Solid Phase Synthesis of an Analogue of Insulin, A0:R glargine, That Exhibits Decreased Mitogenic Activity

Abstract

Numerous analogues of insulin have been prepared over the past three decades for use in diabetic therapy. However, only two long-acting insulins have been approved for clinical use. One is Levemir (Novo Nordisk) and the other is Lantus (Sanofi-Aventis). Glargine (commercial name: Lantus) is characterized by a substitution of Gly in place of Asn at the C terminus of the A-chain and addition of two Arg residues to the C terminus of the B-chain. Despite the clinical advantages of glargine, it is not without concern that its increased affinity for the IGF-1 receptor may correlate with increased mitogenic activity. Recently, a systematic study of modified analogues of glargine showed that placement of an extra Arg residue at the N terminus of the A-chain conferred improved insulin:IGF-1 receptor selectivity without significant loss of pharmacological profile. However, as it is difficult to prepare such an analogue in high yield by recombinant DNA methods, we undertook its chemical assembly by our refined solid phase synthesis method. We describe herein its chemical preparation and biological activity in both insulin receptor binding assays and DNA synthesis assays. The synthetic analogue, A0:R glargine, showed slightly reduced affinity for IR-B (twofold) compared to native insulin. In stimulating DNA synthesis, A0:R glargine was slightly less potent compared to insulin or glargine. This result ultimately confirms the previous report that A0:R glargine has a lower potency in mitogenic assays compared to glargine. This glargine analogue thus could be a potential lead compound for drug design and development for the treatment of diabetes.