CHIR-124 is a quinolone-based small molecule that is structurally unrelated to other known inhibitors of Chk1. CHIR-124 potently and selectively inhibits Chk1 in vitro. CHIR-124 interacts synergistically with topoisomerase poisons (e.g., camptothecin or SN-38) in causing growth inhibition in several p53-mutant solid tumor cell lines. CHIR-124 abrogates the SN-38-induced S and G(2)-M checkpoints and potentiates apoptosis in MDA-MD-435 breast cancer cells. CHIR-124 treatment can restore the level of cdc25A protein, which is normally targeted by Chk1 for degradation following DNA damage, indicating that Chk1 signaling is suppressed in the presence of CHIR-124. In an orthotopic breast cancer xenograft model, CHIR-124 potentiates the growth inhibitory effects of irinotecan by abrogating the G(2)-M checkpoint and increasing tumor apoptosis. The combination of gemcitabine and CHIR-124 in the multicellular tumor spheroid model enhanced the sensitivity to the gemcitabine antiproliferative effect in correlation with an increase in DNA damage and apoptosis. CHK1 inhibition by Chir-124 sensitizes HCT116 cancer cells to radiation.

MK-8776 (SCH-900776) is a checkpoint kinase 1 inhibitor which was developed by Merck for the treatment of cancer. The drug was tested in phase II clinical trials on patients suffering from acute myeloid leukemia (in combination with cytarabine) and in phase I on patients suffering from solid tumors or lymphoma (as monotherapy and in combination with gemcitabine).

Adenosine triphosphate (ATP) is an adenine nucleotide containing three phosphate groups esterified to the sugar moiety. Adenosine triphosphate is the energy source in living cells. In physiological conditions, the average concentration varies from 3150 mM in mammalian cells to 1500–1900 mM in human blood cells. Extracellular adenosine and adenosine triphosphate (ATP) are involved in biological processes including neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation, signal transduction and secretion in a variety of cell types. A large family of membrane-bound receptors mediates cell signalling by ATP and adenosine. These purinergic receptors ultimately determine the variety of effects induced by extracellular ATP and adenosine. ATP and adenosine have strong negative chronotropic and dromotropic effects on the mammalian heart. The sensitivity of the sinus node and the atrioventricular node to ATP and adenosine manifests pronounced variability among species. For more than three decades, ATP has been used routinely in Europe in the acute therapy of paroxysmal supraventricular tachycardia. ATPace™, an injectable formulation of adenosine 5′-triphosphate (ATP), was developed by Cordex Pharma, Inc. (Cordex) as a diagnostic and therapeutic drug for the management of cardiac bradyarrhythmias. Extracellular ATP exerts multiple effects in various cell types by activating cell-surface receptors known as P2 receptors. In the heart, ATP suppresses the automaticity of cardiac pacemakers and atrioventricular (AV) nodal conduction via adenosine, the product of its degradation by ecto-enzymes, as well as by triggering a cardio-cardiac vagal reflex. ATP, given as a rapid intravenous bolus injection, has been used since the late 1940s as a highly effective and safe therapeutic agent for the acute termination of reentrant paroxysmal supraventricular tachycardia (PSVT) involving the AV node. In addition, preliminary studies have shown that ATP can also be used as a diagnostic agent for the identification of several cardiac disorders including sinus node dysfunction (sick sinus syndrome), dual AV nodal pathways, long QT syndrome, and bradycardic syncope. The US Food and Drug Administration has approved Cordex formulation for ATP as an Investigational New Drug and two pathways for its marketing approval; one therapeutic, i.e., acute termination of paroxysmal PSVT, and the other diagnostic, i.e., the identification of patients with bradycardic syncope who can benefit from pacemaker therapy. However later ATPace development for the treatment of bradycardia and paroxysmal supraventricular tachycardia was discontinued.

LY2606368 (Prexasertib) is a small-molecule Chk-1 inhibitors invented by Array and being developed by Eli Lilly and Company. Lilly is responsible for all clinical development and commercialization activities. LY2606368 is advancing in Phase 2 clinical trials for cancer. Prexasertib preferentially binds to and inhibits CHK1 and, to a lesser extent, inhibits CHK2. Chk-1 is a protein kinase that regulates the tumor cell's response to DNA damage often caused by treatment with chemotherapy. In response to DNA damage, Chk-1 blocks cell cycle progression in order to allow for repair of damaged DNA, thereby limiting the efficacy of chemotherapeutic agents. Inhibiting Chk-1 in combination with chemotherapy can enhance tumor cell death by preventing these cells from recovering from DNA damage.

LY2606368 (Prexasertib) is a small-molecule Chk-1 inhibitors invented by Array and being developed by Eli Lilly and Company. Lilly is responsible for all clinical development and commercialization activities. LY2606368 is advancing in Phase 2 clinical trials for cancer. Prexasertib preferentially binds to and inhibits CHK1 and, to a lesser extent, inhibits CHK2. Chk-1 is a protein kinase that regulates the tumor cell's response to DNA damage often caused by treatment with chemotherapy. In response to DNA damage, Chk-1 blocks cell cycle progression in order to allow for repair of damaged DNA, thereby limiting the efficacy of chemotherapeutic agents. Inhibiting Chk-1 in combination with chemotherapy can enhance tumor cell death by preventing these cells from recovering from DNA damage.

LY2606368 (Prexasertib) is a small-molecule Chk-1 inhibitors invented by Array and being developed by Eli Lilly and Company. Lilly is responsible for all clinical development and commercialization activities. LY2606368 is advancing in Phase 2 clinical trials for cancer. Prexasertib preferentially binds to and inhibits CHK1 and, to a lesser extent, inhibits CHK2. Chk-1 is a protein kinase that regulates the tumor cell's response to DNA damage often caused by treatment with chemotherapy. In response to DNA damage, Chk-1 blocks cell cycle progression in order to allow for repair of damaged DNA, thereby limiting the efficacy of chemotherapeutic agents. Inhibiting Chk-1 in combination with chemotherapy can enhance tumor cell death by preventing these cells from recovering from DNA damage.

LY2606368 (Prexasertib) is a small-molecule Chk-1 inhibitors invented by Array and being developed by Eli Lilly and Company. Lilly is responsible for all clinical development and commercialization activities. LY2606368 is advancing in Phase 2 clinical trials for cancer. Prexasertib preferentially binds to and inhibits CHK1 and, to a lesser extent, inhibits CHK2. Chk-1 is a protein kinase that regulates the tumor cell's response to DNA damage often caused by treatment with chemotherapy. In response to DNA damage, Chk-1 blocks cell cycle progression in order to allow for repair of damaged DNA, thereby limiting the efficacy of chemotherapeutic agents. Inhibiting Chk-1 in combination with chemotherapy can enhance tumor cell death by preventing these cells from recovering from DNA damage.

LY2606368 (Prexasertib) is a small-molecule Chk-1 inhibitors invented by Array and being developed by Eli Lilly and Company. Lilly is responsible for all clinical development and commercialization activities. LY2606368 is advancing in Phase 2 clinical trials for cancer. Prexasertib preferentially binds to and inhibits CHK1 and, to a lesser extent, inhibits CHK2. Chk-1 is a protein kinase that regulates the tumor cell's response to DNA damage often caused by treatment with chemotherapy. In response to DNA damage, Chk-1 blocks cell cycle progression in order to allow for repair of damaged DNA, thereby limiting the efficacy of chemotherapeutic agents. Inhibiting Chk-1 in combination with chemotherapy can enhance tumor cell death by preventing these cells from recovering from DNA damage.

Adenosine triphosphate (ATP) is an adenine nucleotide containing three phosphate groups esterified to the sugar moiety. Adenosine triphosphate is the energy source in living cells. In physiological conditions, the average concentration varies from 3150 mM in mammalian cells to 1500–1900 mM in human blood cells. Extracellular adenosine and adenosine triphosphate (ATP) are involved in biological processes including neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation, signal transduction and secretion in a variety of cell types. A large family of membrane-bound receptors mediates cell signalling by ATP and adenosine. These purinergic receptors ultimately determine the variety of effects induced by extracellular ATP and adenosine. ATP and adenosine have strong negative chronotropic and dromotropic effects on the mammalian heart. The sensitivity of the sinus node and the atrioventricular node to ATP and adenosine manifests pronounced variability among species. For more than three decades, ATP has been used routinely in Europe in the acute therapy of paroxysmal supraventricular tachycardia. ATPace™, an injectable formulation of adenosine 5′-triphosphate (ATP), was developed by Cordex Pharma, Inc. (Cordex) as a diagnostic and therapeutic drug for the management of cardiac bradyarrhythmias. Extracellular ATP exerts multiple effects in various cell types by activating cell-surface receptors known as P2 receptors. In the heart, ATP suppresses the automaticity of cardiac pacemakers and atrioventricular (AV) nodal conduction via adenosine, the product of its degradation by ecto-enzymes, as well as by triggering a cardio-cardiac vagal reflex. ATP, given as a rapid intravenous bolus injection, has been used since the late 1940s as a highly effective and safe therapeutic agent for the acute termination of reentrant paroxysmal supraventricular tachycardia (PSVT) involving the AV node. In addition, preliminary studies have shown that ATP can also be used as a diagnostic agent for the identification of several cardiac disorders including sinus node dysfunction (sick sinus syndrome), dual AV nodal pathways, long QT syndrome, and bradycardic syncope. The US Food and Drug Administration has approved Cordex formulation for ATP as an Investigational New Drug and two pathways for its marketing approval; one therapeutic, i.e., acute termination of paroxysmal PSVT, and the other diagnostic, i.e., the identification of patients with bradycardic syncope who can benefit from pacemaker therapy. However later ATPace development for the treatment of bradycardia and paroxysmal supraventricular tachycardia was discontinued.