Dec 192013


An antidiabetic agent that inhibits sodium-dependent glucose cotransporter 2 (SGLT2).

Taisho (Originator), PHASE 3


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WO 2010119990


TS-071, an SGLT-2 inhibitor, is in phase III clinical development at Taisho for the oral treatment of type 1 and type 2 diabetes

In 2012, the product was licensed to Novartis and Taisho Toyama Pharmaceutical by Taisho in Japan for comarketing for the treatment of type 2 diabetes.

Diabetes is a metabolic disorder which is rapidly emerging as a global health care problem that threatens to reach pandemic levels. The number of people with diabetes worldwide is expected to rise from 285 million in 2010 to 438 million by 2030. Diabetes results from deficiency in insulin because of impaired pancreatic β-cell function or from resistance to insulin in body, thus leading to abnormally high levels of blood glucose.

Diabetes which results from complete deficiency in insulin secretion is Type 1 diabetes and the diabetes due to resistance to insulin activity together with an inadequate insulin secretion is Type 2 diabetes. Type 2 diabetes (Non insulin dependent diabetes) accounts for 90-95 % of all diabetes. An early defect in Type 2 diabetes mellitus is insulin resistance which is a state of reduced responsiveness to circulating concentrations of insulin and is often present years before clinical diagnosis of diabetes. A key component of the pathophysiology of Type 2 diabetes mellitus involves an impaired pancreatic β-cell function which eventually contributes to decreased insulin secretion in response to elevated plasma glucose. The β-cell compensates for insulin resistance by increasing the insulin secretion, eventually resulting in reduced β-cell mass. Consequently, blood glucose levels stay at abnormally high levels (hyperglycemia).

Hyperglycemia is central to both the vascular consequences of diabetes and the progressive nature of the disease itself. Chronic hyperglycemia leads to decrease in insulin secretion and further to decrease in insulin sensitivity. As a result, the blood glucose concentration is increased, leading to diabetes, which is self-exacerbated. Chronic hyperglycemia has been shown to result in higher protein glycation, cell apoptosis and increased oxidative stress; leading to complications such as cardiovascular disease, stroke, nephropathy, retinopathy (leading to visual impairment or blindness), neuropathy, hypertension, dyslipidemia, premature atherosclerosis, diabetic foot ulcer and obesity. So, when a person suffers from diabetes, it becomes important to control the blood glucose level. Normalization of plasma glucose in Type 2 diabetes patients improves insulin action and may offset the development of beta cell failure and diabetic complications in the advanced stages of the disease.

Diabetes is basically treated by diet and exercise therapies. However, when sufficient relief is not obtained by these therapies, medicament is prescribed alongwith. Various antidiabetic agents being currently used include biguanides (decrease glucose production in the liver and increase sensitivity to insulin), sulfonylureas and meglitinides (stimulate insulin production), a-glucosidase inhibitors (slow down starch absorption and glucose production) and thiazolidinediones (increase insulin sensitivity). These therapies have various side effects: biguanides cause lactic acidosis, sulfonylurea compounds cause significant hypoglycemia, a-glucosidase inhibitors cause abdominal bloating and diarrhea, and thiazolidinediones cause edema and weight gain. Recently introduced line of therapy includes inhibitors of dipeptidyl peptidase-IV (DPP-IV) enzyme, which may be useful in the treatment of diabetes, particularly in Type 2 diabetes. DPP-IV inhibitors lead to decrease in inactivation of incretins glucagon like peptide- 1 (GLP-1) and gastric inhibitory peptide (GIP), thus leading to increased production of insulin by the pancreas in a glucose dependent manner. All of these therapies discussed, have an insulin dependent mechanism.

Another mechanism which offers insulin independent means of reducing glycemic levels, is the inhibition of sodium glucose co-transporters (SGLTs). In healthy individuals, almost 99% of the plasma glucose filtered in the kidneys is reabsorbed, thus leading to only less than 1% of the total filtered glucose being excreted in urine. Two types of SGLTs, SGLT-1 and SGLT-2, enable the kidneys to recover filtered glucose. SGLT-1 is a low capacity, high-affinity transporter expressed in the gut (small intestine epithelium), heart, and kidney (S3 segment of the renal proximal tubule), whereas SGLT-2 (a 672 amino acid protein containing 14 membrane-spanning segments), is a low affinity, high capacity glucose ” transporter, located mainly in the S 1 segment of the proximal tubule of the kidney. SGLT-2 facilitates approximately 90% of glucose reabsorption and the rate of glucose filtration increases proportionally as the glycemic level increases. The inhibition of SGLT-2 should be highly selective, because non-selective inhibition leads to complications such as severe, sometimes fatal diarrhea, dehydration, peripheral insulin resistance, hypoglycemia in CNS and an impaired glucose uptake in the intestine.

Humans lacking a functional SGLT-2 gene appear to live normal lives, other than exhibiting copious glucose excretion with no adverse effects on carbohydrate metabolism. However, humans with SGLT-1 gene mutations are unable to transport glucose or galactose normally across the intestinal wall, resulting in condition known as glucose-galactose malabsorption syndrome.

Hence, competitive inhibition of SGLT-2, leading to renal excretion of glucose represents an attractive approach to normalize the high blood glucose associated with diabetes. Lower blood glucose levels would, in turn, lead to reduced rates of protein glycation, improved insulin sensitivity in liver and peripheral tissues, and improved cell function. As a consequence of progressive reduction in hepatic insulin resistance, the elevated hepatic glucose output which is characteristic of Type 2 diabetes would be expected to gradually diminish to normal values. In addition, excretion of glucose may reduce overall caloric load and lead to weight loss. Risk of hypoglycemia associated with SGLT-2 inhibition mechanism is low, because there is no interference with the normal counter regulatory mechanisms for glucose.

The first known non-selective SGLT-2 inhibitor was the natural product phlorizin

(glucose, 1 -[2-P-D-glucopyranosyloxy)-4,6-dihydroxyphenyl]-3-(4-hydroxyphenyl)- 1 – propanone). Subsequently, several other synthetic analogues were derived based on the structure of phlorizin. Optimisation of the scaffolds to achieve selective SGLT-2 inhibitors led to the discovery of several considerably different scaffolds.

C-glycoside derivatives have been disclosed, for example, in PCT publications

W.O20040131 18, WO2005085265, WO2006008038, WO2006034489, WO2006037537, WO2006010557, WO2006089872, WO2006002912, WO2006054629, WO2006064033, WO2007136116, WO2007000445, WO2007093610, WO2008069327, WO2008020011, WO2008013321, WO2008013277, WO2008042688, WO2008122014, WO2008116195, WO2008042688, WO2009026537, WO2010147430, WO2010095768, WO2010023594, WO2010022313, WO2011051864, WO201 1048148 and WO2012019496 US patents US65151 17B2, US6936590B2 and US7202350B2 and Japanese patent application JP2004359630. The compounds shown below are the SGLT-2 inhibitors which have reached advanced stages of human clinical trials: Bristol-Myers Squibb’s “Dapagliflozin” with Formula A, Mitsubishi Tanabe and Johnson & Johnson’s “Canagliflozin” with Formula B, Lexicon’s “Lx-421 1” with Formula C, Boehringer Ingelheim and Eli Lilly’s “Empagliflozin” with Formula D, Roche and Chugai’s “Tofogliflozin” with Formula E, Taisho’s “Luseogliflozin” with Formula F, Pfizer’ s “Ertugliflozin” with Formula G and Astellas and Kotobuki’s “Ipragliflozin” with Formula H.


Figure imgf000005_0001

Formula G                                                                                                                  Formula H

In spite of all these molecules in advanced stages of human clinical trials, there is still no drug available in the market as SGLT-2 inhibitor. Out of the potential candidates entering the clinical stages, many have been discontinued, emphasizing the unmet need. Thus there is an ongoing requirement to screen more scaffolds useful as SGLT-2 inhibitors that can have advantageous potency, stability, selectivity, better half-life, and/ or better pharmacodynamic properties. In this regard, a novel class of SGLT-2 inhibitors is provided herein

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      Example 5

    • Figure imgb0035

Synthesis of 2,3,4,6-tetra-O-benzyl-1-C-[2-methoxy-4-methyl-(4-ethoxybenzyl)phenyl]-5-thio-D-glucopyranose

    • Five drops of 1,2-dibromoethane were added to a mixture of magnesium (41 mg, 1.67 mmol), 1-bromo-3-(4-ethoxybenzyl)-6-methoxy-4-methylbenzene (0.51 g, 1.51 mmol) and tetrahydrofuran (2 mL). After heated to reflux for one hour, this mixture was allowed to stand still to room temperature to prepare a Grignard reagent. A tetrahydrofuran solution (1.40 mL) of 1.0 M i-propyl magnesium chloride and the prepared Grignard reagent were added dropwise sequentially to a tetrahydrofuran (5 mL) solution of 2,3,4,6-tetra-O-benzyl-5-thio-D-glucono-1,5-lactone (0.76 g, 1.38 mmol) while cooled on ice and the mixture was stirred for 30 minutes. After the reaction mixture was added with a saturated ammonium chloride aqueous solution and extracted with ethyl acetate, the organic phase was washed with brine and dried with anhydrous magnesium sulfate. After the desiccant was filtered off, the residue obtained by evaporating the solvent under reduced pressure was purified by silica gel column chromatography (hexane:ethyl acetate =4:1) to obtain (0.76 g, 68%) a yellow oily title compound.
      1H NMR (300 MHz, CHLOROFORM-d) δ ppm 1.37 (t, J=6.92 Hz, 3 H) 2.21 (s, 3 H) 3.51 – 4.20 (m, 12 H) 3.85 – 3.89 (m, 3 H) 4.51 (s, 2 H) 4.65 (d, J=10.72 Hz, 1 H) 4.71 (d, J=5.75 Hz, 1 H) 4.78 – 4.99 (m, 3 H) 6.59 – 7.43 (m, 26 H)

Example 6

    • [0315]
      Figure imgb0036

Synthesis of (1S)-1,5-anhydro-2,3,4,6-tetra-O-benzyl-1-[2-methoxy-4-methyl-5-(4-ethoxybenzyl)phenyl]-1-thio-D-glucitol

    • An acetonitrile (18 mL) solution of 2,3,4,6-tetra-O-benzyl-1-C-[2-methoxy-4-methyl-5-(4-ethoxybenzyl)phenyl]-5-thio-D-glucopyranose (840 mg, 1.04 mmol) was added sequentially with Et3SiH (0.415 mL, 2.60 mmol) and BF3·Et2O (0.198 mL, 1.56 mmol) at -18°C and stirred for an hour. After the reaction mixture was added with a saturated sodium bicarbonate aqueous solution and extracted with ethyl acetate, the organic phase was washed with brine and then dried with anhydrous magnesium sulfate. After the desiccant was filtered off, the residue obtained by evaporating the solvent under reduced pressure was purified by silica gel column chromatography (hexane:ethyl acetate=4:1) to obtain the title compound (640 mg, 77%).
      1H NMR (600 MHz, CHLOROFORM-d) δ ppm 1.35 (t, J=6.88 Hz, 3 H) 2.21 (s, 3 H) 3.02 – 3.21 (m, 1 H) 3.55 (t,J=9.40 Hz, 1 H) 3.71 (s, 1 H) 3.74 – 3.97 (m, 10 H) 4.01 (s, 1 H) 4.45 – 4.56 (m, 3 H) 4.60 (d, J=10.55 Hz, 2 H) 4.86 (s, 2 H) 4.90 (d, J=10.55 Hz, 1H) 6.58 – 6.76 (m, 5 H) 6.90 (d, J=7.34 Hz, 1 H) 7.09 – 7.19 (m, 5 H) 7.23 – 7.35 (m, 15 H).
      ESI m/z = 812 (M+NH4).

Example 7

    • Figure imgb0037

Synthesis of (1S)-1,5-anhydro-1-[3-(4-ethoxybenzyl)-6-methoxy-4-methylphenyl]-1-thio-D-glucitol

  • A mixture of (1S)-1,5-anhydro-2,3,4,6-tetra-O-benzyl-1-[2-methoxy-4-methyl-5-(4-ethoxybenzyl)phenyl]-1-thio-D-glucitol (630 mg, 0.792 mmol), 20% palladium hydroxide on activated carbon (650 mg) and ethyl acetate (10 mL) – ethanol (10 mL) was stirred under hydrogen atmosphere at room temperature for 66 hours. The insolubles in the reaction mixture were filtered off with celite and the filtrate was concentrated. The obtained residue was purified by silica gel column chromatography (chloroform:methanol =10:1) to obtain a colorless powdery title compound (280 mg, 81%) as 0.5 hydrate. 1H NMR (600 MHz, METHANOL- d4) δ ppm 1.35 (t, J=6.9 Hz, 3 H) 2.17 (s, 3 H) 2.92 – 3.01 (m, 1 H) 3.24 (t, J=8.71 Hz, 1 H) 3.54 – 3.60 (m, 1 H) 3.72 (dd, J=11.5, 6.4 Hz, 1 H) 3.81 (s, 3 H) 3.83 (s, 2 H) 3.94 (dd, J=11.5, 3.7 Hz, 1 H) 3.97 (q, J=6.9 Hz, 2 H) 4.33 (s, 1 H) 6.77 (d, J=8.3 Hz, 2 H) 6.76 (s, 1 H) 6.99 (d, J=8.3 Hz, 2 H) 7.10 (s, 1 H). ESI m/z = 452 (M+NH4+), 493 (M+CH3CO2-). mp 155.0-157.0°C. Anal. Calcd for C23H30O6S·0.5H2O: C, 62.28; H, 7.06. Found: C, 62.39; H, 7.10.

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