Research map / Large language models / Language, safety and interpretability
Concept Bottleneck Language Models For Protein Design
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Introduces CB-pLM, a masked protein language model with a concept bottleneck layer of 718 interpretable concepts that enables controllable generation, interpretation via a linear decoder, and debugging.
Problem
Protein language models are opaque, making it hard to control generated sequences, interpret what they learned, or debug them, which limits trust in high-stakes drug discovery settings.
Approach
Insert a concept bottleneck layer (one interpretable neuron per concept, with an orthogonal unknown embedding) into a masked language model, feed a linear decoder from concepts and unknown embedding, and intervene on concept values with gradient-based token attribution for coordinate selection.
Key results
- CB-pLM achieves about 3x larger change in desired concept values than other conditional models and over 15% higher control accuracy in single-concept interventions.
- CB-pLM reaches 94% control accuracy on multi-concept (GRAVY and charge) interventions, outperforming the second-best conditional model by 34%.
- CB-pLM 24M/150M/650M/3B perplexity on Mason dataset is 4.29/3.20/2.48/2.50, comparable to conditional baselines and ESM2 (4.84/3.41/3.01 at 150M/650M/3B).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use CB-pLM instead of other conditional language models for single-concept intervention | Conditional protein language models · 14 biophysical concepts, single-concept intervention | control accuracy: over 15% | Helped |
| Use CB-pLM instead of other conditional language models for single-concept intervention | Conditional protein language models · 14 biophysical concepts, single-concept intervention | change in desired concept value: 3× | Helped |
| Use CB-pLM for multi-concept intervention | Conditional protein language models · GRAVY and charge at pH 7, multi-concept intervention | control accuracy: 94% | Helped |
| Use CB-pLM rather than the second-best conditional model for multi-concept intervention | Conditional protein language models · GRAVY and charge at pH 7, multi-concept intervention | control accuracy: 34% | Helped |
| Use single-step integrated gradients rather than random masking for coordinate selection | CB-pLM · Protein concept interventions | control effectiveness: 2 × | Helped |
| Increase CB-pLM model size (ablation) | CB-pLM · Protein concept interventions | control | No clear effect |
| Change aromaticity normalization to make the concept difficult to learn (ablation) | CB-pLM 24M · Aromaticity intervention | control | Hurt |
| Use CB-pLM instead of other conditional language models | Conditional protein language models · Mason dataset | perplexity | Mixed |
| Use CB-pLM rather than LaMBO-2 for Siltuximab redesign | Protein design models · Siltuximab GRAVY reduction | GRAVY distribution shift | Hurt |
| Use CB-pLM rather than ESM2 or Hydrophilic Resample for Siltuximab redesign | Protein design models · Siltuximab redesign | naturalness | Helped |
Surprising findings
- On Siltuximab GRAVY redesign, CB-pLM ranks second to LaMBO-2 in concept distribution shift, though it is a general-purpose model trained on 718 concepts.
- Increasing model size from 150M to larger CB-pLM improved perplexity but gave no control improvement.
Limitations
- Requires training data annotated with predefined concepts.
- Unknown embedding is needed; reliance on it can let the model ignore concepts and orthogonality only encourages disentanglement.
- Generalization to unseen concept combinations is only shown on a toy color-MNIST task, not on proteins.
Experimental setup
Datasets: UniRef50 SWISS-PROT Mason dataset OAS
Benchmarks: Mason dataset perplexity Siltuximab GRAVY redesign
Metrics: perplexity concept control accuracy change in concept value naturalness (TAP scores) percentage passing naturalness filter
Baselines: C-pLM CC-pLM ESM2 LBSTER LaMBO-2 PropEn Discrete Walk-Jump Sampling Hydrophilic Resample
Builds on: concept bottleneck models concept bottleneck generative models ESM2 integrated gradients
Closest papers by meaning
- Training Compute-Optimal Protein Language Models (NeurIPS 2024 · similarity 0.90)
- How to make the most of your masked language model for protein engineering (NeurIPS 2026 · similarity 0.89)
- Steering Protein Language Models (ICML 2025 · similarity 0.89)
- Diffusion Language Models Are Versatile Protein Learners (ICML 2024 · similarity 0.88)
- From Mechanistic Interpretability to Mechanistic Biology: Training, Evaluating, and Interpreting Sparse Autoencoders on Protein Language Models (ICML 2025 · similarity 0.88)
- Elucidating the Design Space of Multimodal Protein Language Models (ICML 2025 · similarity 0.88)
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