JMP Securities analyst Michael King called Celgene's (CELG) collaboration agreement with Prothena (PRTA) a "significant step" toward Celgene's realizing its long-alluded-to plans to enter the neurodegenerative space and he believes the company has the capacity to leverage its protein homeostasis expertise to eventually make notable strides in the area. He also considers the back-end weighted nature of the agreement as favorable for Celgene. However, he still thinks it will require either "astonishing clinical data" or "transformative M&A" to move Celgene shares back into favor with investors so King maintains his Market Perform rating on the stock.