Date of Award

12-2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program

Pharmaceutical Sciences

Research Advisor

Charles R. Yates, Pharm.D., Ph.D.

Committee

Mostafa W. Gaber, Ph.D. Bernd Meibohm, Ph.D. Duane D. Miller, Ph.D. Scott Sinclair, M.D.

Abstract

The possibility of an incident involving radiation exposure is at the forefront of public attention in the current global environment. With a greater number of entities possessing nuclear weapons and increased demand for nuclear power, the concern for uncontained exposure to radiation is increasing. In light of these developments, the need for treatments that may be easily stored and administered to large numbers of people who have been exposed to high doses of total body irradiation (TBI) is more urgent than ever before.

Our goal was to identify and develop novel, drug-like small molecules that would exhibit radiomitigating activity for use in Acute Radiation Syndrome (ARS). Hot water extracts of Cat’s Claw containing quinic acid have been shown to possess activity in increasing circulating white blood cells as well as promoting DNA repair. Our group previously synthesized and evaluated a series of quinic acid derivatives. Quinic acid derivative KZ-41 was identified and described as highly water soluble and orally available. We have, therefore, identified a novel quinic acid derivative, KZ-41, as our initial lead molecule for evaluation, characterization, and development in the setting of ARS.

Initial efficacy was tested in vivo by evaluating the impact KZ-41 had on the primary endpoint of mortality in lethally irradiated C57BL/6 mice 30 days after exposure. To investigate the potential mechanisms related to the enhanced survival following TBI, we investigated the effect of KZ-41 on parameters important to initial wound healing. We developed an imaging model to specifically investigate the effect of KZ-41 on clotting following TBI and vascular injury. This model also allowed us to gain insight into “combined injury” which is also of critical importance when discussing the “real-life” implications of ARS. .

To further evaluate mechanisms of effect, we developed an in vitro model using human monocytes (U937) cells. Using the in vitro model developed, we characterized the effect KZ-41 had on intrinsic and extrinsic apoptotic cell death, focusing on the impact in the “bystander effect” model. We also utilized the in vitro model to identify potential more potent analogues and next-generation compounds. Initial pre-clinical pharmacokinetic characterization of a next-generation compound was also conducted.

We have shown KZ-41 to be effective in improving survival of lethally irradiated mice, enhancing the critical wound healing events of initial thrombus formation and in restoring vascular flow in combined injury. In an in vitro bystander effect model, KZ-41 can mitigate apoptosis when administered after the radiation event. Initial, identification, and pharmacokinetic characterization of a potent next-generation compound for use in ARS is also described herein.

DOI

10.21007/etd.cghs.2010.0316

Comments

Two year embargo expired December 2012