Humanigen's COVID-19 prospect flunks NIH trial, sinking stock and raising doubts about its future

Humanigen’s COVID-19 program has ended in defeat. After failing to win emergency authorization on the strength of its phase 3 trial, the New Jersey-based biotech has seen its prospect flunk a National Institutes of Health (NIH) study, sinking the stock and raising doubts about its future.

Last year, Humanigen posted phase 3 data on lenzilumab in hospitalized subjects with severe or critical COVID-19 pneumonia, linking the anti-human GM-CSF monoclonal antibody to a 54% improvement in the likelihood of survival without ventilation. However, the FDA was unable to say whether lenzilumab’s benefits outweighed its risks, leading the agency to knock back Humanigen’s filing for emergency authorization. The biotech changed the primary endpoint twice during the study.

Humanigen looked to the NIH’s ACTIV-5 Big Effect Trial for data to convince the FDA. The lenzilumab part of the study randomized 473 hospitalized COVID-19 patients to receive the drug or placebo on top of Gilead’s Veklury.  

On Day 29, the NIH found the proportions of patients in the primary endpoint analysis who were alive and without mechanical ventilation were statistically the same in the lenzilumab and control groups. The finding caused the study to miss its primary endpoint. Participants aged under 85 with baseline levels of C-reactive protein, an inflammation biomarker, of less than 150 mg/L were included in the analysis.

Humanigen identified “a non-significant trend toward a reduction in mortality” in the overall population, plus the lack of new safety signals, as positives. However, the failure on the primary endpoint deals a big blow to Humanigen’s hopes of using the study to allay the FDA’s doubts about the candidate. Shares in the biotech fell more than 50% in after-hours trading, sinking to around $1.30.

If lenzilumab has no future in COVID-19, Humanigen will need to drum up enthusiasm for the candidate in the prevention of toxicities related to CAR-T therapy. Humanigen is working toward a phase 3 trial in the indication but has limited money to pump into the program. 

At the end of March, the biotech had $69 million in the bank. While that is more than some of its peers—and it has an at-the-market facility for selling stock—Humanigen also had current liabilities of $71 million.