الفهرس 
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Abstract
During the early days of drug discovery, a drug could have demonstrated good in-vitro potency results but would later fail in-vivo efficacy tests.
This was mainly due to the archaic approach to drug design, in which the designers did not screen the molecule’s drug-like properties until the molecules reach the development stage, making it the main reason of attritions during drug discovery process.
Drug-like properties or “Pharmaceutical properties” can be described as the bio-pharmaceutical and physicochemical properties of a molecule.
These properties such as solubility, efflux by transporters and permeability greatly affect the pharmacokinetics (absorption, distribution, metabolism and excretion “ADME”) of the drug, so certain aspects of these properties make for better drug efficacy and safety.
The introductory part of this thesis includes a brief review on some critical drug-like properties and their sub-optimal presentation.
A new important class of drugs known as direct acting antivirals (DAAs) was developed for the treatment of hepatitis C virus (HCV) infections, many of which having some sub-optimal drug-like properties.
HCV isconsidered one of the most prevalent diseases in Egypt and is responsible for a major number of deaths all over the world.
Accordingly, some DAAs were granted voluntary licensing for generic manufacturing.
One of which is the antiviral drug combination of sofosbuvir / ledipasvir that is considered one of the most essential DAAs combination for the treatment of the prevalent genotype in Egypt.
Thus, it is important to understand and evaluate their pharmaceutical properties that could possibly lead to a product with low therapeutic efficacy.
This thesis will focus mainly on the effect of sofosbuvir’s polymorphism on its solubility and the dissolution rate of formulated tablets and improving the solubility of ledipasvir through simple techniques.