Protein Production and Bioprocessing

What is protein production?

Protein production systems, also referred to as an expression system, are commonly utilized by the pharmaceutical industry to produce novel medicines.

Protein production is the biotechnological process of generating a specific protein. It is achieved by the manipulation of gene expression in an organism such that it expresses large amounts of a recombinant gene.

This expression process includes the transcription of the recombinant DNA to messenger RNA (mRNA). When the mRNA is translated into polypeptide chains, the chain folds into functional proteins and can then be targeted to specific subcellular or extracellular locations.

Protein production, to produce a protein or antibody of interest, is a multi-step process.

Steps for starting protein production
 

Protein production starts by first defining what protein you want to produce. Such proteins selected are used to treat specific diseases. The drug development steps for the discovery and production of novel protein drug candidates are:

1. Target Identification
   The first step of drug discovery is to identify the biological origin of a disease, and the potential targets for intervention.
2. Target Validation
   The second step of the drug discovery process is to prove if an identified target is directly involved in a specific disease and if modulation of this target is likely to have a therapeutic effect.
3. Hit Identification and Lead Generation (H2L)
   The next early drug discovery step utilizes a high throughput screening (HTS) process to evaluate and optimize promising lead compounds previously identified as potential targets. These lead compounds undergo more extensive optimization in subsequent steps of drug discovery in the lead optimization (LO) step.
4. Lead Optimization 
   The objective of this drug discovery phase is to synthesize the lead compounds in order to improve properties. Lead optimization includes experimental testing for the confirmation of the identified compound(s). Optimization refers to optimizing binding affinity, selectivity and/or efficacy. Once this process is confirmed, these drug candidates can be registered or patented for intellectual property protection.
5. Preclinical Testing
   In this preclinical step it is vital to determine if the drug candidate has promising activity against the biologic target relevant to the disease of interest. Additionally, sufficient safety and drug-like properties prior to human testing must be identified. Defining safe dosing for human studies is a key aspect of preclinical testing process.
   Preclinical results can be submitted to regulatory authorities (e.g. US - FDA) as an Investigational New Drug (IND) and must be finalized before moving to the clinical phase.
6. Clinical Phase
   Clinical studies consist of 4 phases:
   1. Phase I – first human studies – mainly safety testing on healthy persons
   2. Phase II – testing different doses on patients
   3. Phase III – expanding test panel, efficacy, and meeting primary and secondary endpoints
   4. Phase IV – posting marketing safety study, tackling safety concerns, different populations, and sometimes rare side effects
7. Market Ready
   When the biologic is approved for market release; protein production on a large scale is required.

Transient or stable transfection for protein production?

Transient transfection
 

Transient transfection is ideal for the rapid production for small scale antibody (Ab) production. Transient protein production can be realized in 5-14+ days, depending on the method.

Stable transfection
 

Stable transfection often begins transiently but through a process of careful selection and amplification, stable clones are generated. Within stable transfected cells, the foreign gene becomes part of the host genome and is therefore replicated. Descendants of these transfected cells express the foreign gene and become a stable cell line. Because this transfection process is complex and time consuming, it is more often used for large scale Ab production.