Doctor of Philosophy (PhD)
17β-Hydroxysteroid dehydrogenases (17β-HSDs) are essential enzymes in steroid metabolism. More and more evidence points to the pivotal contributions of these enzymes in various other metabolic pathways. Therefore, the latest research results give new insights into the complex metabolic interconnectivity of the 17β-HSDs with human diseases. This dissertation focuses on the metabolic activities of type 5 and 10 17β-HSDs. More specifically, regarding 17β-HSD5 contributions to the progression of prostate cancer (PCa) and 17β-HSD10 aggravation of amyloid-beta (Aβ)-induced toxicity in Alzheimer's disease (AD).
The second leading cause of cancer-related death in males is PCa, with the highest incidence rate of all cancers reported in the U.S. The treatment paradigm is dependent on androgen deprivation therapy (ADT) via surgical or medical castration, targeting the production of androgens, primarily testosterone, in the Leydig cells of the testis. This therapy usually leads to an initial clinical improvement with concomitant suppression of prostate-specific antigen (PSA) levels. However, within 2-3 years, castration-resistant prostate cancer (CRPC) develops in most patients, despite low circulating androgens levels and has more significant metastatic potential. Such adaptations lead to increased intratumoral androgen biosynthesis, along with an increase in tumor responsiveness to circulating castrate levels of androgens. The enzyme 17β-HSD5 is responsible for androgen biosynthesis, and a significant upregulation of its expression is observed in CRPC patient tumor samples. It plays a vital role in the downstream synthesis of dihydrotestosterone (DHT), the predominant intracellular transcriptional signal to androgen-responsive genes in intact human prostate cells. Hence, the delivery of 17β-HSD5 inhibitor represents a promising therapeutic target to manage CRPC and combat the emergence of resistance to clinically employed therapy. In our lab, we developed a highly potent and selective 17β-HSD5 inhibitor, KV-49g (IC50 = 70 nM, >2800-fold selectivity over its homologous isoforms). The work described herein continues to elucidate the structure-activity relationship (SAR) around this chemotype in inhibiting 17β-HSD5 activity. Further, we show PCa cells' resistance to newly approved AR antagonists, apalutamide and darolutamide. This resistance was abstained with 24 hours pre-treatment of KV-49g and led to PCa cells death in vitro, showing potentiation to AR antagonists' chemotherapeutic effect. Further, we showed that the combination therapy's synergic effect translated to a significant decrease in PSA expression. These results demonstrate a promising therapeutic strategy for treating drug-resistant CRPC that invariably develops in PCa patients following initial treatment with AR antagonists.
The most common form of dementia is AD, affecting an estimated 46.8 million people worldwide in 2015, a number predicted to increase to 74.7 million by 2030 and 131.5 million by 2050. Current therapeutic agents against AD are palliative in nature, managing symptoms without addressing the underlying cause, and thus, disease progression and patient death remain a certainty. Whereas the leading underlying cause for the development of AD was initially thought to be an abnormal deposition of the soluble oligomeric form of Aβ-derived plaques within the brain, the failure of several high-profile therapeutic agents, which were shown to reduce the plaque burden without improving cognition, has recently prompted a shift in focus to disease-modifying therapy. A therapy that aims to restore a normal target's function that has been compromised by Aβ accumulation, alleviating Aβ-induced toxicity. Soluble Aβ oligomers have been identified in various subcellular compartments, including the mitochondria, where they form a complex with the 17β-HSD10 enzyme resulting in cytotoxicity. The latter suggests two therapeutic approaches that may hold merit in treating AD: disrupting the interaction between the 17β-HSD10 enzyme and Aβ, or directly inhibiting the catalytic activity of the 17β-HSD10 enzyme. AG18051 was identified as a small molecule 17β-HSD10 inhibitor. The work described herein details the synthesis of AG18051 and its analogues to elucidate the SAR around this chemotype. Further, the generation of robust screening assays allowing the catalytic activity of the 17β-HSD10 enzyme to be measured in vitro and the neuroprotective effects of 17β-HSD10 inhibitors in ameliorating Aβ-induced toxicity to be assessed. As a result, we have identified more potent compounds than AG18501, with more 'drug-like' structures, that showed significant protection from Aβ toxicity. As such, we now have a number of hit compounds that will form the basis for the generation of subsequent series of derivatives with improved potency, as well as the robust assays required to measure such criteria, potentially leading to the generation of novel therapeutic agents against AD.
Morsy, Ahmed, "Design, Synthesis and Evaluation of Novel Inhibitors of Type 5 and 10 17β-Hydroxysteroid Dehydrogenases" (2021). Theses & Dissertations. 513.
Available for download on Friday, April 14, 2023