ADR3, a next generation i-body to human RANKL, inhibits osteoclast formation and bone resorption

Area of Science:

• Biochemistry
• Immunology
• Orthopedics

Background:

• Osteoporosis is a prevalent skeletal disease causing low bone mass and microarchitectural deterioration, increasing fracture risk.
• Conventional osteoporosis treatments have limitations, necessitating novel therapeutic agents.
• I-bodies, a class of single-domain antibodies, offer potential advantages due to their small size and unique binding capabilities.

Purpose of the Study:

• To identify and characterize a novel i-body targeting human receptor activator of nuclear factor-κB ligand (RANKL).
• To evaluate the therapeutic potential of the identified i-body, ADR3, in preclinical models of bone loss.

Main Methods:

• Identification of a human RANKL-specific i-body (ADR3).
• Assessment of ADR3 binding affinity, stability (differential scanning fluorimetry), and effects on osteoclast differentiation and function in vitro.
• Investigation of ADR3's mechanism of action on hRANKL-mediated signaling pathways.

Main Results:

• ADR3 demonstrated high binding affinity to human RANKL (hRANKL) without affecting bone marrow-derived macrophage survival.
• ADR3 exhibited stability across a range of temperatures and pH.
• In vitro studies confirmed ADR3's dose-dependent inhibition of osteoclast differentiation, podosome belt formation, and bone resorption, mediated by inhibiting hRANKL signaling.

Conclusions:

• The identified hRANKL antagonist i-body, ADR3, effectively attenuates osteoclast differentiation and bone resorption.
• ADR3 shows potential as a novel therapeutic agent for protecting against bone loss in osteoporosis.