RD DDU’s PET Imaging GBA: GCB PET vs Lysosomotropic PET, BD study, Pharmacological modulation, Sample size estimation

PE1

is clearly differentiated from other approaches in clinical development. This differentiation should be more clearly explained with respect to the major competitive mechanisms.

GCB PET vs Lysosomotropic PET

	GCB PET	Lysosomotropic PET
Direct labeling of fusion protein.
Traditionally, the positron-emitting isotopes 124I (t1/2 = 4.18 d), 86Y (t1/2 = 14.7 hr), and 64Cu (t1/2 = 12.7 hr) have been used to label antibodies for PET imaging. More recently, however, the field has witnessed a dramatic increase in the use of the positron-emitting radiometal 89Zr. 86Y and 64Cu have proven promising in preclinical investigations, both isotopes possess physical half-lives that are too short to be effective for imaging in humans. 124I, in contrast, has a nearly ideal physical half-life for imaging with antibodies, but it is expensive and has suboptimal decay characteristics that lead to relatively low resolution clinical images. 89Zr-DFO-labeled Antibodies: 89Zr (Zirconium) is a nearly ideal radioisotope for PET imaging with immunoconjugates, as it possesses a physical half-life (t1/2 = 78.4 hr) that is compatible with the in vivo pharmacokinetics of antibodies and emits a relatively low energy positron that produces high resolution images. Furthermore, antibodies can be straightforwardly labeled with 89Zr using the siderophore-derived chelator desferrioxamine (DFO). The most common chelator used in 89Zr-labeled radioimmunoconjugates is desferrioxamine (DFO).
If CSF lysosomal BM by Comp Bio turns negative this is critical! If CSF lysosomal BM by Comp Bio turns positive this is for regional confirmation

Feasibility / BD study / Pharmacological modulation study

Feasibility	질환모델 불필요	Baseline Lysosomal alteration 필수
20231215 BD study	Once team gets good tool candidates for labeling. - Labeling a tool or in-house VHH GCB protein - Labeling of (<3 CN) candidates - Biodistribution study in TfR TG mouse? - JS: NHP?	Once appropriate GBA deficient mouse model, it worth testing these molecules. The cross breeding has started at Taconic and Gabi will update Bambos regarding timelines from Taconic. Team will discuss further in ad hoc meeting in Jan regarding appropriate models. Brain uptake 가 LCMs 로 완료, IHC 와의 calibration 은 완료되었으므로, 1. Next step should be PET BD study in simple model (eg D409 mouse) 2. 결국 IVC 필요한데...
Pharmacological modulation study	따로 불필요 i) Downstream other BM 과 관계되는 것은 the sum of endogenous GCB and Delivered GCB 이므로,, ii) 이것은 functional marker 아니므로, IVC 는 불필요하고 나중에 CSF GBA activity로 하자. 꼭 GBA-PD model? 아님 그냥 GD model? aSyn load 가 공존해야 할 듯 한데.
VC vs ?	VC vs CSF GBA activity ↑ VC vs CSF lysosomal BM VC vs CSF aSyn VC vs DA

Sharefoldr / team meeting / 001 PE preparation

• 20240219 PJ Mtg
• 001 PE preparation

PE: Lysosomotropic PET (only last resort)

Lc3 etc are commonly used. EPOC possible options: digital, vmat2, Mention blood, clinical benchmark, ivc → refine,

	aSyn PFF-treated D409V/D409V TG mouse	Rat (CBE-Cyno)
cells / activity	CBE → ↓ gba activity? CBE → ↑ gba activity?	MED exposure 에서의 GBA activity delta 를 observe. → propose clinical target as a range
Dose는 기결정정이므로 one dose 만 투여후 CSF BM = Observe commercial rGCase and its 3D structure are unavailable. 4-MUG (Mishra, 2020 #2767) 96% query cover (Fig. 1), 88% identity, 59% similarity to dermentzai, ↓ GBA activity.
Worsening, focus on pathway engagement, RELATIONSHIP, assay, natural Hx, IVC.

Sample size estimation

1. Natural Hx study

Goal: when Max PE difference? PK 고려 X

Power?: observational study 이므로 불필요 일것.

Use: i) observational study 이므로 불필요일것. i) 0을 포함하지 않도록 design 필요? 그럼 결국 two mean difference 용 SSE 됨 : delta (benchmark, 그것보단 MED 에서의 brain에서의 observed delta, efficacy readout 후 시작해야겠네), SD이용 (ask Otake)

scenario 2: GlcSph, 30% delta, 30.3% CV (GBA GT IVC), 1 tail, 70% power, → 8 per group.

Tx (PAD) vs non-Tx 군간에 관찰된 difference 가 significant 하다 (magnitude는 상관 X)

Mouse is the only model to see lipid-a syn relationship so that CBE PK seems to be required to avoid overdose prediction in human. We need more investigation which method is more feasible though, if we take LC-MS method, optimization is more or less needed. Method development should be started at least 3-6 month before in-life study.

2. Pharmacological study

Goal: 30% delta와 association 되는 exposure 를 찾음. 그럴려면 여러 dose 를 test해야 하는데. SSE: 30%, SD: ? 결국 another large biology study 되네. Imaging 아니라 histology로만 가능하겠네.

기존재인 aSyn MED 이용:

Goal: MED exposure 에서의 DAT delta 를 observe → propose clinical target as a range.

Dose는 기결정정이므로 one dose 만 투여후 DAT을 Observe.

m) 0을 포함하지 않도록 design 필요? 그럼 결국 two mean difference 용 SSE 됨 : delta (only clinical benchmark이용, ie 30% from UF), SD이용 (ask Paul Mc)

• scenario 1: 30% delta, 40% CV, 1 tail, 70% power, → 14 per group.
• scenario 2: 30% delta, 26.7% CV, 1 tail, 70% power, → 7 per group. (then, dat imaging is feasible? vs histology)
• scenario 3: 30% delta, 35% CV, 1 tail, 70% power, → 11 per group
• scenario 4: 30% delta, 20.6% CV ((Park 2020, #1680, mean sd of control group)), 1 tail, 70% power, → 5 per group

CBE-treated A53T SNCA Tg mouse, (Tbos 구매사용 가능하나 neurodegeneration 없으므로 안될 것)