Sick Kids spinout Radiant developing ‘supercharged’ antibody drugs to target HIV, complex cancers

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A spinout from Toronto’s Hospital for Sick Children that aims to treat cancer, HIV and other complex diseases with a new type of supercharged, antibody-laden molecule has raised $35-million in venture capital co-led by the Bill and Melinda Gates Foundation and Canada’s Amplitude Ventures.

Radiant Biotherapeutics is built around science developed in the Sick Kids laboratories of senior scientist Jean-Philippe Julien, an associate professor at University of Toronto’s Temerty Faculty of Medicine. The company was created by Montreal-based Amplitude four years ago, after its investment team went searching for cutting-edge antibody-creation platform technologies.

Amplitude principal Bharat Srinivasa learned of Dr. Julien’s work while judging a Sick Kids competition for a grant won by his lab. The work in Dr. Julien’s lab “really hit that nail on the head,” Dr. Srinivasa said in an interview.

Y-shaped antibodies typically grab onto targets with their two upper branches, known as fabs, but sometimes lose their grip, disabling their ability to deliver their therapeutic effect. Dr. Julien’s team had created a structure known as a “Multabody” – a round, burr-like scaffolding made from cellular material known as light chain apoferritin with eight to 24, or even more, antibodies or antibody parts attached to them like Lego pieces.

All those fabs working in tandem make for a much firmer grasp on their target, meaning they can help deliver far greater potency with the force of “a really strong sledgehammer to get a real therapeutic response,” for ailments that have been harder to solve with standard antibodies, Mr. Srinivasa said.

“No one has taken antibodies to this level with this amount of power,” Dr. Julien said in an interview. “It’s a supercharged antibody that can go after complex biology, complex diseases.”

Amplitude licensed the lab’s platform technology from Sick Kids and the University of Toronto, incorporated Radiant and led its seed investment four years ago. It also recruited biopharma industry veterans Arthur Fratamico and Jo Hulme to serve as the company’s chief executive and chief scientific officer. (Mr. Julien, a co-founder, is chair of Radiant’s scientific advisory board.)

Radiant is starting out by developing a Multabody molecule to target a receptor known as 4-1BB on cancer-fighting T cells produced by the human body. Mr. Fratamico, who is based in the Philadelphia area, said that, while current antibody treatments work well for certain health issues, targeting the 4-1BB required a cluster-grasping approach, which “traditional antibodies can’t do.”

By grasping onto the receptors in clusters, the hope is that the molecule will activate the T cells to make them more effective at attacking tumours. Radiant hopes to improve on two previous attempts by drug developers to target the 4-1BB receptor. Bristol Myers-Squibb abandoned a drug called urelumab after two patients died in safety trials owing to liver toxicity caused by the treatment, while Pfizer’s utomilumab proved to be ineffective.

Radiant is also working on an HIV program with the Gates foundation in which a differently-built Multabody would bind firmly to receptors on the virus, neutralizing its devastating negative health effects and triggering the body’s natural immune response.

Mr. Fratamico said early preclinical work by the 14-person company has shown the Multabody delivers vastly greater potency in neutralizing viruses than both traditional antibodies and drug cocktails composed of three different antibodies.

“As we look at what the Multabody can deliver compared to parent antibody, typically we win,” the CEO said. He added that Radiant’s platform could be used to build many different types of molecules with different antibody tops for a range of ailments.

Radiant has yet to prove its technology works in humans, however. The company expects to file an investigational new drug application with regulators some time in early 2025, which would kick off years of work to conduct safety and efficacy trials in humans for its 4-1BB drug.

That’s a process that will likely require Radiant to raise hundreds of millions of dollars to fund research and development. The company, which has already done research collaborations with several pharmaceutical and biotechnology companies, also has yet to disclose which specific cancers it will target with the drug.

Other investors backing the Radiant financing, which was announced last week, include Scottish investment company Abrdn PLC, Alexandria Venture Investments and three domestic government-funded bodies: Business Development Bank of Canada, Toronto Innovation Acceleration Partners and Fight Against Cancer Innovation Trust.