Design and Synthesis of a PD-L1 Radioligand for Diagnostic Imaging and Development and Optimization of a Potent Liver Receptor Homolog-1 Agonist Open Access
Zecca, Henry (Fall 2021)
Published
Abstract
Immune checkpoint inhibitors have revolutionized the way cancer is treated; instead of broadly cytotoxic therapies that “kill the patient, but kill the cancer faster”, these therapeutics enable the immune system’s ability to detect and clear tumors. The first therapies to be approved based on the genetic makeup of a tumor instead of the anatomical location and approved for over 15 indications, antibody drugs targeting programmed cell death protein 1 (PD-1) and its ligand (PD-L1) are the premier example of immune checkpoint inhibitors. However, these drugs will only work if the tumor is expressing the PD-L1 protein. Unfortunately, the current assays used to determine PD-L1 expression levels are poorly effective; biopsy samples fail to generate a complete picture of heterogeneous tumors, PD-L1 expression is tightly regulated by hormones that are only present in vivo, and the assays themselves are subjectively scored with variable definitions of PD-L1 positivity. This uncertainty related to a patient’s potential response hampers the effective deployment of this revolutionary class of drugs.
Positron emission tomography (PET) has been used for decades as a powerful diagnostic technique for diagnosing and tracking tumors in patients. This technology, aided by a radiotracer such as 18F-fluorodeoxyglucose, allows oncologists to visualize the tumors in their patients and with modern mutation- or protein-specific tracers, allows clinicians to formulate treatment plans.
Herein we describe the design, synthesis, and optimization of a PET tracer to visualize PD-L1 mutational status. Based on a PD-L1 binding small molecule, this radiotracer is easy to synthesize and selectively binds to PD-L1 with nanomolar potency.
Table of Contents
Chapter 1 Thesis Introduction.. 16
1.1 Translational Chemistry. 16
1.2 Manipulation of chemical properties to better interrogate biological systems. 18
1.3 Collaborative Multidisciplinary Science. 18
Chapter 2 Visualizing Tumor Mutational Burden: Development of Radioligands for PD-L1. 20
2.1 Chemotherapeutic Agents in Oncology. 22
2.1.1 Nitrogen Mustard. 22
2.1.2 Antifolates. 23
2.1.3 Natural products. 24
2.2 Targeted Therapies. 24
2.3 The Immuno-Oncology Revolution. 25
2.3.1 Interleukin-2. 26
2.4 Immune Checkpoint Inhibitors. 27
2.4.1 CTLA-4. 27
2.4.2 PD-1/PD-L1. 27
2.4.3 Companion Diagnostics. 29
2.5 Positron Emission Tomography. 31
2.6 Small Moleucle Inhibitors of PD-L1. 42
2.6.1 Disclosed Inhibitors of PD-L1. 42
2.7 Structural Biology of PD-1/PD-L1 Antagonism.. 45
2.8 Design of PD-L1 Radiotracers. 48
2.8.1 Properties of a PET tracer. 48
2.8.2 First generation design of PD-L1 PET tracer. 49
2.8.3 Second generation design of PD-L1 PET tracer. 50
2.8.4 Third generation of PD-L1 PET tracer. 51
2.9 In vitro characterization of a small molecule PD-L1 PET tracer. 53
2.10 In vivo characterization of a small molecule PD-L1 PET tracer. 54
2.11 Conclusion. 54
2.12 Supporting Information. 55
2.12.1 General Information. 55
2.12.2 Evaluation of Purity. 56
2.12.3 Chemical Synthesis. 57
2.12.4 Radiochemical Synthesis of 18F Labeled Tracer. 70
2.12.5 Binding Affinity by Surface Plasmon Resonance. 71
Chapter 3 : Development of a Highly Potent and Efficacious Liver Receptor Homolog-1 Agonist. 72
3.1 Liver Receptor Homolog 1 (LRH-1) 74
3.1.1 Orphan Nuclear Receptors. 74
3.1.2 Activation of LRH-1. 75
3.1.3 Natural Agonists of LRH-1. 77
3.1.4 Synthetic Agonists of LRH-1. 78
3.2 LRH-1 in Human Disease. 80
3.2.1 Cardiovascular disease. 81
3.2.2 Non-alcoholic fatty liver disease. 82
3.3 Introduction. 82
3.4 Results. 85
3.5 Conclusion. 95
3.6 Supporting Information. 96
3.6.1 Chemistry. 96
3.6.2 Biology. 104
Chapter 4 : Lead Optimization of a Potent LRH-1 Agonist. 112
4.1 Introduction. 114
4.2 ADME Properties in Drug Development. 115
4.3 Design. 117
4.4 Synthesis. 122
4.4.1 Aryl Linked Tails. 122
4.4.2 Ether Tails. 124
4.5 In-vitro evaluation. 130
4.5.1 LRH-1 Agonism.. 130
4.5.2 Solubility. 133
4.5.3 Metabolic Stability. 134
4.5.4 Permeability. 135
4.6 In-vivo evaluation. 137
4.6.1 Tissue Distribution. 137
4.6.2 Scale-up Synthesis. 139
4.6.3 Pharmacokinetics. 141
4.6.4 Target Engagement 144
4.7 Conclusion. 145
4.8 Supporting Information 146
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