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 > starting points for drug development 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 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.

CDPK5 Predicted CDPK functions CDPK1 CDPK4 CDPK1 CDPK4 CDPK1

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

, ,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