Linaclotide inhibits in vitro [¹²⁵I]-STa binding to intestinal mucosal membranes from wt mice in a concentration-dependent manner. On the other hand, there is a significant decrease in [¹²⁵I]-STa binding to these membranes from GC-C null mice. Linacelotide is totally broken down after 30 minutes of in vitro incubation in jejunal fluid[1]. Linaclotide improves defecation by increasing the secretion of water into the lumen and inhibiting the absorption of sodium ions through its action on guanylate cyclase-C receptors on the luminal membrane. The drug is only slightly absorbed into the systemic circulation[2].

Oral bioavailability is extremely low, according to pharmacokinetic analysis (0.10%). In models of intestinal secretion and transit, linaclotide shows notable pharmacological effects in wt mice, but not in GC-C null mice: elevated levels of cyclic guanosine-3',5-monophosphate are secreted along with accelerated gastrointestinal transit when increased fluid secretion is induced into surgically ligated jejunal loops[1]. In patients with chronic constipation, linaclotide reduces abdominal pain and significantly increases weekly spontaneous bowel movements and complete spontaneous bowel movements (CSBMs)[2].

Mice: Three groups (n=3) of female CD-1 mice receive linaclotide (8 mg/kg) intravenously (i.v.), and two groups (n=3) receive linaclotide (8 mg/kg) by gavage (p.o.) in order to assess oral bioavailability. After allowing blood to clot for five minutes, serum is collected and kept at -80°C until sample preparation and LC-MS/MS analysis[1]. The blood is then centrifuged at 13,000×g for three minutes.

Absorption, Distribution and Excretion
Linaclotide is minimally absorbed with negligible systemic availability following oral administration; however, systemic exposure is not of importance for the maximal effects of linaclotide, as the ligand-binding domain of the GC-C target is located on the luminal surface of intestinal epithelial cells. There is no available information regarding the area under the curve (AUC) and peak plasma concentrations (Cmax) as the concentrations of linaclotide and its active metabolite in plasma are below the limit of quantitation.
Following once-daily administration of 290 mcg linaclotide for seven days, the average active peptide recovery in the stool samples of fed and fasted healthy subjects was 3% and 5%, respectively. The recovered active peptide constituted the active metabolite.
Given that linaclotide plasma concentrations following recommended oral doses are not measurable, linaclotide is not expected to be distributed to tissues to any clinically relevant extent.
No information is available.
Given that linaclotide plasma concentrations following therapeutic oral doses are not measurable, linaclotide is expected to be minimally distributed to tissues.
Active peptide recovery in the stool samples of fed and fasted subjects following the daily administration of 290 mcg of Linzess for seven days averaged about 5% (fasted) and about 3% (fed) and virtually all as the active metabolite.
Linzess is minimally absorbed with low systemic availability following oral administration. Concentrations of linaclotide and its active metabolite in plasma are below the limit of quantitation after oral doses of 145 ug or 290 ug were administered. Therefore, standard pharmacokinetic parameters such as area under the curve (AUC), maximum concentration (Cmax), and half-life cannot be calculated.
It is not known whether linaclotide is distributed into human milk.
For more Absorption, Distribution and Excretion (Complete) data for Linaclotide (8 total), please visit the HSDB record page.

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Metabolism / Metabolites
Linaclotide is metabolized in the small intestine, where it loses its C-terminal tyrosine moiety to form a principal active metabolite, MM-419447. The disulfide bonds of linaclotide and MM-419447 are reduced in the intestinal lumen, followed by proteolysis and degradation to form smaller peptides and naturally occurring amino acids which are absorbed through the intestine. In rats _in vitro_, linaclotide was resistant to enzymatic hydrolysis by pepsin, trypsin, aminopeptidase or chymotrypsin.
The metabolism of linaclotide was investigated in a set of experiments, predominantly in rodents. Linaclotide is metabolised in the intestine by immediate break down of the disulfide bridges which prone linaclotide to further digestion by the enzymes present in the gastrointestinal environment. Several breakdown products containing 3-13 amino acids have been identified. Only one metabolite, MM-419447, was shown to be pharmacodynamic active.
Linaclotide is metabolized within the gastrointestinal tract to its principal, active metabolite by loss of the terminal tyrosine moiety. Both linaclotide and the metabolite are proteolytically degraded within the intestinal lumen to smaller peptides and naturally occurring amino acids.
... We examined the metabolic stability of linaclotide in conditions that mimic the gastrointestinal tract and characterized the metabolite MM-419447 (CCEYCCNPACTGC), which contributes to the pharmacologic effects of linaclotide. Systemic exposure to these active peptides is low in rats and humans, and the low systemic and portal vein concentrations of linaclotide and MM-419447 observed in the rat confirmed both peptides are minimally absorbed after oral administration. Linaclotide is stable in the acidic environment of the stomach and is converted to MM-419447 in the small intestine. The disulfide bonds of both peptides are reduced in the small intestine, where they are subsequently proteolyzed and degraded. After oral administration of linaclotide, <1% of the dose was excreted as active peptide in rat feces and a mean of 3-5% in human feces; in both cases MM-419447 was the predominant peptide recovered. MM-419447 exhibits high-affinity binding in vitro to T84 cells, resulting in a significant, concentration-dependent accumulation of intracellular cyclic guanosine-3',5'-monophosphate (cGMP). In rat models of gastrointestinal function, orally dosed MM-419447 significantly increased fluid secretion into small intestinal loops, increased intraluminal cGMP, and caused a dose-dependent acceleration in gastrointestinal transit. These results demonstrate the importance of the active metabolite in contributing to linaclotide's pharmacology.

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Biological Half-Life
There is no available information regarding the half-life as the concentrations of linaclotide and its active metabolite in plasma are below the limit of quantitation.
Two male and two female monkeys were intravenously dosed for seven consecutive days with 15 mg/kg/day linaclotide. ... /The/ mean half life was approximately 1.5 hr on day 1 and 7 for both genders.

Toxicity Summary
IDENTIFICATION AND USE: Linaclotide is a white to off-white powder. Linaclotide is used in adults in adults for the treatment of irritable bowel syndrome with constipation. It is also used in adults for the treatment of chronic idiopathic constipation. HUMAN EXPOSURE AND TOXICITY: There is limited experience with overdose of linaclotide. During the clinical development program of linaclotide, single doses of 2897 ug were administered to 22 healthy volunteers; the safety profile in these subjects was consistent with that in the overall linaclotide-treated population, with diarrhea being the most commonly reported adverse reaction. Linaclotide is contraindicated in infants and children younger than 6 years of age and should be avoided in children and adolescents 6-17 years of age. While safety and effectiveness has not been established in pediatric patients less than 18 years of age, linaclotide caused deaths in young juvenile mice when administered in single, clinically relevant, adult oral doses. Linaclotide was not genotoxic in the in vitro chromosomal aberration assay in cultured human peripheral blood lymphocytes. ANIMAL STUDIES: In rats, there was no detectable systemic exposure to linaclotide at single oral dose levels of up to 5.0 mg/kg. There were no linaclotide-related effects observed on survival, body weight, food consumption, clinical observations, or macroscopic evaluations. Cynomolgus monkeys were administered a single oral dose of linaclotide at dose levels of 0.5, 1.5, 3.0, and 5.0 mg/kg. The monkeys that were administered a single oral dose of linaclotide (1.5 mg/kg or greater) exhibited changes in stool consistency (non-formed and/or liquid feces), qualitatively reduced food consumption, and/or abdominal distention. There were no significant changes in individual body weight data for these animals. A monkey dosed orally for five consecutive days at 1.5 mg/kg/day exhibited non-formed and liquid feces over the course of the dosing period, with mild abdominal distention occurring on the fourth dosing day. These results demonstrated that linaclotide was well tolerated by Cynomolgus monkeys following a single oral dose at dose levels up to 5.0 mg/kg. However, deaths in juvenile mice were seen when linaclotide was administered in clinically relevant adult doses. In neonatal mice, linaclotide caused deaths at 10 ug/kg/day after oral administration of 1 or 2 daily doses on post-natal day 7. These deaths were due to rapid and severe dehydration. Supplemental subcutaneous fluid administration prevented death after linaclotide administration in neonatal mice. In studies conducted without supplemental fluid administration, tolerability to linaclotide increases with age in juvenile mice. In 2-week-old mice, linaclotide was well tolerated at a dose of 50 ug/kg/day, but deaths occurred after a single oral dose of 100 ug/kg. In 3-week-old mice, linaclotide was well tolerated at 100 ug/kg/day, but deaths occurred after a single oral dose of 600 ug/kg. Linaclotide was well tolerated and did not cause death in 4-week-old juvenile mice at a dose of 1,000 ug/kg/day for 7 days and in 6-week-old juvenile mice at a dose of 20,000 ug/kg/day for 28 days. The potential for linaclotide to cause teratogenic effects was studied in rats, rabbits and mice. Oral administration of up to 100 mg/kg/day in rats and 40 mg/kg/day in rabbits produced no maternal toxicity and no effects on embryo-fetal development. In mice, oral dose levels of at least 40 mg/kg/day produced severe maternal toxicity including death, reduction of gravid uterine and fetal weights, and effects on fetal morphology. Oral doses of 5 mg/kg/day did not produce maternal toxicity or any adverse effects on embryo-fetal development in mice. Linaclotide had no effect on fertility or reproductive function in male and female rats at oral doses of up to 100,000 ug/kg/day. Linaclotide was not genotoxic in an in vitro bacterial reverse mutation (Ames) assay.

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Hepatotoxicity
In clinical trials, linaclotide therapy was not associated with significant changes in serum enzyme levels or episodes of clinically apparent liver injury. Minor transient ALT elevations arose in
Likelihood score: E (unlikely cause of clinically apparent liver injury).

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Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
Linaclotide is minimally absorbed from the gastrointestinal tract and the drug and its active metabolite are not measurable in milk following administration of doses up to 290 mcg daily. Linaclotide appears to be acceptable in nursing mothers and no special precautions are required.
◉ 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.

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Protein Binding
No information is available.

[1]. Linaclotide is a potent and selective guanylate cyclase C agonist that elicits pharmacological effects locally in the gastrointestinal tract. Life Sci. 2010 May 8;86(19-20):760-5.

[2]. Linaclotide: a novel agent for chronic constipation and irritable bowel syndrome. Am J Health Syst Pharm. 2014 Jul 1;71(13):1081-91.

Therapeutic Uses
Linzess (linaclotide) is indicated in adults for the treatment of irritable bowel syndrome with constipation (IBS-C). /Included in US product label/
Linzess is indicated in adults for the treatment of chronic idiopathic constipation (CIC). /Included in US product label/

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Drug Warnings
/BOXED WARNING/ WARNING: PEDIATRIC RISK. Linzess is contraindicated in pediatric patients up to 6 years of age; in nonclinical studies, administration of a single, clinically relevant adult oral dose of linaclotide caused deaths due to dehydration in young juvenile mice. Avoid use of Linzess in pediatric patients 6 through 17 years of age. The safety and efficacy of Linzess has not been established in pediatric patients under 18 years of age.
Linaclotide is contraindicated in infants and children younger than 6 years of age and should be avoided in children and adolescents 6-17 years of age. Safety and efficacy of linaclotide in pediatric patients have not been established, and the drug has caused deaths in toxicology studies in juvenile mice 1-3 weeks of age (approximately equivalent to infants younger than 2 years of age). The deaths in young juvenile mice occurred following 1 or 2 doses of linaclotide 10 ug/kg administered once daily beginning on postnatal day 7, single oral doses of 100 ug/kg on day 14, and single oral doses of 600 ug/kg on day 21. Although no deaths occurred in juvenile mice 6 weeks of age (approximately equivalent to adolescents 12-17 years of age) receiving linaclotide 20,000 ug/kg daily for 28 days, use of the drug in children and adolescents 6-17 years of age should be avoided because of the deaths reported in younger mice and the lack of safety and efficacy data in pediatric patients.1 No data are available for mice between 3 and 6 weeks of age.
Severe diarrhea was reported in clinical trials in 2% of patients receiving linaclotide for treatment of either irritable bowel syndrome (IBS) with constipation or chronic idiopathic constipation. If severe diarrhea occurs, treatment with the drug should be interrupted or discontinued.
It is not known whether linaclotide is distributed into human milk. Although plasma concentrations of linaclotide and its active metabolite are not measurable following oral administration at recommended dosages, caution is advised when linaclotide is administered to nursing women.
For more Drug Warnings (Complete) data for Linaclotide (10 total), please visit the HSDB record page.

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Pharmacodynamics
Linaclotide is a laxative with visceral analgesic and secretory activities. In animal studies and clinical trials, linaclotide improved constipation and gastrointestinal symptoms in patients with irritable bowel syndrome with predominant constipation and chronic idiopathic constipation. In animal models, linaclotide has been shown to both accelerate gastrointestinal transit and reduce intestinal pain. In an animal model of visceral pain, linaclotide reduced abdominal muscle contraction and decreased the activity of pain-sensing nerves. Taking linaclotide with a high-fat meal results in looser stools and a higher stool frequency than taking it in the fasted state. Linaclotide binds to its target, guanylate cyclase-C (GC-C), with high affinity and selectivity. Linaclotide and its active metabolite act locally on the luminal surface of the intestinal epithelium. As linaclotide is stable under a highly acidic pH environment, it acts in a pH-independent manner.

C59H79N15O21S6

1526.74000

1525.389

C, 46.41; H, 5.22; N, 13.76; O, 22.01; S, 12.60

851199-59-2

851199-60-5 (acetate); 851199-59-2

16158208

White to off-white solid powder

1.6±0.1 g/cm3

2045.0±65.0 °C at 760 mmHg

1190.5±34.3 °C

0.0±0.3 mmHg at 25°C

1.712

-5.84

19

28

13

101

3030

14

O=C1[C@H](CC(=O)N)NC(=O)[C@@H]2CSSC[C@@H](C(N[C@@H]3C(N[C@H](C(N[C@H](C(N[C@H](C(N2)=O)CSSC[C@@H](C(=O)N[C@H](C(=O)O)CC2C=CC(O)=CC=2)NC(=O)CNC(=O)[C@H]([C@H](O)C)NC(=O)[C@H](CSSC3)NC(=O)[C@H](C)NC(=O)[C@@H]2CCCN12)=O)CC1C=CC(O)=CC=1)=O)CCC(=O)O)=O)=O)N

KXGCNMMJRFDFNR-WDRJZQOASA-N

InChI=1S/C59H79N15O21S6/c1-26-47(82)69-41-25-101-99-22-38-52(87)65-33(13-14-45(80)81)49(84)66-34(16-28-5-9-30(76)10-6-28)50(85)71-40(54(89)72-39(23-97-96-20-32(60)48(83)70-38)53(88)67-35(18-43(61)78)58(93)74-15-3-4-42(74)56(91)63-26)24-100-98-21-37(64-44(79)19-62-57(92)46(27(2)75)73-55(41)90)51(86)68-36(59(94)95)17-29-7-11-31(77)12-8-29/h5-12,26-27,32-42,46,75-77H,3-4,13-25,60H2,1-2H3,(H2,61,78)(H,62,92)(H,63,91)(H,64,79)(H,65,87)(H,66,84)(H,67,88)(H,68,86)(H,69,82)(H,70,83)(H,71,85)(H,72,89)(H,73,90)(H,80,81)(H,94,95)/t26-,27+,32-,33-,34-,35-,36-,37-,38-,39-,40-,41-,42-,46-/m0/s1

(2S)-2-[[(1R,4S,7S,13S,16R,21R,24R,27S,30S,33R,38R,44S)-21-amino-13-(2-amino-2-oxoethyl)-27-(2-carboxyethyl)-44-[(1R)-1-hydroxyethyl]-30-[(4-hydroxyphenyl)methyl]-4-methyl-3,6,12,15,22,25,28,31,40,43,46,51-dodecaoxo-18,19,35,36,48,49-hexathia-2,5,11,14,23,26,29,32,39,42,45,52-dodecazatetracyclo[22.22.4.216,33.07,11]dopentacontane-38-carbonyl]amino]-3-(4-hydroxyphenyl)propanoic acid

MM 416775; MM416775; MD-1100 acetate; MM-416775; Linzess; Linaclotide acetate; Linzess Constela

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, avoid exposure to moisture.

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

DMSO: ~50 mg/mL (~32.8 mM)
H2O: ~16.7 mg/mL (~10.9 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (1.64 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.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (1.64 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 (1.64 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: 4.17 mg/mL (2.73 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication (<60°C).

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