Clodfelter D K, Pekar A H, Rebhun D M, Destrampe K A, Havel H A, Myers S R, Brader M L
Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
Pharm Res. 1998 Feb;15(2):254-62. doi: 10.1023/a:1011918719017.
To utilize an acylated peptide as a model system to investigate the relationships among solution peptide conformation, non-covalent self-association, subcutaneous absorption and bioavailability under pharmaceutically relevant solution formulation conditions.
CD spectroscopy, FTIR spectroscopy, equilibrium sedimentation, dynamic light scattering, and size exclusion chromatography were employed to characterize the effects of octanoylation on conformation and self-association of the 31 amino acid peptide derivative des-amino-histidine(7) arginine(26) human glucagon-like peptide (7-37)-OH (IP(7)R(26)GLP-1). Hyperglycemic clamp studies were performed to compare the bioavailability, pharmacokinetics, and pharmacodynamics of solution formulations of oct-IP(7)R(26)GLP-1 administered subcutaneously to normal dogs.
Octanoylation of IP(7)R(26)GLP-1 was shown to confer the propensity for a major solvent-induced conformational transition with an accompanying solvent- and temperature-dependent self-association behavior. Formulations were characterized that give rise to remarkably different pharmacodynamics and pharmacokinetics that correlate with distinct peptide conformational and self-association states. These states correspond to: (i) a minimally associated alpha-helical form (apparent molecular weight = 14 kDa), (ii) a highly associated, predominantly beta-sheet form (effective molecular diameter 20 nm), and (iii) an unusually large, micelle-like soluble beta-sheet aggregate (effective molecular diameter 50 nm).
Bioavailability and pharmacokinetics of a self-associating peptide can be influenced by aggregate size and the ease of disruption of the non-covalent intermolecular interactions at the subcutaneous site. Hydrophobic aggregation mediated by seemingly innocuous solution formulation conditions can have a dramatic effect on the subcutaneous bioavailability and pharmacokinetics of a therapeutic peptide and in the extreme, can totally preclude its absorption. A size exclusion chromatographic method is identified that distinguishes subcutaneously bioavailable aggregated oct-IP(7)R(26)GLP-1 from non-bioavailable aggregated oct-IP(7)R(26)GLP-1.
利用一种酰化肽作为模型系统，在药学相关溶液制剂条件下，研究溶液中肽的构象、非共价自缔合、皮下吸收和生物利用度之间的关系。
采用圆二色光谱（CD光谱）、傅里叶变换红外光谱（FTIR光谱）、平衡沉降、动态光散射和尺寸排阻色谱法，表征辛酰化对31个氨基酸肽衍生物去氨基组氨酸(7)精氨酸(26)人胰高血糖素样肽(7 - 37)-OH（IP(7)R(26)GLP-1）构象和自缔合的影响。进行高血糖钳夹研究，以比较皮下注射给正常犬的辛酰化IP(7)R(26)GLP-1溶液制剂的生物利用度、药代动力学和药效学。
结果表明，IP(7)R(26)GLP-1的辛酰化赋予了其在主要溶剂诱导的构象转变倾向，并伴随有溶剂和温度依赖性的自缔合行为。对制剂进行了表征，其产生了与不同肽构象和自缔合状态相关的显著不同的药效学和药代动力学。这些状态对应于：(i) 一种最低程度缔合的α-螺旋形式（表观分子量 = 14 kDa），(ii) 一种高度缔合、主要为β-折叠形式（有效分子直径20 nm），以及(iii) 一种异常大的、类似胶束的可溶性β-折叠聚集体（有效分子直径50 nm）。
自缔合肽的生物利用度和药代动力学可受聚集体大小以及皮下部位非共价分子间相互作用的破坏难易程度影响。看似无害的溶液制剂条件介导的疏水聚集可对治疗性肽的皮下生物利用度和药代动力学产生显著影响，在极端情况下，可完全阻止其吸收。确定了一种尺寸排阻色谱方法，可区分皮下生物可利用的聚集辛酰化IP(7)R(26)GLP-1和非生物可利用的聚集辛酰化IP(7)R(26)GLP-1。
