Difelikefalin acetate

Difelikefalin acetate

ジフェリケファリン酢酸塩

CAS 1024829-44-4

D-Phe-D-Phe-D-Leu-D-Lys-[ω(4-aminopiperidine-4- carboxylic acid)]-OH

FDA APPROVED, 2021/8/23, FORSUVA

Analgesic, Antipruritic, Opioid receptor agonist

Treatment of moderate-to-severe pruritus associated with chronic kidney disease in adults undergoing hemodialysis

Difelikefalin, CR-845; MR-13A-9; MR-13A9

4-amino-1- (D-phenylalanyl-D-phenylalanyl-D-leucyl-D-lysyl) piperidine-4-carboxylic acid

C36H53N7O6, 679.40573

Difelikefalin, sold under the brand name Korsuva , is an analgesic opioid peptide used for the treatment of moderate-to-severe pruritus. It acts as a peripherally specific, highly selective agonist of the κ-opioid receptor (KOR).^[3][4][5][6]

Difelikefalin was approved for medical use in the United States in August 2021.^[2][7][8]

Difelikefalin acts as an analgesic by activating KORs on peripheral nerve terminals and KORs expressed by certain immune system cells.^[3] Activation of KORs on peripheral nerve terminals results in the inhibition of ion channels responsible for afferent nerve activity, causing reduced transmission of pain signals, while activation of KORs expressed by immune system cells results in reduced release of proinflammatory, nerve-sensitizing mediators (e.g., prostaglandins).^[3]

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Research

It is under development by Cara Therapeutics as an intravenous agent for the treatment of postoperative pain.^[3][4][6] An oral formulation has also been developed.^[6] Due to its peripheral selectivity, difelikefalin lacks the central side effects like sedation, dysphoria, and hallucinations of previous KOR-acting analgesics such as pentazocine and phenazocine.^[3][4] In addition to use as an analgesic, difelikefalin is also being investigated for the treatment of pruritus (itching).^[3][4][5] Difelikefalin has completed phase II clinical trials for postoperative pain and has demonstrated significant and “robust” clinical efficacy, along with being safe and well tolerated.^[4][6] It has also completed a phase III clinical trial for uremic pruritus in hemodialysis patients.^[9]Kappa opioid receptors have been suggested as targets for intervention for treatment or prevention of a wide array of diseases and conditions by administration of kappa opioid receptor agonists. See for example, Jolivalt et al., Diabetologia, 49(11):2775-85; Epub Aug. 19, 2006), describing efficacy of asimadoline, a kappa receptor agonist in rodent diabetic neuropathy; and Bileviciute-Ljungar et al., Eur. J. Pharm. 494:139-46 (2004) describing the efficacy of kappa agonist U-50,488 in the rat chronic constriction injury (CCI) model of neuropathic pain and the blocking of its effects by the opioid antagonist, naloxone. These observations support the use of kappa opioid receptor agonists for treatment of diabetic, viral and chemotherapy- induced neuropathic pain. The use of kappa receptor agonists for treatment or prevention of visceral pain including gynecological conditions such as dysmenorrheal cramps and endometriosis has also been reviewed. See for instance, Riviere, Br. J. Pharmacol. 141:1331-4 (2004).[0004] Kappa opioid receptor agonists have also been proposed for the treatment of pain, including hyperalgesia. Hyperalgesia is believed to be caused by changes in the milieu of the peripheral sensory terminal occur secondary to local tissue damage. Tissue damage (e.g., abrasions, burns) and inflammation can produce significant increases in the excitability of polymodal nociceptors (C fibers) and high threshold mechanoreceptors (Handwerker et al. (1991) Proceeding of the VIth World Congress on Pain, Bond et al., eds., Elsevier Science Publishers BV, pp. 59-70; Schaible et al. (1993) Pain 55:5-54). This increased excitability and exaggerated responses of sensory afferents is believed to underlie hyperalgesia, where the pain response is the result of an exaggerated response to a stimulus. The importance of the hyperalgesic state in the post-injury pain state has been repeatedly demonstrated and appears to account for a major proportion of the post-injury/inflammatory pain state. See for example, Woold et al. (1993) Anesthesia and Analgesia 77:362-79; Dubner et al.(1994) In, Textbook of Pain, Melzack et al., eds., Churchill-Livingstone, London, pp. 225-242.[0005] Kappa opioid receptors have been suggested as targets for the prevention and treatment of cardiovascular disease. See for example, Wu et al. “Cardioprotection of Preconditioning by Metabolic Inhibition in the Rat Ventricular Myocyte – Involvement of kappa Opioid Receptor” (1999) Circulation Res vol. 84: pp. 1388-1395. See also Yu et al. “Anti-Arrhythmic Effect of kappa Opioid Receptor Stimulation in the Perfused Rat Heart: Involvement of a cAMP-Dependent Pathway”(1999) JMoI Cell Cardiol, vol. 31(10): pp. 1809-1819.[0006] It has also been found that development or progression of these diseases and conditions involving neurodegeneration or neuronal cell death can be prevented, or at least slowed, by treatment with kappa opioid receptor agonists. This improved outcome is believed to be due to neuroprotection by the kappa opioid receptor agonists. See for instance, Kaushik et al. “Neuroprotection in Glaucoma” (2003) J. Postgraduate Medicine vol. 49 (1): pp. 90-95. [0007] The presence of kappa opioid receptors on immune cells (Bidlak et al.,(2000) Clin. Diag. Lab. Immunol. 7(5):719-723) has been implicated in the inhibitory • action of a kappa opioid receptor agonist, which has been shown to suppress HIV-I expression. See Peterson PK et al, Biochem Pharmacol 2001, 61(19):1145-51. [0008] Walker, Adv. Exp. Med. Biol. 521: 148-60 (2003) appraised the antiinflammatory properties of kappa agonists for treatment of osteoarthritis, rheumatoid arthritis, inflammatory bowel disease and eczema. Bileviciute-Ljungar et al., Rheumatology 45:295-302 (2006) describe the reduction of pain and degeneration in Freund’s adjuvant-induced arthritis by the kappa agonist U-50,488.[0009] Wikstrom et al, J. Am. Soc. Nephrol. 16:3742-7 (2005) describes the use of the kappa agonist, TRK-820 for treatment of uremic and opiate-induced pruritis, and Ko et al., J. Pharmacol. Exp. Ther. 305: 173-9 (2003) describe the efficacy of U- 50,488 in morphine-induced pruritis in the monkey. [0010] Application of peripheral opioids including kappa agonists for treatment of gastrointestinal diseases has also been extensively reviewed. See for example, Lembo, Diges. Dis. 24:91-8 (2006) for a discussion of use of opioids in treatment of digestive disorders, including irritable bowel syndrome (IBS), ileus, and functional dyspepsia.[0011] Ophthalmic disorders, including ocular inflammation and glaucoma have also been shown to be addressable by kappa opioids. See Potter et ah, J. Pharmacol. Exp. Ther. 309:548-53 (2004), describing the role of the potent kappa opioid receptor agonist, bremazocine, in reduction of intraocular pressure and blocking of this effect by norbinaltorphimine (norBNI), the prototypical kappa opioid receptor antagonist; and Dortch-Carnes et al, CNS Drug Rev. 11(2): 195-212 (2005). U.S. Patent 6,191,126 to Gamache discloses the use of kappa opioid agonists to treat ocular pain. Otic pain has also been shown to be treatable by administration of kappa opioid agonists. See U.S. Patent 6,174,878 also to Gamache.[0012] Kappa opioid agonists increase the renal excretion of water and decrease urinary sodium excretion (i.e., produces a selective water diuresis, also referred to as aquaresis). Many, but not all, investigators attribute this effect to a suppression of vasopressin secretion from the pituitary. Studies comparing centrally acting and purportedly peripherally selective kappa opioids have led to the conclusion that kappa opioid receptors within the blood-brain barrier are responsible for mediating this effect. Other investigators have proposed to treat hyponatremia with nociceptin peptides or charged peptide conjugates that act peripherally at the nociceptin receptor, which is related to but distinct from the kappa opioid receptor (D. R. Kapusta, Life ScL, 60: 15-21, 1997) (U.S. Pat. No. 5,840,696). U.S. Pat Appl. 20060052284.
PATENTJpn. Tokkyo Koho, 5807140US 20090156508WO 2008057608

PATENTUS 20100075910https://patents.google.com/patent/US8236766B2/en

Example 2Synthesis of Compound (2): D-Phe-D-Phe-D-Leu-D-Lys-[ω(4-aminopiperidine-4-carboxylic acid)]-OHSee the scheme of FIG. 3 and Biron et al., Optimized selective N-methylation of peptides on solid support. J. Peptide Science 12: 213-219 (2006). The amino acid derivatives used were Boc-D-Phe-OH, Fmoc-D-Phe-OH, Fmoc-D-Leu-OH, Fmoc-D-Lys(Dde)-OH, and N-Boc-amino-(4-N-Fmoc-piperidinyl)carboxylic acid. HPLC and MS analyses were performed as described in the synthesis of compound (1) described above.The fully protected resin-bound peptide was synthesized manually starting from 2-Chlorotrityl chloride resin (1.8 g, 0.9 mmol; Peptide International). Attachment of N-Boc-amino-(4-N-Fmoc-piperidinyl)carboxylic acid followed by peptide chain elongation and deprotection of Dde in D-Lys(Dde) at Xaa₄ was carried out according to the procedure described in the synthesis of compound (1). See above. The resulting peptide resin (0.9 mmol; Boc-D-Phe-D-Phe-D-Leu-D-Lys-(N-Boc-amino-4-piperidinylcarboxylic acid)-[2-Cl-Trt resin]) was split and a portion of 0.3 mmol was used for subsequent cleavage. The peptide resin (0.3 mmol) was then treated with a mixture of TFA/TIS/H₂O (15 ml, v/v/v=95:2.5:2.5) at room temperature for 90 minutes. The resin was then filtered and washed with TFA. The filtrate was evaporated in vacuo and the crude synthetic peptide amide (0.3 mmol; D-Phe-D-Phe-D-Leu-D-Lys-[ω(4-aminopiperidine-4-carboxylic acid)]-OH) was precipitated from diethyl ether.For purification, the crude synthetic peptide amide (0.3 mmol) was dissolved in 2% acetic acid in H₂O (50 ml) and the solution was loaded onto an HPLC column and purified using TEAP buffer system with a pH 5.2 (buffers A=TEAP 5.2 and B=20% TEAP 5.2 in 80% ACN). The compound was eluted with a linear gradient of buffer B, 7% B to 37% B over 60 minutes. Fractions with purity exceeding 95% were pooled and the resulting solution was diluted with two volumes of water. The diluted solution was then loaded onto an HPLC column for salt exchange and further purification with a TFA buffer system (buffers A=0.1% TFA in H₂O and B=0.1% TFA in 80% ACN/20% H₂O) and a linear gradient of buffer B, 2% B to 75% B over 25 minutes. Fractions with purity exceeding 97% were pooled, frozen, and dried on a lyophilizer to yield the purified synthetic peptide amide as white amorphous powder (93 mg). HPLC analysis: t_R=16.43 min, purity 99.2%, gradient 5% B to 25% B over 20 min; MS (MH⁺): expected molecular ion mass 680.4, observed 680.3.Compound (2) was also prepared using a reaction scheme analogous to that shown in FIG. 3 with the following amino acid derivatives: Fmoc-D-Phe-OH, Fmoc-D-Leu-OH, Fmoc-D-Lys(Boc)-OH, and Boc-4-amino-1-Fmoc-(piperidine)-4-carboxylic acid.The fully protected resin-bound peptide was synthesized manually starting from 2-Chlorotrityl chloride resin (PS 1% DVB, 500 g, 1 meq/g). The resin was treated with Boc-4-amino-1-Fmoc-4-(piperidine)-4-carboxylic acid (280 g, 600 mmol) in a mixture of DMF, DCM and DIEA (260 mL of each) was added. The mixture was stirred for 4 hours and then the resin was capped for 1 h by the addition of MeOH (258 mL) and DIEA (258 mL).The resin was isolated and washed with DMF (3×3 L). The resin containing the first amino acid was treated with piperidine in DMF (3×3 L of 35%), washed with DMF (9×3 L) and Fmoc-D-Lys(Boc)-OH (472 g) was coupled using PyBOP (519 g) in the presence of HOBt (153 g) and DIEA (516 mL) and in DCM/DMF (500 mL/500 mL) with stiffing for 2.25 hours. The dipeptide containing resin was isolated and washed with DMF (3×3.6 L). The Fmoc group was removed by treatment with piperidine in DMF(3×3.6 L of 35%) and the resin was washed with DMF (9×3.6 L) and treated with Fmoc-D-Leu-OH (354 g), DIC (157 mL) and HOBt (154 g) in DCM/DMF (500 mL/500 mL) and stirred for 1 hour. Subsequent washing with DMF (3×4.1 L) followed by cleavage of the Fmoc group with piperidine in DMF (3×4.2 L of 35%) and then washing of the resin with DMF (9×4.2 L) provided the resin bound tripeptide. This material was treated with Fmoc-D-Phe-OH (387 g), DIC (157 mL) and HOBt (153 g) in DCM/DMF (500 mL/500 mL) and stirred overnight. The resin was isolated, washed with DMF (3×4.7 L) and then treated with piperidine in DMF (3×4.7 L of 35%) to cleave the Fmoc group and then washed again with DMF (9×4.7 L). The tetrapeptide loaded resin was treated with Fmoc-D-Phe-OH (389 g), DIC (157 mL) and HOBt (154 g) in DCM/DMF (500 mL/500 mL) and stirred for 2.25 hours. The resin was isolated, washed with DMF (3×5.2 L) and then treated piperidine (3×5.2 L of 35%) in DMF. The resin was isolated, and washed sequentially with DMF (9×5.2 L) then DCM (5×5.2 L). It was dried to provide a 90.4% yield of protected peptide bound to the resin. The peptide was cleaved from the resin using TFA/water (4.5 L, 95/5), which also served to remove the Boc protecting groups. The mixture was filtered, concentrated (⅓) and then precipitated by addition to MTBE (42 L). The solid was collected by filtration and dried under reduced pressure to give crude synthetic peptide amide.For purification, the crude synthetic peptide amide was dissolved in 0.1% TFA in H₂O and purified by preparative reverse phase HPLC (C18) using 0.1% TFA/water—ACN gradient as the mobile phase. Fractions with purity exceeding 95% were pooled, concentrated and lyophilized to provide pure synthetic peptide amide (>95.5% pure). Ion exchange was conducted using a Dowex ion exchange resin, eluting with water. The aqueous phase was filtered (0.22 μm filter capsule) and freeze-dried to give the acetate salt of the synthetic peptide amide (2) with overall yield, 71.3%, >99% purity.Hydrochloride, hydrobromide and fumarate counterions were evaluated for their ability to form crystalline salts of synthetic peptide amide (2). Approximately 1 or 2 equivalents (depending on desired stoichiometry) of hydrochloric acid, hydrobromic acid or fumaric acid, as a dilute solution in methanol (0.2-0.3 g) was added to synthetic peptide amide (2) (50-70 mg) dissolved in methanol (0.2-0.3 g). Each individual salt solution was added to isopropyl acetate (3-5 mL) and the resulting amorphous precipitate was collected by filtration and dried at ambient temperature and pressure. Crystallization experiments were carried out by dissolving the 10-20 mg of the specific amorphous salt obtained above in 70:30 ethanol-water mixture (0.1-0.2 g) followed by the addition of ethanol to adjust the ratio to 90:10 (˜0.6-0.8 mL). Each solution was then seeded with solid particles of the respective precipitated salt. Each sample tube was equipped with a magnetic stir bar and the sample was gently stirred at ambient temperature. The samples were periodically examined by plane-polarized light microscopy. Under these conditions, the mono- and di-hydrochloride salts, the di-hydrobromide salt and the mono-fumarate salt crystallized as needles of 20 to 50 μm in length with a thickness of about 1 μm.PATENT

WO 2008057608

https://patents.google.com/patent/WO2008057608A2/en Compound (2): D-Phe-D-Phe-D-Leu-D-Lys-[ω(4-aminopiperidine-4- carboxylic acid)]-OH (SEQ ID NO: 2):

EXAMPLE 2: Synthesis of compound (2)[00288] D-Phe-D-Phe-D-Leu-D-Lys-[ω(4-aminopiperidine-4-carboxylic acid)]-OH (SEQ ID NO: 2):[00289] See the scheme of Figure 2 and B iron et al., Optimized selective N- methylation of peptides on solid support. J. Peptide Science 12: 213-219 (2006). The amino acid derivatives used were Boc-D-Phe-OH, Fmoc-D-Phe-OH, Fmoc-D-Leu- OH, Fmoc-D-Lys(Dde)-OH, and N-Boc-amino-(4-N-Fmoc-piperidinyl) carboxylic acid. HPLC and MS analyses were performed as described in the synthesis of compound (1) described above.[00290] The fully protected resin-bound peptide was synthesized manually starting from 2-Chlorotrityl chloride resin (1.8 g, 0.9 mmol; Peptide International). Attachment of N-Boc-amino-(4-N-Fmoc-piperidinyl) carboxylic acid followed by peptide chain elongation and deprotection of Dde in D-Lys(Dde) at Xa^ was carried out according to the procedure described in the synthesis of compound (1). See above. The resulting peptide resin (0.9 mmol; Boc-D-Phe-D-Phe-D-Leu-D-Lys-(N- Boc-amino-4-piperidinylcarboxylic acid)-[2-Cl-Trt resin]) was split and a portion of 0.3 mmol was used for subsequent cleavage. The peptide resin (0.3 mmol) was then treated with a mixture of TFA/TIS/H₂O (15 ml, v/v/v = 95:2.5:2.5) at room temperature for 90 min. The resin was then filtered and washed with TFA. The filtrate was evaporated in vacuo and the crude peptide (0.3 mmol; D-Phe-D-Phe-D- Leu-D-Lys-[ω(4-aminopiperidine-4-carboxylic acid)]-OH) was precipitated from diethyl ether.[00291] For purification, the crude peptide (0.3 mmol) was dissolved in 2% acetic acid in H₂O (50 ml) and the solution was loaded onto an HPLC column and purified using TEAP buffer system with a pH 5.2 (buffers A = TEAP 5.2 and B = 20% TEAP 5.2 in 80% ACN). The compound was eluted with a linear gradient of buffer B, 7%B to 37%B over 60 min. Fractions with purity exceeding 95% were pooled and the resulting solution was diluted with two volumes of water. The diluted solution was then loaded onto an HPLC column for salt exchange and further purification with a TFA buffer system (buffers A = 0.1% TFA in H₂O and B = 0.1% TFA in 80% ACN/20% H₂O) and a linear gradient of buffer B, 2%B to 75%B over 25 min. Fractions with purity exceeding 97% were pooled, frozen, and dried on a lyophilizer to yield the purified peptide as white amorphous powder (93 mg). HPLC analysis: t_R = 16.43 min, purity 99.2%, gradient 5%B to 25%B over 20 min; MS (M+H⁺): expected molecular ion mass 680.4, observed 680.3.[00292] Compound (2) was also prepared using a reaction scheme analogous to that shown in figure 2 with the following amino acid derivatives: Fmoc-D-Phe-OH, Fmoc-D-Leu-OH, Fmoc-D-Lys(Boc)-OH, and Boc-4-amino-l-Fmoc-(piperidine)-4- carboxylic acid.[00293] The fully protected resin-bound peptide was synthesized manually starting from 2-Chlorotrityl chloride resin (PS 1%DVB, 500 g, 1 meq/g). The resin was treated with Boc-4-amino-l-Fmoc-4-(piperidine)-4-carboxylic acid (280 g, 600 mmol) in a mixture of DMF, DCM and DIEA (260 mL of each) was added. The mixture was stirred for 4 hours and then the resin was capped for Ih by the addition of MeOH (258 mL) and DIEA[00294] (258 mL). The resin was isolated and washed with DMF (3 x 3 L). The resin containing the first amino acid was treated with piperidine in DMF (3 x 3 L of 35%), washed with DMF (9 x 3 L) and Fmoc-D-Lys(Boc)-OH (472 g) was coupled using PyBOP (519 g) in the presence of HOBt (153 g) and DIEA (516 mL) and in DCM/DMF (500 mL/ 500 mL) with stirring for 2.25 hours. The dipeptide containing resin was isolated and washed with DMF (3 x 3.6 L). The Fmoc group was removed by treatment with piperidine in DMF [00295] , (3 x 3.6 L of 35%) and the resin was washed with DMF (9 x 3.6 L) and treated with Fmoc-D-Leu-OH (354 g), DIC (157 mL) and HOBt (154 g) in DCM/DMF (500 mL / 500 mL) and stirred for 1 hour. Subsequent washing with DMF (3 x 4.1 L) followed by cleavage of the Fmoc group with piperidine in DMF (3 x 4.2 L of 35%) and then washing of the resin with DMF (9 x 4.2 L) provided the resin bound tripeptide. This material was treated with Fmoc-D-Phe-OH (387 g), DIC (157 mL) and HOBt (153 g) in DCM/DMF (500 mL / 500 mL) and stirred overnight. The resin was isolated, washed with DMF (3 x 4.7 L) and then treated with piperidine in DMF (3 x 4.7 L of 35%) to cleave the Fmoc group and then washed again with DMF (9 x 4.7 L). The tetrapeptide loaded resin was treated with Fmoc-D-Phe-OH (389 g), DIC (157 mL) and HOBt (154 g) in DCM/DMF (500 mL / 500 mL) and stirred for 2.25 hours. The resin was isolated, washed with DMF (3 x 5.2 L) and then treated piperidine (3 x 5.2 L of 35%) in DMF. The resin was isolated, and washed sequentially with DMF (9 x 5.2 L) then DCM (5 x 5.2 L). It was dried to provide a 90.4% yield of protected peptide bound to the resin. The peptide was cleaved from the resin using TFA/ water (4.5 L, 95/5), which also served to remove the Boc protecting groups. The mixture was filtered, concentrated (1/3) and then precipitated by addition to MTBE (42 L). The solid was collected by filtration and dried under reduced pressure to give crude peptide.[00296] For purification, the crude peptide was dissolved in 0.1% TFA in H₂O and purified by preparative reverse phase HPLC (C 18) using 0.1% TF A/water – ACN gradient as the mobile phase. Fractions with purity exceeding 95% were pooled, concentrated and lyophilized to provide pure peptide (> 95.5% pure). Ion exchange was conducted using a Dowex ion exchange resin, eluting with water. The aqueous phase was filtered (0.22 μm filter capsule) and freeze-dried to give the acetate salt of the peptide (overall yield, 71.3%, >99% pure).

PATENT

WO 2015198505

κ opioid receptor agonists are known to be useful as therapeutic agents for various pain. Among, kappa opioid receptor agonist with high selectivity for peripheral kappa opioid receptors, are expected as a medicament which does not cause the central side effects. Such as peripherally selective κ opioid receptor agonist, a synthetic pentapeptide has been reported (Patent Documents 1 and 2).　The following formula among the synthetic pentapeptide (A)

[Formula 1] Being Represented By Compounds Are Useful As Pain Therapeutics. The Preparation Of This Compound, Solid Phase Peptide Synthesis Methods In Patent Documents 1 And 2 Have Been Described.Document 1 Patent: Kohyo 2010-510966 JP
Patent Document 2: Japanese Unexamined Patent Publication No. 2013-241447　Compound (1) or a salt thereof and compound (A), for example as shown in the following reaction formula, 4-aminopiperidine-4-carboxylic acid, D- lysine (D-Lys), D- leucine (D-Leu) , it can be prepared by D- phenylalanine (D-Phe) and D- phenylalanine (D-Phe) sequentially solution phase peptide synthesis methods condensation.[Of 4]The present invention will next to examples will be described in further detail.Example
1 (1) Synthesis of Cbz-D-Lys (Boc) -α-Boc-Pic-OMe (3)
to the four-necked flask of 2L, α-Boc-Pic- OMe · HCl [α-Boc-4 – aminopiperidine-4-carboxylic acid methyl hydrochloride] were charged (2) 43.7g (148mmol), was suspended in EtOAc 656mL (15v / w). To the suspension of 1-hydroxybenzotriazole (HOBt) 27.2g (178mmol), while cooling with Cbz-D-Lys (Boc) -OH 59.2g (156mmol) was added an ice-bath 1-ethyl -3 – (3-dimethylcarbamoyl amino propyl) was added to the carbodiimide · HCl (EDC · HCl) 34.1g (178mmol). After 20 minutes, stirring was heated 12 hours at room temperature. After completion of the reaction, it was added and the organic layer was 1 N HCl 218 mL of (5.0v / w). NaHCO to the resulting organic layer ₃ Aq. 218ML (5.0V / W), Et ₃ N 33.0 g of (326Mmol) was stirred for 30 minutes, and the mixture was separated. The organic layer HCl 218ML 1N (5.0V / W), NaHCO ₃ Aq. 218mL (5.0v / w), NaClaq . Was washed successively with 218ML (5.0V / W), Na ₂ SO ₄　dried addition of 8.74g (0.2w / w). Subjected to vacuum filtration, was concentrated under reduced pressure resulting filtrate by an evaporator, and pump up in the vacuum pump, the Cbz-D-Lys (Boc) -α-Boc-Pic-OMe (3) 88.9g as a white solid obtained (96.5% yield, HPLC purity 96.5%).[0033](2) D-Lys (Boc) Synthesis Of -Arufa-Boc-Pic-OMe (4)
In An Eggplant-Shaped Flask Of 2L, Cbz-D-Lys (Boc) -Arufa-Boc-Pic-OMe (3) 88.3g (142mmol) were charged, it was added and dissolved 441mL (5.0v / w) the EtOAc. The 5% Pd / C to the reaction solution 17.7g (0.2w / w) was added, After three nitrogen substitution reduced pressure Atmosphere, Was Performed Three Times A Hydrogen Substituent. The Reaction Solution Was 18 Hours With Vigorous Stirring At Room Temperature To Remove The Pd / C And After The Completion Of The Reaction Vacuum Filtration. NaHCO The Resulting Filtrate ₃ Aq. 441ML And (5.0V / W) Were Added For Liquid Separation, And The Organic Layer Was Extracted By The Addition Of EtOAc 200ML (2.3V / W) In The Aqueous Layer. NaHCO The Combined Organic Layer ₃ Aq. 441ML And (5.0V / W) Were Added for liquid separation, and the organic layer was extracted addition of EtOAc 200mL (2.3v / w) in the aqueous layer. NaClaq the combined organic layers. 441mL and (5.0v / w) is added to liquid separation, was extracted by the addition EtOAc 200ML Of (2.3V / W) In The Aqueous Layer. The Combined Organic Layer On The Na ₂ SO ₄　Dried Addition Of 17.7 g of (0.2W / W), Then The Filtrate Was Concentrated Under Reduced Pressure Obtained Subjected To Vacuum Filtration By an evaporator, and pump up in the vacuum pump, D-Lys (Boc) -α-Boc-Pic- OMe (4) to give 62.7g (90.5% yield, HPLC purity 93.6%).(3) Cbz-D-Leu -D-Lys (Boc) -α-Boc-Pic-OMe synthesis of (5)
in the four-necked flask of 2L, D-Lys (Boc) -α-Boc-Pic-OMe (4) was charged 57.7 g (120 mmol), was suspended in EtOAc 576mL (10v / w). HOBt 19.3g (126mmol) to this suspension, was added EDC · HCl 24.2g (126mmol) while cooling in an ice bath added Cbz-D-Leu-OH 33.4g (126mmol). After 20 minutes, after stirring the temperature was raised 5 hours at room temperature, further the EDC · HCl and stirred 1.15 g (6.00 mmol) was added 16 h. After completion of the reaction, it was added liquid separation 1N HCl 576mL (10v / w) . NaHCO to the resulting organic layer ₃ Aq. 576ML (10V / W), Et ₃ N 24.3 g of (240Mmol) was stirred for 30 minutes, and the mixture was separated. The organic layer HCl 576ML 1N (10V / W), NaHCO ₃ Aq. 576mL (10v / w), NaClaq . Was washed successively with 576ML (10V / W), Na ₂ SO ₄　dried addition of 11.5g (0.2w / w). After the filtrate was concentrated under reduced pressure obtained subjected to vacuum filtration by an evaporator, and pump up in the vacuum pump, the Cbz-D-Leu-D- Lys (Boc) -α-Boc-Pic-OMe (5) 85.8g It was obtained as a white solid (98.7% yield, HPLC purity 96.9%).(4) D-Leu-D -Lys (Boc) -α-Boc-Pic-OMe synthesis of (6)
in an eggplant-shaped flask of 1L, Cbz-D-Leu- D-Lys (Boc) -α-Boc-Pic -OMe the (5) 91.9g (125mmol) were charged, was added and dissolved 459mL (5.0v / w) the EtOAc. The 5% Pd / C to the reaction solution 18.4g (0.2w / w) was added, After three nitrogen substitution reduced pressure atmosphere, was performed three times a hydrogen substituent. The reaction solution was subjected to 8 hours with vigorous stirring at room temperature to remove the Pd / C and after the completion of the reaction vacuum filtration. NaHCO the resulting filtrate ₃ Aq. 200mL (2.2v / w) were added to separate liquid, NaHCO to the organic layer ₃ Aq. 200mL (2.2v / w), NaClaq . It was sequentially added washed 200mL (2.2v / w). To the resulting organic layer Na ₂ SO ₄　dried added 18.4g (0.2w / w), to the filtrate concentrated under reduced pressure obtained subjected to vacuum filtration by an evaporator, and a pump-up with a vacuum pump. The resulting amorphous solid was dissolved adding EtOAc 200mL (2.2v / w), was crystallized by the addition of heptane 50mL (1.8v / w). Was filtered off precipitated crystals by vacuum filtration, the crystals were washed with a mixed solvent of EtOAc 120mL (1.3v / w), heptane 50mL (0.3v / w). The resulting crystal 46.1g to added to and dissolved EtOAc 480mL (5.2v / w), was crystallized added to the cyclohexane 660mL (7.2v / w). Was filtered off under reduced pressure filtered to precipitate crystals, cyclohexane 120mL (1.3v / w), and washed with a mixed solvent of EtOAc 20mL (0.2v / w), and 30 ° C. vacuum dried, D-Leu- as a white solid D-Lys (Boc) -α- Boc-Pic-OMe (6) to give 36.6 g (48.7% yield, HPLC purity 99.9%).(5) Synthesis of Cbz-D-Phe-D- Leu-D-Lys (Boc) -α-Boc-Pic-OMe (7)
to the four-necked flask of 1L, D-Leu-D- Lys (Boc) -α-Boc-Pic-OMe with (6) 35.8g (59.6mmol) was charged, it was suspended in EtOAc 358mL (10v / w). To this suspension HOBt 9.59g (62.6mmol), Cbz- D-Phe-OH 18.7g was cooled in an ice bath is added (62.6mmol) while EDC · HCl 12.0g (62.6mmol) It was added. After 20 minutes, a further EDC · HCl After stirring the temperature was raised 16 hours was added 3.09 g (16.1 mmol) to room temperature. After completion of the reaction, it was added and the organic layer was 1N HCl 358mL of (10v / w). NaHCO to the resulting organic layer ₃ Aq. 358ML (10V / W), Et ₃ N 12.1 g of (119Mmol) was stirred for 30 minutes, and the mixture was separated. The organic layer HCl 358ML 1N (10V / W), NaHCO ₃ Aq. 358mL (10v / w), NaClaq . Was washed successively with 358ML (10V / W), Na ₂ SO ₄　dried addition of 7.16g (0.2w / w). After the filtrate was concentrated under reduced pressure obtained subjected to vacuum filtration by an evaporator, and pump up in the vacuum pump, Cbz-D-Phe-D -Leu-D-Lys (Boc) -α-Boc-Pic-OMe (7) was obtained 52.5g as a white solid (yield quant, HPLC purity 97.6%).(6) D-Phe-D -Leu-D-Lys (Boc) synthesis of -α-Boc-Pic-OMe ( 8)
in an eggplant-shaped flask of 2L, Cbz-D-Phe- D-Leu-D-Lys ( Boc) -α-Boc-Pic- OMe (7) the 46.9g (53.3mmol) were charged, the 840ML EtOAc (18V / W), H ₂ added to and dissolved O 93.8mL (2.0v / w) It was. The 5% Pd / C to the reaction mixture 9.38g (0.2w / w) was added, After three nitrogen substitution reduced pressure atmosphere, was performed three times a hydrogen substituent. The reaction solution was subjected to 10 hours with vigorous stirring at room temperature to remove the Pd / C and after the completion of the reaction vacuum filtration. NaHCO the resulting filtrate ₃ Aq. 235mL (5.0v / w) were added to separate liquid, NaHCO to the organic layer ₃ Aq. 235mL (5.0v / w), NaClaq . It was added sequentially cleaning 235mL (5.0v / w). To the resulting organic layer Na ₂ SO ₄　dried addition of 9.38g (0.2w / w), then the filtrate was concentrated under reduced pressure obtained subjected to vacuum filtration by an evaporator, pump up with a vacuum pump to D-Phe -D-Leu-D-Lys ( Boc) -α-Boc-Pic-OMe (7) was obtained 39.7g (yield quant, HPLC purity 97.3%).351mL was suspended in (10v / w). To this suspension HOBt 7.92g (51.7mmol), Boc-D-Phe-OH HCl HCl(8) D-Phe-D -Phe-D-Leu-D-Lys-Pic-OMe Synthesis Of Hydrochloric Acid Salt (1)
In An Eggplant-Shaped Flask Of 20ML Boc-D-Phe-D -Phe-D- Leu-D- lys (Boc) -α -Boc- Pic-OMe (9) and 2.00gg, IPA 3.3mL (1.65v / w), was suspended by addition of PhMe 10mL (5v / w). It was stirred at room temperature for 19 hours by addition of 6N HCl / IPA 6.7mL (3.35v / w). The precipitated solid was filtered off by vacuum filtration and dried under reduced pressure to a white solid of D-Phe-D-Phe- D- Leu-D-Lys-Pic- OMe 1.59ghydrochloride (1) (yield: 99 .0%, HPLC purity 98.2%) was obtained.(9) D-Phe-D -Phe-D-Leu-D-Lys-Pic-OMe Purification Of The Hydrochloric Acid Salt (1)
In An Eggplant-Shaped Flask Of 20ML-D-Phe-D- Phe D-Leu -D-Lys- pic-OMe hydrochloride crude crystals (1) were charged 200mg, EtOH: MeCN = 1: after stirring for 1 hour then heated in a mixed solvent 4.0 mL (20v / w) was added 40 ° C. of 5 , further at room temperature for 2 was time stirring slurry. Was filtered off by vacuum filtration, the resulting solid was dried under reduced pressure a white solid ((1) Purification crystals) was obtained 161 mg (80% yield, HPLC purity 99.2% ).(10) D-Phe-D -Phe-D-Leu-D-Lys-Pic Synthesis (Using Purified
(1)) Of (A) To A Round-Bottomed Flask Of 10ML D-Phe-D-Phe-D- -D-Lys Leu-Pic-OMe Hydrochloride Salt (1) Was Charged With Purified Crystal 38.5Mg (0.0488Mmol), H ₂ Was Added And Dissolved O 0.2ML (5.2V / W). 1.5H Was Stirred Dropwise 1N NaOH 197MyuL (0.197mmol) at room temperature. After completion of the reaction, concentrated under reduced pressure by an evaporator added 1N HCl 48.8μL (0.0488mmol), to obtain a D-Phe-D-Phe- D-Leu-D-Lys- Pic (A) (yield: quant , HPLC purity 99.7%).

D-Phe-D-Phe- D-Leu-D-Lys-Pic-OMe (1) physical properties ¹ H NMR (400 MHz, 1M DCl) [delta] ppm by: 0.85-1.02 (yd,. 6 H), 1.34-1.63 ( m, 5 H), 1.65-2.12 ( m, 5 H), 2.23-2.45 (m, 2 H), 2.96-3.12 (m, 4 H), 3.19 (ddt, J = 5.0 & 5.0 & 10.0 Hz), 3.33-3.62 (m, 1 H), 3.68-3.82 (m, 1 H), 3.82-3.95 (m, 4 H), 3.95-4.18 (m, 1 H), 4.25-4.37 (m, 2 H), 4.61-4.77 (M, 2 H), 7.21-7.44 (M, 10 H) ¹³ C NMR (400MHz, 1M DCl) Deruta Ppm: 21.8, 22.5, 24.8, 27.0, 30.5, 30.8, 31.0, 31.2, 31.7, 37.2 , 37.8, 38.4, 39.0, 39.8, 40.4, 40.6, 41.8, 42.3, 49.8, 50.2, 52.2, 52.6, 54.6, 55.2, 57.7, 57.9, 127.6, 128.4, 129.2, 129.6, 129.7, 129.8 dp 209.5 ℃Example 2
(Trifluoroacetic Acid (TFA)
Use) (1) D-Phe-D-Phe-D-Leu-D-Lys-Pic-OMe TFA Synthesis Of Salt (1)
TFA 18ML Eggplant Flask Of 50ML (18V / W) , 1- Dodecanethiol 1.6ML (1.6V / W), Triisopropylsilane 0.2ML (0.2V / W), H ₂ Sequentially Added Stirring The O 0.2ML (0.2V / W) Did. The Solution To The Boc-D-Phe- D- Phe-D-Leu-D -Lys (Boc) -α-Boc-Pic-OMe the (9) 1.00g (1.01mmol) was added in small portions with a spatula. After completion of the reaction, concentrated under reduced pressure by an evaporator, it was added dropwise the resulting residue in IPE 20mL (20v / w). The precipitated solid was filtered off, the resulting solid was obtained and dried under reduced pressure to D-Phe-D-Phe- D-Leu -D-Lys-Pic-OMe · TFA salt as a white solid (1) (Osamu rate 93.0%, HPLC purity 95.2%).(2) D-Phe-D -Phe-D-Leu-D-Lys-Pic synthesis of (A)
to a round-bottomed flask of 10mL D-Phe-D-Phe -D-Leu-D-Lys-Pic-OMe TFA were charged salt (1) 83mg (0.0843mmol), was added and dissolved H2O 431μL (5.2v / w). Was 12h stirring dropwise 1N NaOH 345μL (0.345mmol) at room temperature. After completion of the reaction, concentrated under reduced pressure by an evaporator added 1N HCl 84.3μL (0.0843mmol), to obtain a D-Phe-D-Phe- D-Leu-D-Lys-Pic (A) ( yield: quant, HPLC purity 95.4%).Example
3 (HCl / EtOAc
Use) (1) In An Eggplant-Shaped Flask Of 30ML Boc-D-Phe-D -Phe-D-Leu-D-Lys (Boc) -Arufa-Boc-Pic-OMe (9) 1. It was charged with 00g (1.01mmol ), was added and dissolved EtOAc7.0mL (7.0v / w). 4N HCl / EtOAc 5.0mL (5.0v / w) was added after 24h stirring at room temperature, the precipitated solid was filtered off by vacuum filtration, washed with EtOAc 2mL (2.0v / w). The resulting solid D-Phe-D-Phe- D-Leu-D-Lys-Pic-OMe hydrochloride (1) was obtained 781mg of a white solid was dried under reduced pressure (the 96.7% yield, HPLC purity 95.4%).(2) D-Phe-D -Phe-D-Leu-D-Lys-Pic (A) Synthesis of
eggplant flask of 10mL D-Phe-D-Phe -D-Leu-D-Lys-Pic-OMe hydrochloride were charged salt (1) 90 mg (0.112 mmol), H ₂ was added and dissolved O 0.47mL (5.2v / w). Was 12h stirring dropwise 1N NaOH 459μL (0.459mmol) at room temperature. After completion of the reaction, concentrated under reduced pressure by an evaporator added 1N HCl 0.112μL (0.112mmol), was obtained D-Phe-D-Phe- D-Leu-D-Lys-Pic (A) ( yield: quant, HPLC purity 93.1%).4 Example
Compound (1) Of The Compound By Hydrolysis Synthesis Of (The A) (Compound (1) Without
Purification) Eggplant Flask 10ML D-Phe-D-Phe -D-Leu-D-Lys-Pic-OMe (1) Charged Hydrochloride Were (Without Pre-Step Purification) 114.5Mg (0.142Mmol), H ₂ Was Added And Dissolved O 595MyuL (5.2V / W). Was 14H Stirring Dropwise 1N NaOH 586MyuL (0.586Mmol) At Room Temperature. After Completion Of the reaction, concentrated under reduced pressure by an evaporator added 1N HCl 0.15μL (0.150mmol), was obtained D-Phe-D-Phe- D-Leu-D-Lys-Pic (A) (yield: quant, HPLC purity 95.2 %).Example 1 Comparative
Path Not Via The Compound (1) (Using Whole Guard Boc-D-Phe-D-Phe-D-Leu-D-Lys (Boc) -Alpha-Boc-Pic-OMe
(A)) (1) D–Boc Phe- D-Phe-D-Leu-D-Lys (Boc) -Arufa-Boc-Pic-OH Synthesis Of
Eggplant Flask Of 30ML Boc-D-Phe-D -Phe-D-Leu-D- Lys (Boc) -α- Boc-Pic -OMe (9) were charged 1.00g (1.00mmol), was added and dissolved MeOH 5.0mL (5.0v / w). After stirring for four days by the addition of 1N NaOH 1.1 mL (1.10mmol) at room temperature, further MeOH 5.0mL (5.0v / w), 1N NaOH 2.0mL the (2.0mmol) at 35 ℃ in addition 3h and the mixture was stirred. After completion of the reaction, 1 N HCl 6.1 mL was added, After distilling off the solvent was concentrated under reduced pressure was separated and the organic layer was added EtOAc 5.0mL (5.0mL) .NaClaq. 5.0mL (5.0v / w) Wash the organic layer was added, the organic layer as a white solid was concentrated under reduced pressure to Boc-D-Phe-D- Phe-D-Leu-D-Lys (Boc) – α-Boc-Pic-OH 975.1mg (99.3% yield, HPLC purity 80.8% )(2) D-Phe-D -Phe-D-Leu-D-Lys-Pic synthesis of (A)
to a round-bottomed flask of 20mL Boc-D-Phe-D -Phe-D-Leu-D-Lys (Boc) It was charged -α-Boc-Pic-OH ( 10) 959mg (0.978mmol), was added and dissolved EtOAc 4.9mL (5.0v / w). And 4h stirring at room temperature was added dropwise 4N HCl / EtOAc 4.9mL (5.0mL) at room temperature. After completion of the reaction, it was filtered under reduced pressure, a white solid as to give D-Phe-D-Phe- D-Leu-D-Lys-Pic the (A) (96.4% yield, HPLC purity 79.2%) .　If not via the compound of the present invention (1), the purity of the compound obtained (A) was less than 80%. 

PATENThttp://www.google.com/patents/US20110212882

References

1. ^ Janecka A, Perlikowska R, Gach K, Wyrebska A, Fichna J (2010). “Development of opioid peptide analogs for pain relief”. Curr. Pharm. Des. 16 (9): 1126–35. doi:10.2174/138161210790963869. PMID 20030621.
2. ^ Jump up to:^a b https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/214916s000lbl.pdf
3. ^ Jump up to:^{a b c d e f g h i j} Raymond S. Sinatra; Jonathan S. Jahr; J. Michael Watkins-Pitchford (14 October 2010). The Essence of Analgesia and Analgesics. Cambridge University Press. pp. 490–491. ISBN 978-1-139-49198-3.
4. ^ Jump up to:^{a b c d e} Jeffrey Apfelbaum (8 September 2014). Ambulatory Anesthesia, An Issue of Anesthesiology Clinics. Elsevier Health Sciences. pp. 190–. ISBN 978-0-323-29934-3.
5. ^ Jump up to:^a b Alan Cowan; Gil Yosipovitch (10 April 2015). Pharmacology of Itch. Springer. pp. 307–. ISBN 978-3-662-44605-8.
6. ^ Jump up to:^a b c d Charlotte Allerton (2013). Pain Therapeutics: Current and Future Treatment Paradigms. Royal Society of Chemistry. pp. 56–. ISBN 978-1-84973-645-9.
7. ^ “Korsuva: FDA-Approved Drugs”. U.S. Food and Drug Administration. Retrieved 24 August 2021.
8. ^ “Vifor Pharma and Cara Therapeutics announce U.S. FDA approval of Korsuva injection for the treatment of moderate-to-severe pruritus in hemodialysis patients” (Press release). Vifor Pharma. 24 August 2021. Retrieved 24 August 2021 – via Business Wire.
9. ^ Fishbane S, Jamal A, Munera C, Wen W, Menzaghi F (2020). “A phase 3 trial of difelikefalin in hemodialysis patients with pruritus”. N Engl J Med. 382 (3): 222–232. doi:10.1056/NEJMoa1912770. PMID 31702883.

External links

• “Difelikefalin”. Drug Information Portal. U.S. National Library of Medicine.
• Clinical trial number NCT03422653 for “A Study to Evaluate the Safety and Efficacy of CR845 in Hemodialysis Patients With Moderate-to-Severe Pruritus (KALM-1)” at ClinicalTrials.gov
• Clinical trial number NCT03636269 for “CR845-CLIN3103: A Global Study to Evaluate the Safety and Efficacy of CR845 in Hemodialysis Patients With Moderate-to-Severe Pruritus (KALM-2)” at ClinicalTrials.gov

//////////Difelikefalin acetate, FDA 2021,  APPROVALS 2021, FORSUVA, ジフェリケファリン酢酸塩 , Difelikefalin, CR 845,  MR 13A-9, MR-13A9, PEPTIDE