Somatostatin receptors

Lanreotide (BIM 23014) (100 nM; 0-48 h) increases the apoptosis caused by radiation [1]. The development of GH3 cell colonies was decreased by lanreotide in a dose-dependent manner. Cell survival rates were 75%, 56%, 39%, and 27% at lanreotide doses of 1, 10, 100, and 1000 nM, respectively. 57 nM is the IC50[1]. In vitro, lanreotide suppresses the growth and hormone release of pituitary adenoma cells that secrete growth hormone [2].

---

Dose–responses of GH3 cells to Lanreotide and γ radiation [1]
As shown in Fig. 1A, treatment with Lanreotide resulted in a dose-dependent decrease in GH3 cell colony forming units. Lanreotide at doses of 1, 10, 100, and 1000 nM resulted in cell survival rates of 75, 56, 39 and 27% respectively. The IC50 (50% inhibition of cell growth) was 57 nM. The radiation survival curves are shown in Fig. 1B. GH3 cells had a typical radiation dose–response survival curve with an initial shoulder at doses below 5 Gy and a straight line at high dose. The SF at 2 Gy (SF2, a dose commonly used in daily fractionated radiotherapy) was 40%.

---

Effect of Lanreotide on radiation response of GH3 cells [1]
GH3 cells were plated in tissue culture dishes overnight. The radiation survival curves are shown in Fig. 2. Treatment with Lanreotide alone at doses of either 100 or 1000 nM for 48 h without radiation reduced clonogenic survival compared with untreated controls by 5–10%. Radiation alone without lanreotide produced a dose-dependent survival curve with a SF2 of 48–55%. Treatment with lanreotide at a dose of 100 nM for 48 h either before (48 h prelanreotide and 24 h prelanreotide) or at the time of radiation (0 h prelanreotide) produced survival curves that were slightly shifted downward and separated at doses of 7–10 Gy from the survival curve produced by radiation alone without lanreotide (Fig. 2A) indicating that the radiation response of GH3 cells was enhanced by lanreotide. The SF at 10 Gy was 0.0006, 0.00022, 0.00040, and 0.00042 respectively, for radiation alone, 48 h pre-, 24 h pre- and 0 h pre-exposure to lanreotide (Fig. 2C). However, treatment with 1000 nM lanreotide did not alter the shape and slopes of the radiation survival curves, indicating there was no radioprotection (or radiosensitization) effect under these experimental conditions (Fig. 2B).

---

Effect of Lanreotide and radiation on apoptosis and cells cycle distribution [1]
The percentage of cells in sub-G1, G1, S, and G2/M phases at 48 h was 1.4±0.2, 73.2±1.0, 8.4±1.0, and 16.9±1.8% respectively. Treatment with 100 nM Lanreotide alone resulted in the sub-G1, G1, S, and G2/M phase distribution of 2.28±0.3, 73.8±1.1, 7.72±0.8, and 16.2±0.5% respectively, indicating that the cell cycle profile was not significantly affected by treatment with lanreotide compared with the untreated control, except for a moderate increase in apoptotic sub-G1 cells from 1.4 to 2.28%. Treatment with 10 Gy radiation resulted in a decrease in the proportion of cells in G1 phase from 73.2 to 51.5% at 48 h. Meanwhile, the G2/M phase cells increased from 16.9% before radiation to 35.7% at 48 h after irradiation, and cells were arrested at G2/M phase for up to 168 h without release. The subdiploid cell population, representing apoptotic cells, increased steadily following radiation from a baseline of 1.4% to a peak of ∼12% at 168 h (Fig. 3). Combined treatment of GH3 cells with radiation and lanreotide produced a cell cycle profile that was similar to that seen in irradiated cells without lanreotide, except for the increase in apoptotic sub-G1 proportion. As shown in Fig. 3, at 48 h after irradiation, the apoptotic sub-G1 cells increased from 4.9% for radiation alone to 8.6, 9.3, and 13.4% for the combination of radiation with 48, 24, and 0 h pre-exposure of lanreotide respectively, representing an increase of 77–173% compared with radiation alone (P<0.01). At 168 h after radiation, the sub-G1 cell fraction was 12% for radiation alone and 20–22% for radiation plus lanreotide, representing an increase of 67–83% (P<0.01).

---

All the adenomas analysed expressed at least one somatostatin receptor subtype mRNA. SSTR2 mRNA was identified in 77% of the adenomas, SSTR1 and SSTR3 in 69% and SSTR5 in 60%. Somatostatin and Lanreotide inhibited cell proliferation in phorbol ester (PMA)-stimulated conditions (10/13 adenomas), as well as after fetal calf serum (3/3 adenomas) or IGF-I stimulation (2/2 adenomas). Conversely, GHRH or forskolin treatments did not significantly affect DNA synthesis in adenoma cells in the presence or absence of somatostatin (2/2 and 4/4 adenomas, respectively). Vanadate pretreatment reversed somatostatin inhibition of PMA-induced DNA synthesis suggesting an involvement of tyrosine phosphatase in this effect (2/2 adenomas); this was confirmed by the direct induction of tyrosine phosphatase activity in two adenomas after somatostatin treatment. Somatostatin and also lanreotide caused significant inhibition of phorbol ester, forskolin, GHRH and KCl-dependent increase of GH secretion in the culture medium. Moreover, voltage-sensitive calcium channel activity induced by 40 mm KCl depolarization in microfluorimetric analysis, was significantly reduced (5/5 adenomas).
Conclusions: These data show that somatostatin and Lanreotide inhibit human GH-secreting pituitary adenoma cell proliferation and hormone release in vitro, and suggest that the activation of tyrosine phosphatases may represent intracellular signals mediating the antiproliferative effects and that the inhibition of the voltage-dependent calcium channels and adenylyl cyclase activities may control GH secretion [2].

Tumor development is inhibited by lanreotide acetate (2.5–10 mg/kg; subcutaneous injection; once daily for 5 days) [1].

---

Dose–responses of GH3 tumors to Lanreotide [1]
Groups of nude mice with established GH3 xenograft tumors were treated subcutaneously with 2.5, 5, 10, 20, or 50 mg/kg Lanreotide daily for 5 days. Doses were based on prior studies utilizing lanreotide administration in vivo (Prevost et al. 1994, Melen-Mucha et al. 2004). As shown in Fig. 4, there was a bell-shaped dose dependent effect of lanreotide on GH3 tumor growth, with a narrow range of optimal doses. The maximum tumor growth inhibition (i.e. the longest TGD time of 13.1±4.7 days) occurred with a daily lanreotide dose of 10 mg/kg. When the daily lanreotide dose was either higher (i.e. 20 and 50 mg/kg) or lower (2.5 and 5 mg/kg) than 10 mg/kg, the effects of lanreotide on GH3 tumor growth were diminished.

In these studies, Lanreotide at all doses tested did not cause significant decrease in body weight compared with untreated control mice (data not shown). Also, there was no notable change in the general appearance and daily activity of tumor-bearing mice treated with lanreotide.

---

Comparison of Lanreotide dose regimen of once daily versus twice daily [1]
To determine the importance of lanreotide dose regimen on tumor growth, we compared tumor size after single daily dose (qd) and two doses daily (bid). GH3 tumor-bearing nude mice were injected s.c. with lanreotide at doses of 2.5, 5 or 10 mg/kg for 5 days either once daily or twice daily (8 h interval). As shown in Fig. 5, there were no statistically significant differences between groups treated either once daily or twice daily at the same dose (P=0.3–0.9). However, lanreotide at 10 mg/kg once daily produced the longest TGD time (4.9±2.1 days) of all dose regimens studied (P<0.05). Notably, this was longer than that (1.1±3.1 days) following 5 mg/kg twice daily. Analogously, a single daily dose of 5 mg/kg qd produced a longer TGD time than did 2.5 mg/kg bid. These data suggest that a single dose of Lanreotide produced at least as much tumor growth inhibition than a fractionated dose regimen at the same total daily dose. Therefore, further studies utilized the single daily dosing regimen.

---

Combination therapy of Lanreotide and fractionated radiation [1]
To study the effect of lanreotide on tumor responses to radiation therapy, nude mice with established GH3 tumors were treated with: 1) 10 mg/kg lanreotide daily for 5 days; 2) local tumor radiation daily for 5 consecutive days at doses of 250, 200, or 150 cGy/fraction per day; 3) a combination of Lanreotide and local tumor radiation as above; or 4) a s.c. injection of normal saline (0.005 ml/g body weight) daily as an untreated control. In combination therapy, lanreotide was injected 20 min before radiation. Data are shown in Fig. 6 (tumor growth curves). Lanreotide alone at a dose of 10 mg/kg moderately inhibited the growth of GH3 tumors, with a 4× TGD time that ranged from 4.5 to 8.3 days (P=0.3–0.06, compared with the relevant control groups). Fractionated local tumor radiation alone significantly inhibited tumor growth and produced TGD times of 35.1±5.7 days for 250 cGy fractions, 21.7±5.5 days for 200 cGy fractions, and 16.7±1.7 days for 150 cGy fractions respectively. The combination of lanreotide with radiation of 250, 200, or 150 cGy/fraction for 5 days inhibited tumor growth and produced the TGD times that were similar to radiation alone (P>0.05). Also, the combined treatment of lanreotide and fractionated radiation did not cause any further decrease in animal body weight compared with fractionated radiation therapy alone.

---

Preadministration of Lanreotide in combination with radiation therapy [1]
To study whether preadministration of Lanreotide could modulate radiation effects on tumor growth, nude mice with GH3 xenograft tumors were treated with: 1) 10 mg/kg lanreotide daily for 10 days; 2) 150 cGy local tumor radiation daily for 5 consecutive days; and 3) 10 mg/kg lanreotide for 5 days followed by combined administration of lanreotide and 150 cGy radiation daily for 5 days. A group of tumor-bearing mice that was injected s.c. with normal saline daily for 10 days was also included as an untreated control. As shown in Fig. 7, lanreotide at a dose of 10 mg/kg for 10 days moderately inhibited tumor growth (4× TGD, 8.3±8.3 days, P=0.06 versus control). Local tumor radiation of 150 cGy inhibited tumor growth and gave a TGD time of 15.5.0±8.8 days (P<0.05 versus control and lanreotide alone). The combination therapy of preadministration of lanreotide and radiation in this treatment regimen resulted in a TGD time of 15.1±8.6 days, similar to that produced by radiation therapy alone (15.5±8.8 days; P>0.05). There were two mice with complete regression of tumors in both radiation alone and combination therapy groups, without tumor regrowth when the study was terminated after 60 days. Furthermore, lanreotide alone and in combination with radiation did not produce any obvious signs of systemic toxicity in terms of the loss of body weight, general appearance, skin reaction or activity level of the mice (data not shown).

Apoptosis analysis[1]
Cell Types: GH3
Tested Concentrations: 100 nM
Incubation Duration: 48 hrs (hours), 24 hrs (hours) or immediately before irradiation (0 hrs (hours))
Experimental Results: Increased proportion of apoptotic sub-G1 compared to irradiation alone.

---

In vitro clonogenic assay [1]
The dose–response of GH3 cells to the treatment of both Lanreotide and radiation was characterized using a clonogenic assay. GH3 cells were detached with 0.05% trypsin-EDTA solution, counted and plated in 60 mm Petri dishes at appropriate dilutions of 100–100 000 cells/dish in triplicate in fresh growth media. Lanreotide was added to the plates at final concentrations of 0–1000 nM. Cells were irradiated with 0–10 Gy at room temperature using a 137Cs source with a dose rate of 300 cGy/min. Following exposure to lanreotide or γ radiation, the media was removed, and dishes were washed twice with PBS solution and filled with fresh growth media. After incubation at 37 °C for 21 days, cells were stained with 0.25% crystal violet. Colonies containing ≥50 cells were counted under a dissecting microscope and survival curves were generated. The plating efficiency (PE) was calculated as the percentage of cells plated that grew into colonies. The surviving fraction (SF) was defined as the fraction of cells surviving an intervention, i.e. number of colonies/(number of colonies plated×PE). [1]
For the irradiation experiments, Lanreotide at final concentrations of 100 or 1000 nM (determined by experiments shown in Fig. 1) was added at 48, 24, or 0 h before radiation. Cells were irradiated with 0–10 Gy in the presence of lanreotide at room temperature with a Cs-137 γ irradiator. Following radiation, cells with 24 h or 0 h pre-exposure to lanreotide were incubated in lanreotide-containing media for an additional 24 or 48 h respectively. After a total of 48 h exposure, lanreotide-containing media was removed, and dishes were washed twice with PBS solution and then filled with fresh growth media. Dishes that were irradiated without lanreotide exposure were also washed twice with PBS and refilled with fresh media. Cells were incubated for 21 days for colony formation.

---

Apoptosis and cell cycle analysis [1]
GH3 cells were placed in 60 mm Petri dishes (500 000 cells/dish) and grown overnight. Lanreotide at 100 nM was added at 48 h, 24 h, or immediately (0 h) before radiation. Cells were irradiated with 10 Gy γ radiation at room temperature. Cells were collected 48, 72, 96, and 168 h after irradiation, and washed with cold PBS plus 5 mM EDTA. Cells were resuspended in cold PBS–EDTA solution and fixed with cold 100% ethanol. After incubation for 30 min at room temperature, cells were pelleted and treated with 100 μg/ml of RNase A in PBS-EDTA solution for 30 min at room temperature. Propidium iodide (PI) was added to a final concentration of 50 μg/ml. The DNA content was analyzed with a FACScan flow cytometer. The percentage of cells in the sub-G1 (apoptotic), G1, S, and G2/M phases was calculated. Control cells without any treatment showed a consistent cell cycle distribution within 168 h (data not shown).

---

Cell treatment [2]
GH-secreting adenoma cells were plated at the density of 1 × 105 in 24-well plates. After 24 h, cells were serum- and growth factor-starved for 24 h. Subsequently, cells were treated with the test substances for 16 h. At the end of the incubation time, in some cases when a small amount of cells were available, an aliquot of the medium was removed for GH determination and then 2 µCi/ml of [3H]-thymidine were added for 4 h before the proliferation assay. However, when possible independent treatments for cell proliferation and GH release were performed.

---

Proliferation assay [2]
DNA synthesis activity was measured by means of the [3H]-thymidine uptake assay as previously reported (Florio et al., 1992). Briefly, cells, treated as indicated, were trypsinized (15 min at 37 °C), extracted in 10% trichloroacetic acid (TCA) and filtered under vacuum through fibreglass filters. The filters were then washed sequentially, under vacuum with 10% and 5% TCA and 95% ethanol. The TCA insoluble fraction was then counted in a scintillation counter.

---

In vitro GH release measurement [2]
GH was measured by commercial immunoradiometric assay as previously reported (Giusti et al., 2002). Media from cell cultures were diluted from 1 : 10 to 1 : 100 in phosphate-buffered saline (PBS) buffer to allow better evaluation of GH content. All samples from the same experiment were measured in the same assay. The results are expressed as µg/well. Absolute and percent variation from control data are reported as mean ± SEM.

---

PTP assay [2]
Cells, plated at 50% confluence in 6-cm Petri dishes, were preincubated with the test substances for 1 h in FCS-free medium at 37 °C in a CO2 incubator. Then the cells were washed with PBS and mechanically scraped in a buffer containing 0·32 m sucrose, 10 mm Tris, pH 7·5, 5 mm EGTA, 1 mmol/l EDTA and sonicated. Cell lysate was then centrifuged at 15 000 g at 4 °C for 60 min, resuspended in a buffer containing 250 mm HEPES, pH 7·2, 140 mm NaCl, 1% NP40 and phenylmethylsulphonyl fluoride (PMSF) and leupeptin as protease inhibitors, and assayed for protein content using the method of Bradford (1976) with bovine serum albumin as standard and the Bio-Rad reagent. Twenty micrograms of control or treated membranes were used in the PTP assay. PTP assay was performed using the synthetic substrate para-nitro-phenylphosphate (p-Npp) in a spectrophotometric assay. p-Npp is a general phosphatase substrate that in presence of inhibitors of Ser/Thr phosphatases is specific for PTPs (Pan et al., 1992). Membranes were preincubated for 5 min at 30 °C in 80 µl volume containing 20 µl of a 5× reaction buffer [250 mm HEPES, pH 7·2, 50 mm dithiothreitol (DTT), 25 mm EDTA, and 500 nm microcystin–leucine–arginine, Alamone Laboratories, Jerusalem Israel, as a Ser/Thr phosphatases inhibitor]. The reaction was started by adding 20 µl of 50 mmp-Npp, carried out for 30 min at 30 °C and stopped by adding 900 µl of 0·2 N NaOH. The absorbance of the sample, directly proportional to the amount of dephosphorylated substrate, was measured at 410 nm. The extinction coefficient for p-Npp, at this wavelength is 1·78 × 104m/cm.

---

Measurement of intracellular calcium concentrations at single-cell level [2]
Cells were plated on 25-mm clean glass coverslips, previously coated with poly-l-lysine (10 µg/ml) and transferred to a 35-mm Petri dishes. After 24–48 h cells were serum-starved for further 24 h. On the day of the experiment the cells were washed for 10 min with a balanced salt solution (HEPES 10 mm, pH 7·4; NaCl 150 mm; KCl 5·5 mm; CaCl2 1·5 mm; MgSO4 1·2 mm; glucose 10 mm). Then adenomatous cells were loaded with Fura-2 penta-acetoxymethyl ester (4 µm) for 60 min at room temperature. Fluorescence measurements were performed as previously reported (Florio et al., 1999b). Briefly, coverslips were mounted on a coverslip chamber and fura-2 fluorescence was imaged with an inverted Nikon diaphot microscope using a Nikon 40X/1·3 NA Fluor DL objected lens. Cells were illuminated with a Xenon lamp with quartz collector lenses. A shutter and a filter wheel containing the two different excitation filters (340 nm and 380 nm) were controlled by computer. Emitted light was passed through a 400-nm dichroic mirror, filtered at 490 nm and collected by CCD camera connected with a light intensifier. Images were digitalized and averaged in an image processor connected to a computer equipped with the Quanticell software. For the calibration of fluorescence signals, we used cells loaded with Fura-2; Rmax and Rmin are ratios at saturating and zero [Ca2+]i, respectively, and were obtained perfusing the cells with a salt solution containing CaCl2 (10 mm), digitonin (2·5 µm) and ionomycin (2 µm) and subsequently with a Ca2+-free salt solution containing EGTA (10 mm). The values of obtained Rmax and Rmin, expressed as grey level mean, were used to calculate the intracellular Ca2+ concentration ([Ca2+]i), using the Quanticell software, according to the equation of Grynkiewicz et al. (1985).

Animal/Disease Models: Male nude mouse, 8 weeks old, weighing 20-25 g (GH3 tumor-bearing nude mouse) [1]
Doses: 2.5, 5, 10 mg/kg
Route of Administration: subcutaneous injection; one time/day for 5 days.
Experimental Results: Produce tumor growth inhibition effect.

---

Mouse xenograft tumor model and therapy [1]
Male nude mice, 8 weeks old and 20–25 g in body weight were tested and found to be negative for specific pathogens. The mice were normally bred and maintained under specific pathogen-free conditions, and sterilized food and water were available ad libitum. Mice were injected subcutaneously in the right flank with 5×106 tumor cells in 100 μl of a Hank's solution and Matrigel 1:1 mixture. One tumor per mouse was inoculated. When tumors reached an average size of 120 mm3 (80–200 mm3), mice were randomly assigned to the different treatment groups. Five to eight mice were used in each group. Lanreotide was injected s.c. at doses specified in each experiment. For radiation, the unanesthetized tumor-bearing mice were placed in individual lead boxes with tumors protruding through a cutout window at the rear of each box. The radiation was delivered using a Philips RT-250 200 kVp X-ray unit (12.5 mA; half value Layer, 1.0-mm Cu) at a dose rate of 138 cGy/min. Tumors were locally irradiated with a dose of 150–250 cGy per fraction daily for 5 consecutive days as specified in each experiment. The length and width of the tumors were measured with calipers before treatment by the same investigator, and three times a week thereafter until the tumor volume reached at least four times (4×) the pretreatment volume. The tumor volume was calculated using the formula: tumor volume (mm3)=π/6×length×width2. The tumor volume quadrupling (4×) time was determined by a best-fit regression analysis. The tumor growth delay (TGD) time (in days) is the difference between the tumor volume quadrupling time of treated tumors compared with that of untreated control tumors. Both the tumor volume quadrupling time and TGD time were calculated for each individual animal and then averaged for each group. In some experiments, a complete regression of tumors was recorded if a tumor completely shrunk to the point that it was not palpable at the end of the experiment. Body weight was measured twice a week.

Absorption, Distribution and Excretion
Lanreotide forms a drug depot at the site of injection; therefore, there are 2 phases that describe the absorption of Lanreotide: 1. Initial rapid subcutaneous release during the first few days of treatment where drug that has not precipitated is rapidly absorbed. 2. Slow release of drug from the depot via passive diffusion. Absorption is independent of body weight, gender, and dosage.
<5% of lanreotide is excreted in urine, and less than 0.5% is excreted unchanged in the feces suggesting biliary excretion involvement.
Estimated Volume of Distribution = 15.1 L
Estimated Clearance = 23.1 L/h

---

Biological Half-Life
Half-life is approximately 22 days

Hepatotoxicity
In preregistration studies of lanreotide, serum enzyme levels did not change appreciably and there were no reports of clinically apparent acute liver injury. Pooled analyses reported that there were no overall changes in serum ALT, AST or alkaline phosphatase levels during therapy or instances of clinically meaningful elevations with treatment. Prolonged therapy with lanreotide, as with other somatostatin analogues, was associated with a high rate of biliary sludge and cholelithiasis, probably due to inhibition of gall bladder contractility and decrease in bile secretion. In long term studies, cholelithiasis developed in 20% to 33% of lanreotide treated patients. In some instances, symptomatic cholecystitis occurred which can be accompanied by mild-to-moderate elevations in serum enzymes and bilirubin. However, most lanreotide associated gallstones were asymptomatic. Unlike octreotide, lanreotide and other long acting somatostatin analogues have not been liked to cases of clinically apparent liver injury, independent of cholelithiasis or biliary sludge, although they have had more limited use and have not been used in many of the clinical situations that were treated with octreotide (portal hypertension, variceal hemorrhage and infants with congenital hyperinsulinemia).
Likelihood score: E* (unproven but suspected rare cause of clinically apparent hepatobiliary injury).

---

Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
The excretion of lanreotide into breastmilk has not been studied. However, because it has a high molecular weight of 1096 daltons it is likely to be poorly excreted into breastmilk and it is a peptide that is likely digested in the infant's gastrointestinal tract, so it is unlikely to reach the clinically important levels in infant serum. Lanreotide has been given by injection to newborn infants with congenital hyperinsulinemia; reversible mild elevation of liver enzymes occurred in some infants. The manufacturer states that women should not breastfeed during treatment with depot lanreotide and for 6 months following the last dose.
◉ Effects in Breastfed Infants
A woman with acromegaly was treated with lanreotide Autogel 120 mg monthly, cabergoline 2 mg weekly and pegvisomant 80 mg weekly. She breastfed (extent not stated) her infant and they were followed for 12 years. Her child had normal growth and development.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

[1]. Lanreotide promotes apoptosis and is not radioprotective in GH3 cells.Endocr Relat Cancer. 2009 Sep;16(3):1045-55.

[2]. Characterization of the intracellular mechanisms mediating somatostatin and lanreotide inhibition of DNA synthesis and growth hormone release from dispersed human GH-secreting pituitary adenoma cells in vitro.Clin Endocrinol (Oxf). 2003 Jul;59(1):115-28.

Lanreotide is a drug employed in the management of acromegaly (a hormonal condition caused by excess growth hormone) in addition to symptoms caused by neuroendocrine tumors, especially carcinoid syndrome. This drug is a long-acting analog of the drug somatostatin, a growth hormone inhibitor. Lanreotide is manufactured by the company, Ipsen Pharmaceuticals as lanreotide acetate, and marketed as Somatuline. It is approved in several countries worldwide, including the United Kingdom, Australia, and Canada. Lanreotide was first approved for use in the United States by the FDA on August 30, 2007.
Lanreotide is a synthetic polypeptide analogue of somatostatin that resembles the native hormone in its ability to suppress levels and activity of growth hormone, insulin, glucagon and many other gastrointestinal peptides. Because its half-life is longer than somatostatin, lanreotide can be used clinically to treat neuroendocrine tumors that secrete excessive amounts of growth hormone (acromegaly) or other active hormones or neuropeptides. Lanreotide has many side effects including suppression of gall bladder contractility and bile production, and maintenance therapy may cause cholelithiasis and pancreatitis as well accompanying liver injury.
Lanreotide is a synthetic cyclic octapeptide analogue of somatostatin. Lanreotide binds to somatostatin receptors (SSTR), specifically SSTR-2 and also to SSTR-5 with a lesser affinity. However, compare with octreotide, this agent is less potent in inhibiting the release of growth hormone from the pituitary gland. Furthermore, lanreotide has an acute effect on decreasing circulating total and free insulin-like growth factor 1 (IGF-I). This agent is usually given as a prolonged-release microparticle or Autogel formulation for the treatment of acromegaly and to relieve the symptoms of neuroendocrine tumors.
Lanreotide Acetate is the acetate salt of a synthetic cyclic octapeptide analogue of somatostatin. Lanreotide binds to somatostatin receptors (SSTR), specifically SSTR-2 and also to SSTR-5 with a lesser affinity. However, compare with octreotide, this agent is less potent in inhibiting the release of growth hormone from the pituitary gland. Furthermore, lanreotide has an acute effect on decreasing circulating total and free insulin-like growth factor 1 (IGF-I). This agent is usually given as a prolonged-release microparticle or Autogel formulation for the treatment of acromegaly and to relieve the symptoms of neuroendocrine tumors.
See also: Lanreotide Acetate (has salt form).

---

Drug Indication
Lanreotide is indicated for the long-term treatment of patients with acromegaly who have had an inadequate response to, or cannot be treated with, surgery and/or radiotherapy. It is also indicated in the treatment of adult patients with unresectable, well- or moderately-differentiated, locally advanced or metastatic gastroenteropancreatic neuroendocrine tumors (GEP-NETs) to improve progression-free survival. Lanreotide is additionally indicated for the treatment of adults with carcinoid syndrome - when used, it reduces the frequency of short-acting somatostatin analog rescue therapy.
FDA Label
Treatment of acromegaly, Treatment of gastrointestinal fistulae, Treatment of metastases to peritoneum, Treatment of pituitary gigantism, Treatment of pituitary neoplasms

---

Mechanism of Action
Lanreotide is a somatostatin analogue (SSA) and has mainly inhibitory effects which are mediated via somatostatin receptors (SSTRs) 2 and 5 and include inhibition of growth hormone release in the brain. Tumor SSTR activation induces downstream cell cycle arrest and/or apoptosis, and also results in blunted production of substances that support tumor growth as well as tumor angiogenesis. This leads to the anti-proliferative effects of Lanreotide.

---

Somatostatin analogs are a mainstay of medical therapy in patients with GH producing human pituitary tumors, and it has been suggested that somatostatin analogs may be radioprotective. We utilized GH secreting rat GH3 cells to investigate whether a somatostatin analog may limit the effects of radiation on proliferation and apoptosis in vitro and on tumor growth in vivo. Treatment with lanreotide alone at doses of either 100 or 1000 nM for 48 h reduced clonogenic survival by 5-10%. Radiation alone produced a dose-dependent survival curve with a SF2 of 48-55%, and lanreotide had no effect on this curve. The addition of lanreotide resulted in a 23% increase in the proportion of apoptotic sub-G1 cells following irradiation (P<0.01). In a mouse GH3 tumor xenograft model, lanreotide 10 mg/kg moderately inhibited the growth of GH3 tumors, with a 4x tumor growth delay (TGD) time that ranged from 4.5 to 8.3 days. Fractionated local tumor radiation alone significantly inhibited tumor growth and produced a TGD of 35.1+/-5.7 days for 250 cGy fractions. The combination of lanreotide, either antecedent to or concurrent, with radiation of 250, 200 or 150 cGy/fraction for 5 days inhibited tumor growth and produced the TGD times that were similar to radiation alone (P>0.05). Pretreatment with lanreotide had the most significant radiosensitizing effect. These studies demonstrate that the somatostatin analog lanreotide is not radioprotective in GH3 cells, and further studies are necessary to determine the impact of lanreotide on apoptosis.[1]

---

In summary, using a mouse xenograft model, we have demonstrated that the somatostatin analog lanreotide does not protect pituitary tumor cells from the effects of ionizing radiation, but does promote radiation induced apoptosis in rat GH3 cells. Further studies, both in vitro and in vivo, are needed to determine the potential clinical relevance of these findings to the management of patients with neuroendocrine tumors, such as acromegaly, and whether somatostatin analogs should be administered concurrently with radiation therapy. These preliminary findings also suggest that lanreotide may enhance radiation-induced apoptosis and warrant further study. In addition, further studies are necessary to elucidate the mechanisms underlying this potential synergistic action of lanreotide and radiation on apoptosis induction.[1]

---

Objective: Somatostatin is an endogenous inhibitor of hormone secretion and cell proliferation. Treatment with somatostatin analogues in humans causes a reduction in size and secretory activity of endocrine tumours, including GH-secreting pituitary adenomas. This study was aimed to characterize the intracellular mechanisms mediating the in vitro antiproliferative and antisecretory effects of somatostatin and its analogue lanreotide, on primary cultures of GH-secreting pituitary adenoma cells. Design: Thirteen GH-secreting pituitary adenoma postsurgical specimens were analysed for somatostatin receptor (SSTR) mRNA expression and a subset of them was analysed in vitro for the effect of somatostatin on cell proliferation, assessed by means of [3H]-thymidine uptake, and GH release, using an immunoradiometric assay. Moreover, the intracellular signalling involved in such effects has been studied.[2]

---

In conclusion, our data show that, in GH-secreting adenomatous cells, the in vitro activation of SSTR by somatostatin or Lan causes a reduction in both DNA synthesis and GH secretion. This effect is correlated to an increase in phosphotyrosine phosphatase PTP activity for the antiproliferative effects, and an inhibition of voltage-dependent calcium channel activity for the antihormonal effects, that represent possible intracellular effectors of SSTR activation in pituitary adenoma cells.[2]

C56H73N11O12S2

1156.37533068657

1155.488

C, 59.16; H, 6.34; N, 14.05; O, 14.59; S, 5.85 Lanreotide acetate

2378114-72-6

Lanreotide;108736-35-2;Lanreotide diTFA;1024499-83-9

6918010

White to off-white solid powder

14

16

17

81

2030

9

S1C[C@@H](C(N[C@H](C(N)=O)[C@@H](C)O)=O)NC([C@H](C(C)C)NC([C@H](CCCCN)NC([C@@H](CC2=CNC3C=CC=CC2=3)NC([C@H](CC2C=CC(=CC=2)O)NC([C@H](CS1)NC([C@@H](CC1C=CC2C=CC=CC=2C=1)N)=O)=O)=O)=O)=O)=O.OC(C)=O

DEXPIBGCLCPUHE-UISHROKMSA-N

InChI=1S/C54H69N11O10S2.C2H4O2/c1-29(2)45-54(75)63-44(53(74)65-46(30(3)66)47(57)68)28-77-76-27-43(62-48(69)38(56)23-32-15-18-33-10-4-5-11-34(33)22-32)52(73)60-41(24-31-16-19-36(67)20-17-31)50(71)61-42(25-35-26-58-39-13-7-6-12-37(35)39)51(72)59-40(49(70)64-45)14-8-9-21-55;1-2(3)4/h4-7,10-13,15-20,22,26,29-30,38,40-46,58,66-67H,8-9,14,21,23-25,27-28,55-56H2,1-3H3,(H2,57,68)(H,59,72)(H,60,73)(H,61,71)(H,62,69)(H,63,75)(H,64,70)(H,65,74);1H3,(H,3,4)/t30-,38-,40+,41+,42-,43+,44+,45+,46+;/m1./s1

acetic acid;(4R,7S,10S,13R,16S,19R)-10-(4-aminobutyl)-N-[(2S,3R)-1-amino-3-hydroxy-1-oxobutan-2-yl]-19-[[(2R)-2-amino-3-naphthalen-2-ylpropanoyl]amino]-16-[(4-hydroxyphenyl)methyl]-13-(1H-indol-3-ylmethyl)-6,9,12,15,18-pentaoxo-7-propan-2-yl-1,2-dithia-5,8,11,14,17-pentazacycloicosane-4-carboxamide

Lanreotide acetate; 127984-74-1; 10-(4-Aminobutyl)-19-[(2-amino-3-naphthalen-2-yl-propanoyl)amino]-N-(1 -carbamoyl-2-hydroxy-propyl)-16-[(4-hydroxyphenyl)methyl]-13-(1H-indol -3-ylmethyl)-6,9,12,15,18-pentaoxo-7-propan-2-yl-1,2-dithia-5,8,11,14, 17-pentazacycloicosane-4-carboxamide; 10-(4-aminobutyl)-N-(1-amino-3-hydroxy-1-oxobutan-2-yl)-19-[(2-amino-3-naphthalen-2-ylpropanoyl)amino]-16-[(4-hydroxyphenyl)methyl]-13-(1H-indol-3-ylmethyl)-6,9,12,15,18-pentaoxo-7-propan-2-yl-1,2-dithia-5,8,11,14,17-pentazacycloicosane-4-carboxamide; Angiopeptin acetate;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture and light.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~100 mg/mL (~86.48 mM)
H2O : ~25 mg/mL (~21.62 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (2.16 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

---

Solubility in Formulation 2: ≥ 2.5 mg/mL (2.16 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

---

View More

Solubility in Formulation 3: ≥ 2.5 mg/mL (2.16 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

---

 (Please use freshly prepared in vivo formulations for optimal results.)