Development of biopharmaceuticals is a challenging issue in bioethics. Unlike conventional, small molecular weight drugs, biopharmaceuticals are proteins derived from DNA technology and hybrid techniques with complex three dimensional structures. Immunogenicity of biopharmaceuticals should always be tested in clinical settings due to low predictive value of preclinical animal models. However, non-human primates (NHP) and transgenic mice could be used to address certain aspects of immunogenicity. Substantial efforts have been made to reduce NHP use in biopharmaceutical drug development, e.g. study design improvements and changes in regulatory policy. In addition, several expert groups are active in this field (e.g. NC3Rs, BioSafe, and Biopharmaceutical Technical Group). Despite that, there is an increasing trend of use of NHP in preclinical safety testing of biopharmaceuticals, especially regarding monoclonal antibodies. Other potential bioethical issues related biopharmaceutical drug development are their cost/effectiveness ratio, clinical safety assessment, production of biosimilars, and comparison of their efficacy with placebo in countries without intention to market. Identification of the human genome has opened many new bioethical issues. Development of biopharmaceuticals is an important bioethical issue for several reasons. It connects all aspects of contemporary bioethics: biomedicine (e.g. clinical trials in vulnerable subjects), animal welfare and the most recent advances in biotechnology. In particular, biopharmaceutical drug development is a challenging issue regarding treatment of rare diseases.