Synthesizable Molecular Generation via Soft-constrained GFlowNets with Rich Chemical Priors

Fuente: arXiv
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Autores principales: Kim, Hyeonah, Kim, Minsu, Roget, Celine, Biton, Dionessa, Vaillancourt, Louis, Brun, Yves V., Bengio, Yoshua, Hernandez-Garcia, Alex
Formato: Preprint
Publicado: 2026
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author Kim, Hyeonah
Kim, Minsu
Roget, Celine
Biton, Dionessa
Vaillancourt, Louis
Brun, Yves V.
Bengio, Yoshua
Hernandez-Garcia, Alex
author_facet Kim, Hyeonah
Kim, Minsu
Roget, Celine
Biton, Dionessa
Vaillancourt, Louis
Brun, Yves V.
Bengio, Yoshua
Hernandez-Garcia, Alex
contents The application of generative models for experimental drug discovery campaigns is severely limited by the difficulty of designing molecules de novo that can be synthesized in practice. Previous works have leveraged Generative Flow Networks (GFlowNets) to impose hard synthesizability constraints through the design of state and action spaces based on predefined reaction templates and building blocks. Despite the promising prospects of this approach, it currently lacks flexibility and scalability. As an alternative, we propose S3-GFN, which generates synthesizable SMILES molecules via simple soft regularization of a sequence-based GFlowNet. Our approach leverages rich molecular priors learned from large-scale SMILES corpora to steer molecular generation towards high-reward, synthesizable chemical spaces. The model induces constraints through off-policy replay training with a contrastive learning signal based on separate buffers of synthesizable and unsynthesizable samples. Our experiments show that S3-GFN learns to generate synthesizable molecules ($\geq 95\%$) with higher rewards in diverse tasks.
format Preprint
id arxiv_https___arxiv_org_abs_2602_04119
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Synthesizable Molecular Generation via Soft-constrained GFlowNets with Rich Chemical Priors
Kim, Hyeonah
Kim, Minsu
Roget, Celine
Biton, Dionessa
Vaillancourt, Louis
Brun, Yves V.
Bengio, Yoshua
Hernandez-Garcia, Alex
Machine Learning
Quantitative Methods
The application of generative models for experimental drug discovery campaigns is severely limited by the difficulty of designing molecules de novo that can be synthesized in practice. Previous works have leveraged Generative Flow Networks (GFlowNets) to impose hard synthesizability constraints through the design of state and action spaces based on predefined reaction templates and building blocks. Despite the promising prospects of this approach, it currently lacks flexibility and scalability. As an alternative, we propose S3-GFN, which generates synthesizable SMILES molecules via simple soft regularization of a sequence-based GFlowNet. Our approach leverages rich molecular priors learned from large-scale SMILES corpora to steer molecular generation towards high-reward, synthesizable chemical spaces. The model induces constraints through off-policy replay training with a contrastive learning signal based on separate buffers of synthesizable and unsynthesizable samples. Our experiments show that S3-GFN learns to generate synthesizable molecules ($\geq 95\%$) with higher rewards in diverse tasks.
title Synthesizable Molecular Generation via Soft-constrained GFlowNets with Rich Chemical Priors
topic Machine Learning
Quantitative Methods
url https://arxiv.org/abs/2602.04119