Screens, posters, preprints – degradation everywhere, as if more degradation automatically means more progress. But beneath the champagne and the conference glow, there’s a truth almost no one wants to confront:

They are degrading proteins they don’t fully understand. They are entering the clinic without knowing the liabilities they carry. They have no map of the proteome-wide consequences of their own molecules.

A small, serious contingent has been whispering the warning for years: Look more broadly. Look at the proteome. Look at the consequences. But this group doesn’t know how to do it, nor have the resources. They don’t have the tools, the assays, the proteomics, the cell-state logic, the substrate-universe modeling. They don’t have the infrastructure.

VistaraBio Is the Only Entity That Put the Entire Problem Together

The field needed:

• Holistic, proteome-wide substrate discovery
• Context-dependent degrader liability mapping
• Cell-cycle stratified CRBN engagement
• Surrogate-substrate detection
• PTM-state profiling
• Cohort-level toxicity prediction.
• No one had all of it. No one even had half of it. Except VistaraBio

VistaraBio built:

• The E3 ligase – substrate engine.

• PINTAC technology for biologically validating glue candidates and substrate contexts.

• TSA-CRBN assay system assay for validating glue actions.

• The D1B Glue screening platform – 85,000 degrader candidates screened per year.

The screening-efficacy-neosubstrate-safety logic all combined in one convenient system – something the field has been pretending doesn’t exist.

Welcome to Degrader OS

Not a platform. Not an assay. Not a pipeline. A full operating system for degrader development – the first of its kind.

Degrader OS means:

• A unified substrate universe
• A mechanistic safety layer
• A proteome-wide liability map
• A cell-state-aware degrader engine
• A clinical-phase risk eliminator
• A discovery-to-IND operating system

It’s the only environment where degraders can be developed at a breathtaking throughput; yet responsibly, mechanistically, and clinically safely.

Degrader safety is not only about the target — it’s about the ligase ecosystem.

Cereblon Is Not an E3 Ligase — It Is the Substrate‑Recruitment Subunit of CRL4Cereblon (CRBN) is fundamentally a substrate‑recruitment module of the CRL4 ubiquitin ligase complex, which includes DDB1, DDB2, RBX1, and Cul4.

It does not function as an E3 ligase on its own. Instead, it operates as one node within a multi‑protein ubiquitin engine, where substrate selection, adaptor availability, and complex stoichiometry determine proteome‑wide outcomes. Recruiting CRBN with degraders therefore does more than redirect a single ligase — it perturbs the entire CRL4 ecosystem.

CRL4 Dysregulation: The Hidden Liability of CRBN‑Based Degraders

A complete degrader safety analysis requires hundreds of proteins, not a handful. TSA‑CRBN is the first CRBN assay engineered for mechanistic safety, not just target degradation. When a degrader aggressively binds CRBN, it can:

• Redistribute CRL4 subunits across competing complexes
• Disrupt native protein–protein contacts within the CRL4 pool
• Alter proteostasis for dozens to hundreds of natural substrates
• Trigger unintended degradation of proteins that mimic degron‑like motifs
• Collapse native ubiquitin logic by sequestering CRBN away from essential cellular functions

This is not theoretical — it is mechanistic. CRL4 is a hub, and perturbing a hub has network‑level consequences.

VistaraBio Has Mapped CRL4 Contact Points and incorporated the data into the MG-OS system

VistaraBio has completed protein–protein contact mapping across CRL4 complexes, identifying: Interaction surfaces among CRBN, DDB1, DDB2, RBX1, Cul4A/B, context‑dependent assembly states, substrate‑proximal docking geometries, and cohort‑level substrate clusters that respond to CRL4 perturbation. This map is the foundation for substrate determination, complex‑state modeling, and mechanistic safety prediction of degraders.