Black Friday is still weeks away, but Exelixis Inc. has gone shopping and inked two deals that together are potentially worth more than $1 billion, bolstering its pipeline with cancer drugs from Cybrexa Inc. and Sairopa B.V. Both deals are eye-catching, not just because of their potential value but also because of the technologies involved. Cybrexa’s drug is a peptide-drug conjugate, a class where only one drug is FDA approved and established, and Sairopa is working on an antibody targeting SIRPα, a potential next-generation immunotherapy.