[BojanaL]

Scientists at Princeton University have developed a synthetic enzyme that will modulate ingested drug to prevent its metabolic degradation and reduce both toxicity and dose needed for expected medical effect.

Long and healthy life of the average man is dependent on the productive pharmaceutical industry. Thousands of drugs are available all over the globe. Despite having healing effect, drugs are associated with more or less severe adverse effects. Ingested chemicals are undergoing metabolic transformation before they are eliminated from the body. Metabolites (end products of drug degradation) could be reactive and inflict damage to the nearby healthy tissue. Liver is essential organ for drug transformation; it could be imagined as waste factory of the human body, where different chemicals are degraded thanks to numerous enzymatically enhanced biochemical processes.

Drug (xenobiotic) metabolism facilitates drug elimination from the organism by converting lipophilic compounds into hydrophilic metabolites. This process decreases pharmaceutical potential of the drug. Higher concentration of the drug is always applied to ensure desired medical effect. Enzymes responsible for drug metabolism are known as CYP enzymes (located mainly in the liver); they provoke either detoxification, when toxic compound is metabolized into less toxic metabolite, or toxication, when non-toxic compound is transformed into harmful metabolite. Xenobiotic metabolism is divided in couple of phases. In the first phase mixed function oxydases will eliminate hydrogen or add oxygen to create more polar compound that could be easily excreted from the body. Some drugs will be eliminated after this phase. Some other demand further transformation: endogenous substrate will bond to the newly added functional groups and increase polarity of the created conjugate. In the second phase, interaction of the polar functional groups of the phase I metabolites result in detoxified product. Conjugation reactions including methylation, acetylation, sulphation, glucuronidation on the carboxyl, hydroxyl, amino and sulfhydryl groups are turning reactive phase I conjugates into less active metabolites that could be excreted easily.

Scientists from the Chemical department of Princeton University and Caltech group of California Institute of Technology's Materials and Process Simulation Center teamed up to develop synthetic enzyme that will modulate ingested drug to prevent its metabolic degradation and reduce both toxicity and dose needed for expected medical effect. Created enzyme is acting like a catalyst that is replacing certain hydrogen with fluoride atoms. Altered drug molecule is stable and “safe” from the liver enzymes with the same (or even increased) pharmaceutical potential. Without metabolic degradation, level of available drug in the body is high and dose could be easily reduced. Addition of fluorine results in increased lipophilicity of a drug (essential for all in vivo acting molecules). It also increases fat solubility resulting in elevated drug bioavailability. Fluoride enhances binding of the drug to the enzymatic or receptor sites. Carbon and fluorine create strong bond with a higher oxidative and thermal stability compared to carbon – hydrogen bond. Some other functional groups could also make reversible electrostatic bonds with fluoride. This kind of substitution is useful when developing drugs where stable covalent bonds with molecular targets are needed.

Synthetic enzyme that is responsible for hydrogen – fluoride substitution is similar to cytochrome P450 that replaces hydrogen for oxygen atoms. However, unlike iron based cytochrome P450 enzyme, newly developed enzyme is manganese based. This enzyme is developed two years ago with a goal to increase drug reactivity by replacing hydrogen atoms with chlorine atoms. Scientists assumed that manganese based cytochrome P450 could also work properly if fluoride atoms are offered. They experimented with couple of fluoride materials and discovered that combination of silver fluoride and tetrabutylammonium fluoride trihydrate is the easiest and the safest way to incorporate fluoride into drug molecule. Computational methods are further used to test drug safety and pharmaceutical activity. Besides being effective in decreasing toxicity and dose applied, this method could be used in designing radioactive tracer drugs as easiest and less expensive method in medical imaging (to determine mechanism of action and exact reactive site of the drug in the organism). Already marketed drugs are currently under investigation for the potential improvement using fluorination method. Scientists are especially focused on steroid drugs because this class of drugs is widely used. All kind of hormone replacement therapy and/or birth control pills and various anti-inflammatory drugs are typical representatives of steroid drugs.

Further experiments will show if fluorination could alleviate unwanted side effects and provide safe and efficient drug treatment.