Is End-Stage Knee Osteoarthritis the Key to Faster Drug Approvals?
"New research explores using end-stage knee osteoarthritis incidence as a proxy for knee replacement in clinical trials, potentially speeding up the evaluation of new treatments."
Osteoarthritis (OA) is a significant health challenge, especially as populations age. The quest for effective treatments, particularly disease-modifying osteoarthritis drugs (DMOADs), is ongoing. These drugs aim to not only alleviate symptoms but also alter the course of the disease, potentially regenerating cartilage and improving joint structure.
Regulatory agencies require extensive Phase 3 trials to demonstrate changes in joint space width on X-rays and improvements in patient symptoms before a DMOAD can be approved. However, the real-world value of these drugs also depends on their acceptance by healthcare systems, which prioritize treatments that save resources.
Since joint replacements are costly, a DMOAD that reduces the need for surgery could be highly valuable. However, using knee joint replacement (KJR) as a primary endpoint in clinical trials presents challenges. KJR indications vary widely, and KJR is not considered a fully validated endpoint. New research explores using the incidence of end-stage knee osteoarthritis (esKOA) as a more practical proxy for KJR in clinical trials, potentially leading to faster drug approvals.
The DMOAD Development Challenge
Osteoarthritis is described as the most common form of arthritis and a major cause of disability and impaired quality of life in older adults. A 2016 review examined several ambitious but failed attempts to develop joint structure-modifying treatments. Later reviews discuss emerging technologies and modalities for disease-modifying osteoarthritis drug development, while also noting limitations in the tools used to evaluate candidates.
From Hypertrophic Arthritis to Osteoarthritis
The history of osteoarthritis-osteoarthrosis has been traced through historical literature, paleopathological findings in skeletal remains, artwork, and changing concepts of disease pathophysiology. Historical accounts also describe osteoarthritis in ancient times and the emergence of early medical treatises. The term “osteoarthritis” was first used to denote hypertrophic arthritis in 1886 by John Kent Spender of Bath, England.
Why End-Stage Knee Osteoarthritis Could Be the Answer
Researchers have been exploring the idea of using esKOA as a clinical endpoint. In a study utilizing data from the Osteoarthritis Initiative (OAI), a multicenter cohort study in the United States, researchers analyzed various factors to determine the potential of esKOA as a more viable endpoint than KJR. The study looked at data from 4,796 adults with or at risk for symptomatic knee OA.
- Knee pain and function (using the WOMAC scale)
- Radiographic severity (Kellgren-Lawrence grade)
- Number of compartments affected
- Joint stability and range of motion
Endpoints for End-Stage Knee Osteoarthritis
A scoping review of clinical studies on authorised drugs considered for osteoarthritis repurposing reports that demonstrating a 50% reduction in the incidence of end-stage knee osteoarthritis may require around 200 patients per arm. That estimate applies to patients aged 50 years or older who have Kellgren-Lawrence scores of 2–3 at baseline. Separately, Osteoarthritis Initiative analyses have followed knee-based outcomes from baseline through the first four annual follow-up visits, with knee replacement data collected through the fifth yearly contact.
The Six-Year Course of Hand Osteoarthritis
A study of hand osteoarthritis investigated both the clinical and radiographic course of the disease. It also examined determinants of poor clinical outcome and radiographic progression. The follow-up period was six years and included 289 patients with hand osteoarthritis.
The Future of Osteoarthritis Drug Development
The research indicates that using esKOA as an endpoint could significantly reduce the sample sizes needed for clinical trials, making them more feasible. The study found that the incidence of both esKOA and KJR increased with age, OA severity, and in female patients. However, detecting DMOAD efficacy was considerably easier when focusing on reducing esKOA incidence rather than KJR incidence.
Toward Personalised Disease Modification
Because osteoarthritis varies substantially in its clinical and structural manifestations, a one-size-fits-all treatment strategy may not be appropriate. The Lancet review states that personalised treatment should be considered and notes that most existing disease-modifying osteoarthritis drugs target the cartilage-driven endotype. This perspective supports evaluating therapies according to distinct disease mechanisms rather than assuming that one treatment will suit every patient.
While generating health-economic data is increasingly vital for securing drug reimbursement, this study suggests that clinical trials in the OA field can be more practical. By selecting esKOA as an endpoint, studies can potentially involve a few hundred participants per study arm. Future research will need to validate esKOA as a clinical outcome, particularly for regulatory purposes.
Ultimately, this work, combined with other studies, highlights new aspects in DMOAD research, emphasizing clinically meaningful outcomes beyond just structural and symptomatic improvements. By demonstrating the potential for more manageable trial sizes, it paves the way for trials with health-economic aspects that do not require insurmountable budgets.