Is There a Difference Between PD-1 and PD-L-1?

Ibi, I want to ask you a real broad question that goes beyond lung cancer in general. Is there any way to separate out IOs in terms of equis-y, tolerability, PD-1 versus PD-L-1? You know, generally speaking, the message we've been getting in general on college year over the years is you really can't separate them out. Are they different epitopes? They have different half-lives or more likely to elicit antibody drug or antibody, anti-drug antibodies? But these differences are too subtle. So I think the only meaningful differences in the clinic today are in indication and cost.