Friday, April 24, 2015

Drugs in Clinical Pipeline: PFK-158

PFK-158 [(E)-1-(pyridin-4-yl)-3-(7-(trifluoromethyl)quinolin-2-yl)prop-2-en-1-one] is a novel anti-cancer agent that inhibits glucose uptake in cancer cells. PFK-158 more potent PFKFB3 inhibitor than PFK-015 with improved PK properties for testing in clinical trials. Such reasons catapult PFK158 to be the first PFKFB3 inhibitor to be examined in a phase I trial, where it might have significant clinical utility when combined with agents that target driver oncogenes.

The activity of PFK-158 is as follows:

IC50 (PFKFB3 enzyme assay) = 137 ± 15 nM
IC50 (PFKFB3 enzymatic activity in cells) = 1.6 ± 0.8 uM
IC50 (Inhibition of deoxyglucose uptake) = 0.8 ± 0.1 uM
IC50 (Toxicity of Jurkat) = 0.33 ± 0.1 uM

Common Name: PFK-158
Synonyms:  PFK-158; PFK 158; PFK158; ACT-PFK-158
IUPAC Name: (E)-1-(pyridin-4-yl)-3-(7-(trifluoromethyl)quinolin-2-yl)prop-2-en-1-one
CAS Number: 1462249-75-7 (E-isomer); 1462249-69-9 (E- and Z- isomers)
Mechanism of Action: Kinase Inhibitor; PFKFB3 Inhibitor
Indication: Various Cancers; Glioblastomas
Development Stage: Phase I
Company: Advanced Cancer Therapeutics

The glycolytic pathway is a ten-step series of reactions that forms the major metabolic pathway in nearly all organisms. Flux through the glycolytic pathway is adjusted in response to conditions both inside and outside the cell. Irreversible glycolytic reactions are those catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase. In metabolic pathways, such enzymes are potential targets for control, and all three enzymes serve this purpose in glycolysis. The PFKFB enzymes (PFKFB 1-4) synthesize fructose-2,6-bisphosphate (F2,6BP) which activates 6-phosphofructo-1- kinase (PFK-1), an essential control point in the glycolytic pathway. Neoplastic cells preferentially utilize glycolysis to satisfy their increased needs for energy and biosynthetic precursors. Malignant tumor cells have glycolytic rates that are up to 200 times higher than those of their normal tissues of origin. One cancer attack strategy has been to treat cancer by starving cancerous cells in various ways. Reducing or blocking the enhanced glycolytic flux mechanism present in cancer cells has stimulated recent interest.

Over-expression of HIF-1a, activation of Ras and loss of p53 tumor suppressor function are associated with the development of human cancers and each of these genetic alterations converge on glycolysis by activating the 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases (PFKFB). The PFKFB enzymes interconvert fructose-6-phosphate (F6P) and fructose-2,6-bisphosphate (F2,6BP) and F2,6BP is an allosteric activator of 6-phosphofructo-1-kinase (PFK-1), a rate-limiting enzyme and control point in the glycolytic pathway. There are four PFKFB family members which are encoded by separate genes (PFKFB1-4) and characterized by distinct kinase:bisphosphatase ratios. The PFKFB3 family member is of particular interest since it has been found to be activated in human cancer cell lines and tumors, to be increased by hypoxic exposure via HIF-1a and by oncogenic Ras, and to be required for tumorigenic growth.

Advanced Cancer Therapeutics (ACT) is developing inhibitors of glycolysis targeting 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), a cancer metabolism target identified as essential for cancer cell growth and licensed by ACT from the James Graham Brown Cancer Center. High glucose consumption is observed in most cancers. PFKFB3 is the enzyme involved in the first irreversible step of glycolysis, and has been validated as a relevant cancer metabolism target. Inhibitors of the PFKFB3 block glucose uptake and inhibit tumor growth.

PFK158, that is markedly more potent than PFK-015, has excellent pharmacokinetic properties and causes ~80% growth inhibition in several mouse models of human-derived tumors. Importantly, IND-enabling safety and toxicity studies have demonstrated that PFK158 is well tolerated in rats and dogs, providing support for a Phase 1 trial in cancer patients planned for early 2014. Once the maximum tolerated dose is identified, researchers intend to conduct multiple phase 1/2 trials of PFK158 in combination with targeted agents given the ability of PFK158 to suppress glucose metabolism and multiple survival mechanisms. One such targeted agent, vemurafenib, is a mutant B-Raf inhibitor that was recently FDA-approved for BRAFV600E-positive melanoma patients. Unfortunately, a multitude of resistance mechanisms have resulted in disease progression in less than one year for the majority of melanoma patients treated with vemurafenib. It is hypothesized that PFK158 would sensitize vemurafenib-resistant melanoma cells and found that the addition of PFK158 to vemurafenib caused a marked increase in the apoptotic death of several melanoma cell lines in vitro. These data provide rationale for the conduct of pre-clinical studies of PFK158 combined with vemurafenib in transgenic BRAFV600E melanoma mouse models which are in turn expected to justify a phase I/II trial of the combination in BRAFV600E-positive melanoma patients [1].

1. O'Neal, J.; et. al. Abstract 962: Identification of a PFKFB3 inhibitor suitable for phase I trial testing that synergizes with the B-Raf inhibitor vemurafenib. Cancer Res 2014, 74, 962.
2. Chand, P.; et. al. Pfkfb3 inhibitor and methods of use as an anti-cancer therapeutic. WO2013148228A1
3. Phase 1 Safety Study of ACT-PFK-158, 2HCl in Patients With Advanced Solid Malignancies. NCT02044861 (retrieved 24-04-2015)
4. Telang, S.; et. al. Discovery of a PFKFB3 inhibitor for phase I trial testing that synergizes with the B-Raf inhibitor vemurafenib. Cancer Metab 2014, 2(Suppl 1), P14.