1. AMPAKINE Compounds for the Treatment of Rett Syndrome
Mark A Varney
Chief Scientific Officer

2. Hypothesis
Depressed Levels of BNDF Contribute to the Phenotype of Rett Syndrome
Lifespan
Motor Activity
Cortical Layer V Firing
Breathing Abnormalities
Increase Brain BDNF to Attenuate Rett Symptoms
Chang et al, Neuron 49, 341–348
Wang et al, J Neurosci 26:10911–5

3. BDNF – A Major Regulator of Synaptic Plasticity
Synthesized and stored in glutamatergic neurons and is released in an activity-dependent manner
Critical for neuronal survival and differentiation
Plays a role in fast excitatory synaptic transmission and synaptic plasticity, including LTP and LTD
Critical for synaptic plasticity and memory processing in the adult brain

4. Strategy
Treat with AMPAKINE Molecules to Increase Endogenous BDNF Levels in Specific Brain Regions
AMPAKINEs are small molecules that positively modulate the AMPA receptor

5. AMPA Receptors Play a Key Role in Glutamatergic Transmission
Glutamate is the major excitatory neurotransmitter in the CNS
Virtually all neurons express glutamate receptors
Fast excitatory transmission is mediated by AMPA receptors
Swanson et al. (2005)
Nat Rev Drug Dis 41:

6. AMPAKINE Molecules
AMPA receptors deactivate and/or desensitize extremely rapidly (~2-10 ms)
AMPAKINEs are allosteric positive modulators of the AMPA receptor
Attenuate deactivation and/or desensitization of AMPA receptors
Strengthen synaptic transmission and facilitate long term potentiation (LTP), widely regarded as the substrate for memory
Stimulate BDNF production

7. AMPAKINEs Have Acute and Chronic Effects In Vivo
AMPAKINE Treatment
Acute Effects
(Lasts with the t½ of the drug)
Memory
Cognition
Psychiatric disorders
Chronic Effects
(Trophic induction lasting ≥ one day)
Memory
Cognition
Psychiatric disorders
Degenerative diseases
Define difference between memory and cognition

8. Chronic Effects of AMPAKINEs
1. Brief treatment with AMPAKINE causes long lasting increases in BDNF
2. Use daily injections of short half-life AMPAKINEs to chronically increase BDNF levels.
3. BDNF then promotes plasticity and neuronal viability

9. Chronic Effects of AMPAKINEs on BDNF
Rat Cortical Cultures
Cultured Hippocampal Slices
In Vivo
0.00
0.05
0.10
0.15
0.20
0.25
0.30
Ctrl
10uM CX929
25uM CX929
50uM CX929
100uM CX929
Protein
6 hr AMPAKINE pulse, protein at 24 hrs
mRNA
3 hr AMPAKINE pulse, mRNA at 18 hrs
Protein
1 injection/day for 7 days, Hippocampus collected 24 hrs after last treatment

10. Huntington’s Disease (HD)
Progressive, hereditary brain disease that causes changes in movement, thinking and behavior
Onset commonly between ages 30-50
30,000 people in US (~1/10,000)
Caused by excessive CAG repeats in the huntingtin gene
Disturbances in executive function are probably earliest manifestation
Neuropathology, particularly in striatum, in later phases
BDNF levels are reduced in HD postmortem brain and transgenic mouse models

11. Reduced BDNF and Defective LTP in Asymptomatic HD Knock-in Mice
TBS: 10 bursts of 4 pulses 100 Hz; separated by 200 msec
Lynch et al., J. Neurosci 2007

12. AMPAKINE Treatment Paradigm
HD Knock-in Mice
CX929 selected because of its short t½ of 15min and robust effects on BDNF
Injected with Vehicle or CX929 at 5 mg/kg/day i.p. for between 4 to 30 days
18-24 hours after the last dose, measure
Hippocampal LTP
Actin Polymerization
Locomotor Effects
BDNF Measurements
Cognition

13. CX929 Up-regulates Mature BDNF in HD Knock-in Mice and Restores LTP
Mature Hippocampal
BDNF Protein
Hippocampal LTP
Normal HD
HD+CX929
Cognitive deficits restored and motor deficits prevented by CX929
Mature hippocampal BDNF and LTP assayed 18 hrs after the last of 30 daily treatments with CX929

14. Current Studies
Evaluate if AMPAKINE treatment corrects Rett phenotypes in Mecp2-/y mice
Respiration
BDNF levels
Other behaviors

15. Summary AMPAKINE molecules increase brain BDNF levels
Transgenic HD mice have deficits in BDNF levels and deficits in hippocampal LTP
The short acting AMPAKINE, CX929 can restore depressed BDNF levels and hippocampal LTP deficits
Rett Mice have deficits in BDNF
Currently testing AMPAKINEs in Rett mice to see if it restores normal phenotype