Clinic development candidate selection

Whether or not an optimized lead ever becomes a candidate going into the clinic depends on what happens in the next stage, called preclinical or maybe clinical development candidate selection. Although, the term preclinical can be taken to broadly mean any new drug activity done prior to clinical trials (TID, LID, etc.), it normally refers specifically to this stage, which marks the transition to the D in R D. As such, it s the point where many things change. 

AMD473 and JM335) and ultimately select two for clinical development. The selection cascade and medicinal chemistry program and selection criteria that lead to the identification of these preclinical candidate compounds is described. The additional preclinical studies and chemical development activities required to qualify these compounds as preclinical leads and ultimately as clinical candidates is described. 

A model for predicting oral bioavailability is an important tool, both in the early phases of drug discovery to select the most promising leads for further optimization, and in the later stages to select candidates for clinical development. The... 

The ex vivo methods lend themselves easily for the performance of mechanistic investigations. In order to optimize selection of drug candidates prior to further clinical development, it is important to decipher the contributive roles of permeation, metabolism, efflux, and toxicity. This will then make it possible to properly channel the optimization process, for instance, by permeation enhancement, mucoadhesion, modification of the physicochemical characteristics of the drug, or even change in the route of administration in case the drug and/or formulation turns out to be too toxic. Regarding permeability studies, it is possible not only to quantify passive diffusion but also to identify and characterize (compound)-specific carrier-mediated transport routes. These tools have been used to identify and characterize the relative contribution of... 

DOS seems mainly important for lead identification. Based on the lead structure, additional structural complexity can be introduced in a direct manner by generating focused libraries. For the synthesis of complex molecules, total synthesis as it exists today and the development of selective reactions that accompany, it remain of major importance. Even in case of the successful identification of advanced leads or drug candidates from DOS, an efficient total synthesis is always required in order to provide sufficient amounts of a limited set of derivatives for detailed medicinal chemistry studies up to clinical trials. 

Fig. 1. The Pharmaceutical Pipeline. The different phases of drug development are outlined, starting with a lead compound and moving forward through preclinical and clinical testing towards market approval. (CS candidate selection IND investigational new drug application POC proof of concept NDA new drug application FTIH first time in human).

Lead optimisation is the synthetic modification of a biologically active compound, to fulfill all stereoelectronic, physicochemical, pharmacokinetic and toxicologic required for clinical usefulness (IUPAC). This phase begins with the first chemical lead or lead series selected for optimisation (i.e. the "lead series selected" milestone) and concludes with a decision for an optimized compound to enter preclinical development (i.e. the "pre-clinical candidate selected" milestone). This phase consists of testing of a compound to determine the chemical structure that has the optimum potency and selectivity for the target in question. The phase includes the search for backup compounds and may also include early ADME and toxicity evaluation. 

An optimised (having sufficient potential as a therapeutic candidate to be tested in humans) compound (small molecule) selected to enter pre-clinical development. 

Some of these cytotoxic marine alkaloids are promising candidates for new drugs. For example, ecteinascidins, Fig. (29) are a family of tetrahydroisoquinolone alkaloids isolated from the Caribbean tunicate Ecteinascidici turbinata, which have been selected for clinical development. These compounds are presently in pre-clinical and clinical trials for human cancers [221-225], A series of totally synthetic molecules that are structurally related to the ecteinascidins is currently being prepared and evaluated as antitumor agents [226],... 

Figure 2.10. The microdosing strategy for candidate selection offers the greatest benefit when a stop-development decision is made. This is because the exploratory IND does not forego the submission of a traditional IND to continue testing in the clinic. (IND, Investigational new drug mths, months FIH, First-in-human clinical study Ph1, Phase 1 clinical studies Ph2, Phase 2 clinical studies.)...

The process by which new drug candidates are discovered and developed is both time-consuming and expensive. This is reflected in the high rate of attrition of drug candidates that enter clinical development, such that only approximately 10 percent of drug candidates that are selected for clinical development eventually become marketed drugs. 

The scope of this book covers the entire clinical development continuum from selection of lead candidate to first-in-human studies to ultimate product... 

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