Complex sentence: Biotechnology allows these peptide and protein pharmaceuticals, some of which were previously rare or difficult to obtain, to be produced in large amount, and it also reduces the risks of contaminants such as host viruses, toxins and prions.
Split into simpler sentences: Biotechnology allows these peptide and protein pharmaceuticals, some of which were previously rare or difficult to obtain, to be produced in large amount. It also reduces the risks of contaminants such as host viruses, toxins and prions.