The TDR Network of Compound Evaluation Centres

1
The TDR Network of Compound Evaluation Centres
Perspective of a Principal Investigator Reto
Brun Parasite Chemotherapy Swiss Tropical
Institute Basel, Switzerland
2
Presentation outline

• What is the network
• what does it do
• what has it achieved (with examples)
• what improvements can be made

3
What is the Network

• Integrated, international consortium of Compound
  Assessment Centres
• Led by world-renowned expert scientists in
  tropical parasitology
• Mission to identify novel drug candidates for
  the treatment of diseases in the TDR portfolio -
  Malaria, African and South American
  trypanosomiasis, leishmaniasis, lymphatic
  filariasis, onchocerciasis, schistosomiasis

4
Network Partners
5
Partnerships with others

• Each partner has its own panel of suppliers
• STIs suppliers 2003 2004

6
Partnerships with others

• Links of the network to MMV, DNDi, Gates
  Foundation, COST B22 action, etc.
• Lead compounds can be taken to MMV, DNDi for
  optimization and preclinical or clinical work
• However
• There is a gap for helminths
• ?No other institution deals with RD for
• helminth infections. Good lead compounds are
  difficult to progress rapidly!

7
What does the Network do (1)

• Provides a unique service to evaluate synthetic
  compounds and natural products from industry and
  academia
• Develops and operates primary and secondary test
  systems vs TDR target parasites
• provides international standards for compound
  assessment as used by MMV, DNDi etc.
• SOPs freely available on Web
• www.who.int/tdr/grants/workplans/drug.htm

8
P. falciparum assay with radiolabel incorporation

• Infected human rbc in RPMI 1640 medium with 10
  HS or 0.5 Albumax II
• Incubation in serial drug dilution for 72 hrs
• 3H-hypoxanthine labelling for the last 24 hrs
• Harvesting on glass fiber filters counting
• Calculation of IC50 from inhibition curve

9
What does the Network do (2)

• In association with Chemcore
• proactive in sourcing test compounds
• selecting compounds for appropriate assay
• providing advice to suppliers on follow-up
  actions
• Provides training for staff in other centres of
  the network and in DECs

10
What has the Network achieved (1)

• Participated in generating data to help secure
  funding for projects by other agencies
• Advanced projects
• MMV OZ synthetic peroxides (Phase 2, 2004)
• MMV Semi-synthetic artemisinins (Phase 2, 2004)
• MMV DB289 bisamidines, malaria (Phase 2, 2004)
• Gates DB289 bisamidines, HAT (Phase 2, 2004)

11
Example 1 synthetic peroxides

• Jonathan Vennerstrom collaborates with
  Hoffmann-LaRoche on a synthetic peroxide
• In 1997 Roche stops malaria RD lab, staff and
  technology transfered to STI
• In 1999 project support by TDR
• In 2000 the synthetic peroxides becomes one of
  the first MMV drug discovery projects
• In 2004 Phase 1 and in 2005 Phase 2 clinical
  trials

12
Clinical candidate in Nature
Paul ONeill, Nature, 19 Aug 2004
13
Example 2 CGP40215 story
In Vitro Trypanocidal Activities of New
S-Adenosylmethionine Decarboxylase
Inhibitors RETO BRUN, RONALD KAMINSKY, CYRUS J.
BACCHI, SIMON L. CROFT et al. ANTIMICROBIAL
AGENTS AND CHEMOTHERAPY, June 1996, 40, 1442-1447.
In Vivo Trypanocidal Activities of New
S-Adenosylmethionine Decarboxylase
Inhibitors CYRUS J. BACCHI, RETO BRUN, SIMON L.
CROFT et al. ANTIMICROBIAL AGENTS AND
CHEMOTHERAPY, June 1996, 40, 1448-1453.
14
CGP 40215

• Extremely potent in vitro IC50 2.25 ng/ml
• Cured 15 T.b.rhod isolates _at_ 2.5 - 25 mg/kg for 3
  days
• No cure of the CNS mouse model as monotherapy
• Cure of the CNS mouse model in combination with
  2 eflornithine in drinking water _at_ 25 mg/kg
  given for 14 days
• cured 7/8 African green monkeys (1st stage inf.)
  _at_ 4 mg/kg given for 8 days
• very low CSF levels ? poor CNS penetration
• project at Ciba-Geigy terminated when the merger
  with Sandoz took place
• Prodrug should be possible (information by D.
  Boykin, Atlanta)

15
Example 3 Moxidectin

• Macrocyclic lactone. Semi-synthetic fermentation
  product. Established veterinary drug with
  excellent safety profile.
• In 1995 S. Townson demonstarted that Moxidectin
  was significantly more active than ivermectin
  against oncho in vivo.
• Macrofilaricidal activity seen against lymphatic
  Brugia pahangi in dogs.
• Reasonable expectation that Moxidectin will break
  transmission of human onchocerciasis.
• Moxidectin about to start phase II clinical
  trials.

16
Example 4 Emodepside

• Emodepside (Bayer) is a semi-synthetic derivative
  of a natural compound produced by the fungus
  Mycelia sterilia. This compound is highly active
  against some veterinary nematodes and is
  currently under development.
• S. Townson found that Emodepside is extremely
  active against Onchocerca gutturosa adult worms
  in vitro and Onchocerca lienalis mf in mice.
• Emodepside will be tested against Onchocerca
  volvulus in vitro and is the leading development
  candidate for oncho.
• Bayer has supplied Emodepside toxicology package
  to WHO.

17
Standardized SOPs

• The Drug Discovery Group harmonized the vitro and
  vivo screening and developed standardized SOPs
  for all parasites
• Standard drugs were selected and data compiled
  comparison of results from different labs is now
  possible

18
Database at TDR

• Database at TDR with thousands of cpds including
  the negative ones
• Each screening centre has its own database and
  supplies TDR with data in a compatible form
  

19
SOPs and flow charts

• SOPs and flow charts are available for the 4
  different protozoa and the helminths
• Vitro SOPs
• T. brucei spp., T. cruzi, P. falciparum, L.
  donovani (axe amastigotes macrophage inf.), S.
  mansoni
• Vivo SOPs
• T. brucei (acute CNS model), T. cruzi, P.
  berghei other mouse malaria models, L. donovani
  other leish models S. mansoni others, Brugia
  pahangi, O. gutturosa, O. lienalis
• For each assay/model one leading centre with at
  least one backup centre

20
Master Flow Chart
21
Different approaches
compounds for in vitro screening
22
A heretical suggestion
23
Natural products

• Dr. D. Diallo, Bamako, Mali supplied in 2003 64
  extracts Extract No.63 had outstanding
  antileishmanial activity
• This extract from Cussonia barteri was
  fractionated and 13 fractions tested in vitro
• Collaboration with DNDi and Prof. K. Hostettmann
  (Geneva) for purification and isolation of pure
  cpds

24
Improvements of methods

• In vitro assays and in vivo protocols are
  continuously being improved
• Examples
• Reporter gene assays
• ß-lactamase transfected leihmania
• GFP transfected P. berghei
• ? new protocol with FACS analysis
• ? safes time and is more accurate

25
Improvements of methods

• Examples
• Reporter gene assays
• GFP transfected T. brucei spp. ideal for FACS
  analysis of blood samples
• ? new protocol for in vivo drug screening is
  under evaluation

Blood cells
Green fluorescent trypanosomes
26

• Examples
• Medium throughput screening (MTS)

27
Use of MTS
28
Screening centers in the South

• What is possible
• In vitro screening of natural cpds from local
  sources
• Primary in vivo screening in the T. brucei and
  the P. berghei/ P. chabaudi model
• What is probably not possible
• To do an in debth analysis of natural cpds in
  vitro and in animal models
• screening of synthetic cpds (companies will be
  reluctant to release cpds to partners they do not
  know)
• To keep up with turn-around times and throughput
  achieved in the North (drug screening and
  evaluation is a highly specialized business)

29
How can we improve the Network

• Screening and drug evaluation is a highly
  specialized activity which depends on
  continuation with a critical staff size
• TDR is expected to
• offer midterm contracts which are vital to allow
  continuity of staff
• pay funds promptly and in local currency or be
  adjusted to exchange rates

30
How can we improve the Network

• Network partners have to improve turn-around
  times, especially for in vivo assessment
• Interpretation of the results is needed to guide
  chemists, phytochemists etc.
• Whole cell screening should be on HTS hits or
  rationale driven
• Resources are limitedIntensify networking with
  other organizations in RD for neglected
  diseases, form joint ventures

31
Thanks for your attention