It is either Keytruda (MRK) or Opdivo (BMY). Merck is an aggressive buyer and recently bought out my XLRN for $11.5B in a scenario where the lead asset is luspatercept on which BMY had 80% rights of revenues with the rest going to XLRN. MRK took the $11.5B gamble on XLRN sotatercept asset on which XLRN has 80% rights of revenues and BMY 20%. A huge gamble for them as sotatercept is not yet de-risked. If Precigen opt for Keytruda there is high likelihood of a buyout not partnerships.
Both BMY and MRK are trying to finds means to extend the loss of exclusivity. BMY partnered with Halozyme and by 2025/27 might get Opdivo subcutaneous = new patent formulation. So Merck is more desperate.