1. a closer look at our industry from thought leaders at INC Research
DEVELOPMENT OF BIOSIMILARS,
A CLINICAL PERSPECTIVE
By Hans-Peter Guler, MD
Senior Vice President, Clinical Development, Endocrinology and Cardiovascular
INC Research
INNOVATOR PROTEINS AND FOLLOW-ON BIOLOGICS
With the advent of modern biotechnology, the first recombinant proteins were manufactured starting in the late 1970s
and early 1980s. They were tested in nonclinical and clinical development programs and recombinant insulin and growth
hormone reached the market in the United States in 1982 and 1985, respectively. These initial ground breaking drugs
were followed later by erythropoietin (1989), G-CSF (1991), interferons, fusion proteins, monoclonal antibodies and
vaccines. In 2009, the worldwide market for recombinant therapeutic proteins reached a volume of $128 billion. Today,
numerous medical conditions in endocrinology, nephrology, oncology, hepatology and in autoimmune/inflammatory diseases
(multiple sclerosis, rheumatoid arthritis and others), are treated with recombinant proteins. Many patents of the “pioneer
compounds” have expired or will expire soon. As a result of the increased treatment applicability of recombinant proteins,
a demand for generic options has emerged.
Development of generic proteins called “follow-on biologics” or “biosimilars” has started and should result in reduced cost
due to increased competition which in turn will improve accessibility to these drugs. Currently, the worldwide biosimilar
market is less than $100 million, but by 2014 it is estimated to grow to approximately $2 billion.
The development of biosimilars is not unlike that of most small molecule drugs where generics follow the innovator drugs
once the patents have expired. However, there are very significant differences in the development of biosimilars as compared
to most small molecule generics. Due to their complex, high molecular structure, synthesis, purification and characterization
of proteins, it is a much more complicated process than with small molecules.
PRODUCTION OF THERAPEUTIC PROTEINS
Proteins cannot be produced using classical, step-wise chemical synthesis; this would be far too cumbersome on an industrial
scale. Rather, proteins must be produced using microorganisms (E.coli, different yeast species) plants or animal cells that
are “re-programmed” to express a foreign protein. Initially, the master cell bank is used as a seed and then expanded
to a much larger number of working cells placed in a fermentor. The protein is expressed inside the cell or secreted into
the broth, the “soup” in the fermentor. Subsequently, the protein needs to be recovered and purified. In some cases this
involves correct “folding” of the protein, which means that the three dimensional structure of the protein has to be
adjusted to its biologically active form.
Each of these steps can lead to subtle variations of the three-dimensional structure of the molecule, its glycosylation,
its sialic acid content and other physico-chemical properties, including new impurities such as endotoxins. Hence, a
recombinant protein, unlike a small molecule drug, is only similar to the innovator protein. Consequently, second generation
recombinant proteins will never be identical to the originally approved drug products, which is why these products are
called follow-on biologics or biosimilars.
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2. Furthermore, although assays for the analysis of proteins can detect some of the differences between the innovator drug
and the follow-on, it is likely that some differences cannot be detected and are overlooked. Also, in many cases imprecise
bioassays with their inherent large inter- and intra- assay variation must be used to test the potency of proteins. For example,
the strength testing of erythropoietin includes an in vivo assay in mice where reticulocyte count is the read-out.
IMMUNOGENICITY
Adding further complexity, once the recombinant protein enters the body, the immune system will detect even small
differences between it and the body’s own protein. Antibodies may be formed that may or may not have a blocking
effect on the therapeutic protein but also may neutralize the effects of the endogenous protein such as the body’s own
erythropoietin. The most prominent example of complications generated at least in part by antibodies is a biosimilar of
erythropoietin (Eprex). Use of Eprex was associated with pure red cell aplasia (PRCA) in patients with anemia secondary
to chronic renal failure. This occurred almost exclusively when Eprex was administered by the subcutaneous route, when
a certain type of uncoated rubber stopper was used to seal the vial, and after a change in formulation was made (albumin
was substituted with polysorbate-80 and glycine).
The majority of the PRCA cases clustered in France, Canada, Spain, and the UK. Only very few cases were reported
from Germany, Italy or the United States. Other erythropoietin products or even the same product administered by the
intravenous route did not show clinically significant case numbers of PRCA. This example shows that safety issues specifically
linked to one particular biosimilar product produced and formulated in a specific way can become clinically important
both from a safety and an efficacy standpoint. Therefore, comprehensive immunogenicity data is crucial for each biosimilar
development program.
REGULATORY REQUIREMENTS FOR BIOSIMILARS
The philosophy behind all regulatory requirements is that each biosimilar must go through a so-called comparability exercise
in order to be approvable for marketing. This means that from product characterization to nonclinical data to clinical data,
the product must be similar to an earlier approved product. In all cases, the biosimilar must be similar to a recombinant
protein of the innovator, pioneer generation. This is fundamentally different from generic drugs where proof of chemical
identity along with pharmacokinetic (PK) studies is sufficient for a marketing application in most cases.
There is an established regulatory framework for the development of biosimilars in the European Union (see references).
This framework of guidances was developed to omit unnecessary repetition of studies but still assure sufficient data to write
an adequate label. An overarching guidance for biosimilars has been issued and specific guidelines for recombinant
erythropoietin, insulin, growth hormone, and G-CSF have been issued. The approved biosimilar drug products have created
regulatory precedence and help in developing other biosimilars.
Interestingly, studies carried out by one route of administration (for example intravenous use of erythropoietin in chronic
renal failure) will allow claims by the intravenous route in other indications. This is called extrapolation of study data.
In this case, extrapolation of data allows for use of the biosimilar erythropoietin in chemotherapy associated anemia in
cancer patients or in patients prior to major elective surgery in order to reduce the need for blood transfusions.
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3. In the United States, a regulatory framework comparable to the European guidances is being developed. The Patient
Protection and Affordability Act, passed earlier in 2010, defines a regulatory pathway for biosimilars in the United States
(351k), but the implementation of the act must now be accomplished. The 351k pathway to approval would be shorter
than the regular BLA pathway, particularly with regards to the registration studies.
Criteria for “similarity” and “interchangeability” (a more stringent standard) must be created and the extent of data
to support these claims needs to be defined. Interchangeability is a term not used in the European guidance documents
and would mean that a biosimilar product can be prescribed in place of the innovator product just like it is done with
generic small molecule drugs. Achieving interchangeability is a powerful incentive for biosimilar companies but will
undoubtedly require more extensive studies than demonstrating similarity.
The rules for extrapolation of data for a drug studied in one indication but potentially used in another will have to be
defined. There is an ongoing discussion of whether sponsors could alternatively use the regular BLA pathway (351a) for
approval of biosimilars. This pathway does not require a sponsor to disclose any data until the FDA advisory board or, if
there is no advisory board meeting, until approval of the application. In the case of the new 351k pathway, the sponsor
is required to notify the manufacturer of the reference compound as soon as the FDA accepts the marketing application.
This has important intellectual property implications.
CLINICAL REQUIREMENTS FOR APPROVAL OF BIOSIMILARS IN EUROPE
Approved biosimilars in the EU include epoetin (erythropoietin), somatotropin (growth hormone, GH), and filgrastim (G-CSF).
A brief summary of the clinical requirements for each of these drugs is provided below:
Erythropoietin biosimilars: The applicable guidance specifies that sponsors must demonstrate clinical efficacy and safety
in patients with chronic renal failure with two adequately powered, randomized parallel group studies, one using the
subcutaneous route and the other using the intravenous route. One study should be a “correction phase study” and the
other a “maintenance phase study.”
Alternatively, one large trial using one route of administration and PK bridging studies for the other route of administration
can be used. Six month efficacy data and 12-month safety data must be presented. Immunogenicity data particularly for
the subcutaneous route but also the intravenous route is very important. Formation of antibodies against erythropoietins
is not common and if detected during the pre-marketing phase would be considered a serious issue.
Somatotropin biosimilars: A single dose subcutaneous cross-over PK study in healthy volunteers is needed and should
include pharmacodynamic parameters such as IGF-1. At least one adequately powered, randomized, parallel group,
comparative study in growth deficient children is required to demonstrate efficacy. Treatment naïve children with
GH-deficiency are recommended and the study duration must be six to 12 months. The efficacy study is sufficient to show
safety and must include immunogenicity data.
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4. Filgrastim biosimilars: A single dose subcutaneous and intravenous cross-over PK study in healthy volunteers is needed.
The key pharmacodynamic parameters are absolute neutrophil and CD34+ counts. The recommended setting to demonstrate
comparable clinical efficacy is in the prophylaxis of severe neutropenia in a homogenous group of subjects undergoing
cancer chemotherapy. If appropriate, the data can be extrapolated to indications other than the one studied. Antibodies to
filgrastim occur infrequently, as these subjects are immune-compromised; however, post-marketing data on immunogenicity
are still required.
Insulin biosimilars: To show efficacy, a single-dose subcutaneous cross-over study and a cross-over hyperinsulinemic,
euglycemic clamp study are needed. Clamp studies are conducted in specialized laboratories and allow for a quantitative
estimate of how the body disposes of and uses glucose in the liver, muscles, and fat tissue. No further efficacy data is
required if the data from these studies show comparability. To demonstrate safety, immunogenicity data for six to 12 months
(using the subcutaneous route) are required. Antibodies against insulin are common but most often do not affect blood
glucose control.
Monoclonal antibodies: A concept paper issued by EMA is currently circulating among interested parties and a guidance
for monoclonal antibodies will be developed based on this discussion. It is expected that the new guidance will cover
immunomodulators, including anti-TNF-alpha antibodies, cytotoxic antibodies such as anti-CD20, anti-EGFR, anti-Her2
compounds, as well as antimicrobial monoclonal antibodies such as anti-RSV molecules. Monoclonal antibodies are
structurally very complex and may have several functional domains within a single molecule; this will pose unique
challenges as to how similar the biosimilars have to be compared to the innovator protein. Trial design will have to be
defined. Another discussion point is the choice of endpoints for the clinical studies: should it be the most sensitive endpoint
or the clinically most relevant endpoint?
RISK MANAGEMENT PLAN
The timing, nature and clinical consequences of immunogenicity of biosimilar drugs are not predictable. The lesson
learned from the epoetin experience is that clinically significant adverse effects may be detected only after marketing
approval once the product is used widely. Hence, all biosimilar programs must include a detailed post-marketing risk
management plan with immunogenicity assessments. The risk management plan (RMP) has to include identification/
characterization, risk monitoring, risk minimization/mitigation strategies, communication, and monitoring activities to
ensure effectiveness of risk minimization. The RMP is individually tailored to each product depending on the specific data
available at the time of the marketing authorization.
NON-APPROVAL
Refusal of a marketing application by EMA illustrates key points not to be missed in the development of a biosimilar. An
example is the case of a biosimilar INF-alpha-2 where Roferon-A was the reference product. The regulator concluded that
comparability between the biosimilar and reference product was not adequately demonstrated as there were quantitative
and qualitative differences in the impurity profile, a lack of sufficient validation in the manufacturing process, an inability
to adequately assign drug product shelf-life, and a failure to demonstrate clinical comparability. Among other issues in
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5. the clinical data base was the inadequate documentation of immunogenicity. Assays and methods to assess antibody
response were incomplete. Only the occurrence of antibodies was reported and no data for total, binding or neutralizing
antibody titres were submitted. It is not surprising that these latter deficiencies were considered very important and
decisive in light of the history with pure red cell aplasia with epoetin.
CONCLUSION
Cost reductions with biosimilars are not as substantial as with generic small molecule drugs. Savings on the order of 60%
can be achieved in some developing countries but may be only 10 to 25% in a developed country such as the UK. Estimates
for the United States indicate that $3.5 billion could be saved in the first year after approval of a biosimilar and up
to $71 billion over 10 years in case of approval of an epo, GH, insulin, and interferon biosimilar. Biologics will always
be substantially more costly than small molecule drugs and introducing biosimilars is a worthwhile effort that appears to
be profitable for sponsor companies. Increased access to less costly biosimilar drugs will allow more patients to be
treated with life saving medicines.
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ABOUT THE AUTHOR
Hans-Peter Guler, MD has over 20 years of experience in clinical research. Prior to joining INC Research, Dr. Guler served as
Chief Medical Officer/VP Clinical Development at Phenomix for 6 years, after having held positions of increasing responsibility
with Regeneron Pharmaceuticals, Inc., Chiron Corp. and Ciba-Geigy Corp. His work in clinical research included studies
at all stages from first-in-man to large registration trials. Indications studied included diabetes mellitus, obesity, rheumatoid
arthritis, hepatitis C, asthma, sepsis, cardiovascular disease, and renal failure. Prior to accepting his first job in industry,
he conducted some of the early studies with recombinant insulin-like growth factor I in academia. He is an author of
over 30 peer reviewed articles. Dr. Guler trained in Switzerland and received his M.D. from the University of Zurich.
REFERENCES
• Guideline on Immunogenicity Assessment of Biotechnology-Derived Therapeutic Proteins, European Medicines Agency,
13 December 2007
http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500003946.pdf
• Guideline on Similar Biological Medicinal Products, European Medicines Agency, 30 October 2005
http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500003517.pdf
• Concept Paper on the Development of a Guideline on Similar Biological Medicinal Products Containing Monoclonal
Antibodies, European Medicines Agency, 22 October 2009,
http://www.ema.europa.eu/docs/en_GB/document_library/ Scientific_guideline/2009/11/WC500014438.pdf
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