The completed P3, P3 independent peer review, and the other two peer reviews below are quite recent. Additionally, the emerging combo data are only recently beginning to come to light, and the whole idea of combining PD-1 with DC vaccines is a relatively new idea.
As a point of reference, PD-1 technology has only been commercialized for 10 years.
Being acquired “at a much earlier stage” is not necessarily a good thing—the price that any company would pay is lower before efficacy is validated or before regulators approve a new technology.