Saxagliptin

*Kombiglyze extended-release (XR)

Table 1. Basic profile of saxagliptin 

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Table 2. Chemical and physical properties (DrugBank).

*Note: Predicted values may slightly vary from source to source. 

Saxagliptin is an orally active, antidiabetic drug that works by inhibiting the enzyme dipeptidyl peptidase-4 (DPP-4) (Augeri et al., 2005). 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. Saxagliptin is a substrate-like inhibitor of DPP-4. By blocking DPP-4 enzymatic activity, saxagliptin increases the half-life of 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.

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 in complex with saxagliptin. 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). Saxagliptin is shown in ball-and-stick representation (PDB ID: 3bjm; Metzler et al., 2008).

The DPP-4 enzyme functions as a dimer, composed of two copies of the same protein (Figure 3).Saxagliptin is a substrate-like inhibitor of DPP-4, hence it inhibits DPP-4 by forming a covalent but reversible complex. This class of compounds interacts covalently with the catalytically active serine hydroxyl (Ser630) and has a proline-like group that occupies the S1 pocket of the active site.

Figure 3. X-ray crystal structure of the DPP-4 dimer (ribbons), with bound saxagliptin (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: 3bjm; Metzler et al., 2008). Surface of the active site of DPP-4 is shown in the inset. Saxagliptin is shown in a ball-and-stick representation, color-coded by atom type (C: gray; N: blue; O: red). Selected residues in the active sites are shown in the stick representation.

 
Closer examination of the co-crystal structure of DPP-4 and saxagliptin (PDB entry 3bjm, Metzler et al., 2008) reveals multiple interactions of the drug with its pharmacological target, DPP-4 (Figure 4). The methanopyrrolidine ring of the drug occupies the S1 pocket of the enzyme and forms van der Waals interactions with the hydrophobic side-chain residues that form the pocket, while the nitrile group of the drug covalently interacts with the hydroxyl group of Ser630. The drug also forms several hydrogen bonds - the carbonyl oxygen of saxagliptin, forms a hydrogen bond with Asn710, and the primary amine of the drug participates in hydrogen-bonding network with Try662 and Glu205 and Glu206; the adamantane hydroxyl group hydrogen bonds with the side-chain hydroxyl of Tyr547. Together these interactions account for the binding of the drug.

Figure 4. Hydrogen bonding interactions (green lines) between saxagliptin (ball-and-stick) and active site residues (stick figures) (PDB ID: 3bjm; Metzler et al., 2008).	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).

A comparison of the co-crystal structures of DPP-4 with saxagliptin (PDB ID 3bjm, Figure 4) and DPP-4 with its substrate, Diprotin A (Ile-Pro-Ile), (PDB ID 1nu8, Figure 5) reveals that saxagliptin acts by occluding the DPP-4 active site and prevents binding of incretin hormones. The major difference between the interactions of saxagliptin and the non-substrate like inhibitors (eg. sitagliptin) of DPP-4 is the formation of a covalent bond between the drug and the active-site Ser630.

Table 3. Pharmacokinetics: ADMET of saxagliptin

Despite having a short half-life of 2.2-3.8 hours, saxagliptin is able to maintain 24-hour glycemic control with single daily dosage due to the drug’s slow disassociation from the DPP-4 enzyme (Drugs.com). Post-administration of saxagliptin produced a two- or three-fold increase of GLP-1 and GIP levels, which in turn result in decreased glucagon concentrations and increased glucose-dependent insulin secretion from pancreatic β-cells (National Center for Biotechnology Information). The IC₅₀ and K_i of saxagliptin indicate that saxagliptin is an effective competitive inhibitor of DPP-4. 

Although saxagliptin is non-carcinogenic, ≥ 5% of patients treated with saxagliptin have reported adverse effects such as upper respiratory tract infection, urinary tract infection, and headache (DrugBank). According to the National Institutes of Health, <1% of patients in clinical trials displayed elevated serum enzyme levels, and no apparent liver injury was evident. The hepatotoxicity profile of saxagliptin has yet to be published. Administration of saxagliptin did not prolong the QT interval to a clinically significant degree, and thus this drug does not seem to exhibit adverse cardiac effect.

Saxagliptin has significant drug interactions because it is extensively metabolized by CYP 3A4/5 and to a lesser extent CYP 2C8 in the liver (Dave, 2011). The major active metabolite, 5-hydroxy saxagliptin, is only 2-fold less potent than its parent molecule (Capuano et al., 2013). Although saxagliptin and its metabolites are neither inhibitors nor inducers of CYP isoforms, co-administration with strong CYP3A4/5 inducers (e.g. rifampicin) or inhibitors (e.g. ketoconazole) may alter the pharmacokinetics of saxagliptin (Capuano et al., 2013). Concomitant administration of single doses of saxagliptin with insulin secretagogues (e.g. glyburide) or insulin may cause increased risk of hypoglycemia, and thus a reduced dosage is required. Interactions with other drugs (including metformin hydrochloride, famotidine, digoxin, etc.) may alter the pharmacokinetic properties (e.g. peak plasma concentration and AUC) of saxagliptin.

Table 4. Drug interactions and side effects of saxagliptin

Onglyza (saxagliptin) was co-developed by Bristol-Myers Squibb and AstraZeneca, and approved by the US FDA in 2009. It is prescribed as an oral medication in 2.5 or 5 mg once a day, regardless of meals (DrugBank). Both the 2.5 mg and the 5 mg Onglyza cost approximately $351.21 for 30 tablets (Drugs.com).

Onglyza may be co-administered with CYP450 3A4/5 inhibitors, an insulin secretagogue, or with insulin. However, a lower dose may be required to minimize risk of hypoglycemia (Drugs.com). Dosage adjustments may also be necessary if the patient has moderate or severe renal dysfunction.

A combination of the active substances saxaglitin and metformin, called Komboglyze, was produced by the biopharmaceutical company AstraZeneca AB. Komboglyze was granted marketing authorization throughout the European Union by the Committee for Medicinal Products for Human Use (CHMP) on November 24, 2011. It is available as tablets with different strengths (2.5 mg saxagliptin/ 850 mg metformin or 2.5 mg saxagliptin/ 1,000 mg metformin) (Drugs.com). Komboglyze is usually taken as one tablet, twice a day, at mealtimes. If taken in adjunct with insulin or sulfonylurea, the add-on drug dosage may need to be lowered to reduce risk of hypoglycemia (Drugs.com). 

Table 5. Links to relevant resources

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. doi: 10.2337/dc06-0703

Augeri, D. J., Robl, J. A., Betebenner, D. A., Magnin, D. R., Khanna, A., Robertson, J. G., Wang, A., Simpkins, L. M., Taunk, P., Huang, Q., Han, S. P., Abboa-Offei, B., Cap, M., Xin, L., Tao, L., Tozzo, E., Welzel, G. E., Egan, D. M., Marcinkeviciene, J., Chang, S. Y., Biller, S. A., Kirby, M. S., Parker, R. A., and Hamann, L. G. (2005) Discovery and preclinical profile of Saxagliptin (BMS-477118): a highly potent, long-acting, orally active dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes. Journal of Medicinal Chemistry 48, 5025-5037. doi: 10.1021/jm050261p

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. doi: 10.2147/DDDT.S37647

Dave, D. J. (2011). Saxagliptin: A Dipeptidyl Peptidase-4 Inhibitor in the Treatment of Type 2 Diabetes Mellitus. Journal of Pharmacology and Pharmacotherapeutics 2, 230-235. doi: 10.4103/0976-500X.85934

Diagnosing Diabetes and Learning About Prediabetes. American Diabetes Association. http://www.diabetes.org/diabetes-basics/diagnosis/?loc=db-slabnav

Metzler, W. J., Yanchunas, J., Weigelt, C., Kish, K., Klei, H. E., Xie, D., Zhang, Y., Corbett, M., Tamura, J. K., He, B., Hamann, L. G., Kirby, M. S., and Marcinkeviciene, J. (2008) Involvement of DPP-IV Catalytic Residues in Enzyme-Saxagliptin Complex Formation. Protein Science 17, 240-250. doi: 10.1110/ps.073253208

Saxagliptin. Drugbank.ca. https://www.drugbank.ca/drugs/DB06335

Saxagliptin. Livertox.nlm.nih.gov. https://livertox.nlm.nih.gov/Saxagliptin.htm

Saxagliptin. Pubchem.ncbi.nlm.nih.gov. https://pubchem.ncbi.nlm.nih.gov/compound/Saxagliptin

Saxagliptin: Indications, Side Effects, Warnings. Uses, Side Effects & Warnings. Drugs.com. https://www.drugs.com/cdi/saxagliptin.html

Su, H., Boulton, D. W., Barros, A. Jr, Wang, L., Cao, K., Bonacorsi, S. J. Jr, Iyer, R. A., Humphreys, W. G., and Christopher, L. J. (2012) Characterization of the In Vitro and In Vivo Metabolism and Disposition and Cytochrome P450 Inhibition/Induction Profile of Saxagliptin in Human. Drug Metabolism and Disposition  40, 1345-1356. doi: 10.1124/dmd.112.045450

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.  doi: 10.1016/S0969-2126(03)00160-6

Thomas, L., Eckhardt, M., Langkopf, E., Tadayyon, M., Himmelsbach, F., and Mark, M. (2008) (R)-8-(3-Amino-Piperidin-1-Yl)-7-But-2-Ynyl-3-Methyl-1-(4-Methyl-Quinazolin-2-Ylmethyl)-3,7-Dihydro-Purine-2,6-Dione (BI 1356), a Novel Xanthine-Based Dipeptidyl Peptidase 4 Inhibitor, has a Superior Potency and Longer Duration of Action Compared with Other Dipeptidyl Peptidase-4 Inhibitors. Journal of Pharmacology and Experimental Therapeutics 325, 175-182. doi: 10.1124/jpet.107.135723

Wang, A., Dorso, C., Kopcho, L., Locke, G., Langish, R., Harstad, E., Shipkova, P., Marcinkeviciene, J., Hamann, L., and Kirby, M. S. (2012) Potency, Selectivity and Prolonged Binding of Saxagliptin to DPP4: Maintenance of DPP4 Inhibition by Saxagliptin in Vitro and Ex Vivo When Compared To a Rapidly-Dissociating DPP4 Inhibitor. BioMed Central Pharmacology 12, 1-11. doi: 10.1186/1471-2210-12-2