The key safety issue for biosimilars Immunogenicity The key safety issue for biosimilars Prof. Ibrahim A. Alsarra Professor of Pharmaceutics and Pharmaceutical Biotechnology                                    

Immunogenicity: the capability of a specific substance to induce an unwanted immune response that is triggered by more than one single factor. Wanted immunogenicity: is typically related with vaccines, where the injection of an antigen (the vaccine) has to lead to an immune response against the pathogen (the virus, bacterium or substance). Unwantend immunogenicity: is when the organism mounts an immune response against an antigen which is undesired. Unwanted immunogenicity is strongly linked with therapeutic proteins. A fraction of the patient treated with those drugs mount anti-drug-antibodies, which leads to inactivation of the drug and could cause adverse effects. Hermeling S, Crommelin DJ, Schellekens H, Jiskoot W. (2004) Structure-immunogenicity relationships of therapeutic proteins. Pharm Res 21:897–903.

Biotechnology Products Patients Antibody Response 1. Anaphylaxis 2. Infusion Reaction 3. Cross-reactivity to endogenous protein 4- Altered PK 5- Loss of Efficacy 6- No clinical effect detected

Factors influencing immunogenicity Product-related factors include: Protein (structure, primary sequence, oxidation, deamidation). Product impurities, formulation, aggregation, degradation. Properties of the protein, e.g. immunostimulatory, replacement therapy, physiologically important. Dose, route, frequency of administration and duration of therapy. Casadevall N, Nataf J, Viron B, et al. (2002) Pure red-cell aplasia and antierythropoietin antibodies in patients treated with recombinant erythropoietin. N Engl J Med 346:469–475.

Factors influencing immunogenicity Patients-related factors include: Age Gender Genetic make-up Ethnic sensitivity (IFN-alpha 2a more immunogenic in Chinese compared to Caucasian hepatitis patients 39% vs 14%) Immune status Hoesel W, Gross J, Moller R, et al. (2004) Development and evaluation of a new ELISA for the detection and quantification of antierythropoietin antibodies in human sera. J Immunol Methods 294:101–110.

Factors influencing immunogenicity Other factors include: Disease: Typically, the immune reaction against a therapeutic protein is reduced when immunosuppressive agents are used concomitantly. If clinical trials are performed in combination with immunosuppressants, a claim for use of the therapeutic protein in monotherapy must be accompanied by adequate clinical data on the immunogenicity profile in absence of immunosuppressants.

Factors influencing immunogenicity Other factors include: Concomitant treatment: Some patients with chronic infections. In other conditions (e.g. malnutrition, advanced metastatic disease, advanced HIV disease, organ failure). For some products, it has been reported that the development of an antibody response can be different for different therapeutic indications or different stages of the disease.

The problem with immunogenicity is that it is impossible to predict: The clinical consequences and significance The characteristics of the immune response The incidence of unwanted immunogenicity

Immunogenicity of biosimilars: The immunogenicity of the marketed originator product does not influence the need for comparative immunogenicity studies between the originator and biosimilar products. However, if the immunogenicity profiles of marketed and biosimilar products are significantly different, they may be considered dissimilar, making testing for immunogenicity a critical issue when it comes to biosimilars.

Principles for Evaluation of Immunogenicity: The immunogenicity of a similar biological medicinal product must always be investigated. Normally an antibody response in humans cannot be predicted from animal studies. The assessment of immunogenicity requires an optimal antibody testing strategy, characterization of the observed immune response, as well as evaluation of the correlation between antibodies and pharmacokinetics or pharmacodynamics, relevant for clinical safety and efficacy in all aspects.

Principles for Evaluation of Immunogenicity: It is important to consider the risk of immunogenicity in different therapeutic indications separately. Even if efficacy and safety of a biosimilar and the reference product have been shown to be similar, immunogenicity may still be different.

Analysis of immunogenic responses NON-CLINICAL STUDIES: In general, the guideline calls for a risk-based approach to evaluate a biosimilar product on a case-by-case basis. Non-clinical studies should be performed before initiating clinical development. More specifically, in order to assess any difference in biological activity between biosimilar and reference products, data from a number of comparative in vitro studies should be provided.

Analysis of immunogenic responses CLINICAL STUDIES: Biosimilarity should be demonstrated in scientifically appropriately sensitive human models and study conditions, and the applicant should justify that the model is relevant and sensitive to demonstrate comparability in relation to efficacy and safety in the indication(s). In principle, “the most sensitive clinical model should be used in a homogeneous patient population, since this reduces the variability and sample size needed to prove equivalence, and can simplify interpretation.”

Testing for unwanted immunogenicity from biologicals

Analysis of immunogenic responses ELISA: It is a well proven, low cost, open technology platform for detecting high affinity anti-drug antibodies (ADAs).   It has superior drug tolerance, but may miss low affinity ADAs due to the requirement of high sample dilution and multiple wash steps that may disrupt weakly bound ADA-drug complexes.  

Analysis of immunogenic responses Surface Plasmon Resonance: IM assay, has been shown to be efficient in the detection of low affinity ADAs, but overall is not as sensitive as ELISA due to the label free assay configuration and the requirement for sample dilution.  

Analysis of immunogenic responses Rapid Immunogenicity assay: It is capable of detecting both high and low affinity ADAs.  It is very tolerant of acid dissociated samples.   IM assay can be utilized for not only patient sample testing during clinical trials, but more importantly the near- patient monitoring of immunogenic reactions, particularly after the biologic drug/biosimilar is approved.

THE PROBLEM OF IMMUNOGENICITY Case-by-case studies

Case No. 1 Bernhard Hemmer , Olaf St?ve , Bernd Kieseier , Huub Schellekens , Hans-Peter Hartung. Immune response to immunotherapy: the role of neutralizing antibodies to interferon beta in the treatment of multiple sclerosis. The Lancet Neurology Volume 4, Issue 7 2005 403 – 412.

Interferon (IFN) beta: It has already caused many patients to withdraw from treatment. The antibodies inhibit the bioavailability of the cytokine with subsequent decreased clinical effectiveness. Results have led to the cessation of its clinical trials after 13 of 325 healthy volunteers developed treatment-associated thrombocytopenia.

Case No. 2 Johnson & Johnson made a change in the manufacturing process for its EPREX product. EPO is sold in recombinant form (rhEPO) for injection. This product that had been marketed for a decade with no evidence of immunogenicity problems.

Erythropoietin is a glycoprotein which stimulates red blood cell production. It is produced in the kidney and stimulates the division and differentiation of committed erythroid progenitors in the bone marrow. The change caused a serious adverse reaction in a small number of patients.

These patients lost their ability to make red blood cells because they produced an antibody (triggered by the EPREX) that inactivated both the administered protein (EPREX) and the body's natural protein that is essential for red blood cell production. Johnson & Johnson eventually was able to determine the cause of this adverse reaction and correct it, but only after a very lengthy and expensive investigation.

For this reason, post-authorization pharmacovigilance will be critical to reduce the risk of developing unwanted outcomes such as immunogenicity.

Post-marketing surveillance The onset and incidence of immunogenicity is unpredictable; therefore, extended post-marketing surveillance (pharmacovigilance) to monitor potential immunogenicity is very important. Biosimilar guidelines from the EMEA state that a pharmacovigilance plan to address immunogenicity and potential rare adverse events should be included in the data package submitted for the product approval. Locatelli F, Roger S. Comparative testing and pharmacovigilance of biosimilars. Nephrol Dial Transplant 2006;21(Suppl 5):v13-v16.

Such plan must include post-authorization studies which will evaluate: Detection of novel safety signals Occurrence of rare and serious adverse effects previously shown by reference product The safety of extrapolated clinical indications

C o n c l u s i o n s: It is clear that biosimilars are going ahead, with the potential advantage of reducing healthcare costs. However, care must be taken when weighing the immediate advantages of cost savings versus the well-being of the patient.   The development of biosimilars is far more complicated than for synthetic small-molecule generic drugs and, consequently, it is not possible to make an exact copy of the originator protein. Much work needs to be undertaken to ensure that biosimilars are as safe and effective as their originator products.