'Biogenerics': the off-patent biotech products

Medical students' knowledge and awareness levels about biologics and biosimilars: the earlier the better?

BACKGROUND

Although most studies about physician knowledge and attitude toward biosimilars have been conducted on specialists, studies addressing this issue among medical students are missing.

OBJECTIVE

We aimed to evaluate the knowledge and awareness levels of biologics and biosimilars of medical students who will encounter these products soon.

METHODS

In this cross-sectional study, 228 medical students were grouped as preclinical (Years 1,2,3) and clinical (Years 4,5,6). Students were given a survey including demographic (grade and gender) and questions about assessing their knowledge about biologics and biosimilars.

RESULTS

Clinical students' knowledge was better than preclinical students (54% and 25%, respectively). Students did not know much about biosimilars (7-20%) and thought a biosimilar is identical to its generic product (35%). More than 90% of the students thought that a lesson about biologics should be included in the medical curriculum.

CONCLUSIONS

Our study showed that medical students had inadequate knowledge about biosimilars. We suggest that to establish a positive attitude toward prescribing biosimilars, knowledge about biologics and biosimilars should be delivered to physicians early, while they are still medical students, by including this topic into the medical curriculum.

Similar biologics in India: A story of access or potential for compromise?

Biosimilars or similar biotherapeutic products are the biological products approved by regulatory agencies based on the demonstration of similarity in quality, safety and efficacy with reference biologics (or original biologics). Though biosimilars could be considered as interchangeable therapeutic alternatives over original biologics, there are concerns regarding their similarity in effectiveness and safety with reference product along with the level of evidence of similarity required for approval. The biosimilars, particularly, monoclonal antibodies that are developed based on the complex manufacturing processes, require stringent comparative evaluations. The Indian Regulatory Authorities in July 2012 developed the first guidelines for approval of similar biologics, which comprised requirements for the manufacturing process, quality evaluation, preclinical and clinical studies, as well as post-marketing studies. The 2016 guidelines, an update to previous guidelines, were released with the intent to provide a well-defined pathway at par with international regulations for the approval of similar biologics in India. This article highlights the key attributes of the 2016 Regulatory Guidelines and also describes the aspects such as interchangeability, nomenclature and labelling of similar biologics in India. Rigorous consideration is imperative for highly complex similar biologics of monoclonal antibodies on a case-to-case basis.

Variability of Biologics and its Impact on Biosimilar Development

This symposium took place during the International Conference on Malignant Lymphoma (ICML) in Lugano, Switzerland, June 2019, and focussed on scientific aspects associated with development and approval of rituximab biosimilars in lymphoma. The symposium began with an overview presented by Dr Cornes detailing the urgent economic need for biosimilars to improve access to these biologic treatments in oncology and other therapy areas. Prof Schellekens, author of the first paper on biosimilars in 2002, discussed how regulatory strategies for biosimilars were shaped, and how these have evolved in the intervening years. Today, the emphasis of biosimilar development is placed on extensive analytical testing to demonstrate a match with the reference medicine at a fundamental level. Clinical testing plays a confirmatory role, removing any residual uncertainty regarding potential clinical differences between biosimilar and reference medicine. Dr Schiestl presented further detail on analytical perspectives on biosimilars. Development of biosimilars is complicated by the inherent variability of biological synthesis techniques employed in the manufacture of biologics. This variability is further increased by ongoing changes to manufacturing processes, which can result in changes in biological activity. Consistent quality is therefore a cornerstone of biosimilar development. Prof Jurczak provided a comprehensive overview of the factors that must be considered during clinical development of a biosimilar. Clinical trials for biosimilars have a confirmatory role in the development process, rather than the pivotal role played by clinical trials for reference medicines. Therefore, these trials have markedly different objectives compared with reference clinical trials, resulting in differences in the chosen endpoints. In biosimilar trials, response endpoints, which provide rapid and sensitive assessments of equivalence, are preferred to survival endpoints, which require large and lengthy trials for adequate evaluation. Prof Jurczak illustrated this using data from the Phase III clinical trials of the Sandoz rituximab biosimilar. In this trial, Sandoz rituximab demonstrated an equivalent response rate to reference rituximab. Increasing economic pressure on healthcare systems means that biosimilars are likely to play an increasing role in the treatment of cancer in coming years, requiring clinicians to increase their familiarity with these important medicines.

Biosimilar monoclonal antibodies (mAbs) in oncology

Biological medicines are derived from living cells and organisms. Monoclonal antibodies (mAbs) are biological agents that are widely used to treat malignancies including non-Hodgkin's lymphomas and chronic lymphocytic leukaemia. They are effective but expensive. The patents for many mAbs are expiring, so biosimilar medicines, which contain a version of the active ingredient of the original drug, are being developed. Biological medicines cannot be assessed in the same way as standard generic medications because they are difficult to copy and can change over time. A pathway regulates how biosimilars are assessed and compared with the original drug to ensure they are highly similar and have no clinically meaningful differences in terms of structure, function, pharmacodynamics and mechanism of action, pharmacokinetic properties, clinical efficacy and safety. Truxima^{® ▾}(rituximab), the first biosimilar monoclonal antibody to be approved for use in the UK in an oncology setting, is biosimilar to intravenous (IV) rituximab; rituximab improves the effectiveness of standard chemotherapy for lymphoma. The two drugs are comparable in efficacy and safety and have the same indications, dosing regimen and storage procedures.

Population pharmacokinetics of Reditux™, a biosimilar Rituximab, in diffuse large B-cell lymphoma

PURPOSE

Rituximab (MabThera™, Roche) is a chimeric IgG1 monoclonal antibody targeting the CD20 surface antigen on normal and neoplastic B cells. It revolutionized the treatment of non-Hodgkin's lymphoma with superior progression-free and overall survival. However, its prohibitively high cost makes it inaccessible to majority of patients in developing countries. Reditux™ (Dr. Reddy's Laboratories, India), a biosimilar, was introduced in India in 2007 at nearly half the price of the innovator. However, there is a dearth of data regarding the pharmacokinetics and efficacy of Reditux™.

METHODS

Twenty-one patients of diffuse large B-cell lymphoma on R-CHOP regimen were enrolled for the study. Reditux™ was administered as a slow intravenous infusion at a dose of 375 mg/m(2) on day 1 of a 21-day cycle. Pharmacokinetic sampling was performed at pre-dose, post-infusion, 24, 48 h, 7 and 21 days. Rituximab levels were estimated by ELISA. Population pharmacokinetics was performed using NONMEM. In addition, B-cell count was determined at baseline and days 3 and 21 of the first cycle. Survival analysis was performed using Kaplan-Meier plots.

RESULTS

The volume of distribution of central compartment and clearance of Reditux™ were estimated at 0.95 L and 5.98 mL/h, respectively. No covariate effects were seen. B-cell count was completely depleted by day 3 and remained so on day 21. Overall survival was 84.6 % at a median follow-up of 36 months.

CONCLUSION

The pharmacokinetic profile and B-cell response to Reditux™ are comparable with those reported for MabThera™. Thus, MabThera™ can be substituted with Reditux™ for the treatment of B-cell lymphomas.

Biosimilar drugs: Current status

Biologic products are being developed over the past three decades. The expiry of patent protection for many biological medicines has led to the development of biosimilars in UK or follow on biologics in USA. This article reviews the literature on biosimilar drugs that covers the therapeutic status and regulatory guidelines. Appraisal of published articles from peer reviewed journals for English language publications, search from PubMed, and guidelines from European Medicines Agency, US Food Drug Administration (FDA) and India were used to identify data for review. Literature suggest that biosimilars are similar biological products, i.e., comparable but not identical to the reference product, are not generic version of innovator product and do not ensure therapeutic equivalence. Biosimilars present more challenges than conventional generics and marketing approval is also more complicated. To improve access, US Congress passed the Biologics Price Competition and Innovation act 2009 and US FDA allowed “abbreviated pathway” for their approval. U.S law has defined new standards and terms and EMA scientific guidelines have also set detailed approval standards. India being one of the most preferred manufacturing destinations of biosimilars, there is a need for stringent safety and regulatory guidelines. The New India Guidelines “Draft Guidelines on Similar Biologics were announced in June 2012, by Department of Biotechnology at Boston bio and available online.

Review article: biosimilars are the next generation of drugs for liver and gastrointestinal diseases

BACKGROUND

A biosimilar is a copy version of an approved original biological medicine whose data protection has expired.

AIM

To provide an overview of the development of biosimilars worldwide.

METHODS

Literature review of manufacturing processes of biosimilars, differences and similarities between biosimilars and the reference product, approval pathways for biosimilars, challenges in clinical trial study design and available data from clinical trials.

RESULTS

Biosimilars have the same amino acid sequence and highly similar glycosylation patterns that overlap with the originator product. Both efficacy and toxicity are difficult to predict due to subtle molecular changes that might have profound effects on clinical efficacy, safety and immunogenicity. Their main advantage is related to cost savings. Direct evidence of safety and benefit from clinical trials, post-marketing pharmacoviligance and unequivocal identification of the product as a biosimilar are requirements before approval. Non-inferiority or equivalence trials are required by regulatory agencies. Over the past years, several biosimilars have been approved such as erythropoietin or growth factors. Recently, two monoclonal antibodies, Remsima and Inflectra, have been shown to be equivalent to infliximab (INX) in safety and efficacy in rheumatologic conditions. Interchangeability, automatic substitution and switching are key issues when treating patients with biosimilars in clinical practice.

CONCLUSIONS

Biosimilars represent a new generation of drugs in liver and gastrointestinal diseases. On June 27, 2013, Hospira's Inflectra (INX) was the first biosimilar monoclonal antibody to receive positive opinion from European Medicines Agency's Committee for Medicinal Products for Human Use for rheumatoid arthritis, inflammatory bowel disease and plaque psoriasis.

The new world of biosimilars: what diabetologists need to know about biosimilar insulins

Biosimilar pharmaceuticals are emerging as patent protection on the original biopharmaceutical products expires. However, biopharmaceuticals are particularly complex molecules, and biosimilar insulins present special challenges. In part this reflects their structure and chemical modification after synthesis to attain a biologically active form. Their therapeutic window is narrow and the accuracy of their dosing is highly dependent on the formulation and quality of the administration device. For these reasons, the European Medicines Agency has issued stringent guidelines that must be fulfilled in order to receive approval as a biosimilar soluble insulin. Prescribers should therefore consider issues of manufacture, protein quality, formulation, reliability of supply, and other factors that might affect efficacy, safety and tolerability when making choices regarding the selection of biosimilar products.

Lessons learned from biosimilar epoetins and insulins

Patients with diabetes and renal failure may already be receiving biosimilar epoetin and may receive biosimilar insulin in the near future. Because these biosimilar pharmaceuticals (or follow-on biologics) are complex protein molecules manufactured in lengthy and inherently variable processes involving living organisms, they have the potential to induce an immunogenic, rather than a therapeutic, response. This response is dependent as much on the method of manufacture and formulation, as on the protein itself. Apparently small and innocuous differences in manufacture and formulation can lead to unforeseen clinical consequences. This article discusses two case studies illustrating this principle, that of three insulin formulations which were physicochemically similar to comparator insulins, but with pharmacokinetic and pharmacodynamic profiles sufficiently different to have potentially serious clinical consequences and that of Eprex, for which an apparently minor change in one formulation caused an upsurge of cases of pure red cell aplasia which resulted in fatalities or complete transfusion dependence. Comprehensive and rigorous testing and long-term pharmacovigilance programmes are essential to detect and forestall such consequences.

Bioequivalence of two recombinant interferon alpha-2b liquid formulations in healthy male volunteers

OBJECTIVE

Interferon (IFN) alpha-2b is a protein with antiviral, antiproliferative and immunoregulatory properties that is approved for several clinical indications. A new liquid, albumin-free, IFNalpha-2b formulation has recently been developed. This study aimed to evaluate the equivalence of the pharmacokinetic, pharmacodynamic and safety properties of the new formulation with a reference one in healthy male volunteers.

METHODS

A randomised, crossover, double-blind study with a 3-week washout period was performed in which Heberon Alfa R (formulation A) and Viraferon (formulation B) were compared. A single 20 x 10(6) IU IFNalpha-2b dose was administered subcutaneously to 14 apparently healthy male subjects. Serum IFN level was measured over 48 hours by enzyme immunoassay (EIA) and by antiviral activity titration. Clinical and laboratory variables were determined, as were pharmacodynamic and safety criteria.

RESULTS

Groups were homogeneous with regard to all demographic and baseline variables. Pharmacokinetic comparison by EIA did not show differences between the formulations: area under the curve (AUC) 2572 versus 2561 ng x h/L, maximum plasma concentration (Cmax) 318 versus 354 ng/L, time to Cmax (tmax) 8.2 versus 8.5 h, elimination half-life (t(1/2)) 5.87 versus 6.08 h, terminal elimination rate (lambda) 0.122 versus 0.118 h(-1), and mean residence time (MRT) 10.9 versus 12.0 h for formulations A and B, respectively. The differences never reached 20%, which is the clinically significant threshold. The 90% confidence interval of the ratio between them was in all cases within the 0.8, 1.25 range. The two formulations were clinically equivalent with regard to serum IFN antiviral activity titration (0.8, 1.25 criterion) regarding their pharmacokinetic parameters. There were no significant differences with respect to the pharmacodynamic variables: serum beta2-microglobulin and temperature increase. Heart rate and blood pressure changes did not differ either. Both products provoked similar haematological count decreases and had similar safety profiles. The most frequent adverse reactions were fever, tachycardia, headache and arthralgias.

CONCLUSION

The overall analysis strongly suggests the bioequivalence of these two products.

Biochemical assessment of erythropoietin products from Asia versus US Epoetin alfa manufactured by Amgen

We compared the physical and chemical properties of purported copies of recombinant human erythropoietin (rHuEPO) purchased from Korea, China, and India with the innovator product, Epoetin alfa, manufactured by Amgen Inc. The products were characterized for similarity in the types of glycoforms present, the relative degree of unfolding, in vitro potency, presence of covalent aggregates, and presence of cleavage products using established analytical methods. All products were different from Epoetin alfa (Epogen). The purported copies of rHuEPO from Korea, India, and China contained more glycoforms and other impurities. The in vitro relative potency varied for each product when based on the labeled concentration, while the concentration based on ELISA analysis brought the relative potency, for most products closer to 100%. These data emphasize potential biochemical discrepancies resulting from different cell lines and manufacturing processes. Concentrations varied within products and did not always match the information provided on the product label. As it is not possible to reliably correlate such biochemical discrepancies to clinical consequences, or the lack thereof, these data support the need for extensive preclinical testing and clinical testing of all investigational products as not all safety and efficacy aspects can be assessed during preclinical evaluation.

Post-translational modifications of recombinant proteins: significance for biopharmaceuticals

The production of recombinant therapeutic proteins is one of the fastest growing sectors of the pharmaceutical industry, particularly monoclonal antibodies and Fc-fusion proteins. Currently, mammalian cells are the dominant production system for these proteins because they can perform complex post-translational modifications that are often required for efficient secretion, drug efficacy, and stability. These protein modifications include misfolding and aggregation, oxidation of methionine, deamidation of asparagine and glutamine, variable glycosylation, and proteolysis. Such modifications not only pose challenges for accurate and consistent bioprocessing, but also may have consequences for the patient in that incorrect modifications and aggregation can lead to an immune response to the therapeutic protein. This mini-review describes examples analytical and preventative advances in the fields of protein oxidation, deamidation, misfolding and aggregation (glycosylation is covered in other articles in this issue). The feasibility of partially replacing traditional analytical methods such as peptide mapping with high-throughput screens and their use in clone and media selection are evaluated. This review also discusses how further technical advances could improve the manufacturability, potency, and safety of biotherapeutics.

The challenge of biosimilars

BACKGROUND

The purpose of this report was to review issues associated with the introduction of alternative versions of biosimilars used in the oncology setting.

DESIGN

Data were obtained by searches of MEDLINE, PubMed, references from relevant English-language articles, and guidelines from the European Medicines Agency.

RESULTS

When biosimilars are approved in EU, they will be considered 'comparable' to the reference product, but this does not ensure therapeutic equivalence. Inherent differences between biosimilars may produce dissimilarities in clinical efficacy, safety, and immunogenicity. Switching biosimilars should be considered a change in clinical management. Regulatory guidelines have been established for some biosimilar categories but, because of the limited clinical experience with biosimilars at approval, pharmacovigilance programs will be important to establish clinical databases. Guidelines also provide a mechanism for the extrapolation of clinical indications (approved indications for which the biosimilar has not been studied). This may be of concern where differences in biological activity can result in adverse outcomes or when safety is paramount (e.g. stem cell mobilization in healthy donors). These issues should be addressed in biosimilar labeling.

CONCLUSIONS

Biosimilars should provide cost savings and greater accessibility to biopharmaceuticals. A thorough knowledge surrounding biosimilars will ensure the appropriate use of biopharmaceuticals.

Through the looking glass: the protein science of biosimilars

Biopharmaceuticals have revolutionized the treatment and management of many diseases. The advent of recombinant erythropoietins has greatly benefited patients with anemia related to chronic kidney disease and cancer, virtually eliminating the need for blood transfusions. Currently, the patents for many biopharmaceutical molecules have expired or are approaching expiration and a number of biosimilars manufacturers are aiming to claim part of the market share. Unlike the situation for synthetic "small molecule" drugs, identical copies of far more complex biopharmaceuticals cannot be produced. A biopharmaceutical can be 100 to 1000 times larger than a synthetic chemical drug, with extremely complex three-dimensional structure and biological functions which are often not completely understood. Due to their nature and complexity, these fascinating therapeutic molecules are products of highly controlled biological processes. This review takes a look at how biosimilars are fundamentally different from their originator products by examining the biopharmaceutical production process and how it can influence the structure and function of the final drug product.

Procedures for monitoring recombinant erythropoietin and analogues in doping control

The present report summarizes the main analytical strategies developed to identify the presence of recombinant erythropoietin (EPO) administered as a doping agent. Indirect evidence is based on the analysis of blood parameters (haemoglobin, haematocrit, reticulocytes, macrocytes, etc.) and serum markers (concentration of EPO and serum transferrin receptors, etc.). The problem of intertechnique comparison for reliable results evaluation is emphasized, especially for serum markers. Charge differences between isoforms of recombinant EPO and native urinary EPO are the grounds for the isoelectric focusing-double blotting-chemiluminescence detection method presently approved for doping control. Works addressing its advantages and limitations are presented and commented on. The chemical bases of the differential detection are highlighted and some future approaches for detection are also presented. The appearance and detectability of EPO analogues and mimetics susceptible for abuse are also addressed.

The protein science of biosimilars

A sea change is occurring in the off-patent drug manufacturing industry with a first wave of biotechnologically derived products reaching the end of their patent lives. However, recombinant proteins are in a different league from their chemical predecessors in terms of molecular complexity. Small differences in manufacturing processes can affect the efficacy and safety of the recombinant proteins in a manner which is not always measurable using analytical or in vitro techniques. Thus, comparable clinical profiles do not automatically follow from physicochemical likeness and can only be demonstrated through clinical studies. It is essential for patient safety that both innovator and biosimilar manufacturers ensure consistency in their production, by performing rigorous purity and activity profiling between batches, and implement tailored pharmacovigilance plans.

Comparison of two recombinant erythropoietin formulations in patients with anemia due to end-stage renal disease on hemodialysis: a parallel, randomized, double blind study

Background

Recombinant human erythropoietin (EPO) is used for the treatment of last stage renal anemia. A new EPO preparation was obtained in Cuba in order to make this treatment fully nationally available. The aim of this study was to compare the pharmacokinetic, pharmacodynamic and safety properties of two recombinant EPO formulations in patients with anemia due to end-stage renal disease on hemodialysis.

Methods

A parallel, randomized, double blind study was performed. A single 100 IU/Kg EPO dose was administered subcutaneously. Heberitro (Heber Biotec, Havana, formulation A), a newly developed product and Eprex (CILAG AG, Switzerland, formulation B), as reference treatment were compared. Thirty-four patients with anemia due to end-stage renal disease on hemodialysis were included. Patients had not received EPO previously. Serum EPO level was measured by enzyme immunoassay (EIA) during 120 hours after administration. Clinical and laboratory variables were determined as pharmacodynamic and safety criteria until 216 hours.

Results

Both groups of patients were similar regarding all demographic and baseline characteristics. EPO kinetics profiles were similar for both formulations; the pharmacokinetic parameters were very close (i.e., AUC: 4667 vs. 4918 mIU.h/mL; Cmax: 119.1 vs. 119.7 mIU/mL; Tmax: 13.9 vs. 18.1 h; half-life, 20.0 vs. 22.5 h for formulations A and B, respectively). The 90% confidence intervals for the ratio between both products regarding these metrics were close to the 0.8 – 1.25 range, considered necessary for bioequivalence. Differences did not reach 20% in any case and were not determined by a formulation effect, but probably by a patients' variability effect. Concerning pharmacodynamic features, a high similitude in reticulocyte counts increments until 216 hours and the percentage decrease in serum iron until 120 hours was observed. There were no differences between formulations regarding the adverse events and their intensity. The more frequent events were pain at injection site (35.3%) and hypertension (29%). Additionally, further treatment of the patients with the study product yielded satisfactory increases in hemoglobin and hematocrit values.

Conclusion

The formulations are comparable. The newly developed product should be acceptable for long-term application.

Manufacturing, regulatory and commercial challenges of biopharmaceuticals production: a Finnish perspective

Biopharmaceuticals product development is a broad and multidisciplinary field. Science and technology are combined with new manufacturing, regulatory and commercial challenges. However, although there is ample literature on the molecular biology and biochemistry of products, the implementation of processes from test tube to commercial scale has not received similar attention. Consequently, the present study aims to highlight, from practical point of view, some of the key issues involved with manufacturing technologies of biopharmaceuticals at a commercial scale. Regulatory requirements and investments are also addressed based on the practical experiences of start-up and small companies. Finland is used as a case-example of such companies as this is a EU-member state with strong technological growth and rapidly increasing number of biotech companies.

Bioequivalence of two recombinant granulocyte colony-stimulating factor formulations in healthy male volunteers

To evaluate the equivalence of the pharmacokinetic, pharmacodynamic and safety properties of two recombinant G-CSF formulations in healthy male volunteers, a standard 2-way randomized crossover double-blind study, with a 3 week washout period, was conducted. A single 300 microg G-CSF dose was administered subcutaneously. Hebervital (Heber Biotec, Havana, formulation A) and Neupogen (Hoffmann-La Roche S.A, formulation B) were compared. Twenty-four healthy male volunteers were included. The serum G-CSF level was measured by enzyme immunoassay (EIA) during the first 36 h after administration. Absolute neutrophils (ANC), white blood cells (WBC) and CD34+ cells counts were the pharmacodynamic variables measured up to 120 h. Other clinical and laboratory determinations were used as safety criteria. The pharmacokinetic parameters for formulation A and B were very close to each other (i.e. AUC, 235.9 vs 270.0 ng.h/ml; C(max), 29.2 vs 33.4 ng/ml; T(max), 4.2 vs 4.7 h; half-life, 3.2 vs 2.8 h; CL, 260.9 vs 277.2 ml/h; V(d), 1.2 vs 1.1 l; and MRT, 7.58 vs 7.38 h). The confidence intervals for the means ratio of all these parameters were within or very close to the 0.8-1.25 acceptance range. The pharmacodynamics showed high similarity since ANC and WBC had the same profiles for both products and no differences were detected for the estimated parameters. The CD34+ cells count increments were evident for both formulations in a similar way as well. The treatments were well tolerated. Registered adverse events were similar; back/spine pain was the most frequent. According to the overall results these formulations could be considered as clinically comparable.

Clinical comparability of marketed formulations of botulinum toxin

The majority of pharmaceutical products are patented in early phases of their discovery to preclude competition by similar products. Due to unusual circumstances (botulinum toxin is an unpatentable natural product and it is considered to be a biological weapon), technology know-how for botulinum toxin production was classified rather then available in the scientific community. Botulinum toxin type A was marketed in two pharmaceutical distinct formulations from competitor companies. Serendipity proved that the two formulations were not equipotent in terms of mouse units. From a regulatory point of view, differences in potency of distinct formulations are not a matter of concern because each formulation is licensed based on its own set of data. As far as the data in each case is sufficient to prove that a particular formulation is safe and efficacious at its defined dosage, a license for use can be granted. On the other hand, generation of data on comparability is the only way that clinicians and managers can ascertain which product (formulation, serotype) is most cost-effectiveness and to determine whether there are relevant differences in their safety profiles. The results of the systematic review of head-to-head randomised trials comparing BOTOX to Dysport suggest that the two formulations are not bioequivalent whatever the dose relationship. Data on comparative immunogenicity are not available. The indirect comparison of the results obtained in randomised clinical trials comparing BOTOX to placebo and Dysport to placebo support that intrinsic differences are present in the two products. It is concluded that comparative economic evaluations of different botulinum toxin formulations should move away from cost-minimization approaches based on the presumption of bioequivalence and move toward cost-effectiveness or cost-utility models.

Bioequivalence and the immunogenicity of biopharmaceuticals

The expiry of the first patents for recombinant-DNA-derived biopharmaceuticals will open the possibility of marketing generics, if they can be shown to be essentially similar to the innovator product. However, as shown by the problem of immunogenicity, the properties of biopharmaceuticals are dependent on many factors, including downstream processing and formulation. Products from different sources cannot be assumed to be bioequivalent, even if identical genes are expressed in the same host cells and similar production methods are used. Some of the influencing factors are still unknown, which makes it impossible to completely predict biological behaviour, such as immunogenicity, which can sometimes lead to serious side effects.