human EP4 receptor ( Ki = 13 nM ); rat EP4 receptor ( Ki = 20 nM ); EP4 ( Ki = 24 nM ); EP4 ( IC50 = 35 nM )

Grapiprant (0-50 mg/kg; oral administration; every 24 hours; for 9 months; beagles) is safe to give orally to dogs on a long-term basis. Further research is required to determine whether Grapiprant is effective in treating dogs with osteoarthritis[3].

36 beagles of both sexes (9-month-old)
0 mg/kg, 1 mg/kg, 6 mg/kg, or 50 mg/kg
Oral administration; every 24 hours; for 9 months

Absorption, Distribution and Excretion
Studies in animals (horse) have shown the presence of a concentration >0.005 ng/ml in serum 72 hours after initial administration of a dose of 2 mg/kg. It is rapidly absorbed and the reported Cmax in this reports was 31.9 ng/ml in a Tmax of 1.5 hours and AUC of 2000 ng.hr/ml. In the case of bioavailability, grapiprant presents a mean bioavailability of 39%. The bioavailability, time for peak concentration and maximal concentration has been reported to be significantly reduced after food.
Following an oral dose, the majority of the dose an within the first 72 hours. Studies in animals (horse) have shown the presence of a concentration >0.005 ng/ml in urine 96 hours after initial administration of a dose of 2 mg/kg. From the excreted dose, 55%, 15% and 19% of the administered dose is excreted in bile, urine, and feces respectively.
The reported volume of distribution in animal studies (cats) was reported to be 918 ml/kg.
The reported clearance rate in animal studies (cats) was reported to be 173.2 ml/hr.kg.

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Metabolism / Metabolites
_In vitro_ studies with dog microsomes have reported the identification of four metabolites, an N-deamination metabolite which is the major metabolite in urine and feces, two hydroxylated metabolites and one N-oxidation metabolite.

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Biological Half-Life
The reported elimination half-life in animal studies (horse) is of 5.86 hours.

Protein Binding
The serum protein binding of grapiprant was of about 95%. The main protein that binds to grapiprant is albumin.

[1]. Detection and quantification of the selective EP4 receptor antagonist CJ-023423 (grapiprant) in canine plasma by HPLC with spectrofluorimetric detection. J Pharm Biomed Anal. 2016 Jan 25;118:251-8.

[2]. Pharmacology of grapiprant, a novel EP4 antagonist: receptor binding, efficacy in a rodent postoperative pain model, and a dose estimation for controlling pain in dogs. J Vet Pharmacol Ther. 2017 Jun;40(3):285-292.

[3]. Evaluation of the safety of long-term, daily oral administration of grapiprant, a novel drug for treatment of osteoarthritic pain and inflammation, in healthy dogs.Am J Vet Res. 2015 Oct;76(10):853-9.

Grapiprant, also known as AT-001 and CJ-023, is a drug from the piprant class. These molecules were derived from acylsulfonamide and are characterized to be a novel series of para-N-acylaminomethylbenzoic acid known to be prostaglandin receptor antagonists. This type of molecules is currently in development for veterinary patients. This class of drugs was defined in 2013 by the World Health Organization. Grapiprant has been approved in March 2016 by the FDA's Center for Veterinary Medicine as a non-cyclooxygenase inhibiting NSAID for veterinary use.
Grapiprant is an orally bioavailable antagonist of the prostaglandin E receptor subtype 4 (EP4), with potential analgesic, immunomodulating and antineoplastic activities. Upon administration of grapiprant, this agent selectively binds to and inhibits the binding of prostaglandin E2 (PGE2) and prevents the activation of the EP4 receptor. This inhibits PGE2-EP4 receptor-mediated signaling and prevents proliferation in tumor cells in which the PGE2-EP4 signaling pathway is over-activated. In addition, EP4 receptor inhibition modulates the immune system by preventing both interleukin-23 (IL-23) production and the IL-23-mediated expansion of Th17 cells. As EP4 is expressed by peripheral sensory neurons, blockade of EP4-mediated signaling may induce an analgesic effect. EP4, a prostanoid receptor subtype, is a G protein-coupled receptor that is expressed in certain types of cancers; it promotes tumor cell proliferation and invasion.

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Drug Indication
The effects of grapiprant have been investigated in the area of analgesia and anti-inflammation due to the effects that have been reported about this molecule. This molecule has been approved and widely accepted to be used in veterinary for pain reduction in arthritis. In humans, it has been researched to be used in the control of pain and inflammation associated with osteoarthritis. The effect of grapiprant can be explained through the function of prostaglandin E2 (PGE2) which is a key mediator of swelling redness and pain which are classic signs of inflammation. The effect of PGE2 results from its action through four receptor EP1, EP2, EP3 and EP4 from which the EP4 is the primary mediator of PGE2-driven inflammation.
For the treatment of pain associated with mild to moderate osteoarthritis in dogs.

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Mechanism of Action
Grapiprant is an EP4 prostaglandin receptor antagonist and thus the activity of this drug is thought to be completely related to the selective blockade of this receptor. It binds to human and other mammals EP4 prostaglandin receptor with high affinity without interfering with other prostaglandin pathways which are important for a variety of physiological functions. The binding of grapiprant blocks PGE2 binding and hence its biological effect related to the signaling pain and inflammation cascade. Grapiprant has been accepted very greatly in veterinary as its mechanism of action is a targeted approach to pain management by not having any interaction with the production of prostanoids and thus, by not interacting with other prostaglandin receptor pathways.

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Pharmacodynamics
Preclinical studies have shown that grapiprant is very effective to reduce acute and chronic pain and inflammation. The effect of grapiprant seems to be dose-dependent and it is comparable to the effect of rofecoxib and piroxicam. The effects of grapiprant have been reported to be effective in the relief from arthritic pain in canine patients.

C26H29N5O3S

491.61

491.199

C, 63.52; H, 5.95; N, 14.25; O, 9.76; S, 6.52

415903-37-6

11677589

White to off-white solid powder

1.3±0.1 g/cm3

>136 ºC (Grapiprant hydrochloride)

1.647

4.56

2

5

7

35

802

0

S(C1C([H])=C([H])C(C([H])([H])[H])=C([H])C=1[H])(N([H])C(N([H])C([H])([H])C([H])([H])C1C([H])=C([H])C(=C([H])C=1[H])N1C(C([H])([H])C([H])([H])[H])=NC2C(C([H])([H])[H])=NC(C([H])([H])[H])=C([H])C1=2)=O)(=O)=O

HZVLFTCYCLXTGV-UHFFFAOYSA-N

InChI=1S/C26H29N5O3S/c1-5-24-29-25-19(4)28-18(3)16-23(25)31(24)21-10-8-20(9-11-21)14-15-27-26(32)30-35(33,34)22-12-6-17(2)7-13-22/h6-13,16H,5,14-15H2,1-4H3,(H2,27,30,32)

1-[2-[4-(2-ethyl-4,6-dimethylimidazo[4,5-c]pyridin-1-yl)phenyl]ethyl]-3-(4-methylphenyl)sulfonylurea

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

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

Solubility in Formulation 1: ≥ 3 mg/mL (6.10 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 30.0 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: ≥ 3 mg/mL (6.10 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 30.0 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: ≥ 3 mg/mL (6.10 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 30.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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