Explained: How a cancer drug cuts the risk of death in Covid-19 patients

The study, as its primary efficacy endpoint, looked at all-cause mortality, that is, proportion of patients who died during the study up to day 60 compared with placebo in the intent-to-treat population. The key secondary endpoints looked at differences in the trial and placebo arms in the days in the ICU, days on mechanical ventilation, and days in the hospital.

Eligible patients were required to meet the following criteria to be included in the study like being at least 18 years of age with laboratory-confirmed SARS-Cov-2 infection and baseline oxygen saturation (SpO2) level of 94% or lower on room air. Further, they needed to have a WHO-defined 9-point ordinal scale for clinical improvement score of 4, with a documented comorbidity such as asthma, chronic lung disease, diabetes, hypertension, severe obesity, 65 years of age or older, primarily residing in a nursing home or long-term care facility, or immunocompromised status, or WHO 5 status of noninvasive ventilation or high-flow oxygen, or WHO 6 status of intubation and mechanical ventilation.

Among those excluded from the study were pregnant and breast-feeding women, and patients on ventilation plus additional organ support such as long-term pressors, renal replacement therapy, or extracorporeal membrane oxygen.

What were the findings on mortality reduction among hospitalised Covid-19 patients?

According to the study, the “cumulative mortality analysis showed that the reduction in deaths with sabizabulin started within the first week of treatment and the relative reduction in deaths reached 51.8% at day 29”.

With 204 participants in the study — 134 were administered the drug and 70 others a placebo — sabizabulin treatment resulted in a 24.9 percentage point absolute reduction and a 55.2% relative reduction in deaths compared with placebo, among the subjects who were at high-risk for acute respiratory distress syndrome (ARDS) and death, the study notes.

Further, the beneficial effects of sabizabulin were observed starting as early as day 3 after dosing and by day 15, “statistically significant reductions in mortality were observed” with the beneficial effect maintained through day 29, when the mortality rate was observed to be 17% in the sabizabulin group compared to 35.3% in the placebo arm.

This implies, the drug could reduce the risk of mortality by 18.3 percentage points by the 29th day.

From the 29th day to the 60th, the death rate increased by 9.8 percentage points in the placebo group, that is the mortality rate stood at 45.1% at the end of 60th day in the placebo group, and the death rate increased by 3.2 percentage points in the sabizabulin-treated group, that is the mortality rate stood at 20.2 percent for the drug group by the 60th day. This indicates the drug could reduce the mortality risk by 24.9 percentage -points when compared with the placebo group.

Did the drug impact hospitalization?

Further, the study claims that there was a 43 percentage point relative reduction in days in the ICU — with an average of 17.4 days spent by a sabizabulin subject compared to an average of 30.8 days spent by a placebo-arm subject in the ICU. The average days spent on mechanical ventilation too halved for the sabizabulin arm (14.4 days) compared to the placebo arm (28.5 days).

How does sabizabulin work?

The study notes that the drug, by targeting microtubule trafficking, has both dual anti-inflammatory and antiviral activity. According to Veru, the company which developed sabizabulin, the drug has shown in preclinical studies to have efficacy against many tumour types including castration resistant prostate cancer, triple negative breast cancer resistant to anthracyclines and taxanes as well as ovarian cancer, cervical cancer, lung cancer, melanoma, leukaemia, glioma, and pancreatic cancer.