Title : Evaluate the efficacy of AXL inhibitor bemcentinib in the rNLS8 mouse model of amyotrophic lateral sclerosis
Abstract:
Aim and Methods: We aim to evaluate if the pharmacological inhibition of the myeloid/microglial receptor tyrosine kinase AXL could be used as a novel therapeutic approach for Amyotrophic Lateral Sclerosis (ALS). The objective of the present research is to evaluate the efficacy of the bemcentinib drug (BGB) to inhibit the activity of Axl in the brain of a doxycycline regulatable TDP-43 transgenic mouse model of ALS (rNLS8). The specific aims include: 1. To evaluate target engagement in the brain of rNLS8 mice orally dosed with BGB and Vehicle (Veh) used as control. 2. Perform an efficacy study in rNLS8 mice orally dosed with BGB and Veh. To achieve these specific aims, rNLS8 mice were weaned on a diet containing doxycycline (ON Dox) to suppress the expression of the cytoplasmic mutant TDP-43 transgene (hTDP-43NLSm). At the age of 3-4 months, Dox was removed from the diet (OFF Dox) to allow the expression of the transgene for 4 weeks before treatment. rNLS8 mice were divided into two cohorts that received BGB or Veh as control. Mice were dosed once a day for 2 weeks. Mice were anesthetized to collect biofluids, including CSF and plasma and finally perfused to obtain their brains for further analysis.
Results: In the present work, we have used the pharmacological Axl inhibitor BGB, to evaluate the therapeutic potential of targeting Axl signaling in rNLS8 mice. To demonstrate target engagement, we have evaluated the effect of Axl inhibition measuring first changes in total Axl levels and its soluble fragment (sAxl) across the hippocampus, cortex, plasma, and CSF in the brain of rNLS8 mice. We found an upregulation of total Axl levels in the hippocampus and cortex, confirming the previous finding showing that Axl was overexpressed when TDP-43NLSm is expressed in rNLS8 mice. In addition, we noticed an increase of sAxl in CSF of mice OFF Dox. Increases in sAXL levels have been associated with increases in cellular Axl and activity. Unfortunately, we did not observe a significant difference between the cohorts treated with Veh and BGB. The reduced BBB penetrance of the drug could be a potential explanation for not detecting changes in Axl levels as a measure of target engagement. In contrast, we detected that in BGB treated mice, there were significant changes of Akt and Stat3 protein levels in the cortex and hippocampus. These results indicate that the drug could be reaching the brain and indirectly affect the expression levels of its downstream targets. Overall, the preliminary finding demonstrates the potential activity of Axl inhibitor BGB in the brain. Further studies need to be done to confirm the efficacy of the drug targeting microglial cells and affecting its activity in the brain of rNLS8 mice.
Audience Take Away Notes:
- The presentation provides a foundation for the development of novel therapeutic strategies targeting AXL in ALS and possibly other neurodegenerative diseases.
- Participants will gain knowledge on the use of biological markers, such as total Axl levels and its soluble fragment sAxl, in determining the efficacy of drug treatments in ALS research.
- The presentation will explore how Bemcentinib affects downstream protein levels (Akt and Stat3) in the brain, providing insights into the broader impact of drug treatment beyond the primary target.
