Precedo Inc. provides in vitro biological evaluation of VAV1 degraders and in vivo assessment using autoimmune disease models, combined with DMPK studies to comprehensively evaluate their degradation properties and ADME characteristics.

Imagine a bustling city. For this city to run well, it needs a good recycling and waste management service. In our bodies, one of (or the main way of) this "recycling service" is called the Ubiquitin-Proteasome System (UPS). It's a natural and crucial process that breaks down old, damaged, or unneeded proteins.

For decades, the main way we developed drugs was to create small molecules that act like a "key in a lock" to turn off a protein's function. This worked well for many diseases, but there were some big problems: Some proteins are "undruggable" because they don't have a good "lock" for a drug to fit into. Even if you can turn off a protein, what if you need to get rid of it completely for a lasting effect?

This is where the new story begins. Instead of trying to turn a protein off, scientists had a revolutionary idea: what if we could harness the cell's own recycling system to mark the protein for destruction? The key to this is a cellular helper called an E3 ligase. But the E3 doesn't work alone. It's part of a protein complex system that gets the job done.

E1: The "activator" 🔋. This protein "activates" the small ubiquitin molecule, kind of like plugging in a battery.

E2: The "carrier" 🚚. The activated ubiquitin is then passed to an E2 protein, which holds onto it and brings it to the E3.

E3: The "recruiter" 🤝. This is the final and most important protein in our story. The E3 ligase recognizes the specific target protein and brings it together with the ubiquitin-carrying E2. It catalyzes the final transfer of the ubiquitin "tag" onto the target.

The Recycling Process: When a protein is tagged, a chain of ubiquitin is built on it. There are different kinds of these chains, and each one acts as a different signal. The K48 ubiquitin chain is the specific signal for a protein to be destroyed by the proteasome. When the proteasome digests a tagged protein, the ubiquitin chains are not destroyed. Instead, enzymes called deubiquitinases (DUBs) act as a "tag removal service," stripping the ubiquitin molecules off the digested protein pieces. This allows the ubiquitin to be used again and again for the next round of degradation.

Figure 1. The ubiquitin–proteasome system (UPS)[1]

Take home messages

This is the entire natural process we're working with. Now, let's meet our two main characters who use this system for drug therapy.

PROTACs: The Molecular Matchmaker

The first hero is the PROTAC (Proteolysis Targeting Chimera). A PROTAC molecule is like a double-sided sticky tape or a tiny molecular stapler.

• One side of the tape is designed to stick to your target protein (the one you want to destroy).
• The other side is designed to stick to an E3 ligase (the recycler).
• A linker in the middle holds the two sticky ends together.

When a PROTAC is introduced, it brings the target protein and the E3 ligase right next to each other. This forced connection makes the E3 ligase start building the specific ubiquitin chain for destruction on the target protein. Once tagged, the protein is sent off to be destroyed by the proteasome.

Molecular Glues: The Unplanned Connection

Our second hero is the molecular glue. This is a much simpler molecule, more like a drop of glue that creates a new connection where there was none before.

• A molecular glue isn't a double-sided tape. It's a single, small molecule that binds to an E3 ligase.
• This binding changes the shape of the E3 ligase just enough to create a new surface.
• This new surface can now perfectly fit your target protein, "gluing" the two together.

Current Key Targets in Targeted Protein Degradation

The vastness of the human proteome means that targeted protein degrader is being trialed against a wide range of targets. Initial efforts focused on “de-risked” targets already known to be clinically tractable, such as hormone receptors. As the technology matured, attention shifted dramatically to proteins long regarded as “undruggable.”

Table 1. Key Targeted Protein Degrader Targets, Modalities, and Corporate Engagement

The Mechanism: Molecular Glue Degraders Targeting VAV1

VAV1 is a guanine nucleotide exchange factor (GEF) that activates Rho family GTPases (Rac1, Cdc42) downstream of both the T‑cell receptor (TCR) and B‑cell receptor (BCR).

In normal immune signaling:

1. TCR/BCR engagement → phosphorylation of VAV1 by Src family kinases (Lck/Fyn in T cells, Lyn in B cells).
2. Activated VAV1 → GDP to GTP exchange on Rac1/Cdc42 → actin cytoskeleton remodeling, immune synapse formation, and downstream MAPK/NF‑κB/NFAT activation.

Molecular glue degrader binds to an E3 ubiquitin ligase (CRBN, cereblon) and reshapes its surface to recruit VAV1 as a neosubstrate.

Checklist Toolkit: How to Evaluate Targeted Protein Degrader (TPD) Candidates

The distinct mode of action of degraders means that traditional inhibitor evaluation paradigms are insufficient. A comprehensive toolkit covers biological efficacy profiles.

Biological Evaluation Criteria

• Ternary Complex Formation: In vitro, CRBN alone is not the full E3 ligase — adding DDB1 (often as a CRBN–DDB1 complex) mimics the physiological CRL4^CRBN assembly, which is what the degrader will actually engage in cells.

Figure 3. Ternary complex formation between VAV1, CRBN/DDB1, and TPD measured by AlphaLISA. 

• Degradation Potency (D_max, DC50): Quantified with HiBiT, Abby/Western—requires dose-response and time course in multiple cell types (e.g., HEK293T-VAV1-HiBiT screening).

Figure 4. VAV1 degradation potency in 293T‑VAV1‑HiBiT cells. 

Figure 5. VAV1 degradation in Jurkat (human T‑cell leukemia line) assessed by (A) Western blot and (B) Abby Western system. 

Figure 6. VAV1 degradation in Raji (human Burkitt’s lymphoma B‑cell line).

Figure 7. VAV1 degradation in REC‑1 (human mantle cell lymphoma line).

• Immune Cell Functionality: T/B cell assays for proliferation, activation (CD69), cytokine production (IL-2, IL-17A), TH17 polarization.

Figure 8. T‑cell assays: Human peripheral blood T cells were stimulated through the T‑cell receptor (TCR) and treated with increasing concentrations of degrader.

Figure 9. B‑cell assays: Human B cells were stimulated via the B‑cell receptor (BCR) and treated with degrader.

• Ex-vivo and in-vivo Validation: Disease models (colitis, arthritis) for efficacy, biomarker modulation, and tissue protection.

Figure 10. Ex‑vivo VAV1 degradation in mouse PBMCs and splenocytes treated with degrader.

Figure 11. MOG₃₅₋₅₅‑induced experimental autoimmune encephalomyelitis mouse model for degrader evaluation. In the MOG‑induced EAE mouse model, therapeutic administration of MRT‑6160 significantly suppressed disease progression, with a clear pharmacological effect observed at the 0.3 mg/kg dose. MRT‑6160 did not markedly inhibit splenomegaly in the EAE model. MRT‑6160 markedly improved myelin preservation in the spinal cord and reduced inflammatory cell infiltration.

Figure 12. collagen‑induced arthritis (CIA) mouse model for degrader evaluation. MRT‑6160 alleviated type II collagen‑induced arthritis symptoms in a dose‑dependent manner, with a clear pharmacological effect observed at 0.3 mg/kg. MRT‑6160 also dose‑dependently inhibited CIA‑associated splenomegaly.

Figure 13. Naïve CD4⁺ T‑cell transfer‑induced IBD mouse model for degrader evaluation. In the naïve CD4⁺ T‑cell transfer‑induced IBD model, therapeutic MRT‑6160 significantly suppressed disease progression, with clear efficacy at 0.3 mg/kg. The model features shortened, heavier colons; MRT‑6160 improved the colon weight‑to‑length ratio and reduced splenomegaly, both evident at 0.3 mg/kg, and ameliorated colonic histopathology.

Figure 14. Imiquimod (IMQ)‑induced psoriasis mouse model for degrader evaluation. In the IMQ‑induced psoriasis model, MRT‑6160 at 0.3 mg/kg and 1 mg/kg showed no clear therapeutic effect, although it significantly reduced IMQ‑induced splenomegaly. Increasing the dose to 10 mg/kg likewise did not produce a marked therapeutic benefit.

Reference

[1] Bachiller, S., Alonso-Bellido, I. M., Real, L. M., Pérez-Villegas, E. M., Venero, J. L., Deierborg, T., Armengol, J. Á., & Ruiz, R. (2020). The Ubiquitin Proteasome System in Neuromuscular Disorders: Moving Beyond Movement. International Journal of Molecular Sciences, 21(17), 6429. 

[2] Shah K, Al-Haidari A, Sun J, Kazi JU. T cell receptor (TCR) signaling in health and disease. Signal Transduct Target Ther. 2021 Dec 13;6(1):412. doi: 10.1038/s41392-021-00823-w. PMID: 34897277; PMCID: PMC8666445. 

[3] Tanaka, S., Baba, Y. (2020). B Cell Receptor Signaling. In: Wang, JY. (eds) B Cells in Immunity and Tolerance. Advances in Experimental Medicine and Biology, vol 1254. Springer, Singapore. https://doi.org/10.1007/978-981-15-3532-1_2