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Scalable and Cost-Efficient de Novo Template-Based Molecular Generation
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Proposes SCENT, a template-based GFlowNet that uses recursive cost guidance on the backward policy, an exploitation penalty, and a dynamic building-block library to cut synthesis cost and scale to large fragment libraries.
Problem
Template-based molecular generation with GFlowNets suffers from high synthesis cost, poor scaling to large building block libraries, and weak performance with small fragment sets.
Approach
Recursive Cost Guidance trains a learned surrogate to approximate the recursive synthesis cost (and decomposability) of backward transitions, steering the backward policy toward cheap, viable precursors; an exploitation penalty counters the resulting exploitation, and a dynamic library adds high-reward intermediates as reusable building blocks to enable full synthesis trees.
Key results
- On sEH MEDIUM (threshold 8.0), SCENT (C+D+P) reports 32761 modes and 86081 scaffolds vs RGFN's 4755 modes and 10638 scaffolds, and SCENT (C+P) reaches 37714 modes.
- In SMALL sEH, SCENT (C+D+P) finds 715 modes vs 538 for RGFN and reduces cost of high-reward paths to 20.7 vs 37.7 for RGFN.
- SCENT (C+D+P) achieves the highest reward in SMALL (7.66) and LARGE (7.78) sEH settings.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add Synthesis Cost Guidance (ablation) | SCENT without cost guidance · sEH SMALL | synthesis cost: 37.1 \std{1.0} -> 23.7 \std{4.0} | Helped |
| Add Synthesis Cost Guidance (ablation) | SCENT without cost guidance · sEH MEDIUM | scaffolds > 8.0: 11478 \std{823} -> 52340 \std{4303} | Helped |
| Add Synthesis Cost Guidance (ablation) | SCENT without cost guidance · sEH SMALL, reward threshold 7.2 | modes: 13862 \std{422} -> 11978 \std{197} | Hurt |
| Add Exploitation Penalty to cost-guided SCENT (ablation) | SCENT (C) · sEH SMALL, reward threshold 7.2 | modes: 11978 \std{197} -> 14631 \std{206} | Helped |
| Add Dynamic Library to cost-guided SCENT (ablation) | SCENT (C) · sEH SMALL | modes > 8.0: 478 \std{11} -> 596 \std{19} | Helped |
| Add Decomposability Guidance to cost-guided SCENT (ablation) | SCENT (C) · sEH MEDIUM | scaffolds > 8.0: 52340 \std{4303} -> 52607 \std{1352} | No clear effect |
| Set decomposability guidance temperature alpha_D to 2 instead of 5 (ablation) | SCENT (C+D+P) · sEH MEDIUM | modes > 8.0: 16373 ± 1827 -> 20023 ± 1484 | Helped |
| Set decomposability guidance temperature alpha_D to 10 instead of 5 (ablation) | SCENT (C+D+P) · sEH MEDIUM | modes > 8.0: 16373 ± 1827 -> 20444 ± 2055 | Helped |
| Set synthesis cost guidance temperature alpha_S to 10 instead of 5 (ablation) | SCENT (C+D+P) · sEH MEDIUM | synthesis cost: 1163 ± 81 -> 898 ± 42 | Helped |
| Set dynamic library size L to 200 instead of 400 (ablation) | SCENT (C+D+P) · sEH MEDIUM | modes > 8.0: 16373 ± 1827 -> 19700 ± 1919 | Helped |
| Set exploitation penalty initial gamma_0 to 0.5 instead of 1.0 (ablation) | SCENT (C+D+P) · sEH MEDIUM | modes > 8.0: 16373 ± 1827 -> 20690 ± 1512 | Helped |
Surprising findings
- Synthesis Cost Guidance improved mode discovery as well as cost, which the authors initially found counterintuitive.
- RxnFlow and SynFlowNet perform far below RGFN and SCENT in most settings under the unified benchmark, and SynFlowNet could not match its reported 7.2-threshold results.
Limitations
- Synthesis cost model is a simplified first-order heuristic omitting solvents, purification, and conditions; yields and prices are approximate.
- Performance varies across biological targets, and the number of reaction templates scaling was not assessed.
- No toxicity or ADMET consideration and no wet-lab validation.
Experimental setup
Datasets: Enamine REAL building blocks (64k MEDIUM, 128k LARGE subsets) curated SMALL fragment set SynFlowNet reaction templates
Benchmarks: sEH proxy GSK3beta proxy JNK3 proxy
Metrics: modes (ECFP6 Tanimoto < 0.5) above threshold unique Bemis-Murcko scaffolds above threshold average reward synthesis cost of high-reward paths AiZynthFinder success rate SA score
Baselines: RGFN SynFlowNet RxnFlow FGFN FGFN (SA)
Builds on: RGFN trajectory balance Guided Trajectory Balance SynFlowNet ActionPiece
Closest papers by meaning
- SynFlowNet: Design of Diverse and Novel Molecules with Synthesis Constraints (ICLR 2025 · similarity 0.90)
- RGFN: Synthesizable Molecular Generation Using GFlowNets (NeurIPS 2024 · similarity 0.90)
- Generative Flows on Synthetic Pathway for Drug Design (ICLR 2025 · similarity 0.89)
- Pretraining Generative Flow Networks with Inexpensive Rewards for Molecular Graph Generation (ICML 2025 · similarity 0.86)
- Generative Flow Networks for Lead Optimization in Drug Design (Student Abstract) (AAAI 2025 · similarity 0.86)
- Compositional Flows for 3D Molecule and Synthesis Pathway Co-design (ICML 2025 · similarity 0.86)
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