Formation of neutralizing antibodies during intranasal synthetic salmon calcitonin treatment of postmenopausal osteoporosis

Abstract

Nineteen patients with postmenopausal osteoporosis were treated with 200 u (15 nmol) synthetic salmon calcitonin (sCT) intranasally per day for 15 months. Six months after the start of the nasal administration of sCT, antibodies were recognized in 7, and after 15 months in 10 of the 19 patients studied. The half-maximal dilution of serum binding to 60 pmol/l [125I]sCT (dilution-50) ranged from 2 to 490, and half-maximal inhibition of [125I]sCT binding (60 pmol/l) from 91 to 221 pmol/l sCT. In a cultured breast cancer cell line (T47D) cAMP production was stimulated by sCT (EC50 70 pmol/l). Stimulated cAMP production by sCT (50 pmol/l) was reduced to between 4% and 23% in the presence of serum from patients with antibody dilution-50 of [125I]sCT binding exceeding 32. In patients with lower titer antibodies cAMP production was only marginally suppressed. The values of patients with postmenopausal osteoporosis were in the range of those of earlier studied patients with Paget's disease and clinical resistance to sCT. There was a linear relation between the antibody dilution-50 and the serum dilution required for half-maximal inhibition of cAMP production (P less than 0.01). In conclusion, neutralizing antibodies to sCT may contribute to the decreased responsiveness of bone mineral loss during prolonged treatment with sCT.

Rational design of aggregation-resistant bioactive peptides: Reengineering human calcitonin

“…The combined plot has a linear correlation coefficient of r ϭ 0.87 (P Ͻ 0.02) and a slope of 1.01. The correlation between the predicted and experimental values for the CT [10][11][12][13][14][15][16][17][18][19][20][21] variants is highly significant, showing that the empirical algorithm can be applied successfully to predict the changes in aggregation rates resulting from multiple as well as just single substitutions. At the end of the experiment, the amount of peptide remaining in solution was also measured for all samples.…”

“…The substantially reduced number of sequence differences from hCT in these reengineered variants compared to sCT, together with their lower-aggregation propensities, also should minimize the risk of undesired immunogenic responses (19)(20)(21)(22)(23) or gastric dysfunctions, such as anorexia, nausea, and vomiting (17), that have been reported to occur in patients under treatment with sCT. It has been suggested that the first nine residues at the N terminus of sCT could be particularly important in promoting anorexia (18).…”

“…However, the use of sCT has been shown to cause side effects, such as anorexia and vomiting (17,18), as well as to trigger immune reactions that could severely limit its effectiveness as a drug (19)(20)(21)(22)(23). Interestingly, it has been reported that hCT shows a much higher potency than the salmon variant under specific conditions where aggregation is prevented (24).…”

Calcitonin in Osteoporosis

“…Development of resistance to calcitonin in patients with Paget's bone disease has been correlated with appearance of antibodies against the exogenous peptide [126,127]. In osteoporotic populations, the presence of neutralizing antibodies has never been linked to loss of response, despite the fact that formation of antibodies against salmon calcitonin has been demonstrated in 60-75% of subjects treated for 15 months or longer, using either injectable or nasal spray preparations [40,[128][129][130]. This notion has been corroborated by the results of the PROOF study, where calcitonin-binding antibodies were found in up to 34% of treated subjects, but without any correlation between their presence and skeletal response [51].…”

Contribution of Conformationally Constrained Calcitonin (Ct) Analogs to the Understanding of the Structural and Conformational Requirements of Calcitonin Bioactivity and to the Design of Potent Agonists

“…It has also been suggested that residues of the Cterminal half of sCt are important for binding to the rat C1a, C1b and to the hCt receptors. Interestingly, the chimeric analog ACT-15 ((1-16)hCt/(17-32)sCt) shows a similar in vivo bioactivity to sCt in animal models, at the same time being devoid of the antigenicity and the gastrointestinal side effects of sCt [75][76][77][78].…”