Case Study
Healthy volunteer study,
delivered with 100% completion.
How early recruitment planning, careful pre-screening, and close site coordination helped deliver a demanding single-site clinical study in Bulgaria.
42
participants enrolled
23
visits per participant
100%
participant completion
ON TIME
study delivery
Study overview
Convex partnered with a UK-based biotechnology company to conduct a single-site clinical study evaluating the pharmacokinetic profile and safety of a somatostatin analogue administered intramuscularly at high doses in healthy volunteers. The study required enrollment of 42 participants from a highly specific target population.
Each participant had to complete 23 study visits over approximately two months, including an initial 48-hour inpatient stay. The protocol did not allow enrolled participants who discontinued to be replaced. This made participant retention as important as recruitment itself.
The challenge
01
Narrow target population
Strict age and BMI parameters, non-smoking status, alcohol restrictions, and continuous availability significantly reduced the eligible volunteer pool.
02
Intensive commitment
Every participant was expected to complete 23 visits in about two months, beginning with a 48-hour inpatient stay and followed by frequent study procedures.
03
No room for attrition
Because discontinued participants could not be replaced, the team needed volunteers who met protocol criteria and could realistically complete the full schedule.
Our approach
Recruit early. Screen carefully.
Plan for completion.
Convex began recruitment preparation approximately two months before site initiation. Starting early gave the recruitment team time to understand the target population, develop appropriate outreach channels, build a candidate pool, and conduct preliminary conversations before formal screening began.
Rather than relying on broad advertising alone, recruitment focused on communities more likely to include candidates matching the study profile, including sports communities and university student populations in Bulgaria. The goal was not simply to generate leads, but to create a sufficiently qualified pool from which the investigator team could identify eligible participants.
Recruitment funnel
210
identified
97
potentially suitable
74
invited
42
enrolled
42
completed
Participant readiness
Given the intensity of the schedule and the importance of retention, two psychologists supported pre-screening discussions with potential volunteers.
The conversations focused on availability, understanding of study restrictions, and the practical commitment required over the full two-month period. Final eligibility was determined by the investigator team according to the protocol-defined criteria.
Dedicated study team
Operational coordination
With 42 participants completing up to 23 scheduled visits, the study required close daily coordination between recruitment, medical, nursing, and clinical operations teams. Participant schedules, study procedures, sample collection, documentation, and follow-up activities had to remain aligned throughout the program.
The outcome
42 enrolled. 42 completed.
100% participant completion.
Despite the narrow eligibility criteria, intensive visit schedule, and the importance of avoiding discontinuations, the study was completed according to the timeline agreed with the biotechnology company.
42 / 42
completed
23
visits each
100%
completion rate
ON TIME
delivery
Operational delivery
- All required participant visits were completed.
- Study data were collected and documented according to the study plan.
- Required blood samples were processed and shipped for analysis.
- The study was delivered within the agreed sponsor timeline.
From successful delivery to a new study
Following completion, Convex received a positive written recommendation from the biotechnology company recognizing the site’s performance in delivering a complex single-site study.
The sponsor subsequently selected Convex to conduct an additional clinical study involving a smaller group of healthy volunteers – a strong indication of confidence in the team’s delivery and operational capabilities.
Why it worked
Planning a clinical study in Bulgaria?
Convex supports biotech, pharmaceutical, and CRO partners with local recruitment and hands-on clinical operations.
