Download Targeting the organism: present and future

Targeting the organism:
present and future
18th Annual Conference of the
Union North America Region
Saturday, March 1, 2014
Anna M. Upton Ph.D.
TB Alliance, New York, NY
Outline
Targeting the organism: present and future
• Attributes of ideal new TB drug regimens and relevance of targets
• Targets of currently used TB drugs
• Targets of promising new TB drugs
• Emerging targets: early discovery efforts against novel target pathways
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Desired Profile for New TB Regimens
•
•
•
•
•
•
Active against both DS- and DR-TB
Shorter duration
Co-administration with ART: low potential for DDI
Safe: good safety and tolerability profile
Convenient: orally bioavailable, once daily dosing
Affordable: low cost of goods
• Profile is desired for the regimen
• Component drugs must combine to provide this overall profile
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Desired Profile for New TB Regimens – Role of Targets
• Active against both DS- and DR-TB:
– Target different to those of current TB drugs
– Same target as current drugs, but no cross-resistance
• Shorter duration:
– Bactericidal and sterilizing regimen:
Targets that are collectively essential to all sub-populations of bacteria
residing in environments and metabolic states found during infection
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Clinically Validated TB Drug Targets
DNA Gyrase (GyrA/GyrB)
 Quinolones (Moxi, Gati)
Folic Acid Metabolism
 p-Aminosalicylic acid
Cell wall synthesis
 SQ-109
 Isoniazid
 Ethionamide
 Cycloserine
 Ethambutol
 PA-824
 Delamanid
DHFA
PABA
DNA
Ribosome (50S)
 Linezolid
 Sutezolid
mRNA
ADP
H+
ATP Reactive
Species
Reduction
Energy Metabolism
 PZA
 Bedaquiline
RNA Polymerase
 Rifampicin
 Rifapentine
 Rifabutin
Reactive Species
PA-824
 Delamanid
Peptide
Ribosome (30S)
 Aminoglycosides
• Streptomycin
• Kanamycin
• Amikacin
 Capreomycin
 Viomycin
Cell wall biosynthesis inhibition
Drug
Target
Inhibits synthesis of
Isoniazid,
Ethionamide
Enoyl-[acyl-carrierprotein] reductase
Mycolic acids
Ethambutol
Arabinosyl transferases
Arabinogalactan
Cycloserine
d-alanine racemase and
ligase
Peptidoglycan
SQ109
MMpl3
(export of trehalose
monomycolate)
Mycolic acids
Nitroimidazoles Unknown
PA-824,
Delamanid
Mycolic acids
(part of mode of
action)
General characteristics of cell wall inhibitors:
• Bactericidal against replicating bacteria only (in vitro)
• Efforts ongoing to target inhA
Kaur D. et al, Adv Appl Microbiol
2009, 69, 23–78
Cell wall biosynthesis inhibition: New targets
DprE1 Inhibitors:
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•
•
•
•
Discovered by whole cell screening
Target: decaprenylphosphoryl-D-ribose- 2’-epimerase
Effect: inhibits arabinogalactan biosynthesis
Example: BTZ043
Multiple additional series discovered
Mmpl3 Inhibitors:
• Discovered by whole cell screening
• Export of trehalose monomycolate
• Multiple series; drug resistant mutants harbor
mutations in mmpl3
• Example: AU1235*
*Grzegorzewicz, A. et al. Nature Chem. Biol., 2012, 8, 334–341
Makarov, V, et al., Science, 2009,
324, 801-804
Transcription and translation inhibition
Drug
Target
Inhibits
Rifampicin
(Rifamycins)
RNA Polymerase, beta subunit
Transcription
Streptomycin
S12, 16S rRNAs of 30S ribosomal subunit
Protein synthesis
Moxifloxacin
(Quinolones)
DNA gyrase
DNA supercoiling
Kanamycin,
Amikacin
30S ribosomal subunit
Protein synthesis
Capreomycin
Interbridge B2a between 30S and 50S
Protein synthesis
Linezolid,
Sutezolid
50S ribosomal subunit
Protein synthesis
Characteristics vary broadly:
• Rifamycins and quinolones: bactericidal against replicating and non-replicating M.tb.
• Protein synthesis inhibition: may be bacteriostatic in vitro; varied activity
Efforts to hit these target continue:
• Spectinomides, macrolides, novel gyrase inhibitors (DC159a)
PMF and ATP Synthesis Inhibition: Bedaquiline and Beyond
Pyrazinamide (PZA)
Bedaquiline
(c ring of F0)
- Q203
(QcrB)
- Pa-824 (?)
NDH:
- Phenothiazines
- Clofazimine
Adapted from: Boshoff, H and Barry CE 3rd , Nat Rev Microbiol, 2005, 3, 70-80
Nitroimidazoles – RNS producers (and more)
• Requires reductive activation by a specific
mycobacterial enzyme system for activity
• Downstream effects by metabolites and
RNS include
– Inhibition of mycolic acid biosynthesis
– Inhibition of protein synthesis
– RNS (including NO) damage including
respiratory poisoning
•
Predominant MOA against replicating and
non-replicating bacteria may differ
Stover et al, Nature (2000) 405, 962; Manjunatha et al , PNAS (2006) 103, 431 ; Anderson et al, OrgBioMolChem (2008) 6, 1973; Singh et
al, Science (2008) 322, 1392; Manjunatha et al, CommIntBiol (2009) 2, 215
Efficacy of Bedaquiline/PZA Regimens in Mice
Treatment
group
Proportion (%) with positive M.tb cultures 3 mo after completing
treatment for:
2 mo
3 mo
2HZR/3HR
BDQ-Z
BDQ-Z +
(R, M, L or Pa)
BDQ-Z +
(P or C)
0%
(0/15)
4 mo
5 mo
6 mo
50%
(7/14)
14%
(2/14)
0%
(0/14)
0%
(0/15)
0% (0/15)
0-7%
(0-1/15)
0% (0/15)
0-7%
(0-1/15)
0% (0/15)
BDQ-Z-containing combinations accomplish in 2-3 months what takes the
standard regimen 5-6 months
Tasneen et al, AAC (2011);55:5485
Efficacy of Bedaquiline/PZA Regimens in Mice
Lung CFU Counts
Untreated
PZM
D-17
4.41 ± 0.08
D0
8.32 ± 0.26
% (Proportion) Relapsing
W4 (+12)
W6 (+12)
W8 (+12)
W10 (+12)
46.7%
(7/15)
13.3%
(2/15)
53.3%
(8/15)*
BDQ-Z
93.3%
(14/15)
66.7%
(10/15)
BDQ-ZP
33.3%
(5/15)
0%
(0/15)
BDQ-ZC
6.7%
(1/15)
0%
(0/15)
BDQ-ZU
53.3%
(8/15)
40%
(6/15)
BDQ-ZPC
26.7%
(4/15)
0%
(0/15)
Tasneen et al, AAC (2011);55:5485
Efficacy of RHZ-Sparing Regimens in Mice
Lung CFU Counts
M1
M2
2RHZ/4RH
4.73 + 0.29
3.04 + 0.27
BUCPa
3.48 + 0.57
0.37 + 0.75
93% (14/15)
BUC
3.37 + 0.74
0
BUPa
3.99 + 0.89
0.97 + 1.18
BCPa
4.39 ± 0.51
1.55 ± 1.14
UCPa
4.47 + 0.39
0.82 + 1.64
87%
(13/15)
100%
(15/15)
100%
(15/15)
100%
(15/15)
Untreated
D-13
D0
3.54
7.25
% (Proportion) Relapsing
M2 (+3)
M3 (+3)
M4 (+3)
100%
(15/15)
13%
(2/15)1,2
27%
(4/15)1,2
43%
(6/14)1,2
60%
(9 /15)
100%
(15/15)
64%
(9/14)
7%
(1/15)
7%
(1/15)
0%
(0/15)
33%
(5/15)
100%
(15/15)
• Combinations of bedaquiline, sutezolid, PA-824 and Clofazimine cure mice in 4 months
• Suggests effectiveness of targeting ATP synthesis, ribosome and cell wall/RNS production
Antimicrob Agents Chemother. 2012, 56(6):3114-20.
Emerging Targets and Pathways of Interest
Central carbon metabolism
• Enzymes essential to survival of Mtb in mice
Fatty acids
– Isocitrate lyase
-oxidation
– Malate synthase
Acetyl-CoA
– PckA
– Lpd, DlaT (pyruvate dehydrogenase)
• First demonstration of efficacy in mice with
Oxaloacetate
Citrate
Acetyl-CoA
MalateMalate Synthase
ICL1/ICL2
Glyoxylate
Fumarate
Isocitrate
CO2
a-Ketoglutarate
malate synthase inhibitors *
CO2
(phenyl-keto acids)
Succinate
Succinyl-CoA
*Krieger I, Chem Biol, 2012, 19, 1556-1567
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Summary
Targeting the organism: present and future
• Cell wall biosynthesis and transcription-translation continue to be rich sources of
TB drug targets:
– New cell wall targets: DprE1 and Mmpl3
• Newer target pathways deserve further exploitation
• Preclinical data suggests targeting ATP synthesis and RNS production are
effective
• Central carbon metabolism is one potential target pathway of the future
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