Recovering a Phase 2 Rheumatoid Arthritis Enrollment Timeline 

By Mila Grieg, MD, PhD, Vice President, Medical Affairs, ACE Therapeutic Strategy Head, Immunology & Inflammation, Evgenia Stankova, MD, PhD, Senior Director, Global Project Leadership, and Tracy Farmer, Project Director, Global Project Leadership

Site selection and patient-population strategy that delivered last-patient-in four months ahead of schedule, on a trial that went on to meet its primary and key secondary efficacy endpoints 

Study Background: Situation and Challenges 

A biopharma sponsor engaged Allucent to complete recruitment for a Phase 2 study in moderate-to-severe rheumatoid arthritis (RA) within an aggressive, benchmarking-driven timeline. The protocol called for a difficult-to-source patient mix: at least 60% conventional synthetic DMARD (csDMARD) failures combined with at least 40% biologic or targeted synthetic DMARD (b/tsDMARD) failures: a population that is inherently slower to identify and enroll than a typical rheumatoid arthritis study. 

The sponsor’s planning assumption of roughly four patients per site per year was above what Allucent’s benchmarked experience predicted for this profile: 0.15 to 0.3 patients per site per month (p/s/m), depending on country and level of competing trials. That gap put the study’s enrollment timeline at risk from the outset. 

Allucent’s Solutions 

Site Selection 

The sponsor’s initial 130-site strategy (targeting 400+ patients) mirrored a competitor program that relied heavily on U.S. sites across 12 countries. Allucent proposed the same number of countries: 12, but fewer sites – 70+ sites based on thorough feasibility and targeting countries with less competition.  

Enrollment Rate Management 

Allucent tracked enrollment pace continuously against the benchmarked range and adjusted site and country mix in response, rather than holding to the original plan. A higher-than-anticipated screen failure rate (42%, driven primarily by lab results that did not meet entry criteria) was absorbed without derailing the timeline. 
 
 
Patient-Population Strategy 

The protocol’s value depended on a high proportion of b/tsDMARD-refractory patients, so Allucent prioritized early activation of countries expected to over-index on that population. The first country activated was projected to deliver roughly 90% b/tsDMARD-failure patients. Delays in activating comparably high-yield countries under the EU Clinical Trials Information System (CTIS): not online until April 2024, seven to eight months after this first country, required the team to manage sponsor decision-making on country and site selection while feasibility assessments continued in parallel. 

Results, Impact and Achievements 

• Last patient in (LPI) was achieved in Q3 2024: four months ahead of the original Q4 2024 target. 

• Actual enrollment rate reached ~0.42 p/s/m, roughly double the top of the projected/budgeted range (0.15–0.3 p/s/m) and ahead of a comparable competitor program’s observed rate of ~0.29 p/s/m. Excluding two exceptionally high-performing sites in Eastern Europe, the rate was ~0.39 p/s/m, still comfortably above plan. 

• The protocol’s target of ≥40% b/tsDMARD-refractory patients was achieved, preserving the scientific integrity of the study population despite the accelerated timeline. 

• Faster-than-planned enrollment allowed the sponsor to close out sites and countries that were not yet contributing, reducing the final study footprint and associated operational cost. 

• The study went on to meet its primary endpoint and key secondary efficacy endpoints, with statistically significant separation from placebo across all doses tested (Table 1). 

What Drove the Pace 

Two operational levers had an outsized effect on timeline: 

• First, milestone timing: the team scrutinized the gap between IRB/EC submission and approval, budget and contract negotiation cycles, and the interval from site activation to first patient screened and enrolled, then targeted the slowest links.  

• Second, site operating characteristics: sites with low staff turnover, strong data quality, and efficient visit scheduling consistently outperformed. For sites at risk of missing activation, the team diagnosed the specific roadblock, increased in-country vendor oversight, and streamlined CTIS and other regulatory submissions.

A Note on Placebo Response: One of RA’s Persistent Trial Risks 

Elevated placebo response is one of the most consistent challenges in rheumatoid arthritis drug development because of composite disease-activity measures (DAS28-CRP, ACR response criteria, CDAI) combine subjective and objective components, and since patients typically remain on background conventional therapy throughout the trial, placebo arms in rheumatoid arthritis trials routinely show meaningful improvement, which narrows the window in which an investigational treatment can demonstrate a clear effect. 

This study was no exception: the placebo arm’s response was on the higher end of what is typically observed in rheumatoid arthritis trials of this design, based on the topline results the sponsor has since made public. Despite that, the investigational treatment achieved statistical significance on the primary endpoint (mean change from baseline in DAS28-CRP at Week 12) across every dose tested and reached statistical significance on key secondary endpoints: ACR20, ACR50, and CDAI low disease activity, with numerical superiority over placebo at every dose. Response rates deepened further at Week 14, reaching some of the highest levels reported to date on these measures. 

A precisely characterized, harder-to-treat patient population and consistent site quality do not eliminate placebo-response risk, but they help protect a study’s ability to still show a clean treatment effect when that risk materializes, which is what this program’s design and execution were built to support.

Enrollment Performance by Country 

Table 1: Enrolment rate is shown in average patients randomized per site per month (p/s/m) by country. 

Key Takeaways 

• In rheumatoid arthritis trials with strict patient-mix requirements, enrolment speed and patient-population precision must be managed together: optimizing for one population alone can undermine the study’s scientific objective. 

• Site operating characteristics (staff turnover, data quality, visit-scheduling efficiency) are leading indicators of enrolment performance and are worth screening for before activation, not just after. 

• Milestone-level timing analysis: IRB/EC approval cycles, contracting, activation-to-first patient can surface the specific bottlenecks worth fixing, rather than treating the whole timeline as one lever. 

• Elevated placebo response remains one of the hardest risks to plan around in Rheumatoid Arthritis trials; rigorous site and patient selection can help preserve a study’s ability to detect a treatment effect even when that risk materializes. 

Allucent brings this combination of patient-population strategy, site selection, enrollment management, and therapeutic expertise to clinical development across immunology & inflammation. With experience spanning rheumatoid arthritis, psoriatic arthritis, lupus and other immune-mediated conditions, Allucent helps sponsors address operational challenges across complex patient populations while protecting integral study endpoints. 

Contact us to learn more about how we help sponsors achieve their autoimmune study objectives.