Shares of INmune Bio Inc. /zigman2/quotes/206182062/composite INMB +3.56% plummeted 31.4% toward a 22-month low in premarket trading Tuesday, after the Florida-based biotechnology company said it received an email from U.S. Food and Drug Administration, saying that it placed the Investigational New Drug (IND) application to initiate its Phase 2 trial of its XPro Alzheimer's treatment on clinical hold. Also in the email, the FDA requested additional information around Chemistry Manufacturing and Controls (CMC) regarding the company's newly manufactured XPro1595. The company said the Phase 2 trial of XPro remains open in Australia. B. Riley analyst Mayank Mamtani followed by downgrading the company to neutral from buy, and halved his stock price target to $7 from $14, citing indications from the company of "limited visibility to the required corrective measures and magnitude of potential delay." The stock, which is on track to open at the lowest level seen during regular-session hours since July 2020, has plunged 66.8% year to date through Monday, while the iShares Biotechnology ETF /zigman2/quotes/206189322/composite IBB -0.30% has dropped 23.7% and the S&P 500 /zigman2/quotes/210599714/realtime SPX -0.33% has lost 16.6%.