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.

Inclusion criteria

• Rheumatoid arthritis (RA), psoriatic arthritis (PsA), or ankylosing spondylitis (AS) diagnosed according to established criteria.
• Persistent moderate (grade 2) or severe (grade 3) swelling due to inflammatory arthritis in at least one peripheral joint eligible for injection.
• For subjects with RA, an adequate trial of at least one disease-modifying drug (DMARD) prior to screening.
• For subjects currently on DMARD(s), a stable regimen of inflammatory arthritis for the previous three months, with no changes in doses four weeks prior to screening.
• Age greater than 18 years and less than 75 years at the time of screening.
• Willingness to practice effective birth control measures during the study (through week 36), if male or female of reproductive ability.
• Able to give written informed consent.

Exclusion criteria

• Disease severe enough to warrant a change in regimen for inflammatory arthritis in the next three months.
• Discontinuation of etanercept in the past because of safety concerns.
• Current use of anakinra (Kineret®)or abatacept (Orencia®).
• Corticosteroid therapy at doses higher than the equivalent of 10 mg prednisone per day.
• Steroid or hyaluronate injection in the target joint or receipt of an investigational agent less than four weeks prior to screening.
• Class IV ACR functional status (Hochberg et al., 1992).
• Any of the following laboratory values: Hemoglobin <8.5 gm/dL, white blood cell count <3500 per mm cube, platelet <100 K/uL, creatinine >2 mg/dL, bilirubin >2 mg/dL, AST or ALT >2 times the upper limit of normal, or abnormal coagulation profiles (>2 seconds beyond upper range of normal PT or PTT).
• Known HIV infection, known hepatitis C infection, or known positive serologic test for hepatitis B surface antigen.
• Positive PPD, unless previously treated with appropriate prophylaxis.
• Pregnancy or lactation, either at the time of screening or planned in the next 18 months.
• Inflammatory bowel disease, such as Crohn's disease or ulcerative colitis.
• Serious medical disease, such as severe liver or kidney disease, uncompensated congestive heart failure, myocardial infarction within six months, unstable angina, uncontrolled hypertension, severe pulmonary disease or uncontrolled asthma, demyelinating neurological disease, history of cancer (other than cutaneous basal and squamous cell carcinoma) with less than five years documentation of a disease-free state, insulin-dependent diabetes, recurrent opportunistic infections or other concurrent medical condition that, in the opinion of the investigator, would make the subject unsuitable for the study.
• Unlikely to comply with protocol.