Study of Intra-articular Delivery of tgAAC94 in Inflammatory Arthritis Subjects

tgAAC94 is a recombinant adeno-associated virus serotype 2 (AAV2) vector genetically engineered to contain the cDNA for a human tumor necrosis factor receptor (TNFR)-immunoglobulin (IgG1) Fc fusion (TNFR:Fc) gene. The DNA sequence of TNFR:Fc in tgAAC94 codes for a protein sequence identical to etanercept (Enbrel®). TNF-alpha has been strongly implicated as a major participant in the inflammatory cascade that leads to joint damage and destruction in diseases such as rheumatoid arthritis (RA), psoriatic arthritis (PsA) and ankylosing spondylitis (AS). Intra-articular delivery of the TNFR:Fc gene (tgAAC94) should result in expression of the secreted protein in the joint space and provide local high concentrations of soluble TNFR:Fc for an extended period of time without requiring frequent administration. Thus, this proposed therapy would be useful in those inflammatory arthritis patients who have a persistently problematic joint despite the use of systemic TNF-alpha blockade or who have a limited number of arthritic joints. Extensive preclinical studies using rAAV2 containing several different transgenes in a variety of animal models have shown efficient and persistent gene transfer and expression with minimal toxicity. The parent virus (wild-type AAV2) is a naturally occurring, non-replicating virus that depends on a helper virus, such as adenovirus, for replication. The recombinant AAV2 vector is unable to replicate in target host cells because it lacks the AAV genes, whose protein products are also required in trans, for replication and packaging of progeny virus. Extensive epidemiological studies have found AAV2 to be non-pathogenic. Although there is no cure for arthritis, treatment has been revolutionized by the advent of anti-TNF-alpha therapies. These include etanercept (Enbrel®), infliximab (Remicade®) and adalimumab (Humira®), which consist of soluble TNF receptors, chimeric human-mouse anti-TNF-alpha monoclonal antibodies and fully human anti-TNF-alpha monoclonal antibodies, respectively. Clinical studies have shown these products to improve the signs and symptoms, inhibit the structural damage, and impact functional outcomes in patients with these inflammatory arthritides.