Antigenicity of desamido-insulin and monocomponent insulin

Impact of product-related factors on immunogenicity of biotherapeutics

All protein therapeutics have the potential to be immunogenic. Several factors, including patient characteristics, disease state, and the therapy itself, influence the generation of an immune response. Product-related factors such as the molecule design, the expression system, post-translational modifications, impurities, contaminants, formulation and excipients, container, closure, as well as degradation products are all implicated. However, a critical examination of the available data shows that clear unequivocal evidence for the impact of these latter factors on clinical immunogenicity is lacking. No report could be found that clearly deconvolutes the clinical impact of the product attributes on patient susceptibility. Aggregation carries the greatest concern as a risk factor for immunogenicity, but the impact of aggregates is likely to depend on their structure as well as on the functionality (e.g., immunostimulatory or immunomodulatory) of the therapeutic. Preclinical studies are not yet capable of assessing the clinically relevant immunogenicity potential of these product-related factors. Simply addressing these risk factors as part of product development will not eliminate immunogenicity. Minimization of immunogenicity has to begin at the molecule design stage by reducing or eliminating antigenic epitopes and building in favorable physical and chemical properties.

Immunogenicity of intraperitoneal insulin infusion using programmable implantable devices

Intraperitoneal insulin infusion using implantable devices in insulin-dependent diabetic (IDDM) patients is promising since it improves diabetic control and decreases frequency of hypoglycaemia. However, preliminary data show a striking increase in plasma levels of anti-insulin antibodies with this therapy. In order to more precisely evaluate the immunogenicity and its consequences, anti-insulin antibody levels in 62 IDDM patients were assessed every 3 months during a 2-year period following pump implantation. At the same time, diabetes control was evaluated with HbA1c, mean blood glucose levels, standard deviation of the daily blood glucose levels and the frequency of low blood glucose (< 3.58 mmol/l). Factors involved in antibody formation such as age, gender, HLA typing, and complement C4 alleles were also studied. After implantation, anti-insulin antibody levels increased significantly from 3.14% (range 0-26%) to 8.34% (0-49%) after 1 year and remained elevated. Patients were divided into two groups: responders able to show at least one antiinsulin antibody titre higher than 15% and non-responders whose titres were always lower than 6%. None of the factors studied was shown to statistically influence the anti-insulin antibody titres. Non-responders had significantly better metabolic results than the responders. Severe hypoglycaemic episodes decreased dramatically in both groups. Insulin requirements were comparable at time 0 and decreased initially in both groups. They remained low for the non-responders but returned to pre-implantation values for responders. Intraperitoneal insulin infusion led to a high immunogenetic response towards insulin in about half of the patients, leading to only moderately deleterious effects on metabolic control.(ABSTRACT TRUNCATED AT 250 WORDS)

The potential immunogenicity of human insulin and insulin analogues evaluated in a transgenic mouse model

Transgenic mice with tissue-specific expression of the human insulin gene in the beta cells of the pancreas do not produce insulin-specific antibodies when injected with human insulin. Tolerant transgenic mice injected with human or porcine insulin reflect the clinical situation. When injected with bovine insulin the transgenic mice produce antibodies. The potential immunogenicity of 12 recombinant human insulin analogues has been tested in this transgenic model. The analogues were designed either to prevent hexamer formation or to improve chemical stability or both. The analogues have amino acid substitutions or deletions at residue 8, 10 and 21 in the A-chain and residue 3, 9, 27 and 28 in the B-chain. The results show that substitution of single amino acids in the A-chain loop of human insulin for the corresponding amino acids in bovine insulin at residues A8 or A10 is sufficient to elicit an antibody response in responder mice. Only human insulin analogues with substitutions at residues 8 or 10 in the A-chain elicit antibody formation in the transgenic mice, whereas non-transgenic control groups respond to insulin and all analogues. Antibodies developed against the human insulin analogues are cross reactive with recombinant human insulin. Antibodies developed against an immunogenic analogue could therefore neutralize both the analogue and the native insulin and thereby aggravate the patient's condition. This transgenic mouse immunogenicity model should be useful as an in vivo model to map immunogenic areas of recombinant proteins.

Chemical stability of insulin in a delivery system environment

Exposure of insulin solutions to elevated temperatures for prolonged periods of time will inevitably lead to chemical modifications of the hormone. Contact with different materials in dosing devices, other design-related factors and motion appear to be chemically more detrimental than storage in glass vials at the same temperature. An in vitro test, designed to mimic the in vivo situation, consisted of delivery of insulin at 37 degrees C while the device was constantly moved on a shaking apparatus. Insulin quality was assessed using high performance liquid chromatography. A polyethylenepolypropylene glycol-stabilized neutral human insulin solution (HOE 21 PH) was used. A single insulin derivative is the major modification product which, after passage of the complete infusion system, amounts to up to 10%. The biological potency of the derivative is indistinguishable from native insulin. Delivery of acidic insulin under implant conditions, leads to extensive and multiple insulin derivatization, even though the biological potency remains 95% after 4 weeks.