PDX is still mouse: reading the human in vivo evidence carefully

One of the strongest-sounding numbers in SunVax's public talks is the 92-94% delivery efficacy in PDX models. It's a real number, and it was disclosed at a peer conference, which earns a grade-A evidence label. But the number is often misread.

PDX stands for patient-derived xenograft. The tumor tissue is human, harvested from a real patient and grown into an immunodeficient mouse. The host that circulates the LNP, the host's immune cells, and the host's liver-sinusoidal endothelium that filters out most circulating particles — all of those are still mouse. So a 92-94% PDX number is "good delivery into a human tumor inside a mouse," not "good delivery in a human."

Why does this matter? Two reasons. First, the rate of clearance by mouse liver is different from human liver. Second, the corona of proteins that adsorbs onto an LNP in mouse plasma is different from the corona in human plasma — and the corona is what determines uptake by many cell types. SunVax themselves acknowledge this. On the same panel, asked about the next step after mouse studies, Yingzhong Li said: "we have identified formulations that perform well in both human primary cells and mouse primary cells." That phrasing is precise: primary cells in vitro, not human in vivo.

So how should a buyer interpret the data on the SV106 (human CD8 T) page? The honest reading is: SV106 has been engineered in the same lipid family that worked in mouse CD8 T cells, with cross-species lipid screening data backing the design choice. Direct human in vivo evidence is the missing link, and SunVax is the first to say so.

We carry this nuance through every product page on this site. When SV106 says "result inferred from cross-species lipid family", we use grade C, not grade A. When SV101 says 79.8% CD8 T in vitro, we use grade A. The grade is the math behind the claim, not a marketing badge.