Blocking Axl Protein Shows Promise for Building Stronger Bones

Osteoporosis steals bone strength over time, leaving millions worldwide more vulnerable to fractures and disability. While today’s therapies can slow loss or stimulate growth, many anabolic options are expensive and often require repeated injections—driving interest in safer, more practical ways to boost the body’s own bone-building machinery.

A new study published online on July 6, 2026, in Bone Research points to an unexpected lever for bone formation: blocking the AXL receptor tyrosine kinase (Axl). Researchers report that inhibiting Axl enhances the maturation and activity of osteoblasts, the cells responsible for generating mineralized bone, resulting in increased bone mass in mice.

To find this pathway, the team ran a kinome-wide RNA interference screen, systematically shutting down protein kinase genes to identify regulators of osteoblast differentiation. Among hundreds of candidates, Axl emerged as a previously underappreciated brake on osteoblast function.

The brake was tested with two strategies. First, the researchers reduced Axl activity using genetic approaches. Second, they applied BGB324, a small-molecule Axl inhibitor. Both approaches produced consistent results: osteoblasts differentiated more effectively and formed more mineralized matrix in lab-based experiments and in animal models.

In mice, BGB324 treatment led to measurable gains in bone mass in long bones and vertebrae. The study also showed an increased number of osteocytes—cells integral to maintaining healthy bone structure—suggesting that Axl inhibition supports broader aspects of bone development rather than merely accelerating early-stage differentiation.

Mechanistically, the work links Axl signaling to interferon-stimulating gene 15 (Isg15). Blocking Axl increased Isg15 activity, which the authors interpret as removal of a molecular restraining signal that normally limits osteoblast maturation and downstream bone-forming programs.

Notably, BGB324 is already being explored in cancer-related clinical contexts because Axl can influence tumor growth and immune regulation. Although this osteoporosis research is still preclinical, the existence of a studied inhibitor could streamline future translational efforts.

The findings position Axl as a promising therapeutic target for anabolic osteoporosis strategies, offering a biologically grounded rationale for developing treatments that encourage the skeleton to rebuild. Further studies will be needed to determine whether this mechanism translates into safe, effective benefits in humans.

News Publication Date: 6-Jul-2026
Article Title: Inhibition of AXL receptor tyrosine kinase increases osteoblast function and bone mass
Web References: http://dx.doi.org/10.1038/s41413-026-00554-0
References: DOI: 10.1038/s41413-026-00554-0
Image Credits: Credit: Dr. Mubashir Ahmad, Dr. Anita Ignatius, and Dr. Jan Tuckermann from Ulm University, Germany
Keywords: osteoporosis; AXL; osteoblast differentiation; BGB324; Isg15; Erk1/2; bone mass; osteocytes; osteoimmunology; receptor tyrosine kinase