Yes, IBR 403 was identified through a chemical screen using both mobilized and non-mobilized adult peripheral blood CD34+ cells, confirming by design that it works in adult CD34+ populations. Work is ongoing to refine protocols for these adult cells, building on an already well-defined protocol established for cord blood HSEs. In parallel, the team is exploring the use of IBR in iPSC-derived HSEs, where it is being tested as a tool to expand intermediate progenitor populations rather than drive differentiation. This approach addresses a key challenge in the iPSC space: while differentiated iPSCs can be expanded extensively, differentiation initiates a limited window for population doublings, making early progenitor expansion particularly valuable. 

We do measure day-zero CD34+ cells, but we often see discrepancies between vendor-reported values and what we measure, which is already a challenge. We’ve also observed that similar starting CD34+ yields across different donors can result in dramatically different outcomes — sometimes a 1,000- to 10,000-fold expansion of CD34+ cells. Because the cells themselves are the product, it’s more useful for us to focus on readouts that are practical and reliable to measure. This isn’t to dismiss the value of analyzing CD34+ cells in cord blood — there are many published, multi-trial validation efforts in this area — but for a small start-up, it’s not always the best place to start if it isn’t required to keep development moving. For cord blood specifically, normalizing CD34+ yield per milliliter of the cord blood unit matters because units are inherently limited, variable, and expensive; total CD34+ output alone can be misleading, so yield-per-milliliter is the fairest way to compare processes as the workflow is developed.

We’re looking into it. It’s definitely very interesting, because if they do engraft, it could open up additional possibilities, and potentially even ways to support mouse vendors and similar applications. More to come! 

Using a GMP-grade medium early in process development is important because GMP-grade raw materials, in this case the cell culture medium, provide strict lot-to-lot reproducibility along with defined traceability and quality control. This consistency is critical as therapies are built, because it supports regulatory compliance while also avoiding unnecessary optimization steps later on. A smooth transition from R&D to process development and ultimately to GMP manufacturing requires a consistently high-quality, chemically defined, xeno-free medium that performs reproducibly throughout the process. In our case, the GMP-grade medium also demonstrated stable, controlled, and consistent performance across different feeding strategies, supporting scalable HSC expansion. Starting with a GMP-compliant, animal-component–free basal medium also helps future-proof development, since requirements can change over time, and changing something as fundamental as the basal medium later — particularly after Phase 1 or Phase 1–2 trials — can set a program back significantly.