CD44-Targeted Peptide-Colchicine Conjugates for Acute Gout Attacks

K.A. Zoghebi, K.A. Elsaid, K. Parang
Chapman University,
United States

Keywords: gout, drug delivery, peptide, CD44

Summary:

Gout is inflammatory arthritis that is the result of the precipitation of serum urate into crystallized deposits of monosodium urate (MSU) in and around the joint. Gout has gained a huge significance in many countries because of its prevalence has increased among populations. Resident macrophages play a vital role in initiating the inflammation cascade that leads to acute gout attacks. CD44 is a macrophage transmembrane glycoprotein that has various functions in cell division, migration, adhesion, and signaling. The CD44 receptor is overexpressed in many diseases including inflammation, therefore, could be used as targeted delivery for colchicine, which is considered a drug of choice for treatment of gout to reduce its side effects. Recently, peptide P6 ligand (FDAIAEIGNQLYLFKDGKYW) has been found that targets CD44 receptor. The objective of this project was to design CD44-targeting peptide conjugated with colchicine via a hydrolyzable linker to provide specificity and selectivity toward resident macrophages. Peptide P6 and peptide-colchicine conjugate were synthesized using Fmoc/tBu solid phase and solution phase chemistry, respectively, purified by reversed phase HPLC (RP-HPLC), and characterized using Matrix Assisted Laser Desorption/Ionization (MALDI) mass spectrometry. Glutaric anhydride was used as the linker and attached to N-deacetyl colchicine in solution phase to generate colchicine glutaryl ester. Alternatively, the conjugation of P6 and colchicine-glutaryl ester conjugate was carried out on a solid support. Binding studies between the designed conjugate and CD44 were conducted to confirm that the conjugation is binding as the natural ligand does. Furthermore, a comparative study of the stability of the ligand in synovial fluids from normal, mild to moderate, versus severely inflamed joints was carried out to assess P6 peptide stability . Preliminary data of the binding to the CD44 receptor of the conjugate and peptide alone compared to positive control (hyaluronic acid) showed similar binding affinity. Furthermore, P6 showed 50% stability when incubated for 1.5 hours with mild to moderately inflamed synovial fluid. These data suggest that P6 peptide-colchicine conjugate can be synthesized with CD4 binding affinity and moderate stability. This study provides insights into the targeted delivery of colchicine to reduce the associated side affects. This strategy could be beneficial for patients with recurrent episodes of acute gout attacks.