Targeted protein degradation: advances in drug discovery and clinical practice

Review

Ramar Vanajothi | 1. Microbiology, Biochemistry and Immunology, Morehouse School of Medicine, 720, Westview Drive SW, 30310, Atlanta, United States Proteolysis-targeting chimeras (PROTACs) represent a transformative paradigm in drug discovery, fundamentally altering how we approach protein-targeted therapeutics by harnessing the ubiquitin-proteasome system for selective protein degradation. This comprehensive review examines the evolution of PROTAC technology from its conceptual origins in 2001 to its current clinical validation, with over 30 molecules in various stages of clinical development as of 2024. We explore the mechanistic foundations of PROTAC action, including the catalytic mode of protein degradation that distinguishes event-driven from occupancy-driven pharmacology, and examine the structural design principles governing heterobifunctional architecture, linker optimization, and E3 ligase recruitment strategies. The review analyzes current therapeutic applications across oncology, autoimmune diseases, and neurodegenerative disorders, highlighting the clinical success of compounds like ARV-471 and ARV110 in Phase III trials. Critical challenges including physicochemical property optimization, resistance mechanisms, and bioavailability limitations are addressed alongside emerging solutions through computational design, artificial intelligence integration, and next-generation platforms including conditional degraders, nano-PROTACs, and expanded E3 ligase recruitment. Recent advances in molecular glue degraders, which represent 66% of FDA-approved degraders, and the development of precision medicine approaches through biomarker-guided therapy are also examined. The review concludes with an assessment of future directions, including E3 ligase repertoire expansion beyond the current focus on CRBN and VHL, targeting of previously undruggable proteins, and the integration of PROTAC technology with combination therapies and precision medicine strategies.

1. Introduction The concept of targeted protein degradation has emerged as one of the most significant paradigms shifts in modern drug discovery, offering unprecedented opportunities to eliminate disease-causing proteins through precise manipulation of cellular degradation machinery (He et al. 2025; Yim et al. 2024). At the forefront of this revolution are proteolysis-targeting chimeras (PROTACs), heterobifunctional molecules that have transformed the traditional approach from protein inhibition to complete protein elimination (Fan et al. 2025; Zhong et al. 2024). PROTACs represent a fundamental departure from occupancy-driven pharmacology, where drugs must continuously occupy their target to maintain therapeutic effect, to event-driven pharmacology, where a catalytic mechanism enables sustained protein degradation with transient drug exposure (Faryal et al. 2026; Liu et al. 2022). Owing to this catalytic mechanistic feature, PROTACs could overcome the several limitations of small molecule inhibitors, specifically, the molecules which require deep binding pockets and high target occupancy and have the poor ability to address the non-enzymatic protein function (Martin-Acosta and Xiao 2021; Nalawansha and Crews 2020). Craig Crews and colleagues in 2001, developed a technology to demonstrate the proof-of-concept for inducing degradation of target protein using chimeric molecules (Yao et al. 2022; Zou et al. 2019). Since then, the progress of PROTACs has shown exponential growth in both academic and clinical studies (Bekes et al. 2022; Li et al. 2022b). The first clinical trials with PROTAC began in 2019, owing to the exponential growth as of 2024, there are 30 PROTAC that were identified and used in various stages of clinical trials, for instance, ARV-110 and ARV-471 were in Phase III trials (Hakem et al. 2025; Xi et al. 2022). Current clinical studies reported that the therapeutic potential of PROTACs with minimal toxicity in limited dose in phase I trials for leading compounds dose range from 420-700 mg (Kubryn et al. 2025; Wang et al. 2024b). Both androgen and estrogen receptor degrader ARV110 and ARV-471 shows significant success in metastatic castration-resistant prostate and breast cancer respectively and has been validated in clinical trials (Hamilton et al. 2025; Ma and Zhou 2025). The significance of PROTAC technology significantly extends in several applications beyond their therapeutic approach, in the field of chemical biology (Cai et al. 2025; Liu et al. 2026). Journal of Medico Informatics ©Aayvu Publications Private Limited

It has been used for target validation, exploration of known undruggable proteins, and functional protein studies and have opened a new path for developing the effective drug molecules (Crews 2010; Xie et al. 2023). PROTAC has the unique ability to reach the target protein and leads to their degradation with spatial and temporal control, hence understanding the protein function and disease mechanisms is very crucial (Paiva and Crews 2019; Qi et al. 2021). The current review emphasizes the role of PROTAC technology in chemical biology and drug discovery, and how PROTAC bridges the gap between these domains. Also, we explore the basic mechanistic action of PROTAC, required strategies to design the effective molecules to target protein degradation in both research and clinical aspects (Zhao et al. 2022). Recent advance studies including artificial intelligence computational applications and their integration in PROTAC design are also discussed, alongside the next generation platforms, current challenges and opportunities that define the future of transformative technology is also focused on this context (Park and Jeon 2025).

2. Mechanisms of Action 2.1. The Ubiquitin-Proteasome System Protein degradation is significantly influenced by ubiquitin-proteosome system (UPS) hence, it may act as primary control mechanism. In addition, it also maintains the cellular homeostasis by removing the misfolded, surplus and damaged proteins (Jia et al. 2025; Kandel et al. 2024). This complex mechanism offers the basic information on which PROTAC approach has effectively operates and making deep insights of Received on Revised on Accepted on Published Online Review Model No. of Reviewers Edited by Vol and Issue Page No Plagiarism Level Correspondence Contact Author

2025-10-23 2025-12-20 2025-12-21 2026-04-28 Single-Blind Review Two Dr Chandrabose Selvaraj 02 (02) 14-22 11% and 00% (AI) Dr. R. Vanajothi Key Words: PROTAC Protein degradation E3 ligase E3 ubiquitination Molecules Healthcare Innovation DOI: 10.64659/jomi/215914

This article is licensed Running Title: PROTAC Inhibitors for Protein Degradation Vol: 02; Issue 02 (April – June 2026) 14 ISSN: 3108-2696 (Online) Abstract

UPS mechanisms are highly crucial for developing effective degrader. UPS system has highly activated enzymatic cascade mechanism; there are three major classes of enzymes such as E1 activating enzymes, which initiates the process by binding with ATP-dependent activation of ubiquitin via strong high-energy thioester bond (Melvin et al. 2013). This activates ubiquitin transferred to another class of enzyme E2 conjugating enzymes via trans-thiolation (Stewart et al. 2016). Finally, E3 ubiquitin ligase enzyme enhances the transfer of ubiquitin from E2 to lysine residues on target proteins and producing the polyubiquitin chain which act as degradation signals (Figure 1). Approximately, 600 E3 ligase enzymes were found in human, hence it representing as a largest and most diverse component in the UPS mechanism. This most diversity also being one of the challenges for developing effective PROTAC. These enzymes offer few unique properties like substrate specificity which helpful for determining which protein is target for degradation under specific conditions, besides, it also provides the opportunity to make to design therapeutically effective protein degrader (Wang et al. 2025a).

2.3. Catalytic Mode of Action The catalytic mechanism of PROTACS offers the number of advantages on the traditional inhibitors. Initially the event-driven nature of protein degradation that transient drug exposure which leads to constant effects as protein resynthesis is essential to restore their target levels. This feature offers the lower dosing frequencies and effectively diminished the side effects. Second, the catalytic mechanism enables sub-stoichiometric dose, where the concentration of PROTAC is very low, however it achieves the effective degradation (Pettersson and Crews 2019). This pharmacological opportunity is helping to targeting the valuable proteins or achieving the systemic drug exposure even in lower dose. This nature offers an additional layer of selectivity, even it binds with multiple proteins degradation those targets can form ternary complexes with E3 ligase. Recent studies on the mechanism have also reported that PROTACs effectively overcome resistance mechanisms associated with traditional inhibitors such as target protein overexpression and mutation that can reduce binding of drug molecules (Lai and Crews 2017).

3. Structural Design Principles 3.1. Heterobifunctional Architecture

2.2. PROTAC Mechanism of Action Owing to their binding nature PROTACs function as molecular bridges, it binds with their target proteins at the same time it also links the E3 ubiquitin ligase by which it bridges the two proteins and forms a ternary complex. this activated binding enables the E3 ligases to transfer ubiquitin molecules to the target proteins and leads the proteasomal degradation (Ebadi et al. 2025; Li and Crews 2022). The formation of ternary complex is crucial for determining the efficacy of PROTAC, because this complex sufficiently stable to allow several ubiquitin transfers and maintaining their spatial orientation for optimal ubiquitination (Dale et al. 2021; Kudo et al. 2025). The degradation mechanism involves several steps, including the binding of PROTAC with protein of interest or E3 ligases, then formation of binary and ternary complex via recruitment of other component and ubiquitination of target protein, proteasomal degradation, finally recycling of PROTAC (Konstantinidou et al. 2019; Osman et al. 2025). All these steps have the potential points of optimization that should be considered in developing degrader (Sincere et al. 2023; Wang et al. 2020). Journal of Medico Informatics ©Aayvu Publications Private Limited

3.2. Linker Design and Optimization Linker molecule is another crucial component of PROTAC; however, it is underappreciated component in the process of drug design. This linker acts as bridges between protein of interest and E3 ligase while preserving the binding affinity of these two ligand molecules and enhances the formation of ternary complex. this linker molecules and its optimization highly balancing the several parameters including, flexibility, composition, binding points and length (Troup et al. 2020). The length of the linker optimization initially starts with longer and flexible linkers that gradually shortened to finding the optimal spacing for ternary complex. the typical length of the linker depends on the specific protein-protein interaction geometry that are essential for ubiquitination and can vary dramatically between the different PROTAC pairs (Han 2020). Computational modelling and structural analysis are recently applied to design the linker and predict the optimal geometries. The chemical composition of these linkers also highly influences the PROTAC properties like permeability, solubility and metabolic stability (Abeje et al. 2025). For instance, the polyethylene glycol (PEG) provides the excellent solubility in water, enhanced flexibility, but may compromise cell permeability (Christoforou et al. 2025). Another linker, alkyl chains offer the enhanced membrane permeability, but the solubility is reduced. Hybrid linkers that incorporating the flexibility and rigid elements that offers the optimal balance of properties. Recently, the developing of Running Title: PROTAC Inhibitors for Protein Degradation

Figure1: Schematic representation of PROTAC-12–mediated targeted protein degradation. PROTAC-12 is a heterobifunctional small molecule composed of a ligand for the protein of interest (POI) linked to an E3 ubiquitin ligase recruiter through an optimized linker. Upon simultaneous binding to the POI and E3 ligase, PROTAC-12 induces ternary complex formation, bringing the target protein into close proximity with the ubiquitination machinery, including the E2 ubiquitin-conjugating enzyme. This interaction promotes transfer of ubiquitin (Ub) molecules to the POI, resulting in polyubiquitination. The polyubiquitinated target is subsequently recognized and degraded by the 26S proteasome, while PROTAC-12 is released and can participate in additional degradation cycles.

Basically, the PROTAC composed of three essential components such as a ligand which bind the protein of interest, and ligand for E3 ubiquitin ligase and a linker molecule that connect these two ligand elements. This heterobifunctional design of PROTAC offers the simultaneous engagement of two major protein, which creating an artificial proteinprotein interaction that would not happen naturally (Bricelj et al. 2021). The ligand component that binds with target proteins often refers to warhead which can be derived from either known inhibitors, novel chemical compounds or natural ligands. The key requirements are very critical for binding and selectivity of the target protein, though it has less stringent than the traditional inhibitors (Kim et al. 2025). This flexibility offers the opportunity to repurposing of weak binders or failed drug candidates as PROTACs. The component of E3 ligase recruits the cellular degradation machinery to the vicinity of target protein. Currently used E3 ligase effectively targets cereblon (CRBN), mouse double minute 2 (MDM2), von-Hippel-Lindau (VHL) and inhibitors of apoptosis proteins (IAPs). The presence of E3 ligase significantly influenced the impact of PROTAC efficiency, and selectivity (Diehl and Ciulli 2022).

3.3. E3 Ligase Recruitment Strategies The selection of appropriate E3 ligases is a critical step in the design the effective PROTACs. Currently, the PROTAC designing highly relies on limited number of E3 ligase ligands with CRBN and VHL ligands that are highly dominating the clinical development. This concentration is essential for effective resistance mechanisms and need for E3 ligase repertories. For example, the CRBN-targeting PROTACs significantly used immunomodulatory drugs (IMiDs) like lenalidomide, thalidomide as E3 ligands, which offers the compact size, and well-characterized binding properties and synthetic accessibility. However, the expression of CRBN varies in several tissue and cell types, potentially limiting the therapeutic window of these PROTACs (Lee et al. 2022). In case of VHLtargeting PROTACs performed ligands based on hydroxyprolinecontaining peptides or their optimized small molecule mimetics. Typically, the VHL ligands results as larger PROTAC and offers the advantage in protein expression pattern and substrate compatibility. The designing of more compact VHL ligands is emerging the E3 ligases that recruitment strategies involved the development of ligases such as RNF114, DCAF11, and DCAF15. These efforts expand the druggable E3 ligase spaces and offer the effective and alternative option for PROTAC development (Diehl and Ciulli 2022).

3.4. Ternary Complex Formation and Stability Ternary complex formation is the key determinant of PROTAC efficiency; hence the formation of stable and productive complex is crucial in this process. Mainly, this complex involves the thermodynamics and kinetic consideration that are not studied by individual binding interactions. The binding sites and formation of the ternary complex where it thermodynamically favours the individual binary complex also essential for effective degradation (Bai et al. 2021). The interaction of POI and E3 ligases components is important for PROTAC ternary complexes are revealed by structural analysis. These interactions are essential for providing the efficient binding energy and specificity to the ternary complex. the concept “Positive cooperativity” is the situation where the ternary complex is significantly enhanced via favourable protein-protein interactions which leads the more degradation (Scott et al. 2024). Conversely, the negative cooperativity occurs when the geometric constraints of the ternary complex and resulting the diminished degradation. The advanced computational approach has been employed to predict the geometries of ternary complex, thought it also have the significant limitation in modelling these complex multi-protein systems (Mostofian et al. 2023).

4. Computational and AI Approaches 4.1. Computational Design Frameworks Owing to the complexity of PROTAC development leads the utilization of advanced computational approaches. In the traditional drug design approach, single protein targets are mainly focused and are insufficient for multi-protein system of PROTAC pharmacology (Kubryn et al. 2025). Development of PROTAC via computational approaches typically involves the number of steps such as molecular docking to find the binding site and interactions and molecular dynamics simulation to assess the stability of the complex, and free energy calculation to estimate the binding affinities (Tunjic et al. 2023). These computational approaches should be optimized to handle the limitation of PROTAC system including the formation of ternary complex and the nature of binding. The crystal structure of PROTAC ternary complex were employed in structure based- design applications to guide the rational design efforts (Danishuddin et al. 2023). These structures offer the critical Journal of Medico Informatics ©Aayvu Publications Private Limited

understanding on protein-protein interactions that stabilize the formation of complexes and inform the linker optimization strategies. Though, there is limited number of ternary complexes is one of the significant disadvantages. Homology modelling and docking applications have been used to evaluate the geometries of PROTAC in absence of experimental structures (Hong et al. 2025; Rui et al. 2023).

4.2. Machine Learning Applications In the PROTAC development, recent approaches like machine learning have been emerged as efficient tools for design the optimization, which offering the potential to identify the pattern in complex structures-activity relationships that are very difficult to distinguish via traditional approaches. These applications can incorporate the diverse data including the sequence, chemical structures and experimental degradation data. Another AI model deep learning approach also recently employed in the prediction of PROTAC degradation activity based on the chemical structure and target information (Danishuddin et al. 2023). These models offer the prediction accuracy of 70-80% in some cases and offers the valuable methods for virtual screening and lead optimization. Though, the size limitation of training datasets remains a significant limitation for model design. Application of reinforcement learning in the optimization of PROTAC structure via iterative design cycles (Wang et al. 2025b). These applications can explore the large chemical structure and identify the promising structures and maximize the predicted degradation efficiency while maintaining the favorable pharmaceutical properties. Another approach Graph-based neural network algorithm shows the efficacy in developing the promising PROTAC and represents the molecular structure of PROTAC and interactions with target proteins. This approach offers the opportunity to understand the relationship between complex and chemical structures and biological activity that are not be apparent via traditional approaches (Li et al. 2022a).

4.3. Predictive Modeling and Virtual Screening Predictive modelling is another major computational approach highly applied to predictive models for PROTAC activity; these models are highly focused on the degradation efficiency, pharmaceutical properties and selectivity based on the chemical structures of target protein. The successful models effectively accelerated the development of PROTAC by reducing the requirement for extensive synthesis and testing. The prediction of novel PROTAC structure via virtual screening applications from large chemical libraries (Liu et al. 2025). These methods combine the molecular docking and pharmacophore prediction and machine learning algorithms to predict the effective molecules for experimental validation. The integration of artificial intelligence and experimental applications has been used for the development of active learning applications to optimize the PROTAC structure via iterative cycles of prediction, synthesis and testing (Koirala et al. 2025). These methods effectively diminish the number of compounds that need to optimization the structures. Recent advanced applications like transfer-based neural networks specifically employed for PROTAC generation. These methods predict the novel PROTAC structures with optimized pharmacokinetic properties via reinforcement learning demonstrating the efficacy of AIdriven development approaches (Luo et al. 2025).

5. Therapeutic Applications and Clinical Development 5.1. Oncology Applications In the field of oncology applications, PROTAC is used as promising therapeutic molecules that accounting for most clinical programs. for instance, the ARV-110, is the first PROTAC in the clinical trials that act as estrogen and androgen receptor degraders. It effectively targeting nuclear hormone receptors and used for the treatment of metastatic castrationresistant prostate cancer (Anaya et al. 2025). The compound effectively Running Title: PROTAC Inhibitors for Protein Degradation

linker-free also emerged as a novel approach to overcome the limitation of traditional linker (Zhao et al. 2026).

Table 1. Currently used PROTACs in Clinical Trials for various Diseases Drug Target Status Timeline BGBBTK Phase Phase III launched Apr 2025 16673 III ARV-110 AR Phase II Phase I/II initiated earlier (circa 2019-2021) ARV-766 AR Phase II Phase 1/2 started: September 2, 2021 GT-20029 AR Phase II Phase I (US/China): Dosing first subject Feb 2022 KT-474 IRAK4 Phase II Phase I: Study start Feb 23, 2021 PRT3789 BTK Phase II Phase II start: ~2024–2025 CFT1946 BRAF Phase II Phase II start: 2023–2024 ASP-3082 KRAS G12D Phase I Phase I start: 2024 ABBV-101 BTK Phase I Phase I start: 2022–2023 ARV-393 ER Phase I Phase I-first human start: Q2 2024 BG-60366 EGFR Phase I NA HRS-1358 AR Phase II Phase II start: 2023–2024

5.2. Autoimmune and Inflammatory Diseases In the context of autoimmune and inflammatory disease PROTAC application shows significant progress specially for targets which involved in immune cell activation and signaling. Due to their ability to achieve the target protein provide significant advantages over traditional immunosuppressive approaches. For instance, KT-474 is specifically designed to target IRAK4 and has been used in Phase II clinical trials for the treatment of hidradenitis suppurativa and atopic dermatitis (Galla et al. 2024). The dose dependent studies of this compound reported that it significantly degrades the IRAK4 in peripheral blood mononuclear cell and efficiently reduce the inflammatory cytokines production in patients. The pharmacodynamics studies with PROTAC observed the protein degradation and downstream effects beyond the detectable drug levels. This phenomenon is highly responsible for the catalytic mechanism of action of PROTAC and offers the effective therapeutic advantages including the dose-reducing frequency and sustained efficacy. The expression E3 ligases specifically in tissues may offers the new way for targeting the immune cells same time it protects the other tissues. This tissue-specific feature may reduce the systemic immunosuppression associated with traditional therapies (Agarwal et al. 2025).

5.3. Neurodegenerative Diseases Neurodegenerative disorders are another promising field where the application of PROTAC is significantly employed to eliminate the Journal of Medico Informatics ©Aayvu Publications Private Limited

aggregated or misfolded proteins that are highly responsible for neurodegeneration. Tau-targeting PROTAC is one of the widely accepted one to address the tauopathies including Alzheimer's diseases (Zhou et al. 2025). These PROTACs selectively target the hyperphosphorylated tau species and leads its degradation without affecting the normal tau function which represents a precision approach in the field of neurodegenerative disease management. In context of Huntington’s disease, PROTAC applications are effectively focused on selective degradation of mutant huntingtin proteins, but it is preserving the wildtype function (Yao et al. 2024). This approach offers the wide range of therapeutic benefits and avoiding the toxicity associated with complete removal. However, in neurodegenerative disease, blood-brain barrier is one of the significant challenges while delivering the PROTACs to the central nervous system. Hence, the designing an effective brain-penetrant PROTACs are highly required for careful optimization of other physicochemical properties and may benefit from advanced delivery strategies (Mohapatra et al. 2024).

5.4. Clinical Development Challenges The clinical development of PROTACs has the potential to targets the proteins with selectivity, though it has unique challenges that differ from the traditional small molecule drugs. Owing the complexity of protein degradation, the finding of novel approaches is highly required for biomarker development, dose selection and safety assessment. To address the challenges in PROTAC pharmacology, recent advanced studies such pharmacodynamic modelling has been applied, this models efficiently quantify the target occupancy, deconvolve the degradation from inhibition effects and find the downstream pharmacodynamics responses (Gioiello et al. 2025). Biomarker advancement for PROTAC clinical trials expects techniques to observe target protein levels and degradation kinetics. This may include the development of pharmacodynamic assays, imaging approaches, and circulating biomarkers that can specify real-time information about drug activity Several chemical biology studies used PROTACs as facilitators for functional integration of proteins and revealing the phenotypes. PROTACs demonstrate the direct translation of chemical biology to clinically relevant therapeutics (Liu et al. 2024). Several case studies have been conducted with AR degrader, ER degrader and IRAK4 degrader which demonstrate the mechanistic understanding of PROTAC degradation and formation of ternary complex. Understanding the dual role of PROTACs as functional biology probes and therapeutic candidates, reinforcing the special position at the interface of chemical biology and drug discovery (Nunes et al. 2019).

6. Challenges and Limitations 6.1. Physicochemical Property Challenges Owing to the heterobifunctional feature of PROTAC offers the molecules that violate traditional drug-like criteria, provides the significant limitations for pharmaceutical development (Cai et al. 2025). Typically, the molecular weight of PROTACs ranges from 700-1500 Da, but, over the 500 Da limit suggested by Lipinski’s Rule of Five (An and Fu 2018; Antermite et al. 2023). The increased size of the PROTACs is due to the higher number of hydrogen bond donors and acceptors, which also increase the polar surface area and increase the log P values (Syahputra et al. 2025). The violation of drug-likeness criteria may influence the practical challenge for PROTAC development, and adequate oral bioavailability (Edmondson et al. 2019). Recent studies reported that identification of specific physicochemical parameters which correlates with oral absorption, which is important for limiting the exposed hydrogen bond donors (Hornberger and Araujo 2023; Rej et al. 2024). According to Beyond Rule of Five (bRo5) PROTACs minimize the hydrogen bond donors, molecular flexibility, and achieving appropriate polarity ratios (Egbert et al. 2019; Ermondi et al. 2021). Running Title: PROTAC Inhibitors for Protein Degradation

encouraging efficiency in phase II trials, with specific benefits observed in AR mutated patients that conder resistance to traditional therapies. Hence the success of ARV-110 has been validated the PROTAC application for clinical development. ARV-471 is another sex hormone receptors degrader, specially targets the estrogen receptor which is also applied in phase III trials for ER-positive breast cancer (Table 1). The compound has effectively enhanced the efficiency of PROTAC compared to the conventional estrogen receptor degraders (Snyder et al. 2025). Beyond the hormone receptors, PROTAC has been applied in several oncology targets including transcription factors, protein kinases and epigenetic regulators. Recently developed PROTACs that are used in clinical trials effectively targets the BRD4, BTK and other oncology targets, which demonstrate the wide range of approaches. For successful completion of phase I trial compounds such as CFT8634 (BRD9 degrader) and NX-2127 (BTK degrader) require further validation (Fan et al. 2025).

In order to improve the oral bioavailability of PROTAC, several strategies have been developed, such as modification of structural aspects and enhanced the cellular permeability. The creation of intracellular hydrogen bonds that can reduce the molecular polarity in membrane environments (Abeje et al. 2025). The chameleonic behavior of PROTAC adopting several conformations in aqueous membrane permeability. In addition, prodrug strategies also been applied to improve the PROTAC bioavailability following absorption. This approach has reported the significant increase the oral bioavailability for several PROTACs. Formulation approaches like nanosuspensions, amorphous solid dispersion and lipid-based system have been developed to overcome the solubility limitations and significantly improve the oral absorption of PROTACs with maintain their degradation activity (Zhao and Dekker 2022).

6.3. Resistance Mechanisms Drug resistance mechanisms is one of the challenges that limits the clinical success of PROTACs and limits the therapeutic efficacy. These resistance mechanisms are diverse and may alter the target protein expression, and function of E3 ligase or proteosome activity. Alteration or mutant in target protein significantly reduce the binding affinity of PROTAC by which it enhances the resistance mechanism (Kim et al. 2022). However, the constraint for only temporary binding may make this mechanism less problematic for PROTAC compared to traditional compounds. Additionally, PROTAC can target multiple sites on the same protein which give the opportunity to overcome single-site resistance mutations. E3 ligase downregulation or mutation also have been observed as resistant mechanisms in therapeutic approaches (Bouvier et al. 2024). The development PROTAC that targeting alternative E3 ligases offers the strategies to overcome this resistance. Dysfunction and proteosome inhibition also confer the PROTAC resistance by preventing the degradation of ubiquitinated proteins Even though the PROTACs used as effective targeted therapy, resistance the remains a biologically predictable and challenging rather than a solved problem. But the mechanism of resistance is multifactorial which significantly involving alterations of target protein, cellular adaptation and E3 ligase machinery (Danishuddin et al. 2023).

7. Future Directions and Emerging Technologies 7.1. Next-Generation PROTAC Platforms The next-generation PROTAC Platform application provides the advances in both design strategy and technological advancement. Conditional PROTACs have emerged as emerging technologies to achieve improved selectivity and reduced off-target effectiveness via spatial and temporal control of protein degradation activity. The incorporation of lightactivated PROTAC with photo caging groups used to remove the specific wavelength of light and enabling precise control over degradation timing and location (Wang et al. 2024a). This approach also used to require temporal control of protein. For instance, the hypoxia-responsive PROTAC offers another conditional application, that utilizing linkers are that effectively cleaved under low-oxygen conditions under tumor microenvironments. Cell-penetrating PROTAC incorporates the incorporating peptides to enhance cellular uptake. This approach significantly the enhance the tissue specificity, particularly with limited vascular access or high drug efflux ability, in addition to this it effectively addresses the fundamental challenges (Yim et al. 2024).

7.2. Nano-PROTAC Platforms Nano-PROTAC platforms is the combination of nanotechnology with PROTAC development for processing the enhanced drug delivery, improved pharmacokinetics and diminished toxicity. Nano-PROTAC Journal of Medico Informatics ©Aayvu Publications Private Limited

platform composed of several approaches such as encapsulation, conjugation and development of self-assembling PROTAC nanostructures. Liposomal formulation of PROTAC also increased the bioavailability and distribution while reducing the systemic exposure. This formulation can also offer the sustained reducing systemic exposure (Wu et al. 2025). Also, this formulation releases the PROTAC and may enables enhanced accumulation in target tissues via passive or active targeting mechanisms. Polymeric nanoparticles provide the additional supports for PROTAC delivery with controlled release of kinetic and incorporate targeting ligands for improved selectivity. Another approach, semi-responsive polymers release PROTAC in response to specific cellular condition offers an advanced application to selective drug delivery (Moon et al. 2023).

7.3. Artificial Intelligence and Machine Learning The integration of artificial intelligence and machine learning application significantly transform the PROTAC design and optimization. The integration of advanced applications provides the potential to accelerate the identification novel design strategies, improve success rates that may be apparent via traditional approaches. These models explore wide range of chemical spaces and propose structure that optimize the multiple objectives simultaneously, including degradation activity, selectivity and pharmaceutical properties (Lin et al. 2026). Deep learning application in the production of PROTAC have achieved 70-80% of the accuracy and provides the valuable tools for virtual screening and lead optimization. The continued development of these applications combined with selective datasets are expected to further enhancement of accuracy. Reinforcement learning approaches also been used to optimize the PROTAC structures via iterative design cycles for identifying successful compounds (Han and Sun 2023).

7.4. Expanding E3 Ligase Diversity The selection of E3 ligase in the PROTAC development represents the crucial steps in this field. Around 300 genes were encoded E3 ligases in the human genome, the current focus on handful of well-characterized ligases were significantly used for degradation machinery. Highthroughput screening application has been used for the identification E3 ligase ligands via success rates remain low owing to the challenging nature of the protein-protein interaction (Liu et al. 2023). Heterobifunctional screening libraries is the alternative screening approaches that used DNAencoded libraries to find the E3 ligase binders. Development of tissuespecific E3 ligases strategies offers the enhanced selectivity for PROTAC therapy, this approach effectively controls the differential expression patterns of E3 ligases, where the expression was controlled by external stimuli, represent another approach to achieving the selective protein degradation (Michaelides and Collie 2023).

7.5. Precision Medicine and Biomarker Development The production of efficient precision medicine approaches with application of PROTAC guided biomarkers now beginning to emerge. These approaches mainly involve the finding of patient population most likely to benefit from specific PROTAC treatment based on the biomarker profiles, both genetic and proteomic markers (Rutherford and McManus 2024; Zhang et al. 2025). This biomarker based PROTAC treatment directly quantifies the target protein level and assesses the pathway modulation and downstream response. Hence the development of standardized biomarkers is crucial for effective and successful PROTAC therapy (Kamaraj et al. 2024). Production of personalized PROTAC therapies based on individual patients requires some characteristics features including mutation in target protein or E3 ligase expression profiles. This strategy significantly enhances the therapeutic efficacy while diminishing the toxicity (Mancarella et al. 2023; Wang et al. 2025c). Running Title: PROTAC Inhibitors for Protein Degradation

The application of combination therapy with PROTACs is recently has attention as an important strategic direction for maximizing therapeutic effectiveness while diminishing the drug resistance. These approaches significantly increase the therapeutic values with traditional therapeutics and multiple PROTACs targeting different proteins degradation (Sincere et al. 2023). Mechanistic studies of combination of PROTAC with kinase inhibitors revealed that the combination therapy can overcome the drug resistance and enhanced the therapeutic efficacy. This approach highly addresses the cellular reprograming that occurs during chronic PROTAC exposure, and multitarget PROTAC can simultaneously degrade the multiple proteins and disease networks than single-target proteins (Burke et al. 2022).

8. Conclusion The application of PROTAC for targeted protein degradation has undergone remarkable transformation since 2001. As of now around 30 compounds were in clinical trials due to their conceptual framework and clinically validated therapeutic modality. The present review has emphasised the fundamental mechanism of action and function of PROTAC, the strategic approach to develop the promising target specific molecules. To expand the utility of this approach in current therapeutic approach, the understanding of mechanistic foundations of PROTAC action and exploitation of the UPS is highly required. This information offers the catalytic approach for elimination of misfold proteins that provides the distinct advantages over conventional therapeutic approaches. The event-driven approach of protein degradation offers the sustainable therapeutic efficacy from transient drug exposure and improve the safety profile as well. Hence, the design principles of PROTAC application recently matured significantly with advanced linker chemistry, E3 ligase recruitment strategies. The integration of recent advancement like artificial intelligence and machine learning approaches is highly accelerating the finding of effective and optimal PROTAC structures and diminishing the empirical burden of traditional optimization approaches. Although these successes, there is significant challenges in the development of PROTAC, due to their limitation in physicochemical property, oral bioavailability, and the resistance mechanism. Hence there is need more focus on this to address these challenges via innovative approaches including developing conditional degraders, expansion of E3 ligase diversity, and nano-PROTAC platforms. The future technology integration in PROTAC with next-generation platforms may offers the enhanced selectivity, pharmaceutical properties, and expanded therapeutic applications. The integration specific and unique strategies of medicine and combination therapies may expand the therapeutic potential of targeted protein degradation. In future, the development of PROTAC should have great attention specifically, the three approaches like, E3 ligase, incorporation of AI-driven application and implementing precision medicine and exploring combination therapy application to improve the clinical benefit. PROTACs have been applied in various therapeutic approaches, but still their translation to the clinical phases has several obstacles. The key challenges like optimization of pharmacokinetic and penetration into the tissues, and minimizing off-target degradation is also should be addressed to offer the safe, efficient and widely accessible PROTAC therapeutics. The bridging of two different domains such as chemical biology and drug discovery via PROTAC application also represents a paradigm shift in how we approach protein targets and therapeutic intervention. It creates a new path and opportunities for addressing the undruggable protein while providing the powerful tools for understanding the function of protein in health and disease.

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9. Disclosure Statements 9.1. Author Contribution RV: Data collection, literature review, manuscript preparation along with Conceptualization, supervision, manuscript writing and revision. The corresponding author have read and approved the final manuscript.

9.2. Declaration of Generative AI No generative artificial intelligence (AI) or AI-assisted technologies were used in the preparation, writing, analysis, or interpretation of this review article. The content presented is the original work of the authors, developed through critical analysis and synthesis of the scientific literature.

9.3. Ethics approval (for clinical/animal studies) Not applicable. This review article is based solely on the analysis and synthesis of previously published literature and does not involve any new studies with human participants or animal subjects. Therefore, ethical approval from an institutional review board or ethics committee was not required.

9.4. Informed Consent Statement Not applicable. This review article does not involve human participants, patient data, or identifiable personal information; therefore, informed consent was not required.

9.5. Data Availability Statement No new data were generated or analyzed in this study. All information presented in this review article is derived from previously published literature, and the relevant sources are cited within the manuscript.

9.6. Acknowledgment The authors thankfully acknowledge the Microbiology, Biochemistry and Immunology, Morehouse School of Medicine, 720, Westview Drive SW, 30310, Atlanta, United States for providing necessary facilities for performing this study.

9.7. Funding Statement This research received no external funding. The study was conducted without any financial support from public, commercial, or not-for-profit funding agencies. All resources utilized for this work were provided by the author respective institutions.

9.8. Conflicts of Interest The authors declare that there are no conflicts of interest regarding the publication of this article. The authors have no financial, commercial, or personal relationships that could have influenced the work reported in this manuscript.

9.9. Corresponding Author Contact Information The corresponding author Dr. Ramar Vanajothi can be contacted via email drvanajothi[at]gmail.com. 9.10. Supplementary Information No supplementary material is available for this article.

9.11. ORcID Information Vanajothi 0000-0002-6786-6971 9.12. Handling Editor Information This manuscript was handled and edited by Dr. Chandrabose Selvaraj, Professor, Bioinformatics Division, Department of Marine Biotechnology, AMET University (Academy of Maritime Education and Training) (Deemed to be University), East Coast Road, Kanathur, Chennai, Tamil Nadu – 603112, India. Editor contact email: jomi[at]aayvu.com Running Title: PROTAC Inhibitors for Protein Degradation

Vol: 02; Issue 02 (April – June 2026) 19 7.6. Combination Therapies

Abeje YE, Wieske LHE, Poongavanam V, Maassen S, Atilaw Y, Cromm P, Lehmann L, Erdelyi M, Meibom D, Kihlberg J. (2025), Impact of Linker Composition on VHL PROTAC Cell Permeability, J Med Chem, 68(1):638-657. doi:10.1021/acs.jmedchem.4c02492. PMID: 39693386. Agarwal S, McDonald AA, Campbell V, Chen D, Davis J, Rong H, Mishkin A, Slavin A, Gollerkeri A, Gollob JA. (2025), Pharmacokinetics and Pharmacodynamics of KT-474, a Novel Selective Interleukin-1 ReceptorAssociated Kinase 4 (IRAK4) Degrader, in Healthy Adults, Clin Transl Sci, 18(3):e70181. doi:10.1111/cts.70181. PMID: 40055981. An S, Fu L. (2018), Small-molecule PROTACs: An emerging and promising approach for the development of targeted therapy drugs, EBioMedicine, 36:553-562. doi:10.1016/j.ebiom.2018.09.005. PMID: 30224312. Anaya YA, Barragan M, Bracho RP, Shaham SH, Bandyopadhyay D, George E, Nguyen D, Tripathi MK. (2025), Proteolysis-targeting chimeras in cancer therapy: Targeted protein degradation for next-generation treatment, Cancer, 131(21):e70132. doi:10.1002/cncr.70132. PMID: 41108678. Antermite D, Friis SD, Johansson JR, Putra OD, Ackermann L, Johansson MJ. (2023), Late-stage synthesis of heterobifunctional molecules for PROTAC applications via ruthenium-catalysed C‒H amidation, Nat Commun, 14(1):8222. doi:10.1038/s41467-023-43789-9. PMID: 38086825. Bai N, Miller SA, Andrianov GV, Yates M, Kirubakaran P, Karanicolas J. (2021), Rationalizing PROTAC-Mediated Ternary Complex Formation Using Rosetta, J Chem Inf Model, 61(3):1368-1382. doi:10.1021/acs.jcim.0c01451. PMID: 33625214. Bekes M, Langley DR, Crews CM. (2022), PROTAC targeted protein degraders: the past is prologue, Nat Rev Drug Discov, 21(3):181-200. doi:10.1038/s41573-021-00371-6. PMID: 35042991. Bouvier C, Lawrence R, Cavallo F, Xolalpa W, Jordan A, Hjerpe R, Rodriguez MS. (2024), Breaking Bad Proteins-Discovery Approaches and the Road to Clinic for Degraders, Cells, 13(7) doi:10.3390/cells13070578. PMID: 38607017. Bricelj A, Steinebach C, Kuchta R, Gutschow M, Sosic I. (2021), E3 Ligase Ligands in Successful PROTACs: An Overview of Syntheses and Linker Attachment Points, Front Chem, 9:707317. doi:10.3389/fchem.2021.707317. PMID: 34291038. Burke MR, Smith AR, Zheng G. (2022), Overcoming Cancer Drug Resistance Utilizing PROTAC Technology, Front Cell Dev Biol, 10:872729. doi:10.3389/fcell.2022.872729. PMID: 35547806. Cai J, Chen C, Wang J, Zhang X, Cui Y, Zhu Q, Sun H. (2025), PROTAC: a revolutionary technology propelling small molecule drugs into the next golden age, Front Oncol, 15:1676414. doi:10.3389/fonc.2025.1676414. PMID: 41220927. Christoforou I, Kalatzis A, Siamidi A, Vlachou M, Pispas S, Pippa N. (2025), The Ubiquitous Use of Polyethylene Glycol in Pharmaceutical Design and Development: Technological Aspects and Future Perspectives, Nanomaterials (Basel), 15(23) doi:10.3390/nano15231762. PMID: 41369439. Crews CM. (2010), Targeting the undruggable proteome: the small molecules of my dreams, Chem Biol, 17(6):551-5. doi:10.1016/j.chembiol.2010.05.011. PMID: 20609404. Dale B, Cheng M, Park KS, Kaniskan HU, Xiong Y, Jin J. (2021), Advancing targeted protein degradation for cancer therapy, Nat Rev Cancer, 21(10):638-654. doi:10.1038/s41568-021-00365-x. PMID: 34131295. Danishuddin, Jamal MS, Song KS, Lee KW, Kim JJ, Park YM. (2023), Revolutionizing Drug Targeting Strategies: Integrating Artificial Intelligence and Structure-Based Methods in PROTAC Development, Pharmaceuticals (Basel), 16(12) doi:10.3390/ph16121649. PMID: 38139776. Diehl CJ, Ciulli A. (2022), Discovery of small molecule ligands for the von Hippel-Lindau (VHL) E3 ligase and their use as inhibitors and PROTAC degraders, Chem Soc Rev, 51(19):8216-8257. doi:10.1039/d2cs00387b. PMID: 35983982. Ebadi P, Stratton CM, Olsen SK. (2025), E3 ubiquitin ligases in signaling, disease, and therapeutics, Trends Biochem Sci, 50(11):960-976. doi:10.1016/j.tibs.2025.07.009. PMID: 40940201. Journal of Medico Informatics ©Aayvu Publications Private Limited

Edmondson SD, Yang B, Fallan C. (2019), Proteolysis targeting chimeras (PROTACs) in 'beyond rule-of-five' chemical space: Recent progress and future challenges, Bioorg Med Chem Lett, 29(13):1555-1564. doi:10.1016/j.bmcl.2019.04.030. PMID: 31047748. Egbert M, Whitty A, Keseru GM, Vajda S. (2019), Why Some Targets Benefit from beyond Rule of Five Drugs, J Med Chem, 62(22):10005-10025. doi:10.1021/acs.jmedchem.8b01732. PMID: 31188592. Ermondi G, Garcia-Jimenez D, Caron G. (2021), PROTACs and Building Blocks: The 2D Chemical Space in Very Early Drug Discovery, Molecules, 26(3) doi:10.3390/molecules26030672. PMID: 33525371. Fan G, Chen S, Zhang Q, Yu N, Shen Z, Liu Z, Guo W, Tang Z, Yang J, Liu M. (2025), Proteolysis-Targeting Chimera (PROTAC): Current Applications and Future Directions, MedComm (2020), 6(10):e70401. doi:10.1002/mco2.70401. PMID: 41049269. Faryal B, Ul Abideen Z, Irfan M, Ahmed H, Jalilov F, Abduraximova L, Ashraf GA. (2026), Targeted Protein Degradation in Cancer: PROTACs, New Targets, and Clinical Mechanisms, Biomolecules, 16(2) doi:10.3390/biom16020325. PMID: 41750393. Galla MS, Sharma N, Mishra P, Shankaraiah N. (2024), Recent insights of PROTAC developments in inflammation-mediated and autoimmune targets: a critical review, RSC Med Chem, 15(8):2585-2600. doi:10.1039/d4md00142g. PMID: 39149114. Gioiello L, Di Martino RMC, Pirali T. (2025), Expanding the Scope of PROTACs: Opportunities and Challenges in Topical Delivery, J Med Chem, 68(22):23676-23689. doi:10.1021/acs.jmedchem.5c01911. PMID: 41255358. Hakem F, Abdelwaly A, Alshaman R, Alattar A, Alanazi FE, Zaitone SA, Helal MA. (2025), Recent Advances in the Development of Pro-PROTAC for Selective Protein Degradation, Pharmaceutics, 17(9) doi:10.3390/pharmaceutics17091160. PMID: 41012497. Hamilton EP, Jeselsohn RM, Vahdat LT, Hurvitz SA. (2025), PROteolysis TArgeting Chimera (PROTAC) Estrogen Receptor Degraders for Treatment of Estrogen Receptor-Positive Advanced Breast Cancer, Target Oncol, 20(3):431-444. doi:10.1007/s11523-025-01137-5. PMID: 40327300. Han B. (2020), A suite of mathematical solutions to describe ternary complex formation and their application to targeted protein degradation by heterobifunctional ligands, J Biol Chem, 295(45):15280-15291. doi:10.1074/jbc.RA120.014715. PMID: 32859748. Han X, Sun Y. (2023), PROTACs: A novel strategy for cancer drug discovery and development, MedComm (2020), 4(3):e290. doi:10.1002/mco2.290. PMID: 37261210. He S, Dong G, Sheng C. (2025), Strategies for Precise Modulation of Protein Degradation, Acc Chem Res, 58(8):1236-1248. doi:10.1021/acs.accounts.5c00003. PMID: 40132213. Hong SH, Nguyen T, Ongkingco JF, Nazzaro A, Arora PS. (2025), From Concepts to Inhibitors: A Blueprint for Targeting Protein-Protein Interactions, Chem Rev, 125(14):6819-6869. doi:10.1021/acs.chemrev.5c00046. PMID: 40553022. Hornberger KR, Araujo EMV. (2023), Physicochemical Property Determinants of Oral Absorption for PROTAC Protein Degraders, J Med Chem, 66(12):8281-8287. doi:10.1021/acs.jmedchem.3c00740. PMID: 37279490. Jia S, Li Q, Rui X, Qin W, Zhang W, Dou J, Zhang X. (2025), The ubiquitinproteasome system in Alzheimer's disease: mechanism of action and current status of treatment, Front Aging Neurosci, 17:1730206. doi:10.3389/fnagi.2025.1730206. PMID: 41415890. Kamaraj R, Ghosh S, Das S, Sen S, Kumar P, Majumdar M, Dasgupta R, Mukherjee S, Das S, Ghose I, Pavek P, Raja Karuppiah MP, Chuturgoon AA, Anand K. (2024), Targeted Protein Degradation (TPD) for Immunotherapy: Understanding Proteolysis Targeting Chimera-Driven Ubiquitin-Proteasome Interactions, Bioconjug Chem, 35(8):1089-1115. doi:10.1021/acs.bioconjchem.4c00253. PMID: 38990186. Kandel R, Jung J, Neal S. (2024), Proteotoxic stress and the ubiquitin proteasome system, Semin Cell Dev Biol, 156:107-120. doi:10.1016/j.semcdb.2023.08.002. PMID: 37734998. Running Title: PROTAC Inhibitors for Protein Degradation

Journal of Medico Informatics ©Aayvu Publications Private Limited

68(14):14129-14136. doi:10.1021/acs.jmedchem.5c01818. PMID: 40702893. Mancarella C, Morrione A, Scotlandi K. (2023), PROTAC-Based Protein Degradation as a Promising Strategy for Targeted Therapy in Sarcomas, Int J Mol Sci, 24(22) doi:10.3390/ijms242216346. PMID: 38003535. Martin-Acosta P, Xiao X. (2021), PROTACs to address the challenges facing small molecule inhibitors, Eur J Med Chem, 210:112993. doi:10.1016/j.ejmech.2020.112993. PMID: 33189436. Melvin AT, Woss GS, Park JH, Waters ML, Allbritton NL. (2013), Measuring activity in the ubiquitin-proteasome system: from large scale discoveries to single cells analysis, Cell Biochem Biophys, 67(1):75-89. doi:10.1007/s12013-013-9621-9. PMID: 23686610. Michaelides IN, Collie GW. (2023), E3 Ligases Meet Their Match: FragmentBased Approaches to Discover New E3 Ligands and to Unravel E3 Biology, J Med Chem, 66(5):3173-3194. doi:10.1021/acs.jmedchem.2c01882. PMID: 36821822. Mohapatra P, Gopikrishnan M, Doss CG, Chandrasekaran N. (2024), How Precise are Nanomedicines in Overcoming the Blood-Brain Barrier? A Comprehensive Review of the Literature, Int J Nanomedicine, 19:24412467. doi:10.2147/IJN.S442520. PMID: 38482521. Moon Y, Jeon SI, Shim MK, Kim K. (2023), Cancer-Specific Delivery of Proteolysis-Targeting Chimeras (PROTACs) and Their Application to Cancer Immunotherapy, Pharmaceutics, 15(2) doi:10.3390/pharmaceutics15020411. PMID: 36839734. Mostofian B, Martin HJ, Razavi A, Patel S, Allen B, Sherman W, Izaguirre JA. (2023), Targeted Protein Degradation: Advances, Challenges, and Prospects for Computational Methods, J Chem Inf Model, 63(17):54085432. doi:10.1021/acs.jcim.3c00603. PMID: 37602861. Nalawansha DA, Crews CM. (2020), PROTACs: An Emerging Therapeutic Modality in Precision Medicine, Cell Chem Biol, 27(8):998-1014. doi:10.1016/j.chembiol.2020.07.020. PMID: 32795419. Nunes J, McGonagle GA, Eden J, Kiritharan G, Touzet M, Lewell X, Emery J, Eidam H, Harling JD, Anderson NA. (2019), Targeting IRAK4 for Degradation with PROTACs, ACS Med Chem Lett, 10(7):1081-1085. doi:10.1021/acsmedchemlett.9b00219. PMID: 31312412. Osman J, Thompson PE, Jorg M, Scanlon MJ. (2025), Methods to accelerate PROTAC drug discovery, Biochem J, 482(13):921-37. doi:10.1042/BCJ20243018. PMID: 40570202. Paiva SL, Crews CM. (2019), Targeted protein degradation: elements of PROTAC design, Curr Opin Chem Biol, 50:111-119. doi:10.1016/j.cbpa.2019.02.022. PMID: 31004963. Park KS, Jeon M. (2025), Advancing PROTAC Discovery Through Artificial Intelligence: Opportunities, Challenges, and Future Directions, Pharmaceuticals (Basel), 18(12) doi:10.3390/ph18121793. PMID: 41471282. Pettersson M, Crews CM. (2019), PROteolysis TArgeting Chimeras (PROTACs) - Past, present and future, Drug Discov Today Technol, 31:1527. doi:10.1016/j.ddtec.2019.01.002. PMID: 31200855. Qi SM, Dong J, Xu ZY, Cheng XD, Zhang WD, Qin JJ. (2021), PROTAC: An Effective Targeted Protein Degradation Strategy for Cancer Therapy, Front Pharmacol, 12:692574. doi:10.3389/fphar.2021.692574. PMID: 34025443. Rej RK, Allu SR, Roy J, Acharyya RK, Kiran INC, Addepalli Y, Dhamodharan V. (2024), Orally Bioavailable Proteolysis-Targeting Chimeras: An Innovative Approach in the Golden Era of Discovering Small-Molecule Cancer Drugs, Pharmaceuticals (Basel), 17(4) doi:10.3390/ph17040494. PMID: 38675453. Rui H, Ashton KS, Min J, Wang C, Potts PR. (2023), Protein-protein interfaces in molecular glue-induced ternary complexes: classification, characterization, and prediction, RSC Chem Biol, 4(3):192-215. doi:10.1039/d2cb00207h. PMID: 36908699. Rutherford KA, McManus KJ. (2024), PROTACs: Current and Future Potential as a Precision Medicine Strategy to Combat Cancer, Mol Cancer Ther, 23(4):454-463. doi:10.1158/1535-7163.MCT-23-0747. PMID: 38205881. Scott DC, Dharuman S, Griffith E, Chai SC, Ronnebaum J, King MT, Tangallapally R, Lee C, Gee CT, Yang L, Li Y, Loudon VC, Lee HW, Ochoada J, Miller DJ, Jayasinghe T, Paulo JA, Elledge SJ, Harper JW, Chen Running Title: PROTAC Inhibitors for Protein Degradation

Kim G, Grams RJ, Hsu KL. (2025), Advancing Covalent Ligand and Drug Discovery beyond Cysteine, Chem Rev, 125(14):6653-6684. doi:10.1021/acs.chemrev.5c00001. PMID: 40404146. Kim H, Park J, Kim JM. (2022), Targeted Protein Degradation to Overcome Resistance in Cancer Therapies: PROTAC and N-Degron Pathway, Biomedicines, 10(9) doi:10.3390/biomedicines10092100. PMID: 36140200. Koirala M, Yan L, Mohamed Z, DiPaola M. (2025), AI-Integrated QSAR Modeling for Enhanced Drug Discovery: From Classical Approaches to Deep Learning and Structural Insight, Int J Mol Sci, 26(19) doi:10.3390/ijms26199384. PMID: 41096653. Konstantinidou M, Li J, Zhang B, Wang Z, Shaabani S, Ter Brake F, Essa K, Domling A. (2019), PROTACs- a game-changing technology, Expert Opin Drug Discov, 14(12):1255-1268. doi:10.1080/17460441.2019.1659242. PMID: 31538491. Kubryn N, Fijalkowski L, Nowaczyk J, Jamil A, Nowaczyk A. (2025), PROTAC Technology as a New Tool for Modern Pharmacotherapy, Molecules, 30(10) doi:10.3390/molecules30102123. PMID: 40430296. Kudo G, Hirao T, Harada R, Shigeta Y, Hirokawa T, Yoshino R. (2025), Construction of PROTAC-Mediated Ternary Complex Structure Distribution Profiles Using Extensive Conformational Search, J Chem Inf Model, 65(13):6939-6948. doi:10.1021/acs.jcim.5c00102. PMID: 40550492. Lai AC, Crews CM. (2017), Induced protein degradation: an emerging drug discovery paradigm, Nat Rev Drug Discov, 16(2):101-114. doi:10.1038/nrd.2016.211. PMID: 27885283. Lee J, Lee Y, Jung YM, Park JH, Yoo HS, Park J. (2022), Discovery of E3 Ligase Ligands for Target Protein Degradation, Molecules, 27(19) doi:10.3390/molecules27196515. PMID: 36235052. Li F, Hu Q, Zhang X, Sun R, Liu Z, Wu S, Tian S, Ma X, Dai Z, Yang X, Gao S, Bai F. (2022a), DeepPROTACs is a deep learning-based targeted degradation predictor for PROTACs, Nat Commun, 13(1):7133. doi:10.1038/s41467-022-34807-3. PMID: 36414666. Li K, Crews CM. (2022), PROTACs: past, present and future, Chem Soc Rev, 51(12):5214-5236. doi:10.1039/d2cs00193d. PMID: 35671157. Li X, Pu W, Zheng Q, Ai M, Chen S, Peng Y. (2022b), Proteolysis-targeting chimeras (PROTACs) in cancer therapy, Mol Cancer, 21(1):99. doi:10.1186/s12943-021-01434-3. PMID: 35410300. Lin CT, Shiau YP, Lin CC. (2026), Machine learning in targeted protein degradation drug design: a technical review of PROTACs and molecular glues, Drug Discov Today, 31(1):104563. doi:10.1016/j.drudis.2025.104563. PMID: 41318024. Liu J, Roy MJ, Isbel L, Li F. (2025), Accurate PROTAC-targeted degradation prediction with DegradeMaster, Bioinformatics, 41(Supplement_1):i342i351. doi:10.1093/bioinformatics/btaf191. PMID: 40662822. Liu Y, Liang J, Zhu R, Yang Y, Wang Y, Wei W, Li H, Chen L. (2024), Application of PROTACs in Target Identification and Target Validation, Acta Mater Med, 3(1):72-87. doi:10.15212/amm-2024-0010. PMID: 39373008. Liu Y, Yang J, Wang T, Luo M, Chen Y, Chen C, Ronai Z, Zhou Y, Ruppin E, Han L. (2023), Expanding PROTACtable genome universe of E3 ligases, Nat Commun, 14(1):6509. doi:10.1038/s41467-023-42233-2. PMID: 37845222. Liu Y, Zhang X, Chen X, Zhang F. (2026), Proteolysis-targeting chimera (PROTAC) nanomedicines toward cancer treatment: From synthesis to therapeutic delivery, Biomaterials, 325:123621. doi:10.1016/j.biomaterials.2025.123621. PMID: 40819599. Liu Z, Hu M, Yang Y, Du C, Zhou H, Liu C, Chen Y, Fan L, Ma H, Gong Y, Xie Y. (2022), An overview of PROTACs: a promising drug discovery paradigm, Mol Biomed, 3(1):46. doi:10.1186/s43556-022-00112-0. PMID: 36536188. Luo H, Tian Y, Abdullah R, Zhang B, Ma Y, Zhang G. (2025), Advancing Design Strategy of PROTACs for Cancer Therapy, MedComm (2020), 6(7):e70258. doi:10.1002/mco2.70258. PMID: 40567248. Ma Z, Zhou J. (2025), NDA Submission of Vepdegestrant (ARV-471) to U.S. FDA: The Beginning of a New Era of PROTAC Degraders, J Med Chem,

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Running Title: PROTAC Inhibitors for Protein Degradation Vol: 02; Issue 02 (April – June 2026) 22 Journal of Medico Informatics ©Aayvu Publications Private Limited

Yim J, Park J, Kim G, Lee HH, Chung JS, Jo A, Koh M, Park J. (2024), Conditional PROTAC: Recent Strategies for Modulating Targeted Protein Degradation, ChemMedChem, 19(22):e202400326. doi:10.1002/cmdc.202400326. PMID: 38993102. Zhang G, Yan S, Liu Y, Du Z, Min Q, Qin S. (2025), PROTACs coupled with oligonucleotides to tackle the undruggable, Bioanalysis, 17(4):261-276. doi:10.1080/17576180.2025.2459528. PMID: 39895280. Zhao C, Dekker FJ. (2022), Novel Design Strategies to Enhance the Efficiency of Proteolysis Targeting Chimeras, ACS Pharmacol Transl Sci, 5(9):710723. doi:10.1021/acsptsci.2c00089. PMID: 36110375. Zhao L, Zhao J, Zhong K, Tong A, Jia D. (2022), Targeted protein degradation: mechanisms, strategies and application, Signal Transduct Target Ther, 7(1):113. doi:10.1038/s41392-022-00966-4. PMID: 35379777. Zhao M, Li B, Gao Y, Zhang R, Ahmattohti S, Li J, Shi X. (2026), Linker Engineering in Stapled Peptides for Enhanced Membrane Permeability: Screening and Optimization Strategies, Int J Mol Sci, 27(7) doi:10.3390/ijms27073077. PMID: 41977264. Zhong G, Chang X, Xie W, Zhou X. (2024), Targeted protein degradation: advances in drug discovery and clinical practice, Signal Transduct Target Ther, 9(1):308. doi:10.1038/s41392-024-02004-x. PMID: 39500878. Zhou Q, Wang W, Deng C. (2025), Advancements in Proteolysis Targeting Chimeras for Targeted Therapeutic Strategies in Alzheimer's Disease, Mol Neurobiol, 62(8):9686-9709. doi:10.1007/s12035-025-04838-0. PMID: 40133753. Zou Y, Ma D, Wang Y. (2019), The PROTAC technology in drug development, Cell Biochem Funct, 37(1):21-30. doi:10.1002/cbf.3369. PMID: 30604499.

T, Lee RE, Schulman BA. (2024), Principles of paralog-specific targeted protein degradation engaging the C-degron E3 KLHDC2, Nat Commun, 15(1):8829. doi:10.1038/s41467-024-52966-3. PMID: 39396041. Sincere NI, Anand K, Ashique S, Yang J, You C. (2023), PROTACs: Emerging Targeted Protein Degradation Approaches for Advanced Druggable Strategies, Molecules, 28(10) doi:10.3390/molecules28104014. PMID: 37241755. Snyder LB, Neklesa TK, Willard RR, Gordon DA, Pizzano J, Vitale N, Robling K, Dorso MA, Moghrabi W, Landrette S, Gedrich R, Lee SH, Taylor ICA, Houston JG. (2025), Preclinical Evaluation of Bavdegalutamide (ARV110), a Novel PROteolysis TArgeting Chimera Androgen Receptor Degrader, Mol Cancer Ther, 24(4):511-522. doi:10.1158/1535-7163.MCT23-0655. PMID: 39670468. Stewart MD, Ritterhoff T, Klevit RE, Brzovic PS. (2016), E2 enzymes: more than just middle men, Cell Res, 26(4):423-40. doi:10.1038/cr.2016.35. PMID: 27002219. Syahputra EW, Lee H, Cho H, Park HJ, Park KS, Hwang D. (2025), PROTAC Delivery Strategies for Overcoming Physicochemical Properties and Physiological Barriers in Targeted Protein Degradation, Pharmaceutics, 17(4) doi:10.3390/pharmaceutics17040501. PMID: 40284496. Troup RI, Fallan C, Baud MGJ. (2020), Current strategies for the design of PROTAC linkers: a critical review, Explor Target Antitumor Ther, 1(5):273312. doi:10.37349/etat.2020.00018. PMID: 36046485. Tunjic TM, Weber N, Brunsteiner M. (2023), Computer aided drug design in the development of proteolysis targeting chimeras, Comput Struct Biotechnol J, 21:2058-2067. doi:10.1016/j.csbj.2023.02.042. PMID: 36968015. Wang C, Zhang Y, Chen W, Wu Y, Xing D. (2024a), New-generation advanced PROTACs as potential therapeutic agents in cancer therapy, Mol Cancer, 23(1):110. doi:10.1186/s12943-024-02024-9. PMID: 38773495. Wang H, Peng J, Li H, Lan Y, Guo J, Qiu Q, Huang X. (2025a), E3 Ubiquitin Ligases: Structures, Biological Functions, Diseases, and Therapy, MedComm (2020), 6(12):e70528. doi:10.1002/mco2.70528. PMID: 41362701. Wang Q, Sun B, Yi Y, Velkov T, Shen J, Dai C, Jiang H. (2025b), Progress of AIDriven Drug-Target Interaction Prediction and Lead Optimization, Int J Mol Sci, 26(20) doi:10.3390/ijms262010037. PMID: 41155330. Wang S, He F, Tian C, Sun A. (2024b), From PROTAC to TPD: Advances and Opportunities in Targeted Protein Degradation, Pharmaceuticals (Basel), 17(1) doi:10.3390/ph17010100. PMID: 38256933. Wang Y, Jiang X, Feng F, Liu W, Sun H. (2020), Degradation of proteins by PROTACs and other strategies, Acta Pharm Sin B, 10(2):207-238. doi:10.1016/j.apsb.2019.08.001. PMID: 32082969. Wang Z, Zhang D, Inuzuka H, Wei W. (2025c), PROTAC technology for prostate cancer treatment, Acta Mater Med, 4(1):99-121. doi:10.15212/amm-2024-0075. PMID: 40832004. Wu X, Shu Y, Zheng Y, Zhang P, Cong H, Zou Y, Cai H, Zha Z. (2025), Recent Advances in Nanomedicine: Cutting-Edge Research on Nano-PROTAC Delivery Systems for Cancer Therapy, Pharmaceutics, 17(8) doi:10.3390/pharmaceutics17081037. PMID: 40871058. Xi JY, Zhang RY, Chen K, Yao L, Li MQ, Jiang R, Li XY, Fan L. (2022), Advances and perspectives of proteolysis targeting chimeras (PROTACs) in drug discovery, Bioorg Chem, 125:105848. doi:10.1016/j.bioorg.2022.105848. PMID: 35533582. Xie X, Yu T, Li X, Zhang N, Foster LJ, Peng C, Huang W, He G. (2023), Recent advances in targeting the "undruggable" proteins: from drug discovery to clinical trials, Signal Transduct Target Ther, 8(1):335. doi:10.1038/s41392023-01589-z. PMID: 37669923. Yao D, Li T, Yu L, Hu M, He Y, Zhang R, Wu J, Li S, Kuang W, Yang X, Liu G, Xie Y. (2024), Selective degradation of hyperphosphorylated tau by proteolysis-targeting chimeras ameliorates cognitive function in Alzheimer's disease model mice, Front Pharmacol, 15:1351792. doi:10.3389/fphar.2024.1351792. PMID: 38919259. Yao T, Xiao H, Wang H, Xu X. (2022), Recent Advances in PROTACs for Drug Targeted Protein Research, Int J Mol Sci, 23(18) doi:10.3390/ijms231810328. PMID: 36142231.