sst1 ( pKi = 8.2 ); sst2 ( pKi = 9.0 ); sst3 ( pKi = 9.1 ); sst4 ( pKi < 7.0 ); sst5 ( pKi = 9.9 )

Pasireotide acetate binds to the human somatostatin receptor (subtype sst1/2/3/4/5, pKi=8.2/9.0/9.1/<7.0/9.9) with a particularly high affinity [1]. GH release in primary cultures of pituitary cells stimulated by growth hormone (GRH) with an IC50 of 0.4 nM [1].

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The strategy pursued in this research has been rewarded with the demonstrated superiority of Pasireotide/25 compared to 2. Pharmacological studies in vitro have clearly shown that Pasireotide/25 effectively inhibited the growth hormone releasing hormone (GHRH) induced growth hormone (GH) release in primary cultures of rat pituitary cells with an IC50 of 0.4 ± 0.1 nmol/L (n = 5) [1].

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Pasireotide is a somatostatin analogue with high binding affinity to somatostatin receptor subtypes sst1,2,3 and sst5, as shown in competitive binding studies using CHO-K1 cells expressing human recombinant somatostatin receptors (Table 2) (Bruns et al., 2002, Schmid and Schoeffter, 2004). In CCL39 cells expressing human recombinant sst receptors, pasireotide and somatostatin (SRIF-14) inhibited forskolin-stimulated cAMP accumulation with approximately the same efficacy and potency. Compared with octreotide, the functional activity (based on EC50 values) of pasireotide on sst1, sst3 and sst5 was >30-, 11- and 158-fold higher, respectively, but 7-fold lower on sst2 (Schmid and Schoeffter, 2004).
Based on the differences in binding affinity and functional activity of Pasireotide and octreotide, it can be speculated that in cells and tissues that express sst receptors other than the sst2 receptor subtype, pasireotide will have a stronger inhibitory effect on hormone secretion than octreotide [3].

Pasireotide acetate (160 mg/kg/month; subcutaneously for 4 months) dramatically decreases plasma insulin, boosts plasma plasma levels, reduces tumor growth, and increases Pdx1-Cre cells [2]. Pasireotide acetate (2-50 μg/kg; subcutaneously, twice daily for 42 days) produces analgesic and anti-inflammatory effects via SSTR2 receptors in immune-mediated arthritis models [4].

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In vivo, Pasireotide/25 also potently suppressed GH secretion in rats. The ED50 values determined at 1 and 6 h after injection of 25 indicated its very long duration of action in vivo. In the rat, 25 strongly decreases IGF-1 plasma levels, with the efficacy being markedly enhanced compared with the effects elicited by 2 after 7 days of treatment. Furthermore, in rats, dogs, and rhesus monkeys, 25 potently and dose-dependently decreased IGF-1 levels for prolonged periods of time without desensitization as observed with SMS 201-995 (2).[1]

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Background: Pasireotide (SOM230), a long-acting somatostatin analogue (LAR), has improved agonist activity at somatostatin receptors. We tested the effect of SOM230 on insulin secretion, serum glucose concentrations, tumor growth, and survival using an MEN1 transgenic mouse model.
Methods: Eight 12-month-old conditional Men1 knockout mice with insulinoma were assessed. The treatment (n = 4) and control groups (n = 4) received monthly subcutaneous injections of SOM230 or PBS. Serum insulin and glucose levels were determined by enzyme-linked immunosorbent assay and enzymatic colorimetric assay, respectively. Tumor activity, growth, and apoptosis were determined by microPET/CT scan and histologic analysis.
Results: On day 7, there was a decrease in serum insulin levels from 1.06 ± 0.28 μg/L to 0.37 ± 0.17 μg/L (P = .0128) and a significant increase in serum glucose from 4.2 ± 0.45 mmol/L to 7.12 ± 1.06 mmol/L (P = .0075) in the treatment group but no change in the control group. Tumor size was less in the treatment group (2,098 ± 388 μm(2)) compared with the control group (7,067 ± 955 μm(2); P = .0024). Furthermore, apoptosis was increased in the treatment group (6.9 ± 1.23%) compared with the control group (0.29 ± 0.103%; P = .002).
Conclusion: SOM230 demonstrates antisecretory, antiproliferative, and proapoptotic activity in our MEN1 model of insulinoma. Further studies of the effects of SOM230 in PNET patients with MEN1 mutations are warranted.[2]

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Objective: Clinical and preclinical evidence suggests that somatostatin exhibits potent antiinflammatory and antinociceptive properties. However, it is not known which of the 5 somatostatin receptor subtypes (SSTRs 1-5) is involved in these actions. The purpose of this study was to assess the effects of the stable somatostatin analogs octreotide and Pasireotide (SOM230) in a mouse model of antigen-induced arthritis (AIA).
Methods: Studies were performed in SSTR2-deficient mice (SSTR2(-/-)) and their wild-type littermates (SSTR2(+/+)). The expression of SSTR1, SSTR2A, SSTR3, and SSTR5 in dorsal root ganglia was examined by immunohistochemistry.
Results: Untreated SSTR2(-/-) mice with AIA displayed joint swelling and mechanical hyperalgesia similar to that seen in SSTR2(+/+) mice. In wild-type mice, both octreotide and Pasireotide significantly attenuated knee joint swelling and histopathologic manifestations of arthritis to an extent comparable to that of dexamethasone. In SSTR2(-/-) mice, the antiinflammatory effects of both octreotide and pasireotide were completely abrogated. Prolonged administration of Pasireotide also inhibited joint swelling and protected against joint destruction during AIA flare reactions. In addition, both octreotide and pasireotide reduced inflammatory hyperalgesia. The antinociceptive actions of octreotide were abolished in SSTR2(-/-) mice, but those of pasireotide were retained. In dorsal root ganglia of naive wild-type mice, only SSTR1 and SSTR2A, but not SSTR3 or SSTR5, were detected in a subset of small- and medium-diameter neurons.
Conclusion: Our findings indicate that the antinociceptive and antiinflammatory actions of octreotide and Pasireotide are largely mediated via the SSTR2 receptor. In addition, we identified the SSTR1 receptor as a novel pharmacologic target for somatostatin-mediated peripheral analgesia in inflammatory pain [4].

Pharmacological Characterization. Radioligand Binding Assays. [1]
Radioligand binding assays were performed as described previously. Briefly, membranes from CHO and COS cells expressing the respective human SRIF receptor subtype were incubated with the SRIF receptor ligand Tyr11[125I]-SRIF in the presence or absence of various concentrations of SRIF receptor ligands. The incubation was stopped after 1 h by rapid filtration through Whatman GF/C filters. Inhibition curves were analyzed, and IC50 values were calculated.

Apoptosis analysis [2]
Apoptotic status in endocrine tumor tissues was measured in control and treated mice by Terminal deoxynucleotidyl transferase dUTP Nick End-Labeling (TUNEL) assay. For quantification of apoptosis, the TUNEL assay was performed according to the manufacturer on paraffin-embedded sections with an In Situ Cell Death Detection Kit. The tissue sections were deparaffinized and treated with proteinase K (10 μg/ml) for 20 min. The sections were then washed twice with PBS, labeled and stained with the TUNEL reaction mixture (label plus enzyme solutions) for 60 min at 37°C, and washed twice with PBS in the dark. The slides were mounted in Vectashield mounting medium with DAPI. The apoptotic fluorescent cells were counted under a fluorescent microscope and the numbers were expressed as the percentage of total cells ± standard deviation (SD). A negative control without enzyme treatment and a positive control with DNase I treatment were also performed.

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SSTR detection [2]
The detection of sstr1-5 in pancreatic endocrine tumor tissue was measured in our mouse model. Immunofluorescent (IF) staining for sstr1-5 on sections was performed using rabbit or goat anti-sstr1, sstr2, sstr3, sstr4, and sstr5 antibodies (Abs) and were incubated at a 1:50 dilution overnight at 4° C, respectively. Pig anti-insulin Ab was also used for identification of β-cells. Sections were then washed with PBS and were incubated with a 1:200 dilution of anti-rabbit or anti-goat Alexa Fluor 488 and anti-pig Alexa Fluor 647 secondary antibodies for 45 min in the dark, respectively. A negative control without primary antibody was also performed.

Animal/Disease Models: 12-month-old conditional Men1 gene knockout mice with insulinoma [2]
Doses: 160 mg/kg/oral
Route of Administration: monthly subcutaneous injection for 4 months
Experimental Results: diminished serum insulin from 1.060 μg/L to 0.3653 μg/L, increasing serum glucose from 4.246 mM to 7.122 mM. Dramatically diminished tumor size and increased apoptosis.

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SOM230/Pasireotide and PBS Administration [2]
Mice were anesthetized using halothane and then shaved on their flank for subcutaneous injection of either phosphate buffered saline (PBS) buffer or Pasireotide/SOM230 at a concentration of 160mg/Kg/month (64mg/ml) every month for 4 months.

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Treatment protocol and drugs. [4]
Mice were randomly allocated to the following groups (8–10 animals per experimental condition): 0.9% saline; 2, 20, or 50 μg/kg of octreotide; or 2, 20, or 50 μg/kg of Pasireotide. These doses have been shown to elicit long-lasting therapeutic effects on pituitary hormone secretion in rodents and humans. Octreotide and Pasireotide were a kind gift from Novartis and were administered subcutaneously in a volume of 0.1 ml/kg of body weight. Treatment was started 12 hours before the induction of AIA and was continued for 3, 21, or 42 days, with administration every 12 hours for the indicated time periods. Flare reactions were provoked by injecting the right knee joint cavity with 100 μg of mBSA dissolved in 20 μl of PBS on days 21 and 35 of AIA. An additional group received 0.6 mg/kg of dexamethasone palmitate by intraperitoneal injection. Dexamethasone treatment was carried out for 5 days, followed by a 2-day pause starting 12 hours before AIA induction.

Absorption, Distribution and Excretion
The peak plasma concentration of pasireotide occurs in 0.25-0.5 hours. After administration of single and multiple doses, there is dose-proportionoal increases in Cmax and AUC.
Pasireotide is eliminated mostly by hepatic clearance (biliary excretion)(about 48%) with some minor renal clearance (about 7.63%).
Pasireotide is widely distributed and has a volume of distribution of >100L.
The clearance in healthy patient is ~7.6 L/h and in Cushing’s disease patients is ~3.8 L/h.

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Metabolism / Metabolites
Metabolism is minimal.

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Biological Half-Life
The half-life is 12 hours.

Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
The excretion of pasireotide into breastmilk has not been studied. However, because it has a high molecular weight of 1047 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. It is unlikely to reach the clinically important levels in infant serum. However, the manufacturer states that nursing mothers should not use pasireotide. An alternate drug is preferred.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

[1]. A novel somatostatin mimic with broad somatotropin release inhibitory factor receptor binding and superior therapeutic potential. J Med Chem. 2003 Jun 5;46(12):2334-44.

[2]. Pasireotide (SOM230) is effective for the treatment of pancreatic neuroendocrine tumors (PNETs) in a multiple endocrine neoplasia type 1 (MEN1) conditional knockout mouse model. Surgery. 2012 Dec;152(6):1068-77.

[3]. Pasireotide (SOM230): development, mechanism of action and potential applications. Mol Cell Endocrinol. 2008 May 14;286(1-2):69-74.

[4]. Differential antiinflammatory and antinociceptive effects of the somatostatin analogs octreotide and pasireotide in a mouse model of immune-mediated arthritis. Arthritis Rheum. 2011 Aug;63(8):2352-62.

Pasireotide is a six-membered homodetic cyclic peptide composed from L-phenylglycyl, D-tryptophyl, L-lysyl, O-benzyl-L-tyrosyl, L-phenylalanyl and modified L-hydroxyproline residues joined in sequence. A somatostatin analogue with pharmacologic properties mimicking those of the natural hormone somatostatin; used (as its diaspartate salt) for treatment of Cushing's disease. It has a role as an antineoplastic agent. It is a homodetic cyclic peptide and a peptide hormone. It is a conjugate base of a pasireotide(2+).
Pasireotide is a synthetic long-acting cyclic hexapeptide with somatostatin-like activity. It is marketed as a diaspartate salt called Signifor, which is used in the treatment of Cushing's disease.
Pasireotide is a Somatostatin Analog. The mechanism of action of pasireotide is as a Somatostatin Receptor Agonist.
Pasireotide 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, pasireotide can be used clinically to treat neuroendocrine pituitary tumors that secrete excessive amounts of growth hormone causing acromegaly, or adrenocorticotropic hormone (ACTH) causing Cushing disease. Pasireotide has many side effects including suppression of gall bladder contractility and bile production, and maintenance therapy can cause cholelithiasis and accompanying elevations in serum enzymes and bilirubin.
Pasireotide is a synthetic long-acting cyclic peptide with somatostatin-like activity. Pasireotide activates a broad spectrum of somatostatin receptors, exhibiting a much higher binding affinity for somatostatin receptors 1, 3, and 5 than octreotide in vitro, as well as a comparable binding affinity for somatostatin receptor 2. This agent is more potent than somatostatin in inhibiting the release of human growth hormone (HGH), glucagon, and insulin.
See also: Pasireotide Diaspartate (is active moiety of); Pasireotide Pamoate (is active moiety of).

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Drug Indication
For the treatment of Cushing’s disease, specifically for those patients whom pituitary surgery has not been curative or is not an option.
FDA Label
Signifor is indicated for the treatment of adult patients with Cushing's disease for whom surgery is not an option or for whom surgery has failed. Signifor is indicated for the treatment of adult patients with acromegaly for whom surgery is not an option or has not been curative and who are inadequately controlled on treatment with another somatostatin analogue.
Treatment of acromegaly and pituitary gigantism
Overproduction of pituitary ACTH, Pituitary dependant Cushing's disease, Pituitary dependant hyperadrenocorticism

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Mechanism of Action
Pasireotide activates a broad spectrum of somatostatin receptors, exhbiting a much higher binding affinity for somatostatin receptors 1, 3, and 5 than octreotide in vitro, as well as a comparable binding affinity for somatostatin receptor 2. The binding and activation of the somatostatin receptors causes inhibition of ACTH secretion and results in reduced cortisol secretion in Cushing's disease patients. Also this agent is more potent than somatostatin in inhibiting the release of human growth hormone (HGH), glucagon, and insulin.

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Pharmacodynamics
Signifor® is an analogue of somatostatin that promotes reduced levels of cortisol secretion in Cushing's disease patients.

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A rational drug design approach, capitalizing on structure-activity relationships and involving transposition of functional groups from somatotropin release inhibitory factor (SRIF) into a reduced size cyclohexapeptide template, has led to the discovery of SOM230 (25), a novel, stable cyclohexapeptide somatostatin mimic that exhibits unique high-affinity binding to human somatostatin receptors (subtypes sst1-sst5). SOM230 has potent, long-lasting inhibitory effects on growth hormone and insulin-like growth factor-1 release and is a promising development candidate currently under evaluation in phase I clinical trials. [1]

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Pasireotide (SOM230) is a multi-receptor ligand somatostatin analogue with high binding affinity for somatostatin receptor subtypes sst(1,2,3) and sst(5). Pasireotide potently suppresses GH, IGF-I and ACTH secretion, indicating potential efficacy in acromegaly and Cushing's disease. The prolonged inhibition of hormone secretion by pasireotide in animal models and expression of multiple sst receptors in carcinoid tumors suggests that pasireotide may have clinical advantages over octreotide in patients with carcinoid tumors. Direct and indirect antitumor activity has been observed in vitro with pasireotide, including sst receptor-mediated apoptosis and antiangiogenesis, suggesting a possible role for pasireotide in antineoplastic therapy. In summary, preclinical evidence, as well as preliminary results from clinical studies suggests that pasireotide is a promising new treatment for patients with symptoms of metastatic carcinoid tumors refractory or resistant to octreotide, de novo or persistent acromegaly, and that pasireotide has the potential to be the first directed medical therapy for Cushing's disease.[3]

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In summary, this study is the first of its kind to demonstrate the antisecretory, antiproliferative and proapoptotic actions of the novel long acting release somatostatin analogue SOM230 in a mouse model of insulinomas with improved overall survival. The enhanced spectrum of activity of SOM230 is a result of its enhanced activity at 4 of the 5 sstr subtypes: sstr5, sstr2, sstr3, and sstr1. This is of particular clinical importance in unresectable or metastatic insulinomas that are relatively unresponsive to traditional therapy with octreotide and/or diazoxide. Treatment with SOM230 may facilitate symptomatic relief and result in tumor regression. We believe that this novel strategy of targeted therapy with SOM230 will be of benefit to patients with PNETs. While these data strongly support the effects of pasireotide in this model, we acknowledge that further studies with larger sample sizes are warranted to advance this novel approach toward clinical trials. [2]

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We also studied the progression of histopathologic changes of chronic inflammation after prolonged administration of pasireotide. These changes become particularly evident upon repeated injections of the antigen into the joint. The present data clearly show that in this model of immune-mediated arthritis, not only the acute inflammatory reaction, but also the chronic inflammatory/destructive process, can be dampened by SSTR agonists. Due to their antiinflammatory actions (equivalent to dexamethasone) and their antinociceptive actions, SSTR agonists are of interest for clinical therapy. In fact, in a pilot study in RA patients, significant clinical improvement was noted after treatment with octreotide. The present observations suggest that pasireotide and octreotide would exhibit similar antiinflammatory effects; however, pasireotide would be expected to provide better pain control than octreotide in RA. As an important aspect, treatment with somatostatin analogs is considered to be relatively safe and well tolerated. Moreover, for prolonged use, long-acting versions of both octreotide and pasireotide are available; these need to be administered only once a month, thus eliminating the need for daily subcutaneous injections.
In conclusion, we provide evidence of potent antiinflammatory and antinociceptive effects of the somatostatin receptor agonists octreotide and pasireotide. We identify SSTR2 as an important target involved in the antiinflammatory effects of somatostatin. Both SSTR2 and SSTR1 mediate antinociception. Concerning the clinical use of SSTR agonists, it should be considered that pan-SSTR agonists may be superior to selective SSTR2 agonists.[4]

C60H70N10O11

1107.26

1106.522

396091-76-2

Pasireotide L-aspartate salt;396091-77-3;Pasireotide pamoate;396091-79-5;Pasireotide;396091-73-9;Pasireotide (diaspartate);1421446-02-7

72205932

Cyclo[{4-(NH2-C2H4-NH-CO-O-)Pro}-Phg-{D-Trp}-K-{Tyr(4-Bzl)}-F]

White to off-white solid powder

10

13

18

81

1970

7

CC(=O)O.C1[C@H](CN2[C@@H]1C(=O)N[C@H](C(=O)N[C@@H](C(=O)N[C@H](C(=O)N[C@H](C(=O)N[C@H](C2=O)CC3=CC=CC=C3)CC4=CC=C(C=C4)OCC5=CC=CC=C5)CCCCN)CC6=CNC7=CC=CC=C76)C8=CC=CC=C8)OC(=O)NCCN

WFKFNBBHVLMWQH-QKXVGOHISA-N

InChI=1S/C58H66N10O9.C2H4O2/c59-27-13-12-22-46-52(69)64-47(30-38-23-25-42(26-24-38)76-36-39-16-6-2-7-17-39)53(70)66-49(31-37-14-4-1-5-15-37)57(74)68-35-43(77-58(75)61-29-28-60)33-50(68)55(72)67-51(40-18-8-3-9-19-40)56(73)65-48(54(71)63-46)32-41-34-62-45-21-11-10-20-44(41)45;1-2(3)4/h1-11,14-21,23-26,34,43,46-51,62H,12-13,22,27-33,35-36,59-60H2,(H,61,75)(H,63,71)(H,64,69)(H,65,73)(H,66,70)(H,67,72);1H3,(H,3,4)/t43-,46+,47+,48-,49+,50+,51+;/m1./s1

(3S,6R,9S,12S,15S,19R,20aS)-6-((1H-indol-3-yl)methyl)-9-(4-aminobutyl)-15-benzyl-12-(4-(benzyloxy)benzyl)-1,4,7,10,13,16-hexaoxo-3-phenylicosahydropyrrolo[1,2-a][1,4,7,10,13,16]hexaazacyclooctadecin-19-yl (2-aminoethyl)carbamate acetate

SOM 230; SOM-230; Pasireotide acetate; 396091-76-2; Pasireotide acetate salt [MI]; UNII-662X0VFR9L; 662X0VFR9L; Cyclo((2S)-2-phenylglycyl-D-tryptophyl-L-lysyl-O-(phenylmethyl)-L-tyrosyl-L-phenylalanyl-(4R)-4-((((2-aminoethyl)amino)carbonyl)oxy)-L-prolyl), monoacetate; Pasireotide acetate salt; Pasireotide (acetate); SOM230; trade name: Signifor; Signifor LAR.

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 (~90.31 mM)
H2O : ~1 mg/mL (~0.90 mM)

Solubility in Formulation 1: 2.5 mg/mL (2.26 mM) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), suspension solution; with sonication.
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.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (2.26 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.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (2.26 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.

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Solubility in Formulation 4: 2 mg/mL (1.81 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication.

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