Biosimilar Drugs in Oncology

Introduction

Biosimilars are preparations very similar to the original reference biological drug. The structure of biologics cannot be defined as precisely as the structure of chemical drugs, so biosimilars may have minor differences in inactive ingredients compared to the original. However, their pharmacological and clinical effects do not differ significantly. In Europe, the first biosimilar product was approved in 2006, and by 2021, 68 such products were registered. Moreover, several patents on biological drugs used in oncology expired by 2020, thus a wave of new oncology biosimilars is expected.

Safety and Effectiveness

In clinical practice, the most important parameters are the safety and effectiveness of a drug. However, if the same level of evidence for the approval of biosimilars as for original biological drugs were required, it would not result in a significant price reduction of the preparation. This does not mean that no clinical or preclinical studies are conducted with biosimilars. A biosimilar drug must prove to the regulatory authority that it is similar to the reference product and that there are no significant differences in qualitative properties, biological activity, efficacy, and safety. The approval of biosimilars operates on the principle of extrapolation. If similarity is demonstrated within one indication, it is extrapolated to other indications of the reference product, and thus clinical evaluations of the biosimilar product are not needed for these indications.

The integration of a biosimilar product into clinical practice should be largely left to the experience and judgment of the physician. Physicians also play a crucial role in post-approval monitoring of biosimilars. After the preparation enters the market, it is essential to continue collecting data on its use, efficacy, and especially safety, which may not have been evident during clinical evaluations. Post-approval surveillance can refine information on the optimal use of the drug in various populations and reflect changes in the summary of product characteristics (SPC).

Interchangeability and Substitution

According to European and American legislation, two preparations are considered interchangeable if the same clinical outcome is expected in any patient, regardless of the order in which the patient is exposed to them. However, interchangeability is assessed by the regulatory authorities, and the method of assessment continues to evolve as medicine gains longer-term experience with these preparations. For example, the American Food and Drug Administration (FDA) requires evidence of the safety and efficacy of switching from the original product to the biosimilar and back.

Conclusion

Biosimilars are drugs that have a similar structure to currently used original biological drugs. In the future, they may play a significant role in the care of cancer patients and improve access to modern treatments. Although many biosimilars will be available in the coming years, their actual use and impact on care outcomes and costs will largely depend on the acceptance by patients, physicians, and healthcare payers, and thus on a good understanding of the safety and efficacy of these substances.

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Sources:
1. Lyman G. H., Balaban E., Diaz M. et al. American Society of Clinical Oncology Statement: Biosimilars in Oncology. J Clin Oncol 2018; 36 (12): 1260–1265, doi: 10.1200/JCO.2017.77.4893.
2. Soares J. C. S., Cavalcanti I. D. L., de Albuquerque Vasconcelos J. L. Can biosimilar products be interchangeable? Pharmaceutical perspective in the implementation of biosimilars in oncology. J Oncol Pharm Pract 2021; May 14: 10781552211016099, doi: 10.1177/10781552211016099.