Waiving in vivo studies for monoclonal antibody biosimilar development: National and global challenges.

Biosimilars are biological medicinal products that contain a version of the active substance of an already authorised original biological medicinal product (the innovator or reference product). The first approved biosimilar medicines were small proteins, and more recently biosimilar versions of innovator monoclonal antibody (mAb) drugs have entered development as patents on these more complex proteins expire. In September 2013, the first biosimilar mAb, infliximab, was authorised in Europe.

Prolonged in vivo residence times of antibody fragments associated with albumin.

Antibody fragments can be expressed at a high level in microbial systems, but they may have limited therapeutic value because they are rapidly eliminated from the body. We demonstrate here that site-specific conjugation or binding of bacterially derived Fab' to the long-lived protein serum albumin allows full retention of the antibody's binding characteristics while imparting the albumin's longevity in vivo. In rats the area under the curve for Fab' conjugated to rat serum albumin was 17-fold greater than for the control of Fab' conjugated to cysteine.

F(ab')2 molecules made from Escherichia coli produced Fab' with hinge sequences conferring increased serum survival in an animal model.

Fab's with hinges based on the human gamma1 sequence containing 1, 2, or 4 cysteines have been produced by high level Escherichia coli periplasmic secretion, and coupled in vitro by reduction/oxidation to form F(ab')2. We find that the F(ab')2 made with hinges containing 2 or 4 cysteines have a high level (approximately 70%) of multiple disulphide bonds. These F(ab')2 molecules have an increased pharmacokinetic stability as measured by area under the curve compared to those made by direct coupling through a single disulphide bond.

Immune enhancing effects of dehydroepiandrosterone and dehydroepiandrosterone sulphate and the role of steroid sulphatase.

Steroid hormones, such as glucocorticoids (GC), influence immune and inflammatory responses through their suppressive actions. Recent evidence suggests that another steroid hormone, dehydroepiandrosterone (DHEA), provides an immunostimulatory influence opposing the effect of GC. DHEA circulates in its inactive sulphated form, DHEAS, requiring conversion to DHEA by a steroid sulphatase (SS) enzyme for biological activity.

Increased cyclosporine sensitivity of T cells from cord blood compared with those from the adult.

Despite the increasing numbers of paediatric transplants performed, little is known about the immune responses of T lymphocytes in human neonates. Here we have compared the effects of cyclosporine on the phytohaemagglutinin (PHA) response of immature (cord) and mature (adult) lymphocytes using the following parameters of activation: (i) proliferation, measured by 3H-thymidine uptake; (ii) expression of cell surface IL-2 receptor; (iii) release of IL-2 into the supernatant. Cyclosporine was added to cultures of PHA-stimulated lymphocytes at doses ranging from 5 to 5000 ng/ml.