Gene Therapy for Osteoarthritis: Pharmacokinetics of Intra-Articular Self-Complementary Adeno-Associated Virus Interleukin-1 Receptor Antagonist Delivery in an Equine Model

Abstract

Toward the treatment of osteoarthritis (OA), the authors have been investigating self-complementary adeno-associated virus (scAAV) for intra-articular delivery of therapeutic gene products. As OA frequently affects weight-bearing joints, pharmacokinetic studies of scAAV gene delivery were performed in the joints of the equine forelimb to identify parameters relevant to clinical translation in humans. Using interleukin-1 receptor antagonist (IL-1Ra) as a secreted therapeutic reporter, scAAV vector plasmids containing codon-optimized cDNA for equine IL-1Ra (eqIL-1Ra) were generated, which produced eqIL-1Ra at levels 30- to 50-fold higher than the native sequence. The most efficient cDNA was packaged in AAV2.5 capsid, and following characterization in vitro, the virus was injected into the carpal and metacarpophalangeal joints of horses over a 100-fold dose range. A putative ceiling dose of 5 × 10 viral genomes was identified that elevated the steady-state eqIL-1Ra in the synovial fluids of injected joints by >40-fold over endogenous levels and was sustained for at least 6 months. No adverse effects were seen, and eqIL-1Ra in serum and urine remained at background levels throughout. Using the 5 × 10 viral genome dose of scAAV, and green fluorescent protein as a cytologic marker, the local and systemic distribution of vector and transduced cells following intra-articular injection scAAV.GFP were compared in healthy equine joints and in those with late-stage, naturally occurring OA. In both cases, 99.7% of the vector remained within the injected joint. Strikingly, the pathologies characteristic of OA (synovitis, osteophyte formation, and cartilage erosion) were associated with a substantial increase in transgenic expression relative to tissues in healthy joints. This was most notable in regions of articular cartilage with visible damage, where foci of brilliantly fluorescent chondrocytes were observed. Overall, these data suggest that AAV-mediated gene transfer can provide relatively safe, sustained protein drug delivery to joints of human proportions.

Editorial: Arthritis Gene Therapy Using Interleukin‐1 Receptor Antagonist

“…Safety is an overriding concern when using gene therapy for nonlethal diseases such as OA. Several detailed studies, the present one included, have demonstrated no evidence of persistent viral genomes outside the injected joint, and no major adverse events have been reported , thus providing reassurance on this issue.…”

“…Detailed in vitro studies by Bajpayee and colleagues have shown that particles larger than ~10 nm, depending on shape and charge, do not penetrate the extracellular matrix of normal cartilage. However, AAV, which is ~20 nm in size, is able to transduce chondrocytes in situ after injection into equine joints . This may be enabled by the pumping action that occurs in cartilage as the horse moves.…”

Detection of intra‐articular gene therapy in horses using quantitative real time PCR in synovial fluid and plasma

“…The recombinant AAV (rAAV) DNA is expressed and incorporated into the viral vector capsule using a plasmid system in a packaging cell line 12 . There are many serotypes of AAV and appropriate rAAV vectors are chosen for specific applications based on tissue tropism and transduction efficiency 13–16 . In horses, rAAVs have predominantly been used for intra‐articular delivery of anti‐inflammatory or anabolic genes such as IL1‐RA, 14,15,17,18 IGF‐1, 19,20 and most recently, IL‐10 21 …”

Control of cartilage homeostasis and osteoarthritis progression by mTORC1/4E-BP/eIF4E axis

“…Importantly, IL-1β production is associated with cartilage degeneration in OA (20), and it was shown that inflammatory molecules produced by synovium can induce ECM loss (21). The importance of IL-1 signaling was also highlighted in animal models of posttraumatic OA (22–24). Potential clinical relevance of identified translationally controlled targets, such as Fn1 and an orphan receptor Nr4a1, was tested in diseased cartilage and in a rat model of post-traumatic OA.…”

“…Recent publications from two independent groups have highlighted the importance of IL-1 signaling in various small and larger animal models of posttraumatic OA (22–25). For example, IL-1 receptor antagonist therapy significantly improved cartilage, synovial membrane parameters, and disease-modifying effects in the equine OA model (26).…”