Discovery and Optimization of 4,5-Diarylisoxazoles as Potent Dual Inhibitors of Pyruvate Dehydrogenase Kinase and Heat Shock Protein 90

Glycolysis, the sweet appetite of the tumor microenvironment

Cancer cells display an altered metabolic phenotype, characterised by increased glycolysis and lactate production, even in the presence of sufficient oxygen - a phenomenon known as the Warburg effect. This metabolic reprogramming is a crucial adaptation that enables cancer cells to meet their elevated energy and biosynthetic demands. Importantly, the tumor microenvironment plays a pivotal role in shaping and sustaining this metabolic shift in cancer cells. This review explores the intricate relationship between the tumor microenvironment and the Warburg effect, highlighting how communication within this niche regulates cancer cell metabolism and impacts tumor progression and therapeutic resistance. We discuss the potential of targeting the Warburg effect as a promising therapeutic strategy, with the aim of disrupting the metabolic advantage of cancer cells and enhancing our understanding of this complex interplay within the tumor microenvironment.

Targeting HSP90 for Cancer Therapy: Current Progress and Emerging Prospects

Heat shock protein 90 (HSP90), a highly conserved member of the heat shock protein family, regulates various proteins and signaling pathways involved in cancer, making it a promising target for cancer therapy. Traditional HSP90 inhibitors have demonstrated significant antitumor potential in preclinical trials, with over 20 compounds advancing to clinical trials and showing promising results. However, the limited clinical efficacy and shared toxicity of these inhibitors restrict their further clinical use. Encouragingly, developing novel inhibitors using conventional medicinal chemistry approaches─such as selective inhibitors, dual inhibitors, protein-protein interaction inhibitors, and proteolysis-targeting chimeras─is expected to address these challenges. Notably, the selective inhibitor TAS-116 has already been successfully marketed. In this Perspective, we summarize the structure, biological functions, and roles of HSP90 in cancer, analyze the clinical status of HSP90 inhibitors, and highlight the latest advancements in novel strategies, offering insights into their future development.

Recent advances in pyruvate dehydrogenase kinase inhibitors: Structures, inhibitory mechanisms and biological activities

Metabolism is reprogrammed in a variety of cancer cells to ensure their rapid proliferation. Cancer cells prefer to utilize glycolysis to produce energy as well as to provide large amounts of precursors for their division. In this process, cancer cells inhibit the activity of pyruvate dehydrogenase complex (PDC) by upregulating the expression of pyruvate dehydrogenase kinases (PDKs). Inhibiting the activity of PDKs in cancer cells can effectively block this metabolic transition in cancer cells, while also activating mitochondrial oxidative metabolism and promoting apoptosis of cancer cells. To this day, the study of PDKs inhibitors has become one of the research hotspots in the field of medicinal chemistry. Novel structures targeting PDKs are constantly being discovered, and some inhibitors have entered the clinical research stage. Here, we reviewed the research progress of PDKs inhibitors in recent years and classified them according to the PDKs binding sites they acted on, aiming to summarize the structural characteristics of inhibitors acting on different binding sites and explore their clinical application value. Finally, the shortcomings of some PDKs inhibitors and the further development direction of PDKs inhibitors are discussed.

Protection against Aβ-induced neuronal damage by KU-32: PDHK1 inhibition as important target

A feature of most neurodegenerative diseases is the presence of "mis-folded proteins" that form aggregates, suggesting suboptimal activity of neuronal molecular chaperones. Heat shock protein 90 (Hsp90) is the master regulator of cell responses to "proteotoxic" stresses. Some Hsp90 modulators activate cascades leading to upregulation of additional chaperones. Novobiocin is a modulator at the C-terminal ATP-binding site of Hsp90. Of several novobiocin analogs synthesized and tested for protection against amyloid beta (Aβ)-induced neuronal death, "KU-32" was the most potent in protecting primary neurons, but did not increase expression of other chaperones believed to help clear misfolded proteins. However, KU-32 reversed Aβ-induced superoxide formation, activated Complex I of the electron transfer chain in mitochondria, and blocked the Aβ-induced inhibition of Complex I in neuroblastoma cells. A mechanism for these effects of KU-32 on mitochondrial metabolism appeared to be the inhibition of pyruvate dehydrogenase kinase (PDHK), both in isolated brain mitochondria and in SH-SY5Y cells. PDHK inhibition by the classic enzyme inhibitor, dichloroacetate, led to neuroprotection from Aβ25-35-induced cell injury similarly to KU-32. Inhibition of PDHK in neurons would lead to activation of the PDH complex, increased acetyl-CoA generation, stimulation of the tricarboxylic acid cycle and Complex I in the electron transfer chain, and enhanced oxidative phosphorylation. A focus of future studies may be on the potential value of PDHK as a target in AD therapy.

Small-molecule dual inhibitors targeting heat shock protein 90 for cancer targeted therapy

Heat shock protein 90, also known as Hsp90, is an extensively preserved molecular chaperone that performs a critical function in organizing various biological pathways and cellular operations. As a potential drug target, Hsp90 is closely linked to cancer. Hsp90 inhibitors are a class of drugs that have been extensively studied in preclinical models and have shown promise in a variety of diseases, especially cancer. However, Hsp90 inhibitors have encountered several challenges in clinical development, such as low efficacy, toxicity, or drug resistance, few Hsp90 small molecule inhibitors have been approved worldwide. Nonetheless, combining Hsp90 inhibitors with other tumor inhibitors, such as HDAC inhibitors, tubulin inhibitors, and Topo II inhibitors, has been shown to have synergistic antitumor effects. Consequently, the development of Hsp90 dual-target inhibitors is an effective strategy in cancer treatment, as it enhances potency while reducing drug resistance. This article provides an overview of Hsp90's domain structure and biological functions, as well as a discussion of the design, discovery, and structure-activity relationships of Hsp90 dual inhibitors, aiming to provide insights into clinical drug research from a medicinal chemistry perspective and discover novel Hsp90 dual inhibitors.

Design and Synthesis of Hsp90 Inhibitors with B-Raf and PDHK1 Multi-Target Activity

The design of multi-target ligands has become an innovative approach for the identification of effective therapeutic treatments against complex diseases, such as cancer. Recent studies have demonstrated that the combined inhibition of Hsp90 and B-Raf provides synergistic effects against several types of cancers. Moreover, it has been reported that PDHK1, which presents an ATP-binding pocket similar to that of Hsp90, plays an important role in tumor initiation, maintenance and progression, participating also to the senescence process induced by B-Raf oncogenic proteins. Based on these premises, the simultaneous inhibition of these targets may provide several benefits for the treatment of cancer. In this work, we set up a design strategy including the assembly and integration of molecular fragments known to be important for binding to the Hsp90, PDHK1 and B-Raf targets, aided by molecular docking for the selection of a set of compounds potentially able to exert Hsp90-B-Raf-PDHK1 multi-target activities. The designed compounds were synthesized and experimentally validated in vitro. According to the in vitro assays, compounds 4 a, 4 d and 4 e potently inhibited Hsp90 and moderately inhibited the PDHK1 kinase. Finally, molecular dynamics simulations were performed to provide further insights into the structural basis of their multi-target activity.

Targeting pyruvate dehydrogenase kinase signaling in the development of effective cancer therapy

Pyruvate is irreversibly decarboxylated to acetyl coenzyme A by mitochondrial pyruvate dehydrogenase complex (PDC). Decarboxylation of pyruvate is considered a crucial step in cell metabolism and energetics. The cancer cells prefer aerobic glycolysis rather than mitochondrial oxidation of pyruvate. This attribute of cancer cells allows them to sustain under indefinite proliferation and growth. Pyruvate dehydrogenase kinases (PDKs) play critical roles in many diseases because they regulate PDC activity. Recent findings suggest an altered metabolism of cancer cells is associated with impaired mitochondrial function due to PDC inhibition. PDKs inhibit the PDC activity via phosphorylation of the E1a subunit and subsequently cause a glycolytic shift. Thus, inhibition of PDK is an attractive strategy in anticancer therapy. This review highlights that PDC/PDK axis could be implicated in cancer's therapeutic management by developing potential small-molecule PDK inhibitors. In recent years, a dramatic increase in the targeting of the PDC/PDK axis for cancer treatment gained an attention from the scientific community. We further discuss breakthrough findings in the PDC-PDK axis. In addition, structural features, functional significance, mechanism of activation, involvement in various human pathologies, and expression of different forms of PDKs (PDK1-4) in different types of cancers are discussed in detail. We further emphasized the gene expression profiling of PDKs in cancer patients to prognosis and therapeutic manifestations. Additionally, inhibition of the PDK/PDC axis by small molecule inhibitors and natural compounds at different clinical evaluation stages has also been discussed comprehensively.

Synthesis, biological evaluation and structure-activity relationship of novel dichloroacetophenones targeting pyruvate dehydrogenase kinases with potent anticancer activity

Pyruvate dehydrogenase kinases (PDKs) are promising therapeutic targets that have received increasing attentions in cancer metabolism. In this paper, we report the synthesis and biological evaluation of a series of novel dichloroacetophenones as potent PDKs inhibitors. Structure-activity relationship analysis enabled us to identify a potent compound 6u, which inhibited PDKs with an EC₅₀ value of 0.09 μM, and reduced various cancer cells proliferation with IC₅₀ values ranging from 1.1 to 3.8 μM, while show weak effect against non-cancerous L02 cell (IC₅₀ > 10 μM). In the A375 xenograft model, 6u displayed an obvious antitumor activity at a dose of 5 mg/kg, but with no negative effect to the mice weight. Molecular docking suggested that 6u formed direct hydrogen bond interactions with Ser75 and Gln61 in PDK1, and meanwhile the aniline skeleton in 6u was sandwiched by the conserved hydrophobic residues Phe78 and Phe65, which contribute to the biochemical activity improvement. Moreover, 6u induced A375 cell apoptosis and cell arrest in G1 phase, and inhibited cancer cell migration. In addition, 6u altered glucose metabolic pathway in A375 cell by decreasing lactate formation and increasing ROS production and OCR consumption, which could serve as a potential modulator to reprogram the glycolysis pathway in cancer cell.

Structural basis for the inhibition of PDK2 by novel ATP- and lipoyl-binding site targeting compounds

Pyruvate dehydrogenase kinase (PDK) controls the activity of pyruvate decarboxylase complex (PDC) by phosphorylating key serine residues on the E1 subunit, which leads to a decreased oxidative phosphorylation in mitochondria. Inhibition of PDK activity by natural/synthetic compounds has been shown to reverse the Warburg effect, a characteristic metabolism in cancer cells. PDK-PDC axis also has been associated with diabetes and heart disease. Therefore, regulation of PDK activity has been considered as a promising strategy to treat related diseases. Here we present the X-ray crystal structure of PDK2 complexed with a recently identified PDK4 inhibitor, compound 8c, which has been predicted to bind at the lipoyl-binding site and interrupt intermolecular interactions with the E2-E3bp subunits of PDC. The co-crystal structure confirmed the specific binding location of compound 8c and revealed the remote conformational change in the ATP-binding pocket. In addition, two novel 4,5-diarylisoxazole derivatives, GM10030 and GM67520, were synthesized and used for structural studies, which target the ATP-binding site of PDK2. These compounds bind to PDK2 with a sub-100nM affinity as determined by isothermal titration calorimetry experiments. Notably, the crystal structure of the PDK2-GM10030 complex displays unprecedented asymmetric conformation of human PDK2 dimer, especially in the ATP-lids and C-terminal tails.

Multi-Targeting Anticancer Agents: Rational Approaches, Synthetic Routes and Structure Activity Relationship

We live in a world with complex diseases such as cancer which cannot be cured with one-compound one-target based therapeutic paradigm. This could be due to the involvement of multiple pathogenic mechanisms. One-compound-various-targets stratagem has become a prevailing research topic in anti-cancer drug discovery. The simultaneous interruption of two or more targets has improved the therapeutic efficacy as compared to the specific targeted based therapy. In this review, six types of dual targeting agents along with some interesting strategies used for their design and synthesis are discussed. Their pharmacology with various types of the molecular interactions within their specific targets has also been described. This assemblage will reveal the recent trends and insights in front of the scientific community working in dual inhibitors and help them in designing the next generation of multi-targeted anti-cancer agents.

High-throughput screening of novel pyruvate dehydrogenase kinases inhibitors and biological evaluation of their in vitro and in vivo antiproliferative activity

Overexpression of pyruvate dehydrogenase kinases (PDKs) has been widely noticed in a variety of human solid tumors, which could be regarded as an attractive therapeutic target for cancer therapy. In this paper, we present an enzymatic screening assay and multiple biological evaluations for the identification of potential PDKs, especially PDK1 inhibitors. We identified 9 potential PDKs inhibitors from the screening of an in-house small molecule library, all of the identified inhibitors reduced pyruvate dehydrogenase (PDH) complex phosphorylation. Among which, 4, 5, and 9 displayed the most potent PDKs inhibitory activities, with EC₅₀ values of 0.34, 1.4, and 1.6 μM in an enzymatic assay, respectively. A kinase inhibition assay suggested that 4, 5, and 9 were pan-isoform PDK inhibitors, but more sensitive to PDK1. Meanwhile, the three compounds inhibited HSP90, with IC₅₀ values of 0.78, 3.58, and 2.70 μM, respectively. The cell viability assay indicated that 4 inhibited all of the tested cancer cells proliferation, with a GC₅₀ value of 2.3 μM against NCIH1975 cell, but has little effect on human normal lung cell BEAS-2B cell. In the NCIH1975 xenograft models, 4 displayed strong antitumor activities at a dose of 10 and 20 mg/kg, but with no negative effect on the mice weight. In addition, 4 decreased the ECAR and lactate formation, increased OCR and ROS level in NCIH1975 cancer cell, which could be used as a promising modulator to reprogram the glucose metabolic pathways in NCIH1975 cancer cells.

Discovery of novel pyruvate dehydrogenase kinases inhibitors by screening of an in-house small molecule library for anti-lung cancer therapeutics

Pyruvate dehydrogenase kinases (PDKs) are widely over-expressed in various human solid cancers, making them attractive therapeutic targets for cancer treatment. Herein, we report the identification of structurally novel PDKs inhibitors by screening of an in-house small molecule library. Biochemical assay indicated that the identified compounds 1-4 inhibited PDK1 activity with EC₅₀ values of 0.50, 1.99, 4.64, and 0.42 µM, respectively. The ITC analysis suggested that the identified compounds 1-4 were pan-isoform PDK inhibitors, which bound to and inhibited the four PDK isoforms. Moreover, 1-4 dose-dependently reduced pyruvate dehydrogenase complex phosphorylation in NCI-H1975 cell. Molecular docking suggested that the most potent compound 4 docked well in the ATP binding pocket of the four PDK isoforms, forming direct hydrogen bond interactions with the conserved amino acids Thr and Asp in ATP binding pocket of PDKs. The cell viability assay demonstrated that 4 potently blocked NCI-H1975 cell proliferation (IC₅₀ = 3.32 µM), but had little effect on human normal lung cell MRC-5 even with the tested concentration up to 40 µM. All the data demonstrated that 4 was a promising lead for the development of structurally novel PDKs inhibitor for the cancer treatment.

Discovery of potent pyruvate dehydrogenase kinase inhibitors and evaluation of their anti-lung cancer activity under hypoxia

Targeting pyruvate dehydrogenase kinases (PDKs) reverses the Warburg effect, which could be a potential therapeutic target for anti-cancer drug discovery. In this paper, we identified 12 potential PDK inhibitors by virtual ligand screening of a chemical library, and then further verified them by an enzymatic assay, in which 6, 7, and 11 strongly inhibited the function of PDKs, with IC₅₀ values of 1.26, 0.62, and 0.41 μM against PDK1, respectively, and showed a similar inhibitory effect on PDK2, PDK3, and PDK4. However, we failed to correlate the observed inhibitory activity against PDKs with cellular activity under normal conditions. In contrast, 7 and 11 inhibited NCI-H1975 cell proliferation under hypoxia, with EC₅₀ values of 4.66 and 3.88 μM, respectively, suggesting that 7 and 11 could be promising leads for further development of PDK inhibitors in cancer treatment.

Methods to validate Hsp90 inhibitor specificity, to identify off-target effects, and to rethink approaches for further clinical development

The molecular chaperone Hsp90 is one component of a highly complex and interactive cellular proteostasis network (PN) that participates in protein folding, directs misfolded and damaged proteins for destruction, and participates in regulating cellular transcriptional responses to environmental stress, thus promoting cell and organismal survival. Over the last 20 years, it has become clear that various disease states, including cancer, neurodegeneration, metabolic disorders, and infection by diverse microbes, impact the PN. Among PN components, Hsp90 was among the first to be pharmacologically targeted with small molecules. While the number of Hsp90 inhibitors described in the literature has dramatically increased since the first such small molecule was described in 1994, it has become increasingly apparent that not all of these agents have been sufficiently validated for specificity, mechanism of action, and lack of off-target effects. Given the less than expected activity of Hsp90 inhibitors in cancer-related human clinical trials, a re-evaluation of potentially confounding off-target effects, as well as confidence in target specificity and mechanism of action, is warranted. In this commentary, we provide feasible approaches to achieve these goals and we discuss additional considerations to improve the clinical efficacy of Hsp90 inhibitors in treating cancer and other diseases.

Therapeutic Targeting of the Pyruvate Dehydrogenase Complex/Pyruvate Dehydrogenase Kinase (PDC/PDK) Axis in Cancer

The mitochondrial pyruvate dehydrogenase complex (PDC) irreversibly decarboxylates pyruvate to acetyl coenzyme A, thereby linking glycolysis to the tricarboxylic acid cycle and defining a critical step in cellular bioenergetics. Inhibition of PDC activity by pyruvate dehydrogenase kinase (PDK)-mediated phosphorylation has been associated with the pathobiology of many disorders of metabolic integration, including cancer. Consequently, the PDC/PDK axis has long been a therapeutic target. The most common underlying mechanism accounting for PDC inhibition in these conditions is post-transcriptional upregulation of one or more PDK isoforms, leading to phosphorylation of the E1α subunit of PDC. Such perturbations of the PDC/PDK axis induce a "glycolytic shift," whereby affected cells favor adenosine triphosphate production by glycolysis over mitochondrial oxidative phosphorylation and cellular proliferation over cellular quiescence. Dichloroacetate is the prototypic xenobiotic inhibitor of PDK, thereby maintaining PDC in its unphosphorylated, catalytically active form. However, recent interest in the therapeutic targeting of the PDC/PDK axis for the treatment of cancer has yielded a new generation of small molecule PDK inhibitors. Ongoing investigations of the central role of PDC in cellular energy metabolism and its regulation by pharmacological effectors of PDKs promise to open multiple exciting vistas into the biochemical understanding and treatment of cancer and other diseases.

Identification of pyruvate dehydrogenase kinase 1 inhibitors with anti-osteosarcoma activity

Overexpression of pyruvate dehydrogenase kinases (PDKs), especially PDK1 has been observed in a variety of cancers. Thus, targeting PDK1 offers an attractive opportunity for the development of cancer therapies. In this letter, we reported the identification of two novel PDK1 inhibitors as anti-osteosarcoma agents. We found that TM-1 and TM-2 inhibited PDK1 with the IC₅₀ values of 2.97 and 3.41 μM, respectively. Furthermore, TM-1 and TM-2 dose-dependently reduced phosphorylation of pyruvate dehydrogenase complex in MG-63 osteosarcoma cells. Finally, TM-1 and TM-2 were found to inhibit the proliferation of MG-63 cells with the EC₅₀ values of 14.5, and 11.0 μM, respectively, meaning TM-1 and TM-2 could be promising leads for the discovery of potent PDK1 inhibitors.

Development of the First Generation of Disulfide-Based Subtype-Selective and Potent Covalent Pyruvate Dehydrogenase Kinase 1 (PDK1) Inhibitors

Pyruvate dehydrogenase kinases (PDKs) are overexpressed in most cancer cells and are responsible for aberrant glucose metabolism. We previously described bis(4-morpholinyl thiocarbonyl)-disulfide (JX06, 16) as the first covalent inhibitor of PDK1. Here, on the basis of the scaffold of 16, we identify two novel types of disulfide-based PDK1 inhibitors. The most potent analogue, 3a, effectively inhibits PDK1 both at the molecular (k_inact/K_i = 4.17 × 10³ M^-1 s^-1) and the cellular level (down to 0.1 μM). In contrast to 16, 3a is a potent and subtype-selective inhibitor of PDK1 with >40-fold selectivity for PDK2-4. 3a also significantly alters glucose metabolic pathways in A549 cells by decreasing ECAR and increasing ROS. Moreover, in the xenograft models, 3a shows significant antitumor activity with no negative effect to the mice weight. Collectively, these data demonstrate that 3a may be an excellent lead compound for the treatment of cancer as a first-generation subtype-selective and covalent PDK1 inhibitor.

Application of Off-Rate Screening in the Identification of Novel Pan-Isoform Inhibitors of Pyruvate Dehydrogenase Kinase

Libraries of nonpurified resorcinol amide derivatives were screened by surface plasmon resonance (SPR) to determine the binding dissociation constant (off-rate, k_d) for compounds binding to the pyruvate dehydrogenase kinase (PDHK) enzyme. Parallel off-rate measurements against HSP90 and application of structure-based drug design enabled rapid hit to lead progression in a program to identify pan-isoform ATP-competitive inhibitors of PDHK. Lead optimization identified selective sub-100-nM inhibitors of the enzyme which significantly reduced phosphorylation of the E1α subunit in the PC3 cancer cell line in vitro.

Unexpected Discovery of Dichloroacetate Derived Adenosine Triphosphate Competitors Targeting Pyruvate Dehydrogenase Kinase To Inhibit Cancer Proliferation

Pyruvate dehydrogenase kinases (PDKs) have recently emerged as an attractive target for cancer therapy. Herein, we prepared a series of compounds derived from dichloroacetate (DCA) which inhibited cancer cells proliferation. For the first time, we have successfully developed DCA derived inhibitors that preferentially bind to the adenosine triphosphate (ATP) pocket of PDK isoform 1 (PDK1).

Polypharmacology in Precision Oncology: Current Applications and Future Prospects

Over the past decade, a more comprehensive, large-scale approach to studying cancer genetics and biology has revealed the challenges of tumor heterogeneity, adaption, evolution and drug resistance, while systems-based pharmacology and chemical biology strategies have uncovered a much more complex interaction between drugs and the human proteome than was previously anticipated. In this mini-review we assess the progress and potential of drug polypharmacology in biomarker-driven precision oncology. Polypharmacology not only provides great opportunities for drug repurposing to exploit off-target effects in a new single-target indication but through simultaneous blockade of multiple targets or pathways offers exciting opportunities to slow, overcome or even prevent inherent or adaptive drug resistance. We highlight the many challenges associated with exploiting known or desired polypharmacology in drug design and development, and assess computational and experimental methods to uncover unknown polypharmacology. A comprehensive understanding of the intricate links between polypharmacology, efficacy and safety is urgently needed if we are to tackle the enduring challenge of cancer drug resistance and to fully exploit polypharmacology for the ultimate benefit of cancer patients.

Synthesis of 3,4,5-Trisubstituted Isoxazoles from Morita-Baylis-Hillman Acetates by an NaNO2 /I2 -Mediated Domino Reaction

An efficient NaNO2 /I2 -mediated one-pot transformation of Morita-Baylis-Hillman (MBH) acetates into alkyl 3-nitro-5-(aryl/alkyl)isoxazole-4-carboxylates is described. In a cascade event, initial Michael addition of NaNO2 to the MBH acetate furnishes the allylnitro intermediate which undergoes I2 -catalyzed oxidative α-CH nitration of the nitromethyl subunit followed by [3+2] cycloaddition to afford the title compounds. Structural elaborations of these highly substituted isoxazoles by SN Ar reactions and hydrogenolysis allows access to useful products.

The pyruvate dehydrogenase complex in cancer: An old metabolic gatekeeper regulated by new pathways and pharmacological agents

Cancer cells exhibit an altered metabolism which is characterized by a preference for aerobic glycolysis more than mitochondrial oxidation of pyruvate. This provides anabolic support and selective growth advantage for cancer cells. Recently, a new concept has arisen suggesting that these metabolic changes may be due, in part, to an attenuated mitochondrial function which results from the inhibition of the pyruvate dehydrogenase complex (PDC). This mitochondrial complex links glycolysis to the Krebs cycle and the current understanding of its regulation involves the cyclic phosphorylation and dephosphorylation by specific pyruvate dehydrogenase kinases (PDKs) and pyruvate dehydrogenase phosphatases (PDPs).

Development of pyruvate dehydrogenase kinase inhibitors in medicinal chemistry with particular emphasis as anticancer agents

Many cancer cells demonstrate a high rate of glucose consumption via glycolysis to provide intermediates for macromolecule biosynthesis. To accomplish this metabolic change, the expression of pyruvate dehydrogenase kinases (PDKs) is rapidly increased in cancer cells. Inhibition of PDKs could promote the function of mitochondria by increasing the oxidative metabolism of pyruvate, resulting in the death of cancer cells. In this review, we provide an overview of the structural information available for PDKs and their connections to known therapeutic effects. We then describe the development of small molecule PDK inhibitors in medicinal chemistry with particular emphasis as anticancer agents. Finally, directions for further development of PDK inhibitors as potential anticancer agents are discussed.