intro to kinase drug discovery

Question 1

what are kinases and their major families

Answer 1

enzymes that use ATP to transfer phosphate to target. protein kinases phosphorylate proteins.
catalytic domain binds ATP and binding site binds target

ex:
PROTEIN KINASE A/G/C FAMILY: mainly serine/threonine
TYROSINE KINASES: act on tyrosine eg: EGFR VEGFR
TYR KİNASE LİKE: ex: raf
CGMC family: ex: CDK GSK3 MAPK. act on ser,tyr dual specific: MEK

Question 2

describe basic RTK signaling using the EGF model.

Answer 2

1. Growth factor binds ex: EGF
2. receptor dimerises
3. tyrosine kinase on one receptor phosphorylates its partner. (receptor activation requires phosphorylation.)
4. Signalling proteins are recruited (have SH2 domain to recognise phospho-tyr bond and surrounfing amino acids)
   depending on signalling protein different pathways are activated.

Question 3

describe the MAPk pathway activation via RTKS.

Answer 3

GRB2 (signalling protein) binds to RTK using its SH2 domain
then binds to SOS.
SOS binds to ras and facilitates its GDP to exchange to GTP.
this is RAS’s active form whicg activates raf then MEK then MAPk kinases which leads to increased gene expression and cell proliferation.

Question 4

outline JAK signalling which is a part of the sub family non receptor tyrosine kinases

Answer 4

Macrophages release the pro-inflammatory cytokine IL-6
IL-6 activates the IL-6 receptor and the GP130 co-receptors found on each side of IL-6R
TYR K jak is recruited to the activated receptor. This leads to the recruitment then phosphorylation of the transcription factor stat.
phosphorylated stat dimerises and moves to the nucleus to increase the expression of pro-inflammatory genes.

Question 5

describe challenges with drugs targeting the catalytic domain of kinases.

Answer 5

Small molecules that can fit in the ATP site are theoretical possible targets for all kinases.
challenges:
1. atp binding site domains are conserved so its a challenge to achieve selectivity.
2. inhibitors need to be able to work against high ATP concentrations already present
3. target is intracellular. drug needs to have good permeability
4. overcoming resistance

Question 6

where can antibody based therapeutics target kinases? give examples of drugs and challenges

Answer 6

1. the growth factor itself (for RTKS)
   ex: bevacuzimab anti vegf
2. targetting extracellular binding domain
   ex: cetuximab anti egfr

challenges:
1. resistance
2. selectivity hard to generate between close isoforms
3. delivery and access is hard for solid tumors or when BBB needs to be crossed.
4. can provoke immune response (immunogenic)

Question 7

what effects of kinase inhibitors are observed in cancer pathology

Answer 7

1. EGFR responsible for proliferation and survival
2. VEGFR responsible for angiogenesis
3. invasion and metastasis related to cMet.
4. TAM kinases like MER and axl lead to immunosupression seen in cancer

Question 8

describe chronic myeloid leukemia and how it can be treated with imatinib

Answer 8

genes encoding kinases BCR and ABL are rearranged so that chromosome 9 abl moves to chromosome 22 next to bcr.

this leads to myeloid cells in bone marrow to start growing in an unregulated manner and the proliferation of granulocytes like neutrophils
Kinase protein BCR-abl is overexpressed
(oncogenic addiction. one pathway is required for tumor survival)

imatinib inhibits Abl.

death rate was halved for CML.

Question 9

give an example for a kinase inhibitor used for a condition that is not cancer.

Answer 9

Tofacinib used to control inflammation for IBD by inhibiting the jak kinase which increases transcription of pro inflammatory IL-6.