Ciaran CroninDr. Ciarán N. Cronin, Head of Parallel Protein Production Group, and Group Leader of Gene-to-Structure, Pfizer Global R&D, recently spoke with Cambridge Healthtech Institute on his upcoming presentation, "Production of Human Aldehyde Oxidase (AO) in Baculovirus-Infected Insect Cells (BEVS)" taking place at the Protein Purification Technologies conference from 16-17 November 2017 as part of the 9th Annual PEGS Europe event in Lisbon, Portugal.

Dr. Ciarán N. Cronin heads the Parallel Protein Production Group (PPPG) at Pfizer’s La Jolla campus in San Diego, California. The Group is part of Pfizer’s Global Chemistry line and is responsible for protein expression construct screening and scale-up for all proteins required to support Pfizer’s small molecule oncology drug discovery pipeline. The Group also has responsibilities for gene-to-protein crystal efforts on a number of in-house structure-based drug design (SBDD) targets. Dr Cronin joined Pfizer in 2004 from Syrrx Inc., where he was Associate Director of Molecular Biology and Protein Chemistry. Prior to Syrrx, Dr Cronin was an Assistant Research Biochemist at the University of California San Francisco (1995-2001) and held Senior Scientist positions with Bioresearch Ireland (1992-1994), Biotrin Research, Ireland (1990-1992), and Qlone Ltd., Australia (1988-1989). Dr Cronin received both his Ph.D. and his primary honors degree in Biochemistry from Trinity College, Dublin, Ireland.

To learn more about his presentation and the PEGS Europe Summit, visit

Production of Human Aldehyde Oxidase (AO) in Baculovirus-Infected Insect Cells (BEVS)

What is Aldehyde oxidase (AO), and what is its role in the industry?

Aldehyde oxidase catalyzes the oxidation of a wide variety of compounds, particularly N-heterocyclics which often form the building blocks of modern day drug discovery initiatives. Oxidation of a potential drug candidate by AO will alter its pharmacokinetic profile and generally render the compound ineffective. In certain instances, the oxidized metabolite may cause toxic effects. The specificity of human AO differs from the AO enzymes found in common pre-clinical laboratory test animals. Therefore, it is essential that a compounds potential exposure to the human form of AO be determined prior to entering the compound into clinical trials.

How does Pfizer use recombinant human AO?

Pfizer uses recombinant human AO produced in insect cells to determine the potential exposure of new drug-like compounds to AO oxidation. All compounds with a potential exposure to AO oxidation are centrally screened at Pfizers Laboratories in Groton, CT.

Q: Why not use commercially-available AO?

There is currently only one source of recombinant human AO. However, that enzyme, which is produced in Escherichia coli, is impure and has relatively low enzyme activity. The enzyme produced in insect cells at Pfizer's Laboratories in San Diego, CA is pure and has a thousand-fold greater specific enzyme activity.

Why is recombinant human AO so difficult to produce?

Human AO is a complex enzyme, being a homodimer of 150 kDa subunits, with each monomer containing multiple prosthetic groups to form the active holoenzyme. Each monomer contains a FAD, two iron-sulfur centers and a molybdopterin co-factor that serves as the initial electron acceptor. The molybdopterin group is synthesized de novo from GTP using a seven enzyme biosynthetic pathway. Thus, numerous essential minerals and enzyme activities are required to come together for the production of this complex 300 kDa protein.


To learn more about his presentation and the PEGS Europe Summit, visit