Contents

## EFFECT OF CHRONOMODULATED ARTESUNATE ON RENAL AND HAEMATOLOGICAL TOXICITY IN CISPLATIN-TREATED WISTAR RATS

ABSTRACT

CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND

Cisplatin with the chemical name, cis-diamminedichloroplatinum (CDDP), a platinum based chemotherapeutic compound is one of the most active drugs against a large spectrum of common solid tumours (Asna et al., 2004) including testicular germ cell cancers, with 90% reported cure rate (Raghavan, 2003). However, in addition to being efficacious is a dose related array of serious toxicities including, gastro-intestinal, neurotoxicity, renal toxicity and myelosuppression (Burton et al., 2007; Windebank and Grisold, 2008; Gutiérrez-Gutiérrez et al., 2010). It‘s renal and blood toxicities are however some of the major side-effects that have limited its use in clinical practice (Gulec et al., 2013). The pathophysiologic mechanisms of these toxicities include oxidative damage, inflammation and apoptotic cell death (Gill and Windebank, 1998; Englander, 2013). Therefore, effective strategies to reduce the severity of damage following chemotherapy are intensively being investigated. However, changing the timing of administration along the 24-hour time scale has profoundly modified the extent of dose-limiting toxicities of anticancer agents both in rodents and in humans (Levi, 2001; Levi et al., 2010). Circadian administration of several cancer chemotherapy regimens to improve their safety as well as their antitumour activity in patients has been validated (Hrushesky et al.,, 1982; Levi et al., 2010). Cisplatin as well as its analogs have been studied in the context of their circadian pharmacodynamics (chronopharmacodynamics), tolerability (chronotolerability) and toxicity (chronotoxicity) (Levi et al., 2010). The results of the above studied showed that with proper timing of their administration, cisplatin as well as other drugs with narrow efficacy-toxicity dosage ratio index could have their toxicities significantly reduced on healthy tissues, and maximize their attack on tumour cells.

Artesunate, a semisynthetic derivative of artemisinin, is an endoperoxide compound extracted from the Chinese herb qinghaosu (Artemisia annua L., annual wormwood or sweet wormwood), (Wood and Hrushesky, 1996), It is widely used as an antimalarial and has replaced chloroquine and quinine for the treatment of Plasmodium falciparum (P. falciparum) parasite which causes malaria in endemic regions. This strain of malaria parasite is responsible for nearly all the mortalities in some 1 million people each year (WHO, 2012). Furthermore, antitumor activity of artemisinin has also been documented in animal models (Zhang et al., 2008) and individual clinical cases (Breman et al., 2004: Singh and Lai, 2004; Berger et al., 2005). In addition, artesunate used in cancer therapy has demonstrated good tolerability and lack of significant side effects (Lai and Singh, 1995).

It has been reported that reactive oxygen species (ROS) as well as inflammatory response play an important role in cisplatin triggered kidney toxicity (Masuda et al., 1994) and subsequently renal failure (Jaggi and Singh, 2012; Kamisli et al., 2015) resulting in oxidant-antioxidant imbalance (Jin-Gang and Lindup, 1993; Khynriam and Prasad, 2002). The antimalarial and anticancer effects of artesunate are largely attributed to the release of highly alkylating carbon-centered radicals and generation of ROS (Du et al., 2010; Mercer et al., 2011). However, this drug is distributed into other organs making such organs possible target of toxicity. When malaria and cancer co-exist, treatment of co-morbid patients could be challenging due to the burden of disease and possible drug interaction of the pharmacological agents involved in their management.

### 1.2 STATEMENT OF RESEARCH PROBLEM

Common toxicities of cisplatin are blood related toxicities which typically manifests predominantly as transient leukopenia and thrombocytopenia (Han and Smith, 2013), and an irreversible renal damage (Hrushesky et al., 1982; Yao et al., 2007). This has resulted not only to increasing the burden of disease, but also limiting dosage, thus, leading to suboptimal pharmacotherapy (Windebank and Grisold, 2008; Podratz et al., 2011), resulting to inevitable discontinuation of therapy (Podratz et al., 2011). Cisplatin in the kidneys has been demonstrated to accumulate in proximal tubular cells, its primary site of nephrotoxicity, which in turn results in secondary tubular degeneration (Cavaletti et al., 1992; Mc Donald et al., 2005). Conversely, Ho et al. (2013) and Akman et al. (2014) have shown involvement of renal haemodynamics and vascular injury in the pathogenesis of cisplatin-induced acute kidney injury (AKI). Thus, it is arguable that its underlying pathomechanisms are still poorly understood and treatment options are limited (Huehnchen et al., 2013), suggesting further research.

Artemisinin and its derivatives produce toxic effects on erythropoiesis as measured by the number of counts of reticulocytes in both animal experiments and human studies. (Genovese et al., 2000; Gordi and Lepist, 2004; Nontprasert et al., 2008). Again, artesunate undergoes bioactivation in the liver to artenimol, the active antimalarial agent, which results in the generation of reactive oxygen species (ROS) or free radicals (Li et al., 2005). This toxic specie could explain the alteration seen in enzyme activity and tissues of the kidneys (Rajput, 2013). More so, results obtained have shown artesunate to clearly alter the functional capacities of the kidneys (Campos et al., 2001; cheng et al., 2011; Rajput, 2013).

Adding to the complexity of managing co-morbid patients are drug-drug interactions (DDIs) between agents used for the management of malaria and cancer (Extermann et al., 1998). Thus, the co-administration of cisplatin and artesunate especially in malaria endemic regions such as sub-Saharan Africa is rational, hence the need to study their toxicological interaction and try to proffer solution to their tolerability as it relate to time of their administration.

### 1.3 JUSTIFICATION

Animal studies and human trials have been carried out on toxicological aspects of a number of chemotherapeutic drugs. However, majority do not consider the rhythmicity of the biological system (chronopharmacokinetics) and the synchrony with chemotherapeutic agents (chronopharmacodynamics). The results of such single time-of-day studies are representative of only one circadian phase. Thus, the tradition of drug administration at evenly spaced time intervals throughout the day, in an attempt to maintain constant drug levels within a time period of 24 hr, may be changing as on-going researches are aimed at coordinated administration with day-night patterns and biological rhythms.

Malaria is the world’s most prevalent of human parasitic infections and is endemic in sub-Saharan Africa. Co morbid conditions are however, common with neoplastic diseases and could have implications in their treatment and care, including the timing and choice of drugs. Cisplatin, a common antineoplatic drug, with narrow therapeutic index poses a greater potential for causing harmful side effects in high-risk individuals. Thus, understanding its toxicological interaction with antimalarial drug such as artesunate is essential for its safe and effective use. Furthermore, chronomodulation of these two pharmacological agents along a 24 hours‘ time scale could reduce the possible cumulative drug-induced toxicity and improve their tolerability when co-administered.

### 1.4 AIM AND OBJECTIVES

#### 1.4.1 Aim

To investigate the effect of time of artesunate administration on the ameliorative benefits of chronomodulated cisplatin administration on some toxicological effects of cisplatin in wistar rats.

#### 1.4.2 Specific Objectives

1. To investigate the ameliorative effect of time of cisplatin administration on renal and haematological toxicity in Wistar rats.

2. To investigate the effect of time of artesunate administration on the ameliorative effect of chronomodulated cisplatin on renal toxicity

3. To investigate the influence of time of artesunate administration on the ameliorative effect of chronomodulated cisplatin on haematological toxicities.

### 1.5 HYPOTHESIS

Chronomodultated artesunate does not negate the ameliorative effect of timed cisplatin administration on renal and haematological toxicity in Wistar rats.