Presentation on theme: "Calcium dependent protein kinases and Malaria: Identification of chemical start point for drug discovery Symposium: Academic Drug Discovery: Challenges."— Presentation transcript:
Calcium dependent protein kinases and Malaria: Identification of chemical start point for drug discovery Symposium: Academic Drug Discovery: Challenges and perspectives Imperial College London, March 2011 Oliver Billker & Katie Chapman
Antimalarial drugs No longer useful against P. falciparum Wide spread resistance Artemisinin Chloroquine First-line treatment of P. falciparum Component of a combination. Reduced efficacy observed in SE Asia. Important to develop a well supplied pipeline of new antimalarials.
Antimalarial drug development Antimalarials are not economically attractive to the pharmaceutical industry. Public-private partnerships play a key role. E.g. Medicines for Malaria Venture, Wellcome Trust, Bill & Melinda Gates Foundation Opportunity and need for academic institutions to make an impact.
A paradigm shift in antimalarial screening Cell based screens Libraries of >20.000 starting points for drug development https://www.ebi.ac.uk/chembl/ Target based screening Genetic tools for target identification at scale (Sanger team) Identify mechanism of induced resistance. Screen against validated targets Prioritise by chemistry, IP, etc.
2 million GSK compounds 13533 inhibitors of P. falciparum growth IC 50 < 1 µM 242 inhibitors P. falciparum CDPK 1, 4 or 5 Nature, March 2010
Systematic prioritisation of parasite kinase targets in a malaria parasite of rodents Gene deletion analysis of 65 protein kinases. Kinomes are highly conserved across Plasmodium species. >1/3 of parasite protein kinases are redundant in blood stages.
Comparative analysis of Plasmodium kinomes Different in P. falciparumRedundant in P. berghei Rita Tewari
calmodulin-like domain kinase domain Calcium dependent protein kinases (CDPKs) Plant-like kinases with a unique activation mechanism. Billker & Doerig 2010
Target selection Redundant in P. berghei CamK Plant like Opportunity for selectivity Family Opportunity for multi-target inhibitor. CDPK1 and 5: Essential in blood stages. CDPK1 and 4 Essential for transmission.
Host cell lysis Male gamete formation Differential gene expression Guanlyl cyclase cGMP PKG Phospho- diesterases Map-2 CDPK4 is required for male gamete formation SRPK PKG
Comparative profiling of recombinant PfCDPK1 and 4 unselectiveC1 selectiveC4 selective Katie Chapman, Imperial College Drug Discovery
cdpk4 CDPK4 is required for male gamete formation
DMSO1NM-PP1 DMSO 1NM-PP1 The CDPK4 inhibitor 1NM-PP1 blocks parasite transmission to mosquitoes Lotta Burström
P. berghei CDPK1-GFP is expressed throughout life cycle ookinete gametocytes oocyst sporozoites Sarah Sebastian schizont
cdpk1 knock down blocks development… WT ookinete zygote ookinete retort Sarah Sebastian
1 20 120 0.05 2,400 2 35 275 0.09 3,000 average oocysts/midgut feed n WT CDPK1 fold change …and prevents transmission of P. berghei to mosquitoes Sarah Sebastian
Target prioritisation: CDPK5 is also essential for blood stage development. Science 238 (2010)
CDPK1, 4 & 5 are individually essential for parasite development at different life cycle stages. Absence of redundancy due to different subcellular localisations (lipid modification), expression patterns, substrate preferences. Pan-CDPK inhibitor could exploit synergies and delay emergence of resistance. Target summary Aim: Screen P. falciparum versions of all three targets to explore feasibility of pan-CDPK inhibition