Targeted Protein Degradation: Clinical Advances in the Field of Oncology

Targeting KRAS-G12C in lung cancer: The emerging role of PROTACs in overcoming resistance

In lung cancer, KRAS mutations, especially the G12C, favor aggressive tumor growth and resistance to standard therapies. Although first-generation inhibitors of KRAS G12C, such as sotorasib and adagrasib, are highly effective in early-phase studies, resistance invariably develops under selective inhibition pressure and rarely leads to sustained long-term treatment benefits. As a novel approach to targeting KRAS mutations in lung cancer, PROTAC (Proteolysis Targeting Chimera) technology is explored in this review. The PROTACs take advantage of the cell's ubiquitin-proteasome system to selectively degrade KRAS proteins, overcoming the dilemma of a lack of traditional binding sites and the means of resistance. We review recent progress with KRAS-specific PROTACs and their mechanisms, clinical application, and effectiveness at targeting primary KRAS oncogenes and secondary drivers and signaling pathways contributing to therapeutic resistance. Also, the synergies between PROTACs and immunotherapies or chemotherapies are further amplified. This review also underscores PROTAC technology's promise to advance precision medicine by providing durable treatment options for KRAS-driven lung cancers. It addresses future directions for optimizing PROTAC efficacy, bioavailability, and patient-specific applications.

Revolutionizing lung cancer treatment: Introducing PROTAC therapy as a novel paradigm in targeted therapeutics

This comprehensive review explores the transformative potential of PROTAC (Proteolysis-Targeting Chimeras) therapy as a groundbreaking approach in the landscape of lung cancer treatment. The introduction provides a succinct overview of current challenges in lung cancer treatment, emphasizing the significance of targeted therapies. Focusing on PROTAC therapy, the article elucidates its mechanism of action, comparing it with traditional targeted therapies and highlighting the key components and design principles of PROTAC molecules. In the context of lung cancer, the review meticulously summarizes preclinical evidence, emphasizing efficacy and specificity gleaned from studies evaluating PROTAC therapy. It delves into the implications of this preclinical data, discussing potential advantages over existing targeted therapies. An update on ongoing clinical trials involving PROTAC therapy for lung cancer offers a snapshot of the current progress, with a summary of key outcomes and advancements in early-phase trials. The mechanistic insights into PROTAC therapy's impact on lung cancer cells are explored, alongside a discussion on potential biomarkers for patient stratification and response prediction. The influence of tumor heterogeneity on PROTAC therapy outcomes is also addressed. Safety and tolerability assessments, encompassing preclinical and clinical studies, are comprehensively evaluated, including a comparative analysis with traditional targeted therapies and strategies to mitigate side effects. Looking forward, the article discusses the future perspectives of PROTAC therapy in lung cancer treatment and addresses ongoing challenges, providing a nuanced exploration of potential combination therapies and synergistic approaches. In conclusion, the review summarizes key findings and insights, underscoring the tremendous potential of PROTAC therapy as a promising and innovative avenue in pursuing more effective lung cancer treatments.

Unleashing the Power of Covalent Drugs for Protein Degradation

Targeted protein degradation (TPD) has emerged as a significant therapeutic approach for a variety of diseases, including cancer. Advances in TPD techniques, such as molecular glue (MG) and lysosome-dependent strategies, have shown substantial progress since the inception of the first PROTAC in 2001. The PROTAC methodology represents the forefront of TPD technology, with ongoing evaluation in more than 20 clinical trials for the treatment of diverse medical conditions. Two prominent PROTACs, ARV-471 and ARV-110, are currently undergoing phase III and II clinical trials, respectively. Traditional PROTACs are encountering obstacles such as limited binding affinity and a restricted range of E3 ligase ligands for facilitating the protein of interest (POI) degradation. Covalent medicines offer the potential to enhance PROTAC efficacy by enabling the targeting of previously considered "undruggable" shallow binding sites. Strategic alterations allow PROTAC to establish covalent connections with particular target proteins, including Kirsten rat sarcoma viral oncogene homolog (KRAS), Bruton's tyrosine kinase (BTK), epidermal growth factor receptor (EGFR), as well as E3 ligases such as DDB1 and CUL4 associated factor 16 (DCAF16) and Kelch-like ECH-associated protein 1 (Keap1). The concept of covalent degradation has also been utilized in various new forms of degraders, including covalent molecule glue (MG), in-cell click-formed proteolysis targeting chimera (CLIPTAC), HaloPROTAC, lysosome-targeting chimera (LYTAC) and GlueTAC. This review focuses on recent advancements in covalent degraders beyond covalent PROTACs and examines obstacles and future directions pertinent to this field.

Immunoconjugates as an Efficient Platform for Drug Delivery: A Resurgence of Natural Products in Targeted Antitumor Therapy

The present review provides a detailed and comprehensive discussion on antibody-drug conjugates (ADCs) as an evolving new modality in the current therapeutic landscape of malignant diseases. The principle concepts of targeted delivery of highly toxic agents forsaken as stand-alone drugs are examined in detail, along with the biochemical and technological tools for their successful implementation. An extensive analysis of ADCs' major components is conducted in parallel with their function and impact on the stability, efficacy, safety, and resistance profiles of the immunoconjugates. The scope of the article covers the major classes of currently validated natural compounds used as payloads, with an emphasis on their structural and mechanistic features, natural origin, and distribution. Future perspectives in ADCs' design are thoroughly explored, addressing their inherent or emerging challenges and limitations. The survey also provides a comprehensive overview of the molecular rationale for active tumor targeting of ADC-based platforms, exploring the cellular biology and clinical relevance of validated tumor markers used as a "homing" mechanism in both hematological and solid tumor malignancies.

Development of natural product-based targeted protein degraders as anticancer agents

Targeted protein degradation (TPD) has emerged as a powerful approach for eliminating cancer-causing proteins through an "event-driven" pharmacological mode. Proteolysis-targeting chimeras (PROTACs), molecular glues (MGs), and hydrophobic tagging (HyTing) have evolved into three major classes of TPD technologies. Natural products (NPs) are a primary source of anticancer drugs and have played important roles in the development of TPD technology. NPs potentially expand the toolbox of TPD by providing a variety of E3 ligase ligands, protein of interest (POI) warheads, and hydrophobic tags (HyTs). As a promising direction in the TPD field, NP-based degraders have shown great potential for anticancer therapy. In this review, we summarize recent advances in the development of NP-based degraders (PROTACs, MGs and HyTing) with anticancer applications. Moreover, we put forward the challenges while presenting potential opportunities for the advancement of future targeted protein degraders derived from NPs.

Targeted protein degradation: current molecular targets, localization, and strategies

Targeted protein degradation (TPD) has revolutionized drug discovery by selectively eliminating specific proteins within and outside the cellular context. Over the past two decades, TPD has expanded its focus beyond well-established targets, exploring diverse proteins beyond cancer-related ones. This evolution extends the potential of TPD to various diseases. Notably, TPD can target proteins at demanding locations, such as the extracellular matrix (ECM) and cellular membranes, presenting both opportunities and challenges for future research. In this review, we comprehensively examine the exciting opportunities in the burgeoning field of TPD, highlighting different targets, their cellular environment, and innovative strategies for modern drug discovery.

Targeted nanoliposomes of oncogenic protein degraders: Significant inhibition of tumor in lung-cancer bearing mice

With 60 % of non-small cell lung cancer (NSCLC) expressing epidermal growth factor receptor (EGFR), it has been explored as an important therapeutic target for lung tumors. However, even the well-established EGFR inhibitors tend to promptly develop resistance over time. Moreover, strategies that could impede resistance development and be advantageous for both EGFR-Tyrosine kinase inhibitor (TKI)-sensitive and mutant NSCLC patients are constrained. Based on the critical relationship between EGFR, c-MYC, and Kirsten rat sarcoma virus (K-Ras), simultaneous degradation of EGFR and Bromodomain-containing protein 4 (BRD4) using "Proteolysis Targeting Chimeras (PROTACs)" could be a promising approach. PROTACs are emerging class of oncoprotein degraders but very challanging to deliver in vivo. Compared to individual IC50s, strong synergism was observed at 1:1 ratio of BPRO and EPRO in NSCLC cell lines with diverse mutation. Significant inhibition of cell growth with higher cellular apoptosis was observed in 2D and 3D-based cell assays in nanomolar concentrations. EGFR activation assay revealed 47.60 % EGFR non-expressing cells confirming EGFR-degrading potential of EPRO. A lung cancer specific nanoliposomal formulation of EGFR and BRD4-degrading PROTACs (EPRO and BPRO) was prepared and characetrized. Successful encapsulation of the two highly lipophilic molecules was achieved in EGFR-targeting nanoliposomal carriers (T-BEPRO) using a modified hydration technique. T-BEPRO revealed a particle size of 109.22 ± 0.266 nm with enhanced cellular uptake and activity. Remarkably, parenterally delivered T-BEPRO in tumor-bearing mice showed a substantially higher % tumor growth inhibition (TGI) of 77.6 % with long-lasting tumor inhibitory potential as opposed to individual drugs.

Inhibitors to degraders: Changing paradigm in drug discovery

The chemical understanding of biological processes provides not only a deeper insight but also a solution to abnormal biological functioning. Protein degradation, a natural biological process for debris removal in the cell, has been studied for years. The recent finding that natural degradation pathways can be utilized for therapeutic purposes is a paradigm shift in the drug discovery approach. Methods such as Proteolysis Targeting Chimera (PROTAC), lysosomal targeting chimera, hydrophobic tagging, AUtophagy TArgeting Chimera, AUTOphagy TArgeting Chimera and several other variants of these methods have made a considerable impact on the way of drug design. Few selected examples testify that a huge wave of change is on the way. The drug design based on the targeted protein degradation is a powerful tool in our arsenal. More molecules will be invented that will uncover the hidden secrets of biological functioning and provide enduring solutions to several unmet medical needs.

Targeted Protein Degraders- The Druggability Perspective

Targeted Protein degraders (TPDs) show promise in harnessing cellular machinery to eliminate disease-causing proteins, even those previously considered undruggable. Especially if protein turnover is low, targeted protein removal bestows lasting therapeutic effect over typical inhibition. The demonstrated safety and efficacy profile of clinical candidates has fueled the surge in the number of potential candidates across different therapeutic areas. As TPDs often do not comply with Lipinski's rule of five, developing novel TPDs and unlocking their full potential requires overcoming solubility, permeability and oral bioavailability challenges. Tailored in-vitro assays are key to precise profiling and optimization, propelling breakthroughs in targeted protein degradation.

Transcription factors in fibroblast plasticity and CAF heterogeneity

In recent years, research focused on the multifaceted landscape and functions of cancer-associated fibroblasts (CAFs) aimed to reveal their heterogeneity and identify commonalities across diverse tumors for more effective therapeutic targeting of pro-tumoral stromal microenvironment. However, a unified functional categorization of CAF subsets remains elusive, posing challenges for the development of targeted CAF therapies in clinical settings.The CAF phenotype arises from a complex interplay of signals within the tumor microenvironment, where transcription factors serve as central mediators of various cellular pathways. Recent advances in single-cell RNA sequencing technology have emphasized the role of transcription factors in the conversion of normal fibroblasts to distinct CAF subtypes across various cancer types.This review provides a comprehensive overview of the specific roles of transcription factor networks in shaping CAF heterogeneity, plasticity, and functionality. Beginning with their influence on fibroblast homeostasis and reprogramming during wound healing and fibrosis, it delves into the emerging insights into transcription factor regulatory networks. Understanding these mechanisms not only enables a more precise characterization of CAF subsets but also sheds light on the early regulatory processes governing CAF heterogeneity and functionality. Ultimately, this knowledge may unveil novel therapeutic targets for cancer treatment, addressing the existing challenges of stromal-targeted therapies.

Revolutionizing Drug Targeting Strategies: Integrating Artificial Intelligence and Structure-Based Methods in PROTAC Development

PROteolysis TArgeting Chimera (PROTAC) is an emerging technology in chemical biology and drug discovery. This technique facilitates the complete removal of the target proteins that are "undruggable" or challenging to target through chemical molecules via the Ubiquitin-Proteasome System (UPS). PROTACs have been widely explored and outperformed not only in cancer but also in other diseases. During the past few decades, several academic institutes and pharma companies have poured more efforts into PROTAC-related technologies, setting the stage for several major degrader trial readouts in clinical phases. Despite their promising results, the formation of robust ternary orientation, off-target activity, poor permeability, and binding affinity are some of the limitations that hinder their development. Recent advancements in computational technologies have facilitated progress in the development of PROTACs. Researchers have been able to utilize these technologies to explore a wider range of E3 ligases and optimize linkers, thereby gaining a better understanding of the effectiveness and safety of PROTACs in clinical settings. In this review, we briefly explore the computational strategies reported to date for the formation of PROTAC components and discuss the key challenges and opportunities for further research in this area.

Target protein degradation by protacs: A budding cancer treatment strategy

Cancer is one of the most common causes of death. So, its lethal effect increases with time. Near about hundreds of cancers are known in humans. Cancer treatment is done to cure or prolonged remission, and shrinkage of the tumor. Cytotoxic agents, biological agents/targeted drugs, hormonal drugs, surgery, radiotherapy/proton therapy, chemotherapy, immunotherapy, and gene therapy are currently used in the treatment of cancer but their cost is high and cause various side effects. Seeing this, some new targeted strategies such as PROTACs are the need of the time. Proteolysis targeting chimera (PROTAC) has become one of the most discussed topics regarding cancer treatment. Few of the PROTAC molecules are in the trial phases. PROTACs have many advantages over other strategies such as modularity, compatibility, sub-stoichiometric activity, acting on undruggable targets, molecular design, and acts on intracellular targets, selectivity and specificity can be recruited for any cancer, versatility, and others. PROTACs are having some unclear questions on their pharmacokinetics, heavy-molecular weight, etc. PROTACs are anticipated to bring about a conversion in current healthcare and will emerge as booming treatments. In this review article we summarize PROTACs, their mechanism of action, uses, advantages, disadvantages, challenges, and future aspects for the successful development of potent PROTACs as a drug strategy.

SOHO State of the Art Updates and Next Questions: Updates on BTK Inhibitors for the Treatment of Chronic Lymphocytic Leukemia

Over the last decade, targeted inhibition of Bruton's tyrosine kinase (BTK) has led to a paradigm shift in the way chronic lymphocytic leukemia (CLL) is managed. BTK inhibitors (BTKi) are broadly classified as covalent BTKI and noncovalent BTKi (cBTKi and ncBTK) Ibrutinib, as the first approved cBTKi, vastly improved outcomes for patients with CLL over prior chemoimmunotherapy regimens. However, long-term use is limited by both intolerance and resistance. The second generation of more selective BTKi were developed to improve tolerability. While these agents have led to an improved safety profile in comparison to Ibrutinib (both acalabrutinib and zanubrutinib), and improved efficacy (zanubrutinib), intolerance occasionally occurs, and resistance remains a challenge. The third generation of BTKi, which noncovalently or reversibly inhibits BTK, has shown promising results in early phase trials and are being evaluated in the phase 3 setting. These drugs could be an effective treatment option in patients with either resistance and intolerance to cBTKi. The most recent development in therapeutic agents targeting BTK is the development of BTK degraders. By removing BTK, as opposed to inhibiting it, these drugs could remain efficacious irrespective of BTK resistance mutations, however clinical data are limited at this time. This review summarizes the evolution and ongoing development of newer BTKi and BTK degraders in the management of CLL, with a focus of future directions in this field, including how emerging clinical data could inform therapeutic sequencing in CLL management.

Genetic manipulation and targeted protein degradation in mammalian systems: practical considerations, tips and tricks for discovery research

Gaining a mechanistic understanding of the molecular pathways underpinning cellular and organismal physiology invariably relies on the perturbation of an experimental system to infer causality. This can be achieved either by genetic manipulation or by pharmacological treatment. Generally, the former approach is applicable to a wider range of targets, is more precise, and can address more nuanced functional aspects. Despite such apparent advantages, genetic manipulation (i.e., knock-down, knock-out, mutation, and tagging) in mammalian systems can be challenging due to problems with delivery, low rates of homologous recombination, and epigenetic silencing. The advent of CRISPR-Cas9 in combination with the development of robust differentiation protocols that can efficiently generate a variety of different cell types in vitro has accelerated our ability to probe gene function in a more physiological setting. Often, the main obstacle in this path of enquiry is to achieve the desired genetic modification. In this short review, we will focus on gene perturbation in mammalian cells and how editing and differentiation of pluripotent stem cells can complement more traditional approaches. Additionally, we introduce novel targeted protein degradation approaches as an alternative to DNA/RNA-based manipulation. Our aim is to present a broad overview of recent approaches and in vitro systems to study mammalian cell biology. Due to space limitations, we limit ourselves to providing the inexperienced reader with a conceptual framework on how to use these tools, and for more in-depth information, we will provide specific references throughout.

Cancer-Specific Delivery of Proteolysis-Targeting Chimeras (PROTACs) and Their Application to Cancer Immunotherapy

Proteolysis-targeting chimeras (PROTACs) are rapidly emerging as a potential therapeutic strategy for cancer therapy by inducing the degradation of tumor-overexpressing oncogenic proteins. They can specifically catalyze the degradation of target oncogenic proteins by recruiting E3 ligases and utilizing the ubiquitin-proteasome pathway. Since their mode of action is universal, irreversible, recyclable, long-lasting, and applicable to 'undruggable' proteins, PROTACs are gradually replacing the role of conventional small molecular inhibitors. Moreover, their application areas are being expanded to cancer immunotherapy as various types of oncogenic proteins that are involved in immunosuppressive tumor microenvironments. However, poor water solubility and low cell permeability considerably restrict the pharmacokinetic (PK) property, which necessitates the use of appropriate delivery systems for cancer immunotherapy. In this review, the general characteristics, developmental status, and PK of PROTACs are first briefly covered. Next, recent studies on the application of various types of passive or active targeting delivery systems for PROTACs are introduced, and their effects on the PK and tumor-targeting ability of PROTACs are described. Finally, recent drug delivery systems of PROTACs for cancer immunotherapy are summarized. The adoption of an adequate delivery system for PROTAC is expected to accelerate the clinical translation of PROTACs, as well as improve its efficacy for cancer therapy.