Current Drug Metabolism, 2006, 7, 15-2115
1389-2002/06 $50.00+.00© 2006 Bentham Science Publishers Ltd.
Early Development of Therapeutic Biologics – Pharmacokinetics
Research Laboratories, Schering AG, Berlin, Germany
Abstract: Modern biologics are biotechnology-derived pharmaceuticals. They are mostly used for diagnosis, prevention
and treatment of serious and chronic diseases. Today, therapeutic biologics range from traditional biologics like blood and
blood components, fractionated blood products, and antitoxins to modern biologics such as monoclonal antibodies, cyto-
kines (e.g. interferon, interleukine), tissue growth factors, vaccines directed against non-infectious disease targets, and
gene transfer products.
Chemical as well as pre-clinical development are major challenges for biologics due to their different physicochemical
properties (mostly protein structure) compared to small molecules. They demonstrate much more complex pharmacoki-
netic behaviour, which strongly influences their pre-clinical testing strategy. Biologics are often highly species-specific in
action and immunogenic in test animal species and humans. Immunogenicity of therapeutic biologics may influence their
pharmacokinetic behaviour as well as pharmacodynamics and toxicity. Biologics are frequently regulated by different
procedures compared to small molecules. New guidances are evolving which reflect the rapid development of new tech-
nologies in this field. Bioanalytical method development and validation is a prerequisite not exclusively for pharmacoki-
netic studies but for the whole pre-clinical and clinical development. Due to their unique properties, different kinds of
bioanalytical assays (mass assays, activity assays, immunogenicity assays) are necessary in early development of biol-
Key Words: Biologics, Proteins, Biotech Products, Pharmacokinetics, Immunogenicity, Bioanalytics, Drug Development.
Therapeutic biologic(al)s (biotherapeutics, protein thera-
peutics, biopharmaceuticals, biological medicinal products,
health products, biotech products) are drugs comprising
various compound classes. Traditionally, blood products as
well as human and animal cells have been classified as biol-
ogics. Modern biologics, however, are defined as biotech-
nology-derived therapeutics e.g. recombinant therapeutic
proteins like monoclonal antibodies, cytokines and growth
factors. Evolving biotechnological products which are still
less visible on the market include gene therapy and cellular
products. The biopharmaceutical industry has dramatically
expanded the number of recombinant proteins marketed as
therapeutics through development of innovative products and
production methods over the past 10 years which mainly
comprise antibodies and cytokines. Already about one third
of new medical entities launched are biologics . Addition-
ally, patents covering the first wave of biologics in the
1980‘s are beginning to expire, creating opportunities for
off-patent use . However, the concept of generics as it’s
used for small molecules cannot be applied to biologics. The
complex physicochemical properties of proteins make it dif-
ficult to demonstrate equality of the same biologics if they
are produced by differing processes. Currently the FDA has
approved no generic biologic and so far there is no regula-
tory path in place for approval of generic biologics.
Chemically, biologics are mainly represented by (glyco)
proteins. Peptide drugs (including oligos, and antisense) and
*Address correspondence to this author at the Schering AG; 13342 Berlin,
Germany; Tel: ++49 30 468 - 17450; E-mail: email@example.com
gene therapy products are not covered in this review due to
their different properties and behaviour as well as different
regulatory issues in the case of gene therapy products. These
are discussed in detail elsewhere [3-5].
Pharmacokinetics of biologics cannot be summarised for
the whole compound class because of the wide variety of
compounds (e.g. monoclonal antibodies, antibody fragments,
cytokines, enzymes etc.). Rather, one has to address a spe-
cific compound class (e.g. antibodies) to describe the phar-
macokinetics and pharmacodynamics. Therefore, only gen-
eral differences in the behaviour of biologics (meaning pro-
teins) compared to small molecules are addressed in this
The first part of this article provides background infor-
mation on common pre-clinical developmental issues of bi-
ologics compared to small molecules. Biologics are fre-
quently regulated by different procedures. New regulatory
guidances are evolving which reflect the rapid development
of this compound class. Chemical as well as pre-clinical de-
velopment are major challenges for biologics due to their
complex physicochemical properties.
The major part of this review focuses on the pharmacoki-
netic behaviour of biologics. In many cases, pharmacokinet-
ics of biologics is not only different but much more complex
compared to small molecules. Immunogenicity of protein
therapeutics may influence their pharmacokinetic behaviour
as well as pharmacodynamics and toxicity. Bioanalytical
method development and validation is a prerequisite not ex-
clusively for pharmacokinetic studies but for the whole pre-
clinical and clinical development. Due to their unique prop-
erties, different kinds of assays (mass assays, activity assays,
immunogenicity assays) are necessary in early development.
Early Development of Therapeutic Biologics – PharmacokineticsCurrent Drug Metabolism, 2006, Vol. 7, No. 1 21
most significant effects for proteins smaller than 70 kDa .
However, conjugation of the protein may also alter receptor
affinity and biodistribution, changing the concentration-
response profile for the protein independent of effects on
pharmacokinetics. Pegylation can also reduce immunogenic-
ity and aggregation . Methods of rational structure-based
design using computational protein: design methods are also
used to reduce immunogenicity as well as to improve other
Clearance mechanisms based on the availability of the
target, which might change during drug treatment, may trig-
ger individualization of dosage and end up with a personal-
ised medicine. This especially holds true for antibodies.
The combination of pharmacodynamic and pharmacoki-
netic information into integrated PK/PD models is generally
considered a promising tool for rationalizing and accelerat-
ing drug development. They can be helpful in defining con-
centration-response relationships in animal models and in
providing a dosing rationale for the first human studies. Pre-
clinical PK/PD-studies are still not common for therapeutic
biologics. They should be conducted in more than one spe-
cies since biologics may frequently exhibit altered affinity
for the target receptor ligand in different animal species .
Identifying biomarkers and methods to analyse them are in-
creasing challenges in the biologics field.
Biologics are not just big chemicals. Based on their dif-
ferent physicochemical properties compared to small mole-
cules, they demonstrate much more complex pharmacoki-
netic behaviour which strongly influences their pre-clinical
testing strategy. There is no way of simply copying our ex-
perience from small molecules to therapeutic biologics. The
development of therapeutic biologics needs a well designed
pre-clinical development program including pharmacokinetic
studies appropriately balancing risks and benefits.
The increasing use and knowledge of this heterogenic
class of compounds is triggering new technologies to over-
come limitations in exploring its pharmacokinetic behaviour.
As we have observed in the past for small molecules, the
high attrition rates in the development process can be re-
duced by such improvements.
The author thanks Prof. Tom Tozer, South San Francisco
and Dr. R. Zierz, Schering AG, Berlin for their inspiring
 Tang, L., Persky, A.M., Hochhaus, G., Meibohm, B. (2004) J.
Pharmaceut. Sci. 93, 2184-2204.
Schellekens, H. (2004) Trends Biotechnol. 22, 406-410.
Levin, A.A. (1999) Biochim. Biophys. Acta 1489, 69-84.
Kamiya, H., Akita, H., Harashima, H. (2003) Drug Discov. Today
Nakagawa, S., Mayumi, T. (2003) Drug Metab. Pharmacokin.
 Jason, T.L.H., Koropatnick, J., Berg, R.W. (2004) Toxicol. Applied
Pharmacol. 201, 66-83.
Crommelin, D.J.A., Storm. G., Verrijk, R., Leede, L., Jiskoot, W.,
Hennink, W.E. (2003) Intern. J. Pharmaceut. 266, 3-16.
Marshal, S.A., Lazar G.A., Chirino, A.J., Desjarlais, J.R. (2003)
Drug Discov. Today 8, 212-221.
Walsh, G. (2003) Eur. J. Pharmaceut. Biotherapeut. 55, 3-10.
Walsh, G. (2004) Eur. J. Pharmaceut. Biotherapeut. 58, 185-196.
Dempster, M.A (2000) Biotechnol. Ann. Rev. 5, 221-258.
Galluppi, G.R., Rogge, M.C., Roskos, L.K., Lesko, L.J., Green,
M.D., Feigal, D.W., Peck, C.C. (2001) Clin. Pharmacol. Ther. 69,
Elmquist, W.F., Miller, D.W. (2000) J. Pharmaceut. Sci. 90, 422-
Green, M.D. (1997) Intern. J. Toxicol. 16, 33-40.
Guidance for Industry, S 6 Pre-clinical Safety Evaluation of Bio-
technology-derived Pharmaceuticals, ICH, July 1997.
Toon, S. (1996) Eur. J. Drug Meatabol. Pharmacokinet. 21, 93-
Mahmood, I. (2003) J. Pharmaceut. Sci. 93, 177-185.
Supersaxo, A., Hein W.R., Steffen, H. (1990) Pharm. Res. 7, 167-
Beshyah, S.A., Anyaoku, V., Niththyananthan, R., Sharp, P., and
Johnston, D.G. (1991) Clin. Endocrinol. 35, 409-412.
Cleland, L., Daugherty, A., Mrsny, R. (2001) Curr. Opin. Biotech-
nol. 12, 212-219.
Banerjee, P.S., Hosny, E.A., Robinson, J.R. (1990) In: Lee, V.H.L.,
editor. Peptide and Protein Drug delivery, New York, Basel, Hong
Kong, Marcel Dekker, 507.
Mohler, A.M., Cook, J.E., Baumann, G. (1992) In: Ferraiolo, B.L.,
Mohler, M.A., Gloff, C.A., editors. Protein Pharmacokinetics and
Metabolism New York, London, Plenum Press, 35-71.
Hasbach, M., Klein, C., Schirner, M., Baumann, A. (2005) Inter-
national Research Meeting, Schering AG.
Lobo, E.D., Hansen, R.J., Balthasar, J.P. (2004) J. Pharmaceut.
Sci. 93, 2645 –2268.
Working, P., Cossum, P. (1991) In: Garzone P., Colburn, W.,
Mokotoff, M., editors. Peptides, peptoids, and proteins. Vol. 3,
Cincinatti, OH: Harvey Whitney Books, 158-168.
Wadhwa, M., Bird, C., Dilger, P., Gaines-Das, R., Thorpe, R.
(2003) J. Immunol. Methods 278, 1-17.
Schellekens, H., Casadevall, N. (2004) J. Neurol. 251(Suppl 2),
US Food and Drug administration.Guidance for industry – Immu-
notoxicological Evaluation of Investigational New Drugs.
Washington, DC: Center for Drug Evaluation and Research,
Chirino, A.J., Ary, M.L., Marshall, S.A. (2004) Drug Discov.
Today, 9, 82-90.
Mire-Sluis, A.R., Barrett, Y.C., Devananrayan, V., Koren, E., Liu,
H., Maia, M., Parish, T., Scott, G., Shankar, G., Shores, E.,
Swanson, S., Taniguchi, G., Wierda, D., Zuckerman, L.A. (2004) J.
Immunol. Methods 289, 1-16.
Quin C.J., Rodila, R., Gage, E.M., El-Shourbagy, T.A. (2004) Am.
Pharmaceut. Rev. 7, 4-89.
DeSilva, B., Smith, W., Weiner, R., Kelley, M., Smolec, J., Lee,
B., Khan, M., Tacey, R., Hill, H., Cleniker, A. (2003) Pharmaceut.
Res. 20, 1885-1900.
US Food and Drug administration.Guidance for industry – bioana-
lytical method validation.Washington, DC: Center for Drug
Evaluation and Research, (2001), May.
Rolan, P., Atkinson, A.J., Lesko, J. (2003) Clin. Pharmacol. Ther.
Colburn W.A., Lee, J.W. (2003) Clin. Pharmacokinet. 42, 997-
Luo, P., Hayes, R.J., Chan, C., Stark, D.M., Hwang, M.Y., Jacinto,
J.M., Juvvadi P., Chung H.S., Kundu A., Ary, M.L., Dahiyat B.I.
(2002) Protein Sci. 11, 1218-1226.
Mordenti, J., Chen, S.A., Moore, J.A., Ferraiolo, B.L., Green J.D.
(1991) Pharm. Res. 8, 1351-1359.
Baxter, L.T., Zhu, H., Mackensen, D.G., Butler, W.F., Jain, R.K.
(1995) Cancer Res. 55, 4611-4622.
Harris, J.M., Martin, N.E., Modi, M. (2001) Pharmacokinetics 40,
Received: July 19, 2005Revised: August 4, 2005 Accepted: August 8, 2005