 Shares of Humanigen Inc. plunged 67.9 in premarket trading on Wednesday, the day after the company said a National Institutes of Health clinical trial testing lenzilumab and Gilead Sciences Inc.s Veklury in hospitalized COVID-19 patients did not produce the same benefit as it did in previous studies. Humanigens stock is down 19.6 this year, while the SP 500 has declined 19.9. 