Monday, May 4, 2015

Drugs in Clinical Pipeline: PF-04937319

PF-04937319 [N,N-dimethyl-5-((2-methyl-6-((5-methylpyrazin-2-yl)carbamoyl) benzofuran-4-yl)oxy) pyrimidine-2-carboxamide] is an orally available activator of glucokinase (GCK) which is under trials in patients with Type 2 Diabetes Mellitus (T2DM).

Glucokinase is unique among the members of the hexokinase family given its low substrate affinity (Km nearly 8 mM), positive substrate cooperativity and lack of product inhibition. As a monomeric enzyme, glucokinase achieves this cooperativity through equilibration between multiple protein conformations. In their pioneering work, Grimsby and coworkersa demonstrated that small molecule activators were capable of binding to glucokinase at an allosteric site 20 Å remote from the active site and influencing the enzyme’s kinetic profile by modulating both Km for glucose (also known as S0.5) and Vmax. PF-04937319 was initially evaluated in the biochemical activation assay measuring potency (EC50 = 188 ± 74 uM) as well as effects on Km (0.10 ± 0.02) and Vmax (0.87 ± 0.03). Additionally, human liver microsome (HLM) stability, passive permeability, kinetic solubility (463 uM) and dofetilide binding (0% @ 10 uM), as a surrogate for hERG inhibitory activity, were evaluated [2].

The activity of PF-04937319 is as follows:

EC50 (Biochemical activation assay) = 188 ± 74 uM

Common Name: PF-04937319
Synonyms:  PF-04937319; PF04937319; PF 04937319
IUPAC Name: N,N-dimethyl-5-((2-methyl-6-((5-methylpyrazin-2-yl)carbamoyl)benzofuran-4-yl)oxy)pyrimidine-2-carboxamide
CAS Number: -
Mechanism of Action: Kinase Activator; Glucokinase Activator; GCK activator
Indication: Diabetes; Type II Diabetes; T2DM
Development Stage: Phase I/II
Company: Pfizer

Glucokinase is one of four members of the hexokinase family of enzymes. Its expression is limited to the major organs (such as the pancreas, liver, brain and the gastrointestinal tract) that are thought to have an integrated role in glucose sensing. In the liver, phosphorylation of glucose by glucokinase promotes glycogen synthesis, whereas in the β-cells, it results in insulin release. Studies of glucokinase-linked genetically-modified mice and mutations in humans have illustrated the important roles played by glucokinase in whole-body glucose homeostasis, and suggest that the use of pharmacological agents that augment glucokinase activity could represent a viable treatment strategy in patients with type 2 diabetes. Many glucokinase activators (GKAs) have been developed, and their ability to lower the blood glucose has been shown in several animal models of type 2 diabetes. Also, in mouse models that GKAs also have the effect of stimulating the proliferation of β-cells. However, the results of recent phase II trials have shown that GKAs lose their efficacy within several months of use, and that their use is associated with a high incidence of hypoglycemia; furthermore, patients treated with GKAs frequently developed dyslipidemia [1].

Metabolic profiling in rat, dog, and human hepatocytes revealed that PF-04937319 is metabolized via oxidative (major) and hydrolytic pathways (minor). N-Demethylation to metabolite M1 [N-methyl-5-((2-methyl-6-((5-methylpyrazin-2-yl)carbamoyl)benzofuran-4-yl)oxy)pyrimidine-2-carboxamide] was the major metabolic fate of PF-04937319 in human (but not rat or dog) hepatocytes, and was catalyzed by CYP3A and CYP2C isoforms. Qualitative examination of circulating metabolites in humans at the 100- and 300-mg doses from a 14-day multiple dose study revealed unchanged parent drug and M1 as principal components. Examination of primary pharmacology revealed M1 was less potent as a glucokinase activator than the parent drug (compound PF-04937319: EC50 = 0.17 µM; M1: EC50 = 4.69 µM). Furthermore, M1 did not inhibit major human P450 enzymes (IC50 greater than 30 µM), and was negative in the Salmonella Ames assay, with minimal off-target pharmacology, based on CEREP broad ligand profiling [3].

1. Nakamura, A.; et. al. Present status of clinical deployment of glucokinase activators. J Diabetes Investig 2015, 6(2), 124-132.
2. Pfefferkorn, J. A.; et. al. Designing glucokinase activators with reduced hypoglycemia risk: discovery of N,N-dimethyl-5-(2-methyl-6-((5-methylpyrazin-2-yl)-carbamoyl) benzofuran-4-yloxy)pyrimidine-2-carboxamide as a clinical candidate for the treatment of type 2 diabetes mellitus. Med Chem Commun 2011, 2, 828-839. (gives synthesis and pre-clinical activity)
3. Sharma, R.; et. al. Metabolites in safety testing assessment in early clinical development: a case study with a glucokinase activator. Drug Metab Dispos 2014, 42(11), 1926-1939.
4. A Trial To Assess The Safety, Tolerability, Pharmacokinetics, And Pharmacodynamics Of Single Doses Of PF-04937319 In Subjects With Type 2 Diabetes Mellitus. NCT01044537 (retrieved 01-05-2015)
5. Study To Understand Efficacy And Safety Of Investigational Agent (PF-04937319) Compared To Approved Agent (Glimepiride) In Patients With Diabetes On Metformin. NCT01517373 (retrieved 01-05-2015)
6. Phase 2 Study To Evaluate Safety And Efficacy Of Investigational Drug - PF04937319 In Patients With Type 2 Diabetes. NCT01475461 (retrieved 01-05-2015)

a: For Grimsby, J.; et. al. see Science, 2003, 301, 370.