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About tendon injuries

Tendon injuries are very common, affecting up to 1 in 2,000 people each year, with injuries specific to the hand and wrist alone occurring in up to 1 in 2,700 people each year. Flexor tendon injuries currently account for >100,000 significant disabilities in the US annually. These injuries can result from trauma, overuse, or degeneration from work, daily life, and sports activities.


The majority of tendon injuries require surgical treatment to optimize functionality of the injured site. Challengingly, intra-synovial tendons have scarce vascularity and are nourished mainly by synovial fluid. Hence, tendons are among the body tissues that have the poorest healing potential. This poor healing capacity remains problematic for hand surgeons since it exposes their patients to rupture of the repaired tendons, either during rehabilitation and/or through post-operative adhesion formation if immobilization is prolonged.


Tendon injury also poses a huge economic burden on patients and the healthcare system with most injuries occurring in individuals of working age with physical jobs, causing a direct economic impact for payers, suppliers and providers. Societal costs of this medical condition also include indirect costs. Direct costs are those associated with medical care, while indirect costs include lost income, missed workdays, and disability payments.


While certain elite surgeons such as PAX Advisor Dr. Jin Bo Tang have outcomes that are excellent, the typical outcome from repair surgery of a flexor tendon is that up to 20% of the repairs re-rupture leading to significant disability. Even when the repair remains patent, limited mobility, stiffness and pain often result due to adhesions that form during the immobilization post-op. The time required for immobilization and physical therapy pose significant economic burdens, particularly since many of these injuries occur in working adults. For professional athletes, the healing and rehab time, even if the ultimate outcome is acceptable have even higher monetary implications for the athlete and their team.


Despite the incidence of tendon injuries and their disabling impact, no effective interventions have been developed to optimize healing for either humans or animals.


We developed our product candidate PAX-001 using an AAV2 vector to deliver a gene for a growth factor, to optimize healing of both tendons and ligaments.

PAX-001 will be injected in the tendon or ligament either during surgery or through the skin, depending on the type of injury.


Summary of PAX-001:

  • PAX-001 is an adeno-associated viral type 2 (AAV2) vector encoding a growth factor.

  • Efficacy demonstrated in the best animal model for human tendon healing, and PAX-001 is anticipated to also work for horses and dogs based on its mechanism.

  • Small doses are given locally.

  • AAV2 gene delivery enables optimal duration of expression just during healing phase (12-16 weeks).

    • PAX-001 is better than recombinant protein which has too short of a half-life.

    • AAV2 is considered safe and is used in many clinical trials.

    • Limited cellularity of tendons means that while transduction and expression of the growth factor is adequate for local activity for 12-16 weeks, expression is local and does not persist.

    • AAV2 is already licensed as a vector for use in children demonstrating that the approval pathway for this vector approach is well-accepted.

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