Pub Date : 2025-12-01DOI: 10.1186/s13321-025-01121-1
Amelia Villegas-Morcillo, Gijs J Admiraal, Marcel J T Reinders, Jana M Weber
Advancing protein design is crucial for breakthroughs in medicine and biotechnology. Traditional approaches for protein sequence representation often rely solely on the 20 canonical amino acids, limiting the representation of non-canonical amino acids and residues that undergo post-translational modifications. This work explores discrete diffusion models for generating novel protein sequences using the all-atom chemical representation SELFIES. By encoding the atomic composition of each amino acid in the protein, this approach expands the design possibilities beyond standard sequence representations. Using a modified ByteNet architecture within the discrete diffusion D3PM framework, we evaluate the impact of this all-atom representation on protein quality, diversity, and novelty, compared to conventional amino acid-based models. To this end, we develop a comprehensive assessment pipeline to determine whether generated SELFIES sequences translate into valid proteins containing both canonical and non-canonical amino acids. Additionally, we examine the influence of two noise schedules within the diffusion process-uniform (random replacement of tokens) and absorbing (progressive masking)-on generation performance. While models trained on the all-atom representation struggle to consistently generate fully valid proteins, the successfully generated proteins show improved novelty and diversity compared to their amino acid-based model counterparts. Furthermore, the all-atom representation achieves structural foldability results comparable to those of amino acid-based models. Lastly, our results highlight the absorbing noise schedule as the most effective for both representations. Data and code are available at https://github.com/Intelligent-molecular-systems/All-Atom-Protein-Sequence-Generation.
{"title":"All-atom protein sequence design using discrete diffusion models.","authors":"Amelia Villegas-Morcillo, Gijs J Admiraal, Marcel J T Reinders, Jana M Weber","doi":"10.1186/s13321-025-01121-1","DOIUrl":"https://doi.org/10.1186/s13321-025-01121-1","url":null,"abstract":"<p><p>Advancing protein design is crucial for breakthroughs in medicine and biotechnology. Traditional approaches for protein sequence representation often rely solely on the 20 canonical amino acids, limiting the representation of non-canonical amino acids and residues that undergo post-translational modifications. This work explores discrete diffusion models for generating novel protein sequences using the all-atom chemical representation SELFIES. By encoding the atomic composition of each amino acid in the protein, this approach expands the design possibilities beyond standard sequence representations. Using a modified ByteNet architecture within the discrete diffusion D3PM framework, we evaluate the impact of this all-atom representation on protein quality, diversity, and novelty, compared to conventional amino acid-based models. To this end, we develop a comprehensive assessment pipeline to determine whether generated SELFIES sequences translate into valid proteins containing both canonical and non-canonical amino acids. Additionally, we examine the influence of two noise schedules within the diffusion process-uniform (random replacement of tokens) and absorbing (progressive masking)-on generation performance. While models trained on the all-atom representation struggle to consistently generate fully valid proteins, the successfully generated proteins show improved novelty and diversity compared to their amino acid-based model counterparts. Furthermore, the all-atom representation achieves structural foldability results comparable to those of amino acid-based models. Lastly, our results highlight the absorbing noise schedule as the most effective for both representations. Data and code are available at https://github.com/Intelligent-molecular-systems/All-Atom-Protein-Sequence-Generation.</p>","PeriodicalId":617,"journal":{"name":"Journal of Cheminformatics","volume":" ","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145652885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-01DOI: 10.1186/s13321-025-01114-0
Bruno Macedo, Inês Ribeiro Vaz, Tiago Taveira Gomes
<p><p>Generative artificial intelligence has the potential to open new vast chemical search spaces, yet existing reinforcement-guided generative adversarial networks (GANs) struggle to produce non-fragmented and property-oriented molecules at scale without compromising other properties. To overcome these limitations, we present Policy-Optimised Wasserstein GAN (POWGAN), a graph-based generator that incorporates a dynamically scaled reward into adversarial training. The scaling factor increases when progress stalls, keeping gradients informative while steadily steering the generator towards user-defined objectives. When POWGAN replaces the loss function in a previous MedGAN architecture, using graph connectivity (non-fragmentation) as the target property, attains 1.00 fully connected quinoline-like molecules, compared to previous 0.62, while maintaining novelty (0.93) and uniqueness (0.95). The resulting model R-MedGAN produces > 12,000 novel quinoline-like, a significant increase over its predecessor under identical experimental conditions. Chemical space visualizations demonstrate that these molecules populate regions not present in the training dataset or MedGAN, confirming genuine scaffold innovation. By achieving a new architecture capable of orienting generative process towards a reward, our study also showed this strategy is capable of progressing towards druglikeness properties. Synthetic Accessibility Scores (SAS) measured by Erlth algorithm between 1 and 6, and lipophilicity measured as LogP between 1.35 and 1.80, both increased the proportion from 8 to 65% and 17% to 45%, respectively, compared to baseline. Our study shows R-MedGAN architecture, incorporating POWGAN loss, is also generalizable for models trained with different molecular scaffolds other than quinoline originally tested in MedGAN (R-MedGAN-QNL). For indole (R-MedGAN-IND) and imidazole (R-MedGAN-IMZ) datasets, connectivity increased from 0.38 and 0.50 up to 1.00 during training. This study provides evidence that an adaptive reward-scaling policy in a Wasserstein GAN can simultaneously guide the generative training towards a reward by enhancing molecular connectivity, expand generative throughput, preserve diversity, and improve drug-likeness properties. By eliminating the limitation trade-off between property optimisation and sample diversity, POWGAN and its R-MedGAN implementation advance the state of the art in molecule-generating GANs and deploys a robust, scalable platform for high-throughput, goal-directed chemical exploration in early-stage drug discovery. These findings underscore the effectiveness of adaptive reinforcement-driven strategies in generative adversarial networks oriented by rewards for molecular discovery. SCIENTIFIC CONTRIBUTION: In this work we introduce POWGAN, a policy-optimized Wasserstein GAN that uses adaptive reward scaling to improve goal-directed molecule generation. Integrated into MedGAN (R-MedGAN), it increases the number of valid, connect
{"title":"Novel molecule design with POWGAN, a policy-optimized Wasserstein generative adversarial network.","authors":"Bruno Macedo, Inês Ribeiro Vaz, Tiago Taveira Gomes","doi":"10.1186/s13321-025-01114-0","DOIUrl":"https://doi.org/10.1186/s13321-025-01114-0","url":null,"abstract":"<p><p>Generative artificial intelligence has the potential to open new vast chemical search spaces, yet existing reinforcement-guided generative adversarial networks (GANs) struggle to produce non-fragmented and property-oriented molecules at scale without compromising other properties. To overcome these limitations, we present Policy-Optimised Wasserstein GAN (POWGAN), a graph-based generator that incorporates a dynamically scaled reward into adversarial training. The scaling factor increases when progress stalls, keeping gradients informative while steadily steering the generator towards user-defined objectives. When POWGAN replaces the loss function in a previous MedGAN architecture, using graph connectivity (non-fragmentation) as the target property, attains 1.00 fully connected quinoline-like molecules, compared to previous 0.62, while maintaining novelty (0.93) and uniqueness (0.95). The resulting model R-MedGAN produces > 12,000 novel quinoline-like, a significant increase over its predecessor under identical experimental conditions. Chemical space visualizations demonstrate that these molecules populate regions not present in the training dataset or MedGAN, confirming genuine scaffold innovation. By achieving a new architecture capable of orienting generative process towards a reward, our study also showed this strategy is capable of progressing towards druglikeness properties. Synthetic Accessibility Scores (SAS) measured by Erlth algorithm between 1 and 6, and lipophilicity measured as LogP between 1.35 and 1.80, both increased the proportion from 8 to 65% and 17% to 45%, respectively, compared to baseline. Our study shows R-MedGAN architecture, incorporating POWGAN loss, is also generalizable for models trained with different molecular scaffolds other than quinoline originally tested in MedGAN (R-MedGAN-QNL). For indole (R-MedGAN-IND) and imidazole (R-MedGAN-IMZ) datasets, connectivity increased from 0.38 and 0.50 up to 1.00 during training. This study provides evidence that an adaptive reward-scaling policy in a Wasserstein GAN can simultaneously guide the generative training towards a reward by enhancing molecular connectivity, expand generative throughput, preserve diversity, and improve drug-likeness properties. By eliminating the limitation trade-off between property optimisation and sample diversity, POWGAN and its R-MedGAN implementation advance the state of the art in molecule-generating GANs and deploys a robust, scalable platform for high-throughput, goal-directed chemical exploration in early-stage drug discovery. These findings underscore the effectiveness of adaptive reinforcement-driven strategies in generative adversarial networks oriented by rewards for molecular discovery. SCIENTIFIC CONTRIBUTION: In this work we introduce POWGAN, a policy-optimized Wasserstein GAN that uses adaptive reward scaling to improve goal-directed molecule generation. Integrated into MedGAN (R-MedGAN), it increases the number of valid, connect","PeriodicalId":617,"journal":{"name":"Journal of Cheminformatics","volume":" ","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145652913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bioactive peptides are an important class of natural products with great functional versatility. Chemical modifications can improve their pharmacology, yet their structural diversity presents unique challenges for computational modeling. Furthermore, data for standard peptides (composed of the 20 canonical amino acids) is more abundant than for modified ones. Thus, we set out to identify whether predictive models fitted to standard data are reliable when applied to modified peptides. To do this, we first considered two critical aspects of the modeling problem, namely, choice of similarity function for guiding dataset partitioning and choice of molecular representation. Similarity-based dataset partitioning is an evaluation technique that divides the dataset into train and test subsets, such that the molecules in the test set are different from those used to fit the model.
{"title":"How to build machine learning models able to extrapolate from standard to modified peptides.","authors":"Raúl Fernández-Díaz, Rodrigo Ochoa, Thanh Lam Hoang, Vanessa Lopez, Denis C Shields","doi":"10.1186/s13321-025-01115-z","DOIUrl":"https://doi.org/10.1186/s13321-025-01115-z","url":null,"abstract":"<p><p>Bioactive peptides are an important class of natural products with great functional versatility. Chemical modifications can improve their pharmacology, yet their structural diversity presents unique challenges for computational modeling. Furthermore, data for standard peptides (composed of the 20 canonical amino acids) is more abundant than for modified ones. Thus, we set out to identify whether predictive models fitted to standard data are reliable when applied to modified peptides. To do this, we first considered two critical aspects of the modeling problem, namely, choice of similarity function for guiding dataset partitioning and choice of molecular representation. Similarity-based dataset partitioning is an evaluation technique that divides the dataset into train and test subsets, such that the molecules in the test set are different from those used to fit the model.</p>","PeriodicalId":617,"journal":{"name":"Journal of Cheminformatics","volume":" ","pages":""},"PeriodicalIF":5.7,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145626959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nipah Virus (NiV) came into limelight due to an outbreak in Kerala, India. NiV infection can cause severe respiratory and neurological problems with fatality rate of 40–70%. It is a public health concern and has the potential to become a global pandemic. Lack of treatment has forced the containment methods to be restricted to isolation and surveillance. WHO’s ‘R&D Blueprint list of priority diseases’ (2018) indicates that there is an urgent need for accelerated research & development for addressing NiV. In the quest for druglike NiV inhibitors (NVIs) a thorough literature search followed by systematic data curation was conducted. Rigorous data analysis was done with curated NVIs for prioritising curated compounds. Our efforts led to the creation of Nipah Virus Inhibitor Knowledgebase (NVIK), a well-curated structured knowledgebase of 220 NVIs with 142 unique small molecule inhibitors. The reported IC50/EC50 values for some of these inhibitors are in the nanomolar range—as low as 0.47 nM. Of 142 unique small-molecule inhibitors, 124 (87.32%) compounds cleared the PAINS filter. The clustering analysis identified more than 90% of the NVIs as singletons signifying their diverse structural features. This diverse chemical space can be utilized in numerous ways to develop druglike anti-nipah molecules. Further, we prioritised top 10 NVIs, based on robustness of assays, physicochemical properties and their toxicity profiles. All the NVIs related information including their structures, physicochemical properties, similarity analysis with FDA approved drugs and other chemical libraries along with predicted ADMET profiles are freely accessible at https://datascience.imtech.res.in/anshu/nipah/. The NVIK has the provision to submit new inhibitors as and when reported by the community for further enhancement of the NVIs landscape.
Scientific contribution
The NVIK is a dedicated resource for NiV drug discovery containing manually curated NVIs. The NVIs are structurally mapped with known chemical space to identify their structural diversity and recommend strategies for chemical library expansion. Also, in NVIK a combined evidence-based strategy is used to prioritise these inhibitors.