- Gritstone Oncology will work with the National Institutes of Health to develop a second-generation coronavirus vaccine, announcing Tuesday plans to begin a study of its experimental shot in human volunteers early this year.
- California-based Gritstone aims for its vaccine to stimulate a stronger response from virus-killing T cells that are activated by viral proteins other than the “spike” targeted by currently authorized vaccines. The approach, Gritstone claims, could produce a shot that can be used broadly against coronaviruses other than SARS-CoV-2.
- Some public health experts have raised concerns that emerging mutations in the SARS-CoV-2 genome could make vaccines and treatments now in testing less effective. There is no conclusive evidence, however, that newly detected coronavirus variants can evade them.
With nearly 100 million cases now reported worldwide, SARS-CoV-2 threatens to become an endemic virus in humans even after newly authorized vaccine curb its rampant spread. Little is known about how long the shots developed by Pfizer and BioNTech and Moderna can protect people from COVID-19 or whether they will continue to be effective as coronavirus mutations gather over time.
Before the pandemic, Gritstone’s focus was on developing immunotherapies to combat cancer. As with a vaccine for viruses, its technology aims to stimulate an immune response from a type of white blood cell called a T cell to target specific proteins on a tumor and attack it. So-called cancer vaccines have been in development for years with limited success.
Gritstone is betting its coronavirus vaccine candidate can stimulate a broader T cell response than the authorized vaccines, which appear to primarily rely on antibodies to combat coronavirus infection. The company’s focus is on a type of T cell called CD8+, which help clear viruses from infected cells. Moderna’s vaccine stimulated low levels of CD8+ cells, while the Pfizer and BioNTech vaccine led to a CD8+ T cell response in some patients.
“We started life focused in on oncology and the generation of … CD8 T cells, which was obviously a daunting problem when we began,” Gritstone CEO Andrew Allen said in a conference call Tuesday. “Our data suggests that we’ve overcome many of the challenges associated with that.”
The company has signed a clinical trial agreement with the National Institutes of Health to support Phase 1 testing, which Allen said is set to begin in the first quarter of the year. Preclinical work has been supported by the Bill & Melinda Gates Foundation.
Gritstone’s vaccine combines two technologies in a prime-boost shot regimen. The first is a viral vector vaccine, using a chimp adenovirus to deliver genetic instructions for antigens that can stimulate an immune response. The boost is a self-amplifying messenger RNA that does a similar job through a different cellular mechanism.
Vaccines in development from AstraZeneca and Johnson & Johnson rely on viral vectors. The authorized vaccines from Pfizer and BioNTech and Moderna use mRNA.