Sitagliptin

Table 1. Basic profile of sitagliptin

Description Oral anti-diabetic drug
Target(s) Dipeptidyl peptidase-4 (DPP-4)
Generic Sitagliptin
Commercial Name Januvia® (United States, United Kingdom, Canada)
Combination Drug(s) Janumet®, Janumet® XR* (Janumet extended-release with sitagliptin and metformin)
Other Synonyms Sitagliptan, Sitagliptin phosphate, Sitaglipina, Sitagliptine, Sitagliptum, MK-0431
IUPAC Name (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine
Ligand Code in PDB 715
3D Structure of sitagliptin bound to target protein DPP-4 PDB ID 1x70
RotateHydrogensLabels
Figure 1. 2D and 3D structures of Sitagliptin (PDB ligand code: 715).

Drug Information

Table 2. Chemical and physical properties (DrugBank).

Chemical Formula C16H15F6N5O
Molecular Weight 407.31 g/mol
Calculated Predicted Partition Coefficient: cLogP 1.5
Calculated Predicted Aqueous Solubility: cLogS -4.1
Solubility (in water) 0.034 mg/mL (sparingly soluble)
Predicted Topological Polar Surface Area (TPSA) 77.04 Å2

Drug Target

Sitagliptin is an orally active, antidiabetic drug that works by inhibiting the enzyme dipeptidyl peptidase-4 (DPP-4) (Ahrén, 2002). In response to food intake, endocrine cells in the gastrointestinal tract release incretin hormones, GLP-1 and GIP, to stimulate insulin secretion. Normally, DPP-4 degrades the incretin hormones within a few minutes of their release, thereby playing a key role in regulating the duration of incretin hormone function. Sitagliptin is a non-substrate-like inhibitor of DPP-4. By blocking DPP-4 enzymatic activity, sitagliptin increases the half-life of the incretin hormones, which in turn stimulates increased secretion of insulin by pancreatic β-cells, and reduces secretion of glucagon by pancreatic α-cells. Collectively, these functions lower blood glucose levels. Since the incretins, GLP-1 and GIP, are only released after eating, DPP-4 inhibitors typically do not induce hypoglycemia (Aschner et al., 2006).

Learn more about DPP-4 here.

Drug-Target Complex

Each molecule of the DPP-4 enzyme is a transmembrane glycoprotein made up of 766 amino acids and consists of five regions:

  • a cytoplasmic region (residues 1–6) not crystallized/not shown
  • a trans-membrane region (residues 7–28) not crystallized/not shown
  • a highly-glycosylated region (residues 29–323) colored cyan
  • a cysteine-rich region (residues 324–551) colored pink
  • a catalytic region (residues 552–766) colored orange

The overall structure of the extracellular portion of the enzyme, showing the highly glycosylated, cysteine-rich, and catalytic regions can be seen in Figure 2.

Figure 2. Overall structure of human DPP-4 monomer, complexed with sitagliptin. The enzyme is shown in ribbon representation highlighting the N- and C-termini, and various regions of the protein - cysteine-rich region (pink), highly glycosylated region (cyan) and catalytic domain (orange). Sitagliptin is shown in ball-and-stick representation in the figure (PDB ID 1x70; Kim et al., 2005).
Figure 2. Overall structure of human DPP-4 monomer, complexed with sitagliptin. The enzyme is shown in ribbon representation highlighting the N- and C-termini, and various regions of the protein - cysteine-rich region (pink), highly glycosylated region (cyan) and catalytic domain (orange). Sitagliptin is shown in ball-and-stick representation in the figure (PDB ID 1x70; Kim et al., 2005).

The DPP-4 enzyme functions as a dimer, composed of two copies of the same protein (Figure 3). Sitagliptin is a non-substrate-like inhibitor of DPP-4. This class of inhibitors binds non-covalently to the DPP-4 enzyme (Figure 3), and the S1 sub-pocket of the active site is occupied by an aromatic group (Figure 3 inset).

Figure 3. X-ray crystal structure of the DPP-4 dimer (ribbons) with bound sitagliptin (ball-and-stick). The DPP-4 monomer on the right is color-coded by region as in Figure 2 and the monomer on the left is shown as a grey ribbon (PDB ID 1x70; Kim et al., 2005). The surface of the active site of DPP-4 is shown in the inset. Sitagliptin is shown in a ball-and-stick representation, color-coded by atom type (C: gray; N: blue; O: red; F: green). Selected residues in the active sites are shown as stick figures.
Figure 3. X-ray crystal structure of the DPP-4 dimer (ribbons) with bound sitagliptin (ball-and-stick). The DPP-4 monomer on the right is color-coded by region as in Figure 2 and the monomer on the left is shown as a grey ribbon (PDB ID 1x70; Kim et al., 2005). The surface of the active site of DPP-4 is shown in the inset. Sitagliptin is shown in a ball-and-stick representation, color-coded by atom type (C: gray; N: blue; O: red; F: green). Selected residues in the active sites are shown as stick figures.

Closer examination of the co-crystal structure of DPP-4 and sitagliptin reveals the interactions of the drug with its pharmacological target, DPP-4 (Figure 4). Sitagliptin makes extensive hydrogen bonding interactions (represented as green lines). The β-amino group forms hydrogen bonds with Tyr662, Gly205, and Gly206. In addition, there are several water-mediated hydrogen bonds that facilitate the binding of this drug (not shown here for clarity). The aromatic moiety (trifluorophenyl group) of the drug, occupies the S1 pocket, lined by several aromatic amino acids, including Tyr662. The triazolopiperazine group binds in the S2 pocket of DPP-4, with the trifluoromethyl group of positioned between the residues Arg358 and Ser209, in the S2 extensive site.

Figure 4. Hydrogen bonding interactions (green lines) between sitagliptin (ball-and-stick) and active site residues (stick figures) (PDB ID 1x70; Kim et al., 2005). Figure 5. Hydrogen bonding interactions (green lines) between Diprotin A (ball-and-stick) and active site residues (stick figures) (PDB ID 1nu8; Thoma et al., 2003).

Comparison of the co-crystal structures of DPP-4 with sitagliptin (PDB ID 1x70, Figure 4) and Diprotin A with DPP-4 (PDB ID 1nu8, Figure 5) reveals that sitagliptin acts by occluding the DPP-4 active site and prevents binding of incretin hormones. Note that the positions and orientations of the DPP-4 active site residues (Ser630, His740, and Asp708) are identical in both complexes.

Pharmacologic Properties and Safety

Table 3. Pharmacokinetics: ADMET of sitagliptin

Features Comment(s) Source
Oral Bioavailability (%) 87% Capuano et al., 2013
IC50 (nM) 18 nM Green et al., 2007
Ki (nM) 9 nM Green et al., 2007
Half-life (hrs) 8-14 hours Capuano et al., 2013
Duration of Action N/A N/A
Absorption Site Human intestine DrugBank
Transporter(s) Multidrug resistance protein 1 DrugBank
Metabolism Cytochrome p450 3A4 and 2C8 DrugBank
Excretion ~87% urine; ~13% feces Capuano et al., 2013
AMES Test (Carcinogenic Effect) probability 0.5487 (non AMES toxic) DrugBank
hERG Safety Test (Cardiac Effect) probability 0.7076 (weak inhibitor) DrugBank
Liver Toxicity Liver injury due to sitagliptin is rare. A single case report of clinically apparent liver injury has been published in a patient who also had hepatitis C LiverTox

Drug Interactions and Side Effects

Although hypoglycemia is rarely observed with sitagliptin as monotherapy (in <1% patients), it does occur more frequently when combined with other oral hypoglycemic agents. Dosage reduction(s) may be recommended for concomitant administration of sitagliptin with other antidiabetic treatments.

Regulatory Approvals/Commercial

Table 4. Drug interactions and side effects of sitagliptin

Features Comment(s) Source
Total Number of Drug Interactions 642 drugs Drugs.com
Major Drug Interactions bexarotene and gatifloxacin Drugs.com
Alcohol/Food Interaction(s) moderate interaction with alcohol (ethanol) Drugs.com
On-target Side Effects nausea, diarrhea, vomiting, flatulence, abdominal Pain, pancreatitis, renal complications Drugs.com
Off-target Side Effects headaches, drowsiness, weakness, joint pain, allergic reaction, upper respiratory infection Drugs.com

Januvia (sitagliptin) was developed by Merck & Co. and approved for use by the US FDA in 2006. It is prescribed as an oral monotherapy in 25 mg, 50 mg, or 100 mg doses and is usually taken once a day. The cost of a 30-day supply of 100 mg tablets of sitagliptin is about US $350 (or US $12/day).

Sitagliptin underwent two double-blind, randomized, and placebo-controlled clinical trials in the U.S. (Herman, 2005).

Merck & Co. has also developed a fixed dose sitagliptin/metformin combination, under the name Janumet® and Janumet® XR.

Links

Table 5. Links to Relevant Resources

DrugBank DB01261
Drugs.com https://www.drugs.com/mtm/sitagliptin.html
Food and Drugs Administration https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/021995s019lbl.pdf
Liver Tox: National Institutes of Health (NIH https://www.ncbi.nlm.nih.gov/books/NBK548083/

References

Ahrén, B., Simonsson, E., Larsson, H., Landin-Olsson, M., Torgeirsson, H., Jansson, P. A., Sandqvist, M., Båvenholm, P., Efendic, S., Eriksson, J. W., Dickinson, S., and Holmes, D. (2002) Inhibition of Dipeptidyl Peptidase IV Improves Metabolic Control Over a 4-week Study Period in Type 2 Diabetes Diabetes Care 25, 869-875. https://doi.org/10.2337/diacare.25.5.869

American Diabetes Association. (2013) Economic costs of diabetes in the US in 2012. Diabetes Care 36, 1033-1046. https://doi.org/10.2337/dc12-2625

Aschner, P., Kipnes, M. S., Lunceford, J. K., Sanchez, M., Mickel, C., and Williams-Herman, D. E. (2006) Effect of the Dipeptidyl Peptidase-4 Inhibitor Sitagliptin as Monotherapy on Glycemic Control in Patients with Type 2 Diabetes. Diabetes Care 29, 2632-2637. https://doi.org/10.2337/dc06-0703

Capuano, A., Sportiello, L., Maiorino, M. I., Rossi, F., Giugliano, D., and Esposito, K. (2013) Dipeptidyl Peptidase-4 Inhibitors in Type 2 Diabetes Therapy – Focus on Alogliptin. Drug, Design, Development and Therapy 213, 989-1001. https://doi.org/10.2147/DDDT.S37647

Diabetes. World Health Organization.http://www.who.int/mediacentre/factsheets/fs312/en/

Gadsby, R. (2009) Efficacy and Safety of Sitagliptin in the Treatment of Type 2 Diabetes. Clinical Medicine Insights: Therapeutics 1, 53-62. https://doi.org/10.1016/j.diabres.2008.10.009

Green, B., Flatt, P., and Bailey, C. (2007) Gliptins: DPP-4 Inhibitors to Treat Type 2 Diabetes. Future Prescriber 8, 6-12. https://doi.org/10.1002/fps.33

Herman, G., Stevens, C., Vandyck, K., Bergman, A., Yi, B., Desmet, M., Snyder, K., Hillard, D., Tanen, M., and Tanaka, W. (2005) Pharmacokinetics and pharmacodynamics of sitagliptin, an inhibitor of dipeptidyl peptidase IV, in healthy subjects: Results from two randomized, double-blind, placebo-controlled studies with single oral doses. Clinical Pharmacology & Therapeutics 78, 675-688. https://doi.org/10.1016/j.clpt.2005.09.002

Januvia. Goodrx.com. http://www.goodrx.com/januvia

Kim, D., Wang, L., Beconi, M., Eiermann, G., Fisher, M., He, H., Hickey, G., Kowalchick, J., Leiting, B., Lyons, K., Marsilio, F., McCann, M., Patel, R., Petrov, A., Scapin, G., Patel, S., Roy, R., Wu, J., Wyvratt, M., Zhang, B., Zhu, L., Thornberry, N., and Weber, A. (2005) (2R)-4-Oxo-4-[3-(Trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin- 7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine: A Potent, Orally Active Dipeptidyl Peptidase IV Inhibitor for the Treatment of Type 2 Diabetes. Journal of Medicinal Chemistry 48, 141-151. https://doi.org/10.1021/jm0493156

Sitagliptin - DrugBank. Drugbank.ca. http://www.drugbank.ca/drugs/DB01261

Sitagliptin: Indications, Side Effects, Warnings. Drugs.com. https://www.drugs.com/cdi/sitagliptin.html

Sitagliptin (Januvia). Glucagon.com. http://www.glucagon.com/sitagliptin.html

Thoma, R., Loffler, B., Stihle, M., Huber, W., Ruf, A., and Hennig, M. (2003) Structural basis of proline-specific exopeptidase activity as observed in human dipeptidyl peptidase-IV. Structure 11, 947-959. https://doi.org/10.1016/S0969-2126(03)00160-6

April 2017, Peter T. Davis, Jennifer Jiang, Dr. Sutapa Ghosh; Reviewed by Drs. John Kozarich and Stephen K. Burley
http://dx.doi.org/10.2210/rcsb_pdb/GH/DM/drugs/dppi/sitagliptin