Following Bayer’s full Phase 3 Factor XIa stroke readout, the market appears to be positioning BMY/JNJ’s milvexian as a structurally disadvantaged, late entrant. The central debate is whether differentiation remains plausible or whether share is effectively locked. Our work suggests the probability of clinically meaningful separation is not being fully reflected in positioning, creating asymmetric equity implications across BMY-BAYN in a multi-billion-dollar stroke market, with additional optionality in AF that is currently treated as zero.