Design and Synthesis of Pyrimidine Fused Heterocycles as Single Agents with Combination Chemotherapy Potential

This dissertation describes the design, synthesis and biological evaluation of pyrimidine fused heterocycles as single agents with combination chemotherapy potential. Major limitations of cancer chemotherapy include dose limiting toxicities of clinically used agents and the development of multidrug resistance by the tumor. Agents that interfere with microtubules are important antitumor agents. Tumor angiogenic mechanisms that are vital for tumor growth and metastasis are targeted by antiangiogenic agents. Antiangiogenic agents are usually not tumoricidal but are mainly cytostatic. Combination chemotherapy with antiangiogenic and cytotoxic agents have shown significant promise and several studies with such combinations are in progress in the clinic. Single agents with both antiangiogenic activities as well as cytotoxicity would afford single agents that circumvent pharmacokinetic problems of multiple agents, avoid drug–drug interactions, could be used at lower doses to alleviate toxicity, be devoid of overlapping toxicities, and delay or prevent tumor cell resistance. The work in this dissertation is centered on the design and synthesis of single entities that have both antiangiogenic effects and cytotoxic effects. These efforts led to the identification of structural features that are necessary for inhibition of tubulin polymerization. Structural modifications also led to the identification of novel antiangiogenic agents which inhibit one or more of the receptor tyrosine kinases (RTKs)– vascular endothelial growth factor receptor–2 (VEGFR2), platelet derived growth factor receptor–β (PDGFRβ) and epidermal growth factor receptor (EGFR). The complexity of the angiogenic pathways in tumors implies that disrupting a single mechanism of angiogenesis may not result in significant clinical success. Multiple RTKs are co–activated in tumors and redundant inputs drive and maintain downstream signaling, thereby limiting the efficacy of therapies targeting single RTKs. This work reviews the role of RTKs in angiogenesis, microtubules as antitumor targets, the vascular normalization theory and multitargeted agents. This work also reviews the synthesis of substituted pyrrolo[3,2–d]pyrimidines, furo[3,2–d]pyrimidines, pyrimido[5,4–b]indoles and b]. A discussion of methods employed in the synthesis of pyrimidine fused heterocycles as single agents with combination chemotherapy potential is provided

A new anti-glioma therapy, AG119: Pre-clinical assessment in a mouse GL261 glioma model

Background: High grade gliomas (HGGs; grades III and IV) are the most common primary brain tumors in adults, and their malignant nature ranks them fourth in incidence of cancer death. Standard treatment for glioblastomas (GBM), involving surgical resection followed by radiation and chemotherapy with temozolomide (TMZ) and the anti-angiogenic therapy bevacizumab, have not substantially improved overall survival. New therapeutic agents are desperately needed for this devastating disease. Here we study the potential therapeutic agent AG119 in a pre-clinical model for gliomas. AG119 possesses both anti-angiogenic (RTK inhibition) and antimicrotubule cytotoxic activity in a single molecule. Methods: GL261 glioma-bearing mice were either treated with AG119, anti-VEGF (vascular endothelial growth factor) antibody, anti c-Met antibody or TMZ, and compared to untreated tumor-bearing mice. Animal survival was assessed, and tumor volumes and vascular alterations were monitored with morphological magnetic resonance imaging (MRI) and perfusion-weighted imaging, respectively. Results: Percent survival of GL261 HGG-bearing mice treated with AG119 was significantly higher (p \u3c 0.001) compared to untreated tumors. Tumor volumes (21-31 days following intracerebral implantation of GL261 cells) were found to be significantly lower for AG119 (p \u3c 0.001), anti-VEGF (p \u3c 0.05) and anti-c-Met (p \u3c 0.001) antibody treatments, and TMZ-treated (p \u3c 0.05) mice, compared to untreated controls. Perfusion data indicated that both AG119 and TMZ were able to reduce the effect of decreasing perfusion rates significantly (p \u3c 0.05 for both), when compared to untreated tumors. It was also found that IC50 values for AG119 were much lower than those for TMZ in T98G and U251 cells. Conclusions: These data support further exploration of the anticancer activity AG119 in HGG, as this compound was able to increase animal survival and decrease tumor volumes in a mouse GL261 glioma model, and that AG119 is also not subject to methyl guanine transferase (MGMT) mediated resistance, as is the case with TMZ, indicating that AG119 may be potentially useful in treating resistant gliomas

Discovery and preclinical evaluation of 7-benzyl-N-(substituted)-pyrrolo[3,2-d]pyrimidin-4-amines as single agents with microtubule targeting effects along with triple-acting angiokinase inhibition as antitumor agents

The utility of cytostatic antiangiogenic agents (AA) in cancer chemotherapy lies in their combination with cytotoxic chemotherapeutic agents. Clinical combinations of AA with microtubule targeting agents (MTAs) have been particularly successful. The discovery, synthesis and biological evaluations of a series of 7-benzyl-N-substituted-pyrrolo[3,2-d]pyrimidin-4-amines are reported. Novel compounds which inhibit proangiogenic receptor tyrosine kinases (RTKs) including vascular endothelial growth factor receptor-2 (VEGFR-2), platelet-derived growth factor receptor-β (PDGFR-β) and epidermal growth factor receptor (EGFR), along with microtubule targeting in single molecules are described. These compounds also inhibited blood vessel formation in the chicken chorioallantoic membrane (CAM) assay, and some potently inhibited tubulin assembly (with activity comparable to that of combretastatin A-4 (CA)). In addition, some of the analogs circumvent the most clinically relevant tumor resistance mechanisms (P-glycoprotein and β-III tubulin expression) to microtubule targeting agents (MTA). These MTAs bind at the colchicine site on tubulin. Two analogs displayed two to three digit nanomolar GI50values across the entire NCI 60 tumor cell panel and one of these, compound 7, freely water soluble as its HCl salt, afforded excellent in vivo antitumor activity against an orthotopic triple negative 4T1 breast cancer model and was superior to doxorubicin

Sterically induced conformational restriction: Discovery and preclinical evaluation of novel pyrrolo[3,2-d]pyrimidines as microtubule targeting agents

The discovery, synthesis and biological evaluations of a series of nine N5-substituted-pyrrolo[3,2-d]pyrimidin-4-amines are reported. Novel compounds with microtubule depolymerizing activity were identified. Some of these compounds also circumvent clinically relevant drug resistance mechanisms (expression of P-glycoprotein and ?III tubulin). Compounds 4, 5, and 8–13 were one to two-digit nanomolar (IC50) inhibitors of cancer cells in culture. Contrary to recent reports (Banerjee et al. J. Med. Chem. 2018, 61, 1704–1718), the conformation of the most active compounds determined by 1H NMR and molecular modeling are similar to that reported previously and in keeping with recently reported X-ray crystal structures. Compound 11, freely water soluble as the HCl salt, afforded statistically significant inhibition of tumor growth in three xenograft models [MDA-MB-435, MDA-MB-231 and NCI/ADR-RES] compared with controls. Compound 11 did not display indications of animal toxicity and is currently slated for further preclinical development

Discovery of Antitubulin Agents with Antiangiogenic Activity as Single Entities with Multitarget Chemotherapy Potential

Antiangiogenic agents (AA) are cytostatic, and their utility in cancer chemotherapy lies in their combination with cytotoxic chemotherapeutic agents. Clinical combinations of vascular endothelial growth factor receptor-2 (VEGFR2) inhibitors with antitubulin agents have been particularly successful. We have discovered a novel, potentially important analogue, that combines potent VEGFR2 inhibitory activity (comparable to that of sunitinib) with potent antitubulin activity (comparable to that of combretastatin A-4 (CA)) in a single molecule, with GI₅₀ values of 10^–7 M across the entire NCI 60 tumor cell panel. It potently inhibited tubulin assembly and circumvented the most clinically relevant tumor resistance mechanisms (P-glycoprotein and β-III tubulin expression) to antimicrotubule agents. The compound is freely water-soluble as its HCl salt and afforded excellent antitumor activity <i>in vivo</i>, superior to docetaxel, sunitinib, or Temozolomide, without any toxicity