Ostra: Clinical trial recruitment in weeks, not months

Finding patients is the slowest part of most clinical trials. Ostra matches trial eligibility criteria against de-identified records from partner hospital networks, then works through each patient’s own physician to make the introduction. Sponsors using Ostra have filled oncology trials in an average of 11 weeks, against an industry norm of six months or more.

Rachel had run trial operations at a mid-sized biotech and lost count of the studies held up by slow enrolment, while Ben had built data systems for a large hospital group. We led the seed round in 2019, and Amira joined the board as the company grew its network to 90 health systems across the United States.

Calder Health acquired Ostra in 2025 to bring recruitment into its contract research business. Rachel now leads Calder’s patient access division, and the Boston team has more than doubled since the deal.