USEFUL INFO. - Click here to read - Preclinical & Clinical Trails- the backbone of Drug Development Process "D9"

Preclinical or nonclinical studies, is a stage of drug development process which begins prior to the humans testing of investigational drug (Clinical trials).  Preclinical studies approve or reject thein silico conceptions of drug’s efficacy in biological system. Preclinical studies are conducted in animals to explore the early efficacy of investigational product through pharmacodynamics and kinetics testing. Moreover, thorough investigation of drug’s safety is performed which includes organ system toxicity, besides potential hazards of carcinogenicity, mutagenicity, and teratogenicity. The preclinical findings form the basis of clinical research and allow researchers to estimate a safe starting dose for human testing.

Clinical trials involve healthy human volunteers or patients depending on its stage of testing. These trials are conducted to find if the product:works efficiently in the human volunteers, has an acceptable level of side effects with no adverse effects and at least as effective as any existing treatment.  Larger numbers of participants take part in each progressing trial phase than the prior one, to help evaluating the efficacy and safety of the test compound before allowing it to be used as a therapeutic agent.

Traditionally, clinical trials are divided in 4 stages- Phase I- Phase IV; phase-0 and phase-V, the two additional stages are seldom involved.Phase-0 or micodosing studies are conducted in very small population (a maximum of 15-20)with sub-therapeutic doses. The objective of these studies is to ensure the early bioavailability and pharmacodynamics of drug to minimise the losses if the drug fails in later stages. Drugs undergoing phase-0 trials often skip phase-1. Phase I are dose escalation, tolerability studies, conducted in healthy volunteers largely. Data from phase-I establish the therapeutic dose level,  pharmacodynamics and kinetics. Phase II are exploratory studies which explore the safety and efficacy in 100-300 volunteers. In this phase, the drug is not presumed to have any therapeutic effect whatsoever and required to be proved all over in phase II. Phase III are confirmatory trials conducted upon a large population (1000-2000) to further substantiate Phase II findings. Phase IV, the post-marketing studies are conducted after the drug’s marketing approval. Personal clinicians monitor their patients for long term safety and efficacy of drug. A therapeutic use of the drug other than the approved indication could also be explored in this phase. Phase V is translational research which does not involve any dosing or monitoring instead the research on collected data.Interestingly,the objectives of a study do not remain confined to that phase only but, another study in subsequent phases could also have the same objective. For instance, the pharmacodynamics is studied under phase II however; it may be studied under phase III as well. Therefore, ICH E8 recommends addressing the different phases of clinical trials on the basis of study objective rather than the phase I-V.

U.S. National Institutes of Health (NIH) provides another classification based on the therapeutic objectives. Prevention trials are conducted to prevent a disease in disease naïve population or to prevent the reoccurrence. Screening trials investigate the best way to detect certain diseases or health conditions.Diagnostic trials try to find out a better diagnostic procedure for a particular disease or condition. Treatment trials test experimental treatments, new combination of existing drugs, or new approaches to surgery or radiation therapy. Quality of life trials explore ways to improve comfort for individuals with a chronic illness.Compassionate use or expanded access trials provide partially tested, unapproved therapeutics to a small number of patients who have no other realistic options.

Preclinical trials provide the first substantial, biological data by testing the drug in animals and lay down the foundation for clinical studies. By exploring the potentially hazardous drug in nonhuman animals, preclinical phase not only protects human volunteers for toxic exposure but also provides researcher an opportunity to explore detailed safety/toxicology profile. Thriving upon the preclinical findings, clinical trials extrapolate preclinical safety and efficacy findings to human system where the drug is finally destined to be used and thus lead the deserving candidate drugs to the therapeutics.

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