07 Targeted Cancer Therapies (Kinase Inhibitors) Flashcards
What are Targeted Cancer Therapies?
Drugs or other substances that block the growth and spread of cancer by interfering with specific molecules involved in tumor growth and progression. They interfere with cancer cell division (proliferation) and spread in different ways
What are the general characteristics of Kinase Inhibitors?
Very few kinases have been found mutated in human cancers (cAbl, MET, b-RAF). Several receptor tyrosine kinases are amplified in specific tumors (EGFR, ERB-B2)
What are the two classes of Tyrosine Kinase Inhibitors?
Non-Receptor Tyrosine Kinases (BRC-Abl, C-Src, Jak2). Receptor Tyrosine Kinases (VEGFR, EGFR)
What are the general characteristics of BCR-Abl Kinase?
Chromosome translocation results in fusion protein BCR-Abl. BCR-Abl kinase is constitutively active, i.e. it does not require activation by other cellular messaging proteins (always “On”). Activates a number of cell cycle-controlling proteins and enzymes, speeding up cell division and genomic unstability. Involved in Ph+ Leukemias (CML, AML)
What are the general characteristics of Imatinib (Inhibitor of BCR-Abl Kinase)?
Gleevec. 2-Phenylaminopyrimidine was found as a BCR-Abl inhibitor. Introduction of methyl and benzamide groups gave original lead enhanced binding properties, resulting in Imatinib. Imatinib binds to Tyr kinase active site
What else does Imatinib (Gleevec) inhibit?
c-Abl, c-kit, and PDGF-R, but not other known Tyr kinases (TK)
What is Imatinib used for?
Treat Leukemia and other types of cancer (notably I Stromal Tumors).
How is Imatinib administered?
Oral agent and has low toxicity
What is the PK/PD of Imatinib?
Rapidly absorbed when administered PO (BA 90%). Metabolized by liver (CYP 450). Main metabolite is a N-demethylated piperazine derivative. Mostly secreted through the bile/feces
What are the problems with Imatinib Therapy?
Many CML (Chronic Myelogenous Leukemia) patients relapse when treated with Imatinib. Sequencing of the BCR-Abl gene in resistant tumors show that secondary mutations have occurred in the ATP binding region of the kinase (TK active site)
Besides Imatinib, what are the two other oral BCR-Abl inhibitors?
Nilotinib. Dasatinib
How does Dasatinib work?
Inhibits all BCR-Abl mutants, except mutation T315l, which also confers resistance to both Dasatinib, Nilotinib, and Imatinib in vitro
What is the benefit of Nilotinib?
Shows a favorable safety profile and shows activity in cases of CML resistant to treatment with Imatinib
What potential toxicity is there with Nilotinib?
Potential heart complications
What is Vascular Endothelial Growth Factor (VEGF)?
VEGF activates VEGFR, a receptor Tyrosine Kinase (RTK). Primary mediator of angiogenesis and vasodilation. Promotes endothelial cell viability and proliferation
What is the rational for Inhibition of VEGF?
Inhibits metastasis (Blocks VEGF-induced peritumor lymph drainage. Blocks VEGF(A)-induced dysfunctional angiogenesis. Inhibits invasion of circulation by the tumor. Decreases vascular density of tumor). Increases killing of established tumors (Improves chemotherapy delivery to tumor)
What is Sunitinib (Sutent)?
Oral, small-molecule, multi-targeted receptor tyrosine kinase (RTK) inhibitor. Inhibits vascular endothelial growth factor receptors (VEGFRs). Simultaneous inhibition of these targets therefore leads to both reduced tumor vascularization and cancer cell death, and ultimately tumor shrinkage
What else does Sunitinib inhibit?
Also inhibits C-kit RTK (KIT or CD117). Continuous activation of C-Kit drives the majority of GI Stromal Cell tumors. Other RTKs inhibited are: RET, CSF-1R, and flt3
What is Sunitinib used for?
Treatment of renal cell carcinoma (RCC) and Imatinib-resistant GI Stromal Tumor (GIST)
What is the PK/PD of Sunitinib?
Unaffected by food. Metabolized in liver by CYP 450. Main metabolite is N-desetylated derivative (active). Excretion fecal (61%) and renal (16%)
What are the toxicity and side-effects associated with Sunitinib?
Fatigue, diarrhea. Nausea, HTN. Anorexia. Stomatitis (inflammation of the mucous lining of any of the structures in the mouth)
Besides Sunitinibh, what are the other VEGF Kinase Inhibitors?
Sorafenib (Nexavar). Pazopanib (Votrient)
What is Her2 Receptor?
Belongs to the Epidermal Growth Factor Receptors (EGFR) family (TRK)
What does activation of Her2 Receptor do?
Activation of anti-apoptotic Ras signaling cascade (Apoptosis Inhibition). The result of gene amplification is an abnormally high cell replication response to normal levels of growth factor (increased cell replication, increased tumorigenicity)
What is Gefitinib (Iressa)?
EGFR Tyrosine Kinase Inhibitor. Inhibits Akt-mediated anti-apoptotic pathway preventing malignant cells to grow
What is Gefinitib used for?
To treat locally advanced or metastatic non-small cell lung cancer (NSCLC) in patients who have previously received chemotherapy
How is Gefinitib administered?
Orally (BA 59%)
What are the Toxicity and side-effects associated with Gefinitib?
Acne. N/V/D. Anorexia. Stomatitis. Gefitinib is a selective chemotherapeutic agent, its tolerability profile is far superior to previous cytotoxic agents
What is Bortezomib (Velcade)?
Ubiquitin Protease Inhibitor. Highly selective, reversible inhibitor of the 26S proteasome (used for recycling of short-lived proteins). The boron atom in bortezomib binds the catalytic site of the 26S proteasome with high affinity and specificity. May prevent Ub-mediated degradation of pro-apoptotic factors, permitting activating of programmed cell death in neoplastic cells dependent upon suppression of pro-apoptotic pathways