Pichia pastoris An alternative yeast species proposed as a recombinant expression system. It performs post-translational modifications that are more similar to human protein modifications than those performed by other yeasts used in fermentation.

pilot plant A medium-scale bioprocessing facility used as an intermediate in scaling up processes from the laboratory to commercial production.

placebo A fake treatment (usually the same formulation used for the real product, but without the active ingredient) administered to the control group in a controlled clinical trial so that the specific and nonspecific effects of the experimental treatment can be distinguished. The experimental treatment must produce better results than the placebo to be considered effective.

polar solvent A solvent for molecules that have permanent electric dipoles.

polishing The final purification step(s) in a biopharmaceutical manufacturing process, usually involving an affinity or other refined chromatography method. Often this step uses the most expensive technique in the process because it handles the smallest amount of material.

polyacrylamide A high molecular-weight polymer of acrylamide (a neurotoxin) used as a support and separations matrix in electrophoresis and gel chromatography.

In pharmaceutical development, analysts generate information-rich and reliable analytical methods to support IND and NDA submissions for innovative medicines.

polymerase An enzyme that catalyzes the production of nucleic acid molecules.

polymerize To undergo or subject to polymerization, a chemical reaction in which two or more molecules combine to form larger molecules that contain repeating structural units.

polymorphism A single mutation in a gene at one nucleotide locus that potentially changes gene expression with a modified protein that may possess different properties, for example, the activity of an enzyme with a drug.

polysaccharide A kind of complex carbohydrate (macromolecule composed of long chains of simple sugars). Several polysaccharides from microorganisms have important commercial uses.

polysorbate 80 A hydrophilic surfactant commonly used as a pharmaceutical excipient, among other things.

polysorbates Complex mixtures of polyoxyethylene ethers used as emulsifiers or dispersing agents in pharmaceuticals.

polyvinyl A polymer prepared from polyvinyl acetates by replacement of the acetate groups with hydroxyl groups. It is used as a pharmaceutic aid (a substance with little or no therapeutic value that is necessary in the manufacture, compounding, or storage of pharmaceutical preparations or drug dosage forms). Polyvinyls are used as solvents, diluting agents, suspending agents, and emulsifying agents.

polyvinyl alcohol A synthetic polymer used as a fixative and an adhesive and as an emulsifying agent, thickener, and stabilizer. Specimens can remain in PVA without damage for long periods of time.

postapproval changes Changes (scale-up, for example) made to a biopharmaceutical manufacturing process after the drug has been approved for marketing.

postmarketing surveillance Phase 4 clinical trials, which provide additional details about a product's safety (while the product is on the market) and efficacy and may be used to evaluate formulations, dosages, durations of treatment, medicine interactions, additional indications, and other factors.

post-translational modification (PTM) After a DNA sequence has been interpreted and a protein has been created, it may be modified by the addition of sugar (glycosylation) or other molecules. This protein processing is done by the Golgi bodies after proteins have been constructed by ribosomes.

potency The measure of the biological activity using a suitably quantitative biological assay (also call potency assay or bioassay), based on the attribute of the product that is linked to the relevant biological properties. [From ICH Q6B]

PQ Performance qualification; Documented verification that all aspects of a facility, utility or equipment perform as intended in meeting predetermined acceptance criteria.