We have not measured C5a in the experimental models. We have also not measured C5aR1 expression after drug treatment.
However, as C5a is mostly cleared by its receptor (https://pubmed.ncbi.nlm.nih.gov/33028618/), we may expect C5a levels to acutely increase with drug-treatment. C5aR1 expression is not expected to be directly impacted by C5aR1 antagonism, although broad reduction in microglial activation / neuroinflammation chronically would likely reduce C5a and C5aR1 expression.
BM
TE
js: unclear! i) Target 인 C5aR1은 drug response 가 없다고 하니 ii) C5a 가 Bm 가능성 이지만 : a, but not tested. b. plausible but not sure. c. quantitative relationship 가능할지?
We have not measured C5a in the experimental models. We have also not measured C5aR1 expression after drug treatment.
However, as C5a is mostly cleared by its receptor (https://pubmed.ncbi.nlm.nih.gov/33028618/), we may expect C5a levels to acutely increase with drug-treatment.
C5aR1 expression is not expected to be directly impacted by C5aR1 antagonism, although broad reduction in microglial activation / neuroinflammation chronically would likely reduce C5a and C5aR1 expression
PD
[neutrophil]js: unclear!
We are interested in whether neutrophil count can be a peripheral target engagement for a C5aR1 inhibitor? Is the neutrophil count correlated with the level of C5a or C5aR1?
→ We have not looked at neutrophils in PD patients, and are usure if this would be a reliable biomarker. Neutrophil numbers can be associated with C5a levels, although the correlation is complicated due to mobilised neutrophils expressing more C5a receptors that can deplete 'free' C5a concentrations (see Fig 1 here: https://pubmed.ncbi.nlm.nih.gov/33028618/).
PD
[pERK] js: unclear and unlikely
whether pERK can be used as a target engagement/pharmacodynamic marker for a C5aR1 inhibitor. It is deemed that C5a/C5aR1 activation exerts its pathogenic effects in PD via ERK pathway. Is there cell type specificity for this? Is there evidence that pERK level is increased in PD patients?
→ In my view, pERK is too ubiquitous and transitory to be a reliable biomarker. All myeloid cells (including microglia) signal through pERK following C5a (and some non-immune cells too - eg. stem cells). An enourmous number of other ligands also signal through ERK however. I am unsure if pERK is increased in PD.
PD
[microglia] unclear
We may want to explore the possibility of using microglial imaging (eg. TSPO or CSF1R) to monitor activated C5a or C5aR1 in human brains. Could you share any thoughts/information whether C5a/C5aR1 activation leads to upregulation of these microglial proteins? → We have not directly studied this, but I believe this to be a fruitful line on enquiry. Based on our PFF-Syn data with PMX205, we do see reductions in TSPO PET signal. C5aR1 microglial activation is also known to drive many inflammatory pathways.
PD
NLRP3 as downstream?
Well 100mg for me is too small for my purposes, I believe, because of the open questions around NLRP3. My question was whether TCAL can use 100mg and I keep 400mg for 2 projects
Progress
20220111
Additional questions for UQ;
Whether Takeda can obtain PMX-318 TFA salt (10 mg should be sufficient) as a positive control of cytotox assessment just in case Takeda in-house cytotox study were to show a trend of cytotoxicity
Solubility differences between TFA salt vs. acetate/HCl salt form, which may result in observed cytotoxicity in serum-free condition
Takeda internal timeline
Mouse PK study: 4 weeks from material arrival until data outcome
Cellular cytotox: To be confirmed with Ron
Solubility: To be confirmed with Andre
C5aR1 Euroscreen: 4 weeks from the PMX-318 arrival at Euroscreen
Mouse PK and cytotoxicity studies are the gating study in initiating in vivo pharmacology study, in particular 6-OHDA study
Neutrophilia study: We may run this study in-house
6-OHDA study: 3-4 months from PMX-318 dosing until all data outcome including IHC or WB of TH in the brain
6-OHDA study will be run at Axcelead
Axcelead study slot will not become available until April-May at earliest
Takeda internal Evaluation will be completed by end of August and then Takeda can make data-driven decision whether we wish licensing of PMX-318 or not in September
TM plan
Entry indication to be considered after we decide licensing of PMX-318 and have PMX-318 in our hands
Although there is a paper suggesting C5a-C5aR1 contribution in Gaucher disease (i.e. under GBA mutation), GBA-PD and GD are quite different from each other; therefore it is still too early to assume GBA-PD is the primary indication
GBA
MOA
GlcCer → GlcCer-specific IgG autoantibodies (in Gba19V/-mice and patients with Gaucher) → local and systemic C5a generation. → C5aR1 activation
↑ GlcCer accumulation → innate and adaptive immune cell recruitment
C-specific IgG antibodies(g) and C5a (h) concentrations in the serum (역시 BRAin 에서의 TV 필요!) of healthy human individuals (n = 15 per group) and Gaucher disease patients (n = 10 per group).
team:
…lhi: Biology Lead (TCAL)
…ne: DMPK Lead (TCAL)
…n: DSRE Lead (TCAL)
…ki: IP Lead (JPN)
…re are additional members on board;
…lre: Chemistry Lead (TCAL)
…san: PS Lead (JPN)
Takeda plan for PMX318 evaluation under MTA with UQ
[workflow diagram]
Step 1: In vitro Studies + PK Studies + Neutrophilia Study → Data Review
In case Step 1 is positive, then 1. Talk to Ceri to get endorsement about CEI-BD engagement; 2. Talk to CEI-BD about our plan
CNS pharmacokinetic studies were performed, which confirmed that oral dosing with 20 mg/kg was well tolerated and resulted in brain concentrations substantially above the IC50 for NLRP3 activation over a 24-hour period (Fig. 3G).
PMX301 IC50=64nM
6-OHDA
IV? Brain?
Background
Complement
Complement activation → generates activation fragments C3a and C5a → that interact with cellular receptors → to recruit and/or activate phagocytes (including microglia)
Complement (Protein) Fragments
The activation of the complement cascade, a cornerstone of the innate immune response, produces a number of small (74-77 amino acid) fragments, termed anaphylatoxins, that are potent chemoattractants and secretagogues that act on a wide variety of cell types. These fragments, are C5a, C4a, and C3a,
ents
Corresponding receptors
C3aR
Complement receptors on white blood cells are able to bind iC3b, so iC3b functions as an opsonin.
(Loeffler, 2006 #1685) ↑ iC3b deposition in PD brains (IH
Uncertain Spans
location
transcription
uncertainty
GBA inline figure (panel g & h)
IgG sub-class bar heights and C5a values
Inline bar charts kept as evidence; bar values not transcribed (panel g y-axis 0.5-2.5, panel h y-axis up to 700,000 pg/mL).
Team list leftmost names
”lhi / ne / n / ki / re / lre / san”
Names are partially cropped on the left; preserved as legible suffixes.
Background table top-left header
”ents” partial label
Header column text is cropped on the left edge; preserved as-seen.