Mechanism of Action

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

●    Empagliflozin selectively inhibited SGLT2 (IC₅₀ = 1.3 nM), resulting in decrease renal glucose re-absorption, and thereby increasing urinary glucose excretion (UGE) and lowered plasma glucose (PG) in patients with type 2 diabetes.

●    Empagliflozin showed no inhibition of ligands binding on any of other targets at up to 10 µM, in a penal of 98 human, rat, mouse, and rabbit enzymes and receptors, as well as, a panel of 106 human proteome consisting of 49 receptors, 21 ion channels, 29 enzymes.^[12]

In Vivo Efficacy

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

v    In db/db mice: MED = 3 mg/kg.

v    In ZDF diabetic rats: MED = 3 mg/kg.

v    In DIO rats: MED = 10 mg/kg.

v    In beagle dogs: ED₅₀= 0.9 mg/kg.

v    In BTBR ob/ob mice: Induced UGE at 300 ppm for 12 weeks.

●    Decreased blood glucose concentration and blood glucose AUC:

v    In db/db mice:

Ø    Normal test: Dose-dependently reduced blood glucose during 0-7h, ED₅₀ = 0.6 mg/kg.

Ø    OGTT: Dose-dependently reduced glucose AUC_0-2h at ≥0.3mg/kg.

v    In ZDF rats:

Ø    Normal test: Significantly reduced blood glucose concentration at ≥0.3mg/kg during 0-24 h, ED₅₀ = 0.6 mg/kg.

Ø    OGTT: Reduced blood glucose AUC_0-3h at ≥1 mg/kg in chronic treatments.

v    In BTBR ob/ob mice: Significantly lowered blood glucose at 300 ppm.

●    Protection of insulin secretion: Increased insulin levels in ZDF rats.

●    Decreased HbA1c level in ZDF rats from 7.93 to 6.84 at 3 mg/kg (P <0.006).

●    Attenuated body weight gain in DIO rats by 8.2% compared to control at 60 mg/kg (P <0.001).

Absorption of Empagliflozin

●    Exhibited a linear pharmacokinetics in humans following oral dosing.  The AUC appeared to be dose-proportional increased at the dose range of 10-100 mg empagliflozin.

●    Had a high oral bioavailability in mice (89.8%-96.7%) and dogs (92.1%-102%), but moderate in rats (31.0%).

●    Was absorbed rapidly (T_max = 0.33-0.67 h) in mice, rats and dogs, but moderately in humans (T_max = 1-2 h).

●    Showed a half-life of 8.57-13.1 h in humans, much longer than those in mice (4.31-5.59 h), rats (6.32 h) and dogs (3.6-5.16 h), after oral administration.

●    Had a moderate clearance in rats (14.8 mL/min/kg) and mice (33.0-40.1 mL/min/kg), but low in dogs (1.65-1.76 mL/min/kg), compared to liver blood flow, after intravenous administration.  The Cl/F in humans was 167-177 mL/min after oral administration.

●    Exhibited an extensive distribution in mice, rats and dogs, with apparent volume of distribution at 0.868-1.17, 0.818 and 0.868-1.08 L/kg, respectively, after intravenous administration.  The apparent volume of distribution in humans was 168-172 L after oral administration.

Distribution of Empagliflozin

●    Exhibited moderate plasma protein binding in humans (82%-84.5%), rats (89.9%-91.2%), dogs (88.2%-89.3%) and mice (87.5%-88.5%).  Note that the drug was mainly bound to HSA.

●    Had a C_b:C_p ratio of 0.3 in humans, suggesting little penetration into red blood cells.

●    Rats following a single oral administration:

v    The drug was rapidly and well distributed into some tissues, except for the central nervous system (CNS).

v    Relatively higher concentration levels were observed in those involved with absorption and elimination processes such as the gastrointestinal tract, liver and kidneys, compared to other organs.

v    All tissue with measurable concentrations of empagliflozin had maximum concentrations at 1 h post-dose.

v    Tissues where empagliflozin concentrations were absent included the brain, spinal cord, bone, bone marrow, eyes, eye lens, testis and uveal tract.

v    The empagliflozin concentration in all organs declined over 24-168 h indicating a lack of drug accumulation.

Metabolism of Empagliflozin

●    Was metabolized moderately in rat and dog liver microsomes and hepatocytes, but lowly in human liver microsomes and hepatocytes.

●    Overall, the parent drug represented the most abundant component, with glucuronide metabolites (empagliflozin-2-O-, 3-O-and 6-O-glucuronide) were the most abundant metabolites in the human plasma (3%-7%).  Oxidative metabolism predominates in the nonclinical species with up to 31%, 20% and 17% oxidative metabolism occurring in mice rats and dogs, respectively.^[13]

●    The recombinant UGT isoforms responsible for the formation of empagliflozin glucuronides were UGT1A3, 1A8, 1A9 and 2B7.

Excretion of Empagliflozin

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

●    Was predominantly eliminated in feces in mice, rats and dogs, with parent as the most significant component in mouse, rat and dog feces.

Drug-Drug Interaction

●    In addition, empagliflozin and its three glucuronide metabolites minimally inhibited human liver microsomal CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4.

●    Empagliflozin was also found not induce human hepatocyte CYP1A2, 2B6 or 3A4 mRNA or enzyme activity.

●    Empagliflozin was a substrate of both P-gp and BCRP, but did not inhibit P-gp or BCRP.

●    Empagliflozin was a substrate of transporters OAT3, OATP1B1 and OATP1B3, but not OAT1 and OCT2.

●    Empagliflozin also inhibited OATP1B1, OATP1B3 and OAT2B1with an IC₅₀ in the range 45-295 μM, but not inhibit OAT1 or OCT2.

Single-Dose Toxicity

●    Few acute toxicities of the p.o./i.p. route were identified in rodents.

v    Mouse LD₅₀ by p.o. ≥2000 mg/kg, LD₅₀ by i.p. was not definite.

v    Rat LD₅₀ of both routes ≥2000 mg/kg.

Repeated Dose Toxicity

●    Sub- and chronic toxicological information of the oral route was comprehensively accounted through the 13-week (mouse), 26-week (rat) and 52-week (monkey) studies, the longest ones employed in each species.

v    For mice, NOAEL was 62 × and 98 × MRHD for male and female respectively.

v    For rats, NOAEL was not established due to adrenal and hepatic vacuolation in all treatment groups, and the major target organs included the kidney, adrenal gland and liver.

v    For dogs, NOAEL was 55 and 50 × MRHD for male and female respectively; dose related increase in severity of vacuolation of adrenal gland; nephritis and cortical tubular degeneration with fibrosis at HD.

Safety Pharmacology

●    No cardiovascular, neurological, pulmonary, renal and gastrointestinal effects.

Genotoxicity

●    Empagliflozin got least potential for genotoxicity, confirmed by a sufficient battery of genotoxilogical studies.

Reproductive and Developmental Toxicity

●    Fertility and early embryonic development in rats:

v    Putting paternal and maternal systemic toxicities aside, there were no effects on fertility or reproductive performance in both sexes, as the NOAEL was 700 mg/kg, approximately 155 × MRHD.

●    Fetal-embryonic development in rats and rabbits:

v    The maternal toxicities in cross-species concordance, reduced body weight, etc., occurred at high exposure multiples in both the rat (48 × MRHD) and rabbit (139 × MRHD).  Empagliflozin was also not teratogenic at 48 × and 128 × MRHD in the rat and rabbit, respectively.

v    The limited findings and the high safety margins suggest empagliflozin is unlikely to be teratogenic in humans at the MRHD.

●    Pre- and postnatal development in rats:

v    Likely due to lactational exposure, reduced body weight/body weight gain were observed in F₁ pups during weaning, which in turn led to deficits in memory and learning.  This might be a sign of risk that nursing or exposure to empagliflozin should be discontinued in nursing mothers.

●    Empagliflozin is able to transfer through placental barrier and present in fetal tissues.

●    Milk excretion of empagliflozin was also found in lactating rats, and the milk-to-plasma ratio of emplagliflozin ranged from 0.6 to 5 and was greater than 1.0 from 2 to 24 h post-dose.

Carcinogenicity

●    Empagliflozin poses minimal carcinogenic risk to humans based on the high exposure multiples at the NOAEL in the rat (17-21 × MRHD) and the mouse (4-7 × MRHD).