Mechanism of Action

●    Ipragliflozin is an inhibitor of SGLT2, which is the major transporter involved in the reabsorption of glucose in the kidneys.

●    Ipragliflozin selectively inhibited hSGLT1 (IC50 = 7.38 nM, selectivity: 254 folds), resulting in decrease renal glucose re-absorption, and thereby increasing urinary glucose excretion (UGE) and lowering plasma glucose (PG) in patients with type 2 diabetes.

●    Ipragliflozin exhibited no significant affinity and inhibition at 10 μM in a penal of 54 types of transporters, ion channels and 3 types of enzyme, except weak affinity for 5-HT2B (IC50 = 9.21 μM), serotonin dopamine transporter (IC50 = 5.54 μM).[7]

In Vivo Efficacy

●    Increased urinary glucose excretion (UGE) and volume of urine:

v    Normal ICR mice: Increased UGE at 0.3 mg/kg and urine volume at 3 mg/kg, respectively.

v    NA/STZ diabetic mice: Increased UGE at 0.3 mg/kg and urine volume at 3 mg/kg, respectively.

v    KK-A^y diabetic mice:

Ø    Normal test: Significantly increased UGE at 0.3 mg/kg, but had no effect on the volume of urine.

Ø    After 28 days treatment: Significantly increased UGE at 1 mg/kg/day on day 30.

●    Decreased blood glucose concentration and blood glucose AUC:

v    KK-A^y diabetic mice:

Ø    Normal test: Decreased blood glucose AUC_0-8 at 0.1 mg/kg.

Ø    Glucose loading: Decreased blood glucose AUC_0-8 at 0.1 mg/kg (sigle dose) and 1 mg/kg (p.o., QD × 28).

v    NA/STZ diabetic mice: Decreased blood glucose AUC_0-12 at 0.1 mg/kg.

Ø    Glucose loading: Decreased blood glucose AUC_0-6, at 0.1 mg/kg.

Ø    Fasting: Decreased blood glucose AUC_0-6 at 10 mg/kg.

v    Wistar diabetic rats: Significantly reduced blood glucose AUC_0-8, MED = 0.1 mg/kg.

●    Decreased HbA1c level:

v    KK-A^y diabetic mouse: MED = 0.3 mg/kg.

v    db/db mosue: MED = 0.1 mg/kg.

●    Ipragliflozin improved pancreatic β cell protection and insulin secretion:

v    KK-A^y diabetic mice: Significant increased pancreatic insulin content at 1 mg/kg/day.

v    db/db mice: Inhibited the decrease in insulin-positive granules in the pancreas at ≥0.1 mg/kg and significantly increased the pancreatic insulin content and plasma insulin levels at 1 mg/kg.

Absorption of Ipragliflozin

●    Had high oral bioavailabilities in rats (78.2%-90.7%), monkeys (74.5%-75.3%) and humans (90.2%).

●   Was absorbed rapidly (T_max = 0.5-1 h) in rats, moderately in monkeys (1.75-2 h), but rapidly to moderately in humans (0.75-2.60 h).

●   Showed a half-life of 16.8 h in humans, much longer than those in rats (3.85 h) and monkeys (9.45 h), after intravenous administration.

●   Had low clearances in humans (10.9 L/h), rats (0.433 L/h/kg) and monkeys (0.252 L/h/kg), compared to liver blood flow, after intravenous administration.

●   Exhibited extensive tissue distributions in rats, monkeys and humans, with apparent volumes of distribution at 1.68, 2.32 L/kg and 127 L, respectively, after intravenous administration.

Distribution of Ipragliflozin

●   Exhibited high plasma protein bindings in humans and in all nonclinical species (92%-97%).

●   Had a blood cell partition ratio of 16.9%-19.1% in humans, suggesting little penetration into red blood cells.

●   Albino rats and pigmented rats after oral administration:

v    The drug was rapidly and well distributed into most tissues except for the central nervous system (CNS), with little or no radioactivity in the brain.

v    Relatively higher concentration levels were observed in kidneys, liver, adrenal gland and stomach.

v    Radioactivity concentrations decreased below the lower limit of quantification in all tissues at 24 h post-dose.

Metabolism of Ipragliflozin

●   Ipragliflozin underwent low oxidative metabolism by numerous human cytochrome P450 enzymes.

●   Overall, the parent drug represented the most abundant component, with the glucuronide conjugate of ipragliflozin (M2) as the major metabolite in human plasma.

●   M2 and M4 was the major human metabolite formed in the kidneys and the liver.

●   Ipragliflozin was metabolized by multiple UGT enzymes and primary metabolic enzyme was UGT2B7, with UGT2B4, 1A8 and 1A9 involved in metabolism of ipragliflozin.

●   No unique ipragliflozin human metabolites were identified.

Excretion of Ipragliflozin

●   Was predominantly eliminated in urine in humans, with M2 as the significant component in human urine.

●   About 83.6% of ipragliflozin was recovered via biliary excretion in bile duct-cannulated (BDC) rats.

Drug and Drug Interaction

●   Ipragliflozin minimally inhibited multiple CYP450 enzymes with an IC₅₀ of >58 μM in vitro.

●   Ipragliflozin was not an inducer of CYP3A4 and CYP1A2 in vitro.

●   Ipragliflozin was not an inhibitor of UGT2B7, UGT1A1, UGT1A4, UGT1A6 and UGT1A9 with an IC₅₀ > 100 μM in vitro.

●   Ipragliflozin was a substrate for P-gp, but had no inhibiton for P-gp.

●   Ipragliflozin was not a substrate of BCRP, MRP2, OATP1B1 or OATP1B3 in vitro.

●   Ipragliflozin was a weak inhibitor of OATP1B1, OAT3 and OCT1, but it did not inhibit the activities of transporters of BCRP, MRP2, MATE, OAT1 or OCT2 in vitro.

Single-Dose Toxicity

●    Single-dose toxicities by the oral route in rodent and non-rodent species:

v    Rat MTD (p.o.): 2000 mg/kg (male); 500 mg/kg (female).

v    Monkey MTD (p.o.): 2000 mg/kg.

Repeated Dose Toxicity

●    Sub- and chonic toxicity by the oral route in rats (up to 26 weeks) and monkeys (up to 52 weeks):

v    Osmotic diuretic-like effects in all species, and ipragliflozin induced food and water consumption.

v    For the 26-week rat study, NOAEL was 0.1 mg/kg/day which is 0.02 fold of MRHD for male and 0.03 fold of MRHD for female, determined by the increase of urinary β2-microglobulin excretion, urinary NAG excretion, and the increase of kidney weight were also observed at 1 mg/kg/day.   Most toxicities found were kidneys and bladder lesions derived from osmolality changes, nevertheless, bone marrow, lungs, GI track, liver, and spleen lesions were also observed.^[1]

v    For the 52-week monkey study, NOAEL was 10 mg/kg/day 5 fold of MRHD in males and 1 mg/kg/day 0.4 fold of MRHD in females, determined by the increase of urinary β2-microglobulin excretion, urinary NAG excretion, and the primary target organ were liver and GI-tract.

Safety Pharmacology

●    Core battery of studies to evaluate safety pharmacology:

v    Least potential for QT prolongation, based on17.4 % inhibition of hERG tail current at the highest concentration tested.

v    In cynomolgus monkeys dosed up to 1000 mg/kg, no effects were observed on BP, HR, ECG, blood gas and respiratory rate.

Genotoxicity

●    Based on in vitro studies, while ipragliflozin was negative for mutagenicity in Ames assay, chromosome structural aberrations occurred in mammalian cells, but which were associated with severe cytotoxicity.  Furthermore, the positive results were not repeated in either in vivo study employed, given the weights of evidence, ipragliflozin was considered no genotoxic risk.

Reproductive and Developmental Toxicity

●    Fertility and early embryonic development in rats:

v    NOAEL was 300 mg/kg/day which was 86-174 fold exposure of MRHD.

●    Embryo-fetal development in rats and rabbits:

v    NOAEL was 100 for dam and does, whilst 300 mg/kg/day for fetal development in both species.

●    Pre- and postnatal developmentalin rats:

v    NOAEL was 100 mg/kg/day which was 25 fold of MRHD.

●    Ipragliflozin distributed through placenta to fetus in pregnant rats.^[7]

●    Milk excretion of ipragliflozin was also found in lactating rats.^[7]

Carcinogenicity

●    No significant malignant or benign neoplasmia found in 2-year standard carcinogenicity studies of mice.

●    Tumorigenicity to adrenal medulla emerged in rats, as for humans, it was not considered to be an indicator of carcinogenic risk.