AADC PET tail, Rationale of GBA PET, GBA expression evaluation, DDU/MJFF PET Imaging GBA, GBA Activator PRC1
AADC PET tail
protein 에 PET Tracer 붙는 것임. Term: AADC tracer라고 함. (AADC ligand 는?)
| 순서 | Purpose (deliverables) |
|---|---|
| HV | to understand the normal GBA expression levels (and its variability in different tissues) normal level 모르면 PKPD 못 하겠구나! |
| Patients | to provide the PK/PD relationship for GT |
(unilateral) MPTP, 8주후 PET. To confirm the PET results, histological assessment of the brains was performed. Regional: fig 2 showed striatum & SN, respectively.
(Eberling, 2003 #517) 위와 비슷한데, 더 나아가서 PET 을 quantification 했음. (PET AADC-FMT update (ie ratio to cerebellum)).
MJFF for GBA
Rationale of GBA PET
PK-PD-Efficacy relationship
- Protein is the main PK readout for PK-PD analysis (CSF GBA protein ‘s caveats)
- We need to see SN
- SN의 Signal change가 most clinically meaningful PD index일 것이다
- 비록, (Efficacy 없이) PK-PD relationship 관점만 보면 (가장 가능성 있는 PD index인) CSF GlcCer 와 가장 잘 맞을 것은 CSF (total) GBA protein 혹은 whole brain (total) GBA PET signal 이겠지만,
- 나중에 aSyn PET 과 regional pattern 맞춰봐야함),
[부기적 rationale:]
- CSF GBA protein
- No healthy data (이건 향후 보유 예정)
- No consensus on CSF GBA BL level in PD (only Mullin 2020 Ambroxol P2 data), that shows variability 150-310 pg/mol
- CSF GBA ACTIVITY
- (CSF 내기) Affected by lysosomal- & cellular- seretion
- Variable: adult normal range: 1.1 - 8.1 μmol/L/d): prevail.
- In some patients, undetectable (LLOQ; 0.56 μmol/L/d)
GBA expression evaluation by imaging
- Dynamic range with the normal GBA1-specific probe
- Dynamic range with the GBA1-nonselective probe
Step 1: To test if the PET probe can capture GBA1 with enough S/N ratio in the control matrix
Step 2: To confirm if the probe can capture GBA1 in GBA-PD matrix with reduced GBA1 protein expression
Groups: Control, GBA-PD (Hetero), GBA-PD (Hetero) + GT.
Series: Mutant GBA1 vs Normal GBA1.
Key No-Go decision
- Narrow dynamic range
- No specific binding in the control matrix
DDU’s PET Imaging GBA
Team
- Chemistry: Sarav Narayanan
- Imaging: Talakad Lohith
Questions
- Label GBA without distinguishing endogenous GBA and transgene-origin?
- Yours Can be used for CNS?
- Do they have the intention?
- BBB penetrance
- Process
- Bmax when?
- recently identified a potential active site probes for GCB (Narayanan Sarav). 우리는 Bmax 먼저 하는데? 아래거는 imaging 용인가? Below is a small molecule, so
- ‘direct method’ js: this is for GBA biodistribution, not competition/occupancy study with GBA activator!
Probe table
| No. | Compound ID | Structure | Quantity | Timeline | Status | note |
|---|---|---|---|---|---|---|
| 1 | MDW933 | (structural drawing) | 100 mg | 09/27/2020 | In progress | Tajito Kojima 20200730: It's a probe which binds catalytic center by irreversible (js, so not ok for (in vitro) Bmax assessment) way (forming covalent bonding with GBA) to measure active GBA in lysosome. It a kind of hybrid molecule of CBE, known covalent inhibitor of GBA, and fluorescence moiety. We use it to evaluate chaperone effect - when the compound treatment promotes translocation from ER to lysosome, we can see enhanced signal of the EPET... |
| 2 | Univ of Saskatchewan | (structural drawing) | 20210121 Makoto Fushimi: irreversible inhibitors could be used for GBA Gene Therapy PET because of its purpose to measure GBA expression level, not target occupancy. As for the attached patent from University of Saskatchewan I'm not sure that they have a promising PET probe... |
MJFF 소개해주자: Next step?
MJFF’s PET Imaging GBA
We had funded David Vocadlo at Simon Fraser University in Canada to develop a Gcase tracer (https://www.michaeljfox.org/researcher/david-vocadlo-phd). He was very early in the process at the time and still had a lot of work to do when his grant ended. I think he ended up working with Prevail Therapeutics. Not sure what progress has been made.”
Other PET Imaging GBA
(Rempel, 2017 #795) review including GBA effort
GBA Activator
GBA activator PRC1 Working document: Link.
| LGE | Criteria | PE Date / Target | CN Dat / Target | CS | IN | D | |
|---|---|---|---|---|---|---|---|
| 20200915 cross-site meeting with RD |
Discussion items
- We are going PE with 2 chemotypes from RD and NS. Go/Nogo decision in Dec 2020, PE: Jan 2021.
- Preparation of PRC1 narrative
- CN criterion: 50% brain GlcSph reduction in L444P tg mice
- Chemotype prioritization before CN based on brain GlcSph
PE Jan 2021 / CN / Clinical visual flow (Takeda CONFIDENTIAL)
| PE Jan 2021 (2 chemotypes, 2 criteria) | CN Mouse brain substrate reduction | Clinical GD type 3 / CSF GlcSph reduction | |
|---|---|---|---|
| NS |
Cell-free enzyme activation: Recombinant human GBA protein (wt, N370S) / artificial substrate 4MU-β-D-glucopyranoside (4MUG) degradation Substrate reduction in the CNS target cell: iPSC-DA neurons (L444P) / GlcSph reduction Mouse brain enzyme activation: WT mouse brain / 4MUG degradation (criterion: statistically significant activation at 100 mg/kg) |
Mouse brain substrate reduction: L444P Tg mouse brain / GlcSph reduction criterion: 50% GlcSph reduction at CN acceptable dose (e.g. 10 mg/kg) |
Ambroxol reduced CSF GlcSph up to 50% in GD2/3 pilot study, which was associated with partial improvement in CNS symptoms (Narita A. 2016). Venglustat reduced CSF GlcSph up to 50% in GD3 Ph2 trial. |
| RD |
Cellular enzyme activation: Fibroblasts (N370S, L444P) / artificial substrate FRETq probe degradation Substrate reduction in the peripheral cell types: Macrophages or fibroblasts (L444P) / GlcSph reduction Mouse peripheral organ substrate reduction and CNS exposure: L444P Tg mouse liver and spleen / GlcSph reduction (150 mg/kg, po) |
enzyme assay with the brain homogenates found that D409V mutant protein is not activated by all tested GBA activators LTI-291, S-181, and our Ct-A cpds.
Lower GBA activator criteria table
| LGE | PE Jan 2021 | CN | |
|---|---|---|---|
| In vitro |
Cell free: enz activation (WT & N370S), 4MUG → criteria: EC350 (3.5 fold of basal activity) ≤ 1 μM In cell ie iPSC DA neurons (L444P): ↓ (50% of cerezyme) GlcSph → criteria: ≤ 1 μM |
Cell free: enz activation (WT & N370S, 둘 반응유사 예상, N370S 만 볼것), 4MUG → criteria: EC350 (3.5 fold of basal activity) at ≤ 100 nM (so far 1.1-2.5 μM 까지) In cell ie iPSC DA neurons (L444P): ↓ (50% of cerezyme) GlcSph → criteria: 100 nM Cf) cerezyme 만큼 감소시키는 것이 100%임. | 2022/02 (monthly update) |
| In vivo |
WT mice brain (js: WT에 작용이 GD 에선 무의미할듯, PD 에선 의미) ↑ gba activity (4MUG), statistically significance, at ≤ 100 mg/kg (single dosing) (so far we got this at 300 mg/kg) |
L444P Tg mouse (RD DDU asset) ↓ GlcSph by 50% at ≤ 10 mg/kg (po, repetitive dosing) GBA-PD model POC |
Uncertain Spans
| location | transcription | uncertainty |
|---|---|---|
| GBA expression evaluation diagram | bar / matrix layout | only the text labels are transcribed; the bar layout is small. |
| Probe table / MDW933 note | we can see enhanced signal of the EPET... | trailing ... indicates the sentence is clipped at the right edge of the cell. |