Complex sentence: Organ rejection by the recipient's immune system is a bigger challenge researchers face, therefore current research is underway to use the CRISPR/Cas9 complex to disable proteins in the pig that triggers immune responses in humans.
Split into simpler sentences: Organ rejection by the recipient's immune system is a bigger challenge researchers face. Therefore, current research is underway to use the CRISPR/Cas9 complex to disable proteins in the pig that trigger immune response in humans.