I-Mab thinks cytokine storm drug can take on Humanigen's lenzilumab in sickest COVID-19 patients

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I-Mab’s therapy targets a certain cytokine that plays a critical role in acute and chronic inflammation. (Tempura/Getty Images)

I-Mab’s experimental COVID-19 treatment reduced the mechanical ventilation rate in patients, putting the Chinese biotech in the game with Humanigen in trying to improve treatment options for the sickest patients.

The ongoing phase 2/3 study is testing I-Mab’s plonmarlimab for the treatment of cytokine release syndrome, an over-active immune response associated with a higher death rate in COVID-19 patients.

Currently, physicians treat such severe patients with steroids and Gilead’s remdesivir, but there remains a need for more efficacious therapies, especially as the new Delta variant grips the U.S. and the world, bumping up hospitalizations once again.

I-Mab’s therapy targets a certain cytokine that plays a critical role in acute and chronic inflammation. The study’s main goal is to examine plonmarlimab’s safety, efficacy and effect on cytokine levels in patients with severe COVID-19.

Plonmarlimab, or TJM2, improved the rate of mechanical ventilation free treatment compared to placebo, at a rate of 83.6% vs 76.7% by day 30. The therapy was also associated with a lower mortality rate of 4.9% vs 13.3% and higher recovery rates. I-Mab also said the therapy reduced recovery time and hospitalization duration.

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There’s a lot to unpack there, and the details were short in I-Mab’s statement. Many of the improvement percentages compared to placebo are not too far off—but they could be significant to these very sick patients who have few other options.

I-Mab threw down the gauntlet against Humanigen, which has a COVID-19 therapeutic already under review in the U.S. and U.K. Lenzilumab also tries to stop cytokine storms.

“The magnitudes of the clinical improvements are comparable to those observed with lenzilumab in a similar patient population,” I-Mab said.

Humanigen has estimated that lenzilumab caused 37% more recoveries than standard of care in hospitalized COVID-19 patients in a phase 3 trial.

The study has an adaptive trial design, meaning patients can only stay enrolled if the interim analysis shows an average improvement in recoveries of 29% or more. The improvement rate was calculated based on enrollment requested by the data safety monitoring board.

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Whether the two therapies can be compared apples to apples remains to be seen, as they are not examining the exact same outcome. But improvement is improvement when a patient has severe COVID-19, and drug regulators are scrambling to incentivize the development of more effective treatments. 

Analysts have predicted that Humanigen's drug could become the standard of care for the sickest hospitalized COVID-19 patients and bring in $1 billion in sales in the first 12 months after approval. GlaxoSmithKline is also investigating a cytokine release drug.