Prothena plummets after amyloidosis failure

Prothena Corp. plc (NASDAQ:PRTA) sank $25.34 (69%) to $11.50 on Monday after it discontinued development of amyloid light-chain (AL) amyloidosis candidate NEOD001. The company said the humanized mAb targeting amyloid missed the primary and secondary endpoints in the Phase IIb PRONTO trial, and an IDMC recommended discontinuing the Phase III VITAL trial following a futility analysis.

As of Dec. 31, 2017, Prothena had $417.6 million in cash and a 12-month operating loss of $155 million. Monday's stock move shaved nearly $1 billion from Prothena's market cap, which dipped below $450 million...