pasireotide Lar in Acromegaly Resistant to First-Generation Somatostatin Analogs: A Single Center 1-Year Observation

Introduction: First generation somatostatin analogs (SSAs) are the treatment of choice in persistent acromegaly after transsphenoidal surgery. However, they are effective in 25% to 45 % of patients and a second generation SSA - pasireotide LAR may be a more effective alternative. Aim Our aim was to evaluate the impact of 1-year treatment with pasireotide LAR on disease control and on glucose metabolism in patients with acromegaly after debulking surgery resistant to first-generation SSAs. Material and methods In this single-center prospective study 29 consecutive patients with resistant acromegaly were treated with pasireotide LAR. The initial drug dose was 40 mg i.m. every 28 days. If patient did not achieve biochemical control (GH <2.5 ng/mL and IGF-1 ≤ULN for age and sex) at month 3, the dose was increased to 60 mg i.m. every 28 days. Assessment (GH, IGF-1, glucose, HbA1c) was performed at month 3, 6, 9 and 12. Results: In total, 22 patients (10 females, 12 males) completed a 1-year treatment. Mean age was 41.8±13.8 years. Twelve patients (54.5%) were ≤ 40 years old (including 6 (27.3%) patients of age ≤30 years). At baseline, mean IGF-1 level was 2.3 (SD 0.7) x ULN (age- and sex-specific) (583.9 ng/mL; SD 182.2) and mean GH concentration was 3.9 (SD 2.8) ng/mL. Both values decreased significantly after 1 year of treatment (P<0.001). Pasireotide LAR dose was increased to 60 mg in 16 (72.7%) patients and decreased to 20 mg in one patient patient due to worsening of diabetes control. The magnitude of mean GH level decrease was the largest within first 6 months (mean change from baseline: -1.75 ng/mL, 95% CI: -2.64, -0.85, P=0.0006). Mean IGF-1 level decreased rapidly within the first 3 months (mean change from baseline: -153.20 ng/mL, 95% CI: -203.20, -103.19, P<0.0001) and remained low during 12-month follow-up. GH level ≤ 1 ng/mL and ≤2.5 ng/mL was achieved by 7 (31.8%) and 17 (77.3%) patients, respectively. Six patients (27.3%) achieved normal IGF-1 level (IGF-1 ≤1 x ULN) (P=0.0275). IGF-1 ≤1.3 x ULN was observed in 11 (50.0%) of patients. Full biochemical control (GH ≤1 ng/mL and IGF-1 ≤1 x ULN) was achieved in 3 (13.6%) patients. Pasireotide LAR treatment resulted in significant increase of mean fasting glucose level: 119.2 (SD 17.3) vs. 107.5 (SD 13.9) mg/dL, P<0.001. The largest change was observed in first 3 months, and it remained stable until month 12. HbA1c level also increased significantly during first 3 months and stayed on similar level during follow-up (mean for month 12: 6.3 (SD 0.6) vs. 5.9 (SD 0.5) % at baseline, P<0.001). Conclusions: Pasireotide LAR is an effective treatment in most patients with persistent acromegaly after surgical debulking resistant to first generation SSAs. The largest increase of glycemia occurs during first 3 months of treatment and it remains stable afterwards.

Pasireotide LAR in acromegaly resistant to first generation somatostatin analogs – single-center prospective interventional study

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Pasireotide therapy in a patient with pituitary macroadenoma and asymptomatic acromegaly resistant to first generation somatostatin analogues

Pasireotide therapy in a patient with pituitary macroadenoma and asymptomatic acromegaly resistant to first generation somatostatin analogues

OR23-06 Is the Improved Glucose Homeostasis in Patients with Acromegaly Treated with Pegvisomant Caused by Improved Glucagon Secretion?

Context: Active acromegaly is associated with impaired glucose metabolism, which improves upon treatment. Treatment with first generation somatostatin analogues (SSA) has a detrimental effect on insulin secretion, but the effect on glucose homeostasis is neutralized by the reduction in growth hormone (GH) and Insulin-like growth factor-1 (IGF-1). Treatment with GH receptor antagonists has a more favorable effect on glucose homeostasis. Objective: To describe the secretion of glucose, insulin, glucagon, glucagon-like peptide-1 (GLP1), and glucose-dependent insulinotropic polypeptide (GIP) in surgically treated patients with acromegaly treated or not with somatostatin analogues, either as monotherapy (SSA) or in co-treatment with pegvisomant (SSA+PEG), respectively, compared to healthy controls. Methods: Descriptive study of data from 23 surgically treated, non-diabetic patients with acromegaly and 6 healthy controls. After an overnight fast, all participants underwent a three-hour 75 g oral glucose tolerance test (OGTT) and subsequently a three-hour isoglycaemic intravenous glucose infusion on a separate day. Analysis: Baseline hormone concentrations, time to peak and area under the curve (AUC) on the OGTT-day, and the incretin effect in the patient groups and controls were compared using analysis of variance with post-hoc analysis. Results: The total group of patients treated with somatostatin analogues (N=15) had numerically impaired glucose, insulin, GLP1 and glucagon responses (AUC, P>0.05 respectively), and an impaired GIP-response (AUC, P=0.007) during OGTT as compared to patients not treated with somatostatin analogues and healthy controls. Similarly, the incretin effect was numerically impaired.Patients co-treated with pegvisomant (SSA+PEG, N=4) had a numerically increased secretion of insulin and glucagon compared to patients on SSA (N=11) during OGTT (insulin AUC mean (SEM), SSA+PEG 49 nmol/l*min (8.3) vs SSA 25 (3.4), P>0.05) [healthy controls 62 (13.6)]; glucagon AUC, SSA+PEG 823 pmol/l*min (194) vs SSA 332 (69), P>0.05) [healthy controls 946 (233)]). GIP secretion remained significantly impaired, whereas GLP1 secretion was numerically increased with PEG (SSA+PEG 3088 pmol/l*min (366) vs SSA 2401 (239), P>0.05) [healthy controls 3972 (451)] but remained without a glucose-dependant increase as in SSA. The incretin effect numerically increased in SSA+PEG compared to SSA (SSA+PEG 49.9% (13.9) vs SSA 33.6% (47.4), P>0.05) [healthy controls 55.5% (7.7)]. Conclusion: Somatostatin analogues impaired the secretion of both insulin, glucagon and incretin hormones secretion. Co-treatment with pegvisomant seemed to counteract the somatostatinergic inhibition of the glucagon secretion and improved the insulin response to OGTT. We speculate that pegvisomant exerts its action via GH-receptors on pancreatic δ-cells.

Evaluation of the Efficacy and Safety of Switching to Pasireotide in Patients With Acromegaly Inadequately Controlled With First-Generation Somatostatin Analogs.

Introduction: Acromegaly is a rare, serious endocrine disorder characterized by excess growth hormone (GH) secretion by a pituitary adenoma and overproduction of insulin-like growth factor I (IGF-I). Transsphenoidal surgery is the treatment of choice, although many patients require additional interventions. First-generation somatostatin analogs (SSAs) are the current standard of medical therapy; however, not all patients achieve control of GH and IGF-I. Outcomes from a Phase IIIb open-label study of patients with uncontrolled acromegaly on first-generation SSAs switching to pasireotide are reported.Methods: Adults with uncontrolled acromegaly (mean GH [mGH] ≥1 μg/L from a five-point profile over 2 h, and IGF-I >1.3× upper limit of normal [ULN]) despite ≥3 months' treatment with maximal approved doses of long-acting octreotide/lanreotide received open-label long-acting pasireotide 40 mg/28 days. Pasireotide dose could be increased (maximum: 60 mg/28 days) after week 12 if biochemical control was not achieved, or decreased (minimum: 10 mg/28 days) for tolerability. Patients who completed 36 weeks' treatment could continue receiving pasireotide during an extension (weeks 36–72) when concomitant medication for acromegaly was permitted. Primary endpoint was proportion of patients with mGH <1 μg/L and IGF-I <ULN at week 36. Biochemical control was also assessed during the extension. Safety was assessed throughout.Results: One hundred and twenty-three patients were enrolled and received pasireotide; 88 patients continued into the extension. Overall, 18 [14.6% (95% CI: 8.9–22.1)] patients achieved mGH <1 μg/L and IGF-I <ULN at week 36; biochemical control was achieved in 42.9% with screening mGH 1.0–2.5 μg/L and 6.4% with screening mGH >2.5 μg/L. For patients who entered the extension, 14.8% (95% CI: 8.1–23.9), 12.5% (95% CI: 6.4–21.3), 14.8% (95% CI: 8.1–23.9) and 11.4% (95% CI: 5.6–19.9) had mGH <1 μg/L and IGF-I <ULN at weeks 36, 48, 60, and 72, respectively. During the overall study period, most frequent investigator-reported drug-related adverse events were hyperglycemia (41.5%), diabetes mellitus (23.6%), and diarrhea (11.4%).Conclusions: Switching to long-acting pasireotide provided biochemical control in some patients, which was sustained with continued treatment. Long-term safety and tolerability of long-acting pasireotide was consistent with the known safety profile. These data support long-acting pasireotide for some patients with acromegaly who are uncontrolled on first generation SSAs.Clinical Trial Registration: clinicaltrials.gov, identifier: NCT02354508.

&lt;p&gt;Burden of diabetes mellitus in patients with acromegaly treated with second-line pharmacotherapy in Spain&lt;/p&gt;

ObjectiveTo evaluate the burden of diabetes mellitus (DM) in adult patients with acromegaly treated with second-line pharmacotherapy, from the perspective of the Spanish National Health System (NHS).MethodsA Markov model was developed including three states: normal glucose metabolism, DM and death. The evolution of a hypothetical cohort of acromegaly patients requiring second-line pharmacological treatment (pegvisomant or pasireotide) after first generation somatostatin analogues therapy was analyzed. Direct healthcare costs regarding acromegaly management, diabetes management and drugs costs were obtained from Spanish sources. Transition probabilities between health states were obtained from published studies. Deterministic and probabilistic sensitivity analyses were undertaken.ResultsCompared to pasireotide, pegvisomant increased the likelihood of glucose normalization and reduced the likelihood of DM. Consequently, in a cohort of 1,000 patients with acromegaly, treatment with pegvisomant compared to pasireotide would prevent 243, 413 and 453 cases of DM after 1, 2 and 5 years, respectively, and would reduce mortality by 0.1% after 5 years of treatment. This would result in 1 million euros savings for the NHS in 5 years. These health benefits would be obtained with savings of €1,512, €3,422 and €10,162 per patient treated with pegvisomant, after 1, 2 and 5 years, respectively. After 5 years of treatment, the probability that pegvisomant generated savings versus pasireotide would be 65.3%.ConclusionThe favorable effects of pegvisomant on glucose metabolism would allow a considerable number of cases of DM to be avoided compared to pasireotide, resulting in savings for the NHS in Spain.

Prognostic value of short-acting pasireotide test for response prediction to pasireotide LAR in patients with acromegaly resistant to first-generation analogs. Can a short-acting pasireotide test predict the response of long-acting pasireotide treatment in patients with acromegaly resistant to first generation somatostatin analogs?

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

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.

GSTP1 gene methylation and AHR rs2066853 variant predict resistance to first generation somatostatin analogs in patients with acromegaly

Biomarkers of clinical and therapeutic outcome in acromegaly are needed. Polymorphisms or epigenetic changes of detoxification genes, such as those coding for the aryl hydrocarbon receptor (AHR) and the glutathione-S-transferase-P1 (GSTP1), could have a role in GH secreting pituitary tumors' pathophysiology and clinical expression. In this study, we assessed the contribution of GSTP1 gene promoter methylation status, per se or in combination with the occurrence of the AHR gene rs2066853 variant, on clinical features and response to somatostatin analogs (SSA) treatment in acromegaly patients. This is an observational, retrospective study, carried out in the Endocrine Unit of an Italian University Hospital. We enrolled 77 wild-type AIP gene acromegaly patients, who have been screened for germline AHR rs2066853 variant and GSTP1 gene promoter methylation. Clinical and biochemical parameters were compared after patients' stratification according to GSTP1 methylation status and the presence of AHR rs2066853. We also evaluated the response to SSA treatment in 71 cases. 17 patients carried the AHR rs2066853 variant and 26 had methylated GSTP1 (GSTP1-methyl) gene promoter. GSTP1-methyl patients showed a higher prevalence of diabetes mellitus (p = 0.01), colonic polyps (p = 0.05), and were more resistant to SSA (p = 0.02) as compared to GSTP1 unmethylated patients (GSTP1-unmethyl). Patients GSTP1-unmethyl and AHR wild-type were the most sensitive to SSA treatment, while those with both GSTP1-methyl and AHR rs2066853 variant were all resistant to SSA (p = 0.01). In acromegaly, GSTP1 gene methylation associates with resistance to SSA treatment, especially in patients carrying also the AHR rs2066853 variant, and with increased prevalence of colonic polyps and diabetes mellitus.

Changes in metabolic parameters and cardiovascular risk factors after therapeutic control of acromegaly vary with the treatment modality. Data from the Bicêtre cohort, and review of the literature.

Untreated acromegaly is associated with increased morbidity and mortality due to malignant, cardiovascular, and cerebrovascular disorders. Effective treatment of acromegaly reduces excess mortality, but its impact on cardiovascular risk factors and metabolic parameters are poorly documented. We analyzed changes in cardiovascular risk factors and metabolic parameters in patients receiving various treatment modalities. We retrospectively studied 96 patients with acromegaly, both at diagnosis and after IGF-I normalization following surgery alone (n = 51) or medical therapy with first generation somatostatin analogues (SSA, n = 23), or pegvisomant (n = 22). Duration of follow-up was 77 (42-161) months, 75 (42-112) months, and 62 (31-93) months, in patients treated with surgery alone, SSA, and pegvisomant, respectively. In all the cases except four, patients treated medically had underwent previous unsuccessful surgery. IGF-I normalization was associated with increased body weight, decreased systolic blood pressure (SBP) in hypertensive patients, decreased fasting plasma glucose (FPG) and HOMA-IR and HOMA-B levels, increased HDL cholesterol (HDLc); whereas, LDL cholesterol (LDLc) was not significantly different. Plasma PCSK9 levels were unchanged in patients with available values. Cardiovascular and metabolic changes varied with the treatment modality: surgery, but not pegvisomant, had a beneficial effect on SBP; FPG decreased after surgery but increased after SSA; the decline in HOMA-IR was only significant after surgery; pegvisomant significantly increased LDLc and total cholesterol; whereas SA increased HDLc and had no effect on LDLc levels. Treatments used to normalize IGF-I levels in patients with acromegaly could have differential effects on cardiovascular risk factors and metabolic parameters.

Pasireotide: A potential therapeutic alternative for resistant prolactinoma

ContextAbout 10% of prolactinomas are resistant to dopamine-agonists (DAs). The only alternatives for tumor and prolactin control are surgery or radiotherapy. While studies on first generation somatostatin analogs have shown no efficacy against prolactinomas, no study has been conducted on the new multireceptor-targeted somatostatin receptor ligand pasireotide, which presents high affinity for 5, 3, 2 and 1 receptor subtypes. Case descriptionA 41 year-old woman presented with a macroprolactinoma showing resistance to all available DAs. She was first diagnosed at 17 years old after which she had undergone two incomplete debulking surgeries. Under pasireotide long-acting release (LAR) treatment, plasma prolactin levels normalized and symptoms disappeared within one month after initiation. The clinical benefits of the monotherapy (specifically, prolactin levels within normal range and stable tumor volume) were maintained for seven years. Glucose tolerance was satisfactory. Pathological analysis of the tumor revealed high SSTR5 and low SSTR2 expression (25 and 5% of cells respectively). ConclusionThis is a promising first report of a patient with a DA-resistant macroprolactinoma who achieved long-term control, in terms of prolactin normalization and tumor volume, under pasireotide treatment alone. Pasireotide could thus be an alternative in prolactinomas resistant to DA. SSTR expression analysis on pathology could guide patient selection.

AIP and the somatostatin system in pituitary tumours.

Classic somatostatin analogues aimed at somatostatin receptor type 2, such as octreotide and lanreotide, represent the mainstay of medical treatment for acromegaly. These agents have the potential to decrease hormone secretion and reduce tumour size. Patients with a germline mutation in the aryl hydrocarbon receptor-interacting protein gene, AIP, develop young-onset acromegaly, poorly responsive to pharmacological therapy. In this review, we summarise the most recent studies on AIP-related pituitary adenomas, paying special attention to the causes of somatostatin resistance; the somatostatin receptor profile including type 2, type 5 and truncated variants; the role of G proteins in this pathology; the use of first and second generation somatostatin analogues; and the role of ZAC1, a zinc-finger protein with expression linked to AIP in somatotrophinoma models and acting as a key mediator of octreotide response.

Effect of AP102, a subtype 2 and 5 specific somatostatin analog, on glucose metabolism in rats.

Somatostatin analogs are widely used to treat conditions associated with hormonal hypersecretion such as acromegaly and metastatic neuroendocrine tumors. First generation somatostatin analogs, such as octreotide and lanreotide, have high affinity for somatostatin receptor subtype 2 (SSTR2), but have incomplete efficacy in many patients. Pasireotide targets multiple SSTRs, having the highest affinity for SSTR5, but causes hyperglycemia and diabetes mellitus in preclinical and clinical studies. AP102 is a new somatostatin analogs with high affinity at both SSTR2 and SSTR5. We aimed to characterize the effects of AP102 vs. pasireotide on random and dynamic glucose levels, glucoregulatory hormone concentrations and growth axis measures in healthy Sprague-Dawley rats. Three doses of each compound were evaluated under acute conditions (1, 10, and 30 µg/kg s.c.), and two doses during a chronic (4-week) infusion (3 and 10 µg/kg/h s.c.). Neither acute nor chronic AP102 administration altered blood glucose concentrations or dynamic responses following an intraperitoneal glucose tolerance test. In contrast, acute and chronic pasireotide dosing increased random and post-intraperitoneal glucose tolerance test blood glucose measures, compared to vehicle-treated controls. Both AP102 and pasireotide acutely suppressed growth hormone levels, although insulin-like growth factor-1 and somatic growth was suppressed to a greater extent with pasireotide. AP102 is a new dual SSTR2/SSTR5-specific somatostatin analog that acutely reduces growth hormone but does not cause hyperglycemia during acute or chronic administration in a healthy rat model. Further studies in diabetic animals and in humans are necessary to determine the potential utility of AP102 in the clinical setting.

Acromegaly: the effect of somatostatin analogues on tumour volume shrinkage

Acromegaly is a rare disease, caused by growth hormone (GH) hypersecretion and secondarily elevated insulin-like growth hormone 1 (IGF-1) level. Nearly all patients with acromegaly suffer from somatotroph pituitary adenoma. The main goal of treatment is to normalise both GH and IGF-1 levels, which reduces symptoms, complications and mortality. Transsphenoidal selective adenomectomy performed by an experienced neurosurgeon is the first-line therapy of choice. Therapy with somatostatin analogues (SSA) is used as a neoadjuvant treatment prior to surgery and in a persistent disease following the surgery. The long-acting somatostatin analogues reduce serum GH/IGF-1 levels and tumour volume. In this clinical review, mechanisms and role of 1st and 2nd generation somatostatin analogues in the treatment of patients with acromegaly are presented, with particular emphasis on the effects on somatotroph pituitary adenoma volume reduction.

Pasireotide for treating acromegaly

ABSTRACTIntroduction: Uncontrolled acromegaly can lead to serious illness and premature death. Currently, treatment options include surgery, medical therapy and radiotherapy. Somatostatin analogues (SAs) are the medical treatment of choice. Nevertheless, a percentage of patients do not adequately respond to first generation SAs, lanreotide and octreotide, monotherapy. In this context, the multi-ligand SA pasireotide, which has a broader binding profile, appears as an option.Areas covered: The aim of this paper is to review pasireotide as an option for acromegalic patients. It will provide an overview, emphasizing its mechanism of action, clinical efficacy, adverse effects and indications. In addition to Google Scholar, a PubMed search using key words was conducted, and relevant articles published in English peer-reviewed journals were retrieved. Only those papers that directly addressed pasireotide treatment for acromegaly were retained for extensive review.Expert opinion: Pasireotide has been shown to overcome resistance to the first generation SAs in a subset of acromegalic patients, becoming an important tool in the treatment algorithm of acromegaly. Nevertheless, due to the higher prevalence of hyperglycemia-related events under its use, in our opinion pasireotide treatment should be reserved for those acromegalic patients inadequately controlled by first generation SAs, lanreotide and octreotide.

Effects of Somatostatin Analogues on Glucose Metabolism in Acromegaly: Friend of Foe?

Effects of Somatostatin Analogues on Glucose Metabolism in Acromegaly: Friend of Foe?