(T1230-03-16) How to Improve in Solubility of Water-Insoluble Cyclic Peptide with HA Nanogel : Over 100,000-Fold Solubilization

Purpose: Cyclic peptides have been attracting attention in recent years as a new drug discovery modality due to their unique structure. Cyclic peptides have properties that differ from those of peptides on linear chains. First, the absence of terminal carboxyl and amino groups makes them highly resistant to hydrolysis by peptidases; second, they have high membrane permeability; and third, their rigid backbone allows for greater selectivity and affinity to the target. These properties provide effective therapy in vivo. However, while cyclic peptides have high potential, the kinetic solubility of drugs is very low, forcing drug development to be interrupted. In our group, cholesterol-modified hyaluronic acid (CHHA), forming nano-sized hydrogel (HA nanogel) in water, having versatile encapsulation property of small-sized molecules, middle-sized molecules, peptide including cyclic peptides, and proteins, have been developed. Herein, we present a novel DDS substrate (HA nanogel) that increases the aqueous solubility of the cyclic peptides by more than 70,000-fold.

Methods: Solubilization of cyclic peptide with HA nanogel: The cyclic peptide powder was added to 1.8mL of CHHA solution in water and stirred with CHHA at 20 ℃< for 24 hours ([CHHA] = 20~24 mg/mL, [Peptide] = 2999~3994μM ). Then, the solutions was filtered using a 0.22μm PES syringe filter. The solubility of peptide in HA nanogel formulation was analyzed using a high performance liquid chromatography.

Results: For a low solubility basic peptide (Cyclic peptide_A) with a molecular weight of 2201 and a ring size of 16, solubility increased to 2187 μM in the presence of 24 mg/mL of HA nanogel. The saturation solubility of the peptide with HA nanogel was almost 70,000 times higher than without. For a low solubility neutral peptide (Cyclic peptide_B) with a molecular weight of 1036 and a ring size of 8, solubility was increased to 4209 μM in the presence of 24 mg/mL of HA nanogel. The saturation solubility of the peptide with HA nanogel was almost 140,000 times higher than without. The cyclic peptide-containing HA nanogel formulation was sterile filterable and easily passed through a 30 G needle.

Conclusion: From the above results, we have concluded that the water-insoluble basic or neutral cyclic peptide-containing HA nanogel formulation have enormous potential to enhance the solubility in water without organic solvent (DMSO, EtOH etc.). We believe HA nanogel can dramatically improve the solubility of your peptides and show a great impact on the patient’s life and their family’s life

References: WO2010-053140

Figure 1. Basic physical properties of Cyclic peptides



Figure 2. Solubility of Water-insoluble cyclic peptides with (blue bar) and without (red bar) HA nanogel after sterile filtration.