A tuberculosis (TB) vaccine candidate that has shown modest efficacy rates received a $550 million boost from the Bill and Melinda Gates Foundation (BMGF) and Wellcome Trust, which announced on Tuesday that they will cover its Phase 3 clinical trials.

The candidate vaccine, M72, showed modest 54% efficacy in preventing the development of symptomatic TB in a Phase 2b trial involving over 3500 adults with latent TB.

The third phase of the clinical trials is expected to have 26,000 participants, including those living with HIV and without TB infection, across more than 50 sites in Africa and Southeast Asia. 

If this phase of the trials returns effective results, M72 will be the first vaccine targeting adults and adolescents, protecting those who already have latent TB infection from developing severe infection.

Around 5%-10% of those with latent TB infection go on to develop TB disease. People with weak immune systems, especially those living with HIV, are at a higher risk for developing the disease. 

Although M72’s efficacy is modest, a TB vaccine for adults with at least 50% efficacy can avert up to 8.5 million TB deaths and up to 76 million new infections by 2050.

“To support the M72 Phase III clinical trial, which will cost an estimated US$550 million, Wellcome is providing up to $150 million and the Gates Foundation will fund the remainder, about $400 million,” a press release from BMGF said. 

“TB remains one of the world’s deadliest infectious diseases,” said Julia Gillard, chair of the Board of Governors at Wellcome. “Sustainable progress against TB and wider disease threats will depend on global collaboration, financial backing, and political will.”

The only TB vaccine in use today, Bacille Calmette-Guérin (BCG), was first given to people in 1921. It helps protect babies and young children against severe systemic forms of TB but offers limited protection against pulmonary TB among adolescents and adults.

“With TB cases and deaths on the rise, the need for new tools has never been more urgent,” said Bill Gates, co-chair of the BMGF. 

“Greater investment in safe and effective TB vaccines alongside a suite of new diagnostics and treatments could transform TB care for millions of people, saving lives and lowering the burden of this devastating and costly disease.”

M72 was initially developed by GlaxoSmithKline (GSK) in partnership with Aeras and the International AIDS Vaccine Initiative (IAVI), but GSK has since transferred the vaccine’s license to the Gates Medical Research Institute (Gates MRI), an affiliate of the BMGF. 

M72 is one of 17 TB vaccine candidates currently in the development pipeline. 

Image Credits: Photo by Diana Polekhina on Unsplash.